Positive electrode active material, method for manufacturing same, and secondary battery

Abstract

One embodiment of the present invention provides a novel positive electrode active material. Also provided is a secondary battery that is highly safe. A positive electrode active material is produced by: obtaining a nickel compound (also referred to as a precursor) that contains nickel, cobalt and manganese through a coprecipitation process; mixing a lithium compound and the nickel compound, heating the mixture at a first temperature, and pulverizing or crushing the mixture; heating the pulverized or crushed mixture at a second temperature which is higher than the first temperature, and mixing magnesium thereinto; and subjecting the resulting mixture to a third heating treatment.

Description

Positive electrode active material, method for producing same, and secondary battery

[0001] 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, a manufacture, or a composition of matter. One embodiment of the present invention relates to a power storage device including a secondary battery, a semiconductor device, a display device, a light-emitting device, a lighting device, an electronic device, or a manufacturing method thereof.

[0002] In this specification, the term "electronic device" refers to any device having a power storage device, and includes electro-optical devices having a power storage device, information terminal devices having a power storage device, and the like.

[0003] In recent years, there has been active development of various types of energy storage devices, such as lithium-ion secondary batteries, lithium-ion capacitors, air batteries, and all-solid-state batteries. Demand for high-power, high-capacity lithium-ion secondary batteries has expanded rapidly in line with the development of the semiconductor industry, and they have become indispensable in today's information society as a rechargeable energy source.

[0004] In particular, there is a high demand for secondary batteries with a large discharge capacity per weight and excellent cycle characteristics for mobile electronic devices, etc. To meet this demand, active materials for the positive electrodes of secondary batteries have been actively improved (see, for example, Patent Document 1).

[0005] JP 2020-068210 A

[0006] An object of one embodiment of the present invention is to provide a positive electrode active material that is not easily deteriorated.Another object is to provide a novel positive electrode active material.Another object is to provide a secondary battery that is safe or highly reliable.Another object is to provide a secondary battery that is not easily deteriorated.Another object is to provide a secondary battery with a long lifetime.Another object is to provide a novel secondary battery.

[0007] 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 of the specification, drawings, and claims.

[0008] Lithium ion secondary batteries are LiNi Ｘ Co Ｙ Mn Ｚ O ２ The so-called NCM, expressed as (X + Y + Z = 1), is commonly used. Materials containing equal amounts of transition metals, such as Ni:Co:Mn = 1:1:1, tend to be costly because they contain a large amount of the precious metal cobalt. Attempts to increase the capacity of batteries have been made by reducing the amount of cobalt used and increasing the amount of nickel used.

[0009] NCMs with a high nickel content have the problem of being prone to oxygen desorption and degradation, as well as the problem of a phenomenon known as cation mixing, in which transition metals such as nickel and manganese enter the sites where lithium ions are absorbed or desorbed during charging and discharging.

[0010] NCM consists of secondary particles formed by the aggregation of multiple primary particles. Charging or discharging causes the absorption or desorption of lithium ions, causing the primary particles to expand or contract. The expansion or contraction of the primary particles results in a volume change, and the secondary particles crack or become finer as the primary particles disaggregate. One of the reasons for the cracking or finer formation is that repeated charging or discharging changes the a-axis or c-axis of the NCM crystal, increasing the size of the voids between the primary particles. Note that the term "voids between primary particles" does not refer to space; in a secondary battery, an electrolyte exists in the voids. However, in an all-solid-state battery, it is a void.

[0011] In addition, secondary batteries use positive electrodes in which a positive electrode active material layer is formed on a current collector by mixing powdered NCM with a conductive additive and binding the mixture with a binder. The secondary particles contained in the positive electrode active material layer contain primary particles, and volume changes occur during charging and discharging of the secondary battery. If cracks or micro-particles occur between the primary particles, the life characteristics of the secondary battery deteriorate and the resistance increases. If cracks or micro-particles of the NCM secondary particles occur, the area in the positive electrode where electronic conductivity is not ensured increases, increasing internal resistance and reducing the life characteristics of the secondary battery.

[0012] Therefore, in order to solve at least one of the above problems, adding magnesium to NCM reduces cracks that occur between primary particles during charge and discharge, and improves the life characteristics of secondary batteries. It is desirable that the practitioner weigh out and add magnesium in a desired amount in the range of 0.5 atomic % to 3 atomic % so that the magnesium is contained in a desired amount, taking into account the composition of the nickel compound before addition.

[0013] Secondary particles are aggregates of multiple primary particles, with gaps between the primary particles. Primary particles can be polycrystalline or monocrystalline. When a secondary battery is manufactured, not only the outer surface of a secondary particle formed by the aggregation of multiple primary particles, but also the internal voids and areas where the bonding between primary particles is incomplete, come into contact with the electrolyte. Therefore, the area in contact with the electrolyte allows for lithium insertion and extraction, which has the advantage of improving capacity characteristics. On the other hand, if the area in contact with the electrolyte is unstable, this area may be prone to deterioration, resulting in a decrease in cycle characteristics.

[0014] In the configuration disclosed in this specification, a nickel compound (also referred to as a precursor) containing nickel, cobalt, and manganese is obtained by a coprecipitation method, and then the nickel compound is mixed with a lithium compound, the mixture is heated at a first temperature, the mixture is crushed or pulverized, and then a magnesium compound is mixed with the mixture, and the mixture is heated at a second temperature that is higher than the first temperature, to produce a positive electrode active material.

[0015] More specifically, this is a method for producing a positive electrode active material, which includes supplying an aqueous solution containing a water-soluble salt of nickel, a water-soluble salt of cobalt, and a water-soluble salt of manganese, and an alkaline solution, and mixing them inside the reaction tank to precipitate a compound containing at least nickel, cobalt, and manganese, heating a first mixture obtained by mixing the compound and a lithium compound at a first heating temperature, crushing or pulverizing the first mixture, and then heating it at a second heating temperature, mixing the crushed or pulverized first mixture with a magnesium compound, and heating the resulting second mixture at a third heating temperature.

[0016] After the water is removed by heating at a first temperature, the mixture is heated at a second temperature higher than the first temperature, and by performing two heat treatments in total, the mixed state of the mixture is improved, and when a secondary battery is fabricated, the voids in the secondary particles can be reduced. Furthermore, by performing two heat treatments in total, the crystallinity can be improved.

[0017] The first heating temperature is set to a range of 400°C or more and 750°C or less.

[0018] The second heating temperature and the third heating temperature are in the range of more than 750°C and not more than 1050°C.

[0019] The coprecipitation method for precipitating the nickel compound involves supplying an aqueous solution containing a water-soluble salt of nickel, a water-soluble salt of cobalt, and a water-soluble salt of manganese, and an alkaline solution to a reaction vessel, and mixing them inside the reaction vessel to precipitate a nickel compound (a hydroxide containing cobalt, manganese, and nickel). This reaction may be referred to as a neutralization reaction, an acid-base reaction, or a coprecipitation reaction, and the compound containing at least nickel, cobalt, and manganese may be referred to as at least a cobalt compound, or a precursor of lithium cobalt oxide, even if the cobalt content is at most. The nickel compound and lithium compound are then mixed to obtain a mixture.

[0020] As the aqueous solution containing a water-soluble salt of nickel, an aqueous solution of nickel sulfate or an aqueous solution of nickel nitrate can be used.

[0021] The aqueous solution containing a water-soluble salt of cobalt may be an aqueous solution of cobalt sulfate or cobalt nitrate.

[0022] As the aqueous solution containing a water-soluble salt of manganese, an aqueous manganese sulfate solution or an aqueous manganese nitrate solution can be used.

[0023] The pH of the mixture in the reaction vessel is preferably 9.0 or more and 12.0 or less, and more preferably 10.0 or more and 11.5 or less.

[0024] A chelating agent is added when the aqueous solution and the alkaline solution are mixed to precipitate the cobalt compound. Examples of chelating agents include glycine, oxine, 1-nitroso-2-naphthol, 2-mercaptobenzothiazole, and EDTA (ethylenediaminetetraacetic acid). Multiple agents selected from glycine, oxine, 1-nitroso-2-naphthol, and 2-mercaptobenzothiazole may also be used. The chelating agent is dissolved in pure water to form a chelating aqueous solution. The chelating agent is a complexing agent that forms a chelate compound and is preferable to general complexing agents. Of course, a complexing agent may be used instead of a chelating agent, and ammonia water may be used as the complexing agent.

[0025] The use of a chelate aqueous solution is preferred because it facilitates control of the pH of the mixed solution present in the reaction vessel when obtaining the cobalt compound. The use of a chelate aqueous solution is also preferred because it suppresses the generation of unwanted crystal nuclei and promotes growth. Suppressing the generation of unwanted nuclei suppresses the generation of fine particles, thereby producing a complex oxide with a good particle size distribution. The use of a chelate aqueous solution also slows the acid-base reaction, allowing the reaction to proceed gradually, resulting in the production of nearly spherical secondary particles. Glycine has the effect of maintaining a constant pH value at or near a pH of 9.0 to 10.0. Therefore, using a glycine aqueous solution as the chelate aqueous solution is preferred because it facilitates control of the pH of the reaction vessel when obtaining the cobalt compound. Furthermore, the glycine concentration of the glycine aqueous solution is preferably 0.05 mol / L to 0.09 mol / L in the aqueous solution.

[0026] The positive electrode active material obtained by the above method has secondary particles, and each secondary particle has a plurality of primary particles.

[0027] The positive electrode active material obtained by the above method has crystals with a hexagonal layer structure. The crystals are not limited to single crystals (also called crystallites). In the case of polycrystals, several crystallites aggregate to form primary particles. A primary particle refers to a particle that is recognized as a single grain when observed under an SEM. A secondary particle refers to a mass of aggregated primary particles. The aggregation of primary particles does not depend on the bonding force acting between multiple primary particles. It may be a covalent bond, an ionic bond, a hydrophobic interaction, a van der Waals force, or other intermolecular interaction, or multiple bonding forces may be acting.

[0028] When coprecipitation is used, secondary particles may be formed.

[0029] The crystal having a hexagonal layer structure has one or more selected from the group consisting of a first transition metal, a second transition metal, and a third transition metal. Specifically, the first transition metal is nickel, the second transition metal is cobalt, the third transition metal is manganese, and LiNi ｘ Co ｙ Mn ｚ O ２ A NiCoMn-based material (also referred to as NCM) represented by (x > 0, y > 0, z > 0, 0.8 < x + y + z < 1.2) can be used. Specifically, for example, it is preferable to satisfy 0.1x < y < 8x and 0.1x < z < 8x. As an example, it is preferable that x, y, and z satisfy x:y:z = 1:1:1 or a value thereabout. As another example, it is preferable that x, y, and z satisfy x:y:z = 5:2:3 or a value thereabout. As another example, it is preferable that x, y, and z satisfy x:y:z = 8:1:1 or a value thereabout. As another example, it is preferable that x, y, and z satisfy x:y:z = 9:0.5:0.5 or a value thereabout. As another example, it is preferable that x, y, and z satisfy x:y:z = 6:2:2 or a value thereabout. Alternatively, as an example, it is preferable that x, y, and z satisfy the relationship x:y:z=1:4:1 or values ​​close thereto.

[0030] The cathode active material has secondary particles, each of which has a plurality of primary particles, and at least one of the primary particles has a surface layer containing magnesium, the thickness of which is 1 nm to 10 nm. Adding magnesium to the NCM reduces cracks that occur between the primary particles during charge and discharge, improving the life characteristics of the secondary battery.

[0031] A secondary battery using the above-described positive electrode active material is also one of the configurations disclosed in this specification. The secondary battery has a positive electrode having a positive electrode active material and a negative electrode having a negative electrode active material. A separator is also provided between the positive electrode and the negative electrode. The separator is used to prevent short circuits, and a safe and reliable secondary battery can be provided.

[0032] According to one embodiment of the present invention, two heat treatments improve the mixing state of the mixture, thereby reducing voids in the secondary particles when a secondary battery is fabricated. Furthermore, three heat treatments, two before the addition of magnesium and one after the addition, can improve crystallinity. Therefore, a positive electrode active material that is relatively stable even after repeated charge and discharge can be provided. Alternatively, a secondary battery with high safety and reliability can be provided.

[0033] 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, and claims, and it is possible to extract other effects from the description in the specification, drawings, and claims.

[0034] FIG. 1A is a schematic diagram illustrating the appearance of a secondary particle, and FIG. 1B is a schematic diagram illustrating an example of a cross section of a secondary particle. FIG. 2A is a diagram illustrating an example of a cross section of a secondary particle, and FIG. 2B is a schematic diagram illustrating an example of a cross section of a secondary particle. FIG. 3 is an example of a flow diagram of a manufacturing process illustrating one embodiment of the present invention. FIG. 4 is an example of a flow diagram of a manufacturing process illustrating one embodiment of the present invention. FIG. 5A is an exploded perspective view of a coin-type secondary battery, FIG. 5B is a perspective view of the coin-type secondary battery, and FIG. 5C is a cross-sectional perspective view thereof. FIG. 6A illustrates an example of a cylindrical secondary battery. FIG. 6B illustrates an example of a cylindrical secondary battery. FIG. 6C illustrates an example of a plurality of cylindrical secondary batteries. FIG. 6D illustrates an example of a power storage system including a plurality of cylindrical secondary batteries. FIGS. 7A and 7B are diagrams illustrating an example of a secondary battery, and FIG. 7C is a diagram illustrating the internal state of the secondary battery. FIGS. 8A to 8C are diagrams illustrating an example of a secondary battery. FIGS. 9A and 9B are diagrams illustrating the appearance of a secondary battery. 10A to 10C are diagrams illustrating a method for fabricating a secondary battery. FIG. 11A is a perspective view of a battery pack illustrating one embodiment of the present invention, FIG. 11B is a block diagram of the battery pack, and FIG. 11C is a block diagram of a vehicle including the battery pack. FIGS. 12A to 12D are diagrams illustrating an example of a transportation vehicle. FIG. 12E is a diagram illustrating an example of an artificial satellite. FIG. 13A is a diagram illustrating an electric bicycle, FIG. 13B is a diagram illustrating a secondary battery for the electric bicycle, and FIG. 13C is a diagram illustrating a scooter. FIGS. 14A to 14D are diagrams illustrating an example of an electronic device. FIG. 15 is a planar SEM photograph of the positive electrode active material of this example. FIG. 16A is a diagram illustrating the results of a cycle test in which the vertical axis represents discharge capacity, and FIG. 16B is a diagram illustrating the results of a cycle test in which the vertical axis represents capacity retention.

[0035] 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.

[0036] In this specification and the like, the term "particle" is not limited to referring only to spherical particles (having a circular cross-sectional shape), and examples of the cross-sectional shape of individual particles include ellipsoids, rectangles, trapezoids, cones, squares with rounded corners, and asymmetric shapes, and further, individual particles may have an irregular shape.

[0037] Homogeneity refers to a state in which a certain element (e.g., A) is distributed with similar characteristics in a specific region of a solid composed of multiple elements (e.g., A, B, C). It is sufficient that the concentrations of elements in the specific regions are substantially the same. For example, it is sufficient that the difference in the detected amount of a certain element (e.g., the number of counts in STEM-EDX) between the specific regions is within 10%. Examples of specific regions include a surface layer, a surface, a convex portion, a concave portion, and an interior.

[0038] A cathode active material to which an additive element is added may be referred to as a composite oxide, a cathode material, a cathode ingredient, a cathode material for a secondary battery, or the like. In this specification and the like, the cathode active material of one embodiment of the present invention preferably includes a compound. In this specification and the like, the cathode active material of one embodiment of the present invention preferably includes a composition. In this specification and the like, the cathode active material of one embodiment of the present invention preferably includes a composite.

[0039] Furthermore, when describing the characteristics of individual particles of the positive electrode active material in the following embodiments, etc., it is not necessary for all particles to have that characteristic. For example, if 50% or more, preferably 70% or more, and more preferably 90% or more of three or more randomly selected particles of the positive electrode active material have that characteristic, it can be said that the effect of sufficiently improving the characteristics of the positive electrode active material and a secondary battery containing it is achieved.

[0040] 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 the short circuit current be suppressed even at a high charging voltage. The positive electrode active material of one embodiment of the present invention suppresses the short circuit current even at a high charging voltage. Therefore, a secondary battery that achieves both high discharge capacity and safety can be obtained.

[0041] Unless otherwise specified, the materials (positive electrode active material, negative electrode active material, electrolyte, separator, etc.) contained in the secondary battery are described in their pre-degradation state. Note that a decrease in discharge capacity due to aging treatment (which may also be called burn-in treatment) during secondary battery manufacturing is not considered to be degradation. For example, a lithium-ion secondary cell or lithium secondary battery pack (hereinafter referred to as a lithium-ion secondary battery) that has a discharge capacity of 97% or more of its rated capacity can be considered to be in its pre-degradation state. For lithium-ion secondary batteries for portable devices, the rated capacity conforms to JIS C 8711:2019. For other lithium-ion secondary batteries, the rated capacity conforms not only to the above JIS standard but also to various JIS and IEC standards for electric vehicle propulsion, industrial use, etc.

[0042] Furthermore, the state of the materials in a secondary battery before deterioration is sometimes referred to as an initial product or initial state, and the state after deterioration (the state when the secondary battery has a discharge capacity of less than 97% of its rated capacity) is sometimes referred to as a product in use or in use state, or a used product or used state.

[0043] Embodiment 1 In this embodiment, a positive electrode active material 101 of one embodiment of the present invention will be described with reference to FIGS.

[0044] The positive electrode active material 101 contains lithium, a transition metal M, and oxygen. The transition metal M is one or more selected from nickel, manganese, and cobalt. It is preferable that the positive electrode active material 101 further contains magnesium as an additive element. Alternatively, the positive electrode active material 101 may contain lithium nickel-manganese-cobalt oxide to which the additive element has been added.

[0045] A positive electrode active material of a lithium-ion secondary battery needs to contain a transition metal capable of oxidation and reduction in order to maintain charge neutrality even when lithium ions are inserted or extracted. The positive electrode active material 101 of one embodiment of the present invention contains nickel, manganese, and cobalt as the transition metal M responsible for the oxidation and reduction reaction.

[0046] Fig. 1A is a schematic diagram showing an example of the appearance of a positive electrode active material 101. As shown in Fig. 1A, a plurality of primary particles 100 aggregate to form one secondary particle. Note that Fig. 1A does not show a layer 100m containing magnesium.

[0047] FIG. 1B shows an example of a schematic cross-sectional view of the positive electrode active material 101 .

[0048] Figure 1B shows several variations in the case where a magnesium-containing layer is provided on the primary particles that make up the secondary particles. Some primary particles and their surface layers are indicated by arrows in Figure 1B.

[0049] In some cases, a magnesium-containing layer 100m is provided over the entire surface of the primary particle 100, and in other cases, primary particles 100 without a magnesium-containing layer are mixed. In other cases, magnesium-containing layers 100m1 and 100m2 are provided on both ends of the primary particle 100. In other cases, even primary particles located in the center of secondary particles may have a magnesium-containing layer 100m provided over the entire surface of the primary particle 100. In other cases, a magnesium-containing layer 100m3 is provided on only one surface. In other cases, a magnesium-containing layer 100m4 common to two primary particles is provided.

[0050] 2A shows an example of a cross-sectional schematic diagram of the positive electrode active material 101a. In FIG. 2A, a layer 100m5 containing magnesium is provided so as to cover the entire outer surface of the positive electrode active material 101a.

[0051] 2B also shows an example of a cross-sectional schematic diagram of the positive electrode active material 101b. In FIG. 2B, an example is shown in which a magnesium-containing layer 100m6 is provided on a surface layer portion of the positive electrode active material 101b. In FIG. 2B, the surface layer portion of the positive electrode active material 101b and the magnesium-containing layer 100m6 are coincident with each other.

[0052] Depending on various conditions such as the manufacturing method of the positive electrode active material, specifically the heating temperature, the amount of magnesium source to be mixed, the material of the magnesium source, and the timing of adding magnesium, it is possible to obtain any one of the configurations of the positive electrode active material 101 in FIG. 1B , the positive electrode active material 101 a in FIG. 2A , and the positive electrode active material 101 b in FIG. 2B , or a configuration similar thereto.

[0053] An example of a method for producing the positive electrode active material 101 will be described below with reference to FIGS.

[0054] 3, first, transition metal M sources, i.e., nickel source (Ni source), cobalt source (Co source), and manganese source (Mn source), are prepared. These are preferably mixed in a ratio of nickel, cobalt, and manganese that allows a layered rock-salt crystal structure to be formed.

[0055] In particular, a high content of nickel as the transition metal M in the positive electrode active material 101 is preferable because the raw material may be cheaper than a high content of cobalt and the charge / discharge capacity per weight may increase. For example, nickel preferably accounts for more than 25 atomic % of the transition metal M, more preferably 60 atomic % or more, and even more preferably 80 atomic % or more. However, if the proportion of nickel is too high, chemical stability and heat resistance may decrease. Therefore, it is preferable that nickel accounts for 95 atomic % or less of the transition metal M.

[0056] When cobalt is contained as the transition metal M, the average discharge voltage is high, and the cobalt contributes to stabilizing the layered rock salt structure, so that a highly reliable secondary battery can be obtained, which is preferable.

[0057] The inclusion of manganese as the transition metal M is preferable because it improves heat resistance and chemical stability. However, if the proportion of manganese is too high, the discharge voltage and discharge capacity tend to decrease. Therefore, for example, it is preferable that the manganese content of the transition metal M is 2.5 atomic % or more and 34 atomic % or less.

[0058] The transition metal M source is prepared as an aqueous solution containing the transition metal M. An aqueous solution of a nickel salt can be used as the nickel source. Examples of nickel salts that can be used include nickel sulfate, nickel chloride, nickel nitrate, and hydrates thereof. Organic acid salts of nickel, such as nickel acetate, and hydrates thereof can also be used. An aqueous solution of a nickel alkoxide or an organic nickel complex can also be used as the nickel source. In this specification and the like, organic acid salts refer to compounds of metals and organic acids, such as acetic acid, citric acid, oxalic acid, formic acid, and butyric acid.

[0059] Similarly, an aqueous solution of a cobalt salt can be used as the cobalt source. Examples of the cobalt salt include cobalt sulfate, cobalt chloride, cobalt nitrate, and hydrates thereof. Organic acid salts of cobalt, such as cobalt acetate, and hydrates thereof can also be used. An aqueous solution of a cobalt alkoxide or an organic cobalt complex can also be used as the cobalt source.

[0060] Similarly, an aqueous solution of a manganese salt can be used as the manganese source. Examples of manganese salts that can be used include manganese sulfate, manganese chloride, manganese nitrate, and aqueous solutions of these hydrates. Organic acid salts of manganese, such as manganese acetate, and hydrates of these salts can also be used. An aqueous solution of a manganese alkoxide or an organic manganese complex can also be used as the manganese source.

[0061] In this embodiment, an aqueous solution in which nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved in pure water is prepared as a source of the transition metal M. The atomic ratio of nickel, cobalt, and manganese is Ni:Co:Mn=8:1:1 or approximately this ratio. The aqueous solution is acidic.

[0062] <Step S113> As shown in step S113 of FIG. 3 , a chelating agent may be prepared. Examples of chelating agents include glycine, oxine, 1-nitroso-2-naphthol, 2-mercaptobenzothiazole, and EDTA (ethylenediaminetetraacetic acid). Multiple agents selected from glycine, oxine, 1-nitroso-2-naphthol, and 2-mercaptobenzothiazole may also be used. At least one of these agents is dissolved in pure water to form a chelating aqueous solution. A chelating agent is a complexing agent that forms a chelate compound and is preferable to general complexing agents. Of course, a complexing agent may be used instead of a chelating agent, and ammonia water may be used as the complexing agent. Using a chelating aqueous solution is preferable because it suppresses the generation of unnecessary crystal nuclei and promotes growth. Suppressing the generation of unnecessary nuclei suppresses the generation of fine particles, thereby producing a composite hydroxide with a good particle size distribution. Furthermore, using a chelating aqueous solution can slow the acid-base reaction, allowing the reaction to proceed gradually and resulting in nearly spherical secondary particles. Glycine has the effect of maintaining a constant pH value at a pH of 9 or more and 10 or less, and is therefore preferable when using a glycine aqueous solution as the chelate aqueous solution, as this makes it easier to control the pH of the reaction tank when obtaining the composite hydroxide 98.

[0063] <Step S114> Next, in step S114 of FIG. 3, a transition metal M source and a chelating agent are mixed to prepare an acid solution.

[0064] <Step S121> Next, in step S121 of Fig. 3, an alkaline solution is prepared. As the alkaline solution, for example, an aqueous solution containing sodium hydroxide, potassium hydroxide, lithium hydroxide, or ammonia can be used. An aqueous solution in which these are dissolved in pure water can be used. Alternatively, an aqueous solution in which multiple types selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia are dissolved in pure water may be used.

[0065] The pure water preferably used for the transition metal M source and the alkaline solution is water having 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 satisfying this resistivity requirement has high purity and contains very few impurities.

[0066] <Step S122> As shown in step S122 of Fig. 3, it is preferable to prepare water in the reaction tank. This water may be an aqueous solution of a chelating agent, but pure water is more preferable. The use of pure water promotes nucleation, making it possible to produce composite hydroxides with small particle sizes. The water prepared in the reaction tank can be referred to as a filling liquid or an adjusting liquid for the reaction tank. When using an aqueous chelating agent solution, the description of step S13 can be taken into consideration.

[0067] 3, the acid solution and the alkaline solution are mixed and reacted with each other, which can be called a co-precipitation reaction, a neutralization reaction, or an acid-base reaction.

[0068] During the coprecipitation reaction in step S131, it is preferable to adjust the pH of the reaction system to 9.0 or more and 11.5 or less.

[0069] For example, when an alkaline solution is placed in a reaction tank and an acid solution is added dropwise to the reaction tank, it is advisable to maintain the pH of the aqueous solution in the reaction tank within the above-mentioned range. The same applies when an acid solution is placed in a reaction tank and an alkaline solution is added dropwise. When the solution in the reaction tank is 200 mL or more and 350 mL or less, it is preferable to set the drop rate of the acid or alkaline solution to 0.01 mL / min or less, as this makes it easier to control the pH conditions. The reaction tank has a reaction vessel or the like.

[0070] The aqueous solution may be stirred in the reaction tank 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 means may be 800 rpm to 1200 rpm. Baffle plates may also be provided in the reaction tank to change the stirring direction and flow rate. The provision of baffle plates improves mixing efficiency, allowing for the synthesis of more uniform composite hydroxide particles.

[0071] The temperature of the reaction vessel is preferably adjusted to be 50° C. or higher and 90° C. or lower. The dropping of the alkaline solution or acid solution may be started after the reaction vessel has reached the appropriate temperature.

[0072] The reaction vessel may be filled with an inert atmosphere, such as nitrogen or argon. When a nitrogen atmosphere is used, nitrogen gas may be introduced at a flow rate of 0.5 L / min to 2 L / min.

[0073] The reactor may also be equipped with a reflux condenser, which allows nitrogen gas to be released from the reactor and water vapor to be returned to the reactor.

[0074] By the above coprecipitation reaction, a composite hydroxide 98 containing the transition metal M is precipitated.

[0075] <Step S132> To recover the composite hydroxide 98, filtration is preferably performed as shown in step S132 of Fig. 3. The filtration is preferably suction filtration. During filtration, the reaction product precipitated in the reaction tank may be washed with pure water, and then an organic solvent (e.g., acetone) may be used.

[0076] <Step S133> As shown in step S133 of Fig. 3, the composite hydroxide 98 after filtration may be dried. For example, it may be dried under vacuum at a temperature of 60°C to 200°C for 0.5 hours to 20 hours. For example, it may be dried for 12 hours. In this manner, the composite hydroxide 98 can be obtained.

[0077] In this manner, a composite hydroxide 98 containing a transition metal M can be obtained. In this specification and the like, the composite hydroxide 98 refers to a hydroxide of multiple types of metals. The composite hydroxide 98 can be said to be a precursor of the positive electrode active material 101.

[0078] 4, a lithium source is prepared. For example, when the sum of the atoms of nickel, cobalt, and manganese is 1, it is more preferable that the ratio of lithium is close to 1.0 (atomic ratio).

[0079] Examples of lithium sources that can be used include lithium hydroxide, lithium carbonate, and lithium nitrate. It is particularly preferable to use a material with a low melting point among lithium compounds, such as lithium hydroxide (melting point 462°C). Since positive electrode active materials with a high nickel content are more susceptible to cation mixing than lithium cobalt oxide and the like, heating in step S143 and other steps must be performed at low temperatures. Therefore, it is preferable to use a material with a low melting point.

[0080] Furthermore, a smaller particle size of the lithium source is preferable because the reaction proceeds more smoothly. For example, a lithium source pulverized using a fluidized bed jet mill can be used. The particle size referred to here is the average particle size (also referred to as the average particle diameter) of the particle size distribution. The average particle diameter refers to D50 when the particle size distribution is symmetrical. D50 refers to the particle diameter at 50% of the cumulative distribution of secondary particles calculated using a particle size distribution analyzer (Shimadzu SALD-2200) using a laser diffraction / scattering method. Measurement of particle size is not limited to laser diffraction particle size distribution measurement; the major axis of the particle cross section may also be measured using analysis such as SEM or TEM (Transmission Electron Microscope). For example, a method for measuring D50 using SEM or TEM analysis can involve measuring 20 or more particles, creating an accumulated particle amount curve, and determining the particle diameter at which the accumulated amount accounts for 50% as D50.

[0081] <Step S142> Next, in step S142 of FIG. 4, the composite hydroxide 98 and the lithium source are mixed. Mixing can be performed by a dry method or a wet method. For example, a ball mill, a bead mill, or the like can be used for mixing. When using a ball mill, it is preferable to use zirconia balls as the media. Furthermore, when using a ball mill, a bead mill, or the like, it is preferable to set the peripheral speed to 100 mm / sec or more and 2000 mm / sec or less in order to suppress contamination from the media or materials. The cobalt compound and the lithium compound may be pulverized simultaneously with mixing.

[0082] <Step S143> Next, the mixture of composite hydroxide 98 and the lithium source is heated. To distinguish from other heating steps, in Fig. 4, step S143 may be referred to as the first heating, step S145 as the second heating, and step S153 as the third heating.

[0083] An electric furnace or a rotary kiln can be used as a firing device for these heating processes. The crucible, sheath, setter, and container used during heating are preferably made of materials that do not easily release impurities. For example, it is recommended to use a crucible made of aluminum oxide with a purity of 99.9%. For mass production, for example, mullite-cordierite (Al ２ O ３ SiO ２ It is recommended to use a sheath made of MgO. It is also preferable to heat these containers with the lids on.

[0084] The heating temperature in step S143 is preferably 400° C. to 750° C., more preferably 650° C. to 750° C. The heating time in step S143 is preferably 1 hour to 30 hours, more preferably 2 hours to 20 hours.

[0085] The heating atmosphere is preferably an oxygen-containing atmosphere or a so-called dry air atmosphere containing oxygen with little water (for example, a dew point of -50°C or less, more preferably a dew point of -80°C or less).

[0086] It is also preferable to have a crushing step after heating as step S144. Crushing can be carried out in a mortar, for example. Furthermore, classification can be carried out using a sieve.

[0087] Next, heating is performed in step S145. The heating temperature in step S145 is preferably higher than the heating temperature in step S142. The heating in step S142 may be referred to as pre-baking, and the heating in step S145 may be referred to as main baking.

[0088] The heating temperature in step S145 is preferably higher than 750° C. and equal to or lower than 1050° C. The heating time in step S145 is preferably 1 hour to 30 hours, more preferably 2 hours to 20 hours.

[0089] Furthermore, it is preferable to have a crushing step after heating as step S146. Crushing can be carried out, for example, in a mortar. Furthermore, classification can be carried out using a sieve. Through the above steps, a composite oxide is obtained.

[0090] <Step S151> Next, in step S151, a magnesium source is prepared. As the magnesium source, magnesium carbonate, magnesium fluoride, or magnesium hydroxide is used.

[0091] <Step S152> Next, the composite oxide obtained in step S146 is mixed with the above-mentioned Mg source.

[0092] <Step S153> Next, the mixture of the composite oxide and the Mg source is heated. The heating in step S153 is preferably performed at a sufficiently high temperature to increase the crystallite size of the positive electrode active material 101, but the heating temperature range may vary depending on the composition of the transition metal M.

[0093] When the proportion of nickel in the transition metal M is high, for example, 70% or more, a temperature of 750°C or higher is preferable. On the other hand, if the heating temperature in step S153 is too high, there is a risk that the transition metal M, such as nickel, may be reduced to a divalent state. Therefore, for example, a temperature of 950°C or lower is preferable, 920°C or lower is more preferable, and 900°C or lower is even more preferable.

[0094] When the proportion of nickel in the transition metal M is 40% or more and less than 70%, for example, 850° C. or more is preferable, 900° C. or more is more preferable, and 1000° C. or less is more preferable. On the other hand, if the heating temperature in step S153 is too high, there is a risk of the same disadvantages as described above occurring, so 1050° C. or less is preferable. For other heating conditions, the description of step S145 can be referred to.

[0095] It is also preferable to have a crushing step after heating as step S154. The description of step S144 can be referred to for the crushing step.

[0096] 4 illustrates a method in which the Mg source is mixed in step S151 and then the heating is performed in step S153, but this is not a limitation of the present invention. The heating in step S153 may be performed two or more times.

[0097] Through the above steps, the positive electrode active material 101 can be produced.

[0098] This embodiment mode can be freely combined with other embodiment modes.

[0099] Embodiment 2 In this embodiment, an example of the shape of a secondary battery using the positive electrode active material 101 manufactured by the manufacturing method described in the previous embodiment will be described.

[0100] [Coin-Type Secondary Battery] An example of a coin-type secondary battery will be described. Fig. 5A is an exploded perspective view of a coin-type (single-layer flat) secondary battery, Fig. 5B is an external view, and Fig. 5C is a cross-sectional view thereof. Coin-type secondary batteries are mainly used in small electronic devices.

[0101] 5A is a schematic diagram that shows the overlapping of components (upper and lower positions and positional relationships) for ease of understanding, and therefore, FIGS. 5A and 5B are not completely identical corresponding views.

[0102] In Fig. 5A, a positive electrode 304, a separator 310, a negative electrode 307, a spacer 322, and a washer 312 are stacked. These are sealed with a negative electrode can 302 and a positive electrode can 301 by a gasket. Note that the gasket for sealing is not shown in Fig. 5A. 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.

[0103] The 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. A slurry containing the positive electrode active material 101 is applied to the current collector and dried to form the positive electrode active material layer 306. Pressing may be performed after the positive electrode active material layer 306 is formed. The slurry contains a conductive material and a solvent in addition to the positive electrode active material 101. Note that a carbon material such as graphite or carbon fiber is used as the conductive material.

[0104] FIG. 5B is a perspective view of the completed coin-type secondary battery.

[0105] 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.

[0106] It is to be noted that the positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 each only need to have an active material layer formed on one side.

[0107] 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., they are preferably coated with nickel, aluminum, or the like. 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.

[0108] These negative electrode 307, positive electrode 304, and separator 310 are immersed in an electrolyte solution, and as shown in FIG. 5C , 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.

[0109] By having the above configuration, the coin-type secondary battery 300 can be made to have excellent safety.

[0110] [Cylindrical Secondary Battery] An example of a cylindrical secondary battery will be described with reference to Fig. 6A. As shown in Fig. 6A, 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.

[0111] 6B is a schematic diagram showing a cross section of a cylindrical secondary battery. The cylindrical secondary battery shown in Fig. 6B 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.

[0112] Inside a hollow cylindrical battery can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 sandwiched between them. Although not shown, the wound body, in which the strip-shaped positive electrode 604 and the negative electrode 606 are wound with the separator 605 sandwiched between them, is wound around a central axis. The battery can 602 is closed at one end and open at the other end. The battery can 602 can be made of a metal such as nickel, aluminum, or titanium, or an alloy thereof, or an alloy of these with another metal (e.g., stainless steel), which is corrosion-resistant to the electrolyte. Furthermore, to prevent corrosion by the electrolyte, the battery can 602 is preferably coated with nickel, aluminum, or the like. Inside the battery can 602, the wound body, in which the positive electrode, the negative electrode, and the separator are wound, is sandwiched between a pair of opposing insulating plates 608 and 609. A non-aqueous electrolyte (not shown) is poured into the battery can 602 in which the wound body is provided. The non-aqueous electrolyte may be the same as that used in coin-type secondary batteries.

[0113] 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.

[0114] By using the positive electrode active material 101 obtained in Embodiment 1 for the positive electrode 604, a cylindrical secondary battery 616 with excellent safety can be provided.

[0115] 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.

[0116] 6C 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 each secondary battery 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 each secondary battery are electrically connected to the control circuit 620 via wiring 626. The control circuit 620 may be a charge / discharge control circuit that performs charging and discharging, or a protection circuit that prevents overcharging and / or overdischarging.

[0117] 6D shows an example of a power storage system 615. The power storage system 615 has multiple secondary batteries 616, which are sandwiched between a conductive plate 628 and a conductive plate 614. The multiple secondary batteries 616 are electrically connected to the conductive plate 628 and the conductive plate 614 by wiring 627. The multiple 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 multiple secondary batteries 616, it is possible to extract a large amount of power.

[0118] A plurality of secondary batteries 616 may be connected in parallel, and then the set may be further connected in series.

[0119] Furthermore, 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.

[0120] 6D , 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.

[0121] [Another Example of Secondary Battery Structure] An example of the structure of a secondary battery will be described with reference to FIGS. 7 and 8. FIG.

[0122] The secondary battery 913 shown in FIG. 7A 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. 7A , the housing 930 is shown separated for convenience, 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.

[0123] 7B, the housing 930 shown in Fig. 7A may be formed of a plurality of materials. For example, the secondary battery 913 shown in Fig. 7B 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.

[0124] 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.

[0125] 7C 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.

[0126] Alternatively, a secondary battery 913 may be provided that has a wound body 950a as shown in Fig. 8. The wound body 950a shown in Fig. 8A has a negative electrode 931, a positive electrode 932, and a separator 933. The negative electrode 931 has a negative electrode active material layer 931a. The positive electrode 932 has a positive electrode active material layer 932a.

[0127] By using the positive electrode active material 101 obtained in Embodiment 1 for the positive electrode 932, the secondary battery 913 can have excellent safety.

[0128] 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.

[0129] 8B , the negative electrode 931 is electrically connected to a terminal 951 by ultrasonic bonding, welding, or crimping. The terminal 951 is electrically connected to a terminal 911a. The positive electrode 932 is electrically connected to a terminal 952 by ultrasonic bonding, welding, or crimping. The terminal 952 is electrically connected to a terminal 911b.

[0130] 8C , the wound body 950 a and the electrolyte are covered by the housing 930 to form the secondary battery 913. It is preferable to provide the housing 930 with a safety valve, an overcurrent protection element, etc. The safety valve is a valve that opens when the inside of the housing 930 reaches a predetermined internal pressure to prevent the battery from exploding.

[0131] As shown in Fig. 8B, the secondary battery 913 may have a plurality of wound bodies 950a. By using a plurality of wound bodies 950a, the secondary battery 913 can have a larger discharge capacity. For other elements of the secondary battery 913 shown in Figs. 8A and 8B, the descriptions of the secondary battery 913 shown in Figs. 7A to 7C can be referred to.

[0132] 9A and 9B 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.

[0133] 10A 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. Note that the area or shape of the tab regions of the positive electrode and negative electrode are not limited to the example shown in FIG. 10A .

[0134] <Method of Manufacturing Laminated Secondary Battery> An example of a method of manufacturing the laminated secondary battery whose external view is shown in FIG. 9A will be described with reference to FIGS. 10B and 10C.

[0135] First, the negative electrode 506, separator 507, and positive electrode 503 are stacked. FIG. 10B shows the stacked negative electrode 506, separator 507, and positive electrode 503. Here, an example is shown in which five pairs of negative electrodes and four pairs of positive electrodes are used. This can also be called a laminate consisting of a negative electrode, a separator, and a positive electrode. Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For example, ultrasonic welding or the like may be used for joining. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0136] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are arranged on the outer casing 509 .

[0137] Next, as shown in Fig. 10C, 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 or the like 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.

[0138] 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.

[0139] By using the positive electrode active material 101 obtained in Embodiment 1 for the positive electrode 503, the secondary battery 500 can be highly safe.

[0140] Embodiment 3 In this embodiment, an example of a vehicle including a secondary battery of one embodiment of the present invention will be described.

[0141] The secondary battery can be applied to a typical vehicle, such as an automobile. Examples of the automobile include next-generation clean energy automobiles, such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHEVs or PHVs). The secondary battery can be used as one of the power sources mounted on the automobile. The vehicle is not limited to an automobile. Examples of the vehicle include trains, monorails, ships, submersibles (deep-sea exploration vessels, unmanned submersibles), aircraft (helicopters, unmanned aerial vehicles (drones), airplanes, rockets, and artificial satellites), electric bicycles, and electric motorcycles. The secondary battery of one embodiment of the present invention can be applied to these vehicles.

[0142] 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.

[0143] The internal structure of the first battery 1301a may be a wound type as shown in FIG. 7C or FIG. 8A, or a stacked type as shown in FIG. 9A or FIG. 9B.

[0144] 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.

[0145] 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.

[0146] 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 the electric power steering 1307, heater 1308, and defogger 1309) via the 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.

[0147] 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.

[0148] Next, the first battery 1301a will be described with reference to FIG. 11A.

[0149] FIG. 11A 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 the 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 (such as from the road surface), it is preferable to fix multiple secondary batteries using the fixing portions 1413 and 1414 or a battery housing box. Furthermore, one electrode is electrically connected to the control circuit unit 1320 by wiring 1421. The other electrode is electrically connected to the control circuit unit 1320 by wiring 1422.

[0150] Next, an example of a block diagram of the battery pack 1415 shown in FIG. 11A is shown in FIG. 11B.

[0151] 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 current from the outside or the upper limit of the output current to the outside. The range between the lower limit and the upper limit of the secondary battery's voltage 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 / or 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).

[0152] The switch unit 1324 can be configured by combining n-channel transistors or p-channel transistors. The switch unit 1324 is not limited to a switch having a Si transistor using single crystal silicon, and may be formed of a power transistor having, 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), or GaOx (gallium oxide; x is a real number greater than 0).

[0153] 11C shows an example of applying lithium-ion batteries to an electric vehicle (EV). First batteries 1301a and 1301b mainly supply power to on-board equipment of the 42V system (high voltage system), and second battery 1311 supplies power to on-board equipment of the 14V system (low voltage system). Lead-acid batteries are often used as the second battery 1311 due to their cost advantage.

[0154] In this embodiment, an example is shown in which lithium ion batteries are used as both the first battery 1301a and the second battery 1311. The second battery 1311 may be a lead storage battery, an all-solid-state battery, or an electric double layer capacitor.

[0155] 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 via the motor controller 1303 or 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.

[0156] 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.

[0157] Although not shown, when an external charger is connected, the charger's outlet or the charger's 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 the control circuit unit 1320 to prevent overcharging. The control circuit unit 1320 may also be provided in the connection cable or the charger's connection cable. 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 includes a microcomputer. The ECU uses a CPU or a GPU.

[0158] External chargers installed at charging stations and the like include 100V-200V outlets, or three-phase 200V and 50kW. Charging can also be performed by receiving power from external charging equipment using a wireless power supply system or the like.

[0159] When rapid charging is performed, a secondary battery that can withstand high voltage charging is desired in order to charge in a short time.

[0160] 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 decline and maintaining high capacity even when the electrode layer is thickened and the amount of graphene supported is increased. This is particularly effective for secondary batteries used in vehicles, and it is possible to provide a vehicle with a long driving range, specifically a driving distance of 500 km or more per charge, without increasing the ratio of the weight of the secondary battery to the total weight of the vehicle.

[0161] In particular, the secondary battery of the present embodiment described above can increase the operating voltage of the secondary battery by using the positive electrode active material 101 described in Embodiment 1, and can increase the usable capacity as the charging voltage increases. Furthermore, by using the positive electrode active material 101 described in Embodiment 1 for the positive electrode, a secondary battery for vehicles with excellent safety can be provided.

[0162] 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.

[0163] 6D, 8C, and 11A 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 agricultural machinery, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, electric carts, ships, submarines, aircraft, rockets, artificial satellites, space probes, planetary probes, or 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.

[0164] 12A to 12D illustrate examples of transportation vehicles using one embodiment of the present invention. The automobile 2001 shown in FIG. 12A 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 5 is installed in one or more locations. The automobile 2001 shown in FIG. 12A 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 includes a charge control device electrically connected to the secondary battery module.

[0165] Furthermore, automobile 2001 can charge its secondary battery by receiving power supply from an external charging facility using a plug-in system, a contactless power supply system, or the like. Charging may be performed using a predetermined charging method or connector standard, such as CHAdeMO (registered trademark) or Combo, as appropriate. The charging facility 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 an electric storage device mounted on 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.

[0166] Furthermore, 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 or moving. For such contactless power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0167] 12B 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 FIG. 12A , and therefore a description thereof will be omitted.

[0168] FIG. 12C 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, a maximum voltage of 600 V, which is obtained by connecting in series one hundred or more secondary batteries with a nominal voltage of 3.0 V or more and 5.0 V or less. Therefore, a secondary battery with little characteristic variation is required. By using a secondary battery using the positive electrode active material 101 described in any of the first to third embodiments as a positive electrode, a secondary battery with stable battery characteristics can be manufactured, and mass production at low cost is possible from the viewpoint of yield. Furthermore, except for the number of secondary batteries constituting the secondary battery module of the battery pack 2202, the battery pack 2202 has the same functions as those shown in FIG. 14A , and therefore a description thereof will be omitted.

[0169] Fig. 12D shows, as an example, an aircraft 2004 having an engine that burns fuel. Since the aircraft 2004 shown in Fig. 12D has wheels for takeoff and landing, it can also be said to be part of a transportation vehicle, and has a battery pack 2203 that includes a secondary battery module formed by connecting multiple secondary batteries and the secondary battery module and a charge control device.

[0170] The secondary battery module of the aircraft 2004 has, for example, eight 4 V secondary batteries connected in series, with 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. 12A, and therefore a description thereof will be omitted.

[0171] 12E shows an example of an artificial satellite 2005 equipped with a secondary battery 2204. Since the artificial satellite 2005 is used in outer space, it is desirable that the artificial satellite 2005 does not malfunction due to fire, and it is preferable that the artificial satellite 2005 be equipped with the secondary battery 2204, which is an embodiment of the present invention and has excellent safety. It is further preferable that the secondary battery 2204 be mounted inside the artificial satellite 2005 while being covered with a heat insulating member.

[0172] Embodiment 4 In this embodiment, an example in which a lithium-ion battery according to one embodiment of the present invention is mounted on a motorcycle or a bicycle will be described as an example in which a secondary battery is mounted on a vehicle.

[0173] 13A 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. 13A. The power storage device of one embodiment of the present invention includes, for example, a plurality of storage batteries and a protection circuit.

[0174] 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. 13B . 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 a display unit 8703 can display the remaining battery charge and other information. 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 6. The control circuit 8704 is electrically connected to the positive electrode and negative electrode of the storage battery 8701. Furthermore, a synergistic effect in terms of safety can be obtained by combining the power storage device 8702 with a secondary battery using the positive electrode active material 101 obtained in Embodiment 1 for its positive electrode. The secondary battery and the control circuit 8704 using the positive electrode active material 101 obtained in Embodiment 1 for its positive electrode are highly safe and can significantly contribute to eliminating accidents, such as fires, caused by secondary batteries.

[0175] 13C 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. 13C 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 101 obtained in Embodiment 1 for its positive electrode, can have a high capacity and contribute to miniaturization.

[0176] 13C 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.

[0177] Embodiment 5 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.

[0178] 14A shows an example of a mobile phone. The mobile phone 2100 includes a display portion 2102 built into a housing 2101, an operation button 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. Note that the mobile phone 2100 includes a secondary battery 2107. By including the secondary battery 2107 using the positive electrode active material 101 described in Embodiment 1 for its positive electrode, a high capacity can be achieved, and a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0179] 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.

[0180] 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.

[0181] 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.

[0182] The mobile phone 2100 also includes an external connection port 2104, and can directly exchange data 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.

[0183] Furthermore, the mobile phone 2100 preferably has a sensor. As the sensor, for example, a fingerprint sensor, a pulse sensor, a body temperature sensor or other human body sensor, a touch sensor, a pressure sensor, an acceleration sensor, or the like is preferably mounted.

[0184] FIG. 14B 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 which is 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 101 obtained in Embodiment 1 for its positive electrode has high energy density and high safety; therefore, it can be used safely for a long period of time and is suitable as a secondary battery to be installed in the unmanned aerial vehicle 2300.

[0185] Fig. 14C shows an example of a robot. A robot 6400 shown in Fig. 14C 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.

[0186] 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.

[0187] 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.

[0188] The upper camera 6403 and the lower camera 6406 have the function of capturing images of the surroundings of the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize the surrounding environment and move safely using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407.

[0189] 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 an internal region thereof. The secondary battery using the positive electrode active material 101 obtained in Embodiment 1 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.

[0190] 14D 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, an operation button 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 the dust from a suction port arranged on the bottom surface.

[0191] 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, when 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 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. The secondary battery using the positive electrode active material 101 obtained in Embodiment 1 for its positive electrode has high energy density and high safety, and therefore can be used safely for a long period of time and is suitable as the secondary battery 6306 to be mounted on the cleaning robot 6300.

[0192] In this example, a positive electrode active material of one embodiment of the present invention was fabricated and its shape was evaluated.

[0193] In this example, a composite hydroxide (Ni) having a mixture ratio of nickel, cobalt, and manganese of Ni:Co:Mn=8:1:1 was prepared according to the method shown in the first embodiment. ０．８ Co ０．１ Mn ０．１ (OH) ２ The obtained composite hydroxide and lithium hydroxide were mixed, heated, crushed, and further heated to obtain a composite oxide. The heating conditions after mixing (S143) were 700°C for 10 hours, and the subsequent heating conditions (S145) were 800°C for 10 hours. The obtained composite oxide contained Li １．０１ Ni ０．８ Co ０．１ Mn ０．１ O ２ It can be written as:

[0194] Magnesium carbonate was then used as the Mg source and mixed with the composite oxide. The mixture was mixed so that the magnesium concentration relative to the total of nickel, manganese, and cobalt was 1 atomic %. After mixing, a heat treatment was performed to obtain a positive electrode active material (sample). A planar SEM photograph of the obtained positive electrode active material is shown in FIG. 15. The heating conditions (S153) after mixing with magnesium carbonate were 800°C and 10 hours.

[0195] Then, a half cell was assembled using the above cathode active material, and the battery characteristics were evaluated. Evaluation of battery characteristics using a half cell is a suitable evaluation method for verifying the characteristics of the cathode active material. In this example, a coin-shaped half cell was used, and cycle characteristics were evaluated as the battery characteristics of the half cell.

[0196] Acetylene black was used as the conductive additive for the positive electrode. Positive electrode active materials corresponding to the sample, comparative example 1, and comparative example 2 were prepared as the positive electrode active materials, and each was mixed with acetylene black, a binder (PVDF), and a solvent (NMP) to prepare a slurry. The slurry was then applied to an aluminum current collector (thickness: 20 μm). After the slurry was applied to the current collector, the solvent used for mixing was evaporated. Then, a pressure of 210 kN / m was applied using a roll press. The roll temperature was set to 120°C. A positive electrode was obtained through the above process.

[0197] Using the prepared positive electrode, a CR2032 type half cell (coin-type battery cell) (diameter 20 mm, height 3.2 mm) was prepared.

[0198] The counter electrode of the half cell was lithium metal.

[0199] The electrolyte for the half cell was 1 mol / L lithium hexafluorophosphate (LiPF ６ The solvent used was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3:7. 2 wt % of vinylene carbonate (VC) was added as an additive to the mixed solvent.

[0200] The separator of the half cell was made of polypropylene having a thickness of 25 μm.

[0201] The positive electrode can and the negative electrode can of the half cell were made of stainless steel (SUS).

[0202] In evaluating the cycle characteristics, the charging voltage was 4.5 V, and the temperature of the incubator in which the half-cell was placed was 45°C. Charging was performed at a constant current (CC) / constant voltage (CV) at a rate of 0.5 C (1 C is 200 mA / g), and charging was terminated when the rate reached 0.05 C. Discharging was performed at a constant current (CC) at a rate of 0.5 C (1 C is 200 mA / g), and discharge was terminated when the voltage reached 2.5 V. A rest period may be provided between one discharge and the next charge; in this example, a 10-minute rest period was provided. As a cycle test to evaluate the cycle characteristics, the above charge and discharge were repeated 100 times.

[0203] 16A and 16B show the cycle test results for the sample, Comparative Example 1, and Comparative Example 2. In Fig. 16A and Fig. 16B, the sample is indicated by a solid line, Comparative Example 1 by a dashed line, and Comparative Example 2 by a broken line. In Fig. 16A, the vertical axis represents the discharge capacity and the horizontal axis represents the number of cycles, and in Fig. 16B, the vertical axis represents the discharge capacity retention rate and the horizontal axis represents the number of cycles.

[0204] Comparative Example 1 (ref1) uses a cathode active material that was not mixed with the Mg source. The heat treatment conditions were the same. That is, the heating conditions after mixing with lithium hydroxide (S143) were 700°C for 10 hours, and the subsequent heating conditions (S145) were 800°C for 10 hours.

[0205] In Comparative Example 2 (ref2), magnesium carbonate was also mixed with lithium hydroxide. The heat treatment conditions were the same. The heating conditions after mixing lithium hydroxide and magnesium carbonate were 700°C for 10 hours, and the subsequent heating conditions were 800°C for 10 hours.

[0206] 16A and 16B, the sample of this example exhibited the best cycle characteristics compared to Comparative Examples 1 and 2. In other words, the cycle characteristics showed a small decrease in discharge capacity even with a large number of cycles. Therefore, it was found that although the cycle characteristics can be improved by mixing magnesium carbonate with NCM, it is more effective to mix lithium hydroxide, heat the mixture, and then mix magnesium carbonate and heat the mixture, rather than mixing lithium hydroxide and magnesium carbonate and heating the mixture.

[0207] 98: composite hydroxide, 100m magnesium-containing layer, 100: primary particles, 101: positive electrode active material, 101a positive electrode active material, 101b Positive electrode active material, 300: secondary battery, 301: positive electrode can, 302: negative electrode can, 303: gasket, 304: positive electrode, 305: positive electrode current collector, 306: positive electrode active material layer, 307: negative electrode, 308: negative electrode current collector, 309: negative electrode active material layer, 310: separator, 312: washer, 322: spacer, 500: secondary battery, 501: positive electrode current collector, 502: positive electrode active material layer, 503: positive electrode, 504: negative electrode current collector, 505: negative electrode active material layer, 506: negative electrode, 507: separator, 509: exterior body, 510: positive electrode lead electrode, 511: negative electrode lead electrode, 6 601: positive electrode cap, 602: battery can, 603: positive electrode terminal, 604: positive electrode, 605: separator, 606: negative electrode, 607: negative electrode terminal, 608: insulating plate, 609: insulating plate, 611: PTC element, 613: safety valve mechanism, 614: conductive plate, 615: power storage system, 616: secondary battery, 620: control circuit, 621: wiring, 622: wiring, 623: wiring, 624: conductor, 625: insulator, 626: wiring, 627: wiring, 628: conductive plate, 911a: terminal, 911b: terminal, 913: secondary battery, 930a: housing, 930b: housing, 9 30: housing, 931a: negative electrode active material layer, 931: negative electrode, 932a: positive electrode active material layer, 932: positive electrode, 933: separator, 950a: wound body, 950: wound body, 951: terminal, 952: terminal, 1300: prismatic secondary battery, 1301a: first battery, 1301b: first battery, 1302: battery controller, 1303: motor controller, 1304: motor, 1305: gear, 1306: DCDC circuit, 1307: electric power steering, 1308: heater, 1309: defogger, 1310: DCDC circuit road, 1311: second battery, 1312: inverter, 1313: audio, 1314: power window, 1315: lamps, 1316: tires, 1317: rear motor, 1320: control circuit section, 1321: control circuit section, 1322: control circuit, 1324: switch section, 1413: fixed section, 1414: fixed section, 1415: battery pack, 1421: wiring, 1422: wiring, 2001: automobile, 2002: transport vehicle, 2003: transport vehicle, 2004: aircraft, 2005: artificial satellite, 2100: mobile phone, 2101: housing,2102: Display unit, 2103: Operation buttons, 2104: External connection port, 2105: Speaker, 2106: Microphone, 2107: Secondary battery, 2200: Battery pack, 2201: Battery pack, 2202: Battery pack, 2203: Battery pack, 2204: Secondary battery, 2300: Unmanned aerial vehicle, 2301: Secondary battery, 2302: Rotor, 2303: Camera, 6300: Cleaning robot, 6301: Housing, 6302: Display unit, 6303: Camera, 6304: Brush, 6305: Operation buttons, 6306: Secondary Battery, 6310: Garbage, 6400: Robot, 6401: Illuminance sensor, 6402: Microphone, 6403: Upper camera, 6404: Speaker, 6405: Display unit, 6406: Lower camera, 6407: Obstacle sensor, 6408: Moving mechanism, 6409: Secondary battery, 8600: Scooter, 8601: Side mirror, 8602: Power storage device, 8603: Turn signal light, 8604: Under-seat storage, 8700: Electric bicycle, 8701: Storage battery, 8702: Power storage device, 8703: Display unit, 8704: Control circuit,

Claims

1. This is a method for producing a positive electrode active material. An aqueous solution containing water-soluble salts of nickel, cobalt, and manganese is supplied to a reaction vessel, along with an alkaline solution, and the mixture is carried out inside the reaction vessel to precipitate a compound containing at least nickel, cobalt, and manganese. The first mixture, which is a mixture of the aforementioned compound and a lithium compound, is heated at a first heating temperature, then crushed or pulverized, Furthermore, it is heated at a second heating temperature, A method for producing a positive electrode active material, comprising heating a second mixture obtained by mixing the crushed or pulverized first mixture with a magnesium compound at a third heating temperature.

2. A method for producing a positive electrode active material, wherein the alkaline solution is an aqueous solution containing sodium hydroxide, according to claim 1.

3. A method for producing a positive electrode active material according to claim 1, wherein the pH of the mixture obtained by mixing the aqueous solution and the alkaline solution is 9.0 or higher and 12.0 or lower.

4. A method for producing a positive electrode active material, wherein, when mixing the aqueous solution and the alkaline solution to precipitate the compound, an aqueous solution containing glycine is added.

5. A method for producing a positive electrode active material according to claim 1, wherein the range of the first heating temperature is in the range of 400°C to 750°C.

6. A method for producing a positive electrode active material according to claim 1, wherein the range of the second heating temperature and the range of the third heating temperature are in the range of higher than 750°C and 1050°C or less.