Positive electrode active material particles

Abstract

A positive electrode active material particle with minimal degradation is provided. Alternatively, a power storage device with minimal degradation is provided. Alternatively, a power storage device with high safety is provided. A positive electrode active material particle includes a first crystal grain, a second crystal grain, and a grain boundary between the first crystal grain and the second crystal grain, wherein the first crystal grain and the second crystal grain contain lithium, a transition metal, and oxygen, the grain boundary contains magnesium and oxygen, and the positive electrode active material has a region in which the ratio of the atomic concentration of magnesium in the grain boundary to the atomic concentration of the transition metal in the first crystal grain and the second crystal grain is greater than 0.010 and less than 0.50.

Description

[0001] This application is a divisional application of a patent application with an application date of "May 1, 2018", application number "201880025517.2", and invention name "Positive Electrode Active Material Particles". Technical Field

[0002] One embodiment of the present invention relates to an article, method, or manufacturing method. Alternatively, one embodiment of the present invention relates to a process, machine, product, or composition of matter. One embodiment of the present invention relates to a method for manufacturing a semiconductor device, a display device, a light-emitting device, a storage device, a lighting device, or 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 a secondary battery.

[0003] Note that in this specification, the term "electrical storage device" refers to any element or device that has an electrical storage function. For example, this category includes lithium-ion secondary batteries (also called secondary batteries), lithium-ion capacitors, and electric double-layer capacitors.

[0004] Note that in this specification, electronic equipment refers to any device having a power storage device. Examples of electronic equipment include electro-optical devices and information terminal devices having a power storage device. Background Art

[0005] In recent years, research and development of various energy storage devices, including lithium-ion secondary batteries, lithium-ion capacitors, and air batteries, has become increasingly intense. In particular, with the development of the semiconductor industry, which is used in portable information devices such as mobile phones, smartphones, and notebook personal computers, portable music players, digital cameras, medical equipment, and next-generation clean energy vehicles such as hybrid electric vehicles (HEVs), electric vehicles (EVs), and plug-in hybrid electric vehicles (PHEVs), demand for high-output, large-capacity lithium-ion secondary batteries has skyrocketed. As a rechargeable energy source, they have become indispensable in the modern information society.

[0006] Therefore, in order to improve the cycle characteristics and increase the capacity of lithium-ion secondary batteries, studies have been conducted on improving the positive electrode active material (Patent Documents 1 and 2).

[0007] Furthermore, characteristics required of power storage devices include improved safety and long-term reliability in various operating environments.

[0008] [Prior technical literature]

[0009] [Patent Document]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2012-018914

[0011] [Patent Document 2] Japanese Patent Application Publication No. 2016-076454 Summary of the Invention

[0012] Technical problem to be solved by the invention

[0013] There is a demand for improvements in lithium-ion secondary batteries and the positive electrode active materials used therein in terms of capacity, cycle characteristics, charge and discharge characteristics, reliability, safety, and cost.

[0014] In view of the above problems, one object of one embodiment of the present invention is to provide a positive electrode active material particle that exhibits minimal degradation. Another object of one embodiment of the present invention is to provide a novel positive electrode active material particle. Another object of one embodiment of the present invention is to provide a power storage device that exhibits minimal degradation. Another object of one embodiment of the present invention is to provide a power storage device with high safety. Another object of one embodiment of the present invention is to provide a novel power storage device.

[0015] Note that the description of the above-mentioned purpose does not preclude the existence of other purposes. Furthermore, one embodiment of the present invention does not necessarily achieve all of the above-mentioned purposes. Furthermore, purposes other than those described above can be understood and extracted from the description of the specification, drawings, claims, and the like.

[0016] Means of solving technical problems

[0017] A positive electrode active material particle according to one embodiment of the present invention includes first crystal grains, second crystal grains, and a grain boundary between the first crystal grains and the second crystal grains, wherein the first crystal grains and the second crystal grains contain lithium, a transition metal, and oxygen, and the grain boundary contains magnesium and oxygen.

[0018] The positive electrode active material particles preferably have a region where the atomic concentration ratio of magnesium to the atomic concentration of the transition metal is 0.010 or more and 0.50 or less.

[0019] In the positive electrode active material particles, it is preferred that the grain boundaries further contain fluorine.

[0020] The positive electrode active material particles preferably have a region where the atomic concentration ratio of fluorine to the atomic concentration of the transition metal is 0.020 or more and 1.00 or less.

[0021] In the positive electrode active material particles, the transition metal preferably includes one or more of iron, cobalt, nickel, manganese, chromium, titanium, vanadium, and niobium.

[0022] Effects of the Invention

[0023] According to one embodiment of the present invention, a positive electrode active material particle with minimal degradation can be provided. Furthermore, a novel positive electrode active material particle can be provided. Furthermore, a power storage device with minimal degradation can be provided. Furthermore, a power storage device with high safety can be provided. Furthermore, a novel power storage device can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a diagram illustrating an example of positive electrode active material particles.

[0025] FIG. 2 is a diagram illustrating the concentration distribution within positive electrode active material particles.

[0026] [ Figure 3 ] is a diagram illustrating an example of a method for producing positive electrode active material particles.

[0027] FIG4 is a cross-sectional view of an active material layer when a graphene compound is used as a conductive auxiliary agent.

[0028] [ Fig. 5 ] is a diagram illustrating a coin-type secondary battery.

[0029] [ Fig. 6 ] is a diagram illustrating a cylindrical secondary battery.

[0030] [ Fig. 7 ] is a diagram illustrating an example of a secondary battery.

[0031] [ Fig. 8 ] is a diagram illustrating an example of a secondary battery.

[0032] [ Fig. 9 ] is a diagram illustrating an example of a secondary battery.

[0033] [ Fig. 10 ] is a diagram illustrating an example of a secondary battery.

[0034] [ Figure 11 ] is a diagram illustrating an example of a secondary battery.

[0035] [ Fig. 12 ] is a diagram illustrating a laminated secondary battery.

[0036] [ Fig. 13 ] is a diagram illustrating a laminated secondary battery.

[0037] [ Figure 14 ] is a diagram showing the appearance of a secondary battery.

[0038] [ Figure 15 ] is a diagram showing the appearance of a secondary battery.

[0039] [Figure 16] is a diagram illustrating a method for manufacturing a secondary battery.

[0040] FIG. 17 is a diagram illustrating a bendable secondary battery.

[0041] FIG. 18 is a diagram illustrating a bendable secondary battery.

[0042] [Figure 19] is a diagram illustrating an example of an electronic device.

[0043] [Figure 20] is a diagram illustrating an example of an electronic device.

[0044] [ Figure 21 ] is a diagram illustrating an example of an electronic device.

[0045] [Figure 22] is a diagram illustrating an example of an electronic device.

[0046] FIG. 23 is a TEM image of a cross section of a positive electrode active material particle according to an example and a schematic diagram thereof.

[0047] FIG. 24 is a STEM image of a cross section of a positive electrode active material particle according to an example.

[0048] [ Figure 25 ] is a diagram illustrating a HAADF-STEM image and EDX point analysis of positive electrode active material particles according to an example.

[0049] [ Figure 26 ] is a diagram showing the EDX spectrum and quantitative results of the positive electrode active material particles according to the example.

[0050] [ Figure 27 ] is a diagram showing the EDX spectrum and quantitative results of the positive electrode active material particles according to the example.

[0051] [ Figure 28 ] is a diagram showing the EDX spectrum and quantitative results of the positive electrode active material particles according to the example.

[0052] [ Figure 29 ] is a diagram showing the EDX spectrum and quantitative results of the positive electrode active material particles according to the example.

[0053] [ Figure 30 ] is a diagram showing the EDX spectrum and quantitative results of the positive electrode active material particles according to the example.

[0054] FIG. 31 is an EDX surface analysis image showing positive electrode active material particles according to the example.

[0055] FIG. 32 is an EDX surface analysis image showing positive electrode active material particles according to the example.

[0056] FIG. 33 is a diagram illustrating EDX line analysis of positive electrode active material particles according to an example.

[0057] FIG. 34 is a graph showing the atomic concentration of positive electrode active material particles according to the embodiment in EDX line analysis.

[0058] FIG. 35 is a graph showing the atomic concentration of positive electrode active material particles according to an example in EDX line analysis.

[0059] FIG. 36 is a diagram showing the atomic number ratio in EDX line analysis of positive electrode active material particles according to an example.

[0060] FIG. 37 is an EDX surface analysis image showing positive electrode active material particles according to the example.

[0061] FIG. 38 is an EDX surface analysis image showing positive electrode active material particles according to the example.

[0062] FIG. 39 is a graph showing the atomic concentration of positive electrode active material particles according to the embodiment in EDX line analysis.

[0063] FIG. 40 is a graph showing the atomic concentration of positive electrode active material particles according to an example in EDX line analysis.

[0064] FIG. 41 is a diagram showing the atomic number ratio in EDX line analysis of positive electrode active material particles according to an example.

[0065] FIG. 42 is a TEM image and a schematic diagram showing a cross section of a positive electrode active material particle according to an example.

[0066] FIG43 is a STEM image of a cross section of a positive electrode active material particle according to an example.

[0067] FIG. 44 is an EDX surface analysis image showing positive electrode active material particles according to the example. FIG.

[0068] FIG. 45 is an EDX surface analysis image showing positive electrode active material particles according to the example. FIG.

[0069] FIG. 46 is a diagram illustrating EDX line analysis of positive electrode active material particles according to an example.

[0070] FIG. 47 is a graph showing the atomic concentration of positive electrode active material particles according to an example in EDX line analysis.

[0071] FIG. 48 is a graph showing the atomic concentration of positive electrode active material particles according to an example in EDX line analysis.

[0072] FIG. 49 is a diagram showing the atomic number ratio in EDX line analysis of positive electrode active material particles according to an example.

[0073] FIG. 50 is an EDX surface analysis image showing positive electrode active material particles according to the example.

[0074] FIG. 51 is an EDX surface analysis image showing positive electrode active material particles according to an example.

[0075] FIG. 52 is a graph showing the atomic concentration of positive electrode active material particles according to an example in EDX line analysis.

[0076] FIG. 53 is a graph showing the atomic concentration of positive electrode active material particles according to an example in EDX line analysis.

[0077] FIG. 54 is a diagram showing the atomic number ratio in EDX line analysis of positive electrode active material particles according to an example.

[0078] Modes for Carrying Out the Invention

[0079] The following describes embodiments of the present invention in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following description, and those skilled in the art will readily appreciate that its methods and details can be modified in various forms. Furthermore, the present invention should not be construed as being limited solely to the following embodiments.

[0080] In addition, in the drawings described in this specification, the sizes and thicknesses of various components, such as the positive electrode, negative electrode, active material layer, separator, and outer packaging, are sometimes exaggerated for clarity. Therefore, the sizes of the components are not limited, and the relative sizes of the components are not limited.

[0081] In addition, in the structure of the present invention described in this specification, the same reference numerals are used in common between different drawings to represent the same parts or parts having the same function, and their repeated descriptions are omitted. In addition, the same hatching is sometimes used to represent parts having the same function without adding a special reference numeral.

[0082] In crystallography, numbers are preceded by superscript horizontal bars to indicate crystal planes and orientations. However, in this specification and other documents, due to the symbol restrictions in patent applications, numbers are preceded by - (minus sign) to indicate crystal planes and orientations instead of superscript horizontal bars. In addition, "[]" indicates an individual orientation within a crystal, "<>" indicates a collective orientation of all equivalent crystal directions, "()" indicates an individual face of a crystal face, and "{}" indicates a collective face with equivalent symmetry.

[0083] In this specification and the like, segregation refers to a phenomenon in which the concentration of a certain element (for example, B) is unevenly distributed in a solid containing a plurality of elements (for example, A, B, and C).

[0084] (Implementation 1)

[0085] [Structure of positive electrode active material]

[0086] Reference Figures 1A to 1C and Figures 2A to 2C A positive electrode active material particle 100 according to one embodiment of the present invention will be described.

[0087] Figure 1A The appearance of the positive electrode active material particles 100 is shown. The positive electrode active material particles 100 are amorphous particles. Figure 1A The shape of the positive electrode active material particles 100 shown is just an example and is not limited thereto.

[0088] The positive electrode active material particle 100 includes a plurality of crystal grains 101 and a plurality of grain boundaries 103 . Figure 1B The positive electrode active material particles 100 include crystal grains 101 and grain boundaries 103. Figure 1B The dotted line represents the grain boundary 103, but sometimes the boundary between the grain 101 and the grain boundary 103 is not clear. Figure 1B The shapes and numbers of the crystal grains 101 and grain boundaries 103 shown are merely examples and are not limited thereto.

[0089] The crystal grains 101 are particles with roughly the same crystal orientation within the crystal grains. Adjacent crystal grains 101 have different crystal orientations, and there is a grain boundary 103 between adjacent crystal grains. In other words, the positive electrode active material particles 100 include a plurality of crystal grains 101 sandwiched between grain boundaries 103, and the positive electrode active material particles 100 can also be referred to as polycrystalline. The positive electrode active material particles 100 may also include crystal defects 105 or amorphous regions. Note that in this specification, etc., crystal defects refer to bulk defects, surface defects, point defects, or structures with other elements entering the crystals that can be observed through TEM images, etc. Note that crystal grains are sometimes referred to as crystallites.

[0090] The grains 101 and grain boundaries 103 in the positive electrode active material particles 100 can be confirmed by using X-ray diffraction (XRD: X-ray Diffraction), neutron diffraction, electron diffraction (ED: Electron Diffraction), transmission electron microscope (TEM: Transmission Electron Microscope) images, scanning transmission electron microscope (STEM: Scanning Transmission Electron Microscopy) images, fast Fourier transform (FFT: Fast Fourier Transformation) analysis of the lattice image obtained corresponding to the TEM image or STEM image, high-angle annular dark field-scanning transmission electron microscope (HAADF-STEM: High-Angle Annular Dark Field Scanning TEM) image, annular bright field-scanning transmission electron microscope (ABF-STEM: Annular Bright-Field Scanning TEM) image, Raman spectroscopy (Raman Spectroscopy), electron backscatter diffraction (EBSD: Electron Backscatter Diffraction), etc. Note that the electron backscatter diffraction method is sometimes referred to as EBSP (Electron Backscatter Diffraction Pattern). For example, in a TEM image, when the concentration (brightness) of the TEM image is roughly uniform, the crystal orientation is roughly consistent, that is, it can sometimes be judged to be a single crystal. In addition, depending on the crystal orientation, the concentration (brightness) of the TEM image is different, so sometimes it can be judged that the area where the concentration (brightness) changes is a grain boundary. However, it is not necessary to observe a clear boundary between the grain 101 and the grain boundary 103 through various analyses.

[0091] 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. Preferably, the grain boundaries 103 also contain fluorine.

[0092] Energy dispersive X-ray spectroscopy (EDX), time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and electron energy loss spectroscopy (EELS) can be used to confirm that the grains 101 and grain boundaries 103 have different compositions. However, it is not necessary to observe a clear boundary between the grains 101 and grain boundaries 103 through various analyses. Note that the desired target element may not be detected depending on the analytical technique. Alternatively, when the concentration of the target element is extremely low, the target element may not be detected.

[0093] <Grain Boundary>

[0094] The positive electrode active material particles 100 according to one embodiment of the present invention include grain boundaries 103 containing magnesium and oxygen. The grain boundaries 103 include magnesium oxide. Preferably, the grain boundaries 103 also contain fluorine. Some of the oxygen in the magnesium oxide may be substituted with fluorine. By partially replacing the magnesium oxide with fluorine, for example, lithium diffusivity can be improved without hindering charge and discharge. The inclusion of fluorine in the grain boundaries 103 may make the material less soluble in hydrofluoric acid.

[0095] The grain boundary 103 has a region with a higher magnesium concentration than the crystal grain 101. In other words, the grain boundary 103 has a region where magnesium segregates.

[0096] The grain boundary 103 has a region with a higher fluorine concentration than the crystal grain 101. The grain boundary 103 has a region where fluorine segregates.

[0097] Figure 2B Show Figure 2A An example of the magnesium concentration distribution between the dot-dash line A1-A2 of the positive electrode active material particle 100 is shown in FIG. Figure 2C An example of fluorine concentration distribution is shown. Figure 2B and Figure 2C In the middle, the horizontal axis represents Figure 2A The distance between the dotted line A1-A2 in the figure, the vertical axis represents the magnesium concentration (MgConcentration) and the fluorine concentration (FConcentration), respectively.

[0098] The grain boundaries 103 and the vicinity of the grain boundaries 103 have regions with higher magnesium and fluorine concentrations than the crystal grains 101. In addition, the crystal defects 105 may also have regions with higher magnesium and fluorine concentrations. Figure 2B and Figure 2C The example in which the grain boundary 103 and the crystal defect 105 have the same concentration is shown, but the present invention is not limited to this. In addition, the shape of the concentration distribution of magnesium and fluorine is not limited to Figure 2B and Figure 2C The shape shown.

[0099] Here, the number of transition metal atoms in the crystal grain 101 is represented by Tr-Metal. The number of transition metal atoms in the crystal grain 101 (Tr-Metal) refers to the total number of atoms of each transition metal in the crystal grain 101.

[0100] The positive electrode active material particles 100 preferably have a region where the ratio of the number of magnesium atoms in the grain boundaries 103 to the number of transition metal atoms in the crystal grains 101 (Mg / Tr-Metal) is greater than or equal to 0.010 and less than or equal to 0.50. More preferably, the positive electrode active material particles 100 have a region where the Mg / Tr-Metal ratio is greater than or equal to 0.020 and less than or equal to 0.30. Even more preferably, the positive electrode active material particles 100 have a region where the Mg / Tr-Metal ratio is greater than or equal to 0.030 and less than or equal to 0.20. By having such a Mg / Tr-Metal ratio, degradation of the positive electrode active material can be reduced. In other words, degradation of the power storage device can be suppressed. In addition, a highly safe power storage device can be provided.

[0101] In this specification, transition metals refer to elements in Groups 3 to 12 of the periodic table. These group numbers are based on the periodic table classified into Groups 1 to 18 in the revised version of the Inorganic Chemical Nomenclature of the International Union of Pure and Applied Chemistry (IUPAC) (1989).

[0102] Generally speaking, as a storage device is repeatedly charged and discharged, side reactions such as the dissolution of transition metals such as cobalt and manganese in the positive electrode active material particles contained in the storage device into the electrolyte, oxygen detachment, and unstable crystal structure occur, causing the positive electrode active material particles to continuously deteriorate. When the positive electrode active material particles deteriorate, the degradation may sometimes progress, such as a decrease in the capacity of the storage device. Note that in this specification, etc., the phenomenon of chemical and structural changes in the positive electrode active material particles, such as the dissolution of transition metals in the positive electrode active material particles into the electrolyte, oxygen detachment, and unstable crystal structure, is sometimes referred to as degradation of the positive electrode active material particles. In this specification, etc., a decrease in the capacity of the storage device is sometimes referred to as degradation of the storage device.

[0103] Metals dissolved from the positive electrode active material particles are reduced and deposited on the negative electrode, sometimes hindering the negative electrode reaction. Deposition of metals on the negative electrode can lead to progressive deterioration, such as decreased capacity.

[0104] The crystal lattice of the positive electrode active material particles expands and contracts due to the insertion and extraction of lithium during charging and discharging, sometimes causing volume changes and distortion of the lattice. This volume change and distortion can cause the positive electrode active material particles to break, sometimes leading to progressive degradation such as capacity reduction. Furthermore, the cracking of the positive electrode active material particles sometimes originates at the grain boundaries.

[0105] When high temperatures reach a certain temperature within a battery device, oxygen may be released from the positive electrode active material particles, potentially compromising the device's safety. Furthermore, this oxygen release can alter the crystal structure of the positive electrode active material particles, sometimes leading to progressive degradation such as decreased capacity. Note that oxygen may be released from the positive electrode active material particles due to the intercalation and deintercalation of lithium during charging and discharging.

[0106] On the other hand, magnesium oxide is a chemically and structurally stable material. In energy storage devices like lithium-ion secondary batteries, the magnesium oxide contained in the positive electrode active material particles itself is largely irrelevant to the battery reaction. In other words, magnesium oxide is not susceptible to lithium insertion and removal, making it chemically and structurally stable even during charge and discharge cycles.

[0107] The positive electrode active material particles 100 of one embodiment of the present invention contain magnesium oxide in the grain boundaries 103, which can make the positive electrode active material particles 100 chemically and structurally stable, thereby suppressing structural changes, volume changes and distortion caused by charging and discharging. In other words, the crystal structure of the positive electrode active material particles 100 becomes more stable, and even if charging and discharging are repeated, the crystal structure changes can be suppressed. In addition, the cracking of the positive electrode active material particles 100 can be suppressed. In other words, degradation such as capacity reduction can be suppressed, so it is preferred. When the charging voltage is high and the amount of lithium present in the positive electrode during charging becomes less and less, the crystal structure is unstable and easily degraded. Since the crystal structure of the positive electrode active material particles 100 of one embodiment of the present invention is more stable, degradation such as capacity reduction can be suppressed, so it is particularly preferred.

[0108] Since the positive electrode active material particles 100 of one embodiment of the present invention have a stable crystal structure, elution of transition metal from the positive electrode active material particles can be suppressed. In other words, degradation such as capacity reduction can be suppressed, which is preferable.

[0109] Furthermore, when the positive electrode active material particles 100 according to one embodiment of the present invention fracture along the grain boundaries, the surfaces of the fractured positive electrode active material particles contain magnesium oxide. This means that side reactions can be suppressed in the fractured positive electrode active material, thereby reducing degradation of the positive electrode active material. This in turn reduces degradation of the power storage device.

[0110] The positive electrode active material particles 100 according to one embodiment of the present invention contain magnesium oxide in the grain boundaries 103, thereby suppressing diffusion of oxygen in the positive electrode active material particles 100 into the grain boundaries and suppressing oxygen from being released from the positive electrode active material particles 100. Using the positive electrode active material particles 100 can provide a highly safe electricity storage device.

[0111] In addition, when the crystal defects 105 include magnesium oxide, the crystal structure of the positive electrode active material particles 100 is stabilized, which is preferable.

[0112] The positive electrode active material particles 100 preferably have a region where the ratio of the number of fluorine atoms in the grain boundaries 103 to the number of transition metal atoms in the crystal grains 101 (F / Tr-Metal) is greater than or equal to 0.020 and less than or equal to 1.00. More preferably, the positive electrode active material particles 100 have a region where the F / Tr-Metal is greater than or equal to 0.040 and less than or equal to 0.60. Even more preferably, the positive electrode active material particles 100 have a region where the F / Tr-Metal is greater than or equal to 0.060 and less than or equal to 0.40. By having such an F / Tr-Metal, magnesium can be efficiently segregated at the grain boundaries and in their vicinity. In other words, the degradation of the positive electrode active material can be reduced. The degradation of the storage device can be suppressed. In addition, a highly safe storage device can be provided.

[0113] <Grain>

[0114] In one embodiment of the present invention, the crystal grains 101 of the positive electrode active material particles 100 contain lithium, a transition metal, and oxygen. For example, the crystal grains 101 contain a composite oxide containing lithium, a transition metal, and oxygen. Alternatively, one or more transition metals such as iron, cobalt, nickel, manganese, chromium, titanium, vanadium, and niobium may be used.

[0115] For example, a composite oxide having a layered rock salt crystal structure or a spinel crystal structure can be used as the crystal grains 101. Alternatively, for example, a polyanion positive electrode material can be used as the crystal grains 101. Examples of polyanion positive electrode materials include materials having an olivine crystal structure and Nasicon materials. Alternatively, for example, a positive electrode material containing sulfur can be used as the crystal grains 101.

[0116] Various composite oxides can be used as the crystal grains 101. For example, compounds such as LiFeO2, LiCoO2, LiNiO2, LiMn2O4, Li2MnO3, V2O5, Cr2O5, and MnO2 can be used.

[0117] 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 selected from one or more of Co and Ni. LiCoO2 is preferred due to its advantages such as large capacity, atmospheric stability, and thermal stability. Furthermore, the element M may include one or more of Al and Mn in addition to one or more of Co and Ni.

[0118] For example, LiNi x Mn y Co z O w (For example, x, y, z, and w are respectively x=y=z=1 / 3 or in the vicinity thereof, and w=2 or in the vicinity thereof). In addition, for example, LiNi x Mn y Co z O w (For example, x, y, z, and w are respectively x=0.8 or near it, y=0.1 or near it, z=0.1 or near it, and w=2 or near it.) Alternatively, for example, LiNi x Mn y Co z O w (For example, x, y, z, and w are respectively x=0.5 or near it, y=0.3 or near it, z=0.2 or near it, and w=2 or near it.) Alternatively, for example, LiNi x Mn y Co z O w (For example, x, y, z, and w are respectively x=0.6 or near it, y=0.2 or near it, z=0.2 or near it, and w=2 or near it.) Alternatively, for example, LiNi x Mn y Co z O w (For example, x, y, z, and w are respectively x=0.4 or thereabouts, y=0.4 or thereabouts, z=0.2 or thereabouts, and w=2 or thereabouts).

[0119] “Nearby” refers to, for example, a range greater than 0.9 times a certain value and less than 1.1 times the value.

[0120] As the crystal grain 101, the following materials can also be used: a material in which a part of the transition metal or lithium contained in the crystal grain 101 is replaced with one or more elements selected from Fe, Co, Ni, Cr, Al, Mg, etc.; a material in which the crystal grain 101 is doped with one or more elements selected from Fe, Co, Ni, Cr, Al, Mg, etc.

[0121] As a material having a spinel-type crystal structure, for example, a composite oxide represented by LiM2O4 can be used. As the element M, Mn is preferably included, for example, LiMn2O4 can be used. In addition, by containing Ni as the element M in addition to Mn, the discharge voltage and energy density of the secondary battery can sometimes be improved, so it is preferred. In addition, it is preferred to mix a small amount of lithium nickel oxide (LiNiO2 or LiNi) with a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4. 1- x M x O2 (M=Co, Al, etc.)), thereby improving the characteristics of the secondary battery.

[0122] For example, the average particle size of the primary particles of the positive electrode active material is preferably 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. 2 / g or above and 20m 2 / g or less. In addition, the average particle size of the secondary particles is preferably 5 μm or more and 50 μm or less. In addition, the average particle size can be measured by observation using a scanning electron microscope (SEM: Scanning Electron Microscope) or TEM or by a particle size distribution analyzer using a laser diffraction and scattering method. In addition, the specific surface area can be measured using a gas adsorption method.

[0123] A conductive material such as a carbon layer may also be provided on the surface of the positive electrode active material. By providing a conductive material such as a carbon layer, the conductivity of the electrode can be improved. For example, by mixing carbohydrates such as glucose when calcining the positive electrode active material, a carbon layer covering the positive electrode active material can be formed. In addition, as a conductive material, graphene, multilayer graphene, graphene oxide (GO: Graphene Oxide) or RGO (Reduced Graphene Oxide) can be used. Here, RGO refers to a compound obtained by reducing graphene oxide (GO), for example.

[0124] A layer containing one or more of an oxide and a fluoride may be provided on the surface of the positive electrode active material. The oxide may have a different composition from that of the crystal grains 101. Alternatively, the oxide may have the same composition as that of the crystal grains 101.

[0125] As the polyanion positive electrode material, for example, a composite oxide containing oxygen, element X, metal A, and metal M can be used. Metal M is one or more of Fe, Mn, Co, Ni, Ti, V, and Nb, metal A is one or more of Li, Na, and Mg, and element X is one or more of S, P, Mo, W, As, and Si.

[0126] As a material having an olivine-type crystal structure, for example, a composite material (general formula: LiMPO4, where M is one or more of Fe(II), Mn(II), Co(II), Ni(II))) can be used. As typical examples of LiMPO4, LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, LiFe a Ni b PO4, LiFe a Co b PO4, LiFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4 (a + b is 1 or less, 0 < a < 1, 0 < b < 1), LiFe c Ni d Co e PO4, LiFe c Ni d Mn e PO4, LiNi c Co d Mn e PO4 (c + d + e is 1 or less, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO4 (f + g + h + i is 1 or less, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), and other lithium compounds.

[0127] In particular, LiFePO4 preferably satisfies the required conditions for a cathode active material, such as safety, stability, high capacity density, high potential, and the presence of lithium ions that can be intercalated and deintercalated during initial oxidation (charging).

[0128] For example, the average particle size of the primary particles of the cathode active material having an olivine-type crystal structure is preferably 1 nm or more and 20 μm or less, more preferably 10 nm or more and 5 μm or less, and further preferably 50 nm or more and 2 μm or less. In addition, the specific surface area is preferably 1 m 2 / g or more and 20 m 2 / g or less. In addition, the average particle size of the secondary particles is preferably 5 μm or more and 50 μm or less.

[0129] Alternatively, a material with the general formula Li (2-j)Composite materials such as MSiO4 (where M is one or more of Fe(II), Mn(II), Co(II), Ni(II) and 0 ≤ j ≤ 2), etc. As the general formula Li (2-j) Typical examples of MSiO4 include Li (2-j) FeSiO4, Li (2-j) NiSiO4, Li (2-j) CoSiO4, Li (2-j) MnSiO4, Li (2-j) Fe k Ni l SiO4, Li (2-j) Fe k Co l SiO4, Li (2-j) Fe k Mn l SiO4, Li (2-j) Ni k Co l SiO4, Li[[ID=]] (2-j) Ni k Mn l SiO4 (where 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 (where 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 (where r + s + t + u is 1 or less, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1), etc.

[0130] In addition, composites represented by the general formula A xA Nasicon-type compound represented by M2(XO4)3 (A = Li, Na, Mg, M = Fe, Mn, Ti, V, Nb, X = S, P, Mo, W, As, Si). Examples of Nasicon-type compounds include Fe2(MnO4)3, Fe2(SO4)3, and Li3Fe2(PO4)3. Alternatively, compounds represented by the general formulas Li2MPO4F, Li2MP2O7, and Li5MO4 (M = Fe, Mn) can be used as crystal grains 101.

[0131] In addition, as the crystal grains 101, perovskite fluorides such as NaFeF3 and FeF3, metal chalcogenides (sulfides, selenides, tellurides) such as TiS2 and MoS2, oxides with an inverse spinel crystal structure such as LiMVO4, vanadium oxides (V2O5, V6O 13 , LiV3O8, etc.), manganese oxides, organic sulfur compounds and other materials.

[0132] Alternatively, as the crystal particles 101 , a borate-based positive electrode material represented by the general formula LiMBO 3 (M is one or more of Fe(II), Mn(II), and Co(II)) may be used.

[0133] In addition, as the crystal grains 101, for example, a solid solution of a combination of multiple composite oxides can be used. a O2 and Li2M b O3 solid solution (M a 、M b are independently selected from transition metals) are called lithium excess oxides. For example, LiNi x Mn y Co z The solid solution of O2 (x, y, z>0, x+y+z=1) and Li2MnO3 serves as the crystal grains 101.

[0134] In addition, as the crystal grain 101, it is possible to use a crystal grain having a composition formula of Li a Mn b M c O dHere, the element M is preferably a metal element other than lithium and manganese or silicon, phosphorus, and nickel is more preferably used. In addition, when measuring the particles of the lithium manganese composite oxide as a whole, it is preferred to satisfy 0 <a / (b+c)<2、c>0 and 0.26≤(b+c) / d<0.5 during discharge. In addition, in order to achieve a large capacity, the lithium manganese composite oxide preferably includes regions where the crystal structure, crystal orientation or oxygen content is different in the surface part and the center part. In order to form the above-mentioned lithium manganese composite oxide, for example, it is preferred to satisfy 1.6≤a≤1.848, 0.19≤c / b≤0.935, and 2.5≤d≤3. In addition, it is particularly preferred to use a lithium manganese composite oxide with the composition formula Li 1.68 Mn 0.8062 Ni 0.318 Lithium manganese composite oxide represented by O3. In this specification, the composition formula Li 1.68 Mn 0.8062 Ni 0.318 The lithium manganese composite oxide represented by O3 is a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the raw materials to Li2CO3:MnCO3:NiO=0.84:0.8062:0.318. 1.68 Mn 0.8062 Ni 0.318 O3 indicates, but sometimes slightly different from this composition.

[0135] The composition of metals, silicon, phosphorus, etc. in the entire particles of the lithium-manganese composite oxide can be measured, for example, using ICP-MS (Inductively Coupled Plasma Mass Spectrometry). Furthermore, the oxygen composition of the entire particles of the lithium-manganese composite oxide can be measured, for example, using EDX (energy dispersive X-ray spectroscopy). Furthermore, the oxygen composition of the entire particles of the lithium-manganese composite oxide can also be calculated using valence evaluation using fusion gas analysis or XAFS (X-ray Absorption Fine Structure) analysis in conjunction with ICP-MS analysis. The lithium-manganese composite oxide refers to an oxide containing at least lithium and manganese, and may further contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, and phosphorus.

[0136] Furthermore, sodium, potassium, strontium, barium, beryllium, etc. may be used as carrier ions instead of lithium. For example, a layered oxide containing sodium may be used.

[0137] As a material containing sodium, for example, NaFeO2, Na 2 / 3 ​[Fe 1 / 2 Mn 1 / 2 ]O2、Na 2 / 3 [Ni 1 / 3 Mn 2 / 3 ]O2, Na2Fe2(SO4)3, Na3V2(PO4)3, Na2FePO4F, NaVPO4F, NaMPO4 (M is one or more of Fe(II), Mn(II), Co(II), Ni(II)), Na2FePO4F, Na4Co3(PO4)2P2O7, etc., containing sodium, are used as positive electrode active materials.

[0138] Furthermore, metal sulfides containing lithium may be used as the positive electrode active material, for example, Li2TiS3, Li3NbS4, etc.

[0139] The above description is based on an example in which the positive electrode active material particles 100 include crystal grains 101 and grain boundaries 103, but one embodiment of the present invention is not limited thereto. Figure 1C As shown, the positive electrode active material particles 100 may also include a region 107. For example, the region 107 may be provided in contact with at least a portion of the crystal grain 101. The region 107 may be a coating containing carbon, such as a graphene compound, or a coating containing lithium or a decomposition product of an electrolyte. When the region 107 is a coating containing carbon, the conductivity between the positive electrode active material particles 100 and the conductivity between the positive electrode active material particles 100 and the current collector can be improved. When the region 107 is a coating containing lithium or a decomposition product of an electrolyte, excessive reaction with the electrolyte can be suppressed, thereby improving the cycle characteristics when the battery is used in a secondary battery.

[0140] If the particle size of the positive electrode active material particles 100 is too large, lithium diffusion becomes difficult. If the particle size of the positive electrode active material particles 100 is too small, problems such as reduced volume density of the electrode and excessive reaction with the electrolyte may occur. Therefore, the particle size is preferably between 1 μm and 100 μm, more preferably between 10 μm and 70 μm. Here, the particle size refers to, for example, the cumulative 50% value (D50) based on volume.

[0141] [Method for producing positive electrode active material]

[0142] Reference Figure 3 A method for producing a positive electrode active material particle 100 including crystal grains 101 and crystal grain boundaries 103 will be described. The crystal grains 101 include a composite oxide containing lithium, a transition metal (M), and oxygen. The crystal grain boundaries 103 contain magnesium, fluorine, and oxygen.

[0143] First, starting materials are prepared (step S11 ), specifically, a lithium source, a transition metal (M) source, a magnesium source, and a fluorine source are weighed.

[0144] As the lithium source, for example, lithium carbonate, lithium fluoride, lithium hydroxide, lithium oxide, or the like can be used.

[0145] 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, and niobium compounds can be used.

[0146] As the cobalt compound, for example, one or more of cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide, cobalt carbonate, cobalt oxalate, cobalt sulfate, and the like can be used.

[0147] 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, and the like can be used.

[0148] As the manganese compound, for example, one or more of manganese oxide, manganese hydroxide, manganese carbonate, manganese chloride, manganese iodide, manganese sulfate, and manganese nitrate can be used.

[0149] 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, and the like can be used.

[0150] As the vanadium compound, for example, one or more of vanadium oxide, vanadium hydroxide, vanadium chloride, and vanadium sulfate can be used.

[0151] As the titanium compound, for example, one or more of titanium fluoride, titanium chloride, titanium bromide, titanium iodide, titanium oxide, titanium sulfide, titanium sulfate, and the like can be used.

[0152] As the molybdenum compound, for example, one or more of molybdenum oxide, diammonium molybdate, phosphomolybdic acid, and the like can be used.

[0153] As the zinc compound, for example, one or more of zinc oxide, zinc hydroxide, zinc nitrate, zinc sulfate, zinc chloride, zinc carbonate, and the like can be used.

[0154] As the indium compound, for example, one or more of indium chloride, indium sulfate, indium nitrate, indium oxide, indium hydroxide, and the like can be used.

[0155] As the gallium compound, for example, one or more of gallium chloride, gallium fluoride, and the like can be used.

[0156] As the copper compound, for example, one or more of copper sulfate, copper chloride, copper nitrate, and the like can be used.

[0157] As the niobium compound, for example, one or more of niobium oxide, niobium chloride, niobium oxysulfate, niobium fluoride, and the like can be used.

[0158] As the magnesium source, for example, one or more of magnesium oxide, magnesium fluoride, magnesium hydroxide, magnesium carbonate, and the like can be used.

[0159] As the fluorine source, for example, one or more of lithium fluoride, magnesium fluoride, etc. In other words, lithium fluoride can be used as both a lithium source and a fluorine source, and magnesium fluoride can be used as both a magnesium source and a fluorine source.

[0160] When the crystal grains 101 include a metal other than the transition metal (M), the source of the metal other than the transition metal is weighed. When the metal other than the transition metal is aluminum, an aluminum compound, for example, can be used as the metal source. The aluminum compound can be one or more of aluminum oxide, aluminum hydroxide, aluminum carbonate, aluminum chloride, aluminum iodide, aluminum sulfate, aluminum nitrate, and the like.

[0161] The atomic number ratio of the transition metal (M) to magnesium in the raw material is described. The ratio m of the number of atoms of magnesium in the raw material Mg(r) relative to the number of atoms of the transition metal in the raw material M(r) is 0.0050 or more and 0.050 or less, that is, in the atomic number of transition metal M(r): the atomic number of magnesium Mg(r) = 1.0:m, preferably 0.0050≤m≤0.050. Furthermore, the atomic number ratio m of magnesium relative to the atomic number of transition metal is preferably 0.010 or thereabouts (1.0% or thereabouts). By adopting the above atomic number ratio, a positive electrode active material containing magnesium in the grain boundary 103 can be efficiently manufactured. In addition, when multiple transition metals are used as raw materials, the total number of multiple transition metal atoms can be used as the atomic number of transition metal M(r) for calculation.

[0162] Nearby refers to a value that is greater than 0.9 times the above value and less than 1.1 times the above value.

[0163] The atomic ratio of magnesium to fluorine in the raw material is described. The ratio n of the number of fluorine atoms F(r) to the number of magnesium atoms Mg(r) in the raw material is preferably 1.50 or greater and 4.0 or less. In other words, in the case of magnesium atoms Mg(r) : fluorine atoms F(r) = 1.0:n, 1.50 ≤ n ≤ 4.0 is preferred. Furthermore, the atomic ratio n of fluorine to magnesium atoms is preferably 2.0 or approximately thereabouts. In other words, the atomic ratio n of magnesium atoms Mg(r) : fluorine atoms F(r) is preferably 1.0:2.0 or approximately thereabouts. By adopting this atomic ratio, magnesium and fluorine can be efficiently segregated at the grain boundaries 103.

[0164] The atomic ratio of the transition metal, magnesium, and fluorine in the raw material can be expressed by Formula 1. Here, m represents the ratio of the number of magnesium atoms (Mg(r)) to the number of transition metal atoms (M(r)). As described above, 0.0050 ≤ m ≤ 0.050 is preferred, with m = 0.010 or thereabouts being more preferred. n represents the ratio of the number of fluorine atoms (F(r)) to the number of magnesium atoms (Mg(r)). As described above, 1.50 ≤ n ≤ 4.0 is preferred, with n = 2.0 or thereabouts being more preferred.

[0165] [Formula 1]

[0166] M(r):Mg(r):F(r)=1.0:m:m×n…(1)

[0167] The following shows an example of raw material ratios for producing LiCoO2 as a positive electrode active material particle. The atomic ratio m of magnesium to the atomic number of cobalt is set to 0.010. The atomic ratio n of fluorine to the atomic number of magnesium is set to 2.0. According to Equation 1, the atomic ratio of cobalt, magnesium, and fluorine in the raw material can be set to Co:Mg:F = 1.0:0.010:0.020.

[0168] Furthermore, the atomic ratio of the raw materials may not match the composition of the positive electrode active material particles 100 obtained by synthesis.

[0169] As the mol ratio of the lithium compound and the transition metal (M) compound in the raw material, the value corresponding to the estimated grain composition can be adopted. In addition, for example, when the lithium composition of the grains obtained relative to the mol ratio of the lithium compound in the raw material is small, the mol ratio of the lithium compound in the raw material can be increased.

[0170] Next, the weighed starting materials are mixed (step S12). For example, the mixing can be performed using a ball mill, a sand mill, or the like.

[0171] Next, the materials mixed in step S12 are first heated (step S13). The first heating is preferably performed at a temperature of 800°C to 1050°C, more preferably 900°C to 1000°C. The heating time is preferably 2 hours to 20 hours. The first heating is preferably performed in an oxygen-containing atmosphere. For example, it is preferably performed in a dry air atmosphere.

[0172] The first heating in step S13 synthesizes a composite oxide containing lithium and a transition metal (M) contained in the crystal grains 101. Furthermore, this first heating causes a portion of the magnesium and fluorine contained in the starting material to segregate in the surface layer of the composite oxide containing lithium and a transition metal (M). However, at this time, a portion of the magnesium and fluorine is solid-dissolved in the composite oxide containing lithium and a transition metal (M).

[0173] Next, the material heated in step S13 is cooled to room temperature (step S14 ). After cooling, the synthesized material is preferably pulverized to reduce the particle size of the positive electrode active material particles 100 .

[0174] Next, the material cooled in step S14 is subjected to a second heating (step S15). The second heating is preferably carried out at a predetermined temperature for a holding time of 100 hours or less, more preferably for 1 hour or more and 70 hours or less, further preferably for 2 hours or more and 50 hours or less, and more preferably for 2 hours or more and 35 hours or less. The predetermined temperature is preferably 500°C or more and 1200°C or less, more preferably 700°C or more and 1000°C or less, and further preferably about 800°C. The second heating is preferably carried out in an oxygen atmosphere. For example, it is preferably carried out in a dry air atmosphere.

[0175] By performing the second heating in step S15 , segregation of magnesium and fluorine contained in the starting material to the grain boundaries can be promoted.

[0176] Finally, the material heated in S15 is cooled to room temperature and recovered (step S16 ), thereby obtaining the positive electrode active material particles 100 .

[0177] As described above, by mixing a magnesium source and a fluorine source as starting materials, a positive electrode active material in which the grain boundaries 103 contain magnesium oxide can be efficiently produced.

[0178] In addition, by mixing a magnesium source and a fluorine source as starting materials, magnesium can be easily segregated to the grain boundaries 103 .

[0179] When oxygen bonded to magnesium is substituted with fluorine, magnesium may easily move around the substituted fluorine.

[0180] Furthermore, the melting point may be lowered by adding magnesium fluoride to magnesium oxide, and when the melting point is lowered, atoms are more likely to move during heating.

[0181] Furthermore, fluorine has a higher electronegativity than oxygen. Therefore, even in stable compounds such as magnesium oxide, the addition of fluorine may cause a charge imbalance and weaken the bond between magnesium and oxygen.

[0182] For the reasons described above, by mixing the magnesium source and the fluorine source as starting materials, magnesium is facilitated to move and segregate to the grain boundaries 103 .

[0183] By using the positive electrode active material particles 100 described in this embodiment, a secondary battery with less degradation and high safety can be manufactured. This embodiment can be used in combination with other embodiments as appropriate.

[0184] (Implementation Method 2)

[0185] This embodiment describes examples of materials that can be used in a secondary battery including the positive electrode active material 100 described in the above embodiment. This embodiment describes a secondary battery in which a positive electrode, a negative electrode, and an electrolyte solution are surrounded by an outer casing.

[0186] [positive electrode]

[0187] The positive electrode includes a positive electrode active material layer and a positive electrode current collector.

[0188] <Positive Electrode Active Material Layer>

[0189] The positive electrode active material layer contains positive electrode active material particles. In addition, the positive electrode active material layer may also contain a conductive auxiliary agent and a binder.

[0190] As the positive electrode active material particles, the positive electrode active material particles 100 described in the above embodiment can be used. By using the positive electrode active material particles 100 described in the above embodiment, a secondary battery with little degradation and high safety can be realized.

[0191] As the conductive additive, carbon materials, metal materials, or conductive ceramic materials can be used. In addition, fibrous materials can also be used as the conductive additive. The proportion of the conductive additive in the total active material layer is preferably from 1 wt% to 10 wt%, more preferably from 1 wt% to 5 wt%.

[0192] The use of conductive additives can form a conductive network within the electrode. They can also maintain conductive pathways between the positive electrode active material particles. Adding conductive additives to the active material layer can create an active material layer with high electrical conductivity.

[0193] As the conductive auxiliary agent, for example, natural graphite, artificial graphite such as mesophase carbon microbeads, carbon fibers, etc. can be used. As carbon fibers, for example, carbon fibers such as mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers can be used. As carbon fibers, carbon nanofibers or carbon nanotubes can be used. For example, carbon nanotubes can be produced by vapor phase growth methods, etc. As the conductive auxiliary agent, for example, carbon materials such as carbon black (acetylene black (AB), etc.), graphite (graphite) particles, graphene, or fullerene can be used. In addition, for example, metal powders or metal fibers of copper, nickel, aluminum, silver, gold, etc., conductive ceramic materials, etc. can be used.

[0194] In addition, a graphene compound may also be used as a conductive auxiliary agent.

[0195] Graphene compounds sometimes have excellent electrical properties such as high conductivity and excellent physical properties such as high flexibility and high mechanical strength. In addition, graphene compounds have a planar shape. Graphene compounds can form surface contacts with low contact resistance. Graphene compounds sometimes have very high conductivity even when thin, so a conductive path can be formed efficiently in a small amount in the active material layer. Therefore, by using a graphene compound as a conductive auxiliary agent, the contact area between the active material and the conductive auxiliary agent can be increased, so it is preferred. In addition, sometimes by using a graphene compound as a conductive auxiliary agent, the resistance can be reduced, so it is preferred. Here, it is particularly preferred to use, for example, graphene, multilayer graphene or Reduced Graphene Oxide (hereinafter, RGO) as the graphene compound. Here, RGO refers to a compound obtained by reducing graphene oxide (GO: Graphene Oxide), for example.

[0196] When using active material particles with a small particle size, for example, active material particles with a particle size of 1 μm or less, the specific surface area of ​​the active material particles is large, so more conductive paths connecting the active material particles are required. Therefore, the amount of conductive additive increases, and sometimes the content of the active material decreases. When the content of the active material decreases, the capacity of the secondary battery also decreases. In this case, since there is no need to reduce the content of the active material, it is particularly preferred to use a graphene compound that can efficiently form a conductive path even in a small amount.

[0197] Hereinafter, an example of the cross-sectional structure of the active material layer 200 including a graphene compound as a conductive auxiliary agent will be described as an example.

[0198] Figure 4A This is a longitudinal cross-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 serving as a conductive additive, and a binder (not shown). Here, as the graphene compound 201, for example, graphene or multilayer graphene can be used. Furthermore, the graphene compound 201 preferably has a sheet shape. The graphene compound 201 can be formed into a sheet by partially overlapping multiple multilayer graphene or (and) multiple single-layer graphene.

[0199] In the longitudinal cross section of the active material layer 200, as shown in FIG. Figure 4A As shown in FIG, the flake-shaped graphene compound 201 is substantially uniformly dispersed inside the active material layer 200. Figure 4AIn the figure, although the graphene compound 201 is schematically represented by a bold line, in reality, the graphene compound 201 is a thin film having a thickness of a single or multiple carbon molecules. Since the plurality of graphene compounds 201 are formed so as to wrap or cover the plurality of granular positive electrode active material particles 100 or to adhere to the surfaces of the plurality of granular positive electrode active material particles 100, the graphene compound 201 is in surface contact with the positive electrode active material 100.

[0200] Here, by bonding multiple graphene compounds to each other, a mesh-like graphene compound sheet (hereinafter referred to as a graphene compound mesh or graphene mesh) can be formed. When the graphene mesh covers the active material, the graphene mesh can be used as a binder to bond the compounds to each other. Therefore, the amount of binder can be reduced or eliminated, thereby increasing the proportion of active material in the electrode volume or electrode weight. In other words, the capacity of the storage device can be increased.

[0201] Here, it is preferred to use graphene oxide as the graphene compound 201, mix this graphene oxide with an active material to form a layer to become the active material layer 200, and then reduce it. By using graphene oxide, which has extremely high dispersibility in a polar solvent, to form the graphene compound 201, the graphene compound 201 can be dispersed approximately uniformly in the active material layer 200. By volatilizing and removing the solvent from the dispersion medium containing the uniformly dispersed graphene oxide and reducing the graphene oxide, the graphene compounds 201 remaining in the active material layer 200 partially overlap and are dispersed in a manner that forms surface contact, thereby forming a three-dimensional conductive path. Alternatively, the reduction of the graphene oxide can be performed, for example, by heat treatment or the use of a reducing agent.

[0202] Therefore, unlike granular conductive additives such as acetylene black, which form point contact with the active material, the graphene compound 201 can form surface contact with low contact resistance. Therefore, the conductivity between the granular positive electrode active material particles 100 and the graphene compound 201 can be improved with a smaller amount of graphene compound 201 than with typical conductive additives. Consequently, the proportion of the positive electrode active material particles 100 in the active material layer 200 can be increased. Consequently, the discharge capacity of the power storage device can be increased.

[0203] Preferred adhesives include, for example, styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene-propylene-diene copolymer. Fluororubber can also be used as the adhesive.

[0204] In addition, as the binder, for example, a water-soluble polymer is preferably used. As the water-soluble polymer, for example, polysaccharides can be used. As the polysaccharide, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose, starch, etc. can be used. More preferably, these water-soluble polymers are used in combination with the above-mentioned rubber material.

[0205] Alternatively, as the adhesive, materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene monomer polymer, polyvinyl acetate, and nitrocellulose are preferably used.

[0206] As the binder, a plurality of the above-mentioned materials may be used in combination.

[0207] For example, it is also possible to combine materials with other materials that have a particularly high viscosity adjustment function and use them. For example, although rubber materials etc. have high bonding strength and high elasticity, it is sometimes difficult to adjust the viscosity when mixed in a solvent. In such a case, for example, it is preferably mixed with a material that has a particularly high viscosity adjustment function. As a material that has a particularly high viscosity adjustment function, for example, a water-soluble polymer can be used. In addition, as a water-soluble polymer that has a particularly good viscosity adjustment function, the above-mentioned polysaccharides can be used, for example, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose and diacetyl cellulose, regenerated cellulose, and starch can be used.

[0208] Note that cellulose derivatives such as carboxymethyl cellulose, when converted to salts such as sodium or ammonium carboxymethyl cellulose, have increased solubility, making them more effective as viscosity modifiers. This increased solubility improves the dispersibility of the active material and other components when forming the electrode slurry. In this specification, cellulose and cellulose derivatives used as electrode binders include their salts.

[0209] By dissolving a water-soluble polymer in water to stabilize its viscosity, the active material and other materials used as a binder, such as styrene-butadiene rubber, can be stably dispersed in the aqueous solution. Because water-soluble polymers contain functional groups, they are expected to readily and stably adhere to the surface of the active material. Cellulose derivatives such as carboxymethyl cellulose often have functional groups such as hydroxyl and carboxyl groups. Because of these functional groups, the polymers are expected to interact with each other and extensively cover the surface of the active material.

[0210] When the binder forms a film covering or contacting the active material surface, it is also expected to function as a passivation film, thereby inhibiting electrolyte decomposition. A passivation film is a film with no or very low conductivity. For example, when formed on the active material surface, the passivation film inhibits electrolyte decomposition at the battery reaction potential. More preferably, the passivation film can transport lithium ions while suppressing conductivity.

[0211] <Positive Electrode Current Collector>

[0212] As the positive electrode current collector, materials with high conductivity such as stainless steel, gold, platinum, aluminum, titanium and alloys thereof can be used. In addition, the material used for the positive electrode current collector is preferably not dissolved by the potential of the positive electrode. In addition, aluminum alloys to which elements such as silicon, titanium, neodymium, scandium, and molybdenum that improve heat resistance are added can also be used. In addition, metal elements that react with silicon to form silicides can also be used. As metal elements that react with silicon to form silicides, there are zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately have shapes such as foil, plate (sheet), mesh, punched metal mesh, and drawn metal mesh. The thickness of the current collector is preferably not less than 5 μm and not more than 30 μm.

[0213] [negative electrode]

[0214] The negative electrode includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also contain a conductive additive and a binder.

[0215] <Negative Electrode Active Material>

[0216] As the negative electrode active material, for example, an alloy material or a carbon material can be used.

[0217] As the negative electrode active material, an element capable of undergoing charge-discharge reactions through alloying / de-alloying reactions with lithium can be used. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium can be used. These elements have a greater capacity than carbon, with silicon, in particular, having a theoretical capacity of 4200 mAh / g. Therefore, silicon is preferably used for the negative electrode active material. Alternatively, compounds containing these elements can be used. Examples include SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, and SbSn. Elements that can undergo charge and discharge reactions through alloying / de-alloying reactions with lithium, and compounds containing these elements are sometimes referred to as alloying materials.

[0218] In this specification, SiO refers to silicon monoxide, for example. Alternatively, SiO can also be expressed as SiO x Here, x preferably represents a value of 1 or a value close thereto. For example, x is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0219] As the carbon-based material, graphite, easily graphitizable carbon (soft carbon), hardly graphitizable carbon (hard carbon), carbon nanotubes, graphene, carbon black, and the like can be used.

[0220] As graphite, artificial graphite or natural graphite can be mentioned. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spherical graphite having a spherical shape can be used as artificial graphite. For example, MCMB sometimes has a spherical shape, so it is preferred. In addition, MCMB is relatively easy to reduce its surface area, so it is sometimes preferred. As natural graphite, examples of flake graphite and spheroidized natural graphite can be mentioned.

[0221] When lithium ions are intercalated in graphite (when lithium-graphite intercalation compounds are generated), graphite exhibits a potential as low as that of lithium metal (0.05 V to 0.3 V vs. Li / Li). + This allows lithium-ion secondary batteries to exhibit high operating voltages. Graphite also has the following advantages: high capacity per unit volume; relatively low volume expansion; low cost; and greater safety compared to lithium metal, making it a preferred material.

[0222] In addition, as the negative electrode active material, oxides such as titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), etc.

[0223] In addition, as the negative electrode active material, LiN-type ... 3-x M x N (M = Co, Ni, Cu). For example, Li 2.6 Co 0.4 N3 shows a larger charge and discharge capacity (900 mAh / g, 1890 mAh / cm 3 ), so it is preferred.

[0224] When a nitride containing lithium and a transition metal is used as the negative electrode active material, lithium ions are contained in the negative electrode active material. Therefore, this negative electrode active material can be combined with a material that does not contain lithium ions, such as V2O5 or Cr3O8, used as the positive electrode active material, which is preferred. Note that when a material containing lithium ions is used as the positive electrode active material, by preliminarily deintercalating the lithium ions contained in the positive electrode active material, a nitride containing lithium and a transition metal can also be used as the negative electrode active material.

[0225] In addition, materials that cause conversion reactions can also be used as negative electrode active materials. For example, transition metal oxides that do not form alloys with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), can be used as negative electrode active materials. Materials that cause conversion reactions can also include oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, CoS 0.89 , NiS, CuS and other sulfides, Zn3N2, Cu3N, Ge3N4 and other nitrides, NiP2, FeP2, CoP3 and other phosphides, FeF3, BiF3 and other fluorides.

[0226] As the conductive additive and binder that may be contained in the negative electrode active material layer, the same materials as those that may be contained in the positive electrode active material layer can be used.

[0227] <Negative Electrode Current Collector>

[0228] As the negative electrode current collector, the same materials as those for the positive electrode current collector can be used. In addition, as the negative electrode current collector, it is preferable to use a material that does not alloy with carrier ions such as lithium.

[0229] [Electrolyte]

[0230] The electrolyte comprises a solvent and an electrolyte. As the solvent of the electrolyte, an aprotic organic solvent is preferably used, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, vinyl chloride carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, ethylene glycol dimethyl ether (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme (methyldiglyme), acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. can be used, or two or more of the above can be used in any combination and ratio.

[0231] Furthermore, by using a flame-retardant fluorine-containing phosphate compound or fluorine-containing carbonate compound as a solvent for the electrolyte, it is possible to prevent rupture or fire of the storage device. Examples of fluorine-containing phosphate compounds include tris(2,2,2-trifluoroethyl)phosphate (TFEP). Examples of fluorine-containing carbonate compounds include bis(2,2,2-trifluoroethyl)carbonate (TFEC).

[0232] Furthermore, when a gelled polymer material is used as the solvent for the electrolyte, safety against leakage is improved. Furthermore, the secondary device can be made thinner and lighter. Typical examples of gelled polymer materials include silicone gel, acrylic acid gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, and fluorine polymer gel.

[0233] In addition, by using one or more ionic liquids (room temperature molten salts) with flame retardancy and low volatility as the solvent of the electrolyte, even if the internal temperature rises due to the internal short circuit, overcharge, etc. of the storage device, the rupture or fire of the storage device can be prevented. The ionic liquid is composed of a cation and anion, including an organic cation and anion. As the organic cation for the electrolyte, aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations and quaternary phosphonium cations or aromatic cations such as imidazolium cations and pyridinium cations can be enumerated. In addition, as the anion for the electrolyte, monovalent amide anions, monovalent methylated anions, fluorosulfonic acid anions, perfluoroalkyl sulfonic acid anions, tetrafluoroborate anions, perfluoroalkyl borate anions, hexafluorophosphate anions or perfluoroalkyl phosphate anions can be enumerated.

[0234] In addition, as the electrolyte dissolved in the above solvent, for example, LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B10 Cl 10 、Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2 and other lithium salts, or two or more of the above can be used in any combination and ratio.

[0235] As the electrolyte for the power storage device, it is preferred to use a highly purified electrolyte with a low content of particulate dust or elements other than the constituent elements of the electrolyte (hereinafter referred to as "impurities"). Specifically, the ratio of impurities to the weight of the electrolyte is 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

[0236] In addition, vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxaloyl borate) (LiBOB), dinitrile compounds such as succinonitrile and adiponitrile, triisopropoxyboroxine (TiPBx), sulfolane, hydrofluoroether (HFE), vinyl acetate (VA), etc. may be added to the electrolyte. For example, the concentration of the added material may be set to 0.1% by weight or more and 5% by weight or less of the total solvent.

[0237] Alternatively, a polymer gel electrolyte obtained by swelling a polymer with an electrolyte solution may be used.

[0238] The use of a polymer gel electrolyte improves safety against leakage and enables thinner and lighter secondary devices.

[0239] As the polymer of gelation, silicone gel, acrylic acid glue, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, fluorine polymer gel etc. can be used.As polymer, for example, polyethylene oxide (PEO) etc. can be used to have the polymer of polyoxyalkylene structure, PVDF and polyacrylonitrile etc. and the copolymer that comprises these etc. For example, PVDF-HFP as the copolymer of PVDF and hexafluoropropylene (HFP) can be used. In addition, formed polymer also can have porous shape.

[0240] Alternatively, solid electrolytes containing inorganic materials such as sulfides or oxides, or polymers such as polyethylene oxide (PEO), can be used instead of electrolytes. Using a solid electrolyte eliminates the need for separators or spacers. Furthermore, since the entire battery can be solidified, there's no risk of leakage, significantly improving safety.

[0241] [Isolated Body]

[0242] The secondary battery preferably includes a separator. Examples of the separator include cellulose fibers such as paper, nonwoven fabrics, glass fibers, ceramics, and synthetic fibers such as nylon (polyamide), vinylon (polyvinyl alcohol-based fibers), polyester, acrylic resin, polyolefin, and polyurethane. The separator is preferably formed into a bag-like shape and positioned so as to surround either the positive or negative electrode.

[0243] The separator can have a multilayer structure. For example, a thin film of an organic material such as polypropylene or polyethylene can be coated with a ceramic material, a fluorine material, a polyamide material, or a mixture thereof. Examples of ceramic materials include aluminum oxide particles and silicon oxide particles. Examples of fluorine materials include PVDF and polytetrafluoroethylene. Examples of polyamide materials include nylon and aromatic polyamides (meta-aramid and para-aramid).

[0244] Applying ceramic materials can improve oxidation resistance, thereby suppressing separator degradation during high-voltage charge and discharge, thereby improving the reliability of the secondary battery. Applying fluorine-based materials facilitates close contact between the separator and the electrode, thereby improving output characteristics. Applying polyamide materials (particularly aromatic polyamide) can improve heat resistance, thereby enhancing the safety of the secondary battery.

[0245] For example, a mixture of aluminum oxide and aramid can be coated on both sides of a polypropylene film. Alternatively, the surface of the polypropylene film that contacts the positive electrode can be coated with a mixture of aluminum oxide and aramid, while the surface that contacts the negative electrode can be coated with a fluorine-based material.

[0246] By adopting a multi-layered separator, the safety of the secondary battery can be ensured even if the total thickness of the separator is small, and thus the capacity per unit volume of the secondary battery can be increased.

[0247] (Implementation 3)

[0248] In this embodiment, an example of the shape of a secondary battery including the positive electrode active material particles 100 described in the above embodiment will be described. Materials used for the secondary battery described in this embodiment can refer to the description of the above embodiment.

[0249] [Coin-type secondary battery]

[0250] First, an example of a coin-type secondary battery will be described. Figure 5A This is the appearance of a coin-type (single-layer flat) secondary battery. Figure 5B It is its cross-sectional view.

[0251] In a coin-type secondary battery 300, a positive electrode can 301, which also serves as a positive terminal, and a negative electrode can 302, which also serves as a negative terminal, are insulated and sealed by a gasket 303 made of polypropylene or the like. A positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact therewith. A negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact therewith.

[0252] In the positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 , the active material layer may be formed on one surface of the positive electrode and the negative electrode, respectively.

[0253] For the positive electrode can 301 and the negative electrode can 302, metals such as nickel, aluminum, and titanium, alloys thereof, or alloys of these with other metals (e.g., stainless steel) that are resistant to corrosion by the electrolyte can be used. Furthermore, to prevent corrosion from the electrolyte, the positive electrode can 301 and the negative electrode can 302 are preferably covered with nickel, aluminum, or the like. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307.

[0254] By impregnating the negative electrode 307, the positive electrode 304 and the separator 310 in an electrolyte, such as Figure 5B As shown, the positive electrode can 301 is placed at the bottom, and the positive electrode 304, separator 310, negative electrode 307 and negative electrode can 302 are stacked in this order. The positive electrode can 301 and negative electrode can 302 are press-fitted with a gasket 303 interposed therebetween to manufacture the coin-type secondary battery 300.

[0255] By using the positive electrode active material particles 100 described in the above embodiment for the positive electrode 304 , a coin-type secondary battery 300 with little degradation and high safety can be realized.

[0256] [Cylindrical secondary battery]

[0257] Next, refer to 6A to 6D An example of a cylindrical secondary battery will be described. Figure 6A The cylindrical secondary battery 600 shown in FIG. Figure 6B As shown in the cross-sectional view of FIG, the positive electrode cover (battery cover) 601 is provided on the top surface, and the battery can (external can) 602 is provided on the side and bottom surfaces. The positive electrode cover and the battery can (external can) 602 are insulated by a gasket (insulating gasket) 610.

[0258] A battery element is provided inside the hollow cylindrical battery can 602, in which a strip-shaped positive electrode 604 and a strip-shaped negative electrode 606 are wound with a separator 605 sandwiched therebetween. Although not shown in the figure, the battery element is wound around a center pin. One end of the battery can 602 is closed and the other end is open. As the battery can 602, metals such as nickel, aluminum, titanium, or alloys thereof, or alloys of these and other metals (such as stainless steel, etc.) that are resistant to corrosion by the electrolyte can be used. In addition, in order to prevent corrosion caused by the electrolyte, the battery can 602 is preferably covered with nickel or aluminum. Inside the battery can 602, the battery element in which the positive electrode, negative electrode, and separator are wound is sandwiched by a pair of opposing insulating plates 608 and 609. In addition, a non-aqueous electrolyte (not shown) is injected into the interior of the battery can 602 in which the battery element is provided. As the non-aqueous electrolyte, the same electrolyte as that of a coin-type secondary battery can be used.

[0259] Because the positive and negative electrodes used in cylindrical secondary batteries are wound, the active material is preferably formed on both surfaces of the current collector. The positive electrode 604 is connected to the positive terminal (positive electrode current collector wire) 603, while the negative electrode 606 is connected to the negative terminal (negative electrode current collector wire) 607. Both the positive terminal 603 and the negative terminal 607 can be made of metal materials such as aluminum. The positive terminal 603 is resistance-welded to the safety valve mechanism 612, while the negative terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 is electrically connected to the positive electrode cap 601 via a PTC (Positive Temperature Coefficient) element 611. When the internal pressure of the battery rises above a specified threshold, the safety valve mechanism 612 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604. The PTC element 611 is a thermally sensitive resistor whose resistance increases as the temperature rises. This increase in resistance limits the current flow to prevent abnormal heating. As the PTC element, barium titanate (BaTiO 3 )-based semiconductor ceramics or the like can be used.

[0260] In addition, if Figure 6C As shown, multiple secondary batteries 600 can be sandwiched between conductive plates 613 and 614 to form a module 615. Multiple secondary batteries 600 can be connected in parallel, in series, or in parallel and then in series. By forming a module 615 including multiple secondary batteries 600, a larger amount of power can be extracted.

[0261] Figure 6D FIG is a top view of the module 615. For the sake of clarity, the conductive plate 613 is represented by a dotted line. Figure 6DAs shown, module 615 may include wires 616 that electrically connect multiple secondary batteries 600. Conductive plates 613 may be placed on wires 616 so as to overlap with the wires 616. Furthermore, temperature control devices 617 may be included between the multiple secondary batteries 600. Temperature control devices 617 can be used to cool the secondary batteries 600 when they are overheated, and to heat the secondary batteries 600 when they are overcooled. This makes the performance of module 615 less susceptible to the effects of external temperature.

[0262] By using the positive electrode active material particles 100 described in the above embodiment as the positive electrode 604 , a cylindrical secondary battery 600 with little degradation and high safety can be realized.

[0263] [Configuration Example of Power Storage Device]

[0264] Refer to Figures 7 to Figure 11 Another configuration example of the power storage device will be described.

[0265] Figure 7A and Figure 7B This is an external view of the power storage device. The power storage device includes a circuit board 900 and a secondary battery 913. A label 910 is attached to the secondary battery 913. Figure 7B As shown, the power storage device includes terminals 951 and 952 , and antennas 914 and 915 .

[0266] Circuit board 900 includes terminal 911 and circuit 912. Terminal 911 is connected to terminal 951, terminal 952, antenna 914, antenna 915, and circuit 912. Alternatively, multiple terminals 911 may be provided, each used as a control signal input terminal, a power supply terminal, or the like.

[0267] Circuit 912 can also be provided on the back side of circuit board 900. In addition, the shapes of antenna 914 and antenna 915 are not limited to coil shapes, and can also be linear or plate-shaped. In addition, antennas such as planar antennas, aperture antennas, traveling wave antennas, EH antennas, magnetic field antennas, or dielectric antennas can also be used. Alternatively, antenna 914 or antenna 915 can also be a flat conductor. The flat conductor can also be used as one of the conductors for electric field coupling. In other words, antenna 914 or antenna 915 can also be used as one of the two conductors of a capacitor. In this way, not only electromagnetic and magnetic fields can be utilized, but also electric fields can be utilized to exchange electric power.

[0268] The line width of the antenna 914 is preferably larger than the line width of the antenna 915. This can increase the amount of power received by the antenna 914.

[0269] The power storage device includes a layer 916 between the antenna 914 and the antenna 915 and the secondary battery 913. The layer 916 has a function of shielding the electromagnetic field from the secondary battery 913. As the layer 916, for example, a magnetic material can be used.

[0270] The structure of the power storage device is not limited to the structure shown in FIG. 7 .

[0271] Or, as Figure 8A1 and Figure 8A2 As shown, in Figure 7A and Figure 7B Different antennas are provided on a pair of opposing surfaces of the secondary battery 913 shown. Figure 8A1 is an external view showing one side of the pair of surfaces, Figure 8A2 is an external view showing the other surface side of the pair of surfaces. Figure 7A and Figure 7B The same parts of the power storage device shown can be appropriately used. Figure 7A and Figure 7B Description of the power storage device shown.

[0272] like Figure 8A1 As shown, an antenna 914 is provided on one of a pair of surfaces of a secondary battery 913 with a layer 916 interposed therebetween. Figure 8A2 As shown, an antenna 915 is provided on the other of the pair of surfaces of the secondary battery 913 with a layer 917 interposed therebetween. The layer 917 has a function of shielding the electromagnetic field from the secondary battery 913. As the layer 917, for example, a magnetic material can be used.

[0273] By adopting the above structure, the sizes of both antenna 914 and antenna 915 can be increased.

[0274] Or, as Figure 8B1 and Figure 8B2 As shown, in Figure 7A and Figure 7B Different antennas are provided on a pair of opposing surfaces of the secondary battery 913 shown. Figure 8B1 is an external view showing one side of the pair of surfaces, Figure 8B2 is an external view showing the other surface side of the pair of surfaces. Figure 7A and Figure 7B The same parts of the power storage device shown can be appropriately used. Figure 7A and Figure 7B Description of the power storage device shown.

[0275] like Figure 8B1 As shown, an antenna 914 and an antenna 915 are provided on one of a pair of surfaces of a secondary battery 913 with a layer 916 interposed therebetween. Figure 8B2As shown, an antenna 918 is provided on the other of the pair of surfaces of a secondary battery 913, sandwiching a layer 917 therebetween. Antenna 918, for example, functions to communicate data with an external device. For example, antennas having the same shape as those used for antennas 914 and 915 can be used as antenna 918. Communication between the power storage device and other devices using antenna 918 can use a communication method such as NFC, which is compatible with power storage devices and other devices.

[0276] Or, as Figure 9A As shown, it can also be Figure 7A and Figure 7B The secondary battery 913 shown is provided with a display device 920. The display device 920 is electrically connected to the terminal 911 via the terminal 919. In addition, the label 910 may not be attached to the portion where the display device 920 is provided. Figure 7A and Figure 7B The same parts of the power storage device shown can be appropriately used. Figure 7A and Figure 7B Description of the power storage device shown.

[0277] The display device 920 may display, for example, an image indicating whether charging is in progress or an image indicating the amount of stored electricity. For example, electronic paper, a liquid crystal display, or an electroluminescent (EL) display may be used as the display device 920. For example, the use of electronic paper can reduce power consumption of the display device 920.

[0278] Or, as Figure 9B As shown, it can also be Figure 7A and Figure 7B The secondary battery 913 shown in FIG. 1 is provided with a sensor 921. The sensor 921 is electrically connected to the terminal 911 via the terminal 922. Figure 7A and Figure 7B The same parts of the power storage device shown can be appropriately used. Figure 7A and Figure 7B Description of the power storage device shown.

[0279] Sensor 921 may have the function of measuring, for example, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, slope, vibration, odor, or infrared light. By providing sensor 921, for example, data indicating the environment in which the power storage device is installed (such as temperature) can be detected and stored in the memory of circuit 912.

[0280] Furthermore, referring to FIG. 10 and Figure 11 An example of the structure of the secondary battery 913 will be described.

[0281] Figure 10A The secondary battery 913 shown includes a wound body 950 provided with terminals 951 and 952 inside a housing 930. The wound body 950 is immersed in an electrolyte inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is prevented from contacting the housing 930 by an insulating material. Note that for the sake of convenience, although Figure 10A Frame 930 is shown separated in the figure, but in reality, wound body 950 is covered by frame 930, and terminals 951 and 952 extend outside frame 930. Frame 930 can be made of a metal material (eg, aluminum) or a resin material.

[0282] In addition, if Figure 10B As shown, multiple materials can also be used to form Figure 10A For example, in the Figure 10B In the secondary battery 913 shown, a frame body 930 a and a frame body 930 b are bonded together, and a wound body 950 is provided in a region surrounded by the frame bodies 930 a and 930 b.

[0283] Frame 930a can be made of an insulating material such as an organic resin. In particular, using a material such as an organic resin to form the antenna surface can reduce shielding by the electric field of secondary battery 913. Alternatively, if shielding by the electric field of frame 930a is minimal, antennas such as antenna 914 or antenna 915 can be provided within frame 930a. Frame 930b can be made of, for example, a metal material.

[0284] Furthermore, Figure 11 The structure of a wound body 950 is shown. The wound body 950 includes a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is formed by stacking the negative electrode 931 and the positive electrode 932 with the separator 933 interposed therebetween to form a laminated sheet, and then winding the laminated sheet. Alternatively, multiple layers of the negative electrode 931, the positive electrode 932, and the separator 933 may be stacked.

[0285] The negative electrode 931 is connected to the terminal 911 shown in Fig. 7 via one of the terminal 951 and the terminal 952. The positive electrode 932 is connected to the terminal 911 shown in Fig. 7 via the other of the terminal 951 and the terminal 952.

[0286] By using the positive electrode active material particles 100 described in the above embodiment for the positive electrode 932 , a secondary battery 913 with little degradation and high safety can be realized.

[0287] [Laminated secondary battery]

[0288] Next, an example of a laminated secondary battery will be described with reference to Figures 12 to 17. When a flexible laminated secondary battery is mounted on an electronic device at least partially flexible, the secondary battery can be bent along with deformation of the electronic device.

[0289] 12, a laminated secondary battery 980 will be described. The laminated secondary battery 980 includes Figure 12A The wound body 993 shown. The wound body 993 includes a negative electrode 994, a positive electrode 995 and a separator 996. Figure 11 Similar to the previously described wound body 950 , the wound body 993 is formed by overlapping the negative electrode 994 and the positive electrode 995 with a separator 996 interposed therebetween to form a laminated sheet, and then winding the laminated sheet.

[0290] The number of stacked layers consisting of the negative electrode 994, the positive electrode 995, and the separator 996 can be appropriately designed according to the required capacity and device volume. The negative electrode 994 is connected to the negative electrode current collector (not shown) via one of the lead electrode 997 and the lead electrode 998, and the positive electrode 995 is connected to the positive electrode current collector (not shown) via the other of the lead electrode 997 and the lead electrode 998.

[0291] like Figure 12B As shown, the wound body 993 is accommodated in a space formed by laminating a film 981 to be an outer packaging body and a film 982 having a recess by heat pressing or the like, thereby manufacturing Figure 12C Secondary battery 980 shown. A wound body 993 includes lead electrodes 997 and 998, and is immersed in an electrolyte in a space surrounded by a film 981 and a film 982 having a recess.

[0292] The film 981 and the film 982 having the recess are made of, for example, a metal material such as aluminum or a resin material. When a resin material is used as the material of the film 981 and the film 982 having the recess, the film 981 and the film 982 having the recess can be deformed when a force is applied from the outside, thereby manufacturing a flexible secondary battery.

[0293] In addition, Figure 12B and Figure 12C Although an example using two films is shown in FIG, one film may be bent to form a space, and the wound body 993 may be accommodated in the space.

[0294] By using the positive electrode active material particles 100 described in the above embodiment for the positive electrode 995 , a secondary battery 980 with little degradation and high safety can be realized.

[0295] Although FIG12 shows an example of a secondary battery 980 including a wound body in a space formed by a film that will serve as an outer packaging body, a secondary battery may also be used in which a plurality of rectangular positive electrodes, separators, and negative electrodes are included in a space formed by a film that will serve as an outer packaging body, as shown in FIG13 .

[0296] Figure 13A The illustrated laminated secondary battery 500 includes a positive electrode 503 including a positive electrode current collector 501 and a positive electrode active material layer 502; a negative electrode 506 including a negative electrode current collector 504 and a negative electrode active material layer 505; a separator 507; an electrolyte 508; and an outer casing 509. Separator 507 is provided between positive electrode 503 and negative electrode 506, which are disposed within outer casing 509. Furthermore, outer casing 509 is filled with electrolyte 508. The electrolyte described in Embodiment 2 can be used as electrolyte 508.

[0297] exist Figure 13A In the illustrated laminated secondary battery 500, the positive electrode current collector 501 and the negative electrode current collector 504 also serve as terminals for external electrical contact. Therefore, portions of the positive electrode current collector 501 and the negative electrode current collector 504 may be exposed outside the outer packaging 509. Alternatively, a lead electrode may be ultrasonically welded to the positive electrode current collector 501 or the negative electrode current collector 504 using a lead electrode to expose the lead electrode outside the outer packaging 509, while preventing the positive electrode current collector 501 and the negative electrode current collector 504 from being exposed outside the outer packaging 509.

[0298] In the laminated secondary battery 500, as the outer packaging body 509, for example, a laminate film with the following three-layer structure can be used: a highly flexible metal film of aluminum, stainless steel, copper, nickel, etc. is arranged on a film composed of materials such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc., and an insulating synthetic resin film of polyamide resin, polyester resin, etc. is arranged on the metal film as the outer surface of the outer packaging body.

[0299] in addition, Figure 13B An example of a cross-sectional structure of a laminated secondary battery 500 is shown. For simplicity, Figure 13A An example including two current collectors is shown, but an actual battery includes a plurality of electrode layers.

[0300] Figure 13B An example of the secondary battery 500 includes 16 electrode layers. In addition, even if the secondary battery 500 includes 16 electrode layers, it has flexibility. Figure 13B The structure shown has 8 layers of negative electrode current collector 504 and 8 layers of positive electrode current collector 501, totaling 16 layers. Figure 13BA cross-section of the negative electrode extraction portion is shown, showing ultrasonic welding of eight layers of negative electrode current collector 504. Of course, the number of electrode layers is not limited to 16 and can be more or less than 16. A larger number of electrode layers allows for a higher capacity secondary battery. Furthermore, a smaller number of electrode layers allows for a thinner and more flexible secondary battery.

[0301] Here, Figure 14 and Figure 15 An example of an external view of a laminated secondary battery 500 is shown. Figure 14 and Figure 15 The battery includes: a positive electrode 503; a negative electrode 506; a separator 507; an outer package 509; a positive electrode lead electrode 510; and a negative electrode lead electrode 511.

[0302] Figure 16A The appearance diagram of the positive electrode 503 and the negative electrode 506 is shown. The positive electrode 503 includes a positive electrode current collector 501, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. In addition, the positive electrode 503 has an area where a portion of the positive electrode current collector 501 is exposed (hereinafter referred to as the tab region). The negative electrode 506 has a negative electrode current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. In addition, the negative electrode 506 has an area where a portion of the negative electrode current collector 504 is exposed, namely the tab region. The area or shape of the tab region of the positive electrode and the negative electrode is not limited to Figure 16A Example shown.

[0303] [Method for manufacturing laminated secondary battery]

[0304] Here, refer to Figure 16B and Figure 16C Right Figure 14 An example of a method for manufacturing a laminated secondary battery will be described, with its appearance shown in FIG.

[0305] First, the negative electrode 506 , the separator 507 , and the positive electrode 503 are stacked. Figure 16B The stacked negative electrode 506, separator 507, and positive electrode 503 are shown. Here, an example using five negative electrode sets and four positive electrode sets is shown. Next, the tab regions of the positive electrodes 503 are bonded together, and the positive lead electrode 510 is bonded to the outermost tab region of the positive electrode. This bonding can be achieved using, for example, ultrasonic welding. Similarly, the tab regions of the negative electrodes 506 are bonded together, and the negative lead electrode 511 is bonded to the outermost tab region of the negative electrode.

[0306] Next, the negative electrode 506 , the separator 507 , and the positive electrode 503 are placed on the outer package 509 .

[0307] Below, as Figure 16C As shown, the outer packaging 509 is folded along the portion indicated by the dotted line. Then, the outer periphery of the outer packaging 509 is joined. For example, heat compression bonding can be used as the joining method. At this time, an area (hereinafter referred to as an inlet) that is not joined to a portion (or one edge) of the outer packaging 509 is provided for subsequent injection of the electrolyte 508.

[0308] Next, the electrolyte 508 is introduced into the outer packaging 509 from an inlet provided in the outer packaging 509. The electrolyte 508 is preferably introduced under a reduced pressure atmosphere or an inert gas atmosphere. Finally, the inlet is joined. In this manner, the laminated secondary battery 500 is manufactured.

[0309] By using the positive electrode active material particles 100 described in the above embodiment for the positive electrode 503 , a secondary battery 500 with little degradation and high safety can be realized.

[0310] [Flexible secondary battery]

[0311] Next, an example of a flexible secondary battery will be described with reference to FIG. 17 and FIG. 18 .

[0312] Figure 17A A schematic top view of a flexible battery 250 is shown. Figure 17B1 、 Figure 17B2 、 Figure 17C Along the Figure 17A Schematic cross-sectional views of the battery 250 are shown along lines C1-C2, C3-C4, and A1-A2. The battery 250 includes an outer packaging body 251, and a positive electrode 211a and a negative electrode 211b housed within the outer packaging body 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 packaging body 251. Furthermore, an electrolyte (not shown) is sealed in the area surrounded by the outer packaging body 251, in addition to the positive electrode 211a and the negative electrode 211b.

[0313] The positive electrode 211 a and the negative electrode 211 b included in the battery 250 will be described with reference to FIG. 18 . Figure 18A It is a perspective view illustrating the stacking order of the positive electrode 211 a , the negative electrode 211 b , and the separator 214 . Figure 18B It is a perspective view showing the lead wires 212a and 212b in addition to the positive electrode 211a and the negative electrode 211b.

[0314] like Figure 18AAs shown, battery 250 includes multiple rectangular positive electrodes 211a, multiple rectangular negative electrodes 211b, and multiple separators 214. Positive electrodes 211a and negative electrodes 211b each include a protruding tab portion and a portion outside the tab. A positive electrode active material layer is formed on the portion outside the tab on one side of the positive electrode 211a, while a negative electrode active material layer is formed on the portion outside the tab on one side of the negative electrode 211b.

[0315] The positive electrode 211 a and the negative electrode 211 b are stacked such that the surfaces of the positive electrode 211 a not having the positive electrode active material layer formed thereon are in contact with each other and the surfaces of the negative electrode 211 b not having the negative electrode active material layer formed thereon are in contact with each other.

[0316] 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. For convenience, the separator 214 is indicated by a dotted line in FIG18 .

[0317] like Figure 18B As shown, a plurality of positive electrodes 211a and a lead wire 212a are electrically connected in a joint 215a. In addition, a plurality of negative electrodes 211b and a lead wire 212b are electrically connected in a joint 215b.

[0318] Next, refer to Figure 17B1 、 Figure 17B2 、 Figure 17C 、 Figure 17D The outer package body 251 will be described.

[0319] The outer packaging body 251 is in the form of a thin film, folded in half to sandwich the positive electrode 211a and the negative electrode 211b. The outer packaging body 251 includes a folded portion 261, a pair of sealing portions 262, and a sealing portion 263. The pair of sealing portions 262 are provided to sandwich the positive electrode 211a and the negative electrode 211b and can also be referred to as side seals. Furthermore, the sealing portion 263 includes a portion that overlaps with the lead wires 212a and 212b and can also be referred to as a top seal.

[0320] The outer package 251 preferably has a corrugated shape with ridge lines 271 and valley lines 272 alternately arranged in the portion overlapping the positive electrode 211a and the negative electrode 211b. The sealing portions 262 and 263 of the outer package 251 are preferably flat.

[0321] Figure 17B1 This is a cross section cut at the portion overlapping with the ridge line 271. Figure 17B2 This is a cross section cut at a portion overlapping with the valley bottom line 272 . Figure 17B1 、 Figure 17B2 Both correspond to cross sections of the battery 250 and the positive electrode 211 a and the negative electrode 211 b in the width direction.

[0322] Here, the distance La is defined as the distance between the end of the negative electrode 211b in the width direction, that is, the end of the negative electrode 211b and the sealing portion 262. When the battery 250 is deformed, such as by bending, as described later, the positive electrode 211a and the negative electrode 211b deform in the longitudinal direction, shifting relative to each other. If the distance La is too short, there is a risk that the outer packaging 251 will rub strongly against the positive electrode 211a and the negative electrode 211b, causing damage to the outer packaging 251. In particular, if the metal film of the outer packaging 251 is exposed, the metal film may be corroded by the electrolyte. Therefore, it is preferable to set the distance La as long as possible. On the other hand, if the distance La is too long, the volume of the battery 250 will increase.

[0323] Furthermore, it is preferable that the distance La between the negative electrode 211 b and the sealing portion 262 be longer as the total thickness of the stacked positive electrode 211 a and negative electrode 211 b increases.

[0324] More specifically, when the total thickness of the stacked positive electrode 211a and negative electrode 211b is thickness t, the distance La is 0.8 to 3.0 times the thickness t, preferably 0.9 to 2.5 times, and more preferably 1.0 to 2.0 times. By setting the distance La within this range, a compact battery with high reliability against bending can be achieved.

[0325] Furthermore, when the distance between the pair of sealing portions 262 is the distance Lb, it is preferable that the distance Lb is sufficiently greater than the width of the positive electrode 211a and the negative electrode 211b (here, the width Wb of the negative electrode 211b). Thus, when the battery 250 is deformed, such as by repeated bending, even if the positive electrode 211a and the negative electrode 211b come into contact with the outer packaging 251, portions of the positive electrode 211a and the negative electrode 211b can be offset in the width direction, effectively preventing friction between the positive electrode 211a and the negative electrode 211b and the outer packaging 251.

[0326] For example, the difference between the distance Lb between the pair of sealing portions 262 and the width Wb of the negative electrode 211b is 1.6 times or more and 6.0 times or less, preferably 1.8 times or more and 5.0 times or less, and more preferably 2.0 times or more and 4.0 times or less, the thickness t of the positive electrode 211a and the negative electrode 211b.

[0327] In other words, the distance Lb, the width Wb, and the thickness t preferably satisfy the following equation 2.

[0328] [Formula 2]

[0329]

[0330] 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.

[0331] in addition, Figure 17C The cross section including the wire 212a corresponds to the cross section of the battery 250, the positive electrode 211a and the negative electrode 211b in the longitudinal direction. Figure 17C As shown, the folded portion 261 preferably includes a space 273 between the ends of the positive electrode 211 a and the negative electrode 211 b in the longitudinal direction and the outer package 251 .

[0332] Figure 17D A schematic cross-sectional view of the battery 250 when it is bent is shown. Figure 17D Equivalent to following Figure 17A The section of the cutoff line B1-B2 in FIG.

[0333] When the battery 250 is bent, a portion of the outer packaging 251 located outside the bend deforms to extend, while another portion of the outer packaging 251 located inside the bend deforms to contract. More specifically, the portion of the outer packaging 251 located outside the bend deforms so that the wave amplitude is small and the wave period is large. On the other hand, the portion of the outer packaging 251 located inside the bend deforms so that the wave amplitude is large and the wave period is small. Deforming the outer packaging 251 in this manner can alleviate the stress applied to the outer packaging 251 due to bending, thereby eliminating the need for the material constituting the outer packaging 251 to be stretchable. As a result, the battery 250 can be bent with minimal force without damaging the outer packaging 251.

[0334] In addition, if Figure 17D As shown, when battery 250 is bent, the positive electrode 211a and the negative electrode 211b are offset relative to each other. At this time, because the ends of the multiple stacked positive electrodes 211a and negative electrodes 211b on the seal portion 263 side are fixed by fixing member 217, they are offset such that the closer they are to the folded portion 261, the greater the offset. This can alleviate the stress applied to the positive electrode 211a and negative electrode 211b, and the positive electrode 211a and negative electrode 211b themselves do not necessarily need to be elastic. As a result, battery 250 can be bent without damaging the positive electrode 211a and negative electrode 211b.

[0335] Furthermore, since the space 273 is provided between the ends of the positive electrode 211a and the negative electrode 211b and the outer casing 251 , the ends of the positive electrode 211a and the negative electrode 211b located inside can be relatively offset so as not to contact the outer casing 251 during bending.

[0336] The battery 250 illustrated in Figures 17 and 18 is a battery that is less susceptible to damage to the outer casing, the positive electrode 211a, and the negative electrode 211b, even when repeatedly bent and stretched, and that does not easily degrade battery characteristics. By using the positive electrode active material particles 100 described in the above embodiment for the positive electrode 211a included in the battery 250, a secondary battery with less degradation and high safety can be realized.

[0337] (Implementation 4)

[0338] In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is incorporated into an electronic device will be described.

[0339] First, FIG19 shows an example of an electronic device in which the flexible secondary battery described in part in Embodiment 3 is incorporated. Examples of electronic devices in which the flexible secondary battery can be used include televisions (also referred to as televisions or television receivers), displays for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also referred to as mobile phones or mobile phone devices), portable game consoles, portable information terminals, audio reproduction devices, and large-scale game consoles such as pinball machines.

[0340] Furthermore, the flexible secondary battery can be assembled along the curved surfaces of the inner or outer walls of houses and buildings, or the interior or exterior of automobiles.

[0341] Figure 19A 1 shows an example of a mobile phone. A mobile phone 7400 includes a display portion 7402 incorporated in a housing 7401, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like. The mobile phone 7400 also includes a secondary battery 7407.

[0342] Figure 19B FIG. 7 shows a state where a 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 therein is also bent. Figure 19C The secondary battery 7407 is shown in a bent state. The secondary battery 7407 is a thin secondary battery. The secondary battery 7407 is fixed in a bent state. The secondary battery 7407 has a lead electrode electrically connected to a current collector.

[0343] Figure 19D An example of a wristband type display device is shown. A portable display device 7100 includes a housing 7101, a display portion 7102, operation buttons 7103, and a secondary battery 7104. Figure 19EA bent secondary battery 7104 is shown. When the bent secondary battery 7104 is placed on the user's arm, the outer casing of the secondary battery 7104 deforms, causing the curvature of part or all of the secondary battery 7104 to change. The value representing the degree of curvature of any point on the curve in terms of the value of the equivalent circle radius is the curvature radius, and the reciprocal of the curvature radius is called the curvature. Specifically, part or all of the main surface of the outer casing or the secondary battery 7104 is deformed within a range of a curvature radius of 40 mm to 150 mm. As long as the curvature radius of the main surface of the secondary battery 7104 is within the range of 40 mm to 150 mm, high reliability can be maintained.

[0344] Figure 19F A portable information terminal 7200 is an example of a wristwatch-type portable information terminal. The portable information terminal 7200 includes a housing 7201, a display portion 7202, a strap 7203, a buckle 7204, operation buttons 7205, input / output terminals 7206, and the like.

[0345] The portable information terminal 7200 can execute various application programs such as mobile phone use, e-mail, article reading and writing, music playback, Internet communication, and computer games.

[0346] The display portion 7202 has a curved display surface, capable of displaying along the curved display surface. Furthermore, the display portion 7202 includes a touch sensor, which allows operation by touching the screen with a finger or a stylus. For example, by touching an icon 7207 displayed on the display portion 7202, an application can be launched.

[0347] In addition to time setting, operation button 7205 may have various functions such as power on / off, wireless communication on / off, silent mode setting and canceling, power saving mode setting and canceling, etc. For example, the function of operation button 7205 can be freely set by utilizing the operating system incorporated in portable information terminal 7200.

[0348] In addition, the portable information terminal 7200 can perform standardized short-range wireless communication. For example, by communicating with a headset capable of wireless communication, a hands-free call can be made.

[0349] Furthermore, the portable information terminal 7200 includes an input / output terminal 7206, which allows data to be directly transmitted to or received from another information terminal via a connector. Furthermore, charging can be performed via the input / output terminal 7206. Furthermore, charging can also be performed using wireless power supply, without using the input / output terminal 7206.

[0350] The display unit 7202 of the portable information terminal 7200 includes a secondary battery according to one embodiment of the present invention. Figure 19EThe secondary battery 7104 shown is incorporated into the interior of the housing 7201 , or the secondary battery 7104 in a bendable state is incorporated into the interior of the strap 7203 .

[0351] The portable information terminal 7200 preferably includes a sensor. Examples of the sensor preferably include a fingerprint sensor, a pulse sensor, a body temperature sensor, and other human body sensors, a touch sensor, a pressure sensor, and an acceleration sensor.

[0352] Figure 19G An example of an armband-type display device is shown. A display device 7300 includes a display portion 7304 and a secondary battery according to one embodiment of the present invention. The display device 7300 may include a touch sensor in the display portion 7304 and be used as a portable information terminal.

[0353] The display surface of the display portion 7304 is curved, and display can be performed along the curved display surface. In addition, the display device 7300 can change the display state by utilizing standardized short-range wireless communication or the like.

[0354] The display device 7300 has input / output terminals, and can directly transmit and receive data to and from other information terminals via a connector. Furthermore, the input / output terminals can be used for charging. Furthermore, charging can be performed wirelessly, rather than using the input / output terminals.

[0355] then, Figure 20A and Figure 20B An example of a tablet terminal that can be folded in half is shown. Figure 20A and Figure 20B The illustrated tablet terminal 9600 includes a housing 9630a, a housing 9630b, a movable portion 9640 connecting the housings 9630a and 9630b, a display portion 9631, a display mode switch 9626, a power switch 9627, a power saving mode switch 9625, a buckle 9629, and an operation switch 9628. By using a flexible panel for the display portion 9631, a tablet terminal with a larger display portion can be realized. Figure 20A The tablet terminal 9600 is shown in an open state. Figure 20B The tablet terminal 9600 is shown in a closed state.

[0356] The tablet terminal 9600 includes a power storage body 9635 inside a housing 9630a and a housing 9630b. The power storage body 9635 is provided in the housing 9630a and the housing 9630b through a movable portion 9640.

[0357] A portion of the display portion 9631 can be used as a touch screen area, and data can be input by touching displayed operation keys. Furthermore, keyboard buttons can be displayed on the display portion 9631 by touching a position of a keyboard display switching button on the touch screen with a finger, a stylus, or the like.

[0358] Furthermore, the display mode switch 9626 can switch the display orientation between portrait and landscape, and select between black and white and color. The power saving mode switch 9625 can set the display brightness to the optimal level based on the amount of external light detected by the built-in optical sensor of the tablet terminal 9600 during use. In addition to the optical sensor, the tablet terminal may also include other detection devices such as sensors for detecting tilt, such as a gyroscope and an accelerometer.

[0359] Figure 20B The tablet terminal is in a closed state and includes a housing 9630, a solar cell 9633, and a charge and discharge control circuit 9634 including a DC-DC converter 9636. A secondary battery according to one embodiment of the present invention is used as the power storage body 9635.

[0360] Furthermore, tablet terminal 9600 can be folded in half, so that housing 9630a and housing 9630b can be folded together when not in use. Folding housing 9630a and housing 9630b protects display portion 9631, thereby improving the durability of tablet terminal 9600. Furthermore, since the power storage element 9635 of the secondary battery using one embodiment of the present invention has a high capacity and excellent cycle characteristics, a tablet terminal that can be used for a long period of time can be provided.

[0361] also, Figure 20A and Figure 20B The tablet terminal shown can also have the following functions: displaying various information (static images, dynamic images, text images, etc.); displaying the calendar, date or time, etc. on the display unit; performing touch input operations or touch input for editing the information displayed on the display unit; controlling processing through various software (programs), etc.

[0362] The solar cell 9633 mounted on the surface of the tablet terminal can supply power to the touch screen, display unit, image signal processing unit, etc. Note that the solar cell 9633 can be provided on one or both surfaces of the housing 9630 and can efficiently charge the power storage body 9635.

[0363] In addition, refer to Figure 20C The block diagram shown is Figure 20B The structure and operation of the charge and discharge control circuit 9634 shown in FIG. Figure 20CThe solar cell 9633, the power storage body 9635, the DCDC converter 9636, the converter 9637, the switches SW1 to SW3, and the display portion 9631 are shown. The power storage body 9635, the DCDC converter 9636, the converter 9637, the switches SW1 to SW3 correspond to Figure 20B The charge and discharge control circuit 9634 is shown.

[0364] First, an example of operation when the solar cell 9633 generates electricity using external light will be described. The DC-DC converter 9636 steps up or down the voltage of the electricity generated by the solar cell to a voltage sufficient to charge the power storage device 9635. Furthermore, when the display portion 9631 is operated using the power from the solar cell 9633, the switch SW1 is turned on, and the converter 9637 steps up or down the voltage to the voltage required by the display portion 9631. Alternatively, when the display portion 9631 is not displaying, the switch SW1 can be turned off and the switch SW2 can be turned on to charge the power storage device 9635.

[0365] Note that although the solar cell 9633 is shown as an example of a power generation unit, the present invention is not limited to this. Other power generation units such as a piezoelectric element or a thermoelectric conversion element (Peltier element) may be used to charge the power storage body 9635. For example, a contactless power transmission module that can transmit and receive power wirelessly (contactlessly) for charging may be used, or other charging methods may be combined for charging.

[0366] Figure 21 Examples of other electronic devices are shown. Figure 21 In the embodiment, the display device 8000 is an example of an electronic device using a secondary battery 8004 according to one embodiment of the present invention. Specifically, the display device 8000 corresponds to a display device for receiving television broadcasts, and includes a housing 8001, a display portion 8002, a speaker portion 8003, and a secondary battery 8004. The secondary battery 8004 according to one embodiment of the present invention is disposed inside the housing 8001. The display device 8000 can receive power from a commercial power source and can also use the power stored in the secondary battery 8004. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the display device 8000 can be used by using the secondary battery 8004 according to one embodiment of the present invention as an uninterruptible power supply.

[0367] As the display portion 8002, a semiconductor display device such as a liquid crystal display device, a light-emitting device having a light-emitting element such as an organic EL element in each pixel, an electrophoretic display device, a DMD (digital micromirror device), a PDP (plasma display panel), and an FED (field emission display) can be used.

[0368] Furthermore, the display device includes not only display devices for receiving television broadcasts but also all display devices for displaying information, such as display devices for personal computers and display devices for displaying advertisements.

[0369] exist Figure 21 In the embodiment of the present invention, the mounting type lighting device 8100 is an example of an electronic device using a secondary battery 8103 according to one embodiment of the present invention. Specifically, the lighting device 8100 includes a housing 8101, a light source 8102, and a secondary battery 8103. Figure 21 The example in FIG. 8 illustrates a case where the secondary battery 8103 is installed inside a ceiling 8104 on which the housing 8101 and the light source 8102 are mounted. However, the secondary battery 8103 may also be installed inside the housing 8101. The lighting device 8100 can receive power from a commercial power source and use the power stored in the secondary battery 8103. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the lighting device 8100 can be used by using the secondary battery 8103 according to one embodiment of the present invention as an uninterruptible power supply.

[0370] In addition, although Figure 21 The example shows a mounted lighting device 8100 installed on the ceiling 8104, but the secondary battery according to one embodiment of the present invention can be used in a mounted lighting device installed outside the ceiling 8104, such as a side wall 8105, a floor 8106 or a window 8107, and can also be used in a desktop lighting device, etc.

[0371] An artificial light source that artificially generates light using electricity can be used as the light source 8102. Specifically, examples of the artificial light source include incandescent bulbs, discharge lamps such as fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements.

[0372] exist Figure 21 In the embodiment of the present invention, 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 embodiment of the present invention. Specifically, the indoor unit 8200 includes a housing 8201, an air outlet 8202, and a secondary battery 8203. Figure 21, the secondary battery 8203 is shown as being installed in the indoor unit 8200. However, the secondary battery 8203 may also be installed in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be installed in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is installed in both the indoor unit 8200 and the outdoor unit 8204, the air conditioner can be used even when power cannot be supplied from the commercial power source due to a power outage or the like, by using the secondary battery 8203 according to one embodiment of the present invention as an uninterruptible power supply.

[0373] In addition, although Figure 21 Although a split-type air conditioner composed of an indoor unit and an outdoor unit is exemplified in the embodiment, the secondary battery according to one embodiment of the present invention may be used in an integrated air conditioner having the functions of an indoor unit and an outdoor unit in one housing.

[0374] exist Figure 21 In the embodiment, the electric refrigerator-freezer 8300 is an example of an electronic device using a secondary battery 8304 according to one embodiment of the present invention. Specifically, the electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator door 8302, a freezer door 8303, and a secondary battery 8304. Figure 21 , secondary battery 8304 is provided inside housing 8301. Electric refrigerator-freezer 8300 can receive power from a commercial power source and can also use the power stored in secondary battery 8304. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, electric refrigerator-freezer 8300 can be used by using secondary battery 8304 according to one embodiment of the present invention as an uninterruptible power supply.

[0375] Furthermore, during periods when electronic devices are not in use, particularly during periods when the ratio of the amount of power actually used to the total amount of power available from the commercial power supply (referred to as the power usage rate) is low, power is stored in the secondary battery. This can suppress increases in the power usage rate during periods other than these periods. For example, in the case of an electric refrigerator-freezer 8300, power is stored in the secondary battery 8304 at night when the temperature is low and the refrigerator door 8302 or the freezer door 8303 is not opened or closed. Furthermore, during the day when the temperature is high and the refrigerator door 8302 or the freezer door 8303 is opened or closed, the secondary battery 8304 is used as an auxiliary power source, thereby suppressing the power usage rate during the day.

[0376] The secondary battery of one embodiment of the present invention is not limited to being installed in the above-mentioned electronic devices, but can also be installed in all electronic devices. By adopting one embodiment of the present invention, a secondary battery with less degradation and high safety can be provided. Therefore, by installing the secondary battery of one embodiment of the present invention in the electronic device described in this embodiment, an electronic device with longer service life and high safety can be provided. This embodiment can be implemented in combination with other embodiments as appropriate.

[0377] (Implementation 5)

[0378] In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle is described.

[0379] When secondary batteries are installed in vehicles, a new generation of clean energy vehicles such as hybrid electric vehicles (HEV), electric vehicles (EV), or plug-in hybrid electric vehicles (PHEV) can be realized.

[0380] FIG. 22 illustrates a vehicle using the secondary battery of one embodiment of the present invention. Figure 22A The illustrated vehicle 8400 is an electric vehicle that uses an electric motor as a driving power source. Alternatively, the vehicle 8400 may be a hybrid vehicle that can appropriately use an electric motor or an engine as a driving power source. By using a secondary battery according to one embodiment of the present invention, a vehicle with a long driving range can be realized. The secondary battery not only drives the electric motor 8406 but also supplies electricity to light-emitting devices such as the headlights 8401 and interior lights (not shown).

[0381] Furthermore, the secondary battery can supply electric power to a display device such as a speedometer and a tachometer included in the automobile 8400. Furthermore, the secondary battery can supply electric power to a semiconductor device such as a navigation system included in the automobile 8400.

[0382] exist Figure 22B In the illustrated automobile 8500 , a secondary battery 8024 included in the automobile 8500 can be charged by receiving electric power from an external charging device using a plug-in method or a contactless power supply method. Figure 22BThe diagram shows a case where a secondary battery 8024 installed in a car 8500 is charged from a ground-mounted charging device 8021 via a cable 8022. When charging, the charging method or connector, etc. may appropriately adopt specifications such as CHAdeMO (registered trademark) or a combined charging system "Combined Charging System". As the charging device 8021, a charging station installed in a commercial facility or a home power supply may also be used. For example, the secondary battery 8024 installed in the car 8500 can be charged by supplying power from the outside using plug-in technology. Charging can be performed by converting AC power into DC power using a conversion device such as an AC / DC converter.

[0383] Although not shown, it is also possible to install a power receiving device in the vehicle and charge it through contactless power supply from a ground-based power transmission device. When using a contactless power supply method, by integrating the power transmission device into the road or an exterior wall, charging can be performed not only while the vehicle is parked but also while it is in motion. Furthermore, this contactless power supply method can be used to send and receive power between vehicles. Furthermore, solar cells can be installed on the exterior of the vehicle to charge the secondary battery while the vehicle is parked or in motion. This contactless power supply can be achieved using electromagnetic induction or magnetic field resonance.

[0384] Figure 22C This is an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. Figure 22C The scooter 8600 shown includes a secondary battery 8602, a rearview mirror 8601, and a turn signal light 8603. The secondary battery 8602 can supply power to the turn signal light 8603.

[0385] In addition, Figure 22C In the illustrated scooter 8600, a secondary battery 8602 can be housed in an under-seat storage portion 8604. Even if the under-seat storage portion 8604 is small, the secondary battery 8602 can be housed in the under-seat storage portion 8604.

[0386] According to one embodiment of the present invention, a secondary battery with less degradation and high safety can be manufactured. To this end, by mounting it on a vehicle, it is possible to suppress the reduction in driving distance and acceleration performance. In addition, a vehicle with high safety can be realized. In addition, the secondary battery installed in the vehicle can be used as a power supply source outside the vehicle. In this case, for example, the use of commercial power supply during peak power demand can be avoided. If the use of commercial power supply during peak power demand can be avoided, it will help save energy and reduce carbon dioxide emissions. In addition, since the secondary battery with less degradation and high safety can be used for a long time, the use of rare metals such as cobalt can be reduced.

[0387] This embodiment mode can be implemented in combination with other embodiment modes as appropriate.

[0388] [Example 1]

[0389] In this embodiment, positive electrode active material particles containing magnesium, fluorine and oxygen at the grain boundaries and their vicinity are manufactured, and the concentration distribution of the grains and grain boundaries in the active material is confirmed by TEM observation and STEM-EDX analysis. The sample adopts a sample of sample A of one embodiment of the present invention. As sample A, nickel-manganese-lithium cobalt oxide containing magnesium, fluorine and oxygen at the grain boundaries and their vicinity is manufactured. Assume that the composition of nickel-manganese-lithium cobalt oxide is LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2.LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2 has a layered rock salt type crystal structure.

[0390] <Preparation of Sample A>

[0391] The preparation of sample A will be described.

[0392] like Figure 3 As shown in step S11 of the flowchart, the starting materials are prepared. Lithium carbonate (Li2CO3) is weighed as a lithium source, nickel oxide (NiO) is weighed as a nickel source, manganese dioxide (MnO2) is weighed as a manganese source, cobalt trioxide (Co3O4) is weighed as a cobalt source, magnesium oxide (MgO) is weighed as a magnesium source, and lithium fluoride (LiF) is weighed as a fluorine source. Specifically, 3.1398g (42.49mmol) of Li2CO3, 2.1159g (28.33mmol) of NiO, 2.4627g (28.33mmol) of MnO2, 2.2033g (9.15mmol) of Co3O4, 0.0343g (0.85mmol) of MgO, and 0.0441g (1.70mmol) of LiF are weighed. As a result, the ratio m of the number of atoms of magnesium to the total number of atoms of nickel, manganese, and cobalt is 0.010 (1.0%). The ratio n of the number of fluorine atoms to the number of magnesium atoms was 2.0. Li₂CO₃ was manufactured by Kojundo Chemical Research Institute Co., Ltd. (Catalog No. LIH06XB). NiO was manufactured by Kojundo Chemical Research Institute Co., Ltd. (Catalog No. NIO04PB). MnO₂ was manufactured by Kojundo Chemical Research Institute Co., Ltd. (Catalog No. MNO03PB). Co₃O₄ was manufactured by Kojundo Chemical Research Institute Co., Ltd. (Catalog No. COO09PB). MgO was manufactured by Kojundo Chemical Research Institute Co., Ltd. (Catalog No. MGO12PB). LiF was manufactured by Kojundo Chemical Research Institute Co., Ltd. (Catalog No. LIH10XB).

[0393] Next, as shown in step S12, mix the starting materials weighed in step S11. The mixing is carried out using a wet ball mill. Specifically, use 3 mmφ balls, acetone as the solvent, and perform crushing and mixing at a rotation speed of 300 rpm for 2 hours.

[0394] Next, as shown in step S13, perform the first heating on the material mixed in step S12. The first heating is carried out using a muffle furnace to raise the temperature from room temperature to 1000 °C at a heating rate of 200 °C / hr, and heat at 1000 °C for 10 hours. The heating is carried out in a dry air atmosphere, and the flow rate of the dry atmosphere is set to 10 L / min.

[0395] Lithium nickel manganese cobalt oxide can be synthesized by the first heating in step S13. Note that at this time, it can be considered that a part of magnesium and fluorine is dissolved in the grain boundaries and grains.

[0396] Next, as shown in step S14, cool the material heated in step S13 to room temperature to obtain Composition 1. After cooling, perform a grinding process on the obtained Composition 1, thereby reducing the particle size of Composition 1. The grinding process uses a 53 μm sieve.

[0397] Next, as shown in step S15, perform the second heating on Composition 1 obtained in step S14. The second heating is carried out using a muffle furnace to raise the temperature from room temperature to 800 °C at a heating rate of 200 °C / hr and heat at 800 °C for 2 hours. The heating is carried out in a dry air atmosphere, and the flow rate of the dry atmosphere is set to 10 L / min.

[0398] 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.

[0399] Next, as shown in step S16, cool the Composition 1 heated in step S15 to room temperature and perform recovery to obtain Sample A.

[0400] <TEM Observation, STEM Observation, EDX Measurement>

[0401] Next, thin-section Sample A using a focused ion beam (FIB: Focused Ion Beam), and observe the cross-section of Sample A using TEM and STEM. In addition, perform a composition analysis on the cross-section of Sample A using EDX measurement. The TEM, STEM observations, and EDX measurements are carried out using JEM-ARM200F manufactured by JEOL Ltd., with an acceleration voltage of 200 kV and an electron beam diameter of approximately 0.1 nmφ.

[0402] For EDX measurements, a JED-2300T energy dispersive X-ray analyzer manufactured by JEOL Ltd. was used as the elemental analyzer, and X-rays were detected using a silicon drift detector. The detection limit for EDX surface analysis is approximately 1 atomic%. Note that EDX measurements can detect elements ranging from boron (B), atomic number 5, to uranium (U), atomic number 92.

[0403] Figure 23A A TEM image (bright field image) of a cross section of Sample A is shown. Figure 23A The magnification is 100,000 times. Figure 23A In the TEM image, the crystal orientation of the region with roughly uniform concentration (brightness) is roughly uniform, and it can be considered to be a single crystal. In addition, the region with varying concentration (brightness) in the TEM image can be considered to be a grain boundary. Figure 23B Show corresponding Figure 23A Schematic diagram of . Figure 23A and Figure 23B As shown, it can be confirmed that the positive electrode active material particles include a plurality of crystal grains 1101 and grain boundaries 1103 between the crystal grains.

[0404] Figure 24A The STEM image (bright field image) of the cross section of sample A is shown. Figure 24B Shown is a HAADF-STEM image of the same section. Figure 24A and Figure 24B The magnification is 8 million times. Figure 24A and Figure 24B In the figure, a lattice pattern is confirmed in the region of the crystal grains.

[0405] Next, a description will be given of the EDX spectrum of the cross section of sample A. In EDX measurement, an electron beam is irradiated to a measurement point, and the energy and number of occurrences of characteristic X-rays generated are measured to obtain an EDX spectrum. Figure 25 Shown are a HAADF-STEM image and EDX-measured portion of a cross section of Sample A. The EDX-measured portion covers five locations: Points 1 to 5. Points 2 to 4 are located near or at the grain boundaries, while Points 1 and 5 are located farther from the grain boundaries, that is, within the grains. Figure 26 The EDX spectrum and quantitative results of point 1 are shown. Figure 27 The EDX spectrum and quantitative results of point 2 are shown. Figure 28 The EDX spectrum and quantitative results of point 3 are shown. Figure 29 The EDX spectrum and quantitative results of point 4 are shown. Figure 30 The EDX spectrum and quantitative results of point 5 are shown. Figures 26 to 30In the figure, the horizontal axis shows the characteristic X-ray energy (Energy) [keV], and the vertical axis shows the characteristic X-ray intensity [Counts].

[0406] Peaks due to electron transitions to the K layer from carbon (C), oxygen (O), fluorine (F), magnesium (Mg), silicon (Si), phosphorus (P), sulfur (S), calcium (Ca), manganese (Mn), cobalt (Co), and nickel (Ni) were observed at points 1 through 5, respectively. The obtained spectrum was separated into individual elements, and the atomic concentrations were determined.

[0407] Next, EDX surface analysis will be described. The method of performing two-dimensional evaluation within an area while scanning the area is sometimes referred to as surface analysis. In this embodiment, EDX measurement is performed on 256 vertical points by 256 horizontal points within the area.

[0408] Figure 31A The figure shows a HAADF-STEM image of a region subjected to EDX surface analysis of sample A. EDX surface analysis was performed on a region including crystal grains and grain boundaries. Figure 31B Show Figure 31A The carbon surface analysis image of the EDX surface analysis area is shown. Figure 31C The surface analysis image of oxygen is shown. Figure 31D The surface analysis image of fluorine is shown. Figure 31E Shows the surface analysis image of magnesium, Figure 31F Shows the surface analysis image of silicon, Figure 32A Showing the surface analysis image of phosphorus, Figure 32B Shows the surface analysis image of sulfur, Figure 32C Showing the surface analysis image of calcium, Figure 32D The surface analysis image of manganese is shown. Figure 32E The surface analysis image of cobalt is shown. Figure 32F A surface analysis image of nickel is shown.

[0409] Figures 31B to 31F and Figures 32A to 32F This shows a surface analysis image of the characteristic X-ray intensity obtained by EDX measurement. Measurement points with low characteristic X-ray intensity are represented by light colors (white), while measurement points with high characteristic X-ray intensity are represented by dark colors (black). In other words, the atomic concentration of light-colored (white) measurement points is low, and the atomic concentration of dark-colored (black) measurement points is high. Note that Figures 31B to 31F and Figures 32A to 32F In order to make the distribution within the region clearer, the scale of the characteristic X-ray intensity is changed for each element.

[0410] like Figures 31B to 31F and Figures 32A to 32F As shown in FIG. 1 , it can be confirmed that the concentrations of fluorine, magnesium, silicon, and calcium are high at the grain boundaries and their vicinity. In addition, it is believed that the reagents used as raw materials contain silicon and calcium.

[0411] from Figures 31B to 31F and Figures 32A to 32F The EDX surface analysis shown extracts data from a linear region and evaluates the distribution of the atomic concentration within the positive electrode active material particles. This one-dimensional evaluation of a linear region is sometimes referred to as line analysis.

[0412] Figure 33A The HAADF-STEM image of the region where EDX line analysis was performed on sample A is shown. Figure 33A In the figure, the areas where EDX line analysis was performed are indicated by arrows. EDX line analysis was performed on the grains, grain boundaries, and areas across the grains.

[0413] Figure 34A Show Figure 33A The atomic concentration of carbon in the EDX analysis of the region shown is Figure 34B Show Figure 33A The atomic concentration of oxygen in the EDX analysis of the region shown is Figure 34C Show Figure 33A The atomic concentration of fluorine in the EDX analysis of the region shown is Figure 34D Show Figure 33A The atomic concentration of magnesium in the EDX analysis of the region shown is Figure 34E Show Figure 33A The atomic concentration of silicon in the EDX analysis of the region shown is Figure 34F Show Figure 33A The atomic concentration of phosphorus in the EDX analysis of the region shown is Figure 35A Show Figure 33A The atomic concentration of sulfur in the EDX analysis of the region shown is Figure 35B Show Figure 33A The atomic concentration of calcium in the EDX analysis of the region shown is Figure 35C Show Figure 33A The atomic concentration of manganese in the EDX analysis of the region shown is Figure 35D Show Figure 33A The atomic concentration of cobalt in the EDX analysis of the region shown is Figure 35E Show Figure 33A The atomic concentration of nickel in the EDX surface analysis of the area shown.

[0414] exist Figures 34A to 34F and Figures 35A to 35E In the figure, the horizontal axis represents distance (Distance) [nm], and the vertical axis represents atomic concentration [atomic %]. Figure 34AThe black circle at one end of the arrow represents the starting point (distance = 0 nm), and the distance increases toward the other end (end point). The atomic concentration on the vertical axis represents the ratio of the number of atoms of each element, assuming the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel is 100 atomic%.

[0415] like Figure 33A 、 Figures 34A to 34F 、 Figures 35A to 35E As shown, it can be confirmed that the concentrations of fluorine, magnesium, silicon, and calcium are higher in the grain boundary and its vicinity than in the crystal grain region. In addition, it is known that the grain boundary and its vicinity have a region with a width of 1 nm to 10 nm.

[0416] Furthermore, it was confirmed that oxygen, magnesium, and fluorine were present at the grain boundaries and their vicinity, and that the grain boundaries and their vicinity contained magnesium oxide. Furthermore, it is believed that part of the oxygen contained in magnesium oxide was replaced by fluorine.

[0417] On the other hand, fluorine, magnesium, silicon, and calcium in the grain region are at the detection limit.

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

[0419] Note that although carbon was detected in both the grains and grain boundaries, the carbon concentrations shown above may include carbon derived from the carbon coating since a carbon coating was used as a protective film. Therefore, the true carbon concentrations in the grains and grain boundaries cannot be determined.

[0420] Furthermore, it was confirmed that the atomic concentrations of transition metals manganese, cobalt, and nickel were lower at the grain boundaries and in the vicinity thereof than in the crystal grains.

[0421] Figure 35F The total atomic concentration of transition metals nickel, manganese and cobalt is shown. Figure 35F In the graph, the horizontal axis represents distance (nm), and the vertical axis represents the total atomic concentration of nickel, manganese, and cobalt (Ni+Mn+Co) [atomic %]. Specifically, the total atomic concentration of nickel, manganese, and cobalt (Ni+Mn+Co) refers to the sum of the atomic concentrations of nickel, manganese, and cobalt at each EDX measurement point. 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 transition metals. Figure 35F It can be seen that the atomic concentration of transition metals in the grain boundaries and their vicinity tends to be lower than that in the grain region. In addition, the atomic concentration of transition metals in the grain region is approximately the same without much difference.

[0422] Figure 36A The atomic concentration ratio of magnesium (Mg) relative to the atomic concentration of transition metals in the grains is shown. Figure 36AIn the graph, the horizontal axis represents distance (Distance) [nm], and the vertical axis represents the atomic concentration ratio of magnesium to the atomic concentration of transition metal in the crystal grains (Mg / Tr-Metal) (arb. Unit: arbitrary unit).

[0423] The atomic concentration of transition metals in the grains (Tr-Metal) is described. The average value of the atomic concentration of transition metals in the grains is used as the atomic concentration of transition metals in the grains (Tr-Metal). Specifically, the region where the atomic concentration of magnesium (Mg) is at the detection lower limit is regarded as the grain region, and the average value of the atomic concentration of transition metals in this region is calculated. The grain region used for the calculation of the average value is Figure 35F Indicated by arrows.

[0424] Depend on Figure 36A It can be seen that the grain boundaries and their vicinity have an area where the atomic concentration ratio of magnesium to the atomic concentration of the transition metal in the grain (Mg / Tr-Metal) is 0.030 or more. It was also found that magnesium segregation is concentrated at the grain boundaries and their vicinity. Therefore, it can be considered that the grain boundaries and their vicinity contain magnesium oxide. Since sample A of one embodiment of the present invention contains magnesium oxide at the grain boundaries and their vicinity, the positive electrode active material particles are chemically and structurally stable, thereby suppressing the degradation of the positive electrode active material such as the dissolution of transition metal into the electrolyte, oxygen detachment, and unstable crystal structure. In addition, the cracking of the positive electrode active material particles can be suppressed. In addition, the detachment of oxygen from the positive electrode active material particles can be suppressed. By adopting the positive electrode active material particles, the degradation of the storage device can be suppressed. In addition, a highly safe storage device can be provided. When the charging voltage is high, the amount of lithium contained in the positive electrode during charging decreases, and the crystal structure of the positive electrode active material particles is easily changed, so it is particularly preferred to use sample A as the positive electrode active material particles.

[0425] Figure 36B The atomic concentration ratio of fluorine to the atomic concentration of transition metal (Tr-Metal) in the grains is shown. Figure 36B In the graph, the horizontal axis represents distance (nm), and the vertical axis represents the atomic concentration ratio of fluorine to the atomic concentration of transition metal in the crystal grains (represented as F / Tr-Metal).

[0426] Depend on Figure 36B It is found that the grain boundaries and their vicinity have regions where the atomic concentration ratio of fluorine to the atomic concentration of transition metal in the grains (F / Tr-Metal) is 0.030 or greater. Furthermore, since fluorine is present in the grain boundaries and their vicinity, magnesium can be efficiently segregated in the grain boundaries and their vicinity.

[0427] Note that in this specification, etc., "atomic concentration ratio" and "atomic number ratio" are synonymous, and "atomic concentration ratio" can also be replaced with "atomic number ratio." In other words, the Mg / Tr-Metal value is the atomic concentration ratio of magnesium relative to the atomic concentration of the transition metal in the crystal grains, or the atomic number ratio of magnesium relative to the atomic number of the transition metal in the crystal grains.

[0428] Figure 36C The atomic concentration ratio of magnesium (Mg) relative to the total atomic concentration of nickel, manganese, and cobalt (Ni+Mn+Co) in each EDX measurement portion is shown. Figure 36C In the graph, the horizontal axis represents distance (nm), and the vertical axis represents the atomic concentration ratio of magnesium (Mg / (Ni+Mn+Co)) to the total atomic concentration of nickel, manganese, and cobalt in each EDX measurement portion.

[0429] The total atomic concentration of nickel, manganese and cobalt (Ni+Mn+Co) in each EDX measurement part is Figure 35F The data shown are the same.

[0430] Depend on Figure 36C It is found that the grain boundaries and their vicinities have regions where the atomic concentration ratio of magnesium to the total atomic concentration of nickel, manganese, and cobalt in the grains (Mg / (Ni+Mn+Co)) is 0.030 or greater. Magnesium segregates at the grain boundaries and their vicinities.

[0431] Figure 36D The atomic concentration ratio of fluorine to the total atomic concentration of nickel, manganese, and cobalt (Ni+Mn+Co) in each EDX measurement portion is shown. Figure 36D In the graph, the horizontal axis represents distance (nm), and the vertical axis represents the atomic concentration ratio of fluorine (F / (Ni+Mn+Co)) to the total atomic concentration of nickel, manganese, and cobalt in each EDX measurement portion.

[0432] Depend on Figure 36D It can be seen that the grain boundaries and their vicinity have regions where the atomic concentration ratio of fluorine to the atomic concentration of transition metals in the grains (F / (Ni+Mn+Co)) is 0.030 or greater. Since the grain boundaries and their vicinity contain fluorine, magnesium can be efficiently segregated at the grain boundaries and their vicinity.

[0433] EDX measurement was similarly performed on other parts of Sample A.

[0434] Figure 37A The figure shows a HAADF-STEM image of a region subjected to EDX surface analysis of sample A. EDX surface analysis was performed on a region including crystal grains and grain boundaries. Figure 37B Show Figure 37A The carbon surface analysis image of the EDX surface analysis area is shown. Figure 37C The surface analysis image of oxygen is shown. Figure 37D The surface analysis image of fluorine is shown. Figure 37E Shows the surface analysis image of magnesium, Figure 37F Shows the surface analysis image of silicon, Figure 38A Showing the surface analysis image of phosphorus, Figure 38B Shows the surface analysis image of sulfur, Figure 38C Showing the surface analysis image of calcium, Figure 38D The surface analysis image of manganese is shown. Figure 38E The surface analysis image of cobalt is shown. Figure 38F A surface analysis image of nickel is shown.

[0435] Figures 37B to 37F and Figures 38A to 38F This shows a surface analysis image of the characteristic X-ray intensity obtained by EDX measurement. Measurement points with low characteristic X-ray intensity are represented by light colors (white), while measurement points with high characteristic X-ray intensity are represented by dark colors (black pigment). In other words, the atomic concentration of light-colored (white) measurement points is low, and the atomic concentration of dark-colored (black pigment) measurement points is high. Note that Figures 37B to 37F and Figures 38A to 38F In order to make the distribution within the region clearer, the scale of the characteristic X-ray intensity is changed for each element.

[0436] like Figures 37B to 37F and Figures 38A to 38F As shown in FIG. 1 , it can be confirmed that the concentrations of fluorine, magnesium, silicon, and calcium are high at the grain boundaries and their vicinity. In addition, it is believed that the reagents used as raw materials contain silicon and calcium.

[0437] from Figures 37B to 37F and Figures 38A to 38F The data of the linear region was extracted by the EDX surface analysis shown, and the distribution within the positive electrode active material particles was evaluated as the atomic concentration.

[0438] Figure 33B The HAADF-STEM image of the region where EDX line analysis was performed on sample A is shown. Figure 33B In the figure, the areas where EDX line analysis was performed are indicated by arrows. EDX line analysis was performed on the grains, grain boundaries, and areas across the grains.

[0439] Figure 39A Show Figure 33B The atomic concentration of carbon in the EDX analysis of the region shown is Figure 39B Show Figure 33B The atomic concentration of oxygen in the EDX analysis of the region shown is Figure 39C Show Figure 33B The atomic concentration of fluorine in the EDX analysis of the region shown is Figure 39D Show Figure 33B The atomic concentration of magnesium in the EDX analysis of the region shown is Figure 39E Show Figure 33B The atomic concentration of silicon in the EDX analysis of the region shown is Figure 39F Show Figure 33B The atomic concentration of phosphorus in the EDX analysis of the region shown is Figure 40A Show Figure 33B The atomic concentration of sulfur in the EDX analysis of the region shown is Figure 40B Show Figure 33B The atomic concentration of calcium in the EDX analysis of the region shown is Figure 40C Show Figure 33B The atomic concentration of manganese in the EDX analysis of the region shown is Figure 40D Show Figure 33B The atomic concentration of cobalt in the EDX analysis of the region shown is Figure 40E Show Figure 33B The atomic concentration of nickel in the EDX surface analysis of the area shown.

[0440] exist Figures 39A to 39F and Figures 40A to 40E In the figure, the horizontal axis represents distance (Distance) [nm], and the vertical axis represents atomic concentration [atomic %]. Figure 33B The black circle at one end of the arrow represents the starting point (distance = 0 nm), and the distance increases toward the other end (end point). The atomic concentration on the vertical axis represents the ratio of the number of atoms of each element, assuming the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel is 100 atomic%.

[0441] like Figure 33B 、 Figures 39A to 39F 、 Figures 40A to 40E As shown, it can be confirmed that the concentrations of fluorine, magnesium, silicon, and calcium are higher in the grain boundary and its vicinity than in the crystal grain region. In addition, it is known that the grain boundary and its vicinity have a region with a width of 1 nm to 10 nm.

[0442] Furthermore, it was confirmed that oxygen, magnesium, and fluorine were present at the grain boundaries and their vicinity, and that the grain boundaries and their vicinity contained magnesium oxide. Furthermore, it is believed that part of the oxygen contained in magnesium oxide was replaced by fluorine.

[0443] On the other hand, fluorine, magnesium, silicon, and calcium in the grain region are at the detection limit.

[0444] Phosphorus and sulfur are at the detection limit in both grains and grain boundaries.

[0445] Note that although carbon was detected in both the grains and grain boundaries, since a carbon coating was used as a protective film, the carbon concentrations shown above are likely due to the carbon in the carbon coating. Therefore, the true carbon concentrations in the grains and grain boundaries cannot be determined.

[0446] Furthermore, it was confirmed that the atomic concentrations of transition metals manganese, cobalt, and nickel were lower at the grain boundaries and in the vicinity thereof than in the crystal grains.

[0447] Figure 40F The total atomic concentration of transition metals nickel, manganese and cobalt is shown. Figure 40F In the figure, 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+Mn+Co) can also be said to be the atomic concentration of transition metals. Figure 40F It can be seen that the atomic concentration of transition metals in the grain boundaries and their vicinity tends to be lower than that in the grain region. In addition, the atomic concentration of transition metals in the grain region is approximately the same without much difference.

[0448] Figure 41A The atomic concentration ratio of magnesium (Mg) relative to the atomic concentration of transition metals in the grains is shown. Figure 41A In the graph, the horizontal axis represents distance (Distance) [nm], and the vertical axis represents the atomic concentration ratio of magnesium to the atomic concentration of transition metal in the crystal grains (Mg / Tr-Metal).

[0449] The average value of the transition metal atomic concentration in the grains (Tr-Metal) is used as the atomic concentration of the transition metal in the grains. The grain area used for the calculation of the average value is Figure 40F Indicated by arrows.

[0450] Depend on Figure 41A It can be seen that the grain boundaries and their vicinity have an area where the atomic concentration ratio of magnesium to the atomic concentration of the transition metal in the grain (Mg / Tr-Metal) is 0.030 or more, and magnesium is segregated at the grain boundaries and their vicinity. It can be considered that the grain boundaries and their vicinity contain magnesium oxide. Since sample A of one embodiment of the present invention contains magnesium oxide at the grain boundaries and their vicinity, the positive electrode active material particles are chemically and structurally stable, thereby suppressing the degradation of the positive electrode active material such as the dissolution of transition metal into the electrolyte, oxygen detachment, and unstable crystal structure. In addition, the cracking of the positive electrode active material particles can be suppressed. In addition, the detachment of oxygen from the positive electrode active material particles can be suppressed. By adopting the positive electrode active material particles, the degradation of the storage device can be suppressed. In addition, a highly safe storage device can be provided. When the charging voltage is high, the amount of lithium contained in the positive electrode during charging is reduced, and the crystal structure of the positive electrode active material particles is easily distorted, so it is particularly preferred to use sample A as the positive electrode active material particles.

[0451] Figure 41B The atomic concentration ratio of fluorine to the atomic concentration of transition metal (Tr-Metal) in the grains is shown. Figure 41BIn the graph, the horizontal axis represents distance (nm), and the vertical axis represents the atomic concentration ratio of fluorine to the atomic concentration of transition metal in the crystal grains (represented as F / Tr-Metal).

[0452] Depend on Figure 41B It is found that the grain boundaries and their vicinity have regions where the atomic concentration ratio of fluorine to the atomic concentration of transition metal in the grains (F / Tr-Metal) is 0.030 or greater. Furthermore, since fluorine is present in the grain boundaries and their vicinity, magnesium can be efficiently segregated in the grain boundaries and their vicinity.

[0453] Figure 41C The atomic concentration ratio of magnesium (Mg) relative to the total atomic concentration of nickel, manganese, and cobalt (Ni+Mn+Co) in each EDX measurement portion is shown. Figure 41C In the graph, the horizontal axis represents distance (nm), and the vertical axis represents the atomic concentration ratio of magnesium (Mg / (Ni+Mn+Co)) to the total atomic concentration of nickel, manganese, and cobalt in each EDX measurement portion.

[0454] The total atomic concentration of nickel, manganese and cobalt (Ni+Mn+Co) in each EDX measurement part is Figure 40F The data shown are the same.

[0455] Depend on Figure 41C It is found that the grain boundaries and their vicinities have regions where the atomic concentration ratio of magnesium to the total atomic concentration of nickel, manganese, and cobalt in the grains (Mg / (Ni+Mn+Co)) is 0.030 or greater. Magnesium segregates at the grain boundaries and their vicinities.

[0456] Figure 41D The atomic concentration ratio of fluorine to the total atomic concentration of nickel, manganese, and cobalt (Ni+Mn+Co) in each EDX measurement portion is shown. Figure 41D In the graph, the horizontal axis represents distance (nm), and the vertical axis represents the atomic concentration ratio of fluorine (F / (Ni+Mn+Co)) to the total atomic concentration of nickel, manganese, and cobalt in each EDX measurement portion.

[0457] Depend on Figure 41D It can be seen that the grain boundaries and their vicinity have regions where the atomic concentration ratio of fluorine to the atomic concentration of transition metals in the grains (F / (Ni+Mn+Co)) is 0.030 or greater. Since the grain boundaries and their vicinity contain fluorine, magnesium can be efficiently segregated at the grain boundaries and their vicinity.

[0458] According to this embodiment, magnesium and fluorine are added as starting materials for the positive electrode active material particles, and magnesium is segregated at the grain boundaries and their vicinity of the positive electrode active material particles. Since the positive electrode active material particles of one embodiment of the present invention contain magnesium oxide at the grain boundaries and their vicinity, the positive electrode active material particles are chemically and structurally stable, thereby suppressing structural changes, volume changes, and distortion caused by charge and discharge. In other words, the crystalline structure of the positive electrode active material particles is more stable, and even repeated charge and discharge can suppress changes in the crystalline structure. In addition, the rupture of the positive electrode active material particles can be suppressed. In other words, degradation such as capacity reduction can be suppressed.

[0459] Energy storage devices containing these positive electrode active material particles exhibit minimal degradation and are therefore suitable for use in portable electronic devices. Furthermore, when used in vehicles such as automobiles, they can avoid the use of commercial power sources during peak periods of power demand, contributing to energy conservation and reductions in carbon dioxide emissions. Furthermore, a highly safe energy storage device can be provided.

[0460] [Example 2]

[0461] In this example, positive electrode active material particles containing magnesium, fluorine, and oxygen at and near the grain boundaries were produced. TEM observation and STEM-EDX analysis were used to confirm the concentration distribution of the active material at the grains and grain boundaries. The sample used was a sample of Sample B according to one embodiment of the present invention. As Sample B, lithium cobalt oxide containing magnesium, fluorine, and oxygen at and near the grain boundaries was produced. The lithium cobalt oxide was assumed to be composed of LiCoO2. LiCoO2 has a layered rock salt-type crystal structure.

[0462] <Preparation of Sample B>

[0463] The preparation of sample B will be described.

[0464] like Figure 3As shown in step S11 of the flowchart, starting materials are prepared. Lithium carbonate (Li2CO3) is weighed as the lithium source, cobalt tetroxide (Co3O4) is weighed as the cobalt source, magnesium oxide (MgO) is weighed as the magnesium source, and lithium fluoride (LiF) is weighed as the fluorine source. 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 are weighed. Thus, the atomic ratio m of magnesium to the number of cobalt atoms is 0.010 (1.0%). In addition, the atomic ratio n of fluorine to the number of magnesium atoms is 2.0. Li2CO3 is manufactured by High-Purity Chemical Research Institute Co., Ltd. (catalog number: LIH06XB). MgO is manufactured by High-Purity Chemical Research Institute Co., Ltd. (catalog number: MGO12PB). LiF is manufactured by High-Purity Chemical Research Institute Co., Ltd. (catalog number: LIH10XB).

[0465] Next, as shown in step S12, the starting materials weighed in step S11 are mixed. Details of the mixing can be referred to the description of Sample A and the description is omitted here.

[0466] Next, as shown in step S13, the materials mixed in step S12 are subjected to a first heating. Details of the first heating can be referred to the description of Sample A and the description is omitted here.

[0467] Next, as shown in step S14, the materials heated in step S13 are cooled to room temperature to obtain Composition 2. After cooling, the obtained Composition 2 is ground, thereby reducing the particle size of Composition 2. A 53 μm sieve is used for the grinding process.

[0468] Next, as shown in step S15, the Composition 2 obtained in step S14 is subjected to a second heating. Details of the second heating can be referred to the description of Sample A and the description is omitted here.

[0469] 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.

[0470] Next, as shown in step S16, the Composition 2 heated in step S15 is cooled to room temperature and recovered to obtain Sample B.

[0471] ]<TEM Observation, STEM Observation, EDX Measurement>

[0472] Next, sample B was thinned using a focused ion beam (FIB), and a cross section of sample B was observed using TEM and STEM. Furthermore, composition analysis was performed on the cross section of sample B using EDX measurement. Details of the TEM, STEM, and EDX measurements can be found in the description of sample A, and their description is omitted.

[0473] Figure 42A A TEM image (bright field image) of a cross section of Sample B is shown. Figure 42A The magnification is 100,000 times. Figure 42A In the TEM image, the crystal orientation of the region with roughly uniform concentration (brightness) is roughly uniform, and it can be considered to be a single crystal. In addition, the region with varying concentration (brightness) in the TEM image can be considered to be a grain boundary. Figure 42B Show corresponding Figure 42A Schematic diagram of . Figure 42A and Figure 42B As shown, it can be confirmed that the positive electrode active material particles include a plurality of crystal grains 1201 and grain boundaries 1203 between the crystal grains.

[0474] Figure 43A The STEM image (bright field image) of the cross section of sample B is shown. Figure 43B Shown is a HAADF-STEM image of the same section. Figure 43A and Figure 43B The magnification is 8 million times. Figure 43A and Figure 43B In the figure, a lattice pattern is confirmed in the region of the crystal grains.

[0475] Figure 44A This figure shows a HAADF-STEM image of a region subjected to EDX surface analysis of sample B. EDX surface analysis was performed on a region including grains and grain boundaries. In this example, EDX measurement was performed on 256 vertical points by 256 horizontal points within the region.

[0476] Peaks originating from electron transitions to the K layer were observed for carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, manganese, cobalt, and nickel. The obtained spectrum was separated into individual elements, and the atomic concentration was determined.

[0477] Figure 44B Show Figure 44A The carbon surface analysis image of the EDX surface analysis area is shown. Figure 44C The surface analysis image of oxygen is shown. Figure 44D The surface analysis image of fluorine is shown. Figure 44E Shows the surface analysis image of magnesium, Figure 44F Shows the surface analysis image of silicon, Figure 45A Showing the surface analysis image of phosphorus, Figure 45B Shows the surface analysis image of sulfur, Figure 45C Showing the surface analysis image of calcium, Figure 45DA surface analysis image of cobalt is shown.

[0478] Figures 44B to 44F and Figures 45A to 45D This shows a surface analysis image of the characteristic X-ray intensity obtained by EDX measurement. Measurement points with low characteristic X-ray intensity are represented by light colors (white), while measurement points with high characteristic X-ray intensity are represented by dark colors (black pigment). In other words, the atomic concentration of light-colored (white) measurement points is low, and the atomic concentration of dark-colored (black pigment) measurement points is high. Note that Figures 44B to 44F and Figures 45A to 45D In order to make the distribution within the region clearer, the scale of the characteristic X-ray intensity is changed for each element.

[0479] like Figures 44B to 44F and Figures 45A to 45D As shown in Figure 2, it can be confirmed that the concentrations of magnesium and calcium are high at the grain boundaries and their vicinity. Almost no fluorine was observed in the area analyzed by EDX. This is probably because fluorine, a light element, is not easily detected by EDX. In addition, it is believed that the reagent used as the raw material contains calcium.

[0480] from Figures 44B to 44F and Figures 45A to 45D The data of the linear region was extracted by the EDX surface analysis shown, and the distribution within the positive electrode active material particles was evaluated as the atomic concentration.

[0481] Figure 46A The HAADF-STEM image of the region of sample B subjected to EDX line analysis is shown. Figure 46A In the figure, the areas where EDX line analysis was performed are indicated by arrows. EDX line analysis was performed on the grains, grain boundaries, and areas across the grains.

[0482] Figure 47A Show Figure 46A The atomic concentration of carbon in the EDX analysis of the region shown is Figure 47B Show Figure 46A The atomic concentration of oxygen in the EDX analysis of the region shown is Figure 47C Show Figure 46A The atomic concentration of fluorine in the EDX analysis of the region shown is Figure 47D Show Figure 46A The atomic concentration of magnesium in the EDX analysis of the region shown is Figure 47E Show Figure 46A The atomic concentration of silicon in the EDX analysis of the region shown is Figure 47F Show Figure 46A The atomic concentration of phosphorus in the EDX analysis of the region shown is Figure 48A Show Figure 46A The atomic concentration of sulfur in the EDX analysis of the region shown is Figure 48B Show Figure 46A The atomic concentration of calcium in the EDX analysis of the region shown is Figure 48C Show Figure 46A The atomic concentration of cobalt in the EDX surface analysis of the area shown.

[0483] exist Figures 47A to 47F and Figures 48A to 48C In the figure, the horizontal axis represents distance (Distance) [nm], and the vertical axis represents atomic concentration [atomic %]. Figure 46A The black circle at one end of the arrow represents the starting point (distance = 0 nm), and the distance increases toward the other end (end point). The atomic concentration on the vertical axis represents the ratio of the number of atoms of each element, assuming the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, and cobalt is 100 atomic%.

[0484] like Figure 46A 、 Figures 47A to 47F 、 Figures 48A to 48C As shown, it can be confirmed that the concentrations of magnesium and calcium are higher in the grain boundary and its vicinity than in the crystal grain region. In addition, it is known that the grain boundary and its vicinity have a region with a width of 1 nm or more and 10 nm or less.

[0485] Furthermore, oxygen and magnesium were confirmed to be present at the grain boundaries and their vicinity. This indicates that the grain boundaries and their vicinity contain magnesium oxide.

[0486] On the other hand, fluorine, magnesium, silicon, and calcium in the grain region are at the detection limit.

[0487] Phosphorus and sulfur are at the detection limit in both grains and grain boundaries.

[0488] Note that although carbon was detected in both the grains and grain boundaries, since a carbon coating was used as a protective film, the carbon concentrations shown above are likely due to the carbon in the carbon coating. Therefore, the true carbon concentrations in the grains and grain boundaries cannot be determined.

[0489] Furthermore, it was confirmed that the atomic concentration of transition metal cobalt was lower in the grain boundaries and their vicinities than in the crystal grains.

[0490] In sample B, the atomic concentration of cobalt can also be called the atomic concentration of transition metals. Figure 48C It can be seen that the atomic concentration of transition metals in the grain boundaries and their vicinity tends to be lower than that in the grain region. In addition, the atomic concentration of transition metals in the grain region is approximately the same without much difference.

[0491] Figure 49A The atomic concentration ratio of magnesium (Mg) relative to the atomic concentration of transition metals in the grains is shown. Figure 49AIn the graph, the horizontal axis represents distance (Distance) [nm], and the vertical axis represents the atomic concentration ratio of magnesium to the atomic concentration of transition metal in the crystal grains (Mg / Tr-Metal).

[0492] The average value of the transition metal atomic concentration in the grains (Tr-Metal) is used as the atomic concentration of the transition metal in the grains. The grain area used for the calculation of the average value is Figure 48D Indicated by arrows.

[0493] Depend on Figure 49A It can be seen that the grain boundaries and their vicinity have an area where the atomic concentration ratio of magnesium to the atomic concentration of the transition metal in the grain (Mg / Tr-Metal) is greater than 0.030, and magnesium is segregated at the grain boundaries and their vicinity. It can be considered that the grain boundaries and their vicinity contain magnesium oxide. Since sample B of one embodiment of the present invention contains magnesium oxide at the grain boundaries and their vicinity, the positive electrode active material particles are chemically and structurally stable, thereby suppressing the degradation of the positive electrode active material such as the dissolution of transition metal into the electrolyte, oxygen detachment, and unstable crystal structure. In addition, the cracking of the positive electrode active material particles can be suppressed. In addition, the detachment of oxygen from the positive electrode active material particles can be suppressed. By adopting the positive electrode active material particles, the degradation of the storage device can be suppressed. In addition, a highly safe storage device can be provided. When the charging voltage is high, the amount of lithium contained in the positive electrode during charging is reduced, and the crystal structure of the positive electrode active material particles is easily distorted, so it is particularly preferred to use sample B as the positive electrode active material particles.

[0494] Figure 49B The atomic concentration ratio of fluorine to the atomic concentration of transition metal (Tr-Metal) in the grains is shown. Figure 49B In the graph, the horizontal axis represents distance (nm), and the vertical axis represents the atomic concentration ratio of fluorine to the atomic concentration of transition metal in the crystal grains (represented as F / Tr-Metal).

[0495] like Figure 47C and Figure 49B As shown, the fluorine concentration in the crystal grains and grain boundaries is below the detection limit in sample B. This is probably because fluorine, a light element, is not easily detected by EDX.

[0496] Figure 49C The atomic concentration ratio of magnesium (Mg) to the atomic concentration of cobalt (Co) in each EDX measurement portion is shown. Figure 49C In the graph, the horizontal axis represents distance (Distance) [nm], and the vertical axis represents the atomic concentration ratio of magnesium to the atomic concentration of cobalt in each EDX measurement portion (Mg / Co).

[0497] Depend on Figure 49CIt is found that the grain boundaries and their vicinities have regions where the atomic concentration ratio of magnesium to the atomic concentration of cobalt in the grains (Mg / Co) is 0.030 or greater. Magnesium is segregated at the grain boundaries and their vicinities.

[0498] Figure 49D The atomic concentration ratio of fluorine to the atomic concentration of cobalt (Co) in each EDX measurement portion is shown. Figure 49D In the graph, the horizontal axis represents distance (nm), and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of cobalt in each EDX measurement portion (F / Co). In sample B, the fluorine concentration in the crystal grains and grain boundaries was below the detection limit.

[0499] EDX measurement was similarly performed on the other parts of Sample B.

[0500] Figure 50A The figure shows a HAADF-STEM image of a region subjected to EDX surface analysis of sample B. EDX surface analysis was performed on a region including crystal grains and grain boundaries. Figure 50B Show Figure 50A The carbon surface analysis image of the EDX surface analysis of the area shown is shown. Figure 50C The surface analysis image of oxygen is shown. Figure 50D The surface analysis image of fluorine is shown. Figure 50E Shows the surface analysis image of magnesium, Figure 50F Shows the surface analysis image of silicon, Figure 51A Showing the surface analysis image of phosphorus, Figure 51B Shows the surface analysis image of sulfur, Figure 51C Showing the surface analysis image of calcium, Figure 51D A surface analysis image showing cobalt is shown.

[0501] Figures 50B to 50F and Figures 51A to 51D This shows a surface analysis image of the characteristic X-ray intensity obtained by EDX measurement. Measurement points with low characteristic X-ray intensity are represented by light colors (white), while measurement points with high characteristic X-ray intensity are represented by dark colors (black pigment). In other words, the atomic concentration of light-colored (white) measurement points is low, and the atomic concentration of dark-colored (black pigment) measurement points is high. Note that Figures 50B to 50F and Figures 51A to 51D In order to make the distribution within the region clearer, the scale of the characteristic X-ray intensity is changed for each element.

[0502] like Figures 50B to 50F and Figures 51A to 51D As shown in Figure 2, it can be confirmed that the concentrations of magnesium and calcium are high at the grain boundaries and their vicinity. Almost no fluorine was observed in the area analyzed by EDX. This is probably because fluorine, a light element, is not easily detected by EDX. In addition, it is believed that the reagent used as the raw material contains calcium.

[0503] from Figures 50B to 50F and Figures 51A to 51D The data of the linear region was extracted by the EDX surface analysis shown, and the distribution within the positive electrode active material particles was evaluated as the atomic concentration.

[0504] Figure 46B The HAADF-STEM image of the region of sample B subjected to EDX line analysis is shown. Figure 46B In the figure, the areas where EDX line analysis was performed are indicated by arrows. EDX line analysis was performed on the grains, grain boundaries, and areas across the grains.

[0505] Figure 52A Show Figure 46B The atomic concentration of carbon in the EDX analysis of the region shown is Figure 52B Show Figure 46B The atomic concentration of oxygen in the EDX analysis of the region shown is Figure 52C Show Figure 46B The atomic concentration of fluorine in the EDX analysis of the region shown is Figure 52D Show Figure 46B The atomic concentration of magnesium in the EDX analysis of the region shown is Figure 52E Show Figure 46B The atomic concentration of silicon in the EDX analysis of the region shown is Figure 52F Show Figure 46B The atomic concentration of phosphorus in the EDX analysis of the region shown is Figure 53A Show Figure 46B The atomic concentration of sulfur in the EDX analysis of the region shown is Figure 53B Show Figure 46B The atomic concentration of calcium in the EDX analysis of the region shown is Figure 53C Show Figure 46B The atomic concentration of cobalt in the EDX surface analysis of the area shown.

[0506] exist Figures 52A to 52F and Figures 53A to 53C In the figure, the horizontal axis represents distance (Distance) [nm], and the vertical axis represents atomic concentration [atomic %]. Figure 46B The black circle at one end of the arrow represents the starting point (distance = 0 nm), and the distance increases toward the other end (end point). The atomic concentration on the vertical axis represents the ratio of the number of atoms of each element, assuming the total number of atoms of carbon, oxygen, fluorine, magnesium, silicon, phosphorus, sulfur, calcium, and cobalt is 100 atomic%.

[0507] like Figure 46B 、 Figures 52A to 52F 、 Figures 53A to 53CAs shown, it can be confirmed that the concentration of magnesium is higher in the grain boundary and its vicinity than in the crystal grain region. In addition, it is known that the grain boundary and its vicinity have a region with a width of 1 nm or more and 10 nm or less.

[0508] Furthermore, oxygen and magnesium were confirmed to be present at the grain boundaries and their vicinity. This indicates that the grain boundaries and their vicinity contain magnesium oxide.

[0509] On the other hand, fluorine, magnesium, silicon, and calcium in the grain region are at the detection limit.

[0510] Phosphorus and sulfur are at the detection limit in both grains and grain boundaries.

[0511] Note that although carbon was detected in both the grains and grain boundaries, since a carbon coating was used as a protective film, the carbon concentrations shown above are likely due to the carbon in the carbon coating. Therefore, the true carbon concentrations in the grains and grain boundaries cannot be determined.

[0512] Furthermore, it was confirmed that the atomic concentration of transition metal cobalt was lower in the grain boundaries and their vicinities than in the crystal grains.

[0513] In sample B, the atomic concentration of cobalt can also be called the atomic concentration of transition metals. Figure 53C It can be seen that the atomic concentration of transition metals in the grain boundaries and their vicinity tends to be lower than that in the grain region. In addition, the atomic concentration of transition metals in the grain region is approximately the same without much difference.

[0514] Figure 54A The atomic concentration ratio of magnesium (Mg) relative to the atomic concentration of transition metals in the grains is shown. Figure 54A In the graph, the horizontal axis represents distance (Distance) [nm], and the vertical axis represents the atomic concentration ratio of magnesium to the atomic concentration of transition metal in the crystal grains (Mg / Tr-Metal).

[0515] The average value of the transition metal atomic concentration in the grains (Tr-Metal) is used as the atomic concentration of the transition metal in the grains. The grain area used for the calculation of the average value is Figure 53D Indicated by arrows.

[0516] Depend on Figure 54AIt can be seen that the grain boundaries and their vicinity have an area where the atomic concentration ratio of magnesium to the atomic concentration of the transition metal in the grain (Mg / Tr-Metal) is greater than 0.030, and magnesium is segregated at the grain boundaries and their vicinity. It can be considered that the grain boundaries and their vicinity contain magnesium oxide. Since sample B of one embodiment of the present invention contains magnesium oxide at the grain boundaries and their vicinity, the positive electrode active material particles are chemically and structurally stable, thereby suppressing the degradation of the positive electrode active material such as the dissolution of transition metal into the electrolyte, oxygen detachment, and unstable crystal structure. In addition, the rupture of the positive electrode active material particles can be suppressed. In addition, the detachment of oxygen from the positive electrode active material particles can be suppressed. By adopting the positive electrode active material particles, the degradation of the storage device can be suppressed. In addition, a highly safe storage device can be provided. When the charging voltage is high, the crystal structure of the positive electrode active material particles is easily distorted, so it is particularly preferred to use sample B as the positive electrode active material particles.

[0517] Figure 54B The atomic concentration ratio of fluorine to the atomic concentration of transition metal (Tr-Metal) in the grains is shown. Figure 54B In the graph, the horizontal axis represents distance (nm), and the vertical axis represents the atomic concentration ratio of fluorine to the atomic concentration of transition metal in the crystal grains (represented as F / Tr-Metal).

[0518] like Figure 52C and Figure 54B As shown, the fluorine concentration in the crystal grains and grain boundaries is below the detection limit in sample B. This is probably because fluorine, a light element, is not easily detected by EDX.

[0519] Figure 54C The atomic concentration ratio of magnesium (Mg) to the atomic concentration of cobalt (Co) in each EDX measurement portion is shown. Figure 54C In the graph, the horizontal axis represents distance (Distance) [nm], and the vertical axis represents the atomic concentration ratio of magnesium to the atomic concentration of cobalt in each EDX measurement portion (Mg / Co).

[0520] Depend on Figure 54C It is found that the grain boundaries and their vicinities have regions where the atomic concentration ratio of magnesium to the atomic concentration of cobalt in the grains (Mg / Co) is 0.030 or greater. Magnesium is segregated at the grain boundaries and their vicinities.

[0521] Figure 54D The atomic concentration ratio of fluorine to the atomic concentration of cobalt (Co) in each EDX measurement portion is shown. Figure 54D In the graph, the horizontal axis represents distance (nm), and the vertical axis represents the ratio of the atomic concentration of fluorine to the atomic concentration of cobalt in each EDX measurement portion (F / Co). In sample B, the fluorine concentration in the crystal grains and grain boundaries was below the detection limit.

[0522] [Explanation of symbols]

[0523] 100: Positive electrode active material particles, 101: Crystal grains, 103: Grain boundaries, 105: Crystal defects, 107: Regions, 200: Active material layer, 201: Graphene compound, 211a: Positive electrode, 211b: Negative electrode, 212a: Lead wire, 212b: Lead wire, 214: Separator, 215a: Joint, 215b: Joint, 217: Fixing member, 250: Battery, 251: Outer packaging, 261: Folded portion, 262: Seal, 263: Seal, 271: Ridge, 272: Valley bottom, 273: 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, 309: negative electrode active material layer, 310: separator, 500: secondary battery, 501: positive electrode current collector, 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 packaging, 510: positive electrode lead electrode, 511: negative electrode lead electrode, 600: secondary battery, 601: positive electrode cover, 602: battery can, 603: positive electrode terminal, 604: positive electrode, 605: separator, 606: negative electrode, 607: negative electrode terminal, 608: insulating plate, 609: insulating plate, 611: PTC element, 61 2: Safety valve mechanism, 900: Circuit board, 910: Label, 911: Terminal, 912: Circuit, 913: Secondary battery, 914: Antenna, 915: Antenna, 916: Layer, 917: Layer, 918: Antenna, 919: Terminal, 920: Display device, 921: Sensor, 922: Terminal, 930: Frame, 930a: Frame, 930b: Frame, 931: Negative electrode, 932: Positive electrode, 933: Separator, 950: Winding, 951: Terminal, 952: Terminal, 980: Secondary battery, 993: Winding, 994: Negative electrode, 995: Positive electrode, 996: Separator, 997: Lead electrode, 998: Lead electrode, 1101: Grain, 1103: Grain boundary , 1201: grain, 1203: grain boundary, 7100: portable display device, 7101: housing, 7102: display portion, 7103: operation button, 7104: secondary battery, 7200: portable information terminal, 7201: housing, 7202: display portion, 7203: strap, 7204: buckle, 7205: operation button, 7206: input / output terminal, 7207: icon, 7300: display device, 7304: display portion, 7400: mobile phone, 7401: housing, 7402: display portion, 7403: operation button, 7404: external connection port, 7405: speaker, 7406: microphone, 7407: secondary battery, 8000: display device,8001: Housing, 8002: Display, 8003: Speaker, 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 : Automobile, 8401: Headlight, 8406: Electric Motor, 8500: Automobile, 8600: Motorcycle, 8601: Rearview Mirror, 8602: Secondary Battery, 8603: Turn Signal Light, 8604: Underseat Storage, 9600: Tablet Terminal, 9625: Switch, 9626: Switch, 9627: Power Switch, 9628: Operation Switch, 9629: Clip, 9630: Housing, 9630a: Housing, 9630b: Housing, 9631: Display, 9633: Solar Cell, 9634: Charge and Discharge Control Circuit, 9635: Storage Body, 9636: DC-DC Converter, 9637: Converter, 9640: Moving Part.

Claims

1. A lithium ion secondary battery comprising positive electrode active material particles, The positive electrode active material particles include grain boundaries and multiple grains. The positive electrode active material particles contain magnesium and oxygen at the grain boundaries or in the vicinity of the grain boundaries. The positive electrode active material particles have a region where a ratio of the atomic concentration of magnesium at the grain boundary or in the vicinity of the grain boundary to the atomic concentration of cobalt in the crystal grains is 0.010 or more and 0.5 or less. The grain boundary and its vicinity have a region with a width of 1 nm to 10 nm.

2. A lithium ion secondary battery comprising positive electrode active material particles, The positive electrode active material particles include grain boundaries and multiple grains. The positive electrode active material particles contain magnesium and oxygen at the grain boundaries or in the vicinity of the grain boundaries. The positive electrode active material particles have a region where the ratio of the atomic concentration of magnesium at the grain boundary or in the vicinity of the grain boundary to the atomic concentration of cobalt in the crystal grains is 0.030 or more. The grain boundary and its vicinity have a region with a width of 1 nm to 10 nm.

3. A lithium ion secondary battery comprising positive electrode active material particles, The positive electrode active material particles include grain boundaries and multiple grains. The positive electrode active material particles contain magnesium, oxygen, and fluorine at the grain boundaries or in the vicinity of the grain boundaries. The positive electrode active material particles have a region where a ratio of the atomic concentration of magnesium at the grain boundary or in the vicinity of the grain boundary to the atomic concentration of cobalt in the crystal grains is 0.010 or more and 0.5 or less. The grain boundary and its vicinity have a region with a width of 1 nm to 10 nm.

4. The lithium ion secondary battery according to any one of claims 1 to 3, wherein The atomic concentration is obtained by line analysis using EDX.

5. The lithium ion secondary battery according to any one of claims 1 to 3, It contains the positive electrode active material particles and a conductive auxiliary agent, The conductive additive includes carbon fibers.

6. The lithium ion secondary battery according to any one of claims 1 to 3, It contains the positive electrode active material particles and a conductive auxiliary agent, The conductive additive includes carbon nanofibers or carbon nanotubes.

7. The lithium ion secondary battery according to claim 5, wherein The conductive additive further includes carbon black, graphite particles, graphene or fullerene.

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