Secondary batteries

Abstract

To provide a positive electrode active material that undergoes minimal degradation. Or, to provide a secondary battery that undergoes minimal degradation. Or, to provide a secondary battery that offers high safety. [Solution] A secondary battery having a positive electrode, wherein the positive electrode has a positive electrode active material, the positive electrode active material comprises lithium, a transition metal, oxygen, and an additive element, the positive electrode active material has a plurality of primary particles, at least a portion of the plurality of primary particles are fixed to form secondary particles, the primary particles have a surface layer and an interior, and the concentration of the additive element on the surface or surface layer of the primary particles is higher than the concentration of the additive element in the interior.

Description

[Technical Field]

[0001] One aspect of the present invention relates to a product or a method of manufacturing; or to a process, machine, manufacture, or composition of matter. Another aspect of the present invention relates to an energy storage device including a secondary battery, a semiconductor device, a display device, a light-emitting device, a lighting device, an electronic device, or a method of manufacturing the same.

[0002] In this specification, the term "energy storage device" refers to all elements and devices that have an energy storage function. For example, this includes rechargeable batteries (also called secondary batteries) such as lithium-ion secondary batteries, lithium-ion capacitors, and electric double-layer capacitors.

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

[0004] In recent years, there has been a great deal of development on various energy storage devices, including lithium-ion secondary batteries, lithium-ion capacitors, air batteries, and all-solid-state batteries. In particular, the demand for lithium-ion secondary batteries, which offer high output and high capacity, has expanded rapidly in line with the development of the semiconductor industry, and they have become indispensable as a source of rechargeable energy in today's information society.

[0005] Therefore, improvements to the positive electrode active material are being considered in order to improve the cycle characteristics and increase the capacity of lithium-ion secondary batteries (Patent Documents 1 and 2).

[0006] Furthermore, the characteristics required of energy storage devices include safety in various operating environments and improved long-term reliability. [Prior art documents] [Patent Documents]

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] In lithium-ion secondary batteries and cathode active materials used therein, improvements are desired in various aspects such as capacity, cycle characteristics, charge-discharge characteristics, reliability, safety, or cost.

[0009] In view of the above, one aspect of the present invention is to provide a cathode active material with less deterioration as one of the problems. Or, one aspect of the present invention is to provide a secondary battery with less deterioration as one of the problems. Or, one aspect of the present invention is to provide a highly safe secondary battery as one of the problems.

[0010] Or, one aspect of the present invention is to provide an active material, a power storage device, or a method for manufacturing them as one of the problems.

[0011] Note that the description of these problems does not prevent the existence of other problems. Note that one aspect of the present invention does not need to solve all of these problems. Note that it is possible to extract other problems from the description of the specification, drawings, and claims.

Means for Solving the Problems

[0012] One aspect of the present invention is a secondary battery having a cathode, the cathode having a cathode active material, the cathode active material having lithium, a transition metal, oxygen, and an additive element, the cathode active material having a plurality of primary particles and secondary particles to which at least a part of the plurality of primary particles are fixed, the primary particles having a surface layer portion and an interior, and the concentration of the additive element on the surface or surface layer portion of the primary particles being higher than the concentration of the additive element in the interior.

[0013] In the above, it is preferable that the concentration of the additive elements has a gradient in which the concentration increases from the inside of the primary particle towards the surface.

[0014] In the above, it is preferable that the additive element is at least one of aluminum, magnesium, fluorine, titanium, zirconium, nickel, yttrium, lanthanum, vanadium, iron, chromium, niobium, hafnium, zinc, silicon, sulfur, nitrogen, phosphorus, boron, and arsenic.

[0015] In the above, the additive element is an additive element compound bonded with oxygen or fluorine, and the additive element compound is preferably zirconium oxide or yttria-stabilized zirconium.

[0016] In the above, the positive electrode preferably has graphene or a graphene compound, and the graphene or graphene compound is preferably positioned to cling to the secondary particles of the positive electrode active material.

[0017] Another aspect of the present invention is an electronic device having the secondary battery described above.

[0018] Another aspect of the present invention is a vehicle having the secondary battery described above. [Effects of the Invention]

[0019] According to one aspect of the present invention, a positive electrode active material with less degradation can be provided. Alternatively, a secondary battery with less degradation can be provided. Alternatively, a secondary battery with high safety can be provided.

[0020] Alternatively, according to one aspect of the present invention, an active material, an energy storage device, or a method for producing the same can be provided.

[0021] 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]

[0022] [Figure 1] Figures 1A and 1B are cross-sectional views of the positive electrode active material. [Figure 2] Figures 2A to 2C illustrate the concentration distribution of additive elements. [Figure 3] Figure 3 illustrates an example of a method for preparing a positive electrode active material. [Figure 4] Figure 4 is a cross-sectional view illustrating an example of the positive electrode of a secondary battery. [Figure 5] Figure 5A is an exploded perspective view of a coin-type rechargeable battery, Figure 5B is a perspective view of a coin-type rechargeable battery, and Figure 5C is a cross-sectional perspective view thereof. [Figure 6] Figure 6A is a perspective view showing an example of a cylindrical secondary battery. Figure 6B is a cross-sectional perspective view showing an example of a cylindrical secondary battery. Figure 6C is a perspective view showing an example of multiple cylindrical secondary batteries. Figure 6D is a perspective view showing an example of an energy storage system having multiple cylindrical secondary batteries. [Figure 7] Figures 7A and 7B illustrate examples of secondary batteries, and Figure 7C shows the inside of a secondary battery. [Figure 8] Figures 8A to 8C illustrate examples of secondary batteries. [Figure 9] Figures 9A and 9B show the external appearance of a secondary battery. [Figure 10] Figures 10A to 10C illustrate the method for manufacturing a secondary battery. [Figure 11] Figures 11A to 11C show examples of battery pack configurations. [Figure 12] Figures 12A and 12B illustrate an example of a secondary battery. [Figure 13] Figures 13A to 13C illustrate an example of a secondary battery. [Figure 14] Figures 14A and 14B illustrate an example of a secondary battery. [Figure 15] Figure 15A is a perspective view of a battery pack showing one aspect of the present invention, Figure 15B is a block diagram of the battery pack, and Figure 15C is a block diagram of a vehicle having a motor. [Figure 16] Figures 16A to 16D illustrate an example of a transport vehicle. [Figure 17] Figures 17A and 17B illustrate an energy storage device according to one aspect of the present invention. [Figure 18] Figure 18A shows an electric bicycle, Figure 18B shows the secondary battery of an electric bicycle, and Figure 18C illustrates an electric motorcycle. [Figure 19] Figures 19A to 19D illustrate an example of an electronic device. [Figure 20] Figure 20A shows an example of a wearable device, Figure 20B shows a perspective view of a wristwatch-type device, and Figure 20C is a diagram illustrating the side view of a wristwatch-type device. Figure 20D is a diagram illustrating an example of wireless earphones. [Modes for carrying out the invention]

[0023] 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.

[0024] 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.

[0025] 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, a composite oxide, 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.

[0026] In this specification, segregation refers to the phenomenon in which a certain element (e.g., B) is spatially non-uniformly distributed in a solid composed of multiple elements (e.g., A, B, C).

[0027] Furthermore, in this specification, the term "crack" is defined not only as one that occurs during the manufacturing process of the positive electrode active material, but also as one that occurs due to subsequent pressurization and charging / discharging.

[0028] In this specification, the surface layer of particles such as active material refers to, for example, the region within 50 nm, more preferably within 35 nm, even more preferably within 20 nm, and most preferably within 10 nm, from the surface toward the center. Surfaces formed by cracks (which may also be called fissures) may also be considered the surface. The region closer to the center than the surface layer is called the interior.

[0029] Furthermore, in this specification, when the term "defect" is used simply, it refers to a crystal defect or a lattice defect. Defects include point defects, dislocations, stacking faults (two-dimensional defects), and voids (three-dimensional defects).

[0030] Furthermore, in this specification, the term "particle" is not limited to spherical shapes (circular cross-sections), but may include elliptical, rectangular, trapezoidal, conical, rounded-cornered quadrilateral, asymmetrical shapes, and individual particles may have irregular shapes.

[0031] Furthermore, Miller indices are used to represent crystal planes and directions in this specification. Individual crystal planes are indicated by ( ). Orientations are indicated by [ ]. Reciprocal lattice points use the same indices, but without parentheses. In crystallography, crystal planes, directions, and space groups are indicated by superscripts above the numbers, but in this specification, due to the constraints of patent application notation, a minus sign (-) may be placed before the number instead of a superscript above it.

[0032] 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.

[0033] 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.

[0034] In layered rock salt crystals and rock salt crystals, the anions adopt a cubic close-packed structure (face-centered cubic lattice structure). When these are in contact, there exists a crystal plane in which the orientation of the cubic close-packed structure composed of anions is aligned. However, the space group of layered rock salt crystals is R-3m, which is different from the space groups Fm-3m (the space group of typical rock salt crystals) and Fd-3m (the space group of rock salt crystals with the simplest symmetry), so the Miller indices of the crystal planes that satisfy the above conditions are different for layered rock salt crystals and rock salt crystals. In this specification, when the orientation of the cubic close-packed structure composed of anions is aligned in layered rock salt crystals and rock salt crystals, it may be said that the crystal orientations are approximately identical, or that they are topotaxy, or epitaxy. Topotaxy refers to having a three-dimensional structural similarity such that the crystal orientations are approximately identical, or that they have the same crystallographic orientation. Epitaxy, on the other hand, refers to the structural similarity of a two-dimensional interface.

[0035] The general agreement of crystal orientation between two regions can be determined from TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle scattering annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as a basis for determination. In HAADF-STEM images, etc., the arrangement of cations and anions can be observed as a repetition of bright and dark lines. When the orientation of the cubic close-packed structure is aligned in layered rock salt crystals and rock salt crystals, it can be observed that the angle between the repetition of bright and dark lines between crystals is 5 degrees or less, more preferably 2.5 degrees or less. Note that light elements such as oxygen and fluorine may not be clearly visible in TEM images, etc., but in such cases, the agreement of orientation can be determined from the arrangement of metallic elements.

[0036] 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 XAh, the current equivalent to 1C is XA. If the battery is discharged with a current of 2XA, it is said to have been discharged at 2C, and if it is discharged with a current of X / 5A, 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 2XA, it is said to have been charged at 2C, and if it is charged with a current of X / 5A, it is said to have been charged at 0.2C.

[0037] 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.

[0038] Furthermore, in this specification, a value in the vicinity of a given numerical value A refers to a value between 0.9 × A and 1.1 × A.

[0039] Furthermore, while this specification and other documents may show an example in which lithium metal is used as the counter electrode in a secondary battery using a positive electrode and positive electrode active material according to one aspect of the present invention, the secondary battery according to one aspect of the present invention is not limited to this. Other materials, such as graphite or lithium titanate, may be used for the negative electrode. The properties of the positive electrode and positive electrode active material according to one aspect of the present invention, such as resistance to crystal structure collapse even after repeated charging and discharging and obtaining good cycle characteristics, are not affected by the material of the negative electrode. Furthermore, while an example of a secondary battery according to one aspect of the present invention may be shown in which charging and discharging is performed at a voltage higher than the typical charging voltage of around 4.7V with a lithium counter electrode, charging and discharging may be performed at a lower voltage. When charging and discharging at a lower voltage, it is expected that the cycle characteristics will be even better than those shown in this specification and other documents.

[0040] Furthermore, unless otherwise specified in this specification, the charging and discharging voltages refer to the voltages when the counter electrode is lithium. However, even with the same positive electrode, the charging and discharging voltages of a secondary battery change depending on the material used for the negative electrode. For example, the potential of graphite is approximately 0.1V (vs Li / Li + Therefore, in the case of a graphite negative electrode, the charge and discharge voltage will be approximately 0.1V lower than in the case of a lithium counter electrode. Furthermore, even if the charging voltage of a secondary battery is, for example, 4.7V or higher in this specification, it is not necessary for it to have only a discharge voltage of 4.7V or higher as a plateau region.

[0041] (Embodiment 1) In this embodiment, a positive electrode active material according to one aspect of the present invention will be described with reference to Figures 1A to 2C.

[0042] Figure 1A shows a cross-sectional view of the positive electrode active material 100. The positive electrode active material 100 has a plurality of primary particles 101. At least some of the plurality of primary particles 101 adhere to form secondary particles 102. There are also primary particles 101 that do not become secondary particles. An enlarged view of the secondary particles 102 is shown in Figure 1B. The positive electrode active material 100 may have voids 105. Note that the shapes of the primary particles 101 and secondary particles 102 shown in Figures 1A and 1B are examples and are not limited thereto.

[0043] In this specification, a primary particle is the smallest solid unit that is recognized as having a clear boundary in a microscopic image such as an SEM image, TEM image, or STEM image. A secondary particle is a particle formed by the sintering, bonding, or aggregation of multiple primary particles. The bonding force acting between the multiple primary particles is irrelevant. It may be a covalent bond, an ionic bond, a hydrophobic interaction, a van der Waals force, or any other intermolecular interaction, and multiple bonding forces may be at work. Furthermore, the term "particle" includes both primary and secondary particles.

[0044] <Contained elements> The positive electrode active material 100 comprises lithium, a transition metal M, oxygen, and an additive element.

[0045] The positive electrode active material 100 can be described as a composite oxide represented by LiMO2 to which one or more additive elements have been added. The positive electrode active material in one embodiment of the present invention only needs to have the crystal structure of a lithium composite oxide represented by LiMO2, and its composition is not strictly limited to Li:M:O=1:1:2.

[0046] As the transition metal M in the positive electrode active material 100, it is preferable to use a metal that can form a layered rock salt type composite oxide belonging to space group R-3m together with lithium. For example, at least one of manganese, cobalt, and nickel can be used as the transition metal M. In other words, only cobalt may be used as the transition metal M, only nickel may be used, two types of cobalt and manganese may be used, two types of cobalt and nickel may be used, or three types of cobalt, manganese, and nickel may be used. In other words, the positive electrode active material 100 can have composite oxides containing lithium and the transition metal M, 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.

[0047] In particular, using cobalt as the transition metal M in the positive electrode active material 100 in an amount of 75 atomic% or more, preferably 90 atomic% or more, and more preferably 95 atomic% or more, offers many advantages, such as being relatively easy to synthesize, easy to handle, and having excellent cycle properties.

[0048] On the other hand, if nickel is used as the transition metal M in the positive electrode active material 100 in an amount of 33 atomic percent or more, preferably 60 atomic percent or more, and more preferably 80 atomic percent or more, the raw materials may be cheaper compared to the case where cobalt is abundant, and the charge / discharge capacity per unit weight may increase, which is preferable.

[0049] Furthermore, if the transition metal M contains nickel along with cobalt, it may suppress the displacement of the layered structure consisting of octahedra of cobalt and oxygen. Therefore, the crystal structure may become more stable, especially in the charged state at high temperatures, which is preferable. This is because nickel can easily diffuse into the interior of lithium cobalt oxide, and while it may be present at the cobalt sites during discharge, it can be located at the lithium sites through cation mixing during charging. Nickel present at the lithium sites during charging is thought to function as pillars supporting the layered structure consisting of octahedra of cobalt and oxygen, contributing to the stabilization of the crystal structure.

[0050] Furthermore, the transition metal M does not necessarily have to include manganese, nickel, or cobalt.

[0051] Preferably, at least one of the following additive elements is used: magnesium, fluorine, aluminum, titanium, zirconium, nickel, yttrium, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, nitrogen, phosphorus, boron, and arsenic. The additive elements are preferably present in the surface layer and / or interior.

[0052] The additive elements are preferably bonded with other elements, such as oxygen and / or fluorine, to form additive element compounds. For example, oxides and fluorides are preferred. In particular, zirconium oxide or yttria-stabilized zirconium is preferred.

[0053] Furthermore, some additive element compounds may be present in the surface layer. Also, some additive element compounds do not necessarily have to be present in the surface layer. For example, they may be present in the protrusions located on the surface of the positive electrode active material 100.

[0054] Zirconium oxide and yttria-stabilized zirconium are preferable because their presence in at least the convex portions of the positive electrode active material 100 may improve the charge-discharge cycle characteristics.

[0055] In particular, the positive electrode active material 100 can be made more durable by adding phosphorus, which is preferable as it allows for a safer secondary battery.

[0056] Furthermore, since manganese, titanium, vanadium, and chromium are materials that readily and stably form the tetravalent state, using them as the transition metal M in the positive electrode active material 100 can sometimes enhance their contribution to structural stability.

[0057] As described later, additive elements may further stabilize the crystal structure of the positive electrode active material 100. In other words, the positive electrode active material 100 can include lithium cobalt oxide with magnesium and fluorine, lithium nickel-cobalt oxide with magnesium and fluorine, lithium cobalt-aluminate with magnesium and fluorine, lithium nickel-cobalt-aluminate, lithium nickel-cobalt-aluminate with magnesium and fluorine, lithium nickel-manganese-cobalt oxide with magnesium and fluorine, etc. In this specification, additive elements may be referred to as mixtures, part of raw materials, impurities, etc.

[0058] Furthermore, it is preferable that the additive elements in the positive electrode active material 100 are added at a concentration that does not significantly alter the crystallinity of the composite oxide represented by LiMO2, and for example, it is preferable that the amount is such that it does not exhibit the Jahn-Teller effect.

[0059] Furthermore, the additive elements do not necessarily have to include aluminum, magnesium, fluorine, titanium, zirconium, nickel, yttrium, lanthanum, vanadium, iron, chromium, niobium, hafnium, zinc, silicon, sulfur, nitrogen, phosphorus, boron, or arsenic.

[0060] <Elemental distribution> It is preferable that at least one of the additive elements in the positive electrode active material 100 has a concentration gradient.

[0061] For example, when a primary particle 101 has a surface layer 101a and an interior layer 101b as shown in Figure 2B or Figure 2C, it is preferable that the surface layer 101a has a higher concentration of additive elements than the interior layer 101b. In Figures 1A and 1B, regions with high concentrations of additive elements in the primary particle 101 are indicated by hatches. In Figures 2B and 2C, the concentration of additive elements is indicated by the density of the hatches. A denser hatch means a higher concentration of additive elements, and a fainter hatch means a lower concentration of additive elements.

[0062] Furthermore, when the interface 103 and the vicinity of the interface 103 between primary particles correspond to the surface layer 101a and the vicinity of the surface layer 101a of the primary particle 101, it is preferable that the concentration of additive elements at the interface 103 and the vicinity of the interface 103 is higher than that at the interior 101b of the primary particle 101. In this specification, the vicinity of the interface 103 refers to the region from the interface 103 to about 10 nm.

[0063] Figure 2A shows an example of the concentration distribution of additive elements between the dashed-dotted line A and B in the positive electrode active material 100 shown in Figure 1B. In Figure 2A, the horizontal axis represents the distance between the dashed-dotted line A and B in Figure 1B, and the vertical axis represents the concentration of the additive elements.

[0064] Compared to the interior 101b of the primary particle 101, the interface 103 and its vicinity have regions with high concentrations of additive elements. Note that the shape of the concentration distribution of additive elements is not limited to the shape shown in Figure 2A.

[0065] Furthermore, if there are multiple additive elements, it is preferable that the concentration distribution differs depending on the additive element, and that the peak positions of the concentrations shown in Figure 2A are different.

[0066] For example, as shown in Figures 1A, 1B, and 2B, preferred additive elements present in the surface layer 101a include magnesium, fluorine, and titanium. It is preferable that magnesium, fluorine, and titanium have a concentration gradient that increases from the interior 101b towards the surface.

[0067] Furthermore, for some other additive elements, it is preferable that the concentration peak is located in a region closer to the interior 10¹b, as shown in Figure 2C, rather than in the distribution of additive elements as shown in Figure 2B. Aluminum is an example of an additive element for which such a distribution is preferable. The concentration peak may be located in the surface layer or deeper than the surface layer. For example, aluminum preferably has a concentration peak in the region between 5 nm and 30 nm from the surface.

[0068] For example, the concentration peaks representing magnesium, fluorine, and titanium are located closer to the surface than the concentration peak representing aluminum.

[0069] Furthermore, it is preferable that some of the additive elements, such as magnesium, have a concentration gradient that increases from the interior 101b towards the surface, as shown in Figure 2B, but it is also preferable that they are thinly distributed throughout the primary particle 101. For example, it is preferable that the magnesium concentration in the surface layer 101a, as measured by XPS or the like, is higher than the average magnesium concentration of the entire particle, as measured by ICP-MS or the like.

[0070] Furthermore, in one embodiment of the present invention, when the positive electrode active material 100 contains one or more metals other than cobalt, such as nickel, aluminum, manganese, iron, and chromium, it is preferable that the concentration of the metal in the near-surface region of the primary particles 101 is higher than the average concentration of the entire particle. For example, it is preferable that the concentration of elements other than cobalt in the surface layer 101a, as measured by XPS or the like, is higher than the average concentration of the elements in the entire particle, as measured by ICP-MS or the like.

[0071] Unlike the interior of the crystal, the surface layer 101a has broken bonds, and during charging, lithium escapes from the surface, making it a region where the lithium concentration tends to be lower than in the interior 101b. Therefore, it is a region that is prone to instability and the crystal structure is easily disrupted. If the concentration of additive elements in the surface layer 101a is high, changes in the crystal structure can be suppressed more effectively. In addition, a high concentration of additive elements in the surface layer 101a can be expected to improve corrosion resistance to hydrofluoric acid produced by the decomposition of the electrolyte.

[0072] Thus, in one aspect of the present invention, it is preferable that the surface layer 101a of the positive electrode active material 100 has a higher concentration of additive elements than the interior 101b. Furthermore, in the positive electrode active material 100, it is preferable that the surface layer 101a has a different composition from the interior 101b. It is also preferable that its composition has a crystalline structure that is stable at room temperature (25°C). Therefore, the surface layer 101a may have a different crystalline structure from the interior 101b. For example, at least a part of the surface layer 101a of the positive electrode active material 100 in one aspect of the present invention may have a rock salt type crystalline structure. Also, if the surface layer 101a and the interior 101b have different crystalline structures, it is preferable that the crystal orientations of the surface layer 101a and the interior 101b are roughly the same.

[0073] However, if the surface layer 101a consists only of additive elements and oxygen, for example, only MgO, or only a solid solution of MgO and CoO(II), then lithium insertion and removal becomes difficult. Therefore, the surface layer 101a must contain at least a transition metal M, and in the discharge state, it must also contain lithium and have a pathway for lithium insertion and removal. Furthermore, it is preferable that the concentration of the transition metal M is higher than that of each additive element.

[0074] The positive electrode active material 100 in one embodiment of the present invention is not limited to this. For example, it may contain additive elements that do not have a concentration gradient.

[0075] Furthermore, it is preferable that the transition metal M, particularly cobalt and nickel, is uniformly dissolved in the entire positive electrode active material 100.

[0076] Furthermore, a portion of the transition metal M present in the positive electrode active material 100, such as manganese, may have a concentration gradient that increases from the interior 101b towards the surface.

[0077] The aforementioned distribution of additive elements reduces the degradation of the positive electrode active material 100 even after charging and discharging. In other words, it suppresses the degradation of the secondary battery. Furthermore, it allows for a highly safe secondary battery.

[0078] Generally, as a secondary battery undergoes repeated charging and discharging, side reactions can occur in the positive electrode active material, such as the leaching of transition metals M (e.g., cobalt and manganese) into the electrolyte, the desorption of oxygen, and the instability of the crystal structure, which can lead to degradation of the positive electrode active material. This degradation can result in a decrease in the capacity of the secondary battery. In this specification, the chemical and structural changes in the positive electrode active material, such as the leaching of transition metals M into the electrolyte, the desorption of oxygen, and the instability of the crystal structure, may be referred to as degradation of the positive electrode active material. In this specification, the decrease in the capacity of the secondary battery may be referred to as degradation of the secondary battery.

[0079] Metals leached from the positive electrode active material can be reduced and deposited at the negative electrode, potentially interfering with the electrode reaction at the negative electrode. This metal deposition at the negative electrode can lead to degradation, such as a decrease in capacity.

[0080] Due to the insertion and removal of lithium during charging and discharging, the crystal lattice of the positive electrode active material may expand and contract, causing volume changes and distortion of the crystal lattice. Volume changes and distortion of the crystal lattice can cause the positive electrode active material to crack, leading to degradation such as a decrease in capacity. Furthermore, cracking of the positive electrode active material may originate at the interface 103 between primary particles.

[0081] When the inside of a secondary battery becomes hot, oxygen may be released from the positive electrode active material, potentially compromising the safety of the battery. Furthermore, oxygen release can alter the crystal structure of the positive electrode active material, leading to degradation such as a decrease in capacity. Oxygen can also be released from the positive electrode active material due to the insertion and removal of lithium during charging and discharging.

[0082] Therefore, the positive electrode active material 100 has an additive element or a compound of an additive element (for example, an oxide of an additive element) on its surface layer 101a or interface 103 that is chemically and structurally more stable than the lithium composite oxide represented by LiMO2. This makes the positive electrode active material 100 chemically and structurally stable, and suppresses structural changes, volume changes, and distortion due to charging and discharging. In other words, the crystal structure of the positive electrode active material 100 becomes more stable, and transformation of the crystal structure can be suppressed even after repeated charging and discharging. Furthermore, cracking of the positive electrode active material 100 can be suppressed. In other words, degradation such as capacity reduction can be suppressed, which is preferable. When the charging voltage is high and the amount of lithium present in the positive electrode during charging becomes smaller, the crystal structure becomes unstable and more susceptible to degradation. By using the positive electrode active material 100 according to one aspect of the present invention, the crystal structure can be made more stable, so degradation such as capacity reduction can be suppressed, which is particularly preferable.

[0083] In one aspect of the present invention, the positive electrode active material 100 has a stable crystal structure, which suppresses the elution of the transition metal M from the positive electrode active material. In other words, it can suppress degradation such as a decrease in capacity, which is preferable.

[0084] Furthermore, in one embodiment of the present invention, when the positive electrode active material 100 cracks along the interface 103 between primary particles 101, the surface of the cracked primary particles 101 has a compound of the additive element. In other words, side reactions can be suppressed even in the cracked positive electrode active material 100, and the degradation of the positive electrode active material 100 can be reduced. In other words, the degradation of the secondary battery can be suppressed.

[0085] <Analysis method> ≪Particle size≫ In one embodiment of the present invention, if the particle size of the positive electrode active material 100 is too large, problems arise such as difficulty in diffusing lithium within the positive electrode active material and excessive roughness of the surface of the active material layer when coated onto a current collector. On the other hand, if the particle size is too small, problems arise such as difficulty in supporting the active material layer when coating onto a current collector and excessive reaction with the electrolyte.

[0086] Therefore, the positive electrode active material 100 having primary particles 101 and secondary particles 102 preferably has an average particle diameter (D50: also called median diameter) measured by a laser diffraction / scattering particle size analyzer of 1 μm to 100 μm, more preferably 2 μm to 40 μm, and even more preferably 5 μm to 30 μm. Or preferably 1 μm to 40 μm. Or preferably 1 μm to 30 μm. Or preferably 2 μm to 100 μm. Or preferably 2 μm to 30 μm. Or preferably 5 μm to 100 μm. Or preferably 5 μm to 40 μm.

[0087] Furthermore, a mixture of positive electrode active materials 100 having two or more different particle sizes may be used. In other words, a positive electrode active material 100 that produces multiple peaks when the particle size distribution is measured by laser diffraction / scattering may be used. In this case, it is preferable to use a mixing ratio that increases the powder packing density, as this can improve the capacity per unit volume of the secondary battery.

[0088] The size of the primary particles 101 in the positive electrode active material 100 can be determined, for example, from the full width at half maximum of the XRD pattern of the positive electrode active material 100. The primary particles 101 are preferably between 50 nm and 200 nm.

[0089] ≪XPS≫ X-ray photoelectron spectroscopy (XPS) allows for analysis of regions from the surface to a depth of 2 nm to 8 nm (usually around 5 nm), enabling quantitative analysis of the concentration of each element in approximately half of the surface layer 101a. Furthermore, narrow-scan analysis allows for the analysis of elemental bonding states. The quantitative accuracy of XPS is typically around ±1 atomic percent, and the detection limit is approximately 1 atomic percent, although this varies depending on the element.

[0090] When XPS analysis is performed on the positive electrode active material 100 according to one embodiment of the present invention, the number of atoms of the additive element is preferably 1.6 to 6.0 times the number of atoms of the transition metal M, and more preferably 1.8 to less than 4.0 times. When the additive element is magnesium and the transition metal M is cobalt, the number of magnesium atoms is preferably 1.6 to 6.0 times the number of cobalt atoms, and more preferably 1.8 to less than 4.0 times. Furthermore, the number of halogen atoms such as fluorine is preferably 0.2 to 6.0 times the number of atoms of the transition metal M, and more preferably 1.2 to 4.0 times.

[0091] For XPS analysis, monochromatic aluminum can be used as the X-ray source, for example. The output can be set to, for example, 1486.6 eV. The extraction angle can be set to, for example, 45°. Under these measurement conditions, as mentioned above, it is possible to analyze a region from the surface to a depth of 2 nm to 8 nm (usually around 5 nm).

[0092] Furthermore, when the positive electrode active material 100 according to one embodiment of the present invention is subjected to XPS analysis, the peak indicating the bond energy between fluorine and other elements is preferably 682 eV or more and less than 685 eV, and more preferably around 684.3 eV. This value is different from both the bond energy of lithium fluoride, which is 685 eV, and the bond energy of magnesium fluoride, which is 686 eV. In other words, when the positive electrode active material 100 according to one embodiment of the present invention contains fluorine, it is preferable that the bond is with something other than lithium fluoride and magnesium fluoride.

[0093] Furthermore, when the positive electrode active material 100 according to one embodiment of the present invention is subjected to XPS analysis, the peak indicating the bond energy between magnesium and other elements is preferably 1302 eV or more and less than 1304 eV, and more preferably around 1303 eV. This value is different from the bond energy of magnesium fluoride, which is 1305 eV, and is close to the bond energy of magnesium oxide. In other words, when the positive electrode active material 100 according to one embodiment of the present invention contains magnesium, it is preferable that the bond is with an element other than magnesium fluoride.

[0094] It is preferable that additive elements that are abundant in the surface layer 101a or interface 103, such as magnesium, aluminum, and titanium, have concentrations measured by XPS or the like that are higher than concentrations measured by ICP-MS (inductively coupled plasma mass spectrometry) or GD-MS (glow discharge mass spectrometry).

[0095] When magnesium, aluminum, titanium, etc., have their cross-sections exposed by processing and the cross-sections are analyzed using TEM-EDX, it is preferable that the concentration in the surface layer 101a or interface 103 is higher than the concentration in the interior 101b. For example, in TEM-EDX analysis, it is preferable that the magnesium concentration is attenuated to 60% or less of the peak at a depth of 1 nm from the peak top. It is also preferable that it is attenuated to 30% or less of the peak at a depth of 2 nm from the peak top. Processing can be carried out, for example, using a FIB (Focused Ion Beam) apparatus.

[0096] In XPS analysis, the number of magnesium atoms is preferably 0.4 to 1.5 times the number of cobalt atoms. On the other hand, the ratio of magnesium atoms (Mg / Co) determined by ICP-MS analysis is preferably 0.001 to 0.06.

[0097] On the other hand, it is preferable that the nickel contained in the transition metal M is not concentrated in the surface layer 101a, but is distributed throughout the entire positive electrode active material 100.

[0098] ≪EPMA≫ EPMA (Electron Probe Microanalysis) allows for the quantitative determination of elements. Surface analysis allows for the analysis of the distribution of each element.

[0099] EPMA analyzes the region from the surface to a depth of approximately 1 μm. Therefore, the concentrations of each element may differ from those measured using other analytical methods. For example, when surface analysis is performed on cathode active material 100, the concentration of additive elements present in the surface layer may be lower than that obtained with XPS. Conversely, the concentration of additive elements present in the surface layer may be higher than that obtained with ICP-MS or the values ​​of the raw material formulation used in the production of the cathode active material.

[0100] When an EPMA surface analysis is performed on a cross-section of the positive electrode active material 100 according to one embodiment of the present invention, it is preferable that the concentration of the additive elements has a concentration gradient that increases from the interior to the surface. More specifically, as shown in Figure 2B, it is preferable that magnesium, fluorine, and titanium have a concentration gradient that increases from the interior to the surface. Also, as shown in Figure 2C, it is preferable that aluminum has a concentration peak in a region deeper than the concentration peaks of the above elements. The aluminum concentration peak may be located at the surface or deeper than the surface.

[0101] Furthermore, the surface and surface layer of the positive electrode active material in one embodiment of the present invention do not contain carbon dioxide, hydroxyl groups, etc., that have been chemically adsorbed after the positive electrode active material has been manufactured. It also does not contain electrolyte, binder, conductive material, or compounds derived therefrom that have adhered to the surface of the positive electrode active material. Therefore, when quantifying the elements present in the positive electrode active material, corrections may be made to exclude carbon, hydrogen, excess oxygen, excess fluorine, etc., which can be detected by surface analysis including XPS and EPMA. For example, XPS allows for the separation of bond types through analysis, and corrections may be made to exclude CF bonds derived from the binder.

[0102] Furthermore, before subjecting the sample to various analyses, the positive electrode active material and positive electrode active material layer may be washed to remove electrolyte, binder, conductive material, or compounds derived therefrom that adhere to the surface of the positive electrode active material. In this case, lithium may dissolve into the solvent used for washing, but even if this occurs, the transition metal M and additive elements are unlikely to dissolve, so it will not affect the atomic ratio of the transition metal M and additive elements.

[0103] ≪Surface roughness and specific surface area≫ In one embodiment of the present invention, the primary particles 101 of the positive electrode active material 100 preferably have a smooth surface with few irregularities. A smooth surface with few irregularities is one factor indicating that the distribution of additive elements in the surface layer 101a is good.

[0104] The smooth surface and minimal irregularities of the primary particles 101 can be determined, for example, from a cross-sectional SEM image or cross-sectional TEM image of the positive electrode active material 100.

[0105] For example, the surface smoothness of the positive electrode active material 100 can be quantified from a cross-sectional SEM image as shown below.

[0106] First, the positive electrode active material 100 is processed using FIB or the like to expose its cross-section. At this time, it is preferable to cover the positive electrode active material 100 with a protective film, protective agent, etc. Next, an SEM image of the interface between the protective film, etc. and the positive electrode active material 100 is taken. Noise processing is performed on the SEM image using image processing software. For example, Gaussian blurring (σ=2) is performed, followed by binarization. Interface extraction is then performed using image processing software. Furthermore, the interface line between the protective film, etc. and the positive electrode active material 100 is selected using an automatic selection tool, etc., and the data is extracted into spreadsheet software, etc. Using the functions of the spreadsheet software, correction is performed from the regression curve (quadratic regression), and parameters for roughness calculation are obtained from the slope-corrected data, and the root mean square surface roughness (RMS) is calculated by calculating the standard deviation. This surface roughness is the surface roughness at least 400 nm from the outer circumference of the particles of the positive electrode active material.

[0107] In this embodiment, the surface roughness (RMS) of the primary particles 101 of the positive electrode active material 100 is preferably less than 3 nm, more preferably less than 1 nm, and more preferably less than 0.5 nm.

[0108] The image processing software used for noise reduction, interface extraction, etc., is not particularly limited.

[0109] The contents described in this embodiment can be used in combination with the contents described in other embodiments.

[0110] (Embodiment 2) In this embodiment, an example of a method for producing a positive electrode active material according to one aspect of the present invention will be described using Figure 3.

[0111] <Step S11> As step S11 in Figure 3, first, a transition metal M source and an additive element source are prepared as materials for a composite oxide (precursor) having a transition metal M, an additive element, and oxygen. To distinguish it from the additive element source that will be mixed in a later step, the additive element source in step S11 may also be called additive element source 1.

[0112] It is preferable to use a metal that can form a layered rock salt type composite oxide with lithium, which belongs to the space group R-3m, as the transition metal M. For example, at least one of manganese, cobalt, and nickel can be used as the transition metal M. More specifically, the transition metal M source may be cobalt only, nickel only, cobalt and manganese, cobalt and nickel, or cobalt, manganese, and nickel.

[0113] When using metals capable of forming layered rock salt-type composite oxides, it is preferable to use a mixing ratio of cobalt, manganese, and nickel within a range that allows for a layered rock salt-type crystalline structure. Furthermore, aluminum may be added to these transition metals within a range that allows for a layered rock salt-type crystalline structure.

[0114] As the transition metal M source, oxides, hydroxides, etc. of the above-mentioned metals exemplified as transition metal M can be used. As the cobalt source, for example, cobalt oxide, cobalt hydroxide, etc. can be used. As the manganese source, manganese oxide, manganese hydroxide, etc. can be used. As the nickel source, nickel oxide, nickel hydroxide, etc. can be used. As the aluminum source, aluminum oxide, aluminum hydroxide, etc. can be used.

[0115] It is preferable to use a high-purity material as the transition metal M source. Specifically, the purity of the material should be 4N (99.99%) or higher, preferably 4N5UP (99.995%) or higher, and even more preferably 5N (99.999%) or higher. Using a high-purity material can increase the charge and discharge capacity of the secondary battery. It can also improve the reliability of the secondary battery.

[0116] In addition, it is preferable that the transition metal M source in this case has single crystal grains.

[0117] When using cobalt, manganese, and nickel, it is preferable that the nickel source, manganese source, and cobalt source are thoroughly mixed and homogenized. Furthermore, if the transition metal M source is in the form of secondary particles, it is preferable to crush or disintegrate it to obtain single crystal grains.

[0118] For example, nickel-manganese-cobalt hydroxide can be produced by coprecipitation, in which the nickel source, manganese source, and cobalt source are thoroughly mixed and homogenized.

[0119] As for the elements contained in additive element source 1, for example, one or more can be selected from aluminum, magnesium, fluorine, titanium, zirconium, nickel, yttrium, lanthanum, vanadium, iron, chromium, niobium, hafnium, zinc, silicon, sulfur, nitrogen, phosphorus, boron, and arsenic.

[0120] The additive element source 1 is preferably an oxide, hydroxide, fluoride, alkoxide, etc., of the above element.

[0121] <Step S12> Next, in step S12, the above-mentioned transition metal M source and additive element source 1 are mixed. They may be crushed while being mixed.

[0122] Mixing methods such as solid-phase, sol-gel, sputtering, CVD, or mechanochemical methods can be used. Solid-phase and sol-gel methods are preferred because they allow for the simple incorporation of additive elements onto the surface of LiMO2 at atmospheric pressure and room temperature.

[0123] In the case of solid-phase processes, the process can be carried out dry or wet. For example, ball mills, bead mills, etc., can be used. When using a ball mill, it is preferable to use zirconia balls as the grinding medium.

[0124] <Step S13> Next, in step S13, the mixed materials are heated. This step is sometimes referred to as the first heating step to distinguish it from later heating steps.

[0125] <Step S14> Next, in step S14, the material heated above is recovered to obtain a precursor having a transition metal M and an additive element. During recovery, the material heated above may be crushed and sieved if necessary.

[0126] <Step S21> Next, in step S21, a lithium source is prepared. Examples of lithium sources that can be used include lithium carbonate, lithium hydroxide, lithium nitrate, and lithium fluoride. Alternatively, some additive element sources may be prepared. To distinguish them from the additive element sources mixed in the previous step, this may be referred to as additive element source 2.

[0127] As elements of additive element source 2, for example, one or more materials selected from aluminum, magnesium, fluorine, titanium, zirconium, nickel, yttrium, lanthanum, vanadium, iron, chromium, niobium, hafnium, zinc, silicon, sulfur, nitrogen, phosphorus, boron, and arsenic can be used.

[0128] The additive element source 2 is preferably an oxide, hydroxide, fluoride, alkoxide, or the like of the above-mentioned element.

[0129] As the second additive element source, a fluorine source may be prepared, for example. As the fluorine source, lithium fluoride can be used, and lithium fluoride can also serve as a lithium source.

[0130] <Steps S31, S32> Next, in step S31, the precursor having the transition metal M and the additive element, the lithium source, and the additive element source 2 are mixed. The mixing can be done dry or wet. For example, a ball mill or a bead mill can be used for mixing. When using a ball mill, it is preferable to use zirconia balls as the grinding media. In this way, a mixture 905 is obtained (step S32).

[0131] <Step S33> Next, in step S33, the mixed material is heated. This step is sometimes referred to as the second heating step to distinguish it from the previous heating step. The heating temperature is preferably close to the melting point of the precursor containing the transition metal M and the additive element.

[0132] Furthermore, when heating mixture 905, it is preferable to control the partial pressure of fluorine or fluoride, which are additive element sources, within an appropriate range. Specifically, it is preferable to cover the container holding mixture 905 and heat it.

[0133] In the manufacturing method described in this embodiment, some materials, such as LiF (a fluorine source), function as a flux. This function allows for a lower annealing temperature, enabling a higher concentration of additive elements, such as fluorine, magnesium, or titanium, in the surface layer compared to the interior, thereby producing a positive electrode active material with excellent properties.

[0134] However, since LiF is lighter than oxygen molecules, it can volatilize and dissipate upon heating. In that case, the amount of LiF in mixture 905 decreases, weakening its function as a flux. Therefore, it is necessary to heat the mixture while suppressing the volatilization of LiF. Even if LiF is not used as a fluorine source, Li and F on the surface of LiMO2 may react to produce LiF, which may then volatilize. Therefore, even if a fluoride with a higher melting point than LiF is used, the same need to suppress volatilization is required.

[0135] Therefore, it is preferable to heat the mixture 905 in an atmosphere containing LiF, that is, to heat the mixture 905 while the partial pressure of LiF in the heating furnace is high. Such heating can suppress the volatilization of LiF in the mixture 905.

[0136] <Step S34> Next, in step S34, the material heated above can be recovered to produce primary particles 101. The primary particles 101 are preferably glossy particles with few surface irregularities, resulting from the fluoride functioning as a flux under the heating conditions described above. Specifically, as described in the previous embodiment, the RMS of the surface of the primary particles is preferably less than 3 nm, more preferably less than 1 nm, and even more preferably less than 0.5 nm.

[0137] Furthermore, under the heating conditions described above, the fluoride acts as a flux, resulting in the formation of shell crystals (surface layer 101a or region having additive element compounds) on the core crystals (internal region 101b or region having LiMO2), and it is preferable that the core and shell are single crystals. For this reason, it is preferable that the orientation of the crystals in the surface layer 101a and the internal region 101b of the primary particle 101 is roughly consistent.

[0138] The shell (additive element compound) formed in this manner functions as a barrier film for the primary particle 101. This barrier film may also be referred to as a coating layer for the primary particle 101.

[0139] <Step S35> Next, in step S35, the primary particles 101 are granulated to form secondary particles. The granulation method can be either dry granulation or wet granulation, or both. More specifically, rolling granulation, fluidized bed granulation, compression granulation, spray granulation, etc., can be used. Wet granulation is particularly preferable due to its high productivity. Spray granulation, such as spray drying, can relatively easily form secondary particles ranging from a few micrometers to several tens of micrometers. Further crushing may be performed on the formed secondary particles.

[0140] <Step S36> The positive electrode active material 100 can be produced through the above process.

[0141] The contents described in this embodiment can be combined with the contents described in other embodiments.

[0142] (Embodiment 3) This embodiment describes a lithium-ion secondary battery containing a positive electrode active material according to one aspect of the present invention. The secondary battery comprises 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 a 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.

[0143] [Positive electrode] The positive electrode comprises a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer preferably contains the positive electrode active material shown in Embodiment 1, and may further contain a binder, a conductive additive, etc.

[0144] Figure 4 shows an example of a schematic diagram of the cross-section of the positive electrode.

[0145] The positive electrode can be formed by applying a slurry onto the current collector 550 and drying it. For example, a metal foil can be used as the current collector 550. Furthermore, after the slurry dries, the coating on the current collector 550 may be pressed. In this way, the positive electrode can be manufactured by forming an active material layer on the current collector 550.

[0146] A slurry is a liquid material used to form an active material layer on a current collector 550, and it contains at least an active material, a binder, and a solvent, preferably further mixed with a conductive additive. The slurry is sometimes called an electrode slurry or an active material slurry, and when forming a positive electrode active material layer, a positive electrode slurry is used, and when forming a negative electrode active material layer, it is sometimes called a negative electrode slurry.

[0147] 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.

[0148] A typical example of a carbon material used as a conductive additive is carbon black (furnace black, acetylene black, graphite, etc.).

[0149] Figure 4 illustrates acetylene black 553, graphene and graphene compounds 554, and carbon nanotubes 555 as conductive additives. Note that the positive electrode active material 100 shown in Embodiment 1, etc., corresponds to the active material 561 in Figure 4A, and includes secondary and primary particles.

[0150] For the positive electrode of a secondary battery, a binder (resin) is mixed with the active material to fix the current collector 550, such as metal foil, to it. 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 in is kept to a minimum.

[0151] Graphene is a carbon material with remarkable electrical, mechanical, and / or chemical properties, making it promising for applications in various fields, including field-effect transistors and solar cells.

[0152] In this specification, the term "graphene compound" includes multilayer graphene, multigraphene, graphene oxide, multilayer graphene oxide, multigraphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, reduced multigraphene oxide, etc. Reduced graphene oxide refers to graphene oxide in which some of the functional groups have been removed by reduction. A graphene compound is a substance that has carbon, has a plate-like or sheet-like shape, and has a two-dimensional structure formed by a six-membered carbon ring. It is also preferable that it has a bent shape. It may also be called a carbon sheet. It is preferable that it has functional groups. Furthermore, the graphene compound may be rolled up to resemble carbon nanofibers.

[0153] Graphene and graphene compounds may possess excellent electrical properties, such as high conductivity, and excellent physical properties, such as high flexibility and high mechanical strength. Furthermore, graphene and graphene compounds may have a sheet-like shape. Graphene and graphene compounds may have curved surfaces, enabling surface contact with low contact resistance. They may also exhibit very high conductivity even when thin, allowing for the efficient formation of conductive paths within the active material layer with a small amount. Therefore, using graphene and graphene compounds as conductive materials can increase the contact area between the active material and the conductive material. It is preferable that graphene or graphene compounds adhere to at least a portion of the active material. Here, the active material includes the primary particles 101 and secondary particles 102 in Figure 1A. It is also preferable that graphene or graphene compounds overlap at least a portion of the active material. Furthermore, it is preferable that the shape of the graphene or graphene compound matches at least a portion of the shape of the active material. The shape of the active material refers, for example, to the irregularities of a single active material particle, or the irregularities formed by multiple active material particles. Furthermore, it is preferable that graphene or a graphene compound surrounds at least a portion of the active material. The graphene or graphene compound may also have pores. Here, pores in graphene or the graphene compound refer to, for example, those with a diameter of 0.9 nm or more.

[0154] In Figure 4, the areas not filled with the active material 561, graphene and graphene compound 554, acetylene black 553, and carbon nanotube 555 have voids, and the binder is located in some of these voids. These voids are necessary for the electrolyte to permeate, but if there are too many voids, the electrode density decreases, and if there are too few voids, the electrolyte will not permeate. If the areas not filled with acetylene black 553 remain as voids after the battery is constructed, the energy density will decrease.

[0155] Furthermore, the conductive additive does not necessarily have to contain all of acetylene black 553, graphene and graphene compounds 554, and carbon nanotubes 555. It is sufficient to have at least one conductive additive.

[0156] By using the positive electrode active material 100 obtained by the manufacturing method described in Embodiment 2, etc., as the positive electrode, a secondary battery with high energy density and good output characteristics can be obtained.

[0157] A secondary battery can be manufactured by using the positive electrode shown in Figure 4, placing a separator on top of the positive electrode, and a negative electrode on top of the separator, then placing the resulting laminate in a container (such as an outer casing or metal can), and filling the container with electrolyte.

[0158] Furthermore, the above configuration is an example of a secondary battery using an electrolyte, but it is not particularly limited.

[0159] For example, a semi-solid-state battery or a fully solid-state battery can be manufactured using the positive electrode active material 100 shown in Embodiment 1, etc.

[0160] 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.

[0161] 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.

[0162] When a semi-solid battery is fabricated using the positive electrode active material 100 shown in Embodiment 1 or the like, the semi-solid battery becomes a secondary battery with a large charge-discharge capacity. Also, a semi-solid battery with a high charge-discharge voltage can be obtained. Alternatively, a semi-solid battery with high safety or reliability can be realized.

[0163] Also, the positive electrode active material described in Embodiment 1 or the like may be mixed with other positive electrode active materials and used.

[0164] Examples of other positive electrode active materials include composite oxides having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure. For example, compounds such as LiFePO4, LiFeO2, LiNiO2, LiMn2O4, V2O5, Cr2O5, and MnO2 can be mentioned.

[0165] Also, as another positive electrode active material, it is preferable to mix lithium-containing materials having a spinel-type crystal structure containing manganese such as LiMn2O4 with lithium nickelate (LiNiO2 or LiNi 1-x M x O2 (0 < x < 1) (M = Co, Al, etc.)). By adopting such a configuration, the characteristics of the secondary battery can be improved.

[0166] Also, as another positive electrode active material, the composition formula Li a Mn b M c O dA lithium manganese composite oxide can be used, which can be represented as follows: Here, element M is preferably a metallic element selected from lithium and manganese, or silicon or phosphorus, and more preferably nickel. Furthermore, when measuring the entire particle of lithium manganese composite oxide, <a / (b+c)<2、かつc>it is preferable that the discharge is 0 0 and 0.26 ≤ (b+c) / d < 0.5. The composition of metals, silicon, phosphorus, etc., of the entire particle of lithium manganese composite oxide can be measured, for example, using ICP-MS (inductively coupled plasma mass spectrometer). The oxygen composition of the entire particle of lithium manganese composite oxide can be measured, for example, using EDX (energy dispersive X-ray spectrometry). In addition, it can be determined by using molten gas analysis and valence evaluation of XAFS (X-ray absorption fine structure) analysis in combination with ICP-MS analysis. Lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may also contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, and phosphorus.

[0167] <Binder> As a binder, it is preferable to use rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, or ethylene-propylene-diene copolymer. Fluororubber can also be used as a binder.

[0168] Furthermore, it is preferable to use a water-soluble polymer as the binder. Examples of water-soluble polymers include polysaccharides. Examples of polysaccharides include cellulose derivatives such as carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, diacetylcellulose, and regenerated cellulose, as well as starch. It is even more preferable to use these water-soluble polymers in combination with the aforementioned rubber material. ​

[0169] Alternatively, it is preferable to use materials such as polystyrene, methyl polyacrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, or nitrocellulose as the binder.

[0170] You may use a combination of several of the binders mentioned above.

[0171] For example, a material with particularly excellent viscosity-modifying properties may be used in combination with other materials. For instance, rubber materials have excellent adhesive and elastic properties, but their viscosity can be difficult to adjust when mixed with a solvent. In such cases, it is preferable to mix them with a material with particularly excellent viscosity-modifying properties. As a material with particularly excellent viscosity-modifying properties, a water-soluble polymer may be used. As a water-soluble polymer with particularly excellent viscosity-modifying properties, the aforementioned polysaccharides, such as carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, and diacetylcellulose, cellulose derivatives such as regenerated cellulose, or starch can be used.

[0172] Furthermore, cellulose derivatives such as carboxymethylcellulose can be made more effective as viscosity modifiers by increasing their solubility, for example, by using salts such as sodium or ammonium salts of carboxymethylcellulose. Increased solubility also improves the dispersibility of the active material and other components when preparing electrode slurries. In this specification, cellulose and cellulose derivatives used as electrode binders include their salts.

[0173] Water-soluble polymers stabilize viscosity by dissolving in water and can stably disperse other materials, such as styrene-butadiene rubber, which are combined as active materials or binders, in aqueous solutions. Furthermore, because they possess functional groups, they are expected to be easily and stably adsorbed onto the surface of the active material. In addition, cellulose derivatives such as carboxymethylcellulose often contain functional groups such as hydroxyl groups or carboxyl groups, and because they have functional groups, the polymers interact with each other and are expected to broadly cover the surface of the active material.

[0174] When a binder covers or is in contact with the surface of the active material, it is expected to act as a passivation film, suppressing the decomposition of the electrolyte. Here, a passivation film is a film that does not conduct electricity, or has extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, the decomposition of the electrolyte can be suppressed at the battery reaction potential. Furthermore, it is even more desirable for the passivation film to suppress electrical conductivity while still allowing lithium ions to conduct.

[0175] <Positive electrode current collector> As the current collector, highly conductive materials such as stainless steel, gold, platinum, aluminum, titanium, and alloys thereof can be used. Furthermore, it is preferable that the material used for the positive electrode current collector does not dissolve at the positive electrode potential. Aluminum alloys with added elements that improve heat resistance, such as silicon, titanium, neodymium, scandium, and molybdenum, can also be used. Alternatively, it may be formed from a metallic element that reacts with silicon to form a silicide. Examples of metallic elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The current collector can be in various shapes, such as foil, plate, sheet, mesh, perforated metal, or expanded metal. The current collector should preferably have a thickness of 5 μm to 30 μm.

[0176] [Negative electrode] The negative electrode comprises a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also contain a negative electrode active material, a conductive additive, and a binder.

[0177] <Negative electrode active material> As the negative electrode active material, for example, alloy-based materials, carbon-based materials, and mixtures thereof can be used.

[0178] 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.

[0179] 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 preferably between 0.3 and 1.2.

[0180] Suitable carbon-based materials include graphite, easily graphitizable carbon (soft carbon), difficult-to-graphitize carbon (hard carbon), carbon nanotubes, graphene, and carbon black.

[0181] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. Here, spherical graphite having a spherical shape can be used as the artificial graphite. For example, MCMB may have a spherical shape, which is preferable. Also, MCMB can relatively easily reduce its surface area, which may be preferable. Examples of natural graphite include flake graphite, spheroidized natural graphite, etc.

[0182] Graphite exhibits a potential as low as that of metallic lithium (0.05 V or more and 0.3 V or less vs. Li / Li + ) when lithium ions are inserted into graphite (when forming a lithium-graphite intercalation compound). Thus, a lithium-ion secondary battery using graphite can exhibit a high operating voltage. Furthermore, graphite has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and high safety compared to metallic lithium, so it is preferable.

[0183] Also, as the negative electrode active material, oxides such as titanium dioxide (TiO2), lithium titanate (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), etc. can be used.

[0184] Also, as the negative electrode active material, Li 3-x M x N (M = Co, Ni, Cu) which is a complex nitride of lithium and a transition metal and has a Li3N-type structure can be used. For example, Li 2.6 Co 0.4 N3 exhibits a large charge-discharge capacity (900 mAh / g, 1890 mAh / cm 3 ) and is preferable.

[0185] 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.

[0186] 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.

[0187] The conductive additive and binder that the negative electrode active material layer may have can be the same materials as those used for the conductive additive and binder that the positive electrode active material layer may have.

[0188] <Negative electrode current collector> In addition to the same materials as the positive electrode current collector, copper and other materials can also be used for the negative electrode current collector. It is preferable to use a material for the negative electrode current collector that does not alloy with carrier ions such as lithium.

[0189] [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.

[0190] 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).

[0191] 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.

[0192] 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.

[0193] 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.

[0194] [Electrolyte] The electrolyte contains a solvent and an electrolyte. The solvent for the electrolyte is preferably an aprotic organic solvent, such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., or two or more of these can be used in any combination and ratio.

[0195] Furthermore, by using one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the solvent for the electrolyte, it is possible to prevent the energy storage device from rupturing or catching fire even if the internal temperature rises due to an internal short circuit or overcharging. Ionic liquids consist of cations and anions, and include organic cations and anions. Examples of organic cations used in the electrolyte include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, as well as aromatic cations such as imidazolium cations and pyridinium cations. Examples of anions used in the electrolyte include monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkyl sulfonate anions, tetrafluoroborate anions, perfluoroalkyl borate anions, hexafluorophosphate anions, or perfluoroalkyl phosphate anions.

[0196] Furthermore, examples of electrolytes to be dissolved in the above solvent include LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, and Li2B. 10 Cl 10 Li2B12 Cl 12 Lithium salts such as LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, lithium bis(oxalate) borate (Li(C2O4)2, LiBOB) can be used individually or in any combination and ratio of two or more of these salts.

[0197] It is preferable to use a highly purified electrolyte in which particulate matter or elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities") are present in small amounts. Specifically, it is preferable that the weight ratio of impurities to the electrolyte be 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

[0198] Furthermore, additives such as vinylene carbonate, propanesultone (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 should be, for example, 0.1 wt% to 5 wt% relative to the total solvent.

[0199] Alternatively, a polymer gel electrolyte, obtained by swelling a polymer with an electrolyte solution, may be used.

[0200] Using polymer gel electrolytes enhances safety against leakage and other issues. Furthermore, it enables the secondary battery to be made thinner and lighter.

[0201] 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, and copolymers containing them can be used. For example, PVDF-HFP, a copolymer of PVDF and hexafluoropropylene (HFP), can be used. Furthermore, the formed polymer may have a porous structure.

[0202] Furthermore, instead of an electrolyte, a solid electrolyte containing inorganic materials such as sulfides or oxides, or a solid electrolyte containing polymeric materials such as PEO (polyethylene oxide), can be used. When a solid electrolyte is used, the installation of separators or spacers becomes unnecessary. In addition, since the entire battery can be solidified, the risk of leakage is eliminated, dramatically improving safety.

[0203] Therefore, the positive electrode active material 100 described in Embodiments 1 and 2 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.

[0204] [Exterior] The outer casing of a secondary battery can be made of a metal material such as aluminum or a resin material. Alternatively, a film-like outer casing can be used. As a film, for example, a three-layer film can be used, in which a highly flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided on a film made of 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.

[0205] The contents described in this embodiment can be combined with the contents described in other embodiments.

[0206] (Embodiment 4) This embodiment describes examples of multiple shapes of secondary batteries having a positive or negative electrode, manufactured by the manufacturing method described in the previous embodiment.

[0207] [Coin-type rechargeable battery] An example of a coin-type rechargeable battery is described below. Figure 5A is an exploded perspective view of a coin-type (single-layer flat type) rechargeable battery, Figure 5B is an external view, and Figure 5C is a cross-sectional view thereof. Coin-type rechargeable batteries are mainly used in small electronic devices. In this specification, the term "coin-type battery" includes button-type batteries.

[0208] Figure 5A is a schematic diagram to show the overlapping of components (up / down relationship and positional relationship). Therefore, Figures 5A and 5B are not perfectly identical corresponding diagrams.

[0209] In Figure 5A, the positive electrode 304, separator 310, negative electrode 307, spacer 322, and washer 312 are stacked. These are sealed with the negative electrode can 302 and the positive electrode can 301. Note that the gasket for sealing is not shown in Figure 5A. The spacer 322 and washer 312 are used to protect the inside or to fix their position within the can when the positive electrode can 301 and the negative electrode can 302 are crimped together. The spacer 322 and washer 312 are made of stainless steel or insulating material.

[0210] The positive electrode 304 is a laminated structure in which a positive electrode active material layer 306 is formed on a positive electrode current collector 305.

[0211] To prevent a short circuit between the positive and negative electrodes, a separator 310 and a ring-shaped insulator 313 are arranged to cover the sides and top surfaces of the positive electrode 304, respectively. The separator 310 has a larger planar area than the positive electrode 304.

[0212] Figure 5B is a perspective view of the completed coin-type rechargeable battery.

[0213] The coin-type secondary battery 300 has a positive electrode casing 301, which also serves as the positive electrode terminal, and a negative electrode casing 302, which also serves as the negative electrode terminal, insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with it. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with it. Furthermore, the negative electrode 307 is not limited to a laminated structure, and lithium metal foil or a lithium-aluminum alloy foil may be used.

[0214] 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.

[0215] The positive electrode can 301 and the negative electrode can 302 can be made of metals such as nickel, aluminum, or titanium, or alloys thereof, or alloys of these with other metals (e.g., stainless steel), which are corrosion-resistant to the electrolyte. Furthermore, it is preferable to coat them with nickel and aluminum, etc., to prevent corrosion by the electrolyte. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307.

[0216] The negative electrode 307, positive electrode 304, and separator 310 are immersed in an electrolyte solution, and as shown in Figure 5C, 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 crimped together via a gasket 303 to manufacture a coin-type secondary battery 300.

[0217] By using a rechargeable battery, a coin-type rechargeable battery 300 can be made with high capacity, high charge / discharge capacity, and excellent cycle characteristics. Furthermore, if a rechargeable battery is used between the negative electrode 307 and the positive electrode 304, the separator 310 can be omitted.

[0218] [Cylindrical rechargeable battery] An example of a cylindrical secondary battery will be explained with reference to Figure 6A. As shown in Figure 6A, the cylindrical secondary battery 616 has a positive electrode cap (battery cover) 601 on the top surface and a battery casing (outer casing) 602 on the sides and bottom. The positive electrode cap 601 and the battery casing (outer casing) 602 are insulated from each other by a gasket (insulating packing) 610.

[0219] Figure 6B is a schematic diagram showing a cross-section of a cylindrical secondary battery. The cylindrical secondary battery shown in Figure 6B has a positive electrode cap (battery cover) 601 on the top surface and a battery casing (outer casing) 602 on the sides and bottom. The positive electrode cap and the battery casing (outer casing) 602 are insulated from each other by a gasket (insulating packing) 610.

[0220] Inside the hollow cylindrical battery casing 602, a battery element is provided, in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 in between. Although not shown, the battery element is wound around a central axis. The battery casing 602 is closed at one end and open at the other. The battery casing 602 can be made of metals such as nickel, aluminum, and titanium, or alloys thereof, or alloys of these with other metals (e.g., stainless steel), which are corrosion-resistant to the electrolyte. Furthermore, it is preferable to coat the battery casing 602 with nickel and aluminum, etc., to prevent corrosion by the electrolyte. Inside the battery casing 602, the battery element, in which the positive electrode, negative electrode, and separator are wound, is sandwiched between a pair of opposing insulating plates 608 and insulating plate 609. In addition, a non-aqueous electrolyte (not shown) is injected into the inside of the battery casing 602 in which the battery element is provided. The non-aqueous electrolyte can be the same as that used in coin-type secondary batteries.

[0221] Since the positive and negative electrodes used in cylindrical storage batteries are wound, it is preferable to form the active material on both sides of the current collector. Figures 6A to 6D illustrate a secondary battery 616 in which the height of the cylinder is greater than the diameter of the cylinder, but the battery is not limited to this configuration. A secondary battery in which the diameter of the cylinder is greater than the height of the cylinder is also possible. Such a configuration allows for, for example, miniaturization of the secondary battery.

[0222] By using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode 604, a cylindrical secondary battery 616 with high capacity, high charge / discharge capacity, and excellent cycle characteristics can be obtained.

[0223] A positive electrode terminal (positive electrode current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collector lead) 607 is connected to the negative electrode 606. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of metal materials such as aluminum. The positive electrode terminal 603 is resistance-welded to the safety valve mechanism 613, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 613 is electrically connected to the positive electrode cap 601 via a PTC element (Positive Temperature Coefficient) 611. The safety valve mechanism 613 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the internal pressure of the battery rises above a predetermined threshold. The PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises, and it prevents abnormal heat generation by limiting the amount of current through the increase in resistance. Barium titanate (BaTiO3) based semiconductor ceramics can be used for the PTC element.

[0224] Figure 6C shows an example of an energy storage system 615. The energy storage system 615 has multiple secondary batteries 616. The positive electrode of each secondary battery is in contact with a conductor 624 separated by an insulator 625 and is electrically connected. The conductor 624 is electrically connected to a control circuit 620 via wiring 623. The negative electrode of each secondary battery is also electrically connected to the control circuit 620 via wiring 626. The control circuit 620 can be a protective circuit to prevent overcharging or over-discharging, etc.

[0225] Figure 6D shows an example of an energy storage system 615. The energy storage system 615 has multiple secondary batteries 616, which are sandwiched between conductive plates 628 and 614. The multiple secondary batteries 616 are electrically connected to conductive plates 628 and 614 by wiring 627. The multiple secondary batteries 616 may be connected in parallel, in series, or connected in parallel and then in series. By configuring an energy storage system 615 with multiple secondary batteries 616, a large amount of power can be extracted.

[0226] Multiple secondary batteries 616 may be connected in parallel and then further connected in series.

[0227] A temperature control device may be provided between the multiple secondary batteries 616. When a secondary battery 616 overheats, it can be cooled by the temperature control device, and when a secondary battery 616 becomes too cold, it can be heated by the temperature control device. This makes the performance of the energy storage system 615 less susceptible to the influence of ambient temperature.

[0228] Furthermore, in Figure 6D, the energy storage system 615 is electrically connected to the control circuit 620 via wiring 621 and wiring 622. Wiring 621 is electrically connected to the positive terminals of the multiple secondary batteries 616 via conductive plate 628, and wiring 622 is electrically connected to the negative terminals of the multiple secondary batteries 616 via conductive plate 614.

[0229] [Other structural examples of secondary batteries] Examples of secondary battery structures will be explained using Figures 7 and 8.

[0230] The secondary battery 913 shown in Figure 7A has a wound body 950 with terminals 951 and 952 inside a housing 930. The wound body 950 is immersed in an electrolyte inside the housing 930. Terminal 952 is in contact with the housing 930, while terminal 951 is not in contact with the housing 930 due to the use of an insulating material or the like. In Figure 7A, the housing 930 is shown separated for convenience, but in reality, the wound body 950 is covered by the housing 930, and terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of a metal material (e.g., aluminum) or a resin material.

[0231] Furthermore, as shown in Figure 7B, the housing 930 shown in Figure 7A may be formed from multiple materials. For example, in the secondary battery 913 shown in Figure 7B, housing 930a and housing 930b are bonded together, and the winding body 950 is provided in the area surrounded by housing 930a and housing 930b.

[0232] For the housing 930a, an insulating material such as organic resin can be used. In particular, by using a material such as organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by housing 930a is small, the antenna may be placed inside housing 930a. For housing 930b, for example, a metal material can be used.

[0233] Furthermore, the structure of the wound body 950 is shown in Figure 7C. The wound body 950 has a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked on top of each other with the separator 933 in between, and the stacked sheets are wound up. Note that multiple stacks of the negative electrode 931, positive electrode 932, and separator 933 may be stacked.

[0234] Alternatively, the secondary battery 913 may have a wound body 950a as shown in Figures 8A to 8C. The wound body 950a shown in Figure 8A has a negative electrode 931, a positive electrode 932, and a separator 933. The negative electrode 931 has a negative electrode active material layer 931a. The positive electrode 932 has a positive electrode active material layer 932a.

[0235] By using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode 932, a secondary battery 913 with high capacity, high charge / discharge capacity, and excellent cycle characteristics can be obtained.

[0236] The separator 933 has a wider width than the negative electrode active material layer 931a and the positive electrode active material layer 932a, and is wound so as to overlap with the negative electrode active material layer 931a and the positive electrode active material layer 932a. Furthermore, it is preferable from a safety standpoint that the negative electrode active material layer 931a is wider than the positive electrode active material layer 932a. A wound body 950a of this shape is also preferable due to its good safety and productivity.

[0237] As shown in Figure 8B, the negative electrode 931 is electrically connected to terminal 951. Terminal 951 is electrically connected to terminal 911a. The positive electrode 932 is electrically connected to terminal 952. Terminal 952 is electrically connected to terminal 911b.

[0238] As shown in Figure 8C, the coiled body 950a and electrolyte are covered by the housing 930, forming a secondary battery 913. It is preferable to provide a safety valve, an overcurrent protection element, etc., in the housing 930. The safety valve is a valve that opens the inside of the housing 930 at a predetermined internal pressure to prevent the battery from rupturing.

[0239] As shown in Figure 8B, the secondary battery 913 may have multiple windings 950a. By using multiple windings 950a, a secondary battery 913 with a larger charge and discharge capacity can be made. Other elements of the secondary battery 913 shown in Figures 8A and 8B can be referenced from the description of the secondary battery 913 shown in Figures 7A to 7C.

[0240] <Laminated rechargeable battery> Next, an example of a laminate-type secondary battery is shown in Figures 9A and 9B, which show an example of its external appearance. The secondary battery 500 shown in Figures 9A and 9B has a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511.

[0241] Figure 10A shows the external views of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a positive electrode current collector 501, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. The positive electrode 503 also has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). The negative electrode 506 has a negative electrode current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. The negative electrode 506 also has a region where the negative electrode current collector 504 is partially exposed, i.e., the tab region. The area and shape of the tab regions of the positive and negative electrodes are not limited to the example shown in Figure 10A.

[0242] <Method for manufacturing laminated rechargeable batteries> Here, an example of a method for manufacturing a laminate-type secondary battery, whose external view is shown in Figure 9A, will be explained using Figures 10B and 10C.

[0243] First, the negative electrode 506, separator 507, and positive electrode 503 are stacked. Figure 10B shows the stacked negative electrode 506, separator 507, and positive electrode 503. Here, an example using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. This can also be called a laminate consisting of negative electrodes, separators, and positive electrodes. Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For joining, ultrasonic welding, for example, can be used. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0244] Next, the negative electrode 506, separator 507, and positive electrode 503 are placed on the outer casing 509.

[0245] Next, as shown in Figure 10C, the outer casing 509 is bent at the portion indicated by the dashed line. Then, the outer periphery of the outer casing 509 is joined. For joining, for example, heat compression bonding may be used. At this time, a region that is not joined (hereinafter referred to as the inlet) is provided on a part (or one side) of the outer casing 509 so that the electrolyte can be added later.

[0246] Next, an electrolytic solution (not shown) is introduced into the exterior body 509 from the inlet provided in the exterior body 509 to the inside of the exterior body 509. The introduction of the electrolytic solution is preferably performed under a reduced-pressure atmosphere or an inert atmosphere. And finally, the inlet is joined. In this way, the laminated secondary battery 500 can be manufactured.

[0247] By using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 for the positive electrode 503, a secondary battery 500 with high capacity, high charge-discharge capacity, and excellent cycle characteristics can be obtained.

[0248] [Example of battery pack] An example of a secondary battery pack according to one aspect of the present invention capable of wireless charging using an antenna will be described with reference to FIGS. 11A to 11C.

[0249] FIG. 11A is a view showing the appearance of the secondary battery pack 531, which has a thin rectangular parallelepiped shape (which can also be called a thick flat plate shape). FIG. 11B is a view for explaining the configuration of the secondary battery pack 531. The secondary battery pack 531 has a circuit board 540 and a secondary battery 513. A label 529 is attached to the secondary battery 513. The circuit board 540 is fixed by a seal 515. Further, the secondary battery pack 531 has an antenna 517.

[0250] The interior of the secondary battery 513 may have a structure with a wound body or a structure with a laminate.

[0251] In the secondary battery pack 531, for example, as shown in FIG. 11B, a control circuit 590 is provided on the circuit board 540. Further, the circuit board 540 is electrically connected to a terminal 514. The circuit board 540 is also electrically connected to an antenna 517, one of the positive electrode lead and the negative electrode lead of the secondary battery 513, and the other of the positive electrode lead and the negative electrode lead 552.

[0252] Alternatively, as shown in FIG. 11C, it may have a circuit system 590a provided on the circuit board 540 and a circuit system 590b electrically connected to the circuit board 540 via the terminal 514.

[0253] Note that the antenna 517 is not limited to a coil shape and may be, for example, linear or plate-shaped. Also, antennas such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, a dielectric antenna, etc. may be used. Alternatively, the antenna 517 may be a flat plate conductor. This flat plate conductor can function as one of the conductors for electric field coupling. That is, the antenna 517 may be made to function as one of the two conductors of the capacitor. Thereby, power exchange can be performed not only by an electromagnetic field and a magnetic field but also by an electric field.

[0254] The secondary battery pack 531 has a layer 519 between the antenna 517 and the secondary battery 513. The layer 519 has a function of, for example, shielding the electromagnetic field by the secondary battery 513. As the layer 519, for example, a magnetic material can be used.

[0255] The content described in this embodiment can be combined with the content described in other embodiments.

[0256] (Embodiment 5) In this embodiment, an example of manufacturing an all-solid-state battery using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 is shown.

[0257] As shown in FIG. 12A, a secondary battery 400 according to an aspect of the present invention has a positive electrode 410, a solid electrolyte layer 420, and a negative electrode 430.

[0258] The positive electrode 410 has a positive electrode current collector 4

[0259] 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, which will be described later.

[0260] 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. By using metallic lithium as the negative electrode active material 431 instead of particles, the negative electrode 430 can be made without the solid electrolyte 421, as shown in Figure 12B. Using metallic lithium in the negative electrode 430 is preferable because it can improve the energy density of the secondary battery 400.

[0261] 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.

[0262] 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·36SiS2·1Li3PO4, 57Li2S·38SiS2·5Li4SiO4, 50Li2S·50GeS2, etc.), sulfide crystallized glass (Li7P3S 11 Li 3.25 P 0.95 It 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.

[0263] Oxide-based solid electrolytes include materials having a perovskite-type crystal structure (La 2 / 3-x Li 3xMaterials 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.

[0264] 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.

[0265] Alternatively, different solid electrolytes may be mixed and used.

[0266] 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 aluminum and titanium, which are elements that may be present in the positive electrode active material used in a secondary battery 400 according to one embodiment of the present invention, and is therefore preferred because a synergistic effect on improving cycle characteristics can be expected. Furthermore, an improvement in productivity can be expected by reducing the number of processes. In this specification, the NASICON type crystal structure refers to a compound represented as M2(XO4)3 (M: transition metal, X: S, P, As, Mo, W, etc.) that has a structure in which MO6 octahedra and XO4 tetrahedra share vertices and are arranged three-dimensionally.

[0267] [Shape of the outer casing and secondary battery] The outer casing of the secondary battery 400 according to one aspect of the present invention can be made of various materials and has a shape, but it is preferable that it has the function of pressurizing the positive electrode, solid electrolyte layer, and negative electrode.

[0268] For example, Figure 13 shows an example of a cell used to evaluate the materials of an all-solid-state battery.

[0269] Figure 13A is a schematic cross-sectional view of the evaluation cell, which has a lower member 761, an upper member 762, and fixing screws or wing nuts 764 that secure them together. The evaluation material is fixed by pressing the electrode plate 753 by rotating the retaining screw 763. An insulator 766 is provided between the lower member 761 and the upper member 762, which are made of stainless steel. An O-ring 765 for sealing is provided between the upper member 762 and the retaining screw 763.

[0270] The evaluation material is placed on an electrode plate 751, surrounded by an insulating tube 752, and pressed from above by an electrode plate 753. Figure 13B is a magnified perspective view of the area around this evaluation material.

[0271] As an example of the evaluated material, an example of a stacked structure consisting of a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is shown, and a cross-sectional view is shown in Figure 13C. Note that the same parts are referred to by the same symbols in Figures 13A to 13C.

[0272] 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.

[0273] Also, for the exterior of the secondary battery according to one aspect of the present invention, it is preferable to use a package with excellent airtightness. For example, a ceramic package or a resin package can be used. Further, when sealing the exterior, it is preferable to perform the sealing in an atmosphere where outside air is blocked and sealed, for example, inside a glove box.

[0274] FIG. 14A shows a perspective view of a secondary battery according to one aspect of the present invention having an exterior and shape different from those in FIG. 13. The secondary battery in FIG. 14A has external electrodes 771 and 772 and is sealed with an exterior having a plurality of package members.

[0275] An example of a cross-section cut along the dashed line in FIG. 14A is shown in FIG. 14B. The laminate having the positive electrode 750a, the solid electrolyte layer 750b, and the negative electrode 750c is surrounded and sealed by a package member 770a provided with an electrode layer 773a on a flat plate, a frame-shaped package member 770b, and a package member 770c provided with an electrode layer 773b on a flat plate. For the package members 770a, 770b, and 770c, an insulating material, for example, a resin material and ceramic can be used.

[0276] The external electrode 771 is electrically connected to the positive electrode 750a through the electrode layer 773a and functions as a positive electrode terminal. Also, the external electrode 772 is electrically connected to the negative electrode 750c through the electrode layer 773b and functions as a negative electrode terminal.

[0277] By using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2, it is possible to realize an all-solid-state secondary battery having a high energy density and good output characteristics.

[0278] The content described in this embodiment can be appropriately combined with the content of other embodiments.

[0279] (Embodiment 6) In this embodiment, an example of application to an electric vehicle (EV) is shown using FIG. 15C.

[0280] Electric vehicles are equipped with a first battery 1301a and 1301b as the main secondary battery for propulsion, and a second battery 1311 that supplies power to the inverter 1312 that starts the motor 1304. The second battery 1311 is also called the cranking battery (or starter battery). The second battery 1311 only needs to be able to output power, and does not require a large capacity, so its capacity is smaller than that of the first batteries 1301a and 1301b.

[0281] The internal structure of the first battery 1301a may be a wound type as shown in Figure 7A or Figure 8C, or a stacked type as shown in Figure 9A or Figure 9B. Furthermore, the first battery 1301a may use the all-solid-state battery of Embodiment 5. Using the all-solid-state battery of Embodiment 5 for the first battery 1301a allows for higher capacity, improved safety, and miniaturization and weight reduction.

[0282] 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.

[0283] 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.

[0284] 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.

[0285] 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.

[0286] Furthermore, the first battery 1301a will be explained using Figure 15A.

[0287] Figure 15A 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, 1414 and a battery housing box. Furthermore, one electrode is electrically connected to the control circuit unit 1320 by wiring 1421, and the other electrode is electrically connected to the control circuit unit 1320 by wiring 1422.

[0288] 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).

[0289] 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) 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.

[0290] 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.

[0291] 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.

[0292] 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.

[0293] Furthermore, a clear boundary may not be observed between the first region and the second region described above.

[0294] 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.

[0295] 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.

[0296] 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.

[0297] Furthermore, since it can be used in high-temperature environments, it is preferable that the control circuit section 1320 uses a transistor made of an oxide semiconductor. To simplify the process, the control circuit section 1320 may 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 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 section 1320 can improve safety. In addition, a synergistic effect on safety can be obtained by combining it with a secondary battery using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode.

[0298] 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 causes of instability such as micro-shorts. Functions to eliminate 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-shorts, and prediction of abnormalities related to micro-shorts. 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.

[0299] 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.

[0300] 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.

[0301] 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.

[0302] Furthermore, an example of a block diagram of the battery pack 1415 shown in Figure 15A is shown in Figure 15B.

[0303] The control circuit unit 1320 includes at least a switch to prevent overcharging, a switch unit 1324 including a switch to prevent over-discharging, a control circuit 1322 that controls the switch unit 1324, and a voltage measurement unit for the first battery 1301a. The control circuit unit 1320 has upper and lower voltage limits set for the secondary battery used, and limits the upper limit of external current and the upper limit of output current to the outside. Within the range between the lower voltage limit and the upper voltage limit of the secondary battery, it is within the voltage range for which use is recommended, and if it goes outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit unit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent over-discharge and overcharge. For example, if the control circuit 1322 detects a voltage that is likely to cause overcharging, it cuts off the current by turning off the switch in 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).

[0304] The switch section 1324 can be constructed by combining an n-channel transistor and a p-channel transistor. The switch section 1324 is not limited to a switch having a Si transistor using single-crystal silicon, but can also be 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), GaO x The switch section 1324 may be formed using a power transistor having a gallium oxide (where x is a real number greater than 0) or the like. 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. Since the volume occupied by the control circuit section 1320 can be reduced, miniaturization becomes possible.

[0305] 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 prone to degradation due to a phenomenon called sulfation compared to lithium-ion secondary batteries. Using a lithium-ion secondary battery for the second battery 1311 offers the advantage of being maintenance-free, but after long-term use, for example more than three years, there is a risk of malfunctions occurring that 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.

[0306] This embodiment shows an example in which lithium-ion secondary batteries are used for both the first battery 1301a and the second battery 1311. The second battery 1311 may be a lead-acid battery, an all-solid-state battery, or an electric double-layer capacitor. For example, the all-solid-state battery of Embodiment 5 may be used. By using the all-solid-state battery of Embodiment 5 for the second battery 1311, high capacity can be achieved, and the device can be made smaller and lighter.

[0307] Furthermore, the regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305 and charged the second battery 1311 via the control circuit unit 1321 from the motor controller 1303 and battery controller 1302. Alternatively, it is charged the first battery 1301a via the control circuit unit 1320 from the battery controller 1302. Alternatively, it is charged the first battery 1301b via the control circuit unit 1320 from the battery controller 1302. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b are capable of rapid charging.

[0308] 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.

[0309] Although not shown in the diagram, when connected to an external charger, the charger's outlet or connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger charges the first batteries 1301a and 1301b via the battery controller 1302. In some chargers, a control circuit is provided, and the functions of the battery controller 1302 may not be used, but it is preferable to charge the first batteries 1301a and 1301b via the control circuit unit 1320 to prevent overcharging. In some cases, the 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 or GPU.

[0310] External chargers installed at charging stations and other locations include 100V outlets, 200V outlets, and 3-phase 200V with 50kW output. Additionally, it is possible to charge by receiving power from external charging equipment using contactless power supply methods.

[0311] For rapid charging, a rechargeable battery capable of withstanding high-voltage charging is desired to achieve short charging times.

[0312] Furthermore, the secondary battery of this embodiment described above uses the positive electrode active material 100 described in Embodiments 1 and 2. In addition, by using graphene as a conductive additive, the capacity reduction is suppressed even when the electrode layer is thickened and the load is increased, and high capacity is maintained. As a synergistic effect, a secondary battery with significantly improved electrical characteristics can be realized. This is particularly effective for secondary batteries used in vehicles, and it is possible to provide a vehicle 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.

[0313] In particular, the secondary battery of this embodiment described above can achieve a higher operating voltage by using the positive electrode active material 100 described in Embodiment 1, etc., and can increase its usable capacity as the charging voltage increases. Furthermore, by using the positive electrode active material 100 described in Embodiment 1, etc., as the positive electrode, a secondary battery for vehicles with excellent cycle characteristics can be provided.

[0314] Next, we will describe an example in which a secondary battery, which is one aspect of the present invention, is implemented in a vehicle, typically a transport vehicle.

[0315] Furthermore, by mounting a secondary battery shown in any one of Figures 6D, 8C, or 15A onto a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV) can be realized. Secondary batteries can also be mounted on agricultural machinery, motorized bicycles including electric-assist bicycles, motorcycles, electric wheelchairs, electric carts, small or large vessels, submarines, aircraft such as fixed-wing and rotary-wing aircraft, rockets, satellites, space probes, planetary probes, and spacecraft. A secondary battery according to one embodiment of the present invention can be a high-capacity secondary battery. Therefore, a secondary battery according to one embodiment of the present invention is suitable for miniaturization and weight reduction, and can be suitably used in transport vehicles.

[0316] Figures 16A to 16D illustrate a transport vehicle using one embodiment of the present invention. The automobile 2001 shown in Figure 16A is an electric vehicle that uses an electric motor as a power source for driving. Alternatively, it is a hybrid vehicle that can appropriately select and use an electric motor and an engine as power sources for driving. When a secondary battery is mounted on the vehicle, one or more examples of the secondary battery shown in Embodiment 4 are installed in one location. The automobile 2001 shown in Figure 16A 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.

[0317] Furthermore, the automobile 2001 can be charged by receiving power from an external charging facility via a plug-in method or a contactless power supply method to the secondary battery of the automobile 2001. When charging, the charging method 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 mounted on the automobile 2001 can be charged by supplying power from an external source using plug-in technology. Charging can be performed by converting AC power to DC power via a conversion device such as an AC / DC converter.

[0318] Although not shown in the diagram, the vehicle can also be charged by mounting a power receiving device on the vehicle and receiving power wirelessly from a ground-based power transmission device. In this wireless power supply method, charging can be performed not only when the vehicle is stopped but also while it is in motion by incorporating the power transmission device into the road or exterior wall. Furthermore, this wireless power supply method can be used to transmit and receive power between two vehicles. In addition, solar panels can be installed on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped and when it is in motion. For such wireless power supply, electromagnetic induction or magnetic resonance methods can be used.

[0319] Figure 16B shows a large transport vehicle 2002 equipped with an electrically controlled motor as an example of a transport vehicle. The secondary battery module of the transport vehicle 2002 has a maximum voltage of 170V, achieved by connecting 48 cells in series, each consisting of four secondary batteries with a nominal voltage of 3.0V to 5.0V. The secondary battery module of the battery pack 2201 has the same functions as Figure 16A, except for differences in the number of secondary batteries that make up the module, so the explanation is omitted.

[0320] Figure 16C shows, as an example, a large transport vehicle 2003 equipped with an electrically controlled motor. The secondary battery module of the transport vehicle 2003 has a maximum voltage of 600V, for example, by connecting 100 or more secondary batteries with a nominal voltage of 3.0V to 5.0V in series. By using a secondary battery with the positive electrode active material 100 described in Embodiment 1 as the positive electrode, it is possible to manufacture a secondary battery with good rate characteristics and charge / discharge cycle characteristics, which can contribute to the high performance and long lifespan of the transport vehicle 2003. Furthermore, since it has the same functions as Figure 16A except for differences in the number of secondary batteries constituting the secondary battery module of the battery pack 2202, the explanation is omitted.

[0321] Figure 16D shows an example of an aircraft 2004 having a fuel-burning engine. The aircraft 2004 shown in Figure 16D has wheels for takeoff and landing, and can therefore be considered part of a transport vehicle. It has a battery pack 2203 which includes a secondary battery module formed by connecting multiple secondary batteries and a charging control device.

[0322] 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 16A, except for differences in the number of secondary batteries that make up the module, so the explanation is omitted.

[0323] The contents described in this embodiment can be appropriately combined with the contents of other embodiments.

[0324] (Embodiment 7) In this embodiment, an example of implementing a secondary battery, which is one aspect of the present invention, in a building will be explained using Figures 17A and 17B.

[0325] The house shown in Figure 17A has a power storage device 2612 having a secondary battery, which is one embodiment of the present invention, and a solar panel 2610. The power storage device 2612 is electrically connected to the solar panel 2610 via wiring 2611, etc. The power storage device 2612 may also be electrically connected to a ground-mounted charging device 2604. The electricity obtained from the solar panel 2610 can be used to charge the power storage device 2612. The electricity stored in the power storage device 2612 can be used to charge the secondary battery of the vehicle 2603 via the charging device 2604. The power storage device 2612 is preferably installed in the underfloor space. By installing it in the underfloor space, the space above the floor can be used effectively. Alternatively, the power storage device 2612 may be installed on the floor.

[0326] 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.

[0327] Figure 17B shows an example of an energy storage device 700 according to one aspect of the present invention. As shown in Figure 17B, an energy storage device 791 according to one aspect of the present invention is installed in the underfloor space 796 of the building 799. Furthermore, the energy storage device 791 may be equipped with the control circuit described in Embodiment 6, and by using a secondary battery with the positive electrode active material 100 obtained as described in Embodiments 1 and 2 as the positive electrode in the energy storage device 791, a long-life energy storage device 791 can be made.

[0328] The energy storage device 791 is equipped with a control device 790, which is electrically connected by wiring to the distribution board 703, the energy storage controller 705 (also called the control device), the display unit 706, and the router 709.

[0329] Power is supplied from the commercial power supply 701 to the distribution panel 703 via the service drop connection section 710. Power is also supplied to the distribution panel 703 from the energy storage device 791 and the commercial power supply 701, and the distribution panel 703 supplies the supplied power to the general load 707 and the energy storage system load 708 via outlets (not shown).

[0330] General loads 707 are electrical equipment such as televisions and personal computers, while energy storage loads 708 are electrical equipment such as microwave ovens, refrigerators, and air conditioners.

[0331] The energy storage controller 705 includes a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 has the function of measuring the amount of electricity consumed by the general load 707 and the energy storage system load 708 during a day (for example, from 0:00 to 24:00). The measurement unit 711 may also have the function of measuring the amount of electricity consumed by the energy storage device 791 and the amount of electricity supplied from the commercial power supply 701. The prediction unit 712 has the function of predicting the amount of electricity demanded by the general load 707 and the energy storage system load 708 during the next day, based on the amount of electricity consumed by the general load 707 and the energy storage system load 708 during the day. The planning unit 713 has the function of planning the charging and discharging of the energy storage device 791 based on the amount of electricity demand predicted by the prediction unit 712.

[0332] The amount of electricity consumed by the general load 707 and the energy storage system load 708, as measured by the measurement unit 711, can be checked on the display unit 706. It can also be checked on electrical equipment such as televisions and personal computers via the router 709. Furthermore, it can be checked on mobile electronic devices such as smartphones and tablets via the router 709. Additionally, the amount of electricity demand for each time period (or hourly) predicted by the prediction unit 712 can be checked on the display unit 706, electrical equipment, and mobile electronic devices.

[0333] The contents described in this embodiment can be appropriately combined with the contents of other embodiments.

[0334] (Embodiment 8) This embodiment shows an example of mounting an energy storage device according to one aspect of the present invention on a motorcycle or bicycle.

[0335] Furthermore, Figure 18A shows an example of an electric bicycle using a power storage device according to one embodiment of the present invention. The power storage device according to one embodiment of the present invention can be applied to the electric bicycle 8700 shown in Figure 18A. The power storage device according to one embodiment of the present invention includes, for example, a plurality of storage batteries and a protection circuit.

[0336] 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 18B 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 14A and 14B, may also be provided in the control circuit 8704. By providing the small solid-state secondary battery shown in Figures 14A and 14B 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 the positive electrode active material 100 described in Embodiments 1 and 2 with a secondary battery that uses the positive electrode as the positive electrode. The secondary battery and control circuit 8704 that use the positive electrode active material 100 described in Embodiments 1 and 2 as the positive electrode can greatly contribute to eliminating accidents such as fires caused by secondary batteries.

[0337] Furthermore, Figure 18C shows an example of a two-wheeled vehicle using a power storage device according to one embodiment of the present invention. The scooter 8600 shown in Figure 18C 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. In addition, the power storage device 8602, which houses multiple secondary batteries using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode, can have a high capacity and contribute to miniaturization.

[0338] Furthermore, the scooter 8600 shown in Figure 18C 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.

[0339] The contents described in this embodiment can be appropriately combined with the contents of other embodiments.

[0340] (Embodiment 9) This embodiment describes an example of mounting a secondary battery, which is one aspect of the present invention, in an electronic device. Examples of electronic devices on which a secondary battery is mounted include television equipment (also called televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game consoles, personal information terminals, sound playback devices, and large game machines such as pachinko machines. Personal information terminals include notebook personal computers, tablet terminals, e-book readers, and mobile phones.

[0341] Figure 19A shows an example of a mobile phone. The mobile phone 2100 includes a display unit 2102 built into the housing 2101, as well as operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. The mobile phone 2100 also has a secondary battery 2107. By using the positive electrode active material 100 described in Embodiment 1 as the positive electrode in the secondary battery 2107, a high capacity can be achieved, and a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0342] 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.

[0343] 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.

[0344] 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.

[0345] 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.

[0346] The mobile phone 2100 preferably has sensors. For example, it is preferable that the sensor includes a human body sensor such as a fingerprint sensor, pulse sensor, or body temperature sensor, as well as a touch sensor, pressure sensor, acceleration sensor, etc.

[0347] Figure 19B 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 positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode has a high energy density and high safety, so it can be used safely for a long period of time over a long period of time and is suitable as a secondary battery to be mounted on the unmanned aerial vehicle 2300.

[0348] Figure 19C shows an example of a robot. The robot 6400 shown in Figure 19C is equipped with a secondary battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406 and an obstacle sensor 6407, a movement mechanism 6408, a computing device, and the like.

[0349] Microphone 6402 has the function of detecting the user's voice and ambient sounds. Speaker 6404 has the function of emitting sound. Robot 6400 can communicate with the user using microphone 6402 and speaker 6404.

[0350] The display unit 6405 has the function of displaying various types of information. The robot 6400 can display the information desired by the user on the display unit 6405. The display unit 6405 may be equipped with a touch panel. The display unit 6405 may also be a detachable information terminal, and by installing it in a fixed position on the robot 6400, charging and data transfer can be made possible.

[0351] The upper camera 6403 and lower camera 6406 have the function of imaging the area around the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize its surrounding environment and move safely using the upper camera 6403, lower camera 6406 and obstacle sensor 6407.

[0352] The robot 6400 is equipped with a secondary battery 6409 according to one aspect of the present invention and a semiconductor device or electronic components in its internal region. The secondary battery using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode has a high energy density and high safety, so it can be used safely for a long period of time over a long period of time and is suitable as the secondary battery 6409 to be mounted on the robot 6400.

[0353] Figure 19D shows an example of a cleaning robot. The cleaning robot 6300 has a display unit 6302 located on the top surface of the housing 6301, multiple cameras 6303 located on the sides, a brush 6304, operation buttons 6305, a secondary battery 6306, and various sensors. Although not shown, the cleaning robot 6300 is equipped with wheels, a suction port, etc. The cleaning robot 6300 is self-propelled, can detect dirt 6310, and can suck up the dirt from a suction port located on the bottom surface.

[0354] For example, the cleaning robot 6300 can analyze images captured by the camera 6303 to determine the presence or absence of obstacles such as walls, furniture, or steps. Furthermore, if the image analysis detects an object that might become entangled in the brush 6304, such as wiring, the rotation of the brush 6304 can be stopped. The cleaning robot 6300 is equipped with a secondary battery 6306 according to one embodiment of the present invention and a semiconductor device or electronic component within its internal region. The secondary battery using the positive electrode active material 100 described in Embodiments 1 and 2 as the positive electrode has high energy density and high safety, allowing for safe use over long periods, making it suitable as a secondary battery 6306 for the cleaning robot 6300.

[0355] 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.

[0356] 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 can be made with good weight balance and a long continuous usage time. The secondary battery using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode has a high energy density and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.

[0357] Furthermore, a secondary battery according to one aspect of the present invention can be mounted in the headset-type device 4001. The headset-type device 4001 has at least a microphone section 4001a, a flexible pipe 4001b, and an earphone section 4001c. The secondary battery can be provided in the flexible pipe 4001b or in the earphone section 4001c. The secondary battery using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode has a high energy density and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.

[0358] Furthermore, a secondary battery according to one embodiment of the present invention can be mounted on a device 4002 that can be directly attached to the body. The secondary battery 4002b can be provided inside the thin housing 4002a of the device 4002. The secondary battery using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode has a high energy density and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.

[0359] Furthermore, a secondary battery according to one embodiment of the present invention can be mounted on a device 4003 that can be attached to clothing. The secondary battery 4003b can be provided inside the thin housing 4003a of the device 4003. The secondary battery using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode has a high energy density and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.

[0360] Furthermore, a secondary battery according to one embodiment of the present invention can be mounted on the belt-type device 4006. The belt-type device 4006 has a belt portion 4006a and a wireless power supply and receiving portion 4006b, and a secondary battery can be mounted in the internal region of the belt portion 4006a. The secondary battery using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode has a high energy density and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.

[0361] Furthermore, a secondary battery according to one embodiment of the present invention can be mounted in the wristwatch-type device 4005. The wristwatch-type device 4005 has a display unit 4005a and a belt unit 4005b, and the secondary battery can be provided in either the display unit 4005a or the belt unit 4005b. The secondary battery using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode has a high energy density and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.

[0362] The display unit 4005a can display not only the time, but also various other information such as incoming emails and phone calls.

[0363] Furthermore, since the wristwatch-type device 4005 is a wearable device that is worn directly on the wrist, it may be equipped with sensors to measure the user's pulse, blood pressure, etc. It can accumulate data on the user's exercise level and health, and manage their health.

[0364] Figure 20B shows a perspective view of the wristwatch-type device 4005 after it has been removed from the arm.

[0365] Figure 20C shows a side view of the wristwatch-type device 4005. Figure 20C shows how the secondary battery 913 is built into the internal region. The secondary battery 913 is the secondary battery shown in Embodiment 4. The secondary battery 913 is located in a position that overlaps with the display unit 4005a, allowing for high density and high capacity, as well as being small and lightweight.

[0366] Since the wristwatch-type device 4005 is required to be small and lightweight, using the positive electrode active material 100 described in Embodiment 1 and Embodiment 2 as the positive electrode of the secondary battery 913 makes it possible to create a secondary battery 913 that is both high in energy density and compact.

[0367] Figure 20D shows an example of wireless earphones. Here, wireless earphones with a pair of main units 4100a and 4100b are illustrated, but they do not necessarily have to be a pair.

[0368] The main unit 4100a and the main unit 4100b have a driver unit 4101, an antenna 4102, and a secondary battery 4103. They may also have a display unit 4104. Preferably, they also have a circuit board on which wireless ICs and other circuits are mounted, charging terminals, etc. They may also have a microphone.

[0369] The case 4110 contains a secondary battery 4111. Preferably, it also has a circuit board on which circuits such as a wireless IC and a charging control IC are mounted, and charging terminals. It may also have a display unit, buttons, etc.

[0370] The main units 4100a and 4100b can communicate wirelessly with other electronic devices such as smartphones. This allows them to play audio data sent from other electronic devices. Furthermore, if the main units 4100a and 4100b have microphones, they can send sound acquired by the microphones to other electronic devices, process the audio data, and then send it back to the main units 4100a and 4100b for playback. This allows them to be used, for example, as a translation device.

[0371] Furthermore, the secondary battery 4103 in the main unit 4100a can be charged from the secondary battery 4111 in the case 4110. The coin-type secondary battery, cylindrical secondary battery, etc., described in the previous embodiment can be used as the secondary battery 4111 and the secondary battery 4103. The secondary battery using the positive electrode active material 100 described in Embodiments 1 and 2 as the positive electrode has a high energy density, and by using it in the secondary battery 4103 and the secondary battery 4111, a configuration that can accommodate space saving due to the miniaturization of wireless earphones can be realized.

[0372] This embodiment can be implemented in appropriate combination with other embodiments. [Explanation of symbols]

[0373] 100: Positive electrode active material, 101: Primary particles, 101a: Surface layer, 101b: Inside, 102: Secondary particles, 103: Interface, 105: Voids

Claims

1. It has a positive electrode and an electrolyte, The positive electrode has a positive electrode active material having a layered rock salt type composite oxide, The positive electrode active material comprises lithium, a transition metal, oxygen, and an additive element. The transition metal is cobalt, The positive electrode active material has a surface layer and an interior, The aforementioned surface layer has a rock salt-type crystalline structure. The aforementioned additive elements include magnesium, titanium, aluminum, and fluorine. The concentration of the additive element in the surface layer is higher than the concentration of the additive element in the interior. A secondary battery in which the concentration peaks of magnesium, fluorine, and titanium in the surface layer are located on the surface side of the aluminum concentration peak.

2. In claim 1, A secondary battery in which magnesium, fluorine, and titanium in the surface layer have a concentration gradient that increases from the interior toward the surface of the positive electrode active material.

3. In claim 1 or claim 2, A secondary battery wherein the aluminum concentration peak in the surface layer is located in a region of 5 nm to 30 nm from the surface of the positive electrode active material.

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