Method for preparing positive electrode active material

Abstract

Provided is a method for producing a highly purified positive electrode active material. Also, provided is a method for producing a positive electrode active material of which the crystal structure is less likely to be collapsed in spite of repeated charge and discharge cycles. This method for producing a positive electrode active material having lithium and a transition metal comprises: a first step for preparing a lithium compound, a phosphorus compound, and water; a second step for mixing the lithium compound, the phosphorus compound, and the water to form a first mixture; a third step for adding a first aqueous solution to the first mixture and adjusting the pH of the first mixture to form a second mixture; a fourth step for mixing an iron(II) compound with the second mixture to form a third mixture; a fifth step for heating the third mixture to form a fourth mixture; and a sixth step for filtering, cleaning, and drying the fourth mixture to obtain a positive electrode active material, wherein high-purity materials are used for the lithium compound, the phosphorus compound, the water, and the iron(II) compound.

Description

Technical Field

[0001] The present invention relates to a method for producing a positive electrode active material, or a method for producing a secondary battery, or an electronic device, a vehicle, etc. having a secondary battery.

[0002] The present invention relates to an article, a method, or a manufacturing method. Or, the present invention relates to a process, a machine, a manufacture, or a composition of matter. In particular, one aspect of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a storage device, their driving methods, their manufacturing methods, or their evaluation methods. In particular, one aspect of the present invention relates to a power storage device and its manufacturing method, or its evaluation method. Or, the present invention relates to a composite oxide and its manufacturing method. Or, the present invention relates to a positive electrode active material and its manufacturing method. Or, the present invention relates to a lithium ion battery. Or, the present invention relates to a battery control unit and an electronic device.

[0003] In the present specification, the semiconductor device refers to all devices that can function by utilizing semiconductor characteristics, and electro-optical devices, semiconductor circuits, and electronic devices are all semiconductor devices.

[0004] In the present specification, the electronic device refers to all devices having a positive electrode active material, a secondary battery, or a power storage device, and electro-optical devices having a positive electrode active material, a secondary battery, or a power storage device, information terminal devices having a power storage device, etc. are all electronic devices.

[0005] In the present specification, the power storage device refers to all elements and devices having a power storage function. For example, it includes power storage devices (also referred to as secondary batteries) such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors.

Background Art

[0006] In recent years, there has been a great deal of development on various energy storage devices, including lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. In particular, lithium-ion secondary batteries, with their high output and high energy density, are seeing rapidly expanding demand in conjunction with the development of the semiconductor industry. They are used in mobile information terminals such as mobile phones, smartphones, and notebook computers, as well as portable music players, digital cameras, medical equipment, and next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), and plug-in hybrid vehicles (PHV). As a rechargeable energy source, they have become indispensable to today's information society.

[0007] Examples of energy storage devices include those having electrodes that use LiFePO4 (lithium iron phosphate), a composite oxide, as the active material. Energy storage devices with electrodes using LiFePO4 have high thermal stability and good cycle characteristics.

[0008] Solubility can be increased in solutions under high temperature and high pressure compared to those at room temperature and atmospheric pressure. Furthermore, the dissolution and precipitation of materials can be controlled by adjusting the pH of the solution (Patent Document 1). Hydrothermal reactions are examples of reactions conducted under high temperature and high pressure.

[0009] For example, a hydrothermal method is used to produce complex oxides such as LiFePO4 (Patent Document 2).

[0010] By using the hydrothermal method, even materials that are poorly soluble in water at room temperature and pressure can be dissolved, enabling the synthesis of substances or crystal growth that cannot be obtained by production methods at room temperature and pressure. Furthermore, the hydrothermal method allows for the easy synthesis of single-crystal nanoparticles of the target substance.

[0011] In the hydrothermal method, for example, a solution containing raw materials is placed in a pressure-resistant container and treated by pressurization and heating. Subsequently, the treated solution is filtered to produce the desired compound. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] International Publication No. 2008 / 091578 [Patent Document 2] Japanese Patent Publication No. 2004-95385 [Overview of the project] [Problems that the invention aims to solve]

[0013] Because the positive electrode active material is one of the most expensive materials in lithium-ion secondary batteries, there is a high demand for improved performance (e.g., higher capacity, improved cycle characteristics, and enhanced reliability or safety). In particular, one challenge in improving performance is increasing the purity of the positive electrode active material in order to achieve higher capacity.

[0014] Therefore, one aspect of the present invention aims to provide a method for producing a highly purified positive electrode active material. Alternatively, it aims to provide a method for producing a positive electrode active material whose crystal structure is less likely to collapse even after repeated charging and discharging. Alternatively, it aims to provide a method for producing a positive electrode active material with excellent charge-discharge cycle characteristics. Alternatively, it aims to provide a method for producing a positive electrode active material with a large charge-discharge capacity. Alternatively, it aims to provide a secondary battery with high reliability or safety.

[0015] Furthermore, one aspect of the present invention aims to provide a novel substance, active material particles, secondary battery, energy storage device, or method for producing the same. Another aspect of the present invention aims to provide a method for producing a secondary battery having one or more characteristics selected from high purity, high performance, and high reliability, or to provide a secondary battery.

[0016] Furthermore, the description of these problems does not preclude the existence of other problems. Moreover, one aspect of the present invention does not need to solve all of these problems. Other problems will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other problems from the description in the specification, drawings, and claims. [Means for solving the problem]

[0017] One aspect of the present invention is a method for producing a positive electrode active material having lithium and a transition metal, comprising: a first step of preparing a lithium compound, a phosphorus compound, and water; a second step of mixing the lithium compound, the phosphorus compound, and the water to form a first mixture; a third step of adding a first aqueous solution to the first mixture to adjust the pH to form a second mixture; a fourth step of mixing an iron(II) compound to the second mixture to form a third mixture; a fifth step of heating the third mixture to form a fourth mixture; and filtering, washing, and drying the fourth mixture to obtain a composite oxide. The method comprises a sixth step, in which, in the first step, a material with a purity of 99.99% or higher is prepared as the lithium compound, a material with a purity of 99% or higher is prepared as the phosphorus compound, and pure water with a resistivity of 15 MΩ·cm or higher is prepared as the water; in the fourth step, a material with a purity of 99.9% or higher is used as the iron(II) compound; in the fourth step, the pH of the third mixture is 3.5 or higher and 5.0 or lower; and the heating in the fifth step is carried out at a pressure of 0.11 MPa or higher and 2 MPa or lower, and at a temperature of 150°C or higher and 250°C or lower, for 1 hour or higher and 10 hours or lower.

[0018] Furthermore, in the above embodiment, it is preferable to use lithium chloride as the lithium compound, phosphoric acid as the phosphorus compound, and iron(II) chloride tetrahydrate as the iron(II) compound.

[0019] Furthermore, in the above embodiment, it is preferable to use pure water with a resistivity of 15 MΩ·cm or more for cleaning. [Effects of the Invention]

[0020] According to one aspect of the present invention, a method for producing a highly purified positive electrode active material can be provided. Alternatively, a method for producing a positive electrode active material whose crystal structure is resistant to collapse even after repeated charging and discharging can be provided. Alternatively, a method for producing a positive electrode active material with excellent charge-discharge cycle characteristics can be provided. Alternatively, a method for producing a positive electrode active material with a large charge-discharge capacity can be provided. Alternatively, a highly reliable or safe secondary battery can be provided.

[0021] Furthermore, according to one aspect of the present invention, it is possible to provide novel materials, active material particles, secondary batteries, energy storage devices, or methods for producing the same. Also, according to one aspect of the present invention, it is possible to provide a method for producing a secondary battery having one or more characteristics selected from high purity, high performance, and high reliability, or a secondary battery.

[0022] Furthermore, the description of these effects does not preclude the existence of other effects. Moreover, one aspect of the present invention does not necessarily have to possess all of these effects. Other effects will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other effects from the description in the specification, drawings, and claims. [Brief explanation of the drawing]

[0023] Figure 1 illustrates an example of a method for producing a positive electrode active material according to one aspect of the present invention. Figure 2 illustrates an example of a method for producing a positive electrode active material according to one aspect of the present invention. Figures 3A and 3B are cross-sectional views of the active material layer when a graphene compound is used as the conductive agent. Figures 4A and 4B illustrate examples of secondary batteries. Figures 5A to 5C illustrate examples of secondary batteries. Figures 6A and 6B illustrate examples of secondary batteries. Figures 7A to 7C illustrate a coin-type rechargeable battery. Figures 8A to 8D illustrate a cylindrical secondary battery. Figures 9A and 9B illustrate examples of secondary batteries. Figures 10A to 10D illustrate examples of secondary batteries. Figures 11A and 11B illustrate an example of a secondary battery. Figure 12 illustrates an example of a secondary battery. Figures 13A to 13C illustrate a laminate-type secondary battery. Figures 14A and 14B illustrate a laminate-type secondary battery. Figure 15 shows the external appearance of a secondary battery. Figure 16 shows the external appearance of a secondary battery. Figures 17A to 17C illustrate the method for manufacturing a secondary battery. Figures 18A to 18E illustrate a rechargeable battery that can be bent. Figures 19A and 19B illustrate a rechargeable battery that can be bent. Figure 20 illustrates an example of an electronic device. Figures 21A to 21C illustrate an example of a vehicle. [Modes for carrying out the invention]

[0024] Embodiments of the present invention will be described in detail below with reference to the drawings. However, it will be readily apparent to those skilled in the art that the present invention is not limited to the following description, and its form and details can be modified in various ways. Furthermore, the present invention is not to be interpreted as being limited to the embodiments described below.

[0025] A secondary battery has, for example, a positive electrode and a negative electrode. The positive electrode is composed of a positive electrode active material. The positive electrode active material is, for example, a substance that performs a reaction that contributes to the charge and discharge capacity. However, the positive electrode active material may also contain a portion of substances that do not contribute to the charge and discharge capacity.

[0026] In this specification, the positive electrode active material of one aspect of the present invention may be expressed as a positive electrode material, a positive electrode material for secondary batteries, a composite oxide, etc. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a compound. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a composition. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a composite.

[0027] Furthermore, in this specification, the term "particle" is not limited to spherical shapes (circular cross-sections), but may include elliptical, rectangular, trapezoidal, triangular, rounded quadrilateral, asymmetrical shapes, and other cross-sectional shapes of individual particles. Individual particles may also be irregular in shape.

[0028] Furthermore, in this specification, a secondary battery having high-purity properties refers to a battery in which at least one or more materials selected from the positive electrode, negative electrode, separator, and electrolyte have high purity. Furthermore, a highly purified positive electrode active material refers to a positive electrode active material in which the materials contained therein have high purity. For example, the purity of the materials that can be used in the positive electrode active material of one aspect of the present invention is 3N (99.9%) or higher for Li2CO3, preferably 4N (99.99%) or higher, more preferably 4N5 (99.995%) or higher, and even more preferably 5N (99.999%) or higher. Also, the purity of LiCl is 3N (99.9%) or higher, preferably 4N (99.99%) or higher, more preferably 4N5 (99.995%) or higher, and even more preferably 5N (99.999%) or higher. Furthermore, the NH4H2PO4 content is 2N (99%) or higher, preferably 3N (99.9%) or higher, more preferably 4N (99.99%) or higher, and even more preferably 4N5 (99.995%) or higher. Also, the FeCl content is 3N (99.9%) or higher, preferably 4N (99.99%) or higher, more preferably 4N5 (99.995%) or higher, and even more preferably 5N (99.999%) or higher. In the case of H3PO4, the content of impurity elements other than H, P, and O in the aqueous solution is less than 1%, preferably less than 0.1%, more preferably less than 0.01%, and even more preferably less than 0.005%. In other words, the purity of H3PO4 is 2N (99%) or higher, preferably 3N (99.9%) or higher, more preferably 4N (99.99%) or higher, and even more preferably 4N5 (99.995%) or higher.

[0029] (Embodiment 1) This embodiment describes a method for producing a positive electrode active material according to one aspect of the present invention.

[0030] [Method for preparing positive electrode active material] A positive electrode active material according to one aspect of the present invention is prepared using a liquid-phase method, more preferably a hydrothermal method.

[0031] A method for producing a positive electrode active material, which is one aspect of the present invention, will be explained with reference to Figure 1.

[0032] In step S21a, lithium compound 803 is prepared. Also, in step S21b, phosphorus compound 804 is prepared.

[0033] Here, let x:y:z be the atomic ratio of lithium, transition metal M, and phosphorus in the composite oxide that is preferably obtained as the positive electrode active material 100, as described later. To obtain LiMPO4, for example, x:y:z = 1:1:1 may be used.

[0034] Representative examples of lithium compounds include lithium chloride (LiCl), lithium acetate (CH3COOLi), lithium oxalate ((COOLi)2), lithium carbonate (Li2CO3), and lithium hydroxide monohydrate (LiOH·H2O).

[0035] Representative examples of phosphorus compounds include phosphoric acid such as orthophosphoric acid (H3PO4), ammonium hydrogen phosphate such as diammonium hydrogen phosphate ((NH4)2HPO4) and ammonium dihydrogen phosphate (NH4H2PO4), and so on.

[0036] Next, in step S21c, solvent 805 is prepared. It is preferable to use water as solvent 805. Alternatively, a mixture of water and another liquid may be used as solvent 805. For example, water and alcohol may be mixed. Here, the reaction products of lithium compound 803 and phosphorus compound 804, or lithium compound 803 and phosphorus compound 804, may have different solubility in water and alcohol. Using alcohol may result in smaller particle sizes. Also, using alcohol, which has a lower boiling point than water, may make it easier to increase the pressure in step S53, which will be described later.

[0037] When water is used as solvent 805, it is preferable to use pure water with a resistivity of 1 MΩ·cm or higher, more preferably 10 MΩ·cm or higher, and even more preferably 15 MΩ·cm or higher, and with few impurities. By using high-purity materials, the capacity of the secondary battery can be increased and / or the reliability of the secondary battery can be improved.

[0038] Next, in step S31, the lithium compound 803, the phosphorus compound 804, and the solvent 805 are mixed to obtain the mixture 811 of step S32. The mixing in step S31 can be carried out in an atmosphere such as air or an inert gas. For example, nitrogen can be used as the inert gas. Here, as an example, the lithium compound 803 prepared in step S21a, the phosphorus compound 804 prepared in step S21b, and the solvent 805 prepared in step S21c are mixed in an air atmosphere. For example, the lithium compound 803 prepared in step S21a and the phosphorus compound 804 prepared in step S21b are added to the solvent 805 prepared in step S21c to form the mixture 811 of step S32.

[0039] In the mixture 811 of step S32, lithium compound 803, phosphorus compound 804, and the reaction product of lithium compound 803 and phosphorus compound 804 may precipitate in the mixture 811, but some will dissolve in the solvent without precipitation, i.e., they will exist in the mixture 811 as ions. Here, if the pH of the mixture 811 is low, the reaction products may dissolve easily in the solvent, and if it is high, the reaction products may precipitate easily.

[0040] Alternatively, instead of mixing lithium compound 803 and phosphorus compound 804 to form the mixture 811 in step S32, a compound containing phosphorus and lithium, such as Li3PO4, Li2HPO4, or LiH2PO4, may be prepared and added to the solvent to form the mixture 811 in step S32.

[0041] If the mixture 811 in step S32 is an aqueous solution, the pH of the mixture 811 is determined by the type and degree of dissociation of the salts contained in the mixture 811. Therefore, the pH of the mixture 811 changes depending on the lithium compound 803 and phosphorus compound 804 used as raw materials. For example, if lithium chloride is used as lithium compound 803 and orthophosphoric acid as phosphorus compound 804, the mixture 811 in step S32 tends to be strongly acidic. Also, for example, if lithium hydroxide monohydrate is used as lithium compound 803, the mixture 811 in step S32 tends to be alkaline.

[0042] Next, in step S33, solution P812 is prepared. Then, in step S35, the mixture 811 from step S32 and the solution P812 prepared in step S33 are mixed to form the mixture 821 from step S41. Here, the pH of the resulting mixture 821 from step S41 and the mixture 831 from step S52 obtained later can be adjusted by adjusting the amount or concentration of the solution P812 added. In step S35, for example, solution P812 can be added dropwise while measuring the pH of the mixture 811 from step S32. As solution P812, an alkaline solution or an acidic solution can be used depending on the pH of the mixture 811 from step S32. Using a weakly alkaline or weakly acidic solution may make it easier to adjust the pH. For example, the pH of an alkaline solution should be between 8 and 12. The pH of an acidic solution should be between 2 and 6. For example, ammonia water can be used as an alkaline solution. It is preferable to determine the pH and mixing amount of solution P812 so that the mixture 831 in step S52, described later, is acidic or neutral.

[0043] Next, in step S42, a transition metal M source 822 is prepared. As the transition metal M source 822, one or more of iron(II) compounds, manganese(II) compounds, cobalt(II) compounds, and nickel(II) compounds (hereinafter referred to as M(II) compounds) can be used.

[0044] Furthermore, it is preferable to use a high-purity material as the transition metal M source used in the synthesis. Specifically, the purity of the material should be 3N (99.9%) or higher, preferably 4N (99.99%) or higher, more preferably 4N5 (99.995%) or higher, and even more preferably 5N (99.999%) or higher. By using a high-purity material, the capacity of the secondary battery can be increased and / or the reliability of the secondary battery can be improved.

[0045] In addition, it is preferable that the transition metal M source has high crystallinity. For example, it is preferable that the transition metal M source has single crystal grains. The crystallinity of the transition metal M source can be evaluated from, for example, TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle scattering annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. Furthermore, X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as criteria for evaluating the crystallinity of the transition metal M source. Note that the above evaluation of crystallinity can be applied not only to the transition metal M source but also to the evaluation of the crystallinity of primary or secondary particles.

[0046] Representative examples of iron(II) compounds include iron chloride tetrahydrate (FeCl2·4H2O), iron sulfate heptahydrate (FeSO4·7H2O), and iron acetate (Fe(CH3COO)2).

[0047] Representative examples of manganese(II) compounds include manganese chloride tetrahydrate (MnCl2·4H2O), manganese sulfate monohydrate (MnSO4·H2O), and manganese acetate tetrahydrate (Mn(CH3COO)2·4H2O).

[0048] Representative examples of cobalt(II) compounds include cobalt chloride hexahydrate (CoCl2·6H2O), cobalt sulfate heptahydrate (CoSO4·7H2O), and cobalt acetate tetrahydrate (Co(CH3COO)2·4H2O).

[0049] Representative examples of nickel(II) compounds include nickel chloride hexahydrate (NiCl2·6H2O), nickel sulfate hexahydrate (NiSO4·6H2O), and nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O).

[0050] In step S42, the above compound may be prepared as an aqueous solution as the transition metal M source 822. When prepared as an aqueous solution, it is desirable that the water used is pure water with a low percentage of impurities, preferably with a resistivity of 1 MΩ·cm or more, more preferably 10 MΩ·cm or more, and even more preferably 15 MΩ·cm or more.

[0051] Next, in step S51, the mixture 821 from step S41 and the transition metal M source 822 are mixed to obtain the mixture 831 from step S52.

[0052] In step S51, the concentration of the mixture 831 in step S52 can be reduced by adding a solvent. For example, in step S51, the mixture 821 from step S41, the transition metal M source 822, and the solvent can be mixed to produce the mixture 831 in step S52.

[0053] Next, in step S53, the mixture 831 from step S52 is placed in a heat-resistant and pressure-resistant container such as an autoclave, and heated at a temperature of 100°C to 350°C, more preferably greater than 100°C and less than 200°C, and at a pressure of 0.11 MPa to 100 MPa, more preferably 0.11 MPa to 2 MPa for 0.5 hours to 24 hours, more preferably 1 hour to 10 hours, and even more preferably 1 hour to less than 5 hours, and then cooled. Subsequently, in step S54, the solution in the heat-resistant and pressure-resistant container is filtered and washed with water. Next, in step S55, after drying, it is recovered to obtain the positive electrode active material 100 from step S56.

[0054] Note that, as the water used in step S54, it is preferably pure water with a specific resistance of 1 MΩ·cm or more, more preferably a specific resistance of 10 MΩ·cm or more, and even more preferably a specific resistance of 15 MΩ·cm or more, and it is desirable that the pure water has few impurities. By washing with high-purity pure water, a high-purity positive electrode active material 100 can be obtained, and the capacity of the secondary battery can be increased and / or the reliability of the secondary battery can be enhanced.

[0055] Here, as the positive electrode active material 100, it is preferable to obtain a composite oxide, for example, LiMPO4 (M is one or more of Fe(II), Ni(II), Co(II), Mn(II)). Depending on the type of M(II) compound, LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, LiFe a Ni b PO4, LiFe a Co b PO4, LiFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4 (a + b is 1 or less, 0 < a < 1, 0 < b < 1), LiFe c Ni d Co e PO4, LiFe c Ni d Mn e PO4, LiNi c Co d Mn e PO4 (c + d + e is 1 or less, 0 < c < 1, 0 < d < 1, 0 < e <) 1), LiFe f Ni g Co h Mn i PO4 (f + g + h + i is 1 or less, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), etc. can be obtained as appropriate. Further, the composite oxide obtained by this embodiment may be a single crystal grain.

[0056] The crystal structure of the positive electrode active material 100 can be determined by performing crystal analysis, such as XRD or electron diffraction. Crystal analysis of the positive electrode active material 100 may yield a crystal structure belonging to the space group Pnma. For example, LiMPO4, which has an olivine-type crystal structure, belongs to the space group Pnma.

[0057] As described above, in one embodiment of the present invention, high-purity materials are used as raw materials during synthesis, and the positive electrode active material is produced in a process that minimizes the inclusion of impurities during synthesis. The positive electrode active material obtained by such a method is a material with a low impurity concentration, in other words, a highly purified material. Furthermore, the positive electrode active material obtained by such a method is a material with high crystallinity. Moreover, the positive electrode active material obtained by the method of producing a positive electrode active material according to one embodiment of the present invention can increase the capacity of a secondary battery and / or improve the reliability of a secondary battery.

[0058] This embodiment can be used in appropriate combination with other embodiments.

[0059] (Embodiment 2) This embodiment describes a method for producing a positive electrode active material according to one aspect of the present invention.

[0060] [Method for preparing positive electrode active material] A positive electrode active material according to one aspect of the present invention is prepared using a liquid-phase method, more preferably a hydrothermal method.

[0061] A method for producing a positive electrode active material, which is one aspect of the present invention, will be explained with reference to Figure 2.

[0062] In step S21a, prepare a solution 806 containing lithium. In step S21b, prepare a solution 807 containing phosphorus.

[0063] The lithium-containing solution 806 can be prepared by dissolving a lithium compound in a solvent. One or more of the following can be used as the lithium compound: lithium hydroxide monohydrate (LiOH·H2O), lithium chloride (LiCl), lithium carbonate (Li2CO3), lithium acetate (CH3COOLi), and lithium oxalate ((COOLi)2). Water can be used as the solvent for dissolving the lithium compound. When water is used as the solvent, it is preferable to use pure water with a resistivity of 1 MΩ·cm or higher, more preferably 10 MΩ·cm or higher, and even more preferably 15 MΩ·cm or higher, with low impurity content. Using high-purity materials can increase the capacity of the secondary battery and / or improve its reliability.

[0064] The phosphorus-containing solution 807 can be prepared by dissolving a phosphorus compound in a solvent. As the phosphorus compound, one or more of the following can be used: phosphoric acid such as orthophosphoric acid (H3PO4), or ammonium hydrogen phosphate such as diammonium hydrogen phosphate ((NH4)2HPO4) or ammonium dihydrogen phosphate (NH4H2PO4). Water can be used as the solvent for dissolving the phosphorus compound. When water is used as the solvent, it is preferable to use pure water with a resistivity of 1 MΩ·cm or higher, more preferably 10 MΩ·cm or higher, and even more preferably 15 MΩ·cm or higher, with low impurity content. Using high-purity materials can increase the capacity of the secondary battery and / or improve its reliability.

[0065] Next, in step S31, the lithium-containing solution 806 and the phosphorus-containing solution 807 are mixed to obtain the mixture 811 of step S32. The mixing in step S31 can be carried out under an atmosphere such as air or an inert gas. For example, nitrogen can be used as the inert gas. Here, as an example, the lithium-containing solution 806 prepared in step S21a and the phosphorus-containing solution 807 prepared in step S21b are mixed under an atmosphere of air.

[0066] Alternatively, instead of mixing the lithium-containing solution 806 and the phosphorus-containing solution 807 to form the mixture 811 in step S32, a compound containing phosphorus and lithium, such as Li3PO4, Li2HPO4, or LiH2PO4, may be prepared and added to the solvent to form the mixture 811 in step S32.

[0067] Next, in step S33, a solution 813 containing the transition metal M is prepared.

[0068] Solution 813 containing the transition metal M can be prepared by dissolving the transition metal M compound in a solvent. One or more of the following can be used as the transition metal M compound: iron(II) compounds, manganese(II) compounds, cobalt(II) compounds, and nickel(II) compounds (hereinafter referred to as M(II) compounds). Water can be used as the solvent for dissolving the transition metal M compound. When water is used as the solvent, it is preferable to use pure water with a resistivity of 1 MΩ·cm or higher, more preferably 10 MΩ·cm or higher, and even more preferably 15 MΩ·cm or higher, with low impurity content. Using high-purity materials can increase the capacity of the secondary battery and / or improve its reliability.

[0069] Furthermore, it is preferable to use a high-purity material as the transition metal M compound used in the synthesis. Specifically, the purity of the material should be 3N (99.9%) or higher, preferably 4N (99.99%) or higher, more preferably 4N5 (99.995%) or higher, and even more preferably 5N (99.999%) or higher. By using a high-purity material, the capacity of the secondary battery can be increased and / or the reliability of the secondary battery can be improved.

[0070] In addition, it is preferable that the transition metal M compound has high crystallinity. For example, it is preferable that the transition metal compound has single crystal grains. The crystallinity of the transition metal compound can be evaluated from, for example, TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle scattering annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. Furthermore, X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as criteria for evaluating the crystallinity of the transition metal M compound. Note that the above evaluation of crystallinity can be applied not only to the transition metal M compound but also to the evaluation of the crystallinity of primary or secondary particles.

[0071] Representative examples of iron(II) compounds include iron chloride tetrahydrate (FeCl2·4H2O), iron sulfate heptahydrate (FeSO4·7H2O), and iron acetate (Fe(CH3COO)2).

[0072] Representative examples of manganese(II) compounds include manganese chloride tetrahydrate (MnCl2·4H2O), manganese sulfate monohydrate (MnSO4·H2O), and manganese acetate tetrahydrate (Mn(CH3COO)2·4H2O).

[0073] Representative examples of cobalt(II) compounds include cobalt chloride hexahydrate (CoCl2·6H2O), cobalt sulfate heptahydrate (CoSO4·7H2O), and cobalt acetate tetrahydrate (Co(CH3COO)2·4H2O).

[0074] Representative examples of nickel(II) compounds include nickel chloride hexahydrate (NiCl2·6H2O), nickel sulfate hexahydrate (NiSO4·6H2O), and nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O).

[0075] Next, in step 35, the mixture 811 from step S32 and the solution 813 containing the transition metal M are mixed to obtain the mixture 823 from step S41.

[0076] Here, let x:y:z be the atomic ratio of lithium, transition metal M, and phosphorus in the composite oxide that is preferably obtained as the positive electrode active material 100, as described later. To obtain LiMPO4, for example, x:y:z = 1:1:1 may be used.

[0077] As a method of mixing in step S35, the mixture 823 of step S41 can be prepared by dropping a small amount of solution 813 containing the transition metal M onto the mixture 811 of step S32 placed in a container. During mixing, it is desirable to stir the solution in the container and the solution used for mixing, and it is also desirable to remove dissolved oxygen by N2 bubbling.

[0078] Alternatively, as a method of mixing in step S35, the mixture 811 from step S32 can be added dropwise in small amounts to the solution 813 containing the transition metal M in a container to prepare the mixture 823 from step S41. During mixing, it is desirable to stir the solution in the container and the solution used for mixing, and it is also desirable to remove dissolved oxygen by N2 bubbling.

[0079] In step S35, the concentration of the mixture 823 from step S41 can be adjusted by adding a solvent. For example, in step S35, the mixture 811 from step S32, the solution 813 containing the transition metal M, and the solvent can be mixed to prepare the mixture 823 from step S41. When water is used as the solvent, it is preferable to use pure water with a low resistivity, preferably with a resistivity of 1 MΩ·cm or more, more preferably with a resistivity of 10 MΩ·cm or more, and even more preferably with a resistivity of 15 MΩ·cm or more.

[0080] Next, in step S53, the mixture 823 from step S41 is placed in a heat-resistant and pressure-resistant container such as an autoclave, and heated at a temperature of 100°C to 350°C, more preferably greater than 100°C and less than 200°C, and at a pressure of 0.11 MPa to 100 MPa, more preferably 0.11 MPa to 2 MPa for 0.5 hours to 24 hours, more preferably 1 hour to 10 hours, and even more preferably 1 hour to less than 5 hours, and then cooled. Subsequently, in step S54, the solution in the heat-resistant and pressure-resistant container is filtered and washed with water. Next, in step S55, after drying, it is recovered to obtain the positive electrode active material 100 from step S56.

[0081] Furthermore, the water used in step S54 is preferably pure water with a resistivity of 1 MΩ·cm or more, more preferably 10 MΩ·cm or more, and even more preferably 15 MΩ·cm or more, and with few impurities. Washing with high-purity pure water makes it possible to obtain a high-purity positive electrode active material 100, which can increase the capacity of the secondary battery and / or improve the reliability of the secondary battery.

[0082] Here, it is preferable that the positive electrode active material 100 is a composite oxide, for example, LiMPO4 (where M is one or more of Fe(II), Ni(II), Co(II), and Mn(II)). Depending on the type of M(II) compound, LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, LiFe a Ni b PO4, LiFe a Co b PO4, LiFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4(a+b is less than or equal to 1, 0 <a<1、0<b<1)、LiFe c Ni d Co e PO4, LiFe c Ni d Mn e PO4, LiNi c Co dMn e PO4 (where c + d + e is less than or equal to 1, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO4 (where f + g + h + i is less than or equal to 1, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), etc. can be obtained as appropriate. Also, the composite oxide obtained by this embodiment may be a single crystal grain.

[0083] By performing crystal structure analysis such as XRD or electron beam diffraction on the positive electrode active material 100 with respect to 100, the crystal structure can be specified. By performing crystal structure analysis on the positive electrode active material 100, a crystal structure belonging to the space group Pnma may be obtained. Here, LiMPO4 having an olivine-type crystal structure belongs to, for example, the space group Pnma.

[0084] As described above, in one aspect of the present invention, a high-purity material is used as the raw material used in the synthesis, and the positive electrode active material is produced in a process with less impurity contamination during the synthesis. The positive electrode active material obtained by such a method for producing a positive electrode active material is a material with a low impurity concentration, or in other words, a highly purified material. Also, the positive electrode active material obtained by such a method for producing a positive electrode active material is a material having high crystallinity. Further, the positive electrode active material obtained by the method for producing a positive electrode active material according to one aspect of the present invention can increase the capacity of the secondary battery and / or improve the reliability of the secondary battery.

[0085] This embodiment can be used in appropriate combination with other embodiments.

[0086] (Embodiment 3) In this embodiment, an example of a secondary battery according to one aspect of the present invention will be described using FIGS. 3 to 6.

[0087] <Configuration Example 1 of Secondary Battery> Hereinafter, a secondary battery in which a positive electrode, a negative electrode, and an electrolyte are wrapped in an exterior body will be described as an example.

[0088] 〔Positive Electrode〕 The positive electrode has a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer has a positive electrode active material and may have a conductive agent and a binder. As the positive electrode active material, any one or a plurality of the positive electrode active materials 100 produced using the production method described in the previous embodiment can be used.

[0089] Also, the positive electrode active material 100 described in the previous embodiment may be mixed with another positive electrode active material and used.

[0090] As another positive electrode active material, it is preferable to mix a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4 with lithium nickelate (LiNiO2 and / or LiNi 1-x M x O2 (0 < x < 1) (M = Co, Al, etc.)). By adopting such a configuration, the characteristics of the secondary battery can be improved.

[0091] Also, as another positive electrode active material, a composition formula Li a Mn b M c O dA lithium manganese composite oxide can be used, which can be represented as follows: Here, element M is preferably a metallic element selected from lithium and manganese, or silicon or phosphorus, and more preferably nickel. When measuring the entire particle of lithium manganese composite oxide, <a / (b+c)<2、かつc>it is preferable that the discharge is 0 0 and 0.26 ≤ (b+c) / d < 0.5. The composition of metals, silicon, phosphorus, etc., of the entire particle of lithium manganese composite oxide can be measured, for example, using ICP-MS (inductively coupled plasma mass spectrometer). The oxygen composition of the entire particle of lithium manganese composite oxide can be measured, for example, using EDX (energy dispersive X-ray spectrometry). It can also be determined by using valence evaluation of molten gas analysis and XAFS (X-ray absorption fine structure) analysis in combination with ICPMS analysis. Lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may also contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, and phosphorus.

[0092] The following describes an example of a cross-sectional configuration when a graphene compound is used as a conductive agent in the active material layer 200.

[0093] Figure 3A shows a longitudinal cross-sectional view of the active material layer 200. The active material layer 200 includes granular positive electrode active material 100, a graphene compound 201 as a conductive agent, and a binder (not shown).

[0094] ​In this specification, graphene compound 201 includes graphene, multilayer graphene, multigraphene, graphene oxide, multilayer graphene oxide, multigraphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, reduced multigraphene oxide, graphene quantum dots, etc. Graphene compound 201 refers to a material having carbon, having a plate-like or sheet-like shape, and possessing a two-dimensional structure formed by a six-membered carbon ring. This two-dimensional structure formed by the six-membered carbon ring may also be called a carbon sheet. Graphene compound 201 may have functional groups. Furthermore, graphene compound 201 preferably has a bent shape. Also, graphene compound 201 may be rolled up to resemble carbon nanofibers.

[0095] In this specification, graphene oxide refers to a material having carbon and oxygen, having a sheet-like structure, and possessing functional groups, particularly epoxy groups, carboxyl groups, or hydroxyl groups.

[0096] In this specification, reduced graphene oxide refers to a material having carbon and oxygen, having a sheet-like shape, and possessing a two-dimensional structure formed by a six-membered carbon ring. It may also be called a carbon sheet. Reduced graphene oxide can function as a single sheet, but multiple sheets may be stacked. It is preferable that reduced graphene oxide has a portion where the carbon concentration is greater than 80 atomic%, and the oxygen concentration is between 2 atomic% and 15 atomic%. With such carbon and oxygen concentrations, it can function as a highly conductive material even in small amounts. It is also preferable that reduced graphene oxide has a G / D intensity ratio of 1 or more in the Raman spectrum. Reduced graphene oxide with such an intensity ratio can function as a highly conductive material even in small amounts.

[0097] In some cases, pores can be created in graphene compound 201 by reducing graphene oxide.

[0098] Alternatively, a material may be used in which the ends of graphene compound 201 are terminated with fluorine.

[0099] Furthermore, it is preferable that the graphene compound 201 has pores in a portion of the carbon sheet. By providing pores in a portion of the carbon sheet of the graphene compound 201 that allow carrier ions such as lithium ions to pass through, the insertion and removal of carrier ions becomes easier on the surface of the active material covered with the graphene compound 201, thereby improving the rate characteristics of the secondary battery. The pores provided in a portion of the carbon sheet may be called voids, defects, or cavities.

[0100] Furthermore, the graphene compound 201 preferably has pores formed by multiple carbon atoms. It is also preferable that these multiple carbon atoms are cyclically bonded, and that one or more of these cyclically bonded carbon atoms are terminated by fluorine atoms. Fluorine has high electronegativity and readily carries a negative charge. When a positively charged lithium ion approaches, an interaction occurs, stabilizing the energy and lowering the barrier energy for lithium ions to pass through the pores. Therefore, because the pores of the graphene compound 201 contain fluorine atoms, lithium ions can easily pass through even small pores, and a graphene compound 201 with excellent conductivity can be realized.

[0101] In the longitudinal section of the active material layer 200, as shown in Figure 3A, sheet-like graphene compounds 201 are dispersed approximately uniformly within the active material layer 200. In Figures 3A and 3B, the graphene compounds 201 are schematically represented by thick lines, but in reality, they are thin films with a single or multilayer thickness of carbon molecules. Multiple graphene compounds 201 are formed to partially cover multiple granular positive electrode active materials 100, or to adhere to the surface of multiple granular positive electrode active materials 100, and are therefore in surface contact with each other.

[0102] Here, multiple graphene compounds can bond together to form a mesh-like graphene compound sheet (hereinafter referred to as a graphene compound net or graphene net). When the active material is coated with the graphene net, the graphene net can also function as a binder that binds the active materials together. Therefore, the amount of binder can be reduced or eliminated, thereby improving the ratio of active material to electrode volume and / or electrode weight. In other words, the capacity of the secondary battery can be increased.

[0103] Here, it is preferable to use graphene oxide as the graphene compound 201, mix it with the active material to form a layer that becomes the active material layer 200, and then reduce it. In other words, it is preferable that the completed active material layer has reduced graphene oxide. By using graphene oxide, which has extremely high dispersibility in polar solvents, for the formation of the graphene compound 201, the graphene compound 201 can be dispersed approximately uniformly within the active material layer 200. By volatilizing and removing the solvent from the dispersion medium containing the uniformly dispersed graphene oxide and reducing the graphene oxide, the graphene compound 201 remaining in the active material layer 200 partially overlaps and is dispersed to the extent that it is in surface contact with each other, thereby forming a three-dimensional conductive path. The reduction of graphene oxide may be carried out, for example, by heat treatment or by using a reducing agent.

[0104] Therefore, unlike granular conductive agents such as acetylene black that make point contact with the active material, the graphene compound 201 enables surface contact with low contact resistance. As a result, the electrical conductivity between the granular positive electrode active material 100 and the graphene compound 201 can be improved with a smaller amount than that of a conventional conductive agent. Consequently, the ratio of positive electrode active material 100 in the active material layer 200 can be increased. This allows for an increase in the discharge capacity of the secondary battery.

[0105] Furthermore, by using a spray-drying device beforehand, it is possible to cover the entire surface of the active material with a graphene compound, which is a conductive agent, to form a coating, and to further form conductive paths between the active materials using the graphene compound.

[0106] <Binder> As a binder, it is preferable to use rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, or ethylene-propylene-diene copolymer. Fluororubber can also be used as a binder.

[0107] Furthermore, it is preferable to use a water-soluble polymer as the binder. Examples of water-soluble polymers include polysaccharides. Examples of polysaccharides include cellulose derivatives such as carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, diacetylcellulose, and regenerated cellulose, as well as starch. It is even more preferable to use these water-soluble polymers in combination with the aforementioned rubber material.

[0108] Alternatively, it is preferable to use materials such as polystyrene, methyl polyacrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, or nitrocellulose as the binder.

[0109] You may use a combination of several of the binders mentioned above.

[0110] For example, a material with particularly excellent viscosity-modifying properties may be used in combination with other materials. For instance, rubber materials have excellent adhesive and elastic properties, but their viscosity can be difficult to adjust when mixed with a solvent. In such cases, it is preferable to mix them with a material with particularly excellent viscosity-modifying properties. As a material with particularly excellent viscosity-modifying properties, a water-soluble polymer may be used. As a water-soluble polymer with particularly excellent viscosity-modifying properties, the aforementioned polysaccharides, such as carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, and diacetylcellulose, cellulose derivatives such as regenerated cellulose, or starch can be used.

[0111] Furthermore, cellulose derivatives such as carboxymethylcellulose can be made more effective as viscosity modifiers by increasing their solubility, for example, by using salts such as sodium or ammonium salts of carboxymethylcellulose. Increased solubility also improves the dispersibility of the active material and other components when preparing electrode slurries. In this specification, cellulose and cellulose derivatives used as electrode binders include their salts.

[0112] Water-soluble polymers stabilize viscosity by dissolving in water and can stably disperse other materials, such as styrene-butadiene rubber, which are combined as active materials or binders, in aqueous solutions. Furthermore, because they possess functional groups, they are expected to be easily and stably adsorbed onto the surface of the active material. In addition, cellulose derivatives such as carboxymethylcellulose often contain functional groups such as hydroxyl groups or carboxyl groups, and because they have functional groups, the polymers interact with each other and are expected to broadly cover the surface of the active material.

[0113] When a binder covers or is in contact with the surface of the active material, it is expected to act as a passivation film, suppressing the decomposition of the electrolyte. Here, a passivation film is a film that does not conduct electricity, or has extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, the decomposition of the electrolyte can be suppressed at the battery reaction potential. Furthermore, it is even more desirable for the passivation film to suppress electrical conductivity while still allowing lithium ions to conduct.

[0114] <Positive electrode current collector> As the current collector, highly conductive materials such as stainless steel, gold, platinum, aluminum, titanium, and alloys thereof can be used. Furthermore, it is preferable that the material used for the positive electrode current collector does not dissolve at the positive electrode potential. Aluminum alloys with added elements that improve heat resistance, such as silicon, titanium, neodymium, scandium, and molybdenum, can also be used. Alternatively, it may be formed from a metallic element that reacts with silicon to form a silicide. Examples of metallic elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The current collector can be in various shapes, such as foil, plate, sheet, mesh, perforated metal, or expanded metal. The current collector should preferably have a thickness of 5 μm to 30 μm.

[0115] [Negative electrode] The negative electrode comprises a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also contain a conductive agent and a binder.

[0116] [Negative electrode active material] For example, alloy-based materials and / or carbon-based materials can be used as the negative electrode active material.

[0117] As the negative electrode active material, elements capable of undergoing charge-discharge reactions through alloying and dealloying reactions with lithium can be used. For example, materials containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc., can be used. Such elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4200 mAh / g. For this reason, it is preferable to use silicon as the negative electrode active material. Compounds containing these elements may also be used. Examples include SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, SbSn, etc. In this context, elements capable of undergoing charge-discharge reactions through alloying and de-alloying reactions with lithium, and compounds containing such elements, are sometimes referred to as alloying materials.

[0118] In this specification, SiO refers to silicon monoxide, for example. Alternatively, SiO refers to SiO x It can also be expressed as follows. Here, it is preferable that x has one neighboring value. For example, x is preferably between 0.2 and 1.5, and more preferably between 0.3 and 1.2.

[0119] Suitable carbon-based materials include graphite, easily graphitizable carbon (soft carbon), difficult-to-graphitize carbon (hard carbon), carbon nanotubes, graphene, and carbon black.

[0120] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spheroidal graphite having a spherical shape can be used as artificial graphite. For example, MCMB may have a spherical shape and is therefore preferable. Furthermore, it is relatively easy to reduce the surface area of ​​MCMB, which may also be preferable. Examples of natural graphite include flake graphite and spheroidized natural graphite.

[0121] When lithium ions are inserted into graphite (during the formation of lithium-graphite intercalation compounds), graphite exhibits a potential as low as that of lithium metal (0.05V to 0.3V vs. Li / Li). + This allows lithium-ion secondary batteries to exhibit a high operating voltage. Furthermore, graphite is preferred because it has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and higher safety compared to lithium metal.

[0122] Furthermore, titanium dioxide (TiO2) and lithium titanium oxide (Li4Ti5O2) are used as negative electrode active materials. 12 ), lithium-graphite intercalation compound (Li x Oxides such as C6, niobium pentoxide (Nb2O5), tungsten oxide (WO2), and molybdenum oxide (MoO2) can be used.

[0123] Furthermore, as the negative electrode active material, a Li3N type structure is used, which is a lithium and transition metal binitride. 3-x M x N (M = Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 The N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm²). 3 ) indicates a preference.

[0124] Using a lithium-transition metal complex nitride is preferable because it contains lithium ions in the negative electrode active material, allowing it to be combined with lithium-ion-free materials such as V2O5 and Cr3O8 as the positive electrode active material. Even when using a lithium-ion-containing material as the positive electrode active material, the lithium-transition metal complex nitride can be used as the negative electrode active material by pre-desorbing the lithium ions contained in the positive electrode active material.

[0125] Furthermore, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example, transition metal oxides that do not form alloys with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), may be used as the negative electrode active material. Other materials that undergo a conversion reaction include oxides such as Fe2O3, CuO, Cu2O, RuO2, Cr2O3, and CoS 0.89 This can also occur with sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N, and Ge3N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3.

[0126] The conductive agent and binder that the negative electrode active material layer can have can be the same materials as those used for the conductive agent and binder that the positive electrode active material layer can have.

[0127] [Negative electrode current collector] The negative electrode current collector can be made of the same material as the positive electrode current collector. However, it is preferable to use a material for the negative electrode current collector that does not alloy with carrier ions such as lithium.

[0128] [Electrolyte] One form of electrolyte can be used: an electrolyte solution comprising a solvent and an electrolyte dissolved in the solvent. As the solvent for the electrolyte, an aprotic organic solvent is preferred. Examples include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, and one of these, or two or more of these, can be used in any combination and ratio.

[0129] Furthermore, by using one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the solvent for the electrolyte, it is possible to prevent the secondary battery from rupturing or igniting even if the internal temperature rises due to an internal short circuit and / or overcharging. Ionic liquids consist of cations and anions, and include organic cations and anions. Examples of organic cations used in the electrolyte include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, and / or aromatic cations such as imidazolium cations and pyridinium cations. Examples of anions used in the electrolyte include monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkyl sulfonate anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, or perfluoroalkyl phosphate anions.

[0130] Furthermore, examples of electrolytes to be dissolved in the above solvent include LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, and Li2B. 10 Cl 10 Li2B 12 Cl 12 Lithium salts such as LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), and LiN(C2F5SO2)2 can be used individually or in any combination and ratio of two or more of these salts.

[0131] For secondary batteries, it is preferable to use a highly purified electrolyte with a low content of particulate matter and / or elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). Specifically, it is preferable that the weight ratio of impurities to the electrolyte be 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

[0132] Furthermore, additives such as vinylene carbonate, propanesultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), and dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the added material should be, for example, 0.1 wt% to 5 wt% relative to the solvent in which the electrolyte is dissolved.

[0133] Alternatively, a polymer gel electrolyte, obtained by swelling a polymer with an electrolyte solution, may be used.

[0134] Using polymer gel electrolytes enhances safety against leakage and other issues. Furthermore, it enables the secondary battery to be made thinner and lighter.

[0135] As the polymer to be gelled, silicone gels, acrylic gels, acrylonitrile gels, polyethylene oxide-based gels, polypropylene oxide-based gels, fluorine-based polymer gels, and the like can be used.

[0136] As polymers, for example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), and / or PVDF, polyacrylonitrile, etc., and copolymers containing them can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. Furthermore, the polymer formed may have a porous structure.

[0137] Furthermore, as the electrolyte, a solid electrolyte containing inorganic materials such as sulfides or oxides, or a solid electrolyte containing polymeric materials such as PEO (polyethylene oxide), can be used. When a solid electrolyte is used, the installation of separators and / or spacers becomes unnecessary. In addition, since the entire battery can be solidified, the risk of leakage is eliminated, and safety is dramatically improved.

[0138] [Separator] Furthermore, secondary batteries preferably have a separator. As the separator, for example, paper, nonwoven fabric, glass fiber, ceramics, or synthetic fibers made of nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, or polyurethane can be used. It is preferable that the separator is processed into an envelope shape and arranged to enclose either the positive or negative electrode.

[0139] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic material, a fluorine material, a polyamide material, or a mixture thereof. Examples of ceramic materials include aluminum oxide particles and silicon oxide particles. Examples of fluorine materials include PVDF and polytetrafluoroethylene. Examples of polyamide materials include nylon and aramid (meta-aramid, para-aramid).

[0140] Coating with ceramic materials improves oxidation resistance, suppressing separator degradation during high-voltage charging and discharging, and thus improving the reliability of secondary batteries. Coating with fluorine-based materials improves adhesion between the separator and electrodes, thereby improving output characteristics. Coating with polyamide materials, particularly aramid, improves heat resistance, thus enhancing the safety of secondary batteries.

[0141] For example, a polypropylene film may be coated on both sides with a mixture of aluminum oxide and aramid. Alternatively, the side of the polypropylene film in contact with the positive electrode may be coated with a mixture of aluminum oxide and aramid, and the side in contact with the negative electrode may be coated with a fluorine-based material.

[0142] By using a multi-layered separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin, thus increasing the capacity per unit volume of the secondary battery.

[0143] [Exterior] For the outer casing of a secondary battery, metal materials such as aluminum and / or resin materials can be used. A film-like outer casing can also be used. As a film, for example, a three-layer film can be used, in which a highly flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided on a film made of materials such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or polyester resin is provided on the metal thin film as the outer surface of the outer casing.

[0144] <Example of a secondary battery configuration 2> The following describes the configuration of a secondary battery using a solid electrolyte layer as an example of a secondary battery configuration.

[0145] As shown in Figure 4A, a secondary battery 400 according to one embodiment of the present invention has a positive electrode 410, a solid electrolyte layer 420, and a negative electrode 430.

[0146] The positive electrode 410 has a positive electrode current collector 413 and a positive electrode active material layer 414. The positive electrode active material layer 414 has a positive electrode active material 411 and a solid electrolyte 421. The positive electrode active material 411 is a positive electrode active material manufactured using the manufacturing method described in the previous embodiment. The positive electrode active material layer 414 may also have a conductive agent and a binder.

[0147] The solid electrolyte layer 420 has a solid electrolyte 421. The solid electrolyte layer 420 is located between the positive electrode 410 and the negative electrode 430 and is a region that does not contain either the positive electrode active material 411 or the negative electrode active material 431.

[0148] The negative electrode 430 has a negative electrode current collector 433 and a negative electrode active material layer 434. The negative electrode active material layer 434 has a negative electrode active material 431 and a solid electrolyte 421. The negative electrode active material layer 434 may also have a conductive agent and a binder. When metallic lithium is used for the negative electrode 430, the negative electrode 430 can be made without the solid electrolyte 421, as shown in Figure 4B. Using metallic lithium for the negative electrode 430 is preferable because it can improve the energy density of the secondary battery 400.

[0149] As the solid electrolyte 421 in the solid electrolyte layer 420, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halogen-based solid electrolyte, etc., can be used.

[0150] Sulfide-based solid electrolytes include thiolysicone-based (Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, etc.), sulfide glass (70Li2S·30P2S5, 30Li2S·26B2S3·44LiI, 63Li2S·36SiS2·1Li3PO4, 57Li2S·38SiS2·5Li4SiO4, 50Li2S·50GeS2, etc.), sulfide crystallized glass (Li7P3S 11 Li 3.25 P 0.95 Sulfide-based solid electrolytes include S4, etc. Sulfide-based solid electrolytes have advantages such as the availability of materials with high conductivity, the ability to be synthesized at low temperatures, and their relatively soft nature which helps maintain conductive paths even after charging and discharging. However, sulfide-based solid electrolytes may generate hydrogen sulfide through reaction with water. Therefore, sufficient attention must be paid to safety. For example, to enhance safety, it is desirable to improve the airtightness of the casing of the secondary battery and / or the housing that contains the secondary battery.

[0151] Oxide-based solid electrolytes include materials having a perovskite-type crystal structure (La 2 / 3-x Li 3x Materials having a NASICON-type crystal structure (Li 1+x Al x Ti 2-x(PO4)3 etc.) Materials having a garnet-type crystal structure (Li7La3Zr2O 12 Materials having a LISICON-type crystal structure (Li 14 ZnGe4O 16 (etc.), oxide glass (Li3PO4-Li4SiO4, 50Li4SiO4·50Li3BO3, etc.), oxide crystallized glass (Li 1.07 Al 0.69 Ti 1.46 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 This includes (PO4)3, etc. Oxide-based solid electrolytes have the advantage of being stable in the atmosphere. In this specification, the NASICON-type crystal structure refers to a compound represented as M2(XO4)3 (M: transition metal, X: S, P, As, Mo, W, etc.) that has a structure in which MO6 octahedra and XO4 tetrahedra share vertices and are arranged three-dimensionally.

[0152] Halide-based solid electrolytes include LiAlCl4, Li3InBr6, LiF, LiCl, LiBr, and LiI. Furthermore, composite materials in which these halide-based solid electrolytes are packed into the pores of porous aluminum oxide or porous silica can also be used as solid electrolytes.

[0153] Alternatively, different solid electrolytes may be mixed and used.

[0154] [Shape of the outer casing and secondary battery] The outer casing of the secondary battery 400 according to one aspect of the present invention can be made of various materials and has a shape, but it is preferable that it has the function of pressurizing the positive electrode, solid electrolyte layer, and negative electrode.

[0155] For example, Figure 5 shows an example of a cell used to evaluate the materials of an all-solid-state battery.

[0156] Figure 5A is a schematic cross-sectional view of the evaluation cell, which has a lower member 761, an upper member 762, fixing screws and / or wing nuts 764 that secure them together, and the evaluation material is fixed by pressing the electrode plate 753 by rotating the retaining screw 763. An insulator 766 is provided between the lower member 761 and the upper member 762, which are made of stainless steel. An O-ring 765 for sealing is also provided between the upper member 762 and the retaining screw 763.

[0157] The evaluation material is placed on an electrode plate 751, surrounded by an insulating tube 752, and pressed from above by an electrode plate 753. Figure 5B is a magnified perspective view of the area around this evaluation material.

[0158] As an example of the evaluated material, an example of a stacked structure consisting of a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is shown, and a cross-sectional view is shown in Figure 5C. Note that the same parts are referred to in Figures 5A, 5B, and 5C.

[0159] The electrode plate 751 and lower member 761, which are electrically connected to the positive electrode 750a, can be considered to correspond to the positive electrode terminal. The electrode plate 753 and upper member 762, which are electrically connected to the negative electrode 750c, can be considered to correspond to the negative electrode terminal. Electrical resistance and other parameters can be measured while applying pressure to the evaluation material via the electrode plates 751 and 753.

[0160] Furthermore, it is preferable to use a package with excellent airtightness for the outer casing of a secondary battery according to one embodiment of the present invention. For example, a ceramic package or a resin package can be used. Also, when sealing the outer casing, it is preferable to block out the outside air and perform the sealing in a sealed atmosphere, for example, inside a glove box.

[0161] Figure 6A shows a perspective view of a secondary battery according to one embodiment of the present invention, having a different exterior and shape from that of Figure 5. The secondary battery in Figure 6A has external electrodes 771 and 772 and is sealed with an exterior having a plurality of package members.

[0162] Figure 6B shows an example of a cross-section cut along the dashed line in Figure 6A. The laminate having a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is enclosed and sealed by a package member 770a with an electrode layer 773a provided on a flat plate, a frame-shaped package member 770b, and a package member 770c with an electrode layer 773b provided on a flat plate. Insulating materials such as resin or ceramic can be used for the package members 770a, 770b, and 770c.

[0163] The external electrode 771 is electrically connected to the positive electrode 750a via the electrode layer 773a and functions as a positive electrode terminal. The external electrode 772 is electrically connected to the negative electrode 750c via the electrode layer 773b and functions as a negative electrode terminal.

[0164] This embodiment can be used in appropriate combination with other embodiments.

[0165] (Embodiment 4) This embodiment describes an example of the shape of a secondary battery having a positive electrode, as described in the previous embodiment. The materials used in the secondary battery described in this embodiment can be referenced to those described in the previous embodiment.

[0166] <Coin-type rechargeable battery> First, let's describe an example of a coin-type rechargeable battery. Figure 7A is an external view of a coin-type (single-layer flat type) rechargeable battery, and Figure 7B is a cross-sectional view thereof.

[0167] The coin-type secondary battery 300 has a positive electrode casing 301, which also serves as the positive electrode terminal, and a negative electrode casing 302, which also serves as the negative electrode terminal, both insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with it. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with it.

[0168] Furthermore, for the positive electrode 304 and negative electrode 307 used in the coin-type secondary battery 300, the active material layer only needs to be formed on one side.

[0169] The positive electrode can 301 and the negative electrode can 302 can be made of metals such as nickel, aluminum, or titanium, or alloys thereof, or alloys of these with other metals (e.g., stainless steel), which are corrosion-resistant to the electrolyte. Furthermore, it is preferable to coat them with nickel and / or aluminum, etc., to prevent corrosion by the electrolyte. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307.

[0170] The negative electrode 307, positive electrode 304, and separator 310 are impregnated with an electrolyte, and as shown in Figure 7B, the positive electrode 304, separator 310, negative electrode 307, and negative electrode 302 are stacked in this order with the positive electrode 301 at the bottom, and the positive electrode 301 and negative electrode 302 are pressed together via a gasket 303 to manufacture a coin-type secondary battery 300.

[0171] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, a coin-type secondary battery 300 with high capacity and excellent cycle characteristics can be obtained.

[0172] Here, Figure 7C is used to explain the flow of current during charging of a secondary battery. When a lithium-ion secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In a lithium-ion secondary battery, the anode and cathode are reversed during charging and discharging, and the oxidation and reduction reactions are reversed. Therefore, the electrode with the higher reaction potential is called the positive electrode, and the electrode with the lower reaction potential is called the negative electrode. Accordingly, in this specification, whether charging or discharging, whether a reverse pulse current is flowing or a charging current is flowing, the positive electrode will be called the "positive electrode" or "+ electrode (positive electrode)," and the negative electrode will be called the "negative electrode" or "- electrode (negative electrode)." Using the terms anode (positive electrode) or cathode (negative electrode) in relation to oxidation or reduction reactions could lead to confusion as they are reversed during charging and discharging. Therefore, the terms anode (positive electrode) and cathode (negative electrode) will not be used in this specification. If the terms anode or cathode are used, it should be specified whether it refers to the charging or discharging phase, and whether it corresponds to the positive or negative electrode.

[0173] A charger is connected to the two terminals shown in Figure 7C, and the secondary battery 300 is charged. As the secondary battery 300 charges, the potential difference between the electrodes increases.

[0174] <Cylindrical rechargeable battery> Next, an example of a cylindrical secondary battery will be described with reference to Figure 8. Figure 8A shows an external view of the cylindrical secondary battery 600. Figure 8B is a schematic cross-section of the cylindrical secondary battery 600. As shown in Figure 8B, the cylindrical secondary battery 600 has a positive electrode cap (battery cover) 601 on the top surface and a battery casing (outer casing) 602 on the sides and bottom. These positive electrode cap and battery casing (outer casing) 602 are insulated by a gasket (insulating packing) 610.

[0175] Inside the hollow cylindrical battery can 602, a battery element is provided, in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 in between. Although not shown, the battery element is wound around a center pin. The battery can 602 is closed at one end and open at the other. The battery can 602 can be made of a metal such as nickel, aluminum, or titanium, or an alloy thereof, or an alloy of these with other metals (e.g., stainless steel), which is corrosion-resistant to the electrolyte. Furthermore, it is preferable to coat the battery can 602 with nickel and / or aluminum to prevent corrosion by the electrolyte. Inside the battery can 602, the battery element in which the positive electrode, negative electrode, and separator are wound is sandwiched between a pair of opposing insulating plates 608 and 609. The inside of the battery can 602 in which the battery element is provided is filled with an electrolyte (not shown). The electrolyte can be the same as that used in coin-type secondary batteries.

[0176] Since the positive and negative electrodes used in cylindrical storage batteries are wound, it is preferable to form active material on both sides of the current collector. A positive electrode terminal (positive electrode current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collector lead) 607 is connected to the negative electrode 606. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of metal materials such as aluminum. The positive electrode terminal 603 is resistance-welded to the safety valve mechanism 612, and the negative electrode 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 cap 601 via a PTC element (Positive Temperature Coefficient) 611. The safety valve mechanism 612 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the rise in the internal pressure of the battery exceeds a predetermined threshold. Furthermore, the PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises, and it prevents abnormal heat generation by limiting the current amount through the increase in resistance. Barium titanate (BaTiO3) based semiconductor ceramics can be used for the PTC element.

[0177] Alternatively, as shown in Figure 8C, a module 615 may be constructed by sandwiching multiple secondary batteries 600 between conductive plates 613 and 614. The multiple secondary batteries 600 may be connected in parallel, in series, or connected in parallel and then in series. By constructing a module 615 with multiple secondary batteries 600, a large amount of power can be extracted.

[0178] Figure 8D is a top view of module 615. For clarity, the conductive plate 613 is shown with a dotted line. As shown in Figure 8D, module 615 may have conductors 616 that electrically connect a plurality of secondary batteries 600. A conductive plate can be superimposed on the conductors 616. A temperature control device 617 may also be provided between the plurality of secondary batteries 600. When a secondary battery 600 is overheated, it can be cooled by the temperature control device 617, and when a secondary battery 600 is too cold, it can be heated by the temperature control device 617. This makes the performance of module 615 less susceptible to the influence of ambient temperature. The heat transfer medium in the temperature control device 617 is preferably insulating and non-flammable.

[0179] By using the positive electrode active material described in the previous embodiment for the positive electrode 604, a cylindrical secondary battery 600 with high capacity and excellent cycle characteristics can be obtained.

[0180] <Example of a secondary battery structure> Another example of a secondary battery structure will be explained using Figures 9 to 13.

[0181] Figures 9A and 9B show the external view of the battery pack. The battery pack includes a secondary battery 913 and a circuit board 900. The secondary battery 913 is connected to the antenna 914 via the circuit board 900. A label 910 is attached to the secondary battery 913. Furthermore, as shown in Figure 9B, the secondary battery 913 is connected to terminals 951 and 952. The circuit board 900 is secured with a seal 915.

[0182] The circuit board 900 has terminal 911 and circuit 912. Terminal 911 is connected to terminal 951, terminal 952, antenna 914, and circuit 912. Multiple terminals 911 may be provided, and each of the multiple terminals 911 may be used as a control signal input terminal, a power supply terminal, etc.

[0183] The circuit 912 may be provided on the back surface of the circuit board 900. The antenna 914 is not limited to a coil shape, but may be, for example, linear or plate-shaped. Alternatively, antennas such as a planar antenna, aperture antenna, traveling wave antenna, EH antenna, magnetic field antenna, or dielectric antenna may be used. Or, the antenna 914 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. In other words, the antenna 914 may function as one of the two conductors of the capacitor. This makes it possible to exchange power not only through electromagnetic and magnetic fields, but also through electric fields.

[0184] The battery pack has a layer 916 between the antenna 914 and the secondary battery 913. The layer 916 has the function of shielding, for example, the electromagnetic field from the secondary battery 913. For the layer 916, a magnetic material can be used, for example.

[0185] Note that the structure of the battery pack is not limited to that shown in Figure 9.

[0186] For example, as shown in Figures 10A and 10B, antennas may be provided on each of the opposing pairs of faces of the secondary battery 913 shown in Figures 9A and 9B. Figure 10A is an external view showing one of the pair of faces, and Figure 10B is an external view showing the other of the pair of faces. For parts that are the same as those of the secondary battery shown in Figures 9A and 9B, the explanation of the secondary battery shown in Figures 9A and 9B can be appropriately referred to.

[0187] As shown in Figure 10A, an antenna 914 is provided on one of the pair of surfaces of the secondary battery 913 with a layer 916 in between, and as shown in Figure 10B, an antenna 918 is provided on the other of the pair of surfaces of the secondary battery 913 with a layer 917 in between. The layer 917 has the function of shielding, for example, the electromagnetic field from the secondary battery 913. For the layer 917, a magnetic material can be used, for example.

[0188] By adopting the above structure, the size of both antenna 914 and antenna 918 can be increased. Antenna 918 has a function that allows for data communication with external devices, for example. Antenna 918 can be fitted with an antenna of a shape that is applicable to antenna 914, for example. As a communication method between the secondary battery and other devices via antenna 918, response methods that can be used between the secondary battery and other devices, such as NFC (Near Field Communication), can be applied.

[0189] Alternatively, as shown in Figure 10C, a display device 920 may be provided on the secondary battery 913 shown in Figures 9A and 9B. The display device 920 is electrically connected to terminal 911. Note that a label 910 does not need to be provided on the part where the display device 920 is provided. Note that for the same parts as the secondary battery shown in Figures 9A and 9B, the explanation of the secondary battery shown in Figures 9A and 9B can be appropriately applied.

[0190] The display device 920 may display, for example, an image indicating whether or not it is charging, or an image indicating the amount of stored power. The display device 920 can be, for example, electronic paper, liquid crystal display, or electroluminescent (EL) display. For example, using electronic paper can reduce the power consumption of the display device 920.

[0191] Alternatively, as shown in Figure 10D, a sensor 921 may be provided on the secondary battery 913 shown in Figures 9A and 9B. The sensor 921 is electrically connected to terminal 911 via terminal 922. For parts that are the same as those of the secondary battery shown in Figures 9A and 9B, the explanation of the secondary battery shown in Figures 9A and 9B can be appropriately applied.

[0192] The sensor 921 may have the function of measuring, for example, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared radiation. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed (such as temperature) can be detected and stored in the memory of the circuit 912.

[0193] Furthermore, an example of the structure of the secondary battery 913 will be explained using Figures 11 and 12.

[0194] The secondary battery 913 shown in Figure 11A has a wound body 950 with terminals 951 and 952 inside a housing 930. The wound body 950 is impregnated with an electrolyte inside the housing 930. Terminal 952 is in contact with the housing 930, while terminal 951 is not in contact with the housing 930 due to the use of an insulating material or the like. In Figure 11A, the housing 930 is shown separated for convenience, but in reality, the wound body 950 is covered by the housing 930, and terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of a metal material (e.g., aluminum) or a resin material.

[0195] Furthermore, as shown in Figure 11B, the housing 930 shown in Figure 11A may be formed from multiple materials. For example, in the secondary battery 913 shown in Figure 11B, housing 930a and housing 930b are bonded together, and the winding body 950 is provided in the area surrounded by housing 930a and housing 930b.

[0196] For the housing 930a, an insulating material such as organic resin can be used. In particular, by using a material such as organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by the housing 930a is small, an antenna such as antenna 914 may be provided inside the housing 930a. For the housing 930b, for example, a metal material can be used.

[0197] Furthermore, the structure of the wound body 950 is shown in Figure 12. The wound body 950 has a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked on top of each other with the separator 933 in between, and the stacked sheets are wound up. Note that multiple stacks of the negative electrode 931, positive electrode 932, and separator 933 may be stacked.

[0198] The negative terminal 931 is connected to terminal 911 shown in Figure 9 via one of terminals 951 and 952. The positive terminal 932 is connected to terminal 911 shown in Figure 9 via the other of terminals 951 and 952.

[0199] By using the positive electrode active material described in the previous embodiment for the positive electrode 932, a secondary battery 913 with high capacity and excellent cycle characteristics can be obtained.

[0200] <Laminated rechargeable battery> Next, an example of a laminated secondary battery will be described with reference to Figures 13 to 19. If a laminated secondary battery has a flexible structure, it can be mounted on electronic devices that have at least a part of a flexible component, and the secondary battery can also be bent in accordance with the deformation of the electronic device.

[0201] A laminated secondary battery 980 will be described using Figure 13. The laminated secondary battery 980 has a wound body 993 as shown in Figure 13A. The wound body 993 has a negative electrode 994, a positive electrode 995, and a separator 996. Similar to the wound body 950 described in Figure 12, the wound body 993 is formed by stacking the negative electrode 994 and the positive electrode 995 with the separator 996 in between, and then winding the stacked sheet.

[0202] The number of layers in the stack consisting of the negative electrode 994, positive electrode 995, and separator 996 can be appropriately designed according to the required capacitance and element volume. The negative electrode 994 is connected to a negative electrode current collector (not shown) via one of the lead electrodes 997 and 998, and the positive electrode 995 is connected to a positive electrode current collector (not shown) via the other of the lead electrodes 997 and 998.

[0203] As shown in Figure 13B, a secondary battery 980 can be manufactured as shown in Figure 13C by housing the aforementioned wound body 993 in a space formed by bonding a film 981, which serves as the outer casing, and a film 982, which has a recess, by thermocompression or the like. The wound body 993 has lead electrodes 997 and 998 and is impregnated with an electrolyte inside the film 981 and the film 982, which has a recess.

[0204] The film 981 and the film 982 having recesses can be made of a metal material such as aluminum, and / or a resin material. If a resin material is used for the film 981 and the film 982 having recesses, the film 981 and the film 982 having recesses can be deformed when an external force is applied, making it possible to create a flexible storage battery.

[0205] Furthermore, although Figures 13B and 13C show an example using two films, a space may be formed by folding a single film, and the aforementioned wound body 993 may be housed in that space.

[0206] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, a secondary battery 980 with high capacity and excellent cycle characteristics can be obtained.

[0207] Furthermore, while Figure 13 illustrates an example of a secondary battery 980 having a wound body in a space formed by a film that serves as the outer casing, a secondary battery having multiple strip-shaped positive electrodes, separators, and negative electrodes in a space formed by a film that serves as the outer casing may also be used, for example, as shown in Figure 14.

[0208] The laminate-type secondary battery 500 shown in Figure 14A comprises a positive electrode 503 having a positive electrode current collector 501 and a positive electrode active material layer 502, a negative electrode 506 having a negative electrode current collector 504 and a negative electrode active material layer 505, a separator 507, an electrolyte 508, and an outer casing 509. The separator 507 is installed between the positive electrode 503 and the negative electrode 506, which are located within the outer casing 509. The outer casing 509 is filled with the electrolyte 508. The electrolyte 508 can be the same as the electrolyte shown in Embodiment 3.

[0209] In the laminate-type secondary battery 500 shown in Figure 14A, the positive electrode current collector 501 and the negative electrode current collector 504 also serve as terminals for obtaining electrical contact with the outside. Therefore, parts of the positive electrode current collector 501 and the negative electrode current collector 504 may be arranged to be exposed to the outside from the outer casing 509. Alternatively, the positive electrode current collector 501 and the negative electrode current collector 504 may not be exposed to the outside from the outer casing 509, and lead electrodes may be used to ultrasonically bond the lead electrodes to the positive electrode current collector 501 or the negative electrode current collector 504, thereby exposing the lead electrodes to the outside.

[0210] In a laminate-type secondary battery 500, the outer casing 509 can be made of a laminate film with a three-layer structure, in which a highly flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or polyester resin is provided on the metal thin film as the outer surface of the outer casing.

[0211] Furthermore, an example of the cross-sectional structure of the laminate-type secondary battery 500 is shown in Figure 14B. For simplicity, Figure 14A shows an example consisting of two current collectors, but in reality, it is composed of multiple electrode layers as shown in Figure 14B.

[0212] Figure 14B shows an example where the number of electrode layers is 16. Even with 16 electrode layers, the secondary battery 500 retains its flexibility. Figure 14B shows a structure with a total of 16 layers: 8 layers of negative electrode current collectors 504 and 8 layers of positive electrode current collectors 501. Figure 14B also shows a cross-section of the negative electrode extraction section, where the 8 layers of negative electrode current collectors 504 are ultrasonically bonded. Of course, the number of electrode layers is not limited to 16; it can be more or fewer. A larger number of electrode layers allows for a secondary battery with greater capacity. Conversely, a smaller number of electrode layers allows for a thinner design and a secondary battery with superior flexibility.

[0213] Here, an example of the external view of a laminate-type secondary battery 500 is shown in Figures 15 and 16. Figures 15 and 16 show a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511.

[0214] Figure 17A shows the external views of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a positive electrode current collector 501, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. The positive electrode 503 also has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). The negative electrode 506 has a negative electrode current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. The negative electrode 506 also has a region where the negative electrode current collector 504 is partially exposed, i.e., the tab region. The area of ​​the tab region of the positive electrode and the negative electrode, and / or the shape of the tab region, are not limited to the example shown in Figure 17A.

[0215] <Method for manufacturing laminated rechargeable batteries> Here, an example of a method for manufacturing a laminate-type secondary battery, whose external appearance is shown in Figure 15, will be explained using Figures 17B and 17C.

[0216] First, the negative electrode 506, separator 507, and positive electrode 503 are stacked. Figure 17B shows the stacked negative electrode 506, separator 507, and positive electrode 503. Here, an example using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For joining, ultrasonic welding, for example, can be used. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0217] Next, the negative electrode 506, separator 507, and positive electrode 503 are placed on the outer casing 509.

[0218] Next, as shown in Figure 17C, the outer casing 509 is bent at the portion indicated by the dashed line. Then, the outer periphery of the outer casing 509 is joined. For joining, for example, heat sealing can be used. At this time, a region that is not joined (hereinafter referred to as the inlet) is provided on a part (or one side) of the outer casing 509 so that the electrolyte 508 can be inserted later.

[0219] Next, the electrolyte 508 (not shown) is introduced into the inside of the outer casing 509 through an inlet provided in the outer casing 509. It is preferable to introduce the electrolyte 508 under reduced pressure or an inert atmosphere. Finally, the inlet is sealed. In this way, a laminate-type secondary battery 500 can be manufactured.

[0220] By using the positive electrode active material described in the previous embodiment for the positive electrode 503, a secondary battery 500 with high capacity and excellent cycle characteristics can be obtained.

[0221] <Bendable rechargeable battery> Next, examples of bendable secondary batteries will be described with reference to Figures 18 and 19.

[0222] Figure 18A shows a schematic top view of a bendable secondary battery 250. Figures 18B, 18C, 18D, and 18E are schematic cross-sectional views along the cutting lines C1-C2, C3-C4, A1-A2, and B1-B2 in Figure 18A, respectively. The secondary battery 250 has an outer casing 251 and a positive electrode 211a and a negative electrode 211b housed inside the outer casing 251. The positive electrode 211a and the negative electrode 211b together form the electrode 210. Leads 212a electrically connected to the positive electrode 211a and lead 212b electrically connected to the negative electrode 211b extend to the outside of the outer casing 251. In addition to the positive electrode 211a and the negative electrode 211b, an electrolyte (not shown) is sealed in the area enclosed by the outer casing 251.

[0223] The positive electrode 211a and negative electrode 211b of the secondary battery 250 will be explained using Figure 19. Figure 19A is a perspective view illustrating the stacking order of the positive electrode 211a, negative electrode 211b, and separator 214. Figure 19B is a perspective view showing the positive electrode 211a and negative electrode 211b, as well as the leads 212a and 212b.

[0224] As shown in Figure 19A, the secondary battery 250 has a plurality of strip-shaped positive electrodes 211a, a plurality of strip-shaped negative electrodes 211b, and a plurality of separators 214. The positive electrodes 211a and negative electrodes 211b each have 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 on one side of the positive electrode 211a, and a negative electrode active material layer is formed on the portion other than the tab on one side of the negative electrode 211b.

[0225] The positive electrode 211a and the negative electrode 211b are stacked such that the surfaces of the positive electrode 211a that do not have a positive electrode active material layer are in contact with each other, and the surfaces of the negative electrode 211b that do not have a negative electrode active material layer are in contact with each other.

[0226] Furthermore, a separator 214 is provided between the surface on which the positive electrode active material layer of the positive electrode 211a is formed and the surface on which the negative electrode active material layer of the negative electrode 211b is formed. In Figures 19A and 19B, the separator 214 is shown as a dotted line for clarity.

[0227] As shown in Figure 19B, multiple positive electrodes 211a and leads 212a are electrically connected at the junction 215a. Multiple negative electrodes 211b and leads 212b are electrically connected at the junction 215b.

[0228] Next, the outer casing 251 will be described using Figures 18B, 18C, 18D, and 18E.

[0229] The outer casing 251 has a film-like shape and is folded in half so as to sandwich the positive electrode 211a and the negative electrode 211b. The outer casing 251 has a folded portion 261, a pair of sealing portions 262, and a sealing portion 263. The pair of sealing portions 262 are provided sandwiching the positive electrode 211a and the negative electrode 211b and can also be called side seals. The sealing portion 263 has a portion that overlaps with leads 212a and 212b and can also be called a top seal.

[0230] The outer casing 251 preferably has a wave-like shape in which ridges 271 and valleys 272 are alternately arranged in the portion that overlaps with the positive electrode 211a and the negative electrode 211b. Furthermore, the sealing portions 262 and 263 of the outer casing 251 are preferably flat.

[0231] Figure 18B shows a cross-section cut at the point where it overlaps with the ridge line 271, and Figure 18C shows a cross-section cut at the point where it overlaps with the valley line 272. Both Figures 18B and 18C correspond to the widthwise cross-sections of the secondary battery 250 and the positive electrode 211a and negative electrode 211b.

[0232] Here, distance La is defined as the distance between the widthwise ends of the positive electrode 211a and the negative electrode 211b, i.e., the ends of the positive electrode 211a and the negative electrode 211b, and the seal portion 262. When the secondary battery 250 is deformed, such as by bending, the positive electrode 211a and the negative electrode 211b deform so that they shift relative to each other in the lengthwise direction, as will be described later. In this case, if distance La is too short, the casing 251 and the positive electrode 211a and the negative electrode 211b will rub strongly against each other, and the casing 251 may be damaged. In particular, if the metal film of the casing 251 is exposed, there is a risk that the metal film will be corroded by the electrolyte. Therefore, it is preferable to set distance La as long as possible. On the other hand, if distance La is made too large, the volume of the secondary battery 250 will increase.

[0233] Furthermore, the greater the combined thickness of the stacked positive electrode 211a and negative electrode 211b, the greater the distance La between the positive electrode 211a and negative electrode 211b and the seal portion 262.

[0234] More specifically, when the total thickness of the stacked positive electrode 211a, negative electrode 211b, and separator 214 (not shown) is t, the distance La is preferably 0.8 to 3.0 times the thickness t, preferably 0.9 to 2.5 times, and more preferably 1.0 to 2.0 times. By setting the distance La within this range, a compact and highly reliable battery against bending can be realized.

[0235] Furthermore, when the distance between the pair of sealing portions 262 is denoted as distance Lb, it is preferable to make the distance Lb sufficiently larger than the width of the positive electrode 211a and the negative electrode 211b (here, the width Wb of the negative electrode 211b). This allows a portion of the positive electrode 211a and the negative electrode 211b to shift in the width direction even when the secondary battery 250 is subjected to repeated bending or other deformation, thereby effectively preventing friction between the positive electrode 211a and the negative electrode 211b and the outer casing 251.

[0236] For example, it is preferable that 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.

[0237] In other words, it is preferable that the distance Lb, width Wb, and thickness t satisfy the relationship shown in Equation 1 below.

[0238]

number

[0239] Here, a satisfies the conditions of 0.8 to 3.0, preferably 0.9 to 2.5, and more preferably 1.0 to 2.0.

[0240] Furthermore, Figure 18D is a cross-section including the lead 212a, and corresponds to the longitudinal cross-section of the secondary battery 250, the positive electrode 211a, and the negative electrode 211b. As shown in Figure 18D, it is preferable that the bent portion 261 has a space 273 between the longitudinal ends of the positive electrode 211a and the negative electrode 211b and the outer casing 251.

[0241] Figure 18E shows a schematic cross-sectional view of the secondary battery 250 when bent. Figure 18E corresponds to the cross-section at the cutting line B1-B2 in Figure 18A.

[0242] When the secondary battery 250 is bent, a portion of the outer casing 251 located on the outside of the bend stretches, while another portion located on the inside contracts. More specifically, the outer portion of the outer casing 251 deforms in such a way that the wave amplitude is small and the wave period is large. On the other hand, the inner portion of the outer casing 251 deforms in such a way that the wave amplitude is large and the wave period is small. In this way, the deformation of the outer casing 251 relieves the stress on the outer casing 251 that accompanies the bending, so the material constituting the outer casing 251 does not need to expand or contract. As a result, the secondary battery 250 can be bent with little force without the outer casing 251 being damaged.

[0243] Also, as shown in FIG. 18E, when the secondary battery 250 is bent, the positive electrode 211a and the negative electrode 211b are displaced relative to each other. At this time, since one end on the seal portion 263 side of the plurality of stacked positive electrodes 211a and negative electrodes 211b is fixed by the fixing member 217, they are displaced so that the amount of displacement increases as it gets closer to the bending portion 261. As a result, the stress applied to the positive electrode 211a and the negative electrode 211b is relaxed, and it is not necessary for the positive electrode 211a and the negative electrode 211b themselves to expand and contract. As a result, the secondary battery 250 can be bent without the positive electrode 211a and the negative electrode 211b being damaged.

[0244] Also, since there is a space 273 between the positive electrode 211a and the negative electrode 211b and the exterior body 251, the positive electrode 211a and the negative electrode 211b located inside when bent can be displaced relative to each other without contacting the exterior body 251.

[0245] The secondary battery 250 exemplified in FIGS. 18 and 19 is a battery in which damage to the exterior body, damage to the positive electrode 211a and the negative electrode 211b, etc. are unlikely to occur even when repeatedly bent and stretched, and the battery characteristics are also unlikely to deteriorate. By using the positive electrode active material described in the previous embodiment for the positive electrode 211a included in the secondary battery 250, a battery with even better cycle characteristics can be obtained.

[0246] In a all-solid-state battery, by applying a predetermined pressure in the stacking direction of the stacked positive electrode and / or negative electrode, the contact state of the interfaces inside can be kept good. By applying a predetermined pressure in the stacking direction of the positive electrode and / or negative electrode, expansion in the stacking direction due to charge and discharge of the all-solid-state battery can be suppressed, and the reliability of the all-solid-state battery can be improved.

[0247] This embodiment can be used in appropriate combination with other embodiments.

[0248] (Embodiment 5) In this embodiment, an example of mounting a secondary battery, which is one aspect of the present invention, on an electronic device will be described.

[0249] FIG. 20 shows an example of an electronic device. In FIG. 20, a display device 8000 is an example of an electronic device using a secondary battery 8004 according to one aspect of the present invention. Specifically, the display device 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, a speaker unit 8003, a secondary battery 8004, and the like. The secondary battery 8004 according to one aspect of the present invention is provided inside the housing 8001. The display device 8000 can receive power supply from a commercial power source or use the power stored in the secondary battery 8004. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, the secondary battery 8004 according to one aspect of the present invention can be used as an uninterruptible power supply, making it possible to use the display device 8000.

[0250] The display unit 8002 can use 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), or a FED (Field Emission Display).

[0251] Note that the display device includes all display devices for information display, such as those for personal computers and advertising displays, in addition to those for receiving TV broadcasts.

[0252] In Figure 20, the fixed-type lighting device 8100 is an example of an electronic device using a secondary battery 8103 according to one aspect of the present invention. Specifically, the lighting device 8100 includes a housing 8101, a light source 8102, a secondary battery 8103, etc. In Figure 20, the case in which the secondary battery 8103 is installed inside the ceiling 8104 on which the housing 8101 and light source 8102 are installed is illustrated, but the secondary battery 8103 may also be installed inside the housing 8101. The lighting device 8100 can receive power from a commercial power source, or it can use power stored in the secondary battery 8103. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the lighting device 8100 can be used by using the secondary battery 8103 according to one aspect of the present invention as an uninterruptible power source.

[0253] Although Figure 20 illustrates a fixed lighting device 8100 installed on the ceiling 8104, the secondary battery according to one aspect of the present invention can also be used in fixed lighting devices installed on surfaces other than the ceiling 8104, such as the side wall 8105, floor 8106, window 8107, etc., or in tabletop lighting devices, etc.

[0254] Furthermore, the light source 8102 can be an artificial light source that artificially generates light using electricity. Specifically, examples of the above artificial light sources include incandescent light bulbs, discharge lamps such as fluorescent lamps, LEDs, and / or light-emitting elements such as organic EL elements.

[0255] In Figure 20, 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 aspect of the present invention. Specifically, the indoor unit 8200 has a housing 8201, an air outlet 8202, a secondary battery 8203, etc. In Figure 20, the case in which the secondary battery 8203 is provided in the indoor unit 8200 is illustrated, but the secondary battery 8203 may also 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 can receive power from a commercial power source, or it can use power stored in the secondary battery 8203. In particular, when both the indoor unit 8200 and the outdoor unit 8204 are equipped with secondary batteries 8203, even when power cannot be supplied from the commercial power source due to a power outage or the like, the air conditioner can be used by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply.

[0256] Although Figure 20 illustrates a separate-type air conditioner consisting of an indoor unit and an outdoor unit, the secondary battery according to one aspect of the present invention can also be used in an integrated-type air conditioner that has the functions of both the indoor and outdoor units in a single housing.

[0257] In Figure 20, the electric refrigerator-freezer 8300 is an example of an electronic device using a secondary battery 8304 according to one aspect of the present invention. Specifically, the electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator door 8302, a freezer door 8303, a secondary battery 8304, etc. In Figure 20, the secondary battery 8304 is installed inside the housing 8301. The electric refrigerator-freezer 8300 can receive power from a commercial power source, or it can use power stored in the secondary battery 8304. Therefore, even when power cannot be supplied from a commercial power source 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 aspect of the present invention as an uninterruptible power source.

[0258] Furthermore, among the electronic devices mentioned above, high-frequency heating devices such as microwave ovens and electric rice cookers require high power in a short period of time. Therefore, by using a secondary battery according to one aspect of the present invention as an auxiliary power source to supplement the power that cannot be supplied by the commercial power supply, it is possible to prevent the commercial power supply circuit breaker from tripping when the electronic device is in use.

[0259] Furthermore, by storing power in the secondary battery during periods when electronic devices are not in use, particularly during periods when the proportion of the total amount of power supplied by the commercial power source that is actually used (referred to as the power usage rate) is low, it is possible to suppress the increase in the power usage rate outside of these periods. For example, in the case of the electric refrigerator-freezer 8300, power is stored in the secondary battery 8304 at night when the temperature is low and the refrigerator door 8302 and freezer door 8303 are not opened or closed. Then, during the daytime when the temperature is high and the refrigerator door 8302 and freezer door 8303 are opened and closed, the secondary battery 8304 can be used as an auxiliary power source, thereby keeping the daytime power usage rate low.

[0260] According to one aspect of the present invention, the cycle characteristics of a secondary battery can be improved, thereby enhancing its reliability. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be created, thereby improving the characteristics of the secondary battery and thus making the secondary battery itself smaller and lighter. Therefore, by incorporating a secondary battery according to one aspect of the present invention into the electronic device described in this embodiment, it is possible to create an electronic device that has a longer lifespan and is lighter.

[0261] This embodiment can be implemented in appropriate combination with other embodiments.

[0262] (Embodiment 6) This embodiment shows an example in which a secondary battery according to one aspect of the present invention is mounted on a vehicle.

[0263] By installing secondary batteries in vehicles, next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV) can be realized.

[0264] Figure 21 illustrates a vehicle using a secondary battery, which is one embodiment of the present invention. The automobile 8400 shown in Figure 21A is an electric vehicle that uses an electric motor as a power source for driving. Alternatively, it is a hybrid vehicle that can appropriately select and use an electric motor and an engine as power sources for driving. By using one embodiment of the present invention, a vehicle with a long driving range can be realized. The automobile 8400 also has a secondary battery. The secondary battery can be used by arranging the secondary battery modules shown in Figures 8C and 8D on the floor of the vehicle. Alternatively, a battery pack combining multiple secondary batteries as shown in Figure 11 may be installed on the floor of the vehicle. The secondary battery can not only drive the electric motor 8406 but also supply power to light-emitting devices such as headlights 8401 or room lights (not shown).

[0265] Furthermore, the secondary battery can supply power to display devices such as the speedometer and tachometer of the 8400 automobile. The secondary battery can also supply power to semiconductor devices such as the navigation system of the 8400 automobile.

[0266] The automobile 8500 shown in Figure 21B can be charged by receiving power from an external charging facility via a plug-in method or a contactless power supply method to the secondary battery of the automobile 8500. Figure 21B shows the state in which the secondary battery 8024 mounted on the automobile 8500 is being charged from a ground-mounted charging device 8021 via a cable 8022. When charging, the charging method and connector specifications may be carried out as appropriate using a prescribed method such as CHAdeMO® or Combo. The charging device 8021 may be a charging station installed in a commercial facility or a household power supply. For example, the secondary battery 8024 mounted on the automobile 8500 can be charged by an external power supply using plug-in technology. Charging can be performed by converting AC power to DC power via a conversion device such as an AC / DC converter.

[0267] Although not shown in the diagram, the vehicle can also be charged by mounting a power receiving device on the vehicle and receiving power wirelessly from a ground-based power transmission device. In this wireless power supply method, charging can be performed not only when the vehicle is stopped but also while it is in motion by incorporating the power transmission device into the road or exterior wall. Furthermore, this wireless power supply method can be used to transmit and receive power between vehicles. In addition, solar cells can be installed on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped and / or while it is in motion. For such wireless power supply, electromagnetic induction and / or magnetic resonance methods can be used.

[0268] Furthermore, Figure 21C shows an example of a two-wheeled vehicle using a secondary battery according to one embodiment of the present invention. The scooter 8600 shown in Figure 21C is equipped with a secondary battery 8602, a side mirror 8601, and a turn signal light 8603. The secondary battery 8602 can supply electricity to the turn signal light 8603.

[0269] In addition, for the scooter 8600 shown in FIG. 21C, the secondary battery 8602 can be stored in the under-seat storage 8604. Even if the under-seat storage 8604 is small, the secondary battery 8602 can be stored in the under-seat storage 8604. The secondary battery 8602 is removable. During charging, the secondary battery 8602 can be carried indoors for charging and then stored before driving.

[0270] According to one aspect of the present invention, the cycle characteristics of the secondary battery can be improved, and the capacity of the secondary battery can be increased. Therefore, the secondary battery itself can be reduced in size and weight. If the secondary battery itself can be reduced in size and weight, it contributes to the weight reduction of the vehicle, so the cruising range can be improved. In addition, the secondary battery mounted on the vehicle can also be used as a power supply source other than the vehicle. In this case, for example, it is possible to avoid using the commercial power supply during the peak of power demand. If it is possible to avoid using the commercial power supply during the peak of power demand, it can contribute to energy saving and reduction of carbon dioxide emissions. In addition, if the cycle characteristics are good, the secondary battery can be used for a long time, so the amount of use of rare metals such as cobalt can be reduced.

[0271] This embodiment can be implemented in appropriate combination with other embodiments.

Description of Reference Numerals

[0272] [[ID={14]] 100: Positive electrode active material, 200: Active material layer, 201: Graphene compound, 803: Lithium compound, 804: Phosphorus compound, 805: Solvent, 806: Solution containing lithium, 807: Solution containing phosphorus, 811: Mixture, 812: Solution P, 813: Solution containing transition metal M, 821: Mixture, 822: Transition metal M source, 823: Mixture, 831: Mixture

Claims

1. A method for producing a positive electrode active material having lithium and a transition metal, The first step is to prepare a lithium compound, a phosphorus compound, and a mixture of water and alcohol. A second step involves mixing the lithium compound, the phosphorus compound, and the mixture of water and alcohol to form a first mixture. A third step involves adding a first aqueous solution to the first mixture to adjust the pH and form a second mixture, A fourth step is to mix an iron(II) compound, a manganese(II) compound, and a nickel(II) compound with the second mixture to form a third mixture, A fifth step is to heat the third mixture to form a fourth mixture, The process includes a sixth step of filtering, washing, and drying the fourth mixture to obtain a positive electrode active material, In the first step described above, a material with a purity of 99.99% or higher is prepared as the lithium compound, a material with a purity of 99% or higher is prepared as the phosphorus compound, and pure water with a resistivity of 15 MΩ·cm or higher is prepared as the water. In the fourth step described above, the iron(II) compound, manganese(II) compound, and nickel(II) compound are materials with a purity of 99.9% or higher. In the fourth step, the pH of the third mixture is 3.5 or more and 5.0 or less. In the mixing of the fourth step described above, N2 bubbling is performed, The heating in the fifth step is carried out at a pressure of 0.11 MPa to 2 MPa and a temperature of 150°C to 250°C for 1 hour to 10 hours. In the sixth step, pure water with a resistivity of 15 MΩ·cm or more is used for the washing. The positive electrode active material has a space group Pnma and an olivine-type crystal structure. The positive electrode active material is LiMPO4, In the LiMPO 4, M is composed of Fe, Mn, and Ni. Method for preparing positive electrode active material.

2. In claim 1, Lithium chloride is used as the lithium compound, phosphoric acid is used as the phosphorus compound, iron(II) chloride tetrahydrate is used as the iron(II) compound, manganese(II) chloride tetrahydrate is used as the manganese(II) compound, and nickel(II) chloride hexahydrate is used as the nickel(II) compound. Method for preparing positive electrode active material.

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