Lithium-ion secondary battery

Abstract

To provide positive electrode active material particles that are less likely to deteriorate, or to provide an electricity storage device that is less likely to deteriorate. Alternatively, a highly safe electricity storage device is provided. A first crystal grain, a second crystal grain, and a crystal grain positioned between the first crystal grain and the second crystal grain. and a grain boundary between the first and second crystal grains, the first and second crystal grains being composed of lithium and a transition metal. , and oxygen, the grain boundary has magnesium and oxygen, the first grain and The atomic concentration of magnesium at the grain boundary relative to the atomic concentration of transition metals in the grains of 2 The positive electrode active material particles have a concentration ratio in the range of 0.010 or more and 0.50 or less.

Description

Technical Field

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

[0002] Note that in this specification, the power storage device refers to an element and a device in general having a power storage function. For example, it includes storage batteries (also referred to as secondary batteries) such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors.

[0003] Also, in this specification, the electronic device refers to a device in general having a power storage device, and an electro-optical device having a power storage device, an information terminal device having a power storage device, etc. are all electronic devices.

Background Art

[0004] In recent years, various power storage devices such as lithium ion secondary batteries, lithium ion capacitors, and air batteries have been actively developed. In particular, lithium ion secondary batteries with high output and high capacity are widely used in portable information terminals such as mobile phones, smartphones, or notebook computers, portable music players, digital cameras, medical devices, or next-generation clean energy automobiles such as hybrid vehicles (HEVs), electric vehicles ( EVs), or plug-in hybrid vehicles (PHEVs). Along with the development of the semiconductor industry, the demand for them has rapidly expanded, and rechargeable energy ​​​It has become an essential component in the modern information society as a source.

[0005] Therefore, in order to improve the cycle characteristics and increase the capacity of lithium-ion secondary batteries, the improvement of the cathode active material has been studied (Patent Document 1 and Patent Document 2).

[0006] In addition, the characteristics required for power storage devices include safety in various operating environments and improvement of long-term reliability and so on.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] Lithium-ion secondary batteries and the cathode active materials used therein are desired to be improved in various aspects such as capacity, cycle characteristics, charge-discharge characteristics, reliability, safety, or cost.

[0009] In view of the above, one aspect of the present invention is to provide cathode active material particles with less deterioration as one of the problems to be solved. Or, one aspect of the present invention is to provide novel cathode active material particles as one of the problems to be solved. Or, one aspect of the present invention is to provide a power storage device with less deterioration as one of the problems to be solved. Or, one aspect of the present invention is to provide a highly safe power storage device as one of the problems . Or, one aspect of the present invention is to provide a novel power storage device as one of the problems.

[0010] Note that the description of these problems does not prevent the existence of other problems. Note that one aspect of the present invention does not necessarily need to solve all of these problems. Note that other problems can be extracted from the description of the specification, drawings, and claims.

Means for Solving the Problems

[0011] One aspect of the present invention has a first crystal grain, a second crystal grain, and a grain boundary located between the first crystal grain and the second crystal grain. The first crystal grain and the second crystal grain contain lithium, a transition metal, and oxygen, and the grain boundary contains magnesium and oxygen. It is a positive electrode active material particle. In the positive electrode active material particle described above, the ratio of the atomic concentration of magnesium to the atomic concentration of the transition metal preferably has a region of 0.010 or more and 0.50 or less.

[0012] In the positive electrode active material particle described above, it is preferable that the grain boundary further contains fluorine.

[0013] In the positive electrode active material particle described above, the ratio of the atomic concentration of fluorine to the atomic concentration of the transition metal preferably has a region of 0.020 or more and 1.00 or less.

[0014]

[0015] The positive electrode active material particle described above preferably contains at least one of iron, cobalt, nickel, manganese, chromium, titanium, vanadium, and niobium as the transition metal.

Advantages of the Invention

[0016] According to one aspect of the present invention, positive electrode active material particles with less deterioration can be provided. In addition, novel positive electrode active material particles can be provided. In addition, a power storage device with less deterioration can be provided. In addition, a highly safe ​​​​​​​​ A power storage device can be provided. Also, a novel power storage device can be provided.

Brief Description of the Drawings

[0017]

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Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art can easily understand that its form and details can be changed variously. Also, the present invention is not construed as being limited to the description of the embodiments shown below.

[0019] In each of the drawings described in this specification, the size, thickness, etc. of each component such as the positive electrode, negative electrode, active material layer, separator, and exterior body may be exaggerated for clarity of individual explanation. Therefore, each component is not necessarily limited to its size, nor is it limited to the relative size between each component.

[0020] Also, in the configuration of the present invention described in this specification, etc., the same parts or parts having the same function are commonly used with the same reference numerals between different drawings, and the repeated explanation thereof is omitted. Also, when referring to parts having the same function, the hatch pattern is the same, and there may be cases where they are not particularly labeled.

[0021] Also, the notation of crystal planes and directions is, in crystallography, indicated by a bar above the number, but in this specification, etc., the notation of crystal planes and directions, due to the constraints of the application notation, instead of putting a bar above the number, is expressed by attaching a -(minus sign) in front of the number. Also, the individual orientation indicating the direction within the crystal is represented by [ ], the set orientation indicating all equivalent directions is represented by < >, the individual plane indicating the crystal plane is represented by ( ), and the set plane having equivalent symmetry is represented by {}, respectively.

[0022] In this specification, etc., segregation refers to a phenomenon in a solid having a plurality of elements (for example, A, B, C) where the concentration of a certain element (for example, B) is unevenly distributed.

[0023] (Embodiment 1) [Structure of the positive electrode active material] Regarding the positive electrode active material particles 100 which are one aspect of the present invention, FIGS. 1(A) to 1(C) and FIGS. 2 (A) to 2(C) will be used for explanation.

[0024] FIG. 1(A) shows the appearance of the positive electrode active material particles 100. The positive electrode active material particles 100 are amorphous particles. Note that the shape of the positive electrode active material particles 100 shown in FIG. 1(A) is an example and is not limited thereto.

[0025] The positive electrode active material particles 100 have a plurality of crystal grains 101 and a plurality of grain boundaries 103. FIG. 1 (B) shows the crystal grains 101 and the grain boundaries 103 of the positive electrode active material particles 100. In FIG. 1 (B), the grain boundaries 103 are shown by broken lines, but the boundaries between the crystal grains 101 and the grain boundaries 103 may not be clear. Note that the shapes and numbers of the crystal grains 101 and the grain boundaries 1 03 shown in FIG. 1(B) are examples and are not limited thereto.

[0026] The crystal grains 101 are particles with a substantially constant crystal orientation within the crystal grains. Adjacent crystal grains 101 have different crystal orientations respectively, and have grain boundaries 103 between adjacent crystal grains. Thus, the positive electrode active material particles 100 have a plurality of crystal grains 101 with a grain boundary 103 sandwiched therebetween. The positive electrode active material particles 100 can be said to be polycrystalline. The positive electrode active material particles 100 may have crystal defects 105 and may have an amorphous region. Note that in this specification and the like, crystal defects refer to bulk defects, surface defects, point defects observable in a TEM image or the like, or a structure in which other elements are incorporated into the crystal, etc. Note that crystal grains may sometimes be called crystallites.

[0027] For the confirmation of the crystal grains 101 and grain boundaries 103 within the positive electrode active material particles 100, X-ray diffraction (XR D: X-ray Diffraction), neutron diffraction, electron diffraction (ED: Ele ctron Diffraction), transmission electron microscope (TEM: Transmis sion Electron Microscope) images, scanning transmission electron microscope (STE M: Scanning Transmission Electron Microsc opy) images, fast Fourier transform (F FT: Fast Fourier Transformation) analysis of the lattice images obtained from TEM images or STEM images, high-angle annular dark field scanning transmission electron microscope (HAADF-STEM: High-Angle Annul ar Dark Field Scanning TEM) images, annular bright field scanning transmission electron microscope (ABF-STEM: Annular Bright-Field Scanni ng TEM) images, Raman spectroscopy, electron backscatter diffraction method (EBSD: Electron Backscatter Diffract ion), etc. can be used. Note that the electron backscatter diffraction method may be called EBSP (Electr on Backscatter Diffraction Pattern). For example, in a TEM image, if the density (brightness) of the TEM image is substantially uniform, it may be determined that the crystal orientation is substantially constant, that is, it is a single crystal. Also, due to differences in the density (brightness) of the TEM image depending on the crystal orientation, it may be determined that the region where the density (brightness) changes is the grain boundary. However, it is not always necessary to clearly observe the boundaries between the crystal grains 101 and grain boundaries 1 03 by various analyses.

[0028] The crystal grains 101 and the grain boundaries 103 have different compositions. The crystal grains 101 contain lithium, a transition metal, and oxygen. The grain boundaries 103 contain magnesium and oxygen. Further, it is preferable that the grain boundaries 103 further contain fluorine.

[0029] The crystal grains 101 and the grain boundaries 103 can be confirmed to have different compositions by energy-dispersive X-ray spectroscopy (EDX), time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), electron energy-loss spectroscopy (EELS), etc. However, it is not always necessary to observe the clear boundaries between the crystal grains 101 and the grain boundaries 103 by various analyses. Also, depending on the analysis method, etc., the desired analysis target element may not be detected. Or, even when the concentration of the analysis target element is extremely low, the analysis target element may not be detected. The grain boundaries 103 of the positive electrode active material particles 100, which is one aspect of the present invention, contain magnesium and oxygen. The grain boundaries 103 contain magnesium oxide. Further, it is preferable that the grain boundaries 103 further contain fluorine. Some of the oxygen contained in magnesium oxide is replaced with fluorine. y Photoelectron Spectroscopy), Auger electron spectroscopy (A ES), electron energy-loss spectroscopy (EELS:Electron Energy-Loss Spectrosc opy), etc., it can be confirmed that they have different compositions. However, it is not always necessary to observe the clear boundaries between the crystal grains 101 and the grain boundaries 103 by various analyses. Also, depending on the analysis method, etc., the desired analysis target element may not be detected. Or, even when the concentration of the analysis target element is extremely low, the analysis target element may not be detected. opy) and the like, it can be confirmed that they have different compositions. However, it is not always necessary to observe the clear boundaries between the crystal grains 101 and the grain boundaries 103 by various analyses. Also, depending on the analysis method, etc., the desired analysis target element may not be detected. Or, even when the concentration of the analysis target element is extremely low, the analysis target element may not be detected. Also, depending on the analysis method and the like, there are cases where the desired analysis target element is not detected. Or, even when the concentration of the analysis target element is extremely low, there are cases where the analysis target element is not detected. Also, depending on the analysis method and the like, there are cases where the desired analysis target element is not detected. Or, even when the concentration of the analysis target element is extremely low, there are cases where the analysis target element is not detected. In the case where the concentration of the analysis target element is extremely low, there are cases where the analysis target element is not detected. There is also a case.

[0030] <Grain Boundary> The grain boundaries 103 of the positive electrode active material particles 100, which is one aspect of the present invention, contain magnesium and oxygen. The grain boundaries 103 contain magnesium oxide. Further, it is preferable that the grain boundaries 103 further contain fluorine. Some of the oxygen in magnesium oxide is replaced by fluorine. It may be. By partially substituting magnesium oxide with fluorine, for example the diffusivity of lithium can be enhanced, and charge and discharge are not hindered. The grain boundary 103 contains fluorine and may be insoluble in hydrofluoric acid.

[0031] Compared with the grain 101, the grain boundary 103 has a region with a high magnesium concentration. It can also be said that the grain boundary 103 has a region where magnesium is segregated. The grain boundary 103 has a region where magnesium is segregated.

[0032] Compared with the grain 101, the grain boundary 103 has a region with a high fluorine concentration. It can also be said that the grain boundary 103 has a region where fluorine is segregated. The grain boundary 103 has a region where fluorine is segregated.

[0033] An example of the magnesium concentration distribution between the dashed lines A1 - A2 of the positive electrode active material particles 100 shown in Fig. 2(A) is shown in Fig. 2(B), and an example of the fluorine concentration distribution is shown in Fig. 2(C). In Fig. 2(B) and Fig. 2(C), the horizontal axis represents the distance between the dashed lines A1 - A2 in Fig. 2(A), and the vertical axis represents the magnesium concentration (Mg Concentration) and the fluorine concentration (F Concentration), respectively. the magnesium concentration (Mg Concentration) and the fluorine concentration (F Concentration), respectively.

[0034] Compared with the grain 101, the grain boundary 103 and the vicinity of the grain boundary 103 have regions with high concentrations of magnesium and fluorine. Also, in the crystal defect 105, there may be a region with high concentrations of magnesium and fluorine. Note that in Fig. 2(B) and Fig. 2(C), an example where the grain boundary 103 and the crystal defect 105 have the same concentration is shown, but it is not limited to this. Also, the shapes of the concentration distributions of magnesium and fluorine are not limited to the shapes shown in Fig. 2(B) and Fig. 2(C). Note that in Fig. 2(B) and Fig. 2(C), an example where the grain boundary 103 and the crystal defect 105 have the same concentration is shown, but it is not limited to this. Also, the shapes of the concentration distributions of magnesium and fluorine are not limited to the shapes shown in Fig. 2(B) and Fig. 2(C). Note that in Fig. 2(B) and Fig. 2(C), an example where the grain boundary 103 and the crystal defect 105 have the same concentration is shown, but it is not limited to this. Also, the shapes of the concentration distributions of magnesium and fluorine are not limited to the shapes shown in Fig. 2(B) and Fig. 2(C). Note that in Fig. 2(B) and Fig. 2(C), an example where the grain boundary 103 and the crystal defect 105 have the same concentration is shown, but it is not limited to this. Also, the shapes of the concentration distributions of magnesium and fluorine are not limited to the shapes shown in Fig. 2(B) and Fig. 2(C).

[0035] Here, the number of atoms of the transition metal in the crystal grain 101 is represented as Tr-Metal. The crystal grain 10 The number of atoms of the transition metal (Tr-Metal) in 1 refers to the total number of atoms of each transition metal that the crystal grain 101 has. of atoms.

[0036] The positive electrode active material particles 100 preferably have a region where the ratio (Mg / Tr-Metal) of the number of atoms of magnesium in the crystal grain boundary 1 03 to the number of atoms of the transition metal in the crystal grain 101 is 0.010 or more and 0.50 or less. Further, the positive electrode active material particles 100 preferably have a region where Mg / Tr-Metal is 0.020 or more and 0.30 or less. Further more, the positive electrode active material particles 100 preferably have a region where Mg / Tr-Metal is 0.030 or more and 0.20 or less . By setting Mg / Tr-Metal as described above, deterioration of the positive electrode active material can be reduced. That is, deterioration of the power storage device can be suppressed. Also, a highly safe power storage device can be obtained.

[0037] In this specification and the like, the transition metal refers to an element belonging to Groups 3 to 12 of the periodic table. The above-mentioned group numbers are based on the periodic table classified into Groups 1 to 18 in the Revised Nomenclature of Inorganic Chemistry (1989) of the International Union of Pure and Applied Chemistry (IUPAC: International l Union of Pure and Applied Chemistry). It is based on the periodic table classified into Groups 1 to 18 in the Revised Nomenclature of Inorganic Chemistry (1989) of the International Union of Pure and Applied Chemistry (IUPAC). continues.

[0038] Generally, as the power storage device repeats charge and discharge, transition metals such as cobalt and manganese elute from the positive electrode active material particles of the power storage device into the electrolytic solution, oxygen desorbs, and the crystal structure becomes unstable . Side reactions such as this may occur, and the deterioration of the positive electrode active material particles may progress. The positive electrode active material particles When this happens, the deterioration of the positive electrode active material particles may progress. When the child deteriorates, deterioration such as a decrease in the capacity of the power storage device may progress. In this specification In the detailed description and the like, the transition metal of the positive electrode active material particles elutes into the electrolytic solution, oxygen desorbs, and the crystal The change in the positive electrode active material particles, such as the structure becoming unstable, chemically and structurally, is sometimes referred to as the deterioration of the positive electrode active material particles. In this specification and the like, the decrease in the capacity of the power storage device is sometimes referred to as the deterioration of the power storage device.

[0039] The metal eluted from the positive electrode active material particles is reduced and deposited at the negative electrode, which may interfere with the electrode reaction of the negative electrode. When metal is deposited on the negative electrode, deterioration such as a decrease in capacity may progress.

[0040] Due to the insertion and desorption of lithium accompanying charge and discharge, the crystal lattice of the positive electrode active material particles expands and contracts, and there may be a volume change and distortion of the crystal lattice. The volume change and distortion of the crystal lattice are the cause of the cracking of the positive electrode active material particles, and deterioration such as a decrease in capacity may progress. Further, the cracking of the positive electrode active material particles may start from the grain boundaries.

[0041] When the inside of the power storage device becomes hot and oxygen desorbs from the positive electrode active material particles, the safety of the power storage device may be impaired. Further, due to the desorption of oxygen, the crystal structure of the positive electrode active material particles changes, and deterioration such as a decrease in capacity may progress. Note that oxygen may also desorb from the positive electrode active material particles due to the insertion and desorption of lithium accompanying charge and discharge.

[0042] On the other hand, magnesium oxide is a chemically and structurally stable material. In a power storage device such as a lithium ion secondary battery, the magnesium oxide contained in the positive electrode active material particles is hardly involved in the battery reaction itself. That is, it is difficult for lithium to be inserted and desorbed with magnesium oxide. ​​​​​​​​ Therefore, magnesium oxide itself is chemically and structurally stable even after charge and discharge.

[0043] The positive electrode active material particles 100, which are one aspect of the present invention, have magnesium oxide at the grain boundaries 103. By doing so, the positive electrode active material particles 100 are chemically and structurally stable, and structural changes , volume changes, and distortion due to charge and discharge can be suppressed. That is, the crystal structure of the positive electrode active material particles 100 becomes more stable, and it is possible to suppress the transformation of the crystal structure even when charge and discharge are repeated. In addition, cracking of the positive electrode active material particles 100 can be suppressed. That is, deterioration such as capacity degradation can be suppressed, which is preferable. When the charging voltage is high and the amount of lithium present in the positive electrode during charging is smaller, the crystal structure becomes unstable and it becomes easier to deteriorate. Since the crystal structure of the positive electrode active material particles 100, which are one aspect of the present invention, is more stable, deterioration such as capacity degradation can be suppressed, which is particularly preferable.

[0044] Since the positive electrode active material particles 100, which are one aspect of the present invention, have a stable crystal structure, elution of transition metals from the positive electrode active material particles can be suppressed. That is, deterioration such as capacity degradation can be suppressed, which is preferable.

[0045] Further, when the positive electrode active material particles 100, which are one aspect of the present invention, crack along the grain boundaries, the surface of the positive electrode active material particles after cracking has magnesium oxide. That is, side reactions can be suppressed even in the positive electrode active material after cracking, and deterioration of the positive electrode active material can be reduced. That is, deterioration of the power storage device can be suppressed.

[0046] The positive electrode active material particles 100, which are one aspect of the present invention, have magnesium oxide at the grain boundaries 103. By doing so, diffusion of oxygen possessed by the positive electrode active material particles 100 to the grain boundaries is suppressed. It is possible to suppress the desorption of oxygen from the positive electrode active material particles 100. By using the positive electrode active material particles 100 it is possible to obtain a highly safe power storage device.

[0047] In addition, when the crystal defect 105 has magnesium oxide, the crystal structure of the positive electrode active material particles 100 is stabilized, which is preferable.

[0048] The positive electrode active material particles 100 have a ratio (F / Tr-Metal) of the number of fluorine atoms in the grain boundary 1 03 to the number of transition metal atoms in the crystal grain 101 in the range of 0.020 or more and 1.00 or less. Further, the positive electrode active material particles 100 preferably have a region where F / Tr-M etal is in the range of 0.040 or more and 0.60 or less. Further, the positive electrode active material particles 100 preferably have a region where F / Tr-Metal is in the range of 0.060 or more and 0.40 or less. By setting the above-mentioned F / Tr-Metal, magnesium can be efficiently segregated at the grain boundary and its vicinity. That is, deterioration of the positive electrode active material can be reduced. Deterioration of the power storage device can be suppressed. In addition, a highly safe power storage device can be obtained.

[0049] <Crystal grain> The crystal grain 101 included in the positive electrode active material particles 100, which is one aspect of the present invention, contains lithium, transition metal and oxygen. For example, the crystal grain 101 has a composite oxide containing lithium, transition metal and oxygen. As the transition metal, one or more of iron, cobalt, nickel, manganese, chromium, titanium tantalum, vanadium, niobium, etc. can be used.

[0050] The crystal grain 101 has, for example, a layered rock salt type crystal structure or a spinel type crystal structure. Composite oxides or the like can be used. Further, as the crystal grains 101, for example, polyanion -based cathode materials can be used. Examples of polyanion-based cathode materials include olivine -type crystal structure materials, NASICON-type materials, and the like. Further, as the crystal grains 101 and, for example, cathode materials containing sulfur can be used.

[0051] Various composite oxides can be used as the crystal grains 101. For example, LiFeO2, LiCoO2, LiNiO2, LiMn2O4, Li2MnO3, V2O5, Cr2O5 , compounds such as MnO2 can be used.

[0052] As a material having a layered rock salt-type crystal structure, for example, a composite oxide represented by LiMO2 can be used. The element M is preferably one or more selected from Co or Ni. LiCoO2 is preferable because it has advantages such as a large capacity, stability in the air, and relatively high thermal stability. Further, in addition to one or more selected from Co and Ni, the element M may have one or more selected from Al and Mn.

[0053] For example, LiNi x Mn y Co z O w (where x, y, z, and w are, for example, x = y = z = 1 / 3 or in the vicinity thereof, w = 2 or in the vicinity thereof) can be used. Further, for example , LiNi x Mn y Co z O w (where x, y, z, and w are, for example, x = 0.8 or in the vicinity thereof, y = 0.1 or in the vicinity thereof, z = 0.1 or in the vicinity thereof, w = 2 or in the vicinity thereof) It can be used near). Also, for example, LiNi x Mn y Co z O w (x, y, z, and w are, for example, x = 0.5 or in the vicinity thereof, y = 0.3 or in the vicinity thereof, z = 0 .2 or in the vicinity thereof, w = 2 or in the vicinity thereof) can be used. Also, for example, L iNi x Mn y Co z O w (x, y, z, and w are, for example, x = 0.6 or in the vicinity thereof, y = 0.2 or in the vicinity thereof, z = 0.2 or in the vicinity thereof, w = 2 or in the vicinity thereof) can be used. Also, for example, LiNi x Mn y Co z O w (x, y, z, and w are, for example, x = 0.4 or in the vicinity thereof, y = 0.4 or in the vicinity thereof, z = 0.2 or in the vicinity thereof, w = 2 or in the vicinity thereof) can be used.

[0054] The vicinity means, for example, a value greater than 0.9 times and less than 1.1 times that value.

[0055] A material obtained by substituting part of the transition metal or lithium in the crystal grain 101 with one or more elements selected from Fe, Co, Ni, Cr, Al, Mg etc., or a material obtained by doping the crystal grain 101 with one or more elements selected from Fe, Co, Ni, C r, Al, Mg, etc. may be used as the crystal grain 101. For example, a composite oxide represented by LiM2O4 can be used as a material having a spinel-type crystal structure. It is preferable that M has Mn as an element. For example, LiMn2O

[0056] ​​4 can be used. Further, by having Ni in addition to Mn as the element M, the discharge voltage of the secondary battery may be improved and the energy density may be improved, which is preferable. Also, for a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4, it is preferable to mix a small amount of lithium nickelate (LiNiO2, LiNi M 1-x M x O2 (M = Co, Al, etc.) ) to improve the characteristics of the secondary battery.

[0057] The positive electrode active material preferably has an average particle diameter of primary particles of 1 nm or more and 100 μm or less, more preferably 50 nm or more and 50 μm or less, and even more preferably 1 μm or more and 30 μm or less. Also, the specific surface area is preferably 1 m 2 / g or more and 20 m 2 / g or less. Also, the average particle diameter of the secondary particles is preferably 5 μm or more and 50 μm or less. The average particle diameter can be measured by observation with a scanning electron microscope (SEM: Scanning Electron 2 Microscope) or TEM, or by a particle size distribution meter using the laser diffraction / scattering method. The specific surface area can be measured by the gas adsorption method. 2 It is preferable that the positive electrode active material has an average particle diameter of secondary particles of 5 μm or more and 50 μm or less. The average particle diameter is measured by observation with a scanning electron microscope (SEM: Scanning Electron Microscope) or TEM, or by a particle size distribution meter using the laser diffraction / scattering method. The specific surface area is measured by the gas adsorption method. ron Microscope) or TEM, or by a particle size distribution meter using the laser diffraction / scattering method. The specific surface area can be measured by the gas adsorption method. A conductive material such as a carbon layer may be provided on the surface of the positive electrode active material. By providing a conductive material such as a carbon layer, the conductivity of the electrode can be improved. For example, the coating of the carbon layer on the positive electrode active material can be formed by mixing a carbohydrate such as glucose during the firing of the positive electrode active material. Also, as the conductive material, graphene, multi-graphene, graphene oxide ( ) can be used.

[0058] A conductive material such as a carbon layer may be provided on the surface of the positive electrode active material. By providing a conductive material such as a carbon layer, the conductivity of the electrode can be improved. For example, the coating of the carbon layer on the positive electrode active material can be formed by mixing a carbohydrate such as glucose during the firing of the positive electrode active material. Also, as the conductive material, graphene, multi-graphene, graphene oxide ( ) can be used. The coating of the carbon layer on the positive electrode active material can be formed by mixing a carbohydrate such as glucose during the firing of the positive electrode active material. Also, as the conductive material, graphene, multi-graphene, graphene oxide ( ) can be used. ​GO (Graphene Oxide) or RGO (Reduced Graphene Oxide) can be used. Here, RGO refers to, for example, a compound obtained by reducing graphene oxide (GO ).

[0059] A layer having one or more of oxides or fluorides may be provided on the surface of the positive electrode active material. The oxide may have a composition different from that of the crystal grains 101. Also, the oxide may have the same composition as the crystal grains 101 .

[0060] As a polyanion-based positive electrode material, for example, a composite oxide having oxygen, element X, metal A, and metal M can be used. Metal M is one or more of Fe, Mn, Co, Ni, Ti, V, N b, and metal A is one or more of Li, Na, Mg, and element X is one or more of S, P, Mo, W, As, Si.

[0061] As a material having an olivine-type crystal structure, for example, a composite material (general formula LiMPO4 (M is , one or more of Fe(II), Mn(II), Co(II), Ni(II))) can be used . Representative examples of the general formula LiMPO4 include LiFePO4, LiNiPO4, L iCoPO4, LiMnPO4, LiFe a Ni b PO4, LiFe a Co b PO4, L iFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4 (a + b is 1 or less, 0 < a < 1, 0 < b < 1), LiFe c Ni d Co e PO4, LiFe c Ni​d M n e PO4, LiNi c Co d Mn e PO4 (where c + d + e is 1 or less, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO4 (where f + g + h + i is 1 or less, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), etc. Lithium compounds can be used for this purpose.

[0062] In particular, LiFePO4 satisfies the requirements for a cathode active material, such as safety, stability, high capacity density, and the presence of lithium ions that can be extracted during initial oxidation (charging), in a well-balanced manner. Therefore it is preferable.

[0063] The cathode active material having an olivine-type crystal structure preferably has an average particle diameter of primary particles of 1 nm or more and 20 μm or less, more preferably 10 nm or more and 5 μm or less and even more preferably 50 nm or more and 2 μm or less. The specific surface area is preferably 1 m 2 / g or more and 20 m 2 / g or less. The average particle diameter of secondary particles is preferably 5 μm or more and 5 0 μm or less.

[0064] Also, composite materials such as the general formula Li (2-j) MSiO4 (where M is one or more of Fe(II), Mn(II), Co(I I), Ni(II), 0 ≤ j ≤ 2), etc. can be used. The general formula Li (2-j) MSiO4 representative examples include Li (2-j) FeSiO4, Li (2- j) NiSiO4, Li (2-j) ​CoSiO4, Li (2-j) MnSiO4, Li ( 2-j) Fe k Ni l SiO4, Li (2-j) Fe k Co l SiO4, Li (2-j) Fe k Mn l SiO4, Li (2-j) Ni k Co l SiO4, Li (2-j) Ni k M n l SiO4 (k + l is 1 or less, 0 < k < 1, 0 < l < 1), Li (2-j) Fe m Ni n Co q SiO4, Li (2-j) Fe m Ni n Mn q SiO4, Li (2-j) Ni m Co n Mn q SiO4 (m + n + q is 1 or less, 0 < m < 1, 0 < n < 1, 0 < q < 1), Li (2-j) Fe r Ni s Co t Mn u SiO4 (r + s + t + u is 1 or less, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1), etc. exist.

[0065] Also, A x M2(XO4)3 (A = Li, Na, Mg, M = Fe, Mn, Ti, V, Nb , X = S, P, Mo, W, As, Si) can be used with the general formula of the NASICON-type compound. As the NASICON-type compound, there are Fe2(MnO4)3, Fe2(SO4)3, Li3Fe2(PO4)3, etc. Also, as the crystal grains 101, Li2MPO4F, L Compounds represented by the general formulas i2MP2O7 and Li5MO4 (M = Fe, Mn) can be used for this purpose. This is possible.

[0066] Also, as the crystal grains 101, perovskite-type fluorides such as NaFeF3 and FeF3, metal chalcogenides (sulfides, selenides, tellurides) such as TiS2 and MoS2, oxides having an inverse spinel crystal structure such as LiMVO4, vanadium oxides (V2O5, V6O, LiV3O8, etc.), manganese oxides, organic sulfur compounds, and other materials can be used. TiS2, MoS2 and other metal chalcogenides (sulfides, selenides, tellurides), LiMVO4 and other oxides having an inverse spinel crystal structure, vanadium oxides (V2O5, V6O, LiV3O8, etc.), manganese oxides, organic sulfur compounds, etc. can be used. VO4 and other oxides having an inverse spinel crystal structure, vanadium oxides (V2O5, V6O, LiV3O8, etc.), manganese oxides, organic sulfur compounds, etc. can be used. O 13 Also, as the crystal grains 101, materials such as vanadium oxides (V2O5, V6O, LiV3O8, etc.), manganese oxides, and organic sulfur compounds can be used. This is possible.

[0067] Also, as the crystal grains 101, borate-based cathode materials represented by the general formula LiMBO3 (M is one or more of Fe(II), Mn(II), Co(II)) can be used. This is possible.

[0068] Also, as the crystal grains 101, for example, solid solutions combining multiple composite oxides can be used. A solid solution of LiMO2 and Li2MO3 (M, M are each independently one or more selected from transition metals) may be called a lithium-excess oxide. For example, a solid solution of LiNiMnCoO2 (x, y, z > 0, x + y + z = 1) and Li2MnO3 can be used as the crystal grains 101. This is possible. LiM a O2 and Li2M b O3 solid solution (M a 、M b are each independently one or more selected from transition metals may sometimes be called a lithium-excess oxide. For example, a solid solution of LiNiMnCoO2 (x, y, z > 0, x + y + z = 1) and Li2MnO3 can be used as the crystal grains 101. x Mn y Co z O2 (x, y, z > 0, x + y + z = 1) and Li2MnO3 can be used as the crystal grains 101. This is possible.

[0069] Also, as the crystal grains 101, lithium manganese composite oxides represented by the composition formula LiMnMO can be used. Here, the element M is other than lithium and manganese. a Mn b M c O d This is possible. Here, the element M is other than lithium and manganese. and can be used. Here, the element M is other than lithium and manganese. It is preferable to use the selected metal element, silicon, or phosphorus, and nickel is more preferable. When measuring the entire particles of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≤ (b + c) / d < 0.5 during discharge. In addition, in order to exhibit a high capacity, it is preferable to use a lithium manganese composite oxide having regions with different crystal structures, crystal orientations, or oxygen contents in the surface layer portion and the central portion. To obtain such a lithium manganese composite oxide, for example, it is preferable to set 1.6 ≤ a ≤ 1.848, 0.19 ≤ c / b ≤ 0.935, and 2.5 ≤ d ≤ 3. Furthermore, it is particularly preferable to use a lithium manganese composite oxide represented by the composition formula LiMnNiO3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. Moreover, when measuring the entire particles of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≤ (b + c) / d < 0.5 during discharge. In addition, in order to exhibit a high capacity, it is preferable to use a lithium manganese composite oxide having regions with different crystal structures, crystal orientations, or oxygen contents in the surface layer portion and the central portion. To obtain such a lithium manganese composite oxide, for example, it is preferable to set 1.6 ≤ a ≤ 1.848, 0.19 ≤ c / b ≤ 0.935, and 2.5 ≤ d ≤ 3. Furthermore, it is particularly preferable to use a lithium manganese composite oxide represented by the composition formula LiMnNiO3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. Moreover, when measuring the entire particles of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≤ (b + c) / d < 0.5 during discharge. In addition, in order to exhibit a high capacity, it is preferable to use a lithium manganese composite oxide having regions with different crystal structures, crystal orientations, or oxygen contents in the surface layer portion and the central portion. To obtain such a lithium manganese composite oxide, for example, it is preferable to set 1.6 ≤ a ≤ 1.848, 0.19 ≤ c / b ≤ 0.935, and 2.5 ≤ d ≤ 3. Furthermore, it is particularly preferable to use a lithium manganese composite oxide represented by the composition formula LiMnNiO3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. Moreover, when measuring the entire particles of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≤ (b + c) / d < 0.5 during discharge. In addition, in order to exhibit a high capacity, it is preferable to use a lithium manganese composite oxide having regions with different crystal structures, crystal orientations, or oxygen contents in the surface layer portion and the central portion. To obtain such a lithium manganese composite oxide, for example, it is preferable to set 1.6 ≤ a ≤ 1.848, 0.19 ≤ c / b ≤ 0.935, and 2.5 ≤ d ≤ 3. Furthermore, it is particularly preferable to use a lithium manganese composite oxide represented by the composition formula LiMnNiO3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. Moreover, when measuring the entire particles of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≤ (b + c) / d < 0.5 during discharge. In addition, in order to exhibit a high capacity, it is preferable to use a lithium manganese composite oxide having regions with different crystal structures, crystal orientations, or oxygen contents in the surface layer portion and the central portion. To obtain such a lithium manganese composite oxide, for example, it is preferable to set 1.6 ≤ a ≤ 1.848, 0.19 ≤ c / b ≤ 0.935, and 2.5 ≤ d ≤ 3. Furthermore, it is particularly preferable to use a lithium manganese composite oxide represented by the composition formula LiMnNiO3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. Moreover, when measuring the entire particles of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≤ (b + c) / d < 0.5 during discharge. In addition, in order to exhibit a high capacity, it is preferable to use a lithium manganese composite oxide having regions with different crystal structures, crystal orientations, or oxygen contents in the surface layer portion and the central portion. To obtain such a lithium manganese composite oxide, for example, it is preferable to set 1.6 ≤ a ≤ 1.848, 0.19 ≤ c / b ≤ 0.935, and 2.5 ≤ d ≤ 3. Furthermore, it is particularly preferable to use a lithium manganese composite oxide represented by the composition formula LiMnNiO3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. Moreover, when measuring the entire particles of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≤ (b + c) / d < 0.5 during discharge. In addition, in order to exhibit a high capacity, it is preferable to use a lithium manganese composite oxide having regions with different crystal structures, crystal orientations, or oxygen contents in the surface layer portion and the central portion. To obtain such a lithium manganese composite oxide, for example, it is preferable to set 1.6 ≤ a ≤ 1.848, 0.19 ≤ c / b ≤ 0.935, and 2.5 ≤ d ≤ 3. Furthermore, it is particularly preferable to use a lithium manganese composite oxide represented by the composition formula LiMnNiO3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. Furthermore, it is particularly preferable to use a lithium manganese composite oxide represented by the composition formula LiMnNiO3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. 1.68 Mn 0.8062 Ni 0.318 O3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. It is particularly preferable to use a lithium manganese composite oxide represented by the composition formula LiMnNiO3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. 1. 68 Mn 0.8062 Ni 0.318 O3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. The lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. The lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. The lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, although the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, it may deviate from this composition. 1.68 Mn 0.80 62 Ni 0.318 O3, but it may deviate from this composition.

[0070] The composition of metals, silicon, phosphorus, etc. in the entire particles of the lithium manganese composite oxide can be measured using, for example, ICP-MS (inductively coupled plasma mass spectrometer). Also, the lithium manganese composite oxide can be measured using, for example, ICP-MS (inductively coupled plasma mass spectrometer). The composition of metals, silicon, phosphorus, etc. in the entire particles of the lithium manganese composite oxide can be measured using, for example, ICP-MS (inductively coupled plasma mass spectrometer). Also, the lithium manganese composite oxide can be measured using, for example, ICP-MS (inductively coupled plasma mass spectrometer). The oxygen composition of the entire particles of the thium manganese composite oxide can be measured, for example, using EDX (Energy Dispersive X-ray Analysis). Also, by using it in combination with ICP-MS analysis and using valence evaluation of melting gas analysis and XAFS (X-ray Absorption Fine Structure) analysis, it can be obtained. Note that the lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molyb bdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, and phosphorus.

[0071] Note that as the carrier ion, instead of lithium, sodium, potassium, strontium ium, barium, beryllium, etc. may be used. For example, a sodium-containing layered oxide can be used .

[0072] Examples of materials having sodium include, for example, NaFeO2 and Na 2 / 3 [Fe 1 / 2 Mn1 / 2 O2, Na 2 / 3 [Ni 1 / 3 Mn 2 / 3 O2, Na2Fe2(SO4)3, N a3V2(PO4)3, Na2FePO4F, NaVPO4F, NaMPO4 (M is one or more of F e(II), Mn(II), Co(II), Ni(II)), Na2FePO4 F, Na4Co3(PO4)2P2O7, etc. Sodium-containing oxides can be used as the positive electrode active material .

[0073] Also, as the positive electrode active material, a lithium-containing metal sulfide can be used. For example, Li 2TiS3, Li3NbS4, etc. can be mentioned.

[0074] Up to now, the positive electrode active material particles 100 have been described as having crystal grains 101 and crystal grain boundaries 103. However, one embodiment of the present invention is not limited thereto. The particle of material 100 may have a region 107. The region 107 may be, for example, a grain 101. The region 107 can be provided so as to be in contact with at least a part of the graphene compound. or a decomposition product of lithium or the electrolyte. When the region 107 is a coating containing carbon, the positive electrode active material particles This can increase the conductivity between the positive electrode active material particles 100 and between the positive electrode active material particles 100 and the current collector. If the region 107 is a film containing lithium or a decomposition product of the electrolyte, the electrolyte and This can suppress excessive reaction and improve the cycle characteristics when used in a secondary battery.

[0075] If the particle diameter of the positive electrode active material particles 100 is too large, it becomes difficult for lithium to diffuse. If it is too thick, the bulk density of the electrode will decrease, and the reaction with the electrolyte will proceed excessively. Therefore, the particle size is preferably 1 μm or more and 100 μm or less, and more preferably 10 μm or more and 70 μm or less. Here, the particle size is, for example, the cumulative 50% on a volume basis. This refers to the value (D50).

[0076] [Method for producing positive electrode active material] A method for producing a positive electrode active material particle 100 having crystal grains 101 and crystal grain boundaries 103 is shown in FIG. The crystal grains 101 are made of a composite oxide containing lithium, a transition metal (M), and oxygen. The grain boundary 103 contains magnesium, fluorine, and oxygen.

[0077] First, prepare the starting materials (step S11). Specifically, weigh a lithium source, a transition metal (M ) source, a magnesium source, and a fluorine source respectively.

[0078] As the lithium source, for example, lithium carbonate, lithium fluoride, lithium hydroxide, lithium oxide, etc. can be used. can be used.

[0079] As the transition metal (M) source, for example, one or more of cobalt compounds, nickel compounds, manganese compounds, iron compounds, vanadium compounds, titanium compounds, molybdenum compounds, zinc compounds, indium compounds, gallium compounds, copper compounds, niobium compounds, etc. can be used.

[0080] As the cobalt compound, for example, one or more of cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide, cobalt carbonate, cobalt oxalate, cobalt sulfate, etc. can be used.

[0081] As the nickel compound, for example, one or more of nickel oxide, nickel hydroxide, nickel carbonate, nickel chloride, nickel bromide, nickel iodide, nickel sulfate, nickel nitrate, nickel formate, etc. can be used. can be used.

[0082] As the manganese compound, for example, one or more of manganese oxide, manganese hydroxide, manganese carbonate, manganese chloride, manganese iodide, manganese sulfate, manganese nitrate can be used.

[0083] As the iron compound, for example, one or more of iron fluoride, iron chloride, iron bromide, iron iodide, iron sulfate, iron phosphate, iron oxalate, iron acetate, etc. can be used. can be used.

[0084] As the vanadium compound, for example, vanadium oxide, vanadium hydroxide, vanadium chloride, One or more vanadium sulfates may be used.

[0085] Examples of titanium compounds include titanium fluoride, titanium chloride, titanium bromide, titanium iodide, and titanium oxide. One or more of titanium dioxide, titanium sulfide, titanium sulfate, etc. can be used.

[0086] Examples of molybdenum compounds include molybdenum oxide, diammonium molybdate, and phosphorus molybdenum. One or more of the above may be used, such as isopropyl alcohol.

[0087] Zinc compounds include, for example, zinc oxide, zinc hydroxide, zinc nitrate, zinc sulfate, zinc chloride, and zinc carbonate. One or more of these can be used, such as zinc.

[0088] Examples of indium compounds include indium chloride, indium sulfate, indium nitrate, and indium acid. Indium oxide, indium hydroxide, and the like can be used.

[0089] As the gallium compound, for example, one or more of gallium chloride, gallium fluoride, etc. may be used. can.

[0090] As the copper compound, for example, one or more of copper sulfate, copper chloride, copper nitrate, etc. can be used.

[0091] Examples of niobium compounds include niobium oxide, niobium chloride, niobium oxide sulfate, and niobium fluoride. One or more of the following can be used.

[0092] Examples of magnesium sources include magnesium oxide, magnesium fluoride, and magnesium hydroxide. One or more of sodium carbonate, magnesium carbonate, etc. can be used.

[0093] As the fluorine source, for example, one or more of lithium fluoride, magnesium fluoride, etc. may be used. This is possible. That is, lithium fluoride can be used as both a lithium source and a fluorine source. This is possible, and magnesium fluoride can be used as both a magnesium source and a fluorine source. This is possible.

[0094] In addition, when the crystal grains 101 contain a metal other than the transition metal (M), the metal source of the metal other than the transition metal is weighed. When the metal other than the transition metal has aluminum , for example, an aluminum compound can be used as the metal source. As the aluminum compound , one or more of aluminum oxide, aluminum hydroxide, aluminum carbonate, aluminum chloride, , aluminum iodide, aluminum sulfate, aluminum nitrate, etc. can be used. This is possible. This is possible.

[0095] The ratio of the number of atoms of the transition metal (M) and magnesium in the raw materials will be described. The ratio m of the number of atoms of magnesium Mg(r) in the raw materials to the number of atoms of the transition metal M(r) is 0.0050 or more and 0.050 or less, that is, in the case of the ratio of the number of atoms of the transition metal M(r): the number of atoms of magnesium Mg(r ) = 1.0:m, 0.0050 ≤ m ≤ 0.050 is preferable. Further, the ratio m of the number of atoms of magnesium to the number of atoms of the transition metal is 0.010 or in the vicinity thereof (1.0% or in the vicinity thereof) is preferable. By setting the ratio of the number of atoms as described above, a positive electrode active material having magnesium in the crystal grain boundary 103 can be efficiently produced. When using a plurality of types of transition metals as raw materials , the total number of atoms of the plurality of types of transition metals may be used for the number of atoms M(r) of the transition metal described above for calculation. This is possible. When using a plurality of types of transition metals as raw materials , it may be calculated by using the total number of atoms of the plurality of types of transition metal atoms for the number of atoms M(r) of the transition metal described above.

[0096] The vicinity means, for example, a value greater than 0.9 times and less than 1.1 times that value.

[0097] The ratio of the number of magnesium atoms to the number of fluorine atoms in the raw material is explained below. The ratio n of the number of fluorine atoms F(r) to the number Mg(r) is 1.50 or more and 4.0 or less. The number of magnesium atoms Mg(r): the number of fluorine atoms F(r) = 1.0: n, 1 It is preferable that n is 0.50≦n≦4.0. Furthermore, the ratio of the number of fluorine atoms to the number of magnesium atoms is 0.50≦n≦4.0. The ratio of the numbers, n, is 2.0 or close to 2.0, that is, the number of magnesium atoms, Mg(r): the number of fluorine atoms. It is more preferable that the number of atoms F(r) is 1.0:2.0 or close to that. By setting the ratio to 103, it is possible to efficiently segregate magnesium and fluorine at the grain boundary 103. can.

[0098] The atomic ratio of the raw material transition metal, magnesium, and fluorine can be expressed by the following formula 1. Here, m is the ratio of the number of magnesium atoms Mg(r) to the number of transition metal atoms M(r). As mentioned above, 0.0050≦m≦0.050 is preferable, and m=0.0 Preferably, n is the number of fluorine atoms relative to the number of magnesium atoms, Mg(r). As mentioned above, 1.50≦n≦4.0 is preferable, and more preferably, For this, n=2.0 or its vicinity is preferred.

[0099]

number

[0100] An example of the ratio of raw materials when LiCoO2 is produced as the positive electrode active material particles is shown below. The ratio m of the number of magnesium atoms to the number of cobalt atoms is 0.010. The ratio n of the number of fluorine atoms to the number of carbon atoms is set to 2.0. The atomic ratio of cobalt, magnesium, and fluorine can be Co:Mg:F = 1.0:0.010 :0.020.

[0101] Note that the atomic ratio of the aforementioned raw materials and the composition of the positive electrode active material particles 100 obtained by synthesis may not match.

[0102] Regarding the molar ratio of the lithium compound and the transition metal (M) compound in the raw materials, a value corresponding to the assumed crystal grain composition may be used. Also, for example, when the lithium composition of the obtained crystal grains is low relative to the molar ratio of the lithium compound in the raw materials, the molar ratio of the lithium compound in the raw materials may be increased.

[0103] Next, the weighed starting materials are mixed (step S12). For mixing, for example, a ball mill, a bead mill, etc. can be used.

[0104] Next, the material mixed in step S12 is subjected to a first heating (step S13). The first heating is preferably carried out at 800°C or higher and 1050°C or lower, more preferably at 900°C or higher and 1000°C or lower. The heating time is preferably 2 hours or more and 20 hours or less. The first heating is preferably carried out in an atmosphere containing oxygen. For example, it is preferably carried out in an atmosphere of dry air.

[0105] By the first heating in step S13, a composite oxide containing lithium and transition metal (M) in the crystal grains 101 can be synthesized. Also, by this first heating, a part of magnesium and fluorine contained in the starting materials segregates to the surface layer of the composite oxide containing lithium and transition metal (M). However, at this point, another part of magnesium and fluorine remains in the lithium and transition ​It is in a state of being dissolved in the composite oxide containing metal (M).

[0106] Next, the material heated in step S13 is cooled to room temperature (step S14). After cooling, When the synthesized material is subjected to a crushing treatment, it is possible to reduce the particle diameter of the positive electrode active material particles 100, which is preferable.

[0107] Next, the material cooled in step S14 is subjected to a second heating (step S15). The second heating is preferably performed with a holding time at a specified temperature of 100 hours or less, more preferably 1 hour or more and 70 hours or less, still more preferably 2 hours or more and 50 hours or less, and still more preferably 2 hours or more and 35 hours or less. The specified temperature is preferably 500°C or higher and 12 00°C or lower, more preferably 700°C or higher and 1000°C or lower, and still more preferably about 800°C. The second heating is preferably performed in an atmosphere containing oxygen. For example, it is preferably performed in an atmosphere of dry air.

[0108] By performing the second heating in step S15, it is possible to promote the segregation of magnesium and fluorine contained in the starting materials to the grain boundaries.

[0109] Finally, the material heated in S15 is cooled to room temperature and recovered (step S16), and the positive electrode active material particles 100 can be obtained.

[0110] As described above, by mixing a magnesium source and a fluorine source as starting materials, a positive electrode active material having magnesium oxide at the grain boundaries 103 can be efficiently produced.

[0111] Also, by mixing a magnesium source and a fluorine source as starting materials, the grain boundaries 10 Magnesium may tend to segregate at 3.

[0112] When oxygen that binds to magnesium is replaced by fluorine, magnesium may tend to move around the substituted fluorine.

[0113] Also, when magnesium fluoride is added to magnesium oxide, the melting point may decrease. When the melting point decreases, the movement of atoms becomes easier during heat treatment.

[0114] Also, fluorine has a higher electronegativity than oxygen. Therefore, even in a stable compound such as magnesium oxide, adding fluorine may cause a charge bias and weaken the bond between magnesium and oxygen.

[0115] For these reasons, by mixing a magnesium source and a fluorine source as starting materials, magnesium may tend to move, and magnesium may tend to segregate at the grain boundary 103.

[0116] By using the positive electrode active material particles 100 described in this embodiment, a secondary battery with less deterioration and high safety can be obtained. This embodiment can be used in appropriate combination with other embodiments.

[0117] (Embodiment 2) In this embodiment, examples of materials that can be used in the secondary battery having the positive electrode active material particles 100 described in the previous embodiment will be described. In this embodiment, a secondary battery in which a positive electrode, a negative electrode, and an electrolyte are wrapped in an exterior body will be described as an example.

[0118] [Positive Electrode] ​​​​​​​​​The positive electrode has a positive electrode active material layer and a positive electrode current collector.

[0119] <Positive electrode active material layer> The positive electrode active material layer has positive electrode active material particles. Further, the positive electrode active material layer may have a conductive assistant and a binder. It may have a binder.

[0120] As the positive electrode active material particles, the positive electrode active material particles 100 described in the previous embodiment can be used. By using the positive electrode active material particles 100 described in the previous embodiment, a secondary battery with less deterioration and high safety can be obtained. By using the positive electrode active material particles 100 described in the previous embodiment, a secondary battery with less deterioration and high safety can be obtained. It can be made into a secondary battery with less deterioration and high safety.

[0121] As the conductive assistant, a carbon material, a metal material, a conductive ceramic material, etc. can be used. Further, a fibrous material may be used as the conductive assistant. The content of the conductive assistant with respect to the total amount of the active material layer is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less. It can be made. Further, a fibrous material may be used as the conductive assistant. The content of the conductive assistant with respect to the total amount of the active material layer is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less. The content of the conductive assistant with respect to the total amount of the active material layer is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less. It is more preferable.

[0122] The conductive assistant can form an electrical conduction network in the electrode. By the conductive assistant, the electrical conduction path between the positive electrode active material particles can be maintained. By adding the conductive assistant to the active material layer, an active material layer having high electrical conductivity can be realized. By the conductive assistant, the electrical conduction path between the positive electrode active material particles can be maintained. By adding the conductive assistant to the active material layer, an active material layer having high electrical conductivity can be realized. By adding the conductive assistant to the active material layer, an active material layer having high electrical conductivity can be realized. It can be achieved.

[0123] As the conductive assistant, for example, natural graphite, artificial graphite such as mesocarbon microbeads, carbon fiber, etc. can be used. As the carbon fiber, for example, carbon fibers such as mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers can be used. Also, as the carbon fiber, carbon nanofibers, carbon nanotubes, etc. can be used. As the carbon fiber, for example, carbon fibers such as mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers can be used. As the carbon fiber, for example, carbon fibers such as mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers can be used. Also, as the carbon fiber, carbon nanofibers, carbon nanotubes, etc. can be used. The tube can be manufactured, for example, by a vapor growth method or the like. Also, as the conductive assistant, for example, carbon materials such as carbon black (such as acetylene black (AB)), graphite (graphite) particles , graphene, fullerene, etc. can be used. Also, for example, metal powders such as copper, nickel, aluminum, silver, gold, metal fibers, conductive ceramic materials, etc. can be used.

[0124] Also, a graphene compound may be used as the conductive assistant.

[0125] The graphene compound may have excellent electrical properties such as high conductivity, and excellent physical properties such as high flexibility and high mechanical strength. Also, the graphene compound has a planar shape. The graphene compound enables surface contact with low contact resistance. Also, it may have very high conductivity even when thin, and can efficiently form a conductive path in the active material layer with a small amount. Therefore, using the graphene compound as the conductive assistant is preferable because it can increase the contact area between the active material and the conductive assistant. Also it is preferable because it may be able to reduce the electrical resistance. Here, as the graphene compound, for example, graphene or multi-graphene or Reduced Graphene Oxide (hereinafter, RGO) is particularly preferably used. Here, RGO refers to a compound obtained by reducing, for example, graphene oxide (GO: Graphene Oxide). When using active material particles with a small particle size, for example, active material particles of 1 μm or less, the specific surface area of the active material particles is large, and more conductive paths connecting the active material particles are required. Therefore

[0126] ​​​The amount of the conductive assistant may increase, and the amount of the active material supported may relatively decrease. When the amount of the active material supported decreases, the capacity of the secondary battery decreases. In such a case, when a graphene compound is used as the conductive assistant as described above, even a small amount of the graphene compound can efficiently form a conductive path, so it is not necessary to reduce the amount of the active material supported, which is particularly preferable.

[0127] Hereinafter, as an example, a cross-sectional configuration example in the case where a graphene compound is used as the conductive assistant in the active material layer 200 will be described.

[0128] FIG. 4(A) shows a longitudinal sectional view of the active material layer 200. The active material layer 200 includes granular positive electrode active material particles 100, a graphene compound 201 as a conductive assistant, a binder (not shown), and . Here, for example, graphene or multi-graphene may be used as the graphene compound 201. Here, it is preferable that the graphene compound 201 has a sheet-like shape. Further, the graphene compound 201 may be a sheet formed by partial overlapping of a plurality of multi-graphenes and / or (and) a plurality of graphenes.

[0129] In the longitudinal section of the active material layer 200, as shown in FIG. 4(A), sheet-like graphene compounds 201 are dispersed substantially uniformly inside the active material layer 200. In FIG. 4(A), the graphene compound 201 is schematically represented by a thick line, but actually it is a thin film having a thickness of a single layer or multiple layers of carbon molecules. A plurality of graphene compounds 201 are formed so as to wrap, cover, or adhere onto the surfaces of a plurality of granular positive electrode active material particles 100, so they are in surface contact with each other.

[0130] ​​​​​​Here, when a plurality of graphene compounds are bonded to each other, a network-like graphene compound sheet (hereinafter referred to as a graphene compound net or a graphene net) can be formed. When the active material is coated with the graphene net, the graphene net can also function as a binder that binds the active materials together. Therefore, the amount of the binder can be reduced or it is not necessary to use it, so that the ratio of the active material in the electrode volume and the electrode weight can be improved. That is, the capacity of the power storage device can be increased.

[0131] Here, it is preferable to use graphene oxide as the graphene compound 201, mix it with the active material to form a layer that becomes the active material layer 200, and then reduce it. By using graphene oxide with extremely high dispersibility in a polar solvent for the formation of the graphene compound 201, the graphene compound 201 can be dispersed substantially uniformly inside the active material layer 200. After removing the solvent by volatilization from the dispersion medium containing uniformly dispersed graphene oxide and reducing the graphene oxide, the graphene compounds 201 remaining in the active material layer 200 partially overlap each other and are dispersed to the extent of surface contact with each other, so that a three-dimensional conductive path can be formed. Note that the reduction of graphene oxide may be performed, for example, by heat treatment or by using a reducing agent.

[0132] Therefore, unlike granular conductive aids such as acetylene black that make point contact with the active material, the graphene compound 201 enables surface contact with low contact resistance, so that the electrical conductivity between the granular positive electrode active material particles 100 and the graphene compound 201 is improved with a smaller amount than that of a normal conductive aid. Therefore, the ratio of the positive electrode active material particles 100 in the active material layer 200 can be increased. This allows the discharge capacity of the power storage device to be increased.

[0133] 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.

[0134] 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.

[0135] Alternatively, the binder may be polystyrene, polymethyl acrylate, or polymethyl methacrylate. Polymethylmethacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), poly Ethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, Polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, poly Ethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylo Nitrile (PAN), Ethylene Propylene Diene Polymer, Polyvinyl Acetate, Nitrocel It is preferable to use a material such as loin.

[0136] The binder may be used in combination with two or more of the above.

[0137] 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.

[0138] 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.

[0139] 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. is expected. Also, cellulose derivatives such as carboxymethyl cellulose, for example, have many materials having functional groups such as hydroxyl groups and carboxyl groups, and due to having functional groups it is expected that polymers interact with each other and exist widely covering the surface of the active material.

[0140] When a binder that covers the surface of the active material or is in contact with the surface forms a film, it is also expected to play a role as a passive film and suppress the decomposition of the electrolyte. Here, a passive film is a film having no electrical conductivity or a very low electrical conductivity. For example, when a passive film is formed on the surface of the active material, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. Also, the passive film suppresses the electrical conductivity and is more preferably capable of conducting lithium ions. and a film having extremely low electrical conductivity, or a film with extremely low electrical conductivity. For example, when a passive film is formed on the surface of the active material, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. Also, the passive film suppresses the electrical conductivity and is more preferably capable of conducting lithium ions. is more desirable.

[0141] <Positive electrode current collector> As the positive electrode current collector, metals such as stainless steel, gold, platinum, aluminum, titanium, and alloys thereof, etc., materials having high conductivity can be used. Also, the material used for the positive electrode current collector is preferably insoluble at the potential of the positive electrode. Also, an aluminum alloy added with elements for improving heat resistance such as silicon, titanium, neodymium, scandium, molybdenum, etc. can be used. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten cobalt, nickel, etc. The current collector can be appropriately used in shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector has a thickness of titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can be appropriately used in shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector has a thickness of sheet-like, net-like, punched metal-like, expanded metal-like, etc. can be appropriately used. The current collector has a thickness of ​​​​It is recommended to use a thickness of 5 μm or more and 30 μm or less.

[0142] [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.

[0143] <Negative electrode active material> As the negative electrode active material, for example, an alloy-based material or a carbon-based material can be used.

[0144] 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.

[0145] In this specification and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO refers to SiO xIt can also be expressed as follows. Here, x preferably has a value of 1 or in the vicinity thereof. For example, x is preferably 0.2 or more and 1.5 or less, more preferably 0.3 or more and 1.2 or less.

[0146] As the carbon-based material, graphite, graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, carbon black, etc. may be used. .

[0147] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. Here, spherical graphite having a spherical shape can be used as the artificial graphite. For example, MCMB may have a spherical shape, which is preferable. Also, MCMB can relatively easily reduce its surface area, which may be preferable. Examples of natural graphite include scaly graphite, spheroidized natural graphite, etc.

[0148] Graphite exhibits a potential as low as that of lithium metal (0.05 V or more and 0.3 V or less vs. Li / L i i + ) when lithium ions are inserted into the graphite (when forming a lithium-graphite intercalation compound). As a result, the lithium-ion secondary battery can exhibit a high operating voltage. Furthermore, graphite has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, [[ID=!40]]

[0149] Also, as the negative electrode active material, titanium dioxide (TiO2), lithium titanate (Li4T i5O 12 ), lithium-graphite intercalation compound (Li xC6), niobium pentoxide (Nb2O5) , oxides such as tungsten oxide (WO2) and molybdenum oxide (MoO2) can be used .

[0150] Also, as the negative electrode active material, Li3N-type structured Li Li 3-x M x N (M = Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 shows a large charge-discharge capacity (900 mAh / g, 1890 mAh / cm 3 ) and is preferable .

[0151] When using a lithium-transition metal complex nitride, since lithium ions are contained in the negative electrode active material, it can be preferably combined with materials such as V2O5 and Cr3O8 that do not contain lithium ions as the positive electrode active material. Even when using a material containing lithium ions for the positive electrode active material , by previously desorbing the lithium ions contained in the positive electrode active material, a lithium-transition metal complex nitride can be used as the negative electrode active material .

[0152] Also, a material that causes a conversion reaction can be used as the negative electrode active material. For example , transition metal oxides such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO) that do not form an alloy with lithium can be used as the negative electrode active material. Materials that cause a conversion reaction include, further, oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3 , sulfides such as CoS , NiS, and CuS, nitrides such as Zn3N2, Cu3N, and Ge3 0.89 N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3 . ​​

[0153] 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.

[0154] <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.

[0155] [Electrolyte] The electrolytic solution contains a solvent and an electrolyte. The solvent for the electrolytic solution is preferably an aprotic organic solvent. Preferably, for example, ethylene carbonate (EC), propylene carbonate (PC), Ethylene carbonate, chloroethylene carbonate, vinylene carbonate, gamma-butyro 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 can be used in combinations and ratios of:

[0156] Also, a phosphate ester compound having fluorine, which is flame-retardant as a solvent for the electrolyte, or By using a fluorine-containing carbonate ester compound, it is possible to prevent explosions and fires in the storage device. is possible. Examples of phosphate ester compounds having fluorine include, for example, tris(2,2, 2-trifluoroethyl) phosphate (TFEP) and the like. Examples of carbonate ester compounds having fluorine include, for example, bis(2,2,2-trifluoroethyl) carbonate (TFEC) and the like.

[0157] In addition, by using a polymer material that gels as a solvent for the electrolytic solution, the safety against liquid leakage and the like is enhanced. Also, the secondary battery can be made thinner and lighter. Representative examples of the gelled polymer materials include silicone gel, acrylic gel, acrylonitrile gel, poly ethylene oxide-based gel, polypropylene oxide-based gel, fluorine-based polymer gel and the like.

[0158] In addition, by using one or more ionic liquids (room temperature molten salts) that are flame retardant and hardly volatile as a solvent for the electrolytic solution, even if the internal temperature rises due to an internal short circuit or overcharging of the power storage device , rupture or ignition of the power storage device can be prevented. An ionic liquid consists of a cation and an anion and contains an organic cation and an anion. Examples of the organic cation used in the electrolytic solution include quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations such as aliphatic onium cations, and aromatic cations such as imidazolium cations and pyridinium cations . Examples of the anion used in the electrolytic solution include monovalent amide-based anions, monovalent methide-based anions, fluorosulfonic acid anions, perfluoroalkyl sulfonate anions, tetrafluoroborate anions, perfluoroalkyl borate anions, hexafluorophosphate anions, or perfluoroalkyl phosphates anions, hexafluorophosphate anions, or perfluoroalkyl phosphates anions, hexafluorophosphate anions, or perfluoroalkyl phosphates Examples include ate anions and the like.

[0159] In addition, examples of the electrolyte dissolved in the above solvent include LiPF6, LiClO4, L iAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO 4, Li2B 10 Cl 10 、Li2B 12 Cl 12 、LiCF3SO3, LiC4F9S O3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2 )2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. of lithium salts, and one kind, or any combination and ratio of two or more of these can be used.

[0160] The electrolytic solution used in the power storage device is preferably a highly purified electrolytic solution with a low content of granular dust and elements other than the constituent elements of the electrolytic solution (hereinafter also simply referred to as " impurities"). Specifically, the weight ratio of impurities to the electrolytic solution is preferably 1% or less, more preferably 0.1% or less, and even more preferably 0.01% or less.

[0161] In addition, vinylene carbonate, propane sultone (PS), tert-butyl benzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxa late) borate (LiBOB), and dinitrile compounds such as succinonitrile and adiponitrile, triisopropoxyboroxine (TiPBx), sulfolane, hydrofluoro roether (HFE), vinyl acetate (VA), etc. may be added. The concentration of the added material may be, for example, 0.1 weight% or more and 5 weight% or less based on the entire solvent. ​

[0162] Alternatively, a polymer gel electrolyte obtained by swelling a polymer with an electrolytic solution may be used.

[0163] By using a polymer gel electrolyte, the safety against liquid leakage and the like is enhanced. Also, the secondary battery can be made thinner and lighter.

[0164] As the polymer to be gelled, silicone gel, acrylic gel, acrylonitrile gel , polyethylene oxide-based gel, polypropylene oxide-based gel, fluorine-based polymer gel, etc. can be used. As the polymer, for example, a polymer having a polyalkylene oxide structure such as polyethylene oxide (PE O), PVDF, and polyacry lonitrile, etc., and copolymers containing them can be used. For example, PVDF -HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. Further, the formed polymer may have a porous shape.

[0165] Alternatively, instead of the electrolytic solution, a solid electrolyte having an inorganic material such as a sulfide-based or oxide-based material, or a solid electrolyte having a polymer material such as polyethylene oxide (PEO)-based can be used. When a solid electrolyte is used, it is not necessary to provide a separator or a spacer. Also, since the entire battery can be solidified, the risk of liquid leakage is eliminated and the safety is dramatically improved.

[0166] [Separator] Also, the secondary battery preferably has a separator. Examples of the separator include fibers having cellulose such as paper , non-woven fabric, glass fiber, ceramics, or na Iron (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, synthetic fibers formed using polyolefin, polyurethane, etc. can be used. The separator is preferably processed into a bag shape and arranged to wrap either the positive electrode or the negative electrode.

[0167] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic-based material, a fluorine-based material, a polyamide-based material, or a mixture thereof. As the ceramic-based material, for example, aluminum oxide particles, silicon oxide particles, etc. can be used. As the fluorine-based material, for example, PVDF, polytetrafluoroethylene, etc. can be used. As the polyamide-based material, for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used.

[0168] Coating with a ceramic-based material improves oxidation resistance, thus suppressing deterioration of the separator during high-voltage charge and discharge and improving the reliability of the secondary battery. Coating with a fluorine-based material makes it easier for the separator and the electrode to adhere, improving the output characteristics. Coating with a polyamide-based material, especially aramid, improves heat resistance, thus improving the safety of the secondary battery.

[0169] For example, a mixed material of aluminum oxide and aramid can be coated on both sides of a polypropylene film. Alternatively, a mixed material of aluminum oxide and aramid can be coated on the surface of the polypropylene film that contacts the positive electrode, and a fluorine-based material can be coated on the surface that contacts the negative electrode. ​​​​​

[0170] When using a separator with a multilayer structure, even if the overall thickness of the separator is thin, the safety of the secondary battery can be maintained, so that the capacity per unit volume of the secondary battery can be increased.

[0171] (Embodiment 3) In this embodiment, an example of the shape of the secondary battery having the positive electrode active material particles 100 described in the previous embodiment will be described. The materials used in the secondary battery described in this embodiment can refer to the description of the previous embodiment.

[0172] [Coin-shaped secondary battery] First, an example of a coin-shaped secondary battery will be described. FIG. 5(A) is an external view of a coin-shaped (single-layer flat type) secondary battery, and FIG. 5(B) is a cross-sectional view thereof.

[0173] The coin-shaped 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, which are insulated and sealed with a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact therewith. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact therewith.

[0174] Note that for the positive electrode 304 and the negative electrode 307 used in the coin-shaped secondary battery 300, the active material layers may be formed only on one side.

[0175] The positive electrode can 301 and the negative electrode can 302 are made of metals such as nickel, aluminum, titanium, or alloys thereof, or alloys of these with other metals (for example, stainless steel etc.) can be used. Also, in order to prevent corrosion by the electrolytic solution, it is preferable to coat with nickel, aluminum, etc. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 30 7 respectively.

[0176] These negative electrode 307, positive electrode 304, and separator 310 are impregnated with the electrolyte, and as shown in FIG. 5(B), with the positive electrode can 301 facing downwards, the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are laminated in this order, and the positive electrode can 301 and the negative electrode can 302 are pressure-bonded via a gasket 303 to manufacture a coin-shaped secondary battery 300. By using the positive electrode active material particles 100 described in the previous embodiment for the positive electrode 304, a coin-type secondary battery 300 with less deterioration and high safety can be obtained.

[0177]

[0178] [Cylindrical Secondary Battery] An example of a cylindrical secondary battery will be described with reference to FIGS. 6(A) to 6(D). The cylindrical secondary battery 600 shown in FIG. 6(A) has a positive electrode cap (battery lid) 601 on the upper surface and a battery can (outer can) 602 on the side surface and the bottom surface as shown in the cross-sectional schematic diagram of FIG. 6(B). The positive electrode cap and the battery can (outer can) 602 are insulated by a gasket (insulating packing) 610.

[0179] Inside the hollow cylindrical battery can 602, a battery element is provided in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 6 05 interposed therebetween. Although not shown, the battery element is wound around a center pin. One end of the battery can 602 is closed and the other end is open. 。The battery can 602 can be made of metals such as nickel, aluminum, and titanium that are corrosion-resistant to the electrolyte , or alloys of these metals or alloys of these and other metals (e.g., stainless steel, etc.). Also, in order to prevent corrosion by the electrolyte, it is preferable to coat with nickel, aluminum, etc. Inside the battery can 602, the battery element wound with the positive electrode, negative electrode, and separator is sandwiched by a pair of opposing insulating plates 608 and 609. Also, the inside of the battery can 602 where the battery element is provided is filled with a non-aqueous electrolyte (not shown). As the non-aqueous electrolyte, the same one as that used in a coin-type secondary battery can be used.

[0180] Since the positive electrode and negative electrode used in a cylindrical secondary battery are wound, it is preferable to form the active material on both sides of the current collector. A positive electrode terminal (positive current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative current collector lead) 607 is connected to the negative electrode 606. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of a metal material such as aluminum. The positive electrode terminal 603 is resistance-welded to the safety valve mechanism 612, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602, respectively. The safety valve mechanism 612 is electrically connected to the positive electrode cap 601 via a PTC element (Positive Temperature Coefficient) 611. The safety valve mechanism 612 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the internal pressure of the battery rises above a predetermined threshold value. Also, the PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises, and it limits the current amount due to the increase in resistance to prevent abnormal heat generation. For the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics, etc. can be used. ​

[0181] 6C, a plurality of secondary batteries 600 are mounted on the conductive plate 613 and the conductive plate 614. A module 615 may be formed by sandwiching the secondary batteries 600 between them. They may be connected in series, or may be connected in parallel and then in series. By configuring a module 615 having a plurality of secondary batteries 600, It is possible to extract a large amount of power.

[0182] 6(D) is a top view of the module 615. The conductive plate 613 is dotted for clarity. As shown in FIG. 6(D), the module 615 is a module that electrically connects a plurality of secondary batteries 600. The conductive plate 613 may be placed on the conductive wire 616. In addition, even if a temperature control device 617 is provided between the plurality of secondary batteries 600, When the secondary battery 600 is overheated, the temperature control device 617 cools it down. If 600 is too cold, it can be heated by the temperature control device 617. This makes the performance of the module 615 less susceptible to the outside temperature.

[0183] By using the positive electrode active material particles 100 described in the previous embodiment for the positive electrode 604, deterioration is reduced. Therefore, the cylindrical secondary battery 600 can be made small and highly safe.

[0184] [Structure example of power storage device] Another structural example of the power storage device will be described with reference to FIGS.

[0185] 7(A) and 7(B) are diagrams showing the appearance of the power storage device. 900 and a secondary battery 913. A label 910 is attached to the secondary battery 913. It exists. Further, as shown in FIG. 7(B), the power storage device includes a terminal 951, a terminal 952, an antenna 914, and an antenna 915.

[0186] The circuit board 900 includes a terminal 911 and a circuit 912. The terminal 911 is connected to the terminal 951 , the terminal 952, the antenna 914, the antenna 915, and the circuit 912. Note that a plurality of terminals 911 may be provided, and each of the plurality of terminals 911 may be used as a control signal input terminal, a power supply terminal , etc.

[0187] The circuit 912 may be provided on the back surface of the circuit board 900. Note that the antenna 914 and the antenna 915 are not limited to a coil shape, and may be, for example, linear or plate-shaped. Also, a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, a dielectric antenna, etc. may be used. Alternatively, the antenna 914 or the antenna 915 may be a flat plate-shaped conductor. This flat plate-shaped conductor can function as one of the conductors for electric field coupling . That is, the antenna 914 or the antenna 915 may be made to function as one of the two conductors of the capacitor. Thereby, power can be exchanged not only by electromagnetic fields and magnetic fields but also by electric fields.

[0188] The line width of the antenna 914 is preferably larger than the line width of the antenna 915. Thereby , the amount of power received by the antenna 914 can be increased.

[0189] The power storage device has a layer 916 between the antenna 914 and the antenna 915 and the secondary battery 913. The layer 916 has, for example, a function of shielding the electromagnetic field by the secondary battery 913. Layer 9 As 16, for example, a magnetic material can be used.

[0190] Note that the structure of the power storage device is not limited to that shown in FIG. 7.

[0191] For example, as shown in FIGS. 8(A-1) and 8(A-2), among the secondary batteries 913 shown in FIGS. 7(A) and 7(B), antennas may be provided on each of a pair of opposing surfaces. FIG. 8(A-1) is an external view of one side of the above pair of surfaces, and FIG. 8(A-2) is an external view of the other side of the above pair of surfaces. Note that for the same parts as the power storage device shown in FIGS. 7(A) and 7(B), the description of the power storage device shown in FIGS. 7(A) and 7(B) can be appropriately incorporated.

[0192] As shown in FIG. 8(A-1), an antenna 914 is provided with a layer 916 sandwiched between one of a pair of surfaces of the secondary battery 913, and as shown in FIG. 8(A-2), an antenna 915 is provided with a layer 917 sandwiched between the other of a pair of surfaces of the secondary battery 913. The layer 917 has a function of shielding an electromagnetic field caused by the secondary battery 913, for example. As the layer 917, for example, a magnetic material can be used. As shown in FIG. 8(A-2), an antenna 915 is provided with a layer 917 sandwiched between the other of a pair of surfaces of the secondary battery 913. The layer 917 has a function of shielding an electromagnetic field caused by the secondary battery 913, for example. As the layer 917, for example, a magnetic material can be used. On the other side of the pair of surfaces of the secondary battery 913, an antenna 915 is provided with a layer 917 sandwiched therebetween. The layer 917 has a function of shielding an electromagnetic field caused by the secondary battery 913, for example. As the layer 917, for example, a magnetic material can be used. On the other side of the pair of surfaces of the secondary battery 913, an antenna 915 is provided with a layer 917 sandwiched therebetween. The layer 917 has a function of shielding an electromagnetic field caused by the secondary battery 913, for example. As the layer 917, for example, a magnetic material can be used. can be.

[0193] By adopting the above structure, the sizes of both the antenna 914 and the antenna 915 can be increased. can be made larger.

[0194] Alternatively, as shown in FIGS. 8(B-1) and 8(B-2), among the secondary batteries 913 shown in FIGS. 7(A) and 7(B), different antennas may be provided on each of a pair of opposing surfaces. FIG. 8(B-1) is an external view of one side of the above pair of surfaces, and FIG. 8(B-2) is an external view of the other side of the above pair of surfaces. Note that for the same parts as the power storage device shown in FIGS. 7(A) and 7(B), For details, the description of the power storage device illustrated in FIGS. 7A and 7B can be used as appropriate.

[0195] As shown in FIG. 8(B-1), a layer 916 is sandwiched between one of the two surfaces of a secondary battery 913. 8B-2, a secondary battery 91 An antenna 918 is provided on the other of the pair of surfaces of the substrate 3, sandwiching a layer 917 therebetween. For example, the antenna 918 has a function of performing data communication with an external device. For example, antennas having shapes applicable to the antennas 914 and 915 can be applied. As a communication method between the power storage device and other devices via antenna 918, NFC is available. It is possible to apply a response method that can be used between the power storage device and other devices, such as Cut.

[0196] Alternatively, as shown in FIG. 9A, the secondary battery 913 shown in FIGS. 7A and 7B may be A display device 920 may be provided. The display device 920 is electrically connected to the terminal 911 via the terminal 919. It is not necessary to provide the label 910 in the area where the display device 920 is provided. Note that the same parts as those of the power storage device shown in FIGS. 7(A) and 7(B) are shown in FIG. The description of the power storage device in FIG. 7B can be used as appropriate.

[0197] 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.

[0198] Alternatively, as shown in FIG. 9(B), a sensor 921 may be provided in the secondary battery 913 shown in FIGS. 7(A) and 7(B). The sensor 921 is electrically connected to the terminal 911 via the terminal 922. For the same parts as those of the power storage device shown in FIGS. 7(A) and 7(B), the description of the power storage device shown in FIGS. 7(A) and 7(B) can be appropriately incorporated. The sensor 921 may be provided in the secondary battery 913 shown in FIGS. 7(A) and 7(B). The sensor 921 is electrically connected to the terminal 911 via the terminal 922. For the same parts as those of the power storage device shown in FIGS. 7(A) and 7(B), the description of the power storage device shown in FIGS. 7(A) and 7(B) can be appropriately incorporated. For the same parts as those of the power storage device shown in FIGS. 7(A) and 7(B), the description of the power storage device shown in FIGS. 7(A) and 7(B) can be appropriately incorporated. (A) and 7(B) can be appropriately incorporated.

[0199] As the sensor 921, for example, it may have a function capable of measuring displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays. By providing the sensor 921, for example, data (such as temperature) indicating the environment where the power storage device is placed can be detected and stored in the memory in the circuit 912. As the sensor 921, for example, it may have a function capable of measuring displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays. By providing the sensor 921, for example, data (such as temperature) indicating the environment where the power storage device is placed can be detected and stored in the memory in the circuit 912. As the sensor 921, for example, it may have a function capable of measuring displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays. By providing the sensor 921, for example, data (such as temperature) indicating the environment where the power storage device is placed can be detected and stored in the memory in the circuit 912. By providing the sensor 921, for example, data (such as temperature) indicating the environment where the power storage device is placed can be detected and stored in the memory in the circuit 912. (such as temperature) can be detected and stored in the memory in the circuit 912.

[0200] Furthermore, a structural example of the secondary battery 913 will be described with reference to FIGS. 10 and 11.

[0201] The secondary battery 913 shown in FIG. 10(A) has a wound body 950 in which a terminal 951 and a terminal 952 are provided inside a housing 930. The wound body 950 is impregnated with an electrolytic solution inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like. In FIG. 10(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used. The wound body 950 is impregnated with an electrolytic solution inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like. In FIG. 10(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered by the housing 93, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used. The terminal 952 is in contact with the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like. In FIG. 10(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used. In FIG. 10(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used. In FIG. 10(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used. In FIG. 10(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used. As the housing 930, a metal material (such as aluminum) or a resin material can be used.

[0202] Note that, as shown in FIG. 10(B), the housing 930 shown in FIG. 10(A) may be formed of a plurality of materials. For example, the secondary battery 913 shown in FIG. 10(B) has a housing 930a and a housing 9 30b bonded together, and a winding body 9 50 is provided in a region surrounded by the housing 930a and the housing 930b.

[0203] As the housing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by the housing 930a is small, antennas such as an antenna 914 and an antenna 915 may be provided inside the housing 930a. As the housing 930b for example, a metal material can be used.

[0204] Furthermore, the structure of the winding body 950 is shown in FIG. 11. The winding body 950 has a negative electrode 931, a positive electrode 932, and a separator 933. The winding body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 overlap and are laminated with the separator 933 interposed therebetween, and the laminated sheet is wound. Note that the lamination of the negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated in multiple layers.

[0205] The negative electrode 931 is connected to the terminal 911 shown in FIG. 7 via one of the terminals 951 and 952. The positive electrode 932 is connected to the terminal 911 shown in FIG. 7 via the other of the terminals 951 and 952.

[0206] By using the positive electrode active material particles 100 described in the previous embodiment for the positive electrode 932, a secondary battery 913 with less deterioration and high safety can be obtained.

[0207] [Laminated secondary battery] Next, an example of a laminated secondary battery will be described with reference to FIGS. 12 to 17. The laminated secondary battery, if configured to be flexible, can be mounted on an electronic device having at least a part of the flexible portion, and the secondary battery can also be bent in accordance with the deformation of the electronic device.

[0208] The laminated secondary battery 980 will be described with reference to FIG. 12. The laminated secondary battery 980 has a wound body 993 shown in FIG. 12(A). The wound body 993 has a negative electrode 994 , a positive electrode 995, and a separator 996. The wound body 993 is similar to the wound body 950 described in FIG. 11, in which the negative electrode 994 and the positive electrode 995 overlap with each other with the separator 996 interposed therebetween, and the laminated sheet is wound.

[0209] Note that the number of laminations of the laminate composed of the negative electrode 994, the positive electrode 995, and the separator 996 may be appropriately designed according to the required capacity and the volume of the element. The negative electrode 994 is connected to a negative electrode current collector (not shown) through one of a lead electrode 997 and a lead electrode 998, and the positive electrode 995 is connected to a positive electrode current collector (not shown) through the other of the lead electrode 997 and the lead electrode 998.

[0210] As shown in FIG. 12(B), the wound body 993 described above is housed in a space formed by thermocompression- bonding or the like a film 981 serving as an exterior body and a film 982 having a concave portion, whereby the secondary battery 980 shown in FIG. 12(C) can be manufactured. The wound body 993 has a lead electrode 997 and a lead electrode 998, and the inside of the space surrounded by the film 981 and the film 982 having a concave portion is impregnated with an electrolytic solution.

[0211] The film 981 and the film 982 having a concave portion can be made of a metal material such as aluminum or a resin material. If a resin material is used as the material of the film 981 and the film 982 having a concave portion, when a force is applied from the outside, the film 981 and the film 982 having a concave portion can be deformed, and a flexible secondary battery can be manufactured.

[0212] In addition, FIGS. 12(B) and 12(C) show an example in which two films are used, but a space may be formed by bending one film, and the above-described winding body 993 may be housed in the space.

[0213] By using the positive electrode active material particles 100 described in the previous embodiment for the positive electrode 995, a secondary battery 980 with less deterioration and high safety can be obtained.

[0214] In addition, in FIG. 12, an example of the secondary battery 9 80 having a winding body in a space formed by a film serving as an exterior body has been described. However, for example, as shown in FIG. 13, a secondary battery having a plurality of strip-shaped positive electrodes, separators, and negative electrodes in a space formed by a film serving as an exterior body may also be used.

[0215] The laminated secondary battery 500 shown in FIG. 13(A) includes a positive electrode 503 having a positive electrode current collector 501 and a positive electrode active material layer 502, a negative electrode 506 having a negative electrode current collector 504 and a negative electrode active material layer 505, a separator 507, an electrolytic solution 508, and an exterior body 509. A separator 507 is installed between the positive electrode 503 and the negative electrode 506 provided in the exterior body 509, and ​​​​​​​It exists. Also, the interior of the exterior body 509 is filled with the electrolytic solution 508. The electrolytic solution 508 can use the electrolytic solution shown in Embodiment 2. It can use the electrolytic solution shown in Embodiment 2.

[0216] In the laminated secondary battery 500 shown in Fig. 13(A), the positive electrode current collector 501 and the negative electrode current collector 504 also serve as terminals for obtaining electrical contact with the outside. Therefore, a part of the positive electrode current collector 501 and the negative electrode current collector 504 may be arranged to be exposed to the outside from the exterior body 509. Also, without exposing the positive electrode current collector 501 and the negative electrode current collector 504 to the outside, the lead electrode may be ultrasonically bonded to the lead electrode and the positive electrode current collector 501 or the negative electrode current collector 504 so that the lead electrode is exposed to the outside. In the laminated secondary battery 500, on the film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. for the exterior body 509, a metal thin film with excellent flexibility such as aluminum, stainless steel, copper, nickel, etc. is provided, and further on the metal thin film, an insulating synthetic resin film such as a polyamide-based resin or a polyester-based resin is provided as the outer surface of the exterior body. A three-layer laminated film can be used.

[0217] In the laminated secondary battery 500, an example of the cross-sectional structure is shown in Fig. 13(B). In Fig. 13( A), for simplicity, an example composed of two current collectors is shown, but actually, it is composed of a plurality of electrode layers. In Fig. 13(B), as an example, the number of electrode layers is 16. Even when the number of electrode layers is 16, the secondary battery 500 has flexibility. In Fig. 13(B), the negative electrode current collector 504 has 8 layers, and In Fig. 13(B), as an example, the number of electrode layers is 16. Even when the number of electrode layers is 16, the secondary battery 500 has flexibility. In Fig. 13(B), the negative electrode current collector 504 has 8 layers, and In Fig. 13(B), as an example, the number of electrode layers is 16. Even when the number of electrode layers is 16, the secondary battery 500 has flexibility. In Fig. 13(B), the negative electrode current collector 504 has 8 layers, and

[0218] Also, an example of the cross-sectional structure of the laminated secondary battery 500 is shown in Fig. 13(B). In Fig. 13( A), for simplicity, an example composed of two current collectors is shown, but actually, it is composed of a plurality of electrode layers. It is composed of a plurality of electrode layers.

[0219] In Fig. 13(B), as an example, the number of electrode layers is 16. Even when the number of electrode layers is 16, the secondary battery 500 has flexibility. Even when the number of electrode layers is 16, the secondary battery 500 has flexibility. In Fig. 13(B), the negative electrode current collector 504 has 8 layers, and The positive electrode current collector 501 has a structure of a total of 16 layers in 8 layers. Note that FIG. 13(B) shows the cross-section of the extraction part of the negative electrode, and the 8-layer negative electrode current collector 504 is ultrasonically bonded. Of course, the number of electrode layers is not limited to 16, and may be more or less. When the number of electrode layers is large, a secondary battery having a larger capacity can be obtained. Also, when the number of electrode layers is small, a thin and highly flexible secondary battery can be obtained.

[0220] Here, an example of the external view of the laminate type secondary battery 500 is shown in FIGS. 14 and 15. FIGS. 1 4 and 15 have a positive electrode 503, a negative electrode 506, a separator 507, an exterior body 509, a positive electrode lead electrode 510 and a negative electrode lead electrode 511.

[0221] FIG. 16(A) shows the external views of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a 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. Also, the positive electrode 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as a tab region). The negative electrode 506 has a negative electrode current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504 . Also, 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 and negative electrodes are not limited to the examples shown in FIG. 16(A) .

[0222] [Manufacturing method of laminate type secondary battery] Here, an example of the manufacturing method of the laminate type secondary battery whose external view is shown in FIG. 14 will be described with reference to FIGS. 16 (B) and 16(C).

[0223] First, the negative electrode 506, the separator 507, and the positive electrode 503 are laminated. As shown laminated in FIG. 16(B) The resulting negative electrode 506, separator 507, and positive electrode 503 are shown. Here, an example of using five sets of negative electrodes and four sets of positive electrodes is shown. Next, the tabs of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For the joining, for example, ultrasonic welding or the like can be used. Similarly, the tabs of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode. Next, the tabs of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For the joining, for example, ultrasonic welding or the like can be used. Similarly, the tabs of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0224] Next, the negative electrode 506, separator 507, and positive electrode 503 are arranged on the exterior body 509.

[0225] Next, as shown in FIG. 16(C), the exterior body 509 is bent at the portion indicated by the broken line. Then, the outer peripheral portion of the exterior body 509 is joined. For the joining, for example, thermocompression bonding or the like can be used. At this time, a region that is not joined (hereinafter referred to as an inlet) is provided in a part (or one side) of the exterior body 509 so that the electrolytic solution 508 can be put in later. Next, as shown in FIG. 16(C), the exterior body 509 is bent at the portion indicated by the broken line. Then, the outer peripheral portion of the exterior body 509 is joined. For the joining, for example, thermocompression bonding or the like can be used. At this time, a region that is not joined (hereinafter referred to as an inlet) is provided in a part (or one side) of the exterior body 509 so that the electrolytic solution 508 can be put in later. At this time, a region that is not joined (hereinafter referred to as an inlet) is provided in a part (or one side) of the exterior body 509 so that the electrolytic solution 508 can be put in later.

[0226] Next, the electrolytic solution 508 is introduced into the interior of the exterior body 509 through the inlet provided in the exterior body 509. The introduction of the electrolytic solution 508 is preferably performed under a reduced pressure atmosphere or an inert gas atmosphere. And finally, the inlet is joined. In this way, a secondary battery 500, which is a laminated secondary battery, can be manufactured. Next, the electrolytic solution 508 is introduced into the interior of the exterior body 509 through the inlet provided in the exterior body 509. The introduction of the electrolytic solution 508 is preferably performed under a reduced pressure atmosphere or an inert gas atmosphere. And finally, the inlet is joined. In this way, a secondary battery 500, which is a laminated secondary battery, can be manufactured. And finally, the inlet is joined. In this way, a secondary battery 500, which is a laminated secondary battery, can be manufactured.

[0227] By using the positive electrode active material particles 100 described in the previous embodiment for the positive electrode 503, a secondary battery 500 with less deterioration and high safety can be obtained.

[0228] [Bendable Secondary Battery] Next, an example of a bendable secondary battery will be described with reference to FIGS. 17 and 18. ​​​​

[0229] Fig. 17(A) shows a schematic top view of the bendable battery 250. Figs. 17(B1), 17(B2) and 17(C) are schematic cross-sectional views taken along the cut lines C1-C2, cut lines C3-C4, and cut line A1-A2 in Fig. 17(A), respectively. The battery 250 has an outer casing 2 51 and a positive electrode 211a and a negative electrode 211b housed inside the outer casing 251. A lead 212a electrically connected to the positive electrode 211a and a lead 212b electrically connected to the negative electrode 211b extend outside the outer casing 251. Also, in the region surrounded by the outer casing 251, in addition to the positive electrode 211a and the negative electrode 211b, an electrolytic solution (not shown) is encapsulated.

[0230] The positive electrode 211a and the negative electrode 211b of the battery 250 will be described with reference to Fig. 18. Fig. 18(A) is a perspective view illustrating the lamination order of the positive electrode 211a, the negative electrode 211b, and the separator 214. Fig. 18(B) is a perspective view showing the leads 2 12a and 212b in addition to the positive electrode 211a and the negative electrode 211b. As shown in Fig. 18(A), the battery 250 has a plurality of strip-shaped positive electrodes 211a, a plurality of strip-shaped

[0231] negative electrodes 211b, and a plurality of separators 214. The positive electrode 211a and the negative electrode 211 b each have a protruding tab portion and a portion other than the tab. A positive electrode active material layer is formed on the portion other than the tab on one surface of the positive electrode 211a, and a negative electrode active material layer is formed on the portion other than the tab on one surface of the negative electrode 211b.

[0232] The surfaces of the positive electrode 211a where the positive electrode active material layer is not formed, and the negative electrode active ​The positive electrode 211a and the negative electrode 211b are laminated such that the surfaces without the formation of the quality layer are in contact with each other. It is laminated.

[0233] Also, a separator 214 is provided between the surface of the positive electrode 211a on which the positive electrode active material layer is formed and the surface of the negative electrode 211b on which the negative electrode active material layer is formed. In FIG. 18, the separator 214 is shown by a dotted line for easy viewing. It is provided. The separator 214 is shown by a dotted line in FIG. 18 for easy viewing. It is shown by a dotted line.

[0234] Also, as shown in FIG. 18(B), the plurality of positive electrodes 211a and the lead 212a are electrically connected at the joint 215a. Also, the plurality of negative electrodes 211b and the lead 212b are electrically connected at the joint 215b. They are electrically connected at the joint 215a. Also, the plurality of negative electrodes 211b and the lead 212b are electrically connected at the joint 215b. They are electrically connected.

[0235] Next, the exterior body 251 will be described with reference to FIGS. 17(B1), 17(B2), 17(C), and 17(D). It will be described.

[0236] The exterior body 251 has a film-like shape and is bent in two so as to sandwich the positive electrode 211a and the negative electrode 211b. The exterior body 251 has a bent portion 261, a pair of seal portions 262, and a seal portion 263. The pair of seal portions 262 are provided sandwiching the positive electrode 211a and the negative electrode 211b and can also be called side seals. Also, the seal portion 263 has a portion overlapping the lead 212a and the lead 212b and can also be called a top seal. It is bent in two so as to sandwich them. It has a bent portion 261, a pair of seal portions 262, and a seal portion 263. The pair of seal portions 262 are provided sandwiching the positive electrode 211a and the negative electrode 211b and can also be called side seals. Also, the seal portion 263 has a portion overlapping the lead 212a and the lead 212b and can also be called a top seal. It can be called.

[0237] The exterior body 251 preferably has a wavy shape in which ridge lines 271 and valley lines 272 are alternately arranged in the portion overlapping the positive electrode 211a and the negative electrode 211b. Also, the seal portions 262 and 263 of the exterior body 251 are preferably flat. It preferably has a wavy shape in which ridge lines 271 and valley lines 272 are alternately arranged. Also, the seal portions 262 and 263 of the exterior body 251 are preferably flat. They are preferably flat.

[0238] FIG. 17(B1) is a cross-section taken along a portion overlapping with the ridge line 271, and FIG. 17(B2) is a cross-section taken along a portion overlapping with the valley line 272. FIGS. 17(B1) and 17(B2) both correspond to a cross-section in the width direction of the battery 250, the positive electrode 211a, and the negative electrode 211b.

[0239] Here, the distance between the end portion of the negative electrode 211b in the width direction, that is, the end portion of the negative electrode 211b and the seal portion 262 is defined as the distance La. When the battery 250 is deformed, such as being bent, the positive electrode 211a and the negative electrode 211b are deformed so as to shift from each other in the length direction as described later. At that time, if the distance La is too short, the exterior body 251 and the positive electrode 211a and the negative electrode 211b will strongly rub against each other, and the exterior body 251 may be damaged. In particular, when the metal film of the exterior body 251 is exposed , there is a risk that the metal film will be corroded by the electrolytic solution. 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 battery 250 will increase. Moreover, the thicker the total thickness of the stacked positive electrode 211a and negative electrode 211b, the more preferably the distance La between the negative electrode 211 b and the seal portion 262 is increased.

[0240] More specifically, when the total thickness of the stacked positive electrode 211a and negative electrode 211b is defined as the thickness t

[0241] , the distance La is preferably 0.8 times or more and 3.0 times or less, preferably 0.9 times or more and 2. 5 times or less, more preferably 1.0 times or more and 2.0 times or less of the thickness t. By setting the distance La within this range, a compact and highly reliable battery against bending can be realized.

[0242] ​Also, when the distance between the pair of seal portions 262 is defined as distance Lb, distance Lb is made sufficiently larger than the widths of the positive electrode 211a and the negative electrode 211b (here, the width Wb of the negative electrode 211b). This is preferable. Thereby, when the battery 250 is repeatedly deformed such as being bent, even if the positive electrode 211a and the negative electrode 211b come into contact with the exterior body 251, a part of the positive electrode 211a and the negative electrode 2 11b can be displaced in the width direction, so that it is possible to effectively prevent the positive electrode 211a and the negative electrode 211b from rubbing against the exterior body 251.

[0243] 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 or more and 5.0 times or less, more preferably 2.0 times or more and 4.0 times or less the thickness t of the positive electrode 211a and the negative electrode 211b. That is, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following formula 2.

[0244] In other words, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following formula 2.

[0245]

Equation

[0246] Here, a is 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, more preferably 1.0 or more and 2.0 or less.

[0247] Also, FIG. 17(C) is a cross section including the lead 212a and corresponds to the cross section in the longitudinal direction of the battery 250, the positive electrode 211a, and the negative electrode 211b. As shown in FIG. 17(C), in the bent portion 2 61, it is preferable to have a space 273 between the longitudinal end portions of the positive electrode 211a and the negative electrode 211b and the exterior body 251. ​​​​

[0248] FIG. 17(D) shows a schematic cross-sectional view when the battery 250 is bent. FIG. 17(D) corresponds to the cross-section at the cutting line B1 - B2 in FIG. 17(A).

[0249] When the battery 250 is bent, a part of the exterior body 251 located on the outer side of the bend extends, and another part located on the inner side deforms so as to contract. More specifically, the part located on the outer side of the exterior body 251 deforms such that the amplitude of the wave is small and the period of the wave is large. On the other hand, the part located on the inner side of the exterior body 251 deforms such that the amplitude of the wave is large and the period of the wave is small. Thus, when the exterior body 251 deforms, the stress applied to the exterior body 251 due to bending is relaxed, so that the material itself constituting the exterior body 251 does not need to expand and contract. As a result, the exterior body 251 can be bent with a small force without being damaged.

[0250] Also, as shown in FIG. 17(D), when the battery 250 is bent, the positive electrode 211a and the negative electrode 211b are displaced relative to each other. At this time, since one end on the seal part 263 side of the plurality of stacked positive electrodes 211a and negative electrodes 211b is fixed by the fixing member 217, they are displaced such that the amount of displacement increases as they approach the bending part 261. Thereby, the stress applied to the positive electrode 211a and the negative electrode 211b is relaxed, and the positive electrode 211a and the negative electrode 211b themselves do not need to expand and contract. As a result, the battery 250 can be bent without the positive electrode 211a and the negative electrode 211b being damaged.

[0251] Also, there is a space 273 between the positive electrode 211a and the negative electrode 211b and the exterior body 251. ​​​​​​​​​​​​​As a result, when bent, the positive electrode 211a and the negative electrode 211b located on the inner side can shift relative to each other without contacting the exterior body 25. 1.

[0252] The battery 250 illustrated in FIGS. 17 and 18 is a battery in which damage to the exterior body, damage to the positive electrode 211a and the negative electrode 211b, etc. are less likely to occur even when repeatedly bent and stretched, and the battery characteristics are also less likely to deteriorate. By using the positive electrode active material particles 100 described in the previous embodiment for the positive electrode 211a of the battery 250, a secondary battery with even less deterioration and high safety can be obtained. (Embodiment 4) In this embodiment, an example of mounting a secondary battery, which is one aspect of the present invention, on an electronic device will be described.

[0253] (Embodiment 4) In this embodiment, an example of mounting a secondary battery that can be bent, which was partially described in Embodiment 3, on an electronic device will be described.

[0254] First, an example of mounting a bendable secondary battery on an electronic device, which was partially described in Embodiment 3, is shown in FIG. 19. Examples of electronic devices to which a bendable secondary battery is applied include, for example, a television set (also referred to as a television or a television receiver), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also referred to as mobile phones or mobile phone devices), portable game machines, portable information terminals, audio playback devices, and large game machines such as pachinko machines.

[0255] In addition, it is also possible to incorporate a secondary battery having a flexible shape along the inner wall or outer wall of a house or building, or along the curved surface of the interior or exterior of an automobile.

[0256] FIG. 19(A) shows an example of a mobile phone. The mobile phone 7400 includes a housing 7401. In addition to the display unit 7402 incorporated therein, there are operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, etc. The mobile phone 7400 has a secondary battery 7407.

[0257] Figure 19(B) shows the state in which the mobile phone 7400 is bent. When the mobile phone 7400 is deformed by an external force and bent as a whole, the secondary battery 7407 provided inside it is also bent. The state of the bent secondary battery 7407 at that time is shown in Figure 19(C). The secondary battery 7407 is a thin secondary battery. The secondary battery 7407 is fixed in the bent state. The secondary battery 7407 has lead electrodes electrically connected to a current collector.

[0258] Figure 19(D) shows an example of a bangle-type display device. The portable display device 7100 includes a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. Also, Figure 19(E) shows the state of the bent secondary battery 7104. When the secondary battery 7104 is bent and worn on the user's arm, the housing deforms and the curvature of part or all of the secondary battery 7104 changes. The degree of bending at any point on the curve is represented by the value of the radius of the corresponding circle, which is called the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, when the radius of curvature is in the range of 40 mm or more and 150 mm or less, part or all of the main surface of the housing or the secondary battery 7104 changes. If the radius of curvature of the main surface of the secondary battery 7104 is in the range of 40 mm or more and 150 mm or less, high reliability can be maintained.

[0259] Figure 19(F) shows an example of a wristwatch-type portable information terminal. The portable information terminal 7200​​​​​​​​​​​​​ , the housing 7201, the display unit 7202, the band 7203, the buckle 7204, the operation button 72 05, input / output terminals 7206, etc. are provided.

[0260] The portable information terminal 7200 can execute various applications such as mobile phones, e-mails, text viewing and creation, music playback, Internet communication, computer games, etc. It can be done.

[0261] The display unit 7202 is provided with a curved display surface, and can perform display along the curved display surface. In addition, the display unit 7202 is provided with a touch sensor and can be operated by touching the screen with a finger or a stylus. For example, by touching the icon 72 07 displayed on the display unit 7202, an application can be launched.

[0262] In addition to time setting, the operation button 7205 can perform various functions such as turning on and off the power, turning on and off wireless communication, executing and canceling the silent mode, and executing and canceling the power saving mode. For example, the functions of the operation button 7205 can also be freely set by the operating system incorporated in the portable information terminal 7200. It can also be set freely.

[0263] In addition, the portable information terminal 7200 can perform communication-standard short-range wireless communication. For example, by communicating with a wireless headset that can perform wireless communication, it is possible to make a hands-free call. It can also be done.

[0264] In addition, the portable information terminal 7200 is provided with input / output terminals 7206, and can directly exchange data with other information terminals via a connector. In addition, charging can be performed via the input / output terminals 7206. This can also be done. Note that the charging operation can be performed by wireless power supply without going through the input / output terminal 7206. This is also acceptable.

[0265] The display unit 7202 of the portable information terminal 7200 has a secondary battery according to one aspect of the present invention. For example, the secondary battery 7104 shown in Fig. 19(E) can be incorporated in a curved state inside the housing 7201 or in a state where it can be curved inside the band 7203. It can be incorporated in a curved state inside the housing 7201 or in a state where it can be curved inside the band 7203.

[0266] The portable information terminal 7200 preferably has a sensor. Examples of the sensor include human body sensors such as fingerprint sensors, pulse sensors, and body temperature sensors, as well as touch sensors, pressure sensors, acceleration sensors, etc. It is preferable that these sensors are mounted. Examples of the sensor include human body sensors such as fingerprint sensors, pulse sensors, and body temperature sensors, as well as touch sensors, pressure sensors, acceleration sensors, etc. It is preferable that these sensors are mounted. It is preferable that these sensors are mounted.

[0267] Fig. 19(G) shows an example of a bracelet-type display device. The display device 7300 has a display unit 7304 and has a secondary battery according to one aspect of the present invention. Also, the display device 7300 can be provided with a touch sensor on the display unit 7304 and can also function as a portable information terminal. The display unit 7304 has a curved display surface, and display can be performed along the curved display surface. Also, the display device 7300 can change the display situation by means of communication-standardized short-range wireless communication or the like. It can also be provided with a touch sensor on the display unit 7304 and can also function as a portable information terminal. This is also acceptable.

[0268] The display unit 7304 has a curved display surface, and display can be performed along the curved display surface. Also, the display device 7300 can change the display situation by means of communication-standardized short-range wireless communication or the like. It can change the display situation.

[0269] In addition, the display device 7300 is provided with input / output terminals and can directly exchange data with other information terminals via a connector. Also, charging can be performed via the input / output terminals. Also, charging can be performed via the input / output terminals. Note that the charging operation can be performed by wireless power supply without going through the input / output terminals. This is also acceptable.

[0270] Next, FIGS. 20(A) and 20(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIGS. 20(A) and 20(B) includes a housing 9630a, a housing 9630b, a movable part 9640 connecting the housing 9630a and the housing 9630b, a display part 9 631, a display mode switching switch 9626, a power switch 9627, a power saving mode switching switch 9625, a fastener 9629, and an operation switch 9628. The display part 9 631 can have a wider display part by using a flexible panel, thus serving as a tablet terminal. FIG. 20(A) shows the tablet terminal 9600 in an open state, and FIG. 20(B) shows the tablet terminal 9600 in a closed state.

[0271] Also, the tablet terminal 9600 has a power storage body 9635 inside the housing 9630a and the housing 9630b. The power storage body 9635 is provided across the movable part 9640 and between the housing 9630a and the housing 9630b.

[0272] Part of the display part 9631 can be a touch panel area, and data can be input by touching the displayed operation keys. Also, by touching the position where the keyboard display switching button of the touch panel is displayed with a finger or a stylus, etc., the keyboard buttons can be displayed on the display part 9631.

[0273] In addition, the display mode switching switch 9626 can select switching of the display orientation such as vertical display or horizontal display, switching between black-and-white display and color display, etc. The power saving mode switching switch 9625 is detected by a light sensor built into the tablet terminal 9600 during use The brightness of the display can be optimized according to the amount of external light. The tablet-type terminal may incorporate not only a light sensor but also other detection devices such as sensors for detecting inclination, such as a gyro and an acceleration sensor.

[0274] FIG. 20(B) shows a closed state, and the tablet-type terminal includes a housing 9630, a solar cell 96 33, and a charge / discharge control circuit 9634 including a DCDC converter 9636. Also, as the power storage body 9635, a secondary battery according to one aspect of the present invention is used.

[0275] Note that since the tablet-type terminal 9600 is foldable in two, the housing 9630a and the housing 9630b can be folded so as to overlap each other when not in use. By folding, the display unit 9631 can be protected, thereby enhancing the durability of the tablet-type terminal 9600. In addition, the power storage body 9635 using the secondary battery according to one aspect of the present invention has a high capacity and good cycle characteristics, and thus a tablet-type terminal that can be used for a long time over a long period can be provided.

[0276] In addition, the tablet-type terminal shown in FIGS. 20(A) and 20(B) can also have functions such as displaying various information (such as still images, moving images, and text images), a calendar, a date, or a time on the display unit, operating or editing the information displayed on the display unit by touch input , a touch input function, a function of controlling processing by various software (programs), etc.

[0277] Power can be supplied to the touch panel, the display unit, or the video signal processing unit, etc. by the solar cell 9633 mounted on the surface of the tablet-type terminal. Note that the solar cell 9633 is provided on the housing ​​It can be provided on one or both sides of the body 9630, and can be configured to efficiently charge the power storage body 9635. It can be configured.

[0278] Also, regarding the configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 20(B), a block diagram is shown and explained in FIG. 20( C). FIG. 20(C) shows a solar cell 9633, a power storage body 963 5, a DCDC converter 9636, a converter 9637, switches SW1 to SW3, and a display unit 9631. The power storage body 9635, the DCDC converter 9636, the converter 9637, and the switches SW1 to SW3 correspond to the locations of the charge / discharge control circuit 96 34 shown in FIG. 20(B).

[0279] First, an example of the operation when power is generated by the solar cell 9633 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 9636 to become a voltage for charging the power storage body 9635. When the power from the solar cell 9633 is used for the operation of the display unit 9631, the switch SW1 is turned on, and the converter 9637 steps up or down the voltage to the required voltage for the display unit 9631. When the display on the display unit 9631 is not performed, the switch SW1 is turned off, the switch SW2 is turned on, and the power storage body 9635 can be charged. For the solar cell 9633, although it is shown as an example of the power generation means, it is not particularly limited, and the power storage body 9635 can be charged by other power generation means such as a piezoelectric element (piezoelectric element) or a thermoelectric conversion element (Peltier element). For example, a contactless power transmission module that wirelessly (non-contact) transmits and receives power for charging, or a configuration that combines other charging means can be used. It can be configured.

[0280] Regarding the solar cell 9633, although it is shown as an example of the power generation means, it is not particularly limited, and the power storage body 9635 can be charged by other power generation means such as a piezoelectric element (piezoelectric element) or a thermoelectric conversion element (Peltier element). For example, a contactless power transmission module that wirelessly (non-contact) transmits and receives power for charging, or a configuration that combines other charging means can be used. It can be configured to charge the power storage body 9635 by other power generation means such as a piezoelectric element (piezoelectric element) or a thermoelectric conversion element (Peltier element). For example, a contactless power transmission module that wirelessly (non-contact) transmits and receives power for charging, or a configuration that combines other charging means can be used. It can be configured to charge the power storage body 9635 by other power generation means such as a piezoelectric element (piezoelectric element) or a thermoelectric conversion element (Peltier element). For example, a contactless power transmission module that wirelessly (non-contact) transmits and receives power for charging, or a configuration that combines other charging means can be used. It can be configured to charge by wirelessly (non-contact) transmitting and receiving power, or a configuration that combines other charging means. It may be.

[0281] Fig. 21 shows an example of another electronic device. In Fig. 21, a display device 8000 is an example of an electronic device using a secondary battery 8004 according to one aspect of the present invention. Specifically, the display device 800 0 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, a speaker unit 8003, a secondary battery 8004, etc. The secondary battery 8004 according to one aspect of the present invention is provided inside the housing 8001. The display device 8000 can be supplied with power from a commercial power source, or can use the power stored in the secondary battery 8004. Therefore , even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8004 according to one aspect of the present invention as an uninterruptible power supply, the display device 8000 can be used . The display unit 8002 can be a light-emitting device having a light-emitting element such as a liquid crystal display device or an organic EL element in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Devi ce), a PDP (Plasma Display Panel), a FED (Field

[0282] Emission Display), etc., and a semiconductor display device can be used. In addition, the display device includes all display devices for information display, such as for personal computers and advertising displays, in addition to those for receiving TV broadcasts. ce), PDP (Plasma Display Panel), FED (Field Emission Display), etc.

[0283] Note that the display device includes all display devices for information display, such as for personal computers and advertising displays, in addition to those for receiving TV broadcasts.

[0284] In Fig. 21, a stationary lighting device 8100 is an example of an electronic device using a secondary battery 81 03 according to one aspect of the present invention. Specifically, the lighting device 8100 includes a housing 8101 and light It has a power source 8102, a secondary battery 8103, etc. In FIG. 21, an example is illustrated where the secondary battery 8103 is provided inside a ceiling 8104 on which a housing 81 01 and a light source 8102 are installed. However, the secondary battery 8103 may be provided inside the housing 8101. The lighting device 8100 can receive power supply from a commercial power source, or can also use the power stored in the secondary battery 8103. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8103 according to one aspect of the present invention as an uninterruptible power supply, the lighting device 8100 can be used. In FIG. 21, an example of a fixed-type lighting device 8100 provided on the ceiling 8104 is illustrated. However, the secondary battery according to one aspect of the present invention can be used not only for the ceiling 8104 but also for, for example, fixed-type lighting devices provided on side walls 8105, floors 8 106, windows 8107, etc., or can also be used for table-top lighting devices and the like. Furthermore, as the light source 8102, an artificial light source that artificially obtains light using power can be used. Specifically, incandescent bulbs, discharge lamps such as fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements can be cited as an example of the above artificial light source.

[0285] In FIG. 21, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is an example of an electronic device using the secondary battery 8203 according to one aspect of the present invention. Specifically, the indoor unit 8200 has a housing 8201, an air outlet 8202, a secondary battery 8203, etc. In FIG. 21 an example is illustrated where the secondary battery 8203 is provided in the indoor unit 8200. However, the secondary battery 8203 may be provided inside the housing 8201. The lighting device 8100 can receive power supply from a commercial power source, or can also use the power stored in the secondary battery 8103. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8103 according to one aspect of the present invention as an uninterruptible power supply,

[0286] the lighting device 8100 can be used. In FIG. 21, an example of a fixed-type lighting device 8100 provided on the ceiling 8104 is illustrated. However, the secondary battery according to one aspect of the present invention can be used not only for the ceiling 8104 but also for, for example, fixed-type lighting devices provided on side walls 8105, floors 8 106, windows 8107, etc., or can also be used for table-top lighting devices and the like.

[0287] In FIG. 21, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is an example of an electronic device using the secondary battery 8203 according to one aspect of the present invention. Specifically, the indoor unit 8200 has a housing 8201, an air outlet 8202, a secondary battery 8203, etc. In FIG. 21 an example is illustrated where the secondary battery 8203 is provided in the indoor unit 8200. However, the secondary battery 8203 may be provided inside the housing 8201. In FIG. 21, an example is illustrated where the secondary battery 8203 is provided in the indoor unit 8200. However, the secondary The battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source, or can also use the power stored in the secondary battery 8203. In particular, when the secondary battery 82 03 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to an aspect of the present invention as an uninterruptible power supply, the air conditioner can be used.

[0288] Note that in FIG. 21, a separate type air conditioner composed of an indoor unit and an outdoor unit is illustrated, but the secondary battery according to an aspect of the present invention can also be used for an integrated type air conditioner having the functions of the indoor unit and the outdoor unit in one housing.

[0289] In FIG. 21, the electric refrigerator 8300 is an example of an electronic device using the secondary battery 8304 according to an aspect of the present invention. Specifically, the electric refrigerator 8300 has a housing 8301, a door 8302 for the storage room, a door 8303 for the freezer room, a secondary battery 8304, etc. In FIG. 21, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator 8300 can receive power supply from a commercial power source, or can also use the power stored in the secondary battery 8304. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8304 according to an aspect of the present invention as an uninterruptible power supply, the electric refrigerator 8300 can be used.

[0290] 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.

[0291] In addition to the electronic devices described above, the secondary battery according to one embodiment of the present invention can be mounted in various electronic devices. According to one embodiment of the present invention, a secondary battery with little deterioration and high safety can be provided. Therefore, when the secondary battery according to one embodiment of the present invention is installed in the electronic device described in this embodiment, This allows the electronic device to have a longer life and higher safety. The present embodiment can be implemented in appropriate combination with other embodiments.

[0292] (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.

[0293] 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). .

[0294] 22A and 22B illustrate an example of a vehicle using a secondary battery according to one embodiment of the present invention. The motor vehicle 8400 shown is an electric vehicle that uses an electric motor as a power source for driving. Alternatively, it is a hybrid vehicle capable of appropriately selecting and using an electric motor and an engine as power sources for driving. By using a secondary battery, which is one aspect of the present invention, a vehicle with a long cruising range can be realized. Also, the motor vehicle 8400 has a secondary battery. The secondary battery can not only drive the electric motor 8406 but also supply power to lighting devices such as the headlight 8401 and the rear light (not shown).

[0295] Furthermore, the secondary battery can supply power to display devices such as the speedometer and tachometer that the motor vehicle 8400 has. Also, the secondary battery can supply power to semiconductor devices such as the navigation system that the motor vehicle 8400 has.

[0296] The motor vehicle 8500 shown in Fig. 22(B) can be charged by receiving power supply from external charging facilities by a plug-in method, a non-contact power supply method, etc. to the secondary battery 8024 that the motor vehicle 8500 has. Fig. 22(B) shows a state in which charging is being performed from the ground-mounted charging device 8021 to the secondary battery 8024 mounted on the motor vehicle 8500 via the cable 8022. When charging, standards such as CHAdeMO (registered trademark) and Combo can be appropriately adopted for the charging method, connector, etc. The charging device 8021 may be a charging station provided in a commercial facility or may also be a household power source. For example, by plug-in technology, the secondary battery 8024 mounted on the motor vehicle 8500 can be charged by external power supply. Charging can be performed by converting AC power into DC power via a conversion device such as an AC-DC converter. ​

[0297] Also, although not shown, a power receiving device can be mounted on a vehicle, and power can be supplied non - contact from a power transmitting device on the ground for charging. In the case of this non - contact power supply method, by incorporating the power transmitting device into a road or an outer wall, charging can be performed not only while the vehicle is stopped but also while it is running. Also, using this non - contact power supply method, power can be transmitted and received between vehicles. Furthermore, a solar cell can be provided on the exterior part of the vehicle to charge the secondary battery when the vehicle is stopped or running. For such non - contact power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0298] Also, Fig. 22(C) is an example of a two - wheel vehicle using a secondary battery according to an aspect of the present invention. The scooter 8600 shown in Fig. 22 (C) includes a secondary battery 8602, a side mirror 8601, and a direction indicator light 8603. The secondary battery 8602 can supply electricity to the direction indicator light 8603.

[0299] Also, the scooter 8600 shown in Fig. 22(C) can store the secondary battery 860 2 in the under - seat storage 8604. Even if the under - seat storage 8604 is small, the secondary battery 8602 can be stored in the under - seat storage 8604.

[0300] According to an aspect of the present invention, a secondary battery with less deterioration and high safety can be obtained. Therefore, by mounting it on a vehicle, a decrease in cruising range, acceleration performance, etc. can be suppressed. Also, a vehicle with high safety can be obtained. Also, the secondary battery mounted on the vehicle can be used as a power supply source other than the vehicle. In this case, for example, using a commercial power supply at the peak of power demand can be avoided. Using a commercial power supply at the peak of power demand ​​ If this can be avoided, it will contribute to energy conservation and reduction of carbon dioxide emissions. In addition, cobalt is used as a secondary battery because it has little deterioration and can be used for a long period of time. This will reduce the amount of rare metals used, including

[0301] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0302] In this example, a positive electrode active material having magnesium, fluorine, and oxygen at and near the grain boundaries The active material was prepared and subjected to TEM observation and STEM-EDX analysis to identify the crystal grains and crystallites in the active material. The concentration distribution at the grain boundaries was confirmed. The sample was one of Sample A, which is one embodiment of the present invention. As material A, nickel-containing magnesium, fluorine, and oxygen at and near the grain boundaries was used. Lithium manganese-cobalt oxide was prepared. Lithium nickel-manganese-cobalt oxide The composition is LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2 is assumed. LiNi 1 / 3 Mn 1 / 3Co 1 / 3 O2 has a layered rock salt type crystal structure.

[0303] <Preparation of Sample A> The preparation of sample A will be described.

[0304] As shown in step S11 of the flow in Figure 3, starting materials were prepared. Lithium oxide (Li2CO3), nickel oxide (NiO) as a nickel source, and manganese source manganese dioxide (MnO2) as a cobalt source, tricobalt tetroxide (Co3O4) as a cobalt source, Magnesium oxide (MgO) was used as the magnesium source, and lithium fluoride (L iF) was weighed. Specifically, 3.1398 g (42.49 mmol) of Li2CO3 , 2.1159 g (28.33 mmol) of NiO, 2.4627 g (28. 33 mmol) of MnO2, 2.2033 g (9.15 mmol) of Co3O4, 0.03 43 g (0.85 mmol) of MgO, and 0.0441 g (1.70 mmol) of LiF were weighed. This is an amount such that the ratio m of the number of magnesium atoms to the total number of atoms of nickel, manganese, and cobalt is 0.010 (1.0%). Also, it is an amount such that the ratio n of the number of fluorine atoms to the number of magnesium atoms is 2.0. Note that high-purity chemical research institute-made Li2CO3 (catalog number: LIH06XB) was used. High-purity chemical research institute-made NiO ( catalog number: NIO04PB) was used. High-purity chemical research institute-made MnO2 (catalog number: MNO03PB) was used. High-purity chemical research institute-made Co3O4 (catalog number: COO09PB) was used. High-purity chemical research institute-made MgO (catalog number: MGO12 PB) was used. High-purity chemical research institute-made LiF (catalog number: LIH10XB) was used. COO09PB) was used. High-purity chemical research institute-made MgO (catalog number: MGO12 PB) was used. High-purity chemical research institute-made LiF (catalog number: LIH10XB) was used.

[0305] Next, as shown in step S12, the respective starting materials weighed in step S11 were mixed. A wet ball mill was used for mixing. Specifically, balls with a diameter of 3 mm and acetone as the solvent were used, and pulverization and mixing were performed at a rotation speed of 300 rpm for 2 hours.

[0306] Next, as shown in step S13, the material mixed in step S12 was subjected to a first heating. The first heating was performed using a muffle furnace, and the temperature was raised from room temperature to 1000 °C at a heating rate of 200 °C / hr. The temperature was raised to °C and heated at °C for 10 hours. The heating was carried out in a dry air atmosphere, and the flow rate of the dry atmosphere was set to 10 L / min.

[0307] By the first heating in step S13, lithium nickel manganese cobalt oxide can be synthesized. At this point, a part of magnesium and fluorine is considered to be in a state of being dissolved in the grain boundaries and grains.

[0308] Next, as shown in step S14, the material heated in step S13 was cooled to room temperature to obtain Composite 1. After cooling, the obtained Composite 1 was crushed to reduce the particle size of Composite 1. A 53-μm mesh was used for the crushing process.

[0309] Next, as shown in step S15, the second heating was performed on Composite 1 obtained in step S14. The second heating was carried out using a muffle furnace, with a heating rate of 200 °C / hr from room temperature to °C and then heated at °C for 2 hours. The heating was carried out in a dry air atmosphere, and the flow rate of the dry atmosphere was set to 10 L / min.

[0310] By performing the second heating in step S15, it is possible to promote the segregation of magnesium and fluorine contained in the starting materials to the grain boundaries of lithium nickel manganese cobalt oxide.

[0311] Next, as shown in step S16, the Composite 1 heated in step S15 was cooled to room temperature and collected to obtain Sample A.

[0312] <TEM Observation, STEM Observation, EDX Measurement> Next, Sample A was prepared by focused ion beam (FIB). ​​​​Thinned, and the cross-section of Sample A was observed by TEM and STEM. Also, the cross-section of Sample A was subjected to compositional analysis by ED X measurement. For TEM, STEM observation, and EDX measurement, J EM-ARM200F manufactured by JEOL Ltd. was used, with an acceleration voltage of 200 kV and a beam diameter of approximately 0.1 nmφ .

[0313] In EDX measurement, the elemental analyzer used was the energy-dispersive X-ray analyzer JED -2300T manufactured by JEOL Ltd., and a Si drift detector was used for X-ray detection. In the EDX surface analysis , the detection limit was approximately 1 atomic%. Note that EDX measurement can detect elements from boron (B) with atomic number 5 to uranium (U) with atomic number 92 .

[0314] The TEM image (bright-field image) of the cross-section of Sample A is shown in Fig. 23(A). The magnification of Fig. 23(A) is 10 times 10,000. In Fig. 23(A), the region where the density (brightness) of the TEM image is substantially uniform has a substantially constant crystal orientation and is considered a single crystal. Also, the region where the density (brightness) of the TEM image changes is considered a grain boundary. A schematic diagram corresponding to Fig. 23(A) is shown in Fig. 23(B). As shown in Fig. 23(A) and Fig. 23(B), it was confirmed that the positive electrode active material particles have a plurality of crystallites 1101 and grain boundaries 1103 between the crystallites .

[0315] The STEM image (bright-field image) of the cross-section of Sample A is shown in Fig. 24(A), and the HAADF-STE M image of the same location is shown in Fig. 24(B). The magnification of Fig. 24(A) and Fig. 24(B) is 8 million times . In Fig. 24(A) and Fig. 24(B), a lattice image was confirmed in the region of the crystallites

[0316] Next, the EDX spectrum of the cross-section of Sample A will be described. In EDX measurement, electrons are applied to the measurement point Line irradiation was performed, and the energy and the number of generated characteristic X-rays were measured, and an EDX spectrum was obtained. The HAADF-STEM image of the cross section of sample A and the EDX measurement locations are shown in Fig. 25. The EDX measurement locations are five locations from point 1 to point 5. Point 2 to point 4 are at the grain boundaries and in the vicinity thereof, and point 1 and point 5 are at positions distant from the grain boundaries, that is, inside the grains. The EDX spectrum and the quantitative results of point 1 are shown in Fig. 26, point 2 in Fig. 27, point 3 in Fig. 28, point 4 in Fig. 29, and poi nt 5 in Fig. 30. In Figs. 26 to 30, the horizontal axis indicates the characteristic X-ray energy (Ene rgy) [keV], and the vertical axis indicates the characteristic X-ray intensity [Counts]. At point 1 to point 5, peaks derived from the electron transitions to the K-shells of carbon (C), oxygen (O), fluorine (F), magnesium (Mg), silicon (Si), phosphorus (P), sulfur (S), calcium (Ca),

[0317] manganese (Mn), cobalt (Co), and nickel (Ni) were observed. The obtained spectra were separated into respective elements, and the atomic concentrations were obtained. Next, the surface analysis of EDX will be described. When measuring while scanning the inside of a region and evaluating the inside of the region two-dimensionally, it may be called surface analysis. In this example, the EDX measurement was performed at 256 points in the vertical direction × 256 points in the horizontal direction within the region. The HAADF-STEM image of the region where the surface analysis of EDX of sample A was performed is shown in Fig. 31(A). The surface analysis of EDX was performed in a region including grains and grain boundaries. The region shown in Fig. 31(A) was used.

[0318] The surface analysis of EDX of sample A was performed in a region including grains and grain boundaries. The HAADF-STEM image of the region where the surface analysis of EDX of sample A was performed is shown in Fig. 31(A). The surface analysis of EDX was performed in a region including grains and grain boundaries. The region shown in Fig. 31(A) was used.

[0319] The HAADF-STEM image of the region where the surface analysis of EDX of sample A was performed is shown in Fig. 31(A). The surface analysis of EDX was performed in a region including grains and grain boundaries. In the surface analysis of EDX, the mapping image of carbon is shown in Fig. 31(B), oxygen in Fig. 31(C), fluorine in Fig. 31(D), magnesium in Fig. 31(E), silicon in Fig. 31(F), phosphorus in Fig. 32(A), sulfur in Fig. 32(B), calcium in Fig. 32(C), manganese in Fig. 32(D ), cobalt in Fig. 32(E), and nickel in Fig. 32(F).

[0320] Figs. 31(B) to 31(F) and Figs. 32(A) to 32(F) show the mapping of characteristic X-ray intensity by EDX measurement, where the measurement points with low characteristic X-ray intensity are shown in light color (white), and the characteristic X-ray intensity is shown in darker color (black) for higher measurement points. That is, the light color (white) measurement points indicate low atomic concentration, and the darker color (black) measurement points indicate high atomic concentration. Note that Figs. 3 1(B) to 31(F) and Figs. 32(A) to 32(F) change the scale of the characteristic X-ray intensity for each element so that the distribution within the region can be easily understood.

[0321] As shown in Figs. 31(B) to 31(F) and Figs. 32(A) to 32(F), it was confirmed that the concentrations of fluorine, magnesium, silicon, and calcium are high at the grain boundaries and in their vicinity. Note that silicon and calcium are considered to be contained in the reagents used as raw materials.

[0322] From the surface analysis of EDX shown in Figs. 31(B) to 31(F) and Figs. 32(A) to 32(F), the data of the linear region were extracted, and the distribution of atomic concentration within the positive electrode active material particles was evaluated for. In this way, the evaluation of the linear region in one dimension is sometimes called line analysis.

[0323] The HAADF-STEM image of the region where the line analysis of EDX of sample A was performed is shown in Fig. 33(A). ​​​​In Fig. 33(A), the region where the line analysis of EDX is performed is indicated by an arrow. The line analysis was performed in the crystal grains, grain boundaries, and regions spanning the crystal grains.

[0324] In the line analysis of EDX for the region shown in Fig. 33(A), the atomic concentration of carbon is shown in Fig. 34(A), oxygen in Fig. 34(B), fluorine in Fig. 34(C), magnesium in Fig. 34(D), silicon in Fig. 34(E), phosphorus in Fig. 34(F), sulfur in Fig. 35(A), calcium in Fig. 35(B), manganese in Fig. 35(C), cobalt in Fig. 35(D), and nickel in Fig. 35(E).

[0325] In Figs. 34(A) to 34(F) and Figs. 35(A) to 35(E), the horizontal axis indicates the distance ( Distance) [nm], and the vertical axis indicates the atomic concentration [atomic%]. The horizontal axis distance starts from the black circle at one end of the arrow shown in Fig. 34(A) (distance = 0 nm) and shows an increase in distance toward the other end (endpoint). The atomic concentration on the vertical axis indicates the ratio of the number of atoms of each element when the total number of atoms of carbon, oxygen , fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel is set to 100 atomic%.

[0326] As shown in Fig. 33(A), Figs. 34(A) to 34(F), and Figs. 35(A) to 35(E), it was confirmed that the grain boundaries and their vicinity have higher concentrations of fluorine, magnesium, silicon and calcium compared to the region of the crystal grains. Also, it was found that the grain boundaries and their vicinity have a region with a width of 1 nm or more and 10 nm or less.

[0327] It was confirmed that the grain boundaries and their vicinity have oxygen, magnesium, and fluorine. It was found that the grain boundaries and their vicinity have magnesium oxide. Also, it is considered that some of the oxygen in the magnesium oxide is replaced by fluorine.

[0328] On the other hand, in the region of the crystal grains, fluorine, magnesium, silicon, and calcium were at the detection lower limit level.

[0329] Phosphorus and sulfur were at the detection lower limit level both in the crystal grains and the grain boundaries.

[0330] Although carbon was detected in the crystal grains and the grain boundaries, a carbon coating film was used as a protective film, and it is considered that the carbon concentration described above includes carbon resulting from the carbon coating film. Therefore, the true carbon concentration of the crystal grains and the grain boundaries could not be determined.

[0331] Compared with the crystal grains, it was confirmed that the atomic concentrations of the transition metals manganese, cobalt, and nickel are lower in the grain boundaries and their vicinity.

[0332] The total atomic concentrations of the transition metals nickel, manganese, and cobalt are shown in Fig. 35(F). In Fig. 35(F), the horizontal axis indicates the distance [nm], and the vertical axis indicates the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) [atomic%]. Specifically, the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) is the value obtained by summing up the atomic concentrations of nickel, manganese, and cobalt for each measurement point of EDX. In sample A, the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) can also be said to be the atomic concentration of the transition metals. As shown in Fig. 35(F), in the region of the crystal grains, It was found that the atomic concentration of transition metals tends to be low at and near the grain boundaries compared to the grains. Also, in the grain region, it was found that there is no significant variation in the atomic concentration of transition metals and it is substantially uniform.

[0333] The ratio of the atomic concentration of magnesium (Mg) to the atomic concentration of transition metals in the grains is shown in Fig. 36(A). In Fig. 36(A), the horizontal axis represents the distance [nm] and the vertical axis represents the ratio of the atomic concentration of magnesium to the atomic concentration of transition metals in the grains ( Mg / Tr-Metal) (arb. unit).

[0334] The atomic concentration of transition metals (Tr-Metal) in the grains will be described. As the atomic concentration of transition metals (Tr-Metal) in the grains, the average value of the atomic concentration of transition metals in the grains was adopted. Specifically, the region where the atomic concentration of magnesium (Mg) is below the detection lower limit level was defined as the grain region, and the average value of the atomic concentration of transition metals in that region was calculated. The grain region used for the calculation of the average value is indicated by an arrow in Fig. 35(F).

[0335] As shown in Fig. 36(A), it was found that the grain boundaries and their vicinity have a region where the ratio of the atomic concentration of magnesium to the atomic concentration of transition metals in the grains (Mg / Tr-Metal) is 0.030 or more. It was found that magnesium is segregated at the grain boundaries and their vicinity. It is considered that the grain boundaries and their vicinity have magnesium oxide. Sample A, which is one embodiment of the present invention, has magnesium oxide at the grain boundaries and their vicinity, and the cathode active material particles become chemically and structurally stable, and transition metals elute into the electrolyte. Oxygen It is possible to suppress deterioration of the positive electrode active material, such as detachment and instability of the crystal structure. Also, it is possible to suppress cracking of the positive electrode active material particles. Further, it is possible to suppress oxygen detachment from the positive electrode active material particles. By using such positive electrode active material particles, deterioration of the power storage device can be suppressed. Moreover, a highly safe power storage device can be obtained. When the charging voltage is increased, the amount of lithium contained in the positive electrode decreases during charging, so the crystal structure of the positive electrode active material particles tends to transform. Therefore, sample A is particularly preferable as the positive electrode active material particles. The ratio of the atomic concentration of fluorine to the atomic concentration of transition metal (Tr-Metal) in the crystal grains is shown in FIG. 36(B). In FIG. 36(B), the horizontal axis represents the distance [nm], and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (denoted as F / Tr-Metal). As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof. In this specification and the like, "ratio of atomic concentrations" and "ratio of atomic numbers" are synonymous, and the "ratio of atomic concentrations" can be replaced with the "ratio of atomic numbers". That is, the value of Mg / Tr-Metal is the ratio of the atomic concentration of magnesium to the atomic concentration of transition metal in the crystal grains, and can also be said to be the ratio of the number of magnesium atoms to the number of transition metal atoms in the crystal grains. When the charging voltage is increased, the amount of lithium contained in the positive electrode decreases during charging, so the crystal structure of the positive electrode active material particles tends to transform. Therefore, sample A is particularly preferable as the positive electrode active material particles. It is possible to suppress deterioration of the positive electrode active material, such as detachment and instability of the crystal structure. Also, it is possible to suppress cracking of the positive electrode active material particles. Further, it is possible to suppress oxygen detachment from the positive electrode active material particles. By using such positive electrode active material particles, deterioration of the power storage device can be suppressed. Moreover, a highly safe power storage device can be obtained.

[0336] The ratio of the atomic concentration of fluorine to the atomic concentration of transition metal (Tr-Metal) in the crystal grains is shown in FIG. 36(B). In FIG. 36(B), the horizontal axis represents the distance [nm], and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (denoted as F / Tr-Metal). As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof. In this specification and the like, "ratio of atomic concentrations" and "ratio of atomic numbers" are synonymous, and the "ratio of atomic concentrations" can be replaced with the "ratio of atomic numbers". That is, the value of Mg / Tr-Metal is the ratio of the atomic concentration of magnesium to the atomic concentration of transition metal in the crystal grains, and can also be said to be the ratio of the number of magnesium atoms to the number of transition metal atoms in the crystal grains. As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof.

[0337] As shown in FIG. 36(B), the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof. As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof. As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof. As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof.

[0338] In this specification and the like, "ratio of atomic concentrations" and "ratio of atomic numbers" are synonymous, and the "ratio of atomic concentrations" can be replaced with the "ratio of atomic numbers". That is, the value of Mg / Tr-Metal is the ratio of the atomic concentration of magnesium to the atomic concentration of transition metal in the crystal grains, and can also be said to be the ratio of the number of magnesium atoms to the number of transition metal atoms in the crystal grains. In this specification and the like, "ratio of atomic concentrations" and "ratio of atomic numbers" are synonymous, and the "ratio of atomic concentrations" can be replaced with the "ratio of atomic numbers". That is, the value of Mg / Tr-Metal is the ratio of the atomic concentration of magnesium to the atomic concentration of transition metal in the crystal grains, and can also be said to be the ratio of the number of magnesium atoms to the number of transition metal atoms in the crystal grains. In this specification and the like, "ratio of atomic concentrations" and "ratio of atomic numbers" are synonymous, and the "ratio of atomic concentrations" can be replaced with the "ratio of atomic numbers". That is, the value of Mg / Tr-Metal is the ratio of the atomic concentration of magnesium to the atomic concentration of transition metal in the crystal grains, and can also be said to be the ratio of the number of magnesium atoms to the number of transition metal atoms in the crystal grains. In this specification and the like, "ratio of atomic concentrations" and "ratio of atomic numbers" are synonymous, and the "ratio of atomic concentrations" can be replaced with the "ratio of atomic numbers". That is, the value of Mg / Tr-Metal is the ratio of the atomic concentration of magnesium to the atomic concentration of transition metal in the crystal grains, and can also be said to be the ratio of the number of magnesium atoms to the number of transition metal atoms in the crystal grains. In this specification and the like, "ratio of atomic concentrations" and "ratio of atomic numbers" are synonymous, and the "ratio of atomic concentrations" can be replaced with the "ratio of atomic numbers". That is, the value of Mg / Tr-Metal is the ratio of the atomic concentration of magnesium to the atomic concentration of transition metal in the crystal grains, and can also be said to be the ratio of the number of magnesium atoms to the number of transition metal atoms in the crystal grains.

[0339] For each EDX measurement location, the ratio of the atomic concentration of magnesium (Mg) to the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) is shown in Fig. 36(C). In Fig. 36( C), the horizontal axis represents the distance [nm], and the vertical axis represents the ratio of the atomic concentration of magnesium to the total atomic concentration of nickel, manganese, and cobalt for each EDX measurement location (Mg / (Ni + Mn + Co)).

[0340] For each EDX measurement location, the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) is the same as the data shown in Fig. 35(F).

[0341] As shown in Fig. 36(C), it was found that the grain boundaries and their vicinity have a region where the ratio of the atomic concentration of magnesium to the total atomic concentration of nickel, manganese, and cobalt in the grains (Mg / (Ni + Mn + Co)) is 0.030 or more. It was found that magnesium is segregated at the grain boundaries and their vicinity.

[0342] For each EDX measurement location, the ratio of the atomic concentration of fluorine to the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) is shown in Fig. 36(D). In Fig. 36(D), the horizontal axis represents the distance [nm], and the vertical axis represents the ratio of the atomic concentration of fluorine to the total atomic concentration of nickel, manganese, and cobalt for each EDX measurement location (F / (Ni + Mn + Co)).

[0343] As shown in Fig. 36(D), the grain boundaries and their vicinity have the atomic concentration of transition metals in the grains The ratio of the atomic concentration of fluorine to the degree (F / (Ni + Mn + Co)) is 0.030 or more. It was found to have a region. By having fluorine at the grain boundaries and in their vicinity, it was found that magnesium can be efficiently segregated at the grain boundaries and in their vicinity.

[0344] EDX measurements were similarly performed at another location of Sample A.

[0345] The HAADF-STEM image of the region where the EDX surface analysis of Sample A was performed is shown in Fig. 37(A). The EDX surface analysis was performed in a region including grains and grain boundaries. The carbon mapping image in the EDX surface analysis of the region shown in Fig. 37(A) is shown in Fig. 37(B), oxygen in Fig. 37(C), fluorine in Fig. 37(D), magnesium in Fig. 37(E), silicon in Fig. 37(F), phosphorus in Fig. 38(A), sulfur in Fig. 38(B), calcium in Fig. 38(C), manganese in Fig. 38(D )), cobalt in Fig. 38(E), and nickel in Fig. 38(F). Figs. 37(B) to 37(F), Figs. 38(A) to 38(F) show the mapping of characteristic X-ray intensities by EDX measurement. Measurement points with low characteristic X-ray intensities are shown in light color (white), and measurement points with higher characteristic

[0346] X-ray intensities are shown in darker color (black). That is, light-colored (white) measurement points indicate low atomic concentrations, and dark-colored (black) measurement points indicate high atomic concentrations. Note that Figs. 3 7(B) to 37(F), Figs. 38(A) to 38(F) change the scale of the characteristic X-ray intensity for each element so that the distribution within the region can be easily understood. As shown in Figs. 37(B) to 37(F), Figs. 38(A) to 38(F), the concentrations of fluorine, magnesium, silicon, and calcium are high at the grain boundaries and in their vicinity.

[0347] ​ It was confirmed that it was possible. Silicon and calcium were considered to be included in the reagents used as raw materials. It was considered that it was included.

[0348] From the EDX surface analysis shown in FIGS. 37(B) to 37(F) and FIGS. 38(A) to 38(F), data of linear regions were extracted, and the distribution of atomic concentrations inside the positive electrode active material particles was evaluated. It was evaluated. It was evaluated.

[0349] The HAADF-STEM image of the region where the EDX line analysis of Sample A was performed is shown in FIG. 33(B). In FIG. 33(B), the region where the EDX line analysis was performed is indicated by an arrow. The EDX line analysis was performed in crystal grains, grain boundaries, and regions spanning crystal grains. The EDX line analysis was performed in crystal grains, grain boundaries, and regions spanning crystal grains.

[0350] In the EDX line analysis of the region shown in FIG. 33(B), the atomic concentration of carbon is shown in FIG. 39(A), oxygen in FIG. 39(B), fluorine in FIG. 39(C), magnesium in FIG. 39(D), silicon in FIG. 39(E), phosphorus in FIG. 39(F), sulfur in FIG. 40(A), calcium in FIG. 40(B), manganese in FIG. 40(C), cobalt in FIG. 40(D), and nickel in FIG. 40(E). The atomic concentration of carbon is shown in FIG. 39(A), oxygen in FIG. 39(B), fluorine in FIG. 39(C), magnesium in FIG. 39(D), silicon in FIG. 39(E), phosphorus in FIG. 39(F), sulfur in FIG. 40(A), calcium in FIG. 40(B), manganese in FIG. 40(C), cobalt in FIG. 40(D), and nickel in FIG. 40(E). The atomic concentration of carbon is shown in FIG. 39(A), oxygen in FIG. 39(B), fluorine in FIG. 39(C), magnesium in FIG. 39(D), silicon in FIG. 39(E), phosphorus in FIG. 39(F), sulfur in FIG. 40(A), calcium in FIG. 40(B), manganese in FIG. 40(C), cobalt in FIG. 40(D), and nickel in FIG. 40(E). The atomic concentration of carbon is shown in FIG. 39(A), oxygen in FIG. 39(B), fluorine in FIG. 39(C), magnesium in FIG. 39(D), silicon in FIG. 39(E), phosphorus in FIG. 39(F), sulfur in FIG. 40(A), calcium in FIG. 40(B), manganese in FIG. 40(C), cobalt in FIG. 40(D), and nickel in FIG. 40(E).

[0351] In FIGS. 39(A) to 39(F) and FIGS. 40(A) to 40(E), the horizontal axis indicates the distance [nm], and the vertical axis indicates the atomic concentration [atomic%]. The distance on the horizontal axis starts from the black circle at one end of the arrow shown in FIG. 33(B) (distance = 0 nm), and is shown such that the distance increases toward the other end (end point). The atomic concentration on the vertical axis indicates the ratio of the number of atoms of each element when the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel is 100 atomic%. The horizontal axis indicates the distance [nm], and the vertical axis indicates the atomic concentration [atomic%]. The distance on the horizontal axis starts from the black circle at one end of the arrow shown in FIG. 33(B) (distance = 0 nm), and is shown such that the distance increases toward the other end (end point). The atomic concentration on the vertical axis indicates the ratio of the number of atoms of each element when the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel is 100 atomic%. The horizontal axis indicates the distance [nm], and the vertical axis indicates the atomic concentration [atomic%]. The distance on the horizontal axis starts from the black circle at one end of the arrow shown in FIG. 33(B) (distance = 0 nm), and is shown such that the distance increases toward the other end (end point). The atomic concentration on the vertical axis indicates the ratio of the number of atoms of each element when the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel is 100 atomic%. The horizontal axis indicates the distance [nm], and the vertical axis indicates the atomic concentration [atomic%]. The distance on the horizontal axis starts from the black circle at one end of the arrow shown in FIG. 33(B) (distance = 0 nm), and is shown such that the distance increases toward the other end (end point). The atomic concentration on the vertical axis indicates the ratio of the number of atoms of each element when the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel is 100 atomic%. The horizontal axis indicates the distance [nm], and the vertical axis indicates the atomic concentration [atomic%]. The distance on the horizontal axis starts from the black circle at one end of the arrow shown in FIG. 33(B) (distance = 0 nm), and is shown such that the distance increases toward the other end (end point). The atomic concentration on the vertical axis indicates the ratio of the number of atoms of each element when the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel is 100 atomic%. The horizontal axis indicates the distance [nm], and the vertical axis indicates the atomic concentration [atomic%]. The distance on the horizontal axis starts from the black circle at one end of the arrow shown in FIG. 33(B) (distance = 0 nm), and is shown such that the distance increases toward the other end (end point). The atomic concentration on the vertical axis indicates the ratio of the number of atoms of each element when the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel is 100 atomic%. The horizontal axis indicates the distance [nm], and the vertical axis indicates the atomic concentration [atomic%]. The distance on the horizontal axis starts from the black circle at one end of the arrow shown in FIG. 33(B) (distance = 0 nm), and is shown such that the distance increases toward the other end (end point). The atomic concentration on the vertical axis indicates the ratio of the number of atoms of each element when the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel is 100 atomic%.

[0352] As shown in FIGS. 33(B), 39(A) to 39(F), and 40(A) to 40(E), it was confirmed that the concentration of fluorine, magnesium, silicon, and calcium is higher in the grain boundary and its vicinity than in the grain region. It was also found that the grain boundary and its vicinity have a region with a width of 1 nm or more and 10 nm or less.

[0353] It was confirmed that the grain boundary and its vicinity contain oxygen, magnesium, and fluorine. It was found that the grain boundary and its vicinity contain magnesium oxide. It is also considered that some of the oxygen in magnesium oxide is replaced by fluorine.

[0354] On the other hand, in the grain region, fluorine, magnesium, silicon, and calcium were at the detection lower limit level.

[0355] Phosphorus and sulfur were also at the detection lower limit level in both the grain and the grain boundary.

[0356] Although carbon was detected in the grain and the grain boundary, a carbon coating film was used as a protective film, and it is considered that the carbon concentration described above includes carbon resulting from the carbon coating film. Therefore, the true carbon concentration of the grain and the grain boundary could not be determined.

[0357] It was confirmed that the atomic concentrations of manganese, cobalt, and nickel, which are transition metals, are lower in the grain boundary and its vicinity than in the grain.

[0358] The total atomic concentration of nickel, manganese, and cobalt, which are transition metals, is shown in FIG. 40(F). . In FIG. 40(F), the horizontal axis represents distance [nm], and the vertical axis represents the total number of atomic concentrations of nickel, manganese, and cobalt (Ni + Mn + Co) [atomic%]. In sample A, the total number of atomic concentrations of nickel, manganese, and cobalt (Ni + M n + Co) can also be said to be the atomic concentration of transition metals. As shown in FIG. 40(F), it was found that the grain boundaries and their vicinity tend to have a lower atomic concentration of transition metals compared to the grain region. Also, in the grain region, it was found that there is no significant variation in the atomic concentration of transition metals and it is substantially uniform.

[0359] The ratio of the atomic concentration of magnesium (Mg) to the atomic concentration of transition metals in the grains is shown in FIG. 41(A). In FIG. 41(A), the horizontal axis represents distance [nm], and the vertical axis represents the ratio of the atomic concentration of magnesium to the atomic concentration of transition metals in the grains ( Mg / Tr-Metal).

[0360] As the atomic concentration of transition metals (Tr-Metal) in the grains, the average value of the atomic concentration of transition metals in the grains was adopted. The region of the grains used for calculating the average value is indicated by an arrow in FIG. 40(F).

[0361] As shown in FIG. 41(A), it was found that the grain boundaries and their vicinity have a region where the ratio of the atomic concentration of magnesium to the atomic concentration of transition metals in the grains (Mg / Tr-Metal) is 0.030 or more. It was found that magnesium is segregated at the grain boundaries and their vicinity. It is considered that the grain boundaries and their vicinity have magnesium oxide. Sample A, which is one aspect of the present invention, has magnesium oxide at the grain boundaries and their vicinity. , the positive electrode active material particles become chemically and structurally stable, the transition metal elutes into the electrolyte, and oxygen desorbs, and the deterioration of the positive electrode active material such as the crystal structure becoming unstable can be suppressed. Also, the cracking of the positive electrode active material particles can be suppressed. Also, the desorption of oxygen from the positive electrode active material particles can be suppressed. By using such positive electrode active material particles, the deterioration of the power storage device can be suppressed. Also , a highly safe power storage device can be obtained. When the charging voltage is increased, the amount of lithium contained in the positive electrode during charging decreases, so the crystal structure of the positive electrode active material particles is likely to transform. Therefore, sample A is particularly preferable as the positive electrode active material particles.

[0362] The ratio of the atomic concentration of fluorine to the atomic concentration of transition metal (Tr-Metal) in the crystal grains is shown in Fig. 41(B). In Fig. 41(B), the horizontal axis represents the distance (Distance) [n m], and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains ( denoted as F / Tr-Metal). ).

[0363] As shown in Fig. 41(B), it was found that the grain boundaries and their vicinity have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and their vicinity, it was found that magnesium can be efficiently segregated at the grain boundaries and their vicinity. .

[0364] The ratio of the atomic concentration of magnesium (Mg) to the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) for each EDX measurement location is shown in Fig. 41(C). In Fig. 41( C), the horizontal axis represents the distance (Distance) [nm], and the vertical axis represents the EDX measurement location The ratio of the atomic concentration of magnesium (Mg / (Ni + Mn + Co)) to the total atomic concentration of nickel, manganese, and cobalt per measurement point is shown. The ratio of the atomic concentration of magnesium (Mg / (Ni + Mn + Co)) to the total atomic concentration of nickel, manganese, and cobalt per measurement point is shown.

[0365] For each EDX measurement point, the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) is the same as the data shown in FIG. 40(F).

[0366] As shown in FIG. 41(C), it was found that the grain boundaries and their vicinity have a region where the ratio of the atomic concentration of magnesium (Mg / (Ni + Mn + Co)) to the total atomic concentration of nickel, manganese, and cobalt in the grains is 0.030 or more. It was found that magnesium is segregated at the grain boundaries and their vicinity. As shown in FIG. 41(C), it was found that the grain boundaries and their vicinity have a region where the ratio of the atomic concentration of magnesium (Mg / (Ni + Mn + Co)) to the total atomic concentration of nickel, manganese, and cobalt in the grains is 0.030 or more. It was found that magnesium is segregated at the grain boundaries and their vicinity.

[0367] For each EDX measurement point, the ratio of the atomic concentration of fluorine to the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) is shown in FIG. 41(D). In FIG. 41(D), the horizontal axis represents the distance [nm], and the vertical axis represents the ratio of the atomic concentration of fluorine (F / (Ni + Mn + Co)) to the total atomic concentration of nickel, manganese, and cobalt for each EDX measurement point. the horizontal axis represents the distance [nm], and the vertical axis represents the ratio of the atomic concentration of fluorine (F / (Ni + Mn + Co)) to the total atomic concentration of nickel, manganese, and cobalt for each EDX measurement point.

[0368] As shown in FIG. 41(D), it was found that the grain boundaries and their vicinity have a region where the ratio of the atomic concentration of fluorine (F / (Ni + Mn + Co)) to the atomic concentration of transition metals in the grains is 0.030 or more. It was found that by having fluorine at the grain boundaries and their vicinity, magnesium can be efficiently segregated at the grain boundaries and their vicinity. It was found that by having fluorine at the grain boundaries and their vicinity, magnesium can be efficiently segregated at the grain boundaries and their vicinity.

[0369] From this example, it is understood that adding magnesium and fluorine as starting materials for the cathode active material particles It has been revealed that magnesium segregates at the grain boundaries of the positive electrode active material particles and in the vicinity thereof. The positive electrode active material particles, which are one aspect of the present invention, have magnesium oxide at the grain boundaries and in the vicinity thereof, so that the positive electrode active material particles are chemically and structurally stable, and structural changes, volume changes, and distortion due to charge and discharge can be suppressed. That is, the crystal structure of the positive electrode active material particles becomes more stable, and the transformation of the crystal structure can be suppressed even when charge and discharge are repeated. Further, cracking of the positive electrode active material particles can be suppressed. That is, deterioration such as a decrease in capacity can be suppressed.

[0370] A power storage device having such positive electrode active material particles has less deterioration, and thus is suitable for portable electronic devices. Furthermore, if it is applied to vehicles including automobiles, it is possible to avoid using commercial power at the peak of power demand, which contributes to energy conservation and reduction of carbon dioxide emissions. In addition, it becomes a highly safe power storage device.

Example

Example

[0371] In this example, positive electrode active material particles having magnesium, fluorine, and oxygen at the grain boundaries and in the vicinity thereof were produced, and the concentration distributions of the grains and grain boundaries in the active material were confirmed by TEM observation and STEM-EDX analysis. The sample is one sample of sample B, which is one aspect of the present invention. As sample B, lithium cobaltate having magnesium, fluorine, and oxygen at the grain boundaries and in the vicinity thereof was produced. The composition of lithium cobaltate was assumed to be LiCoO2. LiCo O2 has a layered rock salt-type crystal structure. The sample is one sample of sample B, which is one aspect of the present invention. As sample B, lithium cobaltate having magnesium, fluorine, and oxygen at the grain boundaries and in the vicinity thereof was produced. The composition of lithium cobaltate was assumed to be LiCoO2. LiCoO2 has a layered rock salt-type crystal structure.

[0372] <Production of Sample B> The production of sample B will be described.

[0373] As shown in step S11 of the flow in FIG. 3, starting materials were prepared. Lithium carbonate (Li2CO3) was used as the lithium source, cobalt tetroxide (Co3O4) as the cobalt source, magnesium oxide (MgO) as the magnesium source, and lithium fluoride (LiF) as the fluorine source. They were weighed. Specifically, 3.1489 g (42.62 mmol) of Li2CO3, 6.7726 g (28.13 mmol) of Co3O4, 0.0344 g (0.85 mmol) of MgO, and 0.0442 g (1.70 mmol) of LiF were weighed. This is an amount such that the ratio m of the number of magnesium atoms to the number of cobalt atoms is 0.010 (1.0%). Also, it is an amount such that the ratio n of the number of fluorine atoms to the number of magnesium atoms is 2.0. Note that Li2CO3 was from High Purity Chemical Research Institute (catalog number: LIH06XB). MgO was from High Purity Chemical Research Institute (catalog number: MGO12PB). Li F was from High Purity Chemical Research Institute (catalog number: LIH10XB).

[0374]

[0375] Next, as shown in step S12, the starting materials weighed in step S11 were mixed. Details of the mixing can be referred to the description of sample A, so the explanation is omitted.

[0375] Next, as shown in step S13, the material mixed in step S12 was subjected to a first heating. Details of the first heating can be referred to the description of sample A, so the explanation is omitted.

[0376] Next, as shown in step S14, the material heated in step S13 was cooled to room temperature to obtain Composition 2. After cooling, the obtained Composition 2 was crushed to reduce the particle size of Composition 2. A 53 μm mesh was used for the crushing process.

[0377] Next, as shown in step S15, a second heating was performed on the composition 2 obtained in step S14. Since the details of the second heating can be referred to the description of sample A, the description is omitted.

[0378] By performing the second heating in step S15, magnesium and fluorine contained in the starting materials can be promoted to segregate to the grain boundaries of lithium cobaltate.

[0379] Next, as shown in step S16, the composition 2 heated in step S15 was cooled to room temperature and recovered to obtain sample B.

[0380] <TEM Observation, STEM Observation, EDX Measurement> Next, sample B was thinned by focused ion beam (FIB), and the cross-section of sample B was observed by TEM and STEM. Also, the cross-section of sample B was subjected to compositional analysis by EDX measurement. For the details of TEM, STEM observation and EDX measurement, the description of sample A can be referred to, so the description is omitted.

[0381] The TEM image (bright field image) of the cross-section of sample B is shown in Fig. 42(A). The magnification of Fig. 42(A) is 10 times 10,000. In Fig. 42(A), the region where the density (luminance) of the TEM image is substantially uniform has a substantially constant crystal orientation and is considered to be a single crystal. Also, the region where the density (luminance) of the TEM image changes is considered to be a grain boundary. A schematic diagram corresponding to Fig. 42(A) is shown in Fig. 42(B). As shown in Fig. 42(A) and Fig. 42(B), it was confirmed that the positive electrode active material particles have a plurality of crystal grains 1201 and grain boundaries 1203 between the crystal grains.

[0382] The STEM image (bright field image) of the cross-section of sample B is shown in Fig. 43(A), and the HAADF-STE of the same location The M image is shown in Fig. 43(B). The magnification of Figs. 43(A) and 43(B) is 8 million times. In Figs. 43(A) and 43(B), the crystal lattice image could be confirmed in the grain region.

[0383] The HAADF-STEM image of the region where the EDX surface analysis of sample B was performed is shown in Fig. 44(A). The EDX surface analysis was performed in the region including the grains and grain boundaries. In this example, the EDX measurement was performed at 256 points vertically and 256 points horizontally within the region.

[0384] Peaks derived from the electron transition to the K shell of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, nickel were observed respectively. The obtained spectra were separated into respective elements to obtain the atomic concentrations.

[0385] The carbon mapping image in the EDX surface analysis of the region shown in Fig. 44(A) is shown in Fig. 44(B ), oxygen in Fig. 44(C), fluorine in Fig. 44(D), magnesium in Fig. 44(E), silicon in Fig. 44(F), phosphorus in Fig. 45(A), sulfur in Fig. 45(B), calcium in Fig. 45(C ), cobalt in Fig. 45(D).

[0386] Figs. 44(B) to Fig. 44(F), Figs. 45(A) to Fig. 45(D) show the mapping of characteristic X-ray intensity by EDX measurement, and the measurement points with low characteristic X-ray intensity are shown in light color (white), and the measurement points with higher characteristic X-ray intensity are shown in darker color (black). That is, the light color (white) measurement points indicate low atomic concentration, and the darker color (black) measurement points indicate high atomic concentration. Note that Figs. 4 4(B) to Fig. 44(F), Figs. 45(A) to Fig. 45(D) change the scale of the characteristic X-ray intensity for each element so that the distribution within the region can be easily understood. read.

[0387] As shown in FIGS. 44(B) to 44(F) and FIGS. 45(A) to 45(D), it was confirmed that the concentrations of magnesium and calcium are high at the grain boundaries and in their vicinity. Regarding fluorine, it was hardly observed in the regions where the surface analysis by EDX was performed. This is considered to be because fluorine, which is a light element, is difficult to detect by EDX. Note that calcium is considered to have been contained in the reagent used as a raw material.

[0388] From the surface analysis by EDX shown in FIGS. 44(B) to 44(F) and FIGS. 45(A) to 45(D), the data of the linear regions were extracted and the distribution of atomic concentrations inside the positive electrode active material particles was evaluated

[0389] The HAADF-STEM image of the region where the line analysis by EDX of Sample B was performed is shown in FIG. 46(A). In FIG. 46(A), the region where the line analysis by EDX was performed is indicated by an arrow. The line analysis by EDX was performed in the grain, grain boundary, and region spanning the grains.

[0390] Regarding the line analysis by EDX of the region shown in FIG. 46(A), the atomic concentration of carbon is shown in FIG. 47(A), oxygen in FIG. 47(B), fluorine in FIG. 47(C), magnesium in FIG. 47(D), silicon in FIG. 47(E), phosphorus in FIG. 47(F), sulfur in FIG. 48(A), and calcium in FIG. 48(B), cobalt in FIG. 48(C).

[0391] In FIGS. 47(A) to 47(F) and FIGS. 48(A) to 48(C), the horizontal axis indicates the distance( Distance) [nm], and the vertical axis indicates the atomic concentration [atomic%]. The horizontal axis distance starts from the black circle at one end of the arrow shown in FIG. 46(A) (distance = 0 nm), and the other end ​​​​(Endpoint) is shown such that the distance increases toward it. The atomic concentration on the vertical axis indicates the ratio of the number of atoms of each element when the total number of atoms of carbon, oxygen , fluorine, magnesium, silicon, phosphorus, sulfur, calcium, and cobalt is 100 atomic %.

[0392] As shown in FIGS. 46(A), 47(A) to 47(F), and 48(A) to 48(C), it was confirmed that the concentration of magnesium and calcium is higher in the grain boundary and its vicinity compared to the grain region. Also, it was found that the grain boundary and its vicinity have a region with a width of 1 nm or more and 10 nm or less.

[0393] It was confirmed that the grain boundary and its vicinity contain oxygen and magnesium. It was found that the grain boundary and its vicinity contain magnesium oxide.

[0394] On the other hand, in the grain region, fluorine, magnesium, silicon, and calcium were at the detection lower limit level.

[0395] Phosphorus and sulfur were at the detection lower limit level both in the grain and the grain boundary.

[0396] Although carbon is detected in the grain and the grain boundary, a carbon coating film is used as a protective film, and it is considered that the carbon concentration described above includes carbon due to the carbon coating film. Therefore, the true carbon concentration of the grain and the grain boundary could not be determined.

[0397] It was confirmed that the atomic concentration of cobalt, which is a transition metal, is lower in the grain boundary and its vicinity compared to the grain.

[0398] In sample B, the atomic concentration of cobalt can also be said to be the atomic concentration of transition metals. Figure 48(C) As shown in , it was found that the atomic concentration of transition metals in the grain boundary and its vicinity is lower than that in the grain region. Also, in the grain region, it was found that the atomic concentration of transition metals has little variation and is substantially uniform.

[0399] The ratio of the atomic concentration of magnesium (Mg) to the atomic concentration of transition metals in the grains is shown in Figure 49(A). In Figure 49(A), the horizontal axis represents the distance [nm] and the vertical axis represents the ratio of the atomic concentration of magnesium to the atomic concentration of transition metals in the grains ( Mg / Tr-Metal).

[0400] As the atomic concentration of transition metals (Tr-Metal) in the grains, the average value of the atomic concentration of transition metals in the grains was adopted. The region of the grains used for calculating the average value is indicated by an arrow in Figure 48(D) as shown in Figure 48(D).

[0401] As shown in Figure 49(A), it was found that the grain boundary and its vicinity have a region where the ratio of the atomic concentration of magnesium to the atomic concentration of transition metals in the grains (Mg / Tr-Metal) is 0.030 or more . It was found that magnesium is segregated at the grain boundary and its vicinity . It is considered that the grain boundary and its vicinity have magnesium oxide. Sample B, which is one aspect of the present invention, has magnesium oxide at the grain boundary and its vicinity , so that the positive electrode active material particles become chemically and structurally stable, and deterioration of the positive electrode active material such as elution of transition metals into the electrolyte, desorption of oxygen , and instability of the crystal structure can be suppressed. Also, cracking of the positive electrode active material particles can be suppressed. Also, desorption of oxygen from the positive electrode active material particles can be suppressed ​​​​ This is possible. By using such cathode active material particles, deterioration of the power storage device can be suppressed. Also , a highly safe power storage device can be obtained. When increasing the charging voltage, during charging, the amount of lithium contained in the cathode decreases, making the crystal structure of the cathode active material particles more likely to transform. Therefore, as the cathode active material particles, Sample B is particularly preferable.

[0402] The ratio of the atomic concentration of fluorine to the atomic concentration of transition metal (Tr-Metal) in the crystal grains is shown in FIG. 49(B). In FIG. 49(B), the horizontal axis represents the distance (Distance) [n m], and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains ( denoted as F / Tr-Metal).

[0403] As shown in FIGS. 47(C) and 49(B), in Sample B, the fluorine concentration in the crystal grains and grain boundaries was below the detection limit. It is considered that fluorine, being a light element, is difficult to detect by EDX.

[0404] The ratio of the atomic concentration of magnesium (Mg) to the atomic concentration of cobalt (Co) for each EDX measurement location is shown in FIG. 49(C). In FIG. 49(C), the horizontal axis represents the distance (Distanc e) [nm], and the vertical axis represents the ratio of the atomic concentration of magnesium to the atomic concentration of cobalt (Mg / Co) for each EDX measurement location.

[0405] As shown in FIG. 49(C), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of magnesium to the atomic concentration of cobalt (Mg / Co) in the crystal grains is 0.030 or more. It was found that magnesium is segregated at the grain boundaries and the vicinity thereof.

[0406] The ratio of the atomic concentration of fluorine to the atomic concentration of cobalt (Co) for each EDX measurement location is shown in Fig 49(D). In Fig 49(D), the horizontal axis represents the distance [nm] and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of cobalt (F / Co) for each EDX measurement location. In sample B, the fluorine concentrations at the crystal grains and grain boundaries were below the detection limit .

[0407] EDX measurements were similarly performed at another location of sample B

[0408] The HAADF-STEM image of the region where the EDX surface analysis of sample B was performed is shown in Fig 50(A). The EDX surface analysis was performed in a region including crystal grains and grain boundaries. The carbon mapping image, oxygen in Fig 50(C), fluorine in Fig 50(D), magnesium in Fig 50(E), silicon in Fig 50(F), phosphorus in Fig 51(A), sulfur in Fig 51(B), calcium in Fig 51(C), and cobalt in Fig 51(D ) of the EDX surface analysis of the region shown in Fig 50(A) are shown .

[0409] Figs 50(B) to 50(F) and Figs 51(A) to 51(D) show the mapping of characteristic X-ray intensities by EDX measurement. The measurement points with low characteristic X-ray intensity are shown in light color (white), and the characteristic X-ray intensity is shown in darker color (black) for measurement points with higher characteristic X-ray intensity. That is, the light-colored (white) measurement points indicate low atomic concentration, and the dark-colored (black) measurement points indicate high atomic concentration. Note that Figs 5 0(B) to 50(F) and Figs 51(A) to 51(D) change the scale of the characteristic X-ray intensity for each element so that the distribution within the region can be easily understood .

[0410] ​As shown in FIGS. 50(B) to 50(F) and FIGS. 51(A) to 51(D), it was confirmed that the concentration of magnesium and calcium is high at the grain boundaries and in the vicinity thereof. Regarding fluorine, it was hardly observed in the region where the surface analysis by EDX was performed. This is considered to be because fluorine, which is a light element, is difficult to detect by EDX. Note that calcium is considered to be contained in the reagent used as a raw material.

[0411] From the surface analysis by EDX shown in FIGS. 50(B) to 50(F) and FIGS. 51(A) to 51(D), the data of the linear region was extracted, and the distribution of the atomic concentration inside the positive electrode active material particles was evaluated .

[0412] The HAADF-STEM image of the region where the line analysis by EDX of Sample B was performed is shown in FIG. 46(B). In FIG. 46(B), the region where the line analysis by EDX was performed is indicated by an arrow. The line analysis by EDX was performed in the grain, grain boundary, and region across the grains.

[0413] Regarding the carbon atomic concentration in the line analysis by EDX of the region shown in FIG. 46(B), FIG. 52(A), oxygen in FIG. 52(B), fluorine in FIG. 52(C), magnesium in FIG. 52(D), silicon in FIG. 52(E), phosphorus in FIG. 52(F), sulfur in FIG. 53(A), and calcium in FIG. 53(B) are shown in FIG. 53(C).

[0414] In FIGS. 52(A) to 52(F) and FIGS. 53(A) to 53(C), the horizontal axis indicates the distance ( Distance) [nm], and the vertical axis indicates the atomic concentration [atomic%]. The horizontal axis distance starts from the black circle at one end of the arrow shown in FIG. 46(B) (distance = 0 nm), and the other end It is shown such that the distance increases toward the (endpoint). The atomic concentration on the vertical axis indicates the ratio of the number of atoms of each element when the total number of atoms of carbon, oxygen , fluorine, magnesium, silicon, phosphorus, sulfur, calcium, and cobalt is set to 100 atomic %.

[0415] As shown in FIG. 46(B), FIGS. 52(A) to 52(F), and FIGS. 53(A) to 53(C), it was confirmed that the concentration of magnesium is higher at the grain boundaries and in the vicinity thereof compared to the grain regions. Also, it was found that the grain boundaries and the vicinity thereof have a region with a width of 1 nm or more and 10 nm or less.

[0416] It was confirmed that the grain boundaries and the vicinity thereof contain oxygen and magnesium. It was found that the grain boundaries and the vicinity thereof contain magnesium oxide.

[0417] On the other hand, in the grain regions, fluorine, magnesium, silicon, and calcium were at the detection lower limit level.

[0418] Phosphorus and sulfur were at the detection lower limit level both in the grains and at the grain boundaries.

[0419] Although carbon is detected in the grains and at the grain boundaries, a carbon coating film is used as a protective film, and it is considered that the carbon concentration described above includes carbon resulting from the carbon coating film. Therefore, the true carbon concentration of the grains and the grain boundaries could not be determined.

[0420] It was confirmed that the atomic concentration of cobalt, which is a transition metal, is lower at the grain boundaries and in the vicinity thereof compared to the grains.

[0421] ​​​​​​​​In Sample B, the atomic concentration of cobalt can also be said to be the atomic concentration of transition metals. Figure 53(C) As shown in , it was found that the atomic concentration of transition metals in the grain boundary and its vicinity is lower than that in the grain region. Also, in the grain region, it was found that the atomic concentration of transition metals has little variation and is substantially uniform.

[0422] The ratio of the atomic concentration of magnesium (Mg) to the atomic concentration of transition metals in the grains is shown in Figure 54(A). In Figure 54(A), the horizontal axis represents the distance [nm], and the vertical axis represents the ratio of the atomic concentration of magnesium to the atomic concentration of transition metals in the grains ( Mg / Tr-Metal).

[0423] As the atomic concentration of transition metals (Tr-Metal) in the grains, the average value of the atomic concentration of transition metals in the grains was adopted. The region of the grains used for calculating the average value is indicated by an arrow in Figure 53(D).

[0424] As shown in Figure 54(A), it was found that the grain boundary and its vicinity have a region where the ratio of the atomic concentration of magnesium to the atomic concentration of transition metals in the grains (Mg / Tr-Metal) is 0.030 or more. It was found that magnesium is segregated at the grain boundary and its vicinity. It is considered that the grain boundary and its vicinity have magnesium oxide. Sample B, which is one aspect of the present invention, has magnesium oxide at the grain boundary and its vicinity, so that the cathode active material particles become chemically and structurally stable, and deterioration of the cathode active material such as elution of transition metals into the electrolyte, desorption of oxygen, and instability of the crystal structure can be suppressed. Also, cracking of the cathode active material particles can be suppressed. Further, desorption of oxygen from the cathode active material particles can be suppressed. ​​​​​​ This is possible. By using such positive electrode active material particles, deterioration of the power storage device can be suppressed. Also , a highly safe power storage device can be obtained. When increasing the charging voltage, since the crystal structure of the positive electrode active material particles is likely to transform, sample B is particularly preferable as the positive electrode active material particles .

[0425] The ratio of the atomic concentration of fluorine to the atomic concentration of transition metal (Tr-Metal) in the crystal grains is shown in Fig. 54(B). In Fig. 54(B), the horizontal axis represents the distance (Distance) [n m], and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains ( denoted as F / Tr-Metal). ).

[0426] As shown in Figs. 52(C) and 54(B), in sample B, the fluorine concentrations at the crystal grains and grain boundaries were below the detection limit. It is considered that fluorine, which is a light element, is difficult to detect by EDX .

[0427] The ratio of the atomic concentration of magnesium (Mg) to the atomic concentration of cobalt (Co) for each EDX measurement location is shown in Fig. 54(C). In Fig. 54(C), the horizontal axis represents the distance (Distanc e) [nm], and the vertical axis represents the ratio of the atomic concentration of magnesium to the atomic concentration of cobalt (Mg / Co) for each EDX measurement location . .

[0428] As shown in Fig. 54(C), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of magnesium to the atomic concentration of cobalt (Mg / Co) in the crystal grains is 0.030 or more . It was found that magnesium is segregated at the grain boundaries and the vicinity thereof . .

[0429] The ratio of the atomic concentration of fluorine to the atomic concentration of cobalt (Co) for each EDX measurement location is shown in Fig. 54(D). In Fig. 54(D), the horizontal axis represents the distance [nm] and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of cobalt (F / Co) for each EDX measurement location. In sample B, the fluorine concentration at the crystal grains and grain boundaries was below the detection limit.

Explanation of symbols

[0430] 100: Positive electrode active material particles, 101: Crystal grains, 103: Grain boundaries, 105: Crystal defects, 10 7: Region, 200: Active material layer, 201: Graphene compound, 211a: Positive electrode, 211b: Negative electrode, 212a: Lead, 212b: Lead, 214: Separator, 215a: Junction, 215b: Junction, 217: Fixing member, 250: Battery, 251: Outer package, 261: Bend section, 262: Seal section, 263: Seal section, 271: Ridge line, 272: Valley line, 273: Space between, 300: Secondary battery, 301: Positive electrode can, 302: Negative electrode can, 303: Gasket, 3,04 : Positive electrode, 305: Positive electrode current collector, 306: Positive electrode active material layer, 307: Negative electrode, 308: Negative electrode current collector body, 309: Negative electrode active material layer, 310: Separator, 500: Secondary battery, 501: Positive electrode current collector body, 502: Positive electrode active material layer, 503: Positive electrode, 504: Negative electrode current collector, 505: Negative electrode active material layer 、506: Negative electrode, 507: Separator, 508: Electrolyte, 509: Outer package, 510: Positive electrode lead electrode, 511: Negative electrode lead electrode, 600: Secondary battery, 601: Positive electrode cap, 60 2: Battery can, 603: Positive electrode terminal, 604: Positive electrode, 605: Separator, 606: Negative electrode, 6 07: Negative electrode terminal, 608: Insulating plate, 609: Insulating plate, 611: PTC element, 612: Safety Switching mechanism, 900: Circuit board, 910: Label, 911: Terminal, 912: Circuit, 913: Two Secondary battery, 914: Antenna, 915: Antenna, 916: Layer, 917: Layer, 918: Ant enna, 919: Terminal, 920: Display device, 921: Sensor, 922: Terminal, 930: Housing , 930a: Housing, 930b: Housing, 931: Negative electrode, 932: Positive electrode, 933: Separator , 950: Wound body, 951: Terminal, 952: Terminal, 980: Secondary battery, 993: Wound body, 994: Negative electrode, 995: Positive electrode, 996: Separator, 997: Lead electrode, 998: Lea d electrode, 1101: Crystal grain, 1103: Crystal grain boundary, 1201: Crystal grain, 1203: Crystal grain boundary, 7100: Portable display device, 7101: Housing, 7102: Display unit, 7103: Operation button , 7104: Secondary battery, 7200: Portable information terminal, 7201: Housing, 7202: Display unit , 7203: Band, 7204: Buckle, 7205: Operation button, 7206: Input / output terminal s, 7207: Icon, 7300: Display device, 7304: Display unit, 7400: Mobile phone set, 7401: Housing, 7402: Display unit, 7403: Operation button, 7404: External connection port s, 7405: Speaker, 7406: Microphone, 7407: Secondary battery, 8000: Display device , 8001: Housing, 8002: Display unit, 8003: Speaker unit, 8004: Secondary battery, 8021: Charging device, 8022: Cable, 8024: Secondary battery, 8100: Lighting device, 8101: Housing, 8102: Light source, 8103: Secondary battery, 810: Ceiling, 8105: Side wall, 8106: Floor, 8107: Window, 8200: Indoor unit, 8201: Housing, 8202: Air outlet , 8203: Secondary battery, 8204: Outdoor unit, 8300: Electric refrigerator-freezer, 8301: Cabinet body, 8302: Refrigerator door, 8303: Freezer door, 8304: Secondary battery, 8400: Self Motor vehicle, 8401: Headlight, 8406: Electric motor, 8500: Automobile, 8600 : Scooter, 8601: Side mirror, 8602: Secondary battery, 8603: Direction indicator, 8 604: Under-seat storage, 9600: Tablet terminal, 9625: Switch, 9626: S witch, 9627: Power switch, 9628: Operation switch, 9629: Fastener, 963 0: Housing, 9630a: Housing, 9630b: Housing, 9631: Display unit, 9633: Solar ele ctric battery, 9634: Charge and discharge control circuit, 9635: Energy storage body, 9636: DCDC converter, 9 637: Converter, 9640: Movable part

Claims

1. having a positive electrode active material, wherein the positive electrode active material contains lithium, cobalt, oxygen and magnesium, wherein the positive electrode active material has a layered rock salt-type crystal structure, when the cross-section of the positive electrode active material is subjected to EDX measurement and the grain boundary between two adjacent crystallites and the region in the vicinity thereof are evaluated by line analysis, the grain boundary and the region in the vicinity thereof, contain oxygen, have a higher magnesium atomic concentration than the regions of the two crystallites, and have a ratio of the magnesium atomic concentration to the total atomic concentration of transition metals at each EDX measurement location of 0.010 or more and 0.50 or less, and having, a lithium ion secondary battery.

2. When the cross-section of the positive electrode active material is subjected to EDX measurement and the grain boundary between two adjacent crystallites and the region in the vicinity thereof are evaluated by line analysis, the grain boundary and the region in the vicinity thereof, have a higher fluorine atomic concentration than the regions of the two crystallites, and have a ratio of the fluorine atomic concentration to the total atomic concentration of transition metals at each EDX measurement location of 0.020 or more and 1.00 or less, and having, the lithium ion secondary battery according to Claim 1.

3. having a positive electrode active material, wherein the positive electrode active material contains lithium, cobalt, oxygen and magnesium, wherein the positive electrode active material has a layered rock salt-type crystal structure, when the cross-section of the positive electrode active material is subjected to EDX measurement and the grain boundary between two adjacent crystallites and the region in the vicinity thereof are evaluated by line analysis, the grain boundary and the region in the vicinity thereof, contain oxygen, have a higher magnesium atomic concentration than the regions of the two crystallites, and have a ratio of the magnesium atomic concentration to the cobalt atomic concentration at each EDX measurement location of 0.030 or more, and having, a lithium ion secondary battery.

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