Positive electrode active material particle

Abstract

To provide a positive electrode active material particle with smaller deterioration, a power storage device with smaller deterioration, or a power storage device with high safety.SOLUTION: A positive electrode active material particle includes a first crystal grain, a second crystal grain, and a crystal grain boundary existing between the first crystal grain and the second crystal grain. The first crystal grain and the second crystal grain include lithium, transition metal, and oxygen. The crystal grain boundary includes a region containing magnesium and oxygen, in which the ratio of the atomic concentration of magnesium at the crystal grain boundary to the atomic concentration of the transition metal in the first crystal grain and the second crystal grain is 0.010 or more and 0.50 or less.SELECTED DRAWING: Figure 1

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 all elements and devices 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 all devices having a power storage device. 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, the development of various power storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries has been actively carried out. In particular, lithium-ion secondary batteries with high output and high capacity are rapidly expanding in demand along with the development of the semiconductor industry, for 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 electric vehicles (HEVs), electric vehicles ( EVs), or plug-in hybrid electric vehicles (PHEVs). The demand for rechargeable energy is rapidly expanding, ​​It has become an essential element 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] In lithium-ion secondary batteries and the cathode active materials used therein, improvements are desired 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 is not required 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, and the first crystal grain and the second crystal grain contain lithium, a transition metal, and oxygen, and the grain boundary contains magnesium and oxygen, and is a positive electrode active material particle.

[0012] In the above-mentioned positive electrode active material particles, 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.

[0013] In the above-mentioned positive electrode active material particles, the grain boundary preferably further contains fluorine.

[0014] In the above-mentioned positive electrode active material particles, 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.

[0015] The above-mentioned positive electrode active material particles preferably contain at least one of iron, cobalt, nickel, manganese, chromium 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. Further, a novel power storage device can be provided.

Brief Description of the Drawings

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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 it will be easily understood by those skilled in the art that its form and details can be variously changed. Also, the present invention is not to be 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 the sake of clarity of individual explanations. 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 and the like, the same part or parts having the same function are commonly used with the same reference numerals among different drawings, and the repeated description thereof is omitted. Also, when referring to parts having the same function, the hatch pattern is the same, and there may be cases where no particular reference numerals are attached.

[0021] Also, in crystallography, the notation for crystal planes and directions has a bar above the number, but in this specification and the like due to the constraints of the application notation, instead of attaching a bar above the number, a -(minus sign) is attached before the number for expression. 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 and the like, segregation refers to a phenomenon in a solid having a plurality of elements (for example, A, B, C) wherein the concentration of a certain element (for example, B) is unevenly distributed.

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

[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 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 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, and there are 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 amorphous regions. Note that in this specification and the like, crystal defects refer to volume defects, surface defects, point defects observable in a TEM image or the like, or structures in which other elements are incorporated into the crystal . Note that crystal grains may sometimes be referred to as crystallites.

[0027] ​For the confirmation of 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, the crystal orientation may be substantially constant, that is, it may be determined to be a single crystal. Also, due to the crystal orientation causing the density (brightness) of the TEM image to vary, a region where the density (brightness) changes may be determined to be a grain boundary . However, it is not necessarily required to clearly observe the boundaries between the crystal grains 101 and the grain boundaries 1 03 through various analyses.

[0028] The grains 101 and the grain boundaries 103 have different compositions. The grain boundaries 103 contain magnesium and oxygen. The grain boundary 103 preferably further contains fluorine.

[0029] The crystal grains 101 and the crystal grain boundaries 103 were analyzed by energy dispersive X-ray analysis (EDX). Dispersive X-ray Spectroscopy (DXS), Time-of-Flight Secondary Imaging Time-of-Flight Secondary Integral Mass Spectroscopy (ToF-SIMS) ion mass spectrometry), X-ray photoelectron spectroscopy (XPS:X-ra y Photoelectron Spectroscopy), Auger Electron Spectroscopy (A ES: Auger Electron Spectroscopy, electron energy loss Electron Energy-Loss Spectrosc (EELS) However, it is possible to confirm that the composition of the material differs depending on the analysis method. Therefore, it is not necessary to clearly observe the boundaries between the crystal grains 101 and the crystal grain boundaries 103. However, depending on the analytical method, the desired target element may not be detected. Even when the concentration of the target element is extremely low, the target element may not be detected. be.

[0030] <Grain boundary> The grain boundaries 103 of the positive electrode active material particles 100 according to one embodiment of the present invention are formed of magnesium and The grain boundaries 103 contain magnesium oxide and oxygen. It is preferable that magnesium oxide further contains fluorine. A part of oxygen in magnesium oxide is replaced with fluorine. It may be. By partially substituting magnesium oxide with fluorine, for example the diffusivity of lithium can be enhanced without hindering charge and discharge. 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.

[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 1 03 has a region where fluorine is segregated.

[0033] An example of the magnesium concentration distribution between the dashed lines A1 - A2 of the cathode 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.

[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 regions 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).

[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.

[0036] The positive electrode active material particles 100 preferably have a region where the ratio of the number of atoms of magnesium (Mg / Tr-Metal) in the 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 moreover, 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 addition, 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 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).

[0038] Generally, as the power storage device repeats charge and discharge, side reactions such as transition metals such as cobalt and manganese eluting from the positive electrode active material particles of the power storage device into the electrolytic solution, oxygen desorbing, and the crystal structure becoming unstable occur, and the positive electrode active material particles may deteriorate. When the positive electrode active material particles deteriorate, ​​When the child deteriorates, deterioration such as a decrease in the capacity of the power storage device may progress. In this specification, etc., the transition metal of the positive electrode active material particles elutes into the electrolytic solution, oxygen desorbs, and the crystal structure becomes unstable, etc., and the chemical and structural changes of the positive electrode active material particles are sometimes referred to as deterioration of the positive electrode active material particles. In this specification, etc., a decrease in the capacity of the power storage device is sometimes referred to as deterioration of the power storage device. 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.

[0039] 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 volume change and distortion of the crystal lattice may occur. The volume change and distortion of the crystal lattice may cause the positive electrode active material particles to crack, and deterioration such as a decrease in capacity may progress. Also, the cracking of the positive electrode

[0040] active material particles may start from the crystal grain boundaries. 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. Also, 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.

[0041] 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 possessed by 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.

[0042] ​ 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 is prone to deterioration. 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. Since the crystal structure of the positive electrode active material particles 100, which are one aspect of the present invention, is stable, 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. When the positive electrode active material particles 100, which are one aspect of the present invention, crack along the grain boundaries, magnesium oxide is present on the surface of the positive electrode active material particles after cracking. That is, side reactions can be suppressed even in the cracked positive electrode active material, and deterioration of the positive electrode active material can be reduced. That is, deterioration of the power storage device can be suppressed.

[0044] Since the crystal structure of the positive electrode active material particles 100, which are one aspect of the present invention, is stable, 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. When the positive electrode active material particles 100, which are one aspect of the present invention, crack along the grain boundaries, magnesium oxide is present on the surface of the positive electrode active material particles after cracking. That is, side reactions can be suppressed even in the cracked positive electrode active material, and deterioration of the positive electrode active material can be reduced. That is, deterioration of the power storage device can be suppressed.

[0045] In addition, when the positive electrode active material particles 100, which are one aspect of the present invention, crack along the grain boundaries, magnesium oxide is present on the surface of the positive electrode active material particles after cracking. That is, side reactions can be suppressed even in the cracked positive electrode active material, and deterioration of the positive electrode active material can be reduced. That is, deterioration of the power storage device can be suppressed. That is, side reactions can be suppressed even in the cracked positive electrode active material, and deterioration of the positive electrode active material can be reduced. That is, deterioration of the power storage device can be suppressed. By having magnesium oxide at the grain boundaries 103, the oxygen possessed by the positive electrode active material particles 100 is suppressed from diffusing along the grain boundaries. 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, the oxygen possessed by the positive electrode active material particles 100 is suppressed from diffusing along the grain boundaries. 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 preferably 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. Furthermore, 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. Furthermore, 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 complex oxide containing lithium, transition metal and oxygen As the transition metal, one or more of iron, cobalt, nickel, manganese, chromium, ti tanium, vanadium, niobium, etc. can be used.

[0050] For example, the crystal grain 101 has 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, polyanions -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] As the crystal grains 101, various composite oxides can be used. 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 air, and relatively high thermal stability. In addition to one or more selected from Co and Ni, the element M may further 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 in the vicinity. Also, for example, LiNi x Mn y Co z O w (where 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 (where 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 (where 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 the element M has Mn. For example, LiMn2O

[0056] ​​4 can be used. Also, as the element M, in addition to Mn, having Ni may improve the discharge voltage and energy density of the secondary battery, which is preferable. Further, a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4 is mixed with a small amount of lithium nickelate (LiNiO2, LiNi MO2 (M = Co, Al, etc.) ), which can improve the characteristics of the secondary battery and is preferable. 1-x M x O2 (M = Co, Al, etc.) ) can be mixed to improve the characteristics of the secondary battery, which is preferable.

[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 / g or more and 20 m / g or less. Further, 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 using a scanning electron microscope (SEM) or TEM, or a particle size distribution meter using the laser diffraction / scattering method. The specific surface area can be measured by the gas adsorption method. 2 / g or more and 20 m 2 / g or less, which is preferable. 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 using a scanning electron microscope (SEM: Scanning Elect ron Microscope) or TEM, or a particle size distribution meter using the laser diffraction / scattering method. The specific surface area can be measured by the gas adsorption method. It is preferable. The average particle diameter can be measured by observation using a scanning electron microscope (SEM: Scanning Electron Microscope) or TEM, or a particle size distribution meter using the laser diffraction / scattering method. The specific surface area can be measured by the gas adsorption method. ron Microscope) or TEM, or 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 ( ), etc.

[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 ( ), etc. 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 ( ), etc. GO: Graphene Oxide) or RGO (Reduced Graphene Oxide) can be used. Here, RGO refers to a compound obtained, for example, 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 well 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). 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. 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 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 representative examples of the general formula Li (2-j) MSiO4 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. are available.

[0065] Also, A x M2(XO4)3 (A = Li, Na, Mg, M = Fe, Mn, Ti, V, Nb , X = S, P, Mo, W, As, Si) represented by the general formula can be used. 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. This is possible.

[0066] Also, as the crystal grains 101, perovskite-type fluorides such as NaFeF3 and FeF3, T Metal chalcogenides (sulfides, selenides, tellurides) such as iS2 and MoS2, LiM Oxides having an inverse spinel-type crystal structure such as VO4, vanadium oxides (V2O5, V6 O 13 , LiV3O8, etc.), manganese oxides, organic sulfur compounds, and other materials 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.

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

[0069] Also, as the crystal grains 101, lithium manganese composite oxides that can be represented by the composition formula Li a Mn b M c O d can be used. Here, the element M is other than lithium and manganese. ​ It is preferable to use a selected metal element, silicon, or phosphorus, and nickel is more preferable. When measuring the entire particle 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 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 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 means a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw material materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, but may deviate from this composition. In addition, the composition of metals, silicon, phosphorus, etc. in the entire particle of the lithium manganese composite oxide can be measured using, for example, ICP-MS (inductively coupled plasma mass spectrometer). 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 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 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. In addition, 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 means a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw material materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, but may deviate from this composition. 1.68 Mn 0.8062 Ni 0.318 O3 of the lithium manganese composite oxide represented by the composition formula In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 means a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw material materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. 1. 68 Mn 0.8062 Ni 0.318 O3 of the lithium manganese composite oxide represented by the composition formula In addition, the composition of metals, silicon, phosphorus, etc. in the entire particle of the lithium manganese composite oxide can be measured using, for example, ICP-MS (inductively coupled plasma mass spectrometer). It is preferable to use a selected metal element, silicon, or phosphorus, and nickel is more preferable. When measuring the entire particle 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 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 and the central portion. 1.68 Mn 0.80 62 Ni 0.318 O3 of the lithium manganese composite oxide represented by the composition formula

[0070] In addition, the composition of metals, silicon, phosphorus, etc. in the entire particle of the lithium manganese composite oxide can be measured using, for example, ICP-MS (inductively coupled plasma mass spectrometer). In addition, the composition of metals, silicon, phosphorus, etc. in the entire particle of the lithium manganese composite oxide can be measured using, for example, ICP-MS (inductively coupled plasma mass spectrometer). The oxygen composition of the entire particle 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, moly 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] So far, an example in which the positive electrode active material particles 100 have crystal grains 101 and grain boundaries 103 has been described, but one aspect of the present invention is not limited to this. For example, as shown in FIG. 1(C), the positive electrode active material particles 100 may have a region 107. The region 107 can be provided, for example, so as to be in contact with at least a part of the crystal grains 101. The region 107 may be a film containing carbon such as a graphene compound, or a film containing lithium or a decomposition product of the electrolytic solution. When the region 107 is a film containing carbon, the conductivity between the positive electrode active material particles 100 and between the positive electrode active material particles 100 and the current collector can be enhanced. When the region 107 is a film containing lithium or a decomposition product of the electrolytic solution, an excessive reaction with the electrolytic solution can be suppressed, and the cycle characteristics can be improved when used in a secondary battery.

[0075] If the particle size of the positive electrode active material particles 100 is too large, it becomes difficult for lithium to diffuse. On the other hand, if the size is too small, problems such as a decrease in the bulk density of the electrode and an excessive reaction with the electrolytic solution occur. 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 refers to, for example, the value (D50) of 50% cumulative volume.

[0076] [Method for producing positive electrode active material] A method for producing the positive electrode active material particles 100 having crystal grains 101 and grain boundaries 103 will be described with reference to FIG. 3. The crystal grains 101 have a composite oxide containing lithium, a transition metal (M), and oxygen. The grain boundaries 103 have 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.

[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.

[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.

[0084] As the vanadium compound, for example, vanadium oxide, vanadium hydroxide, vanadium chloride, ​​​One or more of vanadium sulfate can be used.

[0085] As the titanium compound, for example, one or more of titanium fluoride, titanium chloride, titanium bromide, titanium iodide, titanium oxide, titanium sulfide, titanium sulfate, etc. can be used. One or more of molybdenum compounds such as molybdenum oxide, diammonium molybdate, phosphomolybdic acid, etc. can be used.

[0086] As the zinc compound, for example, one or more of zinc oxide, zinc hydroxide, zinc nitrate, zinc sulfate, zinc chloride, zinc carbonate, etc. can be used. One or more of indium compounds such as indium chloride, indium sulfate, indium nitrate, indium oxide, indium hydroxide, etc. can be used.

[0087] As the gallium compound, for example, one or more of gallium chloride, gallium fluoride, etc. can be used. One or more of copper compounds such as copper sulfate, copper chloride, copper nitrate, etc. can be used.

[0088] As the niobium compound, for example, one or more of niobium oxide, niobium chloride, niobium sulfatooxide, niobium fluoride, etc. can be used. One or more of magnesium sources such as magnesium oxide, magnesium fluoride, magnesium hydroxide, magnesium carbonate, etc. can be used.

[0089] As the fluorine source, for example, one or more of lithium fluoride, magnesium fluoride, etc. can be used. It can be done.

[0090] One or more of copper compounds such as copper sulfate, copper chloride, copper nitrate, etc. can be used.

[0091] As the niobium compound, for example, one or more of niobium oxide, niobium chloride, niobium sulfatooxide, niobium fluoride, etc. can be used. One or more of them can be used.

[0092] As the magnesium source, for example, one or more of magnesium oxide, magnesium fluoride, magnesium hydroxide, magnesium carbonate, etc. can be used. One or more of them can be used.

[0093] As the fluorine source, for example, one or more of lithium fluoride, magnesium fluoride, etc. can 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), a metal source other than the transition metal is weighed. When the metal other than the transition metal is 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.

[0095] The ratio of the number of atoms of the transition metal (M) to 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 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 preferably 0.010 or in the vicinity thereof (1.0% or in the vicinity thereof). 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 a plurality of types of transition metals are used as raw materials, the total number of atoms of the plurality of types of transition metal atoms may be used for the number of atoms M(r) of the transition metal described above for calculation. The vicinity means, for example, a value greater than 0.9 times and less than 1.1 times that value.

[0096]

[0097] ​​​​​The atomic ratio of magnesium and fluorine in the raw materials will be described. The number of magnesium atoms in the raw materials, the ratio n of the number of fluorine atoms F(r) to the number of magnesium atoms Mg(r) is 1.50 or more and 4.0 or less. That is to say, in the case of the number of magnesium atoms Mg(r): the number of fluorine atoms F(r) = 1.0:n, 1 .50 ≤ n ≤ 4.0 is preferable. Further, the ratio n of the number of fluorine atoms to the number of magnesium atoms is 2.0 or in the vicinity thereof. That is, it is more preferable that the number of magnesium atoms Mg(r): the number of fluorine atoms F(r) = 1.0:2.0 or in the vicinity thereof. By setting the ratio of the above-mentioned number of atoms, magnesium and fluorine can be efficiently segregated at the grain boundaries 103.

[0098] The atomic ratio of the transition metal, magnesium, and fluorine in the raw materials can be represented by Equation 1. Here , m represents the ratio of the number of magnesium atoms Mg(r) to the number of transition metal atoms M(r). As described above, 0.0050 ≤ m ≤ 0.050 is preferable, and further, m = 0.0 10 or in the vicinity thereof is preferable. n represents the ratio of the number of fluorine atoms F(r) to the number of magnesium atoms Mg(r). As described above, 1.50 ≤ n ≤ 4.0 is preferable, and further n = 2.0 or in the vicinity thereof is preferable.

[0099]

Equation

[0100] An example of the ratio of raw materials when producing LiCoO2 as the positive electrode active material particles will be shown. The ratio m of the number of magnesium atoms to the number of cobalt atoms is set to 0.010. The ratio n of the number of fluorine atoms to the number of magnesium atoms is set to 2.0. Based on Equation 1, the cobalt in the raw materials ​​​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 above-mentioned 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 of 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 with respect to the molar ratio of the lithium compound of the raw materials, the molar ratio of the lithium compound of the raw materials may be increased.

[0103] Next, the weighed starting materials are mixed (step S12). For mixing, for example, a ball mill, a beads 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 performed 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 performed in an atmosphere containing oxygen. For example, it is preferably performed 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 the 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 the magnesium and fluorine is ​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 preferable to reduce the particle size of the positive electrode active material particles 100. This can be achieved and 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 more and 12 00°C or less, more preferably 700°C or more and 1000°C or less, 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 in 3.

[0112] When oxygen that binds to magnesium is replaced by fluorine, magnesium may tend to move around the substituted fluorine. In some cases, 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 atoms tend to move more easily 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 charge bias and weaken the bond between magnesium and oxygen. In some cases, adding fluorine may cause charge bias and weaken the bond between magnesium and oxygen. In some cases, adding fluorine may cause 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 more easily and segregate at the grain boundaries 103. In some cases, magnesium may tend to move more easily and segregate at the grain boundaries 103. In some cases.

[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. 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. It can be used.

[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. 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. 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.

[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. It can be made. 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.

[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. It is more preferable. It is more preferable.

[0122] The conductive assistant can form an electric conduction network in the electrode. By the conductive assistant, the electric 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 electric conductivity can be realized. By the conductive assistant, the electric 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 electric conductivity can be realized. It can be realized. It can be realized.

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

[0124] Further, a graphene compound may be used as the conductive aid.

[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. Further, 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 a graphene compound as a conductive aid is preferable because it can increase the contact area between the active material and the conductive aid. 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, for example, a compound obtained by reducing graphene oxide (GO: Graphene Oxide). For example, it is particularly preferable to use graphene or multi-graphene or Reduced Graphene Oxide (hereinafter, RGO). Here, RGO refers to, for example, a compound obtained by reducing graphene oxide (GO: Graphene Oxide). For example, it refers to a compound obtained by reducing graphene oxide (GO: Graphene Oxide).

[0126] 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 ​​The amount of the conductive additive may increase, and the amount of the active material supported may relatively decrease. The support of the active material If the amount decreases, the capacity of the secondary battery will decrease. In such a case, when a graphene compound is used as the conductive additive, 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 of using a graphene compound as a conductive additive 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 additive, and a binder (not shown). Here, for example, graphene or multi-graphene may be used as the graphene compound 201. Here, the graphene compound 201 preferably has a sheet-like shape. In addition, the graphene compound 201 may be a plurality of multi-graphenes, or (and) a plurality of graphenes may be partially overlapped to form a sheet shape.

[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 to 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 being in 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 are in 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 can be 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 makes it possible to increase the discharge capacity of the power storage device.

[0133] Examples of binders include styrene-butadiene rubber (SBR) and styrene-isoprene. Acrylonitrile-styrene rubber, butadiene rubber, ethylene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, 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. CMC, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose Cellulose derivatives such as cellulose, diacetyl cellulose, regenerated cellulose, and starch These water-soluble polymers can be used in combination with the above-mentioned rubber materials. It is even better if there is a

[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 of 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, it is possible to mix the material with a particularly excellent viscosity adjusting effect. As a material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer is preferably used. In addition, examples of water-soluble polymers that are particularly effective in adjusting viscosity include the aforementioned polysaccharides, such as calcium carbonate. Carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxy Cellulose derivatives such as propyl cellulose, diacetyl cellulose, and regenerated cellulose For example, starch or starch can be used.

[0138] In addition, cellulose derivatives such as carboxymethyl cellulose are, for example, carboxymethyl The solubility of cellulose increases when it is converted into a salt such as sodium salt or ammonium salt. It is easy to exert its effect as a viscosity adjuster. The higher the solubility, the easier it is to make the electrode slurry. In the preparation of the electrode, the dispersibility of the electrode with the active material and other components can be improved. In this regard, the cellulose and cellulose derivatives used as the binder for the electrodes are as follows: These salts are also included.

[0139] Water-soluble polymers stabilize the viscosity by dissolving in water, and also serve as active materials and binders. Other materials to be combined, such as styrene butadiene rubber, are stable in aqueous solution. In addition, since it has a functional group, it is easy to stably adsorb on 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 because they have 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 passivation film and suppress the decomposition of the electrolyte. Here, a passivation film is a film that has no electrical conductivity or has extremely low electrical conductivity. For example, when a passivation 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 passivation film suppresses the electrical conductivity and is more preferably capable of conducting lithium ions. a film with no electrical conductivity or a film with extremely low electrical conductivity. For example, when a passivation 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 passivation film suppresses the electrical conductivity and is more preferably capable of conducting lithium ions. it is more desirable.

[0141] <Positive current collector> As the positive current collector, metals such as stainless steel, gold, platinum, aluminum, titanium, and alloys thereof, etc., materials with high conductivity can be used. Also, the material used for the positive current collector is preferably one that does not elute at the potential of the positive electrode. Also, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum, etc. to improve heat resistance can be used. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector has a thickness of zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector has a thickness of ​​​​​​Those with a size of 5 μm or more and 30 μm or less may be used.

[0142] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. Further, the negative electrode active material layer may have a conductive assistant and a binder.

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

[0144] As the negative electrode active material, an element capable of performing a charge-discharge reaction by an alloying / dealloying reaction with lithium can be used. For example, silicon, tin, gallium, aluminum, ger manium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Among them, at least one can be used as a material containing it. Such elements have a larger capacity compared to carbon. In particular, silicon has a high theoretical capacity of 4200 mAh / g. Therefore, it is preferable to use silicon as the negative electrode active material. Also, 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, elements capable of performing a charge-discharge reaction by an alloying / dealloying reaction with lithium, and compounds containing such elements, etc. may be referred to as alloy-based materials in some cases. In this specification and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO is

[0145] In this specification and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO is x ​​​It can also be expressed as follows. Here, x preferably has a value of 1 or in its vicinity. 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, it is relatively easy to reduce the surface area of MCMB, and it may be preferable in some cases. 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, a relatively small volume expansion,

[0149] being inexpensive, and having higher safety than lithium metal, and thus is preferable. i5O 12 ) and 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. As materials that cause a conversion reaction , 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 can be mentioned .​

[0153] As the conductive assistant and binder that the negative electrode active material layer can have, materials similar to those of the conductive assistant and binder that the positive electrode active material layer can have can be used.

[0154] <Negative electrode current collector> For the negative electrode current collector, the same materials as those of the positive electrode current collector can be used. It is preferable to use a material that does not alloy with carrier ions such as lithium.

[0155] [Electrolyte solution] The electrolyte solution has a solvent and an electrolyte. As the solvent of the electrolyte solution, an aprotic organic solvent is preferable. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., one kind, or two or more kinds of these can be used in any combination and ratio.

[0156] In addition, by using a phosphate ester compound having fluorine or a carbonate ester compound having fluorine, which is flame retardant, as the solvent of the electrolyte solution, rupture, ignition, etc. of the power storage device can be prevented. ​​​​​​​​​​​​is possible. Examples of the phosphate ester compound having fluorine include tris(2,2, 2-trifluoroethyl) phosphate (TFEP) and the like. Examples of the carbonate ester compound having fluorine include 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 leakage and the like is enhanced. Also, the secondary battery can be made thinner and lighter. Representative examples of the gelled polymer material 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 the 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 sulfonic acid anions, tetrafluoroborate anions, perfluoroalkyl borate anions, hexafluorophosphate anions, or perfluoroalkyl phosphates anions, hexafluorophosphate anions, or perfluoroalkyl phosphates 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 can be used alone or in any combination and ratio of two or more of these.

[0160] The electrolyte used in the power storage device is preferably a highly purified electrolyte with a low content of particulate dust and elements other than the constituent elements of the electrolyte (hereinafter also simply referred to as " impurities"). Specifically, the weight ratio of impurities to the electrolyte 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. Also, 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 using a solid electrolyte, it is not necessary to install 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 made of polyolefin, polyurethane, etc. can be used. The separator is preferably processed into a bag shape and arranged to wrap either the positive or 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),

[0168] Coating with a ceramic-based material improves oxidation resistance, suppresses deterioration of the separator during high-voltage charge and discharge, and can improve the reliability of the secondary battery. Also, coating with a fluorine-based material makes it easier for the separator and the electrode to adhere, and can improve the output characteristics.

[0169] For example, a mixed material of aluminum oxide and aramid can be coated on both sides of a polypropylene film. Also, a mixed material of aluminum oxide and aramid can be coated on the surface of the polypropylene film

[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 for the secondary battery described in this embodiment can refer to the descriptions of the previous embodiment.

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

[0173] The coin-type secondary battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal, 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-type 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 (e.g., stainless steel etc.) can be used. Further, in order to prevent corrosion by the electrolytic solution, it is preferable to coat 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 The electrode can 302 are stacked 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.

[0177] By using the positive electrode active material particles 100 described in the previous embodiment for the positive electrode 304, deterioration is reduced, and a coin-type secondary battery 300 with high safety can be obtained.

[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 has a positive electrode cap (battery lid) 601 on the upper surface and a battery can as shown in the cross-sectional schematic diagram of FIG. 6(B), and has a battery can (outer can) 602 on the side surface and the bottom surface. 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 in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 6 05 interposed therebetween is provided. Although not shown, the battery element is wound around a center pin The battery can 602 has one end closed and the other end open. 。The battery can 602 can be made of metals such as nickel, aluminum, and titanium that are corrosion-resistant to the electrolytic solution , 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 electrolytic solution, it is preferable to coat with nickel, aluminum, etc. Inside the battery can 602, the battery element formed by winding the positive electrode, negative electrode, and separator is sandwiched between a pair of opposing insulating plates 608 and 609. Moreover, the inside of the battery can 602 where the battery element is provided is filled with a non-aqueous electrolytic solution (not shown). As the non-aqueous electrolytic solution, the same one as that used in a coin-type secondary battery can be used.

[0180] Since the positive and negative electrodes 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 sensing 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] Further, as shown in FIG. 6(C), a plurality of secondary batteries 600 may be sandwiched between a conductive plate 613 and a conductive plate 614 to form a module 615. The plurality of secondary batteries 600 may be connected in parallel, may be connected in series, or may be further connected in series after being connected in parallel. By forming the module 615 having the plurality of secondary batteries 600, large amounts of power can be extracted. FIG. 6(D) is a top view of the module 615. For clarity, the conductive plate 613 is shown by a dotted line. As shown in FIG. 6(D), the module 615 may have a conducting wire 616 that electrically connects the plurality of secondary batteries 600. The conductive plate 613 can be superimposed on the conducting wire 616. Further, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 overheats, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Therefore, the performance of the module 615 is less affected by the outside air temperature. By using the positive electrode active material particles 100 described in the previous embodiment for the positive electrode 604, a cylindrical secondary battery 600 with less deterioration and high safety can be obtained.

[0182]

[0183]

[0184] [Structural Example of Power Storage Device] Another structural example of the power storage device will be described with reference to FIGS. 7 to 11.

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

[0186] The circuit board 900 has 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 or the like.

[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 or other antennas 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 an electromagnetic field and a magnetic field but also by an electric field.

[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 antennas 914 and 915 and the secondary battery 913. The layer 916 has, for example, a function of shielding the electromagnetic field generated by the secondary battery 913. Layer 9 As , 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 pair of surfaces, and FIG. 8(A-2) is an external view of the other side of the 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. 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 the layer 917, for example, a magnetic material can be used. can be used.

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

[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 pair of surfaces, and FIG. 8(B-2) is an external view of the other side of the pair of surfaces. Note that for the same parts as the power storage device shown in FIGS. 7(A) and 7(B), Regarding the minutes, the description of the power storage device shown in FIGS. 7(A) and 7(B) can be appropriately cited as needed.

[0195] As shown in FIG. 8(B-1), an antenna 914 and an antenna 915 are provided with a layer 916 sandwiched between one of the pair of surfaces of the secondary battery 913. As shown in FIG. 8(B-2), an antenna 918 is provided with a layer 917 sandwiched between the other of the pair of surfaces of the secondary battery 913. The antenna 918 has a function capable of performing data communication with an external device, for example. For the antenna 918 , an antenna having a shape applicable to the antennas 914 and 915, for example, can be applied. As a communication method between the power storage device and another device via the antenna 918, a response method that can be used between the power storage device and another device, such as NFC, can be applied.

[0196]

[0197]

[0198] Alternatively, as shown in FIG. 9(A), a display device 920 may be provided on the secondary battery 913 shown in FIGS. 7(A) and 7(B). The display device 920 is electrically connected to the terminal 911 via the terminal 919. Note that a label 910 does not have to be provided at the portion where the display device 920 is provided. For the same portions 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)

[0197] and 7(B) can be appropriately cited as needed.

[0198] The display device 920 may display, for example, an image indicating whether charging is in progress, an image indicating the power storage amount, and the like. As the display device 920, for example, an electronic paper, a liquid crystal display device, an electroluminescence (also referred to as EL) display device, or the like can be used. For example, by using an electronic paper, the power consumption of the display device 920 can be reduced.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 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. As the sensor 921, for example, it may have a function 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. Furthermore, a structural example of the secondary battery 913 will be described with reference to FIGS. 10 and 11.

[0199] 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.

[0200]

[0201]

[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 the 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. Note that if the shielding of the electric field by the housing 930a is small, an antenna such as an antenna 914 or 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 multi-layered.

[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. La If the laminated secondary battery has a flexible configuration, when it is mounted on an electronic device having at least a part of a flexible portion, the secondary battery can also be bent in accordance with the deformation of the electronic device. It can be done.

[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, and the negative electrode 994 and the positive electrode 995 overlap with each other with the separator 996 interposed therebetween and are laminated, and the laminated sheet is wound. It is a wound-up product.

[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 element volume. The negative electrode 994 is connected to a negative electrode current collector (not shown) via one of the lead electrodes 997 and the lead electrode 998, and the positive electrode 995 is connected to a positive electrode current collector (not shown) via 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 98 2 having a concave portion, whereby the secondary battery 980 can be manufactured as shown in FIG. 12(C). The wound body 99 3 has lead electrodes 997 and 998, and the inside of the space surrounded by the film 981 and the film 98 2 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 using two films, but a space may be formed by bending one film, and the above-described winding body 993 may be stored 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, 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.

[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 so as to be exposed to the outside from the exterior body 509. Alternatively, the positive electrode current collector 501 and the negative electrode current collector 504 may not be exposed to the outside from the exterior body 509, and 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.

[0217] In the laminated secondary battery 500, the exterior body 509 is provided with a flexible metal thin film made of a material such as polyethylene, poly propylene, polycarbonate, ionomer, polyamide, etc. on a film, and 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 on the metal thin film. A three-layer laminated film can be used.

[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.

[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. In Fig. 13(B), the negative electrode current collector 504 has 8 layers, and ​​​​​​The positive current collector 501 shows 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 ultrasonic bonding is performed on the 8-layer negative current collector 504. Of course , the number of electrode layers is not limited to 16, and it 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 laminated secondary battery 500 is shown in Figs. 14 and 15. Fig. 1 4 and Fig. 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 current collector 50 1, and the positive electrode active material layer 502 is formed on the surface of the positive current collector 501. Also, the positive electrode 503 has a region where the positive current collector 501 is partially exposed (hereinafter referred to as the tab region). The negative electrode 506 has a negative current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative current collector 504 . Also, the negative electrode 506 has a region where the negative current collector 504 is partially exposed, that is, the 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 laminated secondary battery] Here, an example of the manufacturing method of the laminated secondary battery whose external view is shown in Fig. 14 will be described with reference to Figs. 16 (B) and Fig. 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 negative electrode 506, separator 507, and positive electrode 503 are shown. Here, an example is shown in which five negative electrodes and four positive electrodes are used. 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 introduced 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.

[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 cutting lines C1-C2, C3-C4, and 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 enclosed.

[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 stacking 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.

[0231] As shown in FIG. 18(A), the battery 250 has a plurality of strip-shaped positive electrodes 211a, a plurality of strip-shaped negative electrodes 211b, and a plurality of separators 214. The positive 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 materials of the negative electrode 211b ​​​​The positive electrode 211a and the negative electrode 211b are laminated so that the surfaces without the formation of the quality layer are in contact with each other. They are laminated.

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

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

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

[0236] The exterior body 251 has a film-like shape and is bent into two parts 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 with the lead 212a and the lead 212b and can also be called a top seal. The exterior body 251 has a film-like shape and is bent into two parts 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 with the lead 212a and the lead 212b and can also be called a top seal. The exterior body 251 has a film-like shape and is bent into two parts 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 with the lead 212a and the lead 212b and can also be called a top seal. The exterior body 251 has a film-like shape and is bent into two parts 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 with the lead 212a and the lead 212b and can also be called a top seal. The exterior body 251 has a film-like shape and is bent into two parts 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 with the lead 212a and the lead 212b and can also be called a top seal. They are laminated.

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

[0238] FIG. 17(B1) is a cross section taken along a portion overlapping the ridge line 271, and FIG. 17(B2) is a cross section taken along a portion overlapping the valley line 272. FIGS. 17(B1) and 17(B2) both correspond to the 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 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 outer package 251 and the positive electrode 211a and the negative electrode 211b will strongly rub against each other, and the outer package 251 may be damaged. In particular, when the metal film of the outer package 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 thickness t , the distance La is preferably 0.8 times or more and 3.0 times or less, preferably 0.9 times or more and 2.

[0241] 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.

[0244] In other words, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following mathematical 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 a 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 ends 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 a cross-section taken along 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 the bending is relaxed, so that the material itself constituting the exterior body 251 does not need to expand and contract. As a result, the battery 250 can be bent with a small force without the exterior body 251 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 closer to the bent part 261. As a result, 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 inside can be relatively displaced without contacting the exterior body 25. 1.

[0252] The battery 250 illustrated in FIGS. 17 and 18 is less likely to suffer damage to the exterior body, damage to the positive electrode 211a and the negative electrode 211b, etc., and the battery characteristics are also less likely to deteriorate even when repeatedly bent and stretched. It is a battery. By using the positive electrode active material particles 100 described in the previous embodiment for the positive electrode 211a included in the battery 250, it is possible to further reduce deterioration and obtain a secondary battery with high safety.

[0253] (Embodiment 4) In this embodiment, an example of mounting a secondary battery, which is an aspect of the present invention, on an electronic device will be described.

[0254] First, an example of mounting a bendable secondary battery, which was partially described in Embodiment 3, on an electronic device 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, large game machines such as pachinko machines, etc.

[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 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 has a housing 7401. In addition to the display unit 7402 incorporated therein, there are an operation button 7403, an external connection port 7404, a speaker 7405, a microphone 7406, etc. Note that the mobile phone 7400 has a secondary battery 7407. 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. Also, the state of the bent secondary battery 7407 at that time is shown in FIG. 19(C).

[0257] FIG. 19(B) shows a state where the mobile phone 7400 is bent. 0 is deformed by an external force and bent as a whole, the secondary battery 7407 provided inside it is also bent. The secondary battery 7407 is a thin secondary battery. The secondary battery 7407 is fixed in a bent state. Note that the secondary battery 7407 has a lead electrode electrically connected to a current collector.

[0258] FIG. 19(D) shows an example of a bangle-type display device. The portable display device 7100 includes a housing 7101, a display unit 7102, an operation button 7103, and a secondary battery 7104. Also, FIG. 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. Note that the degree of bending at any point on the curve represented by the value of the radius of the corresponding circle is called the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, part or all of the main surface of the housing or the secondary battery 7104 changes within a range where the radius of curvature is 40 mm or more and 150 mm or less. If the radius of curvature on 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] FIG. 19(F) shows an example of a wristwatch-type portable information terminal. , 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 has its display surface provided in a curved shape, 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 displayed on the display unit 7202, an application can be launched. 07, 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 operating system incorporated in the portable information terminal 7200 can also freely set the functions of the operation button 7205. It can also be freely set.

[0263] In addition, the portable information terminal 7200 can execute communication-standardized 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 make a call hands-free.

[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. Also, charging can be performed via the input / output terminals 7206. It can also be charged 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. This is also acceptable.

[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, and acceleration sensors. 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. In addition, 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.

[0268] The display surface of the display unit 7304 is curved, and display can be performed along the curved display surface. In addition, the display device 7300 can change the display state by means of short-range wireless communication conforming to a communication standard or the like.

[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. It can also be charged via the input / output terminals. Note that the charging operation can be performed by wireless power supply without going through the input / output terminals.

[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 unit 9 631, a display mode switch 9626, a power switch 9627, a power saving mode switch 9625, a fastener 9629, and an operation switch 9628. The display unit 9 631 can have a wider display area by using a flexible panel, thereby 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] In addition, the tablet terminal 9600 has a power storage unit 9635 inside the housing 9630a and the housing 9630b. The power storage unit 9635 passes through the movable part 9640 and is provided across the housing 9630a and the housing 9630b.

[0272] Part of the display unit 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 switch button of the touch panel is displayed with a finger or a stylus, etc., the keyboard buttons can be displayed on the display unit 9631.

[0273] The display mode switch 9626 can select switching of the display orientation such as portrait or landscape, switching between black and white display and color display, etc. The power saving mode 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 gyroscopes and acceleration sensors.

[0274] Figure 20(B) shows the 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 an aspect of the present invention is used.

[0275] Since the tablet-type terminal 9600 is foldable in two, when not in use, the housing 9630a and the housing 9630b can be folded so as to overlap each other. By folding, the display unit 9631 can be protected, thus enhancing the durability of the tablet-type terminal 9600. Also, since the power storage body 9635 using the secondary battery according to an aspect of the present invention has a high capacity and good cycle characteristics, 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 terminals shown in FIGS. 20(A) and 20(B) also have functions such as displaying various information (such as still images, moving images, text images, etc.), displaying a calendar, date, or 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, display unit, or 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, the configuration and operation of the charge / discharge control circuit 9634 shown in Fig. 20(B) will be described with reference to the block diagram in Fig. 20( C). Fig. 20(C) shows the solar cell 9633, the power storage body 963 5, the DCDC converter 9636, the converter 9637, the switches SW1 to SW3, and the 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 in 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 obtain 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 is used to step 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 piezoelectric elements (piezoelectric elements) and thermoelectric conversion elements (Peltier elements). 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.

[0280] Note that the solar cell 9633 is shown as an example of the power generation means, but it is not particularly limited, and the power storage body 9635 can be charged by other power generation means such as piezoelectric elements (piezoelectric elements) and thermoelectric conversion elements (Peltier elements). For example, a configuration that charges by wirelessly (non-contact) transmitting and receiving power, or a configuration that combines other charging means can be used. body 9635 may be charged by other power generation means such as piezoelectric elements (piezoelectric elements) and thermoelectric conversion elements (Peltier elements). 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. 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. 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.​ may also be used.

[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 may be provided with a light-emitting device having a light-emitting element such as a liquid crystal display device, an organic EL element, etc. for 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 to being used for receiving TV broadcasts, the display device includes all display devices for information display, such as those for personal computers and advertising displays. 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 those 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, a 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 the ceiling 8104 on which the housing 81 01 and the 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 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

[0285] In FIG. 21, an example of a lighting device 8100 of the installed type provided on the ceiling 8104 is illustrated. However, the secondary battery according to one aspect of the present invention can be used not only on the ceiling 8104 but also on, for example, the side wall 8105, the floor 8 106, the window 8107, etc. for an installed type lighting device provided thereon, or can be used for a desktop type lighting device or the like

[0286]

[0287] 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 the secondary battery 8203 according to one aspect of the present invention can be used as an uninterruptible power supply, enabling the use of the air conditioner to be possible.

[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 one aspect of the present invention can also be used in 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 one aspect of the present invention. Specifically, the electric refrigerator 8300 has a housing 8301, a door 8302 for the storage compartment, a door 8303 for the freezer compartment, 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. Thus, even when power supply from the commercial power source cannot be received due to a power outage or the like the secondary battery 8304 according to one aspect of the present invention can be used as an uninterruptible power supply, enabling the use of the electric refrigerator 8300 to be possible.

[0290] ​​​In addition, during periods when electronic devices are not in use, especially during periods when the total amount of power that can be supplied by commercial power suppliers is low, During times when the ratio of electricity actually used (called the electricity usage rate) is low, By storing power in the battery, it is possible to prevent high power usage outside of the above time periods. For example, in the case of the electric refrigerator-freezer 8300, when the temperature is low, the refrigerator compartment door 830 2. During the night when the freezer door 8303 is not opened or closed, the secondary battery 8304 stores electricity. Then, as the temperature rises, the refrigerator door 8302 and the freezer door 8303 are opened and closed. During the daytime, when the vehicle is turned on, the secondary battery 8304 is used as an auxiliary power source, and the daytime power usage rate is 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 on various electronic devices. According to one embodiment of the present invention, a secondary battery which is less deteriorated and highly safe 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, By doing so, it is possible to provide an electronic device with a longer life and higher safety. The 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), electric vehicle (EV), or powertrain. This will make it possible to realize next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). .

[0294] FIG. 22 illustrates 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. Further, the motor vehicle 8400 has a secondary battery. The secondary battery can not only drive the electric motor 8406, but also supply power to a light-emitting device such as a headlight 8401 and a rear light (not shown).

[0295] In addition, the secondary battery can supply power to display devices such as a speedometer and a tachometer that the motor vehicle 8400 has. Further, the secondary battery can supply power to semiconductor devices such as a 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 an external charging facility by a plug-in method, a non-contact power supply method, or the like, to the secondary battery 8024 that the motor vehicle 8500 has. Fig. 22(B) shows a state in which charging is being performed from a ground-mounted charging device 8021 to the secondary battery 8024 mounted on the motor vehicle 8500 via a cable 8022. At the time of charging, standards such as CHAdeMO (registered trademark) and Combo may 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] Further, although not shown, a power receiving device can be mounted on a vehicle, and power can be supplied non - contact from a power transmission device on the ground for charging. In the case of this non - contact power supply method, by incorporating the power transmission 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. Further, a solar cell can be provided on the exterior 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. 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

[0298] light 8603. The secondary battery 8602 can supply electricity to the direction indicator light 8603. (C) can store the secondary battery 860 2. The secondary battery 8602 can be stored in the under - seat storage 8604 even if the under - seat storage 8604 is small.

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

[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, it is possible to avoid using a commercial power supply during peak power demand. Using a commercial power supply during peak power demand ​​​​ If it can be avoided, it can contribute to energy conservation and reduction of carbon dioxide emissions. . In addition, since a secondary battery with less deterioration and high safety can be used for a long time, the amount of rare metals such as cobalt can be reduced.

[0301] This embodiment can be implemented in appropriate combination with other embodiments.

Example

[0302] In this example, cathode active material particles having magnesium, fluorine, and oxygen at grain boundaries and in the vicinity thereof were prepared, and the concentration distributions of grains and grain boundaries in the active material were confirmed by TEM observation and STEM-EDX analysis. The sample is one sample of Sample A which is one aspect of the present invention. As Sample A, lithium nickel manganese cobalt oxide having magnesium, fluorine, and oxygen at grain boundaries and in the vicinity thereof was prepared. The composition of lithium nickel manganese cobalt oxide was assumed to be LiNi Mn Co O2. LiNi Mn 3Co 1 / 3 Mn 1 / 3 Co 1 / 3 O2 has a layered rock salt-type crystal structure. 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 of FIG. 3, starting materials were prepared. Lithium carbonate (Li2CO3) as a lithium source, nickel oxide (NiO) as a nickel source, manganese dioxide (MnO2) as a manganese source, and cobalt tetroxide (Co3O4) as a cobalt source were used. As a manganese source, manganese dioxide (MnO2), and as a cobalt source, cobalt tetroxide (Co3O4). 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 Li2CO3 manufactured by High Purity Chemical Research Institute (Catalog number: LIH06XB) was used. NiO manufactured by High Purity Chemical Research Institute ( Catalog number: NIO04PB) was used. MnO2 manufactured by High Purity Chemical Research Institute (Catalog number: MNO03PB) was used. Co3O4 manufactured by High Purity Chemical Research Institute (Catalog number: COO09PB) was used. MgO manufactured by High Purity Chemical Research Institute (Catalog number: MGO12 PB) was used. LiF manufactured by High Purity Chemical Research Institute (Catalog number: LIH10XB) was used. COO09PB) was used. MgO manufactured by High Purity Chemical Research Institute (Catalog number: MGO12 PB) was used. LiF manufactured by High Purity Chemical Research Institute (Catalog number: LIH10XB) was used. 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

[0305] were used, and pulverization and mixing were performed at a rotational speed of 300 rpm for 2 hours. 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 at a heating rate of 200 °C / hr from room temperature to 1000

[0306] °C. °C. The temperature was raised to 1000 °C and heated at 1000 °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, part of the magnesium and fluorine is considered to be in a state of solid solution 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 Composition 1. After cooling, the obtained Composition 1 was crushed to reduce the particle size of Composition 1. A 53-μm mesh was used for the crushing process.

[0309] Next, as shown in step S15, a second heating was performed on Composition 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 800 °C and heated at 800 °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 Composition 1 heated in step S15 was cooled to room temperature and recovered to obtain Sample A.

[0312] <TEM Observation, STEM Observation, EDX Measurement> Next, Sample A was processed by a focused ion beam (FIB). ​​​​​​​​Thinned, 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 nm φ .

[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 to be a single crystal. Also, the region where the density (brightness) of the TEM image changes is considered to be 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 crystal 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 The energy and frequency of the characteristic X-rays generated are measured, and the EDX scan is performed. The HAADF-STEM image and EDX measurement points of the cross section of sample A are shown in Figure 25. The EDX measurement points are five points, point 1 to point 5. Point 4 is the grain boundary and its vicinity, and point 1 and point 5 are the grain boundary and its vicinity. The EDX spectrum and quantitative results for point 1 were taken at a position away from the crystal grain, i.e., inside the grain. Figure 26, point 2 in Figure 27, point 3 in Figure 28, point 4 in Figure 29, poi nt5 is shown in FIG. 30. In FIG. 26 to FIG. 30, the horizontal axis represents the characteristic X-ray energy (Ene The vertical axis indicates the characteristic X-ray intensity [Counts].

[0317] At points 1 to 5, carbon (C), oxygen (O), fluorine (F), magnesium Magnesium (Mg), Silicon (Si), Phosphorus (P), Sulfur (S), Calcium (Ca), Manganese (Mn), cobalt (Co), and nickel (Ni) electron transitions to their respective K shells The spectrum obtained was separated into the individual elements, and the atomic concentrations were calculated. I got a degree.

[0318] Next, we will explain EDX area analysis. The area is scanned and measured, and the area is analyzed in two dimensions. In this embodiment, the EDX measurement is performed on the area It was done using 256 vertical x 256 horizontal points.

[0319] FIG. 31(A) shows an HAADF-STEM image of the area of ​​sample A where EDX area analysis was performed. The EDX area analysis was performed on the region including the 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 intensities by EDX measurement. The measurement points with low characteristic X-ray intensities are shown in light color (white), and the measurement points with higher characteristic X-ray intensities are shown in darker color (black). That is, the light-colored (white) measurement points indicate low atomic concentrations, and the dark-colored (black) measurement points indicate high atomic concentrations. 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 . 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 was performed is indicated by an arrow. The line segment 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 indicates that the distance increases towards 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 mentioned above includes carbon due to 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 manganese, cobalt, and nickel, which are transition metals, are lower in the grain boundaries and their vicinity.

[0332] The total atomic concentrations of nickel, manganese, and cobalt, which are transition metals, are shown in Fig. 35(F). In Fig. 35(F), the horizontal axis represents the distance [nm], and the vertical axis represents 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 grain boundaries and their vicinity tend to have a lower atomic concentration of transition metals compared to the matrix. Also, in the region of the grains, it was found that there is no significant variation in the atomic concentration of the transition metal and it is substantially uniform.

[0333] The ratio of the atomic concentration of magnesium (Mg) to the atomic concentration of the transition metal 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 the transition metal in the grains ( Mg / Tr-Metal) (arb. unit).

[0334] The atomic concentration of the transition metal (Tr-Metal) in the grains will be described. As the atomic concentration of the transition metal (Tr-Metal) in the grains, the average value of the atomic concentration of the transition metal 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 region of the grains, and the average value of the atomic concentration of the transition metal in that region was calculated. The region of the grains 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 the transition metal 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, whereby the cathode active material particles become chemically and structurally stable, and the transition metal elutes 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. Further, 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. Further, 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 that 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. 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 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 the present 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 during charging decreases, so that 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. It is possible to suppress deterioration of the positive electrode active material, such as detachment and instability of the crystal structure. Further, 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. Further, 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 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 the present 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), 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 the present 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. In the present 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.

[0338] In the present 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 the present 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 the present 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 the present 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 the present 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] 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. 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] The total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) for each EDX measurement location 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] The ratio of the atomic concentration of fluorine to the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) for each EDX measurement location 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 a higher atomic concentration of transition metals in the grains The ratio of fluorine atom concentration to the concentration (F / (Ni+Mn+Co)) is 0.030 or more. It was found that the grain boundary and its vicinity have fluorine, which It was found that magnesium can be efficiently segregated in and around the area.

[0344] Similarly, EDX measurement was performed on another portion of sample A.

[0345] FIG. 37(A) shows an HAADF-STEM image of the area of ​​sample A where EDX area analysis was performed. The EDX area analysis was performed on the region including the grains and grain boundaries. In the EDX area analysis, the carbon mapping image is shown in FIG. 37(B), the oxygen mapping image is shown in FIG. 37(C), Fluorine in Fig. 37(D), magnesium in Fig. 37(E), silicon in Fig. 37(F), phosphorus in Fig. Figure 38(A), sulfur in Figure 38(B), calcium in Figure 38(C), manganese in Figure 38(D ), cobalt is shown in Figure 38(E), and nickel is shown in Figure 38(F).

[0346] 37(B) to 37(F) and 38(A) to 38(F) show characteristics measured by EDX. The map shows the characteristic X-ray intensity, with measurement points with low characteristic X-ray intensity shown in light color (white) and The measurement points with higher X-ray intensity are shown in darker (black) colors. In other words, the measurement points with lighter (white) colors are The dark (black) measurement points indicate a high atomic concentration, while the low atomic concentration points indicate a low atomic concentration. 7(B) to 37(F) and 38(A) to 38(F) show the distribution within the region. As shown in Fig. 1, the scale of the characteristic X-ray intensity is changed for each element.

[0347] As shown in Figures 37(B) to 37(F) and Figures 38(A) to 38(F), At and near the site, there are high concentrations of fluorine, magnesium, silicon and calcium. This was confirmed. Silicon and calcium were considered to be included in the reagents used as raw materials.

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

[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).

[0351] In FIGS. 39(A) to 39(F) and FIGS. 40(A) to 40(E), the horizontal axis indicates the distance [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 shows an increase in distance towards 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 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. 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. Also, it is considered that some of the oxygen in magnesium oxide is replaced by fluorine.

[0353] On the other hand, in the grain region, fluorine, magnesium, silicon, and calcium were at the detection lower limit level. Phosphorus and sulfur were at the detection lower limit level both in the grain and the grain boundary. 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.

[0354] It was confirmed that the atomic concentration of manganese, cobalt, and nickel, which are transition metals, is lower in the grain boundary and its vicinity compared to the grain.

[0355]

[0356] The total atomic concentration of nickel, manganese, and cobalt, which are transition metals, is shown in FIG. 40(F).

[0357] It was confirmed that the atomic concentration of manganese, cobalt, and nickel, which are transition metals, is lower in the grain boundary and its vicinity compared to 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 atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) [atomic%]. In sample A, the total atomic concentration 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 have a tendency to have a lower atomic concentration of transition metals compared to the grain region. In addition, 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. The grain boundaries and their vicinity are considered to 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. In addition, the cracking of the positive electrode active material particles can be suppressed. Further, 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). is shown.

[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 unit 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 unit is shown.

[0365] 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. 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 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. 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 location. 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 location.

[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 can be seen that adding magnesium and fluorine as starting materials for the positive electrode active material particles It has been clarified 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. By having this, 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 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 can be suppressed. That is, deterioration such as a decrease in capacity can be suppressed. Since the power storage device having such positive electrode active material particles has little deterioration, it 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, and it can contribute to energy saving and reduction of carbon dioxide emissions. In addition, it becomes a highly safe power storage device.

[0370]

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 crystal grains and crystal 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. 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. 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). 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.

[0374] 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.

[0375]

[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 composite 2 obtained in step S14. Details of the second heating can be referred to the description of sample A, so 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 composite 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 a 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. Details of TEM, STEM observation and EDX measurement can be referred to the description of sample A, 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 at 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), a crystal lattice image could be confirmed in the grain region.

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

[0384] Peaks derived from the electron transitions to the K shells 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 mapping image of carbon in the surface analysis of EDX in 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 44(F), Figs. 45(A) to 45(D) show the mapping of the 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-colored (white) measurement points indicate low atomic concentration, and the dark-colored (black) measurement points indicate high atomic concentration. Note that Figs. 4 4(B) to 44(F), Figs. 45(A) to 45(D) change the scale of the characteristic X-ray intensity for each element so that the distribution in 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 the vicinity thereof. 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 for.

[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 ​​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 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 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. 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. On the other hand, in the grain regions, fluorine, magnesium, silicon, and calcium were at the detection lower limit level. Phosphorus and sulfur were also at the detection lower limit level both in the grains and at the grain boundaries.

[0393] Although carbon was detected in the grains and at 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 due to the carbon coating film. Therefore, the true carbon concentration of the grains and the grain boundaries could not be determined. It was confirmed that the concentration of cobalt, which is a transition metal, is lower at the grain boundaries and in the vicinity thereof compared to the grains.

[0394]

[0395]

[0396]

[0397]

[0398] ​​​​​​​​In Sample B, the atomic concentration of cobalt can also be said to be the atomic concentration of transition metals. Fig. 48(C) As shown in , compared with the region of crystal grains, it was found that the atomic concentration of transition metals in the grain boundaries and their vicinity tends to be low. Also, in the region of crystal grains, it was found that there is no significant variation in the atomic concentration of transition metals and it is substantially uniform.

[0399] The ratio of the atomic concentration of magnesium (Mg) to the atomic concentration of transition metals in the crystal grains is shown in Fig. 49(A). In Fig. 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 crystal grains ( Mg / Tr-Metal).

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

[0401] As shown in Fig. 49(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 crystal 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 B, which is one aspect of the present invention, has magnesium oxide at the grain boundaries and their vicinity, by which 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 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 the charging voltage is increased, the amount of lithium contained in the positive electrode decreases during charging, making the crystal structure of the positive electrode active material particles more likely to transform. Therefore, as the positive electrode 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 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.

[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 (F) 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 ) for the EDX surface analysis of the region shown in Fig. 50(A) are shown.

[0409] Figs. 50(B) to 50(F), 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 intensities are shown in light color (white), and the measurement points with higher characteristic X-ray intensities are shown in darker color (black). That is, the light-colored (white) measurement points indicate low atomic concentrations, and the dark-colored (black) measurement points indicate high atomic concentrations. Note that Figs. 5 0(B) to 50(F), 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), data of linear regions were extracted, and the distribution of atomic concentration in 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 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 ​​​​(The end point) is shown such that the distance increases. 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 their vicinity compared to the grain regions. 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.

[0416] It was confirmed that the grain boundaries and their vicinity contain oxygen and magnesium. It was found that the grain boundaries and their vicinity 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 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 their vicinity 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 Fig 54(A). In Fig 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 Fig 53(D) .

[0424] As shown in Fig 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 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. Further, desorption of oxygen from the positive electrode 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 concentration at the crystal grains and grain boundaries was 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: Empty space, 300: Secondary battery, 301: Positive electrode can, 302: Negative electrode can, 303: Gasket, 304 : Positive electrode, 305: Positive electrode current collector, 306: Positive electrode active material layer, 307: Negative electrode, 308: Negative electrode current collector 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: Lead 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 device, 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, 8104: 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: Housing 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. 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 grains and the second crystal grains have lithium, a transition metal, and oxygen; the grain boundaries include magnesium and oxygen; the grain boundary has a region having a higher magnesium concentration than the first crystal grains and the second crystal grains.

2. In claim 1, The positive electrode active material particles have a ratio of the atomic concentration of the magnesium to the atomic concentration of the transition metal in a range of 0.010 or more and 0.50 or less.

3. In claim 1 or 2, the grain boundary further comprises fluorine; the grain boundary has a region having a higher fluorine concentration than the first crystal grains and the second crystal grains.

4. In claim 3, The positive electrode active material particles have a ratio of the atomic concentration of the fluorine to the atomic concentration of the transition metal in a range of 0.020 or more and 1.00 or less.

5. In claim 1 or 2, The positive electrode active material particles contain, as the transition metal, one or more of iron, cobalt, nickel, manganese, chromium, titanium, vanadium, and niobium.

Images