Method for producing a composite oxide, and method for producing a lithium-ion battery

Abstract

Provided is a method for producing a positive electrode active material that can be used in a lithium ion battery having excellent discharge characteristics even in a low-temperature environment. The present invention includes: a first step for heating lithium cobaltate having a median diameter (D50) of 10 μm or less for 1-5 hours at a temperature of 700-1000°C; a second step for mixing the lithium cobaltate that has passed through the first step with a fluorine source and a magnesium source to produce a first mixture; a third step for heating the first mixture for 1-10 hours at a temperature of 800-1100°C; a fourth step for mixing the first mixture that has passed through the third step with a nickel source and an aluminum source to produce a second mixture; and a fifth step for heating the second mixture for 1-5 hours at a temperature of 800-950°C.

Description

[Technical Field]

[0001] The inventions disclosed herein (hereinafter sometimes referred to as "the present invention") relate to energy storage devices, secondary batteries, etc., and more particularly to lithium-ion batteries.

[0002] Alternatively, the present invention relates to a product, method, or method of manufacture. Alternatively, the present invention relates to a process, machine, manufacture, or composition of matter. Alternatively, the present invention relates to a semiconductor device, display device, light-emitting device, energy storage device, lighting device, electronic device, or a method of manufacturing the same. [Background technology]

[0003] In recent years, there has been a great deal of development on various energy storage devices, including lithium-ion batteries, lithium-ion capacitors, and air batteries. In particular, lithium-ion batteries, with their high output and high energy density, have seen a rapid increase in demand alongside the development of the semiconductor industry. They are used in mobile phones, smartphones, notebook computers and other portable information terminals, portable music players, digital cameras, medical equipment, and clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), and plug-in hybrid vehicles (PHV). As a rechargeable energy source, they have become indispensable to today's information society.

[0004] Lithium-ion batteries exhibit varying charging and / or discharging characteristics depending on the charging and / or discharging environment. For example, it is known that the discharge capacity of lithium-ion batteries changes depending on the discharge temperature.

[0005] Therefore, there is a need for lithium-ion batteries that have excellent battery characteristics even in low-temperature environments (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-026608 [Overview of the project] [Problems that the invention aims to solve]

[0007] Patent Document 1 describes how a lithium-ion battery capable of operating even in low-temperature environments (for example, below 0°C) was realized by using a non-aqueous solvent described in Patent Document 1. However, even with the lithium-ion battery described in Patent Document 1, the discharge capacity when discharged in a low-temperature environment is not considered large at the time of this application, and further improvements are desired.

[0008] Furthermore, in order to realize lithium-ion batteries that can operate even in low-temperature environments, it is necessary to develop not only non-aqueous solvents (electrolytes) but also positive and negative electrodes suitable for lithium-ion batteries that can operate in low-temperature environments. More specifically, in the case of positive electrodes, it is necessary to develop positive electrode active materials suitable for lithium-ion batteries that can operate even in low-temperature environments.

[0009] One aspect of the present invention aims to provide a positive electrode active material applicable to lithium-ion batteries that have excellent discharge characteristics even in low-temperature environments. Specifically, one aspect of the present invention aims to provide a positive electrode active material applicable to lithium-ion batteries that have high discharge capacity and / or discharge energy density even when discharged in low-temperature environments.

[0010] In this specification, "low temperature environment" means 0°C or below. When referring to a "low temperature environment" in this specification, it is possible to select any temperature below 0°C. For example, when referring to a "low temperature environment" in this specification, it is possible to select one of the following: 0°C or below, -10°C or below, -20°C or below, -30°C or below, -40°C or below, -50°C or below, -60°C or below, -80°C or below, and -100°C or below.

[0011] Alternatively, one aspect of the present invention aims to provide a lithium-ion battery having excellent discharge characteristics even in a low-temperature environment. Alternatively, one aspect of the present invention aims to provide a lithium-ion battery having excellent charge characteristics even in a low-temperature environment.

[0012] Specifically, one aspect of the present invention aims to provide a lithium-ion battery that has a large discharge capacity and / or discharge energy density even when discharged in a low-temperature environment (for example, 0°C or lower, -20°C or lower, preferably -30°C or lower, more preferably -40°C or lower, still more preferably -50°C or lower, and most preferably -60°C or lower). Alternatively, one aspect of the present invention aims to provide a lithium-ion battery in which the reduction rate is small compared to the value of the discharge capacity and / or discharge energy density when discharged at 25°C even when discharged in a low-temperature environment (for example, 0°C or lower, -20°C or lower, preferably -30°C or lower, more preferably -40°C or lower, still more preferably -50°C or lower, and most preferably -60°C or lower).

[0013] Alternatively, one aspect of the present invention aims to provide a secondary battery with a high charging voltage. Alternatively, one aspect of the present invention aims to provide a secondary battery with high safety or reliability. Alternatively, one aspect of the present invention aims to provide a secondary battery with little deterioration. Alternatively, one aspect of the present invention aims to provide a secondary battery with a long lifespan. Alternatively, one aspect of the present invention aims to provide a novel secondary battery.

[0014] Alternatively, one aspect of the present invention aims to provide a novel substance, active material, power storage device, or a method for producing them.

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

Means for Solving the Problems

[0016] To solve the above problems and the like, one aspect of the present invention has the following configuration.

[0017] One aspect of the present invention is a method for producing a composite oxide, comprising: a first step of heating lithium cobalt oxide having a median diameter (D50) of 10 μm or less at a temperature of 700°C to 1000°C for 1 hour to 5 hours; a second step of mixing a fluorine source and a magnesium source with the lithium cobalt oxide obtained in the first step to produce a first mixture; a third step of heating the first mixture at a temperature of 800°C to 1100°C for 1 hour to 10 hours; a fourth step of mixing a nickel source and an aluminum source with the first mixture obtained in the third step to produce a second mixture; and a fifth step of heating the second mixture at a temperature of 800°C to 950°C for 1 hour to 5 hours.

[0018] Alternatively, in one embodiment of the present invention, the number of magnesium atoms in the magnesium source is 0.3% to 3% of the number of cobalt atoms in the lithium cobalt oxide obtained through the first step.

[0019] Alternatively, in one embodiment of the present invention, the fluorine source is lithium fluoride, the magnesium source is magnesium fluoride, and the number of moles of lithium fluoride is M. LiF And the number of moles M of magnesium fluoride. MgF2 The ratio to is M LiF :M MgF2 = x:1 (0.1 ≤ x ≤ 0.5).

[0020] Alternatively, in one embodiment of the present invention, the number of nickel atoms in the nickel source is 0.05% to 4% of the number of cobalt atoms in the lithium cobalt oxide obtained through the first step.

[0021] Alternatively, in one embodiment of the present invention, the number of aluminum atoms in the aluminum source is 0.05% to 4% of the number of cobalt atoms in the lithium cobalt oxide obtained through the first step.

[0022] Alternatively, in one aspect of the present invention, the first step is carried out in an atmosphere containing oxygen with a lid placed on the sheath containing lithium cobaltate.

[0023] Alternatively, one aspect of the present invention is a method for manufacturing a lithium-ion battery including a positive electrode having a positive electrode active material, an electrolyte, and a negative electrode having a negative electrode active material which is a carbon material, the method including: a first step of heating lithium cobaltate having a median diameter (D50) of 10 μm or less at a temperature of 700°C or higher and 1000°C or lower for 1 hour or longer and 5 hours or shorter; a second step of mixing a fluorine source and a magnesium source with the lithium cobaltate that has undergone the first step to produce a first mixture; a third step of heating the first mixture at a temperature of 800°C or higher and 1100°C or lower for 1 hour or longer and 10 hours or shorter; a fourth step of mixing a nickel source and an aluminum source with the first mixture that has undergone the third step to produce a second mixture; and a fifth step of heating the second mixture at a temperature of 800°C or higher and 1100°C or lower for 1 hour or longer and 5 hours or shorter, thereby forming the positive electrode active material.

[0024] Alternatively, one aspect of the present invention includes a positive electrode having a positive electrode active material, an electrolyte, and a negative electrode having a negative electrode active material which is a carbon material, the electrolyte including ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate, and when the total content of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate is 100 vol%, the volume V EC of ethylene carbonate, the volume V EMC of ethyl methyl carbonate, and the volume V DMC of dimethyl carbonate having a ratio of V EC :V EMC :V DMC=x:y:100 - x - y (where 5 ≤ x ≤ 35 and 0 < y < 65). A method for manufacturing a lithium-ion battery, comprising: a first step of heating lithium cobaltate having a median diameter (D50) of 10 μm or less at a temperature of 700°C or higher and 1000°C or lower for 1 hour or more and 5 hours or less; a second step of mixing a fluorine source and a magnesium source with the lithium cobaltate obtained in the first step to produce a first mixture; a third step of heating the first mixture at a temperature of 800°C or higher and 1100°C or lower for 1 hour or more and 10 hours or less; a fourth step of mixing a nickel source and an aluminum source with the first mixture obtained in the third step to produce a second mixture; and a fifth step of heating the second mixture at a temperature of 800°C or higher and 1100°C or lower for 1 hour or more and 5 hours or less, thereby forming the positive electrode active material.

Advantages of the Invention

[0025] According to one aspect of the present invention, it is possible to provide a composite oxide (positive electrode active material) applicable to a lithium-ion battery having excellent discharge characteristics even in a low-temperature environment. Specifically, it is possible to provide a positive electrode active material applicable to a lithium-ion battery having a large discharge capacity and / or discharge energy density even when discharging in a low-temperature environment.

[0026] Alternatively, according to one aspect of the present invention, it is possible to provide a lithium-ion battery having a large discharge capacity and / or discharge energy density even when discharging at a temperature in a low-temperature environment (for example, 0°C or lower, -20°C or lower, preferably -30°C or lower, more preferably -40°C or lower, still more preferably -50°C or lower, most preferably < -60°C or lower). Alternatively, it is possible to provide a lithium-ion battery having a small reduction rate compared to the values of the discharge capacity and / or discharge energy density when discharging at 25°C even when discharging at a temperature in a low-temperature environment (for example, 0°C or lower, -20°C or lower, preferably -30°C or lower, more preferably -40°C or lower, still more preferably < -50°C or lower, most preferably < -60°C or lower).

[0027] Alternatively, according to one aspect of the present invention, a secondary battery with a high charging voltage can be provided. Alternatively, a secondary battery with high safety or reliability can be provided. Alternatively, a secondary battery with minimal degradation can be provided. Alternatively, a secondary battery with a long lifespan can be provided. Alternatively, a novel secondary battery can be provided.

[0028] Alternatively, according to one aspect of the present invention, novel materials, active materials, energy storage devices, or methods for producing them can be provided. [Brief explanation of the drawing]

[0029] Figures 1A to 1D illustrate the method for preparing the positive electrode active material. Figure 2 illustrates the method for preparing the positive electrode active material. Figures 3A to 3C illustrate the method for preparing the positive electrode active material. Figures 4A to 4D are cross-sectional views illustrating examples of the positive electrode of a secondary battery. 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 6A shows an example of a cylindrical secondary battery. Figure 6B shows an example of a cylindrical secondary battery. Figure 6C shows an example of multiple cylindrical secondary batteries. Figure 6D shows an example of an energy storage system with multiple cylindrical secondary batteries. Figures 7A and 7B illustrate examples of secondary batteries, while Figure 7C shows the inside of a secondary battery. Figures 8A to 8C illustrate examples of secondary batteries. Figures 9A and 9B show the external appearance of a secondary battery. Figures 10A to 10C illustrate the method for manufacturing a secondary battery. Figure 11A shows an example of the battery pack configuration, Figure 11B shows an example of the battery pack configuration, and Figure 11C shows an example of the battery pack configuration. Figure 12A is a perspective view of a battery pack showing one embodiment of the present invention, Figure 12B is a block diagram of the battery pack, and Figure 12C is a block diagram of a vehicle having a motor. Figures 13A to 13D illustrate an example of a transport vehicle. Figure 13E illustrates an example of an artificial satellite. Figures 14A and 14B illustrate an energy storage device according to one aspect of the present invention. Figure 15A shows an electric bicycle, Figure 15B shows a secondary battery for an electric bicycle, and Figure 15C illustrates an electric motorcycle. Figures 16A to 16D illustrate an example of an electronic device. Figure 17A shows an example of a wearable device, Figure 17B shows a perspective view of a wristwatch-type device, and Figure 17C is a diagram illustrating the side view of a wristwatch-type device. Figure 18 is a graph showing the particle size distribution of lithium cobalt oxide as described in Example 1. Figure 19A shows the SEM observation results of lithium cobalt oxide described in Example 1, and Figure 19B shows the SEM observation results of lithium cobalt oxide, the starting material. Figure 20 is a photograph of the external appearance of a secondary battery. Figure 21 is a graph showing the discharge curve (temperature characteristics) of a secondary battery at various temperatures. Figure 22 is a graph showing the charging and discharging curves of a secondary battery at various temperatures. [Modes for carrying out the invention]

[0030] Embodiments of the present invention will be described with appropriate use of 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 that its form and details can be modified in various ways without departing from the spirit and scope of the present invention. Accordingly, in the embodiments of the present invention shown below, the same reference numerals will be common to different drawings.

[0031] Furthermore, in each of the embodiments and examples described below, unless otherwise specified, it is possible to implement them by appropriately combining the embodiments and examples described herein.

[0032] In this specification, "electronic equipment" refers to all devices that have an energy storage device, and all electro-optical devices with an energy storage device, information terminal devices with an energy storage device, etc., are considered electronic equipment.

[0033] In this specification, "energy storage device" refers to all elements and devices that have an energy storage function. For example, this includes energy storage devices such as lithium-ion batteries (also called "secondary batteries"), lithium-ion capacitors, and electric double-layer capacitors.

[0034] In this specification, space groups are expressed using international notation (or Hermann-Mauguin notation) Short notation. Crystal planes and crystal directions are expressed using Miller indices. In crystallography, space groups, crystal planes, and crystal directions are expressed by superscripting numbers, but in this specification, due to formatting constraints, a minus sign (-) may be placed before the number instead of a superscript. Individual orientations indicating directions within a crystal are represented by [ ], collective orientations indicating all equivalent directions are represented by < >, individual crystal planes are represented by ( ), and collective planes with equivalent symmetry are represented by {}. Furthermore, for ease of understanding the structure, trigonal crystals represented by space group R-3m are generally represented as a composite hexagonal lattice, and in this specification, unless otherwise specified, space group R-3m will be represented as a composite hexagonal lattice. In addition, (hkil) may be used as Miller indices, not just (hkl), where i is -(h+k).

[0035] In this specification, the theoretical capacity of the positive electrode active material refers to the amount of electricity when all of the insertable and detachable lithium present in the positive electrode active material has been detached. For example, the theoretical capacity of LiCoO2 is 274 mAh / g, the theoretical capacity of LiNiO2 is 275 mAh / g, and the theoretical capacity of LiMn2O4 is 148 mAh / g.

[0036] Furthermore, the extent to which lithium remains in the positive electrode active material that can be inserted into and removed is determined by x in the composition formula, for example, Li xIt can be expressed as x (the percentage of Li at lithium sites) in CoO2. In the case of the positive electrode active material of a secondary battery, x can be expressed as (theoretical capacity - charging capacity) / theoretical capacity. For example, when a secondary battery using LiCoO2 as the positive electrode active material is charged at 219.2 mAh / g, Li 0.2 It can be expressed as CoO2 or x=0.2. x A small value of x in CoO2 is, for example, x ≤ 0.24. Considering the practical range for use as a lithium-ion battery, for example, 0.1 <x≦0.24であるものとする。

[0037] When lithium cobalt oxide approximately satisfies the stoichiometric ratio, it is LiCoO2, and x=1. Similarly, lithium cobalt oxide contained in a secondary battery after discharge is also LiCoO2, and can be said to be x=1. In general, in lithium-ion batteries using LiCoO2, the discharge voltage drops sharply before reaching 2.5V. For this reason, in this specification, for example, the state where the voltage reaches 2.5V (with lithium as the counter electrode) at a current of 100mA / g or less is considered the state after discharge, and x=1. Therefore, to obtain lithium cobalt oxide when x=0.2, for example, a charge of 219.2mAh / g should be applied from the state after discharge.

[0038] Li x The charging and / or discharging capacities used to calculate x in CoO2 should preferably be measured under conditions where there is little or no influence from short circuits and / or electrolyte decomposition. For example, data from secondary batteries that have experienced abrupt voltage changes or abrupt capacity changes that appear to be short circuits should not be used to calculate x.

[0039] Furthermore, the space group of a crystal structure is identified by methods such as XRD, electron diffraction, and neutron diffraction. Therefore, in this specification, "belonging to a certain space group," "being part of a certain space group," or "being a certain space group" can be rephrased as "being identified to a certain space group."

[0040] Furthermore, if the anion has a structure in which three layers are stacked with a slight offset from each other, such as ABCABC, it will be called a "cubic close-packed structure." Therefore, the anion does not have to be strictly a cubic lattice. At the same time, since real crystals always have defects, the analytical results do not necessarily conform to theory. For example, in FFT (Fast Fourier Transform) patterns such as electron diffraction patterns or TEM images, spots may appear at positions slightly different from the theoretical positions. For example, if the orientation from the theoretical position is 5° or less, or 2.5° or less, it can be said that it has a cubic close-packed structure.

[0041] In this specification, the term "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. It should be noted that defects such as vacancies in cations or anions may be present. Furthermore, strictly speaking, a layered rock salt crystal structure may have a distorted lattice structure of the rock salt crystal.

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

[0043] In this specification, "homogeneous" refers to the phenomenon in which, in a solid composed of multiple elements (e.g., A, B, C), a certain element (e.g., A) is distributed in a specific region with similar characteristics. Specifically, it is sufficient if the concentrations of the elements in the specific regions are substantially the same. For example, the difference in elemental concentrations between the specific regions should be within 10%. Examples of specific regions include the surface, surface layer, convex parts, concave parts, and interior.

[0044] 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). Alternatively, it refers to a situation where the concentration of a certain element differs from that of others. It is synonymous with segregation, precipitation, non-uniformity, bias, or the presence of areas with high and low concentrations.

[0045] 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 inward. Furthermore, surfaces formed by cracks or fissures can be considered as the surface. Also, in this specification, regions deeper than the surface layer may be referred to as the "interior." Furthermore, in this specification, "grain boundary" refers to, for example, a portion where particles are fixed together, a portion where the crystal orientation changes within the particle (including the central portion), a portion containing many defects, or a portion where the crystal structure is disordered. A grain boundary can also be considered a type of surface defect. Furthermore, "near the grain boundary" refers to the region within 20 nm, preferably within 10 nm, from the grain boundary. Also, in this specification, "particle" is not limited to spherical (circular cross-section), but may refer to individual particles with elliptical, rectangular, trapezoidal, conical, rounded quadrilateral, or asymmetrical cross-sections, and individual particles may also have irregular shapes.

[0046] (Embodiment 1) In this embodiment, a method for producing a positive electrode active material applicable to lithium-ion batteries that have excellent discharge characteristics even in low-temperature environments will be explained with reference to Figures 1 to 3.

[0047] <Example 1 of a method for preparing positive electrode active material> An example of a method for producing a positive electrode active material that can be used as one embodiment of the present invention (Example 1 of the method for producing a positive electrode active material) will be explained using Figures 1A to 1D.

[0048] First, in step S10, lithium cobalt oxide is prepared as the starting material. The lithium cobalt oxide used as the starting material has a particle size (strictly speaking, median diameter (D50)) of 10 μm or less (preferably 8 μm or less). In this specification, unless otherwise specified, the median diameter refers to D50 (the particle size at which the cumulative frequency reaches 50%). Lithium cobalt oxide with a median diameter (D50) of 10 μm or less may be known or commercially available (in short, commercially available) lithium cobalt oxide, or lithium cobalt oxide prepared through steps S11 to S14 shown in Figure 1B may be used. A typical example of commercially available lithium cobalt oxide with a median diameter (D50) of 10 μm or less is lithium cobalt oxide manufactured by Nippon Chemical Industrial Co., Ltd. (product name "Cellseed C-5H"). Lithium cobalt oxide (product name "Cellseed C-5H") manufactured by Nippon Chemical Industrial Co., Ltd. has a median diameter (D50) of approximately 7 μm. The following describes a method for obtaining lithium cobalt oxide with a median diameter (D50) of 10 μm or less, via steps S11 to S14.

[0049] <Step S11> In step S11 shown in Figure 1B, lithium sources (Li sources) and cobalt sources (Co sources) are prepared as the starting materials, lithium and transition metals, respectively.

[0050] As a lithium source, it is preferable to use a lithium-containing compound, such as lithium carbonate, lithium hydroxide, lithium nitrate, or lithium fluoride. The lithium source should preferably have high purity; for example, a material with a purity of 99.99% or higher is preferable.

[0051] As a cobalt source, it is preferable to use a compound containing cobalt, such as tricobalt tetroxide or cobalt hydroxide. The cobalt source should preferably have high purity; for example, a material with a purity of 3N (99.9%) or higher, preferably 4N (99.99%) or higher, more preferably 4N5 (99.995%) or higher, and even more preferably 5N (99.999%) or higher is used. By using a high-purity material, impurities in the positive electrode active material can be controlled. As a result, the capacity of the secondary battery is increased and the reliability of the secondary battery is improved.

[0052] In addition, the cobalt source preferably has high crystallinity, for example, it is preferable to have single crystal grains. The crystallinity of the transition metal source can be evaluated by 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., or by X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. The above methods for evaluating crystallinity can be applied not only to transition metal sources but also to the evaluation of other materials.

[0053] <Step S12> Next, as shown in step S12 in Figure 1B, the lithium source and cobalt source are pulverized and mixed to prepare a mixed material. Pulverization and mixing can be carried out dry or wet. Wet pulverization and mixing is preferable to obtain lithium cobaltate with a median diameter (D50) of 10 μm or less as a starting material, as it allows for finer pulverization. When using a wet method, a solvent is prepared. As a solvent, ketones such as acetone, alcohols such as ethanol and isopropanol, ethers, dioxane, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc. can be used, but it is preferable to use an aprotic solvent that does not react easily with lithium. In this embodiment, dehydrated acetone with a purity of 99.5% or higher is used. It is preferable to mix the lithium source and transition metal source with dehydrated acetone with a purity of 99.5% or higher, with a water content of 10 ppm or less, and then pulverize and mix. By using dehydrated acetone of the above purity, the amount of impurities that may be mixed in can be reduced.

[0054] For grinding and mixing, a ball mill or bead mill can be used. When using a ball mill, it is preferable to use aluminum oxide balls or zirconium oxide balls as the grinding media. Zirconium oxide balls are preferable because they produce less impurity. Also, when using a ball mill or bead mill, it is preferable to set the peripheral speed to 100 mm / s or more and 2000 mm / s or less in order to suppress contamination from the media. In this embodiment, the peripheral speed is set to 838 mm / s (rotation speed 400 rpm, ball mill diameter 40 mm).

[0055] <Step S13> Next, as step S13 shown in Figure 1B, the mixed material is heated. The heating is preferably carried out at 800°C to 1100°C, more preferably at 900°C to 1000°C, and even more preferably at around 950°C to 1000°C. If the temperature is too low, the decomposition and melting of the lithium source and transition metal source may be insufficient. On the other hand, if the temperature is too high, defects may occur due to the evaporation of lithium from the lithium source and / or the excessive reduction of cobalt. For example, cobalt may change from trivalent to divalent, inducing oxygen defects, etc.

[0056] If the heating time is too short, lithium cobalt oxide will not be synthesized, but if it is too long, productivity will decrease. Therefore, the heating time should be between 1 hour and 100 hours, preferably between 2 hours and 20 hours, and more preferably between 2 hours and 10 hours.

[0057] The heating rate depends on the target temperature, but a rate between 80°C / h and 250°C / h is generally recommended. For example, when heating to 1000°C for 10 hours, a heating rate of 200°C / h is appropriate.

[0058] Heating is preferably carried out in an atmosphere with little water, such as dry air, for example, an atmosphere with a dew point of -50°C or lower, more preferably an atmosphere with a dew point of -80°C or lower. In this embodiment, heating is carried out in an atmosphere with a dew point of -93°C. In order to suppress impurities that may be mixed into the material, the concentrations of impurities such as CH4, CO, CO2, and H2 in the heating atmosphere should be kept below 5 ppb (parts per billion) each.

[0059] An oxygen-containing atmosphere is preferred as the heating atmosphere. For example, one method is to continuously introduce dry air into the reaction chamber. In this case, the flow rate of the dry air is preferably 10 L / min. The method of continuously introducing oxygen into the reaction chamber and having oxygen flow through the chamber is called flow.

[0060] When the heating atmosphere is an oxygen-containing atmosphere, a method that does not involve flowing oxygen is also acceptable. For example, the reaction chamber can be depressurized and then filled with oxygen, preventing the oxygen from entering or leaving the reaction chamber; this method is called purging. For example, the reaction chamber can be depressurized to -970 hPa and then filled with oxygen up to 50 hPa.

[0061] After heating, natural cooling is acceptable, but it is preferable that the cooling time from the specified temperature to room temperature is between 10 and 50 hours. However, cooling to room temperature is not always necessary; it is sufficient if it cools to a temperature acceptable for the next step.

[0062] Heating in this process may be carried out using a rotary kiln or a roller hearth kiln. When using a rotary kiln, heating can be performed while stirring, whether in a continuous or batch system.

[0063] The container used for heating is preferably an aluminum oxide crucible or aluminum oxide sheath. An aluminum oxide crucible is made of a material that contains almost no impurities. In this embodiment, an aluminum oxide sheath with a purity of 99.9% is used. It is preferable to place a lid on the crucible or sheath before heating, as this prevents the material from volatilizing.

[0064] After heating is complete, the material may be crushed and sieved as needed. When collecting the heated material, it may be transferred from the crucible to a mortar before collection. A mortar made of zirconium oxide or agate is preferable. In addition, the same heating conditions as in step S13 can be applied to the heating processes described later, other than step S13.

[0065] <Step S14> Through the above process, lithium cobalt oxide (LiCoO2) shown in step S14 in Figure 1B can be synthesized. Since the lithium cobalt oxide (LiCoO2) shown in step S14 is an oxide containing multiple metal elements in its structure, it can be called a composite oxide. Alternatively, after step S13, a grinding step and a classification step may be performed to adjust the particle size distribution before obtaining the lithium cobalt oxide (LiCoO2) shown in step S14.

[0066] Although examples of producing composite oxides by a solid-phase method have been shown as in steps S11 to S14, composite oxides may also be produced by a coprecipitation method. Alternatively, composite oxides may be produced by a hydrothermal method.

[0067] By going through steps S11 to S14, lithium cobalt oxide can be obtained as a starting material for obtaining a positive electrode active material applicable to lithium-ion batteries that have excellent discharge characteristics even in low-temperature environments. Specifically, lithium cobalt oxide with a median diameter (D50) of 10 μm or less can be obtained as the starting material.

[0068] <Step S15> Next, as step S15 shown in Figure 1A, the lithium cobalt oxide starting material is heated. The heating in step S15 is the first heating of the lithium cobalt oxide and is therefore sometimes referred to as initial heating in this specification. Alternatively, since it is heated before step S31 shown below, it may be referred to as preheating or pretreatment.

[0069] Initial heating removes lithium compounds and other substances unintentionally remaining on the surface of the lithium cobalt oxide. It is also expected to enhance the internal crystallinity. Furthermore, although the lithium source and / or cobalt source prepared in step S11, etc., may contain impurities, initial heating makes it possible to reduce impurities from the starting material lithium cobalt oxide. The effect of enhancing internal crystallinity refers to, for example, the effect of mitigating strains and displacements caused by differences in shrinkage in the lithium cobalt oxide prepared in step S14.

[0070] Furthermore, initial heating has the effect of smoothing the surface of lithium cobalt oxide. Initial heating also has the effect of mitigating cracks and crystal defects present in lithium cobalt oxide. In this specification, a "smooth" surface refers to a surface with few irregularities, an overall rounded shape, and rounded corners. Alternatively, a surface with few foreign matter adhering to it is also referred to as "smooth." Foreign matter is considered a cause of irregularities, and it is preferable to prevent its adhesion to the surface.

[0071] Furthermore, it is not necessary to separately prepare a lithium compound source, an additive element A source, or a material that functions as a flux for this initial heating.

[0072] If the heating time in this process is too short, sufficient effects will not be obtained, but if it is too long, productivity will decrease. An appropriate range of heating time can be selected from, for example, the heating conditions described in step S13. The heating temperature in step S15 should be lower than the temperature in step S13 in order to maintain the crystal structure of the composite oxide. Also, the heating time in step S15 should preferably be shorter than the time in step S13 in order to maintain the crystal structure of the composite oxide. For example, heating should be performed at a temperature of 700°C to 1000°C (more preferably 800°C to 900°C) for 1 hour to 20 hours (more preferably 1 hour to 5 hours).

[0073] In lithium cobalt oxide, heating in step S13 can create a temperature difference between the surface and the interior. This temperature difference can induce a difference in shrinkage. It is thought that this difference in shrinkage occurs because the fluidity of the surface and the interior differs due to the temperature difference. The energy associated with the difference in shrinkage creates a difference in internal stress in the lithium cobalt oxide. This difference in internal stress is also called strain, and the energy associated with it is sometimes called strain energy. The internal stress is removed by the initial heating in step S15, or in other words, the strain energy is homogenized by the initial heating in step S15. When the strain energy is homogenized, the strain in lithium cobalt oxide is relieved. Consequently, the surface of the lithium cobalt oxide becomes smoother, or it can be said that the surface is improved. That is, by going through step S15, the difference in shrinkage that occurred in lithium cobalt oxide is relieved, and the surface of the composite oxide can be made smoother.

[0074] Furthermore, the difference in shrinkage can cause microscopic displacements in lithium cobalt oxide, such as crystal displacements. To reduce these displacements, it is preferable to perform step S15. By going through step S15, it is possible to homogenize the displacement of the composite oxide (alleviate crystal displacements that have occurred in the composite oxide, or align the crystal grains). As a result, the surface of the composite oxide becomes smooth.

[0075] Using lithium cobalt oxide, which has a smooth surface, as the positive electrode active material reduces degradation during charging and discharging in a secondary battery and prevents cracking of the positive electrode active material.

[0076] As mentioned above, in step S10, pre-synthesized lithium cobalt oxide with a median diameter (D50) of 10 μm or less may be used. In this case, steps S11 to S13 can be omitted. By performing step S15 on the pre-synthesized lithium cobalt oxide, lithium cobalt oxide with a smooth surface can be obtained.

[0077] Since step S15 is not an essential component in one embodiment of the present invention, an embodiment in which step S15 is omitted is also included as an embodiment of the present invention.

[0078] <Step S20> Next, the details of step S20, in which additive element A is prepared as source A, will be explained using Figures 1C and 1D.

[0079] <Step S21> Step S20, shown in Figure 1C, comprises steps S21 to S23. Step S21 involves preparing additive element A. Specific examples of additive element A include one or more selected from magnesium, fluorine, nickel, aluminum, titanium, zirconium, vanadium, iron, manganese, chromium, niobium, arsenic, zinc, silicon, sulfur, phosphorus, and boron. Alternatively, one or more selected from bromine and beryllium may be used. Figure 1C illustrates the case where a magnesium source (Mg source) and a fluorine source (F source) are prepared. In addition to additive element A, a lithium source may also be prepared separately in step S21.

[0080] When magnesium is selected as additive element A, the source of additive element A can be called the magnesium source. Magnesium sources that can be used include magnesium fluoride (MgF2), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), or magnesium carbonate (MgCO3). Multiple magnesium sources may be used.

[0081] When fluorine is selected as additive element A, the source of additive element A can be called a fluorine source. Examples of fluorine sources that can be used include lithium fluoride (LiF), magnesium fluoride (MgF2), aluminum fluoride (AlF3), titanium fluoride (TiF4), cobalt fluoride (CoF2, CoF3), nickel fluoride (NiF2), zirconium fluoride (ZrF4), vanadium fluoride (VF5), manganese fluoride, iron fluoride, chromium fluoride, niobium fluoride, zinc fluoride (ZnF2), calcium fluoride (CaF2), sodium fluoride (NaF), potassium fluoride (KF), barium fluoride (BaF2), cerium fluoride (CeF3, CeF4), lanthanum fluoride (LaF3), or sodium aluminum hexafluoride (Na3AlF6). Among these, lithium fluoride is preferred because it has a relatively low melting point of 848°C and is easily melted in the heating process described later.

[0082] Magnesium fluoride can be used as both a fluorine source and a magnesium source. Lithium fluoride can also be used as a lithium source. Another lithium source used in step S21 is lithium carbonate.

[0083] Furthermore, the fluorine source may be a gas, and may be fluorine (F2), carbon fluoride, sulfur fluoride, or oxygen fluoride (OF2, O2F2, O3F2, O4F2, O5F2, O6F2, O2F), etc., which may be mixed into the atmosphere during the heating process described later. Multiple fluorine sources may be used.

[0084] In this embodiment, lithium fluoride (LiF) is prepared as the fluorine source, and magnesium fluoride (MgF2) is prepared as both the fluorine source and the magnesium source. Mixing lithium fluoride and magnesium fluoride in a molar ratio of approximately LiF:MgF2 = 65:35 maximizes the effect of lowering the melting point. However, if the proportion of lithium fluoride is too high, there is a concern that lithium will be in excess and the cycle characteristics will deteriorate. Therefore, the molar ratio of lithium fluoride to magnesium fluoride is preferably LiF:MgF2 = x:1 (0≦x≦1.9), more preferably LiF:MgF2 = x:1 (0.1≦x≦0.5), and even more preferably LiF:MgF2 = x:1 (x=0.33 and its vicinity). In this specification, unless otherwise specified, "nearby" means a value greater than 0.9 times and less than 1.1 times the value.

[0085] <Step S22> Next, in step S22 shown in Figure 1C, the magnesium source and the fluorine source are crushed and mixed. This step can be performed by selecting from the crushing and mixing conditions described in step S12.

[0086] <Step S23> Next, in step S23 shown in Figure 1C, the material that has been crushed and mixed above is recovered to obtain the additive element A source (A source). The additive element A source shown in step S23 has multiple starting materials and can also be called a mixture.

[0087] The particle size of the above mixture is preferably such that the median diameter (D50) is 100 nm or more and 10 μm or less, and more preferably 300 nm or more and 5 μm or less. Furthermore, even when one type of material is used as the source of additive element A, the median diameter (D50) is preferably such that it is 100 nm or more and 10 μm or less, and more preferably 300 nm or more and 5 μm or less.

[0088] The mixture pulverized in step S22 (including cases where only one additive element is present) is more likely to uniformly adhere to the surface of lithium cobalt oxide when mixed with lithium cobalt oxide in a later step. Uniform adhesion of the mixture to the surface of lithium cobalt oxide is preferable because it facilitates the uniform distribution or diffusion of the additive element to the surface layer of the composite oxide after heating.

[0089] <Step S21> A process different from that shown in Figure 1C will be explained using Figure 1D. Step S20 shown in Figure 1D includes steps S21 to S23.

[0090] In step S21 shown in Figure 1D, four types of additive element A sources are prepared to be added to lithium cobalt oxide. That is, Figure 1D shows different types of additive element A sources than Figure 1C. In addition to the additive element A sources, a lithium source may also be prepared separately.

[0091] Four types of additive element A sources are prepared: a magnesium source (Mg source), a fluorine source (F source), a nickel source (Ni source), and an aluminum source (Al source). The magnesium and fluorine sources can be selected from the compounds described in Figure 1C. Nickel sources such as nickel oxide and nickel hydroxide can be used. Aluminum sources such as aluminum oxide and aluminum hydroxide can be used.

[0092] <Steps S22 and S23> Next, steps S22 and S23 shown in Figure 1D are the same as steps S22 and S23 described in Figure 1C.

[0093] <Step S31> Next, in step S31 shown in Figure 1A, the lithium cobalt oxide that has undergone step S15 (initial heating) is mixed with the additive element A source (Mg source). Here, the ratio of the number of cobalt atoms Co in the lithium cobalt oxide that has undergone step S15 to the number of magnesium atoms Mg in the additive element A is preferably Co:Mg=100:y (0.1≦y≦6), and more preferably Co:Mg=100:y (0.3≦y≦3). Adding additive element A to lithium cobalt oxide that has undergone initial heating allows for even addition of additive element A. For this reason, it is preferable to add additive element A after initial heating (step 15), rather than adding additive element A before initial heating (step 15).

[0094] Furthermore, if nickel is selected as additive element A, it is preferable to perform the mixing in step S31 such that the number of nickel atoms in the nickel source is 0.05% to 4% of the number of cobalt atoms in the lithium cobalt oxide obtained through step S15. Furthermore, if aluminum is selected as additive element A, it is preferable to perform the mixing in step S31 such that the number of aluminum atoms in the aluminum source is 0.05% to 4% of the number of cobalt atoms in the lithium cobalt oxide obtained through step S15.

[0095] The mixing in step S31 is preferably carried out under milder conditions than the grinding and mixing in step S12, in order to avoid destroying the shape of the lithium cobalt oxide. For example, it is preferable to use conditions with a lower rotation speed or shorter duration than the mixing in step S12. Also, dry mixing is generally milder than wet mixing. For mixing, for example, a ball mill or a bead mill can be used. When using a ball mill, it is preferable to use zirconium oxide balls as the media.

[0096] In this embodiment, the mixing is performed dry using a ball mill with zirconium oxide balls with a diameter of 1 mm at 150 rpm for 1 hour. The mixing is carried out in a dry room with a dew point of -100°C or higher and -10°C or lower.

[0097] <Step S32> Next, in step S32 of Figure 1A, the materials mixed above are recovered to obtain mixture 903. During recovery, if necessary, the materials may be crushed and then sieved.

[0098] <Step S33> Next, in step S33 shown in Figure 1A, the mixture 903 is heated. The heating in step S33 is preferably carried out at a temperature of 800°C to 1100°C, more preferably at 800°C to 950°C, and even more preferably at 850°C to 900°C. The heating time in step S33 may be 1 hour to 100 hours, but 1 hour to 10 hours is preferred. The lower limit of the heating temperature in step S33 must be above the temperature at which the reaction between lithium cobalt oxide and the additive element A source proceeds. The temperature at which the reaction proceeds is any temperature at which interdiffusion of the elements in lithium cobalt oxide and the additive element A source occurs, and may be lower than the melting temperature of these materials. For example, using oxides as an example, the melting temperature T m 0.757 times (Tammann temperature T) d Since solid-phase diffusion occurs from ), the heating temperature in step S33 should be 500°C or higher.

[0099] Furthermore, the reaction proceeds more easily if the heating temperature is above the melting point of one or more of the materials selected from the mixture 903. For example, if the additive element A source contains LiF and MgF2, the eutectic point of LiF and MgF2 is around 742°C, so it is preferable to set the lower limit of the heating temperature in step S33 to 742°C or higher.

[0100] Furthermore, when mixture 903 is obtained by mixing LiCoO2:LiF:MgF2 in a molar ratio of 100:0.33:1, an endothermic peak is observed around 830°C in differential scanning calorimetry (DSC measurement). Therefore, a lower limit of the heating temperature of 830°C or higher is more preferable.

[0101] A higher heating temperature is preferable because it facilitates the reaction, shortens the heating time, and increases productivity.

[0102] The upper limit of the heating temperature should be below the decomposition temperature of lithium cobalt oxide (1130°C). At temperatures near the decomposition temperature, there is a concern that lithium cobalt oxide may decompose, albeit in small amounts. Therefore, it is preferable that the temperature be 1000°C or lower, more preferably 950°C or lower, and even more preferably 900°C or lower.

[0103] Furthermore, when heating the mixture 903, it is preferable to control the partial pressure of fluorine or fluoride, which may be caused by a fluorine source, to an appropriate range.

[0104] In the manufacturing method described in this embodiment, some materials, such as LiF, a fluorine source, may function as a flux. This function allows the heating temperature to be lowered to below the decomposition temperature of lithium cobalt oxide, for example, between 742°C and 950°C, enabling the distribution of additive elements, including magnesium, to the surface layer and producing a positive electrode active material with good properties.

[0105] Incidentally, since LiF has a lower specific gravity than oxygen in its gaseous state, heating may cause LiF to volatilize or sublimate, and if it volatilizes, the amount of LiF in mixture 903 will decrease. In this case, its function as a flux will be weakened. Therefore, it is preferable to heat while suppressing the volatilization of LiF. Furthermore, even if LiF is not used as a fluorine source, Li on the surface of LiCoO2 may react with F from the fluorine source to produce LiF, which may then volatilize. Therefore, even if a fluoride with a higher melting point than LiF is used, it is necessary to suppress volatilization in the same way.

[0106] Therefore, it is preferable to heat the mixture 903 in an atmosphere containing LiF, that is, to heat the mixture 903 while the partial pressure of LiF in the heating furnace is high. Such heating can suppress the volatilization of LiF in the mixture 903.

[0107] Furthermore, it is preferable to heat the mixture 903 in a way that prevents the particles from sticking together. If the particles of the mixture 903 stick together during heating, the contact area with oxygen in the atmosphere decreases, and the diffusion pathway of the added elements (e.g., fluorine) is obstructed, which may worsen the distribution of added elements (e.g., magnesium and fluorine) to the surface layer.

[0108] Furthermore, if the additive elements (e.g., fluorine) are uniformly distributed on the surface, a smooth positive electrode active material with few irregularities can be obtained. Therefore, in order to maintain or further improve the smooth surface after heating in step S15 of this process, it is preferable that the particles of mixture 903 do not adhere to each other.

[0109] Furthermore, when heating with a rotary kiln, it is preferable to control the flow rate of the oxygen-containing atmosphere inside the kiln during heating. For example, it is preferable to reduce the flow rate of the oxygen-containing atmosphere, or to purge the atmosphere initially and then not allow the atmosphere to flow after introducing the oxygen atmosphere into the kiln. If oxygen flows, the fluorine source may evaporate, which is undesirable for maintaining surface smoothness.

[0110] When heating by roller hearth kiln, for example, the mixture 903 can be heated in an atmosphere containing LiF by placing a lid on the container containing the mixture 903.

[0111] <Step S34> Next, in step S34 shown in Figure 1A, the heated material is recovered and crushed as necessary to obtain the positive electrode active material 100. At this time, it is preferable to further sift the recovered positive electrode active material 100. Through the above steps, a positive electrode active material 100 (composite oxide) with a median diameter (D50) of 12 μm or less (preferably 10.5 μm or less, more preferably 8 μm or less) can be produced. The positive electrode active material 100 contains additive element A.

[0112] <Example 2 of a method for preparing positive electrode active material> Using Figures 2 and 3, another example of a method for producing a positive electrode active material that can be used as one embodiment of the present invention (Example 2 of the method for producing a positive electrode active material) will be described. In Example 2 of the method for producing a positive electrode active material, the number of times the additive elements are added and the mixing method differ from Example 1 of the method for producing a positive electrode active material described above, but the description of Example 1 of the method for producing a positive electrode active material can be applied to other aspects.

[0113] In Figure 2, steps S10 and S15 are performed in the same manner as in Figure 1A to prepare lithium cobalt oxide that has undergone initial heating. Note that since step S15 is not an essential component in one embodiment of the present invention, an embodiment in which step S15 is omitted is also included in one embodiment of the present invention.

[0114] <Step S20a> Next, a first additive element A1 source (A1 source) is prepared as shown in step S20a. The details of step S20a will be explained with reference to Figure 3A.

[0115] <Step S21> In step S21 shown in Figure 3A, a first additive element A1 source (A1 source) is prepared. The A1 source can be selected from additive element A as described in step S21 shown in Figure 1C. For example, one or more of magnesium, fluorine, and calcium can be used as additive element A1. Figure 3A illustrates the case where a magnesium source (Mg source) and a fluorine source (F source) are used as additive element A1.

[0116] Steps S21 to S23 shown in Figure 3A can be carried out under the same conditions as steps S21 to S23 shown in Figure 1C. As a result, the first additive element A1 source (A1 source) can be obtained in step S23.

[0117] Furthermore, steps S31 to S33 shown in Figure 2 can be manufactured under the same conditions as steps S31 to S33 shown in Figure 1A.

[0118] <Step S34a> Next, the material heated in step S33 is recovered to obtain lithium cobalt oxide containing additive element A1. Here, to distinguish it from the lithium cobalt oxide obtained through step S15 (the first composite oxide), it is also called the second composite oxide.

[0119] <Step S40> In step S40, shown in Figure 2, a second additive element A2 source (A2 source) is prepared. Step S40 will be explained with reference to Figures 3B and 3C.

[0120] <Step S41> In step S40 shown in Figure 3B, a second additive element A2 source (A2 source) is prepared. The A2 source can be selected from additive element A as described in step S20 shown in Figure 1C. For example, one or more of nickel, titanium, boron, zirconium, and aluminum can be suitably used as additive element A2. Figure 3B illustrates the case where a nickel source and an aluminum source are used as additive element A2.

[0121] Steps S41 to S43 shown in Figure 3B can be prepared under the same conditions as steps S21 to S23 shown in Figure 1C. As a result, a second additive element A2 source (A2 source) can be obtained in step S43.

[0122] Steps S41 to S43 shown in Figure 3C are modified versions of those in Figure 3B. In step S41 shown in Figure 3C, a nickel source (Ni source) and an aluminum source (Al source) are prepared, and in step S42a, they are each ground independently. As a result, in step S43, multiple second additive element A2 sources (A2 sources) are prepared. Thus, step S40 in Figure 3C differs from step S40 in Figure 3B in that the additive elements are ground independently in step S42a.

[0123] <Steps S51 to S53> Next, steps S51 to S53 shown in Figure 2 can be carried out under the same conditions as steps S31 to S33 shown in Figure 1A. The conditions for step S53, which relates to the heating process, are preferably lower in temperature and / or shorter in duration than those for step S33 shown in Figure 2. Specifically, the heating temperature is preferably 800°C to 950°C, more preferably 820°C to 870°C, and even more preferably 850°C ± 10°C. The heating time is preferably 0.5 hours to 8 hours, and more preferably 1 hour to 5 hours.

[0124] Furthermore, if nickel is selected as the second additive element A2, it is preferable to perform the mixing in step S51 such that the number of nickel atoms in the nickel source is 0.05% to 4% of the number of cobalt atoms in the lithium cobalt oxide obtained through step S15. Also, if aluminum is selected as the additive element A2, it is preferable to perform the mixing in step S51 such that the number of aluminum atoms in the aluminum source is 0.05% to 4% of the number of cobalt atoms in the lithium cobalt oxide obtained through step S15.

[0125] <Step S54> Next, in step S54 shown in Figure 2, the heated material is recovered and crushed as necessary to obtain the positive electrode active material 100. Through the above steps, a positive electrode active material 100 (composite oxide) with a median diameter (D50) of 12 μm or less (preferably 10.5 μm or less, more preferably 8 μm or less) can be produced. Alternatively, a positive electrode active material 100 applicable to lithium-ion batteries having excellent discharge characteristics even in low-temperature environments can be produced. The positive electrode active material 100 contains a first additive element A1 and a second additive element A2.

[0126] In the example 2 of the manufacturing method described above, as shown in Figures 2 and 3, the additive elements to lithium cobalt oxide are introduced separately as a first additive element A1 and a second additive element A2. By introducing them separately, the depth profile of each additive element can be changed. For example, the first additive element can be profiled to have a higher concentration in the surface layer compared to the interior, and the second additive element can be profiled to have a higher concentration in the interior compared to the surface layer. The cathode active material 100 manufactured through the steps in Figures 1A and 1D has the advantage of being able to be manufactured at low cost because multiple types of additive elements A are added at once. On the other hand, the cathode active material 100 manufactured through Figures 2 and 3 has a relatively higher manufacturing cost because multiple types of additive elements A are added in multiple steps, but it is preferable because it is possible to control the depth profile of each additive element A more accurately.

[0127] (Embodiment 2) [Lithium-ion battery] A lithium-ion battery that can be manufactured according to one aspect of the present invention comprises a positive electrode, a negative electrode, and an electrolyte. If the electrolyte contains an electrolyte solution, a separator is provided between the positive electrode and the negative electrode. Furthermore, it may have an outer casing that covers at least a portion of the area around the positive electrode, the negative electrode, and the electrolyte.

[0128] This embodiment focuses on describing the configuration of a lithium-ion battery necessary to realize a lithium-ion battery that has excellent discharge characteristics even in low-temperature environments (for example, below 0°C, below -20°C, preferably below -30°C, more preferably below -40°C, even more preferably below -50°C, and most preferably below -60°C) and / or a lithium-ion battery that has excellent charging characteristics even in low-temperature environments. Specifically, the positive electrode active material contained in the positive electrode and the electrolyte will be described. Details of the configuration of the lithium-ion battery other than the positive electrode active material and electrolyte will be described in Embodiment 3.

[0129] [Positive electrode] The positive electrode comprises a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer contains a positive electrode active material and may further contain at least one of a conductive material and a binder.

[0130] <Cathode active material> The positive electrode active material has the function of taking in and / or releasing lithium ions during charging and / or discharging. In one embodiment of the present invention, the positive electrode active material used can be a material that does not degrade much (or a material that does not increase resistance much) during charging and / or discharging (hereinafter also referred to as "charging and discharging") in low-temperature environments, even at high charging voltages (hereinafter also referred to as "high charging voltage"). Specifically, a positive electrode active material (composite oxide) with a particle size (strictly speaking, median diameter (D50)) of 12 μm or less (preferably 10.5 μm or less, more preferably 8 μm or less) obtained by the manufacturing method described in Embodiment 1 can be used. This positive electrode active material contains additive element A, or a first additive element A1 and a second additive element A2.

[0131] Furthermore, if the particle size of the positive electrode active material is too small, coating during positive electrode fabrication may become difficult. Alternatively, if the particle size of the positive electrode active material is too small, the surface area may become too large, potentially leading to excessive reaction between the positive electrode active material surface and the electrolyte. Or, if the particle size of the positive electrode active material is too small, it may become necessary to mix in a large amount of conductive material that acts as a conductive path between particles, potentially leading to a decrease in capacity. For these reasons, the particle size (median diameter (D50)) of the positive electrode active material is preferably 1 μm or larger.

[0132] Unless otherwise specified in this specification, "charging voltage" shall be expressed with respect to the potential of lithium metal. Furthermore, in this specification, "high charging voltage" refers to a charging voltage of, for example, 4.6V or higher, preferably 4.65V or higher, more preferably 4.7V or higher, even more preferably 4.75V or higher, and most preferably 4.8V or higher. It should be noted that the positive electrode active material may be made of two or more materials with different particle sizes and / or compositions, provided that the material exhibits little degradation during charging and discharging, even at high charging voltages. In this specification, "different compositions" includes not only cases where the elemental composition of the materials is different, but also cases where the elemental composition of the materials is the same, but the proportions of the elements differ.

[0133] Furthermore, as stated above, in this specification, "high charging voltage" is defined as 4.6V or higher based on the potential when the negative electrode is lithium metal. However, when the negative electrode is a carbon material (e.g., graphite), 4.5V or higher will be referred to as "high charging voltage." In short, in the case of a half-cell using lithium metal as the negative electrode, a charging voltage of 4.6V or higher will be called a high charging voltage, and in the case of a full-cell using a carbon material (e.g., graphite) as the negative electrode, a charging voltage of 4.5V or higher will be called a high charging voltage.

[0134] Even with a high charging voltage, a lithium-ion battery with a large discharge capacity even at low temperatures can be realized by using a material as the positive electrode active material that exhibits little degradation (or little increase in resistance) during charging and discharging in low-temperature environments (e.g., 0°C, -20°C, preferably -30°C, more preferably -40°C, even more preferably -50°C, most preferably -60°C). Alternatively, a lithium-ion battery can be realized in which the discharge capacity value in low-temperature environments (e.g., 0°C, -20°C, preferably -30°C, more preferably -40°C, even more preferably -50°C, most preferably -60°C) is 50% or more (preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, most preferably 90% or more) compared to the discharge capacity value at 25°C. Note that the measurement conditions for the discharge capacity value in low-temperature environments and the discharge capacity value at 25°C are the same except for the discharge temperature (hereinafter referred to as "discharge temperature" in this specification, etc.).

[0135] Alternatively, a lithium-ion battery with a high discharge energy density can be realized even in low-temperature environments (e.g., 0°C, -20°C, preferably -30°C, more preferably -40°C, even more preferably -50°C, most preferably -60°C). Alternatively, a lithium-ion battery can be realized in which the discharge energy density value in low-temperature environments (e.g., 0°C, -20°C, preferably -30°C, more preferably -40°C, even more preferably -50°C, most preferably -60°C) is 50% or more (preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, most preferably 90% or more) compared to the discharge energy density value at 25°C. Note that the measurement conditions other than the temperature during discharge are the same for the discharge energy density value in low-temperature environments and the discharge energy density value at 25°C.

[0136] In this specification, the charging or discharging temperature refers to the temperature of the lithium-ion battery. When measuring battery characteristics at various temperatures, one example is to use a constant temperature bath that maintains a stable temperature at the desired temperature, place the battery to be measured (e.g., a test battery or half-cell) inside the bath, and then begin measurement after a sufficient amount of time (e.g., 1 hour or more) has elapsed until the test cell reaches the same temperature as the bath. However, the measurement is not necessarily limited to this method.

[0137] <Electrolytes> In one aspect of the present invention, the electrolyte used can be a material that exhibits excellent lithium-ion conductivity even when charging and / or discharging (charging and discharging) in a low-temperature environment (for example, 0°C, -20°C, preferably -30°C, more preferably -40°C, even more preferably -50°C, and most preferably -60°C).

[0138] An example of an electrolyte is described below. The electrolyte described in this embodiment, as an example, is a lithium salt dissolved in an organic solvent, and can also be called an electrolyte solution. Furthermore, the electrolyte is not limited to a liquid electrolyte (electrolyte solution) that is liquid at room temperature; a solid electrolyte can also be used. Alternatively, an electrolyte (semi-solid electrochemical substance) containing both a liquid electrolyte (liquid at room temperature) and a solid electrolyte (solid at room temperature) can be used.

[0139] As an example, the organic solvent described in this embodiment includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). When the total content of the ethylene carbonate, the ethyl methyl carbonate, and the dimethyl carbonate is 100 vol%, the volume ratio of the ethylene carbonate, the ethyl methyl carbonate, and the dimethyl carbonate is x:y:100 - x - y (where 5 ≤ x ≤ 35 and 0 < y < 65). Specifically, an organic solvent containing EC, EMC, and DMC in a volume ratio of EC:EMC:DMC = 30:35:35 can be used. The above volume ratio may be the volume ratio before mixing the organic solvents, and the outside air temperature when mixing the organic solvents may be room temperature (typically 25°C).

[0140] EC is a cyclic carbonate and has a high relative dielectric constant, so it has the effect of promoting the dissociation of lithium salts. On the other hand, EC has a high viscosity and a high freezing point (melting point) of 38°C. Therefore, when using EC alone as an organic solvent, it is difficult to use it in a low-temperature environment. Thus, the organic solvent specifically described as one aspect of the present invention contains not only EC alone but also further contains EMC and DMC. EMC is a chain carbonate and has the effect of lowering the viscosity of the electrolyte, and its freezing point is -54°C. Also, DMC is also a chain carbonate and has the effect of lowering the viscosity of the electrolyte, and its freezing point is -43°C. An electrolyte prepared using an organic solvent obtained by mixing EC, EMC, and DMC having such physical properties with the total content of these three organic solvents being 100 vol% and the volume ratio being x:y:100 - x - y (where 5 ≤ x ≤ 35 and 0 < y < 65) has the characteristic that its freezing point is -40°C or lower.

[0141] Conventional electrolytes used in lithium-ion batteries solidify at around -20°C, making it difficult to manufacture batteries that can be charged and discharged at -40°C. The electrolyte described as an example in this embodiment has a solidification point of -40°C or lower, thus enabling the creation of lithium-ion batteries that can be charged and discharged even in extremely low-temperature environments of -40°C.

[0142] Furthermore, examples of lithium salts to be dissolved in the above solvent include LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, and Li2B. 10 Cl 10 Li2B 12 Cl 12 At least one lithium salt from LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, and lithium bis(oxalate)borate (LiBOB) can be used in any combination and ratio.

[0143] Furthermore, it is preferable that the electrolyte has a low content of particulate waste or elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities") and is highly purified. 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.

[0144] Furthermore, to improve safety and other purposes, additives such as vinylene carbonate (VC), propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate) borate (LiBOB), or dinitrile compounds such as succinonitrile or adiponitrile may be added to the electrolyte to form a film (Solid Electrolyte Interphase) at the interface between the electrode (active material layer) and the electrolyte. The concentration of the additive should be, for example, 0.1 wt% to 5 wt% relative to the organic solvent.

[0145] As described above, an example of an electrolyte that can be used in a lithium-ion battery according to one aspect of the present invention has been explained. However, the electrolytes that can be used in a lithium-ion battery according to one aspect of the present invention are not limited to this example. Other materials can also be used as long as they have excellent lithium-ion conductivity even when charging and discharging in low-temperature environments.

[0146] A lithium-ion battery according to one aspect of the present invention, by including at least the above-mentioned positive electrode active material and electrolyte, can realize a lithium-ion battery that has excellent discharge characteristics even in low-temperature environments, and / or a lithium-ion battery that has excellent charging characteristics even in low-temperature environments. More specifically, when a test battery is made containing at least the positive electrode active material and electrolyte described above, and lithium metal is used as the negative electrode, it is possible to realize a lithium-ion battery in which the discharge capacity obtained by constantly charging the test battery at a charge rate of 0.1C or 0.2C (where 1C = 200mA / g) until it reaches a voltage of 4.6V in a 25°C environment, and then discharging it at a constant current rate of 0.1C until it reaches a voltage of 2.5V in a -40°C environment, is 50% or more compared to the discharge capacity obtained by constantly charging the test battery at a charge rate of 0.1C or 0.2C (where 1C = 200mA / g) until it reaches a voltage of 4.6V in a 25°C environment, and then discharging it at a constant current rate of 0.1C until it reaches a voltage of 2.5V in a 25°C environment. In this specification, etc., if the discharge capacity at T°C (where T is any temperature other than 25°C) is 50% or more compared to the discharge capacity at a 25°C environment, then the lithium-ion battery is said to be operable at T°C.

[0147] The contents of this embodiment can be freely combined with the contents of other embodiments.

[0148] (Embodiment 3) In this embodiment, each element constituting the lithium-ion battery will be described.

[0149] [Positive electrode] The positive electrode comprises a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer contains a positive electrode active material and may further contain at least one of a conductive material and a binder. The positive electrode active material can be the one described in Embodiment 1.

[0150] Figure 4A shows an example of a schematic diagram of the cross-section of the positive electrode.

[0151] The current collector 550 can be made of, for example, metal foil. The positive electrode can be formed by applying a slurry to the metal foil and drying it. Pressing may also be applied after drying. The positive electrode is formed by creating an active material layer on the current collector 550.

[0152] A slurry is a liquid material used to form an active material layer on a current collector 550, and it contains an active material, a binder, and a solvent, preferably further mixed with a conductive material. The slurry is also sometimes called an electrode slurry or an active material slurry. 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.

[0153] The positive electrode active material 561 has the function of taking in and / or releasing lithium ions during charging and discharging. In one embodiment of the present invention, the positive electrode active material 561 used can be a material that does not degrade much with charging and discharging, even at high charging voltages. In this specification, unless otherwise specified, the charging voltage is expressed with respect to the potential of the lithium metal. In this specification, a high charging voltage is, for example, a charging voltage of 4.6V or higher, preferably 4.65V or higher, more preferably 4.7V or higher, even more preferably 4.75V or higher, and most preferably 4.8V or higher.

[0154] The positive electrode active material 561 used in one embodiment of the present invention can be any material that exhibits little degradation during charging and discharging, even at high charging voltages, and can be the one described in Embodiment 1 or Embodiment 2. Furthermore, the positive electrode active material 561 can be made from two or more materials with different particle sizes, as long as it exhibits little degradation during charging and discharging, even at high charging voltages.

[0155] Conductive materials, also called conductivity imparters or conductivity enhancers, can be made of carbon. By attaching a conductive material between multiple active materials, the multiple active materials are electrically connected to each other, thereby increasing conductivity. In this specification, "attachment" refers not only to physical contact between the active material and the conductive material, but also to cases where covalent bonding occurs, bonding occurs due to van der Waals forces, the conductive material covers a portion of the surface of the active material, the conductive material fits into surface irregularities of the active material, or where they are electrically connected even if they are not in contact with each other.

[0156] Specific examples of carbon materials that can be used as conductive materials include carbon black (furnace black, acetylene black, graphite, etc.).

[0157] Figure 4A illustrates carbon black 553, an example of a conductive material, and the electrolyte 571 contained in the void between the positive electrode active materials 561.

[0158] As the positive electrode of a secondary battery, a binder (resin) may be mixed to fix the current collector 550, such as metal foil, and the active material. The binder is also called a binding agent. The binder is a polymer material, and if a large amount of binder is included, the proportion of active material in the positive electrode decreases, reducing the discharge capacity of the secondary battery. Therefore, it is preferable to mix in the minimum amount of binder. In Figure 4A, the areas not filled with the positive electrode active material 561, the second positive electrode active material 562, and carbon black 553 represent voids or binder.

[0159] Although Figure 4A shows an example where the positive electrode active material 561 is spherical, it is not particularly limited. For example, the cross-sectional shape of the positive electrode active material 561 may be elliptical, rectangular, trapezoidal, conical, a polygon with rounded corners, or asymmetrical. For example, Figure 4B shows an example where the positive electrode active material 561 has the shape of a polygon with rounded corners.

[0160] Furthermore, in the positive electrode shown in Figure 4B, graphene 554 is used as the carbon material used as the conductive material. Figure 4B shows a positive electrode active material layer formed on the current collector 550, comprising positive electrode active material 561, graphene 554, and carbon black 553.

[0161] In the step of mixing graphene 554 and carbon black 553 to obtain an electrode slurry, it is preferable that the weight of the carbon black to be mixed be 1.5 times or more and 20 times or less the weight of the graphene, preferably 2 times or more and 9.5 times or less.

[0162] Furthermore, when the mixture of graphene 554 and carbon black 553 is within the above range, the dispersion stability of carbon black 553 is excellent during slurry preparation, and aggregation is less likely to occur. Also, when the mixture of graphene 554 and carbon black 553 is within the above range, a higher electrode density can be achieved compared to a positive electrode using only carbon black 553 as the conductive material. By increasing the electrode density, the volume per unit weight can be increased. Specifically, the density of the positive electrode active material layer measured by gravimetric measurement can be 3.5 g / cc or higher.

[0163] Furthermore, although the electrode density is lower compared to positive electrodes using only graphene as the conductive material, rapid charging can be achieved by using a mixture of the first carbon material (graphene) and the second carbon material (acetylene black) within the above range. For this reason, it is particularly effective when used as a secondary battery for automobiles.

[0164] Figure 4C illustrates an example of a cathode using carbon fiber 555 instead of graphene. Figure 4C shows a different example from Figure 4B. Using carbon fiber 555 prevents aggregation of carbon black 553 and improves dispersibility.

[0165] In Figure 4C, the areas not filled with the positive electrode active material 561, carbon fiber 555, and carbon black 553 represent voids or binders.

[0166] Furthermore, Figure 4D illustrates another example of a cathode. Figure 4C shows an example in which carbon fiber 555 is used in addition to graphene 554. Using both graphene 554 and carbon fiber 555 can prevent aggregation of carbon black such as carbon black 553 and further improve dispersibility.

[0167] In Figure 4D, the areas not filled with the positive electrode active material 561, carbon fiber 555, graphene 554, and carbon black 553 represent voids or binders.

[0168] A secondary battery can be manufactured by using one of the positive electrodes shown in Figures 4A to 4D, placing a separator on top of the positive electrode, and placing the resulting laminate on top of the separator, then placing it in a container (such as an outer casing or metal can), and filling the container with electrolyte.

[0169] <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.

[0170] Furthermore, it is preferable to use a water-soluble polymer as the binder. Examples of water-soluble polymers include polysaccharides. Examples of polysaccharides include cellulose derivatives such as carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, diacetylcellulose, and regenerated cellulose, or starch. It is even preferable to use these water-soluble polymers in combination with the aforementioned rubber material.

[0171] 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.

[0172] You may use a combination of several of the binders mentioned above.

[0173] 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.

[0174] Furthermore, cellulose derivatives such as carboxymethylcellulose can be made more soluble by using salts such as sodium or ammonium salts of carboxymethylcellulose, thereby increasing their effectiveness as viscosity modifiers. Increased solubility also improves the dispersibility with active materials or other components when preparing electrode slurries. In this specification, cellulose and cellulose derivatives used as electrode binders include their salts.

[0175] Water-soluble polymers stabilize viscosity by dissolving in water, allowing for stable dispersion of active materials and other materials used as binders, such as styrene-butadiene rubber, in aqueous solutions. Furthermore, their functional groups are expected to facilitate stable adsorption to the surface of the active material. Additionally, cellulose derivatives such as carboxymethylcellulose often possess functional groups like hydroxyl or carboxyl groups, and these functional groups allow the polymers to interact with each other, resulting in a broad coverage of the active material surface.

[0176] 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.

[0177] <Positive electrode current collector> As the positive electrode 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 positive electrode current collector can be in various shapes, such as foil, plate, sheet, mesh, perforated metal, or expanded metal. The positive electrode current collector should preferably have a thickness of 5 μm to 30 μm.

[0178] [Negative electrode] The negative electrode comprises a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also contain a negative electrode active material, a conductive material, and a binder.

[0179] <Negative electrode active material> For example, alloy materials or carbon materials can be used as the negative electrode active material.

[0180] Furthermore, the negative electrode active material can be an element capable of undergoing charge-discharge reactions through alloying and dealloying reactions with lithium. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc., can be used. Such elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4200 mAh / g. For this reason, it is preferable to use silicon as the negative electrode active material. Compounds containing these elements may also be used. 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.

[0181] 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.

[0182] Carbon materials such as graphite, easily graphitizable carbon (soft carbon), difficult-to-graphitize carbon (hard carbon), carbon fibers (carbon nanotubes), graphene, and carbon black can be used.

[0183] Graphite can be artificial graphite or natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Spheroidal graphite, which has a spherical shape, can be used as the artificial graphite. For example, MCMB may have a spherical shape and is therefore preferable. Furthermore, it is relatively easy to reduce the surface area of ​​MCMB, which may also be preferable. Examples of natural graphite include flake graphite and spheroidized natural graphite.

[0184] When lithium ions are inserted into graphite (during the formation of lithium-graphite intercalation compounds), graphite exhibits a potential as low as that of lithium metal (0.05V to 0.3V vs. Li / Li). + This allows lithium-ion batteries using graphite to exhibit a high operating voltage. Furthermore, graphite is preferable because it has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and higher safety compared to lithium metal.

[0185] Furthermore, titanium dioxide (TiO2) and lithium titanium oxide (Li4Ti5O2) are used as negative electrode active materials. 12 ), lithium-graphite intercalation compound (Li x Oxides such as C6, niobium pentoxide (Nb2O5), tungsten oxide (WO2), and molybdenum oxide (MoO2) can be used.

[0186] Furthermore, as the negative electrode active material, a Li3N type structure is used, which is a lithium and transition metal binitride. 3-x M x N(M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 has a large discharge capacity (900mAh / g, 1890mAh / cm²). 3 ) indicates a preference.

[0187] 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.

[0188] 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.

[0189] The conductive material and binder that the negative electrode active material layer can have can be the same materials as the conductive material and binder that the positive electrode active material layer can have.

[0190] <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.

[0191] [Electrolyte] The electrolyte can be the one described in Embodiment 1.

[0192] [Separator] When the electrolyte contains an electrolyte solution, a separator is placed between the positive and negative electrodes. The separator can be made from materials such as paper or other cellulose fibers, nonwoven fabrics, glass fibers, ceramics, or synthetic fibers made from 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.

[0193] 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).

[0194] 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.

[0195] 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.

[0196] 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.

[0197] [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.

[0198] (Embodiment 4) In this embodiment, we will describe an example of the shape of a secondary battery having a positive electrode manufactured by the manufacturing method described in the previous embodiment.

[0199] [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.

[0200] Note that Figure 5A is a schematic diagram to show the overlapping (upper-down and positional) relationships of the components for clarity. Therefore, Figures 5A and 5B are not perfectly identical corresponding diagrams.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] Figure 5B is a perspective view of the completed coin-type rechargeable battery.

[0205] 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.

[0206] 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.

[0207] 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 or aluminum to prevent corrosion caused 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.

[0208] 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 pressed together via a gasket 303 to manufacture a coin-type secondary battery 300.

[0209] By having the above configuration, a coin-type secondary battery 300 can be made that has high capacity, high discharge capacity, and excellent cycle characteristics.

[0210] [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.

[0211] 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 601 and the battery casing (outer casing) 602 are insulated from each other by a gasket (insulating packing) 610.

[0212] 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, 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 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 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.

[0213] 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.

[0214] By using the positive electrode active material 100 obtained in Embodiments 1 and 2 as the positive electrode 604, a cylindrical secondary battery 616 with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0215] 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.

[0216] 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 charge / discharge control circuit that performs charging and discharging, or a protection circuit that prevents overcharging and / or over-discharging.

[0217] 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.

[0218] Multiple secondary batteries 616 may be connected in parallel and then further connected in series.

[0219] Furthermore, a temperature control device may be provided between the multiple secondary batteries 616. When a secondary battery 616 overheats, it can be cooled by the temperature control device, and when a secondary battery 616 becomes too cold, it can be heated by the temperature control device. This makes the performance of the energy storage system 615 less susceptible to the influence of ambient temperature.

[0220] 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.

[0221] [Other structural examples of secondary batteries] Examples of secondary battery structures will be explained using Figures 7 and 8.

[0222] 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.

[0223] 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.

[0224] 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.

[0225] 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.

[0226] Alternatively, the secondary battery 913 may have a wound body 950a as shown in Figure 8. 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.

[0227] By using the positive electrode active material 100 obtained in Embodiments 1 and 2 as the positive electrode 932, a secondary battery 913 with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0228] 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.

[0229] As shown in Figure 8B, the negative electrode 931 is electrically connected to terminal 951 by ultrasonic bonding, welding, or crimping. Terminal 951 is electrically connected to terminal 911a. The positive electrode 932 is electrically connected to terminal 952 by ultrasonic bonding, welding, or crimping. Terminal 952 is electrically connected to terminal 911b.

[0230] 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.

[0231] 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 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.

[0232] <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. Figures 9A and 9B show a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511.

[0233] 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. Note that the area or shape of the tab regions of the positive and negative electrodes are not limited to the example shown in Figure 10A.

[0234] <Method for manufacturing laminated rechargeable batteries> 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.

[0235] 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.

[0236] Next, the negative electrode 506, separator 507, and positive electrode 503 are placed on the outer casing 509.

[0237] 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.

[0238] Next, the electrolyte is introduced into the inside of the outer casing 509 through an inlet provided in the outer casing 509. It is preferable to introduce the electrolyte under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is sealed. In this way, a laminate-type secondary battery 500 can be manufactured.

[0239] By using the positive electrode active material 100 obtained in Embodiments 1 and 2 as the positive electrode 503, a secondary battery 500 with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0240] [Example of a battery pack] An example of a secondary battery pack according to one embodiment of the present invention, which is capable of wireless charging using an antenna, will be explained with reference to Figure 11.

[0241] Figure 11A shows the external appearance of the secondary battery pack 531, which has a thin rectangular parallelepiped shape (it can also be called a thick flat plate shape). Figure 11B is a diagram illustrating 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. The secondary battery pack 531 also has an antenna 517.

[0242] The internal structure of the secondary battery 513 may have a wound structure or a laminated structure.

[0243] In the secondary battery pack 531, for example as shown in Figure 11B, a control circuit 590 is located on the circuit board 540. The circuit board 540 is electrically connected to terminal 514. The circuit board 540 is also electrically connected to the antenna 517, one of the positive and negative leads 551 of the secondary battery 513, and the other of the positive and negative leads 552.

[0244] Alternatively, as shown in Figure 11C, the system 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 terminals 514.

[0245] The antenna 517 is not limited to a coil shape; for example, it may be linear or plate-shaped. Alternatively, antennas such as planar antennas, aperture antennas, traveling wave antennas, EH antennas, magnetic field antennas, and dielectric antennas may be used. Alternatively, the antenna 517 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. In other words, the antenna 517 may function as one of the two conductors of the capacitor. This allows for power exchange not only through electromagnetic and magnetic fields, but also through electric fields.

[0246] The secondary battery pack 531 has a layer 519 between the antenna 517 and the secondary battery 513. The layer 519 has the function of shielding, for example, the electromagnetic field from the secondary battery 513. For the layer 519, a magnetic material can be used, for example.

[0247] (Embodiment 5) This embodiment is a different example from Figure 6D, which shows a cylindrical secondary battery. Figure 12C shows an example of its application to an electric vehicle (EV).

[0248] 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.

[0249] The internal structure of the first battery 1301a may be a wound type as shown in Figure 7C or Figure 8A, 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 6. Using the all-solid-state battery of Embodiment 6 for the first battery 1301a allows for higher capacity, improved safety, and miniaturization and weight reduction.

[0250] 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.

[0251] Furthermore, in the vehicle-mounted secondary battery, a service plug or circuit breaker that can cut off high voltage without using tools is provided in order to interrupt the power from multiple secondary batteries, and this is installed in the first battery 1301a.

[0252] 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.

[0253] Furthermore, the second battery 1311 supplies power to 14V automotive components (such as audio equipment 1313, power windows 1314, and lights 1315) via the DC-DC circuit 1310.

[0254] Next, the first battery 1301a will be explained using Figure 12A.

[0255] Figure 12A shows an example where nine rectangular secondary batteries 1300 are arranged in a single battery pack 1415. In this example, nine rectangular secondary batteries 1300 are connected in series, with one electrode fixed by an insulating fixing part 1413 and the other electrode fixed by an insulating fixing part 1414. While this embodiment shows an example of fixing with fixing parts 1413 and 1414, the batteries may also be housed in a battery housing box (also called a casing). Since vehicles are expected to be subjected to vibrations or shaking from external sources (such as the road surface), it is preferable to fix multiple secondary batteries using fixing parts 1413 and 1414 or a battery housing box. Furthermore, one electrode is electrically connected to the control circuit unit 1320 by wiring 1421, and the other electrode is electrically connected to the control circuit unit 1320 by wiring 1422.

[0256] 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).

[0257] It is preferable to use a metal oxide that functions as an oxide semiconductor. For example, as the oxide, it is advisable to use a metal oxide such as an In-M-Zn oxide (element M is selected from one or more of aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or magnesium, etc.). In particular, the In-M-Zn oxide applicable as the oxide is preferably CAAC-OS (C-Axis Aligned Crystal Oxide Semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor). Also, as the oxide, In-Ga oxide or In-Zn oxide may be used. CAAC-OS is an oxide semiconductor having a plurality of crystal regions, and the c-axis of the plurality of crystal regions is oriented in a specific direction. Here, the specific direction is the thickness direction of the CAAC-OS film, the normal direction of the surface on which the CAAC-OS film is formed, or the normal direction of the surface of the CAAC-OS film. Also, the crystal region is a region having periodicity in the atomic arrangement. When the atomic arrangement is regarded as a lattice arrangement, the crystal region is also a region where the lattice arrangements are aligned.

[0258] Note that "CAC-OS" becomes mosaic-like when the material separates into the first region and the second region, and the first region has a structure distributed in the film (hereinafter also referred to as cloud-like). That is, CAC-OS is a composite metal oxide having a structure in which the first region and the second region are mixed. However, it may be difficult to observe a clear boundary between the first region and the second region.

[0259] For example, in the CAC-OS of In-Ga-Zn oxide, it can be confirmed by EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX: Energy Dispersive X-ray spectroscopy) that the region mainly composed of In (the first region) and the region mainly composed of Ga (the second region) are unevenly distributed and have a mixed structure.

[0260] When CAC-OS is used in a transistor, the conductivity resulting from the first region and the insulating property resulting from the second region act complementarily to impart a switching function (on / off function) to the CAC-OS. That is, CAC-OS has a conductive function in a part of the material and an insulating function in a part of the material, and has a semiconductor function as a whole. By separating the conductive function and the insulating function, both functions can be enhanced to the maximum extent. Therefore, by using CAC-OS in a transistor, a high on-current (I on ), a high field-effect mobility (μ), and a good switching operation can be realized.

[0261] Oxide semiconductors have various structures and each has different characteristics. The oxide semiconductor according to one aspect of the present invention may have two or more of amorphous oxide semiconductors, polycrystalline oxide semiconductors, a-like OS, CAC-OS, nc-OS, and CAAC-OS.

[0262] 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 that uses the positive electrode active material 100 obtained in Embodiments 1 and 2 as the positive electrode. A secondary battery and control circuit unit 1320 using the positive electrode active material 100 obtained in Embodiments 1 and 2 as the positive electrode can greatly contribute to eliminating accidents such as fires caused by secondary batteries.

[0263] 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 causes of secondary battery instability include overcharging prevention, overcurrent prevention, overheating 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, charging current control 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.

[0264] Furthermore, "micro-short" refers to a tiny short circuit inside a secondary battery. It does not mean that the positive and negative electrodes of the secondary battery are short-circuited, making charging and discharging impossible. Rather, it refers to a phenomenon where a small short-circuit current flows through a tiny short circuit. Because even a relatively short-circuit and small area can cause a large voltage change, the abnormal voltage value may affect subsequent estimations.

[0265] 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.

[0266] 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.

[0267] Next, Figure 12B shows an example of a block diagram of the battery pack 1415 shown in Figure 12A.

[0268] The control circuit unit 1320 includes at least a switch to prevent overcharging, a switch unit 1324 including a switch to prevent over-discharging, a control circuit 1322 that controls the switch unit 1324, and a voltage measurement unit for the first battery 1301a. The control circuit unit 1320 has upper and lower voltage limits set for the secondary battery used, and limits the upper limit of external current or the upper limit of output current to the outside. Within the range between the lower voltage limit and the upper voltage limit of the secondary battery, it is within the voltage range for which use is recommended, and if it goes outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit unit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent over-discharge and / or overcharge. For example, if the control circuit 1322 detects a voltage that is likely to cause overcharging, it cuts off the current by turning off the switch 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).

[0269] The switch section 1324 can be constructed by combining n-channel or p-channel transistors. The switch section 1324 is not limited to switches using Si transistors made of single-crystal silicon, but may also be formed using power transistors made of, for example, Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaOx (gallium oxide; x is a real number greater than 0), etc. Furthermore, since memory elements using OS transistors can be freely arranged by stacking them on circuits using Si transistors, integration can be easily achieved. Also, since OS transistors can be manufactured using the same manufacturing equipment as Si transistors, they can be manufactured at low cost. That is, by stacking a control circuit section 1320 using OS transistors on the switch section 1324 and integrating them, it is possible to create a single chip. This makes it possible to reduce the occupied volume of the control circuit section 1320, thus enabling miniaturization.

[0270] The first batteries 1301a and 1301b primarily supply power to 42V (high-voltage) onboard equipment, while the second battery 1311 supplies power to 14V (low-voltage) onboard equipment. Lead-acid batteries are often used for the second battery 1311 due to their cost advantages. Lead-acid batteries have the disadvantage of higher self-discharge and are more susceptible to degradation due to a phenomenon called sulfation compared to lithium-ion batteries. Using a lithium-ion battery for the second battery 1311 offers the advantage of being maintenance-free, but after long-term use, for example more than three years, there is a risk of malfunctions occurring that are difficult to detect at the time of manufacture. In particular, if the second battery 1311, which starts the inverter, becomes inoperable, it will be impossible to start the motor even if the first batteries 1301a and 1301b have remaining capacity. To prevent this, if the second battery 1311 is a lead-acid battery, power is supplied from the first battery to the second battery to keep it constantly charged to a full state.

[0271] This embodiment shows an example in which lithium-ion batteries are used for both the first battery 1301a and the second battery 1311. The second battery 1311 may be a lead-acid battery, an all-solid-state battery, or an electric double-layer capacitor. For example, the all-solid-state battery of Embodiment 6 may be used. By using the all-solid-state battery of Embodiment 6 for the second battery 1311, high capacity can be achieved, and the device can be made smaller and lighter.

[0272] Furthermore, the regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305 and charged to the second battery 1311 via the control circuit unit 1321 from the motor controller 1303 or the battery controller 1302. Alternatively, it is charged to the first battery 1301a via the control circuit unit 1320 from the battery controller 1302. Alternatively, it is charged to the first battery 1301b via the control circuit unit 1320 from the battery controller 1302. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b are capable of rapid charging.

[0273] 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.

[0274] 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.

[0275] External chargers installed at charging stations and other locations may have 100V-200V outlets, or 3-phase 200V and 50kW power supplies. Additionally, it is possible to charge by receiving power from external charging equipment using contactless power supply methods.

[0276] For rapid charging, a rechargeable battery capable of withstanding high-voltage charging is desired to achieve short charging times.

[0277] Furthermore, by using graphene as a conductive material, it is possible to suppress capacity degradation even when the electrode layer is thickened and the load is increased, and maintain high capacity. As a synergistic effect, this can result in a secondary battery with significantly improved electrical characteristics. This is particularly effective for secondary batteries used in vehicles, and it is possible to provide vehicles with a long driving range, specifically a driving range of 500 km or more on a single charge, without increasing the ratio of the weight of the secondary battery to the total weight of the vehicle.

[0278] 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 Embodiments 1 and 2, and can increase its usable capacity as the charging voltage increases. Furthermore, by using the positive electrode active material 100 described in Embodiments 1 and 2 as the positive electrode, a secondary battery for vehicles with excellent cycle characteristics can be provided.

[0279] Next, we will describe an example in which a secondary battery, which is one aspect of the present invention, is implemented in a vehicle, typically a transport vehicle.

[0280] By installing a secondary battery as shown in any one of Figures 6D, 8C, or 12A into a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV) can be realized. Furthermore, secondary batteries can also be installed in agricultural machinery, motorized bicycles including electric-assist bicycles, motorcycles, electric wheelchairs, electric carts, ships, submarines, aircraft, rockets, satellites, space probes, planetary probes, or spacecraft. A secondary battery according to one embodiment of the present invention can be a high-capacity secondary battery. Therefore, a secondary battery according to one embodiment of the present invention is suitable for miniaturization and weight reduction, and can be suitably used in transport vehicles.

[0281] Figures 13A to 13D illustrate a transport vehicle using one embodiment of the present invention. The automobile 2001 shown in Figure 13A 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 13A 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.

[0282] In addition, the motor vehicle 2001 can be charged by receiving power supply from an external charging facility to the secondary battery of the motor vehicle 2001 by means of a plug-in method, a non-contact power supply method, or the like. When charging, the charging method, the standard of the connector, etc. may be appropriately carried out in a predetermined method such as CHAdeMO (registered trademark) or Combo. The secondary battery may be a charging station provided in a commercial facility or a household power source. For example, by plug-in technology, the power storage device mounted on the motor vehicle 2001 can be charged by external power supply. Charging can be performed by converting AC power into DC power through a conversion device such as an AC-DC converter.

[0283] Also, although not shown, a power receiving device can be mounted on the vehicle, and power can be supplied non-contact from a power transmission device on the ground for charging. In the case of this non-contact power supply method, by incorporating the power transmission device into the road or the outer wall, charging can be performed not only while the vehicle is stopped but also while it is running. Also, power transmission and reception can be performed between two vehicles using this non-contact power supply method. Furthermore, a solar cell may be provided on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped or running. For such non-contact power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0284] FIG. 13B shows a large transport vehicle 2002 having an electrically controlled motor as an example of a transport vehicle. The secondary battery module of the transport vehicle 2002 has, for example, four secondary batteries with a nominal voltage of 3.0 V or more and 5.0 V or less as cell units, and a maximum voltage of 170 V with 48 cells connected in series. Since it has the same functions as FIG. 13A except that the number of secondary batteries constituting the secondary battery module of the battery pack 2201 is different, the description is omitted.

[0285] Figure 13C shows a large transport vehicle 2003 equipped with an electrically controlled motor as an example. The secondary battery module of the transport vehicle 2003 has a maximum voltage of 600V, achieved by connecting more than 100 secondary batteries with a nominal voltage of 3.0V to 5.0V in series. Therefore, secondary batteries with small variation in characteristics are required. By using a secondary battery that uses the positive electrode active material 100 described in Embodiments 1 and 2 as the positive electrode, it is possible to manufacture a secondary battery with stable battery characteristics, enabling low-cost mass production from a yield standpoint. 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.

[0286] Figure 13D shows an example of an aircraft 2004 having a fuel-burning engine. The aircraft 2004 shown in Figure 13D can be considered a type of transport vehicle because it has wheels for takeoff and landing, and has a battery pack 2203 which includes a secondary battery module formed by connecting multiple secondary batteries and a charging control device.

[0287] The secondary battery module of aircraft 2004 has a maximum voltage of 32V, for example, by connecting eight 4V secondary batteries in series. The secondary battery module of battery pack 2203 has the same functions as Figure 13A, except for differences in the number of secondary batteries that make up the module, so a detailed explanation is omitted.

[0288] Figure 13E shows an example of a satellite 2005 equipped with a secondary battery 2204. Since satellite 2005 will be used in the extremely cold environment of outer space, it is preferable to equip it with a secondary battery 2204, which is one embodiment of the present invention and has excellent low-temperature resistance. Furthermore, it is even more preferable that the secondary battery 2204 is mounted inside satellite 2005, covered with a heat-insulating material.

[0289] (Embodiment 6) 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 14A and 14B.

[0290] The house shown in Figure 14A 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.

[0291] 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.

[0292] Figure 14B shows an example of an energy storage device according to one aspect of the present invention. As shown in Figure 14B, 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 control circuit described in Embodiment 7 may be provided in the energy storage device 791, and a synergistic effect on safety can be obtained by using a secondary battery with the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as the positive electrode in the energy storage device 791. The control circuit described in Embodiment 7 and the secondary battery with the positive electrode active material 100 described in Embodiments 1, 2, etc. as the positive electrode can greatly contribute to eliminating accidents such as fires caused by the energy storage device 791 having a secondary battery.

[0293] 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.

[0294] 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).

[0295] General load 707 is an electrical device such as a television or personal computer, and energy storage load 708 is an electrical device such as a microwave oven, refrigerator, or air conditioner.

[0296] 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.

[0297] 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 via the router 709 on electrical equipment such as televisions or personal computers. Furthermore, it can be checked via the router 709 on portable electronic devices such as smartphones or tablets. Additionally, the amount of electricity demand predicted by the forecasting unit 712 for each time period (or hourly) can be checked on the display unit 706, electrical equipment, and portable electronic devices.

[0298] (Embodiment 7) This embodiment shows an example of mounting an energy storage device according to one aspect of the present invention on a motorcycle or bicycle.

[0299] Figure 15A shows an example of an electric bicycle using a power storage device according to one aspect of the present invention. The power storage device according to one aspect of the present invention can be applied to the electric bicycle 8700 shown in Figure 15A. The power storage device according to one aspect of the present invention includes, for example, a plurality of batteries and a protection circuit.

[0300] 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 15B shows it detached from the bicycle. The power storage device 8702 also incorporates 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 capable of controlling the charging of a secondary battery or detecting abnormalities, as exemplified in Embodiment 7. The control circuit 8704 is electrically connected to the positive and negative electrodes of the storage battery 8701. Furthermore, by combining it with a secondary battery that uses the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as the positive electrode, a synergistic effect on safety can be obtained. A secondary battery and control circuit 8704 using the positive electrode active material 100 obtained in Embodiments 1 and 2 as the positive electrode can greatly contribute to eliminating accidents such as fires caused by secondary batteries.

[0301] Figure 15C shows an example of a motorcycle using a power storage device according to one embodiment of the present invention. The scooter 8600 shown in Figure 15C 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. Furthermore, the power storage device 8602, which houses multiple secondary batteries using the positive electrode active material 100 obtained in Embodiments 1 and 2 as the positive electrode, can have a high capacity and contribute to miniaturization.

[0302] Furthermore, the scooter 8600 shown in Figure 15C 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.

[0303] (Embodiment 8) 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.

[0304] Figure 16A 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 providing a secondary battery 2107 that uses the positive electrode active material 100 described in Embodiments 1 and 2 as the positive electrode, a high capacity can be achieved, and a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0305] 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.

[0306] 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.

[0307] 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.

[0308] Furthermore, the mobile phone 2100 is equipped with an external connection port 2104, which allows it to directly exchange data with other information terminals via a connector. It can also be charged via the external connection port 2104. However, charging may be performed wirelessly without using the external connection port 2104.

[0309] Furthermore, it is preferable that the mobile phone 2100 has sensors. Preferably, the sensors include, for example, human body sensors such as fingerprint sensors, pulse sensors, and body temperature sensors, as well as touch sensors, pressure sensors, or acceleration sensors.

[0310] Figure 16B 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 obtained in Embodiments 1 and 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 an unmanned aerial vehicle 2300.

[0311] Figure 16C shows an example of a robot. The robot 6400 shown in Figure 16C 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, an obstacle sensor 6407, a movement mechanism 6408, a computing device, and the like.

[0312] 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.

[0313] The display unit 6405 has the function of displaying various types of information. The robot 6400 can display the user's desired information 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 enabled.

[0314] The upper camera 6403 and the lower camera 6406 have the function of imaging the area around the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize its surrounding environment and move safely using the upper camera 6403, the lower camera 6406 and the obstacle sensor 6407.

[0315] 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. A secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. 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 6409 to be mounted on the robot 6400.

[0316] Figure 16D 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.

[0317] The cleaning robot 6300 can analyze images captured by the camera 6303 to determine the presence or absence of obstacles such as walls, furniture, or steps. Furthermore, if the image analysis detects an object that may become entangled in the brush 6304, such as wiring, 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 in its internal region. A secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc., 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 6306 to be installed in the cleaning robot 6300.

[0318] Figure 17A 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.

[0319] 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 17A. The spectacle-type device 4000 has a frame 4000a and a display unit 4000b. By mounting the secondary battery in the temple portion of the curved frame 4000a, a lightweight spectacle-type device 4000 with good weight balance and a long continuous usage time can be made. A secondary battery using the positive electrode active material 100 obtained in Embodiments 1 and 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.

[0320] 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. A secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. 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.

[0321] 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. A secondary battery using the positive electrode active material 100 obtained in Embodiments 1 and 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.

[0322] 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. A secondary battery using the positive electrode active material 100 obtained in Embodiments 1 and 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.

[0323] 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. A secondary battery using the positive electrode active material 100 obtained in Embodiments 1 and 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.

[0324] Furthermore, a secondary battery according to one aspect of the present invention can be mounted in the wristwatch-type device 4005. The wristwatch-type device 4005 has a display unit 4005a and a belt unit 4005b, and the secondary battery can be provided in either the display unit 4005a or the belt unit 4005b. A secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. 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.

[0325] The display unit 4005a can display not only the time, but also various other information such as incoming emails or phone calls.

[0326] 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.

[0327] Figure 17B shows a perspective view of the wristwatch-type device 4005 after it has been removed from the arm.

[0328] A side view is also shown in Figure 17C. Figure 17C 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.

[0329] Since the wristwatch-type device 4005 is required to be small and lightweight, using the positive electrode active material 100 obtained in Embodiments 1 and 2, etc., 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. [Examples]

[0330] <Method for preparing Sample 1> In this embodiment, based on the description in Embodiment 1 and Figures 2 to 3, etc., it will be explained that a positive electrode active material 100 (Sample 1) with a median diameter (D50) of 12 μm or less can be obtained.

[0331] As the starting material lithium cobalt oxide (LiCoO2) shown in step S10 of Figure 2, commercially available lithium cobalt oxide (Cellseed C-5H, manufactured by Nippon Chemical Industrial Co., Ltd.) without any particular additive elements was prepared. Hereafter, in this specification, it will simply be referred to as "C-5H". C-5H has a median diameter (D50) of approximately 7.0 μm and satisfies the condition that the median diameter (D50) is 10 μm or less.

[0332] Next, in step S15, C-5H was placed in a pod (container), covered, and heated in a muffle furnace at 850°C for 2 hours. The muffle furnace was then subjected to an oxygen atmosphere and no flow occurred (O2 purging). When placing the C-5H into the pod, the height of the powder (also called the bulk height) inside the pod was kept to 10 mm or less and flat.

[0333] Next, the first additive element A1 source was prepared according to step S20a shown in Figure 3A. First, lithium fluoride (LiF) was prepared as the F source and magnesium fluoride (MgF2) was prepared as the Mg source. The ratio of LiF to MgF2 was weighed to 1:3 (molar ratio). Next, LiF and MgF2 were mixed in dehydrated acetone and stirred at a rotation speed of 400 rpm for 12 hours. A ball mill was used for mixing, and zirconium oxide balls were used as the grinding media. Approximately 10 g of LiF and MgF2 were added to a 45 mL container of the mixing ball mill along with 20 mL of dehydrated acetone and 22 g of zirconium oxide balls (1 mmφ) and mixed. The mixture was then sieved through a sieve with a mesh size of 300 μm to obtain the first additive element A1 source.

[0334] Next, following step S31 shown in Figure 2, the lithium cobaltate obtained by heating in step S15 (lithium cobaltate after initial heating) was mixed with the first additive element A1 source obtained in step S20a. Specifically, approximately 9 g in total was weighed so that the additive element A1 amounted to 1 mol% relative to the lithium cobaltate, and then the lithium cobaltate after initial heating and the first additive element A1 source were mixed dry. At this time, the mixture was stirred at a rotational speed of 150 rpm for 1 hour. After that, the mixture was sieved through a sieve with a mesh size of 300 μm to obtain mixture 903 (step S32).

[0335] Next, in step S33, the mixture 903 was heated. The heating conditions were 900°C for 5 hours. During heating, a lid was placed over the casing containing the mixture 903. The inside of the casing was kept in an oxygen-containing atmosphere, and the entry and exit of this oxygen was blocked (purged). By heating, a composite oxide containing Mg and F (lithium cobaltate containing Mg and F) was obtained (step S34a).

[0336] Next, a second source of additive element A2 was prepared according to step S40 shown in Figure 3C. First, nickel hydroxide (Ni(OH)2) was prepared as the Ni source, and aluminum hydroxide (Al(OH)3) was prepared as the Al source. Next, nickel hydroxide and aluminum hydroxide were stirred separately in dehydrated acetone at a rotational speed of 400 rpm for 12 hours. A ball mill was used for mixing, and zirconium oxide balls were used as the grinding media. In a 45 mL ball mill container, 20 mL of dehydrated acetone, 22 g of zirconium oxide balls (1 mmφ), and approximately 10 g of nickel hydroxide were added and stirred. Similarly, in a 45 mL ball mill container, 20 mL of dehydrated acetone, 22 g of zirconium oxide balls (1 mmφ), and approximately 10 g of aluminum hydroxide were added and stirred. After that, each was sieved using a sieve with a mesh size of 300 μm to obtain the second source of additive element A2.

[0337] Next, in step S51, the composite oxide containing Mg and F and the second additive element A2 source were mixed dry. Specifically, the mixture was stirred at a rotational speed of 150 rpm for 1 hour. The mixing ratio was such that the nickel hydroxide and aluminum hydroxide contained in the second additive element A2 source were each 0.5 mol% relative to the lithium cobaltate. A ball mill was used for mixing, and zirconium oxide balls were used as the grinding media. Approximately 7.5 g of the Ni source, Al source, and the composite oxide (lithium cobaltate containing Mg and F) obtained in step S34 were added to a 45 mL container of the mixing ball mill along with 22 g of zirconium oxide balls (1 mmφ) and mixed. Finally, the mixture was sieved through a sieve with a mesh size of 300 μm to obtain mixture 904 (step S52).

[0338] Next, in step S53, the mixture 904 was heated. The heating conditions were 850°C for 2 hours. During heating, a lid was placed over the casing containing the mixture 904. The inside of the casing was kept in an oxygen-containing atmosphere, and the entry and exit of this oxygen was blocked (purged). By heating, lithium cobaltate (complex oxide) having Mg, F, Ni, and Al was obtained (step S54). In this specification and elsewhere, the lithium cobaltate having Mg, F, Ni, and Al obtained in this example may hereafter be referred to as Sample 1.

[0339] <Median diameter of Sample 1 (D50)> Figure 18 shows the particle size distribution of Sample 1 as a solid line. The median diameter (D50) of Sample 1 was approximately 9.7 μm. As a result, it was confirmed that the median diameter (D50) of Sample 1 satisfies the requirement of 12 μm or less (10.5 μm or less). The median diameter (D50) can be measured, for example, by observation using an SEM (scanning electron microscope) or TEM, or by a particle size distribution analyzer using laser diffraction / scattering. In this example, the measurement was performed using a laser diffraction particle size distribution analyzer SALD-2200 manufactured by Shimadzu Corporation.

[0340] Figure 18 shows, as Reference Example 1, the particle size distribution of commercially available lithium cobalt oxide (Cellseed C-5H, manufactured by Nippon Chemical Industrial Co., Ltd.), which does not contain any additive elements and was used as the starting material in this example, as a dotted line. The median diameter (D50) of C-5H was approximately 7.0 μm.

[0341] <Surface SEM observation of Sample 1> Next, Figure 19A shows the (surface) SEM observation results of Sample 1. Figure 19B shows the (surface) SEM observation results of lithium cobalt oxide (C-5H), the starting material for Sample 1. In this example, the SEM observations in Figure 19A were performed using a Hitachi High-Tech scanning electron microscope S4800, and Figure 19B was performed using a Hitachi High-Tech scanning electron microscope SU8030. The measurement conditions for both were an acceleration voltage of 5kV and a magnification of 20,000x.

[0342] As shown in Figure 19A, Sample 1 exhibits very little surface roughness. On the other hand, as shown in Figure 19B, lithium cobalt oxide (C-5H), the starting material for Sample 1, exhibits very much surface roughness. [Examples]

[0343] <Fabrication of a half-cell using Sample 1 as the positive electrode active material> This example describes the fabrication conditions for a coin-shaped half-cell using Sample 1, prepared in Example 1, as the positive electrode active material. To confirm the reproducibility of the experiment, half-cells 1 through 7 were fabricated under the same conditions.

[0344] First, Sample 1 was prepared as the positive electrode active material, acetylene black (AB) was prepared as the conductive material, and polyvinylidene fluoride (PVDF) was prepared as the binder. PVDF was prepared by dissolving it in N-methyl-2-pyrrolidone (NMP) at a weight ratio of 5% in advance. Next, a slurry was prepared by mixing the positive electrode active material: AB: PVDF = 95:3:2 (weight ratio), and the slurry was coated on an aluminum positive electrode current collector. NMP was used as the solvent of the slurry.

[0345] Next, after coating the slurry on the positive electrode current collector, the solvent was volatilized.

[0346] Thereafter, in order to increase the density of the positive electrode active material layer on the above positive electrode current collector, pressing treatment was performed using a roll press machine. The condition of the pressing treatment was a linear pressure of 210 kN / m. The upper roll and the lower roll of the roll press machine were both at 120 °C.

[0347] Through the above steps, a positive electrode was obtained. The active material loading amount of the positive electrode was approximately 7 mg / cm 2 and was set as such.

[0348] The electrolytic solutions used in Half Cells 1 to Half Cell 7 contain an organic solvent. The organic solvent contains ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). When the total content of EC, EMC, and DMC is 100 vol%, the volume ratio of EC, EMC, and DMC is x:y:100 - x - y (where 5 ≤ x ≤ 35 and 0 < y < 65). Specifically, an organic solvent containing EC, EMC, and DMC in a volume ratio of EC:EMC:DMC = 30:35:35 was prepared. Lithium hexafluorophosphate (LiPF6) was dissolved in this organic solvent to a concentration of 1 mol / L and used as the electrolytic solution. Hereinafter, in this specification, etc., this electrolytic solution is referred to as "Electrolytic Solution A".

[0349] Conventional electrolytes used in lithium-ion batteries solidify at around -20°C, making it difficult to manufacture batteries that can be charged and discharged at -40°C. The electrolyte used in this embodiment has a solidification point of -40°C or lower, which is a necessary condition for realizing a lithium-ion battery that can be charged and discharged even in an extremely low-temperature environment of -40°C.

[0350] A porous polypropylene film was used as the separator. Lithium metal was used as the negative electrode (counter electrode). Using these components, coin-shaped half-cells (Half-cell 1 to Half-cell 7) were fabricated. Half-cells 1 to 7 can be referred to as test batteries. [Examples]

[0351] In this example, we will describe the results of measuring half-cells 1 to 7 prepared in Example 2.

[0352] <25℃ discharge capacity> The discharge capacity at 25°C was measured using half-cell 1. Charging was performed using a constant current charge of 0.1C (assuming 1C = 200mA / g) until the voltage reached 4.60V, followed by constant voltage charging at 4.60V until the charging current fell below 0.01C. Discharging conditions were set to constant current discharge at a discharge rate of 0.1C (assuming 1C = 200mA / g) until the voltage reached 2.5V (cutoff voltage).

[0353] Half-cells 1 through 7 were repeatedly charged and discharged three times under the above charge / discharge conditions. The 0.1C current value, 25°C discharge capacity (3rd discharge capacity), positive electrode active material weight, and discharge capacity per unit weight of positive electrode active material (3rd discharge capacity) are shown in Table 1. A photograph of the appearance of half-cell 2 is shown in Figure 20.

[0354] [Table 1]

[0355] <Temperature characteristics of discharge capacity> Next, we will explain the temperature characteristics measured using the half-cell 1 described above.

[0356] Using half-cell 1, the discharge capacity was measured under several temperature conditions after the measurements shown in Table 1. The discharge temperatures were set to 25°C, 0°C, -20°C, and -40°C. Before each discharge test at each temperature, charging was performed at 25°C. Charging was performed using a constant current charge of 0.1C (assuming 1C = 200mA / g) until the voltage reached 4.60V, followed by constant voltage charging at 4.60V until the charging current was 0.01C or less. The discharge conditions were identical except for the temperature, and the condition was to discharge at a constant current at a discharge rate of 0.1C (assuming 1C = 200mA / g) until the voltage reached 2.5V (cutoff voltage). Note that the charging and discharging temperatures described in the examples of this specification were set using the temperature of the constant temperature bath in which the half-cell was left for a certain period of time.

[0357] Figure 21 shows the discharge curves for various temperatures during discharge. In the discharge curves in Figure 21, the dotted line shows the result at a discharge temperature of 25°C, the dashed line shows the result at a discharge temperature of 0°C, the dashed line shows the result at a discharge temperature of -20°C, and the solid line shows the result at a discharge temperature of -40°C. Table 2 shows the measured results of discharge capacity, average discharge voltage, and discharge energy density at each temperature. Table 3 shows the ratios (in %) of discharge capacity, average discharge voltage, and discharge energy density normalized by dividing the values ​​at each temperature by the value at a discharge temperature of 25°C. Note that the discharge capacity (in mAh / g) in Table 2 is the value calculated per unit weight of positive electrode active material. Also, the discharge energy density (in mWh / g) in Table 2 is the value calculated by multiplying the discharge capacity by the average discharge voltage (in V).

[0358] [Table 2]

[0359] [Table 3]

[0360] As shown in Figure 21, Table 2, and Table 3, the discharge capacity was very high under 0°C and -20°C conditions, and was almost the same as under 25°C conditions. Specifically, the discharge capacity at 0°C was 99.5% of that at 25°C, and the discharge capacity at -20°C was 98.3% of that at 25°C. Furthermore, a high discharge capacity was also obtained under -40°C conditions. Specifically, the discharge capacity at -40°C was 93.7% of that at 25°C, demonstrating that more than 90% of the discharge capacity at 25°C can be obtained even in an extremely low temperature environment of -40°C.

[0361] Furthermore, the results from Figure 21, Table 2, and Table 3 show that a lithium-ion battery comprising the positive electrode active material obtained by the manufacturing method described in Embodiment 1, etc., and electrolyte A can operate in a temperature range of at least -40°C to 25°C.

[0362] Furthermore, as shown in Figure 21, Table 2, and Table 3, Sample 1 achieved a very high discharge capacity of over 200 mAh / g even at a discharge temperature of -40°C. From another perspective, the discharge capacity at -40°C was more than 90% of that at 25°C, which is an outstanding result. From another perspective, a high discharge energy density of approximately 700 mWh / g was obtained at a discharge temperature of -40°C. From yet another perspective, the discharge energy density at -40°C was 78.3% of that at 25°C. Thus, the results showed that the discharge capacity at a discharge temperature of -40°C was 200 mAh / g or more, the discharge capacity at -40°C was 90% or more compared to the discharge capacity at 25°C, and the discharge energy density at a discharge temperature of -40°C was 650 mAh / g or more, the discharge energy density at -40°C was 75% or more compared to the discharge energy density at 25°C.

[0363] Despite the discharge temperature being low (i.e., under low-temperature conditions), the lithium-ion battery using Sample 1 as the positive electrode active material exhibited a very high discharge capacity. Therefore, it is presumed that the composite oxide (positive electrode active material) and electrolyte A of Sample 1 have very low lithium-ion diffusion resistance even under low-temperature conditions. Based on these results, it has been demonstrated that the positive electrode active material and electrolyte A obtained by the manufacturing method described in Embodiment 1, etc., are very useful as materials for lithium-ion batteries used under low-temperature conditions (e.g., -40°C).

[0364] <Charging and discharging in low-temperature environments> Next, we will explain the discharge capacity temperature characteristics measured using the half-cell 7 described above. In the measurements shown in Figure 21, Table 2, and Table 3 above, charging was performed at 25°C and discharging was performed under multiple temperature conditions. However, in this measurement, charging and discharging were performed under the same temperature conditions, but at multiple temperatures.

[0365] This section describes the charging and discharging conditions for Half Cell 7 in low-temperature environments. Following the charging and discharging at 25°C shown in Table 1, charging and discharging were performed at multiple temperature conditions in the following order: 0°C, 25°C, -20°C, 25°C, and -40°C. For charging and discharging under all temperature conditions, charging was performed with a constant current of 0.1C until the voltage reached 4.60V, followed by constant voltage charging at 4.60V until the current fell below 0.01C. For discharging, the condition was to discharge with a constant current of 0.1C until the voltage reached 2.5V (cutoff voltage). Note that 1C = 200mA / g.

[0366] Figure 22 shows the charging and discharging curves (also called charge-discharge curves) of half-cell 7, which was fabricated using Sample 1.

[0367] In the charge-discharge curves of Figure 22, the dotted line represents the result at a temperature of 25°C during charge-discharge, the dashed line represents the result at a temperature of 0°C during discharge, the dashed line represents the result at -20°C during charge-discharge, and the solid line represents the result at -40°C during charge-discharge. Table 4 shows the measured discharge capacity, average discharge voltage, and discharge energy density at each temperature during charge-discharge. Table 5 shows the ratios (in %) of discharge capacity, average discharge voltage, and discharge energy density normalized by dividing the values ​​at each temperature during discharge by the value at 25°C. Note that the discharge capacity (in mAh / g) in Table 4 is calculated per unit weight of positive electrode active material. The discharge energy density (in mWh / g) in Table 4 is calculated by multiplying the discharge capacity by the average discharge voltage (in V).

[0368] [Table 4]

[0369] [Table 5]

[0370] Furthermore, the results from Figure 22, Table 4, and Table 5 clearly show that a lithium-ion battery equipped with a positive electrode active material and electrolyte A obtained by the manufacturing method described in Embodiment 1, etc., is capable of charging and discharging in a temperature range of at least -40°C to 25°C.

[0371] Furthermore, as shown in Figure 22, Table 4, and Table 5, Sample 7 achieved a very high discharge capacity of 170 mAh / g or more, even at charging and discharging temperatures of -40°C. From another perspective, the discharge capacity at -40°C was more than 80% of the discharge capacity at 25°C, demonstrating outstanding results. Thus, the results showed that the discharge capacity at charging and discharging temperatures of -40°C was 170 mAh / g or more, and that the discharge capacity at -40°C was more than 80% of the discharge capacity at 25°C. [Explanation of symbols]

[0372] 100: Positive electrode active material, 903: Mixture, 904: Mixture

Claims

1. A first step involves heating lithium cobalt oxide having a median diameter (D50) of 10 μm or less at a temperature of 700°C to 1000°C for 1 hour to 5 hours. A second step involves mixing a fluorine source and a magnesium source with the lithium cobalt oxide obtained through the first step to produce a first mixture. A third step involves heating the first mixture at a temperature of 800°C to 1100°C for 1 hour to 10 hours. A fourth step involves mixing a nickel source and an aluminum source into the first mixture obtained through the third step to produce a second mixture, A method for producing a composite oxide, comprising a fifth step of heating the second mixture at a temperature of 800°C to 950°C for 1 hour to 5 hours.

2. In claim 1, A method for producing a composite oxide, wherein the number of magnesium atoms in the magnesium source is 0.3% or more and 3% or less of the number of cobalt atoms in the lithium cobalt oxide obtained through the first step.

3. In claim 2, The fluorine source is lithium fluoride. The magnesium source is magnesium fluoride. The number of moles of lithium fluoride M ＬｉＦ And the number of moles M of magnesium fluoride. ＭｇＦ２ The ratio to is M ＬｉＦ : M ＭｇＦ２ A method for producing a composite oxide such that x = 1 (0.1 ≤ x ≤ 0.5).

4. In claim 3, A method for producing a composite oxide, wherein the number of nickel atoms in the nickel source is 0.05% to 4% of the number of cobalt atoms in the lithium cobalt oxide obtained through the first step.

5. In claim 4, A method for producing a composite oxide, wherein the number of aluminum atoms in the aluminum source is 0.05% to 4% of the number of cobalt atoms in the lithium cobalt oxide obtained through the first step.

6. In claim 5, The first step is a method for producing a composite oxide, which is carried out in an oxygen-containing atmosphere with a lid placed over a casing containing lithium cobalt oxide.

7. A method for manufacturing a lithium-ion battery comprising a positive electrode having a positive electrode active material, an electrolyte, and a negative electrode having a negative electrode active material that is a carbon material, A first step involves heating lithium cobalt oxide having a median diameter (D50) of 10 μm or less at a temperature of 700°C to 1000°C for 1 hour to 5 hours. A second step involves mixing a fluorine source and a magnesium source with the lithium cobalt oxide obtained through the first step to produce a first mixture. A third step involves heating the first mixture at a temperature of 800°C to 1100°C for 1 hour to 10 hours. A fourth step involves mixing a nickel source and an aluminum source into the first mixture obtained through the third step to produce a second mixture, A method for manufacturing a lithium-ion battery, comprising a fifth step of heating the second mixture at a temperature of 800°C to 1100°C for 1 hour to 5 hours, thereby forming the positive electrode active material.

8. A lithium-ion battery manufacturing method comprising a positive electrode having a positive electrode active material, an electrolyte, and a negative electrode having a negative electrode active material which is a carbon material, wherein the electrolyte contains ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate, and when the total content of the ethylene carbonate, the ethyl methyl carbonate, and the dimethyl carbonate is 100 vol%, the volume V ＥＣ of the ethylene carbonate, the volume V ＥＭＣ of the ethyl methyl carbonate, and the volume V ＤＭＣ of the dimethyl carbonate are in a ratio of V ＥＣ :V ＥＭＣ :V ＤＭＣ =x:y:100 - x - y (where 5 ≤ x ≤ 35 and 0 < y < 65). A first step involves heating lithium cobalt oxide having a median diameter (D50) of 10 μm or less at a temperature of 700°C to 1000°C for 1 hour to 5 hours. A second step involves mixing a fluorine source and a magnesium source with the lithium cobalt oxide obtained through the first step to produce a first mixture. A third step involves heating the first mixture at a temperature of 800°C to 1100°C for 1 hour to 10 hours. A fourth step involves mixing a nickel source and an aluminum source into the first mixture obtained through the third step to produce a second mixture, A method for manufacturing a lithium-ion battery, comprising a fifth step of heating the second mixture at a temperature of 800°C to 1100°C for 1 hour to 5 hours, thereby forming the positive electrode active material.

Images