Method for producing positive electrode active material

Abstract

Provided is a method for producing a positive electrode active material for a lithium ion secondary battery. One embodiment of the present invention is a method for manufacturing a positive electrode active material, comprising the steps of: disposing a first container containing a mixture of a lithium oxide, a fluoride, and a magnesium compound in a heating furnace, and disposing the fluoride outside the first container; the heating furnace is heated at a temperature above the temperature at which the fluoride volatilizes or sublimates. More preferably, the fluoride is lithium fluoride and the magnesium compound is magnesium fluoride.

Description

Technical Field

[0001] One embodiment of the present invention relates to a method for manufacturing a positive electrode active material. In addition, the present invention relates to an object, a process, a machine, a product, or a composition of matter. One embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a method for manufacturing the same.

[0002] It should be noted that in this specification, the power storage device refers to all elements and devices having a power storage function. For example, the power storage device includes storage batteries such as lithium-ion secondary batteries (also called secondary batteries), lithium-ion capacitors, all-solid-state batteries, and double-layer capacitors.

[0003] Note that in this specification, electronic equipment refers to any device having a power storage device. An electro-optical device having a power storage device, an information terminal device having a power storage device, and the like are all electronic equipment. Background Art

[0004] In recent years, the research and development of various power storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, air batteries and all-solid batteries has become increasingly popular. In particular, with the development of the semiconductor industry for mobile phones, smart phones, portable information terminals such as notebook personal computers, portable music players, digital cameras, medical equipment, hybrid electric vehicles (HV), electric vehicles (EV) or plug-in hybrid electric vehicles (PHV or PHEV) and other new generation clean energy vehicles, the demand for high-output, large-capacity lithium-ion secondary batteries has increased dramatically, and as a rechargeable energy supply source, it has become an indispensable item in the modern information society.

[0005] Therefore, in order to improve the cycle characteristics and increase the capacity of lithium ion secondary batteries, studies have been conducted on improving the positive electrode active material (Patent Documents 1 and 2).

[0006] In addition, the characteristics required of power storage devices include improvement of safety and long-term reliability in various operating environments. [Prior technical literature] [Patent Document]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2012-018914 [Patent Document 2] Japanese Patent Application Publication No. 2016-076454 [Non-patent literature]

[0008] [Non-patent document 1] Toyoki Okumura et al, "Correlation of lithium iondistribution and X-ray absorption near-edge structure in O3-and O2-lithiumcobalt oxides from first-principle calculation", Journal of MaterialsChemistry, 2012, 22, p.17340-17348 [Non-patent document 2] Motohashi, T. et al., "Electronic phase diagram of the layered cobalt oxide system LixCoO2 (0.0≤x≤1.0)", Physical Review B, 80(16); 165114 Summary of the invention Technical problem to be solved by the invention

[0009] Lithium ion secondary batteries and positive electrode active materials for lithium ion secondary batteries are expected to be improved in various aspects such as capacity, cycle characteristics, charge and discharge characteristics, reliability or safety, and research and development of lithium composite oxide LiMO2, in which a part of LiCoO2 is replaced by a different element, is becoming increasingly popular. In addition, it is expected to develop a method for producing LiMO2 at low cost and in a short time.

[0010] In view of the above problems, one object of one embodiment of the present invention is to provide a method for producing a positive electrode active material. Another object of one embodiment of the present invention is to provide a novel positive electrode active material. Another object of one embodiment of the present invention is to provide a novel power storage device.

[0011] Note that the description of these purposes does not prevent the existence of other purposes. In addition, one mode of the present invention does not need to achieve all of the above purposes. In addition, purposes other than the above purposes can be extracted from the description of the specification, drawings, and claims. Solutions to technical problems

[0012] One embodiment of the present invention is a method for producing a positive electrode active material, comprising the steps of: placing a first container containing a mixture of lithium oxide, fluoride and a magnesium compound in a heating furnace and placing fluoride outside the first container; and heating the heating furnace at a temperature above the temperature at which the fluoride volatilizes or sublimates.

[0013] One embodiment of the present invention is a method for producing a positive electrode active material, comprising the steps of: placing a first container containing a mixture of lithium oxide, fluoride and magnesium compound and a second container containing fluoride in a heating furnace; and heating the heating furnace at a temperature above the temperature at which the fluoride volatilizes or sublimates.

[0014] In the above structure, the fluoride is preferably lithium fluoride (LiF).

[0015] In the above configuration, the heating furnace is preferably heated at 740° C. or higher and 1130° C. or lower.

[0016] In addition, in the above structure, the magnesium compound is preferably magnesium fluoride (MgF2).

[0017] In the above configuration, it is preferable that the heating furnace is heated after the air in the heating furnace is replaced with oxygen. Effects of the Invention

[0018] According to one embodiment of the present invention, a method for producing a positive electrode active material can be provided. According to one embodiment of the present invention, a novel positive electrode active material particle can be provided. According to one embodiment of the present invention, a novel power storage device can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a diagram for explaining an example of a method for producing a positive electrode active material. Figure 2 is a graph illustrating the results of DSC measurement of a mixture of LiF and MgF2. Figure 3 This is a diagram for explaining a method for producing a positive electrode active material according to one embodiment of the present invention. Figure 4A , Figure 4B This is a diagram for explaining a method for producing a positive electrode active material according to one embodiment of the present invention. Figure 5A , Figure 5B This is a diagram for explaining a method for producing a positive electrode active material according to one embodiment of the present invention. Figure 6 This is a diagram for explaining an example of a method for producing a positive electrode active material. Figure 7 This is a diagram for explaining an example of a method for producing a positive electrode active material. Figure 8 This is a diagram for explaining an example of a method for producing a positive electrode active material. Fig. 9 This is a diagram for explaining the crystal structure and magnetic properties of the positive electrode active material. Fig.10It is a diagram for explaining a conventional example of the crystal structure and magnetic properties of a conventional positive electrode active material. Fig.11A and Fig. 11B This is a cross-sectional view of an active material layer when a graphene compound is used as a conductive auxiliary agent. Fig. 12A and Fig. 12B It is a perspective view explaining a coin-type secondary battery. Fig.13A is a perspective view illustrating a cylindrical secondary battery, Fig. 13B It is an exploded stereogram. Fig. 13C is a three-dimensional diagram of a cylindrical secondary battery. Fig.13D It is a top view explaining a cylindrical secondary battery. Fig.14A , Fig. 14B It is a diagram for explaining an example of a secondary battery. Fig.15A , Fig. 15B , Fig. 15C , Fig.15D It is a perspective view explaining an example of a secondary battery. Fig.16A , Fig. 16B It is a perspective view explaining an example of a secondary battery. Fig.17A , Fig. 17B It is a perspective view explaining an example of a secondary battery. Fig.18 It is a perspective view explaining an example of a secondary battery. Fig.19A , Fig.19B , Fig.19C It is a perspective view illustrating a laminate type secondary battery. Fig. 20A is a top view illustrating a laminated secondary battery, Fig. 20B It is a cross-sectional view illustrating a laminate type secondary battery. Fig.21 It is a diagram showing the appearance of a secondary battery. Fig. 22 It is a diagram showing the appearance of a secondary battery. Fig.23A , Fig. 23B , Fig.23C It is a diagram for explaining a method for manufacturing a secondary battery. Fig.24A is a top view of a flexible secondary battery. Fig. 24B , Fig.24C , Fig.24D , Fig.24E is a cross-sectional view illustrating a secondary battery. Fig.25A , Fig.25BIt is a perspective view illustrating a flexible secondary battery. Fig.26A , Fig.26B is a perspective view illustrating an example of an electronic device. Fig.26C is a three-dimensional diagram of a secondary battery. Fig.26D is a diagram illustrating an example of an electronic device. Fig.26E is a three-dimensional diagram of a secondary battery. Fig.26F , Figure 26G It is a diagram for explaining an example of an electronic device. Fig.27A , Fig.27B is a top view illustrating an example of an electronic device, Fig.27C It is a block diagram. Fig.28 It is a diagram for explaining an example of an electronic device. Fig.29A is a three-dimensional image of the vehicle. Fig.29B is a perspective view showing a vehicle being charged, Fig.29C It is a perspective view explaining an electric motorcycle. Fig. 30A , Fig. 30B This is a diagram for explaining an alumina crucible used for annealing. Fig.31 is a diagram illustrating cycle characteristics according to the embodiment. Modes for Carrying Out the Invention

[0020] Below, the embodiments of the present invention are described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following description, and a person skilled in the art can easily understand that the method and details can be transformed into various forms. In addition, the present invention should not be interpreted as being limited to the contents described in the following embodiments.

[0021] In crystallography, numbers are marked with superscripts to indicate crystal planes and orientations. However, in this specification, etc., due to the symbol restrictions in the patent application, - (minus sign) is placed before the numbers to indicate crystal planes and orientations instead of marking the numbers with superscripts. In addition, "[]" indicates individual orientations showing orientations within a crystal, "<>" indicates collective orientations showing all equivalent crystal directions, "()" indicates individual faces showing crystal planes, and "{}" indicates collective faces with equivalent symmetry.

[0022] In the present specification, the fluoride-containing atmosphere refers to an atmosphere of a mixed gas in which at least one constituent component contains a fluoride or an atmosphere under the conditions of the mixed gas.

[0023] (Implementation Method 1) use Figure 1An example of a method for producing a lithium composite oxide LiMO2 (M is two or more metals including Co, and there is no restriction on the substitution position of the metal) is described below. Hereinafter, a positive electrode active material including Mg as a metal element other than Co contained in LiMO2 is described as an example.

[0024] First, a halogen source is prepared as a material for the mixture 902. Chlorides, odorized compounds, and iodides can be used as halogen sources, among which fluorides are preferably used. In the present embodiment, LiF, which is a fluorine source, is prepared as a halogen source. LiF contains cations shared with LiCoO2, so it is preferred. LiF can be used as a lithium source or a fluorine source. In addition, LiF has a low melting point, i.e., 848°C, and LiF is easily melted in the annealing process described later, so it is preferred. Similarly, as a magnesium source for LiMO2, MgF2, which can also be used as a fluorine source, is preferably used. In addition, LiCl can also be used as the above-mentioned halogen source, and MgCl2 can also be used as a magnesium source. In addition, as a combination of a halogen source and a magnesium source, since the melting point drop described later can be utilized, a combination with a eutectic point is preferably used. In addition, a halogen source that can be used in one embodiment of the present invention is not limited to LiF and LiCl. In addition, a magnesium source that can be used in one embodiment of the present invention is not limited to MgF2 and MgCl2.

[0025] In addition, in this specification, the eutectic point refers to the point in the solid phase-liquid phase curve of the two components where the two components do not form a solid solution but are completely dissolved and mixed in the liquid state. For example, when the two metal elements A and B are melted, A and B may not form a solid solution but form solid phases separately, or A and B may form molecular compounds. When A and B are completely dissolved in the liquid phase, the melting point temperature of the mixture of A and B is lower than the single melting point of A or B. The mixture with a certain concentration ratio of A and B presents the lowest melting point. This temperature is called the eutectic point, and the above mixture is called the eutectic mixture. The eutectic point is not limited to two components, and can also be three components, four components, or more than five components.

[0026] In this embodiment, LiF used as a fluorine source is prepared as a halogen source, and MgF2 is prepared as a fluorine source and a magnesium source. Figure 1 Step S11). For this purpose, the molar ratio of LiF and MgF2 is preferably LiF:MgF2=u:1 (0≤u≤1.9), more preferably LiF:MgF2=u:1 (0.1≤u≤0.5), and further preferably LiF:MgF2=u:1 (near u=0.33).

[0027] In addition, when the subsequent mixing and pulverizing steps are performed by a wet method, a solvent is prepared. As the solvent, ketones such as acetone, alcohols such as ethanol and isopropanol, ether, dioxane, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc. can be used. It is preferred to use an aprotic solvent that does not easily react with lithium. In this embodiment, acetone (see Figure 1 Step S11).

[0028] Next, the materials of the mixture 902 are mixed and crushed ( Figure 1 Step S12). Mixing can be performed by dry method or wet method. Wet method is preferred because it can crush the material into smaller size. For example, a ball mill, a sand mill, etc. can be used for mixing. When a ball mill is used, for example, zirconium balls are preferably used as the medium. It is preferred to fully perform the mixing and crushing steps to powder the mixture 902.

[0029] The mixed and crushed materials are recovered ( Figure 1 Step S13) to obtain a mixture 902 ( Figure 1 Step S14).

[0030] As the mixture 902, for example, the average particle diameter (D50) is preferably greater than 600nm and less than 20μm, and more preferably greater than 1μm and less than 10μm. By using the mixture 902 that is powdered in this way, when it is mixed with a composite oxide containing lithium, transition metal and oxygen such as lithium cobalt oxide in a subsequent process, it is easier for the mixture 902 to be uniformly attached to the surface of the composite oxide particles. When the mixture 902 is uniformly attached to the surface of the composite oxide particles, halogen and magnesium can be easily distributed in the entire surface portion of the composite oxide particles after heating, so it is preferred. When there is an area in the surface portion that does not contain halogen and magnesium, it is not easy to form the pseudo-spinel type crystal structure described later in the charged state.

[0031] <Step S25> Next, a lithium source is prepared as shown in step S25. In step S25, a composite oxide containing lithium, a transition metal, and oxygen synthesized in advance is used.

[0032] When using a pre-synthesized composite oxide containing lithium, transition metals and oxygen, it is preferred to use a composite oxide with few impurities. In this specification, etc., as a composite oxide containing lithium, transition metals and oxygen and a positive electrode active material, lithium, cobalt, nickel, manganese, aluminum and oxygen are regarded as their main components, and elements other than the above main components are regarded as impurities. For example, when using glow discharge mass spectrometry analysis (GD-MS), the total impurity concentration is preferably 10,000ppm wt or less, more preferably 5000ppm wt or less. In particular, the total impurity concentration of transition metals such as titanium and arsenic is preferably 3000ppm wt or less, more preferably 1500ppm wt or less.

[0033] For example, as the pre-synthesized lithium cobalt oxide, lithium cobalt oxide particles (trade name: CELLSEED C-10N) manufactured by NIPPON CHEMICALINDUSTRIAL CO., LTD. can be used. The average particle diameter (D50) of the lithium cobalt oxide is about 12 μm, and in the impurity analysis using glow discharge mass spectrometry, the magnesium concentration and the fluorine concentration are 50 ppm wt or less, the calcium concentration, the aluminum concentration and the silicon concentration are 100 ppm wt or less, the nickel concentration is 150 ppm wt or less, the sulfur concentration is 500 ppm wt or less, the arsenic concentration is 1100 ppm wt or less, and the concentration of elements other than lithium, cobalt and oxygen is 150 ppm wt or less.

[0034] The composite oxide containing lithium, transition metal and oxygen in step S25 preferably has a layered rock salt type crystal structure with few defects and deformation. For this reason, it is preferred to use a composite oxide with few impurities. When the composite oxide containing lithium, transition metal and oxygen contains a large number of impurities, the crystal structure is likely to have a large number of defects or deformation.

[0035] Next, the mixture 902 and a composite oxide containing lithium, a transition metal and oxygen ( Figure 1 Step S31). The ratio of the number of transition metal atoms TM in the composite oxide containing lithium, transition metal and oxygen to the number of magnesium atoms MgMix1 in the mixture 902 is preferably TM:MgMix1=1:v(0.005≤v≤0.05), more preferably TM:MgMix1=1:v(0.007≤v≤0.04), and further preferably TM:MgMix1=1:0.02.

[0036] In order not to damage the particles of the composite oxide, the mixing of step S31 is preferably performed under milder conditions than the mixing of step S12. For example, it is preferably performed under conditions with fewer rotations or shorter time than the mixing of step S12. In addition, the dry method is a milder condition than the wet method. For example, a ball mill, a sand mill, etc. can be used for mixing. When a ball mill is used, for example, zirconium balls are preferably used as the medium.

[0037] Recycling of the mixed materials ( Figure 1 Step S32) to obtain a mixture 903 ( Figure 1 Step S33).

[0038] Next, the mixture is heated 903 ( Figure 1 This step is sometimes referred to as annealing. LiMO2 is generated by annealing. Therefore, the conditions for performing step S34, such as temperature, time, atmosphere, and the weight of the mixture 903 to be annealed, are important. In addition, in this specification, "annealing" includes: heating the mixture 903; and heating a heating furnace in which at least the mixture 903 is arranged.

[0039] When the conditions of S34 are not appropriate, a positive electrode active material having good characteristics may not be obtained.

[0040] Here, the present inventors have found that a positive electrode active material having excellent characteristics can be obtained by performing annealing in an atmosphere containing a fluoride (LiF in this embodiment) in the mixture 903 .

[0041] [Effect of Annealing in an Atmosphere Containing Fluoride] The annealing temperature is preferably above the temperature at which the mixture 902 is melted. It is considered that the mixture 902 is melted when the mixture 903 is annealed. For example, it is considered that a mixture of MgF2 (melting point is 1263°C) and LiF (melting point is 848°C) is melted and distributed in the surface layer of the composite oxide particles. In addition, it is considered that when MgF2 is melted, the reaction with LiCoO2 is promoted to generate LiMO2. Therefore, it is preferred that a combination of fluoride and magnesium source that forms a eutectic mixture is used.

[0042] In addition, the annealing temperature is more preferably above the temperature at which the mixture 903 is melted. It is believed that when the fluoride (eg, LiF), the magnesium source (eg, MgF2), and the lithium oxide (eg, LiCoO2) form a common mixture, the generation of LiMO2 is promoted.

[0043] In addition, the annealing temperature needs to be lower than the decomposition temperature of LiCoO2 (1130°C). Therefore, it is preferable to heat at a temperature higher than the eutectic point of the fluoride and the magnesium source and lower than 1130°C.

[0044] In addition, as described later, the eutectic point of LiF and MgF2 is around 735°C. In addition, endothermic peaks of differential scanning calorimetry (DSC measurement) of LiF, MgF2 and LiCoO2 are observed around 820°C. Therefore, the annealing temperature is preferably above 735°C, and more preferably above 820°C. In addition, the decomposition temperature of LiCoO2 is 1130°C, but a slight decomposition of LiCoO2 may occur at a temperature near it. Therefore, the annealing temperature is preferably below 1130°C, and more preferably below 1000°C.

[0045] Therefore, the annealing temperature is preferably 735° C. to 1130° C., more preferably 735° C. to 1000° C. Also, it is preferably 820° C. to 1130° C., more preferably 820° C. to 1000° C.

[0046] Here, DSC measurement of a mixture of LiF and MgF 2 is described.

[0047] The measurement device used was ThermoplusEV02 manufactured by Rigaku Corporation. The measurement was performed in the temperature range of 25°C to 1000°C, and the heating rate was 20°C / min.

[0048] Figure 2 The DSC measurement results of a mixture of LiF and MgF2 (LiF / MgF2=0.33 mol%) are shown. Figure 2 In the experiment, an endothermic peak was observed near 735°C. Therefore, the mixture of LiF and MgF2 has a eutectic point near 735°C.

[0049] In addition, it is considered that LiF, which is a fluoride, is used as a flux in this embodiment. Therefore, it can be predicted that when LiF volatilizes and the LiF in the mixture 903 decreases, MgF2 is not easily melted and the generation of LiMO2 is suppressed. Therefore, it is necessary to heat while suppressing the volatilization of LiF.

[0050] Therefore, by heating the mixture 903 in an atmosphere containing LiF, that is, heating the mixture 903 in a state where the partial pressure of LiF in the heating furnace is high, volatilization of LiF in the mixture 903 can be suppressed and LiMO2 can be efficiently generated. Therefore, a positive electrode active material with good characteristics can be manufactured.

[0051] Here, the weight reduction rate when a mixture of LiF and MgF2 (LiF / MgF2=0.33mol%) is heated at a specified temperature is investigated experimentally. The experimental method is as follows: the mixture of LiF and MgF2 is raised to a specified temperature at 200°C / h, and the specified temperature is maintained for 10 hours. Then, the temperature is lowered for more than 10 hours. In addition, heating is performed while oxygen is allowed to flow at a flow rate of 5.0L / min. Table 1 shows the measurement results of the weight reduction rate. In Table 1, the weight reduction rate (%) is expressed as the result calculated by the weight difference of the mixture before and after heating / the weight of the mixture before heating × 100.

[0052] [Table 1] Heating temperature(℃) Weight reduction rate (%) 600 1 700 2 800 8 900 26

[0053] As shown in Table 1, it was confirmed that the weight of the mixture of LiF and MgF2 decreased at least at 700° C. Therefore, it was found that at a temperature of at least 700° C. or higher, the constituent components of LiF and MgF2 volatilized and disappeared from the reaction system.

[0054] [Annealing 1 using an atmosphere containing fluoride] Below, use Figure 3 An example of a method of performing annealing by making the atmosphere in the heating furnace an atmosphere containing fluoride will be described.

[0055] In this specification, a heating furnace is a device used for heat treatment (annealing) of a substance or mixture, and includes a heater unit and an inner wall that can withstand an atmosphere containing fluoride and at least 600° C. In addition, the heating furnace may be provided with a pump that can reduce or / and increase the pressure inside the heating furnace.

[0056] The heating furnace 100 includes a heating furnace space 102, a hot plate 104, a heater part 106, a thermal insulator 108, a gas supply line 110, a gate valve 112, and a gas exhaust line 114. As a method for annealing the mixture 903 in an atmosphere containing fluorides, the following method can be cited: a container 116 containing the mixture 903 is arranged in the heating furnace space 102, and a fluoride gas is introduced from the gas supply line 110 into the heating furnace space 102 to perform annealing. When using corrosive fluorides, the hot plate 104, the gas supply line 110, the gate valve 112, the gas exhaust line 114, the inner wall of the heating furnace and the container 116 are preferably made or processed using materials that are not invaded by fluorides and have high heat resistance. As the material, a ceramic material can be cited, for example, aluminum oxide can be used. In addition, when using LiF with low reactivity, other materials such as metals with high heat resistance can also be used.

[0057] When introducing the fluoride gas, it is preferred to introduce the gas while heating the furnace space 102 to the solidification point or above of the fluoride. When the temperature of the furnace space 102 is low, the introduced gas may become liquid or solid.

[0058] In addition, the valence of Co (cobalt) in LiMO2 manufactured by one method of the present invention is preferably 3. Co can be 2-valent and 3-valent. Therefore, in order to suppress the reduction of Co, it is preferred that the atmosphere of the space 102 in the heating furnace contains oxygen, and it is more preferred that the ratio of oxygen to nitrogen in the atmosphere of the space 102 in the heating furnace is greater than that of the atmospheric atmosphere, and it is further preferred that the oxygen concentration in the atmosphere of the space 102 in the heating furnace is greater than that of the atmospheric atmosphere. It is preferred that oxygen is introduced through the gas supply line 110 in addition to fluoride. Note that, Figure 3 Although only one gas supply line is shown, more than two lines may be provided. In this case, the fluoride and oxygen may be introduced into the heating furnace space 102 through different lines.

[0059] Note that there is no limitation on the order of the steps of disposing the container 116 containing the mixture 903 and adjusting the atmosphere of the heating furnace space 102 (introducing fluoride gas or adjusting oxygen concentration). That is, the atmosphere of the heating furnace space 102 may be adjusted after disposing the container 116 containing the mixture 903, or vice versa. The container 116 is disposed in the heating furnace space 102, and after adjusting the atmosphere of the heating furnace space 102, the heating furnace 100 is heated, that is, the heating furnace space 102 is heated, so that the mixture 903 can be annealed in an atmosphere containing fluoride.

[0060] Alternatively, the container 116 containing the mixture 903 may be disposed after the heating furnace 100 is heated to adjust the atmosphere of the heating furnace space 102. In this case, the order of the steps of adjusting the atmosphere of the heating furnace space 102 and heating the heating furnace 100 is not particularly limited.

[0061] In addition, there is no particular limitation on the method of disposing the mixture 903 when it is placed in the container 116, but Figure 3 As shown, it is preferred that the top surface of the mixture 903 is flat with respect to the bottom surface of the container 116, that is, the mixture 903 is arranged in such a manner that the height of the top surface of the mixture 903 is uniform.

[0062] [Annealing 2 using an atmosphere containing fluoride] use Figure 4A and Figure 4B An example of a method of performing annealing by making the atmosphere in the heating furnace an atmosphere containing fluoride is described below. Figure 4A and Figure 4B In, use Figure 3The same hatching shows Figure 3 The same function as the part, and sometimes the reference numeral is omitted. Figure 3 Components with the same functions are denoted by the same reference numerals, and detailed description thereof may be omitted.

[0063] Figure 4A and Figure 4B The heating furnace 120 shown includes a heating furnace space 102, a hot plate 104, a heater portion 106, and a thermal insulator 108. Figure 4A As a method for annealing the mixture 903 in an atmosphere containing a fluoride, the following method can be cited: a container 116 containing the mixture 903 is arranged in the space 102 in the heating furnace, and then a container 122 containing a fluoride 906 for the mixture 903 is arranged to heat the container 116 and the container 122 at the same time. When the fluoride 906 placed in the container 122 is volatilized or sublimated, the atmosphere in the heating furnace can be made an atmosphere containing a fluoride. Note that the fluoride 906 can also be arranged in the space 102 in the heating furnace without using the container 122. In addition, in order to make the space 102 in the heating furnace an atmosphere containing the fluoride 906, the space 102 in the heating furnace needs to be heated to a temperature above the temperature at which the fluoride 906 volatilizes or sublimates.

[0064] Note that the fluoride used in the mixture 903 and the fluoride 906 placed in the container 122 may contain the same substance, and the purity may be different or the same. For example, when LiF is used as the fluoride of the mixture 903, the purity of the LiF used in the mixture 903 and the LiF placed in the container 122 may be different or the same. In addition, the fluoride 906 may be a mixture of LiF and another substance as long as no reaction occurs.

[0065] Note that there is no particular limitation on the order in which the container 116 containing the mixture 903 and the container 122 containing the fluoride 906 are placed in the heating furnace 120. The container 116 may be placed before the container 122, or vice versa. Alternatively, the container 116 and the container 122 may be placed at the same time.

[0066] In addition, as described above, annealing is preferably performed at an oxygen concentration of atmospheric pressure or higher in order to suppress reduction of Co. Therefore, annealing is preferably performed after the oxygen concentration in the heating furnace space 102 is increased to atmospheric pressure or higher.

[0067] Here, there is no particular limitation on the order of the steps of placing the container 116 containing the mixture 903 in the heating furnace 120, placing the container 122 containing the fluoride 906 in the heating furnace 120, and adjusting the oxygen concentration of the space 102 in the heating furnace. That is, the container 116 and the container 122 may be placed in the heating furnace 120 after adjusting the oxygen concentration of the space 102 in the heating furnace, or vice versa. Alternatively, the container 116 may be placed in the heating furnace 120, and then the oxygen concentration of the space 102 in the heating furnace may be adjusted, and then the container 122 may be placed in the heating furnace 120. Alternatively, the container 122 may be placed in the heating furnace 120, and then the oxygen concentration of the space 102 in the heating furnace may be adjusted, and then the container 116 may be placed in the heating furnace 120. By heating the heating furnace 120 after performing the above steps, the mixture 903 can be annealed in an atmosphere containing the fluoride. In addition, it is preferable that the step of heating the heating furnace 120 is performed last in the above steps. By heating at the end, it is possible to prevent the fluoride 906 and the mixture 903 from being heated rapidly, so that a uniform chemical reaction or state change can occur, and undesirable phenomena such as bumping can be suppressed.

[0068] Alternatively, the container 116 containing the mixture 903 may be placed in the heating furnace 120 after the steps of heating the heating furnace 120, adjusting the oxygen concentration of the space 102 in the heating furnace, and placing the container 122 containing the fluoride 906 in the heating furnace 120. By heating the container 122 at a temperature at which the fluoride 906 volatilizes or at a sublimation point or higher, the space 102 in the heating furnace can be made an atmosphere containing the fluoride 906. Therefore, by placing the container 116 containing the mixture 903 in the heating furnace 120 after the step of adjusting the atmosphere of the space 102 in the heating furnace (an atmosphere containing the fluoride 906 with an adjusted oxygen concentration), the mixture 903 can be annealed in the atmosphere containing the fluoride.

[0069] When the container 116 containing the mixture 903 is disposed in the heating furnace 120 after the step of adjusting the atmosphere of the space 102 in the heating furnace is performed, there is no particular limitation on the order of the step of heating the heating furnace 120, the step of adjusting the oxygen concentration of the space 102 in the heating furnace, and the step of disposing the container 122 containing the fluoride 906 in the heating furnace 120. For example, the oxygen concentration of the space 102 in the heating furnace may be adjusted after the heating furnace 120 is heated and the container 122 may be disposed in the heating furnace 120, or the oxygen concentration of the space 102 in the heating furnace may be adjusted after the container 122 is disposed in the heating furnace 120 and the heating may be performed.

[0070] In addition, if Figure 4BAs shown, the mixture 903 may be placed in one space of the container 124 provided with the partition 126 and the fluoride 906 may be placed in another space of the container 124. By adopting this structure, the mixture 903 and the fluoride 906 may be simultaneously arranged in the heating furnace 120. In addition, by adopting this structure, the atmosphere of the space 102 in the heating furnace may be an atmosphere containing the fluoride without mixing the mixture 903 and the fluoride 906 when they are melted.

[0071] Note that as described above, the fluoride used in the mixture 903 and the fluoride 906 may contain the same substance and may have different or equal purities. For example, when LiF is used as the fluoride of the mixture 903, the purities of LiF used in the mixture 903 and the fluoride 906 may be different or equal.

[0072] The above annealing is preferably performed at an appropriate temperature and time. The appropriate temperature and time vary depending on the size and composition of the particles of the composite oxide containing lithium, transition metal and oxygen in step S25. When the particles are small, it is sometimes preferred to perform annealing at a lower temperature or for a shorter time than when the particles are large.

[0073] For example, when the average particle diameter (D50) of the particles in step S25 is about 12 μm, the annealing time is preferably 3 hours or longer, and more preferably 10 hours or longer.

[0074] On the other hand, when the average particle diameter (D50) of the particles in step S25 is about 5 μm, the annealing time is preferably, for example, not less than 1 hour and not more than 10 hours, and more preferably about 2 hours.

[0075] The temperature drop time after annealing is preferably, for example, 10 hours to 50 hours.

[0076] The annealed material is recovered ( Figure 1 Step S35) to obtain positive electrode active material 904 ( Figure 1 Step S36).

[0077] FIG5 shows an example of a heating furnace. Figure 3 The same hatching shows Figure 3 The same function as the part, and sometimes the reference numeral is omitted. Figure 3 Components with the same functions are denoted by the same reference numerals, and detailed description thereof may be omitted.

[0078] <Structure of heating furnace> The heating furnace used in one embodiment of the present invention is not particularly limited, and various heating furnaces such as a batch type or a continuous type heating furnace can be used. Figure 5Aand Figure 5B An example thereof is shown.

[0079] Figure 5A The heating furnace 130 shown is an example of a continuous heating furnace. The heating furnace 130 includes a conveyor belt 132. By placing a container 134 containing the mixture 903 on the conveyor belt 132 and processing it in the heating furnace 130, annealing can be performed continuously. By adjusting the moving speed of the conveyor belt, the annealing time can be adjusted. In addition, by placing a fluoride 906 in a container 134 and annealing it simultaneously with the mixture 903, the atmosphere of the space 102 in the heating furnace can be made an atmosphere containing fluoride. By annealing the mixture 903 using the heating furnace 130, a positive electrode active material 904 can be obtained.

[0080] Figure 5B The heating furnace 140 shown is an example of a rotary heating furnace. The heating furnace 140 includes a material placement section 142, an atmosphere control section 144, and a recovery section 146. The mixture 903 is placed into the space 102 in the heating furnace from the material placement section 142. The hot plate 104 has a rotating mechanism, and the hot plate 104 is inclined toward the recovery section 146. By adopting this structure, annealing can be performed while the mixture 903 is flowing. By adjusting the inclination or rotation speed of the hot plate 104, the annealing time can be adjusted. The annealed mixture 903 is recovered in the recovery section 146 to obtain a positive electrode active material 904.

[0081] The atmosphere of the heating furnace space 102 may be made to contain fluoride by the atmosphere control unit 144. As described above, the method of making the atmosphere contain fluoride includes: introducing fluoride gas; and sublimating or volatilizing fluoride.

[0082] (Implementation Method 2) An example of a method for producing LiMO2 is described below. Figure 6 A production method in the case of using a plurality of metal elements other than Co contained in LiMO 2 will be described.

[0083] <<Method for producing positive electrode active material 2>> Figure 6 An example of a manufacturing process of a composite oxide containing Mg, Ni and Al in addition to Co as LiMO2 is shown. This manufacturing method is as follows: each metal element source other than Li and Co is mixed and pulverized, and then the powdered metal element sources are mixed with lithium cobalt oxide and annealed. S11 to S36 are the same as those in Embodiment 1 and Figure 1That is, in step S34, the mixture 903-2 is preferably annealed in an atmosphere containing LiF. Figure 6 The positive electrode active material 904 - 2 is obtained through the manufacturing steps shown.

[0084] <Step S15, Step S16, Step S17> In addition, powdered nickel hydroxide (Ni(OH)2) is prepared for mixing in step S31. The powdered nickel hydroxide is previously mixed with acetone in step S15 and recovered in step S16. Powdered nickel hydroxide can be obtained in step S16 (step S17).

[0085] <Step S18, Step S19, Step S20> In addition, powdered aluminum hydroxide (Al(OH)3) is prepared for mixing in step S31. The powdered aluminum hydroxide is preliminarily subjected to step S18 of mixing aluminum hydroxide and acetone and step S19 of recovering the powdered aluminum hydroxide. Powdered aluminum hydroxide can be obtained through step S19 (step S20).

[0086] In the above steps S15 to S20, nickel hydroxide is used as the nickel (Ni) source and aluminum hydroxide is used as the aluminum (Al) source, but the nickel source and the aluminum source are not limited thereto. Oxides or halides containing the respective elements may also be used.

[0087] <<Method for producing positive electrode active material 3>> Figure 7 An example of a manufacturing process of a composite oxide containing Mg, Ni and Al in addition to Co as LiMO2 is shown. This manufacturing method is as follows: each metal element source other than Li and Co is mixed and pulverized, and then mixed with lithium cobalt oxide and annealed. S31 to S35 are the same as those in Embodiment 1 and Figure 1 That is, in the step S34, the mixture 903-3 is preferably annealed in an atmosphere containing LiF. Figure 7 The positive electrode active material 904 - 3 is obtained through the manufacturing steps shown.

[0088] <Step S22 to Step S24> As in the above-mentioned steps S15 to S17 and S18 to S20, powdered MgF2, Ni(OH)2, and Al(OH)3 are prepared. The powdered aluminum hydroxide is preliminarily mixed with aluminum hydroxide and acetone in step S22 and recovered in step S23. The powdered mixture 902-3 (step S24) can be obtained by step S22.

[0089] <<Method for producing positive electrode active material 4>> Figure 8 An example of a manufacturing process of a composite oxide containing Mg, Ni and Al in addition to Co as LiMO2 is shown. This manufacturing method is a method for manufacturing a composite oxide containing Mg, Ni and Al by adding a Ni source and an Al source after manufacturing a composite oxide represented by LiMO2 containing Mg. S11 to S14 and S31 to S36 are the same as those in Embodiment 1 and Figure 1 That is, in step S34, the mixture 903 is preferably annealed in an atmosphere containing LiF. In addition, steps S15 to S17 can refer to the steps of using Figure 6 You can Figure 8 The positive electrode active material 904 - 4 is obtained through the manufacturing steps shown.

[0090] Next, the positive electrode active material 904 and the powdered nickel hydroxide are mixed as shown in step S50. Then, the mixed material is recovered (step S51). The powdered nickel hydroxide is preliminarily subjected to step S15 of mixing nickel hydroxide and acetone and step S16 of recovering. Powdered nickel hydroxide can be obtained by step S16 (step S17).

[0091] In step S51, the materials mixed in step S50 are recovered to obtain a mixture 908 ( Figure 8 Step S52).

[0092] Next, Al is added through step S53 to step S55. To add Al, for example, a liquid phase method such as a sol-gel method, a solid phase method, a sputtering method, a vapor deposition method, a CVD (chemical vapor deposition) method, a PLD (pulsed laser deposition) method, or the like can be used.

[0093] like Figure 8 As shown, first, in step S52, a metal source is prepared. In addition, when a sol-gel method is used, a solvent for the sol-gel method is prepared. As an Al source, Al alkoxide, Al hydroxide, Al oxide, etc. can be used. For example, when the number of atoms of cobalt contained in lithium cobaltate is 1, the concentration of aluminum contained in the metal source is 0.001 times or more and 0.02 times or less.

[0094] Here, as an example, an example in which a sol-gel method is used in which aluminum isopropoxide is used as a metal source and 2-propanol is used as a solvent is shown.

[0095] Next, aluminum alkoxide is dissolved in 2-propanol and the mixture is mixed 905 ( Figure 8 Step S53).

[0096] The amount of metal alkoxide required varies depending on the particle size of lithium cobalt oxide. For example, when aluminum isopropoxide is used and the particle size (D50) of lithium cobalt oxide is about 20 μm, the concentration of aluminum contained in aluminum isopropoxide is preferably 0.001 times or more and 0.02 times or less, based on the number of cobalt atoms contained in lithium cobalt oxide being 1.

[0097] Next, the mixture of the alcohol solution of the metal alkoxide and the lithium cobalt oxide particles is stirred in an atmosphere containing water. For example, a magnetic stirrer can be used for stirring. The stirring time is sufficient time required for the water in the atmosphere to react with the metal alkoxide by hydrolysis and polycondensation. For example, stirring can be performed at 25° C. for 4 hours at a humidity of 90% RH (Relative Humidity). In addition, stirring can also be performed in an atmosphere where the humidity and temperature are not controlled, such as the atmospheric atmosphere in a ventilated room. In this case, the stirring time is preferably longer, for example, stirring for more than 12 hours at room temperature.

[0098] By reacting the moisture in the atmosphere with the metal alkoxide, the sol-gel reaction can be carried out more slowly than when liquid water is added. In addition, by reacting the metal alkoxide with water at room temperature, for example, the sol-gel reaction can be carried out more slowly than when heating at a temperature exceeding the boiling point of the alcohol of the solvent. By carrying out the sol-gel reaction slowly, a coating layer with uniform thickness and high quality can be formed.

[0099] The precipitate is recovered from the mixed solution after the above treatment ( Figure 8 As a collection method, filtration, centrifugal separation, evaporation and drying and solidification can be used. The precipitate can be washed with the same alcohol as the solvent that dissolves the metal alkoxide. In addition, in the case of evaporation and drying and solidification, the solvent and the precipitate can be separated in this step, for example, the precipitate can be recovered in the drying step of the next step (step S54).

[0100] Next, the recovered residue was dried to obtain a mixture 909 ( Figure 8 The drying step may be, for example, vacuum or ventilation drying at 80° C. for 1 hour or more and 4 hours or less.

[0101] Next, the resulting mixture is heated ( Figure 8 Step S56).

[0102] The heating time is preferably a holding time within the heating temperature range of 1 hour to 80 hours.

[0103] The heating temperature is lower than 1000°C, preferably 700°C to 950°C, and more preferably about 850°C.

[0104] In addition, heating is preferably performed in an atmosphere containing oxygen.

[0105] In this embodiment, heating is performed under the following conditions: heating temperature is 850° C.; holding time is 2 hours; heating rate is 200° C. / h; oxygen flow rate is 10 L / min.

[0106] The heating temperature in step S56 is preferably lower than the heating temperature in step S34.

[0107] <Step S57, Step S58> Next, the cooled particles are recovered ( Figure 8 Step S57). Furthermore, the particles are preferably screened. Through the above steps, the positive electrode active material 904-4 ( Figure 8 Step S58).

[0108] (Implementation method 3) In this embodiment, an example of the structure of a positive electrode active material produced by a production method according to one embodiment of the present invention is described.

[0109] [Structure of positive electrode active material] Materials having a layered rock salt type crystalline structure such as lithium cobalt oxide (LiCoO2) have a high discharge capacity and have been considered to be excellent positive electrode active materials for secondary batteries. As a material having a layered rock salt type crystalline structure, for example, a composite oxide represented by LiMO2 can be cited. As an example of element M, one or more selected from Co and Ni can be cited. In addition, as an example of element M, in addition to one or more selected from Co and Ni, one or more selected from Al and Mg can also be cited.

[0110] The magnitude of the Jahn-Teller effect of transition metal compounds is considered to vary depending on the number of electrons in the d orbital of the transition metal.

[0111] Nickel-containing compounds are sometimes prone to distortion due to the Jan-Taylor effect. Therefore, when LiNiO2 is charged and discharged at a high voltage, there is a concern that the crystalline structure collapses due to distortion. LiCoO2 has a small negative impact of the Jan-Taylor effect and sometimes has better charge and discharge resistance at high voltage, so it is preferred.

[0112] The following reference Fig. 9 and Fig.10 The positive electrode active material is described. Fig. 9 and Fig.10 In the above, the case where cobalt is used as the transition metal contained in the positive electrode active material is described.

[0113] The positive electrode active material manufactured in one embodiment of the present invention can reduce the deviation of the CoO2 layer even if it is repeatedly charged and discharged at a high voltage. Furthermore, the volume change can be reduced. Therefore, the compound can achieve excellent cycle characteristics. In addition, the compound can also have a stable crystalline structure in a high-voltage charging state. As a result, sometimes the compound is not prone to short circuit when maintaining a high-voltage charging state. In this case, the stability is further improved, so it is preferred. In particular, the chemical formula Li (1-x-y) Co (1-a-b) Ni (x+a) Mg (y+b) The compound represented by O2 is preferred because it has good properties when 0<x+a≤0.015 and 0<y+b≤0.06.

[0114] This compound has a small change in crystal structure between a fully discharged state and a state charged at a high voltage, and a small volume difference when compared per the same number of transition metal atoms.

[0115] Fig. 9 The crystal structure of the positive electrode active material 904 before and after charge and discharge is shown. The positive electrode active material 904 is a composite oxide containing lithium, cobalt and oxygen. Preferably, it contains magnesium in addition to the above. In addition, it is preferred to contain halogens such as fluorine and chlorine. In addition, it is preferred to contain aluminum and nickel.

[0116] Fig. 9 The crystal structure of the charge depth 0 (discharge state) is Fig.10 The same R-3m (O3). However, the positive electrode active material 904 has a crystal structure different from the H1-3 type crystal structure when it has a fully charged depth of charge. This structure is a space group R-3m, not a spinel type crystal structure, but ions of cobalt, magnesium, etc. occupy oxygen 6 coordination positions, and the arrangement of cations has a symmetry similar to that of the spinel type. Therefore, in this specification, etc., the above crystal structure is referred to as a pseudo-spinel type crystal structure. In addition, in order to illustrate the symmetry of the cobalt atom and the symmetry of the oxygen atom, in Fig. 9 Although the representation of lithium is omitted in the figure of the pseudo-spinel crystal structure shown, in fact, lithium is present between the CoO2 layers, for example, less than 20 atomic % relative to cobalt. In addition, in both the O3 type crystal structure and the pseudo-spinel crystal structure, a small amount of magnesium is preferably present between the CoO2 layers, i.e., at the lithium position. In addition, a small amount of halogen such as fluorine may also be present irregularly at the oxygen position.

[0117] In addition, in the pseudo-spinel crystal structure, a light element such as lithium may occupy a four-coordinate position with oxygen. In this case, the arrangement of ions also has a symmetry similar to that of the spinel type.

[0118] In addition, the pseudo-spinel crystal structure may have a crystal structure similar to the CdCl2 type crystal structure, although it contains Li irregularly between the layers. This crystal structure similar to the CdCl2 type is similar to the crystal structure of the nickel oxide charged to a charge depth of 0.94 (Li 0.06 However, pure lithium cobalt oxide or layered rock salt-type positive electrode active materials containing a large amount of cobalt generally do not have such a crystal structure.

[0119] The anions of layered rock salt type crystals and rock salt type crystals respectively form a cubic closest packing structure (face-centered cubic lattice structure). It can be inferred that the anions in the pseudo-spinel type crystals also have a cubic closest packing structure. When these crystals are in contact, there are crystal planes with the same orientation of the cubic closest packing structure formed by the anions. The space group of layered rock salt type crystals and pseudo-spinel type crystals is R-3m, which is different from the space group Fm-3m (the space group of general rock salt type crystals) and Fd-3m (the space group of rock salt type crystals with the simplest symmetry) of rock salt type crystals. Therefore, the Miller index of the crystal plane that satisfies the above conditions of layered rock salt type crystals and pseudo-spinel type crystals is different from that of rock salt type crystals. In this specification, sometimes in layered rock salt type crystals, pseudo-spinel type crystals and rock salt type crystals, the orientation of the cubic closest packing structure formed by the anions is consistent, which means that the crystal orientation is roughly consistent.

[0120] In the positive electrode active material 904, the change in the crystal structure when a large amount of lithium is released by high voltage charging is suppressed compared to the positive electrode active material 100C described later. Fig. 9 As shown by the middle dotted line, there is almost no deviation of the CoO2 layer in the above crystal structure.

[0121] In more detail, the positive electrode active material 904 has structural stability even when the charging voltage is high. For example, even at a charging voltage at which the positive electrode active material 100C becomes an H1-3 type crystalline structure, such as a voltage of about 4.6V relative to the potential of lithium metal, the positive electrode active material 904 includes a region of charging voltage that can maintain the crystalline structure of R-3m (O3), and also includes a region of a pseudo-spinel type crystalline structure in a region of a higher charging voltage, such as a voltage of about 4.65V to 4.7V relative to the potential of lithium metal. When the charging voltage is further increased, H1-3 type crystals are observed. For example, in the case of using graphite as the negative electrode active material of a secondary battery, even at a voltage of a secondary battery of more than 4.3V and less than 4.5V, a region of charging voltage that can maintain the crystalline structure of R-3m (O3) is included, and in a region of a higher charging voltage, such as a voltage of more than 4.35V and less than 4.55V relative to the potential of lithium metal, a region of a pseudo-spinel type crystalline structure is included.

[0122] Therefore, even if charge and discharge are repeated at a high voltage, the crystal structure of the positive electrode active material 904 is unlikely to collapse.

[0123] The coordinates of cobalt and oxygen in the unit cell of the pseudo-spinel type crystal structure can be represented by Co(0, 0, 0.5) and O(0, 0, x) (0.20≤x≤0.25), respectively.

[0124] Magnesium that exists irregularly in a small amount between the CoO2 layers, that is, at the lithium position, has the effect of suppressing the deviation of the CoO2 layer. Therefore, when magnesium exists between the CoO2 layers, a pseudo-spinel crystal structure is easily obtained. Therefore, it is preferred that magnesium is distributed throughout the particles of the positive electrode active material 100A-1. In addition, in order to distribute magnesium throughout the particles, it is preferred to perform a heat treatment in the manufacturing process of the positive electrode active material 100A-1.

[0125] However, when the temperature of the heat treatment is too high, cation mixing occurs and the possibility of magnesium invading the cobalt position increases. When magnesium exists at the cobalt position, it does not have the effect of maintaining R-3m. Furthermore, when the temperature of the heat treatment is too high, there is a concern that cobalt is reduced to become divalent, lithium evaporates, and other adverse effects may occur.

[0126] Therefore, it is preferred to add a halogen compound such as a fluorine compound to the lithium cobalt oxide before performing a heat treatment for distributing magnesium throughout the particles. By adding a halogen compound, the melting point of the lithium cobalt oxide is lowered. By lowering the melting point, magnesium can be easily distributed throughout the particles at a temperature where cation mixing is not likely to occur. When the fluorine compound is also present, it can be expected that the corrosion resistance to hydrofluoric acid generated by the decomposition of the electrolyte will be improved.

[0127] Note that when the magnesium concentration is higher than the desired value, the effect of stabilizing the crystal structure sometimes becomes smaller. This is because magnesium not only enters the lithium position but also the cobalt position. The number of magnesium atoms contained in the positive electrode active material manufactured by one method of the present invention is preferably greater than 0.001 times and less than 0.1 times the number of cobalt atoms, more preferably greater than 0.01 times and less than 0.04 times, and further preferably about 0.02. The magnesium concentration shown here can be, for example, a value obtained by elemental analysis of the particles of the positive electrode active material as a whole using ICP-MS or the like, or a value obtained by mixing raw materials in the manufacturing process of the positive electrode active material.

[0128] The number of nickel atoms contained in the positive electrode active material 904 is preferably 7.5% or less of the number of cobalt atoms, more preferably 0.05% or more and 4% or less, and further preferably 0.1% or more and 2% or less. The nickel concentration shown here can be, for example, a value obtained by elemental analysis of the entire particle of the positive electrode active material using ICP-MS or the like, or a value obtained by mixing raw materials in the manufacturing process of the positive electrode active material.

[0129] <<Particle size>> When the particle size of the positive electrode active material 904 is too large, the following problems occur: the diffusion of lithium becomes difficult; when applied on the current collector, the surface of the active material layer is too rough, etc. On the other hand, when the particle size of the positive electrode active material is too small, the following problems occur: it is not easy to support the active material layer when applied on the current collector; the reaction with the electrolyte is excessive, etc. Therefore, the average particle size (D50: median particle size) is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 40 μm or less, and further preferably 5 μm or more and 30 μm or less.

[0130] <Analysis Method> In order to determine whether a certain positive electrode active material shows a pseudo-spinel crystal structure when charged at a high voltage, the positive electrode charged at a high voltage can be determined by using XRD, electron diffraction, neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR) and other analysis. In particular, XRD has the following advantages, so it is preferred: the symmetry of transition metals such as cobalt possessed by the positive electrode active material can be analyzed with high resolution; the height of crystallinity and the orientation of crystals can be compared; the periodic distortion of the lattice and the grain size can be analyzed; sufficient accuracy can also be obtained when directly measuring the positive electrode obtained by disassembling a secondary battery, etc.

[0131] As described above, the positive electrode active material 904 is characterized in that the crystal structure changes little between the high voltage charging state and the discharge state. Materials in which the crystal structure with large changes between high voltage charging and discharging accounts for more than 50wt% are not preferred because they cannot withstand high voltage charging and discharging. Note that sometimes the desired crystal structure cannot be achieved only by adding impurity elements. For example, the positive electrode active material of lithium cobalt oxide containing magnesium and fluorine sometimes has a pseudo-spinel crystal structure of more than 60wt% and sometimes has an H1-3 type crystal structure of more than 50wt% when charged at a high voltage. In addition, when a specified voltage is used, the pseudo-spinel crystal structure becomes almost 100wt%, and when the specified voltage is further increased, the H1-3 type crystal structure is sometimes generated. Therefore, the crystal structure of the positive electrode active material 904 is preferably analyzed by XRD or the like.

[0132] However, sometimes the positive electrode active material in a high voltage charging state or a discharge state changes its crystal structure when exposed to air. For example, sometimes it changes from a pseudo-spinel crystal structure to an H1-3 type crystal structure. Therefore, all samples are preferably processed in an inert atmosphere including an argon atmosphere.

[0133] <Positive Electrode Active Material 100C of Comparative Example> Fig.10 The positive electrode active material 100C shown is lithium cobalt oxide (LiCoO2) to which halogen and magnesium are not added in the manufacturing method described later. Fig.10 As described in Non-Patent Documents 1 and 2, the crystal structure of lithium cobalt oxide changes depending on the depth of charge.

[0134] like Fig.10 As shown, the lithium cobalt oxide with a charge depth of 0 (discharge state) includes a region having a crystalline structure of space group R-3m, including three CoO2 layers in a unit cell. Therefore, this crystalline structure is sometimes referred to as an O3 type crystalline structure. Note that the CoO2 layer refers to a structure in which an octahedral structure formed by cobalt and six coordinated oxygens maintains a state of edge sharing on one plane.

[0135] When the charge depth is 1, it has a crystal structure of space group P-3m1, and the unit cell includes one CoO2 layer. Therefore, this crystal structure is sometimes called an O1-type crystal structure.

[0136] When the depth of charge is about 0.88, lithium cobalt oxide has a crystalline structure of space group R-3m. It can also be said that this structure is a structure in which CoO2 structures such as P-3m1(O1) and LiCoO2 structures such as R-3m(O3) are alternately stacked. Therefore, this crystalline structure is sometimes called H1-3 type crystalline structure. In fact, the number of cobalt atoms in the unit cell of H1-3 type crystalline structure is twice that of other structures. However, Fig.10 In this specification, the c-axis in the H1-3 type crystal structure is represented as 1 / 2 of the unit cell for easy comparison with other structures.

[0137] As an example of an H1-3 type crystalline structure, as disclosed in non-patent document 3, the coordinates of cobalt and oxygen in a unit cell can be represented by Co (O, O, 0.42150 ± 0.00016), O1 (O, O, 0.27671 ± 0.00045), and O2 (O, O, 0.11535 ± 0.00045). O1 and O2 are both oxygen atoms. In this way, the H1-3 type crystalline structure is represented by a unit cell using one cobalt and two oxygens. On the other hand, as described below, it is preferred to represent a pseudo-spinel type crystalline structure of one embodiment of the present invention by a unit cell using one cobalt and one oxygen. This indicates that the difference between the pseudo-spinel type crystalline structure and the H1-3 type crystalline structure lies in the symmetry of cobalt and oxygen, and the pseudo-spinel type crystalline structure has a smaller change from the O3 structure than the H1-3 type crystalline structure. For example, any unit cell may be selected under the condition that the GOF (goodness of fit) value is as small as possible when the XRD pattern is subjected to Rietveld analysis so as to more appropriately represent the crystal structure of the positive electrode active material.

[0138] When high voltage charging with a charging voltage of 4.6 V or more relative to the redox potential of lithium metal or deep charging and discharging with a charging depth of 0.8 or more is repeatedly performed, the crystal structure of lithium cobalt oxide repeatedly changes between the H1-3 type crystal structure and the R-3m (O3) crystal structure in the discharged state (i.e., non-equilibrium phase transition).

[0139] However, the CoO2 layers of the two crystalline structures mentioned above deviate greatly. Fig.10 As shown by the dotted line and arrow in the middle, in the H1-3 crystal structure, the CoO2 layer is significantly deviated from the R-3m (O3). Such dynamic structural changes will have an adverse effect on the stability of the crystal structure.

[0140] Furthermore, the volume difference is also large. When compared per the same number of cobalt atoms, the volume difference between the H1-3 type crystal structure and the O3 type crystal structure in the discharged state is 3.0% or more.

[0141] In addition to the above, the structure of the H1-3 type crystal structure having a continuous CoO2 layer such as P-3m1(O1) is likely to be unstable.

[0142] Therefore, when high voltage charging and discharging are repeated, the crystal structure of lithium cobalt oxide will collapse. The collapse of the crystal structure will cause the deterioration of the cycle characteristics. This is because the collapse of the crystal structure reduces the number of locations where lithium can exist stably, and the insertion and removal of lithium become difficult.

[0143] (Implementation 4) In this embodiment, examples of materials that can be used for a secondary battery including a positive electrode active material produced by a production method according to one embodiment of the present invention are described. In this embodiment, a secondary battery in which a positive electrode, a negative electrode, and an electrolyte are surrounded by an outer package is described as an example.

[0144] [positive electrode] The positive electrode includes a positive electrode active material layer and a positive electrode current collector.

[0145] <Positive Electrode Active Material Layer> The positive electrode active material layer contains positive electrode active material particles. In addition, the positive electrode active material layer may also contain a conductive auxiliary agent and a binder.

[0146] As the positive electrode active material particles, a positive electrode active material produced by the production method of one embodiment of the present invention can be used.

[0147] As the conductive auxiliary agent, a carbon material, a metal material or a conductive ceramic material can be used. In addition, as the conductive auxiliary agent, a fibrous material can also be used. The content of the conductive auxiliary agent in the total amount of the active material layer is preferably 1 wt% to 10 wt%, more preferably 1 wt% to 5 wt%.

[0148] By using a conductive additive, a conductive network can be formed in the electrode. By using a conductive additive, a conductive path between positive electrode active materials can be maintained. By adding a conductive additive to the active material layer, an active material layer with high electrical conductivity can be realized.

[0149] As the conductive aid, for example, natural graphite, artificial graphite such as mesophase carbon microbeads, carbon fiber, etc. can be used. As the carbon fiber, for example, carbon fiber such as mesophase pitch carbon fiber, isotropic pitch carbon fiber, etc. can be used. As the carbon fiber, carbon nanofibers or carbon nanotubes can be used. For example, carbon nanotubes can be manufactured by vapor phase growth method, etc. As the conductive aid, for example, carbon materials such as carbon black (acetylene black (AB), etc.), graphite (black lead) particles, graphene or fullerene can be used. In addition, for example, metal powders or metal fibers of copper, nickel, aluminum, silver, gold, etc., conductive ceramic materials, etc. can be used.

[0150] In addition, a graphene compound may also be used as a conductive auxiliary agent.

[0151] Graphene compounds sometimes have excellent electrical properties such as high conductivity and excellent physical properties such as high flexibility and high mechanical strength. In addition, graphene compounds have a planar shape. Graphene compounds can form surface contacts with low contact resistance. Graphene compounds sometimes have very high conductivity even if they are thin, so a conductive path can be formed efficiently in a small amount in the active material layer. Therefore, by using a graphene compound as a conductive aid, the contact area between the active material and the conductive aid can be increased, so it is preferred. In addition, sometimes by using a graphene compound as a conductive aid, the resistance can be reduced, so it is preferred. Here, it is particularly preferred to use, for example, graphene, multilayer graphene or Reduced Graphene Oxide (hereinafter, RGO) as the graphene compound. Here, RGO refers to a compound obtained by reducing graphene oxide (GO: Graphene Oxide), for example.

[0152] When using active material particles with a small particle size, for example, when using active material particles with a particle size of less than 1 μm, the specific surface area of ​​the active material particles is large, so more conductive paths connecting the active material particles are required. In this case, it is particularly preferred to use a graphene compound that can efficiently form a conductive path even in a small amount.

[0153] Hereinafter, an example of a cross-sectional structure of an active material layer 200 including a graphene compound as a conductive auxiliary agent will be described as an example.

[0154] Fig.11A is a longitudinal cross-sectional view of the active material layer 200. Fig. 11B yes Fig.11A An enlarged view of the area surrounded by dotted lines in FIG. The active material layer 200 includes a granular positive electrode active material 101, a graphene compound 201 used as a conductive aid, and a binder (not shown). Here, as the graphene compound 201, for example, graphene or multilayer graphene can be used. In addition, the graphene compound 201 preferably has a sheet shape. The graphene compound 201 can be formed into a sheet in a manner that a plurality of multilayer graphenes or (and) a plurality of single-layer graphenes partially overlap.

[0155] In the longitudinal cross section of the active material layer 200, as shown in FIG. Fig.11A As shown in FIG. 2 , the flake-shaped graphene compound 201 is dispersed roughly uniformly inside the active material layer 200. Fig.11AIn the figure, although the graphene compound 201 is schematically represented by a thick line, in fact, the graphene compound 201 is a thin film having a thickness of a single layer or multiple layers of carbon molecules. Since the plurality of graphene compounds 201 are formed in a manner of wrapping or covering the plurality of granular positive electrode active materials 101 or in a manner of attaching to the surface of the plurality of granular positive electrode active materials 101, the graphene compound 201 is in surface contact with the positive electrode active material 101.

[0156] Here, by combining a plurality of graphene compounds with each other, a meshed graphene compound sheet (hereinafter referred to as a graphene compound net or graphene net) can be formed. When the graphene net covers the active material, the graphene net can be used as an adhesive for combining the active materials with each other. Therefore, the amount of the adhesive can be reduced or the adhesive does not need to be used, thereby increasing the proportion of the active material in the electrode volume or the electrode weight. In other words, the capacity of the storage device can be increased.

[0157] Here, it is preferred that graphene oxide is used as the graphene compound 201, the graphene oxide and the active material are mixed to form a layer to be the active material layer 200, and then reduced. By using graphene oxide with extremely high dispersibility in a polar solvent in the formation of the graphene compound 201, the graphene compound 201 can be dispersed roughly uniformly in the active material layer 200. The solvent is volatilized and removed from the dispersion medium containing the uniformly dispersed graphene oxide, and the graphene oxide is reduced, so that the graphene compounds 201 remaining in the active material layer 200 partially overlap each other and are dispersed in a manner of forming surface contact, thereby forming a three-dimensional conductive path. In addition, the reduction of graphene oxide can also be performed, for example, by heat treatment or using a reducing agent.

[0158] Therefore, unlike granular conductive additives such as acetylene black that form point contact with the active material, the graphene compound 201 can form a surface contact with low contact resistance, so the conductivity between the granular positive electrode active material 101 and the graphene compound 201 can be improved with less graphene compound 201 than a general conductive additive. Therefore, the ratio of the positive electrode active material 101 in the active material layer 200 can be increased. As a result, the discharge capacity of the power storage device can be increased.

[0159] As the adhesive, preferably used are rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. Fluorine rubber can also be used as the adhesive.

[0160] In addition, as a binder, for example, a water-soluble polymer is preferably used. As a water-soluble polymer, for example, polysaccharides can be used. As polysaccharides, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, regenerated cellulose, starch, etc. can be used. It is more preferred to use these water-soluble polymers and the above-mentioned rubber material in combination.

[0161] Alternatively, as the adhesive, it is preferred to use materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene monomer polymer, polyvinyl acetate, and nitrocellulose.

[0162] As the binder, a plurality of the above-mentioned materials may be used in combination.

[0163] For example, it is also possible to combine materials with other materials that have a particularly high viscosity regulating function. For example, although rubber materials and the like have high cohesive force and high elasticity, it is sometimes difficult to regulate viscosity when mixed in a solvent. In such a case, for example, it is preferably mixed with a material with a particularly high viscosity regulating function. As a material with a particularly high viscosity regulating function, for example, a water-soluble polymer can be used. In addition, as a water-soluble polymer with particularly good viscosity regulating function, the above-mentioned polysaccharides can be used, for example, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose and diacetyl cellulose, regenerated cellulose, and starch can be used.

[0164] Note that cellulose derivatives such as carboxymethyl cellulose, for example, can be easily used as viscosity modifiers by being converted into salts such as sodium salts and ammonium salts of carboxymethyl cellulose to improve their solubility. Due to the increased solubility, the dispersibility of active materials and other components can be improved when forming a slurry for an electrode. In this specification, cellulose and cellulose derivatives used as binders for electrodes include their salts.

[0165] By dissolving a water-soluble polymer in water to stabilize its viscosity, the active material and other materials used as a binder combination, such as styrene-butadiene rubber, can be stably dispersed in an aqueous solution. Since the water-soluble polymer has functional groups, it is expected to be easily and stably attached to the surface of the active material. Most cellulose derivatives such as carboxymethyl cellulose have functional groups such as hydroxyl and carboxyl. Because of the functional groups, the polymer is expected to interact with each other and widely cover the surface of the active material.

[0166] When the binder covering or contacting the surface of the active material forms a film, it is also expected to be used as a passivation film to exert an effect of inhibiting the decomposition of the electrolyte. Here, the passivation film is a film that has no electronic conductivity or extremely low conductivity. For example, when the passivation film is formed on the surface of the active material, it inhibits the decomposition of the electrolyte at the battery reaction potential. More preferably, the passivation film can transmit lithium ions while inhibiting conductivity.

[0167] <Positive Electrode Current Collector> As the positive electrode current collector, materials with high conductivity such as stainless steel, gold, platinum, aluminum, titanium and their alloys can be used. In addition, the material used for the positive electrode current collector is preferably not dissolved due to the potential of the positive electrode. In addition, aluminum alloys to which elements such as silicon, titanium, neodymium, scandium, and molybdenum that improve heat resistance are added can also be used. In addition, metal elements that react with silicon to form silicides can also be used. As metal elements that react with silicon to form silicides, there are zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately have shapes such as foil, plate (sheet), mesh, punched metal mesh, drawn metal mesh, etc. The thickness of the current collector is preferably 5 μm or more and 30 μm or less.

[0168] [negative electrode] The negative electrode includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also include a conductive auxiliary agent and a binder.

[0169] <Negative Electrode Active Material> As the negative electrode active material, for example, an alloy material or a carbon material can be used.

[0170] As the negative electrode active material, an element that can perform a charge and discharge reaction by alloying / de-alloying reaction with lithium can be used. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium and indium can be used. The capacity of such an element is larger than that of carbon, and in particular, the theoretical capacity of silicon is large, which is 4200mAh / g. Therefore, silicon is preferably used for the negative electrode active material. In addition, compounds containing these elements can also be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb and SbSn can be cited. Elements that can undergo charge and discharge reactions through alloying / de-alloying reactions with lithium, compounds containing the elements, and the like are sometimes referred to as alloy-based materials.

[0171] In this specification, SiO refers to silicon monoxide, for example. Alternatively, SiO may also be represented as SiO x Here, x preferably represents a value of 1 or a value close thereto. For example, x is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0172] As the carbon-based material, graphite, easily graphitizable carbon (soft carbon), hardly graphitizable carbon (hard carbon), carbon nanotube, graphene, carbon black, and the like can be used.

[0173] As graphite, artificial graphite or natural graphite can be mentioned. As artificial graphite, for example, mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. can be mentioned. Here, spherical graphite with a spherical shape can be used as artificial graphite. For example, MCMB sometimes has a spherical shape, so it is preferred. In addition, MCMB is easier to reduce its surface area, so it is sometimes preferred. As natural graphite, for example, flaky graphite, spheroidized natural graphite, etc. can be mentioned.

[0174] When lithium ions are intercalated in graphite (when lithium-graphite intercalation compounds are generated), graphite shows a potential as low as that of lithium metal (0.05 V or more and 0.3 V or less vs. Li / Li + ). As a result, lithium-ion secondary batteries can show high operating voltages. Graphite also has the following advantages: large capacity per unit volume; relatively small volume expansion; relatively cheap; and higher safety than lithium metal, so it is preferred.

[0175] In addition, as the negative electrode active material, oxides such as titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), etc.

[0176] In addition, as the negative electrode active material, Li 3N-type structure containing lithium and transition metal nitride can be used. 3-x M x N (M = Co, Ni, Cu). For example, Li 2.6 Co 0.4 N3 shows a large charge and discharge capacity (900 mAh / g, 1890 mAh / cm 3 ), so it is preferred.

[0177] When a nitride containing lithium and a transition metal is used as the negative electrode active material, lithium ions are contained in the negative electrode active material, so the negative electrode active material can be combined with a material that does not contain lithium ions, such as V2O5 and Cr3O8, which is used as a positive electrode active material, so it is preferred. Note that when a material containing lithium ions is used as a positive electrode active material, a nitride containing lithium and a transition metal can also be used as a negative electrode active material by previously removing the lithium ions contained in the positive electrode active material.

[0178] In addition, materials that cause conversion reactions can also be used as negative electrode active materials. For example, transition metal oxides that do not form alloys with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), can be used as negative electrode active materials. Materials that cause conversion reactions can also include oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, CoS 0.89 , sulfides such as NiS, CuS, nitrides such as Zn3N2, Cu3N, Ge3N4, phosphides such as NiP2, FeP2, CoP3, fluorides such as FeF3, BiF3.

[0179] As the conductive aid and the binder which may be contained in the negative electrode active material layer, the same materials as the conductive aid and the binder which may be contained in the positive electrode active material layer can be used.

[0180] <Negative Electrode Current Collector> As the negative electrode current collector, the same material as the positive electrode current collector can be used. In addition, as the negative electrode current collector, it is preferable to use a material that does not alloy with carrier ions such as lithium.

[0181] [Electrolyte] The electrolyte comprises a solvent and an electrolyte. As the solvent of the electrolyte, an aprotic organic solvent is preferably used, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, vinyl chloride carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, ethylene glycol dimethyl ether (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme (methyl diglyme), acetonitrile, benzonitrile, tetrahydrofuran, cyclopentane sulfone, one of sultones, or two or more of the above can be used in any combination and ratio.

[0182] In addition, by using one or more ionic liquids (room temperature molten salts) with flame retardancy and low volatility as solvents for the electrolyte, even if the internal temperature rises due to internal short circuit, overcharge, etc. of the storage device, the rupture or ignition of the storage device can be prevented. The ionic liquid is composed of cations and anions, including organic cations and anions. As organic cations for the electrolyte, aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations and quaternary phosphonium cations or aromatic cations such as imidazolium cations and pyridinium cations can be cited. In addition, as anions for the electrolyte, 1-valent amide anions, 1-valent methylated anions, fluorosulfonic acid anions, perfluoroalkyl sulfonic acid anions, tetrafluoroborate anions, perfluoroalkyl borate anions, hexafluorophosphate anions or perfluoroalkyl phosphate anions can be cited.

[0183] In addition, as the electrolyte dissolved in the above solvent, for example, LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 10 Cl 10 、Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2 and other lithium salts, or two or more of the above can be used in any combination and ratio.

[0184] As an electrolyte for a power storage device, it is preferred to use a highly purified electrolyte with a low content of granular dust or elements other than the constituent elements of the electrolyte (hereinafter referred to as "impurities"). Specifically, the ratio of impurities to the weight of the electrolyte is less than 1%, preferably less than 0.1%, and more preferably less than 0.01%.

[0185] In addition, additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate borate) (LiBOB), or dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the additive may be set to, for example, 0.1 wt% or more and 5 wt% or less in the entire solvent.

[0186] Alternatively, a polymer gel electrolyte obtained by swelling a polymer with an electrolyte solution may be used.

[0187] When a polymer gel electrolyte is used, safety against leakage etc. is improved. In addition, the secondary battery can be made thinner and lighter.

[0188] As the gelled polymer, silicone gel, acrylic glue, acrylonitrile glue, polyethylene oxide glue, polypropylene oxide glue, fluorine polymer glue, etc. can be used. For example, a polymer having a polyoxyalkylene structure such as polyethylene oxide (PEO), PVDF and polyacrylonitrile, etc., and copolymers containing these, etc. can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. In addition, the formed polymer can also have a porous shape.

[0189] In addition, solid electrolytes including inorganic materials such as sulfides or oxides, solid electrolytes including polymer materials such as polyethylene oxide (PEO) can be used instead of electrolytes. When solid electrolytes are used, it is not necessary to set a separator or spacer. In addition, since the entire battery can be solidified, there is no worry about leakage and safety is significantly improved.

[0190] Therefore, the positive electrode active material produced by the production method of one embodiment of the present invention can be applied to all-solid batteries. By applying the positive electrode active material to all-solid batteries, all-solid batteries with high safety and excellent characteristics can be obtained.

[0191] (Implementation 5) In this embodiment, an example of the shape of a secondary battery including a positive electrode active material produced by the production method described in the above embodiment is described. Materials used for the secondary battery described in this embodiment can refer to the description of the above embodiment.

[0192] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. Fig. 12A This is the appearance of a coin-type (single-layer flat) secondary battery. Fig. 12B is its cross-sectional view.

[0193] In the coin-type secondary battery 300, a positive electrode can 301 also serving as a positive terminal and a negative electrode can 302 also serving as a negative terminal are insulated and sealed by a gasket 303 formed of polypropylene or the like. A positive electrode 304 is formed of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact therewith. A negative electrode 307 is formed of a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact therewith.

[0194] In the positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 , the active material layer may be formed on one surface of the positive electrode and the negative electrode, respectively.

[0195] As the positive electrode can 301 and the negative electrode can 302, metals such as nickel, aluminum, titanium, etc., which are resistant to corrosion by the electrolyte, their alloys, or alloys of these and other metals (such as stainless steel, etc.) can be used. In addition, in order to prevent corrosion caused by the electrolyte, the positive electrode can 301 and the negative electrode can 302 are preferably covered with nickel or aluminum. 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.

[0196] By immersing the negative electrode 307, the positive electrode 304 and the separator 310 in an electrolyte, such as Fig. 12B As shown, the positive electrode can 301 is placed at the bottom, the positive electrode 304, the separator 310, the negative electrode 307 and the negative electrode can 302 are stacked in order, and the positive electrode can 301 and the negative electrode can 302 are pressed with the gasket 303 interposed therebetween to manufacture the coin-type secondary battery 300.

[0197] By using the positive electrode active material particles described in the above embodiment for the positive electrode 304 , it is possible to realize the coin-type secondary battery 300 which is less deteriorated and highly safe.

[0198] [Isolated Body] In addition, the secondary battery preferably includes a separator. As the separator, for example, the following materials can be used: fiber containing cellulose such as paper, non-woven fabric, glass fiber, ceramic, or synthetic fiber containing nylon (polyamide), vinylon (polyvinyl alcohol fiber), polyester, acrylic resin, polyolefin, polyurethane, etc. It is preferred that the separator is processed into a bag shape and arranged in a manner to surround either the positive electrode or the negative electrode.

[0199] The separator may have a multilayer structure. For example, a ceramic material, a fluorine material, a polyamide material or a mixture thereof may be coated on a thin film of an organic material such as polypropylene or polyethylene. As a ceramic material, for example, aluminum oxide particles, silicon oxide particles, etc. may be used. As a fluorine material, for example, PVDF, polytetrafluoroethylene, etc. may be used. As a polyamide material, for example, nylon, aromatic polyamide (meta-aramid, para-aramid), etc. may be used.

[0200] By applying ceramic materials, the oxidation resistance can be improved, thereby suppressing the degradation of the separator during high voltage charge and discharge, thereby improving the reliability of the secondary battery. By applying fluorine materials, it is easy to make the separator close to the electrode, which can improve the output characteristics. By applying polyamide materials (especially aromatic polyamide), the heat resistance can be improved, thereby improving the safety of the secondary battery.

[0201] For example, a mixture of aluminum oxide and aramid may be applied to both sides of a polypropylene film. Alternatively, a mixture of aluminum oxide and aramid may be applied to the surface of the polypropylene film in contact with the positive electrode and a fluorine-based material may be applied to the surface in contact with the negative electrode.

[0202] By adopting a separator with a multi-layer structure, the safety of the secondary battery can be ensured even if the total thickness of the separator is small, and thus the capacity per unit volume of the secondary battery can be increased.

[0203] [Cylindrical secondary battery] Next, refer to FIG. 13A to FIG. 13D An example of a cylindrical secondary battery will be described. Fig. 13B As shown in the cross-sectional schematic diagram, Fig.13A The cylindrical secondary battery 600 shown has a positive electrode cover (battery cover) 601 on the top surface and a battery can (outer can) 602 on the side and bottom surfaces. The positive electrode cover and the battery can (outer can) 602 are insulated by a gasket (insulating gasket) 610.

[0204] A battery element is provided inside the hollow cylindrical battery can 602, in which a strip-shaped positive electrode 604 and a strip-shaped negative electrode 606 are wound around a separator 605. Although not shown, the battery element is wound around a center pin. One end of the battery can 602 is closed and the other end is open. As the battery can 602, metals such as nickel, aluminum, titanium, etc., which are resistant to corrosion by the electrolyte, their alloys, or alloys of them and other metals (such as stainless steel, etc.) can be used. In addition, in order to prevent corrosion caused by the electrolyte, the battery can 602 is preferably covered with nickel or aluminum. Inside the battery can 602, the battery element in which the positive electrode, the negative electrode and the separator are wound is sandwiched by a pair of opposing insulating plates 608 and insulating plates 609. In addition, a non-aqueous electrolyte (not shown) is injected into the interior of the battery can 602 in which the battery element is provided. As a non-aqueous electrolyte, the same electrolyte as that of a coin-type secondary battery can be used.

[0205] Because the positive electrode and negative electrode used for the cylindrical secondary battery are wound, the active material is preferably formed on both surfaces of the current collector. The positive electrode 604 is connected to the positive terminal (positive electrode current collecting wire) 603, and the negative electrode 606 is connected to the negative terminal (negative electrode current collecting wire) 607. Metal materials such as aluminum can be used for both the positive terminal 603 and the negative terminal 607. The positive terminal 603 is resistance welded to the safety valve mechanism 612, and the negative terminal 607 is resistance welded to the bottom of the battery can 602. The safety valve mechanism 612 is electrically connected to the positive electrode cover 601 through the PTC element (Positive Temperature Coefficient) 611. When the internal pressure of the battery rises to exceed a specified threshold, the safety valve mechanism 612 cuts off the electrical connection between the positive electrode cover 601 and the positive electrode 604. In addition, the PTC element 611 is a thermally sensitive resistance element whose resistance increases when the temperature rises, and limits the current by increasing the resistance to prevent abnormal heating. As the PTC element, barium titanate (BaTiO 3 )-based semiconductor ceramics or the like can be used.

[0206] In addition, if Fig. 13C As shown, a plurality of secondary batteries 600 may be sandwiched between a conductive plate 613 and a conductive plate 614 to form a module 615. A plurality of secondary batteries 600 may be connected in parallel, in series, or in parallel and then in series. By forming a module 615 including a plurality of secondary batteries 600, a large amount of power may be extracted.

[0207] Fig.13D FIG. 6 is a top view of module 615. For the sake of clarity, conductive plate 613 is represented by a dotted line. Fig.13D As shown, the module 615 may include a wire 616 that electrically connects the plurality of secondary batteries 600. A conductive plate 613 may be provided on the wire 616 in a manner overlapping the wire 616. In addition, a temperature control device 617 may be included between the plurality of secondary batteries 600. When the secondary battery 600 is overheated, it may be cooled by the temperature control device 617, and when the secondary battery 600 is overcooled, it may be heated by the temperature control device 617. Thus, the performance of the module 615 is not easily affected by the external temperature.

[0208] By using the positive electrode active material produced by the production method described in the above embodiment as the positive electrode 604 , it is possible to realize the cylindrical secondary battery 600 which is less deteriorated and highly safe.

[0209] [Configuration Example of Power Storage Device] Refer to Figures 14 to Fig.18 Another configuration example of the power storage device will be described.

[0210] Fig.14A and Fig. 14B9 is a diagram showing the appearance of the power storage device. The power storage device includes a circuit board 900 and a secondary battery 913. A label 910 is attached to the secondary battery 913. Fig. 14B As shown, the power storage device includes terminals 951 and 952 , and antennas 914 and 915 .

[0211] The circuit board 900 includes a terminal 911 and a circuit 912. The terminal 911 is connected to the terminal 951, the terminal 952, the antenna 914, the antenna 915, and the circuit 912. In addition, a plurality of terminals 911 may be provided and used as control signal input terminals, power supply terminals, etc.

[0212] Circuit 912 may also be disposed on the back side of circuit board 900. In addition, the shapes of antenna 914 and antenna 915 are not limited to coil shapes, and may be, for example, linear or plate-shaped. In addition, antennas such as planar antennas, aperture antennas, traveling wave antennas, EH antennas, magnetic field antennas, or dielectric antennas may also be used. Alternatively, antenna 914 or antenna 915 may also be a flat conductor. The flat conductor may also be used as one of the conductors for electric field coupling. In other words, antenna 914 or antenna 915 may also be used as one of the two conductors of a capacitor. Thus, not only electromagnetic and magnetic fields are utilized, but also electric fields may be utilized to exchange electric power.

[0213] The line width of the antenna 914 is preferably larger than the line width of the antenna 915. Thus, the amount of power received by the antenna 914 can be increased.

[0214] The power storage device includes a layer 916 between the antenna 914 and the antenna 915 and the secondary battery 913. The layer 916 has a function of shielding an electromagnetic field from the secondary battery 913, for example. As the layer 916, a magnetic material can be used, for example.

[0215] The structure of the power storage device is not limited to the structure shown in FIG. 14 .

[0216] Or, if Fig.15A and Fig. 15B As shown, in Fig.14A and Fig. 14B Different antennas are provided on a pair of opposing surfaces of the secondary battery 913 shown. Fig.15A is an external view showing one side of the pair of surfaces, Fig. 15B is an external view showing the other surface of the pair of surfaces. Fig.14A and Fig. 14B The same parts of the power storage device shown in the figure can be appropriately used. Fig.14A and Fig. 14B Description of the power storage device shown.

[0217] like Fig.15AAs shown, an antenna 914 is provided on one of a pair of surfaces of a secondary battery 913 via a layer 916. Fig. 15B As shown, an antenna 915 is provided on the other of the pair of surfaces of a secondary battery 913 via a layer 917. The layer 917 has a function of shielding an electromagnetic field from the secondary battery 913, for example. As the layer 917, for example, a magnetic material can be used.

[0218] By adopting the above structure, the sizes of both antenna 914 and antenna 915 can be increased.

[0219] Or, if Fig. 15C and Fig.15D As shown, in Fig.14A and Fig. 14B Different antennas are provided on a pair of opposing surfaces of the secondary battery 913 shown. Fig. 15C is an external view showing one side of the pair of surfaces, Fig.15D is an external view showing the other surface of the pair of surfaces. Fig.14A and Fig. 14B The same parts of the power storage device shown in the figure can be appropriately used. Fig.14A and Fig. 14B Description of the power storage device shown.

[0220] like Fig. 15C As shown, an antenna 914 and an antenna 915 are provided on one of a pair of surfaces of a secondary battery 913 with a layer 916 interposed therebetween. Fig.15D As shown, an antenna 918 is provided on the other of the pair of surfaces of the secondary battery 913 with a layer 917 interposed therebetween. The antenna 918 has, for example, a function of communicating data with an external device. As the antenna 918, for example, an antenna having a shape applied to the antenna 914 and the antenna 915 can be used. As a communication method between the power storage device and other devices using the antenna 918, a response method such as NFC that can be used between the power storage device and other devices can be used.

[0221] Or, if Fig.16A As shown, it can also be Fig.14A and Fig. 14B The secondary battery 913 shown in FIG. 1 is provided with a display device 920. The display device 920 is electrically connected to the terminal 911 via the terminal 919. In addition, the label 910 may not be attached to the portion where the display device 920 is provided. Fig.14A and Fig. 14B The same parts of the power storage device shown in the figure can be appropriately used. Fig.14A and Fig. 14B Description of the power storage device shown.

[0222] The display device 920 may display, for example, an image showing whether charging is in progress, an image showing the amount of stored electricity, etc. As the display device 920, for example, electronic paper, a liquid crystal display device, an electroluminescent (also referred to as EL) display device, etc. may be used. For example, by using electronic paper, the power consumption of the display device 920 can be reduced.

[0223] Or, if Fig. 16B As shown, it can also be Fig.14A and Fig. 14B The secondary battery 913 shown in FIG. 1 is provided with a sensor 921. The sensor 921 is electrically connected to the terminal 911 via the terminal 922. Fig.14A and Fig. 14B The same parts of the power storage device shown in the figure can be appropriately used. Fig.14A and Fig. 14B Description of the power storage device shown.

[0224] The sensor 921 may have a function of measuring, for example, displacement, position, speed, acceleration, angular velocity, number of rotations, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow, humidity, slope, vibration, smell, or infrared. By providing the sensor 921, for example, data (temperature, etc.) showing the environment in which the power storage device is provided can be detected and stored in the memory in the circuit 912.

[0225] Furthermore, referring to FIG. 17 and Fig.18 A structural example of the secondary battery 913 is described.

[0226] Fig.17A The secondary battery 913 shown includes a winding body 950 provided with a terminal 951 and a terminal 952 inside a frame 930. The winding body 950 is impregnated with an electrolyte inside the frame 930. The terminal 952 is in contact with the frame 930, and the terminal 951 is prevented from contacting the frame 930 by an insulating material or the like. Note that for convenience, although Fig.17A Frame 930 is shown separately in the figure, but in reality, winding body 950 is covered by frame 930, and terminals 951 and 952 extend outside frame 930. Frame 930 can be made of a metal material (such as aluminum) or a resin material.

[0227] In addition, if Fig. 17B As shown, multiple materials can also be used to form Fig.17A For example, in the frame 930 shown in FIG. Fig. 17B In the secondary battery 913 shown, a frame body 930 a and a frame body 930 b are bonded together, and a wound body 950 is provided in a region surrounded by the frame bodies 930 a and 930 b.

[0228] As the frame 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin to form the surface of the antenna, it is possible to suppress the shielding of the electric field by the secondary battery 913. In addition, if the shielding of the electric field by the frame 930a is small, an antenna such as the antenna 914 or the antenna 915 can also be provided inside the frame 930a. As the frame 930b, for example, a metal material can be used.

[0229] Furthermore, Fig.18 The structure of the wound body 950 is shown. The wound body 950 includes a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is formed by overlapping the negative electrode 931 and the positive electrode 932 with the separator 933 interposed therebetween to form a laminated sheet, and then winding the laminated sheet. In addition, a plurality of layers of the negative electrode 931, the positive electrode 932, and the separator 933 may be stacked.

[0230] The negative electrode 931 is connected to the terminal 911 shown in Fig. 14 via one of the terminal 951 and the terminal 952. The positive electrode 932 is connected to the terminal 911 shown in Fig. 14 via the other of the terminal 951 and the terminal 952.

[0231] By using the positive electrode active material particles described in the above embodiment for the positive electrode 932 , a secondary battery 913 with little deterioration and high safety can be realized.

[0232] [Laminated secondary battery] Next, an example of a laminated secondary battery will be described with reference to Figures 19 to 24. When a laminated secondary battery having flexibility is mounted on an electronic device having at least a portion thereof being flexible, the secondary battery can be bent along the deformation of the electronic device.

[0233] Reference FIG. 19A to FIG. 19C The laminated secondary battery 980 is described. The laminated secondary battery 980 includes Fig.19A The winding body 993 shown. The winding body 993 includes a negative electrode 994, a positive electrode 995 and a separator 996. Fig.18 Similar to the wound body 950 described above, the wound body 993 is formed by overlapping the negative electrode 994 and the positive electrode 995 with the separator 996 interposed therebetween to form a laminated sheet, and then winding the laminated sheet.

[0234] In addition, the number of stacked layers consisting of the negative electrode 994, the positive electrode 995, and the separator 996 can be appropriately designed according to the required capacity and element volume. The negative electrode 994 is connected to the negative electrode collector (not shown) through one of the lead electrode 997 and the lead electrode 998, and the positive electrode 995 is connected to the positive electrode collector (not shown) through the other of the lead electrode 997 and the lead electrode 998.

[0235] like Fig.19B As shown, the wound body 993 is accommodated in a space formed by laminating a film 981 to be an outer packaging body and a film 982 having a recess by heat pressing or the like, thereby manufacturing Fig.19C Secondary battery 980 is shown. A wound body 993 includes lead electrodes 997 and 998, and is impregnated with an electrolyte in a space surrounded by a film 981 and a film 982 having a recess.

[0236] The film 981 and the film 982 with the concave portion are, for example, made of metal materials such as aluminum or resin materials. When resin materials are used as the materials of the film 981 and the film 982 with the concave portion, the film 981 and the film 982 with the concave portion can be deformed when a force is applied from the outside, and a secondary battery with flexibility can be manufactured.

[0237] In addition, Fig.19B and Fig.19C Although an example using two films is shown in FIG. 1 , one film may be bent to form a space, and the wound body 993 may be accommodated in the space.

[0238] By using the positive electrode active material particles described in the above embodiment for the positive electrode 995 , it is possible to realize the secondary battery 980 which is less deteriorated and highly safe.

[0239] Although in FIG. 19A to FIG. 19C 20 shows an example of a secondary battery 980 including a wound body in a space formed by a film that will become an outer packaging body, but a secondary battery may also be used in which a plurality of rectangular positive electrodes, separators and negative electrodes are included in a space formed by a film that will become an outer packaging body as shown in FIG. 20 .

[0240] Fig. 20A The laminated secondary battery 500 shown includes: a positive electrode 503 including a positive electrode current collector 501 and a positive electrode active material layer 502; a negative electrode 506 including a negative electrode current collector 504 and a negative electrode active material layer 505; a separator 507; an electrolyte 508; and an outer package 509. The separator 507 is provided between the positive electrode 503 and the negative electrode 506 provided in the outer package 509. In addition, the outer package 509 is filled with the electrolyte 508. As the electrolyte 508, the electrolyte shown in Embodiment 4 can be used.

[0241] exist Fig. 20AIn the laminated secondary battery 500 shown, the positive electrode current collector 501 and the negative electrode current collector 504 are also used as terminals for electrical contact with the outside. Therefore, a part of the positive electrode current collector 501 and the negative electrode current collector 504 may be exposed to the outside of the outer packaging body 509. In addition, the lead electrode is ultrasonically welded to the positive electrode current collector 501 or the negative electrode current collector 504 using a lead electrode to expose the lead electrode to the outside of the outer packaging body 509, while the positive electrode current collector 501 and the negative electrode current collector 504 are not exposed to the outside of the outer packaging body 509.

[0242] In the laminated secondary battery 500, as the outer packaging body 509, for example, a laminate film with the following three-layer structure can be used: a highly flexible metal film of aluminum, stainless steel, copper, nickel, etc. is arranged on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc., and an insulating synthetic resin film of polyamide resin, polyester resin, etc. is arranged on the metal film as the outer surface of the outer packaging body.

[0243] in addition, Fig. 20B An example of a cross-sectional structure of a laminated secondary battery 500 is shown. For simplicity, Fig. 20A An example including two current collectors is shown, but an actual battery includes a plurality of electrode layers.

[0244] Fig. 20B An example of the secondary battery 500 includes 16 electrode layers. In addition, even if the secondary battery 500 includes 16 electrode layers, it has flexibility. Fig. 20B The structure shown has 8 layers of negative electrode current collector 504 and 8 layers of positive electrode current collector 501, a total of 16 layers. Fig. 20B The cross section of the extraction portion of the negative electrode is shown, and ultrasonic welding is performed on the 8-layer negative electrode current collector 504. Of course, the number of electrode layers is not limited to 16, and can be more than 16 or less than 16. When the number of electrode layers is large, a secondary battery with a larger capacity can be manufactured. In addition, when the number of electrode layers is small, a secondary battery with thinness and excellent flexibility can be manufactured.

[0245] Here, Fig.21 and Fig. 22 An example of an appearance diagram of a laminated secondary battery 500 is shown. Fig.21 and Fig. 22 The device includes: a positive electrode 503; a negative electrode 506; a separator 507; an outer package 509; a positive electrode lead electrode 510; and a negative electrode lead electrode 511.

[0246] Fig.23AThe appearance diagram of the positive electrode 503 and the negative electrode 506 is shown. The positive electrode 503 includes 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. In addition, the positive electrode 503 has an area (hereinafter referred to as a tab region) where a portion of the positive electrode current collector 501 is exposed. 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. In addition, the negative electrode 506 has an area where a portion of the negative electrode current collector 504 is exposed, namely, the tab region. The area or shape of the tab region of the positive electrode and the negative electrode is not limited to Fig.23A Example shown.

[0247] [Method for producing laminated secondary battery] Here, refer to Fig. 23B and Fig.23C Yes Fig.21 An example of a method for producing a laminated secondary battery whose appearance is shown in FIG. 1 is described below.

[0248] First, the negative electrode 506, the separator 507, and the positive electrode 503 are stacked. Fig. 23B The stacked negative electrode 506, separator 507, and positive electrode 503 are shown. Here, an example using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. Next, the tab regions of the positive electrode 503 are joined to each other, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. As the joining method, ultrasonic welding or the like can be used, for example. Similarly, the tab regions of the negative electrode 506 are joined to each other, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0249] Next, the negative electrode 506 , the separator 507 , and the positive electrode 503 are arranged on the outer packaging body 509 .

[0250] Below, as Fig.23C As shown, the outer package 509 is folded along the portion indicated by the dotted line. Then, the outer periphery of the outer package 509 is joined. As the joining method, for example, heat pressing or the like can be used. At this time, in order to inject the electrolyte 508 later, an area (hereinafter referred to as an introduction port) that is not joined to a portion (or one side) of the outer package 509 is provided.

[0251] Next, the electrolyte 508 is introduced into the inner side of the outer packaging body 509 from the introduction port provided in the outer packaging body 509. The electrolyte 508 is preferably introduced under a reduced pressure atmosphere or an inert atmosphere. Finally, the introduction port is joined. In this way, the secondary battery 500 of the laminated secondary battery can be manufactured.

[0252] By using the positive electrode active material particles described in the above embodiment for the positive electrode 503 , it is possible to realize the secondary battery 500 which is less deteriorated and highly safe.

[0253] [Bendable secondary battery] Next, an example of a flexible secondary battery will be described with reference to FIG. 24 and FIG. 25 .

[0254] Fig.24A A schematic top view of a flexible battery 250 is shown. Fig. 24B , Fig.24C , Fig.24D Along the Fig.24A Schematic cross-sectional view of the cutoff line C1-C2, the cutoff line C3-C4, and the cutoff line A1-A2 in FIG. The battery 250 includes an outer package 251, and a positive electrode 211a and a negative electrode 211b contained in the outer package 251. A lead 212a electrically connected to the positive electrode 211a and a lead 212b electrically connected to the negative electrode 211b extend outside the outer package 251. In addition, an electrolyte (not shown) is sealed in the area surrounded by the outer package 251 in addition to the positive electrode 211a and the negative electrode 211b.

[0255] The positive electrode 211 a and the negative electrode 211 b included in the battery 250 will be described with reference to FIG. 25 . Fig.25A It is a three-dimensional diagram illustrating the stacking order of the positive electrode 211 a , the negative electrode 211 b , and the separator 214 . Fig.25B It is a perspective view showing the lead wire 212a and the lead wire 212b in addition to the positive electrode 211a and the negative electrode 211b.

[0256] like Fig.25A As shown, the battery 250 includes a plurality of rectangular positive electrodes 211a, a plurality of rectangular negative electrodes 211b, and a plurality of separators 214. The positive electrode 211a and the negative electrode 211b respectively include a protruding tab portion and a portion other than the tab. A positive electrode active material layer is formed on the portion other than the tab of one surface of the positive electrode 211a, and a negative electrode active material layer is formed on the portion other than the tab of one surface of the negative electrode 211b.

[0257] The positive electrode 211 a and the negative electrode 211 b are stacked such that the surfaces of the positive electrode 211 a not having the positive electrode active material layer formed thereon are in contact with each other and the surfaces of the negative electrode 211 b not having the negative electrode active material layer formed thereon are in contact with each other.

[0258] In addition, a separator 214 is provided between the surface of the positive electrode 211a on which the positive electrode active material layer is formed and the surface of the negative electrode 211b on which the negative electrode active material layer is formed. For convenience, the separator 214 is indicated by a dotted line in FIG25 .

[0259] like Fig.25B As shown, a plurality of positive electrodes 211a and a lead wire 212a are electrically connected in a joint portion 215a. In addition, a plurality of negative electrodes 211b and a lead wire 212b are electrically connected in a joint portion 215b.

[0260] Next, refer to Fig. 24B , Fig.24C , Fig.24D , Fig.24E The outer package body 251 will be described.

[0261] The outer package 251 has a film shape and is folded in half in a manner that sandwiches the positive electrode 211a and the negative electrode 211b. The outer package 251 includes a folded portion 261, a pair of sealing portions 262, and a sealing portion 263. The pair of sealing portions 262 is provided in a manner that sandwiches the positive electrode 211a and the negative electrode 211b and can also be referred to as a side seal. In addition, the sealing portion 263 includes a portion that overlaps with the lead 212a and the lead 212b and can also be referred to as a top seal.

[0262] The outer package 251 preferably has a corrugated shape in which ridge lines 271 and valley lines 272 are alternately arranged in the portion overlapping the positive electrode 211a and the negative electrode 211b. In addition, the sealing portions 262 and 263 of the outer package 251 are preferably flat.

[0263] Fig. 24B It is a cross section cut at the portion overlapping with the edge line 271. Fig.24C This is a cross section cut at a portion overlapping with the valley bottom line 272 . Fig. 24B , Fig.24C All correspond to the cross sections of the battery 250 and the positive electrode 211 a and the negative electrode 211 b in the width direction.

[0264] Here, the end of the width direction of the negative electrode 211b, that is, the distance between the end of the negative electrode 211b and the sealing portion 262 is the distance La. When the battery 250 is deformed by bending or the like, as described later, the positive electrode 211a and the negative electrode 211b are deformed in a staggered manner in the length direction. At this time, when the distance La is too short, it is possible that the outer packaging body 251 and the positive electrode 211a and the negative electrode 211b are strongly rubbed, causing the outer packaging body 251 to be damaged. In particular, when the metal film of the outer packaging body 251 is exposed, the metal film may be corroded by the electrolyte. Therefore, it is preferred to set the distance La as long as possible. On the other hand, when the distance La is too long, the volume of the battery 250 will increase.

[0265] In addition, it is preferable that the distance La between the negative electrode 211 b and the sealing portion 262 is longer as the total thickness of the stacked positive electrode 211 a and negative electrode 211 b increases.

[0266] More specifically, when the total thickness of the stacked positive electrode 211a and negative electrode 211b is thickness t, the distance La is 0.8 times or more and 3.0 times or less, preferably 0.9 times or more and 2.5 times or less, and more preferably 1.0 times or more and 2.0 times or less of the thickness t. By making the distance La within the above range, a compact battery with high reliability against bending can be realized.

[0267] In addition, when the distance between a pair of sealing portions 262 is a distance Lb, it is preferred that the distance Lb is sufficiently larger than the width of the positive electrode 211a and the negative electrode 211b (here, the width Wb of the negative electrode 211b). Thus, when the battery 250 is repeatedly bent or deformed, even if the positive electrode 211a and the negative electrode 211b are in contact with the outer packaging body 251, a portion of the positive electrode 211a and the negative electrode 211b can be offset in the width direction, so that the positive electrode 211a and the negative electrode 211b can be effectively prevented from rubbing against the outer packaging body 251.

[0268] For example, the difference between the distance Lb between the pair of sealing portions 262 and the width Wb of the negative electrode 211b is 1.6 times or more and 6.0 times or less, preferably 1.8 times or more and 5.0 times or less, and more preferably 2.0 times or more and 4.0 times or less, the thickness t of the positive electrode 211a and the negative electrode 211b.

[0269] In other words, the distance Lb, the width Wb, and the thickness t preferably satisfy the following equation 1.

[0270] [Formula 1]

[0271] Here, a is 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, and more preferably 1.0 or more and 2.0 or less.

[0272] in addition, Fig.24D 21 is a cross section including the wire 212a, corresponding to the cross section in the length direction of the battery 250, the positive electrode 211a and the negative electrode 211b. Fig.24D As shown, it is preferable that the folded portion 261 includes a space 273 between the ends of the positive electrode 211 a and the negative electrode 211 b in the longitudinal direction and the outer package 251 .

[0273] Fig.24E A schematic cross-sectional view of the battery 250 when being bent is shown. Fig.24E Equivalent to following Fig.24A The section along the cutoff line B1-B2 in FIG.

[0274] When the battery 250 is bent, a portion of the outer packaging body 251 located on the outside of the bent portion is deformed to extend, and another portion of the outer packaging body 251 located on the inside of the bent portion is deformed to contract. More specifically, the portion of the outer packaging body 251 located on the outside of the bend is deformed in a manner that the wave amplitude is small and the wave period is large. On the other hand, the portion of the outer packaging body 251 located on the inside of the bend is deformed in a manner that the wave amplitude is large and the wave period is small. By deforming the outer packaging body 251 in the above manner, the stress applied to the outer packaging body 251 due to the bend can be alleviated, and thus the material constituting the outer packaging body 251 itself does not necessarily need to be stretchable. As a result, the battery 250 can be bent with less force without damaging the outer packaging body 251.

[0275] In addition, if Fig.24E As shown, when the battery 250 is bent, the positive electrode 211a and the negative electrode 211b are offset relative to each other. At this time, since the ends of the plurality of stacked positive electrodes 211a and negative electrodes 211b on one side of the sealing portion 263 are fixed by the fixing member 217, they are offset in a manner that the closer they are to the folded portion 261, the greater the offset amount. As a result, the stress applied to the positive electrode 211a and the negative electrode 211b can be alleviated, and the positive electrode 211a and the negative electrode 211b themselves do not necessarily need to be retractable. As a result, the battery 250 can be bent without damaging the positive electrode 211a and the negative electrode 211b.

[0276] In addition, since the space 273 is provided between the positive electrode 211 a and the negative electrode 211 b and the outer casing 251 , the ends of the positive electrode 211 a and the negative electrode 211 b located inside can be relatively offset so as not to contact the outer casing 251 during bending.

[0277] The battery 250 illustrated in Figures 24 and 25 is a battery that is not prone to damage to the outer package and the positive electrode 211a and the negative electrode 211b even when repeatedly bent and stretched, and the battery characteristics are not easily deteriorated. By using the positive electrode active material particles described in the above embodiment for the positive electrode 211a included in the battery 250, a secondary battery with less deterioration and high safety can be realized.

[0278] (Implementation 6) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is incorporated in an electronic device is described.

[0279] First, FIG26 shows an example of installing the flexible secondary battery described in part of Embodiment 4 in an electronic device. As electronic devices to which the flexible secondary battery is applied, for example, there can be cited television devices (also referred to as televisions or television receivers), displays for computers, etc., digital cameras, digital video cameras, digital photo frames, mobile phones (also referred to as mobile phones, mobile phone devices), portable game consoles, portable information terminals, sound reproduction devices, large game consoles such as pinball machines, etc.

[0280] Furthermore, the flexible secondary battery can be assembled along the curved surfaces of the inner or outer walls of houses and buildings, or the interior or exterior of automobiles.

[0281] Fig.26A 7400 includes a display portion 7402 incorporated in a housing 7401 , an operation button 7403 , an external connection port 7404 , a speaker 7405 , a microphone 7406 , and the like. The mobile phone 7400 also includes a secondary battery 7407 .

[0282] Fig.26B The figure shows a state where the mobile phone 7400 is bent. When the mobile phone 7400 is deformed by an external force and the entirety is bent, the secondary battery 7407 provided inside the mobile phone is also bent. Fig.26C The state of the secondary battery 7407 being bent at this time is shown. The secondary battery 7407 is a thin secondary battery. The secondary battery 7407 is fixed in a bent state. The secondary battery 7407 has a lead electrode electrically connected to a current collector.

[0283] Fig.26D An example of a bracelet-type display device is shown. A portable display device 7100 includes a housing 7101, a display portion 7102, operation buttons 7103, and a secondary battery 7104. Fig.26E A bent secondary battery 7104 is shown. When the bent secondary battery 7104 is put on the user's arm, the frame of the secondary battery 7104 is deformed, so that the curvature of a part or all of the secondary battery 7104 changes. The value of the degree of curvature of any point of the curve expressed by the value of the equivalent circle radius is the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, a part or all of the main surface of the frame or the secondary battery 7104 is deformed in a range where the radius of curvature is greater than 40 mm and less than 150 mm. As long as the radius of curvature in the main surface of the secondary battery 7104 is within the range of greater than 40 mm and less than 150 mm, high reliability can be maintained.

[0284] Fig.26FThe portable information terminal 7200 is an example of a wristwatch-type portable information terminal. The portable information terminal 7200 includes a housing 7201, a display portion 7202, a strap 7203, a buckle 7204, operation buttons 7205, an input / output terminal 7206, and the like.

[0285] Portable information terminal 7200 can execute various application programs such as mobile phone, e-mail, article reading and writing, music playing, network communication, computer games, etc.

[0286] The display surface of the display portion 7202 is curved, and display can be performed along the curved display surface. In addition, the display portion 7202 has a touch sensor, and operation can be performed by touching the screen with a finger or a stylus pen. For example, by touching an icon 7207 displayed on the display portion 7202, an application can be started.

[0287] In addition to time setting, operation button 7205 may have various functions such as power switch, wireless communication switch, setting and canceling silent mode, setting and canceling power saving mode, etc. For example, by using an operating system incorporated in portable information terminal 7200, the function of operation button 7205 can be freely set.

[0288] In addition, the portable information terminal 7200 can perform short-range wireless communication standardized by communication. For example, by communicating with a headset capable of wireless communication, a hands-free call can be made.

[0289] In addition, the portable information terminal 7200 has an input / output terminal 7206, and can directly send data to or receive data from other information terminals through a connector. In addition, charging can also be performed through the input / output terminal 7206. In addition, the charging operation can also be performed using wireless power supply without using the input / output terminal 7206.

[0290] The display unit 7202 of the portable information terminal 7200 includes a secondary battery according to one embodiment of the present invention. Fig.26E The secondary battery 7104 shown is incorporated in the housing 7201 , or the secondary battery 7104 in a bendable state is incorporated in the belt 7203 .

[0291] The portable information terminal 7200 preferably includes a sensor. For example, a fingerprint sensor, a pulse sensor, a human body sensor such as a temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, etc. are preferably installed as the sensor.

[0292] Figure 26GAn example of an armband-type display device is shown. The display device 7300 includes a display portion 7304 and a secondary battery of one embodiment of the present invention. The display device 7300 may include a touch sensor in the display portion 7304 and be used as a portable information terminal.

[0293] The display surface of the display portion 7304 is curved, and display can be performed along the curved display surface. In addition, the display device 7300 can change the display state by using short-range wireless communication or the like that has been standardized for communication.

[0294] The display device 7300 has an input / output terminal, and data can be directly sent to or received from other information terminals through a connector. In addition, charging can also be performed through the input / output terminal. In addition, charging can also be performed using wireless power supply instead of using the input / output terminal.

[0295] then, Fig.27A and Fig.27B An example of a tablet terminal that can be folded in half is shown. Fig.27A and Fig.27B The tablet terminal 9600 shown includes a housing 9630a, a housing 9630b, a movable portion 9640 connecting the housing 9630a and the housing 9630b, a display portion 9631, a display mode switching switch 9626, a power switch 9627, a power saving mode switching switch 9625, a fastener 9629, and an operation switch 9628. By using a flexible panel for the display portion 9631, a tablet terminal having a larger display portion can be realized. Fig.27A The tablet terminal 9600 is shown in an open state. Fig.27B The tablet terminal 9600 is shown in a closed state.

[0296] The tablet terminal 9600 includes a power storage body 9635 inside a housing 9630a and a housing 9630b. The power storage body 9635 is provided in the housing 9630a and the housing 9630b through a movable portion 9640 .

[0297] The display portion 9631 may be partially used as a touch screen area, and data can be input by touching displayed operation keys. In addition, keyboard buttons can be displayed on the display portion 9631 by touching a position of a keyboard display switching button on the touch screen with a finger, a stylus pen, or the like.

[0298] In addition, the display mode switching switch 9626 can switch the display direction such as vertical screen display and horizontal screen display and select the switching between black and white display and color display. The power saving mode switching switch 9625 can set the display brightness to the most suitable brightness according to the amount of external light detected by the built-in optical sensor of the tablet terminal 9600 during use. In addition to the optical sensor, the tablet terminal can also have other detection devices such as sensors for detecting inclination such as gyroscopes and acceleration sensors built in.

[0299] Fig.27B The tablet terminal is in a closed state and includes a housing 9630, a solar cell 9633, and a charge and discharge control circuit 9634 including a DCDC converter 9636. As the power storage body 9635, a secondary battery which is one embodiment of the present invention is used.

[0300] In addition, the tablet terminal 9600 can be folded in half, so the frame 9630a and the frame 9630b can be folded in an overlapping manner when not in use. By folding the frame 9630a and the frame 9630b, the display portion 9631 can be protected, and the durability of the tablet terminal 9600 can be improved. In addition, since the storage body 9635 of the secondary battery using one embodiment of the present invention has a large capacity and excellent cycle characteristics, a tablet terminal that can be used for a long period of time can be provided.

[0301] also, Fig.27A and Fig.27B The tablet terminal shown can also have the following functions: displaying various information (static images, dynamic images, text images, etc.); displaying the calendar, date or time, etc. on the display unit; performing touch input operations or touch inputs for editing the information displayed on the display unit; controlling processing through various software (programs), etc.

[0302] By using the solar cell 9633 mounted on the surface of the tablet terminal, power can be supplied to the touch screen, display portion, image signal processing portion, etc. Note that the solar cell 9633 can be provided on one surface or both surfaces of the housing 9630 and can efficiently charge the power storage body 9635.

[0303] In addition, refer to Fig.27C The block diagram shown is Fig.27B The structure and operation of the charge and discharge control circuit 9634 shown are explained. Fig.27C The solar cell 9633, the power storage body 9635, the DCDC converter 9636, the converter 9637, the switches SW1 to SW3, and the display portion 9631 are shown. The power storage body 9635, the DCDC converter 9636, the converter 9637, the switches SW1 to SW3 correspond to Fig.27B The charge and discharge control circuit 9634 is shown.

[0304] First, an example of operation when the solar cell 9633 generates power using external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 9636 so as to be a voltage for charging the power storage body 9635. When the display portion 9631 is operated using the power from the solar cell 9633, the switch SW1 is turned on, and the converter 9637 steps up or steps down the power to a voltage required for the display portion 9631. Alternatively, when the display portion 9631 is not displayed, the switch SW1 is turned off and the switch SW2 is turned on to charge the power storage body 9635.

[0305] Note that the solar cell 9633 is shown as an example of a power generation unit, but the present invention is not limited to this, and other power generation units such as a piezoelectric element or a thermoelectric conversion element (Peltier element) may be used to charge the power storage body 9635. For example, a non-contact power transmission module that can send and receive power in a wireless (non-contact) manner for charging may be used, or other charging methods may be combined for charging.

[0306] Fig.28 Examples of other electronic devices are shown. Fig.28 In the embodiment, the display device 8000 is an example of an electronic device using a secondary battery 8004 according to one embodiment of the present invention. Specifically, the display device 8000 is equivalent to a display device for receiving television broadcasts, and includes a frame 8001, a display unit 8002, a speaker unit 8003, and a secondary battery 8004. The secondary battery 8004 according to one embodiment of the present invention is arranged inside the frame 8001. The display device 8000 can receive power supply from a commercial power source and can use the power stored in the secondary battery 8004. Therefore, even when the power supply from the commercial power source cannot be received due to a power outage, the display device 8000 can be used by using the secondary battery 8004 according to one embodiment of the present invention as an uninterruptible power supply.

[0307] As the display unit 8002, a semiconductor display device such as a liquid crystal display device, a light-emitting device having a light-emitting element such as an organic EL element in each pixel, an electrophoretic display device, a DMD (digital micromirror device), a PDP (plasma display panel), and an FED (field emission display) can be used.

[0308] In addition, the display device includes all display devices for displaying information, such as a display device for a personal computer or a display device for displaying advertisements, in addition to a display device for receiving television broadcasts.

[0309] exist Fig.28 In the embodiment of the present invention, the mounted lighting device 8100 is an example of an electronic device using a secondary battery 8103 according to one embodiment of the present invention. Specifically, the lighting device 8100 includes a housing 8101, a light source 8102, and a secondary battery 8103. Fig.28 , the secondary battery 8103 is shown as being disposed inside a ceiling 8104 on which a housing 8101 and a light source 8102 are mounted, but the secondary battery 8103 may also be disposed inside the housing 8101. The lighting device 8100 can receive power supply from a commercial power source and use power stored in the secondary battery 8103. Therefore, even when power supply from a commercial power source cannot be received due to a power outage or the like, the lighting device 8100 can be used by using the secondary battery 8103 according to one embodiment of the present invention as an uninterruptible power source.

[0310] In addition, although Fig.28 The example shows a mounted lighting device 8100 installed on the ceiling 8104, but a secondary battery according to one embodiment of the present invention can be used in a mounted lighting device installed outside the ceiling 8104, such as a side wall 8105, a floor 8106 or a window 8107, and can also be used in a desktop lighting device.

[0311] An artificial light source that artificially obtains light using electric power can be used as the light source 8102. Specifically, examples of the artificial light source include discharge lamps such as incandescent bulbs and fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements.

[0312] exist Fig.28 In the embodiment of the present invention, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is an example of an electronic device using a secondary battery 8203 according to one embodiment of the present invention. Specifically, the indoor unit 8200 includes a housing 8201, an air outlet 8202, and a secondary battery 8203. Fig.28, the case where the secondary battery 8203 is provided in the indoor unit 8200 is illustrated, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner may receive power supply from a commercial power source, or may use power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when the power supply from the commercial power source cannot be received due to a power outage or the like, the air conditioner can be used by using the secondary battery 8203 according to one embodiment of the present invention as an uninterruptible power supply.

[0313] In addition, although Fig.28 Although a split-type air conditioner composed of an indoor unit and an outdoor unit is exemplified in the embodiment, the secondary battery according to one embodiment of the present invention may be used in an integrated air conditioner having the functions of an indoor unit and an outdoor unit in one housing.

[0314] exist Fig.28 In the embodiment, the electric refrigerator-freezer 8300 is an example of an electronic device using a secondary battery 8304 according to one embodiment of the present invention. Specifically, the electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator door 8302, a freezer door 8303, and a secondary battery 8304. Fig.28 In the embodiment, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator-freezer 8300 can receive power supply from a commercial power source, and can also use the power stored in the secondary battery 8304. Therefore, even when the electric power supply from the commercial power source cannot be received due to a power outage or the like, the electric refrigerator-freezer 8300 can be used by using the secondary battery 8304 according to one embodiment of the present invention as an uninterruptible power source.

[0315] In addition, during the time period when the electronic device is not used, especially during the time period when the ratio of the actual amount of power used to the total amount of power that can be supplied by the commercial power supply source (called the power usage rate) is low, the power is stored in the secondary battery, thereby suppressing the increase of the power usage rate in the time period other than the above time period. For example, in the case of an electric refrigerator-freezer 8300, power is stored in the secondary battery 8304 at night when the temperature is low and the refrigerator door 8302 or the freezer door 8303 is not opened and closed. In addition, during the daytime when the temperature is high and the refrigerator door 8302 or the freezer door 8303 is opened and closed, the secondary battery 8304 is used as an auxiliary power source, thereby suppressing the power usage rate during the daytime.

[0316] The secondary battery of one embodiment of the present invention is not limited to being installed in the above-mentioned electronic device, but can also be installed in all electronic devices. By adopting one embodiment of the present invention, a secondary battery with less degradation and high safety can be provided. Therefore, by installing the secondary battery of one embodiment of the present invention in the electronic device described in this embodiment, an electronic device with longer service life and high safety can be provided. This embodiment can be implemented in combination with other embodiments as appropriate.

[0317] (Implementation 7) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle is described.

[0318] When a secondary battery is installed in a vehicle, a new generation of clean energy vehicles such as a hybrid vehicle (HV), an electric vehicle (EV), or a plug-in hybrid vehicle (PHV or PHEV) can be realized.

[0319] FIG. 29 illustrates a vehicle using a secondary battery according to one embodiment of the present invention. Fig.29A The car 8400 shown is an electric car that uses an electric motor as a power source for traveling. Alternatively, the car 8400 is a hybrid car that can appropriately use an electric motor or an engine as a power source for traveling. By using a secondary battery of one embodiment of the present invention, a vehicle with a long driving distance can be realized. The secondary battery not only drives the electric motor 8406, but also supplies power to a light-emitting device such as a headlight 8401 or an interior light (not shown).

[0320] The secondary battery can also supply electric power to a display device such as a speedometer and a tachometer included in the automobile 8400. The secondary battery can also supply electric power to a semiconductor device such as a navigation system included in the automobile 8400.

[0321] exist Fig.29B In the illustrated automobile 8500 , a secondary battery 8024 included in the automobile 8500 can be charged by receiving electric power from an external charging device using a plug-in method or a contactless power supply method. Fig.29BThe case where a secondary battery 8024 installed in a car 8500 is charged from a ground-mounted charging device 8021 through a cable 8022 is shown. When charging, the specifications of the charging method or connector, etc., can appropriately adopt specifications such as CHAdeMO (registered trademark) or the combined charging system "Combined Charging System". As the charging device 8021, a charging station set up in a commercial facility or a home power supply can also be used. For example, by supplying power from the outside using plug-in technology, the secondary battery 8024 installed in the car 8500 can be charged. Charging can be performed by converting AC power into DC power through a conversion device such as an ACDC converter.

[0322] In addition, although not shown in the figure, it is also possible to install a power receiving device in the vehicle and supply power contactlessly from a power transmission device on the ground for charging. When a contactless power supply method is used, by assembling a power transmission device in a road or an outer wall, charging can be performed not only when the vehicle is parked but also when it is driving. In addition, the contactless power supply method can also be used to send and receive power between vehicles. Furthermore, a solar cell can be set on the outside of the vehicle to charge the secondary battery when the vehicle is parked or driving. Such contactless power supply can be achieved using an electromagnetic induction method or a magnetic field resonance method.

[0323] Fig.29C This is an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. Fig.29C The small motorcycle 8600 shown includes a secondary battery 8602, a rearview mirror 8601, and a turn signal light 8603. The secondary battery 8602 can supply power to the turn signal light 8603.

[0324] In addition, Fig.29C In the illustrated scooter 8600, the secondary battery 8602 can be stored in the under-seat storage section 8604. Even if the under-seat storage section 8604 is small, the secondary battery 8602 can be stored in the under-seat storage section 8604.

[0325] According to one embodiment of the present invention, a secondary battery with less degradation and high safety can be manufactured. For this reason, by mounting it on a vehicle, the reduction in driving distance and acceleration performance can be suppressed. In addition, a vehicle with high safety can be realized. In addition, the secondary battery installed in the vehicle can be used as a power supply source outside the vehicle. In this case, for example, the use of commercial power supplies during peak power demand periods can be avoided. If the use of commercial power supplies during peak power demand periods can be avoided, it will help save energy and reduce carbon dioxide emissions. In addition, since secondary batteries with less degradation and high safety can be used for a long time, the use of rare metals such as cobalt can be reduced.

[0326] This embodiment mode can be implemented in combination with other embodiment modes as appropriate. [Example 1]

[0327] In this example, LiMO2 produced by a production method according to one embodiment of the present invention is described. Figure 1 , Figure 4A And Table 2 illustrates the manufacturing method.

[0328] <Manufacturing of LiMO2 Samples> First, a mixture 902 containing magnesium and fluorine is prepared (steps S11 to S14). LiF and MgF2 are weighed under the condition that the molar ratio of LiF:MgF2 is 1:3, acetone is added as a solvent, and wet mixing and crushing are performed. Mixing and crushing are performed using a ball mill using zirconium balls at 400 rpm for 12 hours. The recycled materials are used to obtain a mixture 902.

[0329] Next, lithium cobalt oxide was prepared as a composite oxide containing lithium and cobalt. More specifically, CELLSEED C-10N manufactured by Nippon Chemical Industry Co., Ltd. was prepared (step S25).

[0330] Next, in step S31, the mixture 902 is weighed so that the atomic weight of magnesium is 0.5 mol% relative to the atomic weight of cobalt in the lithium cobalt oxide. The mixing is performed in a dry process. The mixing is performed in a dry process at 150 rpm for 1 hour using a ball mill using zirconium balls.

[0331] Next, the mixture 903 is placed in an alumina crucible (alumina crucible) and annealed in a muffle furnace (step S34). As shown in Table 2, the annealing conditions are different for each sample. The temperature is raised at 200°C / h and the temperature is lowered for more than 10 hours. The material after the heat treatment is recovered and screened (step S35) to obtain each sample (comparison sample 1 and sample 2) (step S36). In addition, FIG. 30 shows the crucible actually used. Fig. 30A The alumina crucible is shown before the lid is put on. Fig. 30B The alumina crucible is shown with the lid on.

[0332] Sample 2 was manufactured by the manufacturing method of one embodiment of the present invention. Comparative Sample 1 and Sample 2 differ in the conditions of the atmosphere containing LiF.

[0333] [Table 2]

[0334] <Annealing method of each LiMO2 sample> The steps to S33 are the same for all samples. The annealing method of S34 varies depending on the sample. Figure 4A A schematic diagram showing annealing is shown.

[0335] In Table 2, "sample weight" refers to the weight of the mixture 903 that has been annealed.

[0336] In Table 2, "annealing temperature" refers to the temperature at which annealing is performed, and "annealing time" refers to the time for which the annealing temperature is maintained.

[0337] In Table 2, "O2 condition" refers to a method of introducing O2 into the space 102 in the heating furnace, and "flow" refers to a case where annealing is performed while introducing O2 at a flow rate of 10 L / min.

[0338] In Table 2, "Atmosphere containing LiF" indicates whether the container 122 and the fluoride 906 (LiF in this example) are heated simultaneously when the mixture 903 is annealed, "No" indicates the case where only the mixture 903 is annealed without using the container 122 and the fluoride 906, and "Yes" indicates the case where the container 122, the fluoride 906, and the mixture 903 are heated simultaneously. In the case of "Yes", four containers 122 containing 1 g of LiF are arranged in the space 102 in the heating furnace.

[0339] <Manufacturing of battery packs> Next, each positive electrode was manufactured using the comparative sample 1 and sample 2 obtained above as the positive electrode active material. Each positive electrode was formed by mixing the positive electrode active material, AB and PVDF in a ratio of active material: AB: PVDF = 95:3:2 (weight ratio), and applying the slurry to the current collector. NMP was used as the solvent of the slurry.

[0340] After applying the slurry to the current collector, the solvent was evaporated. Then, the pressure was applied at 210 kN / m and then at 1467 kN / m. After the above steps, the positive electrode was obtained. The positive electrode loading was about 7 mg / cm 2 , the electrode density is >3.8g / cc.

[0341] A coin-type battery cell of the CR2032 type (20 mm in diameter and 3.2 mm in height) was produced using the formed positive electrode.

[0342] Lithium metal was used as the counter electrode.

[0343] The electrolyte in the electrolyte solution used 1 mol / L lithium hexafluorophosphate (LiPF6), and the electrolyte solution used ethylene carbonate (EC) and diethyl carbonate (DEC) in the ratio of EC:DEC = 3:7 (volume ratio). In addition, as a secondary battery to be evaluated for charge and discharge efficiency, 2 wt% of vinylene carbonate (VC) was added to the electrolyte solution.

[0344] As the separator, polypropylene with a thickness of 25 μm was used.

[0345] The positive electrode can and the negative electrode can are formed of stainless steel (SUS).

[0346] <Measurement of charge and discharge efficiency> The cycle characteristics of the battery packs manufactured using the obtained comparative sample and sample 2 were measured. CCCV charge (1.0 C, 4.6 V, end current 0.1 C) and CC discharge (1.0 C, 2.5 V) were performed at 25°C to evaluate the cycle characteristics. Fig.31 The results are shown.

[0347] from Fig.31 It is found that Sample 2 manufactured by one embodiment of the present invention exhibits better cycle characteristics than Comparative Sample 1. As described above, it is found that a positive electrode active material exhibiting good characteristics can be manufactured by annealing in an atmosphere containing LiF. [Explanation of symbols]

[0348] 100: heating furnace, 101: positive electrode active material, 100A-1: positive electrode active material, 100C: positive electrode active material, 102: space inside the heating furnace, 104: hot plate, 106: heater unit, 108: heat insulator, 110: gas supply line, 112: gate valve, 114: gas exhaust line, 116: container, 120: heating furnace, 122: container, 124: container, 130: heating furnace, 132: conveyor belt, 134: container, 140: heating furnace, 142: material introduction unit, 144: atmosphere control unit, 146: recovery unit, 200: active material layer, 201: graphene compound, 211a: positive electrode, 211b: negative electrode, 212a: wire, 212b: wire, 214: separator, 215a: joint, 215b: joint, 217: fixing member, 250: battery, 251: outer package, 261: folded portion, 262: sealing portion, 263: sealing portion, 271: ridge, 272: valley bottom line, 273: space, 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, 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, 508: electrolyte, 509: outer packaging body, 510: positive electrode lead electrode, 511: negative electrode lead electrode, 600: secondary battery, 601: positive electrode cover, 602: battery can, 603: positive terminal, 604: positive electrode, 605: separator, 606: negative electrode, 607: negative terminal, 608: insulating plate, 609: insulating plate, 611: PTC element, 612: safety valve mechanism, 613: conductive plate, 614: conductive plate, 615: module, 616: wire, 617: temperature control device, 900: circuit board, 902: mixture, 902-3: mixture, 903: mixture, 903-2: mixture, 903 -3: mixture, 904: positive electrode active material, 904-2: positive electrode active material, 904-3: positive electrode active material, 904-4: positive electrode active material, 905: mixture, 906: fluoride, 908: mixture, 909: mixture, 910: label, 911: terminal, 912: circuit, 913: secondary battery, 914: antenna, 915: antenna, 916: layer, 917: layer, 918: antenna, 919: terminal, 920: display device, 921: sensor, 922: terminal, 930: frame, 930a: frame, 930b: frame, 931: negative electrode, 932: positive electrode, 933: separator, 950: winding body, 951: terminal, 952: terminal,980: secondary battery, 981: film, 982: film, 993: wound body, 994: negative electrode, 995: positive electrode, 996: separator, 997: lead electrode, 998: lead electrode, 7100: portable display device, 7101: housing, 7102: display unit, 7103: operation button, 7104: secondary battery, 7200: portable information terminal, 7201: housing, 7202: display unit, 7203: belt, 7204: buckle, 7205: operation button, 7206: input / output terminal, 720 7: Icon, 7300: Display device, 7304: Display unit, 7400: Mobile phone, 7401: Housing, 7402: Display unit, 7403: Operation button, 7404: External connection port, 7405: Speaker, 7406: Microphone, 7407: Secondary battery, 8000: Display device, 8001: Housing, 8002: Display unit, 8003: Speaker unit, 8004: Secondary battery, 8021: Charging device, 8022: Cable, 8024: Secondary battery, 8100: Lighting device, 8101: Housing body, 8102: light source, 8103: secondary battery, 8104: ceiling, 8105: side wall, 8106: floor, 8107: window, 8200: indoor unit, 8201: frame, 8202: air outlet, 8203: secondary battery, 8204: outdoor unit, 8300: electric refrigerator-freezer, 8301: frame, 8302: refrigerator door, 8303: freezer door, 8304: secondary battery, 8400: automobile, 8401: headlight, 8406: electric engine, 8500: automobile, 8600: small motorcycle 、8601:Rearview mirror、8602:Secondary battery、8603:Direction lamp、8604:Underseat storage section、9600:Tablet terminal、9625:Switch、9626:Switch、9627:Power switch、9628:Operation switch、9629:Fasteners、9630:Frame、9630a:Frame、9630b:Frame、9631:Display section、9633:Solar cell、9634:Charge and discharge control circuit、9635:Electrical storage body、9636:DCDC converter、9637:Converter、9640:Movable section、

Claims

1. A method for producing a positive electrode active material, comprising the following steps: placing a first container containing a mixture of lithium oxide, fluoride and magnesium compound in a heating furnace and placing the fluoride outside the first container; and The heating furnace is heated at a temperature higher than a temperature at which the fluoride volatilizes or sublimates.

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