Method for producing positive electrode active material

Abstract

The purpose of the present invention is to provide a method for producing a novel positive electrode active material. Provided is a method for producing a positive electrode active material, the method comprising mixing a cobalt source with an additive element source to prepare an acid solution, reacting the acid solution with an alkali solution to form a cobalt compound, mixing the cobalt compound with a lithium source to prepare a mixture, and heating the mixture, in which the additive element source is a compound having at least one element selected from gallium, aluminum, boron, nickel and indium.

Description

Method for producing positive electrode active material, secondary battery and vehicle

[0001] BACKGROUND OF THE INVENTION 1. Field of the Invention One embodiment of the present invention relates to a method for manufacturing a positive electrode active material, a method for manufacturing a positive electrode, a method for manufacturing a secondary battery, or a portable information terminal, a power storage system, a vehicle, or the like including a secondary battery.

[0002] One embodiment of the present invention relates to an object, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, manufacture, or a composition of matter. Another embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof. Note that one embodiment of the present invention particularly relates to a method for manufacturing a positive electrode active material or a positive electrode active material. Alternatively, one embodiment of the present invention particularly relates to a method for manufacturing a positive electrode or a positive electrode. Alternatively, one embodiment of the present invention particularly relates to a method for manufacturing a secondary battery or a secondary battery.

[0003] In this specification, the term "semiconductor device" refers to any device that can function by utilizing semiconductor characteristics, and electro-optical devices, semiconductor circuits, and electronic devices are all included in the category of semiconductor devices.

[0004] In this specification, an electronic device refers to a device in general that has a positive electrode active material, a secondary battery, or a power storage device, and electro-optical devices that have a positive electrode active material, a positive electrode, a secondary battery, or a power storage device, and information terminal devices that have a power storage device are all electronic devices.

[0005] In this specification, the term "power storage device" refers to all elements and devices having a power storage function, including, for example, power storage devices such as lithium ion secondary batteries (also called secondary batteries), lithium ion capacitors, and electric double layer capacitors.

[0006] In recent years, various types of power storage devices have been actively developed, such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. In particular, demand for high-power, high-energy-density lithium-ion secondary batteries has rapidly expanded in conjunction with the development of the semiconductor industry, and they are now indispensable in the modern information society as a rechargeable energy source, and are used in portable information terminals such as mobile phones, smartphones, and notebook computers, portable music players, digital cameras, medical devices, home energy storage systems, industrial energy storage systems, and next-generation clean energy vehicles such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs).

[0007] Among these, composite oxides such as lithium cobalt oxide and lithium nickel-cobalt-manganese oxide, which have a layered rock salt structure, are widely used. These materials have useful properties as active materials for energy storage devices, such as high capacity and high discharge voltage. However, to achieve high capacity, the positive electrode must be charged to a high potential during charging. At such a high potential, a large amount of lithium is released, which can reduce the stability of the crystal structure and lead to significant deterioration during charge-discharge cycles. Against this background, efforts have been actively made to improve the positive electrode active materials of secondary battery positive electrodes in order to achieve high capacity and high stability secondary batteries (e.g., Patent Documents 1 to 3).

[0008] JP 2018-088400 A, WO 2018 / 203168 Pamphlet, JP 2020-140954 A

[0009] Although improvements to positive electrode active materials have been actively carried out in the above Patent Documents 1 to 3, there remains room for improvement in various aspects of lithium ion secondary batteries and positive electrode active materials used therein, such as charge / discharge capacity, cycle characteristics, reliability, safety, and cost.

[0010] In view of the above, an object of one embodiment of the present invention is to provide a method for manufacturing a positive electrode active material that is stable in a high potential state (also referred to as a high-voltage charging state) and / or a high-temperature state. Another object is to provide a method for manufacturing a positive electrode active material whose crystal structure is not easily destroyed even after repeated charging and discharging. Another object is to provide a method for manufacturing a positive electrode active material that has excellent charge-discharge cycle characteristics. Another object is to provide a method for manufacturing a positive electrode active material that has large charge-discharge capacity. Another object is to provide a highly reliable or safe secondary battery.

[0011] Another object of one embodiment of the present invention is to provide a method for manufacturing a positive electrode that is stable in a high potential state and / or a high temperature state, a method for manufacturing a positive electrode that has excellent charge-discharge cycle characteristics, a method for manufacturing a positive electrode that has large charge-discharge capacity, or a secondary battery that is highly reliable or safe.

[0012] Another object of one embodiment of the present invention is to provide a novel substance, active material particles, an electrode, a secondary battery, a power storage device, or a manufacturing method thereof.Another object of one embodiment of the present invention is to provide a manufacturing method of a secondary battery or a secondary battery having one or more characteristics selected from high purity, high performance, and high reliability.

[0013] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these can be extracted from the description in the specification, drawings, and claims.

[0014] One aspect of the present invention is a method for producing a positive electrode active material, comprising mixing a cobalt source and an additive element source to form an acid solution, reacting the acid solution with an alkaline solution to form a cobalt compound, mixing the cobalt compound with a lithium source to form a mixture, and heating the mixture, wherein the additive element source includes one or more selected from gallium, aluminum, boron, nickel, and indium.

[0015] Another aspect of the present invention is a method for producing a positive electrode active material, comprising reacting a cobalt source with an alkaline solution to form a cobalt compound, mixing the cobalt compound with a lithium source and an additive element source to form a mixture, and heating the mixture, wherein the additive element source includes one or more selected from gallium, aluminum, boron, nickel, and indium.

[0016] Another aspect of the present invention is a method for producing a positive electrode active material, comprising reacting a cobalt source with an alkaline solution to form a cobalt compound, mixing the cobalt compound with a lithium source to form a first mixture, heating the first mixture to form a composite oxide, mixing the composite oxide with an additive element source to form a second mixture, and heating the second mixture, wherein the additive element source includes one or more selected from gallium, aluminum, boron, nickel, and indium.

[0017] Another aspect of the present invention is a method for producing a positive electrode active material, comprising: mixing a cobalt source with a first additive element source to form an acid solution; reacting the acid solution with an alkaline solution to form a cobalt compound; mixing the cobalt compound with a lithium source to form a first mixture; heating the first mixture to form a composite oxide; mixing the composite oxide with a second additive element source to form a second mixture; and heating the second mixture, wherein the first additive element source contains one or more selected from gallium, aluminum, boron, nickel, and indium; and the second additive element source contains one or more selected from nickel, cobalt, magnesium, calcium, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron.

[0018] Another aspect of the present invention is a method for producing a positive electrode active material, comprising reacting a cobalt source with an alkaline solution to form a cobalt compound, mixing the cobalt compound with a lithium source to form a first mixture, heating the first mixture to form a composite oxide, mixing the composite oxide with a first additive element source and a second additive element source to form a second mixture, and heating the second mixture, wherein the first additive element source includes one or more selected from gallium, aluminum, boron, nickel, and indium, and the second additive element source includes one or more selected from nickel, cobalt, magnesium, calcium, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron.

[0019] Another aspect of the present invention is a method for producing a positive electrode active material, comprising mixing a cobalt source and a first additive element source to form an acid solution, reacting the acid solution with an alkaline solution to form a cobalt compound, mixing the cobalt compound and a lithium source to form a first mixture, heating the first mixture to form a first composite oxide, mixing the first composite oxide and a second additive element source to form a second mixture, heating the second mixture to form a second composite oxide, mixing the second composite oxide and a third additive element source to form a third mixture, and heating the third mixture. a first additive element source including one or more selected from the group consisting of gallium, aluminum, boron, nickel, and indium; a second additive element source and a third additive element source including one or more selected from the group consisting of nickel, cobalt, magnesium, calcium, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron; and an element contained in the second additive element source is different from an element contained in the third additive element source.

[0020] Another aspect of the present invention is a method for producing a positive electrode active material, comprising reacting a cobalt source with an alkaline solution to form a cobalt compound, mixing the cobalt compound with a lithium source to form a first mixture, heating the first mixture to form a first composite oxide, mixing the first composite oxide with a first additive element source to form a second mixture, heating the second mixture to form a second composite oxide, mixing the second composite oxide with a second additive element source and a third additive element source to form a third mixture, and heating the third mixture, and the third additional element source contain one or more selected from nickel, cobalt, magnesium, calcium, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron, the element contained in the first additional element source is different from the element contained in the third additional element source, and the second additional element source contains one or more selected from gallium, aluminum, boron, nickel, and indium.

[0021] In any one of the above methods for producing a positive electrode active material, the alkaline solution preferably has an aqueous solution containing sodium hydroxide, potassium hydroxide, lithium hydroxide, or ammonia.

[0022] In any one of the above methods for producing a positive electrode active material, the water used in the aqueous solution preferably has a resistivity of 1 MΩ·cm or more.

[0023] In any one of the above methods for producing a positive electrode active material, the source of the additional element of gallium preferably contains gallium sulfate, gallium chloride, or gallium nitrate.

[0024] In any one of the above methods for producing a positive electrode active material, the temperature to which the second mixture is heated is preferably lower than the temperature to which the first mixture is heated.

[0025] In any one of the above methods for producing a positive electrode active material, the temperature to which the third mixture is heated is preferably lower than the temperature to which the first mixture is heated.

[0026] According to one embodiment of the present invention, a method for manufacturing a positive electrode active material that is stable at a high potential and / or a high temperature can be provided. Alternatively, a method for manufacturing a positive electrode active material whose crystal structure is not easily deformed even after repeated charge and discharge can be provided. Alternatively, a method for manufacturing a positive electrode active material that has excellent charge and discharge cycle characteristics can be provided. Alternatively, a method for manufacturing a positive electrode active material that has a large charge and discharge capacity can be provided. Alternatively, a highly reliable or safe secondary battery can be provided.

[0027] According to one embodiment of the present invention, a method for manufacturing a positive electrode that is stable at a high potential and / or a high temperature can be provided. Alternatively, a method for manufacturing a positive electrode that has excellent charge-discharge cycle characteristics can be provided. Alternatively, a method for manufacturing a positive electrode that has large charge-discharge capacity can be provided. Alternatively, a highly reliable or safe secondary battery can be provided.

[0028] According to one embodiment of the present invention, a novel substance, active material particles, an electrode, a secondary battery, a power storage device, or a manufacturing method thereof can be provided. Another embodiment of the present invention can provide a manufacturing method of a secondary battery or a secondary battery having one or more characteristics selected from high purity, high performance, and high reliability.

[0029] According to one embodiment of the present invention, a method for producing a positive electrode active material having a large discharge capacity can be provided. Alternatively, according to one embodiment of the present invention, a method for producing a positive electrode active material that can withstand high charge / discharge voltages can be provided. Alternatively, according to one embodiment of the present invention, a method for producing a positive electrode active material that is less likely to deteriorate can be provided. Alternatively, according to one embodiment of the present invention, a novel positive electrode active material can be provided.

[0030] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract other effects from the description in the specification, drawings, claims, etc.

[0031] FIG. 1 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 2 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 3 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 4 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 5 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 6 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 7 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 8 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 9 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 10 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 11 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 12 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 13 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 14 is a flow chart showing a manufacturing process for a cathode active material according to one embodiment of the present invention. FIG. 15 is a flowchart illustrating a manufacturing process of a cathode active material according to one embodiment of the present invention. FIG. 16 is a flowchart illustrating a manufacturing process of a cathode active material according to one embodiment of the present invention. FIG. 17A is a top view of a cathode active material according to one embodiment of the present invention, and FIGS. 17B and 17C are cross-sectional views of the cathode active material according to one embodiment of the present invention. FIG. 18 is a diagram illustrating a cathode active material according to one embodiment of the present invention. FIG. 19 is an XRD pattern calculated from the crystal structure. FIG. 20 is a diagram illustrating a cathode active material according to a comparative example. FIG. 21 is an XRD pattern calculated from the crystal structure. FIGS. 22A and 22B are images of the cathode active material after a cycle test. FIG. 23 is an image of the cathode active material after a cycle test. FIG. 24A is an exploded perspective view of a coin-type secondary battery, FIG. 24B is a perspective view of the coin-type secondary battery, and FIG. 24C is a cross-sectional perspective view thereof. FIG. 25A illustrates an example of a cylindrical secondary battery. FIG. 25B illustrates an example of a cylindrical secondary battery. Fig. 25C shows an example of a plurality of cylindrical secondary batteries. Fig. 25D shows an example of a power storage system having a plurality of cylindrical secondary batteries. Figs. 26A and 26B are diagrams for explaining an example of a secondary battery, and Fig. 26C is a diagram showing the internal state of the secondary battery.FIGS. 27A to 27C are diagrams illustrating an example of a secondary battery. FIGS. 28A and 28B are diagrams illustrating the appearance of a secondary battery. FIGS. 29A to 29C are diagrams illustrating a manufacturing method of a secondary battery. FIGS. 30A to 30C are diagrams illustrating an example of a battery pack. FIGS. 31A and 31B are diagrams illustrating an example of a secondary battery. FIGS. 32A to 32C are diagrams illustrating an example of a secondary battery. FIGS. 33A and 33B are diagrams illustrating an example of a secondary battery. FIG. 34A is a perspective view of a battery pack illustrating one embodiment of the present invention, FIG. 34B is a block diagram of the battery pack, and FIG. 34C is a block diagram of a vehicle having a motor. FIGS. 35A to 35D are diagrams illustrating an example of a transportation vehicle. FIGS. 36A and 36B are diagrams illustrating a power storage device of one embodiment of the present invention. FIG. 37A is a diagram illustrating an electric bicycle, FIG. 37B is a diagram illustrating a secondary battery for the electric bicycle, and FIG. 37C is a diagram illustrating an electric motorcycle. FIGS. 38A to 38D are diagrams illustrating examples of electronic devices. Fig. 39A shows an example of a wearable device, Fig. 39B shows a perspective view of a wristwatch-type device, Fig. 39C is a diagram illustrating a side view of the wristwatch-type device, and Fig. 39D is a diagram illustrating an example of a wireless earphone.

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various modifications can be made to the embodiments and details. Furthermore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0033] In this specification and the like, the term "composite oxide" refers to an oxide containing a plurality of metal atoms in its structure.

[0034] In addition, in this specification, crystal planes and directions are indicated by Miller indices. In crystallography, crystal planes and directions are indicated by a superscript bar. However, in this specification, due to limitations in application notation, instead of a bar above the number, a minus sign (-) may be placed before the number. Individual orientations indicating directions within a crystal are expressed with [ ], collective orientations indicating all equivalent directions with < >, individual planes indicating crystal faces with ( ), and collective planes with equivalent symmetry with {}. In addition, Miller indices for trigonal and hexagonal crystals, including R-3m, may use (hkil) instead of just (hkl). Here, i is -(h+k).

[0035] In this specification, the layered rock-salt type crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure having a rock-salt type ion arrangement in which cations and anions are alternately arranged, and in which the transition metal and lithium are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. Defects such as cation or anion deficiencies may also be present. Strictly speaking, the layered rock-salt type crystal structure may have a distorted rock-salt type crystal lattice.

[0036] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately. Note that the crystal structure may have a deficiency of cations or anions in part.

[0037] In this specification, the theoretical capacity of a positive electrode active material refers to the amount of electricity when all of the intercalable and deintercalable lithium contained in the positive electrode active material is deintercalated. For example, LiFePO ４ The theoretical capacity of LiCoO is 170 mAh / g. ２ The theoretical capacity of LiNiO is 274 mAh / g. ２ The theoretical capacity of LiMn is 275mAh / g. ２ O ４ The theoretical capacity of the battery is 148 mAh / g.

[0038] The amount of lithium remaining in the positive electrode active material that can be inserted or removed can be determined by x in the composition formula, for example, Li ｘ CoO ２ x in, or Li ｘ MO２ In this specification, Li ｘ CoO ２ Li as appropriate ｘ M1O ２ x can be considered as an occupancy rate, and in the case of a positive electrode active material in a secondary battery, x may be expressed as x = (theoretical capacity - charging capacity) / theoretical capacity. For example, LiCoO ２ When a secondary battery using as a positive electrode active material is charged at 219.2 mAh / g, Li ０．２ CoO ２ Or we can say x = 0.2. ｘ CoO ２ The small value of x in the formula means, for example, 0.1<x≦0.24.

[0039] When the lithium cobalt oxide satisfies the stoichiometric ratio, LiCoO ２ The occupancy rate of Li on the lithium site is x = 1. Also, the secondary battery after discharge is also LiCoO ２ In this case, x = 1. The end of discharge here refers to the state where the voltage is 2.5 V (lithium counter electrode) or less at a current of 100 mA / g, for example. In a lithium ion secondary battery, when the occupancy rate of lithium in the lithium site reaches x = 1 and no more lithium can enter, the voltage drops sharply. At this point, discharge can be said to be complete. Generally, LiCoO ２ In the case of a lithium ion secondary battery using the above method, the discharge voltage drops rapidly until it reaches 2.5 V, so it is assumed that the discharge is completed under the above conditions.

[0040] In addition, in this specification and the like, the depth of charge when all of the intercalable / deintercalable lithium in the positive electrode active material is intercalated may be referred to as 0, and the depth of charge when all of the intercalable / deintercalable lithium in the positive electrode active material is deintercalated may be referred to as 1.

[0041] In this specification and the like, the active material may be referred to as an active material particle, but the shape may vary and is not limited to a particle shape. For example, the shape of the active material (active material particle) may be, in addition to a circle, an ellipse, a rectangle, a trapezoid, a triangle, a square with rounded corners, or an asymmetric shape in one cross section.

[0042] In this specification and the like, a smooth surface of an active material can be said to have a surface roughness of at least 10 nm or less when surface irregularity information is quantified from measurement data on a cross section of the active material.

[0043] In this specification and the like, a cross section is a cross section obtained when observing with, for example, a scanning transmission electron microscope (STEM).

[0044] Embodiment 1 In this embodiment, a method for manufacturing a positive electrode active material according to one embodiment of the present invention will be described.

[0045] <Production Method 1> The procedure of Production Method 1 will be described using the flow charts shown in Figures 1 and 2. Note that Figure 2 is a flow chart that details some of the procedures shown in Figure 1, but the detailed procedures are not necessarily required.

[0046] The cobalt source 81 (referred to as "Co source" in the drawings) and the first additive element source 82 (referred to as "X source" in the drawings) shown in Figures 1 and 2 will now be described. Cobalt is one of the transition metals M1 that can form a layered rock-salt type composite oxide belonging to the space group R-3m together with lithium. In addition to cobalt, examples of the transition metal M1 include manganese and nickel.

[0047] <Cobalt Source> The cobalt source 81 is one of the starting materials for the positive electrode active material. The cobalt source 81 is a compound containing cobalt (referred to as a cobalt compound). Examples of the cobalt compound include cobalt sulfate, cobalt chloride, or cobalt nitrate, or hydrates thereof. Cobalt alkoxides or organic cobalt complexes may also be used as the cobalt compound. Furthermore, organic acids of cobalt, such as cobalt acetate, or hydrates thereof may also be used as the cobalt compound. In this specification, the term "organic acid" includes, in addition to acetic acid, citric acid, oxalic acid, formic acid, or butyric acid.

[0048] When a solution is used as the cobalt source 81, an aqueous solution containing the above-mentioned cobalt compound (hereinafter referred to as an aqueous cobalt solution) is prepared.

[0049] Positive electrode active material LiM1O ２In the transition metal M1, the proportion of cobalt is preferably 75 atomic % or more, preferably 90 atomic % or more, and more preferably 95 atomic % or more. Using a cobalt source 81 weighed to achieve the above proportion has many advantages, such as relatively easy synthesis and handling, and excellent cycle characteristics. Cobalt in the above proportion can be described as the main component of the positive electrode active material.

[0050] The positive electrode active material of the present invention may contain manganese as a main component, but more preferably does not substantially contain manganese. A positive electrode active material that does not substantially contain manganese as a main component has the significant advantages of being relatively easy to synthesize and handle, and having excellent cycle characteristics. Being substantially free of manganese as a main component can be considered to mean that the content of manganese in the positive electrode active material is small. Specifically, the weight of manganese in the positive electrode active material is 600 ppm or less, more preferably 100 ppm or less.

[0051] <First Additional Element Source (X Source)> The first additional element source 82 is one of the starting materials for the positive electrode active material, and uses a compound containing a first additional element X. Specific examples of the first additional element X will be described in detail in the second embodiment, but it is preferable that the first additional element X be one or more elements selected from gallium, aluminum, boron, nickel, and indium. It is preferable that the positive electrode active material contains nickel in addition to the above-mentioned cobalt, because this can suppress deviation of the layered structure formed by octahedra of cobalt and oxygen, and may result in a more stable crystal structure of the positive electrode active material in a charged state at high temperatures.

[0052] When the first additive element X is gallium, the first additive element source 82 can be referred to as a gallium source. A gallium-containing compound is used as the gallium source. Examples of the gallium-containing compound include gallium sulfate, gallium chloride, and gallium nitrate, as well as hydrates thereof. Gallium alkoxides or organic gallium complexes may also be used as gallium-containing compounds. Furthermore, organic acids of gallium, such as gallium acetate, or hydrates thereof may also be used as gallium-containing compounds.

[0053] When the first additional element X is aluminum, the first additional element source 82 can be referred to as an aluminum source. An aluminum-containing compound is used as the aluminum source. Examples of the aluminum-containing compound include aluminum sulfate, aluminum chloride, and aluminum nitrate, as well as hydrates thereof. Aluminum alkoxides or organic aluminum complexes may also be used as aluminum-containing compounds. Furthermore, organic aluminum acids such as aluminum acetate, or hydrates thereof may also be used as aluminum-containing compounds.

[0054] When the first additive element X is boron, the first additive element source 82 can be referred to as a boron source. A compound containing boron is used as the boron source. The compound containing boron can be, for example, boric acid or a borate.

[0055] When the first additional element X is nickel, the first additional element source 82 can be referred to as a nickel source. A nickel-containing compound is used as the nickel source. Examples of nickel-containing compounds that can be used include nickel sulfate, nickel chloride, and nickel nitrate, as well as hydrates thereof. Nickel alkoxides or organic nickel complexes may also be used as nickel-containing compounds. Furthermore, nickel organic acids such as nickel acetate, or hydrates thereof may also be used as nickel-containing compounds.

[0056] When the first additive element X is indium, the first additive element source 82 can be referred to as an indium source. An indium-containing compound is used as the indium source. Examples of the indium-containing compound include indium sulfate, indium chloride, and indium nitrate, as well as hydrates thereof. Indium alkoxides or organic indium complexes may also be used as indium-containing compounds. Furthermore, organic acids of indium, such as indium acetate, or hydrates thereof may also be used as indium-containing compounds.

[0057] When a solution is used as the first additive element source 82, an aqueous solution containing the above compound is prepared.

[0058] Here, the chelating agent 83 shown in Fig. 2 will be explained. The use of the chelating agent 83 has the following effects. However, as shown in Fig. 1, a cobalt compound can be obtained without using the chelating agent 83.

[0059] <Chelating Agent> Examples of compounds constituting a chelating agent include glycine, oxine, 1-nitroso-2-naphthol, 2-mercaptobenzothiazole, and EDTA (ethylenediaminetetraacetic acid). It is also possible to use a plurality of compounds selected from glycine, oxine, 1-nitroso-2-naphthol, and 2-mercaptobenzothiazole. At least one of these compounds is dissolved in water (e.g., pure water) to form a chelating aqueous solution. Chelating agents are preferred over general complexing agents in that they are complexing agents that form chelate compounds. Of course, general complexing agents may also be used, and for example, ammonia water or the like may be used instead of a chelating agent.

[0060] The use of the above-described chelate aqueous solution is preferable because it can suppress the generation of unnecessary crystal nuclei and promote crystal growth. Suppressing the generation of unnecessary nuclei suppresses the generation of fine particles, allowing a cobalt compound with a good particle size distribution to be obtained. Furthermore, the use of the chelate aqueous solution can delay the acid-base reaction, allowing the reaction to proceed gradually, resulting in a cobalt compound with a nearly spherical shape.

[0061] Glycine, which is exemplified as a compound contained in the aqueous chelate solution, has the effect of maintaining a constant pH value at or near a pH of 9 to 10. Therefore, using an aqueous glycine solution as the aqueous chelate solution is preferable because it makes it easier to control the pH of the reaction vessel when obtaining the cobalt compound. Furthermore, the glycine concentration of the aqueous glycine solution is preferably 0.05 mol / L to 0.5 mol / L, and more preferably 0.1 mol / L to 0.2 mol / L.

[0062] <Pure Water> The water used in the aqueous solution is preferably pure water. Pure water is water with a resistivity of 1 MΩ cm or more, more preferably 10 MΩ cm or more, and even more preferably 15 MΩ cm or more. Water that satisfies this resistivity requirement has high purity and contains very few impurities.

[0063] <Step S14> Next, step S14 shown in FIGS. 1 and 2 will be described. In step S14, a cobalt source 81 and a first additive element source 82 are mixed. Here, an example is shown in which an aqueous solution containing a gallium compound is used as the first additive element source 82. By mixing, an acidic solution 91 can be obtained in which the cobalt compound and the gallium compound are dissolved in water. The water used may be pure water. Note that it is not essential to prepare the cobalt source 81 and the first additive element source 82 as aqueous solutions, as long as an aqueous solution can be prepared in step S14.

[0064] Next, the alkaline solution 84 shown in FIGS. 1 and 2 will be described.

[0065] <Alkaline Solution> The alkaline solution 84 may be, for example, an aqueous solution containing sodium hydroxide, potassium hydroxide, lithium hydroxide, or ammonia, but is not limited to these aqueous solutions as long as it functions as a pH adjuster. For example, it may be an aqueous solution in which two or more types selected from sodium hydroxide, potassium hydroxide, and lithium hydroxide are dissolved in water. The water used may be pure water.

[0066] Here, we will explain the water 85 shown in Figure 2. Water 85 may be referred to as the charging solution or the adjusting solution, and refers to the aqueous solution in the initial reaction state. It is preferable to use the above-mentioned pure water or an aqueous solution obtained by dissolving the above-mentioned chelating agent in the above-mentioned pure water. Using a chelating agent can suppress the generation of unwanted crystal nuclei and promote growth, as described above. Suppressing the generation of unwanted nuclei suppresses the generation of fine particles, resulting in the production of a cobalt compound with a good particle size distribution. Alternatively, the acid-base reaction can be delayed, and the gradual progress of the reaction allows the production of a cobalt compound with a nearly spherical shape. However, it is possible to obtain a cobalt compound without using water 85 as shown in Figure 1.

[0067] <Step S31> Next, step S31 shown in Figures 1 and 2 will be described. In step S31, the acid solution 91 and the alkaline solution 84 are mixed. By mixing, the acid solution 91 and the alkaline solution 84 react with each other to produce a cobalt compound 95. The cobalt compound 95 has a first additional element X. The first additional element X can be present throughout the cobalt compound 95.

[0068] The reaction in step S31 may be referred to as a neutralization reaction, an acid-base reaction, or a coprecipitation reaction. The obtained cobalt compound 95 may be referred to as a precursor of lithium cobalt oxide, which is the positive electrode active material 100.

[0069] <Reaction Conditions> When reacting the acid solution 91 and the alkaline solution 84 according to the coprecipitation reaction, the pH of the reaction tank is adjusted to 9 or more and 11 or less, preferably 9.8 or more and 10.5 or less. This range is preferable because it allows the particle size of the secondary particles of the obtained cobalt compound to be large. If the pH is outside this range, productivity will be low and the obtained cobalt compound will be more likely to contain impurities.

[0070] When the acid solution 91 is placed in a reaction tank and the alkaline solution 84 is added dropwise to the reaction tank, it is preferable to maintain the pH of the aqueous solution in the reaction tank within the range of the above-mentioned conditions. Also, when the alkaline solution 84 is placed in a reaction tank and the acid solution 91 is added dropwise to the reaction tank, it is preferable to maintain the pH within the range of the above-mentioned conditions.

[0071] 2 may be placed in the reaction tank and an acid solution 91 may be added dropwise to the reaction tank. If the pH of the reaction tank deviates from a predetermined value due to the addition of the acid solution 91, the pH of the reaction tank may be controlled by adding an alkaline solution 84 dropwise.

[0072] The dropping rate of the acid solution 91 or alkaline solution 84 is preferably 0.01 mL / min to 1 mL / min, more preferably 0.1 mL / min to 0.8 mL / min, when the solution in the reaction vessel is 200 mL to 350 mL.

[0073] The solution in the reaction vessel is preferably stirred using a stirring means. The stirring means may have a stirrer or stirring blades. Two to six stirring blades may be provided. For example, when four stirring blades are provided, they may be arranged in a cross shape when viewed from above. The rotation speed of the stirring blades of the stirring means is preferably 800 rpm to 1200 rpm.

[0074] The temperature of the solution in the reaction vessel is adjusted to 50° C. or higher and 90° C. or lower, after which the dropwise addition can be started. The above range is preferable because it allows the particle size of the secondary particles of the obtained cobalt compound to be large.

[0075] The inside of the reaction vessel is preferably kept in an inert atmosphere. For example, when a nitrogen atmosphere is used, nitrogen gas is preferably introduced at a flow rate of 0.5 L / min to 1.2 L / min.

[0076] The reactor may also be equipped with a reflux condenser, which allows nitrogen gas to escape from the reactor and water to return to the reactor.

[0077] After the above reaction, a cobalt compound 95 (referred to as a Co compound in the drawings) is precipitated in the reaction vessel as a reaction product.

[0078] <Steps S32 and S33> The precipitate 92 shown in FIG. 2 , the filtration in step S32, and the drying in step S33 will now be described. The precipitate 92 contains the cobalt compound 95 described above. The precipitate 92 also contains impurities other than the cobalt compound 95. Therefore, in order to recover the cobalt compound 95, the filtration in step S32 is preferably performed. The filtration can be performed by suction filtration or vacuum filtration. Centrifugation may also be used instead of filtration. When suction filtration is used, it is preferable to wash the reaction product precipitated in the reaction tank with pure water and then add an organic solvent with a low boiling point (e.g., acetone) before performing the suction filtration.

[0079] The filtered cobalt compound may be further dried in step S33. For example, the cobalt compound may be dried under vacuum at a temperature of 60° C. to 90° C. for 0.5 hours to 3 hours. In this manner, cobalt compound 95 can be obtained.

[0080] Cobalt Compound 95 contains cobalt hydroxide. Cobalt hydroxide is obtained as secondary particles formed by aggregation of primary particles. In this specification, a primary particle refers to the smallest particle (clump) that does not have a grain boundary when observed at 5000x magnification using a scanning electron microscope (SEM). In other words, a primary particle refers to the smallest particle surrounded by a grain boundary. A secondary particle refers to a particle (particle independent from others) in which the primary particles aggregate to share a portion of the grain boundary (such as the outer periphery of the primary particle) and are not easily separated. In other words, a secondary particle may have a grain boundary.

[0081] Next, a lithium compound is prepared as the lithium source 88 (referred to as Li source in the drawings) shown in FIGS.

[0082] <Lithium Compound> Lithium hydroxide, lithium carbonate, lithium oxide, or lithium nitrate is prepared as the lithium compound. For example, if cobalt hydroxide is obtained as the cobalt compound 95, lithium hydroxide can be used as the lithium compound. In the positive electrode active material, the atomic ratio of cobalt (Co) to lithium (Li) (Li / Co) is 1.0 or more and 1.06 or less, preferably 1.02 or more and 1.05 or less. The lithium compound is weighed so as to satisfy the above range.

[0083] The lithium compound may be pulverized in advance. For example, the mortar may be pulverized for 5 to 15 minutes. The mortar is preferably made of a material that does not easily release impurities. Specifically, an alumina mortar with a purity of 90 wt% or more, preferably 99 wt% or more, may be used. A wet pulverization method using a ball mill or the like may also be used. In the wet pulverization method, acetone may be used as the solvent, and the pulverization may be performed at a rotation speed of 200 to 400 rpm for 10 to 15 hours.

[0084] <Step S51> Next, step S51 shown in Figures 1 and 2 will be described. In step S51, the cobalt compound 95 and the lithium source 88 are mixed. Thereafter, a mixed mixture 97 is obtained. A revolutionary agitator is preferably used as a means for mixing the cobalt compound 95 and the lithium source 88. When media is not used, pulverization is often not performed, and there is little change in the particle size of the cobalt compound 95 and the lithium source 88.

[0085] When mixing and pulverizing the cobalt compound 95 and the lithium source 88 simultaneously, a ball mill or a bead mill may be used. Alumina balls or zirconia balls may be used as media for the ball mill or bead mill. In the ball mill or bead mill, centrifugal force is applied to the media, making it possible to pulverize the material. However, if contamination from the media or the like is a concern, it is preferable to use the zirconia balls and set the peripheral speed to 100 mm / sec or more and 2000 mm / sec or less.

[0086] When mixing and pulverization are performed simultaneously, the pulverization method that can be used includes a dry pulverization method and a wet pulverization method. The dry pulverization method involves pulverization in an inert gas or air, and can pulverize to a particle size of 3.5 μm or less, preferably 3 μm or less. The wet pulverization method involves pulverization in a liquid, and can pulverize to a particle size of 1 μm or less. In other words, if you want to reduce the particle size, you should use the wet pulverization method.

[0087] In this way, mixture 97 is obtained.

[0088] Here, the heating step will be explained in more detail using steps S52 and S53 shown in FIG.

[0089] <Step S52> Next, step S52 shown in FIG. 2 will be described. The heating step may be performed multiple times, and in step S52, heating is performed at a temperature of 400°C or higher and 700°C or lower before step S54, which will be described later. The heating in step S52 is sometimes referred to as pre-baking because it is performed at a lower temperature than step S54. Step S52 may release gas components contained in the cobalt compound 95 or lithium source 88. By using a material from which gas components have been released, a composite oxide with few impurities can be obtained. However, a positive electrode active material can be obtained without performing the pre-baking in step S52, as shown in FIG. 1.

[0090] <Step S53> Next, step S53 shown in Fig. 2 will be described. In step S53, a crushing step is performed. For example, classification may be performed using a sieve with a mesh size of 40 µm or more and 60 µm or less. However, as shown in Fig. 1, the positive electrode active material can be obtained without performing the crushing step of step S53.

[0091] <Step S54> Next, step S54 shown in FIGS. 1 and 2 will be described. In step S54, the mixture obtained through the crushing step in step S53 is heated. By heating, lithium cobalt oxide, a composite oxide, can be obtained. This is the positive electrode active material 100. Step S54 is sometimes referred to as main baking. There are many heating steps, including step S52, but these steps are sometimes referred to as first heating, second heating, etc., with appropriate ordinal numbers added to distinguish them from one another.

[0092] <Heating Conditions> In step S54, the heating temperature is preferably 700° C. or higher and lower than 1100° C., more preferably 800° C. or higher and 1000° C. or lower, and even more preferably 800° C. or higher and 950° C. or lower. When producing cobalt oxide through this heat treatment, heating is performed at a temperature at which at least the cobalt compound 95 and the lithium source 88 diffuse into each other. This temperature is the reason why it is called the main baking.

[0093] The heating time in step S54 can be, for example, 1 hour or more and 100 hours or less, and is preferably 2 hours or more and 20 hours or less.

[0094] The heating atmosphere in step S54 is preferably an oxygen-containing atmosphere or a so-called dry air atmosphere containing little water (for example, a dew point of -50°C or less, more preferably a dew point of -80°C or less).

[0095] For example, when heating at 750°C for 10 hours, the temperature rise rate should be 150°C / hour or more and 250°C / hour or less. The flow rate of dry air that can constitute the drying atmosphere is preferably 3 L / min or more and 10 L / min or less. The temperature drop time is preferably 10 hours or more and 50 hours or less until the temperature drops from the specified temperature to room temperature, and the temperature drop rate can be calculated from the temperature drop time, etc.

[0096] It is preferable that the crucible, sheath, setter, or container used during heating be made of a material that does not easily release impurities. For example, it is recommended to use a crucible made of alumina with a purity of 99.9%. For mass production, mullite-cordierite (Al ２ O ３ , SiO ２ , MgO) sheaths are preferably used.

[0097] Furthermore, when recovering the material after heating, it is preferable to transfer it from the crucible to a mortar and then recover it, since this prevents impurities from being mixed into the material. The mortar is also preferably made of a material that does not easily release impurities, and specifically, a mortar made of alumina or zirconia with a purity of 90 wt% or more, preferably 99 wt% or more, may be used.

[0098] As described above, a positive electrode active material 100 such as lithium cobalt oxide can be produced according to Production Method 1. The positive electrode active material 100 can reflect the shape of the precursor cobalt compound 95. Furthermore, according to Production Method 1, the first additional element X can be present inside or throughout the positive electrode active material 100 (including the inside and the surface layer portion).

[0099] Furthermore, lithium cobalt oxide is preferable because it contains few impurities. However, when sulfide is used as the starting material, sulfur may be detected in the lithium cobalt oxide. The sulfur concentration can be measured by performing elemental analysis of the entire particles of the positive electrode active material using GD-MS (glow discharge mass spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), etc.

[0100] <Production Method 2> The procedure of Production Method 2 will be described using the flow charts shown in Figures 3 and 4. Note that Figure 4 is a flow chart that details some of the procedures shown in Figure 3, but the detailed procedures are not necessarily required.

[0101] The manufacturing method 2 differs from the manufacturing method 1 in the timing of introducing the first additive element source 82, that is, the first additive element source 82 is introduced simultaneously with the lithium source 88 in step S51.

[0102] 3 and 4 , the preferred elements as the first additional element X in Production Method 2 are the same as those in Production Method 1. However, in Production Method 2, the first additional element source 82 does not necessarily have to be an aqueous solution.

[0103] For example, the gallium source may be gallium oxyhydroxide, gallium hydroxide, gallium oxide, or a gallium salt such as gallium sulfate, gallium acetate, or gallium nitrate. Gallium alkoxides may also be used.

[0104] The aluminum source may be aluminum hydroxide, aluminum oxide, or an aluminum salt such as aluminum sulfate, aluminum acetate, or aluminum nitrate. Aluminum alkoxides may also be used.

[0105] The boron source may be, for example, boric acid or a borate.

[0106] The indium source may be, for example, indium sulfate, indium acetate, indium oxide, or indium nitrate. Indium alkoxides may also be used.

[0107] 3 and 4, which illustrate the manufacturing method 2, the description of the manufacturing method 1 can be referred to except for the different configurations and methods described above.

[0108] According to Production Method 2, a positive electrode active material 100 such as lithium cobalt oxide can be produced. The positive electrode active material 100 can reflect the shape of the precursor cobalt compound 95. Furthermore, according to Production Method 2, the first additive element X can be present inside or throughout the positive electrode active material 100 (including the inside and the surface layer portion).

[0109] Furthermore, lithium cobalt oxide is preferable because it contains few impurities. However, when sulfide is used as the starting material, sulfur may be detected in the lithium cobalt oxide. The sulfur concentration can be measured by performing elemental analysis of the entire particles of the positive electrode active material using GD-MS, ICP-MS, etc.

[0110] The positive electrode active material 100 may be produced without using the coprecipitation method. For example, by using cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide, cobalt carbonate, cobalt oxalate, cobalt sulfate, or the like as the cobalt compound 95 shown in Figures 3 and 4, it is possible to obtain the positive electrode active material 100 having the first additional element X inside or throughout the particles (including the inside and the surface layer). For heating conditions, etc., refer to step S54 described above.

[0111] <Manufacturing Method 3> The procedure of manufacturing method 3 will be described using the flow charts shown in Figures 5 and 6. Note that Figure 6 is a flow chart that details some of the procedures shown in Figure 5, but the detailed procedures are not necessarily required.

[0112] In the manufacturing method 3, the timing of introducing the first additive element source 82 is different from that in the manufacturing method 1, and the first additive element source 82 is introduced into the composite oxide 98 .

[0113] <First Additional Element Source (X Source)> A supplementary note will be made regarding the first additional element source 82 shown in Figures 5 and 6. Unlike Production Method 1, Production Method 2 preferably does not contain water as the first additional element source 82. For specific compounds of the first additional element source 82 that does not contain water, reference can be made to Production Method 2.

[0114] 5 and 6 will be described. The composite oxide 98 is formed through the heating in step S54, and is referred to as the positive electrode active material 100 in production methods 1 and 2.

[0115] <Step S71> Step S71 shown in Figures 5 and 6 will be described. In step S71, the first additive element source 82 and the composite oxide 98 are mixed. Then, a mixture 97 is formed. The mixing can be performed by dry mixing or wet mixing. During mixing, the rotation speed is preferably set to 100 rpm or more and 200 rpm or less to prevent the composite oxide 98 from cracking.

[0116] <Step S72> Step S72 shown in Figures 5 and 6 will be described. In step S72, the mixture 97 is heated. For the heating conditions, reference can be made to step S54.

[0117] Here, a supplementary note regarding the heating temperature in step S72 is provided. The heating temperature in step S72 should be lower than the heating temperature in step S54. Because the composite oxide 98 is formed through step S54, it is preferable to adopt a temperature in step S72 that does not destroy the crystal structure of the composite oxide 98.

[0118] Furthermore, the heating in step S72 must be performed at a temperature at which the reaction between the composite oxide 98 and the first additive element source 82 proceeds or higher. The temperature at which the reaction proceeds may be any temperature at which mutual diffusion between the composite oxide 98 and the first additive element source 82 occurs, and may be lower than the melting temperature of these materials. An oxide will be used as an example for explanation, and the melting temperature T ｍ 0.757 times (Tammann temperature T ｄ ) and therefore the heating temperature in step S72 must be at least 500° C. or higher.

[0119] Of course, it is preferable that the temperature is equal to or higher than the temperature at which the composite oxide 98 and the first additive element source 82 are partially melted, since the reaction proceeds easily.

[0120] A higher heating temperature is preferable because the reaction proceeds more easily, the heating time is shorter, and productivity is higher.

[0121] The heating temperature was the decomposition temperature of the composite oxide 98 (LiCoO ２ The decomposition temperature of the composite oxide 98 is set to be less than 1130°C. At temperatures close to the decomposition temperature, there is a concern that the composite oxide 98 may decompose, albeit only slightly. Therefore, the temperature is more preferably 1000°C or less, even more preferably 950°C or less, and even more preferably 900°C or less.

[0122] 5 and 6, which explain manufacturing method 3, the explanations regarding manufacturing methods 1 and 2 can be referred to except for the different configurations and methods described above.

[0123] According to Production Method 3, a positive electrode active material 100 such as lithium cobalt oxide can be produced. The positive electrode active material 100 can reflect the shape of the precursor cobalt compound 95. Furthermore, according to Production Method 3, the first additional element X can be present in the surface layer portion of the positive electrode active material 100.

[0124] Furthermore, lithium cobalt oxide is preferable because it contains few impurities. However, when sulfide is used as the starting material, sulfur may be detected in the lithium cobalt oxide. The sulfur concentration can be measured by performing elemental analysis of the entire particles of the positive electrode active material using GD-MS, ICP-MS, etc.

[0125] <Manufacturing Method 4> The procedure of manufacturing method 4 will be described using the flow charts shown in Figures 7 and 8. Note that Figure 8 is a flow chart that details some of the procedures in Figure 7, but the detailed procedures are not necessarily required.

[0126] In the manufacturing method 4, in addition to the steps of the manufacturing method 1, a second additive element source 89 (referred to as a Y source in the drawing) is introduced into the composite oxide 98.

[0127] <Second Additional Element Source (Y Source)> The second additional element source 89 shown in FIGS. 7 and 8 will be described. The second additional element source 89 is one of the starting materials for the positive electrode active material, and uses a compound containing a second additional element Y. The second additional element source 89 contains an element different from the first additional element source 82. Specific examples of the second additional element Y will be described in detail in the second embodiment. For example, the second additional element Y may be one or more selected from nickel, cobalt, magnesium, calcium, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron, and may be different from the first additional element source X. It is preferable that the positive electrode active material contains nickel in addition to cobalt, because this may suppress misalignment of the layered structure formed by octahedra of cobalt and oxygen, thereby making the crystal structure of the positive electrode active material more stable in a charged state at high temperatures.

[0128] When the second additional element Y is magnesium, the second additional element source 89 can be referred to as a magnesium source. A compound containing magnesium is used as the magnesium source. Examples of the magnesium-containing compound that can be used include magnesium fluoride, magnesium oxide, magnesium hydroxide, and magnesium carbonate. A plurality of the above-mentioned magnesium sources may also be used.

[0129] When the second additive element Y is fluorine, the second additive element source 89 can be referred to as a fluorine source. A fluorine-containing compound is used as the fluorine source. Examples of fluorine-containing compounds that can be used include lithium fluoride, magnesium fluoride, aluminum fluoride, titanium fluoride, cobalt fluoride, nickel fluoride, zirconium fluoride, vanadium fluoride, manganese fluoride, iron fluoride, chromium fluoride, niobium fluoride, zinc fluoride, calcium fluoride, sodium fluoride, potassium fluoride, barium fluoride, cerium fluoride, lanthanum fluoride, and sodium aluminum hexafluoride. Among these, lithium fluoride is preferred because it has a relatively low melting point of 848°C and is easily melted in the heating step described below.

[0130] Magnesium fluoride can be used as both a fluorine source and a magnesium source, and lithium fluoride can be used as both a fluorine source and a lithium source.

[0131] The fluorine source may be a gas, such as fluorine, carbon fluoride, sulfur fluoride, or oxygen fluoride, which may be mixed into the atmosphere during the heating step described below. A plurality of the above-mentioned fluorine sources may also be used.

[0132] When preparing the second additive element source 89, two or more kinds of second additive elements Y can be used. For example, when lithium fluoride and magnesium fluoride are used together to form the second additive element source 89, the molar ratio of lithium fluoride to magnesium fluoride is LiF:MgF ２ =x:1 (0≦x≦1.9), and LiF:MgF ２ =x:1 (0.1≦x≦0.5) is more preferable, and LiF:MgF ２ = x:1 (x = 0.33 or its vicinity) is more preferable. Note that "x = 0.33 or its vicinity" refers to a value that is greater than 0.9 times and less than 1.1 times the value.

[0133] When two or more types of second additive element sources 89 are used, it is preferable to mix the second additive element sources 89 together first. There are two methods for mixing, one in which the raw materials are mixed while being pulverized, and the other in which the raw materials are mixed without being pulverized. When two or more types of second additive element sources 89 are mixed together first, it is preferable to mix them while being pulverized. This is because the particle size of the second additive element sources 89 can be made uniform and the particle size can be further reduced.

[0134] Furthermore, when recovering the second additive element source 89 after mixing, etc., it may be classified using a sieve with an opening diameter of 250 μm to 350 μm. This allows the particle size to be uniform.

[0135] Methods of mixing while pulverizing include dry pulverization and wet pulverization. Wet pulverization is preferred because it can produce smaller particle sizes than dry pulverization. When wet pulverization is performed, a solvent is prepared. Examples of solvents that can be used include ketones such as acetone, alcohols such as ethanol and isopropanol, ether, dioxane, acetonitrile, and N-methyl-2-pyrrolidone (NMP). It is preferable to use dehydrated acetone with a purity of 99.5% or higher as the solvent. Using dehydrated acetone with the above purity can reduce impurities that may be mixed in.

[0136] In the method of mixing while pulverizing, a ball mill or a bead mill can be used. Alumina balls or zirconia balls can be used as the media for the ball mill and the bead mill, respectively. In the ball mill and the bead mill, centrifugal force is applied to the media, which enables microparticulation. However, if contamination from the media or the like is a concern, it is preferable to use the above-mentioned zirconia balls and set the peripheral speed to 100 mm / s or more and 2000 mm / s or less.

[0137] Although the above example shows the case where two types of second additive element sources 89 are prepared, the second additive element source 89 may be one type or a mixture of three or more types.

[0138] The second additive element Y can be introduced into the composite oxide 98 by a solid-phase method, a liquid-phase method including a sol-gel method, a sputtering method, a vapor deposition method, a CVD (chemical vapor deposition) method, a PLD (pulsed laser deposition) method, or the like.

[0139] <Step S71> Step S71 shown in Figures 7 and 8 will be described. In step S71, a second additive element source 89 and a composite oxide 98 are mixed together. Then, a mixture 97 is formed. The mixing can be performed by dry mixing or wet mixing. During mixing, the rotation speed is preferably set to 100 rpm or more and 200 rpm or less to prevent the composite oxide 98 from collapsing.

[0140] 7 and 8 will be described. In step S72, the mixture 97 is heated. Note that the heating conditions in step S72 in production method 4 can refer to the heating conditions in step S72 in production method 3.

[0141] Here, a supplementary note about the heating temperature will be provided. The heating in step S72 must be performed at a temperature at which the reaction between the composite oxide 98 and the second additive element source 89 proceeds or higher. The temperature at which the reaction proceeds may be any temperature at which interdiffusion between the composite oxide 98 and the second additive element source 89 occurs, and may be lower than the melting temperature of these materials. An oxide will be used as an example for explanation, and the melting temperature T ｍ 0.757 times (Tammann temperature T ｄ Therefore, the heating temperature of the second heating step should be 500° C. or higher.

[0142] Of course, the reaction is easily promoted at a temperature equal to or higher than the temperature at which the composite oxide 98 and the second additive element source 89 are partially melted, which is preferable. For example, LiF and MgF are used as the second additive element source 89. ２ In this case, the heating in step S72 is preferably performed at 700° C. or higher. ２ Since the eutectic point of is around 742°C, it is preferable to heat in step S72 to 742°C or higher.

[0143] Also, LiCoO ２ :LiF:MgF ２ When mixture 97 is obtained by mixing the components so that the molar ratio becomes 100:0.33:1, an endothermic peak is observed around 830° C. in differential scanning calorimetry (DSC measurement). Therefore, it is more preferable to heat the components in step S72 to a temperature of 830° C. or higher.

[0144] A higher heating temperature is preferable because the reaction proceeds more easily, the heating time is shorter, and productivity is higher.

[0145] The heating temperature was the decomposition temperature of the composite oxide 98 (LiCoO ２The decomposition temperature of the composite oxide 98 is set to be less than 1130°C. At temperatures close to the decomposition temperature, there is a concern that the composite oxide 98 may decompose, albeit only slightly. Therefore, the temperature is more preferably 1000°C or less, even more preferably 950°C or less, and even more preferably 900°C or less.

[0146] In consideration of these, the heating temperature in step S72 is preferably 500°C to 1130°C, more preferably 700°C to 1000°C, even more preferably 700°C to 950°C, and even more preferably 700°C to 900°C. Also, it is preferably 742°C to 1130°C, more preferably 742°C to 1000°C, even more preferably 742°C to 950°C, and even more preferably 742°C to 900°C. Also, it is preferably 800°C to 1100°C, or 830°C to 1130°C, more preferably 830°C to 1000°C, more preferably 830°C to 950°C, and even more preferably 830°C to 900°C.

[0147] Furthermore, when the mixture 97 is heated, it is preferable to control the partial pressure of fluorine or fluoride resulting from the fluorine source or the like in the heating environment within an appropriate range.

[0148] In this manufacturing method, the fluorine source LiF may function as a flux, which allows the heating temperature in step S72 to be lower than the decomposition temperature of the composite oxide 98, for example, to a temperature between 742°C and 950°C, thereby distributing the second additive element Y, such as magnesium, in the surface layer portion and producing a positive electrode active material with good characteristics.

[0149] However, since LiF has a lower specific gravity in a gaseous state than oxygen, there is a possibility that LiF may sublime when heated, and if it sublimes, the amount of LiF in the mixture 97 will decrease. This will weaken its function as a flux. Therefore, it is necessary to heat the mixture while suppressing the sublimation of LiF. Note that even if LiF is not used as the fluorine source, Li on the surface of the composite oxide 98 may react with F in a fluorine source other than LiF, resulting in the generation of LiF, which may then sublimate. Therefore, even if a fluoride with a higher melting point than LiF is used as a fluorine source other than LiF, it is still necessary to suppress sublimation.

[0150] To suppress sublimation, there is a method of heating the mixture 97 in an atmosphere containing LiF. This method involves making the atmosphere in a heating furnace that heats the mixture 97 into a state where the partial pressure of LiF is high. Another method is to place a lid on the container that contains the mixture 97. By using such a method, it is possible to suppress the sublimation of LiF in the mixture 97, i.e., the decrease in LiF.

[0151] The heating in step S72 can be performed using a roller hearth kiln. In the roller hearth kiln, the mixture 97 can be heated while being moved within the kiln with a lid placed on the container containing the mixture 97. By placing a lid, the mixture 97 can be heated in an atmosphere containing LiF, and the sublimation, i.e., reduction, of LiF in the mixture 97 can be suppressed.

[0152] Alternatively, the heating in step S72 can be performed using a rotary kiln. It is preferable that the atmosphere in the rotary kiln contains oxygen, and heating is performed while controlling the flow rate of oxygen. To suppress the sublimation, i.e., reduction, of LiF in the mixture 97, it is preferable to reduce the flow rate of oxygen. One way to reduce the flow rate of oxygen is to first introduce oxygen into the kiln and hold it there for a certain period of time, and then not introduce oxygen thereafter.

[0153] As described above, it is believed that when LiF is present in the surface layer portion, or when at least fluorine is present in the surface layer portion, a positive electrode active material with a smooth surface and less irregularities can be obtained.

[0154] The heating in step S72 is preferably performed so as not to cause adhesion of particles of the mixture 97. If the particles of the mixture 97 adhere to each other during heating, the contact area with oxygen in the atmosphere will decrease and the path along which one of the second additional elements Y (e.g., fluorine) will diffuse will be blocked, which may result in a deterioration in the distribution of the second additional element Y (e.g., magnesium).

[0155] After heating the mixture 97, it is advisable to classify the mixture using a sieve with an opening diameter of 40 μm to 60 μm, in order to prevent the particles from adhering to each other.

[0156] 7 and 8, which explain manufacturing method 4, the explanations regarding manufacturing methods 1 to 3 can be referred to except for the different configurations and methods described above.

[0157] According to manufacturing method 4, a positive electrode active material 100 such as lithium cobalt oxide can be manufactured. The positive electrode active material 100 can reflect the shape of the precursor cobalt compound 95. Furthermore, according to manufacturing method 4, the first additional element X can be present throughout the positive electrode active material 100, and the second additional element Y can be present in the surface layer portion of the positive electrode active material 100. However, if the ionic radius of the first additional element X is larger than the ionic radius of the transition metal M1, it is difficult for the first additional element X to form a solid solution and may migrate to the surface layer portion.

[0158] Furthermore, lithium cobalt oxide is preferable because it contains few impurities. However, when sulfide is used as the starting material, sulfur may be detected in the lithium cobalt oxide. The sulfur concentration can be measured by performing elemental analysis of the entire particles of the positive electrode active material using GD-MS, ICP-MS, etc.

[0159] <Manufacturing Method 5> The procedure of manufacturing method 5 will be described using the flow charts shown in Figures 9 and 10. Note that Figure 10 is a flow chart that details some of the procedures in Figure 9, but the detailed procedures are not necessarily required.

[0160] Production method 5 differs from production method 3 in that a second additive element source 89 (referred to as a Y source in the drawings) is introduced into the composite oxide 98 together with a first additive element source 82 (referred to as an X source in the drawings).

[0161] 9 and 10, which explain manufacturing method 5, the explanations regarding manufacturing methods 1 to 4 can be referred to except for the different configurations and methods described above.

[0162] According to Production Method 5, a positive electrode active material 100 such as lithium cobalt oxide can be produced. The positive electrode active material 100 can reflect the shape of the precursor cobalt compound 95. Furthermore, according to Production Method 5, the first additional element X and the second additional element Y can be present in the surface layer portion of the positive electrode active material 100.

[0163] Furthermore, lithium cobalt oxide is preferable because it contains few impurities. However, when sulfide is used as the starting material, sulfur may be detected in the lithium cobalt oxide. The sulfur concentration can be measured by performing elemental analysis of the entire particles of the positive electrode active material using GD-MS, ICP-MS, etc.

[0164] <Manufacturing Method 6> The procedure of manufacturing method 6 will be described using the flow charts shown in Figures 11 to 13. Note that Figures 12 and 13 are flow charts that detail some of the procedures in Figure 11, but the detailed procedures are not necessarily required. The procedure continues from A in Figure 12 to A in Figure 13.

[0165] In manufacturing method 6, the second additive element source 89 (referred to as Y source in the drawings) added to the steps of manufacturing method 4 is introduced in two separate batches, respectively, into composite oxide 98 and composite oxide 99. Here, the second additive element source 89 introduced in two separate batches will be described with different ordinal numbers, and will be referred to as the second additive element source 89 and the third additive element source 90, respectively. Note that both the second additive element source 89 and the third additive element source 90 are materials containing the second additive element Y.

[0166] <Second Additional Element Source (Y1 Source), Third Additional Element Source (Y2 Source)> The second additional element source 89 and the third additional element source 90 (referred to as the Y1 source and the Y2 source, respectively, in the drawings) shown in Figures 11 to 13 will be described. The second additional element source can be added in two or more batches. This process will be described for the case where the second additional element source is added in two batches. The elements contained in the second additional element source 89 and the third additional element source 90 can be selected from the elements that can be used as the second additional element Y described above, and it is preferable to select different elements from each other. For example, it is preferable to use a magnesium source and a fluorine source as the Y1 source, and an aluminum source and a nickel source as the Y2 source.

[0167] Although not shown, the source of the second additive element may be added in three or more portions, in which case the Y1 source may be a magnesium source and a fluorine source, the Y2 source may be a nickel source, and the Y3 source may be an aluminum source and a zirconium source. The Y3 source may be added by a sol-gel method using an alkoxide.

[0168] 11 and 13, steps S76 and S77 will be described. In step S76, a source 90 of the third additive element to be added last is mixed with a composite oxide 99 to form a mixture 94, and in step S77, the mixture 94 is heated. Step S72 can be referred to for the heating conditions.

[0169] 11 to 13, which explain the manufacturing method 6, the explanations regarding the manufacturing methods 1 to 5 can be referred to except for the different configurations and methods described above.

[0170] According to Production Method 6, a positive electrode active material 100 such as lithium cobalt oxide can be produced. The positive electrode active material 100 can reflect the shape of the precursor cobalt compound 95. Furthermore, according to Production Method 6, the first additional element X can be present inside or throughout (including the inside and the surface layer portion) of the positive electrode active material 100, and the second additional element Y1 and the second additional element Y2 can be present in the surface layer portion of the positive electrode active material 100.

[0171] Furthermore, lithium cobalt oxide is preferable because it contains few impurities. However, when sulfide is used as the starting material, sulfur may be detected in the lithium cobalt oxide. The sulfur concentration can be measured by performing elemental analysis of the entire particles of the positive electrode active material using GD-MS, ICP-MS, etc.

[0172] <Manufacturing Method 7> The procedure for manufacturing method 7 will be described using the flow charts shown in Figures 14 to 16. Note that Figures 15 and 16 are flow charts that detail some of the procedures in Figure 14, but the detailed procedures are not necessarily required. The procedure continues from B in Figure 15 to B in Figure 16.

[0173] In manufacturing method 7, in manufacturing method 6, the first additive element source 82 is not introduced simultaneously with the cobalt source 81, but the first additive element source 82 is introduced simultaneously with the third additive element source 90 (referred to as Y2 source in the drawings) when the third additive element source 90 is introduced into the composite oxide 99.

[0174] The element selected as the first additional element X (for example, gallium) and the element selected as the third additional element Y2 (for example, aluminum) have the same valence. It is preferable to add such elements with the same valence at the same time. Furthermore, gallium as the first additional element X may be added instead of aluminum as the third additional element Y2.

[0175] 14 to 16, which explain manufacturing method 7, the explanations regarding manufacturing methods 1 to 5 can be referred to except for the different configurations and methods described above.

[0176] According to Production Method 7, a positive electrode active material 100 such as lithium cobalt oxide can be produced. The positive electrode active material 100 can reflect the shape of the precursor cobalt compound 95. Furthermore, according to Production Method 7, the first additional element X, the second additional element Y1, and the third additional element Y2 can be present in the surface layer portion of the positive electrode active material 100.

[0177] Furthermore, lithium cobalt oxide is preferable because it contains few impurities. However, when sulfide is used as the starting material, sulfur may be detected in the lithium cobalt oxide. The sulfur concentration can be measured by performing elemental analysis of the entire particles of the positive electrode active material using GD-MS, ICP-MS, etc.

[0178] <Production Method 8> The procedure for Production Method 8 will be described. Production Method 8 can be applied to any of Production Methods 1 to 7, and is a production method carried out after obtaining the positive electrode active material 100. Note that Production Method 8 does not necessarily have to be carried out.

[0179] The cathode active material 100 according to one embodiment of the present invention may be a cathode active material composite having a coating layer that covers at least a portion of the cathode active material 100. Examples of the coating layer include glass, oxide, and LiMPO ４ (M2 is one or more selected from Fe, Ni, Co, and Mn).

[0180] The glass contained in the coating layer of the positive electrode active material composite can be a material having an amorphous portion. Examples of the material having an amorphous portion include SiO ２ , SiO, Al ２ O３ , TiO ２ , Li ４ SiO ４ , Li ３ P.O. ４ , Li ２ S, SiS ２ , B ２ S ３ , GeS ４ , AgI, Ag ２ O, Li ２ O, P ２ O ５ , B ２ O ３ , and V ２ O ５ A material having one or more selected from the group consisting of Li, ７ P ３ S １１ , or Li １＋ｘ＋ｙ Al ｘ Ti ２−ｘ Si ｙ P ３−ｙ O １２ (0<x<2, 0<y<3), etc., can be used. A material having an amorphous portion can be used in an amorphous state as a whole, or in a partially crystallized state as crystallized glass (also called glass ceramics). The glass desirably has lithium ion conductivity. Lithium ion conductivity can also be said to have lithium ion diffusibility and lithium ion penetration. The glass preferably has a melting point of 800°C or less, more preferably 500°C or less. The glass preferably has electron conductivity. The glass preferably has a softening point of 800°C or less, for example, Li ２ O-B ２ O ３ -SiO ２ Glasses containing fluorine can be used.

[0181] Examples of oxides contained in the coating layer of the positive electrode active material composite include aluminum oxide, zirconium oxide, hafnium oxide, and niobium oxide. ４ (M2 is one or more selected from Fe, Ni, Co, and Mn) ４ , LiNiPO ４, LiCoPO ４ , LiMnPO ４ , LiFe ａ Ni ｂ P.O. ４ , LiFe ａ Co ｂ P.O. ４ , LiFe ａ Mn ｂ P.O. ４ , LiNi ａ Co ｂ P.O. ４ , LiNi ａ Mn ｂ P.O. ４ (a+b is 1 or less, 0<a<1, 0<b<1), LiFe ｃ Ni ｄ Co ｅ P.O. ４ , LiFe ｃ Ni ｄ Mn ｅ P.O. ４ , LiNi ｃ Co ｄ Mn ｅ P.O. ４ (c+d+e is 1 or less, 0<c<1, 0<d<1, 0<e<1), LiFe ｆ Ni ｇ Co ｈ Mn ｉ P.O. ４ (f+g+h+i is 1 or less, 0<f<1, 0<g<1, 0<h<1, 0<i<1), etc.

[0182] A composite treatment can be used to prepare the coating layer of the positive electrode active material composite. Examples of the composite treatment include one or more of the following: composite treatments using mechanical energy, such as mechanochemical, mechanofusion, and ball milling; composite treatments using liquid-phase reactions, such as coprecipitation, hydrothermal, and sol-gel; and composite treatments using gas-phase reactions, such as barrel sputtering, atomic layer deposition (ALD), vapor deposition, and chemical vapor deposition (CVD). For example, Picobond, manufactured by Hosokawa Micron, can be used as a composite treatment using mechanical energy. Furthermore, it is preferable to perform a heat treatment once or multiple times during the composite treatment.

[0183] The positive electrode active material composite reduces contact of the positive electrode active material 100 with the electrolyte solution and the like, thereby suppressing deterioration of the secondary battery.

[0184] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0185] Embodiment 2 In this embodiment, a positive electrode active material of one embodiment of the present invention will be described.

[0186] [Positive Electrode Active Material] Positive electrode active materials of one embodiment of the present invention will be described with reference to FIGS.

[0187] 17A is a schematic top view of a positive electrode active material 100 according to one embodiment of the present invention. Schematic cross-sectional views taken along line A-B in FIG. 17A are shown in FIGS. 17B and 17C.

[0188] [Containing Elements and Distribution] The positive electrode active material 100 contains lithium, a transition metal M1, oxygen, and a first additional element X and / or a second additional element Y. The positive electrode active material 100 contains the first additional element X and / or the second additional element Y, and is represented by the formula LiM1O ２ It can be said that the compound oxide is represented by the formula:

[0189] The transition metal M1 contained in the positive electrode active material 100 is preferably a metal capable of forming a layered rock-salt composite oxide belonging to the space group R-3m with lithium. For example, at least one of manganese, cobalt, and nickel can be used as the transition metal M1. That is, the transition metal M1 contained in the positive electrode active material 100 may be cobalt alone, nickel alone, a combination of cobalt and manganese, or a combination of cobalt and nickel, or three of cobalt, manganese, and nickel. That is, the positive electrode active material 100 may have a composite oxide containing lithium and the transition metal M1, such as lithium cobalt oxide, lithium nickel oxide, lithium cobalt oxide in which some of the cobalt is substituted with manganese, lithium cobalt oxide in which some of the cobalt is substituted with nickel, or nickel-manganese-lithium cobalt oxide.

[0190] The first additive element X contained in the positive electrode active material 100 is preferably one or more selected from gallium, aluminum, boron, nickel, and indium. The positive electrode active material 100 preferably contains a second additive element Y in addition to the first additive element X. The second additive element Y is preferably one or more selected from nickel, cobalt, magnesium, calcium, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron. The first additive element X and / or the second additive element Y may further stabilize the crystal structure of the positive electrode active material 100, as described below. That is, the positive electrode active material 100 may include lithium cobalt oxide doped with gallium, lithium cobalt oxide doped with gallium and magnesium, lithium cobalt oxide doped with gallium, magnesium, and fluorine, lithium cobalt oxide doped with magnesium and fluorine, lithium cobalt oxide doped with magnesium, fluorine, and titanium, lithium nickel-cobalt oxide doped with magnesium and fluorine, lithium cobalt-aluminate doped with magnesium and fluorine, nickel-cobalt-lithium aluminum oxide doped with magnesium and fluorine, nickel-cobalt-lithium aluminum oxide, nickel-cobalt-lithium aluminum oxide doped with magnesium and fluorine, nickel-manganese-cobalt oxide doped with magnesium and fluorine, etc. In this specification and the like, the first additional element X and the second additional element Y may be referred to interchangeably as an additive, a mixture, a part of a raw material, etc.

[0191] 17B , the positive electrode active material 100 has a surface layer portion 100a and an interior portion 100b. The region of the positive electrode active material 100 deeper than the surface layer portion 100a is referred to as the interior portion 100b. The interior portion 100b contains the first additional element X, and it is preferable that the first additional element X is contained throughout the entire region of the interior portion 100b. Note that the first additional element X may be contained not only in the interior portion 100b but also in the surface layer portion 100a.

[0192] Furthermore, in addition to the region having the first additional element X shown in Fig. 17B, the surface layer portion 100a may have a second additional element Y. It is preferable that the concentration of the second additional element Y is higher in the surface layer portion 100a than in the interior portion 100b. When the second additional element Y is present in the surface layer portion 100a, it is preferable that the second additional element Y has a concentration gradient that increases from the interior toward the surface, as shown by the gradation in Fig. 17C. The surface created by a crack may also be considered a surface.

[0193] In the positive electrode active material 100 of one embodiment of the present invention, closed cracks that occur in the interior 100b during charge and discharge are expected to be less likely to occur by having the first additional element X in the interior 100b.

[0194] Furthermore, in the cathode active material 100 according to one embodiment of the present invention, the surface layer 100a having a high concentration of the second additive element Y, i.e., the outer periphery of the particle, reinforces the surface layer 100a having a high concentration of the second additive element Y so that the layered structure formed of octahedra of cobalt and oxygen is not destroyed even when lithium is removed from the cathode active material 100 upon charging. The surface layer 100a having a high concentration of the second additive element Y is desirably provided on at least a portion of the surface layer of the particle, preferably on at least half of the surface layer of the particle, and more preferably on the entire surface layer of the particle.

[0195] In addition, in the positive electrode active material 100 of one embodiment of the present invention, it is desirable that the concentration gradient region of the second additive element Y is provided in at least a part of the surface layer portion of the particle, preferably more than half of the surface layer portion of the particle, and more preferably the entire surface layer portion of the particle. This is because even if a part of the surface layer portion 100a is reinforced, if there is a part without reinforcement, stress may concentrate in the unreinforced part, which is undesirable. If stress concentrates in a part within the particle, defects such as closed cracks and fissures may occur, which may lead to cracking of the positive electrode active material and a decrease in charge / discharge capacity.

[0196] Gallium, aluminum, boron, and indium are trivalent and can exist at the transition metal site in the layered rock salt crystal structure. Gallium, aluminum, boron, and indium can suppress the dissolution of surrounding cobalt. Furthermore, gallium, aluminum, boron, and indium can suppress cation mixing of surrounding cobalt (cobalt moving to the lithium site). Furthermore, gallium, aluminum, boron, and indium have strong bonding strength with oxygen, so they can suppress the detachment of oxygen from around gallium, aluminum, boron, and indium. Therefore, when the first additive element X contains one or more of gallium, aluminum, boron, and indium, the positive electrode active material 100 can be made to have a crystal structure that is less likely to collapse even after repeated charge and discharge.

[0197] Magnesium is divalent and is more stable at the lithium site than at the transition metal site in the layered rock-salt crystal structure, and therefore more likely to enter the lithium site. The presence of magnesium at an appropriate concentration at the lithium site in the surface layer 100a facilitates the maintenance of the layered rock-salt crystal structure. Furthermore, magnesium has a strong bond with oxygen, which can suppress the desorption of oxygen around the magnesium. At an appropriate concentration, magnesium is preferable because it does not adversely affect the intercalation and deintercalation of lithium during charge and discharge. However, excessive magnesium may adversely affect the intercalation and deintercalation of lithium.

[0198] Fluorine is a monovalent anion, and when a portion of the oxygen in the surface layer portion 100a is substituted with fluorine, the lithium desorption energy is reduced. This is because the change in valence of cobalt ions accompanying lithium desorption differs depending on whether or not fluorine is present. For example, the oxidation-reduction potential of cobalt ions differs, from trivalent to tetravalent in the absence of fluorine, and from divalent to trivalent in the presence of fluorine. Therefore, when a portion of the oxygen in the surface layer portion 100a of the positive electrode active material 100 is substituted with fluorine, it can be said that desorption and insertion of lithium ions near the fluorine is more likely to occur smoothly. Therefore, when used in a secondary battery, charge / discharge characteristics, rate characteristics, etc. are improved, which is preferable.

[0199] Titanium oxide is known to have superhydrophilicity. Therefore, by forming the cathode active material 100 with titanium oxide in the surface layer portion 100a, it is possible that the cathode active material 100 has good wettability with highly polar solvents. When formed into a secondary battery, it is possible that the interface between the cathode active material 100 and a highly polar electrolyte solution will have good contact, thereby suppressing an increase in resistance. In this specification and the like, the term "electrolyte solution" may be used interchangeably with "electrolyte."

[0200] As the charging voltage of a secondary battery increases, the voltage of the positive electrode generally increases. The positive electrode active material of one embodiment of the present invention has a stable crystal structure even at high voltages. The stable crystal structure of the positive electrode active material in a charged state can suppress a decrease in capacity due to repeated charge and discharge.

[0201] Furthermore, a short circuit in a secondary battery not only causes problems in the charging and / or discharging operations of the secondary battery, but may also lead to heat generation and fire. To achieve a safe secondary battery, it is preferable that a short circuit current be suppressed even at a high charging voltage. The positive electrode active material 100 of one embodiment of the present invention suppresses a short circuit current even at a high charging voltage. Therefore, a secondary battery that achieves both high capacity and safety can be obtained.

[0202] A secondary battery using the positive electrode active material 100 of one embodiment of the present invention preferably simultaneously satisfies high capacity, excellent charge / discharge cycle characteristics, and safety.

[0203] The concentration gradient of the additive can be evaluated, for example, using energy dispersive X-ray spectroscopy (EDX). EDX can be used in combination with SEM or STEM. Among EDX measurements, evaluation along a line segment connecting two points is sometimes called EDX ray analysis. Among EDX measurements, measurement while scanning a rectangular or other region and two-dimensional evaluation of the region is sometimes called EDX area analysis. In addition, extraction of data of a linear region from EDX area analysis and evaluation of the distribution of atomic concentration in the positive electrode active material are also sometimes called EDX ray analysis.

[0204] EDX area analysis (e.g., element mapping) can quantitatively analyze the concentrations of additives in the surface layer portion 100a, the interior portion 100b, and near the grain boundaries of the positive electrode active material 100. Furthermore, EDX ray analysis can analyze the distribution of the concentrations of the first additive element X and the second additive element Y.

[0205] When EDX-ray analysis is performed on the positive electrode active material 100, the peak of the magnesium concentration (the position where the concentration is maximum) in the surface layer portion 100a is preferably present at a depth of up to 3 nm from the surface toward the center of the positive electrode active material 100, more preferably at a depth of up to 1 nm, and even more preferably at a depth of up to 0.5 nm.

[0206] Furthermore, the fluorine distribution in the positive electrode active material 100 preferably overlaps with the magnesium distribution, and therefore, when EDX-ray analysis is performed, the peak of the fluorine concentration (the position where the concentration is maximum) in the surface layer portion 100 a is preferably present at a depth of up to 3 nm from the surface of the positive electrode active material 100 toward the center, more preferably at a depth of up to 1 nm, and even more preferably at a depth of up to 0.5 nm.

[0207] As mentioned above, an excess of additives in the positive electrode active material 100 may adversely affect the insertion and extraction of lithium. Furthermore, when used in a secondary battery, this may result in an increase in resistance and a decrease in capacity. On the other hand, if the additives are insufficient, they may not be distributed throughout the entire surface layer 100a, resulting in an insufficient effect of maintaining the crystalline structure. Thus, the additives must be present at an appropriate concentration in the positive electrode active material 100, but adjusting this concentration is not easy.

[0208] Therefore, for example, the positive electrode active material 100 may have a region where excess additive is unevenly distributed. The presence of such a region allows the excess additive to be removed from other regions, thereby achieving an appropriate additive concentration in the interior and most of the surface layer of the positive electrode active material 100. By achieving an appropriate additive concentration in the interior and most of the surface layer of the positive electrode active material 100, an increase in resistance and a decrease in capacity when the positive electrode active material 100 is used as a secondary battery can be suppressed. The ability to suppress an increase in resistance of a secondary battery is an extremely desirable characteristic, particularly during high-rate charging and discharging.

[0209] Furthermore, in the positive electrode active material 100 having a region where the excess additive is unevenly distributed, it is permissible to mix the additive in excess to some extent during the manufacturing process, which is preferable because it widens the margin in production.

[0210] In this specification and the like, uneven distribution refers to the concentration of an element in a certain region being different from that in other regions. The uneven distribution may also be referred to as segregation, precipitation, non-uniformity, bias, high concentration, low concentration, etc.

[0211] [Crystal structure] Lithium cobalt oxide (LiCoO ２ Materials having a layered rock salt type crystal structure, such as LiM1O2, have a high discharge capacity and are known to be excellent as positive electrode active materials for secondary batteries. ２ Examples of the composite oxide include those represented by the following formula:

[0212] It is known that the strength of the Jahn-Teller effect in transition metal compounds varies depending on the number of electrons in the d orbital of the transition metal.

[0213] In compounds containing nickel, distortion may easily occur due to the Jahn-Teller effect. ２ When LiCoO is charged and discharged at a high voltage, there is a concern that the crystal structure may be destroyed due to distortion. ２ It is suggested that the influence of the Jahn-Teller effect is small in this case, and the durability of charge and discharge at high voltages may be superior, which is preferable.

[0214] The positive electrode active material will be described with reference to Fig. 18 to Fig. 21. Fig. 18 to Fig. 21 describe a case where cobalt is used as the transition metal contained in the positive electrode active material.

[0215] The positive electrode active material shown in FIG. 20 is a lithium cobalt oxide (LiCoO ２ The crystal structure of the lithium cobalt oxide shown in FIG. 20 changes depending on the charge depth. In other words, LixCoO ２ In this case, the crystal structure changes depending on the occupancy rate x of lithium at the lithium site.

[0216] As shown in FIG. 20, lithium cobalt oxide in the state of x=1 (discharged state) has a region having a crystal structure of the space group R-3m, and CoO ２ There are three layers. Therefore, this crystal structure is sometimes called an O3 type crystal structure. ２ The layer refers to a structure in which octahedral structures in which cobalt is six-coordinated with oxygen atoms are continuous in the plane direction with edge sharing.

[0217] When x = 0, the crystal structure has a space group P-3m1, and CoO ２ There is one layer. Therefore, this crystal structure is sometimes called an O1-type crystal structure (trigonal O1).

[0218] When x is about 0.12, lithium cobalt oxide has a crystal structure of the space group R-3m. This structure is similar to CoO such as P-3m1(O1). ２ and LiCoO such as R-3m(O3). ２ It can also be said that the structure of and the structure of are stacked alternately. Therefore, this crystal structure is sometimes called an H1-3 type crystal structure. Since actual lithium insertion and desorption can be uneven, the H1-3 type crystal structure is experimentally observed from about x = 0.25. In reality, the number of cobalt atoms per unit cell in the H1-3 type crystal structure is twice that of other structures. However, in Figure 20 and other parts of this specification, to make it easier to compare with other structures, the c-axis of the H1-3 type crystal structure is shown as half the unit cell.

[0219] As an example of the H1-3 type crystal structure, the coordinates of cobalt and oxygen in the unit cell are Co(0,0,0.42150±0.00016), O １ (0,0,0.27671±0.00045), O ２ It can be expressed as (0,0,0.11535±0.00045). １ and O ２are oxygen atoms. In this way, the H1-3 crystal structure is represented by a unit cell using one cobalt and two oxygen atoms. On the other hand, as described below, the O3' crystal structure of one embodiment of the present invention is preferably represented by a unit cell using one cobalt and one oxygen atom. This indicates that the symmetry between cobalt and oxygen differs between the O3' crystal structure and the H1-3 structure, and the O3' crystal structure exhibits a smaller change from the O3 structure than the H1-3 structure. The unit cell that is more preferably used to represent the crystal structure of the positive electrode active material may be selected, for example, so as to reduce the goodness of fit (GOF) value in Rietveld analysis of X-ray diffraction (XRD).

[0220] When lithium cobalt oxide is repeatedly charged at a high voltage of 4.6 V or higher based on the redox potential of lithium metal, or when it is deeply charged to a depth of x of 0.24 or lower, and then discharged, the crystal structure of the lithium cobalt oxide repeatedly changes (i.e., undergoes a non-equilibrium phase change) between the H1-3 crystal structure and the R-3m(O3) structure in the discharged state.

[0221] However, these two crystal structures are different from CoO ２ As shown by the dotted lines and arrows in FIG. 20, in the H1-3 type crystal structure, CoO ２ The layers deviate significantly from R-3m(O3). Such dynamic structural changes can adversely affect the stability of the crystal structure.

[0222] Furthermore, the difference in volume is large: when compared per the same number of cobalt atoms, the difference in volume between the H1-3 type crystal structure and the O3 type crystal structure in a discharged state is 3.0% or more.

[0223] In addition, the H1-3 type crystal structure has CoO such as P-3m1(O1). ２ A structure with continuous layers is likely to be unstable.

[0224] Therefore, repeated high-voltage charging and discharging causes the crystalline structure of lithium cobalt oxide to collapse, which leads to a deterioration in cycle characteristics. This is thought to be because the collapse of the crystalline structure reduces the number of sites where lithium can exist stably and makes it difficult for lithium to be inserted and extracted.

[0225] The positive electrode active material 100 of one embodiment of the present invention is a material that can be used in a wide range of applications, including high-voltage charging and discharging. ２ The layer misalignment can be reduced. Furthermore, the volume change can be reduced. Therefore, the positive electrode active material of one embodiment of the present invention can achieve excellent cycle characteristics. Furthermore, the positive electrode active material of one embodiment of the present invention can have a stable crystal structure in a charged state at a high voltage. Therefore, the positive electrode active material of one embodiment of the present invention may be less likely to cause a short circuit when maintained in a charged state at a high voltage. In such a case, safety is further improved, which is preferable.

[0226] In the positive electrode active material of one embodiment of the present invention, the change in crystal structure and the difference in volume per the same number of transition metal atoms between a fully discharged state and a high-voltage charged state are small.

[0227] The crystal structure of the positive electrode active material 100 before and after charge and discharge is shown in Figure 18. The positive electrode active material 100 is a composite oxide containing lithium, cobalt as a transition metal, and oxygen. In addition to the above, it is preferable that the positive electrode active material 100 contains magnesium as the second additional element Y. It is also preferable that the second additional element Y further contains a halogen such as fluorine or chlorine.

[0228] The crystal structure of x=1 (discharged state) in Figure 18 is the same as that of Figure 20, R-3m(O3). On the other hand, when the positive electrode active material 100 is fully charged, it has a crystal structure different from the H1-3 type crystal structure. This structure is in the space group R-3m, and is not a spinel type crystal structure, but ions such as cobalt and magnesium occupy the oxygen hexacoordination positions, and the arrangement of cations has a symmetry similar to that of the spinel type. In addition, the CoO ２The periodicity of the layers is the same as that of the O3 type. Therefore, in this specification and the like, this structure is referred to as an O3' type crystal structure or a pseudo-spinel type crystal structure. Therefore, the O3' type crystal structure may also be referred to as a pseudo-spinel type crystal structure. In the diagram of the O3' type crystal structure shown in FIG. 18, lithium is omitted in order to explain the symmetry of the cobalt atoms and the symmetry of the oxygen atoms, but in reality, CoO ２ Between the layers, for example, 20 atomic % or less of lithium is present relative to cobalt. In both the O3 type crystal structure and the O3' type crystal structure, CoO ２ It is preferable that magnesium is present in a dilute form between the layers, i.e., at the lithium sites, and it is also preferable that halogen such as fluorine is present randomly and dilutely at the oxygen sites.

[0229] The O3'-type crystal structure has random Li atoms between layers, but CdCl ２ It can be said that this crystal structure is similar to that of the CdCl type. ２ A crystal structure similar to the type was formed when lithium nickel oxide was charged to x = 0.06 (Li ０．０６ NiO ２ ), but it is known that pure lithium cobaltate or layered rock salt-type positive electrode active materials containing a large amount of cobalt do not usually adopt this crystal structure.

[0230] In the positive electrode active material 100 of one embodiment of the present invention, when a large amount of lithium is released by charging at a high voltage, the change in the crystal structure is suppressed more than in conventional positive electrode active materials. For example, as shown by the dotted line in FIG. 18 , in these crystal structures, CoO ２ There is almost no layer misalignment.

[0231] More specifically, the cathode active material 100 of one embodiment of the present invention has high structural stability even at high charge voltages. For example, in conventional cathode active materials, there exists a charge voltage region where the R-3m(O3) crystal structure can be maintained even at a charge voltage where the H1-3 crystal structure is formed, for example, at a voltage of about 4.6 V relative to the potential of lithium metal. Furthermore, there exists a region where the O3' crystal structure can be formed even at a higher charge voltage, for example, at a voltage of about 4.65 V to 4.7 V relative to the potential of lithium metal. Furthermore, there exists a region where the H1-3 crystal structure can be formed even at a higher charge voltage, for example, at a voltage of about 4.65 V to 4.7 V relative to the potential of lithium metal. Furthermore, there exists a region where the H1-3 crystal can be formed even at a higher charge voltage, for example, at a voltage of 4.3 V or higher and 4.5 V or lower relative to the potential of lithium metal.

[0232] Therefore, in the positive electrode active material 100 of one embodiment of the present invention, the crystal structure is not easily broken even when charge and discharge are repeated at a high voltage.

[0233] In the positive electrode active material 100, the difference in volume per unit cell between the O3 type crystal structure where x=1 and the O3′ type crystal structure where x=0.2 is 2.5% or less, more specifically 2.2% or less.

[0234] In the O3' type crystal structure, the coordinates of cobalt and oxygen in the unit cell can be expressed within the range of Co(0,0,0.5), O(0,0,x), 0.20≦x≦0.25.

[0235] CoO ２ The second additive element Y, for example, magnesium, which is present randomly and dilutely between the layers, i.e., at the lithium site, is CoO ２ This has the effect of suppressing layer misalignment. ２The presence of magnesium between layers tends to result in an O3'-type crystal structure. Therefore, magnesium is preferably present in at least a portion of the surface layer of the particle of the positive electrode active material 100 of one embodiment of the present invention, preferably in at least half of the surface layer of the particle, and more preferably in the entire surface layer of the particle. Furthermore, in order to distribute magnesium throughout the entire surface layer of the particle, heat treatment is preferably performed in the manufacturing process of the positive electrode active material 100 of one embodiment of the present invention.

[0236] However, if the heat treatment temperature is too high, cation mixing occurs, increasing the possibility that the second additive element Y, for example, magnesium, will enter the cobalt site. Magnesium present at the cobalt site is ineffective in maintaining the R-3m structure in a high-voltage charging state. Furthermore, if the heat treatment temperature is too high, there are concerns about adverse effects such as cobalt being reduced to a divalent state and lithium evaporating.

[0237] Therefore, it is preferable to add a halogen compound such as a fluorine compound to the lithium cobalt oxide before the heat treatment to distribute magnesium throughout the entire surface layer. Adding the halogen compound lowers the melting point of the lithium cobalt oxide. Lowering the melting point makes it easier to distribute magnesium throughout the particles at a temperature where cation mixing is unlikely to occur. Furthermore, the presence of a fluorine compound is expected to improve corrosion resistance to hydrofluoric acid produced by decomposition of the electrolyte.

[0238] Note that if the magnesium concentration is increased above a desired value, the effect on stabilizing the crystal structure may be reduced. This is thought to be because magnesium enters the cobalt site in addition to the lithium site. The number of magnesium atoms in the positive electrode active material of one embodiment of the present invention is preferably 0.001 to 0.1 times the number of transition metal atoms, more preferably more than 0.01 to less than 0.04 times, and even more preferably about 0.02 times. The magnesium concentration shown here may be, for example, a value obtained by performing elemental analysis of the entire particles of the positive electrode active material using ICP-MS or the like, or may be based on the value of the raw material composition in the process of producing the positive electrode active material.

[0239] Transition metals such as nickel and manganese, as well as gallium, aluminum, boron, and indium, are preferably present at the cobalt site, and some may be present at the lithium site, but the less the better. Magnesium is preferably present at the lithium site. Oxygen may be partially substituted with fluorine.

[0240] As the contents of the first additive element X and the second additive element Y in the positive electrode active material of one embodiment of the present invention increase, the capacity of the positive electrode active material may decrease. For example, the cause of this may be that gallium, aluminum, boron, or indium enters the transition metal site, preventing nearby lithium ions from contributing to charge and discharge. Furthermore, the amount of lithium contributing to charge and discharge may decrease when magnesium enters the lithium site. Furthermore, excessive magnesium may produce a magnesium compound that does not contribute to charge and discharge.

[0241] In Figure 18, the symmetry of oxygen atoms is slightly different between the O3 type crystal structure and the O3' type crystal structure. Specifically, in the O3 type crystal structure, oxygen atoms are aligned along the dotted line, whereas in the O3' type crystal structure, oxygen atoms are not aligned strictly. This is because in the O3' type crystal structure, tetravalent cobalt increases with the decrease in lithium, causing Jahn-Teller distortion to increase, resulting in CoO ６ This is because the octahedral structure of CoO is distorted. ２ Another factor is the increased repulsion between oxygen atoms in the layers.

[0242] As described above, the surface layer portion 100a of the positive electrode active material 100 of one embodiment of the present invention preferably has a different composition from the interior portion 100b, i.e., a higher concentration of the second additive element Y, such as magnesium and fluorine, than the interior portion 100b. Furthermore, the composition preferably has a stable crystal structure at room temperature. Therefore, the surface layer portion 100a may have a different crystal structure from the interior portion 100b. For example, at least a portion of the surface layer portion 100a of the positive electrode active material 100 of one embodiment of the present invention may have a rock salt crystal structure. Furthermore, when the surface layer portion 100a and the interior portion 100b have different crystal structures, it is preferable that the crystal orientations of the surface layer portion 100a and the interior portion 100b approximately match.

[0243] The anions in the layered rock salt crystal and the rock salt crystal have a cubic close-packed structure (face-centered cubic lattice structure). It is estimated that the anions in the O3'-type crystal also have a cubic close-packed structure. When they contact, there is a crystal plane where the orientation of the cubic close-packed structure formed by the anions is aligned. However, the space group of the layered rock salt crystal and the O3'-type crystal is R-3m, which is different from the space group of the rock salt crystal, Fm-3m (the space group of a general rock salt crystal) and Fd-3m (the space group of a rock salt crystal with the simplest symmetry). Therefore, the Miller indices of the crystal planes that satisfy the above conditions are different between the layered rock salt crystal and the O3'-type crystal and the rock salt crystal. In this specification, when the orientation of the cubic close-packed structure formed by the anions is aligned in the layered rock salt crystal, the O3'-type crystal, and the rock salt crystal, the crystal orientation may be said to be approximately the same.

[0244] The fact that the crystal orientations of the two regions roughly match can be determined from TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. X-ray diffraction (XRD), electron beam diffraction, neutron beam diffraction, etc. can also be used as materials for determination. When the crystal orientations roughly match, it can be observed in TEM images, etc. that the difference in direction between the rows of linearly alternating cations and anions is 5 degrees or less, more preferably 2.5 degrees or less. Note that light elements such as oxygen and fluorine may not be clearly observed in TEM images, etc., but in such cases, the alignment of the orientations can be determined from the arrangement of metal elements.

[0245] However, if the surface layer 100a is composed of only MgO or only a solid solution of MgO and CoO(II), it becomes difficult to insert and extract lithium. Therefore, the surface layer 100a must contain at least cobalt, and in a discharged state, it must also contain lithium, providing a path for lithium insertion and extraction. It is also preferable that the concentration of cobalt is higher than that of magnesium.

[0246] The second additional element Y is preferably located in the surface layer portion 100a of the particle of the positive electrode active material 100 of one embodiment of the present invention. For example, the positive electrode active material 100 of one embodiment of the present invention may be covered with a coating containing the second additional element Y.

[0247] Like the particle surface, the grain boundary is also a planar defect. Therefore, it is prone to become unstable and changes in the crystal structure are likely to occur. Therefore, if the concentration of the first additional element X and / or the second additional element Y at and near the grain boundary is high, the change in the crystal structure can be more effectively suppressed.

[0248] Furthermore, when the concentrations of the first additional element X and / or the second additional element Y are high at and near the grain boundaries, even if cracks occur along the grain boundaries of particles of the positive electrode active material 100 of one embodiment of the present invention, the concentrations of the first additional element X and / or the second additional element Y become high near the surfaces where cracks occur. Therefore, the corrosion resistance to hydrofluoric acid can be improved even in the positive electrode active material after cracks occur.

[0249] [High-Voltage Charging State of Cathode Active Material] Whether or not a cathode active material is the cathode active material 100 of one embodiment of the present invention that exhibits an O3'-type crystal structure when charged at a high voltage can be determined by analyzing the cathode charged at a high voltage using XRD, electron beam diffraction, neutron beam diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. In particular, XRD is preferable in that it can analyze the symmetry of transition metals such as cobalt contained in the cathode active material with high resolution, can compare the level of crystallinity and crystal orientation, can analyze lattice periodic distortion and crystallite size, and can obtain sufficient accuracy even when measuring a cathode obtained by disassembling a secondary battery as is.

[0250] As described above, the cathode active material 100 of one embodiment of the present invention is characterized by minimal change in crystal structure between a high-voltage charged state and a discharged state. Materials in which a crystal structure that exhibits a significant change between a high-voltage charged state and a discharged state accounts for 50 wt % or more are undesirable because they cannot withstand high-voltage charging and discharging. It should be noted that the desired crystal structure may not be achieved simply by adding an additive. For example, even if both materials share the common feature of being lithium cobalt oxide containing magnesium and fluorine, there are cases in which the O3'-type crystal structure accounts for 60 wt % or more and cases in which the H1-3-type crystal structure accounts for 50 wt % or more when charged at a high voltage. Furthermore, at a certain voltage, the O3'-type crystal structure may be nearly 100 wt %, and further increasing the certain voltage may result in the H1-3-type crystal structure. Therefore, to determine whether a material is the cathode active material 100 of one embodiment of the present invention, analysis of the crystal structure, such as XRD, is required.

[0251] However, when a positive electrode active material is charged or discharged at a high voltage, its crystal structure may change when exposed to air. For example, it may change from an O3'-type crystal structure to an H1-3-type crystal structure. Therefore, it is preferable to handle all samples in an inert atmosphere such as an argon atmosphere.

[0252] <Charging Method 1> High-voltage charging for determining whether a certain composite oxide is the positive electrode active material 100 of one embodiment of the present invention can be performed by preparing a coin cell (CR2032 type, diameter 20 mm, height 3.2 mm) using a lithium counter electrode, for example, and charging the coin cell.

[0253] More specifically, the positive electrode may be prepared by coating a positive electrode current collector made of aluminum foil with a slurry containing a positive electrode active material, a conductive material, and a binder.

[0254] Lithium metal can be used for the counter electrode. When a material other than lithium metal is used for the counter electrode, the potential of the secondary battery differs from the potential of the positive electrode. Unless otherwise specified, voltages and potentials in this specification refer to the potential of the positive electrode.

[0255] The electrolyte contained in the electrolytic solution was 1 mol / L lithium hexafluorophosphate (LiPF ６ ) is used, and the electrolyte may be a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of EC:DEC=3:7 with 2 wt % vinylene carbonate (VC).

[0256] The separator can be made of polypropylene having a thickness of 25 μm.

[0257] The positive electrode can and the negative electrode can may be made of stainless steel (SUS).

[0258] The coin cell prepared under the above conditions is charged at a constant current of 4.6 V and 0.5 C, and then charged at a constant voltage until the current reaches 0.01 C. Here, 1 C is 137 mA / g. The temperature is 25°C. After charging in this manner, the coin cell is disassembled in an argon-atmosphere glove box and the positive electrode is removed to obtain a positive electrode active material charged at a high voltage. When various analyses are performed after this, it is preferable to seal the cell in an argon atmosphere to prevent reactions with external components. For example, XRD can be performed by sealing the cell in an airtight container in an argon atmosphere.

[0259] <XRD> Ideal powder XRD patterns calculated from the O3'-type crystal structure and H1-3-type crystal structure models using CuKα1 radiation are shown in Figures 19 and 21. For comparison, LiCoO ２ (O3) and CoO with x = 0 ２ The ideal XRD pattern calculated from the crystal structure of LiCoO (O1) is also shown. ２ (O3) and CoO ２ The pattern of (O1) was created using Reflex Powder Diffraction, one of the modules of Materials Studio (BIOVIA), from crystal structure information obtained from ICSD (Inorganic Crystal Structure Database). The 2θ range was 15° to 75°, step size = 0.01, and wavelength λ = 1.540562 × 10 −１０ m and λ2 were not set, and the monochromator was single. The pattern of the H1-3 type crystal structure was similarly created from crystal structure information (W.E. Counts et al., Journal of the American Ceramic Society, 1953, 36 [1] pp. 12-17. Fig. 01471). The pattern of the O3' type crystal structure was estimated from the XRD pattern of the positive electrode active material of one embodiment of the present invention, and fitting was performed using TOPAS ver. 3 (crystal structure analysis software manufactured by Bruker), and an XRD pattern was created in the same manner as the others.

[0260] As shown in Figure 19, in the O3' type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° to 19.50°) and 2θ = 45.55 ± 0.10° (45.45° to 45.65°). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° to 19.40°) and 2θ = 45.55 ± 0.05° (45.50° to 45.60°). However, as shown in Figure 21, in the H1-3 type crystal structure and CoO ２In the case of (P-3m1, O1), no peaks appear at these positions. Therefore, the appearance of peaks at 2θ = 19.30 ± 0.20° and 2θ = 45.55 ± 0.10° in a state charged at a high voltage can be said to be a characteristic of the positive electrode active material 100 of one embodiment of the present invention.

[0261] This means that the positions at which the XRD diffraction peaks appear are close between the crystal structure with x = 1 and the crystal structure in the high-voltage charging state. More specifically, the difference in the positions at which two or more, preferably three or more, of the main diffraction peaks of both structures appear is 2θ = 0.7° or less, more preferably 2θ = 0.5° or less.

[0262] Although the positive electrode active material 100 of one embodiment of the present invention has an O3'-type crystal structure when charged at a high voltage, not all of the particles need to have the O3'-type crystal structure. Other crystal structures may be included, or some particles may be amorphous. However, when Rietveld analysis is performed on the XRD pattern, the O3'-type crystal structure is preferably 50 wt % or more, more preferably 60 wt % or more, and even more preferably 66 wt % or more. When the O3'-type crystal structure is 50 wt % or more, more preferably 60 wt % or more, and even more preferably 66 wt % or more, the positive electrode active material can have sufficiently excellent cycle characteristics.

[0263] Furthermore, even after 100 or more charge / discharge cycles from the start of measurement, when Rietveld analysis is performed, the O3' type crystal structure is preferably 35 wt% or more, more preferably 40 wt% or more, and even more preferably 43 wt% or more.

[0264] The crystallite size of the O3'-type crystal structure of the particles of the positive electrode active material is ２ Therefore, even under the same XRD measurement conditions as the positive electrode before charging and discharging, a clear peak of the O3' type crystal structure can be confirmed in the high voltage charging state. ２In this case, even if a part of the crystal structure resembles the O3'-type crystal structure, the crystallite size will be small and the peak will be broad and small. The crystallite size can be determined from the half-width of the XRD peak.

[0265] As described above, the positive electrode active material of one embodiment of the present invention preferably has a small influence of the Jahn-Teller effect. The positive electrode active material of one embodiment of the present invention preferably has a layered rock salt crystal structure and contains cobalt as a transition metal. Furthermore, the positive electrode active material of one embodiment of the present invention may contain the first additional element X and / or the second additional element Y described above in addition to cobalt, as long as the influence of the Jahn-Teller effect is small.

[0266] In addition, in the positive electrode active material of one embodiment of the present invention, when particles of the positive electrode active material in a state where no charging or discharging is performed or in a discharged state are subjected to XRD analysis, a first peak may be observed at 2θ of 18.50° to 19.30°, and a second peak may be observed at 2θ of 38.00° to 38.80°.

[0267] The peaks appearing in the powder XRD pattern reflect the crystalline structure of the interior 100b of the positive electrode active material 100, which occupies the majority of the volume of the positive electrode active material 100. The crystalline structure of the surface layer 100a and the like can be analyzed by electron beam diffraction or the like of a cross section of the positive electrode active material 100.

[0268] [Defects in Positive Electrode Active Material] Examples of defects that may occur in a positive electrode active material are shown in Figures 22 and 23. The positive electrode active material of one embodiment of the present invention is expected to have the effect of suppressing the occurrence of the following defects.

[0269] Charging and discharging under high voltage conditions of 4.5 V or higher or at high temperatures (45° C. or higher) can cause progressive defects (also called closed cracks) to form inside the positive electrode active material.

[0270] To demonstrate an example of a defect, a positive electrode active material not containing the first additive element X was prepared. A slurry containing the positive electrode active material, a conductive material, and a binder was mixed with the slurry and coated onto an aluminum foil positive electrode current collector to prepare a positive electrode sample. A coin cell (CR2032 type, 20 mm diameter, 3.2 mm height) was prepared using the positive electrode sample as the positive electrode and lithium foil as the negative electrode, and the cell was charged and discharged 50 times. The cell was charged at a constant current of 0.5 C to 4.7 V, followed by constant voltage charging until the current reached 0.05 C. The cell was discharged at a constant current of 0.5 C to 2.5 V. Here, 1 C was set to 137 mA / g. Three temperature conditions were used: 25°C, 45°C, and 60°C. After 50 charge and discharge cycles, the coin cell was disassembled in an argon-atmosphere glove box and the positive electrode was removed. The removed and obtained deteriorated positive electrode samples were designated as Sample A, Sample B, and Sample C. Here, the positive electrode after the test at 25°C is designated Sample A, the positive electrode after the test at 45°C is designated Sample B, and the positive electrode after the test at 60°C is designated Sample C.

[0271] <STEM Observation> Next, the cross section of the positive electrode of the secondary battery after 50 cycles was observed using a scanning transmission electron microscope (STEM). Samples were processed for cross-sectional observation using a focused ion beam (FIB). The results of cross-sectional STEM observation of Sample A, Sample B, and Sample C are shown in Figures 22A, 22B, and 23. To obtain the cross-sectional STEM images, a Hitachi High-Tech HD-2700 microscope was used, and the accelerating voltage was set to 200 kV.

[0272] In Sample A, which was cycle-tested at 25°C (as shown in Figure 22A), no closed cracks were observed inside the positive electrode active material. However, in Sample B, which was cycle-tested at 45°C, and Sample C, which was cycle-tested at 60°C (as shown in Figures 22B and 23), closed cracks were observed inside the positive electrode active material. The observed closed cracks extended in a direction parallel to the lattice fringes. The lattice fringes shown in Figures 22A, 22B, and 23 are image contrasts resulting from the atomic arrangement (crystal planes) of the positive electrode active material. In this case, they are thought to be lattice fringes resulting from crystal planes perpendicular to the c-axis.

[0273] [Surface Roughness and Specific Surface Area] The positive electrode active material 100 of one embodiment of the present invention preferably has a smooth surface with few irregularities. A smooth surface with few irregularities is one factor indicating that the second additional element Y is well distributed in the surface layer portion 100 a.

[0274] Whether the surface is smooth and has few irregularities can be determined from, for example, a cross-sectional SEM image or cross-sectional TEM image of the positive electrode active material 100, the specific surface area of ​​the positive electrode active material 100, or the like.

[0275] For example, the surface smoothness can be quantified from a cross-sectional SEM image of the positive electrode active material 100 as follows.

[0276] First, the cathode active material 100 is processed using an FIB or the like to expose a cross section. At this time, it is preferable to cover the cathode active material 100 with a protective film, protective agent, or the like. Next, an SEM image of the interface between the protective film or the like and the cathode active material 100 is taken. The SEM image is subjected to noise processing using image processing software. For example, Gaussian blurring (σ = 2) is performed, followed by binarization. Interface extraction is then performed using image processing software. The interface line between the protective film or the like and the cathode active material 100 is selected using a magic hand tool or the like, and the data is extracted into a spreadsheet or the like. Using the functions of the spreadsheet or the like, correction is performed from the regression curve (quadratic regression), and parameters for calculating roughness are obtained from the data after slope correction, and the root mean square (RMS) surface roughness is calculated from the standard deviation. This surface roughness is the surface roughness at least within 400 nm of the outer periphery of the particle of the cathode active material.

[0277] On the particle surfaces of the positive electrode active material 100 of this embodiment, the root mean square (RMS) surface roughness, which is an index of roughness, is preferably less than 3 nm, more preferably less than 1 nm, and further preferably less than 0.5 nm.

[0278] The image processing software used for noise processing, interface extraction, etc. is not particularly limited, but for example, "ImageJ" can be used. The spreadsheet software is also not particularly limited, but for example, Microsoft Office Excel can be used.

[0279] For example, the actual specific surface area A measured by a gas adsorption method using a constant volume method Ｒ and the ideal specific surface area A ｉ The smoothness of the surface of the positive electrode active material 100 can also be quantified from the ratio of

[0280] The median diameter D50 can be measured by a particle size distribution analyzer using a laser diffraction / scattering method, etc. The specific surface area can be measured by a specific surface area measuring device using a gas adsorption method based on a constant volume method, for example.

[0281] Ideal specific surface area A ｉ is calculated assuming that all particles have the same diameter as D50, the same weight, and an ideal spherical shape.

[0282] The positive electrode active material 100 according to one embodiment of the present invention has an ideal specific surface area A (when considered as a perfect sphere) calculated from the median diameter D50. ｉ and the actual specific surface area A Ｒ Ratio A Ｒ / A ｉ is preferably 1 or more and 2 or less.

[0283] If the particle size of the positive electrode active material 100 of one embodiment of the present invention is too large, problems such as difficulty in diffusing lithium and excessive roughness of the surface of the active material layer when applied to a current collector occur. On the other hand, if the particle size is too small, problems such as difficulty in supporting the active material layer when applied to a current collector and excessive reaction with an electrolyte solution occur. Therefore, the average particle size (D50: also referred to as median diameter) is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 40 μm or less, and even more preferably 5 μm or more and 30 μm or less.

[0284] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0285] Embodiment 3 In this embodiment, examples of a plurality of shapes of secondary batteries including the positive electrode active material 100 manufactured by the manufacturing method described in the previous embodiment will be described.

[0286] [Coin-Type Secondary Battery] An example of a coin-type secondary battery will be described. Fig. 24A is an exploded perspective view of a coin-type (single-layer flat) secondary battery, Fig. 24B is an external view, and Fig. 24C is a cross-sectional view thereof. Coin-type secondary batteries are mainly used in small electronic devices. In this specification, coin-type batteries include button-type batteries.

[0287] 24A is a schematic diagram that shows the overlapping of components (upper and lower relationships and positional relationships) for ease of understanding. Therefore, FIGS. 24A and 24B are not completely identical corresponding views.

[0288] In Fig. 24A, a positive electrode 304, a separator 310, a negative electrode 307, a spacer 322, and a washer 312 are stacked. These are sealed by a negative electrode can 302 and a positive electrode can 301. Note that a gasket for sealing is not shown in Fig. 24A. The spacer 322 and the washer 312 are used to protect the inside or to fix the position inside the can when the positive electrode can 301 and the negative electrode can 302 are crimped together. The spacer 322 and the washer 312 are made of stainless steel or an insulating material.

[0289] A positive electrode 304 has a laminated structure in which a positive electrode active material layer 306 is formed on a positive electrode current collector 305 .

[0290] To prevent short-circuiting between the positive electrode and the negative electrode, a separator 310 and a ring-shaped insulator 313 are arranged so as to cover the side and top surfaces of the positive electrode 304. The separator 310 has a larger planar area than the positive electrode 304.

[0291] FIG. 24B is a perspective view of the completed coin-type secondary battery.

[0292] In the coin-type secondary battery 300, a positive electrode can 301, which also serves as a positive electrode terminal, and a negative electrode can 302, which also serves as a negative electrode terminal, are 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 the positive electrode current collector. 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 the negative electrode current collector. The negative electrode 307 is not limited to a laminated structure, and may be formed of lithium metal foil or a lithium-aluminum alloy foil.

[0293] In addition, in each of the positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300, the active material layer may be formed only on one surface of the current collector.

[0294] The positive electrode can 301 and the negative electrode can 302 can be made of a metal such as nickel, aluminum, or titanium that is corrosion-resistant to the electrolyte, or an alloy of these metals, or an alloy of these metals with other metals (e.g., stainless steel). Furthermore, to prevent corrosion by the electrolyte, etc., it is preferable to coat them with nickel, aluminum, etc. 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.

[0295] These negative electrode 307, positive electrode 304, and separator 310 are immersed in an electrolyte solution, and as shown in FIG. 24C , the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are stacked in this order with the positive electrode can 301 facing downwards, and the positive electrode can 301 and the negative electrode can 302 are crimped together via a gasket 303, thereby producing a coin-shaped secondary battery 300.

[0296] The above-described configuration allows the coin-type secondary battery 300 to have a high capacity, a high charge / discharge capacity, and excellent cycle characteristics. Note that, when a secondary battery having a solid electrolyte layer between the negative electrode 307 and the positive electrode 304 is used, the separator 310 may be unnecessary.

[0297] [Cylindrical Secondary Battery] An example of a cylindrical secondary battery will be described with reference to Fig. 25A. As shown in Fig. 25A, a cylindrical secondary battery 616 has a positive electrode cap (battery lid) 601 on the top surface and a battery can (external can) 602 on the side and bottom surfaces. The positive electrode cap 601 and the battery can (external can) 602 are insulated by a gasket (insulating packing) 610.

[0298] 25B is a schematic diagram showing the cross section of a cylindrical secondary battery. The cylindrical secondary battery shown in Fig. 25B has a positive electrode cap (battery lid) 601 on the top surface and a battery can (external can) 602 on the side and bottom surfaces. The positive electrode cap and battery can (external can) 602 are insulated by a gasket (insulating packing) 610.

[0299] A battery element is provided inside a hollow cylindrical battery can 602, which includes a strip-shaped positive electrode 604 and a negative electrode 606 wound with a separator 605 sandwiched between them. Although not shown, the battery element is wound around a central axis. One end of the battery can 602 is closed and the other end is open. The battery can 602 can be made of a metal, such as nickel, aluminum, or titanium, or an alloy of these metals or alloys of these metals with other metals (e.g., stainless steel), which are corrosion-resistant to the electrolyte. Furthermore, it is preferable to coat the battery can 602 with nickel, aluminum, or the like to prevent corrosion by the electrolyte. Inside the battery can 602, the wound battery element, which includes the positive electrode, negative electrode, and separator, is sandwiched between a pair of opposing insulating plates 608 and 609. A nonaqueous electrolyte (not shown) is poured into the battery can 602, which contains the battery element. The nonaqueous electrolyte may be the same as that used in coin-type secondary batteries.

[0300] Since the positive and negative electrodes used in a cylindrical storage battery are wound, it is preferable to form active materials on both sides of the current collector. While Figures 25A to 25D illustrate a secondary battery 616 in which the height of the cylinder is greater than the diameter, this is not limiting. A secondary battery in which the diameter of the cylinder is greater than the height of the cylinder may also be used. This configuration, for example, can reduce the size of the secondary battery.

[0301] By using the positive electrode active material 100 obtained in the above embodiment for the positive electrode 604, a cylindrical secondary battery 616 having a high capacity, a high charge / discharge capacity, and excellent cycle characteristics can be obtained.

[0302] 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 a metal material such as aluminum. The positive electrode terminal 603 is resistance-welded to a safety valve mechanism 613, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 613 is electrically connected to the positive electrode cap 601 via a PTC (Positive Temperature Coefficient) element 611. The safety valve mechanism 613 cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the increase in internal pressure of the battery exceeds a predetermined threshold. The PTC element 611 is a thermosensitive resistor whose resistance increases as the temperature increases, and the increased resistance limits the amount of current to prevent abnormal heat generation. The PTC element is made of barium titanate (BaTiO ３ )-based semiconductor ceramics, etc. can be used.

[0303] 25C shows an example of a power storage system 615. The power storage system 615 has a plurality of secondary batteries 616. The positive electrodes of the respective secondary batteries are in contact with and electrically connected to conductors 624 separated by insulators 625. The conductors 624 are electrically connected to a control circuit 620 via wiring 623. The negative electrodes of the respective secondary batteries are electrically connected to the control circuit 620 via wiring 626. A protection circuit or the like that prevents overcharging or overdischarging can be applied as the control circuit 620.

[0304] 25D shows an example of a power storage system 615. The power storage system 615 has a plurality of secondary batteries 616, which are sandwiched between a conductive plate 628 and a conductive plate 614. The plurality of secondary batteries 616 are electrically connected to the conductive plate 628 and the conductive plate 614 by wiring 627. The plurality of secondary batteries 616 may be connected in parallel, in series, or in parallel and then further connected in series. By configuring the power storage system 615 to have a plurality of secondary batteries 616, it is possible to extract a large amount of power.

[0305] A plurality of secondary batteries 616 may be connected in parallel and then further connected in series.

[0306] A temperature control device may be provided between the multiple secondary batteries 616. When the secondary batteries 616 are overheated, they can be cooled by the temperature control device, and when the secondary batteries 616 are too cold, they can be heated by the temperature control device. This makes it difficult for the performance of the power storage system 615 to be affected by the outside air temperature.

[0307] 25D , the power storage system 615 is electrically connected to a control circuit 620 via wiring 621 and wiring 622. The wiring 621 is electrically connected to the positive electrodes of the plurality of secondary batteries 616 via a conductive plate 628, and the wiring 622 is electrically connected to the negative electrodes of the plurality of secondary batteries 616 via a conductive plate 614.

[0308] [Another Structural Example of Secondary Battery] Structural examples of secondary batteries will be described with reference to FIGS. 26 and 27. FIG.

[0309] A secondary battery 913 shown in FIG. 26A has a wound body 950 provided with terminals 951 and 952 inside a housing 930. The wound body 950 is immersed in an electrolyte inside the housing 930. The terminal 952 contacts the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like. Note that in FIG. 26A , for convenience, the housing 930 is shown separated, but in reality, the wound body 950 is covered by the housing 930, and the 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.

[0310] 26B, the housing 930 shown in Fig. 26A may be formed from a plurality of materials. For example, the secondary battery 913 shown in Fig. 26B has a housing 930a and a housing 930b bonded together, and a wound body 950 is provided in the area surrounded by the housing 930a and the housing 930b.

[0311] The housing 930a can be made of an insulating material such as organic resin. In particular, by using a material such as organic resin on the surface on which the antenna is formed, it is possible to suppress shielding of the electric field by the secondary battery 913. Note that if the shielding of the electric field by the housing 930a is small, the antenna may be provided inside the housing 930a. The housing 930b can be made of, for example, a metal material.

[0312] 26C shows the structure of the wound body 950. 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 sandwiched therebetween, and the laminated sheet is wound. Note that multiple layers of the negative electrode 931, the positive electrode 932, and the separator 933 may be stacked.

[0313] 27A to 27C may be used as a secondary battery 913 having a wound body 950a. The wound body 950a shown in Fig. 27A includes a negative electrode 931, a positive electrode 932, and a separator 933. The negative electrode 931 includes a negative electrode active material layer 931a. The positive electrode 932 includes a positive electrode active material layer 932a.

[0314] By using the positive electrode active material 100 obtained in the above embodiment for the positive electrode 932, the secondary battery 913 can have a high capacity, a high charge / discharge capacity, and excellent cycle characteristics.

[0315] The separator 933 has a width wider than the negative electrode active material layer 931 a and the positive electrode active material layer 932 a, and is wound so as to overlap the negative electrode active material layer 931 a and the positive electrode active material layer 932 a. From the standpoint of safety, it is preferable that the negative electrode active material layer 931 a be wider than the positive electrode active material layer 932 a. A wound body 950 a having such a shape is preferable due to its high safety and productivity.

[0316] 27B, the negative electrode 931 is electrically connected to a terminal 951. The terminal 951 is electrically connected to a terminal 911a. The positive electrode 932 is electrically connected to a terminal 952. The terminal 952 is electrically connected to a terminal 911b.

[0317] 27C , wound body 950 a and the electrolyte are covered by casing 930 to form secondary battery 913. It is preferable to provide casing 930 with a safety valve, an overcurrent protection element, etc. The safety valve is a valve that opens when the inside of casing 930 reaches a predetermined internal pressure to prevent the battery from exploding.

[0318] As shown in Fig. 27B, the secondary battery 913 may have multiple wound bodies 950a. Using multiple wound bodies 950a allows the secondary battery 913 to have a larger charge / discharge capacity. For other elements of the secondary battery 913 shown in Figs. 27A and 27B, the descriptions of the secondary battery 913 shown in Figs. 26A to 26C can be referred to.

[0319] 28A and 28B show examples of external views of a laminated secondary battery, which includes 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.

[0320] 29A shows an external view of a positive electrode 503 and a negative electrode 506. The positive electrode 503 has a positive electrode current collector 501, and a 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 a tab region). The negative electrode 506 has a negative electrode current collector 504, and a 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., a tab region. The areas and shapes of the tab regions of the positive electrode and negative electrode are not limited to the example shown in FIG. 29A .

[0321] <Method for Manufacturing Laminated Secondary Battery> Here, an example of a method for manufacturing the laminated secondary battery whose external view is shown in FIG. 28A will be described with reference to FIGS. 29B and 29C.

[0322] First, the negative electrode 506, the separator 507, and the positive electrode 503 are stacked. FIG. 29B shows the stacked negative electrode 506, the separator 507, and the positive electrode 503. Here, an example is shown in which five pairs of negative electrodes and four pairs of positive electrodes are used. The stacked negative electrodes, separators, and positive electrodes can be called a laminate. Next, the tab regions of the positive electrodes 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For example, ultrasonic welding or the like may be used for joining. Similarly, the tab regions of the negative electrodes 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0323] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are arranged on the outer casing 509 .

[0324] Next, as shown in Fig. 29C, the exterior body 509 is folded at the portion indicated by the dashed line. Thereafter, the outer periphery of the exterior body 509 is joined. For example, thermocompression bonding may be used for joining. At this time, an area (hereinafter referred to as an inlet) that is not joined is provided in a part (or one side) of the exterior body 509 so that an electrolyte can be introduced later.

[0325] Next, the electrolyte solution is introduced into the inside of the exterior body 509 through an inlet provided in the exterior body 509. The introduction of the electrolyte solution is preferably carried out under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is joined. In this manner, the laminated secondary battery 500 can be produced.

[0326] By using the positive electrode active material 100 obtained in the above-described embodiment for the positive electrode 503, a secondary battery 500 having a high capacity, a high charge / discharge capacity, and excellent cycle characteristics can be obtained.

[0327] [Example of Battery Pack] An example of a secondary battery pack according to one embodiment of the present invention that can be wirelessly charged using an antenna will be described with reference to FIGS. 30A to 30C.

[0328] Fig. 30A is a diagram showing the appearance of secondary battery pack 531, which has a thin rectangular parallelepiped shape (also called a thick flat plate shape). Fig. 30B is a diagram illustrating the configuration of secondary battery pack 531. Secondary battery pack 531 has circuit board 540 and secondary battery 513. Label 529 is affixed to secondary battery 513. Circuit board 540 is fixed with sticker 515. Secondary battery pack 531 also has antenna 517.

[0329] The interior of the secondary battery 513 may have a structure including a wound body or a laminated body.

[0330] 30B , the secondary battery pack 531 has a control circuit 590 on a circuit board 540. The circuit board 540 is electrically connected to the terminals 514. The circuit board 540 is also electrically connected to the antenna 517, one 551 of the positive and negative leads of the secondary battery 513, and the other 552 of the positive and negative leads.

[0331] Alternatively, as shown in FIG. 30C, the device may have a circuit system 590 a provided on the circuit board 540 and a circuit system 590 b electrically connected to the circuit board 540 via the terminals 514 .

[0332] The antenna 517 is not limited to a coil shape and may be, for example, a wire shape or a plate shape. Furthermore, antennas such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, and a dielectric antenna may also 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 a capacitor. This allows power to be exchanged not only by electromagnetic fields and magnetic fields but also by electric fields.

[0333] The secondary battery pack 531 includes a layer 519 between the antenna 517 and the secondary battery 513. The layer 519 has a function of, for example, shielding an electromagnetic field generated by the secondary battery 513. The layer 519 can be formed using, for example, a magnetic material.

[0334] [Positive Electrode] The positive electrode includes a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer includes a positive electrode active material and may include a conductive material and a binder. The positive electrode active material is the positive electrode active material manufactured by the manufacturing method described in the above embodiment.

[0335] The positive electrode active material described in the above embodiment may be mixed with another positive electrode active material.

[0336] Other examples of the positive electrode active material include composite oxides having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure. For example, LiFePO ４ , LiFeO ２ , LiNiO ２ , LiMn ２ O ４ , V ２ O ５ , Cr ２ O ５ , MnO ２ The following compounds are exemplified:

[0337] Other positive electrode active materials include LiMn ２ O ４ Lithium-containing materials having a spinel-type crystal structure containing manganese, such as lithium nickel oxide (LiNiO ２ or LiNi １−ｘ M ｘ O ２ It is preferable to use a mixture of (0<x<1) (M=Co, Al, etc.) This configuration can improve the characteristics of the secondary battery.

[0338] In addition, as another positive electrode active material, the composition formula Li ａ Mn ｂ M ｃ O ｄA lithium-manganese composite oxide that can be expressed by the formula (1) can be used. Here, element M is preferably a metal element selected from among lithium and manganese, or silicon or phosphorus, and more preferably nickel. Furthermore, when measuring the entire lithium-manganese composite oxide particle, it is preferable that 0<a / (b+c)<2, c>0, and 0.26≦(b+c) / d<0.5 are satisfied during discharge. The composition of metals, silicon, phosphorus, etc. in the entire lithium-manganese composite oxide particle can be measured using, for example, ICP-MS. The oxygen composition in the entire lithium-manganese composite oxide particle can be measured using, for example, EDX (energy dispersive X-ray spectroscopy). Furthermore, the composition can be determined by using valence evaluation of fusion gas analysis and XAFS (X-ray absorption fine structure) analysis in combination with ICP-MS analysis. The lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, phosphorus, and the like.

[0339] <Conductive Material> The conductive material is also called a conductive additive or a conductive agent, and is made of a carbon material. By attaching the conductive material between multiple active materials, the multiple active materials are electrically connected to each other, thereby increasing the conductivity. Note that the term "attachment" does not only refer to physical adhesion between the active material and the conductive material, but also includes cases where a covalent bond is formed, bonding due to van der Waals forces, where the conductive material covers part of the surface of the active material, where the conductive material is embedded in the surface irregularities of the active material, and where the materials are electrically connected even when not in contact with each other.

[0340] Carbon black (furnace black, acetylene black, graphite, etc.) is a typical carbon material used as a conductive material.

[0341] It is more preferable to use graphene or a graphene compound as the conductive material.

[0342] In this specification and the like, graphene compounds include multilayer graphene, multigraphene, graphene oxide, multilayer graphene oxide, multi-graphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, reduced multi-graphene oxide, graphene quantum dots, etc. Graphene compounds contain carbon, have a shape such as a plate or sheet, and have a two-dimensional structure formed by six-membered carbon rings. The two-dimensional structure formed by six-membered carbon rings may also be called a carbon sheet. Graphene compounds may have functional groups. Furthermore, graphene compounds preferably have a curved shape. Furthermore, graphene compounds may be rolled up to resemble carbon nanofibers.

[0343] In this specification and the like, graphene oxide refers to a material that contains carbon and oxygen, has a sheet shape, and has a functional group, in particular, an epoxy group, a carboxy group, or a hydroxy group.

[0344] In this specification, reduced graphene oxide refers to a material containing carbon and oxygen, having a sheet-like shape, and having a two-dimensional structure formed by six-membered carbon rings. It may also be called a carbon sheet. A single reduced graphene oxide can function, but multiple sheets may be stacked. Reduced graphene oxide preferably has a portion where the carbon concentration is greater than 80 atomic % and the oxygen concentration is 2 atomic % or more and 15 atomic % or less. By achieving these carbon and oxygen concentrations, reduced graphene oxide can function as a highly conductive material even in small amounts. Furthermore, reduced graphene oxide preferably has an intensity ratio G / D of the G band to the D band in a Raman spectrum of 1 or more. Reduced graphene oxide with such an intensity ratio can function as a highly conductive material even in small amounts.

[0345] Graphene and graphene compounds may have excellent electrical properties, such as high conductivity, and excellent physical properties, such as high flexibility and high mechanical strength. Graphene and graphene compounds may also have a sheet-like shape. Graphene and graphene compounds may have curved surfaces, enabling surface contact with low contact resistance. Even thin graphene and graphene compounds may have high conductivity, allowing a small amount to efficiently form a conductive path within an active material layer. Therefore, using graphene or graphene compounds as a conductive material can increase the contact area between the active material and the conductive material. It is preferable that the graphene or graphene compound covers 80% or more of the active material. It is preferable that the graphene or graphene compound clings to at least a portion of the active material particles. It is also preferable that the graphene or graphene compound overlaps at least a portion of the active material particles. It is also preferable that the shape of the graphene or graphene compound matches at least a portion of the shape of the active material particles. The shape of the active material particles refers, for example, to the irregularities of a single active material particle or the irregularities formed by multiple active material particles. It is also preferable that the graphene or graphene compound surrounds at least a part of the active material particles, and the graphene or graphene compound may have holes.

[0346] When using active material particles with a small particle size, for example, active material particles with a particle size of 1 μm or less, the specific surface area of ​​the active material particles is large, and more conductive paths connecting the active material particles are required. In such cases, it is preferable to use graphene or a graphene compound, which can efficiently form conductive paths even in a small amount.

[0347] Because of the properties described above, graphene compounds are particularly effective as conductive materials for secondary batteries that require rapid charging and rapid discharging. For example, rapid charging and rapid discharging characteristics may be required for secondary batteries for two-wheeled or four-wheeled vehicles, secondary batteries for drones, etc. Rapid charging characteristics may also be required for mobile electronic devices, etc. Rapid charging and rapid discharging may also be referred to as high-rate charging and high-rate discharging. For example, rapid charging and rapid discharging refer to charging and discharging at 1C, 2C, or 5C or higher.

[0348] Furthermore, a material used in forming graphene or a graphene compound may be mixed with the graphene or graphene compound and used in the active material layer. For example, particles used as a catalyst in forming the graphene compound may be mixed with the graphene compound. Examples of catalysts used in forming the graphene compound include silicon oxide (SiO ２ , SiO ｘ (x<2)), aluminum oxide, iron, nickel, ruthenium, iridium, platinum, copper, germanium, etc. The particles preferably have a median diameter (D50) of 1 μm or less, more preferably 100 nm or less.

[0349] <Binder> As the binder, it is preferable to use a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. Furthermore, as the binder, fluororubber can be used.

[0350] Furthermore, it is preferable to use, for example, a water-soluble polymer as the binder. Examples of the water-soluble polymer that can be used include polysaccharides. Examples of the polysaccharide that can be used include cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose, as well as starch. It is even more preferable to use these water-soluble polymers in combination with the above-mentioned rubber material.

[0351] Alternatively, it is preferable to use, as the binder, materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose.

[0352] The binder may be used in combination with two or more of the above.

[0353] For example, a material with a particularly excellent viscosity adjusting effect may be used in combination with other materials. For example, while rubber materials have excellent adhesive strength and elasticity, it may be difficult to adjust the viscosity when mixed with a solvent. In such cases, it is preferable to mix them with a material with a particularly excellent viscosity adjusting effect. For example, a water-soluble polymer may be used as a material with a particularly excellent viscosity adjusting effect. Furthermore, as water-soluble polymers with a particularly excellent viscosity adjusting effect, the above-mentioned polysaccharides, for example, carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose, cellulose derivatives such as regenerated cellulose, and starch may be used.

[0354] In addition, the solubility of cellulose derivatives such as carboxymethyl cellulose can be increased by converting them into salts such as sodium or ammonium salts of carboxymethyl cellulose, making them more effective as viscosity adjusters. Higher solubility can also improve dispersibility with the active material and other components when preparing electrode slurry. In this specification, the cellulose and cellulose derivatives used as electrode binders also include their salts.

[0355] Water-soluble polymers stabilize viscosity by dissolving in water and can stably disperse active materials and other materials combined as binders, such as styrene-butadiene rubber, in aqueous solutions. Furthermore, because they contain functional groups, they are expected to be easily and stably adsorbed onto the surface of active materials. Furthermore, many cellulose derivatives, such as carboxymethyl cellulose, contain functional groups, such as hydroxyl or carboxyl groups, and because of these functional groups, the polymers are expected to interact with each other and widely cover the surface of the active material.

[0356] When the binder covering or contacting the surface of the active material forms a film, it is expected to function as a passive film and have the effect of suppressing decomposition of the electrolyte. Here, the passive film is a film with no electrical conductivity or a film with extremely low electrical conductivity. For example, when a passive film is formed on the surface of the active material, it can suppress decomposition of the electrolyte at the battery reaction potential. Furthermore, it is more desirable that the passive film suppresses electrical conductivity while still allowing lithium ions to conduct.

[0357] <Positive Electrode Current Collector> The positive electrode current collector can be made of a highly conductive material, such as a metal such as stainless steel, gold, platinum, aluminum, or titanium, or an alloy thereof. It is preferable that the material used for the positive electrode current collector does not dissolve at the potential of the positive electrode. Aluminum alloys containing elements that improve heat resistance, such as silicon, titanium, neodymium, scandium, or molybdenum, can also be used. The positive electrode current collector may also be made of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The current collector can be in the form of a foil, plate, sheet, mesh, punched metal, expanded metal, or the like. It is preferable that the current collector have a thickness of 5 μm to 30 μm.

[0358] [Negative Electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also have a conductive material and a binder.

[0359] As the negative electrode active material, an element capable of undergoing a charge-discharge reaction by alloying / de-alloying with lithium can be used. 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. These 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. Alternatively, a compound containing these elements may be used. For example, SiO, Mg ２ Si, Mg ２ Ge, SnO, SnO ２ , Mg ２ Sn, SnS ２ , V ２ Sn ３ , FeSn ２ , CoSn ２ , Ni ３ Sn ２ , Cu ６ Sn ５ , Ag ３ Sn, Ag ３ Sb, Ni ２ MnSb, CeSb ３ , LaSn ３ , La ３ Co ２ Sn ７ , CoSb ３ , InSb, SbSn, etc. Here, elements that can undergo charge-discharge reactions by alloying / dealloying reactions with lithium, and compounds containing such elements, are sometimes referred to as alloy-based materials.

[0360] In this specification and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO refers to SiO ｘ Here, x preferably has a value of 1 or close to 1. For example, x is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0361] Examples of carbonaceous materials that can be used include graphite, easily graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, and carbon black.

[0362] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spherical graphite having a spherical shape can be used as the artificial graphite. For example, MCMB may have a spherical shape and is therefore preferred. Furthermore, it is relatively easy to reduce the surface area of ​​MCMB, and this may be preferred. Examples of natural graphite include flake graphite and spherical natural graphite.

[0363] When lithium ions are inserted into graphite (when a lithium-graphite intercalation compound is formed), graphite exhibits a low potential similar to that of metallic lithium (0.05 V to 0.3 V vs. Li / Li ＋ This allows lithium-ion secondary batteries using graphite to exhibit high operating voltages. Graphite is also preferred because it has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and greater safety than metallic lithium.

[0364] Titanium dioxide (TiO ２ ), lithium titanium oxide (Li ４ Ti ５ O １２ ), lithium-graphite intercalation compound (Li ｘ C ６ ), niobium pentoxide (Nb ２ O ５ ), tungsten oxide (WO ２ ), molybdenum oxide (MoO ２ ) and other oxides can be used.

[0365] In addition, as the negative electrode active material, a composite nitride of lithium and a transition metal, Li ３ Li with N-type structure ３−ｘ M ｘ N (M=Co, Ni, Cu) can be used. For example, Li ２．６ Co ０．４ N ３ has a large charge / discharge capacity (900 mAh / g, 1890 mAh / cm ３ ) and is preferred.

[0366] When a composite nitride of lithium and a transition metal is used, lithium ions are contained in the negative electrode active material, so V, which does not contain lithium ions, can be used as the positive electrode active material. ２ O ５ , Cr ３ O ８ It is preferable that the composite nitride of lithium and a transition metal can be used as the negative electrode active material, even when a material containing lithium ions is used as the positive electrode active material, by first removing the lithium ions contained in the positive electrode active material.

[0367] Furthermore, a material that undergoes a conversion reaction can also be used as the negative electrode active material. For example, a transition metal oxide that does not form an alloy with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), or iron oxide (FeO), can be used as the negative electrode active material. Further examples of materials that undergo a conversion reaction include Fe ２ O ３ ,CuO,Cu ２ O, RuO ２ , Cr ２ O ３ oxides such as CoS ０．８９ , sulfides such as NiS and CuS, Zn ３ N ２ , Cu ３ N, Ge ３ N ４ Nitrides such as NiP ２ , FeP ２ , CoP ３ Phosphides such as FeF ３ , BiF ３ Fluorides such as:

[0368] The conductive material and binder that can be contained in the negative electrode active material layer can be the same as the conductive material and binder that can be contained in the positive electrode active material layer.

[0369] The negative electrode current collector may be made of copper or the like in addition to the same materials as the positive electrode current collector. It is preferable that the negative electrode current collector be made of a material that does not alloy with carrier ions such as lithium.

[0370] [Electrolyte Solution] As one form of electrolyte, an electrolyte solution having a solvent and an electrolyte dissolved in the solvent can be used. The solvent of the electrolyte solution is preferably an aprotic organic solvent, and for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., can be used alone or in any combination and ratio of two or more of these.

[0371] Furthermore, by using one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the solvent for the electrolyte, it is possible to prevent the electricity storage device from exploding or catching fire even if the internal temperature of the electricity storage device rises due to an internal short circuit, overcharging, or the like. The ionic liquid is composed of a cation and an anion, and includes an organic cation and an anion. Examples of organic cations used in the electrolyte include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, and aromatic cations such as imidazolium cations and pyridinium cations. Examples of anions used in the electrolyte include monovalent amide anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkylsulfonate anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, and perfluoroalkylphosphate anions.

[0372] The electrolyte to be dissolved in the solvent is, for example, LiPF ６ , LiClO ４ , LiAsF ６ , LiBF ４ , LiAlCl４ , LiSCN, LiBr, LiI, Li ２ SO ４ , Li ２ B １０ Cl １０ , Li ２ B １２ Cl １２ , LiCF ３ SO ３ , LiC ４ F ９ SO ３ , LiC(CF ３ SO ２ ) ３ , LiC(C ２ F ５ SO ２ ) ３ , LiN(CF ３ SO ２ ) ２ , LiN(C ４ F ９ SO ２ ) (CF ３ SO ２ ), LiN(C ２ F ５ SO ２ ) ２ , lithium bis(oxalato)borate (Li(C) ２ O ４ ) ２ , LiBOB), or two or more of these can be used in any combination and ratio.

[0373] The electrolyte used in the electricity storage device is preferably a highly purified electrolyte with a low content of granular waste or elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). Specifically, the weight ratio of impurities to the electrolyte is preferably 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

[0374] The electrolyte solution may contain additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), or dinitrile compounds such as succinonitrile and adiponitrile. The concentration of the additive may be, for example, 0.1 wt % to 5 wt % relative to the solvent in which the electrolyte is dissolved.

[0375] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0376] The use of a polymer gel electrolyte improves safety against leakage, etc. It also enables the secondary battery to be made thinner and lighter.

[0377] Examples of polymers that can be gelled include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, and fluorine-based polymer gel. For example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and copolymers containing these can be used. For example, PVDF-HFP, a copolymer of PVDF and hexafluoropropylene (HFP), can be used. The polymer formed may also have a porous shape.

[0378] [Separator] The separator may be made of, for example, cellulose-containing fibers such as paper, nonwoven fabric, glass fiber, ceramics, or synthetic fibers such as nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, or polyurethane.

[0379] 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-based material, a polyamide-based material, or a mixture thereof. Examples of ceramic materials include aluminum oxide particles and silicon oxide particles. Note that glass-like materials can also be used as ceramic materials, but unlike the glass used in electrodes, they preferably have low electronic conductivity. Examples of fluorine-based materials include PVDF and polytetrafluoroethylene. Examples of polyamide-based materials include nylon and aramid (meta-aramid, para-aramid).

[0380] Coating with ceramic materials improves oxidation resistance, suppressing separator degradation during high-voltage charging and improving the reliability of secondary batteries. Coating with fluorine-based materials also improves adhesion between the separator and electrodes, improving output characteristics. Coating with polyamide materials, especially aramid, improves heat resistance, improving the safety of secondary batteries.

[0381] For example, both sides of a polypropylene film may be coated with a mixed material of aluminum oxide and aramid, or the surface of the polypropylene film that contacts the positive electrode may be coated with a mixed material of aluminum oxide and aramid, and the surface that contacts the negative electrode may be coated with a fluorine-based material.

[0382] The content of this embodiment mode can be freely combined with the content of other embodiment modes.

[0383] Fourth Embodiment This embodiment shows an example of fabricating an all-solid-state battery using the positive electrode active material 100 obtained in the above-described embodiment.

[0384] As shown in FIG. 31A , a secondary battery 400 of one embodiment of the present invention includes a positive electrode 410 , a solid electrolyte layer 420 , and a negative electrode 430 .

[0385] The positive electrode 410 includes a positive electrode current collector 413 and a positive electrode active material layer 414. The positive electrode active material layer 414 includes a positive electrode active material 411 and a solid electrolyte 421. The positive electrode active material 100 obtained in the above-described embodiment is used for the positive electrode active material 411. The positive electrode active material layer 414 may also include a conductive material and a binder.

[0386] Solid electrolyte layer 420 has solid electrolyte 421. Solid electrolyte layer 420 is located between positive electrode 410 and negative electrode 430, and is a region that has neither positive electrode active material 411 nor negative electrode active material 431.

[0387] The negative electrode 430 includes a negative electrode current collector 433 and a negative electrode active material layer 434. The negative electrode active material layer 434 includes a negative electrode active material 431 and a solid electrolyte 421. The negative electrode active material layer 434 may also include a conductive material and a binder. When metallic lithium is used as the negative electrode active material 431, it is not necessary to form the material into particles, and therefore, as shown in FIG. 31B , the negative electrode 430 can be free of the solid electrolyte 421. Using metallic lithium for the negative electrode 430 is preferable because it can improve the energy density of the secondary battery 400.

[0388] The solid electrolyte 421 of the solid electrolyte layer 420 may be, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a halide-based solid electrolyte.

[0389] The sulfide-based solid electrolytes include thiolithium-based (Li １０ GeP ２ S １２ , Li ３．２５ Ge ０．２５ P ０．７５ S ４ etc.), sulfide glass (70Li ２ S・30P ２ S ５ , 30Li ２ S・26B ２ S ３ ・44LiI, 63Li ２ S・36SiS ２ ・1Li ３ P.O. ４ , 57Li ２ S・38SiS ２ ・5Li ４ SiO４ , 50Li ２ S・50GeS ２ etc.), sulfide crystallized glass (Li ７ P ３ S １１ , Li ３．２５ P ０．９５ S ４ Sulfide-based solid electrolytes have the advantages of being highly conductive, being able to be synthesized at low temperatures, and being relatively soft, which makes it easy to maintain conductive paths even after charging and discharging.

[0390] The oxide-based solid electrolyte includes a material having a perovskite crystal structure (La ２／３−ｘ Li ３ｘ TiO ３ etc.), materials having a NASICON type crystal structure (Li １−Ｙ Al Ｙ Ti ２−Ｙ (P.O. ４ ) ３ etc.), materials having a garnet-type crystal structure (Li ７ La ３ Zr ２ O １２ etc.), materials having a LISICON type crystal structure (Li １４ ZnGe ４ O １６ etc.), LLZO (Li ７ La ３ Zr ２ O １２ ), oxide glass (Li ３ P.O. ４ -Li ４ SiO ４ , 50Li ４ SiO ４ ・50Li ３ BO ３ etc.), oxide crystallized glass (Li １．０７ Al ０．６９ Ti １．４６ (P.O. ４ ) ３ , Li １．５ Al ０．５ Ge １．５ (P.O. ４ ) ３ Oxide-based solid electrolytes have the advantage of being stable in the atmosphere.

[0391] Halide-based solid electrolytes include LiAlCl ４ , Li ３ InBr ６ , LiF, LiCl, LiBr, LiI, etc. Composite materials in which these halide-based solid electrolytes are filled into the pores of porous aluminum oxide or porous silica can also be used as the solid electrolyte.

[0392] Also, different solid electrolytes may be mixed and used.

[0393] Among them, Li having a NASICON type crystal structure １＋ｘ Al ｘ Ti ２−ｘ (P.O. ４ ) ３ (0<x<1) (hereinafter, LATP) is preferable because it contains aluminum and titanium, elements that may be contained in the positive electrode active material used in the secondary battery 400 of one embodiment of the present invention, and therefore a synergistic effect can be expected in improving cycle characteristics. In addition, productivity can be expected to be improved by reducing the number of steps. Note that in this specification and the like, the NASICON-type crystal structure refers to a structure having a NASICON-type crystal structure, which is a structure having a NASICON-type crystal structure, and which is ... ２ (XO ４ ) ３ (M: transition metal, X: S, P, As, Mo, W, etc.), ６ Octahedron and XO ４ It refers to a structure in which tetrahedrons are arranged three-dimensionally with their vertices shared.

[0394] [Exterior Body and Shape of Secondary Battery] Various materials and shapes can be used for the exterior body of the secondary battery 400 of one embodiment of the present invention, but it is preferable that the exterior body has a function of applying pressure to the positive electrode, the solid electrolyte layer, and the negative electrode.

[0395] For example, FIG. 32 shows an example of a cell for evaluating materials for an all-solid-state battery.

[0396] 32A is a cross-sectional schematic diagram of the evaluation cell, which has a lower member 761, an upper member 762, and a fixing screw or wing nut 764 that fixes them together, and electrode plate 753 is pressed to fix the evaluation material by rotating a holding screw 763. An insulator 766 is provided between lower member 761 and upper member 762, both made of stainless steel. An O-ring 765 is also provided between upper member 762 and holding screw 763 to provide a tight seal.

[0397] The evaluation material is placed on electrode plate 751, surrounded by insulating tube 752, and pressed from above by electrode plate 753. Figure 32B is an enlarged perspective view of the evaluation material and its surroundings.

[0398] The evaluation material is an example of a laminate of a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c, and its cross-sectional view is shown in Fig. 32C. Note that the same reference numerals are used for the same parts in Figs. 32A to 32C.

[0399] The electrode plate 751 and the lower member 761, which are electrically connected to the positive electrode 750a, can be said to correspond to a positive electrode terminal. The electrode plate 753 and the upper member 762, which are electrically connected to the negative electrode 750c, can be said to correspond to a negative electrode terminal. Electrical resistance and the like can be measured by applying pressure to the evaluation material via the electrode plate 751 and the electrode plate 753.

[0400] The secondary battery of one embodiment of the present invention preferably uses an airtight package for its exterior. For example, a ceramic package or a resin package can be used. Furthermore, the exterior is preferably sealed in a sealed atmosphere, such as in a glove box, while blocking external air.

[0401] Fig. 33A is a perspective view of a secondary battery of one embodiment of the present invention, which has an exterior body and a shape different from those in Fig. 32. The secondary battery in Fig. 33A has external electrodes 771 and 772 and is sealed in an exterior body having a plurality of package members.

[0402] An example of a cross section taken along the dashed line in Figure 33A is shown in Figure 33B. A stack including a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is enclosed and sealed within a package member 770a having a flat plate with an electrode layer 773a, a frame-shaped package member 770b, and a package member 770c having a flat plate with an electrode layer 773b. The package members 770a, 770b, and 770c can be made of an insulating material, such as a resin material or ceramic.

[0403] The external electrode 771 is electrically connected to the positive electrode 750a via the electrode layer 773a and functions as a positive electrode terminal, while the external electrode 772 is electrically connected to the negative electrode 750c via the electrode layer 773b and functions as a negative electrode terminal.

[0404] By using the positive electrode active material 100 obtained in the above-described embodiment, an all-solid-state secondary battery having high energy density and good output characteristics can be realized.

[0405] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0406] Embodiment 5 In this embodiment, an example in which a secondary battery different from the cylindrical secondary battery shown in FIG. 25D is applied to an electric vehicle (EV) will be described with reference to FIG. 34C.

[0407] The electric vehicle is equipped with first batteries 1301a and 1301b as main driving secondary batteries, and a second battery 1311 that supplies power to an inverter 1312 that starts a motor 1304. The second battery 1311 is also called a cranking battery (also called a starter battery). The second battery 1311 only needs to have high output, and does not need to have a large capacity, and the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

[0408] The internal structure of the first battery 1301a may be a wound type shown in Fig. 26A or 27C or a stacked type shown in Fig. 28A or 28B. The first battery 1301a may use the all-solid-state battery of Embodiment 4. By using the all-solid-state battery of Embodiment 4 for the first battery 1301a, a high capacity can be achieved, safety can be improved, and the battery can be made smaller and lighter.

[0409] In this embodiment, an example is shown in which two first batteries 1301a and 1301b are connected in parallel, but three or more batteries may be connected in parallel. Furthermore, if the first battery 1301a can store sufficient power, the first battery 1301b may be omitted. By configuring a battery pack having multiple secondary batteries, it is possible to extract large amounts of power. The multiple secondary batteries may be connected in parallel, in series, or in series after being connected in parallel. A plurality of secondary batteries is also called a battery pack.

[0410] In addition, in a secondary battery for vehicle use, a service plug or circuit breaker that can cut off high voltage without using tools is provided in the first battery 1301a in order to cut off power from multiple secondary batteries.

[0411] The power of the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but also supplies power to 42V in-vehicle components (such as an electric power steering (power steering) 1307, a heater 1308, and a defogger 1309) via a DCDC circuit 1306. When a rear motor 1317 is provided on the rear wheels, the first battery 1301a is also used to rotate the rear motor 1317.

[0412] In addition, the second battery 1311 supplies power to 14V in-vehicle components (audio 1313, power windows 1314, lamps 1315, etc.) via the DCDC circuit 1310.

[0413] The first battery 1301a will be described with reference to FIG. 34A.

[0414] FIG. 34A shows an example in which nine prismatic secondary batteries 1300 are combined into one battery pack 1415. Furthermore, nine prismatic secondary batteries 1300 are connected in series, with one electrode fixed by a fixing portion 1413 made of an insulator and the other electrode fixed by a fixing portion 1414 made of an insulator. While this embodiment shows an example in which the batteries are fixed by fixing portions 1413 and 1414, they may also be housed in a battery housing box (also called a casing). Because it is expected that a vehicle will be subjected to external vibrations or shaking (e.g., from the road surface), it is preferable to fix multiple secondary batteries using fixing portions 1413 and 1414 and a battery housing box. Furthermore, one electrode is electrically connected to a control circuit unit 1320 by wiring 1421. The other electrode is electrically connected to the control circuit unit 1320 by wiring 1422.

[0415] A memory circuit including a transistor using an oxide semiconductor may be used for the control circuit portion 1320. A charge control circuit or a battery control system including a memory circuit including a transistor using an oxide semiconductor may be referred to as a battery operating system (BTOS) or a battery oxide semiconductor (BTOS).

[0416] It is preferable to use a metal oxide that functions as an oxide semiconductor. For example, a metal oxide such as In-M-Zn oxide (wherein element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium) may be used as the oxide. In particular, the In-M-Zn oxide that can be used as the oxide is preferably a C-Axis Aligned Crystal Oxide Semiconductor (CAAC-OS) or a Cloud-Aligned Composite Oxide Semiconductor (CAC-OS). Alternatively, an In—Ga oxide or an In—Zn oxide may be used as the oxide. A CAAC-OS is an oxide semiconductor having multiple crystalline regions, each with its c-axis aligned in a specific direction. The specific direction refers to the thickness direction of the CAAC-OS film, the normal direction to the surface where the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film. A crystalline region is a region with periodic atomic arrangement. If the atomic arrangement is considered as a lattice arrangement, a crystalline region is also a region with a uniform lattice arrangement. Furthermore, a CAAC-OS has a region where multiple crystalline regions are connected in the a-b plane direction, and the region may have distortion. Note that distortion refers to a portion where the lattice arrangement changes between a region with a uniform lattice arrangement and a region with another uniform lattice arrangement in a region where multiple crystalline regions are connected. In other words, a CAAC-OS is an oxide semiconductor with a c-axis aligned and no clear orientation in the a-b plane direction. CAC-OS is a material in which elements constituting a metal oxide are unevenly distributed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof. Note that hereinafter, a state in which one or more metal elements are unevenly distributed in a metal oxide and regions containing the metal elements are mixed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof, is also referred to as a mosaic or patch state.

[0417] Furthermore, the CAC-OS has a mosaic structure in which a material is separated into a first region and a second region, and the first region is distributed throughout the film (hereinafter also referred to as a cloud structure). That is, the CAC-OS is a composite metal oxide having a structure in which the first region and the second region are mixed.

[0418] Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In—Ga—Zn oxide are denoted as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS in the In—Ga—Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. The second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is a region where [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. The second region is a region where [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

[0419] Specifically, the first region is a region whose main component is indium oxide, indium zinc oxide, or the like. The second region is a region whose main component is gallium oxide, gallium zinc oxide, or the like. In other words, the first region can be referred to as a region whose main component is In. The second region can be referred to as a region whose main component is Ga.

[0420] It should be noted that there are cases where a clear boundary between the first region and the second region cannot be observed.

[0421] For example, in the case of CAC-OS in an In—Ga—Zn oxide, EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX) can confirm that the CAC-OS has a structure in which a region containing In as a main component (first region) and a region containing Ga as a main component (second region) are unevenly distributed and mixed.

[0422] When a CAC-OS is used in a transistor, the conductivity due to the first region and the insulating property due to the second region act complementarily, thereby providing the CAC-OS with a switching function (a function of turning on / off). That is, a CAC-OS has a conductive function in a part of the material and an insulating function in a part of the material, and functions as a semiconductor as a whole. By separating the conductive function and the insulating function, both functions can be maximized. Therefore, by using a CAC-OS in a transistor, a high on-current (I ｏｎ ), high field-effect mobility (μ), and good switching behavior can be achieved.

[0423] Oxide semiconductors have a variety of structures, each of which has different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS.

[0424] Furthermore, because the control circuit unit 1320 can be used in high-temperature environments, it is preferable to use a transistor using an oxide semiconductor. To simplify the process, the control circuit unit 1320 may be formed using a unipolar transistor. Transistors using an oxide semiconductor in the semiconductor layer have a wider operating ambient temperature range than single-crystal Si transistors, from −40° C. to 150° C., and their characteristics change less when the secondary battery is heated than single-crystal Si transistors. The off-current of a transistor using an oxide semiconductor is below the lower limit of measurement even at 150° C., regardless of temperature, whereas the off-current characteristics of single-crystal Si transistors 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 is not sufficiently large. The control circuit unit 1320 can improve safety. Furthermore, a synergistic effect on safety can be achieved by combining the cathode active material 100 obtained in the above-described embodiment with a secondary battery using the cathode.

[0425] The control circuit unit 1320, which uses a memory circuit including transistors using oxide semiconductors, can also function as an automatic control device for the secondary battery to address causes of instability such as micro-short circuits. Functions that eliminate causes of secondary battery instability include overcharging prevention, overcurrent prevention, overheating control during charging, maintaining cell balance in the battery pack, over-discharging prevention, a fuel gauge, automatic control of charging voltage and current according to temperature, control of charging current according to the degree of deterioration, detection of abnormal behavior of micro-short circuits, and prediction of abnormalities related to micro-short circuits, and the control circuit unit 1320 has at least one of these functions. Furthermore, the automatic control device for the secondary battery can be made ultra-compact.

[0426] A micro-short circuit refers to a tiny short circuit within a secondary battery, which is not so severe that the positive and negative electrodes of the secondary battery are short-circuited and render it unable to be charged or discharged, but rather a small short-circuit current flows through the tiny short-circuited area. Even a small area can cause a large voltage change over a relatively short period of time, and this abnormal voltage value may affect the estimation of the subsequent charge / discharge state of the secondary battery.

[0427] One of the causes of micro-short circuits is said to be that multiple charge and discharge cycles cause uneven distribution of the positive electrode active material, resulting in localized current concentration in parts of the positive electrode and negative electrode, causing parts of the separator to stop functioning, or the generation of by-products due to side reactions, resulting in micro-short circuits.

[0428] In addition to detecting micro-shorts, the control circuit 1320 can also be said to detect the terminal voltage of the secondary battery and manage the charge / discharge state of the secondary battery. For example, to prevent overcharging, it can turn off both the output transistor and the cutoff switch of the charging circuit almost simultaneously.

[0429] FIG. 34B shows an example of a block diagram of the battery pack 1415 shown in FIG. 34A.

[0430] The control circuit 1320 includes a switch unit 1324 including at least a switch for preventing overcharging and a switch for preventing overdischarging, a control circuit 1322 for controlling the switch unit 1324, and a voltage measurement unit for the first battery 1301a. The control circuit 1320 sets upper and lower voltage limits for the secondary battery used and limits the upper limit of the external current and the upper limit of the output current. The range between the lower and upper voltage limits of the secondary battery is within the recommended voltage range, and when the secondary battery falls outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent overcharging and overdischarging. For example, if the control circuit 1322 detects a voltage that could cause overcharging, it turns off the switch unit 1324 to cut off the current. Furthermore, a PTC element may be provided in the charge / discharge path to provide a function for cutting off the current in response to an increase in temperature. The control circuit section 1320 also has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0431] The switch unit 1324 can be configured by combining n-channel transistors and p-channel transistors. The switch unit 1324 is not limited to a switch having a Si transistor using single crystal silicon, and may be, for example, Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaO ｘThe switch portion 1324 may be formed using a power transistor having, for example, gallium oxide (x is a real number greater than 0). Furthermore, a memory element using an OS transistor can be freely arranged by stacking it on a circuit using a Si transistor, and therefore integration can be easily achieved. Furthermore, an OS transistor can be manufactured using the same manufacturing equipment as a Si transistor, and therefore can be manufactured at low cost. That is, a control circuit portion 1320 using an OS transistor can be stacked on the switch portion 1324 and integrated into a single chip. The volume occupied by the control circuit portion 1320 can be reduced, enabling miniaturization.

[0432] The first batteries 1301a and 1301b mainly supply power to in-vehicle devices of the 42V system (high voltage system), and the second battery 1311 supplies power to in-vehicle devices of the 14V system (low voltage system).

[0433] In this embodiment, an example in which lithium ion secondary batteries are used for both the first battery 1301a and the second battery 1311 is shown. A lead-acid battery, an all-solid-state battery, or an electric double layer capacitor may be used for the second battery 1311. For example, the all-solid-state battery of Embodiment 4 may be used. By using the all-solid-state battery of Embodiment 4 for the second battery 1311, high capacity can be achieved, and reductions in size and weight can be achieved.

[0434] Furthermore, regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305, and is then charged into the second battery 1311 from the motor controller 1303 and the battery controller 1302 via the control circuit unit 1321. Alternatively, the first battery 1301a is charged from the battery controller 1302 via the control circuit unit 1320. Alternatively, the first battery 1301b is charged from the battery controller 1302 via the control circuit unit 1320. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b be capable of rapid charging.

[0435] 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 charging conditions in accordance with the charging characteristics of the secondary battery used, and can perform rapid charging.

[0436] Although not shown, when the electric vehicle is connected to an external charger, the charger's outlet or charger connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger is charged to the first batteries 1301a and 1301b via the battery controller 1302. Some chargers are provided with a control circuit, and although the functions of the battery controller 1302 may not be used, it is preferable to charge the first batteries 1301a and 1301b via a control circuit unit 1320 to prevent overcharging. The charger's outlet or charger connection cable may also be provided with 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) provided 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 uses a CPU or a GPU.

[0437] External chargers installed at charging stations and the like come in a variety of types, including 100V outlets, 200V outlets, and three-phase 200V and 50kW outlets. Charging can also be performed by receiving power from external charging equipment using a wireless power supply system or the like.

[0438] When rapid charging is performed, a secondary battery that can withstand high voltage charging is desired in order to charge in a short time.

[0439] The secondary battery of the present embodiment described above uses the positive electrode active material 100 obtained in the above-described embodiment. Furthermore, by using graphene as a conductive material, a secondary battery with significantly improved electrical characteristics can be realized, as a synergistic effect of suppressing capacity reduction and maintaining high capacity even when the electrode layer is thickened and the loading amount is increased. This is particularly effective for secondary batteries used in vehicles, and a vehicle with a long cruising range, specifically a cruising range of 500 km or more per charge, can be provided without increasing the ratio of the weight of the secondary battery to the total weight of the vehicle.

[0440] In particular, the secondary battery of the present embodiment described above can increase the operating voltage of the secondary battery by using the cathode active material 100 described in the above embodiment, and can increase the usable capacity as the charging voltage increases. Furthermore, by using the cathode active material 100 described in the above embodiment for the cathode, a secondary battery for vehicles with excellent cycle characteristics can be provided.

[0441] Next, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle, typically a transportation vehicle, will be described.

[0442] 25D, 27C, and 34A can be installed in a vehicle to realize next-generation clean energy automobiles, such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs). Furthermore, the secondary battery can also be installed in transportation vehicles, such as agricultural machinery, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, electric carts, small or large ships, submarines, aircraft such as fixed-wing aircraft and rotary-wing aircraft, rockets, artificial satellites, space probes, planetary probes, and spacecraft. The secondary battery of one embodiment of the present invention can be a high-capacity secondary battery. Therefore, the secondary battery of one embodiment of the present invention is suitable for miniaturization and weight reduction and can be suitably used in transportation vehicles.

[0443] 35A to 35D illustrate a transportation vehicle as an example of a moving object using one embodiment of the present invention. The automobile 2001 illustrated in FIG. 35A is an electric automobile using an electric motor as a power source for traveling. Alternatively, it is a hybrid automobile that can appropriately select and use an electric motor or an engine as a power source for traveling. When a secondary battery is installed in a vehicle, an example of the secondary battery described in Embodiment 3 is installed in one or more locations. The automobile 2001 illustrated in FIG. 35A includes a battery pack 2200, which includes a secondary battery module to which multiple secondary batteries are connected. It is preferable that the automobile further include a charge control device electrically connected to the secondary battery module.

[0444] Furthermore, the automobile 2001 can charge its secondary battery by receiving power from an external charging facility using a plug-in system, a contactless power supply system, or the like. The charging method and connector standards may be appropriately determined using a predetermined system such as CHAdeMO (registered trademark) or Combo. The charging device may be a charging station installed in a commercial facility or a household power source. For example, plug-in technology can be used to charge the power storage device installed in the automobile 2001 using an external power supply. Charging can be performed by converting AC power to DC power via a conversion device such as an AC-DC converter.

[0445] Although not shown, a power receiving device can be mounted on a vehicle and power can be supplied contactlessly from a ground-based power transmitting device to charge the vehicle. In the case of this contactless power supply method, by incorporating a power transmitting device into a road or an exterior wall, charging can be performed not only while the vehicle is stopped but also while the vehicle is moving. This contactless power supply method can also be used to transmit and receive power between two vehicles. Furthermore, solar cells can be installed on the exterior of the vehicle to charge the secondary battery while the vehicle is stopped and while moving. For such contactless power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0446] Figure 35B 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 is, for example, a four-cell unit of secondary batteries with a nominal voltage of 3.0 V to 5.0 V, with 48 cells connected in series to achieve a maximum voltage of 170 V. Apart from the number of secondary batteries constituting the secondary battery module of the battery pack 2201, the transport vehicle 2002 has the same functions as those shown in Figure 35A, and therefore a description thereof will be omitted.

[0447] FIG. 35C shows, as an example, a large transport vehicle 2003 having an electrically controlled motor. The secondary battery module of the transport vehicle 2003 has, for example, 100 or more secondary batteries with a nominal voltage of 3.0 V or more and 5.0 V or less connected in series, with a maximum voltage of 600 V. By using a secondary battery whose positive electrode is the positive electrode active material 100 described in the above embodiment, a secondary battery with excellent rate characteristics and charge / discharge cycle characteristics can be manufactured, contributing to improved performance and a longer life of the transport vehicle 2003. Furthermore, except for the number of secondary batteries constituting the secondary battery module of the battery pack 2202, the same functions as those of FIG. 35A are provided, and therefore further description is omitted.

[0448] Fig. 35D shows, as an example, an aircraft 2004 having an engine that burns fuel. Since the aircraft 2004 shown in Fig. 35D has wheels for takeoff and landing, it can also be considered a type of transport vehicle, and has a battery pack 2203 that includes a secondary battery module formed by connecting multiple secondary batteries and a charge control device.

[0449] The secondary battery module of the aircraft 2004 has, for example, eight 4 V secondary batteries connected in series to produce a maximum voltage of 32 V. Other than the number of secondary batteries constituting the secondary battery module of the battery pack 2203, the secondary battery module has the same functions as those shown in Fig. 35A, and therefore a description thereof will be omitted.

[0450] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0451] Embodiment 6 In this embodiment, an example in which a secondary battery which is one embodiment of the present invention is mounted in a building will be described with reference to FIGS. 36A and 36B.

[0452] The house illustrated in FIG. 36A includes a power storage device 2612 including a secondary battery of 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 or the like. The power storage device 2612 may also be electrically connected to a ground-mounted charging device 2604. The power obtained by the solar panel 2610 can be charged to the power storage device 2612. The power stored in the power storage device 2612 can be charged to a secondary battery included in the vehicle 2603 via the charging device 2604. The power storage device 2612 is preferably installed in an underfloor space. By installing the power storage device 2612 in the underfloor space, the space above the floor can be effectively utilized. Alternatively, the power storage device 2612 may be installed on the floor.

[0453] The power stored in the power storage device 2612 can also be supplied to other electronic devices in the house. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the power storage device 2612 of one embodiment of the present invention can be used as an uninterruptible power supply, enabling the use of electronic devices.

[0454] 36B illustrates an example of a power storage device according to one embodiment of the present invention. As illustrated in FIG. 36B , a power storage device 791 according to one embodiment of the present invention is installed in an underfloor space 796 of a building 799. The control circuit described in Embodiment 5 may be provided in the power storage device 791. The power storage device 791 can have a long lifetime by using a secondary battery in which the positive electrode active material 100 obtained in the above embodiment is used for its positive electrode.

[0455] A control device 790 is installed in the power storage device 791, and the control device 790 is electrically connected to the distribution board 703, the power storage controller 705 (also called the control device), the display 706, and the router 709 by wiring.

[0456] Electric power is sent from commercial power source 701 to distribution board 703 via service line attachment portion 710. Electric power is also sent to distribution board 703 from power storage device 791 and commercial power source 701, and distribution board 703 supplies the sent electric power to general load 707 and power storage load 708 via outlets (not shown).

[0457] The general load 707 is, for example, an electrical appliance such as a television or a personal computer, and the power storage load 708 is, for example, an electrical appliance such as a microwave oven, a refrigerator, or an air conditioner.

[0458] The power storage controller 705 includes a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 has a function of measuring the amount of power consumed by the general load 707 and the power storage load 708 during a day (e.g., from midnight to midnight). The measurement unit 711 may also have a function of measuring the amount of power of the power storage device 791 and the amount of power supplied from the commercial power source 701. The prediction unit 712 has a function of predicting the amount of power demand to be consumed by the general load 707 and the power storage load 708 during the next day based on the amount of power consumed by the general load 707 and the power storage load 708 during the previous day. The planning unit 713 has a function of creating a plan for charging and discharging the power storage device 791 based on the amount of power demand predicted by the prediction unit 712.

[0459] The amount of power consumed by the general load 707 and the power storage load 708 measured by the measurement unit 711 can be confirmed on the display 706. It can also be confirmed on electrical appliances such as televisions and personal computers via the router 709. It can also be confirmed on portable electronic devices such as smartphones and tablets via the router 709. The amount of power demand for each time period (or each hour) predicted by the prediction unit 712 can also be confirmed on the display 706, the electrical appliances, and the portable electronic devices.

[0460] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0461] Embodiment 7 In this embodiment, an example in which a power storage device according to one embodiment of the present invention is mounted on a motorcycle or a bicycle will be described.

[0462] 37A illustrates an example of an electric bicycle using the power storage device of one embodiment of the present invention. The power storage device of one embodiment of the present invention can be applied to an electric bicycle 8700 illustrated in FIG. 37A. The power storage device of one embodiment of the present invention includes, for example, a plurality of storage batteries and a protection circuit.

[0463] The electric bicycle 8700 includes a power storage device 8702. The power storage device 8702 can supply electricity to a motor that assists a rider. The power storage device 8702 is portable and is shown in a state detached from the bicycle in FIG. 37B . The power storage device 8702 includes a plurality of built-in storage batteries 8701, which are included in the power storage device of one embodiment of the present invention, and the remaining battery charge and the like can be displayed on a display unit 8703. The power storage device 8702 also includes a control circuit 8704 that can control charging or detect an abnormality of the secondary battery, an example of which is shown in Embodiment 5. The control circuit 8704 is electrically connected to the positive and negative electrodes of the storage battery 8701. The control circuit 8704 may be provided with the small-sized solid-state secondary battery shown in FIGS. 33A and 33B. By providing the small-sized solid-state secondary battery shown in FIGS. 33A and 33B in the control circuit 8704, power can be supplied to retain data in a memory circuit included in the control circuit 8704 for a long period of time. Furthermore, a synergistic effect in terms of safety can be obtained by combining the positive electrode active material 100 obtained in the above-described embodiment with a secondary battery using the positive electrode active material 100 obtained in the above-described embodiment. The secondary battery using the positive electrode active material 100 obtained in the above-described embodiment and the control circuit 8704 can greatly contribute to eliminating accidents such as fires caused by secondary batteries.

[0464] 37C illustrates an example of a two-wheeled vehicle using the power storage device of one embodiment of the present invention. A scooter 8600 illustrated in FIG. 37C includes a power storage device 8602, a side mirror 8601, and a turn signal light 8603. The power storage device 8602 can supply electricity to the turn signal light 8603. The power storage device 8602, which includes a plurality of secondary batteries each using the positive electrode active material 100 obtained in the above embodiment for its positive electrode, can have a high capacity and contribute to miniaturization.

[0465] 37C can store a power storage device 8602 in an 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.

[0466] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0467] Embodiment 8 In this embodiment, an example of mounting a secondary battery according to one embodiment of the present invention in an electronic device will be described. Examples of electronic devices mounting a secondary battery include television sets (also referred to as televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (also referred to as mobile phones or mobile phone devices), portable game consoles, personal digital assistants, sound players, and large game consoles such as pachinko machines. Examples of personal digital assistants include notebook personal computers, tablet devices, e-book readers, and mobile phones.

[0468] 38A shows an example of a mobile phone. The mobile phone 2100 includes a display unit 2102 incorporated in a housing 2101, operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. The mobile phone 2100 also includes a secondary battery 2107. By including the secondary battery 2107 using the positive electrode active material 100 described in the above embodiment as a 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.

[0469] The mobile phone 2100 can execute various applications such as mobile phone calls, e-mail, document browsing and creation, music playback, internet communication, and computer games.

[0470] The operation button 2103 can be provided with various functions such as time setting, power on / off operation, wireless communication on / off operation, silent mode activation / deactivation, power saving mode activation / deactivation, etc. For example, the functions of the operation button 2103 can be freely set by an operating system incorporated in the mobile phone 2100.

[0471] The mobile phone 2100 is also capable of performing standardized short-range wireless communication, and can also make hands-free calls by communicating with a wirelessly enabled headset, for example.

[0472] The mobile phone 2100 also includes an external connection port 2104, which allows direct data exchange with other information terminals via a connector. Charging can also be performed via the external connection port 2104. Note that charging may be performed by wireless power supply without using the external connection port 2104.

[0473] The mobile phone 2100 preferably has a sensor, such as a fingerprint sensor, a pulse sensor, a body temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, or the like.

[0474] FIG. 38B illustrates an unmanned aerial vehicle 2300 having a plurality of rotors 2302. The unmanned aerial vehicle 2300 is sometimes called a drone. The unmanned aerial vehicle 2300 includes a secondary battery 2301 according to one embodiment of the present invention, a camera 2303, and an antenna (not shown). The unmanned aerial vehicle 2300 can be remotely controlled via the antenna. A secondary battery using the positive electrode active material 100 obtained in the above embodiment for its positive electrode has high energy density and high safety, and therefore can be used safely for a long period of time. Therefore, the secondary battery is suitable as a secondary battery to be mounted on the unmanned aerial vehicle 2300.

[0475] Fig. 38C shows an example of a robot. A robot 6400 shown in Fig. 38C includes a secondary battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6407, a movement mechanism 6408, a computing device, etc.

[0476] The microphone 6402 has a function of detecting the user's speaking voice, environmental sounds, etc. The speaker 6404 has a function of emitting sound. The robot 6400 can communicate with the user using the microphone 6402 and the speaker 6404.

[0477] The display unit 6405 has a function of displaying various information. The robot 6400 can display information desired by the user on the display unit 6405. The display unit 6405 may be equipped with a touch panel. The display unit 6405 may also be a detachable information terminal, which can be installed in a fixed position on the robot 6400 to enable charging and data transfer.

[0478] The upper camera 6403 and the lower camera 6406 have the function of capturing images of the surroundings of the robot 6400. Furthermore, 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 the surrounding environment and move safely using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407.

[0479] The robot 6400 includes a secondary battery 6409 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal region. A secondary battery using the positive electrode active material 100 obtained in the above embodiment for its positive electrode has high energy density and high safety, and therefore can be used safely for a long period of time. Therefore, the secondary battery is suitable as the secondary battery 6409 to be mounted on the robot 6400.

[0480] 38D shows an example of a cleaning robot. The cleaning robot 6300 includes a display unit 6302 arranged on the top surface of a housing 6301, a plurality of cameras 6303 arranged on the side surfaces, a brush 6304, operation buttons 6305, a secondary battery 6306, various sensors, and the like. Although not shown, the cleaning robot 6300 is provided with tires, a suction port, and the like. The cleaning robot 6300 can move by itself, detect dust 6310, and suck up the dust from a suction port arranged on the bottom surface.

[0481] For example, the cleaning robot 6300 can analyze an image captured by the camera 6303 and determine whether or not there is an obstacle such as a wall, furniture, or a step. Furthermore, if an object that may become entangled in the brush 6304, such as a wire, is detected through image analysis, the cleaning robot 6300 can stop the rotation of the brush 6304. The cleaning robot 6300 includes a secondary battery 6306 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal region. A secondary battery using the positive electrode active material 100 obtained in the above embodiment for its positive electrode has high energy density and high safety, and therefore can be used safely for a long period of time. Therefore, the secondary battery 6306 is suitable for use in the cleaning robot 6300.

[0482] 39A shows an example of a wearable device. The wearable device uses a secondary battery as a power source. Furthermore, in order to improve splash-proof, water-resistant, or dust-proof performance when used at home or outdoors, there is a demand for a wearable device that can be charged wirelessly as well as via a wired connection with an exposed connector.

[0483] For example, a secondary battery according to one embodiment of the present invention can be mounted on an eyeglasses-type device 4000 as shown in FIG. 39A . The eyeglasses-type device 4000 includes a frame 4000 a and a display unit 4000 b. Mounting a secondary battery on temples of the curved frame 4000 a makes it possible to provide the eyeglasses-type device 4000 with a lightweight design, a good weight balance, and a long continuous use time. A secondary battery using the positive electrode active material 100 obtained in the above embodiment as its positive electrode has a high energy density and can realize a configuration that can accommodate space saving associated with a miniaturized housing.

[0484] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a headset device 4001. The headset device 4001 includes at least a microphone unit 4001a, a flexible pipe 4001b, and an earphone unit 4001c. The secondary battery can be provided in the flexible pipe 4001b or the earphone unit 4001c. A secondary battery using the positive electrode active material 100 obtained in the above embodiment as a positive electrode has a high energy density and can realize a configuration that can accommodate space saving associated with a miniaturized housing.

[0485] Furthermore, the 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. A secondary battery 4002b can be provided in a thin housing 4002a of the device 4002. A secondary battery using the positive electrode active material 100 obtained in the above embodiment for its positive electrode has high energy density, and a configuration that can accommodate space saving associated with a miniaturized housing can be realized.

[0486] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a device 4003 that can be attached to clothing. A secondary battery 4003b can be provided in a thin housing 4003a of the device 4003. A secondary battery using the positive electrode active material 100 obtained in the above embodiment for its positive electrode has high energy density, and a configuration that can accommodate space saving associated with a miniaturized housing can be realized.

[0487] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on the belt-type device 4006. The belt-type device 4006 includes a belt portion 4006a and a wireless power receiving portion 4006b, and the secondary battery can be mounted in an internal region of the belt portion 4006a. A secondary battery using the positive electrode active material 100 obtained in the above embodiment as a positive electrode has a high energy density and can realize a configuration that can accommodate space saving associated with a miniaturized housing.

[0488] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on the wristwatch device 4005. The wristwatch device 4005 includes a display portion 4005a and a belt portion 4005b, and the secondary battery can be provided in the display portion 4005a or the belt portion 4005b. A secondary battery using the positive electrode active material 100 obtained in the above embodiment as a positive electrode has high energy density, and a configuration that can accommodate space saving associated with miniaturization of the housing can be realized.

[0489] The display unit 4005a can display not only the time but also various other information such as incoming emails and phone calls.

[0490] Furthermore, since the wristwatch device 4005 is a wearable device that is worn directly on the arm, it may be equipped with sensors that measure the user's pulse, blood pressure, etc. Data on the user's exercise volume and health can be accumulated to manage the user's health.

[0491] FIG. 39B shows a perspective view of the wristwatch-type device 4005 removed from the wrist.

[0492] 39C shows a side view of the display portion 4005a. The side view of the display portion 4005a also shows a state in which a secondary battery 913 is built in the internal region. The secondary battery 913 is the secondary battery described in Embodiment 3. The secondary battery 913 is provided in a position overlapping with the display portion 4005a, and can have high density and high capacity, and is small and lightweight.

[0493] Since the wristwatch-type device 4005 is required to be small and lightweight, by using the positive electrode active material 100 obtained in the above-described embodiment as the positive electrode of the secondary battery 913, it is possible to obtain a high-energy density and small-sized secondary battery 913.

[0494] 39D shows an example of a wireless earphone. Here, the wireless earphone is shown having a pair of main bodies 4100a and 4100b, but this does not necessarily have to be a pair.

[0495] The main bodies 4100a and 4100b each have a driver unit 4101, an antenna 4102, and a secondary battery 4103. They may also have a display unit 4104. They also preferably have a substrate on which a circuit such as a wireless IC is mounted, a charging terminal, and the like. They may also have a microphone.

[0496] The case 4110 has a secondary battery 4111. It is preferable that the case 4110 also has a board on which circuits such as a wireless IC and a charge control IC are mounted, and a charging terminal. It may also have a display unit, buttons, and the like.

[0497] The main units 4100a and 4100b can wirelessly communicate with other electronic devices such as smartphones. This allows sound data and the like sent from other electronic devices to be played back on the main units 4100a and 4100b. If the main units 4100a and 4100b have microphones, the sound picked up by the microphones can be sent to the other electronic device, and the sound data after processing by the electronic device can be sent back to the main units 4100a and 4100b for playback. This allows the devices to be used as, for example, translation devices.

[0498] Furthermore, the secondary battery 4103 included in the main body 4100a can be charged from the secondary battery 4111 included in the case 4110. The coin-type secondary battery, the cylindrical secondary battery, or the like described in the above embodiment can be used as the secondary battery 4111 and the secondary battery 4103. A secondary battery using the positive electrode active material 100 obtained in the above embodiment as a positive electrode has high energy density, and by using the secondary battery 4103 and the secondary battery 4111 as the positive electrode, a configuration that can accommodate space saving associated with miniaturization of wireless earphones can be realized.

[0499] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0500] 81: cobalt source, 82: first additional element source, 83: chelating agent, 84: alkaline solution, 85: water, 88: lithium source, 89: second additional element source, 90: third additional element source, 91: acid solution, 92: precipitate, 94: mixture, 95: cobalt compound, 97: mixture, 98: composite oxide, 99: composite oxide, 100: positive electrode active material, 100a: surface layer, 100b: interior

Claims

1. mixing a cobalt source and an additive element source to form an acid solution; reacting the acid solution with the alkaline solution to form a cobalt compound; mixing the cobalt compound with a lithium source to form a mixture; A method for producing a positive electrode active material by heating the mixture, The method for producing a positive electrode active material, wherein the additive element source contains one or more selected from the group consisting of gallium, boron, nickel, and indium.

2. reacting a cobalt source with an alkaline solution to form a cobalt compound; mixing the cobalt compound, a lithium source, and an additive element source to form a mixture; A method for producing a positive electrode active material by heating the mixture, The method for producing a positive electrode active material, wherein the additive element source contains one or more selected from the group consisting of gallium, boron, nickel, and indium.

3. reacting a cobalt source with an alkaline solution to form a cobalt compound; combining the cobalt compound with a lithium source to form a first mixture; heating the first mixture to form a composite oxide; mixing the composite oxide with an additive element source to form a second mixture; A method for producing a positive electrode active material by heating the second mixture, The method for producing a positive electrode active material, wherein the additive element source contains one or more selected from the group consisting of gallium, boron, nickel, and indium.

4. mixing a cobalt source and a first additive element source to form an acid solution; reacting the acid solution with the alkaline solution to form a cobalt compound; combining the cobalt compound with a lithium source to form a first mixture; heating the first mixture to form a composite oxide; mixing the composite oxide with a second additive element source to form a second mixture; A method for producing a positive electrode active material by heating the second mixture, the first additive element source comprises one or more selected from the group consisting of gallium, boron, nickel, and indium; the second additive element source having one or more selected from nickel, cobalt, magnesium, calcium, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron.

5. reacting a cobalt source with an alkaline solution to form a cobalt compound; combining the cobalt compound with a lithium source to form a first mixture; heating the first mixture to form a composite oxide; mixing the composite oxide with a first additive element source and a second additive element source to form a second mixture; A method for producing a positive electrode active material by heating the second mixture, The first additive element source includes at least one selected from the group consisting of gallium, boron, nickel, and indium; the second additive element source is one or more selected from nickel, cobalt, magnesium, calcium, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron.

6. mixing a cobalt source and a first additive element source to form an acid solution; reacting the acid solution with an alkaline solution to form a cobalt compound; combining the cobalt compound with a lithium source to form a first mixture; heating the first mixture to form a first composite oxide; mixing the first composite oxide with a second additive element source to form a second mixture; heating the second mixture to form a second composite oxide; mixing the second composite oxide with a third additive element source to form a third mixture; A method for producing a positive electrode active material, comprising heating the third mixture, The first additive element source includes at least one selected from the group consisting of gallium, boron, nickel, and indium; The second additive element source and the third additive element source each have one or more selected from nickel, cobalt, magnesium, calcium, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron; The method for producing a positive electrode active material, wherein an element contained in the second additive element source is different from an element contained in the third additive element source.

7. reacting a cobalt source with an alkaline solution to form a cobalt compound; combining the cobalt compound with a lithium source to form a first mixture; heating the first mixture to form a first composite oxide; mixing the first composite oxide with a first additive element source to form a second mixture; heating the second mixture to form a second composite oxide; mixing the second composite oxide, a second additive element source, and a third additive element source to form a third mixture; A method for producing a positive electrode active material, comprising heating the third mixture, The first additive element source and the third additive element source each have one or more selected from nickel, cobalt, magnesium, calcium, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron; an element contained in the first additive element source is different from an element contained in the third additive element source; The method for producing a positive electrode active material, wherein the second additive element source contains one or more selected from the group consisting of gallium, boron, nickel, and indium.

8. In any one of claims 1 to 7, The method for producing a positive electrode active material, wherein the alkaline solution has an aqueous solution containing sodium hydroxide, potassium hydroxide, lithium hydroxide, or ammonia.

9. 9. The method for producing a positive electrode active material according to claim 8, wherein the water used in the aqueous solution has a resistivity of 1 MΩ·cm or more.

10. 4. The method for producing a positive electrode active material according to claim 1, wherein the additive element source comprises gallium sulfate, gallium chloride, or gallium nitrate.

11. 7. The method for producing a positive electrode active material according to claim 4, wherein the first additive element source contains gallium sulfate, gallium chloride, or gallium nitrate.

12. The method for producing a positive electrode active material according to claim 7 , wherein the second additive element source comprises gallium sulfate, gallium chloride, or gallium nitrate.

13. In any one of claims 3 to 5, The temperature to which the second mixture is heated is lower than the temperature to which the first mixture is heated.

14. In claim 6 or 7, the temperature to which the third mixture is heated is lower than the temperature to which the first mixture is heated.