Lithium-ion secondary battery

Abstract

To provide a positive electrode active material particle that deteriorates less, a power storage device with little deterioration, alternatively, a highly safe power storage device.SOLUTION: A positive electrode active material particle includes a first crystal grain, a second crystal grain, and a grain boundary located between the first crystal grain and the second crystal grain, the first crystal grain and the second crystal grain have lithium, a transition metal, and oxygen, the grain boundary has magnesium and oxygen, and the positive electrode active material particle has a region in which the ratio of the atomic concentration of magnesium at the 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. Alternatively, 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] 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] In addition, 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 widely used in portable information terminals such as mobile phones, smartphones, or notebook computers, portable music players, digital cameras, medical devices, or next-generation clean energy automobiles such as hybrid electric vehicles (HEV), electric vehicles ( EV), or plug-in hybrid electric vehicles (PHEV). Along with the development of the semiconductor industry, the demand for them has rapidly expanded, and rechargeable energy ​​​It has become an essential component in modern information society as a supply 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. Or, one aspect of the present invention is to provide novel cathode active material particles as one of the problems. Or, one aspect of the present invention is to provide a power storage device with less deterioration as one of the problems. 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 preclude the existence of other problems. Note that one aspect of the present invention does not necessarily need to solve all of these problems. Note that other problems can be extracted from the description of the specification, drawings, and claims.

Means for Solving the Problems

[0011] One aspect of the present invention has a first crystal grain, a second crystal grain, and a grain boundary located between the first crystal grain and the second crystal grain, 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 aforementioned positive electrode active material particles, it is preferable that the ratio of the atomic concentration of magnesium to the atomic concentration of the transition metal has a region of 0.010 or more and 0.50 or less.

[0013] In the aforementioned positive electrode active material particles, it is preferable that the grain boundary further contains fluorine.

[0014] In the aforementioned positive electrode active material particles, it is preferable that the ratio of the atomic concentration of fluorine to the atomic concentration of the transition metal has a region of 0.020 or more and 1.00 or less.

[0015] The aforementioned 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. Also, 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 those skilled in the art can easily understand that its form and details can be changed variously. Further, the present invention is not construed as being limited to the description of the embodiments shown below.

[0019] In each of the drawings described in this specification, the size, thickness, etc. of each component such as the positive electrode, negative electrode, active material layer, separator, and exterior body may be exaggerated for the sake of clarity of the description. Therefore, each component is not necessarily limited to its size, and the relative size between each component is not limited either.

[0020] In the configuration of the present invention described in this specification and the like, the same part or the part having the same function is commonly used with the same reference numeral among different drawings, and the repeated description thereof is omitted. In addition, when referring to parts having the same function, the hatching pattern is the same, and there may be cases where they are not particularly labeled.

[0021] In the notation of crystal planes and directions, in crystallography, a bar is attached 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. In addition, the individual orientation indicating the direction within the crystal is [ ], the set orientation indicating all equivalent directions is < >, the individual plane indicating the crystal plane is ( ), and the set plane having equivalent symmetry is {}, 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) where 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 103 shown in FIG. 1(B) are examples and are not limited thereto.

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

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

[0028] ​​ The crystal grains 101 and the grain boundaries 103 have different compositions. The crystal grains 101 contain lithium, a transition metal, and oxygen. The grain boundaries 103 contain magnesium and oxygen. Further, the grain boundaries 103 preferably contain fluorine.

[0029] The crystal grains 101 and the grain boundaries 103 can be confirmed to have different compositions by energy dispersive X-ray spectroscopy (EDX), time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS), etc. However, it is not always necessary to observe a clear boundary between the crystal grains 101 and the grain boundaries 103 by various analyses. Also, depending on the analysis method, etc., the desired analysis target element may not be detected. Or, even when the concentration of the analysis target element is extremely low, the analysis target element may not be detected.

[0030] <Grain Boundary> The grain boundaries 103 of the positive electrode active material particles 100, which is one aspect of the present invention, contain magnesium and oxygen. The grain boundaries 103 contain magnesium oxide. Further, the grain boundaries 103 preferably contain fluorine. Some of the oxygen contained in magnesium oxide is replaced by fluorine. It may be. By partially substituting magnesium oxide with fluorine, for example the diffusivity of lithium can be enhanced, and charge and discharge are not hindered. The grain boundary 103 has 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. The grain boundary 103 can also be said to have a region where magnesium is segregated.

[0032] Compared with the grain 101, the grain boundary 103 has a region with a high fluorine concentration. The grain boundary 1 03 can also be said to have a region where fluorine is segregated.

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

[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. of the atoms.

[0036] The positive electrode active material particle 100 preferably has a region where the ratio (Mg / Tr-Metal) of the number of atoms of magnesium in the crystal grain boundary 1 03 to the number of atoms of the transition metal in the crystal grain 101 is 0.010 or more and 0.50 or less. Further, the positive electrode active material particle 100 preferably has a region where Mg / Tr-Metal is 0.020 or more and 0.30 or less. Further moreover, the positive electrode active material particle 100 preferably has a region where Mg / Tr-Metal is 0.030 or more and 0.20 or less . By setting the above-mentioned Mg / Tr-Metal, the deterioration of the positive electrode active material can be reduced. That is, the deterioration of the power storage device can be suppressed. Also, a power storage device with high safety 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 l Union of Pure and Applied Chemistry). It is based on the periodic table classified into Groups 1 to 18 in the Revised Nomenclature of Inorganic Chemistry (1989) of the International Union of Pure and Applied Chemistry (IUPAC). It follows.

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

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

[0040] Due to the insertion and desorption of lithium accompanying charge and discharge, the crystal lattice of the positive electrode active material particles expands and contracts, and 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 active material particles may start from the crystal grain boundaries.

[0041] When the inside of the power storage device becomes hot and oxygen desorbs from the positive electrode active material particles, the safety of the power storage device may be compromised. 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.

[0042] On the other hand, magnesium oxide is a chemically and structurally stable material. In a power storage device such as a lithium-ion secondary battery, the magnesium oxide 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. ​ 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 a decrease in capacity can be suppressed, which is preferable. When the charge voltage is high and the amount of lithium present in the positive electrode during charging is smaller, the crystal structure becomes unstable and is more likely to deteriorate. Since the crystal structure of the positive electrode active material particles 100, which are one aspect of the present invention, is more stable, deterioration such as a decrease in capacity can be suppressed, which is particularly preferable.

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

[0045] Further, when the positive electrode active material particles 100, which are one aspect of the present invention, are cracked 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.

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

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

[0048] The positive electrode active material particles 100 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 grains 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, the deterioration of the positive electrode active material can be reduced. The deterioration of the power storage device can be suppressed. In addition, a highly safe power storage device can be obtained.

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

[0050] For example, the crystal grains 101 have 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 Materials having a crystal structure of the type, NASICON-type materials, and the like. Further, as the crystal grains 101 For example, a cathode material 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 the air, and relatively high thermal stability . Further, in addition to one or more selected from Co and Ni, the element M may have one or more selected from Al and Mn.

[0053] For example, LiNi x Mn y Co z O w (where x, y, z, and w are, for example, x = y = z = 1 / 3 or in the vicinity thereof, and 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, and 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 = 0.5 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 contained 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. As a material having a spinel-type crystal structure, for example, a composite oxide represented by LiM2O4 can be

[0056] used. It is preferable that M has Mn as an element. For example, LiMn2O ​4 can be used. Also, as the element M, by having Ni in addition to Mn, the discharge voltage of the secondary battery may be improved, and the energy density may be improved, which is preferable. Also, for a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4, a small amount of lithium nickelate (LiNiO2 or LiNi M 1-x M x O2 (M = Co, Al, etc.) ) is preferably mixed to improve the characteristics of the secondary battery.

[0057] The positive electrode active material preferably has an average particle diameter of primary particles of 1 nm or more and 100 μm or less, more preferably 50 nm or more and 50 μm or less, and even more preferably 1 μm or more and 30 μm or less. Also, the specific surface area is preferably 1 m / g or more and 20 m 2 / g or less. Also, the average particle diameter of the secondary particles is preferably 5 μm or more and 50 μm or less. 2 The average particle diameter can be measured by observation using a scanning electron microscope (SEM) or TEM, or by a particle size distribution meter using the laser diffraction / scattering method. Also, the specific surface area can be measured by the gas adsorption method. Note that the average particle diameter can be measured by observation using a scanning electron microscope (SEM: Scanning Elect ron Microscope) or TEM, or by a particle size distribution meter using the laser diffraction / scattering method. Also, the specific surface area can be measured by the gas adsorption method. It is also possible to provide a conductive material such as a carbon layer 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.

[0058] Also, as the conductive material, graphene, multi-graphene, graphene oxide, can be used. 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, 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 ( ​GO (Graphene Oxide) or RGO (Reduced Graphene Oxide) can be used. Here, RGO refers to, for example, a compound obtained by reducing graphene oxide (GO ).

[0059] A layer having one or more of an oxide or a fluoride 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. Further, 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, 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 , Fe(II), Mn(II), Co(II), Ni(II) one or more)) 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 Nid 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. It is possible.

[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 (M is one or more of Fe(II), Mn(II), Co(I I), Ni(II), 0 ≦ j ≦ 2), etc. can be used. The general formula Li (2-j) MSiO4 representative examples include Li (2-j) FeSiO4, Li (2- j) NiSiO4, Li (2-j) ​CoSiO4, Li (2-j) MnSiO4, Li ( 2-j) Fe k Ni l SiO4, Li (2-j) Fe k Co l SiO4, Li (2-j) Fe k Mn l SiO4, Li (2-j) Ni k Co l SiO4, Li (2-j) Ni k M n l SiO4 (k + l is 1 or less, 0 < k < 1, 0 < l < 1), Li (2-j) Fe m Ni n Co q SiO4, Li (2-j) Fe m Ni n Mn q SiO4, Li (2-j) Ni m Co n Mn q SiO4 (m + n + q is 1 or less, 0 < m < 1, 0 < n < 1, 0 < q < 1), Li (2-j) Fe r Ni s Co t Mn u SiO4 (r + s + t + u is 1 or less, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1), etc. 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) can be used with a NASICON-type compound represented by the general formula. Examples of the NASICON-type compound include 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] Furthermore, as the crystal grains 101, perovskite-type fluorides such as NaFeF3 and FeF3, metal chalcogenides (sulfides, selenides, tellurides) such as TiS2 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] Furthermore, 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] Furthermore, for example, a solid solution in which a plurality of composite oxides are combined can be used as the crystal grains 101. This is possible. LiM a O2 and Li2M b O3 solid solutions (M a , M b are each independently selected from one or more transition metals and 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] Furthermore, 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 the selected metal element, silicon, or phosphorus, and nickel is more preferable. When measuring the entire particle of the lithium manganese composite oxide, during discharge, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≦ (b + c) / d < 0.5. 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 portion and the central portion. To obtain such a lithium manganese composite oxide, for example, it is preferable to set 1.6 ≦ a ≦ 1.848, 0.19 ≦ c / b ≦ 0.935, and 2.5 ≦ d ≦ 3. Furthermore, it is particularly preferable to use a lithium manganese composite oxide represented by the composition formula LiMnNiO3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, 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, for example, using ICP-MS (inductively coupled plasma mass spectrometer). During discharge, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≦ (b + c) / d < 0.5. 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 portion and the central portion. To obtain such a lithium manganese composite oxide, for example, it is preferable to set 1.6 ≦ a ≦ 1.848, 0.19 ≦ c / b ≦ 0.935, and 2.5 ≦ d ≦ 3. In addition, the composition of metals, silicon, phosphorus, etc. in the entire particle of the lithium manganese composite oxide can be measured, for example, using ICP-MS (inductively coupled plasma mass spectrometer). 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. 1.68 Mn 0.8062 Ni 0.318 O3 of the lithium manganese composite oxide. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. 1. 68 Mn 0.8062 Ni 0.318 O3 of the lithium manganese composite oxide. In this specification, etc., the lithium manganese composite oxide represented by the composition formula LiMnNiO3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of raw materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. 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. Therefore, the lithium manganese composite oxide is represented by the composition formula LiMnNiO3, but may deviate from this composition. 1.68 Mn 0.80 62 Ni 0.318 O3, but may deviate from this composition.

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

[0071] 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 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, a lithium-containing metal sulfide can be used as the positive electrode active material. 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 decomposition products 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 decomposition products 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 it 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) at a cumulative 50% on a volume basis.

[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. can be used.

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

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

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

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

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

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

[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 oxysulfate, 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] Also, when the crystal grains 101 have a metal other than the transition metal in addition to the transition metal (M), weigh the metal source other than the transition metal. When having aluminum as the metal other than the transition metal , for example, an aluminum compound can be used as the metal source. As the aluminum compound , one or more of aluminum oxide, aluminum hydroxide, aluminum carbonate, aluminum chloride, , aluminum iodide, aluminum sulfate, aluminum nitrate, etc. can be used. This is possible. This is possible.

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

[0096]

[0097] The vicinity means, for example, a value greater than 0.9 times and less than 1.1 times that value.

[0097] ​The ratio of the number of magnesium atoms in the raw material to the number of fluorine atoms is explained below. The ratio n of the number of fluorine atoms F(r) to the number Mg(r) is 1.50 or more and 4.0 or less. The number of magnesium atoms Mg(r) is the number of fluorine atoms F(r) = 1.0: n is 1 It is preferable that n is 50≦n≦4.0. Furthermore, the ratio of fluorine atoms to the number of magnesium atoms is 50≦n≦4.0. The ratio of the numbers, n, is 2.0 or close to 2.0, that is, the number of magnesium atoms, Mg(r): the number of fluorine atoms. It is more preferable that the number of atoms F(r) is 1.0:2.0 or close to that. By setting the ratio to 103, magnesium and fluorine can be efficiently segregated to the grain boundary 103. can.

[0098] The atomic ratio of the raw material transition metal, magnesium and fluorine can be expressed by the following formula 1. Here, m is the ratio of the number of magnesium atoms, Mg(r), to the number of transition metal atoms, M(r). As mentioned above, 0.0050≦m≦0.050 is preferable, and m=0.0 n is the number of fluorine atoms relative to the number of magnesium atoms Mg(r), and is preferably about 10. As mentioned above, 1.50≦n≦4.0 is preferable, and more preferably, For this, n=2.0 or its vicinity is preferable.

[0099]

number

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

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

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

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

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

[0105] By the first heating in step S13, a composite oxide containing lithium and transition metal (M) in the crystal grains 101 can be synthesized. Also, by this first heating, a part of 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 remains in the lithium and transition metal (M). ​It is in a state of being dissolved in a composite oxide containing a metal (M).

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

[0107] Next, the material cooled in step S14 is subjected to a second heating (step S15). The second heating is preferably performed with a holding time at a specified temperature of 100 hours or less, more preferably 1 hour or more and 70 hours or less, even more preferably 2 hours or more and 50 hours or less, even 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 even 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 to 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 movement of atoms becomes easier during heat treatment.

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

[0115] For these reasons, by mixing a magnesium source and a fluorine source as starting materials, magnesium may tend to move more easily, and magnesium may tend to segregate to the grain boundary 103. In some cases, magnesium may tend to move more easily, and magnesium may tend to segregate to the grain boundary 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. 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. It is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less. It is more preferable.

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

[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. It can be. It can be. The tube can be manufactured, for example, by a vapor growth method or the like. Also, as a conductive aid, for example carbon materials such as carbon black (such as acetylene black (AB)), graphite (graphite) particles , graphene, fullerenes, etc. can be used. Also, for example, metal powders such as copper, nickel , aluminum, silver, gold, metal fibers, conductive ceramic materials, etc. can be used.

[0124] Also, a graphene compound may be used as a 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. Also, the graphene compound has a planar shape. The graphene compound enables surface contact with low contact resistance. Also, it may have very high conductivity even when thin, and can efficiently form a conductive path in the active material layer with a small amount. Therefore, using 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 O xide (hereinafter, RGO) is particularly preferably used. Here, RGO refers to a compound obtained by reducing, for example, 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. When the amount of the active material supported decreases, the capacity of the secondary battery decreases. In such a case, when a graphene compound is used as the conductive additive the graphene compound can efficiently form a conductive path even in a small amount, so that it is not necessary to reduce the amount of the active material supported, which is particularly preferable.

[0127] Hereinafter, as an example, a cross-sectional configuration example in the case where a graphene compound is used as the conductive 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. Further, 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), the sheet-like graphene compound 201 is 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 stick on the surfaces of a plurality of granular positive electrode active material particles 100, so that they are in surface contact with each other.

[0130] ​​​​​Here, when a plurality of graphene compounds are combined with 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 make point contact with the active material, the graphene compound 201 enables surface contact with low contact resistance. Therefore, 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 the polymers interact with each other and widely cover 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 function as a passivation film and suppress the decomposition of the electrolyte. Here, a passivation film is a film having no electrical conductivity or a film having 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. In addition, it is more desirable that the passivation film suppresses the electrical conductivity while allowing lithium ions to conduct. 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 while allowing lithium ions to conduct. and is more desirable.

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

[0142] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also 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, germa nium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. At least one of them can be used as a material. 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

[0145] x ​​​​​​It can also be expressed as follows. Here, x preferably has a value of 1 or in the vicinity thereof. For example, x is preferably 0.2 or more and 1.5 or less, more preferably 0.3 or more and 1.2 or less.

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

[0147] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include meso carbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. Here, as the artificial graphite, spherical graphite having a spherical shape can be used. For example, MCMB may have a spherical shape, which is preferable. Also, it is relatively easy to reduce the surface area of MCMB, which 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 graphite (when a lithium-graphite intercalation compound is formed). As a result, a 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, low cost, and high safety compared to lithium metal, and thus is preferable.

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

[0150] Also, as the negative electrode active material, Li3N-type structure, which is a complex nitride of lithium and transition metal, 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 complex nitride of lithium and transition metal, since lithium ions are contained in the negative electrode active material, it can be combined with materials such as V2O5 and Cr3O8 that do not contain lithium ions as the positive electrode active material, which is preferable. Even when using a material containing lithium ions as the positive electrode active material , by previously desorbing the lithium ions contained in the positive electrode active material, a complex nitride of lithium and transition metal can be used as the negative electrode active material .

[0152] Also, a material that undergoes 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 undergo a conversion reaction , further, oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3 , sulfides such as CoS 0.89 , NiS, and CuS, nitrides such as Zn3N2, Cu3N, and Ge3 N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3 can be mentioned​

[0153] The conductive assistant and binder that can be contained in the negative electrode active material layer are the same as those that can be contained in the positive electrode active material layer. The conductive additive and binder may be the same as those that can be used.

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

[0155] [Electrolyte] The electrolytic solution contains a solvent and an electrolyte. The solvent for the electrolytic solution is preferably an aprotic organic solvent. Preferable examples of the carbonate include ethylene carbonate (EC), propylene carbonate (PC), and Ethylene carbonate, chloroethylene carbonate, vinylene carbonate, gamma-butyro Lactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate DEC, Ethyl methyl carbonate (EMC), Methyl formate, Methyl acetate, Ethyl acetate ethyl, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethylsulfate phthalocyanine, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, One of tetrahydrofuran, sulfolane, sultone, etc., or two or more of these can be used in any combination and ratio.

[0156] In addition, a phosphate ester compound having fluorine, which is flame-retardant as a solvent for the electrolyte, or By using a fluorine-containing carbonate compound, it is possible to prevent explosion or fire of the storage device. Examples of fluorine-containing phosphate ester compounds include tris(2,2, 2-trifluoroethyl)phosphate (TFEP) and other fluorine-containing carbonates. Examples of ester compounds include bis(2,2,2-trifluoroethyl)carbonate. (TFEC), etc.

[0157] In addition, by using a polymer material that gels as a solvent for the electrolyte, the resistance to leakage, etc. Safety is improved. In addition, it is possible to make the secondary battery thinner and lighter. Representative examples of materials include silicone gel, acrylic gel, acrylonitrile gel, and poly Ethylene oxide gel, polypropylene oxide gel, fluorine polymer gel etc.

[0158] In addition, a flame-retardant and non-volatile ionic liquid (room-temperature molten salt) is used as the solvent for the electrolyte. By using one or more, the internal temperature of the storage device can be increased due to an internal short circuit or overcharging. Even if the battery is heated, it can prevent the battery from bursting or catching fire. The electrolyte solution is made of cations and anions. Ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations Aliphatic onium cations such as imidazolium cations and pyridinium cations The aromatic cations are also used as anions in the electrolyte. Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkyl sulfonic acid anion, tetrafluoroborate anion, perfluoroalkyl borate anion phosphate anion, hexafluorophosphate anion, or perfluoroalkyl phosphat 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 electrolytic solution used in the power storage device is preferably a highly purified electrolytic solution with a low content of particulate dust and elements other than the constituent elements of the electrolytic solution (hereinafter also simply referred to as " impurities"). Specifically, it is preferable that the weight ratio of impurities to the electrolytic solution is 1% or less, preferably 0.1% or less, 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 with respect to the entire solvent. ​​

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

[0163] By using the 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 polymer formed 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 a polyethylene oxide (PEO)-based material 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. As the separator, for example, 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, so deterioration of the separator during high-voltage charge and discharge can be suppressed, and the reliability of the secondary battery can be improved. Coating with a polyamide-based material, especially aramid, improves heat resistance, so the safety of the secondary battery can be improved.

[0169] For example, both sides of a polypropylene film can be coated with a mixed material of aluminum oxide and aramid. Also, the side of the polypropylene film in contact with the positive electrode can be coated with a

[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 by a gasket 303 formed of polypropylene or the like. The positive electrode 304 is formed of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact therewith. The negative electrode 307 is formed of 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, etc. that are corrosion-resistant to the electrolytic solution, or alloys of these or alloys of these and other metals (for example, stainless steel etc.) can be used. Also, in order to prevent corrosion by the electrolytic solution, it is preferable to coat with nickel, aluminum, etc. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 30 7 respectively.

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

[0177]

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

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

[0180] Since the positive and negative electrodes used in the 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. Also, the PTC element 611 is a thermal sensing resistor 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. 。 When the temperature rises, the resistance increases, and it limits the current amount to prevent abnormal heat generation. For the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics, etc. can be used. 。

[0181] As shown in FIG. 6C, a plurality of secondary batteries 600 are arranged between conductive plates 613 and 614. A module 615 may be formed by sandwiching the secondary batteries 600 between them. Alternatively, the elements may be connected in series, or may be connected in parallel and then in series. By configuring a module 615 having a plurality of secondary batteries 600, This allows for the extraction of large amounts of power.

[0182] FIG. 6D is a top view of the module 615. The conductive plate 613 is dotted for clarity. As shown in FIG. 6D, the module 615 is a multiple secondary battery 600. The conductive plate 613 may be provided on the conductive wire 616. In addition, even if a temperature control device 617 is provided between multiple secondary batteries 600, When the secondary battery 600 is overheated, the temperature control device 617 cools the secondary battery. If 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 temperature.

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

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

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

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

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

[0189] The power storage device has a layer 916 between the antennas 914 and 915 and the secondary battery 913. The layer 916 has a function of shielding, for example, 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, for example, the secondary battery 913. 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, for example, the secondary battery 913. 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, for example, the secondary battery 913. As the layer 917, for example, a magnetic material can be used. As the layer 917, for example, a magnetic material can be used. As the layer 917, for example, a magnetic material can be used.

[0193] By adopting the above structure, the sizes of both the antenna 914 and the antenna 915 can be increased. By adopting the above structure, the sizes of both the antenna 914 and the antenna 915 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 interposed between one of the pair of surfaces of the secondary battery 913, and as shown in FIG. 8(B-2), an antenna 918 is provided with a layer 917 interposed between the other of the pair of surfaces of the secondary battery 91 3. The antenna 918 has a function capable of performing data communication with an external device, for example. To the antenna 918 For example, an antenna having a shape applicable to the antenna 914 and the antenna 915 can be applied. As a communication method between the power storage device and another device via the antenna 918, NFC For example, a response method or the like that can be used between the power storage device and another device can be applied. and the like.

[0196] Alternatively, as shown in FIG. 9(A), a display device 920 may be provided in 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 may not 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) and 7(B) can be appropriately cited as needed.

[0197] The display device 920 may display, for example, an image indicating whether charging is in progress, an image indicating the power storage amount, or 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.

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

[0199] The sensor 921 may have a function of measuring, for example, 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. The sensor 921 may have a function of measuring, for example, 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. The sensor 921 may have a function of measuring, for example, 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. The sensor 921 may have a function of measuring, for example, 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. The sensor 921 may have a function of measuring, for example, 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.

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

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

[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 that are 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. 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 for 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 stacked in multiple layers.

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

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

[0207] [Laminated secondary battery] Next, an example of a laminated secondary battery will be described with reference to FIGS. 12 to 17. La If the laminated secondary battery has a flexible configuration, if 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 includes 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, with the negative electrode 994 and the positive electrode 995 overlapping with each other with the separator 996 interposed therebetween and laminated, and the laminated sheet is wound.

[0209] Note that the number of laminations of the laminate composed of the negative electrode 994, the positive electrode 995, and the separator 996 may be appropriately designed according to the required capacity and the 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 electrodes 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. Thus, 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 in which two films are used, but a space can be formed by bending one film, and the above-described winding body 993 may be housed in the space .

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

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

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

[0216] In the laminated secondary battery 500 shown in FIG. 13(A), the positive electrode current collector 501 and the negative electrode current collector 504 also serve as terminals for obtaining electrical contact with the outside. Therefore, a part of the positive electrode current collector 501 and the negative electrode current collector 504 may be arranged to be exposed to the outside from the exterior body 509. 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. It may be done.

[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, polypropylene, polycarbonate, ionomer, polyamide, etc. on a film, and further, 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. On the film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc., a flexible metal thin film made of a material such as aluminum, stainless steel, copper, nickel, etc. is provided, and further, 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. It can be used.

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

[0219] In FIG. 13(B), as an example, the number of electrode layers is 16. Even if 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 secondary battery 500 has flexibility. In FIG. 13(B), the negative electrode current collector 504 has 8 layers, and The positive current collector 501 has a structure of a total of 16 layers in 8 layers. Note that FIG. 13(B) shows the cross-section of the extraction part of the negative electrode, and the 8-layer negative current collector 504 is ultrasonically bonded. 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 laminate-type secondary battery 500 is shown in FIGS. 14 and 15. FIGS. 1 4 and 15 have a positive electrode 503, a negative electrode 506, a separator 507, an exterior body 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511.

[0221] FIG. 16(A) shows the external views of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a positive 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 laminate-type secondary battery] Here, an example of the manufacturing method of the laminate-type secondary battery whose external view is shown in FIG. 14 will be described with reference to FIGS. 16 (B) and 16(C).

[0223] First, the negative electrode 506, the separator 507, and the positive electrode 503 are laminated. FIG. 16(B) shows the laminated shows the negative electrode 506, separator 507, and positive electrode 503 thus obtained. Here, an example is shown in which five sets of negative electrodes and four sets of 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 filled 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 type 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 degradation 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, C 3-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 encapsulated.

[0230] The positive electrode 211a and the negative electrode 211b of the battery 250 will be described with reference to Fig. 18. Fig. 18(A) is a perspective view for explaining 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 positive electrode 211a and the negative electrode 211b, in addition to the leads 2 12a and 212b.

[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 The positive electrode 211a and the negative electrode 211b are stacked so that the surfaces without the formation of the mass layer are in contact with each other. They are stacked.

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

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

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

[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. They are stacked.

[0237] The exterior body 251 preferably has a wavy shape in which ridge lines 271 and 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 wavy shape in which ridge lines 271 and 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 with the ridge line 271, and FIG. 17(B2) is a cross-section taken along a portion overlapping with the valley line 272. FIGS. 17(B1) and 17(B2) both correspond to a cross-section in the width direction of the battery 250, the positive electrode 211a, and the negative electrode 211b.

[0239] Here, the distance between the end portion in the width direction of the negative electrode 211b, that is, the end portion of the negative electrode 211b and the seal portion 262 is defined as the distance La. When a deformation such as bending is applied to the battery 250, the positive electrode 211a and the negative electrode 211b are deformed so as to shift from each other in the length direction as described later. At that time, if the distance La is too short, the exterior body 251 and the positive electrode 211a and the negative electrode 211b will strongly rub against each other, and the exterior body 251 may be damaged. In particular, when the metal film of the exterior body 251 is exposed , there is a risk that the metal film will be corroded by the electrolytic solution. Therefore, it is preferable to set the distance La as long as possible. On the other hand, if the distance La is made too large , the volume of the battery 250 will increase. Also, the thicker the total thickness of the stacked positive electrode 211a and negative electrode 211b, the more preferable it is to increase the distance La between the negative electrode 211 b and the seal portion 262.

[0240] More specifically, when the total thickness of the stacked positive electrode 211a and negative electrode 211b is defined as the thickness t , the distance La is preferably 0.8 times or more and 3.0 times or less of the thickness t, more preferably 0.9 times or more and 2.

[0241] 5 times or less, and even more preferably 1.0 times or more and 2.0 times or less. 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 repetitively 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, and more preferably 2.0 times or more and 4.0 times or less of the thickness t of the positive electrode 211a and the negative electrode 211b. This is preferable.

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

[0249] When the battery 250 is bent, a part of the outer package 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 outer package 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 outer package 251 deforms such that the amplitude of the wave is large and the period of the wave is small. In this way, when the outer package 251 deforms, the stress applied to the outer package 251 due to the bending is relaxed, so that the material itself constituting the outer package 251 does not need to expand and contract. As a result, the battery 250 can be bent with a small force without the outer package 251 being damaged.

[0250] Also, as shown in Figure 17(D), when the battery 250 is bent, the positive electrode 211a and the negative electrode 211b are displaced relative to each other. At this time, since one end on the seal part 263 side of the plurality of stacked positive electrodes 211a and negative electrodes 211b is fixed by the fixing member 217, they are displaced such that the amount of displacement increases as they get closer to the bending 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 outer package 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 is also less likely to have its battery characteristics deteriorated 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 of the battery 250, it is possible to obtain a secondary battery with even less deterioration and high safety. (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.

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

[0254] First, an example of mounting a bendable secondary battery, which was partly 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), a monitor for a computer, a digital camera, a digital video camera, a digital photo frame, a mobile phone ( also referred to as a cellular phone or a mobile phone device), a portable game machine, a portable information terminal, an audio playback device, a large game machine such as a pachinko machine, 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 along the curved surface of the interior or exterior of an automobile.

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

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

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

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

[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. can.

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

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

[0263] In addition, the portable information terminal 7200 can perform communication-standardized short-range wireless communication. For example, by communicating with a wireless headset capable of wireless communication, it is also possible to make hands-free calls. calls.

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

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

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

[0267] FIG. 19(G) shows an example of a bracelet-type display device. The display device 7300 has a display unit 7304 and has a secondary battery according to one aspect of the present invention. Also, the display device 7300 can be provided with a touch sensor on the display unit 7304 and can also function as a portable information terminal. The display device 7300 has a display unit 7304 and has a secondary battery according to one aspect of the present invention. Also, the display device 7300 can be provided with a touch sensor on the display unit 7304 and can also function as a portable information terminal. It can also be provided with a touch sensor on the display unit 7304 and can also function as a portable information terminal. This is also acceptable.

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

[0269] Also, 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 perform charging via the input / output terminals. It can also perform charging 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 part 9 631, a display mode switching switch 9626, a power switch 9627, a power saving mode switching switch 9625, a fastener 9629, and an operation switch 9628. The display part 9 631 can have a wider display part by using a flexible panel, thus serving as a tablet terminal. FIG. 20(A) shows the tablet terminal 9600 in an open state, and FIG. 20(B) shows the tablet terminal 9600 in a closed state.

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

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

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

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

[0275] Since the tablet-type terminal 9600 is foldable in two, the housing 9630a and the housing 9630b can be folded so as to overlap each other when not in use. By folding, the display unit 9631 can be protected, 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 terminal shown in FIGS. 20(A) and 20(B) can also have various functions, such as a function of displaying various information (such as still images, moving images, text images, etc.), a function of displaying a calendar, date, or time on the display unit, a function of operating or editing the information displayed on the display unit by touch input, a touch input function, a function of controlling processing by various software (programs), etc.

[0277] Power can be supplied to the touch panel, the display unit, or the video signal processing unit, etc., by the solar cell 9633 mounted on the surface of the tablet-type terminal. Note that the solar cell 9633 is attached to 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] In addition, 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 a solar cell 9633, a power storage body 963 5, a DCDC converter 9636, a converter 9637, switches SW1 to SW3, and a display unit 9631. The power storage body 9635, the DCDC converter 9636, the converter 9637, and the switches SW1 to SW3 correspond to the portions of the charge / discharge control circuit 96 34 shown in FIG. 20(B).

[0279] First, an example of the operation when power is generated by the solar cell 9633 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 9636 to 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. It can be configured like this.

[0280] Note that the solar cell 9633 is shown as an example of a power generation means, but it is not particularly limited. 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 charges by wireless (non-contact) power transmission and reception, or a configuration that combines other charging means can be used. can also be used. may also be used.

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

[0282] Emission Display), etc., and a semiconductor display device can be used. In addition to those for receiving TV broadcasts, the display device includes all display devices for information display, such as those for personal computers and advertising displays. ce), a PDP (Plasma Display Panel), a 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, the stationary lighting device 8100 is an example of an electronic device using the 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, the case where the secondary battery 8103 is provided inside the ceiling 8104 where the housing 81 01 and the light source 8102 are installed is illustrated However, the secondary battery 8103 may be provided inside the housing 8101. The lighting device 8100 can receive power supply from a commercial power source, or can also use the power stored in the secondary battery 8103. Therefore, even when the 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 addition, in FIG. 21, an installed-type lighting device 8100 provided on the ceiling 8104 is illustrated However, the secondary battery according to one aspect of the present invention can be used not only for the ceiling 8104 but also for installed-type lighting devices provided on, for example, side walls 8105, floors 8 106, windows 8107, etc., and can also be used for tabletop type lighting devices and the like.

[0286] Also, as the light source 8102, an artificial light source that artificially obtains light using power can be used Specifically, incandescent bulbs, discharge lamps such as fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements can be cited as an example of the above artificial light source.

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

[0288] Note that in FIG. 21, a separate type of 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 of 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 includes a housing 8301, a door 8302 for the storage compartment, a door 8303 for the freezer compartment, a secondary battery 8304, and the like. In FIG. 21, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator 8300 can receive power supply from a commercial power source, or can also use the power stored in the secondary battery 8304. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like , by using the secondary battery 8304 according to one aspect of the present invention as an uninterruptible power supply, the electric refrigerator 8300 can be used.

[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 of 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 mounted on 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 that can appropriately select and use 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 receive power supply from external charging facilities by a plug-in method, a non-contact power supply method, etc., and charge 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 can be appropriately adopted for the charging method, connector, etc. The charging device 8021 may be a charging station provided in a commercial facility, or may 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 to the vehicle non - contactlessly from a power transmitting device on the ground and used for charging. In the case of this non - contact power supply method, by incorporating the power transmitting device into a road or an outer wall, charging can be performed not only while the vehicle is stopped but also while it is running. Also, using this non - contact power supply method, power can be transmitted and received between vehicles. Furthermore, a solar cell can be provided on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped or running. For such non - contact power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0298] Also, Fig. 22(C) shows 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, side mirrors 8601, and a direction indicator lamp 8603. The secondary battery 8602 can supply electricity to the direction indicator lamp 8603.

[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 the peak period of power demand. Using a commercial power supply during the peak period of 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 use 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 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 A which is one aspect of the present invention. As sample A, lithium nickel manganese cobaltate having magnesium, fluorine, and oxygen at the grain boundaries and in the vicinity thereof was produced. The composition of lithium nickel manganese cobaltate was assumed to be LiNi Mn 1 / 3 Co 1 / 3 Mn 1 / 3 Co 1 / 3 O2. LiNi 1 / Mn 1 / 3 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. 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. PB) was used. LiF manufactured by High Purity Chemical Research Institute (Catalog number: LIH10XB) was used. for it.

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

[0306] Next, as shown in step S13, the material mixed in step S12 was subjected to a first heating. The first heating was performed using a muffle furnace, and the temperature was raised from room temperature to 1000 at a heating rate of 200 °C / hr. 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, the 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 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 surface analysis of EDX , the detection limit was approximately 1 atomic%. Note that EDX measurement can detect elements from boron (B) with atomic number 5 to uranium (U) with atomic number 92 .

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

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

[0316] Next, the EDX spectrum of the cross-section of Sample A will be described. In EDX measurement, electrons are applied to the measurement point 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 intensity by EDX measurement. 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. 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 reagent used as the raw material.

[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 was 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 of EDX analysis was performed in the crystal grains, grain boundaries, and regions spanning 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 distance on the horizontal axis starts from the black circle at one end of the arrow shown in Fig. 34(A) (distance = 0 nm), and the distance increases 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 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 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 resulting from the carbon coating film. Therefore, the true carbon concentration of the crystal grains and the grain boundaries could not be determined.

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

[0332] The total atomic concentrations of the transition metals nickel, manganese, and cobalt are shown in Fig. 35(F). In Fig. 35(F), the horizontal axis indicates the distance [nm], and the vertical axis indicates the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) [atomic%]. Specifically, the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) is the value obtained by summing up the atomic concentrations of nickel, manganese, and cobalt for each measurement point of EDX. In sample A, the total atomic concentration of nickel, manganese, and cobalt (Ni + Mn + Co) can also be said to be the atomic concentration of the transition metals. As shown in Fig. 35(F), in the region of the crystal grains, It was found that the grain boundaries and their vicinity tend to have a lower atomic concentration of transition metals compared to the matrix. In addition, 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 calculating the average value is indicated by an arrow in Fig. 35(F). 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.

[0335] Sample A, which is one aspect of the present invention, has magnesium oxide at the grain boundaries and their vicinity, resulting in the positive electrode active material particles being chemically and structurally stable, and the transition metal eluting 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 the distance [nm], and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (denoted as F / Tr-Metal). As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof. In 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 the distance [nm], and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (denoted as F / Tr-Metal). As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof. In 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. As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof. As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof. As shown in FIG. 36(B), it was found that the grain boundaries and the vicinity thereof have a region where the ratio of the atomic concentration of fluorine to the atomic concentration of transition metal in the crystal grains (F / Tr-Metal) is 0.030 or more. By having fluorine at the grain boundaries and the vicinity thereof, it was found that magnesium can be efficiently segregated at the grain boundaries and the vicinity thereof.

[0338] In 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 total atomic concentration of nickel, manganese and cobalt (Ni+Mn+ The ratio of the atomic concentration of magnesium (Mg) to that of Co is shown in FIG. In C), the horizontal axis indicates distance [nm], and the vertical axis indicates EDX measurement points. The ratio of magnesium atoms to the total atomic concentration of nickel, manganese, and cobalt per The concentration ratio (Mg / (Ni+Mn+Co)) is shown.

[0340] The total atomic concentration of nickel, manganese and cobalt (Ni+Mn+ Co) is the same as the data shown in FIG. 35(F).

[0341] As shown in FIG. 36(C), the grain boundaries and their vicinity are composed of nickel and manganese in the grains. The ratio of the atomic concentration of magnesium to the total atomic concentration of nickel and cobalt (Mg / (Ni+ It was found that there is an area where the Mn+Co) is 0.030 or more. It was found that magnesium was segregated in the vicinity.

[0342] The total atomic concentration of nickel, manganese and cobalt (Ni+Mn+ The ratio of the atomic concentration of fluorine to that of Co is shown in FIG. The horizontal axis shows the distance [nm], and the vertical axis shows the nickel The ratio of the atomic concentration of fluorine to the total atomic concentration of manganese and cobalt (F / (Ni +Mn+Co).

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

[0344] EDX measurement was similarly performed at another location of sample A.

[0345] The HAADF-STEM image of the region where the EDX surface analysis of sample A was performed is shown in Fig. 37(A). The EDX surface analysis was performed in a region including the grains and grain boundaries. The carbon mapping image in the EDX surface analysis of the region shown in Fig. 37(A) is shown in Fig. 37(B), oxygen in Fig. 37(C), fluorine in Fig. 37(D), magnesium in Fig. 37(E), silicon in Fig. 37(F), phosphorus in Fig. 38(A), sulfur in Fig. 38(B), calcium in Fig. 38(C), manganese in Fig. 38(D ) cobalt in Fig. 38(E), and nickel in Fig. 38(F). Fig. 37(B) to Fig. 37(F), Fig. 38(A) to Fig. 38(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 higher the characteristic

[0346] X-ray intensity, the darker (black) it is shown. 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 Fig. 3 7(B) to Fig. 37(F), Fig. 38(A) to Fig. 38(F) change the scale of the characteristic X-ray intensity for each element so that the distribution within the region can be easily understood. As shown in Fig. 37(B) to Fig. 37(F), Fig. 38(A) to Fig. 38(F), the concentrations of fluorine, magnesium, silicon, and calcium are high at the grain boundaries and in the vicinity thereof. and in the vicinity thereof.

[0347] As shown in Fig. 37(B) to Fig. 37(F), Fig. 38(A) to Fig. 38(F), at the grain boundaries and in the vicinity thereof, the concentrations of fluorine, magnesium, silicon, and calcium are high. It was confirmed that. Silicon and calcium were considered to be contained in the reagent used as raw materials.

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

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

[0350] In the line analysis of EDX 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 distance [nm], and the vertical axis indicates atomic concentration [atomic%]. The distance on the horizontal axis takes the black circle at one end of the arrow shown in FIG. 33(B) as the starting point (distance = 0 nm), and shows that the distance increases toward the other end (end point). The atomic concentration on the vertical axis is 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%. ​

[0352] As shown in FIGS. 33(B), 39(A) to 39(F), and 40(A) to 40(E), it was confirmed that the concentration of fluorine, magnesium, silicon, and calcium is higher in the grain boundary and its vicinity than in the grain region. In addition, 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.

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

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

[0355] The detection lower limit levels of phosphorus and sulfur were obtained in both the grain and the grain boundary.

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

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

[0358] The total atomic concentrations of nickel, manganese, and cobalt, which are transition metals, are 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. Also, in the grain region, it was found that there is no significant variation in the atomic concentration of transition metals and it is substantially uniform.

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

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

[0361] As shown in Fig. 41(A), it was found that the grain boundaries and their vicinity have a region where the ratio of the atomic concentration of magnesium to the atomic concentration of transition metals in the grains (Mg / Tr-Metal) is 0.030 or more . It was found that magnesium is segregated at the grain boundaries and their vicinity. It is considered that the grain boundaries and their vicinity have magnesium oxide. Sample A, which is one aspect of the present invention, has magnesium oxide at the grain boundaries and their vicinity . . , the positive electrode active material particles become chemically and structurally stable, the transition metal elutes into the electrolyte, oxygen desorbs, and the degradation of the positive electrode active material such as the crystal structure becoming unstable can be suppressed. Also, the cracking of the positive electrode active material particles can be suppressed. Further, the desorption of oxygen from the positive electrode active material particles can be suppressed. By using such positive electrode active material particles, the degradation 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 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.

[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. It shows the ratio (Mg / (Ni+Mn+Co)).

[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. 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. It shows the ratio (F / (Ni+Mn+Co)).

[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 having fluorine at the grain boundaries and their vicinity can efficiently segregate magnesium at the grain boundaries and their vicinity. 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 having fluorine at the grain boundaries and their vicinity can efficiently segregate magnesium at the grain boundaries and their vicinity. It was found that having fluorine at the grain boundaries and their vicinity can efficiently segregate magnesium at the grain boundaries and their vicinity. It was found that having fluorine at the grain boundaries and their vicinity can efficiently segregate magnesium at the grain boundaries and their vicinity.

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

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

Example

Example

[0371] In this example, positive electrode active material particles having magnesium, fluorine, and oxygen at the grain boundaries and in the vicinity thereof were produced, and the concentration distributions of the grains and grain boundaries in the active material were confirmed by TEM observation and STEM-EDX analysis. The sample is one sample of sample B, which is one aspect of the present invention. As sample B, lithium cobaltate having magnesium, fluorine, and oxygen at the grain boundaries and in the vicinity thereof was produced. The composition of lithium cobaltate was assumed to be LiCoO2. LiCo O2 has a layered rock salt-type crystal structure. O2 has a layered rock salt-type crystal structure. O2 has a layered rock salt-type crystal structure. O2 has a layered rock salt-type crystal structure. O2 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. Since the details of the mixing can be referred to in the description of sample A, the description is omitted. Next, as shown in step S13, the material mixed in step S12 was subjected to a first heating. Since the details of the first heating can be referred to in the description of sample A, the description is omitted. 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.

[0374]

[0375]

[0376] ​​​​​​​​​​

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

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

[0379] Next, as shown in step S16, the 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 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 composition analysis by EDX measurement. For the details of TEM, STEM observation and EDX measurement, the description of sample A can be referred to, so the description is omitted.

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

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

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

[0384] Peaks derived from the electron 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] In the EDX surface analysis of the region shown in Fig. 44(A), the mapping image of carbon 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 ), and 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 intensities by the EDX measurement, where the measurement points with low characteristic X-ray intensity are shown in light color (white), and the characteristic X-ray intensity is shown in darker color (black) for the measurement points with higher intensity. That is, the light color (white) measurement points indicate low atomic concentration, and the darker color (black) measurement points indicate high atomic concentration. Note that Figs. 4 4(B) to 44(F), Figs. 45(A) to 45(D) change the scale of the characteristic X-ray intensity for each element so that the distribution within the region is easy to understand. ​

[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 region where the surface analysis by EDX was performed. This is presumably 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.

[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 region was extracted, and the distribution of atomic concentration 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 segment analysis of EDX was performed in the grain, grain boundary, and region across grains.

[0390] In 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 represents the distance ( Distance) [nm], and the vertical axis represents 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 in the grain boundary and its vicinity compared to the grain region. Also, it was found that the grain boundary and its vicinity have a region with a width of 1 nm or more and 10 nm or less.

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

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

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

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

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

[0398] ​​​​​​​​In Sample B, the atomic concentration of cobalt can also be said to be the atomic concentration of transition metals. Fig. 48(C) As shown in , it was found that the atomic concentration of transition metals in the grain boundary and its vicinity is lower than that in the grain region. Also, in the grain region, it was found that 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 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 grains ( Mg / Tr-Metal).

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

[0401] As shown in Fig. 49(A), it was found that the grain boundary and its vicinity have a region where the ratio of the atomic concentration of magnesium to the atomic concentration of transition metals in the grains (Mg / Tr-Metal) is 0.030 or more. It was found that magnesium is segregated at the grain boundary and its vicinity. It is considered that the grain boundary and its vicinity have magnesium oxide. Sample B, which is one aspect of the present invention, has magnesium oxide at the grain boundary and its vicinity, so that the cathode active material particles become chemically and structurally stable, and deterioration of the cathode active material such as elution of transition metals into the electrolyte, desorption of oxygen, and instability of the crystal structure can be suppressed. Also, cracking of the cathode active material particles can be suppressed. Also, desorption of oxygen from the cathode active material particles can be suppressed. ​​​​​​​​ This is possible. By using such positive electrode active material particles, deterioration of the power storage device can be suppressed. Also , a highly safe power storage device can be obtained. When 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 concentration at the crystal grains and grain boundaries was below the detection limit. It is considered that fluorine, being a light element, is difficult to detect by EDX.

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

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

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

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

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

[0409] Figs. 50(B) to 50(F) and Figs. 51(A) to 51(D) show the mapping of characteristic X-ray intensities by EDX measurement. The measurement points with low characteristic X-ray intensities are shown in light colors (white), and the measurement points with high characteristic X-ray intensities are shown in darker colors (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) and Figs. 51(A) to 51(D) change the scale of the characteristic X-ray intensity for each element so that the distribution within the region can be easily understood.

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

[0411] From the surface analysis by EDX shown in FIGS. 50(B) to 50(F) and FIGS. 51(A) to 51(D), the data of the linear region was extracted, and the distribution of the atomic concentration 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 spanning the grains.

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

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

[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 regions of the crystal grains, 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 crystal grains and at the grain boundaries.

[0419] Although carbon is detected at the crystal grains and grain boundaries, a carbon coating film is used as a protective film, and it is considered that the carbon concentration described above includes carbon due to the carbon coating film. Therefore, the true carbon concentration of the crystal 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 their vicinity compared to the crystal 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 there is no significant variation in the atomic concentration of transition metals and it is substantially uniform.

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

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

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

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

[0426] As shown in Fig. 52(C) and Fig. 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 be detected 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 location measured by EDX 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 location measured by EDX. In sample B, the fluorine concentrations at the crystal grains and grain boundaries were 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: Bent portion, 262: Seal portion, 263: Seal portion, 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: Lea d electrode, 1101: Crystal grain, 1103: Crystal grain boundary, 1201: Crystal grain, 1203: Crystal grain boundary, 7100: Portable display device, 7101: Housing, 7102: Display unit, 7103: Operation button , 7104: Secondary battery, 7200: Portable information terminal, 7201: Housing, 7202: Display unit , 7203: Band, 7204: Buckle, 7205: Operation button, 7206: Input / output terminal , 7207: Icon, 7300: Display device, 7304: Display unit, 7400: Mobile phone machine, 7401: Housing, 7402: Display unit, 7403: Operation button, 7404: External connection port , 7405: Speaker, 7406: Microphone, 7407: Secondary battery, 8000: Display device , 8001: Housing, 8002: Display unit, 8003: Speaker unit, 8004: Secondary battery, 8021: Charging device, 8022: Cable, 8024: Secondary battery, 8100: Lighting device, 8101: Housing, 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 , 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 pow er, 9634: Charge-discharge control circuit, 9635: Energy storage body, 9636: DCDC converter, 9 637: Converter, 9640: Movable part

Claims

1. A lithium ion secondary battery comprising positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate, the lithium cobaltate has a layered rock salt type crystal structure, the positive electrode active material particles have a plurality of crystal grains, the positive electrode active material particles have a region where the magnesium concentration is higher than that inside the crystal grains at the grain boundaries of adjacent crystal grains and in the region near the grain boundaries, the grain boundaries contain magnesium, oxygen, and fluorine, the lithium ion secondary battery, wherein the positive electrode active material particles have a region where the ratio of the atomic concentration of magnesium in the grain boundaries and the region near the grain boundaries to the atomic concentration of cobalt inside the crystal grains is 0.010 or more and 0.50 or less.

2. A lithium ion secondary battery comprising positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate, the lithium cobaltate has a layered rock salt type crystal structure, the positive electrode active material particles have a plurality of crystal grains, the positive electrode active material particles have a region where the magnesium concentration is higher than that inside the crystal grains at the grain boundaries of adjacent crystal grains and in the region near the grain boundaries, the grain boundaries contain magnesium, oxygen, and fluorine, the lithium ion secondary battery, wherein the positive electrode active material particles have a region where the silicon concentration is higher than that inside the crystal grains at the grain boundaries and in the region near the grain boundaries.

3. A lithium ion secondary battery comprising positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate, the lithium cobaltate has a layered rock salt type crystal structure, the positive electrode active material particles have a plurality of crystal grains, the positive electrode active material particles have a region where the magnesium concentration is higher than that inside the crystal grains at the grain boundaries of adjacent crystal grains and in the region near the grain boundaries, the grain boundaries contain magnesium, oxygen, and fluorine, the lithium ion secondary battery, wherein the positive electrode active material particles have a region where silicon is detected exceeding the detection lower limit of energy dispersive X-ray analysis at the grain boundaries and in the region near the grain boundaries.

4. A lithium ion secondary battery comprising positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate, the positive electrode active material particles have a plurality of crystal grains, The positive electrode active material particles have a region where the magnesium concentration is higher than that inside the crystal grains at the grain boundaries of adjacent crystal grains and in the regions near the grain boundaries. The grain boundaries have magnesium, oxygen, and fluorine. The lithium-ion secondary battery includes positive electrode active material particles having a region where at least one selected from silicon and calcium has a higher concentration than that inside the crystal grains at the grain boundaries and in the regions near the grain boundaries.

5. A lithium-ion secondary battery including positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate. The positive electrode active material particles have a plurality of crystal grains. The positive electrode active material particles have a region where the magnesium concentration is higher than that inside the crystal grains at the grain boundaries of adjacent crystal grains and in the regions near the grain boundaries. The grain boundaries have magnesium, oxygen, and fluorine. The positive electrode active material particles have a region where at least one selected from silicon and calcium is detected above the detection lower limit of energy-dispersive X-ray analysis at the grain boundaries and in the regions near the grain boundaries. The positive electrode active material particles have a region where at least one selected from fluorine, magnesium, silicon, and calcium is at the detection lower limit level of energy-dispersive X-ray analysis inside the crystal grains.

6. A lithium-ion secondary battery including positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate. The lithium cobaltate has a layered rock salt-type crystal structure. The positive electrode active material particles have a plurality of crystal grains. The positive electrode active material particles have a region where the magnesium concentration is higher than that inside the crystal grains at the grain boundaries of adjacent crystal grains and in the regions near the grain boundaries. The grain boundaries have magnesium, oxygen, and fluorine. The positive electrode active material particles have a region where silicon is detected above the detection lower limit of energy-dispersive X-ray analysis at the grain boundaries and in the regions near the grain boundaries. The positive electrode active material particles have a region where at least one selected from fluorine, magnesium, silicon, and calcium is at the detection lower limit level of energy-dispersive X-ray analysis inside the crystal grains. The regions of the grain boundaries and the regions near the grain boundaries are regions of 1 nm or more and 10 nm or less sandwiching the grain boundaries. The lithium-ion secondary battery, wherein the positive electrode active material particles have a region where the ratio of the atomic concentration of magnesium in the grain boundary and the region near the grain boundary to the atomic concentration of cobalt inside the crystal grains is 0.010 or more and 0.50 or less.

7. A lithium-ion secondary battery comprising positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate, wherein the positive electrode active material particles have a plurality of crystal grains, wherein the positive electrode active material particles have a region where the magnesium concentration is higher than that inside the crystal grains at the grain boundary between adjacent crystal grains and in the region near the grain boundary, wherein the grain boundary contains magnesium, oxygen, and fluorine, The lithium-ion secondary battery, wherein the positive electrode active material particles have a region where the silicon concentration is higher than that inside the crystal grains at the grain boundary and in the region near the grain boundary.

8. A lithium-ion secondary battery comprising positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate, wherein the positive electrode active material particles have a plurality of crystal grains, wherein the positive electrode active material particles have a region where the magnesium concentration is higher than that inside the crystal grains at the grain boundary between adjacent crystal grains and in the region near the grain boundary, wherein the grain boundary contains magnesium, oxygen, and fluorine, wherein the positive electrode active material particles have a region where the fluorine concentration is higher than that inside the crystal grains at the grain boundary and in the region near the grain boundary, wherein the grain boundary and the region near the grain boundary are regions of 1 nm or more and 10 nm or less sandwiching the grain boundary, wherein the positive electrode active material particles have a region where the ratio of the atomic concentration of magnesium in the grain boundary and the region near the grain boundary to the atomic concentration of cobalt inside the crystal grains is 0.010 or more and 0.50 or less, The lithium-ion secondary battery, wherein the positive electrode active material particles have a region where the ratio of the atomic concentration of fluorine in the grain boundary and the region near the grain boundary to the atomic concentration of cobalt inside the crystal grains is 0.020 or more and 1.00 or less.

9. A lithium-ion secondary battery comprising positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate, wherein the positive electrode active material particles have a plurality of crystal grains, wherein the positive electrode active material particles have a region where the magnesium concentration is higher than that inside the crystal grains at the grain boundary between adjacent crystal grains and in the region near the grain boundary, The grain boundaries have magnesium, oxygen, and fluorine. The positive electrode active material particles have a region where magnesium segregates in the grain boundaries and regions in the vicinity of the grain boundaries. The grain boundaries and regions in the vicinity of the grain boundaries are regions of 1 nm or more and 10 nm or less sandwiching the grain boundaries. The positive electrode active material particles have a region where the ratio of the atomic concentration of magnesium in the grain boundaries and regions in the vicinity of the grain boundaries to the atomic concentration of cobalt in the interior of the grains is 0.010 or more and 0.50 or less, in a lithium ion secondary battery.

10. A lithium ion secondary battery including positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate, the positive electrode active material particles have a plurality of grains, the positive electrode active material particles have a region where the magnesium concentration is higher than that in the interior of the grains, in the grain boundaries between adjacent grains and regions in the vicinity of the grain boundaries, the grain boundaries have magnesium, oxygen, and fluorine, the ends of the grain boundaries are within the grains, the grain boundaries and regions in the vicinity of the grain boundaries are regions of 1 nm or more and 10 nm or less sandwiching the grain boundaries, the positive electrode active material particles have a region where the ratio of the atomic concentration of magnesium in the grain boundaries and regions in the vicinity of the grain boundaries to the atomic concentration of cobalt in the interior of the grains is 0.010 or more and 0.50 or less, in a lithium ion secondary battery.

11. A lithium ion secondary battery including positive electrode active material particles, wherein the positive electrode active material particles contain lithium cobaltate, the positive electrode active material particles have a plurality of grains, the positive electrode active material particles have a region where the magnesium concentration and fluorine concentration are higher than those in the interior of the grains, in the grain boundaries between adjacent grains and regions in the vicinity of the grain boundaries, the grain boundaries have magnesium, oxygen, and fluorine, the ends of the grain boundaries are within the grains, the grain boundaries and regions in the vicinity of the grain boundaries are regions of 1 nm or more and 10 nm or less sandwiching the grain boundaries, the positive electrode active material particles have a region where the ratio of the atomic concentration of magnesium in the grain boundaries and regions in the vicinity of the grain boundaries to the atomic concentration of cobalt in the interior of the grains is 0.010 or more and 0.50 or less, The lithium-ion secondary battery, wherein the positive electrode active material particles have a region where the ratio of the atomic concentration of fluorine in the grain boundary and the region near the grain boundary to the atomic concentration of cobalt inside the crystal grains is 0.020 or more and 1.00 or less.

12. In any one of Claims 1 to 11, the magnesium concentration in the grain boundary and the region near the grain boundary is measured by energy dispersive X-ray analysis with respect to the cross-section of the positive electrode active material particles observed by TEM or STEM, the lithium-ion secondary battery.

13. In any one of Claims 2, 4, and 7, the silicon concentration in the grain boundary and the region near the grain boundary is measured by energy dispersive X-ray analysis with respect to the cross-section of the positive electrode active material particles observed by TEM or STEM, the lithium-ion secondary battery.

14. In Claim 12 or Claim 13, in the energy dispersive X-ray analysis, the beam diameter is 0.1 nmφ, the lithium-ion secondary battery.

15. In any one of Claims 3, 5, and 6, the detection limit is 1 atomic% when an Si drift detector is used for X-ray detection in the energy dispersive X-ray analysis, the lithium-ion secondary battery.

16. In any one of Claims 1 to 11, the inside of the crystal grains is at a position away from the grain boundaries, the lithium-ion secondary battery.

17. In any one of Claims 1 to 11, the lithium-ion secondary battery further has a conductive assistant, and the conductive assistant has a region in surface contact with the positive electrode active material particles, the lithium-ion secondary battery.

18. In any one of Claims 1 to 11, the grain boundary and the region near the grain boundary have a region where the cobalt concentration is lower than that inside the crystal grains, the lithium-ion secondary battery.

19. In any one of Claims 1 to 11, the lithium-ion secondary battery further has an electrolytic solution, and the electrolytic solution has vinylene carbonate, the lithium-ion secondary battery.

20. In any one of Claims 1 to 11, the positive electrode active material particles have a region where phosphorus and sulfur are at the detection limit level of energy dispersive X-ray analysis in the grain boundary and the region near the grain boundary, the lithium-ion secondary battery.

21. In any one of Claim 1, Claim 6, Claim 8, Claim 9, Claim 10, and Claim 11, the lithium ion secondary battery, wherein the positive electrode active material particles have a region where the ratio of the atomic concentration of magnesium in the grain boundary and the region near the grain boundary to the atomic concentration of cobalt inside the crystal grains is 0.030 or more and 0.20 or less.

22. In any one of Claims 1 to 11, the lithium ion secondary battery further has a coating, wherein the coating covers the positive electrode active material particles.

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