Positive electrode active material, secondary battery, and electronic appliance

Abstract

To provide a positive electrode active material in which the decrease in capacity in a charging and discharging cycle is suppressed, or a positive electrode active material whose crystal structure is not easily collapsed even after repeated charging and discharging.SOLUTION: A positive electrode active material contains titanium, nickel, aluminum, magnesium, and fluorine, and titanium, nickel, and magnesium distribute unevenly in a convex part on a surface. It is preferable that aluminum distribute in a surface layer part of the positive electrode active material, not in the convex part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One aspect of the present invention relates to an article, a method, or a manufacturing method. Alternatively, the present invention relates to a process, Pertaining to a machine, manufacture, or composition of matter. One embodiment of the present invention is a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or or a method for producing them.

[0002] In this specification, the term "electronic device" refers to a device having a power storage device in general. Electro-optical devices having a power storage device, and information terminal devices having a power storage device are all electronic devices. [Background technology]

[0003] In recent years, lithium-ion secondary batteries, lithium-ion capacitors, air batteries, all-solid-state batteries, etc. The development of various types of energy storage devices is actively underway, especially lithium-ion batteries, which have high output and capacity. Demand for secondary batteries has rapidly expanded along with the development of the semiconductor industry, and the number of rechargeable energy sources has increased. As a source of supply, it has become an indispensable part of the modern information society.

[0004] In particular, secondary batteries for mobile electronic devices have a large discharge capacity per weight, and There is a high demand for secondary batteries with excellent electrical characteristics. Improvements to the positive electrode active material have been actively pursued (for example, Patent Document 1 and Patent Document 2). In addition, research on the crystal structure of positive electrode active materials is also being conducted (Non-Patent Documents 1 to 4 ).

[0005] X-ray diffraction (XRD) is one of the techniques used to analyze the crystalline structure of positive electrode active materials. ICSD (Inorganic Crystal Structure) introduced in Patent Document 5 By using the Artifact Database, XRD data can be analyzed. can. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-190700 A [Patent Document 2] Special Publication No. 2018-508116 [Non-patent literature]

[0007] [Non-Patent Document 1] Toyoki Okumura et al, “Correlation of lithium ion distribution and X-ray absorption near-edge structure in O3-and O2-lithium cobalt oxides from first-principle calculation”, Journal of Materials Chemistry, 2012, 22, p.17340-17348 [Non-patent document 2] Motohashi, T. et al, “Electronic phase diagram of the layered cobalt oxide system LixCoO2 (0.0≦x≦1.0)”, Physical Review B, 80(16);165114 [Non-patent document 3] Zhaohui Chen et al, “Staging Phase Transitions in LixCoO2”, Journal of The Electrochemical Society, 2002, 149(12) A1604-A1609 [Non-patent document 4] WE Counts et al, “Fluoride Model Systems:II, The Binary Systems CaF2-BeF22, MgF2-BeF2, and LiF-MgF2” Journal of the American Ceramic Society, (1953) 36 [1] 12-17. Fig.01471 [Non-patent document 5] Belsky, A. et al., “New developments in the Inorganic Crystal Structure Database (ICSD): accessibility in support of materials research and design”, Acta Cryst., (2002) B58 364-369. Summary of the Invention [Problem to be solved by the invention]

[0008] However, lithium ion secondary batteries and the positive electrode active materials used therein have a low charge / discharge capacity. There is still room for improvement in various aspects, such as quantity, cycle characteristics, reliability, safety, and cost. are.

[0009] One embodiment of the present invention is to improve the efficiency of charge / discharge cycles by using the present invention in a lithium ion secondary battery. Another object of the present invention is to provide a positive electrode active material in which the decrease in the amount of charge is suppressed. An object of the present invention is to provide a positive electrode active material whose crystal structure is not easily broken even after repeated heating and heating. Another object of the present invention is to provide a positive electrode active material having a large charge / discharge capacity. One of the objects is to provide a highly reliable secondary battery.

[0010] Another embodiment of the present invention is to provide a positive electrode active material, a power storage device, or a manufacturing method thereof. This is one of the challenges.

[0011] The description of these problems does not preclude the existence of other problems. It is not necessary for the embodiments to solve all of these problems. It is possible to extract other problems from the description of the claim. [Means for solving the problem]

[0012] Another embodiment of the present invention is a positive electrode active material containing titanium, which has a recess on a surface thereof, The positive electrode active material has titanium on a portion of the inner wall.

[0013] In the above, the recess preferably has a depth of 100 nm or more and a width of 20 nm or more.

[0014] Another embodiment of the present invention is a positive electrode active material including titanium and magnesium, The positive electrode active material has a region where magnesium and titanium are unevenly distributed.

[0015] In the above, the region where magnesium and titanium are unevenly distributed is on the surface of the positive electrode active material. Preferably present.

[0016] In the above, the positive electrode active material further contains cobalt and oxygen, and the cobalt and oxygen is preferably present uniformly.

[0017] In the above, the positive electrode active material preferably further contains lithium.

[0018] In the above, it is preferable to have a region where magnesium and titanium are uniformly present. It's nice.

[0019] In the above, the region where magnesium and titanium are uniformly present is the surface of the positive electrode active material. Preferably, it is a convex portion on the surface.

[0020] In the above, the convex portions preferably have portions with a height of 50 nm or more.

[0021] In the above, the positive electrode active material further contains nickel, and the region where nickel is unevenly distributed is It is preferable to have

[0022] In the above, the positive electrode active material further contains aluminum, and the positive electrode active material has a surface layer and an inner layer. and a surface portion, and the aluminum concentration in the surface portion is preferably higher than that in the interior portion.

[0023] In the above, the positive electrode active material further contains fluorine and has a region where fluorine is unevenly distributed. It is preferable that

[0024] Another embodiment of the present invention is a secondary battery including the above positive electrode active material.

[0025] Another embodiment of the present invention is an electronic device including the above secondary battery. [Effects of the Invention]

[0026] According to one embodiment of the present invention, by using the compound in a lithium ion secondary battery, It is possible to provide a positive electrode active material in which the decrease in capacity due to repeated charge and discharge is suppressed. It is possible to provide a positive electrode active material whose crystalline structure is not easily broken even when heated. Alternatively, a secondary battery with high safety and reliability can be provided. can be provided.

[0027] According to another embodiment of the present invention, a positive electrode active material, a power storage device, or a manufacturing method thereof can be provided. This can be done.

[0028] The description of these effects does not preclude the existence of other effects. The embodiment does not necessarily have to have all of these effects. , the specification, drawings, claims, etc., and It is possible to extract other effects from the claims and other descriptions. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1A is a top view of the positive electrode active material, and FIG. 1B is a cross-sectional view of the positive electrode active material. [Figure 2] FIG. 2(A) is a top view of the positive electrode active material, and FIG. 2(B) is a cross-sectional view of the positive electrode active material. [Figure 3] FIG. 3(A) is a top view of the positive electrode active material, and FIGS. 3(B) and 3(C) are cross-sectional views of the positive electrode active material. [Figure 4] FIG. 4 is a diagram illustrating the depth of charge and the crystal structure of the positive electrode active material. [Figure 5] FIG. 5 is a diagram illustrating the state of charge and the crystal structure of the positive electrode active material of the comparative example. [Figure 6] FIG. 6 shows the XRD pattern calculated from the crystal structure. [Figure 7] Figures 7(A), 7(B) and 7(C) show the lattice constants calculated from XRD. [Figure 8] Figures 8(A), 8(B) and 8(C) show the lattice constants calculated from XRD. [Figure 9] FIG. 9 is a diagram illustrating a method for producing a positive electrode active material. [Figure 10] FIG. 10 is a diagram illustrating a method for producing a positive electrode active material. [Figure 11] FIG. 11 is a diagram illustrating a method for producing a positive electrode active material. [Figure 12] FIG. 12 is a diagram illustrating a method for producing a positive electrode active material. [Figure 13]13(A) and 13(B) are cross-sectional views of an active material layer in the case where a graphene compound is used as the conductive material. [Figure 14] 14(A) and 14(B) are diagrams illustrating an example of a secondary battery. [Figure 15] 15A to 15C are diagrams illustrating examples of secondary batteries. [Figure 16] 16(A) and 16(B) are diagrams illustrating an example of a secondary battery. [Figure 17] 17A to 17C are diagrams illustrating a coin-type secondary battery. [Figure 18] 18(A) to 18(D) are diagrams illustrating a cylindrical secondary battery. [Figure 19] 19(A) and 19(B) are diagrams illustrating an example of a secondary battery. [Figure 20] 20A to 20D are diagrams illustrating examples of secondary batteries. [Figure 21] 21(A) and 21(B) are diagrams illustrating an example of a secondary battery. [Figure 22] FIG. 22 is a diagram illustrating an example of a secondary battery. [Figure 23] 23(A) to 23(C) are diagrams illustrating a laminated secondary battery. [Figure 24] 24(A) and 24(B) are diagrams illustrating a laminated secondary battery. [Figure 25] FIG. 25 is a diagram showing the appearance of a secondary battery. [Figure 26] FIG. 26 is a diagram showing the appearance of a secondary battery. [Figure 27] 27A to 27C are diagrams illustrating a method for manufacturing a secondary battery. [Figure 28] 28A to 28H are diagrams illustrating examples of electronic devices. [Figure 29] 29A to 29C are diagrams illustrating examples of electronic devices. [Figure 30] FIG. 30 is a diagram illustrating an example of an electronic device. [Figure 31] 31A to 31C are diagrams illustrating examples of electronic devices. [Figure 32] 32A to 32C are diagrams showing examples of electronic devices. [Figure 33] 33(A) to 33(C) are diagrams illustrating an example of a vehicle. [Figure 34] Figures 34(A) and 34(B) are SEM images of the surface of the positive electrode active material, and Figure 34(C) is a graph showing the results of linear EDX analysis of the positive electrode active material. [Figure 35] 35(A) and 35(B) are cross-sectional STEM images of the positive electrode active material. [Figure 36] 36(A) to 36(C) are EDX mapping images of the positive electrode active material. [Figure 37] Figure 37(A) is a surface SEM image of the positive electrode active material, Figure 37(B) is a cross-sectional STEM image of the positive electrode active material, and Figure 37(C) is a cross-sectional STEM image of the positive electrode active material. [Figure 38] 38(A) to 38(E) are EDX mapping images of the positive electrode active material. [Figure 39] Figure 39(A) is a surface SEM image of the positive electrode active material, and Figure 39(B) and Figure 39(C) are cross-sectional STEM images of the positive electrode active material. [Figure 40] 40(A) to 40(G) are EDX mapping images of the positive electrode active material. [Figure 41] Figure 41(A) is a micro-electron beam diffraction image of a protrusion of the positive electrode active material, and Figure 41(B) is a micro-electron beam diffraction image of the interior of the positive electrode active material. [Figure 42] FIG. 42 is a graph showing the cycle characteristics of a secondary battery. [Figure 43] FIG. 43 is a graph showing the cycle characteristics of a secondary battery. [Figure 44] FIG. 44 is a graph showing the cycle characteristics of a secondary battery. [Figure 45] FIG. 45 is an SEM image of the surface of the positive electrode active material. [Figure 46]Fig. 46(A) is an SEM image of the surface of the positive electrode active material, and Fig. 46(B) to Fig. 46(G) are EDX mapping images of the positive electrode active material. [Figure 47] Fig. 47(A) is an SEM image of the surface of the positive electrode active material, and Fig. 47(B) to Fig. 47(H) are EDX mapping images of the positive electrode active material. [Figure 48] FIG. 48 shows the XRD pattern of the positive electrode active material. [Figure 49] 49(A) and 49(B) are XRD patterns of the positive electrode active material. [Figure 50] 50(A) and 50(B) are XRD patterns of the positive electrode active material. [Figure 51] 51(A) and 51(B) are graphs showing the cycle characteristics of the secondary battery. [Figure 52] FIG. 52 is a graph showing the cycle characteristics of a secondary battery. [Figure 53] 53(A) and 53(B) are graphs showing the cycle characteristics of the secondary battery. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and various modifications in form and details are possible by those skilled in the art. Furthermore, the present invention should not be construed as being limited to the description of the following embodiments. It is not something that can be done.

[0031] In this specification and the like, Miller indices are used to indicate crystal planes and directions. Individual faces are represented in ( ). Crystal faces, directions and space groups are represented by the crystallographic notation of numbers with superscripts. However, in this specification, due to limitations on the application notation, instead of adding a bar above the number, It may be expressed by adding a minus sign (-) before it.

[0032] In this specification, segregation refers to the phenomenon in a solid consisting of multiple elements (e.g., A, B, C). This refers to the phenomenon in which a certain element (e.g., B) is distributed spatially non-uniformly.

[0033] In this specification, the term "uniform" refers to a solid material consisting of multiple elements (e.g., A, B, C). In a body, the phenomenon in which a certain element (e.g., A) is distributed with similar characteristics in a specific region is called It is sufficient that the concentrations of elements in the specific regions are substantially the same. The difference in element concentration between the two regions should be within 10%. Examples include recesses, interiors, etc.

[0034] In the present specification and the like, the layered rock salt type crystal structure of a composite oxide containing lithium and a transition metal is The structure has a rock salt type ion arrangement in which cations and anions are arranged alternately, and the transition metal and lithium The lithium atoms are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. It refers to a crystalline structure. It may have defects such as cation or anion deficiencies. Strictly speaking, the rock salt crystal structure is a distorted structure of the rock salt crystal. be.

[0035] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately. It is possible for there to be a deficiency of cations or anions.

[0036] In the present specification and the like, the pseudospinel type composite oxide containing lithium and a transition metal The crystal structure is in the space group R-3m, and although it is not a spinel-type crystal structure, cobalt, Ions such as magnesium ions occupy the 6-coordinated oxygen sites, and the arrangement of cations is similar to that of spinel. The pseudo-spinel type crystal structure is characterized by the symmetry of the crystal structure. may occupy the oxygen tetracoordinate site, and in this case the ionic arrangement also has a symmetry similar to that of the spinel type. It has sexuality.

[0037] The pseudospinel crystal structure has random Li between layers, but the CdCl2 crystal structure It can be said that this crystal structure is similar to the CdCl2 type. The structure is that when lithium nickel oxide is charged to a charge depth of 0.94 (Li 0.06 NiO 2) It has a similar crystal structure to pure lithium cobaltate, or a layered rock containing a large amount of cobalt. It is known that salt-type positive electrode active materials do not usually have this crystal structure.

[0038] Layered rock salt crystals and the anions in rock salt crystals have a cubic close-packed structure (face-centered cubic lattice structure) It is estimated that the anions in pseudospinel crystals also have a cubic close-packed structure. When the anions are in contact, there exists a crystal plane where the cubic close-packed structure formed by the anions is oriented in the same direction. However, the space group of layered rock salt crystals and pseudospinel crystals is R-3m, and the space group of rock salt crystals is R-3m. The crystal space groups Fm-3m (the common rock salt crystal space group) and Fd-3m (the simplest Since the space group is different from that of rock salt crystals with symmetry, the mirror crystals that satisfy the above conditions The index is different between layered rock salt crystals and pseudospinel crystals and rock salt crystals. is composed of anions in layered rock salt crystals, pseudospinel crystals, and rock salt crystals. When the orientation of the resulting cubic close-packed structure is aligned, the crystal orientation is said to be roughly the same. be.

[0039] The crystal orientation of the two regions roughly coincides, as can be seen from TEM (transmission electron microscope) and STEM images. (Scanning Transmission Electron Microscope) image, HAADF-STEM (High Angle Scattering Annular Dark Field Scanning Transmission Electron Microscope) It can be judged from the images of the annular bright-field scanning transmission electron microscope (ABF-STEM), etc. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as materials for judgment. In TEM images, the arrangement of cations and anions is observed as repeated bright and dark lines. When the orientation of the cubic close-packed structure in the layered rock salt crystal and the rock salt crystal is aligned, The angle between the repeated bright and dark lines should be 5 degrees or less, and more preferably 2.5 degrees or less. Light elements such as oxygen and fluorine can be clearly observed in TEM images. In some cases, this is not possible, but in that case, the alignment of the metal elements can be used to determine the alignment. .

[0040] In this specification, the theoretical capacity of the positive electrode active material is the capacity of the positive electrode active material that can be inserted and removed. The theoretical capacity of LiCoO2 is 27 4mAh / g, the theoretical capacity of LiNiO2 is 274mAh / g, the theoretical capacity of LiMn2O4 is 148mAh / g.

[0041] In this specification, the depth of charge when all intercalable and detachable lithium is intercalated is The depth of charge when all the intercalable lithium in the positive electrode active material is deintercalated is defined as 0, and the depth of charge when all the intercalable lithium in the positive electrode active material is deintercalated is defined as 1. That is what I will say.

[0042] In this specification, charging refers to transferring electrons from a positive electrode to a negative electrode in an external circuit. For the positive electrode active material, charging refers to the process of removing lithium ions. Positive charge depth is 0.74 or more and 0.9 or less, more specifically, 0.8 or more and 0.83 or less. The positive electrode active material is the positive electrode active material charged at a high voltage. If the positive electrode active material is charged at 219.2mAh / g at 002, it is In addition, in the case of LiCoO2, the charging voltage is 4.525V or higher in a 25°C environment. 65V or less (in the case of lithium counter electrode), constant current charging, then the current value is 0.01C, Or, after constant voltage charging until the current value becomes 1 / 5 to 1 / 100 of the value during constant current charging, The positive electrode active material is also referred to as a positive electrode active material charged with a high voltage.

[0043] Similarly, discharging refers to the transfer of electrons from the negative electrode to the positive electrode in an external circuit. For active materials, the insertion of lithium ions is called discharging. 6 or less positive electrode active material, or when charged at high voltage, the capacity is 90% or more of the charge capacity. The discharged positive electrode active material is referred to as a fully discharged positive electrode active material. For example, LiCo If the charge capacity is 219.2mAh / g in O2, it is in a state where it is charged at a high voltage. After discharging 197.3mAh / g or more, which is 90% of the charge capacity, the positive electrode active material The positive electrode active material is fully discharged. In addition, the battery The positive electrode active material after constant current discharge until the voltage falls below 3V (in the case of lithium counter electrode) is also sufficiently This refers to the positive electrode active material that has been discharged in minutes.

[0044] In this specification and the like, a secondary battery using a positive electrode and a positive electrode active material of one embodiment of the present invention In some cases, lithium metal is used for the counter electrode. However, other materials such as graphite and lithium titanate may be used for the negative electrode. The positive electrode and positive electrode active material of the present invention have a crystalline structure that is resistant to breakdown even after repeated charge and discharge, and are excellent in The properties of the negative electrode, such as the ability to obtain good cycle characteristics, are not affected by the material of the negative electrode. For such secondary batteries, the counter electrode is lithium and the charging voltage is relatively high, at 4.6V. Although examples of charging and discharging at a lower voltage are shown, charging and discharging at a lower voltage is also possible. When the battery is charged, it is expected that the cycle characteristics will be even better than those shown in this specification.

[0045] (Embodiment 1) In this embodiment, a positive electrode active material of one embodiment of the present invention will be described with reference to FIGS. .

[0046] FIG. 1A is an example of a top view of a positive electrode active material 101 according to one embodiment of the present invention. A schematic cross-sectional view of the structure taken along the line AB is shown in FIG. 1(B).

[0047] <Elements and distribution> The positive electrode active material 101 contains lithium, a transition metal M, oxygen, and impurities. The substance 101 can be said to be a composite oxide represented by LiMO2 with impurities added. .

[0048] The transition metal M contained in the positive electrode active material 101 is a metal that belongs to the space group R-3m together with lithium. It is preferable to use a metal that can form a layered rock salt type composite oxide. For example, manganese At least one of tungsten, cobalt, and nickel can be used. The transition metal in 1 may be cobalt alone or nickel alone. Alternatively, two types of metals, cobalt and manganese, or cobalt and nickel, may be used. In other words, the positive electrode active material 101 may be composed of three types of materials: cobalt, manganese, and nickel. Lithium nickel oxide, lithium nickel oxide, cobalt oxide in which some of the cobalt is replaced by manganese Lithium, lithium cobalt oxide in which some of the cobalt is replaced by nickel, nickel-manganese It is possible to have a composite oxide containing lithium and a transition metal M, such as lithium gallium cobaltate. When nickel is included in addition to cobalt as the transition metal M, the This is preferable because the crystal structure may become more stable in some cases.

[0049] The impurities contained in the positive electrode active material 101 include magnesium, fluorine, aluminum, titanium, and the like. Zirconium, vanadium, iron, chromium, niobium, cobalt, arsenic, zinc, silicon, It is preferable to use at least one of sulfur, phosphorus, and boron. In this way, the crystal structure of the positive electrode active material 101 may be further stabilized. The electrode active material 101 is lithium cobalt oxide doped with magnesium and fluorine, Lithium cobalt oxide doped with sodium, fluorine and titanium, magnesium and fluorine Lithium-doped nickel-cobalt oxide, magnesium- and fluorine-doped Cobalt-lithium aluminum oxide, nickel-cobalt-lithium aluminum oxide, Magnesium and fluorine doped lithium nickel-cobalt-aluminate, magnesium and fluorine doped lithium nickel-manganese-cobalt oxide, etc. In this specification, impurities are those that impair the properties of the positive electrode active material 101. Therefore, instead of impurities, they can be called additives, mixtures, or parts of raw materials.

[0050] As shown in FIG. 1(B), the positive electrode active material 101 has a surface layer 101a and an inner layer 101b. It is preferable that the surface layer 101a has a higher impurity concentration than the inner layer 101b. As shown by the gradient in (B), the impurities have a concentration gradient that increases from the interior to the surface. In this specification, the surface layer 101a is the positive electrode active material 101. The area from the surface to about 10 nm deep is also called the surface. The region deeper than surface layer 101a of positive electrode active material 101 is referred to as interior 101b.

[0051] In the positive electrode active material 101 of one embodiment of the present invention, lithium is extracted from the positive electrode active material 101 by charging. The layer structure consisting of the transition metal M such as cobalt and the oxygen octahedron is not broken even if the Surface layer 101a where the concentration of the material is high, that is, the outer periphery of positive electrode active material 101, is reinforced.

[0052] The concentration gradient of the impurities is the same throughout the entire surface layer 101a of the positive electrode active material 101. It is preferable that the reinforcement resulting from the high impurity concentration is uniformly present in the surface layer portion 101a. Even if a part of the surface layer 101a is reinforced, If there are any missing parts, stress may be concentrated in the missing parts, which is undesirable. When stress is concentrated in a part of the particle, defects such as cracks occur, causing the positive electrode active material to break and This may lead to a decrease in the charge / discharge capacity.

[0053] Magnesium is divalent and is more readily absorbed by lithium than by the transition metal sites in the layered rocksalt crystal structure. Since magnesium is more stable in the lithium site, it is easier for it to enter the lithium site. The presence of an appropriate concentration in the lithium site of the surface layer portion 101a makes the positive electrode active material 101 effective. Magnesium, at the appropriate concentration, can help maintain the layered rock salt crystal structure. This is preferable because it does not adversely affect the insertion and extraction of lithium during charge and discharge. If there is an excess of lithium, it may have a negative effect on the insertion and extraction of lithium. Preferably, the portion 101a has a higher concentration of transition metal than magnesium, for example.

[0054] Aluminum is trivalent and has a strong bond with oxygen. When lithium enters the lithium site, the change in the crystal structure can be suppressed. By adding 101 sulphite, the crystal structure of the positive electrode active material is resistant to breakdown even after repeated charge and discharge. It can be said that:

[0055] As the charging voltage of the secondary battery increases, the voltage of the positive electrode generally increases. The positive electrode active material has a stable crystal structure even at high voltages. The stable crystal structure of the material prevents the capacity from decreasing due to repeated charging and discharging. can be done.

[0056] In addition, a short circuit in the secondary battery can cause problems with the charging and discharging operations of the secondary battery. In order to realize a safe secondary battery, It is preferable that the short circuit current is suppressed even at a low charging voltage. The active material 101 suppresses short-circuit current even at high charging voltages. Therefore, a secondary battery that is both efficient and safe can be obtained.

[0057] The concentration gradient of impurities can be measured, for example, by energy dispersive X-ray spectroscopy (EDX). This can be evaluated using transversive X-ray spectroscopy. EDX is a type of DX measurement in which an area is scanned while being measured and evaluated two-dimensionally. It is also called area analysis. It is also called area analysis, and the atomic concentration of the positive electrode active material particles is measured by scanning the area linearly. Evaluating the distribution within the area is called line analysis. Furthermore, data on linear regions can be obtained from area analysis of EDX. Extracting data from a certain area is sometimes called line analysis. This is called point analysis.

[0058] By EDX surface analysis (for example, element mapping), the surface layer 101a of the positive electrode active material 101 and the inner layer 101b of the positive electrode active material 101 are identified. In the portion 101b and the vicinity of the grain boundary, as well as in the buried portion 102 and the protruding portion 103, which will be described later, The concentration of impurities can be quantitatively analyzed by EDX analysis. The concentration distribution and maximum values ​​can be analyzed.

[0059] When the positive electrode active material 101 contains magnesium as an impurity, EDX analysis reveals that The peak of the magnesium concentration in the surface layer 101a increases from the surface of the positive electrode active material 101 toward the center. Preferably, the surface is present at a depth of up to 3 nm, more preferably at a depth of up to 1 nm. Preferably, it exists to a depth of up to 0.5 nm.

[0060] When the positive electrode active material 101 contains fluorine in addition to magnesium as an impurity, the fluorine The distribution of ions should overlap with the distribution of magnesium. At this time, the peak of the fluorine concentration in the surface layer portion 101a increases from the surface of the positive electrode active material 101 toward the center. Preferably, the surface is present at a depth of up to 3 nm, more preferably at a depth of up to 1 nm. Preferably, it exists to a depth of up to 0.5 nm.

[0061] It is not necessary for all impurities to have the same concentration distribution. When aluminum is present as a component, the distribution is slightly different from that of magnesium and fluorine. For example, when EDX analysis is performed, it is preferable that the aluminum of the surface layer portion 101a is It is preferable that the peak of magnesium concentration is closer to the surface than the peak of hydrogen concentration. The aluminum concentration peak is at a depth of 0.5 nm from the surface to the center of the positive electrode active material 101. Preferably, the surface is present at a depth of 1 nm to 5 nm. is more preferred.

[0062] When the positive electrode active material 101 was subjected to a line analysis or a surface analysis, The ratio (I / M) of the number of atoms of the impurity I to the number of atoms of the transition metal M is preferably 0.05 or more and 1.00 or less. Furthermore, if the impurity is titanium, the ratio of the number of atoms of titanium to the transition metal M (Ti / M) is 0. The ratio is preferably 0.5 or more and 0.4 or less, and more preferably 0.1 or more and 0.3 or less. In the case of magnesium, the ratio of the number of atoms of magnesium to the transition metal M (Mg / M) is 0.4 or more. The range is preferably from 0.45 to 1.00, and more preferably from 0.45 to 1.00. In the case of a fluorine atom, the ratio of the number of fluorine atoms to the number of transition metal atoms (F / M) must be between 0.05 and 1.5. It is preferable that the ratio is 0.3 or more and 1.00 or less.

[0063] Furthermore, when the positive electrode active material 101 was subjected to line analysis or area analysis, the imperfections in the vicinity of the grain boundaries were The ratio of the number of atoms of the pure material I to the number of atoms of the transition metal M (I / M) is preferably 0.020 or more and 0.50 or less. More preferably, it is 0.025 or more and 0.30 or less. Still more preferably, it is 0.030 or more and 0.20 or less. For example, when the impurity is magnesium and the transition metal is cobalt, The ratio of the number of atoms of sodium to cobalt (Mg / Co) is preferably 0.020 or more and 0.50 or less. It is more preferably 0.025 or more and 0.30 or less. It is further preferably 0.030 or more and 0.20 or less. The following is preferred:

[0064] As described above, if the impurities contained in the positive electrode active material 101 are excessive, lithium intercalation and In addition, when the positive electrode active material 101 is used in a secondary battery, the resistance may be adversely affected. On the other hand, if the impurities are insufficient, the surface layer 101a may have a high resistance and a low capacity. If impurities are not distributed throughout the crystal, the effect of maintaining the crystal structure may be insufficient. The concentration of the positive electrode active material 101 must be appropriate, but it is not easy to adjust the concentration.

[0065] Therefore, for example, the positive electrode active material 101 may have a region where impurities are unevenly distributed. The presence of such a region removes excess impurities from the interior 101b, The impurity concentration in the inner portion 101b can be set to an appropriate value. By doing so, it is possible to suppress an increase in resistance and a decrease in capacity when used as a secondary battery. Being able to suppress the increase in resistance of a secondary battery is extremely advantageous, especially during high-rate charging and discharging. This is a desirable characteristic.

[0066] In addition, in the positive electrode active material 101 having a region where impurities are unevenly distributed, It is permissible to mix impurities to a certain extent, which results in a wider margin in production. preferable.

[0067] In this specification, uneven distribution means that the concentration of an element in a certain region is different from that in other regions. It can also be called segregation, precipitation, non-uniformity, bias, high or low concentration, etc. stomach.

[0068] 2A to 3C, a region where impurities are unevenly distributed, which is one embodiment of the present invention, is shown. The impurities in the region where the impurities are unevenly distributed are as follows: For example, titanium exists as a compound. Therefore, when we say that titanium is ubiquitous as an impurity, This means that titanium compounds such as titanium oxide are unevenly distributed. Similarly, when it is said that impurity metals are unevenly distributed, it is not limited to oxides, fluorides, etc. of the impurity metals. This means that compounds of certain impurity metals are unevenly distributed.

[0069] FIG. 2A shows a buried portion 102 as a region where impurities are unevenly distributed, which is one embodiment of the present invention. 2A is a top view of a positive electrode active material 101 having the same structure. Shown in (B).

[0070] As shown in FIGS. 2(A) and 2(B), the positive electrode active material 101 may have recesses 101c. The recess 101c may be any area having a different height from other areas, such as a crack, a depression, a cross section V, etc. The recesses may be 10 nm or more deep, or even 100 nm or more deep. The depth is set to, for example, 5 μm or less, or 1 μm or less. It is preferable to have a buried portion 102 that fills a part of the portion 101c. The adhesive layer 104 adheres to at least a part of the inner wall of the recess 101c. It can be said that the recessed portion 102 is partially embedded in the cavity. The buried portion 102 contains impurities such as titanium, magnesium, and Preferably, at least one of the concentrations of fluorine is higher than that of the interior 101b.

[0071] Titanium is preferably present in the buried portion 102 as a titanium compound, for example, titanium oxide. I wish.

[0072] The recess 101c is one of the defects in the positive electrode active material 101, and the recess 101c is reduced by repeated charging and discharging. 01c may cause transition metal elution, collapse of the crystal structure, and cracks on the surface and inside. However, the presence of the buried portion 102 makes it possible to suppress the elution of transition metals. Therefore, the positive electrode active material 101 can be made to have excellent reliability and cycle characteristics. .

[0073] FIG. 3A shows a semiconductor device having a convex portion 103 as a region where impurities are unevenly distributed, which is one embodiment of the present invention. 3(A) is a top view of the positive electrode active material 101. FIG. 3(B) is a cross-sectional view taken along line EF in FIG. Alternatively, as shown in FIG. 3(C), the convex portion may be any portion having a different height from the other portions, such as a water drop-shaped portion, It can also be called a colony-like portion, a hill-like portion, a protuberance, etc. In addition, when there are multiple protuberances, the shape The convex portions 103 may have a height of, for example, 50 nm or more, or even 10 It is preferable that the height of the protrusions 103 is the height of the surface layer 101a and the protrusions 103. The height of the protrusion 103 from the interface is determined from a microscope image such as an SEM image or a TEM image. can be measured.

[0074] The protrusions 103 are preferably present on the surface of the positive electrode active material 101. It contains both pure fluorine and compounds of metals such as magnesium and titanium. In this case, the convex portion 103 has a high fluorine concentration region 103a and a metal imperfection region as shown in FIG. 3(B). It is preferable that the high impurity concentration region 103b is provided. The fluorine concentration is higher than that of the high metal impurity concentration region 103b. The region 103b has a higher concentration of metal impurities than the interior 101b and the high fluorine concentration region 103a. The positive electrode active material 101 is formed on the positive electrode active material 101 so as to cover the high fluorine concentration region 103a. It is preferable that the metal impurity high concentration region 103b is provided in the semiconductor substrate 100.

[0075] The surface layer 101a of the positive electrode active material 101 contains titanium, magnesium and It is preferable that impurities such as fluorine and the like are present. It is preferable to have a concentration gradient that increases toward the surface.

[0076] When the positive electrode active material 101 contains nickel as the transition metal M, part of the nickel is In this case, the metal impurity high concentration region 103 may be present in the metal impurity high concentration region 103b. b may have a higher nickel concentration than the inner portion 101b and the high fluorine concentration region 103a. .

[0077] Furthermore, as shown in FIG. 3C, the surface layer 101a and the inner layer 101b overlapping the convex portion 103 are A nickel-rich region 101d may be present in a part of the nickel-rich region 101. d indicates the traces of nickel dissolved in the positive electrode active material 101 being attracted to the protrusions 103. The nickel-rich region 101d is formed by the surface layer 101a and the inner layer 101b. The nickel concentration is higher than that of the nickel-rich region 101d of the nickel-rich region 101b. The nickel concentration is lower than that of the high nickel concentration region 103b.

[0078] Furthermore, it is not necessary for all impurities to have the above distribution. If you have aluminum as a component, aluminum is different from magnesium or titanium. For example, aluminum is mostly distributed unevenly in the protrusions 103. It is preferable that the protrusions 101 are not present in the surface layer 101a of the positive electrode active material 101, but are present in the surface layer 101a of the positive electrode active material 101. It is preferable that the aluminum concentration of the surface layer 101a is higher than the aluminum concentration of the surface layer 101b. I wish.

[0079] In this specification and the like, the region where impurities contained in the positive electrode active material 101 are unevenly distributed, for example, For example, the embedded portion 102 and the protruding portion 103 are regions having a different composition from the positive electrode active material 101. The positive electrode active material 101 and the region where impurities are unevenly distributed may have different crystal structures. For example, the positive electrode active material 101 has a layered rock salt type crystal structure and impurities are unevenly distributed. Crystal structure of the rock salt, spinel, rutile, anatase or perovskite regions The region where the impurities are unevenly distributed may be amorphous. By various analyses including DX, cross-sectional TEM, surface SEM, and electron beam diffraction, different compositions can be identified. Alternatively, it can be determined that the region has a crystalline structure.

[0080] Furthermore, the dielectric constant of the buried portion 102 and the protruding portion 103 is the same as that of the surface portion 101a and the inner portion 10 For example, if the dielectric constant of the protrusion 103 is high, the protrusion 103 Then, the protrusion 103 near the negative electrode and the surface layer 101a are polarized. As a result, the lithium ions, which are positive ions, move more easily to the interface. Therefore, when the positive electrode active material 101 is used in a secondary battery, This is preferable because it improves the rate characteristics of the battery.

[0081] For example, if the buried portion 102 and the protruding portion 103 contain magnesium-titanium oxide, It is preferable because it may have a higher dielectric constant than lithium barium oxide.

[0082] In addition, in the positive electrode active material 101, lithium, transition metals, and oxygen, which are not included in the impurities, are uniformly contained. In this specification, the term "uniform" means that the distribution is substantially uniform. For example, the difference in element concentration may be within 10%.

[0083] 2 and 3, the regions where the impurities are unevenly distributed are the buried portion 102 and the protruding portion 103. However, the region where impurities are unevenly distributed in the positive electrode active material 101 of one embodiment of the present invention has been described. However, the region may be any region having a different composition from the positive electrode active material 101. The shape is not limited to a protuberance or a bump.

[0084] Regarding the concentration gradient of impurities in the surface layer 101a of the positive electrode active material 101 shown in FIGS. 2 and 3, For details, please refer to the description in Figure 1.

[0085] <Crystal structure> Materials with a layered rock-salt crystal structure, such as lithium cobalt oxide (LiCoO2), It has a high capacity and is known to be an excellent positive electrode active material for secondary batteries. Layered rock salt crystals An example of a material having this structure is a composite oxide represented by LiMO2.

[0086] The Jahn-Teller effect in transition metal compounds depends on the number of electrons in the d orbital of the transition metal. The strength of the effect is known to vary.

[0087] In compounds containing nickel, distortion may easily occur due to the Jahn-Teller effect. Therefore, when LiNiO2 is charged and discharged at high voltage, the distortion There is a concern that the crystal structure of LiCoO2 may be affected by the Jahn-Teller effect. This suggests that the impact of the charge / discharge is small, and the durability of the charge / discharge at high voltage may be better, which is preferable. stomach.

[0088] The positive electrode active material will be described with reference to Figs. 4 and 5. In Figs. 4 and 5, the positive electrode active material The case where cobalt is used as the transition metal M in the material will be described.

[0089] <Conventional positive electrode active materials> The positive electrode active material shown in FIG. 5 is a material to which halogen and magnesium are added by the manufacturing method described below. The lithium cobalt oxide shown in Figure 5 is a non- As described in Patent Document 1 and Non-Patent Document 2, the crystal structure changes depending on the charge depth. Change.

[0090] As shown in Figure 5, lithium cobalt oxide at a charge depth of 0 (discharged state) is in the space group R-3 m crystal structure, and there are three CoO2 layers in the unit cell. This crystal structure is sometimes called an O3 type crystal structure. The CoO2 layer is a layer of cobalt. This refers to a structure in which an octahedral structure in which oxygen atoms are six-coordinated is connected to a plane in an edge-sharing state.

[0091] At a charge depth of 1, the crystal structure has the space group P-3m1, and CoO exists in the unit cell. There is one layer of two layers. Therefore, this crystal structure is sometimes called the O1 type crystal structure.

[0092] In addition, when the charge depth is about 0.88, lithium cobalt oxide has a crystal structure of the space group R-3m. This structure is similar to the structure of CoO2, such as P-3m1(O1), and R-3m(O3 ) and the structure of LiCoO2, which is stacked alternately. The crystal structure is sometimes called the H1-3 crystal structure. In reality, the H1-3 crystal structure is , the number of cobalt atoms per unit cell is twice that of the other structures. In this specification, the c-axis of the H1-3 type crystal structure is used as a unit to facilitate comparison with other structures. The figure will be shown as half the size of a cell.

[0093] As an example, the H1-3 type crystal structure is described in Non-Patent Document 3, in the unit cell The coordinates of cobalt and oxygen in the (0, 0, 0.27671±0.00045), O2(0, 0, 0.11535±0.0 0045), where O1 and O2 are oxygen atoms. The H1-3 crystal structure is represented by a unit cell with one cobalt and two oxygen atoms. On the other hand, as will be described later, the pseudospinel crystal structure of one embodiment of the present invention is preferably , represented by a unit cell with one cobalt and one oxygen. The symmetry between cobalt and oxygen is different between the Pinel structure and the H1-3 structure. The pseudospinel structure is less different from the O3 structure than the H1-3 type structure. It is more preferable to use any one of the unit cells to represent the crystal structure of the positive electrode active material. The choice of the GOF (goodness of field) is based on the Rietveld analysis of XRD. of fit) should be selected so that the value is smaller.

[0094] High-voltage charging where the charging voltage is 4.6V or higher based on the redox potential of lithium metal Or, if you repeatedly charge and discharge to a deep depth where the charge depth is 0.8 or more, Lithium cobalt oxide has two types of crystal structure: H1-3 type and R-3m(O3) type in discharge state. The crystal structure changes (i.e., non-equilibrium phase changes) repeatedly occur between these two states.

[0095] However, these two crystal structures have a large misalignment of the CoO2 layers. As shown by the arrows, in the H1-3 type crystal structure, the CoO2 layer is significantly larger than the R-3m(O3). Such dynamic structural changes have a negative effect on the stability of the crystal structure. Ugh.

[0096] Furthermore, the difference in volume is large. When comparing the same number of cobalt atoms, the H1-3 type crystal structure The difference in volume between the O3-type crystal structure and the discharged state is more than 3.0%.

[0097] In addition, the H1-3 type crystal structure has continuous CoO2 layers such as P-3m1(O1). The resulting structure is likely to be unstable.

[0098] Therefore, repeated high-voltage charging and discharging causes the crystal structure of lithium cobalt oxide to collapse. The breakdown of the crystal structure causes a deterioration in cycle characteristics. The number of sites where lithium can exist stably decreases, and it becomes difficult to insert and extract lithium. It is thought that this is the case.

[0099] <Positive Electrode Active Material of One Embodiment of the Present Invention> ≪Inside≫ The positive electrode active material 101 of one embodiment of the present invention is a CoO2 layer formed by repeated high-voltage charge and discharge. Furthermore, the change in volume can be reduced. Therefore, the positive electrode active material of one embodiment of the present invention can achieve excellent cycle characteristics. The positive electrode active material of one embodiment of the present invention can have a stable crystal structure in a charged state at a high voltage. Therefore, when the positive electrode active material of one embodiment of the present invention is maintained in a charged state at a high voltage, In some cases, short circuits are less likely to occur. In such cases, safety is improved, so this is preferred. It's nice.

[0100] The positive electrode active material of one embodiment of the present invention has a state in which it is fully discharged and a state in which it is charged at a high voltage. The change in crystal structure and the difference in volume when compared per the same number of transition metal atoms are small. Sai.

[0101] The crystal structure of the positive electrode active material 101 before and after charging and discharging is shown in FIG. and a composite oxide having cobalt as the transition metal M and oxygen. It is preferable to have magnesium as a pure substance. It is preferred that the compound has a halogen.

[0102] The crystal structure at charge depth 0 (discharged state) in Figure 4 is R-3m(O3), the same as in Figure 5. When the positive electrode active material 101 is fully charged, it has a crystal structure different from the H1-3 type. This structure is in the space group R-3m, and is not a spinel-type crystal structure. However, ions such as cobalt and magnesium occupy the oxygen hexacoordinate positions, and the arrangement of cations is It has a symmetry similar to that of the spinel type. Therefore, this structure is referred to as a pseudospinel type crystal in this specification. In the pseudospinel crystal structure shown in Figure 4, the cobalt atoms In order to explain the symmetry of the oxygen atom, the lithium atom is omitted. In reality, there is lithium between the CoO2 layers, for example, 20 atomic % or less relative to cobalt. In addition, in both the O3-type and pseudospinel-type crystal structures, the CoO2 layer It is preferable that magnesium exists in a dilute state between the oxides, that is, at the lithium sites. It is preferable that halogen such as fluorine is present randomly and dilutely at the element sites.

[0103] In addition, the pseudospinel crystal structure is such that light elements such as lithium occupy the oxygen tetracoordination positions. In this case too, the ion arrangement has a symmetry similar to that of the spinel type.

[0104] The pseudospinel crystal structure has random Li between layers, but the CdCl2 crystal structure It can be said that this crystal structure is similar to the CdCl2 type. The structure is that when lithium nickel oxide is charged to a charge depth of 0.94 (Li 0.06 NiO 2) It has a similar crystal structure to pure lithium cobaltate, or a layered rock containing a large amount of cobalt. It is known that salt-type positive electrode active materials do not usually have this crystal structure.

[0105] In the positive electrode active material 101 of one embodiment of the present invention, when a large amount of lithium is released by charging at a high voltage, The change in the crystal structure of the positive electrode active material is suppressed more than that of conventional positive electrode active materials. As shown in Fig. 1, there is almost no misalignment of the CoO2 layers in these crystal structures.

[0106] More specifically, the positive electrode active material 101 of one embodiment of the present invention has a high charge voltage. High structural stability. For example, conventional positive electrode active materials have a potential of, for example, lithium metal. At a voltage of about 4.6 V, the H1-3 crystal structure is obtained. The positive electrode active material 101 can maintain the R-3m(O3) crystal structure even at a voltage of about 4.6 V. There is a region of charging voltage where the charge voltage can be increased further, for example, the potential of lithium metal. Based on this, the pseudospinel crystal structure is maintained even at a voltage of about 4.65V to 4.7V. When the charging voltage is further increased, H1-3 type crystals are finally observed. In addition, when graphite is used as the negative electrode active material in a secondary battery, For example, even when the voltage of the secondary battery is between 4.3V and 4.5V, the crystal structure of R-3m(O3) There is a region of charging voltage where the structure can be maintained, and there is a region where the charging voltage is further increased, for example, The pseudospinel crystal structure is observed even at potentials between 4.35V and 4.55V relative to the metal. There are areas where this structure can be adopted.

[0107] Therefore, the positive electrode active material 101 of one embodiment of the present invention is repeatedly charged and discharged at a high voltage. The crystal structure is also less likely to collapse.

[0108] The pseudospinel crystal structure has the coordinates of cobalt and oxygen in the unit cell as Co( 0,0,0.5), O(0,0,x), and 0.20≦x≦0.25. Cut.

[0109] Impurities, such as mafic acid, exist randomly and dilutely between the CoO2 layers, i.e., at the lithium sites. Magnesium has the effect of suppressing the displacement of the CoO2 layer when charged at high voltage. Therefore, when magnesium exists between the CoO2 layers, it tends to form a pseudospinel type crystal structure. Therefore, magnesium is distributed throughout the particles of the positive electrode active material 101 according to one embodiment of the present invention. In addition, in order to distribute magnesium throughout the particles, it is preferable to use a positive electrode active material according to one embodiment of the present invention. In the manufacturing process of the substance 101, heat treatment is preferably performed.

[0110] However, if the temperature of the heat treatment is too high, cation mixing occurs, resulting in the formation of impurities, e.g. For example, the possibility of magnesium entering the cobalt site increases. Magnesium does not have the effect of maintaining the structure of R-3m during high voltage charging. If the temperature of the process is too high, cobalt will be reduced to divalent and lithium will evaporate. There are also concerns about other adverse effects.

[0111] Therefore, before the heat treatment to distribute magnesium throughout the particles, the cobalt oxide It is preferable to add a halogen compound such as a fluorine compound to the lithium. Adding lithium cobalt oxide causes a decrease in the melting point of the cation. At a temperature where mixing is unlikely to occur, it is easy to distribute magnesium throughout the particles. Furthermore, if a fluorine compound is present, the corrosion resistance against the hydrofluoric acid produced by the decomposition of the electrolyte is improved. It can be expected to improve.

[0112] If the magnesium concentration is increased above a desired value, the effect of stabilizing the crystal structure is small. In addition to the lithium site, magnesium may also occupy the cobalt site. This is thought to be because the magnesium contained in the positive electrode active material of one embodiment of the present invention The number of atoms of M is preferably 0.001 times or more and 0.1 times or less the number of atoms of the transition metal M, and more preferably 0.0 More preferably, it is greater than 1 and less than 0.04, and even more preferably about 0.02. The magnesium concentration shown in is measured by, for example, ICP-MS (Inductively Coupled Plasma Mass Spectroscopy). The positive electrode active material was analyzed using LED Plasma Mass Spectrometry. It may be a value obtained by elemental analysis of the whole particle, or a value obtained by elemental analysis of the raw material in the process of producing the positive electrode active material. The value of the blend may be based on the following formula:

[0113] Lithium cobalt oxide is added with metals other than cobalt (hereinafter referred to as metal Z), such as nickel, aluminum, etc. Adding one or more metals selected from aluminum, manganese, titanium, vanadium and chromium In particular, it is preferable to add one or more of nickel and aluminum. Calcium, titanium, vanadium, and chromium may easily become tetravalent, and structural stability may be improved. The addition of the metal Z may contribute significantly to the qualitative improvement of the positive electrode active material of one embodiment of the present invention. For example, in the case of a material, the crystal structure may become more stable in a charged state at a high voltage. In the positive electrode active material of one embodiment of the present invention, the metal Z increases the crystallinity of the lithium cobalt oxide. It is preferable to add it at a concentration that does not significantly change the amount of the hydroxybenzoate. It is preferable that the amount is such that no effect is exhibited.

[0114] As shown in the legend in Figure 4, transition metals such as nickel and manganese, as well as aluminum The lithium is preferably present at the cobalt site, but some of it is present at the lithium site. It is also preferable that magnesium exists at the lithium site. may be substituted with fluorine.

[0115] As the magnesium concentration of the positive electrode active material of one embodiment of the present invention increases, the capacity of the positive electrode active material decreases. This can be caused by, for example, magnesium entering the lithium site. This may reduce the amount of lithium that contributes to charging and discharging. In some cases, magnesium may produce magnesium compounds that do not contribute to charging and discharging. In one embodiment, the positive electrode active material contains nickel as the metal Z in addition to magnesium. In some cases, the capacity per weight and per volume can be increased. The positive electrode active material of this embodiment contains aluminum as the metal Z in addition to magnesium. This may increase the capacity per weight and per volume. In one embodiment, the positive electrode active material contains nickel and aluminum in addition to magnesium. This may allow for a higher capacity per weight and per volume.

[0116] The concentrations of elements such as magnesium and metal Z contained in the positive electrode active material of one embodiment of the present invention are shown below. , expressed using the number of atoms.

[0117] The number of nickel atoms in the positive electrode active material of one embodiment of the present invention is 7.5% of the number of cobalt atoms. Preferably, the content is 0.05% or more and 4% or less, more preferably, 0.1% or more and 2% or less. The nickel concentration shown here is determined by measuring the nickel concentration in the whole particle of the positive electrode active material using, for example, ICP-MS. The value may be obtained by elemental analysis of the whole, or may be obtained by the blending of raw materials in the process of producing the positive electrode active material. may be based on the value of

[0118] The number of aluminum atoms in the positive electrode active material of one embodiment of the present invention is 0. The Al content is preferably 0.5% or more and 4% or less, and more preferably 0.1% or more and 2% or less. The aluminum concentration can be determined by performing elemental analysis of the entire particle of the positive electrode active material using, for example, ICP-MS. It may be a value determined by the formula or may be based on the value of the blend of raw materials in the process of producing the positive electrode active material. good.

[0119] The positive electrode active material of one embodiment of the present invention preferably contains an element X, and the element X is preferably phosphorus. In addition, the positive electrode active material of one embodiment of the present invention preferably contains a compound containing phosphorus and oxygen. It is more preferable to have

[0120] The positive electrode active material of one embodiment of the present invention contains a compound containing element X, and thus the positive electrode active material can withstand high-voltage charging. When the state is maintained, a short circuit may be less likely to occur.

[0121] When the positive electrode active material according to one embodiment of the present invention contains phosphorus as the element X, the decomposition of the electrolyte The generated hydrogen fluoride may react with phosphorus, reducing the concentration of hydrogen fluoride in the electrolyte. .

[0122] When the electrolyte contains LiPF6, hydrogen fluoride may be generated by hydrolysis. In addition, hydrogen fluoride is produced by the reaction of PVDF, which is used as a component of the positive electrode, with alkali. A decrease in the concentration of hydrogen fluoride in the electrolyte can cause corrosion of the current collector and It may be possible to prevent the coating from peeling off. It also prevents the deterioration of adhesion due to gelation or insolubilization of PVDF. It may be possible to suppress the bottom.

[0123] When the positive electrode active material according to one embodiment of the present invention contains magnesium in addition to the element X, high voltage charging When element X is phosphorus, the number of phosphorus atoms is The number of atoms is preferably 1% or more and 20% or less, more preferably 2% or more and 10% or less, and more preferably 3% or more. It is more preferable that the number of magnesium atoms is 0.8% or less than the number of cobalt atoms. Preferably, the content is 1% or more and 10% or less, more preferably 0.5% or more and 5% or less, and more preferably 0.7% or more and 4% or less. The concentrations of phosphorus and magnesium shown here are, for example, those obtained by ICP-M The value may be a value obtained by performing elemental analysis of the entire particle of the positive electrode active material using S or the like, or may be a value obtained by performing elemental analysis of the positive electrode active material It may be based on the value of the blend of raw materials in the manufacturing process.

[0124] When the positive electrode active material has cracks, phosphorus, more specifically, for example, phosphorus and oxygen, is present inside the cracks. The presence of a compound containing the compound may inhibit the progression of cracks.

[0125] ≪Surface layer part 101a≫ Magnesium is preferably distributed throughout the particles of the positive electrode active material 101 of one embodiment of the present invention. In addition, the magnesium concentration in the surface layer 101a is higher than the average of the whole particle. For example, XPS (X-ray photoelectron spectrometer) The magnesium concentration of the surface layer 101a measured by ICP-MS or the like is It is preferable that the magnesium concentration is higher than the average magnesium concentration of the whole particle measured by the method described above.

[0126] Furthermore, the positive electrode active material 101 according to one embodiment of the present invention may contain an element other than cobalt, such as nickel or aluminum. In the case where the alloy contains one or more metals selected from aluminum, manganese, iron, and chromium, It is preferable that the concentration of the metal in the surface layer 101a is higher than the average concentration of the metal in the entire particle. For example, the concentration of elements other than cobalt in the surface layer 101a measured by XPS or the like is It is preferable that the concentration is higher than the average concentration of the element in the whole particle measured by S or the like.

[0127] The particle surface is essentially a crystal defect, and lithium is released from the surface during charging. As the lithium concentration in the outer layer of the battery increases, it becomes unstable. If the magnesium concentration in the surface layer 101a is high, the crystal structure is easily broken. In this way, the change in the crystal structure can be more effectively suppressed. High ammonium concentration is also expected to improve corrosion resistance against hydrofluoric acid produced by decomposition of the electrolyte. can.

[0128] Furthermore, halogens such as fluorine can also be used in the positive electrode active material 101 according to one embodiment of the present invention. is preferably higher than the average of the entire particle. The presence of halogen in a can effectively improve corrosion resistance to hydrofluoric acid. do.

[0129] As described above, the surface portion 101a of the positive electrode active material 101 according to one embodiment of the present invention is thicker than the inner portion 101b. High concentrations of impurities, such as magnesium and fluorine, and a different composition from the interior It is also preferable that the composition has a stable crystal structure at room temperature. The surface layer 101a may have a different crystal structure from the inner layer 101b. At least a part of the surface layer 101a of the positive electrode active material 101 of this embodiment has a rock salt type crystal structure. In addition, when the surface layer portion 101a and the inner portion 101b have different crystal structures, It is preferable that the crystal orientation of the surface layer portion 101a and the inner portion 101b be roughly the same.

[0130] The fact that the crystal orientations of the surface layer 101a and the interior 101b are roughly the same indicates that the surface layer 101a This means that the positive electrode active material 101 has a stable bond with the inner part 101b. When used in a secondary battery, it effectively suppresses changes in the crystalline structure of the inner 101b that occur during charging and discharging. In addition, even if the lithium is removed from the internal 101b due to charging, the battery remains stable. Cobalt and / or oxygen are transported from the inside 101b through the surface layer 101a having the bond. Furthermore, the area in contact with the electrolyte is chemically stable. Therefore, it is possible to obtain a secondary battery with excellent cycle characteristics. do.

[0131] However, the surface layer 101a is made of only MgO or a structure in which MgO and CoO(II) are solid-solved. Therefore, the surface layer 101a is at least It contains cobalt and also contains lithium in the discharged state, and has a route for lithium insertion and desorption. It is also preferable that the concentration of cobalt is higher than that of magnesium.

[0132] Furthermore, the element X is located in the surface layer portion 101a of the particle of the positive electrode active material 101 according to one embodiment of the present invention. For example, the positive electrode active material 101 of one embodiment of the present invention is preferably covered with a film containing element X. It may also be used.

[0133] ≪Grain boundary≫ Impurities contained in the positive electrode active material 101 of one embodiment of the present invention are present randomly and in a small amount. However, it is more preferable that a portion of the grains segregate at the grain boundaries.

[0134] In other words, the impurity concentration at and near the grain boundaries of the positive electrode active material 101 according to one embodiment of the present invention It is also preferable that the temperature is higher than other regions inside.

[0135] Like the particle surface, the grain boundary is also a planar defect. Therefore, it is prone to instability and changes in the crystal structure. Therefore, if the magnesium concentration at and near the grain boundary is high, This makes it possible to more effectively suppress changes in the crystal structure.

[0136] Furthermore, when the impurity concentration at and near the grain boundary is high, the positive electrode active material 1 according to one embodiment of the present invention Even if a crack occurs along the grain boundary of the 01 particle, the surface crack Therefore, even after cracks occur, the impurity concentration increases in the vicinity of the cracks. Corrosion resistance to acids can be improved.

[0137] In this specification, the vicinity of the grain boundary refers to the region up to about 10 nm from the grain boundary. It shall be so decided.

[0138] ≪Particle size≫ If the particle size of the positive electrode active material 101 according to one embodiment of the present invention is too large, it becomes difficult for lithium to diffuse. However, when the active material layer is applied to the current collector, the surface of the active material layer becomes too rough. If it is too thin, it will be difficult to support the active material layer when it is applied to the current collector, and excessive reaction with the electrolyte may occur. Therefore, the average particle size (D50: also called the median diameter) The thickness is preferably 1 μm or more and 100 μm or less, and more preferably 2 μm or more and 40 μm or less. The thickness is preferably 5 μm or more and more preferably 30 μm or less.

[0139] <Analysis method> In one embodiment of the present invention, a positive electrode active material exhibits a pseudospinel crystal structure when charged at a high voltage. Whether or not the positive electrode active material 101 is the same as the positive electrode active material 101 can be determined by subjecting the positive electrode charged at a high voltage to XRD, electron beam diffraction, etc. , neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. In particular, XRD can be used to determine the symmetry of transition metals such as cobalt contained in the positive electrode active material. High-resolution analysis, comparison of crystallinity and crystal orientation, lattice periodic distortion The positive electrode obtained by disassembling the secondary battery can be measured as it is. This is preferable in that sufficient accuracy can be obtained even when the measurement is performed in a short time.

[0140] As described above, the positive electrode active material 101 of one embodiment of the present invention has a high voltage charging state and a high voltage discharging state. It is characterized by the fact that there is little change in the crystal structure between the charged and discharged states. Materials with a crystal structure that exhibits large changes in state and voltage, accounting for 50 wt% or more, can withstand high-voltage charging and discharging. Furthermore, the desired crystal structure cannot be achieved by simply adding impurity elements. It should be noted that there are cases where the cobalt-containing magnesium and fluorine Although they share the common feature of being lithium nitrate, they form pseudospinel crystals when charged at high voltage. When the structure is 60 wt% or more, and when the H1-3 type crystal structure is 50 wt% or more At a certain voltage, the pseudo-spinel crystal structure becomes almost 100 wt%. If the voltage is further increased, an H1-3 type crystal structure may occur. In order to determine whether the positive electrode active material 101 of one embodiment of the present invention is a material, a method such as XRD can be used. Analysis of the crystal structure is needed.

[0141] However, when the positive electrode active material is in a charged or discharged state at a high voltage, its crystalline structure changes when it comes into contact with the air. For example, a pseudo-spinel crystal structure may change to an H1-3 crystal structure. Therefore, all samples should be handled in an inert atmosphere such as argon. It is preferable to dry the mixture.

[0142] ≪Charging method≫ A high-temperature method for determining whether a certain composite oxide is the positive electrode active material 101 of one embodiment of the present invention Voltage charging is performed using a coin cell (CR2032 type, diameter 20mm, height 2000V) with a lithium counter electrode. 3.2mm) can be created and charged.

[0143] More specifically, the positive electrode is formed by mixing a positive electrode active material, a conductive additive, and a binder in a slurry. Alternatively, a positive electrode current collector made of aluminum foil may be coated with the conductive material.

[0144] The counter electrode can be made of lithium metal. However, if a material other than lithium metal is used for the counter electrode, When the secondary battery is turned on, the potential of the secondary battery and the potential of the positive electrode are different. Unless otherwise specified, the potential is that of the positive electrode.

[0145] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. can be used.

[0146] The separator can be made of polypropylene with a thickness of 25 μm.

[0147] The positive and negative electrode cans can be made of stainless steel (SUS). do.

[0148] The coin cell prepared under the above conditions was charged at a constant current of 4.6 V and 0.5 C, and then the current value Charge at a constant voltage until the temperature reaches 0.01C. Here, 1C is 137mA / g. Temperature After charging in this way, place the coin cell in a globe with an argon atmosphere. By disassembling it in the box and taking out the positive electrode, you can obtain the positive electrode active material charged at high voltage. When various analyses are carried out after the test, the container is sealed in an argon atmosphere to prevent reactions with external components. For example, XRD can be performed in a sealed container under an argon atmosphere. Cut.

[0149] <XRD> CuKα1 radiation calculated from the pseudospinel crystal structure and H1-3 crystal structure model The ideal powder XRD pattern of LiCo at a charge depth of 0 is shown in Figure 6. Ideal XR calculated from the crystal structure of O2 (O3) and CoO2 (O1) at charge depth 1 The patterns of LiCoO2(O3) and CoO2(O1) are also shown. Materials Structure Reflex Powder Di, one of the modules of dio (BIOVIA) The 2θ range was from 15° to 75°, and the Step size=0.01, wavelength λ1=1.540562×10 -10 m, λ2 is not set, M The monochromator was single. The pattern of the H1-3 type crystal structure is non-specific. It was similarly created from the crystal structure information described in Patent Document 3. Pseudospinel crystal structure pattern estimated the crystal structure from the XRD pattern of the positive electrode active material of one embodiment of the present invention, and er.3 (crystal structure analysis software manufactured by Bruker) was used for fitting. The XRD pattern was generated in the same manner.

[0150] As shown in Figure 6, in the pseudospinel crystal structure, 2θ = 19.30 ± 0.20° (19 .10° or more and 19.50° or less), and 2θ = 45.55 ± 0.10° (45.45° More specifically, a diffraction peak appears at 2θ=19.3° or less. 0±0.10° (19.20° or more and 19.40° or less), and 2θ=45.55±0. A sharp diffraction peak appears at 0.5° (between 45.50° and 45.60°). No peaks appear at these positions in the -3 type crystal structure and CoO2 (P-3m1, O1). Therefore, when charged at high voltage, 2θ = 19.30 ± 0.20°, and 2θ The appearance of the peak at 45.55±0.10° indicates that the positive electrode active material 10 according to one embodiment of the present invention This can be said to be a characteristic of 1.

[0151] This is the crystal structure at a charge depth of 0 and the crystal structure when charged at a high voltage. More specifically, the positions of the main diffraction peaks of both are close to each other. The difference in the positions at which the peaks appear in two or more of these, more preferably three or more, is 2θ= It can be said that 2θ is 0.7 or less, and more preferably 2θ=0.5 or less.

[0152] Note that the positive electrode active material 101 of one embodiment of the present invention has a pseudospinel crystal structure when charged at a high voltage. However, not all of the particles need to have a pseudospinel crystal structure. However, the XRD pattern may be When a rhottveld analysis was performed, it was found that the pseudo-spinel crystal structure was preferably 50 wt% or more. It is preferable that the content is 60 wt% or more, and more preferable that the content is 66 wt% or more. It is preferable that the pseudo-spinel type crystal structure is 50 wt% or more, more preferably 60 wt% or more. More preferably, if it is 66 wt % or more, it will be a positive electrode active material with sufficiently excellent cycle characteristics. It is possible.

[0153] In addition, even after more than 100 charge / discharge cycles from the start of measurements, Rietveld analysis showed that The pseudo-spinel crystal structure is preferably 35 wt% or more, and more preferably 40 wt% or more. It is more preferable that the content is 43 wt % or more, and further more preferable that the content is 43 wt % or more.

[0154] The crystallite size of the pseudospinel crystal structure of the positive electrode active material particles varies depending on the discharge state. The charge / discharge current is reduced to only about 1 / 10 of that of LiCoO2(O3). Even under the same XRD measurement conditions, a clear peak of pseudospinel crystal structure was observed after high voltage charging. On the other hand, in simple LiCoO2, some of the crystals have a structure similar to a pseudo-spinel type. Even if the structure can be achieved, the crystallite size will be small and the peak will be broad and small. The crystallite size can be determined from the half-width of the XRD peak.

[0155] As described above, the positive electrode active material according to one embodiment of the present invention is less affected by the Jahn-Teller effect. The positive electrode active material of one embodiment of the present invention has a layered rock salt type crystal structure and a transition The positive electrode active material according to one embodiment of the present invention preferably contains cobalt as a main metal. In terms of quality, in the range where the influence of the Jahn-Teller effect is small, other than cobalt, as mentioned above, It may have a solid metal Z.

[0156] In the positive electrode active material, it was estimated using XRD analysis that the influence of the Jahn-Teller effect is small. We consider the range of lattice constants that can be obtained.

[0157] FIG. 7 shows a positive electrode active material according to one embodiment of the present invention having a layered rock salt crystal structure and containing cobalt and nickel. The lattice constants of the a-axis and c-axis were estimated using XRD in the case of Figure 7(A) shows the results for the a-axis, and Figure 7(B) shows the results for the c-axis. The XRD pattern is of the powder after synthesis of the positive electrode active material, before it is incorporated into the positive electrode. The nickel concentration on the horizontal axis is calculated as the sum of the number of cobalt and nickel atoms, which is 100%. The positive electrode active material includes a lithium source, a cobalt source, a nickel source, and The ingredients were mixed and then heated to prepare the product.

[0158] FIG. 8 shows a positive electrode active material according to one embodiment of the present invention having a layered rock salt crystal structure and containing cobalt and manganese. The lattice constants of the a-axis and c-axis were estimated using XRD in the case of a gun. Figure 8(A) shows the results for the a-axis, and Figure 8(B) shows the results for the c-axis. The XRD pattern shown is of the powder after the synthesis of the positive electrode active material, and before it is incorporated into the positive electrode. The manganese concentration on the horizontal axis is calculated as the sum of the number of cobalt and manganese atoms, which is 100%. The positive electrode active material is a lithium source, a cobalt source, a manganese source, and , and then heated to prepare the composition.

[0159] FIG. 7(C) shows the lattice constants of the positive electrode active materials shown in FIG. 7(A) and FIG. 7(B). The lattice constant of the a-axis divided by the lattice constant of the c-axis (a-axis / c-axis) is shown in Figure 8(C). For the positive electrode active material whose lattice constant results are shown in Figures 8(A) and (B), the lattice constant of the a-axis The value obtained by dividing the constant by the lattice constant of the c-axis (a-axis / c-axis) is shown.

[0160] From Figure 7(C), there is a tendency for the a-axis / c-axis to change significantly when the nickel concentration is 5% or 7.5%. This is thought to be due to the large distortion of the a-axis. When the nickel concentration is less than 7.5%, the Jahn-Teller strain is small. This suggests that an excellent positive electrode active material can be obtained.

[0161] Next, from Figure 8(A), it can be seen that when the manganese concentration is 5% or more, the behavior of the change in lattice constant is different. This suggests that the manganese concentration does not follow Vegard's law. Therefore, the manganese concentration is preferably, for example, 4% or less. stomach.

[0162] The above-mentioned ranges of nickel concentration and manganese concentration are as follows: That is, the surface layer 101a of the particle has a concentration higher than the above. There are cases where it is okay to be higher.

[0163] From the above, a preferable range of the lattice constant was considered, and it was found that the positive electrode In the active material, the state without charging or discharging, which can be estimated from the XRD pattern, In the layered rock salt crystal structure of the positive electrode active material particles in this state, the lattice constant of the a-axis is 2. 814×10 -10 m, 2.817×10 -10 Smaller than m and c-axis lattice The constant is 14.05 x 10 -10 m, 14.07 × 10 -10 It is smaller than m The state in which no charge and discharge is performed is, for example, when preparing a positive electrode for a secondary battery. It may be in the form of a powder.

[0164] Alternatively, the layered structure of the particles of the positive electrode active material in a state where no charge / discharge is performed or in a discharged state may be In the salt-type crystal structure, the lattice constant of the a-axis divided by the lattice constant of the c-axis (a-axis / c-axis) is It is preferably greater than 0.20000 and less than 0.20049.

[0165] Alternatively, the layered structure of the particles of the positive electrode active material in a state where no charge / discharge is performed or in a discharged state may be In the salt-type crystalline structure, when XRD analysis was performed, 2θ was 18.50° or more and 19.30° The first peak is observed below 38.00° and the second peak is observed at 2θ between 38.00° and 38.80°. Peaks may be observed.

[0166] The peaks appearing in the powder XRD pattern represent the peaks that occupy most of the volume of the positive electrode active material 101. This reflects the crystal structure of the inner portion 101b of the positive electrode active material 101. The crystal structure of the inset portion 102 or the protrusion 103 is determined by electron diffraction of a cross section of the positive electrode active material 101. etc. can be analyzed.

[0167] XPS X-ray photoelectron spectroscopy (XPS) measures the surface to a depth of approximately 2 to 8 nm (usually approximately 5 nm). Since it is possible to analyze the area in the depth direction of about half of the surface layer 101a, The concentration of each element can be quantitatively analyzed. The quantitative accuracy of XPS is usually about ±1 atomic percent. The detection limit is approximately 1 atomic %, depending on the element.

[0168] When the positive electrode active material 101 according to one embodiment of the present invention was analyzed by XPS, the number of atoms of the impurities was The number of atoms of the transition metal M is preferably 1.6 times or more and 6.0 times or less, and more preferably 1.8 times or more and less than 4.0 times. It is more preferable that the impurity is magnesium and the transition metal M is cobalt. The number of atoms of ruthenium is preferably 1.6 to 6.0 times the number of atoms of cobalt, and more preferably 1.8 to 4.0 times the number of atoms of cobalt. The number of atoms of halogen such as fluorine is preferably less than 0.0 times the number of atoms of the transition metal M. The ratio is preferably 0.2 times or more and 6.0 times or less, and more preferably 1.2 times or more and 4.0 times or less.

[0169] For example, monochromated aluminum can be used as the X-ray source when performing XPS analysis. The take-off angle may be set to, for example, 45°.

[0170] In addition, when the positive electrode active material 101 of one embodiment of the present invention was analyzed by XPS, fluorine and other elements were The peak showing the bond energy of the element is preferably 682 eV or more and less than 685 eV. It is more preferable that the bond energy of lithium fluoride is about 684.3 eV. 685 eV, the binding energy of magnesium fluoride, and 686 eV In other words, the positive electrode active material 101 of one embodiment of the present invention contains fluorine. If present, it is preferably a bond other than lithium fluoride and magnesium fluoride.

[0171] Furthermore, when the positive electrode active material 101 of one embodiment of the present invention was analyzed by XPS, magnesium The peak showing the binding energy of other elements is between 1302 eV and 1304 eV. It is preferable that the energy is about 1303 eV, and more preferable that the energy is about 1303 eV. The bond energy of magnesium oxide is 1305 eV, which is different from the bond energy of sodium. In other words, the positive electrode active material 101 of one embodiment of the present invention is magnesium. When the bond has the formula (I), it is preferably a bond other than magnesium fluoride.

[0172] Impurities that are preferably present in large amounts in the surface layer portion 101a, such as magnesium and aluminum, The concentration of aluminum measured by XPS etc. is or preferably higher than the concentration measured by GD-MS (glow discharge mass spectrometry) or the like. I wish.

[0173] Magnesium and aluminum were processed to expose their cross sections, and the cross sections were analyzed by TEM-E. When analyzing using DX, the concentration of the surface layer 101a is higher than the concentration of the inside 101b. It is preferable that the processing is carried out by, for example, FIB (Focused Ion Beam). It is possible to do so.

[0174] In XPS (X-ray photoelectron spectroscopy) analysis, the number of magnesium atoms is The preferable range is 0.4 to 1.5 times. The ratio of the number of sodium atoms, Mg / Co, is preferably 0.001 or more and 0.06 or less.

[0175] On the other hand, nickel contained in the transition metal M is not unevenly distributed in the surface layer portion 101a, but is distributed throughout the positive electrode active material 101. However, it is preferable that the metal impurity high concentration region 103b is not present. This does not apply if:

[0176] <Surface roughness and specific surface area> For example, the surface smoothness of the positive electrode active material 101 was quantified from a cross-sectional SEM image as shown below. It is possible.

[0177] First, the positive electrode active material 101 is processed by FIB or the like to expose a cross section. It is preferable to cover the positive electrode active material 101 with a protective agent or the like. Take an SEM image of the interface. Then, use image processing software to remove noise from the SEM image. For example, After applying Gaussian blur (σ=2), the image is binarized. Then, the interface is extracted using image processing software. Furthermore, an automatic selection tool or the like is used to select the interface line between the protective film or the like and the positive electrode active material 101, Extract the data into a spreadsheet or similar software. Use the functions of the spreadsheet or similar software to create a regression curve (quadratic curve). After correction, the parameters for calculating roughness are obtained from the data after the slope correction. The root mean square surface roughness (RMS) was calculated. The material has a surface roughness of at least 400 nm around the particle periphery.

[0178] The particle surfaces of the positive electrode active material 101 of this embodiment have a roughness (R MS: root mean square surface roughness) is less than 3 nm, preferably less than 1 nm, more preferably Preferably, the root mean square surface roughness (RMS) is less than 0.5 nm.

[0179] There is no particular limitation on the image processing software used for noise processing, boundary extraction, etc. For example, "ImageJ" can be used. There are no particular restrictions on spreadsheet software. However, for example, Microsoft Office Excel can be used. do.

[0180] For example, the actual specific surface area A measured by the gas adsorption method using the constant volume method R and the ideal ratio surface area A i The surface smoothness of the positive electrode active material 101 can also be quantified from the ratio of do.

[0181] Ideal specific surface area Ai is that all particles have the same diameter as D50 and have the same weight. The shape is calculated assuming an ideal sphere.

[0182] The median diameter D50 should be measured using a particle size distribution analyzer that uses the laser diffraction and scattering method. The specific surface area can be measured using a specific surface area measuring device that uses the gas adsorption method based on the constant volume method. Therefore, it can be measured.

[0183] The positive electrode active material 101 according to one embodiment of the present invention has an ideal specific surface area calculated from the median diameter D50. A i and the actual specific surface area A R Ratio A R / A i is preferably 2 or less.

[0184] This embodiment can be used in combination with other embodiments.

[0185] (Embodiment 2) An example of a method for manufacturing a positive electrode active material of one embodiment of the present invention will be described with reference to FIGS. 9 and 10. In this embodiment, the transition metal M is cobalt and nickel, and the impurities are nickel. Preparation of the cathode active material 101 shown in FIG. 1 having magnesium, aluminum, and fluorine. An example method will now be described.

[0186] <Step S11> First, as materials for the mixture 902, a halogen source such as a fluorine source or a chlorine source and a magnesium source Prepare the following.

[0187] Fluorine sources include, for example, lithium fluoride (LiF) and magnesium fluoride (MgF2). , aluminum fluoride (AlF3), titanium fluoride (TiF4), cobalt fluoride (Co F2, CoF3), Nickel Fluoride (NiF2), Zirconium Fluoride (ZrF4), Vanadium fluoride (VF5), manganese fluoride, iron fluoride, chromium fluoride, niobium fluoride, Zinc fluoride (ZnF2), calcium fluoride (CaF2), sodium fluoride (NaF) , potassium fluoride (KF), barium fluoride (BaF2), cerium fluoride (CeF2) , lanthanum fluoride (LaF3), sodium aluminum hexafluoride (Na3AlF6), etc. The fluorine source is not limited to solids, and may be, for example, fluorine (F2), Carbon fluoride, sulfur fluoride, oxygen fluoride (OF2, O2F2, O3F2, O4F2, O2F), etc. In the heating step described later, a plurality of fluorine sources may be mixed in the atmosphere. Among them, lithium fluoride has a relatively low melting point of 848°C, and as will be described later, This is preferable because it is easily melted in the annealing step.

[0188] As the chlorine source, for example, lithium chloride, magnesium chloride, etc. can be used.

[0189] Examples of magnesium sources include magnesium fluoride, magnesium oxide, and magnesium hydroxide. Sodium carbonate, magnesium carbonate, etc. can be used.

[0190] As the lithium source, for example, lithium fluoride or lithium carbonate can be used. Therefore, lithium fluoride can be used as both a lithium source and a fluorine source. Magnesium fluoride can be used as both a fluorine source and a magnesium source.

[0191] In this embodiment, lithium fluoride (LiF) is prepared as a fluorine source and a lithium source. Magnesium fluoride (MgF2) is prepared as a fluorine source and magnesium source. Step S11 in Figure 9).

[0192] Lithium fluoride (LiF) and magnesium fluoride (MgF2) have a ratio of LiF:MgF2=65:35 When mixed at a molar ratio of about 100,000 to 100,000, the effect of lowering the melting point is maximized (Non-Patent Document 4). If the amount of lithium fluoride is too high, there is a concern that the lithium content will be too excessive and the cycle characteristics will deteriorate. Therefore, the molar ratio of lithium fluoride LiF to magnesium fluoride MgF2 is Li It is preferable that F:MgF2=x:1 (0≦x≦1.9), and LiF:MgF2=x :1 (0.1≦x≦0.5) is more preferable, and LiF:MgF2=x:1 (x=0.33 (nearby) is more preferred.

[0193] If the subsequent mixing and grinding steps are to be carried out wet, a solvent is prepared. ketones such as ethanol and isopropanol, alcohols such as ethanol and isopropanol, ethers, dioxanes, acetone, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc. can be used. It is more preferable to use an aprotic solvent that is less likely to react with lithium. In this embodiment, acetone is used (see step S11 in FIG. 9).

[0194] <Step S12> Next, the materials of the mixture 902 are mixed and crushed (step S12 in FIG. 9). The process can be carried out by either a dry method or a wet method, but the wet method is preferred because it allows for finer pulverization. For mixing, a ball mill, a bead mill, etc. can be used. When using zirconia balls as media, it is preferable to use zirconia balls as media. It is preferable to carry out the blending and grinding steps sufficiently to pulverize the mixture 902 into fine powder.

[0195] The mixing means is preferably a blender, a mixer, or a ball mill.

[0196] <Steps S13 and S14> The mixed and crushed materials are collected (step S13 in FIG. 9) to obtain a mixture 902 (FIG. 9 step S14).

[0197] The mixture 902 preferably has a D50 of 600 nm or more and 20 μm or less, for example. It is more preferable that the particle size is 10 μm or more and 10 μm or less. If so, when mixed with a composite oxide containing lithium, a transition metal, and oxygen in a later step, This makes it easy to uniformly attach the mixture 902 to the surface of the composite oxide particles. If the mixture 902 is uniformly attached to the surface, it will not leak into the surface layer of the composite oxide particles after heating. It is preferable because it is easy to distribute halogen and magnesium in the surface layer. If there is a region that does not contain magnesium, the pseudospinel crystal structure described above will be formed in the charged state. It may be difficult to construct.

[0198] <Steps S15, S16, and S17> In addition, finely powdered nickel hydroxide (Ni(OH)2) is added for mixing in step S31. The finely powdered nickel hydroxide is prepared by mixing nickel hydroxide with acetone in advance. Step S15 and step S16 are performed to collect the powder. Nickel hydroxide is obtained (step S17).

[0199] <Steps S18, S19, and S20> Also, finely powdered aluminum hydroxide (Al(OH)3 ) to prepare the finely powdered aluminum hydroxide. Step S18 of mixing and step S19 of collecting are carried out. As a result, finely powdered aluminum hydroxide is obtained (step S20).

[0200] In this embodiment, nickel and aluminum are used in steps S15 to S20. However, one embodiment of the present invention is not limited to this. Other impurity elements, including titanium, may be mixed. It is preferable to pulverize and mix the titanium as in steps S15 to S17. As the source, titanium hydroxide, titanium oxide, etc. can be used.

[0201] <Step S25> Also, a lithium source is prepared for mixing in step S31. A composite oxide containing lithium, a transition metal, and oxygen that has been synthesized in advance is used.

[0202] When a composite oxide containing lithium, a transition metal, and oxygen that has been synthesized in advance is used, It is preferable to use a material with few impurities. and a composite oxide containing oxygen, and a positive electrode active material whose main components are lithium, cobalt, and nickel. Nickel, manganese, aluminum and oxygen, and elements other than the above main components are impurities For example, when analyzed by glow discharge mass spectrometry, the total impurity concentration was 10,000ppm. It is preferably m wt or less, and more preferably 5000 ppm wt or less. The total impurity concentration of transition metals such as titanium and arsenic is 3000 ppm wt or less It is preferable that the content of the hydroxybenzoates is 1500 ppm by weight or less, and more preferable that the content of the hydroxybenzoates is 1500 ppm by weight or less.

[0203] For example, pre-synthesized lithium cobalt oxide (LiCoO2) is available from the Japan Chemical Industry Co., Ltd. Lithium cobalt oxide particles (product name: Cellseed C-10N) manufactured by Cellseed Corporation were used. This has an average particle size (D50) of about 12 μm and can be analyzed by glow discharge mass spectrometry (G In the impurity analysis by D-MS, the magnesium concentration and fluorine concentration were 50 ppm. wt or less, calcium concentration, aluminum concentration and silicon concentration are 100 ppm w t or less, nickel concentration is 150 ppm wt or less, sulfur concentration is 500 ppm wt or less, Arsenic concentration is 1100 ppm wt or less, and other elements other than lithium, cobalt and oxygen The lithium cobalt oxide has an element concentration of 150 ppm wt or less.

[0204] The composite oxide having lithium, a transition metal, and oxygen in step S25 is formed by removing defects and strain. It is preferable that the layered rock salt type crystal structure has few impurities. It is preferable that the oxide is an impurity-containing composite oxide having lithium, a transition metal, and oxygen. If there are many of these, the crystal structure is likely to be defective or distorted.

[0205] <Step S31> Next, the mixture 902 and a composite oxide having lithium, a transition metal, and oxygen are mixed and finely pulverized. The aluminum hydroxide and the finely powdered nickel hydroxide are mixed (step S31 in FIG. 9). ) The number of transition metal atoms in a composite oxide containing lithium, transition metal, and oxygen, M, and the mixed The ratio of the number of magnesium atoms Mg contained in the substance 902 is M:Mg=100:y(0.1≦ It is preferable that M:Mg=100:y (0.3≦y≦3). More preferable.

[0206] The mixing in step S31 is performed more slowly than the mixing in step S12 in order to prevent the composite oxide particles from being destroyed. For example, it is preferable to set the rotation speed to be milder than that of the mixing in step S12. It is preferable to use conditions with less heat or shorter time. For example, a ball mill, a bead mill, etc. can be used for mixing. When using a ball mill, for example, zirconia balls can be used as the media. preferable.

[0207] The mixed materials are collected (step S32 in FIG. 9) to obtain a mixture 903 (step S32 in FIG. 9). Step S33).

[0208] Next, the mixture 903 is heated (step S34 in FIG. 9). This is sometimes called ``nari''.

[0209] The annealing is preferably carried out at a suitable temperature and time. Particle size and structure of composite oxides containing lithium, transition metals, and oxygen in Step S25 It depends on the composition and other conditions. Small particles require lower temperatures or shorter times than large particles. A shorter time may be more preferable.

[0210] For example, if the average particle diameter (D50) of the particles in step S25 is about 12 μm, the annealing temperature The annealing temperature is preferably, for example, 700° C. or higher and 950° C. or lower. The annealing time is preferably, for example, 3 hours or longer. Preferably, 10 hours or more is more preferable, and 60 hours or more is even more preferable.

[0211] The temperature drop time after annealing is preferably, for example, 10 hours or more and 50 hours or less.

[0212] When the mixture 903 is annealed, the material with a low melting point (e.g., fluoride) in the mixture 903 is first melted. It is thought that lithium (melting point: 848°C) melts and is distributed in the surface layer of the composite oxide particles. The presence of this molten material then lowers the melting point of other materials, causing them to melt. For example, magnesium fluoride (melting point 1263°C) melts and turns into composite oxide particles. It is thought to be distributed on the surface of the egg.

[0213] The diffusion of the elements contained in the mixture 903 is more pronounced in the surface and grains than in the interior of the composite oxide particles. Therefore, magnesium and halogens are more rapidly dissolved in the surface layer and near the grain boundaries. As will be described later, the magnesium concentration in the surface layer and near the grain boundaries is When the temperature is high, the change in the crystal structure can be more effectively suppressed.

[0214] The annealed material is collected (step S35 in FIG. 9). By the above steps, the positive electrode active material 101 of one embodiment of the present invention can be produced. This can be done (step S36 in FIG. 9).

[0215] Next, another example of a method for manufacturing a positive electrode active material of one embodiment of the present invention will be described with reference to FIGS. Figure 10 is the same as Figure 9 except for some differences, so the same parts are omitted for simplicity. This will be omitted.

[0216] <Steps S11 to S20> In steps S11 to S20, each element source is prepared. For example, prepare thium, magnesium fluoride, nickel hydroxide, and aluminum hydroxide. However, one embodiment of the present invention is not limited to this. It is sufficient to use at least one of them. For example, it may be lithium fluoride only.

[0217] <Step S26> Next, in step S26, a composite oxide is prepared. At this stage, a composite oxide containing some impurities may be used. By using a composite oxide containing titanium, the types of impurities mixed in the subsequent process can be reduced. This is preferable.

[0218] <Steps S31 to S36> Then, in steps S31 to S36, each element source and the composite oxide are mixed. The mixture 903 is then annealed. Through the above steps, the positive electrode active material 101 can be produced. do.

[0219] (Embodiment 3) Another example of a method for manufacturing a positive electrode active material of one embodiment of the present invention will be described with reference to FIGS. This embodiment is the same as the second embodiment except for some differences, so the same parts will be simplified. Therefore, it will be omitted.

[0220] <Steps S11 to S36> As in the second embodiment, various impurity elements and composites containing lithium, transition metals, and oxygen are used. The oxide is mixed and annealed to obtain a mixture 904 (step S36).

[0221] <Steps S42, S43, and S44> Next, steps S42 to S44 are carried out to obtain the positive electrode active material of one embodiment of the present invention. The metal Z is added as one of the impurities. Liquid phase methods such as gel method, solid phase method, sputtering method, evaporation method, CVD (chemical vapor deposition) Methods such as a laser deposition (LD) method and a pulsed laser deposition (PLD) method can be applied.

[0222] As shown in Fig. 11, first, in step S42, a metal source is prepared. , metal alkoxides, metal hydroxides, metal oxides, etc. can be used. When the gel method is applied, a solvent for the sol-gel method is prepared. Alcohol is preferred, and in particular, the same alcohol as the alkoxyl group of the alkoxide used as the additive source is used. The water content of the solvent is preferably 3% by volume or less, and more preferably 0.3% by volume or less. It is more preferable that the solvent is alcohol, which is more effective than the solvent in the case of using water. This can suppress the deterioration of LiCoO2 during the manufacturing process. In this case, for example, the number of cobalt atoms in the lithium cobalt oxide is 1, and the number of cobalt atoms in the metal source is 1. The number of aluminum atoms in the metal Z should be 0.001 times or more and 0.02 times or less. In the case of lithium cobalt oxide, for example, the number of cobalt atoms in lithium cobalt oxide is 1, and the number of cobalt atoms in the metal source is 1. The number of titanium atoms in the alloy should be between 0.001 and 0.02 times. In the case of lithium and titanium, for example, the number of cobalt atoms in lithium cobalt oxide is 1. The number of aluminum atoms in the metal source is 0.001 times or more and 0.02 times or less, and The number of titanium atoms contained in the metal source may be 0.001 times or more and 0.02 times or less.

[0223] As an example, the sol-gel method is applied, and titanium (IV) tetraisopropanol is used as the metal source. An example is shown in which 2-propanol is used as a solvent (step 11 in Figure 11). Top S42).

[0224] Next, the titanium alkoxide was dissolved in 2-propanol, and then lithium cobaltate was added. The rubber particles are mixed (step S43 in FIG. 11).

[0225] The amount of metal alkoxide required varies depending on the particle size of lithium cobalt oxide. When lithium cobalt oxide is used, the particle size (D50) is about 20 μm. If so, the number of cobalt atoms in lithium cobalt oxide is 1, and titanium isopropoxide It is preferable to add titanium so that the number of titanium atoms contained in the oxide is 0.001 times or more and 0.02 times or less. I wish.

[0226] Next, a mixture of an alcohol solution of metal alkoxide and lithium cobalt oxide particles is heated in a steam bath. The mixture is stirred in a gas-containing atmosphere. Stirring can be performed, for example, with a magnetic stirrer. The stirring time is determined based on the time at which the water in the atmosphere and the metal alkoxide undergo hydrolysis and polycondensation reactions. Any time sufficient for this is sufficient, for example, 4 hours, 25°C, 90% RH (relative humidity). Humidity (relative humidity) conditions. In an atmosphere where the temperature is not controlled, such as in a draft chamber, In such a case, it is preferable to carry out the stirring for a longer period of time, e.g. For example, it may be left at room temperature for 12 hours or more.

[0227] By gradually taking in water vapor from the atmosphere and gradually evaporating the alcohol, the water and metal alcohol The alkoxide reacts, allowing the sol-gel reaction to proceed gently. By reacting the oxide with water, for example, by heating at a temperature above the boiling point of the solvent alcohol, The sol-gel reaction can proceed more gently than when the first step is carried out.

[0228] You can also add water actively. If you want to react gently, add alcohol diluted The reaction time can be controlled by gradually adding water or a stabilizer. By promoting the reaction, a coating layer of uniform thickness and good quality can be formed.

[0229] After the above treatment, the precipitate is collected from the mixed solution (step S44 in FIG. 11). The method of filtration, centrifugation, evaporation to dryness, etc. can be applied. It can be washed with the same alcohol as the solvent used to dissolve the oxide. When using a solvent, separation of the solvent and the precipitate is not necessary in this step. For example, the precipitate may be collected in the drying step of the next step (step S44).

[0230] Next, the collected residue is dried to obtain a mixture 904 (Step S44 in FIG. 11). The drying process may be, for example, vacuum or forced air drying at 80° C. for 1 hour to 4 hours.

[0231] <Step S45> Next, the resulting mixture is heated (step S45 in FIG. 11).

[0232] The heating time is preferably 1 hour or more and 80 hours or less within the heating temperature range. In terms of productivity, a time period of 1 hour or more and 20 hours or less is more preferable.

[0233] The heating temperature is preferably less than 1000°C, more preferably 700°C or higher and 950°C or lower. A temperature of about 850°C is more preferable.

[0234] The heating is preferably carried out in an atmosphere containing oxygen.

[0235] In this embodiment, the heating temperature is set to 850°C and held for 2 hours, and the temperature is increased by 200°C. / h, and the oxygen flow rate is 10 L / min.

[0236] The heating temperature in step S45 may be lower than the heating temperature in step S34. preferable.

[0237] <Steps S46 and S47> Next, the cooled particles are collected (step S46 in FIG. 11). By the above steps, the positive electrode active material 101 of one embodiment of the present invention can be produced. This can be done (step S47 in FIG. 11).

[0238] This embodiment can be used in combination with other embodiments.

[0239] (Fourth embodiment) In this embodiment, another example of a method for manufacturing a positive electrode active material of one embodiment of the present invention will be described. This embodiment is the same as the second and third embodiments except for some differences. , the same parts will be omitted for simplicity.

[0240] In the previous embodiment, the impurity element is mixed in step S31 or step S43. However, one embodiment of the present invention is not limited to this. The timing and method of addition will be explained.

[0241] <Step S01> In step S01 of FIG. 12, a composite oxide having lithium, a transition metal M, and oxygen is first formed. As materials for the compound (LiMO2), a lithium source and a transition metal M source are prepared. That is, the first impurity element source may be prepared as one of the raw materials when firing the composite oxide. .

[0242] The first impurity element is magnesium, fluorine, aluminum, titanium, zirconium, Aluminum, vanadium, iron, chromium, niobium, cobalt, arsenic, zinc, silicon, sulfur, phosphorus, phosphate At least one of these acids and iodine can be used as the first impurity element source. Examples of usable compounds include oxides, hydroxides, fluorides, etc.

[0243] As the lithium source, for example, lithium carbonate, lithium fluoride, etc. can be used.

[0244] The transition metal M is a layered rocksalt complex oxide that belongs to the space group R-3m together with lithium. It is preferable to use a metal that can form a crystalline silicon film. For example, manganese, cobalt, and nickel are preferably used. At least one of them can be used. In other words, even if only cobalt is used as the transition metal M source, Alternatively, nickel alone may be used, or two types of cobalt and manganese may be used, or cobalt and manganese may be used. Two types of metals, cobalt and nickel, may be used, or three types of metals, cobalt, manganese, and nickel, may be used. .

[0245] When a metal capable of forming a layered rock salt type composite oxide is used, a layered rock salt type crystal structure can be formed. It is preferable to mix cobalt, manganese, and nickel in the range of the ratio. Aluminum may be added to these transition metals as long as the crystal structure of this type can be obtained.

[0246] As the source of the transition metal M, oxides, hydroxides, etc. of the metals exemplified as the transition metal M are used. As the cobalt source, for example, cobalt oxide, cobalt hydroxide, etc. can be used. As the manganese source, manganese oxide, manganese hydroxide, etc. can be used. Nickel oxide, nickel hydroxide, etc. can be used as the nickel source. The aluminum source may be aluminum oxide, aluminum hydroxide, or the like. do.

[0247] <Step S02> Next, in step S02, the lithium source, the transition metal M source, and the first impurity element source are The mixing can be carried out by a dry method or a wet method. When using a ball mill, for example, a ball mill may be used as the medium. It is preferable to use luconia balls.

[0248] <Step S03> Next, in step S03, the mixed materials are heated. This step is similar to the subsequent heating step. To distinguish between the two, it is sometimes called firing or first heating. Heating is performed at temperatures between 800°C and 1100°C. It is preferable to carry out the heating at a temperature of less than 1000°C, and more preferable to carry out the heating at a temperature of 900°C or more and 1000°C or less. A temperature of about 950° C. is more preferable. If the temperature is too low, the lithium source, the transition metal M source, and the first metal On the other hand, if the temperature is too high, the decomposition and melting of the impurity element source of 1 may be insufficient. The transition metal M is used as the metal responsible for the redox reaction, but the metal is excessively reduced. For example, when cobalt is used as the transition metal M, defects may occur due to the In this case, defects in which cobalt becomes divalent can occur.

[0249] The heating time can be, for example, 1 hour to 100 hours, and can be 2 hours to 20 hours. It is preferable to perform the firing in an atmosphere with little water, such as dry air (for example, a dew point of -50°C or less). For example, it is preferable to carry out the heating at 1000°C for 10 hours. The temperature was increased at 200°C / h and the flow rate of the drying atmosphere was 10 L / min. The heated material can then be cooled to room temperature. The time required for cooling from the temperature of the heating element to room temperature is preferably 10 hours or more and 50 hours or less.

[0250] However, cooling to room temperature in step S03 is not essential. If there is no problem, the cooling may be performed to a temperature higher than room temperature.

[0251] <Step S04> Next, in step S04, the sintered material is recovered, and lithium, a transition metal M, and a first A composite oxide (LiMO2) containing the impurity elements and oxygen is obtained.

[0252] <Steps S11 to S13 and Step S31> In addition, similarly to the method described in the previous embodiment, steps S11 to S13 and As shown in step S31, a composite oxide containing lithium, a transition metal M, and oxygen is mixed. After the first impurity element is formed, a second impurity element source may be mixed. Sium, fluorine, aluminum, titanium, zirconium, vanadium, iron, chromium, niobium At least one of the following elements may be used: aluminum, cobalt, arsenic, zinc, silicon, sulfur, phosphorus, and boron. As the second impurity element source, oxides, hydroxides, fluorides, etc. of these elements can be used. It is possible.

[0253] <Steps S42 and S43> In addition, as in the method described in the previous embodiment, the steps S42 and S43 As shown in the figure, the second impurity element is mixed, annealed, and then the third impurity element source is mixed. The third impurity element may be magnesium, fluorine, aluminum, titanium, or di Ruthenium, vanadium, iron, chromium, niobium, cobalt, arsenic, zinc, silicon, sulfur, At least one of phosphorus and boron can be used as the third impurity element source. Oxides, hydroxides, fluorides, etc. of these compounds can be used.

[0254] Although not shown, a third impurity element source is mixed, and after further annealing, a fourth impurity element source is mixed. The sources of the elements may be mixed.

[0255] In this way, the impurity element source is added at multiple times during the process of producing the positive electrode active material 101. can be mixed with

[0256] The methods for mixing the impurity element sources include liquid phase methods such as the sol-gel method, solid phase methods, and sputtering. Tarring method, evaporation method, CVD (chemical vapor deposition) method, PLD (pulsed laser deposition) method Methods such as the method can be applied.

[0257] The first impurity element source, the second impurity element source, and the third impurity element source are each a different source. For example, magnesium may be the first impurity. It may be used both as a source of a pure element and as a source of a second impurity element.

[0258] Among the impurity element sources, it is preferable to mix magnesium and fluorine at the same time. By adding magnesium and fluorine at the same time, the function of the fluorine source as a flux is fully exerted. As a result, the distribution of magnesium in the surface layer portion of the positive electrode active material 101 becomes good.

[0259] Also, the optimum timing for mixing may differ depending on the impurity element. Nesium and fluorine are mixed as the second and subsequent impurity element sources rather than the first impurity element source. It is preferable to do so.

[0260] Note that in the manufacturing method of one embodiment of the present invention, any one of the first to third impurity element sources is used. In other words, it is sufficient to mix one or more of the impurity element sources shown in FIG. The above method may be adopted, and it is not necessary to mix impurity elements at all times. It doesn't have to be.

[0261] This embodiment mode can be used in combination with other embodiments mode.

[0262] (Embodiment 5) In this embodiment, an example of a secondary battery of one embodiment of the present invention will be described with reference to FIGS. Reveal.

[0263] <Configuration example 1 of secondary battery> The following description will be given taking as an example a secondary battery in which a positive electrode, a negative electrode, and an electrolyte are enclosed in an exterior body. do.

[0264] [Positive electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector. It may have an electrical material and a binder. For the positive electrode active material, use the positive electrode active material produced by the production method described in the previous embodiment.

[0265] Also, the positive electrode active material described in the previous embodiment and another positive electrode active material may be mixed and used.

[0266] <0001%909>Examples of other positive electrode active materials include composite oxides having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure. For example, compounds such as LiFePO4, LiFeO2, LiNiO2, LiMn2O4, V2O5, Cr2O5, and MnO2 can be cited.

[0267] Also, as another positive electrode active material, a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4 is preferably mixed with lithium nickelate (LiNiO2 or LiNiMO2 (0 < x < 1), M = Co, Al, etc.). By adopting this configuration, the characteristics of the secondary battery can be improved. 1-x M x O

[0268] Also, as another positive electrode active material, a lithium manganese composite oxide represented by the composition formula LiMnMO can be used. Here, the element M is preferably a metal element selected from those other than lithium and manganese, or silicon or phosphorus, and more preferably nickel. When measuring the entire particle of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≤ (b + c) / d < 0.5 during discharge. Note that for the entire particle of the lithium manganese composite oxide, the metal, silicon a Mn b M c O d ​​​​​​​​​​​​ The composition of carbon, phosphorus, etc. is measured using, for example, an ICP-MS (inductively coupled plasma mass spectrometer). The oxygen composition of the entire lithium manganese composite oxide particle can be, for example, It can be measured using EDX (energy dispersive X-ray analysis). Combined with P-MS analysis, fused gas analysis and XAFS (X-ray absorption fine structure) analysis for valence evaluation The lithium manganese composite oxide is at least Also refers to oxides containing lithium and manganese, and oxides containing chromium, cobalt, aluminum, nickel Iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium , silicon, and phosphorus, and Good too.

[0269] As an example, a cross section of the active material layer 200 using a graphene compound as a conductive material is shown below. An example configuration will be described.

[0270] 13(A) shows a vertical cross-sectional view of the active material layer 200. The active material layer 200 is made of granular positive electrode active material. The graphene and graphene compounds 201 are used as conductive materials, and the binder (Fig. (not shown) and

[0271] In this specification and the like, graphene compounds include multi-layer graphene, multi-graphene, graphene oxide, graphene, multi-layer graphene oxide, multi-graphene oxide, reduced graphene oxide, reduced Original multi-layer graphene oxide, reduced multi-graphene oxide, graphene quantum dots Graphene compounds include those that contain carbon and have a shape such as a flat plate or sheet. It refers to a two-dimensional structure formed by a six-membered ring. The graphene compound may have a functional group. The graphene compound preferably has a curved shape. The material may be formed into a shape like a carbon nanofiber.

[0272] In this specification and the like, graphene oxide refers to a material containing carbon and oxygen and having a sheet shape, A graphene compound having a functional group, in particular an epoxy group, a carboxy group, or a hydroxy group, say.

[0273] In this specification and the like, reduced graphene oxide refers to a graphene oxide having carbon and oxygen and having a sheet-like shape. It has a two-dimensional structure formed by six-membered carbon rings. Although a single sheet of reduced graphene oxide can function, stacking multiple sheets can also function. Reduced graphene oxide has a carbon concentration greater than 80 atomic % and oxygen It is preferable that the concentration of the fluorine-containing compound is 2 atomic % or more and 15 atomic % or less. By setting the carbon and oxygen concentrations in this range, it is possible to obtain a conductive material with high conductivity even in small amounts. In addition, reduced graphene oxide exhibits a It is preferable that the intensity ratio G / D between the G band and the D band is 1 or more. A certain type of reduced graphene oxide can function as a highly conductive material even in small amounts. Cut.

[0274] In the vertical cross section of the active material layer 200, as shown in FIG. 13(B), In the graphene layer, the sheet-like graphene and graphene compound 201 are dispersed almost uniformly. In Fig. 13(B), graphene and graphene compounds 201 are shown in bold. Although it is called graphene, it is actually a thin film with a thickness of a single layer or multiple layers of carbon molecules. The graphene compound 201 is formed so as to partially cover the plurality of particles of the positive electrode active material 101. or a plurality of granular positive electrode active materials 101 are formed so as to be stuck to the surface thereof, In addition, graphene and graphene compound 201 are in surface contact with each other. It is also preferable that the graphene and graphene compound 2 It is preferable that the graphene and the 01 are overlapped on at least a part of the active material. It is preferable that the shape of the graphene compound 201 corresponds to at least a part of the shape of the active material. The shape of the active material may be, for example, the unevenness of a single active material particle or the unevenness of multiple active material particles. The term "irregularities" refers to the irregularities formed by the surface roughness of graphene and graphene compounds. It is preferable that the active material is at least partially surrounded by graphene. The phenyl compound 201 may have holes.

[0275] Here, a plurality of graphene compounds are bonded to each other to form a mesh-like graphene compound. It is possible to form a graphene sheet (hereinafter referred to as a graphene compound net or graphene net). When the active material is covered with a graphene net, the graphene net can connect the active material to each other. It can also function as a binder to bind the particles together. Therefore, the ratio of the active material to the electrode volume or weight can be reduced. In other words, the capacity of the secondary battery can be increased.

[0276] Here, graphene oxide is used as the graphene and graphene compound 201, and the active material It is preferable to mix the above to form a layer that will become the active material layer 200, and then reduce the layer. The active material layer preferably contains reduced graphene oxide. Graphene oxide, which has extremely high dispersibility in polar solvents, is used to form the graphene compound 201. As a result, graphene and graphene compound 201 are dispersed inside active material layer 200. The graphene oxide particles can be dispersed uniformly. The solvent is evaporated and removed from the active material layer 200, and the graphene oxide is reduced. The graphene and graphene compounds 201 are dispersed to the extent that they partially overlap and are in surface contact with each other. By doing so, a three-dimensional conductive path can be formed. The reduction may be carried out by, for example, heat treatment or by using a reducing agent.

[0277] Therefore, unlike granular conductive materials such as acetylene black, which come into point contact with the active material, graphene In addition, the graphene compound 201 enables surface contact with low contact resistance. The granular positive electrode active material 101, graphene, and graphene compounds 2 are used in smaller amounts than ordinary conductive materials. Therefore, the electrical conductivity between the positive electrode active material 101 and the active material layer 2 can be improved. 00, the discharge capacity of the secondary battery can be increased. It can be done.

[0278] In addition, by using a spray dryer, the entire surface of the active material is covered with a conductive material in advance. The graphene compound is then formed as a coating, and the active material is then electrically conductive through the graphene compound. It is also possible to form a path.

[0279] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer contains a conductive material and It may contain a binder.

[0280] [Negative electrode active material] As the negative electrode active material, for example, an alloy-based material or a carbon-based material can be used.

[0281] As a negative electrode active material, it is possible to carry out charge-discharge reactions by alloying and dealloying reactions with lithium. Any suitable element can be used, such as silicon, tin, gallium, aluminum, Rumanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one of these elements can be used. These elements have a large capacity compared to carbon. Silicon has a particularly high theoretical capacity of 4200mAh / g. It is preferable to use silicon. Alternatively, compounds containing these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V 2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3 Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, I nSb, SbSn, etc. Here, the charge / discharge reaction occurs due to alloying and dealloying reactions with lithium. Elements capable of undergoing a reaction and compounds containing such elements are sometimes called alloy materials. do.

[0282] In this specification and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO refers to SiO x Here, it is preferable that x has a value close to 1. For example, x is 0 A value between 0.2 and 1.5 is preferred, and a value between 0.3 and 1.2 is more preferred.

[0283] Carbon materials include graphite, easily graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). carbon nanotubes, graphene, carbon black, etc. may be used. .

[0284] Examples of graphite include artificial graphite and natural graphite. Examples include carbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, as the artificial graphite, spherical graphite having a spherical shape can be used. For example, the MCMB may have a spherical shape, which is preferable. It is relatively easy to reduce the particle size, which is sometimes preferable. Examples include flake graphite and spherical natural graphite.

[0285] Graphite is formed when lithium ions are inserted into graphite (forming a lithium-graphite intercalation compound) It shows a low potential similar to that of lithium metal (0.05V to 0.3V vs. Li / Li + This allows the lithium-ion secondary battery to exhibit a high operating voltage. Furthermore, graphite has a relatively high capacity per unit volume, a relatively small volume expansion, and is inexpensive. It is preferable because it has advantages such as higher safety compared to metallic lithium.

[0286] In addition, titanium dioxide (TiO2) and lithium titanium oxide (Li4T i5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5) Oxides such as tungsten oxide (WO2) and molybdenum oxide (MoO2) can be used. can.

[0287] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, which has a Li3N structure. Li 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm 3 ) And preferable.

[0288] When a composite nitride of lithium and a transition metal is used, the negative electrode active material contains lithium ions, The positive electrode active material is a combination of materials such as V2O5 and Cr3O8 that do not contain lithium ions. It is preferable that a material containing lithium ions is used as the positive electrode active material. By first removing the lithium ions contained in the positive electrode active material, A complex nitride of lithium and a transition metal can be used.

[0289] In addition, a material that undergoes a conversion reaction can also be used as the negative electrode active material. , cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. A transition metal oxide that does not form an alloy with the metal may be used as the negative electrode active material. Further materials that can be produced include Fe2O3, CuO, Cu2O, RuO2, Cr2O3, etc. oxide, CoS 0.89 , NiS, CuS and other sulfides, Zn3N2, Cu3N, Ge3 Nitrides such as N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. It also occurs with fluoride.

[0290] The conductive material and binder that can be contained in the negative electrode active material layer can be the same as those contained in the positive electrode active material layer. The same materials as the conductive material and binder that can be used can be used.

[0291] [Negative electrode current collector] The negative electrode current collector can be made of the same material as the positive electrode current collector. It is preferable to use a material that does not alloy with carrier ions such as lithium.

[0292] [Electrolyte] The electrolytic solution contains a solvent and an electrolyte. The solvent for the electrolytic solution is preferably an aprotic organic solvent. For example, ethylene carbonate (EC), propylene carbonate (PC), ethylene carbonate, chloroethylene carbonate, vinylene carbonate, gamma-butyrolactone lactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1 ,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfone oxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran One of tetrahydrofuran, sulfolane, sultone, etc., or two or more of these Combinations and ratios may be used.

[0293] In addition, a flame-retardant and non-volatile ionic liquid (room-temperature molten salt) is used as the solvent for the electrolyte. By using one or more batteries, the internal temperature of the secondary battery can be increased due to an internal short circuit or overcharging. Even if the battery is not fully charged, it can prevent the secondary battery from exploding or catching fire. Ionic liquids are made up of cations and anions. The organic cations used in the electrolyte include quaternary cations. Ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, etc. aliphatic onium cations such as imidazolium cations and pyridinium cations Aromatic cations are also used as anions in electrolytes. Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkyl Sulfonate anion, tetrafluoroborate anion, perfluoroalkylborate anion, hexafluorophosphate anion, or perfluoroalkylphosphate anions, etc.

[0294] The electrolyte to be dissolved in the solvent is, for example, LiPF6, LiClO4, Li AsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4 , Li2B 10 Cl 10 , Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO 3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2) 2. Lithium such as LiN(C4F9SO2)(CF3SO2) and LiN(C2F5SO2)2 Use one or more of these ammonium salts in any combination and ratio. can be done.

[0295] The electrolyte used in secondary batteries is free from granular dust and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). It is preferable to use a highly purified electrolyte solution with a low content of ammonium hydroxide. Specifically, the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less, more preferably It is preferably 0.01% or less.

[0296] In addition, the electrolyte contains vinylene carbonate, propane sultone (PS), and tert-butyl ether. Benzene (TBB), Fluoroethylene carbonate (FEC), Lithium bis(oxalate) Lithium borate (LiBOB), as well as dinitriles such as succinonitrile and adiponitrile Additives such as compounds may be added. The concentration of the added material is, for example, It should be between 0.1 wt% and 5 wt%.

[0297] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0298] The use of polymer gel electrolytes increases safety against leakage, etc. It is possible to make the device thinner and lighter.

[0299] The polymers that can be gelled include silicone gel, acrylic gel, acrylonitrile gel, Polyethylene oxide gel, polypropylene oxide gel, fluorine polymer Gel or the like can be used.

[0300] Examples of the polymer include polyalkylene oxides such as polyethylene oxide (PEO). Polymers with a hexagonal structure, PVDF, polyacrylonitrile, etc., and their For example, a copolymer containing PVDF and hexafluoropropylene (H PVDF-HFP, a copolymer of PVDF and PVDF, can be used. The mer may have a porous shape.

[0301] In addition, instead of the electrolyte solution, solid electrolytes containing inorganic materials such as sulfides and oxides, and P A solid electrolyte containing a polymer material such as EO (polyethylene oxide) can be used. When a solid electrolyte is used, there is no need to install a separator or spacer. Since the entire pond can be solidified, there is no risk of leakage, dramatically improving safety.

[0302] [Separator] The secondary battery preferably has a separator. The separator may be made of, for example, paper. , nonwoven fabric, glass fiber, ceramics, or nylon (polyamide), vinylon (poly vinyl alcohol fiber), polyester, acrylic, polyolefin, polyurethane The separator can be made of synthetic fibers or the like. It is preferable that the electrode be processed into a shape such that it wraps around either the positive electrode or the negative electrode.

[0303] The separator may have a multi-layer structure. For example, the separator may be made of an organic material such as polypropylene or polyethylene. The material film is made of ceramic material, fluorine material, polyamide material, or a mixture of these. As a ceramic material, for example, aluminum oxide can be used. Examples of the fluorine-based material include fluorine particles, silicon oxide particles, etc. PVDF, polytetrafluoroethylene, etc. can be used. For example, nylon, aramid (meta-aramid, para-aramid), etc. can be used. can.

[0304] Coating with ceramic materials improves oxidation resistance, making it suitable for separators during high-voltage charging and discharging. This can suppress the deterioration of the battery and improve the reliability of the secondary battery. By coating, the separator and electrodes can be more easily attached to each other, improving output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, which contributes to the safety of secondary batteries. Safety can be improved.

[0305] For example, a polypropylene film is coated on both sides with a mixture of aluminum oxide and aramid. Alternatively, aluminum oxide may be applied to the surface of the polypropylene film that comes into contact with the positive electrode. Alternatively, the surface of the negative electrode that comes into contact with the carbon black may be coated with a mixed material of carbon black and aramid, and then coated with a fluorine-based material.

[0306] By using a multilayer separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin. Since the temperature can be maintained, the capacity per volume of the secondary battery can be increased.

[0307] [Exterior body] The exterior of the secondary battery is made of a metal material such as aluminum or a resin material. Also, a film-like outer casing can be used. For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. On the film made of the material, a highly flexible metal such as aluminum, stainless steel, copper, or nickel is A metal thin film is then formed on the metal thin film, and the outer surface of the exterior body is made of a polyamide resin or polyester. A three-layer film having an insulating synthetic resin film such as a vinyl resin can be used.

[0308] <Configuration example 2 of secondary battery> As an example of the configuration of a secondary battery, the configuration of a secondary battery using a solid electrolyte layer will be described below. Reveal.

[0309] As shown in FIG. 14A, a secondary battery 400 of one embodiment of the present invention includes a positive electrode 410, a solid electrolyte The battery has a porous layer 420 and a negative electrode 430 .

[0310] The positive electrode 410 includes a positive electrode current collector 413 and a positive electrode active material layer 414. The positive electrode active material layer 414 has a positive electrode active material 411 and a solid electrolyte 421. It may also contain auxiliaries and binders.

[0311] The solid electrolyte layer 420 includes a solid electrolyte 421. The solid electrolyte layer 420 is connected to the positive electrode 410. The negative electrode 430 is located between the positive electrode active material 411 and the negative electrode active material 431. It is an area.

[0312] The negative electrode 430 includes a negative electrode current collector 433 and a negative electrode active material layer 434. The negative electrode active material layer 434 has a negative electrode active material 431 and a solid electrolyte 421. The negative electrode 430 may contain an auxiliary agent and a binder. As shown in FIG. 14(B), the negative electrode 430 does not have a solid electrolyte 421. The use of metallic lithium in the negative electrode 430 improves the energy density of the secondary battery 400. This is preferable.

[0313] The solid electrolyte 421 of the solid electrolyte layer 420 may be, for example, a sulfide-based solid electrolyte, an acid A carbide-based solid electrolyte, a halide-based solid electrolyte, or the like can be used.

[0314] Sulfide-based solid electrolytes include thiosilicon-based (Li 10 GeP2S 12 , Li 3.25 Ge 0.25 P 0.75 S4, etc.), sulfide glass (70Li2S・30P2S5, 30Li2 S·26B2S3·44LiI, 63Li2S·38SiS2·1Li3PO4, 57L i2S・38SiS2・5Li4SiO4, 50Li2S・50GeS2, etc.), sulfide crystals Crystallized glass (Li7P3S 11 , Li 3.25 P 0.95 S4, etc.) are included. Solid electrolytes have high conductivity, can be synthesized at low temperatures, and are relatively soft. This has the advantage that the conductive path is easily maintained even after charging and discharging.

[0315] Oxide-based solid electrolytes include materials with a perovskite crystal structure (La 2 / 3-x Li 3x TiO3, etc.), materials with NASICON-type crystal structure (Li 1+X Al X Ti 2- X (PO4)3, etc.), materials with garnet-type crystal structure (Li7La3Zr2O 12 etc. ), materials with LISICON-type crystal structure (Li 14 ZnGeO 16 etc.), oxide gas Glass (Li3PO4-Li4SiO4, 50Li4SiO4·50Li3BO3, etc.), acid Lithium nitride glass-ceramics 1.07 Al 0.69 Ti 1.46 (PO4)3, Li 1.5 A l 0.5 Ge 1.5 Oxide-based solid electrolytes are stable in the atmosphere. This has the advantage that

[0316] Halide solid electrolytes include LiAlCl4, Li3InBr6, LiF, and LiCl These halide-based solid electrolytes are also used as porous Composite materials filled into the pores of aluminum oxide and porous silica can also be used as solid electrolytes. It can be used as such.

[0317] A mixture of multiple solid electrolytes may also be used.

[0318] Among them, Li with NASICON type crystal structure 1+x Al x Ti 2-x (PO4)3( 0≦x≦1) (hereinafter referred to as LATP) is a compound of aluminum and titanium, which is one aspect of the present invention. Since the positive electrode active material used in the secondary battery 400 contains elements that may be contained, the cycle characteristics can be improved. This is desirable as it is expected to have a synergistic effect. In addition, productivity can be improved by reducing the number of processes. In this specification, the NASICON type crystal structure is M2(XO4)3 (M: transition X is a transition metal, and is a compound represented by the formula (X: S, P, As, Mo, W, etc.), and is an MO6 octahedron and XO It refers to a structure in which four tetrahedrons are arranged three-dimensionally with their vertices shared.

[0319] [Shapes of exterior body and secondary battery] The exterior body of the secondary battery 400 according to one embodiment of the present invention can be made of various materials and in various shapes. However, it is preferable that the positive electrode, the solid electrolyte layer, and the negative electrode have a function of applying pressure thereto.

[0320] For example, Figure 15 shows an example of a cell for evaluating materials for all-solid-state batteries.

[0321] FIG. 15(A) is a cross-sectional view of the evaluation cell. The evaluation cell is composed of a lower member 761 and an upper member 762, and a fixing screw and a wing nut 764 that fix them. By rotating it, the electrode plate 753 is pressed and the evaluation material is fixed. An insulator 766 is provided between the lower member 761 and the upper member 762, both of which are made of a material. An O-ring 762 is provided between the upper member 762 and the holding screw 763 for sealing. 65 is provided.

[0322] The material to be evaluated is placed on an electrode plate 751, surrounded by an insulating tube 752, and an electric It is pressed by the electrode plate 753. The figure is shown in Figure 15(B).

[0323] As an example of the evaluation material, a laminate of a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is shown. The cross-sectional view is shown in Figure 15(C). In Figures 15(A), (B), and (C), The same symbols are used for the same parts.

[0324] The electrode plate 751 and the lower member 761 electrically connected to the positive electrode 750a are It can be said that the electrode plate electrically connected to the negative electrode 750c corresponds to a terminal. The electrode plate 753 and the upper member 762 can be said to correspond to the negative terminal. The electrical resistance etc. is measured by applying pressure to the evaluation material through the electrode plate 751 and the electrode plate 753. can be measured.

[0325] In addition, a package with excellent airtightness may be used for the exterior body of the secondary battery according to one embodiment of the present invention. For example, a ceramic package or a resin package can be used. In addition, when sealing the exterior body, it is necessary to shut out the outside air and seal it in a sealed atmosphere, for example, in a glove box. It is preferable to carry out the process in a gas chamber.

[0326] FIG. 16(A) shows a secondary battery of one embodiment of the present invention having an exterior body and a shape different from those in FIG. 15. The secondary battery in FIG. 16(A) has external electrodes 771 and 772 and a plurality of packs. It is sealed with an exterior body having a cage member.

[0327] An example of a cross section taken along the dashed line in FIG. 16(A) is shown in FIG. 16(B). The laminate having the solid electrolyte layer 750b and the negative electrode 750c is formed by providing an electrode layer 773a on a flat plate. The package member 770a is a frame-shaped package member 770b, and the electrode layer 7 The package member 770c on which the semiconductor device 73b is provided is enclosed and sealed. The package members 770a, 770b, and 770c are made of an insulating material, such as a resin material or ceramic. Mix can be used.

[0328] The external electrode 771 is electrically connected to the positive electrode 750a via the electrode layer 773a, and is connected to the positive electrode terminal The external electrode 772 is electrically connected to the negative electrode 750c via the electrode layer 773b. It is electrically connected to the negative terminal.

[0329] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0330] (Embodiment 6) In this embodiment, an example of the shape of the secondary battery having the positive electrode described in the previous embodiment will be described. The materials used in the secondary battery described in this embodiment are the same as those described in the previous embodiment. You can pour drinks.

[0331] <Coin-type secondary battery> First, an example of a coin-type secondary battery will be described. FIG. 17(A) shows a coin-type (single-layer flat type) 17(B) is a cross-sectional view of the secondary battery shown in FIG.

[0332] The coin-type secondary battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal. 302 is insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is composed of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector 305. The negative electrode 307 is formed by a negative electrode current collector 308 and a The negative electrode active material layer 309 is formed by bonding the negative electrode active material layer 309 to the negative electrode active material layer 309 .

[0333] The positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 are each an active material. The barrier layer need only be formed on one side.

[0334] The positive electrode can 301 and the negative electrode can 302 are made of nickel and aluminum, which are corrosion-resistant to the electrolyte. , titanium, or alloys thereof or alloys of these with other metals (e.g. stainless steel) In addition, nickel or aluminum can be used to prevent corrosion by the electrolyte. The positive electrode can 301 is preferably coated with a positive electrode 304, and the negative electrode can 302 is preferably coated with a negative electrode 304. 7 and electrically connect to each other.

[0335] The negative electrode 307, the positive electrode 304, and the separator 310 are impregnated with an electrolyte, and the negative electrode 307, the positive electrode 304, and the separator 310 are then impregnated with an electrolyte. ) the positive electrode can 301 is placed downward, and the positive electrode 304, separator 310, negative electrode 307, The positive electrode can 301 and the negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are secured together with a gasket 303 interposed therebetween. Then, the laminate is pressed to form a coin-type secondary battery 300.

[0336] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, it is possible to achieve high capacity cycling. The coin-type secondary battery 300 can be made to have excellent characteristics.

[0337] Here, the flow of current during charging of the secondary battery will be explained using FIG. 17(C). When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In secondary batteries that use lithium, the anode and cathode are connected by charging and discharging. The cathode (electrode) is switched, and the oxidation reaction and reduction reaction are switched. The electrode with a higher reaction potential is called the positive electrode, and the electrode with a lower reaction potential is called the negative electrode. In this case, even during charging, discharging, or when a reverse pulse current is applied, Even when an electric current flows through the positive electrode, it is called the "positive electrode" or "+ electrode (plus electrode)" and the negative electrode is called the "negative electrode" or "-electrode (minus electrode)". When the terms anode (positive electrode) and cathode (negative electrode) are used, the difference between charging and discharging is Therefore, the anode and cathode are often used interchangeably. The term "anode" (negative electrode) is not used in this specification. When using the terms "positive electrode" or "cathode," specify whether it is charging or discharging, and It will also be noted whether it corresponds to a positive pole (positive electrode) or a negative pole (negative electrode).

[0338] A charger is connected to the two terminals shown in FIG. 17(C) to charge the secondary battery 300. As the charging of the secondary battery 300 progresses, the potential difference between the electrodes increases.

[0339] <Cylindrical secondary battery> Next, an example of a cylindrical secondary battery will be described with reference to FIG. 18. Cylindrical secondary battery 600 18(A) shows an external view of the cylindrical secondary battery 600. FIG. 18(B) shows a schematic cross section of the cylindrical secondary battery 600. As shown in FIG. 18(B), the cylindrical secondary battery 600 has a positive electrode on the top surface. It has a polar cap (battery lid) 601 and a battery can (external can) 602 on the side and bottom. The positive electrode cap 601 and the battery can (external can) 602 are connected by a gasket (insulating packing). It is insulated by 610.

[0340] Inside a hollow cylindrical battery can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are placed between a separator 6 The battery element is wound around the sensor. The battery can 602 is closed at one end and open at the other. The battery can 602 is made of a material that is resistant to corrosion by the electrolyte, such as nickel, aluminum, or titanium. These metals, or their alloys or alloys of these with other metals (e.g., stainless steel, etc.) are used. In addition, to prevent corrosion by the electrolyte, nickel, aluminum, etc. It is preferable to coat the battery can 602. Inside the battery can 602, the positive electrode, the negative electrode, and The battery element with the separator wound around it is sandwiched between a pair of opposing insulating plates 608 and 609. The inside of the battery can 602 in which the battery element is provided is filled with a non-aqueous electrolyte (not shown). The non-aqueous electrolyte can be the same as that used in coin-type secondary batteries. .

[0341] The positive and negative electrodes used in cylindrical storage batteries are wound, so active materials are formed on both sides of the current collector. A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative electrode A negative electrode terminal (negative electrode current collecting lead) 607 is connected to the positive electrode terminal 603. The positive terminal 60 and the positive terminal 607 can be made of a metal material such as aluminum. 3 is resistance-welded to the safety valve mechanism 612, and the negative terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 is a PTC (Positive Temperature Coupling) element. It is electrically connected to the positive electrode cap 601 via a stable (efficient) 611. When the internal pressure of the battery exceeds a predetermined threshold, the valve mechanism 612 closes the positive electrode cap 601 and The PTC element 611 cuts off the electrical connection with the positive electrode 604. It is a thermal resistance element whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current and prevents abnormalities. It prevents heat buildup. The PTC element contains a barium titanate (BaTiO3) based semiconductor. Conductive ceramics or the like can be used.

[0342] 18(C), a plurality of secondary batteries 600 are mounted on conductive plates 613 and 614. The secondary batteries 600 may be sandwiched between the secondary batteries 600 to form a module 615. They may be connected in series, or may be connected in parallel and then connected in series. By configuring a module 615 having a plurality of secondary batteries 600, It can extract a large amount of power.

[0343] FIG. 18(D) is a top view of the module 615. For clarity of illustration, the conductive plate 613 is As shown in FIG. 18(D), the module 615 includes a plurality of secondary batteries 600. The device may have a conductive wire 616 for electrical connection. A conductive plate is provided on the conductive wire 616. Furthermore, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 is overheated, the temperature control device 617 cools the secondary battery 600. If the temperature controller 617 is too cold, it can be heated. The performance of the module 615 is less affected by the outside temperature. The medium is preferably insulating and non-flammable.

[0344] By using the positive electrode active material described in the above embodiment for the positive electrode 604, it is possible to achieve high capacity cycling. The cylindrical secondary battery 600 can be made to have excellent characteristics.

[0345] <Example of secondary battery structure> Another structural example of the secondary battery will be described with reference to FIGS.

[0346] 19(A) and 19(B) are diagrams showing the external appearance of a battery pack. The secondary battery 913 and the circuit board 900 are included. The secondary battery 913 is connected to an antenna 914 via a label 910. Furthermore, as shown in FIG. 19(B), the secondary battery 913 has a terminal 951 and The circuit board 900 is connected to a terminal 952. The circuit board 900 is fixed with a seal 915. do.

[0347] The circuit board 900 has a terminal 911 and a circuit 912. The terminal 911 is connected to a terminal 951. , a terminal 952, an antenna 914, and a circuit 912. Each of the plurality of terminals 911 may be used as a control signal input terminal, a power supply terminal, etc. .

[0348] The circuit 912 may be provided on the back surface of the circuit board 900. The antenna 914 The antenna is not limited to a coil shape, but may be, for example, a wire shape or a plate shape. Antennas such as surface antennas, traveling wave antennas, EH antennas, magnetic field antennas, and dielectric antennas Alternatively, the antenna 914 may be a flat conductor. can function as one of the conductors for electric field coupling. The antenna 914 may function as one of the two conductors. Electric power can be exchanged not only using electromagnetic fields and magnetic fields, but also using electric fields.

[0349] The battery pack has a layer 916 between the antenna 914 and the secondary battery 913. The layer 916 has a function of blocking an electromagnetic field generated by the secondary battery 913, for example. For example, a magnetic material can be used as the material.

[0350] The structure of the battery pack is not limited to that shown in FIG.

[0351] For example, as shown in Figs. 20(A) and 20(B), In the secondary battery 913 shown in FIG. 20(A) is an external view showing one of the pair of surfaces, and FIG. 20(B) is an external view showing one of the pair of surfaces. 19(A) and 19(B). For the same parts, the explanation of the secondary battery shown in FIG. 19(A) and FIG. 19(B) can be used as appropriate. Cut.

[0352] As shown in FIG. 20(A), a layer 916 is sandwiched between one of the two surfaces of a secondary battery 913 and an antenna. As shown in FIG. 20(B), a layer 914 is provided on the other of the pair of surfaces of the secondary battery 913. An antenna 918 is provided across the layer 917. The layer 917 is, for example, a secondary battery 913. The layer 917 has a function of shielding electromagnetic fields. For example, a magnetic material is used. It is possible.

[0353] By adopting the above structure, the size of both the antenna 914 and the antenna 918 can be increased. The antenna 918 can perform data communication with an external device, for example. The antenna 918 has a shape that can be applied to the antenna 914, for example. A communication method between the secondary battery and other devices via the antenna 918 can be applied. For example, NFC (near field communication) can be used between secondary batteries and other devices. A response method that can be applied can be applied.

[0354] Alternatively, as shown in FIG. 20(C), the secondary battery 913 shown in FIGS. 19(A) and 19(B) may be used. A display device 920 may be provided in the display device 920. The display device 920 is electrically connected to the terminal 911. It is not necessary to provide the label 910 in the area where the display device 920 is provided. 19(A) and 19(B) are the same as those in the secondary battery shown in FIG. The description of the secondary battery shown in 19(B) can be used as appropriate.

[0355] The display device 920 displays, for example, an image indicating whether charging is in progress or not, an image indicating the amount of stored power, etc. The display device 920 may be, for example, an electronic paper, a liquid crystal display, an electrophotographic display, or the like. For example, an electroluminescence (EL) display device can be used. By using the par, the power consumption of the display device 920 can be reduced.

[0356] Alternatively, as shown in FIG. 20(D), the secondary battery 913 shown in FIGS. 19(A) and 19(B) may be used. The sensor 921 may be electrically connected to the terminal 911 via a terminal 922. It should be noted that the same parts as those of the secondary battery shown in Fig. 19(A) and Fig. 19(B) are For this purpose, the description of the secondary battery shown in FIGS. 19(A) and 19(B) can be used as appropriate.

[0357] The sensor 921 may be, for example, a sensor for detecting displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, etc. , liquid, magnetic, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow It is sufficient if it has the function of measuring volume, humidity, gradient, vibration, odor, or infrared. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed can be obtained. It is also possible to detect a signal (such as temperature) and store it in memory within the circuit 912.

[0358] Furthermore, an example of the structure of the secondary battery 913 will be described with reference to FIGS.

[0359] The secondary battery 913 shown in FIG. 21(A) has a terminal 951 and a terminal 952 provided inside a housing 930. The winding body 950 is impregnated with an electrolyte inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is in contact with the housing by using an insulating material or the like. 21(A), the housing 930 is not in contact with the housing 930. Although the figure shows the winding body 950, in reality, the winding body 950 is covered by the housing 930, and the terminals 951 and 955 are 2 extends outside the housing 930. The housing 930 is made of a metal material (e.g., aluminum Rubber or resin materials can be used.

[0360] As shown in FIG. 21(B), the housing 930 shown in FIG. 21(A) is made of a plurality of materials. For example, the secondary battery 913 shown in FIG. 21(B) may be formed by a housing 930a and a housing 930b. The wound body 930 is located in the area surrounded by the housing 930a and the housing 930b. 50 are provided.

[0361] The housing 930a can be made of an insulating material such as organic resin. By using a material such as organic resin on the surface on which the secondary battery 913 is formed, If the shielding of the electric field by the housing 930a is small, the shielding of the electric field by the housing 930a can be suppressed. An antenna such as antenna 914 may be provided inside the housing 930b. Metallic materials can be used.

[0362] Furthermore, the structure of the wound body 950 is shown in Fig. 22. The wound body 950 is made up of a negative electrode 931 and a positive electrode 932. The winding body 950 has a pole 932 and a separator 933. The negative electrode 931 and the positive electrode 932 are stacked one on top of the other, and the laminated sheet is wound to form a wound body. The negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated. You can stack several of them.

[0363] The negative electrode 931 is connected to the terminal 911 shown in FIG. 19 via one of the terminals 951 and 952. The positive electrode 932 is connected to the terminal 91 shown in FIG. 19 via the other of the terminals 951 and 952. Connected to 1.

[0364] By using the positive electrode active material described in the above embodiment for the positive electrode 932, it is possible to achieve high capacity cycling. The secondary battery 913 can have excellent characteristics.

[0365] <Laminated secondary battery> Next, an example of a laminated secondary battery will be described with reference to FIGS. If the laminated secondary battery is made flexible, it will have at least one flexible portion. If the secondary battery is mounted in an electronic device that also has a battery, it can be bent according to the deformation of the electronic device. can.

[0366] A laminated secondary battery 980 will be described with reference to Fig. 23. The battery 980 has a wound body 993 shown in FIG. 22, a positive electrode 995, and a separator 996. Similar to the wound body 950, a negative electrode 994 and a positive electrode 995 are stacked with a separator 996 sandwiched therebetween. The laminated sheet is then wound up.

[0367] The number of layers of the negative electrode 994, the positive electrode 995, and the separator 996 is determined as required. The negative electrode 994 is connected to the lead electrode 997 and the lead The positive electrode 995 is connected to a negative electrode current collector (not shown) via one of the lead electrodes 998. The positive electrode 997 and the lead electrode 998 are connected to a positive electrode current collector (not shown).

[0368] As shown in FIG. 23(B), a film 981 that serves as an exterior body and a film 98 having a recess are 2 are bonded together by thermocompression or the like, and the above-mentioned wound body 993 is housed in the space formed. In this way, a secondary battery 980 can be fabricated as shown in FIG. 3 has lead electrodes 997 and 998, and is connected to a film 981 and a recessed portion. The inside of the film 982 is impregnated with an electrolyte.

[0369] The film 981 and the film 982 having the recesses are made of a metal material such as aluminum. The film 981 and the film 982 having the recesses can be made of a material such as a resin. If a resin material is used as the material, when external force is applied, the film 981 and the recessed portion The film 982 can be deformed to produce a flexible storage battery. can.

[0370] Also, although Figures 23(B) and 23(C) show examples using two films, A space is formed by folding one sheet of film, and the above-mentioned wound body 99 is inserted into the space. It may also accommodate 3.

[0371] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, it is possible to achieve high capacity cycling. The secondary battery 980 can have excellent characteristics.

[0372] In addition, in FIG. 23, a secondary battery 9 having a wound body in a space formed by a film that serves as an exterior body is shown. 80 has been explained, but as shown in Figure 24, for example, The space defined by the positive electrode layer may be a secondary battery having a plurality of rectangular positive electrodes, separators, and negative electrodes. stomach.

[0373] The laminated secondary battery 500 shown in FIG. 24(A) includes a positive electrode current collector 501 and a positive electrode active material. a positive electrode 503 having a positive electrode active material layer 502, a negative electrode current collector 504 and a negative electrode active material layer 505 The battery includes a negative electrode 506, a separator 507, an electrolyte 508, and an exterior body 509. A separator 507 is provided between a positive electrode 503 and a negative electrode 506 provided in a body 509. The exterior body 509 is filled with an electrolyte 508. The electrolyte solution shown in the third embodiment can be used.

[0374] In the laminated secondary battery 500 shown in FIG. 24(A), a positive electrode current collector 501 and a negative electrode current collector 502 are The electrode current collector 504 also serves as a terminal for electrical contact with the outside. A part of the current collector 501 and the negative electrode current collector 504 is exposed to the outside from the outer casing 509. In addition, the positive electrode current collector 501 and the negative electrode current collector 504 may be disposed in the outer casing 509. The lead electrode is not exposed to the outside, and the lead electrode is connected to the positive electrode current collector 501 or the negative electrode The lead electrode may be exposed to the outside by ultrasonic bonding to the current collector 504 .

[0375] In the laminated secondary battery 500, the exterior body 509 is made of, for example, polyethylene, poly A film made of propylene, polycarbonate, ionomer, polyamide, etc. is coated with an A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied, and the metal is further On the metallic thin film, an insulating synthetic resin such as polyamide resin or polyester resin is applied as the outer surface of the exterior body. A three-layer laminate film provided with an oil film can be used.

[0376] An example of the cross-sectional structure of a laminated secondary battery 500 is shown in FIG. For simplicity, in A) an example is shown in which two current collectors are used, but in reality, as shown in Figure 24(B) As shown in Figure 1, it is composed of multiple electrode layers.

[0377] In FIG. 24(B), as an example, the number of electrode layers is set to 16. However, the secondary battery 500 has flexibility. In FIG. 24(B), the negative electrode current collector 504 has eight layers. The positive electrode current collector 501 has eight layers, making a total of 16 layers. The cross section of the extraction part is shown, and eight layers of negative electrode current collector 504 are ultrasonically bonded. The number of electrode layers is not limited to 16, and may be more or less. In this case, a secondary battery having a larger capacity can be obtained. In this case, a secondary battery can be made thin and highly flexible.

[0378] An example of the external appearance of a laminated secondary battery 500 is shown in FIGS. 25 and 26. 5 and 26 show a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead The positive electrode 510 and the negative electrode 511 are provided.

[0379] 27(A) shows an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is connected to the positive electrode current collector 50 1, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). 506 has a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. In addition, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, a tab region. The area and shape of the tab regions of the positive electrode and negative electrode are not limited to the example shown in FIG. I can't.

[0380] <Method for manufacturing laminated secondary batteries> Here, an example of a method for manufacturing the laminated secondary battery shown in FIG. 25 will be described with reference to FIG. This will be explained using (B) and (C).

[0381] First, the negative electrode 506, the separator 507, and the positive electrode 503 are stacked. The figure shows five pairs of negative electrodes 506, separators 507, and positive electrodes 503. Next, the bonding of the tab regions of the positive electrode 503 and the bonding of the tabs of the positive electrode on the outermost surface are shown. The positive electrode lead electrode 510 is bonded to the region. For example, ultrasonic welding or the like can be used for bonding. Similarly, the bonding of the tab regions of the negative electrodes 506 to each other and the bonding of the negative electrode leads to the tab region of the negative electrode on the outermost surface are also preferable. Then, the bonded electrode 511 is formed.

[0382] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are placed on the exterior body 509 .

[0383] Next, as shown in FIG. 27(C), the exterior body 509 is folded at the portion indicated by the broken line. After that, the outer periphery of the exterior body 509 is bonded. For example, thermocompression bonding may be used for bonding. , so that the electrolyte 508 can be poured later, An area that is not bonded (hereinafter referred to as an inlet) is provided.

[0384] Next, electrolyte 508 (not shown) is introduced into exterior body 509 through an inlet provided in exterior body 509. The electrolyte 508 is introduced into the inside of the electrode 509 under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is bonded. The secondary battery 500 can be manufactured.

[0385] By using the positive electrode active material described in the above embodiment for the positive electrode 503, it is possible to achieve high capacity cycling. A secondary battery with excellent characteristics can be obtained.

[0386] In all-solid-state batteries, a certain amount of pressure is applied in the stacking direction of the stacked positive and negative electrodes. The contact state of the interface at the stacking portion can be maintained in a good condition. Applying force can suppress expansion in the stacking direction due to charging and discharging of the all-solid-state battery. This makes it possible to improve the reliability of the all-solid-state battery.

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

[0388] (Embodiment 7) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on an electronic device will be described. do.

[0389] First, an example in which a bendable secondary battery is mounted on an electronic device, as described in the previous embodiment, will be described. 28(A) to 28(G) show the electronic device using the bendable secondary battery. Examples of devices include television sets (also called televisions or television receivers), Computer monitors, digital cameras, digital video cameras, digital photos Frame, mobile phone (also called mobile phone or mobile phone device), portable game machine, portable information Examples include terminals, audio playback devices, and large game machines such as pachinko machines.

[0390] In addition, the flexible secondary battery can be mounted on the inner or outer wall of a house or building, or on the inside or outside of a car. It is also possible to incorporate it along the curved surface of the interior or exterior of the vehicle.

[0391] FIG. 28A shows an example of a mobile phone. The mobile phone 7400 has a housing 7401. In addition to the display unit 7402 incorporated in the The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, etc. The secondary battery 7407 is a secondary battery of one embodiment of the present invention. This makes it possible to provide a lightweight, long-lasting mobile phone.

[0392] FIG. 28B shows the mobile phone 7400 in a bent state. When the entire device is deformed by an external force and curved, the secondary battery inside 7407 is also bent. At this time, the state of the bent secondary battery 7407 is shown in FIG. The secondary battery 7407 is a thin storage battery. The secondary battery 7407 is shown in the bent state. The secondary battery 7407 has a lead electrode electrically connected to the current collector. For example, the current collector is made of copper foil, and some of it is alloyed with gallium to form a layer in contact with the current collector. This improves the adhesion between the active material layer and the secondary battery 7407, resulting in a highly reliable structure when the secondary battery 7407 is bent. It has become a success.

[0393] FIG. 28(D) shows an example of a bangle-type display device. The portable display device 7100 includes: The device includes a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. 28(E) shows the state of the bent secondary battery 7104. The secondary battery 7104 is bent. When the device is worn on the user's arm with the device attached, the housing may deform and cause damage to part of the secondary battery 7104 or The total curvature changes. The degree of curvature at any point on the curve is expressed as the radius of the corresponding circle. The value expressed is called the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, the radius of curvature is The area is within the range of 40 mm to 150 mm, and the area is part of the main surface of the casing or the secondary battery 7104. The radius of curvature of the main surface of the secondary battery 7104 is 40 mm or more and 150 mm or less. If the thickness is within the range of 1 mm or less, high reliability can be maintained. By using the secondary battery of one embodiment, a lightweight, long-life portable display device can be provided.

[0394] FIG. 28(F) shows an example of a wristwatch-type portable information terminal. The portable information terminal 7200 is , a housing 7201, a display unit 7202, a band 7203, a buckle 7204, and an operation button 72 05, input / output terminal 7206, etc.

[0395] The portable information terminal 7200 is capable of carrying out mobile phone calls, e-mails, viewing and creating documents, playing music, and internet access. - It can run various applications such as internet communication and computer games. do.

[0396] The display surface of the display unit 7202 is curved, and the display is performed along the curved display surface. The display portion 7202 is provided with a touch sensor, and can be touched with a finger or a stylus. For example, the icon 72 displayed on the display unit 7202 can be operated by touching it. You can launch the application by touching 07.

[0397] The operation button 7205 is used to set the time, turn the power on and off, and turn wireless communication on and off. It has various functions such as operation, silent mode activation and deactivation, power saving mode activation and deactivation, etc. For example, an operating system installed in the portable information terminal 7200 can The function of the operation button 7205 can also be freely set using the stem.

[0398] In addition, the mobile information terminal 7200 is capable of performing standardized short-range wireless communication. For example, by communicating with a wireless headset, hands-free operation is possible. You can also make calls.

[0399] The portable information terminal 7200 also has an input / output terminal 7206, and can be connected to other information terminals via a connector. It is also possible to charge the battery via the input / output terminal 7206. The charging operation can be performed by wireless power supply without going through the input / output terminal 7206. That's fine.

[0400] The display portion 7202 of the portable information terminal 7200 includes the secondary battery of one embodiment of the present invention. By using the secondary battery of one embodiment of the present invention, a lightweight and long-life portable information terminal can be provided. For example, the secondary battery 7104 shown in FIG. 28(E) is curved inside the housing 7201. Alternatively, it can be incorporated in the band 7203 in a bendable state.

[0401] The mobile information terminal 7200 preferably has a sensor. For example, a fingerprint sensor may be used as the sensor. Human body sensors such as pulse sensors and body temperature sensors, as well as touch sensors, pressure sensors, and acceleration sensors It is preferable that a sensor, etc. be installed.

[0402] FIG. 28G shows an example of a wristband-type display device. The display device 7300 includes a display unit 7 304 and includes the secondary battery of one embodiment of the present invention. The display unit 7304 may be provided with a touch sensor, and may function as a portable information terminal. It is also possible.

[0403] The display surface of the display unit 7304 is curved, and images can be displayed along the curved display surface. The display device 7300 can also communicate with the display device 7300 by short-distance wireless communication according to a communication standard. The situation can be changed.

[0404] The display device 7300 also has an input / output terminal, and can directly exchange data with other information terminals via a connector. It is also possible to charge the device via the input / output terminals. The charging operation may be performed by wireless power supply without using the input / output terminals.

[0405] By using the secondary battery of one embodiment of the present invention as the secondary battery included in the display device 7300, This makes it possible to provide a display device with a long life at a low cost.

[0406] In addition, an example in which the secondary battery with good cycle characteristics shown in the above embodiment is mounted on an electronic device is shown in FIG. 28(H), 29 and 30.

[0407] By using the secondary battery of one embodiment of the present invention as a secondary battery in everyday electronic devices, the battery is lightweight and has a long life. For example, we can provide various products such as electric toothbrushes, electric shavers, and These include mobile beauty devices, and the secondary batteries for these products are designed to be easy for users to hold. Therefore, there is a demand for a small, lightweight, stick-shaped secondary battery with a large capacity.

[0408] FIG. 28(H) is a perspective view of a device also called a tobacco-containing smoking device (electronic cigarette). In 28(H), the electronic cigarette 7500 is an atomizer 7501 containing a heating element and an atomizer A secondary battery 7504 that supplies power to the MYZA, and a cart containing a liquid supply bottle, sensors, etc. To enhance safety, the secondary battery 7504 is protected from overcharging and overcharging. A protection circuit for preventing discharge may be electrically connected to the secondary battery 7504. The secondary battery 7504 has an external terminal so that it can be connected to a charging device. The 504 is the tip when held, so the total length is short and the weight is light. Since the secondary battery of one embodiment of the present invention has a high capacity and good cycle characteristics, We offer a compact and lightweight e-cigarette 7500 that can be used for long periods of time. Can be provided.

[0409] Next, Fig. 29(A) and Fig. 29(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIG. 29(A) and FIG. 29(B) includes a housing 9630 a, a housing 9630b, a movable part 9640 connecting the housings 9630a and 9630b, and a display A display unit 9631 having a display unit 9631a and a display unit 9631b, switches 9625 to The display unit 9631 has a switch 9627, a fastener 9629, and an operation switch 9628. By using a flexible panel, it is possible to create a tablet terminal with a larger display area. FIG. 29(A) shows a state in which the tablet terminal 9600 is opened, and FIG. B) shows the tablet terminal 9600 in a closed state.

[0410] The tablet terminal 9600 also includes a battery storage device inside the housing 9630a and the housing 9630b. The power storage unit 9635 is connected to the housing 9630a through the movable portion 9640. It is located across 9630b.

[0411] The entire or a part of the display portion 9631 can be used as a touch panel. By touching images, text, input forms, etc. containing icons displayed in the area, data For example, a keyboard is provided on the entire surface of the display portion 9631a of the housing 9630a. By displaying the button, information such as text and images can be displayed on the display unit 9631b on the housing 9630b. may be displayed and used.

[0412] In addition, a keyboard is displayed on the display unit 9631b on the housing 9630b side, and The display portion 9631a on the side may be used to display information such as text and images. The 9631 is set to display a keyboard display switch button on the touch panel, and the By touching the button with your finger or a stylus, the keyboard will be displayed on the display 9631. You may do so.

[0413] In addition, the touch panel area of ​​the display unit 9631a on the housing 9630a side and the touch panel area of ​​the display unit 9631b on the housing 9630b side Simultaneous touch inputs can also be made to the touch panel area of ​​the display portion 9631b.

[0414] In addition, switches 9625 to 9627 are used to operate the tablet terminal 9600. It is not only an interface for switching between various functions, but also an interface for switching between various functions. For example, at least one of the switches 9625 to 9627 may be One acts as a power on / off switch for the tablet device 9600. Also, for example, at least one of the switches 9625 to 9627 may be The ability to switch between horizontal and vertical display, or between black and white and color display In addition, for example, at least one of the switches 9625 to 9627 may have a function to At least one of the display portions 9631 may have a function of adjusting the brightness of the display portion 9631. The brightness of 1 is the external brightness detected by the light sensor built into the tablet terminal 9600 during use. It can be optimized according to the amount of light. Note that the tablet device has a light sensor. In addition, it also incorporates other detection devices such as gyro, acceleration sensor, etc. to detect tilt. It is also acceptable to do so.

[0415] In FIG. 29A, the display portion 9631a on the housing 9630a side and the display portion 9631b on the housing 9630b side are 9631a and 9631b have almost the same display area. The display area of ​​each of the 631b is not particularly limited, and one size may be different from the other. The display quality may be different, for example, one may have a higher resolution than the other. The display panel may also be capable of performing the above.

[0416] FIG. 29(B) shows the tablet terminal 9600 in a folded state. The terminal 9600 includes a housing 9630, a solar cell 9633, and a DC-DC converter 9636. The power storage unit 9635 includes a charge / discharge control circuit 9634 including a power storage device according to one embodiment of the present invention. A storage battery is used.

[0417] As mentioned above, the tablet terminal 9600 can be folded in half, so when not in use, The housing 9630a and the housing 9630b can be folded so that they overlap each other. By folding, the display portion 9631 can be protected, and therefore the durability of the tablet terminal 9600 can be improved. Furthermore, the power storage unit 9635 using the secondary battery of one embodiment of the present invention can improve the It has a large capacity and good cycle characteristics, making it a tablet that can be used for a long period of time. A portable terminal 9600 can be provided.

[0418] In addition, the tablet terminal 9600 shown in FIG. 29(A) and FIG. 29(B) , functions to display various information (still images, videos, text images, etc.), calendar, date or The function to display the time, etc. on the display, and the function to touch input or edit the information displayed on the display Touch input function, function to control processing by various software (programs), etc. can have:

[0419] The solar cell 9633 attached to the surface of the tablet terminal 9600 generates power. The solar cell 963 can be supplied to a panel, a display unit, a video signal processing unit, etc. 3 can be provided on one or both sides of the housing 9630, and the power storage unit 9635 can be efficiently charged. The power storage unit 9635 can be configured to use a lithium ion battery. This has the advantage of enabling miniaturization.

[0420] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 29(B) are shown in FIG. A block diagram is shown in FIG. 29(C). 5, DC-DC converter 9636, converter 9637, switches SW1 to SW3, table The display unit 9631 is shown, and the storage battery 9635, the DC-DC converter 9636, 29B. This corresponds to 34.

[0421] First, an example of operation when power is generated by the solar cell 9633 using external light will be described. The power generated by the solar cell is converted into a voltage for charging the storage battery 9635. The voltage is increased or decreased by a inverter 9636. When power is used from the 9633, switch SW1 is turned on and the converter 9637 The voltage is increased or decreased to the voltage required for the display unit 9631. When not displaying the display, turn SW1 off and SW2 on to charge the power storage unit 9635. The configuration may be such that electricity is supplied.

[0422] The solar cell 9633 is shown as an example of a power generating means, but is not particularly limited thereto. Power storage using other power generation methods such as piezoelectric elements and thermoelectric conversion elements For example, the power may be transmitted and received wirelessly (contactlessly). It is also possible to combine it with a contactless power transmission module that charges the battery, or other charging means. That's fine.

[0423] Another example of electronic equipment is shown in FIG. 30. In FIG. 30, a display device 8000 is a display device according to one embodiment of the present invention. 8 is an example of an electronic device using a secondary battery 8004 according to an embodiment. 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, and a speaker unit. The secondary battery 8004 according to one embodiment of the present invention includes a housing 8003 and a secondary battery 8004. The display device 8000 is provided inside a body 8001. The display device 8000 receives power from a commercial power source. Alternatively, the power stored in the secondary battery 8004 can be used. Even when power cannot be supplied from a commercial power source due to a power outage or the like, the present invention The display device 8000 can be used by using the secondary battery 8004 as an uninterruptible power supply. do.

[0424] The display unit 8002 includes a liquid crystal display device, an emitting device having a light emitting element such as an organic EL element in each pixel, and Device, electrophoretic display device, DMD (Digital Micromirror Device) ce), PDP (Plasma Display Panel), FED (Field A semiconductor display device such as a reflective LED (emission display) can be used.

[0425] In addition to TV broadcast reception, display devices are also used for personal computers and advertising displays. , including all display devices for displaying information.

[0426] In FIG. 30, a stationary lighting device 8100 includes a secondary battery 81 according to one embodiment of the present invention. 8101, a housing 8102, a light source 8103, and a light source 8104. 30, the secondary battery 8103 is mounted in the housing 81. 8101 and a light source 8102 are installed inside a ceiling 8104. However, the secondary battery 8103 may be provided inside the housing 8101. The device 8100 can receive power from a commercial power source or can store power in a secondary battery 8103. Therefore, if the power supply from the commercial power source is interrupted due to a power outage, etc., Even when the power is not available, the secondary battery 8103 according to one embodiment of the present invention can be used as an uninterruptible power supply. This allows the lighting device 8100 to be used.

[0427] 30 shows an example of a lighting device 8100 that is installed on a ceiling 8104. However, the secondary battery according to one embodiment of the present invention is not limited to the ceiling 8104, but may be installed on other parts such as the side wall 8105 and the floor 8106. 106, it can be used for a fixed lighting device provided in a window 8107, etc., or it can be used for a tabletop lighting device. It can also be used in lighting devices of this type.

[0428] The light source 8102 may be an artificial light source that artificially obtains light using electricity. Specifically, incandescent lamps, fluorescent lamps and other discharge lamps, and light-emitting devices such as LEDs and organic EL elements The element is an example of the artificial light source.

[0429] In FIG. 30, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is 8 is an example of an electronic device using a secondary battery 8203 according to one embodiment of the present invention. The device 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, and the like. 8 illustrates an example in which the secondary battery 8203 is provided in the indoor unit 8200. The battery 8203 may be provided in the outdoor unit 8204. The secondary battery 8203 may be provided in both the air conditioner and the power supply 8204. The power supply can be supplied from a commercial power source, or the power stored in the secondary battery 8203 can be used. In particular, both the indoor unit 8200 and the outdoor unit 8204 may be equipped with secondary batteries 82 If 03 is installed, when power cannot be supplied from the commercial power source due to a power outage, etc. In addition, by using the secondary battery 8203 of one embodiment of the present invention as an uninterruptible power supply, The conditioner can be used.

[0430] In Figure 30, a separate type air conditioner consisting of an indoor unit and an outdoor unit is shown. As an example, it is an all-in-one air conditioner that has the functions of both the indoor unit and the outdoor unit in a single housing. The secondary battery according to one embodiment of the present invention can also be used in the conditioner.

[0431] In FIG. 30, an electric refrigerator-freezer 8300 includes a secondary battery 8304 according to one embodiment of the present invention. Specifically, an electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator It has a storage compartment door 8302, a freezer compartment door 8303, a secondary battery 8304, etc. A secondary battery 8304 is provided inside the housing 8301. The electric refrigerator-freezer 8300 is It can receive power from a commercial power source, or use the power stored in the secondary battery 8304. Therefore, when power cannot be supplied from the commercial power source due to a power outage, etc. However, by using the secondary battery 8304 of one embodiment of the present invention as an uninterruptible power supply, It will be possible to use the 8300-capacity refrigerator.

[0432] Among the above-mentioned electronic devices, high-frequency heating devices such as microwave ovens and electric rice cookers are Equipment requires high power for a short period of time, so it supplements the power that cannot be supplied by commercial power. By using a secondary battery according to one embodiment of the present invention as an auxiliary power source for This prevents the commercial power breaker from tripping during use.

[0433] In addition, during times when electronic devices are not in use, especially when the total amount of power that can be supplied by the commercial power supplier is low, During the time period when the ratio of the amount of electricity actually used (called the electricity usage rate) is low, By storing power in the battery, it is possible to prevent power usage rates from increasing outside of the above time periods. For example, in the case of the electric refrigerator-freezer 8300, when the temperature is low and the refrigerator compartment door 830 2. During the night when the freezer door 8303 is not opened or closed, the secondary battery 8304 stores power. Then, as the temperature rises, the refrigerator door 8302 and the freezer door 8303 are opened and closed. By using the secondary battery 8304 as an auxiliary power source during the daytime, the daytime power usage rate can be kept low.

[0434] According to one embodiment of the present invention, the cycle characteristics of the secondary battery are improved, and the reliability is improved. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be obtained. This improves the characteristics of the secondary battery, thereby making it possible to reduce the size and weight of the secondary battery itself. Therefore, the secondary battery according to one embodiment of the present invention can be used in the electronic devices described in this embodiment. By incorporating such a device, electronic devices can be made lighter and have a longer lifespan.

[0435] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0436] (Embodiment 8) In this embodiment, examples of electronic devices using the secondary battery described in the previous embodiment are shown. 31 to 32.

[0437] FIG. 31(A) shows an example of a wearable device. It uses a secondary battery as a power source. In addition, when the user uses it at home or outdoors, To improve splash, water or dust resistance, the connectors are exposed. There is a demand for wearable devices that can be charged wirelessly as well as by wire.

[0438] For example, a secondary lens according to one aspect of the present invention is applied to a glasses-type device 4000 as shown in FIG. 31(A). The eyeglass-type device 4000 includes a frame 4000a and a display. The secondary battery is mounted on the temple of the curved frame 4000a. This allows for a lightweight, well-balanced eyeglass-type device that can be used continuously for a long time. By including the secondary battery according to one embodiment of the present invention, the size of the housing can be reduced. It is possible to realize a configuration that can accommodate space saving associated with molding.

[0439] In addition, the headset device 4001 may be equipped with a secondary battery according to one embodiment of the present invention. The headset type device 4001 includes at least a microphone unit 4001a and a frame. The flexible pipe 4001b and the earphone part 4001c are included. A secondary battery can be provided in the earphone unit 4001b or the earphone unit 4001c. By using a variety of secondary batteries, the structure can be adapted to space saving due to the miniaturization of the housing. It can be realized.

[0440] In addition, a device 4002 that can be directly attached to the body is equipped with a secondary battery according to one embodiment of the present invention. The device 4002 can be mounted with a secondary battery 400 in a thin housing 4002a. By providing the secondary battery according to one embodiment of the present invention, the housing can be made smaller. It is possible to realize a configuration that can accommodate space-saving requirements that accompany the increase in the number of devices.

[0441] In addition, a device 4003 that can be attached to clothing is equipped with a secondary battery according to one embodiment of the present invention. The device 4003 has a thin housing 4003a and a secondary battery 4003b. By providing the secondary battery according to one embodiment of the present invention, the housing can be made smaller. It is possible to realize a configuration that can accommodate the space-saving that accompanies this.

[0442] In addition, the belt-type device 4006 can be equipped with a secondary battery according to one embodiment of the present invention. The belt-type device 4006 includes a belt part 4006a and a wireless power receiving part 4006b. 06b, and a secondary battery can be mounted inside the belt portion 4006a. By providing a secondary battery, which is one aspect of the above, it is possible to save space due to the miniaturization of the housing. The configuration can be realized.

[0443] In addition, the secondary battery of one embodiment of the present invention can be mounted on the wristwatch device 4005. The wristwatch type device 4005 has a display part 4005a and a belt part 4005b. A secondary battery can be provided in the display part 4005a or the belt part 4005b. By providing a secondary battery as one aspect, the structure can accommodate space saving due to the miniaturization of the housing. This makes it possible to achieve this.

[0444] The display unit 4005a displays not only the time but also various information such as incoming emails and phone calls. It is possible.

[0445] The wristwatch type device 4005 is a wearable device that can be worn directly on the wrist. Therefore, sensors for measuring the user's pulse, blood pressure, etc. may be installed. It is also possible to accumulate health-related data and manage health.

[0446] FIG. 31(B) shows a perspective view of the wristwatch type device 4005 removed from the wrist.

[0447] A side view is shown in Fig. 31(C). Fig. 31(C) shows a device with a built-in secondary battery 913. The secondary battery 913 is the secondary battery shown in the fifth embodiment. The battery 913 is provided in a position overlapping the display unit 4005a, and is small and lightweight. .

[0448] FIG. 32(A) shows an example of a cleaning robot. The cleaning robot 6300 is a housing 63 01 A display unit 6302 arranged on the top surface, multiple cameras 6303 arranged on the side, and a brush 6304, operation buttons 6305, a secondary battery 6306, various sensors, etc. Although not shown, the cleaning robot 6300 is equipped with tires, a suction nozzle, etc. The robot 6300 moves by itself, detects the debris 6310, and ejects it from the suction port on the bottom. It can suck up mi.

[0449] For example, the cleaning robot 6300 analyzes the image captured by the camera 6303 and detects the walls, furniture, etc. It can also determine whether there are obstacles such as steps or wiring by image analysis. If an object that may become entangled in the brush 6304 is detected, the rotation of the brush 6304 is stopped. The cleaning robot 6300 includes a secondary battery 630 according to one embodiment of the present invention. 6 and a semiconductor device or electronic component. By using it in the cleaning robot 6300, the cleaning robot 6300 can be operated for a long time and with high reliability. It can be a simple electronic device.

[0450] Figure 32(B) shows an example of a robot. The robot 6400 shown in Figure 32(B) is , secondary battery 6409, illuminance sensor 6401, microphone 6402, upper camera 640 3, a speaker 6404, a display unit 6405, a lower camera 6406, and an obstacle sensor 640 7, equipped with a moving mechanism 6408, a computing device, etc.

[0451] The microphone 6402 has a function of detecting the user's voice and environmental sounds. The speaker 6404 has a function of emitting sound. The device can communicate with the user using the microphone 6402 and the speaker 6404. It is possible.

[0452] The display unit 6405 has a function of displaying various information. The display unit 6405 can display desired information. The display unit 6405 may be a detachable information terminal. By placing it in a fixed position on the Robot 6400, charging and data transfer can be performed. It is possible.

[0453] The upper camera 6403 and the lower camera 6406 are used to capture images of the surroundings of the robot 6400. The obstacle sensor 6407 also detects the obstacles in the robot 640 by using the movement mechanism 6408. Robot 64 can sense whether there are any obstacles in its path as it moves forward. 00 uses an upper camera 6403, a lower camera 6406, and an obstacle sensor 6407 It is possible to recognize the surrounding environment and move safely.

[0454] The robot 6400 includes a secondary battery 6409 according to one embodiment of the present invention and a semiconductor device. The secondary battery according to one embodiment of the present invention can be used in a robot 6400. This allows the robot 6400 to be an electronic device with a long operating time and high reliability.

[0455] FIG. 32(C) shows an example of an aircraft. The aircraft 6500 shown in FIG. 32(C) is a plane It has a lopeller 6501, a camera 6502, and a secondary battery 6503, and flies autonomously. It has the function of

[0456] For example, image data captured by the camera 6502 is stored in the electronic component 6504. Part 6504 can analyze image data and detect the presence or absence of obstacles when moving. In addition, the electronic component 6504 can detect the change in the storage capacity of the secondary battery 6503. The remaining amount of the battery can be estimated. The secondary battery 6503 is provided. This allows the Air Vehicle 6500 to be an electronic device with a long operating time and high reliability.

[0457] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0458] (Embodiment 9) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle will be described.

[0459] When a secondary battery is installed in a vehicle, it becomes a hybrid vehicle (HEV), an electric vehicle (EV), or It will be possible to realize next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). do.

[0460] FIG. 33 illustrates a vehicle using a secondary battery according to one embodiment of the present invention. The automobile 8400 shown in FIG. 1 is an electric automobile that uses an electric motor as a power source for driving. Alternatively, an electric motor and an engine can be selected as the power source for driving. By using one aspect of the present invention, it is possible to improve the driving range of a hybrid vehicle. A long vehicle can be realized. The automobile 8400 also has a secondary battery. 18(C) and 18(D) are mounted on the floor of the vehicle. In addition, a battery pack consisting of multiple secondary batteries as shown in FIG. The battery may be installed on the floor of the vehicle. In addition, it also supplies power to light-emitting devices such as headlights 8401 and room lights (not shown). can be supplied.

[0461] In addition, the secondary battery is used for the displays of the car 8400, such as the speedometer and tachometer. The secondary battery can supply power to the navigation system of the automobile 8400. The power supply can be used to power semiconductor devices such as gating systems.

[0462] The automobile 8500 shown in FIG. 33(B) has a plug-in secondary battery. It can be charged by receiving power from an external charging facility using a method such as contactless power supply. FIG. 33(B) shows a case where a charging device 8021 is installed on a ground and a charging device 8022 is installed on a vehicle 8500. The secondary battery 8024 is shown being charged via a cable 8022. The charging method and connector specifications are specified by CHAdeMO (registered trademark) and Combo. The charging device 8021 is a charging station installed in a commercial facility. For example, plug-in technology can be used to The secondary battery 8024 installed in the automobile 8500 can be charged by the power supply. Charging is performed by converting AC power to DC power via a converter such as an AC-DC converter. It is possible.

[0463] Although not shown, a power receiving device is mounted on the vehicle, and power is supplied contactlessly from a power transmitting device on the ground. In this case, the power transmission device is installed on the road or on the exterior wall. By incorporating this, charging can be done not only when the vehicle is stopped but also while the vehicle is moving. The vehicle may transmit and receive power between them using the same method. A solar cell may be provided in the vehicle so that the secondary battery can be charged when the vehicle is stopped or running. To supply power in the above, an electromagnetic induction method or a magnetic field resonance method can be used.

[0464] 33C shows an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. The scooter 8600 shown in FIG. 3(C) includes a secondary battery 8602, side mirrors 8601, and a directional indicator. The secondary battery 8602 supplies electricity to the direction indicator light 8603. can be done.

[0465] In addition, the scooter 8600 shown in FIG. 33(C) has a secondary battery 86 in the storage space under the seat 8604. The secondary battery 8602 can be stored in the under-seat storage 8604, which is small. The secondary battery 8602 can be stored in the under-seat storage 8604. When charging, the secondary battery 8602 is brought indoors, charged, and then stored away before driving. Just pay it.

[0466] According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery is increased. Therefore, the secondary battery itself can be made smaller and lighter. If the battery itself can be made smaller and lighter, it will contribute to reducing the vehicle's weight, which will improve the cruising range. In addition, the secondary battery installed in the vehicle can be used as a power supply source for other purposes. In this case, for example, it is possible to avoid using commercial power sources during peak power demand periods. If we can avoid using commercial power sources during peak power demand periods, we can save energy and This can contribute to reducing carbon dioxide emissions. Since the secondary battery can be used for a long period of time, the amount of rare metals used, including cobalt, can be reduced. It is possible.

[0467] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0468] In this example, the positive electrode active material described in the first embodiment was prepared, its characteristics were analyzed, and its properties were evaluated. It was worth it.

[0469] <Preparation and analysis of positive electrode active material> The sample produced in this example will be described with reference to the production method shown in FIG.

[0470] As a positive electrode active material containing cobalt as the transition metal M and no particular impurities, commercially available cobalt Lithium phosphate (Cellseed C-10N, manufactured by Nippon Chemical Industry Co., Ltd.) was used. The sample was designated as Sample 1 (Comparative Example).

[0471] Titanium oxide was added to Sample 1 by the sol-gel method in the same manner as in steps S42 to S44 of FIG. When the number of cobalt atoms in sample 1 is taken as 100, the number of titanium atoms is TTIP was added so that the pH became 0.5. Then, heating was carried out in the same manner as in step S45. The thermal conditions were 850°C, 2 hours, and oxygen atmosphere (flow rate 10 L / min). A positive electrode active material containing cobalt as the metal M and titanium as an impurity was designated as Sample 2. Ta.

[0472] Sample 1 is subjected to the solid phase method in the same manner as steps S11 to S14 and step S31 of FIG. Lithium fluoride and magnesium fluoride were added at 100. When the number of molecules of lithium fluoride is 0.17, the number of molecules of magnesium fluoride is 0.5. Then, heating was carried out in the same manner as in step S34. The raw materials were placed in the container and the lid was placed on top. The heating conditions were 850°C and 60 hours. A positive electrode active material having cobalt as group M and magnesium and fluorine as impurities This was designated as sample 3.

[0473] Sample 1 is subjected to the solid phase method in the same manner as steps S11 to S14 and step S31 of FIG. Lithium fluoride and magnesium fluoride were added at 100. When the number of molecules of lithium fluoride is 0.17, the number of molecules of magnesium fluoride is 0.5. Then, the mixture was heated in the same manner as in step S34. The heating conditions were 900°C, 20 Next, steps S42 to S44 were performed in an oxygen atmosphere (flow rate of 10 L / min). Titanium oxide was added by the sol-gel method in the same way as in 4. The amount of titanium added and the heating conditions were the same as in the sample. The transition metal M is cobalt, and the impurity is magnesium. The positive electrode active material containing aluminum, fluorine, and titanium was designated as Sample 4.

[0474] Sample 1 is subjected to steps S11 to S20 and step S31 in FIG. In the solid phase method, lithium fluoride, magnesium fluoride, nickel hydroxide and aluminum hydroxide When the number of cobalt atoms is 100, the number of lithium fluoride molecules is 0. .33, the number of molecules of magnesium fluoride is 1, the number of atoms of nickel is 0.5, and the number of atoms of aluminum is The number of atoms was 0.5. Then, heating was performed in the same manner as in step S34. Heating conditions The conditions were 900°C for 10 hours, and after heating, the particles were broken down by hitting them with a pestle. The process of breaking down the adhesion was repeated three times. and a positive electrode active material containing magnesium, fluorine, and aluminum as impurities. Sample 5 was selected.

[0475] Titanium oxide was added to sample 5 by the sol-gel method in the same manner as in steps S42 to S44. The amount of titanium added and the heating conditions were the same as those for Sample 2. Cobalt and nickel are the main components, and magnesium, fluorine, aluminum are the impurities. The positive electrode active material containing aluminum and titanium was designated as Sample 6.

[0476] The manufacturing conditions for Samples 1 to 6 are shown in Table 1.

[0477] [Table 1]

[0478] FIG. 34(A) is a surface SEM image of Sample 2. As shown in FIG. 34(A), the positive electrode active material It was observed that the material had depressions that appeared to be cracks. The results of linear EDX analysis of the linear portion of Figure 34(B) are shown in Figure 34(C). ) shown.

[0479] As shown in Figure 34(C), it was confirmed that the titanium concentration in the recessed portion was higher than in other regions. In other words, it was confirmed that titanium was present on part of the inner wall of the recess. Therefore, it is assumed that titanium oxide is embedded in the recesses.

[0480] Cobalt was detected uniformly in all areas of the positive electrode active material. Oxygen was slightly reduced in the recesses. It was detected slightly, but more or less uniformly from other parts.

[0481] Figure 35(A) is a cross-sectional STEM image of Sample 2. The area enclosed by the white dotted line in Figure 35(A) is enlarged. The larger image is shown in Figure 35(B). The protective film 1001 is made of C and Pt and is formed for the purpose of the positive electrode active material 1000. The EDX mapping image of the layer area, enclosed by the white dotted square in Figure 35(B), is shown in Figure 36(A). 36(A) shows oxygen, 36(B) shows cobalt, and 36(C) shows titanium. This is a mapping image for the

[0482] Oxygen and cobalt were uniformly distributed throughout the surface and interior of the positive electrode active material. Titanium is embedded in the recesses as shown by the white dotted circles in Figures 36(C) and 35(B). It was observed that the particles existed as if they were particles.

[0483] Thus, it is believed that titanium oxide was selectively deposited in the recesses.

[0484] From the above results, it can be seen that sample 2 has the recess 101c and the embedded portion 102, and the embedded portion It was shown that the positive electrode active material 101 had a higher titanium concentration in the surface layer 102 than in the surface layer 101.

[0485] FIG. 37(A) is a surface SEM image of Sample 4. As indicated by the arrows, the positive electrode has a protruding portion. The cross-sectional STEM image of the white dotted line area in Figure 37(A) is shown in Figure 37(B). Figure 37(C) shows an enlarged cross-sectional STEM image of the convex portion enclosed by the white dotted line in Figure 37(B). show.

[0486] The EDX mapping images of the white dotted square area in Figure 37(C) are shown in Figures 38(A) to 38(C). E). Figure 38(A) shows oxygen, Figure 38(B) shows fluorine, and Figure 38(C) shows magnesium. 38(D) is a mapping image for titanium, and FIG. 38(E) is a mapping image for cobalt. In EDX, fluorine has a peak close to that of cobalt, so the detection accuracy is low. In this example, the internal fluorine is at background level.

[0487] From FIG. 38(B), the convex part has a fluorine concentration different from the background, It was confirmed that the fluorine concentration in the high fluorine concentration region is higher than that in the high impurity metal concentration region. was higher than the area.

[0488] Also, from Figures 38(C) and 38(D), the convex parts have the internal concentrations of magnesium and titanium. It was confirmed that the impurity metal high concentration region is higher than the fluorine high concentration region. In this way, it was confirmed that the convex portion has a high fluorine concentration region and a high impurity metal concentration region. The excess magnesium and titanium in the positive electrode active material are trapped in the high impurity metal concentration region. In addition, since the high fluorine concentration region exists near the center of the convex part, Therefore, it was suggested that the presence of high fluorine concentration regions may be the trigger for the aggregation of impurities. .

[0489] Furthermore, oxygen and cobalt were uniformly present inside and on the surface of the positive electrode active material. In addition, oxygen, magnesium, and titanium are uniformly distributed in the convex portions excluding the high fluorine concentration regions. It existed.

[0490] Figure 39(A) is an SEM image of the surface of Sample 6. As indicated by the arrows, there are many protrusions. The cross-sectional STEM image of the white dotted line in Figure 39(A) is shown in Figure 39(B). ) is shown in Figure 39(B). A cross-sectional STEM image of the convex portion enclosed by the white dotted line in Figure 39(B) is enlarged. C).

[0491] The EDX mapping images of the white dotted square area in Figure 39(C) are shown in Figures 40(A) to 40(C). G). Figure 40(A) shows oxygen, Figure 40(B) shows fluorine, and Figure 40(C) shows magnesium. ,Fig. 40(D) ​​is titanium, Fig. 40(E) is nickel, Fig. 40(F) is aluminum, Fig. 4 0(G) is a mapping image for cobalt.

[0492] From Fig. 40(A) to Fig. 40(G), the convex portion has a fluorine concentration in the surface layer, the interior, and the impurity metal. It was confirmed that the high fluorine concentration region was higher than the high concentration region. The concentrations of sodium, titanium, and nickel are higher than those in the surface, inner, and fluorine-rich regions. It was confirmed that the silicon dioxide had a high concentration region of impurity metals.

[0493] The nickel mapping image in Figure 40(E) shows that there are high concentrations of nickel in the surface and some parts of the interior. It was confirmed that there exists a region where excess magnesium, titanium and It is presumed that nickel and nickel are agglomerated in the high concentration impurity metal region. Ni is attracted from the inner portion 101b to the high concentration region of impurity metals. It was suggested that the high nickel concentration areas may be traces of this.

[0494] On the other hand, the aluminum concentration in the surface layer was higher than in the interior or protruding parts. It was confirmed that the pure metal did not aggregate in the high concentration region, but remained in the surface layer.

[0495] FIG. 41(A) shows a micro-electron diffraction image of the convex portion of Sample 6. This shows the cubic

[0110] Therefore, the convex part has a spinel or rock salt crystal structure. It was estimated that. Figure 41(B) shows the micro-electron diffraction image of the inside of Sample 6. Therefore, it was speculated that the interior has a layered rock salt type crystal structure.

[0496] No concave or convex portions were observed in Samples 1, 3, and 5. .

[0497] <Production and evaluation of secondary batteries> Secondary batteries were fabricated using the positive electrode active materials of Samples 1 to 6. The positive electrode active materials of Sample 6, AB and PVDF were mixed at a ratio of active material:AB:PVDF=95:3 :2 (by weight) to prepare a slurry, which was then applied to an aluminum current collector. NMP was used as the solvent for the slurry.

[0498] After the slurry was applied to the current collector, the solvent was evaporated and then a pressure of 210 kN / m was applied. After that, a pressure of 1467 kN / m was applied. Through the above steps, a positive electrode was obtained. The loading amount is approximately 7 mg / cm 2 The density was 3.8 g / cc or more.

[0499] The positive electrode was used to make a CR2032 type coin-shaped battery (diameter 20 mm, height 3.2 mm). We produced a battery cell of

[0500] The counter electrode was made of lithium metal.

[0501] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), and vinylene carbonate (VC) was added to the mixture. The material containing 100% by weight of Zn was used.

[0502] The separator was made of polypropylene with a thickness of 25 μm.

[0503] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0504] The charge-discharge cycle characteristics of the secondary batteries of Samples 1 and 2 are shown in Figure 42. The charge-discharge cycle characteristics of the secondary batteries of Sample 5 and Sample 6 are shown in Fig. 43. The charge-discharge cycle characteristics of the secondary battery are shown in Figure 44. All measurements were taken at 45°C. / CV (0.5C, 4.6V, 0.05C cut), discharge is CC (0.5C, 2.5V ut), and a 10-minute rest period was provided before the next charge. 00mA / g.

[0505] Samples 3 to 6, which contain magnesium and fluorine as impurities, were heated at 45°C and Despite the relatively high temperature, good cycle characteristics were observed.

[0506] Samples 2 and 4 have concave or convex portions as regions where impurities are unevenly distributed. In all cases, Sample 6 had a higher discharge capacity than samples without these elements under the same conditions. For example, the discharge capacity of sample 1 was 215.5 mAh / g, while that of sample The discharge capacity of sample 2 was 221.1 mAh / g. The discharge capacity of sample 3 was 228.9 mAh / g. h / g, whereas the discharge capacity of Sample 4 was 232.7 mAh / g. The discharge capacity of sample 5 was 221.5 mAh / g, while that of sample 6 was 2 The energy density was 27.2mAh / g.

[0507] In Samples 2, 4, and 6, which contain titanium as an impurity, the positive electrode active material The surface of the cathode has titanium oxide, and the presence of titanium oxide allows the cathode active material to This is thought to have improved the wettability at the interface between the two materials. It is thought that this facilitates desolvation and reduces the resistance of the secondary battery.

[0508] In sample 2, the presence of regions where impurities are unevenly distributed prevents dissolution of transition metals from cracks. It is believed that the discharge capacity increased as a result of suppressing the breakdown of the crystal structure and cracking of the internal 101b. In addition, in Samples 4 and 6, the presence of regions where impurities are unevenly distributed resulted in , excess impurities such as magnesium are removed from the inner portion 101b, and the inner portion 101b is The impurity concentration was appropriate. Therefore, when used as a secondary battery, the resistance was suppressed and the discharge capacity was increased. was thought to have increased. [Example]

[0509] In this example, a positive electrode active material was produced using the method described in the second embodiment, and its characteristics were analyzed. The properties were evaluated.

[0510] <Preparation and analysis of positive electrode active material> The sample produced in this example will be described with reference to the production method shown in FIGS. 9 and 10. Reveal.

[0511] As a positive electrode active material containing cobalt as the transition metal M and not containing any impurities, The same sample 1 (comparative example) was prepared.

[0512] Sample 1 is fixed in the same manner as steps S11 to S20 and step S25 of FIG. In the phase method, lithium fluoride, magnesium fluoride, nickel hydroxide and aluminum hydroxide When the number of cobalt atoms is 100, the number of lithium fluoride molecules is 0.3. 3. The number of magnesium fluoride molecules is 1, the number of nickel atoms is 0.5, and the number of aluminum atoms is The number was added to 0.5. Then, heating was performed in the same manner as in step S34. The heating conditions were The temperature was 850°C for 60 hours. , a sample of a positive electrode active material containing magnesium, fluorine, and aluminum as impurities was used. I chose 11.

[0513] As in steps S11 to S14 and step S26 of FIG. 10, the solid phase method Lithium fluoride was added to the composite oxide containing the pure substance. The impurities used were titanium, aluminum, and magnesium. When the number of cobalt atoms in the composite oxide containing The mixture was added so that the concentration became 0.17. Then, the mixture was heated in the same manner as in step S34. The heating conditions were 8 The temperature was 50°C for 20 hours. A positive electrode active material containing magnesium, fluorine, aluminum, and titanium was used as sample 12. Ta.

[0514] When the number of cobalt atoms in the composite oxide containing impurities is 100, the number of lithium fluoride atoms is The positive electrode active material was prepared in the same manner as Sample 12, except that the number of molecules was 1.17. This was designated sample 13.

[0515] When the number of cobalt atoms in the composite oxide containing impurities is 100, the number of lithium fluoride atoms is The positive electrode active material was prepared in the same manner as Sample 12, except that the number of molecules was 2.33. This was designated sample 14.

[0516] As in steps S11 to S14 and step S26 of FIG. 10, the solid phase method Lithium fluoride and magnesium fluoride were added to the composite oxide containing the pure material. The composite oxides containing titanium, aluminum, and magnesium as impurities are When the number of cobalt atoms in the composite oxide containing impurities is taken as 100, The number of molecules of lithium fluoride is 0.17 and the number of molecules of magnesium fluoride is 0.5. Then, heating was performed in the same manner as in step S34. The heating conditions were 900°C, 10 hours, and acid. The atmosphere was nitrogen (flow rate: 10 L / min). The cathode active material containing magnesium, fluorine, aluminum, and titanium as pure substances was prepared. The pull was 15.

[0517] As in steps S11 to S20 and step S26 of FIG. 10, the solid phase method The composite oxide containing pure material is treated with lithium fluoride, magnesium fluoride, nickel hydroxide and water. Aluminum oxide was added. The composite oxide containing impurities was titanium, The composite oxide containing aluminum and magnesium was used. When the number of cobalt atoms is 100, the number of lithium fluoride molecules is 0.33, and the number of mag fluoride molecules is 0.33. The number of atoms of nesium is 1, the number of atoms of nickel is 0.5, and the number of atoms of aluminum is 0.5. Then, heating was carried out in the same manner as in step S34. The heating conditions were 900°C, 10 In this way, the transition metals M are cobalt and nickel, and the impurities are The positive electrode active material containing magnesium, fluorine, aluminum, and titanium was designated as Sample 16. did.

[0518] The positive electrode active material was prepared in the same manner as Sample 13 except that the heating time was set to 2 hours. did.

[0519] Sample 18 was prepared using a positive electrode active material prepared in the same manner as Sample 13, except that the heating time was set to 60 hours. It was decided.

[0520] In addition to lithium fluoride, nickel hydroxide and aluminum hydroxide are added to the composite oxide containing impurities. A positive electrode active material was prepared in the same manner as in Sample 13 except that ammonium was added, and designated Sample 19. When the number of cobalt atoms in the composite oxide containing impurities is taken as 100, the number of nickel atoms is The number of atoms of ZnO was 0.5 and the number of atoms of aluminum was 0.5.

[0521] Table 2 shows the preparation conditions for Sample 1 and Samples 11 to 19.

[0522] [Table 2]

[0523] Figure 45 is an SEM image of the surface of Sample 13. No cracks were observed, and the surface had little unevenness. It was confirmed that the shape was smooth.

[0524] Figure 46(A) is a surface SEM image of another part of Sample 13. (G) is an EDX mapping image of the same area as in Figure 46(A). ,Figure 46(C) is titanium, Figure 46(D) is oxygen, Figure 46(E) is magnesium, Figure 46( Figure 46(F) is a mapping image for carbon, and Figure 46(G) is a mapping image for aluminum.

[0525] From Fig. 46(B) to Fig. 46(G), it can be seen that Sample 13 is made of titanium, magnesium, and aluminum. It was confirmed that the positive electrode active material has an area where titanium and magnesium are unevenly distributed. The areas where the rheology was unevenly distributed partially overlapped.

[0526] Figure 47(A) is an SEM image of the surface of Sample 19. Here too, no cracks were observed, and no depressions were observed. It was confirmed that the shape was smooth with few protrusions.

[0527] Figures 47(B) to (H) are SEM-EDX mapping images of the same area as Figure 47(A). Figure 47(B) is nickel, Figure 47(C) is cobalt, Figure 47(D) is titanium, Figure 47( E) is oxygen, Figure 47(F) is magnesium, Figure 47(G) is carbon, Figure 47(H) is aluminum The nickel in Figure 47(B) is at the background level. The carbon was used in the conductive tape used to fix the sample, and this was not detected. Although not shown, fluorine was at background levels.

[0528] As shown in Figures 47(B) to 47(H), cobalt and oxygen are present in almost all regions. On the other hand, titanium, magnesium, and aluminum were detected unevenly. Titanium and magnesium are present in the same region, while aluminum Thus, sample 19 also contains titanium, magnesium, and aluminum. It was confirmed that the positive electrode active material had a region where aluminum was unevenly distributed.

[0529] In addition, sample 19 was prepared by adding nickel hydroxide in the same manner as in steps S13 to S17. Although the nickel concentration is at background level in SEM-EDX, Nickel was dissolved in the interior 101b of the positive electrode active material 101 more easily than other impurity elements. It was assumed to be easy.

[0530] <Preparation of secondary battery> The positive electrode active materials of Samples 1, 11, and 18 prepared above were used to carry out the experiments. A secondary battery was fabricated in the same manner as in Example 1, except that no pressure was applied in the process of fabricating the positive electrode. The amount of support on the positive electrode is 20 mg / cm 2 More than 21mg / cm 2 The following is the result.

[0531] <Crystal structure after charging> Crystal structure after charging for secondary batteries of Samples 11, 13, and 15 The results were analyzed by XRD. First, a single charge / discharge was performed to confirm the capacity. The charge was CC / CV ( 0.2C, 4.5V, 0.05C cut), discharge is CC (0.2C, 3.0V cut) Next, the cells were charged at 4.50 V, 4.55 V, or 4.6 V to analyze the structure after charging. Charging was performed in CC / CV (0.2C, each voltage, 0.02C cut). The charge / discharge and XRD measurements were performed at 1C of 191mA / g. The measurement was carried out at 25°C.

[0532] The charge capacities for post-charge structural analysis are shown in Table 3.

[0533] [Table 3]

[0534] Then, the charged secondary battery was disassembled in an argon atmosphere glove box to remove the positive electrode. The electrode was then washed with DMC (dimethyl carbonate) to remove the electrolyte. The analysis was carried out by powder XRD using a single beam. The XRD equipment was a Bruker D8 Advance. The sample height was set to the measurement surface required by the instrument. The sample was set flat without being curved.

[0535] Figure 48 shows the powder XRD patterns of Samples 11, 13, and 15 after charging. The pattern enlarged around 2θ=20° is shown in Figure 49(A), and the pattern enlarged around 2θ=38° is shown in Figure 49(B). The pattern is shown in Figure 49(B), the enlarged pattern around 2θ=45° is shown in Figure 50(A), and An enlarged pattern around θ=61° is shown in Figure 50(B). For comparison, pseudospinel and H1 The XRD patterns of Cr-3 and CoO2 are also shown.

[0536] Samples 11 and 13 charged at 4.6 V have a pseudospinel crystal structure. It was also confirmed that the peak was sharp, suggesting high crystallinity.

[0537] The lattice constant of sample 11 calculated from these XRD patterns at 4.6 V is The lattice constant of sample 13 was 2.818 Å for the a-axis and 13.79 Å for the c-axis. The a-axis was 2.816 Å and the b-axis was 13.74 Å. -10 m.

[0538] Sample 15, charged at 4.6 V, has a different crystal structure from pseudospinel and H1-3. The main peaks in sample 15 were at 2θ of 19.27°, 37.37°, and 45.11°. , occurred around 66.37° and 69.64°.

[0539] <Cycle characteristics> FIG. 51(A) is a graph showing the cycle characteristics of Sample 1, Sample 11 to Sample 14. Figure 51(B) shows the sizes of Sample 1, Sample 11, Sample 15 and Sample 16. Figure 52 shows the characteristics of Sample 1, Sample 11, Sample 13, and Sample 53(A) and (B) are graphs of the cycle characteristics of Samples 17 and 18. 1 is a graph showing the cycle characteristics of Sample 1, Sample 13, and Sample 19.

[0540] All measurements were taken at 45°C. Charging was performed with CC / CV (0.5C, 4.6V, 0.05C cut ) and discharge was CC (0.5C, 2.5V cut). In the measurement, 1C was set to 200mA / g.

[0541] As shown in FIG. 51(A), the titanium and magnesium content is higher than that of Sample 1, which does not contain any impurities. Samples 11 to 14, which contain impurities such as fluorine and ammonium, have extremely good chromaticity. Sample 14 was tested 28 times due to a defect caused by the secondary battery manufacturing process. Although the cycle characteristics can only be evaluated up to this point, good characteristics were observed before the failure occurred.

[0542] The number of lithium fluoride molecules when the number of cobalt atoms is 100 is 0.17 to 2.33. All of Samples 12 to 14, in which the temperature was changed up to 100°C, exhibited good cycle characteristics. Sample 13, in which the value was 1.17, showed the best characteristics.

[0543] As shown in FIG. 51(B), the magnesium and fluorine contents were higher than those of Sample 1, which did not contain any impurities. Samples 15 and 16, which contain impurities such as fluorine, show better cycle characteristics. did.

[0544] As shown in FIG. 52, the titanium, magnesium, and Samples 11, 13, and 17 contain impurities such as aluminum and fluorine. Sample 18 and Sample 20 showed better cycle characteristics.

[0545] Samples 13, 17, and 1 were heated for a period ranging from 2 to 60 hours. All of the samples 8 had good cycle characteristics. 13 showed the best characteristics.

[0546] Figure 53(A) is a graph of the discharge capacity, and Figure 53(B) is a graph of the discharge capacity retention rate. Sample 1 containing impurities such as titanium, magnesium, and fluorine is more Samples 13 and 19 showed better cycle characteristics. Sample 19, to which the Kel source and aluminum source were added, showed the best characteristics.

[0547] The initial discharge capacity of sample 1 was 215.5 mAh / g, while that of sample 13 was 226.6mAh / g, and sample 19 was 226.5mAh / g. After 30 cycles The discharge capacity retention rate of Sample 1 was 61.3%, while that of Sample 13 was 91. 3%, and sample 19 was 93.9%. [Explanation of symbols]

[0548] 101 Cathode active material 101a Surface layer 101b internal 101c Recess 101d High nickel concentration region 102 Embedded part 103 Convex part 103a High fluoride concentration region 103b High metal impurity concentration region 1000 Cathode active material 1001 protective film

Claims

1. A positive electrode active material having particles containing cobalt, oxygen, lithium, magnesium, titanium, nickel, aluminum, and fluorine, the particle has a surface layer portion, an interior portion, and a protrusion portion on the surface layer portion, the protrusion has a first region in which the concentration of fluorine is higher than the concentration of fluorine in the surface layer portion, the protrusion has a second region in which the magnesium concentration is higher than the magnesium concentration in the surface layer portion and the first region, the concentration of fluorine in the first region is higher than the concentration of fluorine in the second region; the second region has a higher titanium concentration than the surface layer portion and the first region; the second region has a higher nickel concentration than the surface layer portion and the first region; the surface layer portion has a third region in which the aluminum concentration is higher than the aluminum concentration in the protruding portion.

2. A positive electrode active material having particles containing cobalt, oxygen, lithium, magnesium, titanium, nickel, aluminum, and fluorine, the particle has a surface layer portion, an interior portion, and a protrusion portion on the surface layer portion, the protrusion has a first region in which the concentration of fluorine is higher than the concentrations of fluorine in the surface layer portion and the interior portion, the protrusion has a second region in which the magnesium concentration is higher than the magnesium concentrations in the surface layer portion, the interior, and the first region; the concentration of fluorine in the first region is higher than the concentration of fluorine in the second region; the second region has a higher titanium concentration than the titanium concentrations in the surface layer portion, the interior portion, and the first region; the second region has a higher nickel concentration than the surface layer portion, the interior portion, and the first region; the surface layer portion has a third region in which the aluminum concentration is higher than the aluminum concentration in the interior and the protruding portions.

3. In claim 1 or claim 2, The particles further have recesses.

4. In claim 3, The recess has titanium on a part of an inner wall thereof.

5. In claim 3 or claim 4, The recess has a portion with a depth of 100 nm or more and a width of 20 nm or more.

6. In any one of claims 1 to 5, The positive electrode active material, wherein the protrusions have portions with a height of 50 nm or more.

7. A secondary battery comprising the positive electrode active material according to claim 1 .

8. An electronic device comprising the secondary battery according to claim 7.

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