Lithium-ion secondary battery

Abstract

To provide a positive electrode active material for a lithium ion secondary battery with high capacity and an excellent charging and discharging cycle characteristic.SOLUTION: A positive electrode whose crystal structure changes less in a charged state and a discharged state is provided. For example, the positive electrode active material having a crystal structure of a layered rock salt type in the discharged state and having a crystal structure of a pseudo-spinel type in a charged state with high voltage of about 4.6 V changes less in crystal structure and volume before and after the charging and discharging compared with the existing positive electrode active material. In order to manufacture the positive electrode active material with the pseudo-spinel type crystal structure in the charged state, it is preferable to synthesize lithium cobaltate, add and mix lithium fluoride and magnesium fluoride, and heat the mixture at proper temperature for proper time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One aspect of the present invention relates to an article, a method, or a manufacturing method. Alternatively, the present invention relates to a process, Pertaining to a machine, manufacture, or composition of matter. One embodiment of the present invention is a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, or an electronic device. In particular, the present invention relates to a positive electrode active material that can be used in a secondary battery. The present invention relates to a secondary battery and an electronic device having a secondary battery.

[0002] In this specification, the term "power storage device" refers to elements and devices in general that have a power storage function. For example, lithium-ion secondary batteries and other storage batteries (also called secondary batteries) This includes silicon ion capacitors and electric double layer capacitors.

[0003] In addition, in this specification, the term "electronic device" refers to a device in general that has a power storage device. Electro-optical devices having a power storage device, and information terminal devices having a power storage device are all electronic devices. [Background technology]

[0004] In recent years, various types of energy storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have become available. In particular, lithium-ion batteries, which have high output and high energy density, are being developed. The secondary battery is used in mobile phones, smartphones, tablets, or laptop computers. Mobile information terminals, portable music players, digital cameras, medical equipment, next-generation clean energy - Automobiles (Hybrid Vehicles (HEV), Electric Vehicles (EV), Plug-in Hybrid Vehicles) Demand for rechargeable vehicles (PHEVs, etc.) is rapidly expanding along with the development of the semiconductor industry. As a source of energy, it has become indispensable in today's information society.

[0005] The characteristics required for lithium-ion secondary batteries are higher energy density, These include improved cycle characteristics, safety in various operating environments, and improved long-term reliability.

[0006] Therefore, we aimed to improve the cycle characteristics and capacity of lithium-ion secondary batteries by developing a positive electrode active material. Improvements to the material have been investigated (Patent Documents 1 and 2). Research into the structure is also being conducted (Non-Patent Documents 1 to 3).

[0007] X-ray diffraction (XRD) is one of the techniques used to analyze the crystalline structure of positive electrode active materials. ICSD (Inorganic Crystal Structure) introduced in Patent Document 5 By using the Artifact Database, XRD data can be analyzed. can. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-216760 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-261132 [Non-patent literature]

[0009] [Non-Patent Document 1] Toyoki Okumura et al, “Correlation of lithium ion distribution and X-ray absorption near-edge structure in O3-and O2-lithium cobalt oxides from first-principle calculation”, Journal of Materials Chemistry, 2012, 22, p.17340-17348 [Non-patent document 2] Motohashi, T. et al, “Electronic phase diagram of the layered cobalt oxide system LixCoO2 (0.0≦x≦1.0)”, Physical Review B, 80(16);165114 [Non-patent document 3] Zhaohui Chen et al, “Staging Phase Transitions in LixCoO2”, Journal of The Electrochemical Society, 2002, 149(12) A1604-A1609 [Non-patent document 4] WE Counts et al, Journal of the American Ceramic Society,(1953) 36 [1] 12-17. Fig.01471 [Non-patent document 5] Belsky, A. et al., “New developments in the Inorganic Crystal Structure Database (ICSD): accessibility in support of materials research and design”, Acta Cryst., (2002) B58 364-369. Summary of the Invention [Problem to be solved by the invention]

[0010] One aspect of the present invention is a cathode for a lithium ion secondary battery having high capacity and excellent charge-discharge cycle characteristics. It is an object of the present invention to provide an electrode active material and a manufacturing method thereof. Another object of the present invention is to provide a method for manufacturing a positive electrode active material. When used in lithium-ion secondary batteries, the capacity loss during charge / discharge cycles is suppressed. Another object of the present invention is to provide a positive electrode active material. Another object of the present invention is to provide a battery having excellent charge-discharge characteristics. One of the objectives is to provide a secondary battery that can maintain a charged state at a high voltage for a long period of time. The object of the present invention is to provide a positive electrode active material in which the elution of transition metals such as cobalt is suppressed even when the electrode is heated. Another embodiment of the present invention is to provide a secondary battery with high safety or reliability. This is one of the challenges.

[0011] Another embodiment of the present invention is a novel substance, active material particles, a power storage device, or a manufacturing method thereof. One of our goals is to provide the following.

[0012] The description of these problems does not preclude the existence of other problems. It is not necessary for the embodiments to solve all of these problems. It is possible to extract other problems from the description of the claim. [Means for solving the problem]

[0013] In order to achieve the above object, a positive electrode active material according to one embodiment of the present invention has a characteristic that For example, when discharged, the layered rock salt type crystals are It has a crystalline structure, and when charged at a high voltage of about 4.6 V, it exhibits a pseudo-spinel crystalline structure. The positive electrode active material has a crystal structure and volume that change less during charging and discharging than known positive electrode active materials. There are few.

[0014] In order to prepare a positive electrode active material that has a pseudo-spinel crystal structure in the charged state, lithium After synthesizing the composite oxide particles containing ammonium, a transition metal, and oxygen, a fluorine source and a salt are added. A halogen source such as a halogen source and a magnesium source are added and mixed, and the resulting mixture is then heated and heated for an appropriate time. It is preferable to heat at .

[0015] Halogens and magnesium are impurities in the layered rock salt crystal structure. First, by synthesizing composite oxide particles with few impurities, a layered rock salt type crystal structure with few defects was obtained. The material may contain a halogen source such as a fluorine source or a chlorine source, and By adding a magnesium source and heating at an appropriate temperature and time, it is possible to obtain a highly porous and highly porous composite with few defects. In this way, a positive electrode active material having a pseudospinel crystal structure in an electrically charged state can be produced.

[0016] One aspect of the present invention is a method for producing a first mixture by mixing a lithium source, a fluorine source, and a magnesium source. a composite oxide having lithium, a transition metal, and oxygen; and a first mixing the mixture with the second mixture to form a second mixture; and heating the second mixture. The present invention relates to a method for producing a positive electrode active material having the above structure.

[0017] In addition, the composite oxide containing lithium, a transition metal, and oxygen can be used in glow discharge. When analyzed by electrochemical mass spectrometry, the concentration of elements other than lithium, transition metals, and oxygen was 500 It is preferably 0 ppm wt or less.

[0018] In the above, the first mixture contains lithium fluoride L as a lithium source and a fluorine source. It is preferred to have iF.

[0019] In the above, magnesium fluoride MgF2 was used as the fluorine source and magnesium source. The molar ratio of lithium fluoride LiF and magnesium fluoride MgF2 is LiF:MgF It is preferable that 2=x:1 (0.1≦x≦0.5).

[0020] In the above, the second mixture contains lithium, a transition metal, and oxygen. The transition metal TM contained in the composite oxide and the magnesium Mg contained in the first mixture Mix1 M ix1 The atomic ratio of TM to Mg is Mix1 = 1:y (0.001≦y≦0.01) It is preferable that

[0021] In the above, the heating temperature in the step of heating the second mixture is 600°C or higher and 95 It is preferable that the temperature is 0°C or lower.

[0022] In the above, the heating time in the step of heating the second mixture is 2 hours or more. It is more preferable that the time is 60 hours or more.

[0023] Another aspect of the present invention is a battery comprising a positive electrode having a positive electrode active material produced by the above method and a negative electrode. It is a secondary battery having a [Effects of the Invention]

[0024] According to one aspect of the present invention, a lithium ion secondary battery having high capacity and excellent charge / discharge cycle characteristics is provided. Furthermore, it is possible to provide a positive electrode active material for a battery and a method for producing the same. It is also possible to provide a method for producing the material. This makes it possible to provide a positive electrode active material that suppresses the decrease in capacity during charge-discharge cycles. In addition, a high-capacity secondary battery can be provided. Furthermore, even if the battery is kept in a high-voltage charged state for a long time, the cobalt It is possible to provide a positive electrode active material in which the elution of transition metals such as ZnO, Ni, and NiO is suppressed. It is possible to provide a highly reliable secondary battery. The present invention can provide a device or a method for making the same. [Brief explanation of the drawings]

[0025] [Figure 1] 1A to 1C illustrate an example of a method for manufacturing a positive electrode active material of one embodiment of the present invention. [Figure 2] 1A to 1C illustrate another example of a method for manufacturing a positive electrode active material of one embodiment of the present invention. [Figure 3] 1A and 1B are diagrams illustrating the depth of charge and the crystal structure of a positive electrode active material according to one embodiment of the present invention. [Figure 4] 1A and 1B are diagrams illustrating the depth of charge and the crystal structure of a conventional positive electrode active material. [Figure 5] XRD pattern calculated from the crystal structure. [Figure 6] 1A and 1B are diagrams illustrating the crystal structure and magnetism of a positive electrode active material of one embodiment of the present invention. [Figure 7] 1A and 1B are diagrams illustrating the crystal structure and magnetism of a conventional positive electrode active material. [Figure 8] FIG. 10 is a cross-sectional view of an active material layer in the case where a graphene compound is used as a conductive additive. [Figure 9] FIG. 2 is a diagram illustrating a method for charging a secondary battery. [Figure 10] FIG. 2 is a diagram illustrating a method for charging a secondary battery. [Figure 11]FIG. 2 is a diagram illustrating a method of discharging a secondary battery. [Figure 12] FIG. 2 is a diagram illustrating a coin-type secondary battery. [Figure 13] FIG. 2 is a diagram illustrating a cylindrical secondary battery. [Figure 14] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 15] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 16] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 17] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 18] FIG. 1 is a diagram illustrating a laminated secondary battery. [Figure 19] FIG. 1 is a diagram illustrating a laminated secondary battery. [Figure 20] FIG. 2 is a diagram showing the appearance of a secondary battery. [Figure 21] FIG. 2 is a diagram showing the appearance of a secondary battery. [Figure 22] 1A to 1C are diagrams illustrating a method for manufacturing a secondary battery. [Figure 23] 1A and 1B are diagrams illustrating a bendable secondary battery. [Figure 24] 1A and 1B are diagrams illustrating a bendable secondary battery. [Figure 25] 1A to 1C illustrate examples of electronic devices. [Figure 26] 1A to 1C illustrate examples of electronic devices. [Figure 27] 1A to 1C illustrate examples of electronic devices. [Figure 28] FIG. 1 is a diagram illustrating an example of a vehicle. [Figure 29] 2 is a graph of particle size distribution of LiF, MgF2, and the first mixture of Example 1. [Figure 30] 1A and 1B are graphs illustrating XPS analysis of the positive electrode active material of Example 1 and a diagram illustrating particles. [Figure 31] 1 is a graph of an XPS analysis of the positive electrode active material of Example 1. [Figure 32] 1 is an SEM image of the positive electrode active material of Example 1. [Figure 33] 1 shows an XRD pattern of the positive electrode active material of Example 1. [Figure 34]1 shows an XRD pattern of the positive electrode active material of Example 1. [Figure 35] 1 shows an XRD pattern of the positive electrode active material of Example 1. [Figure 36] 1 shows an XRD pattern of the positive electrode active material of Example 1. [Figure 37] 1 shows an XRD pattern of the positive electrode active material of Example 1. [Figure 38] Cycle characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 39] Cycle characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 40] Cycle characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 41] Cycle characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 42] 1 shows the rate characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 43] 1 shows the rate characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 44] 1 is a graph showing the charge capacity and voltage of Sample 1 and Sample 15 in Example 1. [Figure 45] 1 is a graph showing dQ / dV vs. V of Sample 1 and Sample 15 in Example 1. [Figure 46] 1 is a graph of dQ / dV vs. V for Sample 1 in Example 1. [Figure 47] 1 is a graph of dQ / dV vs. V for Sample 1 in Example 1. [Figure 48] 1 is a graph showing the discharge capacity and voltage of Sample 1 and Sample 4 in Example 1. [Figure 49] 1 is a graph showing dQ / dV vs. V of Sample 1 and Sample 4 in Example 1. [Figure 50] XRD patterns of Sample 21 and Sample 22 in Example 2. [Figure 51] XRD patterns of Sample 21 and Sample 22 in Example 2. [Figure 52] XRD patterns of Samples 23 and 24 in Example 2. [Figure 53] XRD patterns of Samples 25 and 26 in Example 2. [Figure 54] Charge / discharge cycle characteristics. [Figure 55] DSC evaluation results. [Figure 56] XRD patterns. [Figure 57] XRD patterns. [Figure 58] Charge / discharge cycle characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and various modifications in form and details are possible by those skilled in the art. Furthermore, the present invention should not be construed as being limited to the description of the following embodiments. It is not something that can be done.

[0027] In this specification, crystal planes and directions are indicated by Miller indices. In the above, numbers are usually surrounded by superscript bars in crystallography, but in this specification and other documents, due to limitations on the notation used in the application, numbers are used as superscript bars. Instead of putting a bar above the number, a minus sign (-) may be placed before the number. Also, individual orientations that indicate directions within a crystal are [ ], and collective orientations that indicate all equivalent directions are < >, individual faces that represent crystal faces are ( ), and collective faces with equivalent symmetry are {}. Express it.

[0028] In this specification, segregation refers to the phenomenon in a solid consisting of multiple elements (e.g., A, B, C). This refers to the phenomenon in which a certain element (e.g., B) is distributed spatially non-uniformly.

[0029] In this specification, the surface layer of particles of active material or the like refers to the region from the surface to about 10 nm. The surface caused by cracks or fractures can also be called the surface. It's called inside.

[0030] In the present specification and the like, the layered rock salt type crystal structure of a composite oxide containing lithium and a transition metal is The structure has a rock salt type ion arrangement in which cations and anions are arranged alternately, and the transition metal and lithium The lithium atoms are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. It refers to a crystalline structure. It may have defects such as cation or anion deficiencies. Strictly speaking, the rock salt crystal structure is a distorted structure of the rock salt crystal. be.

[0031] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately. It is possible for there to be a deficiency of cations or anions.

[0032] In the present specification and the like, the pseudospinel type composite oxide containing lithium and a transition metal The crystal structure is in the space group R-3m, and although it is not a spinel-type crystal structure, cobalt, Ions such as magnesium ions occupy the 6-coordinated oxygen sites, and the arrangement of cations is similar to that of spinel. The pseudo-spinel type crystal structure is characterized by the symmetry of the crystal structure. may occupy the oxygen tetracoordinate site, and in this case the ionic arrangement also has a symmetry similar to that of the spinel type. It has sexuality.

[0033] The pseudospinel crystal structure has random Li between layers, but the CdCl2 crystal structure It can be said that this crystal structure is similar to the CdCl2 type. The structure is that when lithium nickel oxide is charged to a charge depth of 0.94 (Li 0.06 NiO 2) It has a similar crystal structure to pure lithium cobaltate, or a layered rock containing a large amount of cobalt. It is known that salt-type positive electrode active materials do not usually have this crystal structure.

[0034] Layered rock salt crystals and the anions in rock salt crystals have a cubic close-packed structure (face-centered cubic lattice structure) It is estimated that the anions in pseudospinel crystals also have a cubic close-packed structure. When the anions are in contact, there exists a crystal plane where the cubic close-packed structure formed by the anions is oriented in the same direction. However, the space group of layered rock salt crystals and pseudospinel crystals is R-3m, and the space group of rock salt crystals is R-3m. The crystal space groups Fm-3m (the common rock salt crystal space group) and Fd-3m (the simplest Since the space group is different from that of rock salt crystals with symmetry, the mirror crystals that satisfy the above conditions The index is different between layered rock salt crystals and pseudospinel crystals and rock salt crystals. is composed of anions in layered rock salt crystals, pseudospinel crystals, and rock salt crystals. When the orientation of the resulting cubic close-packed structure is aligned, the crystal orientation is said to be roughly the same. be.

[0035] The crystal orientation of the two regions roughly coincides, as can be seen from TEM (transmission electron microscope) and STEM images. (Scanning Transmission Electron Microscope) image, HAADF-STEM (High Angle Scattering Annular Dark Field Scanning Transmission Electron Microscope) It can be judged from the images of the annular bright-field scanning transmission electron microscope (ABF-STEM), etc. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as materials for judgment. In TEM images, the arrangement of cations and anions is observed as repeated bright and dark lines. When the orientation of the cubic close-packed structure in the layered rock salt crystal and the rock salt crystal is aligned, The angle between the repeated bright and dark lines should be 5 degrees or less, and more preferably 2.5 degrees or less. Light elements such as oxygen and fluorine can be clearly observed in TEM images. In some cases, this is not possible, but in that case, the alignment of the metal elements can be used to determine the alignment. .

[0036] In this specification, the theoretical capacity of the positive electrode active material is the capacity of the positive electrode active material that can be inserted and removed. The theoretical capacity of LiCoO2 is 274 mAh / g, the theoretical capacity of LiNiO2 is 274mAh / g, and the theoretical capacity of LiMn2O4 is It is 148mAh / g.

[0037] In this specification, the depth of charge when all intercalable and detachable lithium is intercalated is The depth of charge when all the intercalable lithium in the positive electrode active material is deintercalated is defined as 0, and the depth of charge when all the intercalable lithium in the positive electrode active material is deintercalated is defined as 1. That is what I will say.

[0038] In this specification, charging refers to transferring lithium ions from the positive electrode to the negative electrode in the battery. This refers to the movement of electrons from the negative electrode to the positive electrode in an external circuit. In this case, charging refers to the process of releasing lithium ions. 0.9 or less, more specifically, a positive electrode active material with a charge depth of 0.8 to 0.83 is charged at a high voltage. For example, in the case of LiCoO2, 219. If the charge is 2mAh / g, the positive electrode active material is charged at a high voltage. In 2, in a 25°C environment, the charging voltage is 4.525V or more and 4.65V or less (counter electrode lithium After that, the current value is 0.01C, or the voltage during constant current charging is The positive electrode active material after constant voltage charging until the current value is about 1 / 5 to 1 / 100 of the original value is also This is referred to as a charged positive electrode active material.

[0039] Similarly, discharging means transferring lithium ions from the negative electrode to the positive electrode within the battery and discharging them from an external circuit. The positive electrode active material is lithium. The insertion of ions is called discharging. Also, the positive electrode active material with a charge depth of 0.06 or less, or The positive electrode active material was discharged to 90% or more of its charge capacity from a high voltage charged state. For example, in the case of LiCoO2, the charge capacity is 21 If the battery is charged at a high voltage, it is at 90% of its capacity. The positive electrode active material after discharging 197.3mAh / g or more is considered to be a fully discharged positive electrode active material. In addition, in the case of LiCoO2, the battery voltage is 3V or less (counter electrode lithium) in a 25°C environment. The positive electrode active material after constant current discharge until the That is what I will say.

[0040] In this specification, a non-equilibrium phase change refers to a phenomenon that causes a non-linear change in a physical quantity. For example, the capacitance (Q) is differentiated by the voltage (V) to obtain d A non-equilibrium phase change occurs before and after the peak in the Q / dV curve, and the crystal structure changes significantly. It is thought that this is the case.

[0041] (Embodiment 1) [Method for producing positive electrode active material] First, an example of a method for producing a positive electrode active material 100 according to one embodiment of the present invention will be described with reference to FIG. Another example of a specific manufacturing method is shown in FIG.

[0042] <Step S11> As shown in step S11 of FIG. 1, first, a fluorine source and a chlorine source are used as materials for the first mixture. A halogen source such as fluorine-containing fluorine and a magnesium source are prepared. It is also preferable to prepare a lithium source. It's nice.

[0043] As the fluorine source, for example, lithium fluoride, magnesium fluoride, etc. can be used. Among them, lithium fluoride has a relatively low melting point of 848°C, and it melts in the annealing process described below. The chlorine source is preferably lithium chloride, magnesium chloride, or the like. The magnesium source can be, for example, magnesium fluoride, magnesium oxide, etc. The lithium source can be sodium, magnesium hydroxide, magnesium carbonate, etc. For example, lithium fluoride and lithium carbonate can be used. Magnesium fluoride can be used as both a lithium source and a fluorine source. The fluorine source can be used as a source of magnesium.

[0044] In this embodiment, lithium fluoride (LiF) is prepared as a fluorine source and a lithium source. Magnesium fluoride (MgF2) is prepared as a fluorine source and magnesium source. Step S11 in Figure 2). Lithium fluoride LiF and magnesium fluoride MgF2 are Mixing F:MgF2 at a molar ratio of approximately 65:35 will maximize the effect of lowering the melting point. On the other hand, if the amount of lithium fluoride is too large, the lithium becomes excessive and the cysteine Therefore, lithium fluoride (LiF) and magnesium fluoride (MgF) The molar ratio of LiF to MgF is preferably LiF:MgF=x:1 (0≦x≦1.9). More preferably, LiF:MgF2 = x:1 (0.1 ≤ x ≤ 0.5), and LiF:MgF 2=x:1 (x=near 0.33) is more preferable. The value shall be greater than 0.9 times and less than 1.1 times that value.

[0045] If the subsequent mixing and grinding steps are to be carried out wet, a solvent is prepared. ketones such as ethanol and isopropanol, alcohols such as ethanol and isopropanol, ethers, dioxanes, acetone, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc. can be used. It is more preferable to use an aprotic solvent that is less likely to react with lithium. In this embodiment, acetone is used (see step S11 in FIG. 2).

[0046] <Step S12> Next, the materials of the first mixture are mixed and crushed (step S1 in FIGS. 1 and 2). 2) Mixing can be done either dry or wet, but wet mixing allows for smaller particles to be crushed. For mixing, a ball mill, a bead mill, etc. can be used. When using a ball mill, it is preferable to use, for example, zirconia balls as media. It is preferable to carry out this mixing and grinding step sufficiently to pulverize the first mixture into fine powder.

[0047] <Steps S13 and S14> The mixed and crushed materials are collected (step S13 in FIGS. 1 and 2), and the first mixture is (Step S14 in FIGS. 1 and 2).

[0048] The first mixture may have an average particle diameter (D50: also referred to as median diameter) of 600 nm or more. It is preferable that the thickness is between 20 μm and 10 μm, and more preferable that the thickness is between 1 μm and 10 μm. The first mixture thus finely pulverized can be used in the subsequent process to extract lithium, transition metals, and When mixed with the oxygen-containing composite oxide, the first mixture is uniformly dispersed on the surface of the composite oxide particles. When the first mixture is uniformly adhered to the surface of the composite oxide particles, After heating, halogen and magnesium are easily distributed throughout the surface layer of the composite oxide particles. If there is a region on the surface that does not contain halogen or magnesium, charging In this state, it may be difficult to form a pseudospinel crystal structure, which will be described later.

[0049] <Step S21> Next, as shown in step S21 of FIG. 1, a composite having lithium, a transition metal, and oxygen is formed. As the oxide material, a lithium source and a transition metal source are prepared.

[0050] As the lithium source, for example, lithium carbonate, lithium fluoride, etc. can be used.

[0051] The transition metal may be at least one of cobalt, manganese, and nickel. The composite oxides containing lithium, transition metals, and oxygen have a layered rock salt type crystal structure. Therefore, the mixture ratio of cobalt, manganese, and nickel that can form a layered rock salt structure is In addition, it is preferable to use these transition metals within a range in which a layered rock salt type crystal structure can be formed. Aluminum may also be added.

[0052] As the transition metal source, oxides, hydroxides, etc. of the above transition metals can be used. Examples of usable manganese sources include cobalt oxide and cobalt hydroxide. As the nickel source, manganese oxide, manganese hydroxide, etc. can be used. As the aluminum source, nickel oxide, nickel hydroxide, etc. can be used. Aluminum oxide, aluminum hydroxide, etc. can be used.

[0053] <Step S22> Next, the lithium source and the transition metal source are mixed (step S22 in FIG. 1). The mixing can be carried out in a dry or wet manner. For example, a ball mill, a bead mill, etc., can be used for mixing. When using a ball mill, for example, zirconia balls are used as the media. It is preferable that

[0054] <Step S23> Next, the mixed material is heated. This process is called "sintering" to distinguish it from the subsequent heating process. It is also sometimes called the first heating. The heating is preferably carried out at a temperature of 800°C or higher and lower than 1100°C. It is preferable to carry out the treatment at a temperature of 900°C or higher and 1000°C or lower, and more preferably at about 950°C. If the temperature is too low, the starting materials may not be sufficiently decomposed and melted. On the other hand, if the temperature is too high, the transition metals may be excessively reduced, or lithium may evaporate. Defects may occur, such as a defect in which cobalt becomes divalent.

[0055] The heating time is preferably 2 hours or more and 20 hours or less. It is recommended to carry out the process in a dry atmosphere (for example, a dew point of -50°C or less, more preferably -100°C or less). For example, heating at 1000°C for 10 hours at a temperature increase rate of 200°C / h in a dry atmosphere is preferred. The flow rate of the ambient air is preferably 10 L / min. After that, the heated material is cooled to room temperature. For example, the time required for cooling from a specified temperature to room temperature can be between 10 and 50 hours. It is preferable to set the following.

[0056] However, cooling to room temperature in step S23 is not essential. 4. There is no problem in carrying out the steps S25 and S31 to S34. If desired, cooling may be to a temperature above room temperature.

[0057] <Steps S24 and S25> The calcined material is recovered (step S24 in FIG. 1), and lithium, transition metals, and oxygen are separated. A composite oxide having the following structure is obtained (Step S25 in FIG. 1). Specifically, lithium cobalt oxide , lithium manganese oxide, lithium nickel oxide, cobalt oxide in which a part of the cobalt is replaced by manganese Lithium baltic oxide, or lithium nickel-manganese-cobalt oxide, is obtained.

[0058] In step S25, a compound having lithium, a transition metal, and oxygen synthesized in advance is prepared. In this case, steps S21 to S22 may be performed using a composite oxide (see FIG. 2). 4 can be omitted.

[0059] When a composite oxide containing lithium, a transition metal, and oxygen that has been synthesized in advance is used, It is preferable to use a material with few impurities. and a composite oxide containing oxygen, and a positive electrode active material whose main components are lithium, cobalt, and nickel. Nickel, manganese, aluminum and oxygen, and elements other than the above main components are impurities For example, when analyzed by glow discharge mass spectrometry, the total impurity concentration was 10,000ppm. It is preferably m wt or less, and more preferably 5000 ppm wt or less. The total impurity concentration of transition metals such as titanium and arsenic is 3000 ppm wt or less It is preferable that the content of the hydroxybenzoates is 1500 ppm by weight or less, and more preferable that the content of the hydroxybenzoates is 1500 ppm by weight or less.

[0060] For example, as a pre-synthesized lithium cobalt oxide, Lithium valerate particles (product name: Cellseed C-10N) can be used. The average particle size (D50) is approximately 12 μm, and the measurement by glow discharge mass spectrometry (GD-MS) In the impurity analysis, the magnesium concentration and fluorine concentration were 50 ppm wt or less, and calcium Sium concentration, aluminum concentration and silicon concentration are 100 ppm wt or less, nickel Concentration is 150 ppm wt or less, sulfur concentration is 500 ppm wt or less, arsenic concentration is 110 0 ppm wt or less, other elements other than lithium, cobalt and oxygen concentration is 150 ppm pm wt or less, lithium cobalt oxide.

[0061] Alternatively, lithium cobalt oxide particles (product name: Cellseed C-5) manufactured by Nippon Chemical Industry Co., Ltd. H) can also be used. This has an average particle size (D50) of about 6.5 μm, and GD- In the MS impurity analysis, the concentration of elements other than lithium, cobalt, and oxygen was C-1 It is lithium cobalt oxide, which is the same as or lower than 0N.

[0062] In this embodiment, cobalt is used as the transition metal, and pre-synthesized lithium cobaltate is used. We used titanium particles (Cellseed C-10N manufactured by Nippon Chemical Industry Co., Ltd.) (Figure 2 reference).

[0063] The composite oxide having lithium, a transition metal, and oxygen in step S25 is formed by removing defects and strain. It is preferable that the layered rock salt type crystal structure has few impurities. It is preferable that the oxide is an impurity-containing composite oxide having lithium, a transition metal, and oxygen. If there are many of these, the crystal structure is likely to be defective or distorted.

[0064] <Step S31> Next, the first mixture is mixed with a composite oxide containing lithium, a transition metal, and oxygen. (Step S31 in FIGS. 1 and 2) The transition metal TM in the oxide and the magnesium Mg in the first mixture Mix1 Mix1 Nohara The molecular ratio is TM:Mg Mix1 = 1:y (0.0005≦y≦0.03) Preferably, TM:Mg Mix1 It is more preferable that y = 1:y (0.001≦y≦0.01). Preferably, TM:Mg Mix1 A ratio of about 1:0.005 is even more preferable.

[0065] The mixing in step S31 is performed more slowly than the mixing in step S12 in order to prevent the composite oxide particles from being destroyed. For example, it is preferable to set the rotation speed to be milder than that of the mixing in step S12. It is preferable to use conditions with less heat or shorter time. For example, a ball mill, a bead mill, etc. can be used for mixing. When using a ball mill, for example, zirconia balls can be used as the media. preferable.

[0066] <Steps S32 and S33> The mixed materials are collected (step S32 in FIGS. 1 and 2) to obtain a second mixture. (Step S33 in Figures 1 and 2).

[0067] In this embodiment, the mixture of lithium fluoride and magnesium fluoride is Although the present invention has been described as a method of adding a small amount of lithium cobalt oxide to the Instead of the second mixture in step S33, a starting material of lithium cobalt oxide may be used. Alternatively, a magnesium source and a fluorine source may be added to the raw material and then calcined. Steps S11 to S14 and steps S21 to S25 Since there is no need to separate the processes, it is simple and highly productive.

[0068] Alternatively, lithium cobalt oxide pre-doped with magnesium and fluorine can be used. Magnesium and fluorine doped lithium cobalt oxide can be used to This is simpler and allows the steps up to step S32 to be omitted.

[0069] Furthermore, lithium cobalt oxide, to which magnesium and fluorine had been added in advance, was further A magnesium source and a fluorine source may be added to the above.

[0070] <Step S34> Next, the second mixture is heated. This step is called annealing or heating to distinguish it from the previous heating step. This is sometimes called second heating.

[0071] The annealing is preferably carried out at a suitable temperature and time. Particle size and structure of composite oxides containing lithium, transition metals, and oxygen in Step S25 It depends on the composition and other conditions. Small particles require lower temperatures or shorter times than large particles. A shorter time may be more preferable.

[0072] For example, if the average particle diameter (D50) of the particles in step S25 is about 12 μm, the annealing temperature The annealing temperature is preferably, for example, 600° C. or higher and 950° C. or lower. The annealing time is preferably, for example, 3 hours or longer. Preferably, 10 hours or more is more preferable, and 60 hours or more is even more preferable.

[0073] On the other hand, when the average particle diameter (D50) of the particles in step S25 is about 5 μm, the annealing temperature The annealing temperature is preferably, for example, 600° C. or higher and 950° C. or lower. The annealing time is, for example, 1 hour to 10 hours. Preferably, it is less than 1 hour, and more preferably about 2 hours.

[0074] The temperature drop time after annealing is preferably, for example, 10 hours or more and 50 hours or less.

[0075] When the second mixture is annealed, the material with a lower melting point (e.g., fluoride) in the first mixture is first melted. It is thought that lithium (melting point: 848°C) melts and is distributed in the surface layer of the composite oxide particles. The presence of this molten material then lowers the melting point of other materials, causing them to melt. For example, magnesium fluoride (melting point 1263°C) melts and turns into composite oxide particles. It is thought to be distributed on the surface of the egg.

[0076] The elements contained in the first mixture distributed in the surface layer are lithium, transition metals, and oxygen. It is believed that the metal is dissolved in the composite oxide.

[0077] The diffusion of the elements contained in this first mixture occurs more in the surface layer and the grains than in the interior of the composite oxide particles. Therefore, magnesium and halogens are more rapidly dissolved in the surface layer and near the grain boundaries. As will be described later, the magnesium concentration in the surface layer and near the grain boundaries is When the temperature is high, the change in the crystal structure can be more effectively suppressed.

[0078] <Step S35> The annealed material is recovered to obtain the positive electrode active material 100 according to one embodiment of the present invention.

[0079] When fabricated using the methods shown in Figures 1 and 2, pseudo-spiral structures with few defects are formed when charged at high voltage. It is possible to produce a positive electrode active material with a pseudo-spinel crystal structure. Positive electrode active materials with a crystalline structure of 50% or more are considered to have excellent cycle and rate characteristics. It is an active material.

[0080] To prepare a positive electrode active material having a pseudo-spinel crystal structure after high-voltage charging, the positive electrode active material must be It is made by containing magnesium and fluorine and annealing at the appropriate temperature and time. It is effective to add a magnesium source and a fluorine source to the starting material of the composite oxide. However, when added to the starting material of the composite oxide, the magnesium source and fluorine If the melting point of the fluorine source is higher than the firing temperature, the magnesium source and the fluorine source will not melt and diffusion will be difficult. This can cause many defects or distortions in the layered rock salt crystal structure. Therefore, the pseudospinel crystal structure after high voltage charging also has defects or There is a risk of distortion.

[0081] Therefore, we first investigated the layered rock salt type crystal structure with few impurities and few defects or distortions. It is preferable to obtain a composite oxide containing the magnesium source. and a fluorine source are mixed and annealed to introduce magnesium and fluorine into the surface layer of the composite oxide. By producing it in this way, defects or This makes it possible to prepare a positive electrode active material that has a pseudo-spinel structure with little distortion.

[0082] In addition, the positive electrode active material 100 produced in the above process may be further coated with another material. Further heating may be carried out.

[0083] For example, the positive electrode active material 100 can be mixed with a compound containing phosphoric acid. By mixing a compound containing phosphoric acid, it can be heated at high voltage. Even when the battery is kept in a charged state for a long time, the elution of transition metals such as cobalt is suppressed. By heating after mixing, phosphoric acid can be coated more uniformly. It can be overturned.

[0084] Examples of compounds containing phosphoric acid include lithium phosphate and ammonium dihydrogen phosphate. The mixing can be carried out by, for example, a solid phase method. The heating can be carried out at, for example, 800°C. This can be done for 2 hours.

[0085] [Positive electrode active material structure] Next, referring to FIGS. 3 and 4, a positive electrode according to one embodiment of the present invention that can be produced by the above method will be described. The active material 100 and conventional positive electrode active materials will be described, and the differences between them will be discussed. 4 illustrates the case where cobalt is used as the transition metal in the positive electrode active material. The conventional positive electrode active material described in Figure 4 contains elements other than lithium, cobalt, and oxygen. Simple cobalt that has not been processed by adding it to the surface or coating it on the surface. It is lithium cobalt oxide (LiCoO2).

[0086] <Conventional positive electrode active materials> Lithium cobalt oxide (LiCoO2), one of the conventional positive electrode active materials, is described in Non-Patent Document 1 and Non-Patent Document 2. As stated in Reference 2, the crystal structure changes depending on the depth of charge. A typical crystal structure of thium is shown in Figure 4.

[0087] As shown in Figure 4, lithium cobalt oxide at a charge depth of 0 (discharged state) is in the space group R-3 m crystal structure, and there are three CoO2 layers in the unit cell. This crystal structure is sometimes called an O3 type crystal structure. The CoO2 layer is a layer of cobalt. This refers to a structure in which an octahedral structure in which oxygen atoms are six-coordinated is connected to a plane in an edge-sharing state.

[0088] At a charge depth of 1, the crystal structure has the space group P-3m1, and CoO exists in the unit cell. There is one layer of two layers. Therefore, this crystal structure is sometimes called the O1 type crystal structure.

[0089] In addition, when the charge depth is about 0.88, lithium cobalt oxide has a crystal structure of the space group R-3m. This structure is similar to the structure of CoO2, such as P-3m1(O1), and R-3m(O3 ) and the structure of LiCoO2, which is stacked alternately. The crystal structure is sometimes called the H1-3 crystal structure. In reality, the H1-3 crystal structure is , the number of cobalt atoms per unit cell is twice that of the other structures. In this specification, the c-axis of the H1-3 type crystal structure is used as a unit to facilitate comparison with other structures. The figure will be shown as half the size of a cell.

[0090] Repeated high voltage charging and discharging to a charge depth of about 0.88 or more. Lithium cobalt oxide has a H1-3 type crystal structure and a R-3m(O3) structure in the discharged state. The crystal structure changes (i.e., non-equilibrium phase changes) between these two states.

[0091] However, these two crystal structures have a large misalignment of the CoO2 layers. As shown by the arrows, in the H1-3 type crystal structure, the CoO2 layer is significantly larger than the R-3m(O3). Such dynamic structural changes have a negative effect on the stability of the crystal structure. Ugh.

[0092] Furthermore, the difference in volume is large. When comparing the same number of cobalt atoms, the H1-3 type crystal structure The difference in volume between the O3-type crystal structure and the discharged state is more than 3.5%.

[0093] In addition, the H1-3 type crystal structure has continuous CoO2 layers such as P-3m1(O1). The resulting structure is likely to be unstable.

[0094] Therefore, repeated high-voltage charging and discharging causes the crystal structure of lithium cobalt oxide to collapse. The breakdown of the crystal structure causes a deterioration in cycle characteristics. The number of sites where lithium can exist stably decreases, and it becomes difficult to insert and extract lithium. It is thought that this is the case.

[0095] <Positive Electrode Active Material of One Embodiment of the Present Invention> ≪Inside≫ In contrast, the positive electrode active material 100 of one embodiment of the present invention has a sufficiently discharged state and a high voltage The change in the crystal structure and the number of transition metal atoms in the charged state were compared. The difference in volume is small.

[0096] The crystal structure of the positive electrode active material 100 before and after charging and discharging is shown in FIG. It is a composite oxide containing cobalt and oxygen. It is also preferable that the compound contains a halogen such as fluorine or chlorine.

[0097] The crystal structure at charge depth 0 (discharged state) in Figure 3 is R-3m(O3), the same as in Figure 4. The positive electrode active material 100 according to one embodiment of the present invention has a sufficiently charged state of about 0.88. 4. This crystal structure of space group R-3m is referred to herein as This is called a pseudo-spinel crystal structure. In the structural diagram, the lithium ion is used to explain the symmetry of the cobalt atom and the symmetry of the oxygen atom. Although the display of the material is omitted, in reality, there is about 12 atomic % of cobalt between the CoO2 layers. Lithium is present. In both the O3 and pseudospinel crystal structures, It is preferable that magnesium exists dilutely between the CoO2 layers, i.e., at the lithium site. It is also known that halogens such as fluorine exist randomly and dilutely at oxygen sites. preferable.

[0098] In the positive electrode active material 100, when a large amount of lithium is released by charging at a high voltage, the crystal structure changes. For example, as shown by the dotted line in Figure 3, These crystal structures have almost no misalignment of the CoO2 layers.

[0099] In addition, the positive electrode active material 100 has an O3-type crystal structure at a charge depth of 0 and a pseudo-sintered structure at a charge depth of 0.88. The difference in volume per unit cell of the Pinel crystal structure is 2.5% or less, more specifically, 2.2 % or less.

[0100] Therefore, the crystal structure is less likely to collapse even when repeatedly charged and discharged at high voltage.

[0101] The pseudospinel crystal structure has a unit cell with the coordinates of cobalt and oxygen as Co(0 ,0,0.5), O(0,0,x), 0.20≦x≦0.25. do.

[0102] Magnesium, which exists randomly and dilutely between the CoO2 layers, i.e., on the lithium sites, This has the effect of suppressing the displacement of the O2 layers. Therefore, magnesium exists between the CoO2 layers. Therefore, magnesium is easily converted into a pseudo-spinel crystal structure. It is preferable that magnesium is distributed throughout the particles. In the process of manufacturing the positive electrode active material 100, heat treatment is preferably performed.

[0103] However, if the heat treatment temperature is too high, cation mixing occurs and magnesium When magnesium is present in the cobalt site, The effect of maintaining the structure of R-3m is lost. Furthermore, if the heat treatment temperature is too high, There are concerns about adverse effects such as cobalt being reduced to divalent and lithium evaporating. do.

[0104] Therefore, before the heat treatment to distribute magnesium throughout the particles, the cobalt oxide It is preferable to add a halogen compound such as a fluorine compound to the lithium. Adding lithium cobalt oxide causes a decrease in the melting point of the cation. At a temperature where mixing is unlikely to occur, it is easy to distribute magnesium throughout the particles. Furthermore, if a fluorine compound is present, the corrosion resistance against the hydrofluoric acid produced by the decomposition of the electrolyte is improved. It can be expected to improve.

[0105] It should be noted that the positive electrode active material 100 has been previously described as a composite oxide having lithium, cobalt, and oxygen. In the above description, the case where the material is a single material is described, but it may contain nickel in addition to cobalt. In the case of cobalt, the number of nickel atoms in the sum of the number of cobalt and nickel atoms (Co+Ni) is The ratio Ni / (Co+Ni) is preferably less than 0.1, and more preferably 0.075 or more. It is more preferable that it is below.

[0106] If the battery is charged at a high voltage for a long period of time, transition metals will leach out of the positive electrode active material into the electrolyte, However, by having nickel in the above ratio, the positive electrode active material It may be possible to suppress the elution of transition metals from the material 100.

[0107] By adding nickel, the charge / discharge voltage is reduced, so for the same capacity, the voltage is reduced and the charge / discharge voltage is increased. This may result in suppressing the elution of transition metals and the decomposition of the electrolyte. Here, the charge / discharge voltage refers to, for example, a voltage in the range from a charge depth of zero to a predetermined charge depth.

[0108] ≪Surface layer≫ It is preferable that magnesium is distributed throughout the particles of the positive electrode active material 100. In addition, it is more preferable that the magnesium concentration in the surface layer of the particle is higher than the average of the entire particle. In other words, the magnesium concentration in the particle surface measured by XPS etc. is It is more preferable that the magnesium concentration is higher than the average magnesium concentration of the whole particle. If this happens, it is all due to crystal defects, and when charging, lithium is released from the surface, so This is the part where the lithium concentration is likely to be lower than that of the other parts. If the magnesium concentration in the surface layer is high, the change in the crystal structure will be more likely to occur. In addition, if the magnesium concentration in the surface layer is high, the electrolyte decomposes. It is also expected that the corrosion resistance against the hydrofluoric acid generated by the process will be improved.

[0109] In addition, the concentration of halogens such as fluorine in the surface layer of the positive electrode active material 100 is higher than the average of the entire particle. The presence of halogen in the surface layer, which is the region in contact with the electrolyte, Corrosion resistance to fluoric acid can be effectively improved.

[0110] In this way, the surface layer of the positive electrode active material 100 has a higher concentration of magnesium and fluorine than the inside. It is preferable that the composition of the inner layer is different from that of the inner layer. Therefore, the surface layer may have a different crystal structure from the interior. For example, at least a part of the surface layer of the positive electrode active material 100 has a rock salt type crystal structure. In addition, when the surface layer and the inside have different crystal structures, the crystal orientation of the surface layer and the inside may be It is preferable that these values ​​approximately match.

[0111] However, if the surface layer is made of only MgO or a solid solution of MgO and CoO(II), Therefore, the surface layer must contain at least cobalt, In the discharged state, it must also contain lithium and have a path for lithium insertion and desorption. Also, it is preferred that the concentration of cobalt is higher than that of magnesium.

[0112] ≪Grain boundary≫ The magnesium or halogen contained in the positive electrode active material 100 is present randomly and dilutely inside. However, it is more preferable that a portion of the metal is segregated at the grain boundaries.

[0113] In other words, the magnesium concentration at and near the grain boundaries of the positive electrode active material 100 is also It is preferable that the halogen concentration at the grain boundary and its vicinity is higher than that in other regions. It is preferable that the thickness is higher than other areas.

[0114] Like the particle surface, the grain boundary is also a planar defect. Therefore, it is prone to instability and changes in the crystal structure. Therefore, if the magnesium concentration at and near the grain boundary is high, This makes it possible to more effectively suppress changes in the crystal structure.

[0115] In addition, when the magnesium and halogen concentrations at and near the grain boundaries are high, the positive electrode active material Even if a crack occurs along the grain boundary of a grain with a quality of 100, the surface The magnesium and halogen concentrations are high near the surface. The corrosion resistance of the positive electrode active material to hydrofluoric acid can also be improved.

[0116] In this specification, the vicinity of the grain boundary refers to the region up to about 10 nm from the grain boundary. It shall be so decided.

[0117] ≪Particle size≫ If the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse. On the other hand, if the size is too small, the surface of the active material layer becomes too rough. There are also problems such as difficulty in supporting the active material layer when applied to the body and excessive reaction with the electrolyte. Therefore, D50 is preferably 1 μm or more and 100 μm or less, and more preferably 2 μm or more and 40 μm or less. It is more preferable that the thickness is 5 μm or less, and further more preferable that the thickness is 5 μm or more and 30 μm or less.

[0118] <Analysis method> One embodiment of the present invention is that a certain positive electrode active material exhibits a pseudospinel crystal structure when charged at a high voltage. Whether or not the positive electrode active material 100 is the positive electrode active material 100 can be determined by examining the positive electrode charged at a high voltage using XRD, electron beam diffraction, Analysis using neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. In particular, XRD can be used to determine the symmetry of transition metals such as cobalt contained in the positive electrode active material. It can be analyzed with high resolution, the degree of crystallinity and the orientation of the crystal can be compared, and the periodic distortion of the lattice and crystallite size can be analyzed. This is preferable in that sufficient accuracy can be obtained.

[0119] As described above, the positive electrode active material 100 according to one embodiment of the present invention is in a state where it is charged at a high voltage and in a state where it is discharged. It is characterized by the fact that there is little change in the crystal structure between the charged and discharged states. Materials with a crystal structure that exhibits large changes in state and voltage, accounting for 50 wt% or more, can withstand high-voltage charging and discharging. Furthermore, the desired crystal structure cannot be achieved by simply adding impurity elements. It should be noted that there are cases where the cobalt-containing magnesium and fluorine Although they share the common feature of being lithium nitrate, they have a pseudospinel crystal structure when charged at high voltage. When the H1-3 type crystal structure accounts for 60 wt% or more, and when the H1-3 type crystal structure accounts for 50 wt% or more, At a certain voltage, the pseudo-spinel crystal structure is almost 100 wt %. If the voltage is increased to a certain level, the H1-3 type crystal structure may occur. In order to determine whether the positive electrode active material 100 is one of the above embodiments, it is necessary to measure the crystal structure by XRD or the like. Analysis of the structure is necessary.

[0120] However, when the positive electrode active material is in a charged or discharged state at a high voltage, its crystalline structure changes when it comes into contact with the air. For example, the pseudo-spinel crystal structure may change to an H1-3 crystal structure. Therefore, all samples should be handled in an inert atmosphere such as argon. Ringing is preferred.

[0121] ≪Charging method≫ A high-temperature method for determining whether a certain composite oxide is the positive electrode active material 100 of one embodiment of the present invention Voltage charging is performed using a coin cell (CR2032 type, diameter 20mm, height 2000V) with a lithium counter electrode. 3.2mm) can be created and charged.

[0122] More specifically, the positive electrode is formed by mixing a positive electrode active material, a conductive additive, and a binder in a slurry. Alternatively, a positive electrode current collector made of aluminum foil may be coated with the conductive material.

[0123] The counter electrode can be made of lithium metal. However, if a material other than lithium metal is used for the counter electrode, When the secondary battery is turned on, the potential of the secondary battery and the potential of the positive electrode are different. Unless otherwise specified, the potential is that of the positive electrode.

[0124] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. can be used.

[0125] The separator can be made of polypropylene with a thickness of 25 μm.

[0126] The positive and negative electrode cans can be made of stainless steel (SUS). do.

[0127] The coin cell prepared under the above conditions was charged at a constant current of 4.6 V and 0.5 C, and then the current value Charge at a constant voltage until the temperature reaches 0.01C. Here, 1C is 137mA / g. Temperature After charging in this way, place the coin cell in a globe with an argon atmosphere. By disassembling it in the box and taking out the positive electrode, you can obtain the positive electrode active material charged at high voltage. When various analyses are carried out after the test, the container is sealed in an argon atmosphere to prevent reactions with external components. For example, XRD can be performed in a sealed container under an argon atmosphere. Cut.

[0128] <XRD> The CuKα1 line calculated from the pseudo-spinel crystal structure and H1-3 crystal structure model The ideal powder XRD pattern obtained by this method is shown in Figure 5. For comparison, the LiCoO 2(O3) and the ideal XRD calculated from the crystal structure of CoO2(O1) at charge depth 1 The patterns of LiCoO2(O3) and CoO2(O1) are also shown. SD (Inorganic Crystal Structure Database) (See Non-Patent Document 5) Reflex Powder Diffr, one of the modules of (BIOVIA) The 2θ range was from 15° to 75°, and the step size was e=0.01, wavelength λ1=1.540562×10 -10 m, λ2 is not set, Mono The chromator was set to single. The pattern of the H1-3 type crystal structure was The pseudospinel pattern was similarly created from the crystal structure information described in 3. The crystal structure was estimated from the XRD pattern of the positive electrode active material and analyzed using TOPAS ver. The XRD patterns were fitted using the crystal structure analysis software (manufactured by ER) and analyzed in the same way as the others. I created a new one.

[0129] As shown in Figure 5, in the pseudospinel crystal structure, 2θ = 19.30 ± 0.20° (19. 10° or more and 19.50° or less), and 2θ=45.55±0.10° (45.45° or more) A diffraction peak appears at 2θ=19.30° (below 45.65°). ±0.10° (19.20° or more and 19.40° or less), and 2θ=45.55±0.0 A sharp diffraction peak appears at 5° (45.50° or more and 45.60° or less). No peaks appear at these positions in the type crystal structure and CoO2 (P-3m1, O1). Therefore, when charged at high voltage, 2θ=19.30±0.20° and 2θ=4 The appearance of the peak at 5.55±0.10° indicates that the positive electrode active material 100 according to one embodiment of the present invention It can be said to be a characteristic.

[0130] This is the crystal structure at a charge depth of 0 and the crystal structure when charged at a high voltage. More specifically, the positions of the main diffraction peaks of both are close to each other. The difference in the positions at which the peaks appear in two or more of these, more preferably three or more, is 2θ= It can be said that 2θ is 0.7 or less, and more preferably 2θ=0.5 or less.

[0131] The positive electrode active material 100 according to one embodiment of the present invention has a pseudo-spinel crystal structure when charged at a high voltage. However, not all of the particles need to have a pseudospinel crystal structure. However, the XRD pattern may be When a rhottveld analysis was performed, it was found that the pseudo-spinel crystal structure was preferably 50 wt% or more. It is preferable that the content is 60 wt% or more, and more preferable that the content is 66 wt% or more. It is preferable that the pseudo-spinel crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably If the content is preferably 66 wt % or more, the positive electrode active material will have sufficiently excellent cycle characteristics. can be done.

[0132] In addition, even after more than 100 charge / discharge cycles from the start of measurements, Rietveld analysis showed that The pseudo-spinel crystal structure is preferably 35 wt% or more, and more preferably 40 wt% or more. It is more preferable that the content is 43 wt % or more, and further more preferable that the content is 43 wt % or more.

[0133] The crystallite size of the pseudo-spinel structure of the positive electrode active material particles is The O2 (O3) content decreases to only about 1 / 10 of that of the positive electrode before charging and discharging. Even under the measurement conditions of D, a clear peak of the pseudospinel crystal structure was observed after high-voltage charging. On the other hand, in simple LiCoO2, some of the structures resembled pseudospinel crystal structures. Even if the crystallite size is small, the peak becomes broad and small. , can be determined from the half-width of the XRD peak.

[0134] In addition, the layered rock salt structure of the particles of the positive electrode active material in the discharged state, which can be estimated from the XRD pattern, In the crystal structure, it is preferable that the lattice constant of the c-axis is small. When a foreign element substitutes for the Λ site, or when cobalt enters the oxygen tetracoordinate site (A site), Therefore, first, there is little Co3O4 with a different element substitution and a spinel-type crystal structure. In other words, a complex oxide with a layered rock salt type crystal structure with few defects is created, and then magnesium The magnesium inserted into the lithium site by mixing the sodium and fluorine sources provides good support. It is believed that it is possible to prepare a positive electrode active material that exhibits cycling characteristics.

[0135] The c-axis lattice constant of the crystal structure of the positive electrode active material in the discharged state is 14.060 before annealing. x10 -10 m or less is preferable, and 14.055 × 10 -10 m or less is more preferable, and 14 .051×10 -10 The lattice constant of the c-axis after annealing is 14. 060×10 -10 m or less is preferable.

[0136] In order to keep the c-axis lattice constant within the above range, it is preferable to have a small amount of impurities, especially cobalt. The amount of transition metals other than manganese and nickel added is preferably small. It is preferable that the content is 0 ppm wt or less, and more preferably 1500 ppm wt or less. It is also preferable that the cation mixing between lithium and cobalt, manganese, or nickel is small. It is preferable to do so.

[0137] The characteristics revealed from the XRD pattern are those of the internal structure of the positive electrode active material. In the case of a positive electrode active material with an average particle diameter (D50) of about 1 μm to 100 μm, the In comparison, the volume of the surface layer is very small, so the surface layer of the positive electrode active material 100 is different from the inside. Even if the material has a crystal structure, it is highly likely that it will not appear in the XRD pattern.

[0138] ESR Here, the difference between the pseudospinel crystal structure and other crystal structures will be explained using FIGS. 6 and 7. The case of using ESR to make this determination is explained below. In the case of a pseudospinel crystal structure, Fig. 3 and As shown in Figure 6(A), cobalt exists in the site where oxygen is six-coordinated. In the case of cobalt with 6 oxygen coordination, the 3d orbitals are e g Orbit and t 2g split into orbits, and oxygen is present t, an orbit that avoids the direction of the 2g Low orbital energy. Oxygen hexacoordinated site The part of the cobalt that 2g Diamagnetic Co with all orbitals filled 3+ The cobalt However, the other part of the cobalt present in the oxygen hexacoordinated site is paramagnetic Co 2+ or Co 4 + This paramagnetic cobalt may be Co 2+ and Co 4+ In either case In the case of ions, there is only one unpaired electron, so they cannot be distinguished by ESR. However, the valence of the surrounding elements determines the Therefore, either valence can be used.

[0139] On the other hand, conventional positive electrode active materials are spinel-type materials that do not contain lithium in the surface layer when charged. In this case, the spinel shown in Figure 7(A) can be used. The resulting material has a Co3O4 crystal structure.

[0140] When spinel is described by the general formula A[B2]O4, element A is tetracoordinated and element B is hexacoordinated. Therefore, in this specification, the site with 4-coordinated oxygen atoms is referred to as the A site, and the site with 6-coordinated oxygen atoms is referred to as the B site. The site is sometimes called the B site.

[0141] In the spinel-type crystal structure of Co3O4, not only the B site with 6 oxygen atoms but also the B site with 4 oxygen atoms are Cobalt also exists at the A site. As shown in Figure 7(B), in the case of cobalt with 4 oxygen coordination, Split e g Orbit and t 2g Of the orbitals, e g The orbital energy is low. Co. 2+ , Co 3+ and Co 4+ All of these have unpaired electrons and are paramagnetic. Therefore, if particles with sufficient spinel-type Co3O4 are analyzed by ESR etc., it is found that Co 2+ , Co 3+ or Co 4+ A peak due to paramagnetic cobalt should be detected. do.

[0142] However, in the positive electrode active material 100 according to one embodiment of the present invention, the paramagnetic cobalt with four oxygen atoms is Therefore, the pseudospinel referred to in this specification and elsewhere does not include the positive Unlike spinel, it does not contain ESR-detectable amounts of tetracoordinated cobalt. Therefore, compared to conventional examples, the positive electrode active material of one embodiment of the present invention has a higher spin that can be detected by ESR or the like. The peaks due to the Co3O4 type may be small or too few to be recognized. Since spinel-type Co3O4 does not contribute to the charge / discharge reaction, the less spinel-type Co3O4 there is, the better. As can be seen from the ESR analysis, the positive electrode active material 100 is different from conventional examples. It can be determined that this is the case.

[0143] XPS X-ray photoelectron spectroscopy (XPS) measures the surface to a depth of approximately 2 to 8 nm (usually approximately 5 nm). Since it is possible to analyze the area, the concentration of each element can be quantified for about half of the surface area. Furthermore, narrow scan analysis can be used to analyze the bonding state of elements. The quantitative accuracy of XPS is usually about ±1 atomic %, and the detection limit varies depending on the element. It depends on the material, but it is about 1 atomic %.

[0144] When XPS analysis was performed on 100% of the positive electrode active material, the cobalt concentration was set to 1. The relative value of the magnesium concentration is preferably 0.4 or more and 1.5 or less, and 0.45 or more and less than 1.00. The relative value of the concentration of halogen such as fluorine is preferably 0.05 or more and 1.5 or less. It is preferably 0.3 or more and 1.00 or less.

[0145] In addition, when the positive electrode active material 100 was analyzed by XPS, the bond energy between fluorine and other elements was The peak showing the ion exchange reaction is preferably 682 eV or more and less than 685 eV, and more preferably 684.3 eV This is about the same as the binding energy of lithium fluoride, 68 5 eV, and the binding energy of magnesium fluoride, 686 eV. In other words, when the positive electrode active material 100 contains fluorine, the lithium fluoride and fluorine Bonds other than magnesium fluoride are preferred.

[0146] Furthermore, when the positive electrode active material 100 was analyzed by XPS, the bond between magnesium and other elements was The peak showing the energy is preferably 1302 eV or more and less than 1304 eV, It is more preferable that the bond energy of magnesium fluoride is about 1303 eV. This is a different value from the 1305 eV, which is the energy of magnesium oxide. In other words, when the positive electrode active material 100 contains magnesium, magnesium fluoride Preferably, the bond is other than the following.

[0147] EDX Among EDX measurements, ED is a method of measuring while scanning an area and evaluating the area two-dimensionally. It is sometimes called EDX area analysis. Data on linear areas can be extracted from EDX area analysis and used to Evaluating the distribution of the molecular concentration within the positive electrode active material particles is sometimes called line analysis.

[0148] EDX surface analysis (e.g., elemental mapping) was performed to identify the internal, surface, and grain boundary regions. The magnesium and fluorine concentrations can be quantitatively analyzed. The analysis allows for peaks in magnesium and fluorine concentrations to be analyzed.

[0149] When EDX analysis was performed on the positive electrode active material 100, the peak of magnesium concentration in the surface layer It is preferable that the particles are present at a depth of up to 3 nm from the surface of the positive electrode active material 100 toward the center. It is preferable that the depth of the pores is within 1 nm, and more preferable that the depth of the pores is within 0.5 nm. is more preferable.

[0150] In addition, the distribution of fluorine in the positive electrode active material 100 preferably overlaps with the distribution of magnesium. Therefore, when EDX analysis is performed, the peak of the fluorine concentration in the surface layer is It is preferable that the surface of 100 is located at a depth of 3 nm from the center, and the depth of 1 nm It is more preferable that the surface is present up to a depth of 0.5 nm, and even more preferable that the surface is present up to a depth of 0.5 nm. stomach.

[0151] When the positive electrode active material 100 is subjected to a line analysis or a surface analysis, the microstructure in the vicinity of the grain boundaries is The ratio of the number of magnesium and cobalt atoms (Mg / Co) is preferably 0.020 or more and 0.50 or less. It is more preferable that the ratio is 0.025 or more and 0.30 or less. It is even more preferable that the ratio is 0.030 or more and 0. 20 or less is preferable.

[0152] ≪dQ / dVvsV curve≫ Furthermore, the positive electrode active material of one embodiment of the present invention can be charged at a high voltage and then discharged at a low current of, for example, 0.2 C or less. When discharging at a certain rate, a characteristic voltage change may appear near the end of the discharge. is in the range of 3.5V to 3.9V in the dQ / dV vs V curve obtained from the discharge curve. , which can be clearly seen by the presence of at least one peak.

[0153] (Embodiment 2) In this embodiment, a secondary battery having the positive electrode active material 100 described in the previous embodiment is used. In this embodiment, the positive electrode, the negative electrode, and the electrolyte solution However, the following description will be given taking as an example a secondary battery enclosed in an exterior body.

[0154] [Positive electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector.

[0155] <Cathode active material layer> The positive electrode active material layer contains at least a positive electrode active material. In addition, other substances such as a coating on the surface of the active material, a conductive additive, or a binder may be included.

[0156] The positive electrode active material 100 described in the previous embodiment can be used as the positive electrode active material. By using the positive electrode active material 100 described in the previous embodiment, it is possible to achieve high capacity and good cycle characteristics. An excellent secondary battery can be obtained.

[0157] As the conductive additive, a carbon material, a metal material, a conductive ceramic material, or the like can be used. A fibrous material may also be used as the conductive additive. The content of the electrical auxiliary agent is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less. is more preferred.

[0158] The conductive additive can form an electrically conductive network in the active material layer. The conductive agent can maintain the electrical conduction path between the positive electrode active materials. By adding an electrical auxiliary agent, it is possible to realize an active material layer with high electrical conductivity. .

[0159] Examples of the conductive additive include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon fiber. Examples of carbon fibers that can be used include mesophase pitch carbon fibers. Carbon fibers such as isotropic pitch-based carbon fibers can be used. Carbon nanofibers and carbon nanotubes can be used. The tube can be produced by, for example, vapor phase growth method. For example, carbon black (acetylene black (AB) etc.), graphite particles Carbon materials such as graphene and fullerene can be used. Metal powders and fibers such as nickel, aluminum, silver, and gold, as well as conductive ceramic materials, etc. It can be used.

[0160] A graphene compound may also be used as the conductive additive.

[0161] Graphene compounds have excellent electrical properties, such as high conductivity, as well as high flexibility and high In addition, graphene may have excellent physical properties such as high mechanical strength. The graphene compound has a planar shape, which allows for surface contact with low contact resistance. In addition, even if they are thin, they can have very high conductivity, and even a small amount can be used to efficiently conduct electricity within the active material layer. Therefore, the graphene compound can be used as a conductive additive. This is preferable because it is possible to increase the contact area between the active material and the conductive additive. By using a laser dryer, the entire surface of the active material is covered with graphene, which is a conductive additive. It is preferable to form the compound as a coating. In addition, electrical resistance may be reduced. Here, examples of the graphene compound include graphene, multigraphene, It is particularly preferable to use RGO. Here, RGO is, for example, graphene oxide (g It refers to a compound obtained by reducing ethylenediaminetetraacetic acid (GO).

[0162] When using an active material with a small particle size, for example, an active material with a particle size of 1 μm or less, the specific surface area of ​​the active material is Therefore, a large amount of conductive additive is required. This tends to result in a relative decrease in the amount of active material carried. If the amount of the conductive additive decreases, the capacity of the secondary battery will decrease. When graphene compounds are used, they efficiently form conductive paths even in small amounts. This is particularly preferable because it is possible to avoid reducing the amount of the active material carried.

[0163] As an example, in the case where a graphene compound is used as a conductive additive in the active material layer 200, An example of the cross-sectional structure will be described.

[0164] 8(A) shows a vertical cross-sectional view of the active material layer 200. The active material layer 200 is made of granular positive electrode active material. 100, a graphene compound 201 as a conductive additive, and a binder (not shown). Here, the graphene compound 201 may be, for example, graphene or multi-graphene. Here, the graphene compound 201 preferably has a sheet shape. In addition, the graphene compound 201 may be a multi-graphene or (and) a multi-graphene. The graphene may be partially overlapped to form a sheet.

[0165] In the vertical cross section of the active material layer 200, as shown in FIG. 8(B), In FIG. 8(B), the sheet-like graphene compound 201 is dispersed almost uniformly. The graphene compound 201 is shown schematically in bold, but in reality it is a single layer or multiple layers of carbon molecules. The graphene compounds 201 are thin films having a thickness of 1000 nm. The positive electrode active material 100 is partially covered with the positive electrode active material 100 or is attached to the surface of a plurality of particles of the positive electrode active material 100. Since they are formed as described above, they are in surface contact with each other.

[0166] Here, a plurality of graphene compounds are bonded to each other to form a mesh-like graphene compound. It is possible to form a graphene sheet (hereinafter referred to as a graphene compound net or graphene net). When the active material is covered with a graphene net, the graphene net can connect the active material to each other. It can also function as a binder to bind the particles together. Therefore, the ratio of the active material to the electrode volume or weight can be reduced. In other words, the capacity of the secondary battery can be increased.

[0167] Here, graphene oxide is used as the graphene compound 201, and is mixed with an active material to form an active material. After forming the layer that will become the layer 200, it is preferable to reduce it. By using graphene oxide, which has extremely high dispersibility in polar solvents, The mixture 201 can be dispersed approximately uniformly inside the active material layer 200. The solvent is evaporated from the dispersion medium containing the dispersed graphene oxide, and the graphene oxide is reduced. Therefore, the graphene compound 201 remaining in the active material layer 200 partially overlaps with each other. By dispersing the particles so that they are in surface contact with each other, a three-dimensional conductive path can be formed. The reduction of graphene oxide may be performed by, for example, heat treatment or by using a reducing agent. It is also possible.

[0168] Therefore, unlike granular conductive additives such as acetylene black, which come into point contact with the active material, graphite Since the compound 201 enables surface contact with low contact resistance, it is more effective than ordinary conductive additives. The amount of the positive electrode active material 100 is smaller than that of the graphene compound 201, and the electrical conductivity between the positive electrode active material 100 and the graphene compound 201 is improved. Therefore, the ratio of the positive electrode active material 100 in the active material layer 200 can be increased. This makes it possible to increase the discharge capacity of the secondary battery.

[0169] In addition, by using a spray dryer, the entire surface of the active material is covered with a conductive additive in advance. A graphene compound is formed as a coating, and the active material is then conductively bonded to the graphene compound. An electrical path can also be formed.

[0170] Examples of binders include styrene-butadiene rubber (SBR) and styrene-isoprene. Acrylonitrile-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene It is preferable to use a rubber material such as a propylene-diene copolymer. Fluorine rubber can be used.

[0171] As the binder, it is preferable to use, for example, a water-soluble polymer. As the molecule, for example, polysaccharides can be used. cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose Cellulose derivatives such as cellulose, diacetyl cellulose, and regenerated cellulose, as well as starch These water-soluble polymers can be used in combination with the rubber materials described above. It is even better if there is one.

[0172] Alternatively, the binder may be polystyrene, polymethyl acrylate, or polymethyl methacrylate. (Polymethyl methacrylate, PMMA), Sodium polyacrylate, Polyvinyl Alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, Polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene Polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, It is preferable to use materials such as polyvinyl acetate and nitrocellulose.

[0173] The binder may be used in combination with two or more of the above.

[0174] For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with other materials. For example, rubber materials have excellent adhesive strength and elasticity, but it is difficult to adjust the viscosity when mixed with a solvent. In such cases, for example, mixing with a material that has a particularly excellent viscosity adjusting effect can As a material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer is preferably used. Furthermore, examples of water-soluble polymers that are particularly effective in adjusting viscosity include the aforementioned polysaccharides, such as carbohydrates. Carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxy Cellulose derivatives such as propyl cellulose, diacetyl cellulose, and regenerated cellulose Carbohydrates and starches can be used.

[0175] The cellulose derivatives such as carboxymethyl cellulose are, for example, By converting cellulose into salts such as sodium salts or ammonium salts, the solubility increases, It is easier to exert its effect as a viscosity adjuster. The increased solubility makes it easier to make electrode slurry. When preparing a substrate, it is also possible to improve the dispersibility of the active material and other components. In this case, the cellulose and cellulose derivatives used as binders for electrodes include These salts are also included.

[0176] Water-soluble polymers stabilize viscosity by dissolving in water, and also act as active materials and binders. Other materials to be combined, such as styrene butadiene rubber, are stably dispersed in aqueous solution. In addition, since it has functional groups, it can be easily and stably adsorbed onto the surface of the active material. It is expected that cellulose derivatives such as carboxymethyl cellulose will For example, many materials have functional groups such as hydroxyl groups and carboxyl groups. It is expected that the polymers will interact with each other and widely cover the surface of the active material.

[0177] When the binder that covers or contacts the surface of the active material forms a film, it is called a passive film. It is expected that the passive film will also play a role in suppressing the decomposition of the electrolyte. It is a film with no electrical conductivity or extremely low electrical conductivity, and is When a dynamic membrane is formed, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. In addition, the passive film suppresses electrical conductivity while allowing lithium ions to conduct. And even more desirable.

[0178] <Positive electrode current collector> The positive electrode current collector may be made of metals such as stainless steel, gold, platinum, aluminum, titanium, or the like. Highly conductive materials such as alloys of these can be used. It is preferable that silicon, titanium, neodymium, scavenger, etc. are not eluted at the potential of the positive electrode. Aluminum alloys containing elements such as indium and molybdenum that improve heat resistance are used. It can also be formed from a metal element that reacts with silicon to form silicide. Metal elements that react with silicon to form silicide include zirconium, titanium, and Tantalum, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten , cobalt, nickel, etc. Current collectors are available in foil, plate (sheet), mesh, and punched shapes. The current collector may be in the form of a metal, an expanded metal, or the like. It is recommended to use a thickness of 5 μm or more and 30 μm or less.

[0179] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer contains a conductive additive and and a binder.

[0180] <Negative electrode active material> As the negative electrode active material, for example, an alloy-based material or a carbon-based material can be used.

[0181] As a negative electrode active material, it is possible to carry out charge-discharge reactions by alloying and dealloying reactions with lithium. Any suitable element can be used, such as silicon, tin, gallium, aluminum, Rumanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one of these elements can be used. These elements have a large capacity compared to carbon. Silicon has a particularly high theoretical capacity of 4200mAh / g. It is preferable to use silicon. Alternatively, compounds containing these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V 2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3 Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, I nSb, SbSn, etc. Here, the charge / discharge reaction occurs due to alloying and dealloying reactions with lithium. Elements capable of undergoing a reaction and compounds containing such elements are sometimes called alloy materials. do.

[0182] In this specification and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO refers to SiO x Here, it is preferable that x has a value close to 1. For example, x is 0 A value between 0.2 and 1.5 is preferred, and a value between 0.3 and 1.2 is more preferred.

[0183] Carbon materials include graphite, easily graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). carbon nanotubes, graphene, carbon black, etc. may be used. .

[0184] Examples of graphite include artificial graphite and natural graphite. Examples include carbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, as the artificial graphite, spherical graphite having a spherical shape can be used. For example, the MCMB may have a spherical shape, which is preferable. It is relatively easy to reduce the particle size, which is sometimes preferable. Examples include flake graphite and spherical natural graphite.

[0185] Graphite is formed when lithium ions are inserted into graphite (forming a lithium-graphite intercalation compound) It shows a low potential similar to that of lithium metal (0.05V to 0.3V vs. Li / Li + This allows the lithium-ion secondary battery to exhibit a high operating voltage. Furthermore, graphite has a relatively high capacity per unit volume, a relatively small volume expansion, and is inexpensive. It is preferable because it has advantages such as higher safety compared to metallic lithium.

[0186] In addition, titanium dioxide (TiO2) and lithium titanium oxide (Li4T i5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5) Oxides such as tungsten oxide (WO2) and molybdenum oxide (MoO2) can be used. can.

[0187] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, which has a Li3N structure. Li 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm 3 ) And preferable.

[0188] When a composite nitride of lithium and a transition metal is used, the negative electrode active material contains lithium ions, The positive electrode active material is a combination of materials such as V2O5 and Cr3O8 that do not contain lithium ions. It is preferable that a material containing lithium ions is used as the positive electrode active material. By first removing the lithium ions contained in the positive electrode active material, A complex nitride of lithium and a transition metal can be used.

[0189] In addition, a material that undergoes a conversion reaction can also be used as the negative electrode active material. , cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. A transition metal oxide that does not form an alloy with the metal may be used as the negative electrode active material. Further materials that can be produced include Fe2O3, CuO, Cu2O, RuO2, Cr2O3, etc. oxide, CoS 0.89 , NiS, CuS and other sulfides, Zn3N2, Cu3N, Ge3 Nitrides such as N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. It also occurs with fluoride.

[0190] The conductive additive and binder that can be contained in the negative electrode active material layer are the same as those that can be contained in the positive electrode active material layer. The same materials as the conductive additive and binder can be used.

[0191] <Negative electrode current collector> The negative electrode current collector can be made of the same material as the positive electrode current collector. It is preferable to use a material that does not alloy with carrier ions such as lithium.

[0192] [Electrolyte] The electrolytic solution contains a solvent and an electrolyte. The solvent for the electrolytic solution is preferably an aprotic organic solvent. For example, ethylene carbonate (EC), propylene carbonate (PC), ethylene carbonate, chloroethylene carbonate, vinylene carbonate, gamma-butyrolactone lactone, 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 sulfone oxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran One of tetrahydrofuran, sulfolane, sultone, etc., or two or more of these Combinations and ratios may be used.

[0193] In addition, a flame-retardant and non-volatile ionic liquid (room-temperature molten salt) is used as the solvent for the electrolyte. By using one or more batteries, the internal temperature of the secondary battery can be increased due to an internal short circuit or overcharging. Even if the battery is not fully charged, it can prevent the secondary battery from exploding or catching fire. Ionic liquids are made up of cations and anions. The organic cations used in the electrolyte include quaternary cations. Ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, etc. aliphatic onium cations such as imidazolium cations and pyridinium cations Aromatic cations are also used as anions in electrolytes. Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkyl Sulfonate anion, tetrafluoroborate anion, perfluoroalkylborate anion, hexafluorophosphate anion, or perfluoroalkylphosphate anions, etc.

[0194] The electrolyte to be dissolved in the solvent is, for example, LiPF6, LiClO4, Li AsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4 , Li2B 10 Cl 10 , Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO 3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2) 2. Lithium such as LiN(C4F9SO2)(CF3SO2) and LiN(C2F5SO2)2 Use one or more of these ammonium salts in any combination and ratio. can be done.

[0195] The electrolyte used in secondary batteries is free from granular dust and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). It is preferable to use a highly purified electrolyte solution with a low content of ammonium hydroxide. Specifically, the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less, more preferably It is preferably 0.01% or less.

[0196] In addition, the electrolyte contains vinylene carbonate, propane sultone (PS), and tert-butyl ether. Benzene (TBB), Fluoroethylene carbonate (FEC), Lithium bis(oxalate) Lithium borate (LiBOB), as well as dinitriles such as succinonitrile and adiponitrile Additives such as compounds may be added. The concentration of the added material is, for example, It should be between 0.1 wt% and 5 wt%.

[0197] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0198] The use of polymer gel electrolytes increases safety against leakage, etc. It is possible to make the device thinner and lighter.

[0199] The polymers that can be gelled include silicone gel, acrylic gel, acrylonitrile gel, Polyethylene oxide gel, polypropylene oxide gel, fluorine polymer Gel or the like can be used.

[0200] Examples of the polymer include polyalkylene oxides such as polyethylene oxide (PEO). Polymers with a hexagonal structure, PVDF, polyacrylonitrile, etc., and their For example, a copolymer containing PVDF and hexafluoropropylene (H PVDF-HFP, a copolymer of PVDF and PVDF, can be used. The mer may have a porous shape.

[0201] In addition, instead of the electrolyte solution, solid electrolytes containing inorganic materials such as sulfides and oxides, and P A solid electrolyte containing a polymer material such as EO (polyethylene oxide) can be used. When a solid electrolyte is used, there is no need to install a separator or spacer. Since the entire pond can be solidified, there is no risk of leakage, dramatically improving safety.

[0202] [Separator] The secondary battery preferably has a separator. The separator may be made of, for example, paper. , nonwoven fabric, glass fiber, ceramics, or nylon (polyamide), vinylon (poly Vinyl alcohol fiber), polyester, acrylic, polyolefin, polyurethane The separator can be made of synthetic fibers or the like. It is preferable that the electrode be processed into a shape such that it wraps around either the positive electrode or the negative electrode.

[0203] The separator may have a multi-layer structure. For example, the separator may be made of an organic material such as polypropylene or polyethylene. The material film is made of ceramic material, fluorine material, polyamide material, or a mixture of these. As a ceramic material, for example, aluminum oxide can be used. Examples of the fluorine-based material include fluorine particles, silicon oxide particles, etc. PVDF, polytetrafluoroethylene, etc. can be used. For example, nylon, aramid (meta-aramid, para-aramid), etc. can be used. can.

[0204] Coating with ceramic materials improves oxidation resistance, making it suitable for separators during high-voltage charging and discharging. This can suppress the deterioration of the battery and improve the reliability of the secondary battery. By coating, the separator and electrodes can be more easily attached to each other, improving output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, which contributes to the safety of secondary batteries. Safety can be improved.

[0205] For example, a polypropylene film is coated on both sides with a mixture of aluminum oxide and aramid. Alternatively, aluminum oxide may be applied to the surface of the polypropylene film that comes into contact with the positive electrode. Alternatively, the surface of the negative electrode that comes into contact with the carbon black may be coated with a mixed material of carbon black and aramid, and then coated with a fluorine-based material.

[0206] By using a multilayer separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin. Since the temperature can be maintained, the capacity per volume of the secondary battery can be increased.

[0207] [Exterior body] The exterior of the secondary battery is made of a metal material such as aluminum or a resin material. Also, a film-like outer casing can be used. For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. On the film made of the material, a highly flexible metal such as aluminum, stainless steel, copper, or nickel is A metal thin film is then formed on the metal thin film, and the outer surface of the exterior body is made of a polyamide resin or polyester. A three-layer film having an insulating synthetic resin film such as a vinyl resin can be used.

[0208] [Charge / discharge method] The secondary battery can be charged and discharged, for example, as follows.

[0209] ≪CC charging≫ First, we will explain CC charging as one of the charging methods. CC charging is a method in which the battery is constantly charged for the entire charging period. This is a charging method in which a constant current flows through the secondary battery and charging stops when the voltage reaches a specified level. Assuming that the secondary battery is an equivalent circuit with internal resistance R and secondary battery capacity C as shown in Figure 9(A), In this case, the secondary battery voltage V B is the voltage V across the internal resistance R R and the secondary battery capacity C Applied voltage V C It is the sum of.

[0210] During CC charging, the switch is turned on and a constant voltage is applied, as shown in Figure 9(A). Current I flows through the secondary battery. During this time, current I is constant, so V R = R × I Ohm's Law According to the law, the voltage V across the internal resistance R R On the other hand, the voltage applied to the secondary battery capacity C is also constant. Pressure V C increases over time. Therefore, the secondary battery voltage V B As time passes, Both rise.

[0211] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, charging stops. When CC charging is stopped, the switch is turned off and the current I = 0, as shown in Figure 9(B). Therefore, the voltage V applied to the internal resistance R R Therefore, the secondary battery voltage V B is decreasing.

[0212] The secondary battery voltage V during CC charging and after CC charging is stopped B and charging current An example is shown in Figure 9(C). The secondary battery voltage V B But C C It shows a slight decrease after charging is stopped.

[0213] ≪CCCV charging≫ Next, we will explain CCCV charging, which is a charging method different from the above. First, charge the battery up to a specified voltage using CC charging, then use CV (constant voltage) charging to reduce the current that flows. This is a charging method in which charging is continued until the current becomes low, specifically until the end current value is reached.

[0214] During CC charging, the constant current power supply is switched on, as shown in Figure 10(A). The constant voltage power supply is switched off, and a constant current I flows through the secondary battery. During this time, the current I Since is constant, V R According to Ohm's law, the voltage V applied to the internal resistance R is R too On the other hand, the voltage V applied to the secondary battery capacity C is constant. C increases over time. Therefore, the secondary battery voltage V B increases over time.

[0215] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, the CC charge is switched to C During CV charging, the constant voltage voltage is switched to V charging, as shown in Figure 10(B). The power supply switch is turned on, the constant current power supply switch is turned off, and the secondary battery voltage V B is constant On the other hand, the voltage V applied to the secondary battery capacity C C V increases over time. B =V R +V C Therefore, the voltage V across the internal resistance R R becomes smaller over time. Voltage V across internal resistance R R As becomes smaller, V R By Ohm's law, = R × I, The current I flowing through the secondary battery also becomes smaller.

[0216] When the current I flowing through the secondary battery reaches a predetermined current, for example, a current equivalent to 0.01C, When CCCV charging is stopped, all switches are turned off as shown in Figure 10(C). The switch is turned off and the current I becomes 0. Therefore, the voltage V applied to the internal resistance R R is 0V However, the voltage V applied to the internal resistance R due to CV charging R was small enough Therefore, even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B hardly descends at all.

[0217] The secondary battery voltage V during CCCV charging and after CCCV charging is stopped B and An example of the charging current is shown in Figure 10(D). Even if CCCV charging is stopped, the secondary battery voltage V B Gahoto It shows that the aircraft is barely descending.

[0218] ≪CC discharge≫ Next, we will explain CC discharge, which is one of the discharge methods. CC discharge is a method in which the A constant current flows from the secondary battery, and the secondary battery voltage V B becomes a certain voltage, for example 2.5V. This is a discharge method in which the discharge is stopped when

[0219] The secondary battery voltage V during CC discharge B An example of the discharge current is shown in Figure 11. According to the secondary battery voltage V B is shown to be descending.

[0220] Next, the discharge rate and charge rate will be explained. It is the relative ratio of the current during discharge and is expressed in units of C. For a battery with a rated capacity of X (Ah), In this case, the current equivalent to 1C is X(A). When discharging with a current of 2X(A), the current is 2C. If it is discharged at a current of X / 5(A), it is said to be discharged at 0.2C. The same applies to the charging rate; if you charge with a current of 2X (A), it will be charged at 2C. When charging with a current of X / 5(A), it was said to be charged at 0.2C. .

[0221] (Embodiment 3) In this embodiment, the shape of the secondary battery having the positive electrode active material 100 described in the previous embodiment is The material used in the secondary battery described in this embodiment is the same as that in the previous embodiment. The description of the condition can be taken into consideration.

[0222] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. 12(B) is a cross-sectional view of the secondary battery shown in FIG.

[0223] The coin-type secondary battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal. 302 is insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is composed of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector 305. The negative electrode 307 is formed by a negative electrode current collector 308 and a The negative electrode active material layer 309 is formed by bonding the negative electrode active material layer 309 to the negative electrode active material layer 309 .

[0224] The positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 are each an active material. The barrier layer need only be formed on one side.

[0225] The positive electrode can 301 and the negative electrode can 302 are made of nickel and aluminum, which are corrosion-resistant to the electrolyte. , titanium, or alloys thereof or alloys of these with other metals (e.g. stainless steel) In addition, nickel or aluminum can be used to prevent corrosion by the electrolyte. The positive electrode can 301 is preferably coated with a positive electrode 304, and the negative electrode can 302 is preferably coated with a negative electrode 304. 7 and electrically connect to each other.

[0226] The negative electrode 307, the positive electrode 304, and the separator 310 are impregnated with an electrolyte, and the resulting structure is shown in FIG. ) the positive electrode can 301 is placed downward, and the positive electrode 304, separator 310, negative electrode 307, The positive electrode can 301 and the negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are secured together with a gasket 303 interposed therebetween. Then, the laminate is pressed to form a coin-type secondary battery 300.

[0227] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, it is possible to achieve high capacity cycling. The coin-type secondary battery 300 can be made to have excellent characteristics.

[0228] Here, the flow of current during charging of the secondary battery will be explained using FIG. 12(C). When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In secondary batteries that use lithium, the anode and cathode are connected by charging and discharging. The cathode (electrode) is switched, and the oxidation reaction and reduction reaction are switched. The electrode with a higher reaction potential is called the positive electrode, and the electrode with a lower reaction potential is called the negative electrode. In this case, even during charging, discharging, or when a reverse pulse current is applied, Even when an electric current flows through the positive electrode, it is called the "positive electrode" or "+ electrode (plus electrode)" and the negative electrode is called the "negative electrode" or "-electrode (minus electrode)". When the terms anode (positive electrode) and cathode (negative electrode) are used, the difference between charging and discharging is Therefore, the anode and cathode are often used interchangeably. The term "anode" (negative electrode) is not used in this specification. When using the terms "positive electrode" or "cathode," specify whether it is charging or discharging, and It will also be noted whether it corresponds to a positive pole (positive electrode) or a negative pole (negative electrode).

[0229] A charger is connected to the two terminals shown in FIG. 12(C) to charge the secondary battery 300. As the charging of the secondary battery 300 progresses, the potential difference between the electrodes increases.

[0230] [Cylindrical secondary battery] Next, an example of a cylindrical secondary battery will be described with reference to FIG. 13. Cylindrical secondary battery 600 13(A) shows an external view of the cylindrical secondary battery 600. FIG. 13(B) shows a schematic cross section of the cylindrical secondary battery 600. As shown in FIG. 13(B), the cylindrical secondary battery 600 has a It has a positive electrode cap (battery lid) 601 and a battery can (external can) 602 on the side and bottom. The positive electrode cap and the battery can (external can) 602 are connected by a gasket (insulating packing) )610.

[0231] Inside a hollow cylindrical battery can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are placed between a separator 6 The battery element is wound around the sensor. The battery can 602 is closed at one end and open at the other. The battery can 602 is made of a material that is resistant to corrosion by the electrolyte, such as nickel, aluminum, or titanium. These metals, or their alloys or alloys of these with other metals (e.g., stainless steel, etc.) are used. In addition, to prevent corrosion by the electrolyte, nickel, aluminum, etc. It is preferable to coat the battery can 602. Inside the battery can 602, the positive electrode, the negative electrode, and The battery element with the separator wound around it 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 a non-aqueous electrolyte (not shown). The non-aqueous electrolyte can be the same as that used in coin-type secondary batteries. .

[0232] The positive and negative electrodes used in cylindrical storage batteries are wound, so active materials are formed on both sides of the current collector. A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative electrode A negative electrode terminal (negative electrode current collecting lead) 607 is connected to the positive electrode terminal 603. The positive terminal 60 and the positive terminal 607 can be made of a metal material such as aluminum. 3 is resistance-welded to the safety valve mechanism 612, and the negative terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 is a PTC (Positive Temperature Coupling) element. It is electrically connected to the positive electrode cap 601 via a stable (efficient) 611. When the internal pressure of the battery exceeds a predetermined threshold, the valve mechanism 612 closes the positive electrode cap 601 and The PTC element 611 cuts off the electrical connection with the positive electrode 604. It is a thermal resistance element whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current and prevents abnormalities. It prevents heat buildup. The PTC element contains a barium titanate (BaTiO3) based semiconductor. Conductive ceramics or the like can be used.

[0233] 13(C), a plurality of secondary batteries 600 are mounted on conductive plates 613 and 614. The secondary batteries 600 may be sandwiched between the secondary batteries 600 to form a module 615. They may be connected in series, or may be connected in parallel and then connected in series. By configuring a module 615 having a plurality of secondary batteries 600, It can extract a large amount of power.

[0234] FIG. 13(D) is a top view of the module 615. For clarity of illustration, the conductive plate 613 is As shown in FIG. 13(D), the module 615 includes a plurality of secondary batteries 600. The device may have a conductive wire 616 for electrical connection. A conductive plate is provided on the conductive wire 616. Furthermore, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 is overheated, the temperature control device 617 cools the secondary battery 600. If the temperature controller 617 is too cold, it can be heated. The performance of the module 615 is less affected by the outside temperature. The medium is preferably insulating and non-flammable.

[0235] By using the positive electrode active material described in the above embodiment for the positive electrode 604, it is possible to achieve high capacity cycling. The cylindrical secondary battery 600 can be made to have excellent characteristics.

[0236] [Example of secondary battery structure] Another structural example of the secondary battery will be described with reference to FIGS.

[0237] 14(A) and 14(B) are diagrams showing the external appearance of the secondary battery. , and are connected to antennas 914 and 915 via circuit board 900. In addition, a label 910 is attached to the secondary battery 913. Furthermore, as shown in FIG. As shown, the secondary battery 913 is connected to the terminal 951 and the terminal 952 .

[0238] The circuit board 900 has a terminal 911 and a circuit 912. The terminal 911 is connected to a terminal 951. , terminal 952, antenna 914, antenna 915, and circuit 912. A plurality of terminals 911 are provided, and each of the plurality of terminals 911 is used as a control signal input terminal, a power supply terminal, etc. may also be used.

[0239] The circuit 912 may be provided on the back surface of the circuit board 900. The antenna 915 is not limited to a coil shape, but may be, for example, a wire shape or a plate shape. Planar antenna, aperture antenna, traveling wave antenna, EH antenna, magnetic field antenna, dielectric Alternatively, antenna 914 or antenna 915 may be used. The flat conductor may function as one of the conductors for electric field coupling. In other words, the capacitor has two conductors, one of which is an annulus. The antenna 914 or the antenna 915 may be activated. Instead, power can be exchanged using an electric field.

[0240] The line width of antenna 914 is preferably larger than the line width of antenna 915. This allows the amount of power received by the antenna 914 to be increased.

[0241] The secondary battery has a layer 916 between the antenna 914 and the antenna 915 and the secondary battery 913. The layer 916 has a function of shielding an electromagnetic field generated by the secondary battery 913, for example. The layer 916 may be made of, for example, a magnetic material.

[0242] The structure of the secondary battery is not limited to that shown in FIG.

[0243] For example, as shown in FIGS. 15(A-1) and 15(A-2), In the secondary battery 913 shown in (B), an antenna may be provided on each of a pair of opposing surfaces. FIG. 15(A-1) is an external view showing one of the pair of surfaces, and FIG. 15(A-2) is an external view showing the pair of surfaces. 14(A) and 14(B) are external views showing the other of the pair of surfaces. The same parts as those of the secondary battery shown in Fig. 14(A) and Fig. 14(B) The explanations can be used as appropriate.

[0244] As shown in FIG. 15(A-1), a layer 916 is sandwiched between one of the two surfaces of a secondary battery 913. As shown in FIG. 15(A-2), an antenna 914 is provided, and the pair of surfaces of the secondary battery 913 On the other hand, an antenna 918 is provided across a layer 917. The layer 917 is, for example, a secondary battery 91 The layer 917 has a function of shielding the electromagnetic field generated by the magnetic material 3. can be used.

[0245] By adopting the above structure, the size of both the antenna 914 and the antenna 918 can be increased. The antenna 918 can perform data communication with an external device, for example. The antenna 918 has a shape that can be applied to the antenna 914, for example. A communication method between the secondary battery and other devices via the antenna 918 can be applied. For example, NFC (near field communication) can be used between secondary batteries and other devices. A response method that can be applied can be applied.

[0246] Alternatively, as shown in FIG. 15(B-1), the secondary battery 9 shown in FIG. 14(A) and FIG. 14(B) A display device 920 may be provided in the display device 13. The display device 920 is electrically connected to the terminal 911. It is not necessary to provide the label 910 in the area where the display device 920 is provided. 14(A) and 14(B) are the same as those in the secondary battery shown in FIG. The explanation of the secondary battery shown in FIG. 14(B) can be used as appropriate.

[0247] The display device 920 displays, for example, an image indicating whether charging is in progress or not, an image indicating the amount of stored power, etc. The display device 920 may be, for example, an electronic paper, a liquid crystal display, an electrophotographic display, or the like. For example, an electroluminescence (EL) display device can be used. By using the par, the power consumption of the display device 920 can be reduced.

[0248] Alternatively, as shown in FIG. 15(B-2), the secondary battery 9 shown in FIG. 14(A) and FIG. 14(B) 13 may be provided with a sensor 921. The sensor 921 is connected to the terminal 911 via a terminal 922. The secondary battery shown in FIG. 14(A) and FIG. 14(B) is electrically connected to the same part. In this regard, the description of the secondary battery shown in FIGS. 14(A) and 14(B) can be used as appropriate.

[0249] The sensor 921 may be, for example, a sensor for detecting displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, etc. , liquid, magnetic, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow It is sufficient if it has the function of measuring volume, humidity, gradient, vibration, odor, or infrared. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed can be obtained. It is also possible to detect a signal (such as temperature) and store it in memory within the circuit 912.

[0250] Furthermore, an example of the structure of the secondary battery 913 will be described with reference to FIGS.

[0251] The secondary battery 913 shown in FIG. 16(A) has a terminal 951 and a terminal 952 provided inside a housing 930. The winding body 950 is impregnated with an electrolyte inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is in contact with the housing by using an insulating material or the like. 16A, the housing 930 is not in contact with the housing 930. For convenience, the housing 930 is shown separated. Although the figure shows the winding body 950, in reality, the winding body 950 is covered by the housing 930, and the terminals 951 and 955 are 2 extends outside the housing 930. The housing 930 is made of a metal material (e.g., aluminum Rubber or resin materials can be used.

[0252] As shown in FIG. 16(B), the housing 930 shown in FIG. 16(A) is made of a plurality of materials. For example, the secondary battery 913 shown in FIG. 16B may be formed by a housing 930a and a housing 930b. The wound body 930 is located in the area surrounded by the housing 930a and the housing 930b. 50 are provided.

[0253] The housing 930a can be made of an insulating material such as organic resin. By using a material such as organic resin on the surface on which the secondary battery 913 is formed, If the shielding of the electric field by the housing 930a is small, the shielding of the electric field by the housing 930a can be suppressed. Antennas such as antenna 914 and antenna 915 may be provided inside the housing 930b. For example, a metal material can be used.

[0254] Furthermore, the structure of the wound body 950 is shown in Fig. 17. The wound body 950 is made up of a negative electrode 931 and a positive electrode 932. The winding body 950 has a pole 932 and a separator 933. The negative electrode 931 and the positive electrode 932 are stacked one on top of the other, and the laminated sheet is wound to form a wound body. The negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated. You can stack several of them.

[0255] The negative electrode 931 is connected to the terminal 911 shown in FIG. 14 via one of the terminals 951 and 952. The positive electrode 932 is connected to the terminal 91 shown in FIG. 14 via the other of the terminals 951 and 952. Connected to 1.

[0256] By using the positive electrode active material described in the above embodiment for the positive electrode 932, it is possible to achieve high capacity cycling. The secondary battery 913 can have excellent characteristics.

[0257] [Laminated secondary battery] Next, an example of a laminated secondary battery will be described with reference to FIGS. If the laminated secondary battery is made flexible, it will have at least one flexible portion. If the secondary battery is mounted in an electronic device that also has a battery, it can be bent according to the deformation of the electronic device. can.

[0258] A laminated secondary battery 980 will be described with reference to FIG. The battery 980 has a wound body 993 shown in FIG. 17, a positive electrode 995, and a separator 996. Similar to the wound body 950, a negative electrode 994 and a positive electrode 995 are stacked with a separator 996 sandwiched therebetween. The laminated sheet is then wound up.

[0259] The number of layers of the negative electrode 994, the positive electrode 995, and the separator 996 is determined as required. The negative electrode 994 is connected to the lead electrode 997 and the lead The positive electrode 995 is connected to a negative electrode current collector (not shown) via one of the lead electrodes 998. The positive electrode 997 and the lead electrode 998 are connected to a positive electrode current collector (not shown).

[0260] As shown in FIG. 18(B), a film 981 that serves as an exterior body and a film 98 having a recess are 2 are bonded together by thermocompression or the like, and the above-mentioned wound body 993 is housed in the space formed. In this way, a secondary battery 980 can be fabricated as shown in FIG. 3 has lead electrodes 997 and 998, and is connected to a film 981 and a recessed portion. The inside of the film 982 is impregnated with an electrolyte.

[0261] The film 981 and the film 982 having the recesses are made of a metal material such as aluminum. The film 981 and the film 982 having the recesses can be made of a material such as a resin. If a resin material is used as the material, when external force is applied, the film 981 and the recessed portion The film 982 can be deformed to produce a flexible storage battery. can.

[0262] In addition, although Fig. 18(B) and Fig. 18(C) show examples using two films, A space is formed by folding one sheet of film, and the above-mentioned wound body 99 is inserted into the space. 3 may be accommodated.

[0263] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, it is possible to achieve high capacity cycling. The secondary battery 980 can have excellent characteristics.

[0264] In addition, in FIG. 18, a secondary battery 9 having a wound body in a space formed by a film that serves as an exterior body is shown. 80 has been explained, but as shown in Figure 19, for example, The space defined by the positive electrode layer may be a secondary battery having a plurality of rectangular positive electrodes, separators, and negative electrodes. stomach.

[0265] The laminated secondary battery 500 shown in FIG. 19(A) includes a positive electrode current collector 501 and a positive electrode active material. a positive electrode 503 having a positive electrode active material layer 502, a negative electrode current collector 504 and a negative electrode active material layer 505 The battery includes a negative electrode 506, a separator 507, an electrolyte 508, and an exterior body 509. A separator 507 is provided between a positive electrode 503 and a negative electrode 506 provided in a body 509. The exterior body 509 is filled with an electrolyte 508. The electrolyte solution shown in the second embodiment can be used.

[0266] In the laminated secondary battery 500 shown in FIG. 19(A), a positive electrode current collector 501 and a negative electrode current collector The electrode current collector 504 also serves as a terminal for electrical contact with the outside. A part of the current collector 501 and the negative electrode current collector 504 is exposed to the outside from the outer casing 509. In addition, the positive electrode current collector 501 and the negative electrode current collector 504 may be disposed in the outer casing 509. The lead electrode is not exposed to the outside, and the lead electrode is connected to the positive electrode current collector 501 or the negative electrode The lead electrode may be exposed to the outside by ultrasonic bonding to the current collector 504 .

[0267] In the laminated secondary battery 500, the exterior body 509 is made of, for example, polyethylene, poly A film made of propylene, polycarbonate, ionomer, polyamide, etc. is coated with an A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied, and the metal is further On the metallic thin film, an insulating synthetic resin such as polyamide resin or polyester resin is applied as the outer surface of the exterior body. A three-layer laminate film provided with an oil film can be used.

[0268] An example of the cross-sectional structure of a laminated secondary battery 500 is shown in FIG. For simplicity, in A), an example consisting of two current collectors is shown, but in reality, as shown in Figure 19(B), As shown in Figure 1, it is composed of multiple electrode layers.

[0269] In FIG. 19(B), as an example, the number of electrode layers is set to 16. However, the secondary battery 500 has flexibility. In FIG. 19(B), the negative electrode current collector 504 has eight layers. The positive electrode current collector 501 has eight layers, making a total of 16 layers. The cross section of the extraction part is shown, and eight layers of negative electrode current collector 504 are ultrasonically bonded. The number of electrode layers is not limited to 16, and may be more or less. In this case, a secondary battery having a larger capacity can be obtained. In this case, a secondary battery can be made thin and highly flexible.

[0270] An example of the external appearance of a laminated secondary battery 500 is shown in FIGS. 20 and 21. 21 shows a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead The positive electrode 510 and the negative electrode 511 are provided.

[0271] 22(A) shows an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is connected to the positive electrode current collector 50 1, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). 506 has a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. In addition, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, a tab region. The area and shape of the tab regions of the positive electrode and negative electrode are not limited to the example shown in FIG. I can't.

[0272] [Method for manufacturing laminated secondary batteries] Here, an example of a method for manufacturing the laminated secondary battery shown in FIG. 20 will be described with reference to FIG. This will be explained using (B) and (C).

[0273] First, the negative electrode 506, the separator 507, and the positive electrode 503 are stacked. The figure shows five pairs of negative electrodes 506, separators 507, and positive electrodes 503. Next, the bonding of the tab regions of the positive electrode 503 and the bonding of the tabs of the positive electrode on the outermost surface are shown. The positive electrode lead electrode 510 is bonded to the region. For example, ultrasonic welding or the like can be used for bonding. Similarly, the bonding of the tab regions of the negative electrodes 506 to each other and the bonding of the negative electrode leads to the tab region of the negative electrode on the outermost surface are also preferable. The bonded electrode 511 is then bonded.

[0274] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are placed on the exterior body 509 .

[0275] Next, as shown in FIG. 22(C), the exterior body 509 is folded at the portion indicated by the broken line. After that, the outer periphery of the exterior body 509 is bonded. For example, thermocompression bonding may be used for bonding. , and a part (or one side) of the outer casing 509 so that the electrolyte 508 can be poured therein later. An area that is not bonded (hereinafter referred to as an inlet) is provided.

[0276] Next, electrolyte 508 (not shown) is introduced into exterior body 509 through an inlet provided in exterior body 509. The electrolyte 508 is introduced into the inside of the electrode 509 under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is bonded. The secondary battery 500 can be manufactured.

[0277] By using the positive electrode active material described in the above embodiment for the positive electrode 503, it is possible to achieve high capacity cycling. The secondary battery 500 can have excellent characteristics.

[0278] [Bendable secondary battery] Next, an example of a bendable secondary battery will be described with reference to FIGS. 23 and 24. .

[0279] FIG. 23(A) shows a schematic top view of a bendable secondary battery 250. ), (B2), and (C) are cut along the cutting lines C1-C2 and C3- C4 is a schematic cross-sectional view taken along the cutting line A1-A2. The battery has a positive electrode 211a and a negative electrode 211b housed inside an exterior body 251. A lead 212a electrically connected to the negative electrode 211a, and a lead 212b electrically connected to the negative electrode 211b. The cord 212b extends outside the exterior body 251. In addition to the positive electrode 211a and the negative electrode 211b, an electrolyte (not shown) is enclosed in the .

[0280] The positive electrode 211a and the negative electrode 211b of the secondary battery 250 will be described with reference to FIG. 24. FIG. 24(A) shows the stacking order of the positive electrode 211a, the negative electrode 211b, and the separator 214. FIG. 24(B) shows a perspective view of the positive electrode 211a and the negative electrode 211b, as well as a lead wire. 2 is a perspective view showing a lead 212a and a lead 212b.

[0281] As shown in FIG. 24(A), the secondary battery 250 includes a plurality of rectangular positive electrodes 211a, a plurality of short The battery has a strip-shaped negative electrode 211b and a plurality of separators 214. Each of the positive electrodes 211a and 211b has a protruding tab portion and a portion other than the tab. A positive electrode active material layer is formed on the surface of the negative electrode 211b except for the tab. A negative electrode active material layer is formed thereon.

[0282] The surfaces of the positive electrode 211a on which the positive electrode active material layer is not formed and the surfaces of the negative electrode 211b on which the negative electrode active material layer is not formed are The positive electrode 211a and the negative electrode 211b are stacked so that the surfaces without the layer are in contact with each other. can be.

[0283] In addition, the surface of the positive electrode 211a on which the positive electrode active material is formed and the surface of the negative electrode 211b on which the negative electrode active material is formed are A separator 214 is provided between the two surfaces. 214 is shown by a dotted line.

[0284] As shown in FIG. 24(B), the positive electrodes 211a and the leads 212a are connected to each other at the joints 215. The negative electrodes 211b and the leads 212b are electrically connected at the joints 211a and 212b. Electrical connection is made at 15b.

[0285] Next, the exterior body 251 will be described with reference to FIGS. 23(B1), (B2), (C), and (D). do.

[0286] The exterior body 251 has a film-like shape and is configured to sandwich the positive electrode 211a and the negative electrode 211b. The exterior body 251 is folded in two at the folded portion 261 and a pair of sealing portions 2 The pair of sealing portions 262 are connected to the positive electrode 211a and the negative electrode 211b. The seal portion 26 is provided on either side of the pole 211b and can also be called a side seal. 3 has a portion overlapping with the lead 212a and the lead 212b, and is also called a top seal. This can be done.

[0287] The exterior body 251 has a ridge line 271 and a valley line 272 at the portion overlapping the positive electrode 211a and the negative electrode 211b. It is preferable that the sealing portion 26 of the exterior body 251 has a wave shape in which the grooves 72 are arranged alternately. 2 and the seal portion 263 are preferably flat.

[0288] FIG. 23(B1) is a cross section cut at the part overlapping with the ridge line 271, and FIG. 23(B2) is a cross section cut at the part overlapping with the ridge line 271. The cross section is cut at the part overlapping with the valley line 272. Figures 23(B1) and (B2) are both secondary It corresponds to a cross section in the width direction of the battery 250, the positive electrode 211a, and the negative electrode 211b.

[0289] Here, the ends in the width direction of the positive electrode 211a and the negative electrode 211b, i.e., the positive electrode 211a and the negative electrode 211b, The distance between the end of the negative electrode 211b and the seal portion 262 is defined as La. When deformation such as bending is applied to the positive electrode 211a and the negative electrode 211b, as will be described later, At this time, if the distance La is too short, the exterior body 251 and the The positive electrode 211a and the negative electrode 211b may rub against each other strongly, and the exterior body 251 may be damaged. In particular, if the metal film of the exterior body 251 is exposed, the metal film may be corroded by the electrolyte. Therefore, it is preferable to set the distance La as long as possible. On the other hand, if the distance La is made too large, the volume of the secondary battery 250 increases.

[0290] In addition, the greater the total thickness of the stacked positive electrode 211a and negative electrode 211b, the greater the It is preferable to increase the distance La between the negative electrode 211a and the seal portion 262. .

[0291] More specifically, the stacked positive electrode 211a and negative electrode 211b and a separator (not shown) are When the total thickness of the data 214 is t, the distance La is 0.8 to 3.0 times the thickness t. Preferably, the ratio is 0.9 to 2.5 times, more preferably 1.0 to 2.0 times. By setting the distance La in this range, it is possible to make the device compact and resistant to bending. This makes it possible to realize a highly reliable battery.

[0292] In addition, when the distance between the pair of seal portions 262 is a distance Lb, the distance Lb is and is sufficiently larger than the width of the negative electrode 211b (here, the width Wb of the negative electrode 211b). This is preferable. When the secondary battery 250 is repeatedly bent or deformed, Even if the positive electrode 211a and the negative electrode 211b come into contact with the exterior body 251, the positive electrode 211a and the negative electrode 211b Since a part of the electrode 211b can be shifted in the width direction, the positive electrode 211a and the negative electrode 211b This effectively prevents the exterior body 251 from rubbing against each other.

[0293] For example, the difference between the distance Lb between the pair of seal 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, the thickness t of 211a and the negative electrode 211b It is preferable that the ratio is 2.0 times or more and 5.0 times or less, and more preferably 2.0 times or more and 4.0 times or less. .

[0294] In other words, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following formula 1: It's nice.

[0295]

number

[0296] Here, a is 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, and more preferably is between 1.0 and 2.0.

[0297] FIG. 23(C) is a cross section including the lead 212a, and shows the secondary battery 250, the positive electrode 211a, 23(C), the bending portion 211b corresponds to the cross section of the negative electrode 211b in the longitudinal direction. In the portion 261, the ends of the positive electrode 211a and the negative electrode 211b in the length direction and the outer casing 251 It is preferable to have a space 273 between them.

[0298] Fig. 23(D) shows a schematic cross-sectional view of the secondary battery 250 when bent. corresponds to the cross section taken along the cutting line B1-B2 in FIG. 23(A).

[0299] When the secondary battery 250 is bent, a part of the exterior body 251 located on the outside of the bend stretches, and a part located on the inside More specifically, the other part positioned outside the exterior body 251 is deformed so as to shrink. The part of the outer casing 2 deforms so that the amplitude of the wave becomes smaller and the period of the wave becomes larger. The part located inside 51 is deformed so that the wave amplitude is large and the wave period is small. In this way, the exterior body 251 is deformed, and as it is bent, Since the stress is alleviated, the material that constitutes the exterior body 251 does not need to stretch. As a result, the exterior body 251 is not damaged and the secondary battery 250 can be bent with a small force. Cut.

[0300] Furthermore, as shown in FIG. 23(D), when the secondary battery 250 is bent, the positive electrode 211a and the negative electrode At this time, the plurality of stacked positive electrodes 211a and 211b are displaced relative to each other. The negative electrode 211b is fixed at one end on the seal portion 263 side by the fixing member 217, so that it is not folded. The deviation increases as the distance from the bent portion 261 increases. The stress applied to the positive electrode 211a and the negative electrode 211b is relieved, and the positive electrode 211a and the negative electrode 211b As a result, the positive electrode 211a and the negative electrode 211b do not need to be broken. Therefore, the secondary battery 250 can be bent without any bending.

[0301] In addition, a space 273 is provided between the positive electrode 211a and the negative electrode 211b and the exterior body 251. As a result, the positive electrode 211a and the negative electrode 211b located on the inner side when bent are attached to the exterior body 251. can be displaced relative to one another without contacting each other.

[0302] The secondary battery 250 illustrated in FIGS. 23 and 24 has a sheath that can withstand repeated bending and stretching. The battery characteristics are also less likely to deteriorate. The positive electrode 211a of the secondary battery 250 has the same structure as that described in the previous embodiment. By using a positive electrode active material, a battery with even better cycle characteristics can be obtained.

[0303] (Fourth embodiment) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on an electronic device will be described. do.

[0304] First, as explained in part of the third embodiment, a bendable secondary battery is mounted on an electronic device. Examples are shown in Figures 25(A) to 25(G). Examples of devices include television sets (also called televisions or television receivers), Computer monitors, digital cameras, digital video cameras, digital photos Frame, mobile phone (also called mobile phone or mobile phone device), portable game machine, portable information Examples include terminals, audio playback devices, and large game machines such as pachinko machines.

[0305] In addition, the flexible secondary battery can be mounted on the inner or outer wall of a house or building, or on the inside or outside of a car. It is also possible to incorporate it along the curved surface of the interior or exterior of the vehicle.

[0306] FIG. 25A shows an example of a mobile phone. The mobile phone 7400 has a housing 7401. In addition to the display unit 7402 incorporated in the The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, etc. The secondary battery 7407 is a secondary battery of one embodiment of the present invention. This makes it possible to provide a lightweight, long-lasting mobile phone.

[0307] FIG. 25B shows the mobile phone 7400 in a bent state. When the entire device is deformed by an external force and curved, the secondary battery inside 7407 is also bent. At this time, the state of the bent secondary battery 7407 is shown in FIG. The secondary battery 7407 is a thin storage battery. The secondary battery 7407 is shown in the bent state. The secondary battery 7407 has a lead electrode electrically connected to the current collector. For example, the current collector is made of copper foil, and some of it is alloyed with gallium to form a layer in contact with the current collector. This improves the adhesion between the active material layer and the secondary battery 7407, resulting in a highly reliable structure when the secondary battery 7407 is bent. It has become a success.

[0308] FIG. 25(D) shows an example of a bangle-type display device. The portable display device 7100 includes: The device includes a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. 25(E) shows the state of the bent secondary battery 7104. The secondary battery 7104 is bent. When the device is worn on the user's arm with the device attached, the housing may deform and cause damage to part of the secondary battery 7104 or The total curvature changes. The degree of curvature at any point on the curve is expressed as the radius of the corresponding circle. The value expressed is called the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, the radius of curvature is The area is within the range of 40 mm to 150 mm, and the area is part of the main surface of the casing or the secondary battery 7104. The radius of curvature of the main surface of the secondary battery 7104 is 40 mm or more and 150 mm or less. If the thickness is within the range of 1 mm or less, high reliability can be maintained. By using the secondary battery of one embodiment, a lightweight, long-life portable display device can be provided.

[0309] FIG. 25(F) shows an example of a wristwatch-type portable information terminal. The portable information terminal 7200 is , a housing 7201, a display unit 7202, a band 7203, a buckle 7204, and an operation button 72 05, input / output terminal 7206, etc.

[0310] The portable information terminal 7200 is capable of carrying out mobile phone calls, e-mails, viewing and creating documents, playing music, and internet access. - It can run various applications such as internet communication and computer games. do.

[0311] The display surface of the display unit 7202 is curved, and the display is performed along the curved display surface. The display portion 7202 is provided with a touch sensor, and can be touched with a finger or a stylus. For example, the icon 72 displayed on the display unit 7202 can be operated by touching it. You can launch the application by touching 07.

[0312] The operation button 7205 is used to set the time, turn the power on and off, and turn wireless communication on and off. It has various functions such as operation, silent mode activation and deactivation, power saving mode activation and deactivation, etc. For example, an operating system installed in the portable information terminal 7200 can The function of the operation button 7205 can also be freely set using the stem.

[0313] In addition, the mobile information terminal 7200 is capable of performing standardized short-range wireless communication. For example, by communicating with a wireless headset, hands-free operation is possible. You can also make calls.

[0314] The portable information terminal 7200 also has an input / output terminal 7206, and a connector for connecting to other information terminals. Data can be exchanged directly via the input / output terminal 7206. The charging operation can be performed by wireless power supply without going through the input / output terminal 7206. It is also possible.

[0315] The display portion 7202 of the portable information terminal 7200 includes the secondary battery of one embodiment of the present invention. By using the secondary battery of one embodiment of the present invention, a lightweight and long-life portable information terminal can be provided. For example, the secondary battery 7104 shown in FIG. 25E is curved inside the housing 7201. Alternatively, it can be incorporated in the band 7203 in a bendable state.

[0316] The mobile information terminal 7200 preferably has a sensor. For example, a fingerprint sensor may be used as the sensor. Human body sensors such as pulse sensors and body temperature sensors, as well as touch sensors, pressure sensors, and acceleration sensors It is preferable that a sensor, etc. be installed.

[0317] FIG. 25G shows an example of a wristband-type display device. The display device 7300 includes a display unit 7 304 and includes the secondary battery of one embodiment of the present invention. The display unit 7304 may be provided with a touch sensor, and may function as a portable information terminal. It is also possible.

[0318] The display surface of the display unit 7304 is curved, and images can be displayed along the curved display surface. The display device 7300 can also communicate with the display device 7300 by short-distance wireless communication according to a communication standard. The situation can be changed.

[0319] The display device 7300 is also equipped with an input / output terminal, and can be directly connected to other information terminals via a connector. It is also possible to charge the device via the input / output terminals. The charging operation may be performed by wireless power supply without using the input / output terminals.

[0320] By using the secondary battery of one embodiment of the present invention as the secondary battery included in the display device 7300, This makes it possible to provide a display device with a long life at a low cost.

[0321] In addition, an example in which the secondary battery with good cycle characteristics shown in the above embodiment is mounted on an electronic device is shown in FIG. 25(H), and will be explained using FIGS. 26 and 27.

[0322] By using the secondary battery of one embodiment of the present invention as a secondary battery in everyday electronic devices, the battery is lightweight and has a long life. For example, we can provide various products such as electric toothbrushes, electric shavers, and These include mobile beauty devices, and the secondary batteries for these products are designed to be easy for users to hold. Therefore, there is a demand for a small, lightweight, stick-shaped secondary battery with a large capacity.

[0323] FIG. 25(H) is a perspective view of a device also called a tobacco-containing smoking device (electronic cigarette). In 25(H), the electronic cigarette 7500 is an atomizer 7501 containing a heating element and an atomizer A secondary battery 7504 that supplies power to the MYZA, and a cart containing a liquid supply bottle, sensors, etc. To enhance safety, the secondary battery 7504 is protected from overcharging and overcharging. A protection circuit for preventing discharge may be electrically connected to the secondary battery 7504. The secondary battery 7504 has an external terminal so that it can be connected to a charging device. The 504 is the tip when held, so the total length is short and the weight is light. Since the secondary battery of one embodiment of the present invention has a high capacity and good cycle characteristics, We offer a compact and lightweight e-cigarette 7500 that can be used for long periods of time. Can be provided.

[0324] Next, Fig. 26(A) and Fig. 26(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIG. 26(A) and FIG. 26(B) includes a housing 9630 a, a housing 9630b, a movable part 9640 connecting the housings 9630a and 9630b, and a display A display unit 9631 having a display unit 9631a and a display unit 9631b, switches 9625 to The display unit 9631 has a switch 9627, a fastener 9629, and an operation switch 9628. By using a flexible panel, it is possible to create a tablet terminal with a larger display area. FIG. 26(A) shows a state in which the tablet terminal 9600 is opened, and FIG. B) shows the tablet terminal 9600 in a closed state.

[0325] The tablet terminal 9600 also includes a battery storage device inside the housing 9630a and the housing 9630b. The power storage unit 9635 is connected to the housing 9630a through the movable portion 9640. It is located across 9630b.

[0326] The entire or a part of the display portion 9631 can be used as a touch panel. By touching images, text, input forms, etc. containing icons displayed in the area, data For example, a keyboard is provided on the entire surface of the display portion 9631a of the housing 9630a. By displaying the button, information such as text and images can be displayed on the display unit 9631b on the housing 9630b. may be displayed and used.

[0327] In addition, a keyboard is displayed on the display unit 9631b on the housing 9630b side, and The display portion 9631a on the side may be used to display information such as text and images. The 9631 is set to display a keyboard display switch button on the touch panel, and the By touching the button with your finger or a stylus, the keyboard will be displayed on the display 9631. You may do so.

[0328] In addition, the touch panel area of ​​the display unit 9631a on the housing 9630a side and the touch panel area of ​​the display unit 9631b on the housing 9630b side Simultaneous touch inputs can also be made to the touch panel area of ​​the display portion 9631b.

[0329] In addition, switches 9625 to 9627 are used to operate the tablet terminal 9600. It is not only an interface for switching between various functions, but also an interface for switching between various functions. For example, at least one of the switches 9625 to 9627 may be One acts as a power on / off switch for the tablet device 9600. Also, for example, at least one of the switches 9625 to 9627 may be The ability to switch between horizontal and vertical display, or between black and white and color display In addition, for example, at least one of the switches 9625 to 9627 may have a function to At least one of the display portions 9631 may have a function of adjusting the brightness of the display portion 9631. The brightness of 1 is the external brightness detected by the light sensor built into the tablet terminal 9600 during use. It can be optimized according to the amount of light. Note that the tablet device has a light sensor. In addition, it also incorporates other detection devices such as gyro, acceleration sensor, etc. to detect tilt. It is also acceptable to do so.

[0330] In FIG. 26A, the display portion 9631a on the housing 9630a side and the display portion 9631b on the housing 9630b side are 9631a and 9631b have almost the same display area. The display area of ​​each of the 631b is not particularly limited, and one size may be different from the other. The display quality may be different, for example, one may have a higher resolution than the other. The display panel may also be capable of performing the above.

[0331] FIG. 26(B) shows the tablet terminal 9600 in a folded state. The terminal 9600 includes a housing 9630, a solar cell 9633, and a DC-DC converter 9636. The power storage unit 9635 includes a charge / discharge control circuit 9634 including a power storage device according to one embodiment of the present invention. A storage battery is used.

[0332] As mentioned above, the tablet terminal 9600 can be folded in half, so when not in use, The housing 9630a and the housing 9630b can be folded so that they overlap each other. By folding, the display portion 9631 can be protected, and therefore the durability of the tablet terminal 9600 can be improved. Furthermore, the power storage unit 9635 using the secondary battery of one embodiment of the present invention can improve the It has a large capacity and good cycle characteristics, making it a tablet that can be used for a long period of time. A portable terminal 9600 can be provided.

[0333] In addition, the tablet terminal 9600 shown in FIG. 26(A) and FIG. 26(B) , functions to display various information (still images, videos, text images, etc.), calendar, date or The function to display the time, etc. on the display, and the function to touch input or edit the information displayed on the display Touch input function, function to control processing by various software (programs), etc. It can have:

[0334] The solar cell 9633 attached to the surface of the tablet terminal 9600 generates power. The solar cell 963 can be supplied to a panel, a display unit, a video signal processing unit, etc. 3 can be provided on one or both sides of the housing 9630, and the power storage unit 9635 can be efficiently charged. The power storage unit 9635 can be configured to use a lithium ion battery. This has the advantage of enabling miniaturization.

[0335] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 26(B) are shown in FIG. A block diagram is shown in FIG. 26(C) and will be explained. In FIG. 26(C), a solar cell 9633 and a power storage unit 963 5, DC-DC converter 9636, converter 9637, switches SW1 to SW3, table The display unit 9631 is shown, and the storage battery 9635, the DC-DC converter 9636, 26B. This corresponds to 34.

[0336] First, an example of operation when power is generated by the solar cell 9633 using external light will be described. The power generated by the solar cell is converted into a voltage for charging the storage battery 9635. The voltage is increased or decreased by a inverter 9636. When power is used from the 9633, switch SW1 is turned on and the converter 9637 The voltage is increased or decreased to the voltage required for the display unit 9631. When not displaying the display, turn SW1 off and SW2 on to charge the power storage unit 9635. The configuration may be such that electricity is supplied.

[0337] The solar cell 9633 is shown as an example of a power generating means, but is not particularly limited thereto. Power storage using other power generation methods such as piezoelectric elements and thermoelectric conversion elements For example, the power may be transmitted and received wirelessly (contactlessly). It is also possible to combine it with a contactless power transmission module that charges the battery, or other charging means. That's fine.

[0338] Another example of electronic equipment is shown in FIG. 27. In FIG. 27, a display device 8000 is a display device according to one embodiment of the present invention. 8 is an example of an electronic device using a secondary battery 8004 according to an embodiment. 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, and a speaker unit. The secondary battery 8004 according to one embodiment of the present invention includes a housing 8003 and a secondary battery 8004. The display device 8000 is provided inside a body 8001. The display device 8000 receives power from a commercial power source. Alternatively, the power stored in the secondary battery 8004 can be used. Even when power cannot be supplied from a commercial power source due to a power outage or the like, the present invention The display device 8000 can be used by using the secondary battery 8004 as an uninterruptible power supply. do.

[0339] The display unit 8002 includes a liquid crystal display device, an emitting device having a light emitting element such as an organic EL element in each pixel, and Device, electrophoretic display device, DMD (Digital Micromirror Device) ce), PDP (Plasma Display Panel), FED (Field A semiconductor display device such as a reflective LED (emission display) can be used.

[0340] In addition to TV broadcast reception, display devices are also used for personal computers and advertising displays. , including all display devices for displaying information.

[0341] In FIG. 27, a stationary lighting device 8100 includes a secondary battery 81 according to one embodiment of the present invention. 8101, a housing 8102, a light source 8103, and a light source 8104. 27, the secondary battery 8103 is mounted in the housing 81. 8101 and a light source 8102 are installed inside a ceiling 8104. However, the secondary battery 8103 may be provided inside the housing 8101. The device 8100 can receive power from a commercial power source or can store power in a secondary battery 8103. Therefore, if the power supply from the commercial power source is interrupted due to a power outage, etc., Even when the power is not available, the secondary battery 8103 according to one embodiment of the present invention can be used as an uninterruptible power supply. This allows the lighting device 8100 to be used.

[0342] 27 shows an example of a lighting device 8100 that is installed on a ceiling 8104. However, the secondary battery according to one embodiment of the present invention is not limited to the ceiling 8104, but may be installed on other parts such as the side wall 8105 and the floor 8106. 106, it can be used for a fixed lighting device provided in a window 8107, etc., or it can be used for a tabletop lighting device. It can also be used in lighting devices of this type.

[0343] The light source 8102 may be an artificial light source that artificially obtains light using electricity. Specifically, incandescent lamps, fluorescent lamps and other discharge lamps, and light-emitting devices such as LEDs and organic EL elements The element is an example of the artificial light source.

[0344] In FIG. 27, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is 8 is an example of an electronic device using a secondary battery 8203 according to one embodiment of the present invention. The device 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, and the like. 8 illustrates an example in which the secondary battery 8203 is provided in the indoor unit 8200. The battery 8203 may be provided in the outdoor unit 8204. Both the power supply 8201 and the power supply 8204 may be provided with a secondary battery 8203. The power supply can be supplied from a commercial power source, or the power stored in the secondary battery 8203 can be used. In particular, both the indoor unit 8200 and the outdoor unit 8204 may be equipped with secondary batteries 82 If 03 is installed, when power cannot be supplied from the commercial power source due to a power outage, etc. In addition, by using the secondary battery 8203 of one embodiment of the present invention as an uninterruptible power supply, The conditioner can be used.

[0345] In Figure 27, a separate type air conditioner consisting of an indoor unit and an outdoor unit is shown. As an example, it is an all-in-one air conditioner that has the functions of both the indoor unit and the outdoor unit in a single housing. The secondary battery according to one embodiment of the present invention can also be used in the conditioner.

[0346] In FIG. 27, an electric refrigerator-freezer 8300 includes a secondary battery 8304 according to one embodiment of the present invention. Specifically, an electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator It has a storage compartment door 8302, a freezer compartment door 8303, a secondary battery 8304, etc. A secondary battery 8304 is provided inside the housing 8301. The electric refrigerator-freezer 8300 is It can receive power from a commercial power source, or use the power stored in the secondary battery 8304. Therefore, when power cannot be supplied from the commercial power source due to a power outage, etc. However, by using the secondary battery 8304 of one embodiment of the present invention as an uninterruptible power supply, It will be possible to use the 8300 freezer refrigerator.

[0347] Among the above-mentioned electronic devices, high-frequency heating devices such as microwave ovens and electric rice cookers are Equipment requires high power for a short period of time, so it supplements the power that cannot be supplied by commercial power. By using a secondary battery according to one embodiment of the present invention as an auxiliary power source for This prevents the commercial power breaker from tripping during use.

[0348] In addition, during times when electronic devices are not in use, especially when the total amount of power that can be supplied by the commercial power supplier is low, During the time period when the ratio of the amount of electricity actually used (called the electricity usage rate) is low, By storing power in the battery, it is possible to prevent power usage rates from increasing outside of the above time periods. For example, in the case of the electric refrigerator-freezer 8300, when the temperature is low and the refrigerator compartment door 830 2. During the night when the freezer door 8303 is not opened or closed, the secondary battery 8304 stores power. Then, as the temperature rises, the refrigerator door 8302 and the freezer door 8303 are opened and closed. By using the secondary battery 8304 as an auxiliary power source during the daytime, the daytime power usage rate can be kept low.

[0349] According to one embodiment of the present invention, the cycle characteristics of the secondary battery are improved, and the reliability is improved. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be obtained. This improves the characteristics of the secondary battery, thereby making it possible to reduce the size and weight of the secondary battery itself. Therefore, the secondary battery according to one embodiment of the present invention can be used in the electronic devices described in this embodiment. By incorporating the above, it is possible to make the electronic device lighter and with a longer life span. The present embodiment can be implemented in appropriate combination with other embodiments.

[0350] (Embodiment 5) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle will be described.

[0351] When a secondary battery is installed in a vehicle, it becomes a hybrid vehicle (HEV), an electric vehicle (EV), or a powertrain. This will enable the realization of next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). .

[0352] 28A and 28B illustrate an example of a vehicle using a secondary battery according to one embodiment of the present invention. The automobile 8400 shown in FIG. 1 is an electric automobile that uses an electric motor as a power source for driving. Alternatively, an electric motor and an engine can be selected as the power source for driving. By using one aspect of the present invention, it is possible to extend the driving range. Furthermore, the automobile 8400 has a secondary battery. 13(C) and 13(D) are mounted on the floor of the vehicle. In addition, a battery pack using a combination of multiple secondary batteries as shown in FIG. The secondary battery may be installed on the floor of the vehicle. In addition, it supplies power to light-emitting devices such as headlights 8401 and room lights (not shown). can be provided.

[0353] In addition, the secondary battery is used to power the speedometer, tachometer, and other displays of the automobile 8400. The secondary battery can supply power to the navigation device of the automobile 8400. The present invention can provide power to semiconductor devices such as mobile terminals.

[0354] The automobile 8500 shown in FIG. 28(B) has a plug-in type secondary battery. It can be charged by receiving power from an external charging facility using a contactless power supply system or other methods. FIG. 28(B) shows a diagram of a charging device 8021 installed on a ground and a charging station 8022 installed on a vehicle 8500. The secondary battery 8024 is shown being charged via a cable 8022. For charging methods and connector specifications, please refer to the specified CHAdeMO (registered trademark) or Combo. The charging device 8021 is a charging station installed in a commercial facility. For example, plug-in technology can be used to The secondary battery 8024 installed in the automobile 8500 can be charged by the power supply. Charging is performed by converting AC power to DC power via a converter such as an AC-DC converter. It is possible.

[0355] Although not shown, a power receiving device is mounted on the vehicle and power is supplied contactlessly from a power transmitting device on the ground. In this case, a power transmission device is installed on the road or exterior wall. By incorporating this technology, charging can be carried out not only when the vehicle is stopped but also while the vehicle is moving. This method may be used to transmit and receive power between vehicles. A solar cell may be provided to charge the secondary battery when the vehicle is stopped or running. The power can be supplied by an electromagnetic induction method or a magnetic resonance method.

[0356] 28C shows an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. The scooter 8600 shown in (C) has a secondary battery 8602, side mirrors 8601, and a turn signal. The secondary battery 8602 can supply electricity to the direction indicator light 8603. can.

[0357] In addition, the scooter 8600 shown in FIG. 28(C) has a secondary battery 860 in the storage space under the seat 8604. 2 can be stored. The secondary battery 8602 can be stored even if the under-seat storage 8604 is small. The secondary battery 8602 can be stored in the under-seat storage 8604. When charging, the secondary battery 8602 is brought indoors, charged, and stored before driving. Just do that.

[0358] According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery is increased. Therefore, the secondary battery itself can be made smaller and lighter. If the body can be made smaller and lighter, it will contribute to reducing the weight of the vehicle, which will improve the driving range. In addition, the secondary battery installed in the vehicle can be used as a power supply source for other purposes. In this case, for example, it is possible to avoid using commercial power sources during peak power demand periods. If we can avoid using commercial power sources during peak power demand periods, we can save energy and This can contribute to reducing carbon dioxide emissions. Since the battery can be used for a long period of time, the amount of rare metals used, including cobalt, can be reduced. It is possible.

[0359] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0360] In this example, a positive electrode active material according to one embodiment of the present invention and a positive electrode active material according to a comparative example were prepared, and XP The characteristics were analyzed using SEM and XRD. Sex was evaluated.

[0361] [Preparation of positive electrode active material] <Sample 1> Sample 1 was fabricated using the method shown in FIG. 2 of the first embodiment, but containing cobalt as a transition metal. First, the molar ratio of LiF to MgF2 was LiF:MgF2=1: The mixture was weighed to a weight of 3, and acetone was added as a solvent, followed by wet mixing and pulverization. The powder was crushed and pulverized in a ball mill using zirconia balls at 150 rpm for 1 hour. The treated material was collected and used as the first mixture (steps S11 to S14 in FIG. 2). ).

[0362] The particle size distribution of LiF and MgF2 before mixing and the first mixture after mixing are shown in Figure 29. The particle size distribution was measured using a laser diffraction particle size distribution analyzer, SALD-2200 (Shimadzu Corporation). The D50 of the first mixture was 3.561 μm and the mode diameter was 4.008 μm. From Figure 29 and these results, it was confirmed that the first mixture was sufficiently pulverized. was done.

[0363] In Sample 1, lithium cobalt oxide was synthesized in advance and used as a CellSeed C-10N manufactured by CellSeed Co., Ltd. was used (step S25 in FIG. 2). As explained in the first embodiment, the cobalt oxide has a D50 of about 12 μm and is low in impurities. It is lithium.

[0364] Next, the ratio of magnesium atoms contained in the first mixture to the molecular weight of lithium cobalt oxide is calculated. The mixture was weighed so that the amount was 0.5 atomic % and mixed in a dry state. The mixture was ball milled at 150 rpm for 1 hour. The treated material was collected and used as a second mixture. (Steps S31 to S33 in FIG. 2).

[0365] Next, the second mixture was placed in an alumina crucible and heated at 850°C for 60 minutes in a muffle furnace in an oxygen atmosphere. The alumina crucible was covered during annealing. The oxygen flow rate was 10 L. The temperature was increased at 200°C / hr and decreased over 10 hours. The treated material was used as the positive electrode active material of Sample 1 (steps S34 and S35 in FIG. 2). ).

[0366] <Sample 2> The sample was prepared in the same manner as Sample 1, except that the annealing time in step S34 of FIG. 2 was set to 2 hours. The product thus produced was designated as Sample 2 (Comparative Example).

[0367] <<Sample 3>> The sample was fabricated in the same manner as Sample 1, except that annealing was not performed in step S34 of FIG. The resultant was designated as Sample 3 (Comparative Example).

[0368] <<Sample 4>> Cobalt oxide without any special treatment (without performing steps S31 to S35 in FIG. 2) Lithium (CellSeed C-10N) was used as Sample 4 (Comparative Example).

[0369] <<Sample 5>> In sample 5, the lithium cobalt oxide was synthesized in advance and sold by the Japan Chemical Industry Co., Ltd. CellSeed C-5H manufactured by CellSeed Corporation was used (step S25 in FIG. 2). Annealing was performed at 900°C for 2 hours in the same manner as in Sample 1. Made.

[0370] <<Sample 6>> Lithium cobalt oxide without any special treatment (without steps S31 to S35) The resulting mixture (Cellseed C-5H) was used as Sample 6 (Comparative Example).

[0371] <<Sample 7>> In sample 7, a magnesium source and a fluorine source were added to the lithium cobalt oxide starting material. The lithium cobalt oxide containing magnesium and fluorine was synthesized by calcining the mixture. The survey was conducted.

[0372] Specifically, lithium carbonate is used as the lithium source, cobalt oxide is used as the cobalt source, and magnesium is used as the cobalt source. Magnesium oxide is used as the ammonium source, and lithium fluoride is used as the fluorine source. Co 0.99 Mg 0.01 O 1.98 F 0.02 and mixed in a ball mill. did.

[0373] Next, the mixture was placed in an alumina crucible, which was then covered and heated in a muffle furnace in a dry air atmosphere for 95 minutes. The sample was baked at 0°C for 10 hours. The dry air flow rate was 10 L / min. The temperature was increased at 200°C / h. The temperature was lowered over a period of 10 hours. After the heat treatment, the material was mixed with magnesium and fluorine. The lithium cobalt oxide containing

[0374] Next, lithium cobalt oxide containing magnesium and fluorine was placed in an alumina crucible and the lid was placed on it. The sample was then annealed in a muffle furnace in an oxygen atmosphere at 800°C for 2 hours. The oxygen flow rate was 10 L. The temperature was increased at 200°C / hr and decreased over 10 hours. The treated material was designated as Sample 7.

[0375] <<Sample 8>> The lithium cobalt oxide (commercially available) containing magnesium and fluorine (Nippon Chemical Industry Co., Ltd.) The molten metal (Cellseed C-20F manufactured by the company) was placed in an alumina crucible, the lid was placed on it, and the crucible was placed in a muffle oven with an oxygen atmosphere. The sample was annealed in a furnace at 800°C for 2 hours. The oxygen flow rate was 10 L / min. The temperature was lowered at 00°C / hr over 10 hours. It was decided.

[0376] <<Sample 9>> No particular processing is performed (steps S31 to S35 are not performed), magnesium and Lithium cobalt oxide containing silicon and fluorine (Cellseed C-20F manufactured by Nippon Chemical Industry Co., Ltd.) was used as a sample. The result was designated as Plu 9 (comparative example).

[0377] <<Sample 10>> In sample 10, Aldrich Cobalt oxide was used as the pre-synthesized lithium cobalt oxide. Lithium baltic oxide (catalog No. 442704, D50 is approximately 11 μm) was used (Fig. 2, step S25). Also, in step S34 of FIG. 2, annealing was performed at 850° C. for 20 The other conditions were the same as for Sample 1.

[0378] <<Sample 11>> Lithium cobalt oxide without any special treatment (without steps S31 to S35) The resulting mixture (Aldrich Co., No. 442704) was used as Sample 11 (Comparative Example).

[0379] <<Sample 12>> Sample 12 (comparison example) is a pre-synthesized lithium cobalt oxide (LiCO3) manufactured by Nippon Kayaku Co., Ltd. CellSeed C-5hV (D50 is about 6 μm) manufactured by Gakushu Kogyo Co., Ltd. was used (step S2 in Figure 2). 5) This is lithium cobalt oxide containing titanium as an impurity at about 5100 ppm by weight. In step S34 of FIG. 2, annealing was performed at 800° C. for 2 hours. The conditions for preparation were the same as for Sample 1.

[0380] <<Sample 13>> Sample 13 (comparative example) was annealed at 850° C. and 60° C. in step S34 of FIG. The sample was prepared in the same manner as Sample 12, except that the time was set to 0.

[0381] <<Sample 14>> Lithium cobalt oxide without any special treatment (without steps S31 to S35) The PET film (Cellseed C-5hV manufactured by Nippon Chemical Industry Co., Ltd.) was used as Sample 14 (Comparative Example).

[0382] <<Sample 15>> In Sample 15 (comparison example), pre-synthesized lithium cobalt oxide (Nippon Chemical Industry Co., Ltd.) was used. A layer containing aluminum was formed on the surface of the ceramic substrate (CellSeed C-5H manufactured by CellSeed Co., Ltd.) using the sol-gel method. After formation, it was annealed at 500°C for 2 hours.

[0383] Specifically, aluminum isopropoxide and 2-propanol are mixed, and cobalt is added to the mixture. Lithium cobaltate (C-5H) was added. The weight of the methylisopropoxide was adjusted to 0.0092 times that of the methylisopropoxide. Stir in a constant temperature bath with a humidity of 90% and dissolve the H2O and aluminum isopropoxide in the atmosphere. The reaction was carried out to form a layer containing aluminum on the surface of the lithium cobalt oxide. The precipitate was collected by filtration and dried under reduced pressure at 70°C for 1 hour.

[0384] The lithium cobalt oxide having the aluminum layer formed on the surface thereof was dried as described above and then mixed with an alumina The mixture was placed in a crucible, covered, and annealed at 500°C (heating rate: 200°C / hour). The holding time was 2 hours, and the oxygen flow rate was 10 L / min. The mixture was cooled for 15 hours or less, and the collected product was designated as Sample 15.

[0385] The preparation conditions for Samples 1 to 15 are shown in Table 1.

[0386] [Table 1]

[0387] [XPS] The surfaces of Samples 1 to 4 prepared above were subjected to XPS analysis. The element concentrations (atomic %) are shown in Table 2.

[0388] [Table 2]

[0389] Figure 30(A) shows a graph of magnesium and fluorine data extracted from Table 2. In Sample 4, to which lithium fluoride and magnesium fluoride were not added, The concentrations of silicon and magnesium were low. Sample 3, which was doped with magnesium chloride but not annealed, also showed a significant increase in the amount of fluorine and magnesium. The concentration of sodium did not increase significantly. This is due to the nature of the surface XPS analysis. ) on a particle 1001 that does not contain a certain element. When 2 is attached, the area 100 containing a large area of ​​elements is as shown in Figure 30(B2). This is thought to be because certain elements are more difficult to detect from the detection area 1010 than when the detection area 1010 has a can be.

[0390] In addition, a sample that had been annealed for 2 hours after adding lithium fluoride and magnesium fluoride 2, the fluorine concentration increased significantly. In sample 1, which was doped with magnesium and annealed for 60 hours, the magnesium concentration also increased significantly. there was.

[0391] Comparing Sample 2 and Sample 1, when annealing is performed, lithium fluoride ( It is speculated that the lithium cobaltate (melting point 848°C) melts and is distributed in the surface layer of the lithium cobalt oxide particles. Further increasing the annealing time increases the amount of magnesium fluoride due to the presence of molten lithium fluoride. The melting point of cobalt (melting point 1263°C) drops, and magnesium fluoride melts and becomes cobalt. It was presumed that the ions were distributed in the surface layer of the lithium oxide particles.

[0392] Next, FIG. 31 shows the region showing the carbon bonding state in the narrow scan analysis of XPS. In the unannealed sample 3, the peak of CO3 bond was high. The CO3 bond in sample 2 annealed for 60 hours decreased, while the CO3 bond in sample 1 annealed for 60 hours decreased. The CO3 bond in the surface layer of lithium cobalt oxide was further reduced by lithium carbonate (Li 2Co3), so annealing will cause an excess of lithium. It is believed that this suppresses the oxidation and allows the production of excellent lithium cobalt oxide.

[0393] [SEM] Next, SEM images of Samples 1 to 4 are shown in FIG. 32. FIG. 32(A1) shows Sample 1. 32(A2) is an enlarged view of the SEM image of sample 2. Fig. 32(C1) is an SEM image of Sample 3, and Fig. 32(B2) is an enlarged view. 3(C2) is an enlarged view of the same. Fig. 32(D1) is an SEM image of Sample 4, and Fig. 32(D2) ) is an enlarged view.

[0394] Sample 4, which is lithium cobalt oxide that has not undergone any special treatment, has many irregularities on the surface. In sample 3, lithium fluoride and magnesium fluoride were observed. The adhesion of fine particles was observed.

[0395] In contrast, the surfaces of annealed Sample 2 and Sample 1 are smooth and have no irregularities. Sample 1, which was annealed for a longer time, had less unevenness than Sample 2. There was a tendency not to.

[0396] [Secondary battery production] Next, using the samples 1, 2, 4 to 15 prepared above, A coin-type secondary battery of the CR2032 type (diameter 20 mm, height 3.2 mm) was fabricated.

[0397] The positive electrode was made of the positive electrode active material prepared above, acetylene black (AB), and polyvinyl fluoride. PVDF was mixed with the cathode active material in a ratio of AB:PVDF=95:3:2 (by weight). The resulting slurry was applied to a current collector.

[0398] Lithium metal was used as the counter electrode.

[0399] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. We used the following.

[0400] The separator was made of polypropylene with a thickness of 25 μm.

[0401] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0402] The positive electrode of the secondary battery using Sample 7 was pressurized with 210 kN. No pressure was applied to the positive electrode of the next battery.

[0403] [Lattice constant calculated from XRD before charging] Before charging using Sample 1, Sample 4, Sample 5 to Sample 12, and Sample 14 The positive electrode was subjected to powder XRD analysis using CuKα1 radiation. XRD was measured in air. The electrodes were attached to a glass plate to maintain flatness. The height of the sample was adjusted to fit the measurement surface required by the instrument.

[0404] The obtained XRD patterns were analyzed using DIFFRAC.EVA (Bruker XRD data analyzer). The background and Kα2 were removed using the analysis software. Signals from agents and binders, as well as sealed containers, etc., are also removed.

[0405] The lattice constants were then calculated using TOPAS. At this time, no optimization of atomic positions was performed. Only the lattice constants were fitted. GOF (good of fitness), estimated The crystallite size and the lattice constants of the a-axis and c-axis are shown in Table 3.

[0406] [Table 3]

[0407] Samples 12 and 14 contain titanium as an impurity at approximately 5100 ppm wt. , the c axis tended to be larger than the others.

[0408] [XRD after first charge] The secondary batteries using Samples 1, 2, 7 and 9 were charged at 4.6V. CCCV charging was performed. Specifically, after charging at a constant current of 0.5C up to 4.6V, the current value was reduced to 0. The battery was charged at a constant voltage until the battery reached 0.1 C. Here, 1 C was 137 mA / g. The secondary battery in the charged state was disassembled in an argon atmosphere glove box to remove the positive electrode. The electrolyte was removed by washing with MC (dimethyl carbonate). The mixture was sealed in a sealed container and subjected to XRD analysis.

[0409] Figure 33 shows the results of the secondary batteries using Samples 1, 2, 7 and 9. The XRD pattern of the positive electrode after charging at 0.6 V is shown. For comparison, a pseudospinel crystal structure The crystal structure patterns of H1-3 type are also shown.

[0410] After charging to 4.6 V, Samples 1 and 7 were found to have a pseudospinel crystal structure. In addition, sample 7, in which a magnesium source and a fluorine source were added to the starting material, However, sample 1, which is a mixture of lithium cobalt oxide with a magnesium source and a fluorine source, The sharper the pattern, the higher the crystallinity was inferred to be.

[0411] On the other hand, Sample 2, which was insufficiently annealed, and Sample 9, which was not annealed, After charging to 4.6 V, it was found that the sample had an H1-3 type crystal structure. The pattern of sample 2 was clearly broader than that of sample 1, suggesting that the crystallinity was lower.

[0412] [XRD after first charge by charging depth] Next, the positive electrode active materials of Sample 1 and Sample 2 were used, and the positive electrode active materials were charged from 4.5 V to 4.65 V. XRD analysis of the state of charge was performed on secondary batteries that were charged at varying voltages.

[0413] Figure 34 shows the results for the positive electrode active material of Sample 1 at 4.5V, 4.525V, 4.55V, and 4. XRD patterns of the positive electrode after one CCCV charge at 575V, 4.6V, and 4.65V For comparison, the pseudospinel crystal structure, the H1-3 crystal structure, and Li 0.35 Co The crystal structure (space group R-3m, O3) pattern for O2 (charge depth 0.65) Shown below.

[0414] As can be seen from FIG. 34, the positive electrode active material of Sample 1 exhibited L i 0.35 It was found to have the crystal structure of CoO2(O3).

[0415] Also, when charging at 4.55V, Li 0.35 Crystal structure of CoO2(O3) and pseudospinel Since both peaks of the α-type crystal structure were observed, it is believed that these two crystal structures coexist. was speculated.

[0416] When the battery was charged at 4.575 V, a peak corresponding to a pseudospinel crystal structure was observed.

[0417] When further charged at 4.6 V, in addition to the peak of the pseudospinel crystal structure, a slight H The peak of the 1-3 crystal structure was observed, indicating that these two crystal structures coexist. was speculated.

[0418] When charged at 4.65 V, the peaks of the H1-3 type crystal structure were mainly observed. The peaks were broad, suggesting that the crystallinity had decreased.

[0419] Thus, in the fully annealed sample 1, the charge voltage was about 4.55 V, and Li0 .35 The phase changes from CoO2(O3) crystal structure to pseudo-spinel crystal structure, and the charging voltage is 4 It was found that the pseudo-spinel crystal structure is maintained up to about 0.6V. The change was in the charging voltage of about 4.65V.

[0420] Figure 35 shows the results for the positive electrode active material of Sample 2, measured at 4.5V, 4.55V, 4.6V, and 4. The XRD pattern of the positive electrode after one CCCV charge at 65 V is shown. H1-3 type crystal structure, Li 0.35 The crystal structure of CoO2(O3) The pattern and the pattern of the CoO2(O1) type crystal structure are also shown.

[0421] As can be seen from Figure 35, the positive electrode active material of Sample 2 exhibits the same properties as Sample 1 when charged at 4.5 V. Li 0.35 It was found to have the crystal structure of CoO2(O3).

[0422] However, when charged at 4.55V, unlike sample 1, Li 0.35 CoO2(O3) Peaks from both the crystalline structure and the H1-3 type crystalline structure were observed.

[0423] Furthermore, when charged at 4.6 V, the peaks of the H1-3 type crystal structure were predominant, unlike sample 1. was observed.

[0424] When charged at 4.65 V, the H1-3 type crystal structure and the CoO2(O1) type crystal structure were observed. The peaks were quite broad, indicating a significant decrease in crystallinity. It was speculated that this was the case.

[0425] As shown above, in Sample 2, which was not annealed sufficiently, the charge voltage increased rapidly at around 4.55 V. MoLi 0.35 The phase changed from the CoO2(O3) crystal structure to the H1-3 type crystal structure.

[0426] As explained in the first embodiment, the H1-3 type crystal structure is obtained by converting the crystal structure in the discharged state into CoO2 The layers are significantly shifted, and the volume difference is large, so the structure changes to the H1-3 type crystal structure repeatedly. It is thought that the crystal structure will collapse as a result of repeated heating. It is necessary to determine the upper limit of the charging voltage so that the crystal structure does not change to the H1-3 type.

[0427] Therefore, as in sample 2, the phase changes to the H1-3 type crystal structure at a charging voltage of around 4.55 V. The upper limit of the charge voltage for the positive electrode active material is less than 4.55V, for example, 4.5V.

[0428] On the other hand, the positive electrode active material such as Sample 1 maintains a pseudospinel crystal structure even at a charging voltage of 4.6 V. In this case, the upper limit of the charging voltage can be set to 4.6V. If the positive electrode active material is used, the capacity per weight of the positive electrode active material can be increased, and a high-capacity secondary battery can be obtained. can.

[0429] [XRD after 10 charge / discharge cycles (discharged state)] Next, the secondary batteries using Sample 1 and Sample 2 were charged and discharged 10 times at a high voltage. Specifically, the charge and discharge cycle is repeated 10 times, with CCCV charging (4.6V) followed by CC discharging (2.5V). After the cycle, the discharged secondary battery was disassembled, the positive electrode was taken out, and an XRD analysis was performed.

[0430] Figure 36 shows the positive electrode of secondary batteries using Sample 1 and Sample 2 after 10 charge / discharge cycles. The XRD pattern is shown, along with the pattern of the ideal crystal structure of lithium cobalt oxide for comparison. is also shown.

[0431] The pattern of sample 2, which was insufficiently annealed and took on the H1-3 type crystal structure during high-voltage charging, is It is brighter than Sample 1, which is sufficiently annealed and takes on a pseudospinel crystal structure upon high-voltage charging. It was apparently broad and was presumed to have low crystallinity.

[0432] [XRD after 100 charge / discharge cycles (charged state)] Next, the secondary batteries using Sample 1 and Sample 2 were subjected to CCCV charging (4.45V). After repeating charge and discharge 100 times, charge the battery at 4.6V and discharge it at 2.5V. The secondary battery was disassembled, the positive electrode was taken out, and XRD analysis was performed.

[0433] Figure 37 shows the results of the high voltage test of secondary batteries using Sample 1 and Sample 2 after 100 charge / discharge cycles. The XRD patterns of the positive electrodes charged at high pressure are shown. For comparison, the pseudospinel crystal structure and The H1-3 crystal structure pattern is also shown.

[0434] As shown in FIG. 37, even after 100 cycles, the positive electrode active material of Sample 1 remained in the pseudo-stable state. It had a spinel crystal structure. Rietveld analysis revealed that it had a pseudospinel crystal structure. The proportion of the H1-3 type crystal structure was 43.6 wt%, and the proportion of the H1-3 type crystal structure was 56.4 wt%.

[0435] On the other hand, almost all of the positive electrode active material of Sample 2 had an H1-3 type crystal structure. The peak was quite broad, suggesting that the crystallinity had decreased significantly.

[0436] [Cycle characteristics] Next, sample 1, sample 2, sample 4, sample 5, sample 7, sample 10, The cycle characteristics of the secondary batteries using Samples 12 and 13 were evaluated. The results are shown in Figures 38 and 39. The secondary batteries evaluated here were is 7mg / cm 2 Over 8mg / cm 2 These are as follows:

[0437] Figure 38 shows Sample 1, Sample 2, Sample 4, Sample 10, Sample 12 and Sample 3. For sample 13, charging was performed at 25°C using CCCV (0.5C, 4.6V, final current 0.0 The results are shown for 50 cycles of charge / discharge at CC (0.5C, 2.5V). 38(A) shows the discharge capacity, and 38(B) shows the discharge capacity retention rate. The current value per weight of the electrode active material was 137 mA / g.

[0438] Sample 1, which has a pseudospinel crystal structure after annealing for 60 hours and high voltage charging, shows extremely The discharge capacity retention rate after 50 cycles was 96.1%. .

[0439] On the other hand, Sample 4, which was not particularly treated, and Sample 5, which was annealed for 2 hours and then charged at a high voltage, were Sample 2, which has a 1-3 type crystal structure, was significantly deteriorated. The retention rate was below 60% in all cases.

[0440] Aldrich No. 442704 was used as the pre-synthesized lithium cobalt oxide. However, sample 10, which was mixed with the magnesium source and the fluorine source and then annealed, showed good surface roughness. The discharge capacity retention rate after 50 cycles was 79.8%.

[0441] On the other hand, lithium cobalt oxide containing titanium as an impurity at about 5100 ppm wt was used. In the case of Samples 12 and 13, after mixing with the magnesium source and fluorine source, Despite the annealing, the deterioration was significant. This is because the annealing time was short. This was also the case for both the long sample 12 and the long sample 13.

[0442] Figure 39 shows the results of 100 cycles at 45°C for Samples 1, 5, and 7. The measurement results are shown in Figure 39(A) for the discharge capacity and Figure 39(B) for the discharge capacity retention rate. In FIG. 39, 1C is a current value per weight of the positive electrode active material of 160 mA / g. The measurement conditions are as follows: Charge is CCCV (1.0C, 4.55V, final current 0.05C), discharge is CC (1.0C , 3.0V).

[0443] Even when measured at 45°C, Sample 1 showed extremely good cycle characteristics. The discharge capacity retention rate after the test was 93.3%. Sample 5 was prepared in the same manner as Sample 1 except that the annealing time was 2 hours. The battery showed excellent cycle characteristics.

[0444] Furthermore, a magnesium source and a fluorine source are added to the starting material, and the material is baked and then annealed. Sample 7 also showed good cycle characteristics.

[0445] 38 and 39 for Sample 1 and Sample 4. The results of evaluating the cycle characteristics by changing the electrolyte and charging voltage are shown in Figure 40 and Shown in Figure 41.

[0446] All of the secondary batteries used for evaluation had a positive electrode active material layer loading of 20 mg / cm 2 That's all. The electrolyte solution was made of ethylene carbonate (EC) and diethyl carbonate (DEC). ) mixed with EC:DEC=3:7 (volume ratio) and vinylene carbonate Two types of batteries were used, each containing 2 wt% of VC. or 4.6V.

[0447] Figure 40 shows the results of the electrolytic solution mixed with EC:DEC = 3:7 (volume ratio). Figure 40(A) shows the cycle characteristics of Sample 1 and Sample 4. The charging voltage was set to 4.5 V. FIG. 40(B) shows the cycle characteristics when the charging voltage was 4.6V.

[0448] In addition, Figure 41 shows the electrolyte solution of EC:DEC = 3:7 (volume ratio) with vinylene carbonate ( The cycle characteristics of Sample 1 and Sample 4, which further contain 2 wt% of VC, were Figure 41(A) shows the case when the charging voltage is 4.5V, and Figure 41(B) shows the case when the charging voltage is 4. This is the cycle characteristics at 6V.

[0449] As is clear from FIGS. 40 and 41, the amount of the positive electrode active material layer, the electrolyte, and the charging voltage Even when the temperature was changed, Sample 1 exhibited extremely good cycle characteristics.

[0450] From the above analysis results, it was found that when charged at a high voltage of 4.6 V, a pseudospinel crystal structure It has been revealed that the positive electrode active material having the formula (I) exhibits extremely good cycle characteristics. In order to form a pseudospinel crystal structure after high voltage charging, it is necessary to add magnesium and fluorine. It has become clear that annealing at an appropriate temperature and time is effective. The appropriate annealing time depends on the particle size or composition of the lithium cobalt oxide. It was assumed to be different.

[0451] In addition, lithium cobalt oxide, which is a starting material containing magnesium and fluorine, is used. Although annealing is possible, magnesium and fluorine are added to lithium cobalt oxide with few impurities. It was found that mixing and annealing the mixture was more effective.

[0452] In addition, a comparison of the lattice constant and cycle characteristics reveals that the c-axis lattice constant is 14.060×10 -10 m The following lithium cobalt oxide is used, and the magnesium source and fluorine source are mixed and annealed. It has become clear that this tends to result in a positive electrode active material that exhibits good cycle characteristics. First, the layered rock salt type crystal with little Co3O4 of the foreign element substitution and spinel type crystal structure Then, a magnesium source and a fluorine source are mixed to form a complex oxide. Inserting sodium into the lithium site allows the creation of a positive electrode active material that exhibits good cycling properties. It was thought that...

[0453] [Rate characteristics] Next, Sample 1, which exhibits extremely good cycle characteristics as described above, and the magnesium source and The secondary battery using Sample 4, which is a comparative example in which no fluorine source is mixed, was The results of evaluating the characteristics are shown in Figs. 42 and 43.

[0454] The coin cell used for rate characteristic evaluation had a positive electrode active material layer loading of 20.8 mg / cm 2 2 more 1.0 mg / cm 2 The coin cell for XRD measurement was prepared in the same manner as described above, except for the following. The upper limit for the initial charge is 4.5V or 4.6V, and the following conditions are met: CCCV, 0.2C, 4.6V, The cut-off current was 0.05 C. The first discharge was CC, 0.2 C, and the cut-off voltage was 3.0 V. Here, 1C is a current value per weight of the positive electrode active material of 200 mA / g. From the second charge and discharge onwards, only the discharge rate was changed, 0.2C charge / 0.2C discharge, 0.2 C charge / 0.5C discharge, 0.2C charge / 1.0C discharge, 0.2C charge / 2.0C discharge The measurement temperature was 25°C.

[0455] Figure 42(A) shows the discharge curves at each rate for sample 1 when the charge voltage is 4.5 V, and Figure 42( B) shows the discharge curves at each rate for sample 1 when the charging voltage is 4.6 V. ) is the discharge curve at each rate of sample 4 when the charge voltage is 4.5V, and Fig. 43(B) is the charge 10 shows the discharge curves of Sample 4 at various rates at a voltage of 4.6V.

[0456] As is clear from FIGS. 42 and 43, the secondary battery using Sample 1 has a low In comparison, it shows good rate characteristics when charged at high voltage, and this tendency becomes stronger as the rate increases. This was particularly evident.

[0457] In addition, in the secondary battery using Sample 1, when discharging at a low rate such as 0.2 C, It became clear that there was a characteristic voltage change near the end of the test.

[0458] [Charging curve and dQ / dV vs V curve] Next, Sample 1, which is one embodiment of the present invention, was subjected to the formation of an aluminum-containing layer on the surface thereof, and then The charging curve and dQ for the secondary battery using sample 15 annealed at 500°C for 2 hours were The results of comparing the / dV vs V curves are shown.

[0459] The secondary batteries using Sample 1 and Sample 15 were charged at 10 mAh / g up to 4.9 V at 25°C. The charging curves are shown in Figure 44. The solid line is for Sample 1 and the dashed line is for Sample 15. Two secondary batteries using each sample were measured.

[0460] The dQ / dV vs. V curve, which shows the change in voltage relative to the charge capacity, was obtained from the data in Figure 44. The results are shown in Figure 45. Figure 45(A) shows the d for sample 1, and Figure 45(B) shows the d for sample 15. This is the Q / dV vs V curve.

[0461] As is clear from Figures 45(A) and 45(B), both Sample 1 and Sample 15 In this case, peaks were observed at voltages of approximately 4.06 V and 4.18 V. The change in capacity was nonlinear. Between these two peaks, the result at a charge depth of 0.5 The space group P2 / m at a charge depth of 0.5 is shown in Figure 1. As shown in Figure 4, the lithium atoms are aligned. Energy is used to align the lithium atoms. This is thought to be why the change in capacitance with respect to voltage became nonlinear.

[0462] In addition, in the comparative example, sample 15, a large peak was observed at approximately 4.54V and 4.61V. The area between these two peaks is thought to be a crystal structure of the H1-3 phase type. .

[0463] On the other hand, Sample 1, which shows extremely good cycle characteristics, shows a small peak at around 4.55 V. However, it was not clear. Therefore, the dQ / d The VvsV curves are shown in Figures 46 and 47. Figure 47 is an enlarged view of Figure 46.

[0464] As shown in Figure 47, detailed measurements reveal that peaks occur at approximately 4.55V and 4.63V. The area between these two peaks is thought to be a pseudo-spinel crystal structure. The region between the peaks at approximately 4.63 V and 4.64 V is considered to be an H1-3 type crystal structure. can be done.

[0465] As can be seen, in the dQ / dV vs V curve of sample 1, some peaks are extremely broad or In such cases, two crystal structures may coexist. For example, two phases of O3 and pseudospinel coexist, or two phases of pseudospinel and H1-3 coexist. It is possible that

[0466] [Discharge curve and dQ / dV vs V curve] Next, a secondary battery using Sample 1, which is one embodiment of the present invention, and Sample 4, which is a comparative example, was prepared. The results of comparing the discharge curve and the dQ / dV vs V curve are shown below.

[0467] FIG. 48(A) shows the discharge curve of Sample 1, and FIG. 48(B) shows the discharge curve of Sample 4. In both cases, the battery was discharged after CCCV charging at 4.6V. The discharge was CC discharge down to 2.5V. The discharge rate was 0.05 C (1 C = 200 mA / g).

[0468] As shown in Figure 48(A), in sample 1, the discharge was almost completed (the area surrounded by the dashed line in the figure). A characteristic voltage change was observed. This is the same as the voltage observed in the low-rate discharge in Figure 40. It is the same as change.

[0469] The dQ / dV vs. V curve, which shows the change in voltage relative to the discharge capacity, was obtained from the data in Figure 48. The dQ / dVv of Sample 1 is shown in Fig. 49(A), and that of Sample 4 is shown in Fig. 49(B). This is an sV curve. In order to clearly depict the peak, the graph covers the voltage range of 3.5V or higher.

[0470] As shown in FIG. 49(B), Sample 4, which does not contain a magnesium source and a fluorine source, In the case of the saturation voltage, two large downward convex peaks were observed at approximately 4.37 V and 3.87 V. It became clear that there were two inflection points in the discharge curve of Sample 4.

[0471] On the other hand, as is clear from FIG. 49(A), Sample 1 has many more downward convex peaks. The largest peak was observed at about 3.9 V. As shown in the figure, there was at least one peak in the range of 3.5 V to 3.9 V. The peak indicates the change in voltage in the area surrounded by the dashed line in FIG. 48(A).

[0472] As described above with reference to FIGS. 40, 48, and 49, the sample according to one embodiment of the present invention The positive electrode active material of PULSE 1 is charged at a high voltage and then discharged at a low rate of, for example, 0.2 C or less. It was found that a characteristic voltage change appears near the end of discharge. At least one peak in the dQ / dV vs V curve between 3.5V and 3.9V can be clearly seen by the existence of [Example]

[0473] In this example, a positive electrode active material containing cobalt and nickel as transition metals was prepared, and X The features were analyzed using RD.

[0474] [Preparation of positive electrode active material] <<Sample 21>> As sample 21, a cobalt and nickel source was prepared by the method shown in FIG. 1 of the first embodiment. The ratio of the number of nickel atoms (Ni) to the total number of atoms (Co + Ni) is Ni / (Co + Ni ) was prepared as a positive electrode active material having a .01.

[0475] First, as in steps S11 to S14 of the first embodiment and in Example 1, LiF A first mixture was prepared in which the molar ratio of LiF to MgF2 was 1:3.

[0476] Next, as in steps S21 and S22 of the first embodiment, Li:Ni:Co The atomic ratio of Ni / (Co+Ni) was 1:0.01:0.99 (Ni / (Co+Ni)=0.01). The materials were weighed and mixed. The lithium source was lithium carbonate, and the cobalt source was cobalt oxide. The mixture was stirred at 300 rpm for 20 hours, and nickel hydroxide was used as the nickel source. Seton was added and the mixture was wet.

[0477] Next, as in steps S23 to S25 of the first embodiment, the mixture is mixed in a dry air atmosphere. After baking in a furnace at 900°C for 10 hours, the material was recovered and the lithium, cobalt, nickel and A composite oxide containing oxygen was obtained. The flow rate of dry air was 10 L / min. The temperature was raised by 20 The temperature was lowered at 0°C / hr over 10 hours or more.

[0478] Next, as in steps S31 to S33 of the first embodiment, the first mixture and lithium A second mixture is prepared by mixing a complex oxide having aluminum, cobalt, nickel, and oxygen. The ratio of magnesium atoms in the first mixture to the sum of the number of cobalt and nickel atoms was The atomic weight of the rubber was mixed to be 0.5 atomic %.

[0479] Next, as in steps S34 and S35 of the first embodiment, the second mixture is The cathode active material was obtained after annealing in a muffle furnace in an oxygen atmosphere at 850°C for 2 hours and then recovering it. The oxygen flow rate was 10 L / min. The temperature rise rate was 200°C / hr, and the temperature drop rate was 10 hours or more. The positive electrode active material thus obtained was designated as Sample 21.

[0480] <<Sample 22>> In step S11, LiF and MgF2 are not added, and in step S34, A positive electrode active material prepared in the same manner as Sample 21 except for not performing annealing was used as Sample 22. (Comparative Example).

[0481] <<Sample 23>> In step S21, the raw materials were weighed so that Ni / (Co+Ni)=0.075. A positive electrode active material prepared in the same manner as Sample 21 was designated as Sample 23.

[0482] <<Sample 24>> In step S11, LiF and MgF2 are not added, and in step S34, The positive electrode active material was prepared in the same manner as Sample 23 except that annealing was not performed. (Comparative Example).

[0483] <<Sample 25>> In step S21, the raw materials were weighed so that Ni / (Co+Ni)=0.1. A positive electrode active material prepared in the same manner as Sample 21 was designated as Sample 25.

[0484] <<Sample 26>> In step S11, LiF and MgF2 are not added, and in step S34, The positive electrode active material was prepared in the same manner as Sample 25 except that annealing was not performed. (Comparative Example).

[0485] Table 4 shows the preparation conditions for Samples 21 to 26.

[0486] [Table 4]

[0487] [Secondary battery production] Next, using the samples 21 to 26 prepared above, coins were produced in the same manner as in Example 1. A secondary battery of this type was fabricated.

[0488] [XRD after first charge] The secondary batteries using Samples 21 to 26 were subjected to CC charging at 4.6 V in the same manner as in Example 1. After CV charging, the positive electrode was taken out and subjected to XRD analysis.

[0489] Figures 50 and 51 show the results of the secondary batteries using Sample 21 and Sample 22 at 4.6 V. The XRD pattern of the positive electrode after charging is shown in Figure 51(A). The part of 2θ=20° is shown enlarged. The area at 2θ=46° is shown enlarged. For comparison, the pseudospinel crystal structure, H1- Type 3 crystal structure and Li 0.35 The crystal structure pattern of CoO2 (charge depth 0.65) The pseudo-spinel type crystal structure, H1-3 type crystal structure, and Yobi Li 0.35 The comparison patterns of the crystal structure of CoO2 are all transition metals. The calculations were performed for a structure that only had nickel and no nickel.

[0490] In sample 21, which was added with Mg and F sources and annealed, a pseudo-spinel crystal structure was obtained. The peaks were observed. 0.35 CoO2 crystal The peaks of the structure were also observed. Also, some peaks were shifted from the comparative pattern. , which was thought to be an effect of nickel.

[0491] On the other hand, in sample 22, which was not subjected to the addition of the Mg source and the F source and annealing, pseudo-spinel However, the peaks of the H1-3 type crystal structure and Li 0.35 The peaks of the crystalline structure of CoO2 were observed.

[0492] Figure 52 shows the results of charging the secondary batteries using Samples 23 and 24 at 4.6 V. The XRD pattern of the positive electrode is shown. For comparison, the pseudospinel crystal structure and the H1-3 crystal structure are also shown. and Li 0.35 The crystal structure pattern for CoO2 (charge depth 0.65) is also included. This is shown.

[0493] In sample 23, which was annealed after adding Mg and F sources, a pseudo-spinel crystal structure and Although peaks of the H1-3 crystal structure were observed, the peaks of the pseudospinel crystal structure were dominant. It was.

[0494] On the other hand, in sample 24, which was not subjected to the addition of Mg and F sources and annealing, the H1-3 type Crystal structure and Li 0.35 The peak of the crystal structure of CoO2 was observed. The peaks were broad and the crystallinity was presumed to be low.

[0495] Figure 53 shows the results of charging the secondary batteries using Samples 25 and 26 at 4.6 V. The XRD pattern of the positive electrode is shown. For comparison, the pseudospinel crystal structure and the H1-3 crystal structure are also shown. and Li 0.35 The crystal structure pattern for CoO2 (charge depth 0.65) is also included. This is shown.

[0496] In Samples 25 and 26, where Ni / (Co+Ni) was 0.1, the crystal structure No significant difference was observed. In addition, this crystal structure is similar to the pseudospinel crystal structure, H1-3 Crystal structure and Li 0.35 It was speculated that neither CoO2 nor

[0497] 50 to 53, the positive electrode active material containing lithium, a transition metal, and oxygen has the following main components: When cobalt and nickel are used as transition metals, Ni / (Co+Ni) is less than 0.1. It has been found that the Ni / ( When the content of Co+Ni is within the above range, the addition of a Mg source and a F source and annealing can This is because the material has a pseudo-spinel crystal structure when charged to 4.6 V. As described in the previous examples, the positive electrode active material having a pseudo-spinel crystal structure in this state has good It exhibits good cycle characteristics. [Example]

[0498] In this example, a secondary battery using a positive electrode active material according to one embodiment of the present invention was fabricated, and a differential scanning calorimeter (DSC) was used. Differential scanning calorimetry (DS) C) and charge endurance tests were performed.

[0499] <<Sample 27>> The lithium phosphate was pulverized in a zirconia mortar.

[0500] The lithium phosphate that had been crushed in a mortar was mixed with the sample 1 prepared in the previous example. The amount of lithium phosphate mixed is equivalent to 0.04 mol per 1 mol of sample 1. The mixing was carried out in a ball mill using zirconia balls at 150 rpm and 1 After mixing, the mixture was sieved through a 300 μm φ sieve. The mixture was placed in a crucible, covered, and annealed in an oxygen atmosphere at 850°C for 2 hours. Sample 27 was obtained by sieving through a 3 μm diameter sieve.

[0501] <<Sample 28>> Lithium phosphate was crushed in a ball mill using zirconia balls. The mixture was crushed at 1000 rpm for 60 hours, and then sieved through a 300 μm diameter sieve.

[0502] Pulverized lithium phosphate was mixed with Sample 1 prepared in the previous example. The amount of lithium phosphate mixed is equivalent to 0.06 mol per 1 mol of sample 1. The mixture was mixed in a ball mill using zirconia balls at 150 rpm for 1 hour. After mixing, the mixture was sieved through a 300 μm φ sieve. The mixture was placed in a pot, covered, and annealed in an oxygen atmosphere at 750°C for 20 hours. The mixture was sieved through a 100 μm diameter sieve to obtain sample 28.

[0503] [Secondary battery production] Next, Samples 27 and 28 prepared above and Sample 1 shown in the previous example were compared. A CR2032 type coin-type secondary battery was fabricated using the above.

[0504] For the positive electrode, Sample 1, Sample 27, or Sample 28 was used as the active material. A slurry of PVDF mixed with active material:AB:PVDF = 95:3:2 (weight ratio) The current collector was coated with the above.

[0505] Lithium metal was used as the counter electrode.

[0506] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The secondary battery whose charge / discharge characteristics were evaluated later was made of ethylene carbonate (E C) and diethyl carbonate (DEC) were mixed at a volume ratio of EC:DEC = 3:7. The secondary battery for which the cycle characteristics were evaluated, as described below, contained ethylene carbonate (EC). Diethyl carbonate (DEC) was used in a volume ratio of EC:DEC=3:7, and vinylene carbonate was used in a volume ratio of EC:DEC=3:7. The material used was a mixture of 2 wt% VC.

[0507] The separator was made of polypropylene with a thickness of 25 μm.

[0508] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0509] The positive electrode of the secondary battery was pressurized with 210 kN / m, and then further pressurized with 1467 kN / m. The amount of support on the positive electrode using Sample 1 was approximately 21 mg / cm 2 , the electrode density is approximately 3.9g / cm 3 The amount of support on the positive electrode using Sample 28 was approximately 20 mg / cm m 2 , electrode density is approximately 3.7 g / cm 3 It was.

[0510] [Charge / discharge characteristics] The secondary batteries using Sample 1 and Sample 28 were charged by CCCV (0.05C, 4. 5V or 4.6V, final current 0.005C), discharge at CC (0.5C, 2.5V) The initial charge capacity, discharge capacity, and coulomb efficiency are shown in Table 5. What is coulomb efficiency? The discharge capacity is normalized by the charge capacity and expressed as a percentage. Ron efficiency was obtained.

[0511] [Table 5]

[0512] [Cycle characteristics] The secondary batteries using Sample 1 and Sample 28 were charged by CCCV (0.05C, 4. 5V or 4.6V, final current 0.005C), discharge CC (0.05C, 2.5V) The measurement was carried out for two cycles at 25°C.

[0513] Thereafter, the secondary batteries using Sample 1 and Sample 28 were charged at 25°C. CCV (0.2C, 4.5V or 4.6V, final current 0.02C), discharge CC (0. The cycle characteristics were evaluated by repeatedly charging and discharging at 2C and 2.5V. The capacity retention rate of sample 1 was 99.0% at a charging voltage of 4.5V and 99.0% at a charging voltage of 4.6V. For sample 28, the charge rate was 96.1% under the condition of a charging voltage of 4.5V, and for sample 30, the charge rate was 99.0% under the condition of a charging voltage of 4.5V. The capacity retention rate after 50 cycles was 97.8% at a voltage of 4.6 V. The charge voltage was 4.5V and the charge rate was 97.3%, 4.6V and 80.0%, respectively. In sample 28, the charge rate was 96.6% at a charging voltage of 4.5V and 93% at a charging voltage of 4.6V. Figure 54(A) shows the change in discharge capacity at a charge voltage of 4.5V, and Figure 5 4(B) shows the change in discharge capacity under the condition of a charging voltage of 4.6V. The horizontal axis of each graph shows the number of cycles, and the vertical axis shows the discharge capacity. In the case of the battery 28, the charge / discharge capacity is reduced by the weight of the lithium phosphate, but the cycle characteristics are improved. This is because the lithium phosphate coating prevents metals such as cobalt from the positive electrode active material. This is thought to be the result of suppressing the elution of ions and the decomposition of the electrolyte.

[0514] [Differential scanning calorimetry] The secondary batteries using Sample 1, Sample 27, and Sample 28 were charged by CCCV (0 0.05C, 4.5V or 4.6V, final current 0.005C), discharge to CC (0.05C , 2.5V) at 25°C for two cycles.

[0515] Then, the secondary batteries using Sample 1, Sample 27, and Sample 28 were charged in CC mode. The test was performed with CV (0.05C, 4.5V or 4.6V, final current 0.005C). The charged secondary battery was disassembled in a glove box under an argon atmosphere and the positive electrode was removed. The electrolyte was removed by washing with DMC, and then punched out to a diameter of 3 mm.

[0516] 1 μL of electrolyte was dropped onto the punched positive electrode and placed in a sealed container made of SUS. The electrolyte used was 1 mol / L lithium hexafluorophosphate (LiPF6), and the electrolyte solution was , ethylene carbonate (EC) and diethyl carbonate (DEC) are EC:DEC=3 A mixture of 1:7 (volume ratio) was used.

[0517] Evaluation was carried out using DSC. Measurements were carried out using a Rigaku Thermo p high-sensitivity differential scanning calorimeter. The measurement conditions were room temperature to 400°C, The temperature rise rate was set to 5°C / min.

[0518] The results of the DSC measurement are shown in Figure 55. The horizontal axis shows the temperature and the vertical axis shows the Heat flow is shown in Figure 55(A) for a comparison of Sample 1 and Sample 27. FIG. 55(B) shows a comparison of Sample 1 and Sample 28, respectively.

[0519] From Figure 55(A), peaks were observed around 171°C and 251°C in Sample 1. In sample 27, the temperature rose to around 188°C and 252°C, respectively, and The area intensity, which indicates the amount of heat, decreased. An increase in cracking and a decrease in area strength were observed, especially in the range of 150 to 200°C. A significant decrease in the area intensity was observed. From the above, it is considered that phosphoric acid was used in the manufacturing process of the positive electrode active material. It was suggested that mixing with a compound that has the same thermal stability as the hydroxybenzoates improves the thermal stability.

[0520] [Charging endurance test] The secondary batteries using Sample 1 and Sample 28 were charged by CCCV (0.05C, 4. 5V or 4.6V, final current 0.005C), discharge CC (0.05C, 2.5V) The measurement was carried out for two cycles at 25°C.

[0521] Then, the battery was charged at 60°C with CCCV (0.05C). The upper limit voltage was 4.55V. or 4.65V, and the termination condition is when the secondary battery voltage reaches the upper limit voltage minus 0.01V ( The time until the voltage of the secondary battery dropped below 4.55V was measured. If the voltage falls below the upper limit voltage, a phenomenon such as a short circuit may have occurred. 1C was set to 200mA / g.

[0522] Table 6 shows the times measured for each secondary battery.

[0523] [Table 6]

[0524] In sample 28, it took a long time for the voltage of the secondary battery to drop, and the positive electrode active material was It was suggested that mixing the compound with phosphoric acid improves charging durability. [Example]

[0525] In this example, a secondary battery using a positive electrode active material according to one embodiment of the present invention was fabricated, and atomic absorption spectrometry was performed. Metal elution was evaluated by measurement.

[0526] [Secondary battery production] First, using the sample 27 prepared above and the sample 1 shown in the previous example, A laminate type secondary battery was fabricated.

[0527] For the positive electrode, Sample 1 or Sample 27 was used as the active material, and the mixture of AB and PVDF was used. A slurry of the active material, AB, and PVDF mixed at a weight ratio of 95:3:2 was applied to one side of the current collector. The coated material was used.

[0528] The negative electrode uses graphite as the active material, and is made of VGCF (registered trademark), CMC-Na, and SBR. The composition of the active material was VGCF (registered trademark): CMC-Na: SBR = 96:1:1:2 (by weight) The slurry was mixed in the ratio of 1 / 2 and the viscosity was adjusted with pure water. The slurry was then applied to one side of the current collector, dried, and the pure water was then added. The volatilized material was used. A copper foil with a thickness of 18 μm was used as the current collector. The amount of support was approximately 14 mg / cm 2 It was.

[0529] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. We used the following.

[0530] The separator was made of polypropylene with a thickness of 25 μm.

[0531] The secondary battery was then charged and discharged at a low rate to remove gas for the purpose of aging. I went there a few times.

[0532] A positive electrode having Sample 1 or Sample 27 and a negative electrode having graphite were combined to form a After aging the secondary battery, charge it at CCCV (0.05C, 4.4 The discharge was performed at CC (0.05C, 2.5V, final current 0.005C). It was set to approximately 200 mA / g.

[0533] Then, charging was performed using CCCV (0.05C, 4.45V, final current 0.005C). Thereafter, the secondary battery was stored at 60° C. for 14 days.

[0534] Then, discharge was performed at 25°C in CC (0.05C, 2.5V). It was expressed as mA / g.

[0535] [Atomic absorption measurement] Next, the secondary battery was disassembled in an argon atmosphere glove box to remove the negative electrode, and the DM The electrolyte was removed by washing with HCl. Then, the current collector was removed. The powder of the active material layer was mixed. Approximately 0.1 mg was taken out and subjected to atomic absorption measurement.

[0536] The amount of cobalt was measured using furnace atomic absorption spectrometry. ContrAA 600 Continuum Source Atomic Absorption Spectroscopy by Analytic Jena In the measurement, cobalt was atomized at 2500°C and the wavelength was 235.8183 nm. Two secondary batteries were fabricated for each of Sample 1 and Sample 27. The measurement was carried out 20 times for each cell, and the average value was calculated.

[0537] The amount of cobalt obtained was 9722 ppm for sample 1 and 597 ppm for sample 27. The amount of cobalt was 1 ppm. The amount of cobalt was normalized by the amount of cobalt contained in the positive electrode active material layer. Specifically, the amount of cobalt contained in the entire negative electrode of the secondary battery is calculated from the obtained measurements. The amount of cobalt in the positive electrode of the secondary battery was used as the standard. The amount of phosphate was reduced. This suppressed the elution of cobalt from the positive electrode active material and reduced the amount deposited on the negative electrode. It is suggested that... [Example]

[0538] In this example, a positive electrode active material according to one embodiment of the present invention was prepared and its characteristics were analyzed using XRD. In addition, the cycle characteristics under high voltage charging were evaluated.

[0539] <<Sample 51>> The same procedure as in Example 1 was repeated except that the annealing time in step S34 of FIG. Sample 51 was prepared in the same manner as Sample 1.

[0540] <<Sample 52>> The same procedure as in Example 1 was repeated except that the annealing time in step S34 of FIG. Sample 52 was prepared in the same manner as Sample 1.

[0541] [XRD after first charge] As in Example 1, a secondary battery was fabricated using Sample 51 and Sample 52, and the initial charge The battery was charged and the XRD was evaluated after the first charge.

[0542] Figure 56 shows the positive and negative polarity of the secondary batteries using Sample 51 and Sample 52 after charging at 4.6 V. The XRD patterns of the poles are shown.

[0543] After charging to 4.6 V, Sample 52 was found to have a pseudospinel crystal structure. On the other hand, sample 51 suggested an H1-3 type crystal structure. This suggests that a better cathode active material can be obtained with a 30-hour heating period than with an 8-hour heating period. It was suggested that the annealing time should be longer than 8 hours.

[0544] [Cycle characteristics] As in Example 1, the secondary batteries using Samples 51 and 52 were cycled. The characteristics were evaluated.

[0545] At 25°C, charging is CCCV (1C, 4.6V, final current 0.01C), discharging is CC (0. The cycle characteristics were evaluated at 1 C and 2.5 V. The discharge capacity retention rate after 40 charge / discharge cycles was 47.8% for sample 28. %, Sample 29 was 98.4%, and Sample 1 prepared in Example 1 was 97.6%. Ta.

[0546] At 45°C, charging is CCCV (1C, 4.55V, final current 0.05C), discharging is CC (1 The cycle characteristics were evaluated at 1 C (3.0 V). The discharge capacity retention rate after 100 charge / discharge cycles was 39. 4% and in sample 52 it was 78.4%.

[0547] Sample 52 exhibited excellent cycle characteristics at both 25°C and 45°C. This indicates that an excellent positive electrode active material can be obtained by annealing for 30 hours. was suggested. [Example]

[0548] In this example, a positive electrode active material according to one embodiment of the present invention was prepared and its characteristics were analyzed using XRD. In addition, the cycle characteristics under high voltage charging were evaluated.

[0549] <<Sample 61>> In step S11 of FIG. 2, MgF2 was not added, and the other conditions were the same as those in Example 1. Sample 61 was prepared in the same manner as Sample 1. Molecular weight of lithium cobalt oxide The first mixture was weighed so that the atomic weight of lithium in the first mixture was 1.17 atomic %. Dry mixed.

[0550] <Sample 62> In step S11 of FIG. 2, LiF and MgF2 are not added, but instead Mg(OH) The other conditions were the same as those for Sample 1 in Example 1. The molecular weight of the lithium cobalt oxide was set to 62. The aluminum was weighed so that the atomic weight of the aluminum was 0.5 atomic % and mixed in a dry state.

[0551] [XRD after first charge] As in Example 1, a secondary battery was fabricated using Sample 61 and Sample 62, and the initial charge The battery was charged and the XRD was evaluated after the first charge.

[0552] Figure 57 shows the positive and negative polarity of the secondary batteries using Sample 61 and Sample 62 after charging at 4.6 V. The XRD patterns of the poles are shown.

[0553] After charging to 4.6 V, both Sample 61 and Sample 62 have a H1- rather than a pseudospinel-type crystal structure. The results suggest that the crystal structure is type 3. When using a compound containing lithium and a compound containing fluorine, a better positive It was suggested that an electrode active material could be obtained.

[0554] [Cycle characteristics] As in Example 1, the secondary batteries using Samples 61 and 62 were cycled. Figure 58(A) shows the results of cycle measurements at 25°C and a charging voltage of 4.6V. Figure 58(B) shows the results of charging at 45°C with a charging voltage of 4.55V. Both Sample 61 and Sample 62 were compared with Sample 1 shown in Example 1 in terms of cycle time. The decrease in capacity due to the high voltage charging was more pronounced. This is probably because it was not measured. [Explanation of symbols]

[0555] 100 Cathode active material 1001 particles 1002 Fine particles 1003 area 1010 detection area

Claims

1. having a positive electrode, the positive electrode has a positive electrode active material layer, the positive electrode active material layer includes a plurality of positive electrode active material particles and a graphene compound, the positive electrode active material particles contain lithium cobalt oxide, the positive electrode active material particles contain magnesium and fluorine, the positive electrode active material particles have a surface layer portion and an interior portion, the magnesium concentration in the surface layer portion is higher than the magnesium concentration in the interior portion, the fluorine concentration in the surface layer portion is higher than the fluorine concentration in the interior portion, the positive electrode active material particles have a rock salt crystal structure in a part of the surface layer portion, the positive electrode active material particles have a crystal structure therein, the crystal orientation of which is substantially the same as that of the rock salt crystal structure; Lithium-ion secondary battery.

2. In claim 1, The graphene compound has graphene or multigraphene. Lithium-ion secondary battery.

3. In claim 1 or 2, The graphene compound is in a sheet form. Lithium-ion secondary battery.

4. having a positive electrode, the positive electrode has a positive electrode active material layer, the positive electrode active material layer includes a plurality of positive electrode active material particles and carbon fibers, the positive electrode active material particles contain lithium cobalt oxide, the positive electrode active material particles contain magnesium and fluorine, the positive electrode active material particles have a surface layer portion and an interior portion, the magnesium concentration in the surface layer portion is higher than the magnesium concentration in the interior portion, the fluorine concentration in the surface layer portion is higher than the fluorine concentration in the interior portion, the positive electrode active material particles have a rock salt crystal structure in a part of the surface layer portion, the positive electrode active material particles have a crystal structure therein, the crystal orientation of which is substantially the same as that of the rock salt crystal structure; Lithium-ion secondary battery.

5. In claim 4, The carbon fiber comprises a carbon nanofiber or a carbon nanotube. Lithium-ion secondary battery.

6. In any one of claims 1 to 5, The positive electrode active material layer does not contain a binder. Lithium-ion secondary battery.

7. In any one of claims 1 to 6, The positive electrode is A coin-type secondary battery having the positive electrode, a counter electrode using lithium metal, and a separator using polypropylene was prepared, and the coin-type secondary battery was charged at a constant current of 0.5 C until a voltage of 4.575 V was reached (where 1 C is the current value per positive electrode active material, which is 137 mA / g). Thereafter, the coin-type secondary battery that had been subjected to the constant current charging was subjected to a constant voltage charging at a voltage of 4.575 V until a current value of 0.01 C was reached. Thereafter, in a glove box in an argon atmosphere, the positive electrode was removed from the coin-type secondary battery that had been subjected to the constant voltage charging, and the removed positive electrode was sealed in a sealed container. Thereafter, the positive electrode sealed in the sealed container was subjected to a constant voltage charging with CuKα １ In the XRD pattern when powder XRD analysis was performed using X-rays, having diffraction peaks at least at 2θ=19.30±0.20° and 2θ=45.55±0.10°; Lithium-ion secondary battery.

8. In any one of claims 1 to 6, The positive electrode is A coin-type secondary battery having the positive electrode, a counter electrode using lithium metal, and a separator using polypropylene was prepared, and the coin-type secondary battery was charged at a constant current of 0.5 C until the voltage reached 4.6 V (where 1 C is the current value per positive electrode active material, 137 mA / g). Thereafter, the coin-type secondary battery that had been subjected to the constant current charging was subjected to a constant voltage charging at a voltage of 4.6 V until the current value reached 0.01 C. Thereafter, in a glove box in an argon atmosphere, the positive electrode was removed from the coin-type secondary battery that had been subjected to the constant voltage charging, and the removed positive electrode was sealed in a sealed container. Thereafter, the positive electrode sealed in the sealed container was subjected to a constant voltage charging with CuKα １ In the XRD pattern when powder XRD analysis was performed using X-rays, having diffraction peaks at least at 2θ=19.30±0.20° and 2θ=45.55±0.10°; Lithium-ion secondary battery.

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