Lithium-ion secondary battery

Abstract

To provide a positive electrode active material capable of improving cycle characteristics of a secondary battery.SOLUTION: Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. An inner region is a non-stoichiometric compound containing a transition metal such as titanium, and an outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy. Since these are topotaxy, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since an outer coating layer in contact with an electrolyte is a compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.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, a machine, a manufacture, or a composition of matter. One aspect of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, or an electronic apparatus, or a manufacturing method thereof. In particular, it relates to a positive electrode active material that can be used in a secondary battery, a secondary battery, and an electronic device having the secondary battery.

[0002] In this specification, the power storage device refers to all elements and devices having a power storage function. For example, it includes storage batteries (also referred to as secondary batteries) such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors.

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

Background Art

[0004] In recent years, various power storage devices such as lithium ion secondary batteries, lithium ion capacitors, and air batteries have been actively developed. In particular, lithium ion secondary batteries with high output and high energy density have rapidly expanded in demand along with the development of the semiconductor industry, for portable information terminals such as mobile phones, smartphones, tablets, or notebook computers, portable music players, digital cameras, medical devices, or next-generation clean energy vehicles such as hybrid vehicles ( HEV), electric vehicles (EV), or plug-in hybrid vehicles (PHEV). , as a source of rechargeable energy, has become essential in modern information society.

[0005] The characteristics required for lithium-ion secondary batteries include further high energy density, improvement of cycle characteristics, safety in various operating environments, and improvement of long-term reliability.

[0006] Therefore, improvement of the positive electrode active material has been studied to improve the cycle characteristics and increase the capacity of lithium-ion secondary batteries. (Patent Document 1 and Patent Document 2)

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] There is room for improvement in various aspects such as charge-discharge characteristics, cycle characteristics, reliability, safety, or cost in lithium-ion secondary batteries and the positive electrode active materials used therein.

[0009] One aspect of the present invention is to provide a positive electrode active material that suppresses a decrease in capacity during charge-discharge cycles when used in a lithium-ion secondary battery. Or, one aspect of the present invention is to provide a high-capacity secondary battery. Or, one aspect of the present invention is to provide a secondary battery with excellent charge-discharge characteristics. Or, one aspect of the present invention is to provide a secondary battery with high safety or reliability. Or, one aspect of the present invention is to provide a secondary battery with high safety or reliability as one of the problems.

[0010] Alternatively, one aspect of the present invention is to provide a novel substance, an active material particle, a secondary battery, or a method for producing them. One of the problems is to provide them.

[0011] Note that the description of these problems does not prevent the existence of other problems. One aspect of the present invention is not required to solve all of these problems. It is possible to extract other problems from the description of the specification, drawings, and claims.

Means for Solving the Problems

[0012] To achieve the above object, in one aspect of the present invention, two different regions from the internal region are provided in the surface layer portion of the positive electrode active material. The inner region is a non-stoichiometric compound, and the outer region is preferably a stoichiometric compound. The inner region preferably contains titanium, and the outer region preferably contains magnesium. Further, these two regions may overlap.

[0013] Also, the inner region is preferably formed through a coating process such as the sol-gel method, and the outer region is preferably formed by segregation accompanying heating.

[0014]

[0015] One aspect of the present invention is a positive electrode active material, the positive electrode active material having a first region, a second region, and a third region, the first region existing inside the positive electrode active material, the second region and the third region existing in the surface layer portion of the positive electrode active material, the third region existing in a region closer to the surface of the positive electrode active material than the second region, the first region having an oxide of lithium and a first transition metal and having a layered rock salt-type crystal structure, and the second region having a non-stoichiometric compound having an oxide of a second transition metal. has, the non-stoichiometric compound has a rock-salt type crystal structure, and the third region has a compound of typical elements, The compound of typical elements is a cathode active material having a rock-salt type crystal structure.

[0016] In the above, the first transition metal is cobalt, the second transition metal is titanium, and the compound of typical elements is preferably magnesium oxide.

[0017] In the above, the third region may have fluorine. Also, the second region and the third region may have cobalt.

[0018] In the above, it is preferable that the crystal orientation of the first region partially coincides with that of the second region, and the crystal orientation of the second region partially coincides with that of the third region. It is preferable that the degree of mismatch between the (1-1-4) plane of the layered rock-salt type crystal structure of the first region or the plane orthogonal to the (

[0019] 1-1-4) plane and the {100} plane of the rock-salt type crystal structure of the second region is 0.12 or less, and the degree of mismatch between the {100} plane of the rock-salt type crystal structure of the second region and the {100} plane of the rock-salt type crystal structure of the third region is 0.12 or less. It is preferably 0.12 or less. and the degree of mismatch between the {100} plane of the rock-salt type crystal structure of the third region is 0.12 or less. This is preferable.

[0020] Also, another aspect of the present invention is a cathode active material, the cathode active material includes lithium, titanium cobalt, magnesium, oxygen, and fluorine, present in the surface layer portion of the cathode active material, when the concentration of cobalt measured by X-ray photoelectron spectroscopy is set to 1, the titanium concentration is 0.0 5 or more and 0.4 or less, the magnesium concentration is 0.4 or more and 1.5 or less, and the fluorine concentration is 0.05 or more and 1.5 or less, which is a cathode active material.

[0021] ​Another aspect of the present invention is a lithium source, a cobalt source, a magnesium source, and a fluorine source mixing step, and a mixture of a lithium source, a cobalt source, a magnesium source, and a fluorine source is heated at 800 °C or higher and 1100 °C or lower for 2 hours or more and 20 hours or less to obtain particles having lithium, cobalt , magnesium, oxygen, and fluorine, a step of dissolving titanium alkoxide in alcohol, a step of mixing particles having lithium, cobalt, magnesium, oxygen, and fluorine into an alcohol solution of titanium alkoxide, and stirring in an atmosphere containing water vapor , a step of recovering a precipitate from the mixture, and a step of heating the recovered precipitate in an atmosphere containing oxygen at 500 °C or higher and 1200 °C or lower for a holding time of 50 hours or less , which is a method for producing a positive electrode active material.

[0022] In the above production method, the ratio of the number of lithium atoms in the lithium source to the number of cobalt atoms in the cobalt source is preferably 1.00 ≦ Li / Co < 1.07.

[0023] In the above production method, the ratio of the number of fluorine atoms contained in the fluorine source to the number of magnesium atoms contained in the magnesium source is preferably Mg:F = 1:x (1.5 ≦ x ≦ 4).

[0024] In the above production method, the number of magnesium atoms contained in the magnesium source is preferably 0.5 atomic% or more and 1.5 atomic% or less of the number of cobalt atoms contained in the cobalt source.

[0025] In the above production method, lithium carbonate is used as the lithium source, and cobalt oxide is used as the cobalt source Using cobalt, magnesium oxide as the magnesium source, and lithium fluoride as the fluorine source can be used.

[0026] Also, by covering the surface of the positive electrode active material with a film to protect the above-described crystal structure, it is possible to suppress a decrease in capacity during charge and discharge cycles. The film covering the surface of the positive electrode active material is preferably a film having carbon (a film containing a graphene compound), or a film having lithium or a decomposition product of the electrolytic solution. Specifically, it is preferable to obtain a powder in which the surface of the positive electrode active material is coated with graphene oxide using a spray drying apparatus. The spray drying apparatus is a manufacturing apparatus using a spray drying method in which hot air is supplied to a suspension to remove the dispersion medium.

[0027] By repeatedly performing charge and discharge cycles, there is a risk that cracks or fractures may occur in the particles of the positive electrode active material, resulting in shape changes. Such shape changes may expose new surfaces of the positive electrode active material, and these surfaces may come into contact with the electrolytic solution, causing decomposition reactions and the like, which are said to reduce the cycle characteristics and charge and discharge characteristics of the secondary battery.

[0028] Therefore, it is preferable to provide a coating film that can prevent shape changes such as cracking or fracturing of the particles of the positive electrode active material.

[0029] However, in order to coat the surface of the positive electrode active material, which is heavy per unit volume, with relatively light graphene oxide, a suspension was prepared and a rotation-revolution mixer was used

[0030] However, the coating was insufficient.

[0031] Therefore, in order to coat the particle surface of the positive electrode active material with graphene oxide, The phenanthrene and a polar solvent (such as water) are mixed and ultrasonically treated, and then particles of the positive electrode active material are mixed. A preferred method is to prepare a suspension by mixing the ingredients together, and then produce a dry powder using a spray dryer. The dry powder produced in this manner is sometimes called a composite.

[0032] The size of a droplet of sprayed liquid sprayed from the nozzle of a spray dryer depends on the nozzle diameter.

[0033] If the particle diameter is small compared to the nozzle diameter, multiple particles will be present in one droplet of sprayed liquid. The particle surface after drying is determined under the condition that the maximum particle diameter is smaller than the nozzle diameter. Upon inspection, some areas were found to be coated with graphene oxide, but it was unclear whether the coating was sufficient. I couldn't say it.

[0034] When the nozzle diameter of the spray dryer is set to be approximately the same as the maximum particle diameter of the active material, the active material can be easily dispersed. This is preferable because the coating of the material is good. In the production of the active material, it is preferable to adjust the maximum particle size of the positive electrode active material.

[0035] Graphene oxide disperses well in water, so ultrasonic stirring is used to disperse the water and graphene oxide. A suspension of phenanthrene can be prepared. A positive electrode active material is added to the suspension, and the suspension is used. By spraying the graphene oxide onto the surface of the positive electrode active material using a spray dryer, A coated powder can be obtained.

[0036] Note that the suspension becomes more acidic as the amount of graphene oxide increases. There is a risk of etching a part of the surface (for example, LiCoO2 containing Mg or F). Therefore, it is preferable to adjust the hydrogen ion exponent (pH) of the suspension before spraying to approach about pH7, that is, to approach neutrality, or to make it pH8 or higher, that is, alkaline. For this pH adjustment, it is preferable to use an aqueous LiOH solution. Also, for example, when using LiCoO2 as the positive electrode active material, if only pure water is used as the dispersion medium of the suspension, the surface of the positive electrode active material may be damaged. Therefore, by using a mixture of ethanol and water as the dispersion medium of the suspension, damage to the surface of the active material may be reduced.

[0037] By preparing the suspension as described above, a positive electrode active material efficiently coated with graphene oxide on the surface can be prepared. By coating the surface with graphene oxide, it is possible to prevent shape changes such as cracks or fractures in the particles of the positive electrode active material. In addition, the positive electrode active material with its surface coated with graphene oxide can be prevented from undergoing quality changes or deterioration even when it comes into contact with the atmosphere after production. Here, after production means, for example, the period from the end of production of the positive electrode active material to the production of a secondary battery using the positive electrode active material, and includes the storage and transportation of the positive electrode active material. Moreover, by forming the film, it is possible to prevent the direct contact and reaction between the positive electrode active material and the electrolyte solution. Therefore, when a secondary battery is manufactured, the reliability of the secondary battery is improved. Also, for the spray drying method, known devices can be used. For example, a countercurrent type pressure nozzle type spray drying device, a co-current type nozzle type pressure spray drying device, etc. can be used.

[0038] Moreover, for the spray drying method, known devices can be utilized. For example, a countercurrent type pressure nozzle type spray drying device, a co-current type nozzle type pressure spray drying device, etc. can be utilized.

[0039] In addition, when used in a secondary battery, the graphene oxide covering the surface of the active material may be reduced. This reduced graphene oxide may sometimes be referred to as "RGO (Reduced Graphene Oxi de)". Note that in RGO, some oxygen or atomic groups containing oxygen may remain in a state bonded to carbon. For example, RGO may have functional groups such as epoxy groups, carbonyl groups such as carboxyl groups, or hydroxyl groups.

[0040] Another aspect of the present invention is a secondary battery having a positive electrode having the above positive electrode active material or the above positive electrode active

[0041] material covered with a film, and a negative electrode. In addition, for the secondary battery, various shapes can be used according to the device to be used. For example, a cylindrical shape, a rectangular shape, a coin-shaped shape, a laminate (flat plate) shape, etc. can be mentioned.

[0042] According to one aspect of the present invention, by using it in a lithium-ion secondary battery, a positive electrode active material with suppressed capacity reduction during charge and discharge cycles can be provided. In addition, a secondary battery with excellent charge and discharge characteristics can be provided. In addition, a secondary battery with high safety or reliability can be provided. In addition, a novel substance, active material particles, secondary battery, or a manufacturing method

[0043]

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Mode for Carrying Out the Invention

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that its form and details can be variously changed. Also, the present invention is not construed to be limited to the description content of the embodiments shown below.

[0045] In each of the drawings described in this specification, the size, thickness, etc. of each component such as the positive electrode, negative electrode, active material layer, separator, and exterior body may be exaggerated for the sake of clarity of individual explanations. Therefore, each component is not necessarily limited to its size, and the phase between each component is also It is not limited to a specific size.

[0046] In addition, in the configuration of the present invention described in this specification and the like, the same parts or parts having the same function are commonly used with the same reference numerals among different drawings, and repeated descriptions thereof are omitted. Also , when referring to parts having the same function, the hatch patterns are the same, and there may be cases where they are not particularly labeled with reference numerals.

[0047] In addition, in this specification and the like, Miller indices are used for the notation of crystal planes and directions. In the notation of Miller indices, in crystallography, a bar is placed above the number, but in this specification and the like, for the notation of crystal planes and directions, due to notation constraints, instead of placing a bar above the number, a -(minus sign) is placed in front of the number for expression. Also, the individual orientation indicating the direction within the crystal is represented by [], and the set orientation indicating all equivalent directions is represented by <>, the individual plane indicating the crystal plane is represented by (), and the set plane having equivalent symmetry is represented by {} respectively. Note that the notation of crystal planes and directions in the drawings is performed using the original notation with a bar placed above the numbers in crystallography. Also, 1 Å (angstrom) is 10 10 -10 -10 m.

[0048] In this specification and the like, segregation refers to a phenomenon in a solid composed of a plurality of elements (for example, A, B, C) wherein a certain element (for example, B) is unevenly distributed.

[0049] In this specification and the like, the layered rock salt-type crystal structure of the composite oxide containing lithium and transition metals means that it has a rock salt-type ion arrangement in which cations and anions are alternately arranged, and transition metals and lithium are regularly arranged to form a two-dimensional plane, so that two-dimensional diffusion of lithium is possible. It refers to a crystal structure. Note that there may be defects such as cation or anion deficiencies. Also, the layer The layered rock salt-type crystal structure, strictly speaking, may be a structure in which the lattice of the rock salt-type crystal is distorted exists.

[0050] Also, in this specification and the like, the rock salt-type crystal structure refers to a structure in which cations and anions are alternately arranged Note that there may be cation or anion deficiencies.

[0051] The anions of the layered rock salt-type crystal and the rock salt-type crystal adopt a cubic close-packed structure (face-centered cubic lattice structure). When the layered rock salt-type crystal and the rock salt-type crystal are in contact, there is a crystal plane where the orientations of the cubic close-packed structures composed of anions are aligned. However, since the space group of the layered rock salt-type crystal is R-3m while the space groups of the rock salt-type crystal are Fm-3m (the space group of a general rock salt-type crystal) and Fd-3m ( the space group of the rock salt-type crystal with the simplest symmetry), the Miller indices of the crystal planes satisfying the above conditions are different for the layered rock salt-type crystal and the rock salt-type crystal. In this specification, for the layered rock salt-type crystal and the rock salt-type crystal, when the orientations of the cubic close-packed structures composed of anions are aligned it is assumed that the crystal orientations are approximately the same. The coincidence of the crystal orientations of the two regions can be determined from TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle annular dark-field scanning transmission electron microscope

[0052] ) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. X-ray diffraction, electron diffraction, neutron diffraction, etc. can also be used as materials for determination. In TEM images etc., the arrangement of cations and anions can be observed as a repetition of bright lines and dark lines. In the layered rock salt type crystal etc., When the orientations of the cubic close-packed structures are aligned in the salt-type crystal and the rock-salt-type crystal, it can be observed that the angle formed by the repetition of bright lines and dark lines between crystals is 5 degrees or less, more preferably 2.5 degrees or less. Note that in TEM images and the like, light elements such as oxygen and fluorine may not be clearly observable. In such a case, the coincidence of the orientations can be determined by the arrangement of metal elements.

[0053] In this specification and the like, the similarity to the structure of the two-dimensional interface is referred to as epitaxy. Furthermore, crystal growth having a similarity to the structure of the two-dimensional interface is referred to as epitaxial growth. Also, having a three-dimensional structural similarity or being crystallographically in the same orientation is referred to as topotaxy. Therefore, in the case of topotaxy, when a part of the cross-section is observed, the crystal orientations of two regions (for example, the underlying region and the region formed by growth) are generally consistent.

[0054] (Embodiment 1) [Structure of the positive electrode active material] First, with reference to FIG. 1, the positive electrode active material 100, which is one aspect of the present invention, will be described. The positive electrode active material 100 refers to a material containing a transition metal that can electrochemically occlude or release lithium ions. As shown in FIG. 1(A), the positive electrode active material 100 has a first region 101 inside and a second region 102 and a third region 103 in the surface layer portion.

[0055] As shown in FIG. 1(B), the second region 102 does not necessarily cover all of the first region 101. Similarly, the third region 103 does not necessarily cover all of the second region 102. Also, the third region 103 may be present in contact with the first region 101.

[0056] Furthermore, even if the thicknesses of the second region 102 and the third region 103 vary depending on the location it is acceptable.

[0057] Also, the third region 103 may be present inside the positive electrode active material 100. For example, when the first region 101 is polycrystalline, the third region 103 may be present near the grain boundary. Also the third region 103 may be present in a portion with crystal defects, a crack portion, and the vicinity thereof in the positive electrode active material 100. In FIG. 1(B), a part of the grain boundary is indicated by a dotted line. Note that in this specification etc., the crystal defect refers to a defect observable in a TEM image etc., that is, a structure in which other elements are incorporated into the crystal, a cavity, etc. Also, the crack portion refers to a crack or a fissure that occurs in a particle, such as the crack portion 106 shown in FIG. 1(C).

[0058] Similarly, as shown in FIG. 1(B), the second region 102 may be present inside the positive electrode active material 100. For example, when the first region 101 is polycrystalline, the second region 102 may be present near the grain boundary. Also, the second region 102 may be present in a portion with crystal defects, a crack portion, and the vicinity thereof in the positive electrode active material 100. Also, the third region 103 and the second region 102 inside the positive electrode active material 100 may overlap.

[0059] <First region 101> The first region 101 has a composite oxide of lithium and a first transition metal. Also, the first region 101 may be said to have lithium, a first transition metal, and oxygen.

[0060] The composite oxide of lithium and the first transition metal preferably has a layered rock salt-type crystal structure.

[0061] ​​​​​​​​​ As the first transition metal, only cobalt may be used, or two types of cobalt and manganese may be used as the first transition metal, or three types of cobalt, manganese, and nickel may be used. That is, the first region may include lithium cobaltate, lithium manganate, lithium nickelate, lithium cobaltate in which a part of cobalt is substituted with manganese, lithium nickel-manganese-cobaltate, and the like. In addition to the transition metal, the first region 101 may also contain a metal other than the transition metal such as aluminum.

[0062] That is, the first region functions as a region that particularly contributes to the charge-discharge reaction among the positive electrode active materials 100. In order to increase the capacity when the positive electrode active material 100 is used in a secondary battery, it is preferable that the volume of the first region 101 is larger than that of the second region and the third region. A material having a layered rock salt type crystal structure has characteristics such as a high discharge capacity and low resistance because lithium can diffuse two-dimensionally, and is preferable as the first region 101. Further, when the first region 101 has a layered rock salt type crystal structure, segregation of typical elements such as magnesium described later is likely to occur. Note that the first region 101 may be a single crystal or a polycrystal. For example, the first region 101 may be a polycrystal having an average crystallite size of 280 nm or more and 630 nm or less. When it is a polycrystal, crystal grain boundaries may be observable by TEM or the like. The average crystal grain size can be calculated from the half-value width of XRD.

[0063]

[0064]

[0065]

[0066] Since the polycrystal has a distinct crystal structure, the paths for the two-dimensional diffusion of lithium ions are sufficiently secured. In addition, since it is easier to produce than a single crystal, it is preferable as the first region 101 .

[0067] Also, not all of the first region 101 needs to have a layered rock-salt type crystal structure. For example, a part of the first region 101 may be amorphous or may have other crystal structures.

[0068] <The second region 102> The second region 102 has an oxide of a second transition metal. The second region 102 may be said to have a second transition metal and oxygen.

[0069] As the second transition metal, it is preferable to use a metal with non-stoichiometry. The second region 10 2 may be said to preferably have a non-stoichiometric compound. For example, at least one of titanium, vanadium, manganese, iron, chromium, niobium, cobalt, zinc, zirconium, nickel, etc. can be used as the second transition metal. However, the second transition metal is preferably an element different from the first transition metal.

[0070] In this specification etc., a metal with non-stoichiometry refers to a metal that can take multiple valences. Also, a non-stoichiometric compound refers to a compound of a metal that can take multiple valences and other elements.

[0071] Also, the second region 102 preferably has a rock-salt type crystal structure.

[0072] The second region 102 functions as a buffer region connecting the first region 101 and the third region 103 described later. The non-stoichiometric compound, due to the change in the valence of the metal The interatomic distance can change. Also, non-stoichiometric compounds often have cation or anion deficiencies or form dislocations (so-called Magnéli phases). Therefore, the second region 102 can absorb the strain generated between the first region 101 and the third region 103 as a buffer region .

[0073] In addition, the second region 102 may contain lithium in addition to the second transition metal and oxygen . For example, it may have lithium titanate, lithium manganate, etc. Furthermore, the second region 102 may have typical elements that the third region 103 described later has. It is preferable for the second region 102 to contain the elements that the first region 101 has, including lithium, and the elements that the third region 103 has, as a buffer region

[0074] That is, the second region 102 can have lithium titanate, titanium oxide, vanadium oxide, manganese oxide , iron oxide, copper oxide, chromium oxide, niobium oxide, cobalt oxide, zinc oxide, etc .

[0075] The second region 102 may also have the first transition metal. For example, the second transition metal may be present in a part of the first transition metal sites of a composite oxide having the first transition metal .

[0076] For example, when the second transition metal is titanium, titanium may exist as titanium oxide (TiO2) in the second region 102, or may exist as lithium titanate (LiTiO2) . Also, in the second region 102, a part of the first transition metal sites of a composite oxide having lithium and the first transition metal may be substituted with titanium .

[0077] ​​Furthermore, the second region 102 may contain fluorine.

[0078] Also, the second region 102 preferably has the same crystal structure as the third region 103 described later. In this case, the crystal orientations of the second region 102 and the third region 103 are likely to match. .

[0079] Note that the second region 102 preferably has a rock-salt type crystal structure, but not all of the second region 10 2 needs to have a rock-salt type crystal structure. For example, the second region 102 may have a spinel type crystal structure, an olivine type crystal structure, a corundum type crystal structure, a rutile type crystal structure, or any other crystal structure.

[0080] Also, as long as the structure in which six oxygen atoms are adjacent to the cation is maintained, there may be a distortion in the crystal structure. Also, there may be a cation deficiency in a part of the second region 102.

[0081] Also, a part of the second region 102 may be amorphous.

[0082] If the second region 102 is too thin, its function as a buffer region will deteriorate, but if it is too thick, there is a risk of causing a decrease in capacity. Therefore, the second region 102 preferably exists from the surface of the positive electrode active material 100 to a depth of 20 nm, more preferably up to 10 nm in the depth direction. Also, the second transition metal may have a concentration gradient.

[0083] <The third region 103> The third region 103 contains a compound of a typical element. The compound of a typical element is a stoichiometric compound. As the compound of a typical element, a compound composed of electrochemically stable typical elements is It is preferable to use, for example, at least one of magnesium oxide, calcium oxide, beryllium oxide, lithium fluoride, and sodium fluoride.

[0084] The third region 103 is a region that comes into contact with the electrolyte when the positive electrode active material 100 is used in a secondary battery. Therefore, the material used for the third region 103 is preferably a material that undergoes few electrochemical changes during the charge and discharge process and is less likely to deteriorate upon contact with the electrolyte. Compounds of typical elements that are stoichiometric compounds and are electrochemically stable are preferable for the third region 103. By having the third region 103 in the surface layer portion of the positive electrode active material 100, the stability of the secondary battery during charge and discharge can be improved. Here, a high stability of the secondary battery means, for example, that the crystal structure of the composite oxide containing lithium and the first transition metal possessed by the first region 101 is more stable. Alternatively, it means that the change in the capacity of the secondary battery is small even when charge and discharge are repeated. Alternatively, it means that the change in the valence of the metal possessed by the positive electrode active material 100 is suppressed even after charge and discharge are repeated.

[0085] Also, the third region 103 may contain fluorine. When the third region 103 contains fluorine, a part of the anions in the compound of the typical element may be substituted with fluorine.

[0086] By partially substituting the anions in the compound of the typical element with fluorine, for example, the diffusivity of lithium can be increased. Therefore, even if the third region 103 exists, it becomes difficult to hinder charge and discharge. Also, when fluorine is present in the surface layer portion of the positive electrode active material particles, the corrosion resistance against hydrofluoric acid generated by the decomposition of the electrolyte may be improved.

[0087] ​​​​​​​​​​​​​Further, the third region 103 may contain lithium, a first transition metal, and a second transition metal. It may be.

[0088] Also, the compound of the typical element contained in the third region 103 preferably has a rock-salt type crystal structure. When the third region 103 has a rock-salt type crystal structure, the crystal orientation thereof is likely to be consistent with that of the second region 102. When the crystal orientations of the first region 101, the second region 102, and the third region 103 are substantially consistent, the second region 102 and the third region 103 can function as a more stable coating layer.

[0089] However, not all of the third region 103 needs to have a rock-salt type crystal structure. For example, the third region 103 may have other crystal structures such as a spinel type crystal structure, an olivine type crystal structure, a cordierite type crystal structure, and a rutile type crystal structure.

[0090] Also, as long as the structure in which six oxygens are adjacent to the cation is maintained, the crystal structure may be distorted. Further, a part of the third region 103 may have a cation deficiency.

[0091] Also, a part of the third region 103 may be amorphous.

[0092] If the third region 103 is too thin, the function of improving the stability during charge and discharge will be reduced, but if it is too thick, it will cause a decrease in capacity. Therefore, the thickness of the third region 103 is preferably 0.5 nm or more and 50 nm or less, and more preferably 0.5 nm or more and 2 nm or less.

[0093] When the third region 103 contains fluorine, the fluorine is magnesium fluoride (MgF2). , it is preferably present in a bonding state other than lithium fluoride (LiF) and cobalt fluoride (CoF2). Specifically, when the vicinity of the surface of the positive electrode active material 100 is analyzed by XPS, the peak position of the binding energy of fluorine is preferably 682 eV or more and 685 eV or less, and more preferably about 684.3 eV. This is a binding energy that does not match any of MgF2, LiF, and CoF2. When analyzing the vicinity of the surface of the positive electrode active material 100 by XPS, the peak position of the binding energy of fluorine is preferably 682 eV or more and 685 eV or less, and more preferably about 684.3 eV. This is a binding energy that does not match any of MgF2, LiF, and CoF2. When analyzing the vicinity of the surface of the positive electrode active material 100 by XPS, the peak position of the binding energy of fluorine is preferably 682 eV or more and 685 eV or less, and more preferably about 684.3 eV. This is a binding energy that does not match any of MgF2, LiF, and CoF2. When analyzing the vicinity of the surface of the positive electrode active material 100 by XPS, the peak position of the binding energy of fluorine is preferably 682 eV or more and 685 eV or less, and more preferably about 684.3 eV. This is a binding energy that does not match any of MgF2, LiF, and CoF2. When analyzing the vicinity of the surface of the positive electrode active material 100 by XPS, the peak position of the binding energy of fluorine is preferably 682 eV or more and 685 eV or less, and more preferably about 684.3 eV. This is a binding energy that does not match any of MgF2, LiF, and CoF2.

[0094] <( In this specification and the like, the peak position of the binding energy of a certain element when analyzed by XPS refers to the value of the binding energy at which the intensity of the energy spectrum is maximized within the range corresponding to the binding energy of that element. In this specification and the like, the peak position of the binding energy of a certain element when analyzed by XPS refers to the value of the binding energy at which the intensity of the energy spectrum is maximized within the range corresponding to the binding energy of that element. In this specification and the like, the peak position of the binding energy of a certain element when analyzed by XPS refers to the value of the binding energy at which the intensity of the energy spectrum is maximized within the range corresponding to the binding energy of that element.

[0095] Generally, as the positive electrode active material repeats charge and discharge, side reactions such as the elution of the first transition metals such as manganese, cobalt, and nickel into the electrolyte, the release of oxygen, and the instability of the crystal structure occur, and the deterioration progresses. However, the positive electrode active material 100 according to one aspect of the present invention has both a second region 102 that functions as a buffer region and a third region 103 that is electrochemically stable. Therefore, it is possible to effectively suppress the elution of the first transition metal and make the crystal structure of the composite oxide containing lithium and the transition metal in the first region 101 more stable. Therefore, the cycle characteristics of the secondary battery having the positive electrode active material 100 can be significantly improved. Also, when charging and discharging at a voltage exceeding 4.3 V (vs. Li / Li Generally, as the positive electrode active material repeats charge and discharge, side reactions such as the elution of the first transition metals such as manganese, cobalt, and nickel into the electrolyte, the release of oxygen, and the instability of the crystal structure occur, and the deterioration progresses. However, the positive electrode active material 100 according to one aspect of the present invention has both a second region 102 that functions as a buffer region and a third region 103 that is electrochemically stable. Therefore, it is possible to effectively suppress the elution of the first transition metal and make the crystal structure of the composite oxide containing lithium and the transition metal in the first region 101 more stable. Therefore, the cycle characteristics of the secondary battery having the positive electrode active material 100 can be significantly improved. Also, when charging and discharging at a voltage exceeding 4.3 V (vs. Li / Li Generally, as the positive electrode active material repeats charge and discharge, side reactions such as the elution of the first transition metals such as manganese, cobalt, and nickel into the electrolyte, the release of oxygen, and the instability of the crystal structure occur, and the deterioration progresses. However, the positive electrode active material 100 according to one aspect of the present invention has both a second region 102 that functions as a buffer region and a third region 103 that is electrochemically stable. Therefore, it is possible to effectively suppress the elution of the first transition metal and make the crystal structure of the composite oxide containing lithium and the transition metal in the first region 101 more stable. Therefore, the cycle characteristics of the secondary battery having the positive electrode active material 100 can be significantly improved. Also, when charging and discharging at a voltage exceeding 4.3 V (vs. Li / Li However, the positive electrode active material 100 according to one aspect of the present invention has both a second region 102 that functions as a buffer region and a third region 103 that is electrochemically stable. Therefore, it is possible to effectively suppress the elution of the first transition metal and make the crystal structure of the composite oxide containing lithium and the transition metal in the first region 101 more stable. Therefore, it is possible to effectively suppress the elution of the first transition metal and make the crystal structure of the composite oxide containing lithium and the transition metal in the first region 101 more stable. Therefore, the cycle characteristics of the secondary battery having the positive electrode active material 100 can be significantly improved. Also, when charging and discharging at a voltage exceeding 4.3 V (vs. Li / Li Therefore, the cycle characteristics of the secondary battery having the positive electrode active material 100 can be significantly improved. Also, when charging and discharging at a voltage exceeding 4.3 V (vs. Li / Li + ) and especially at a high voltage of 4.5 V (vs. Li / Li + ) or higher, the configuration of one aspect of the present invention exhibits a remarkable effect. When charging and discharging at a voltage exceeding 4.3 V (vs. Li / Li

[0096] <Heteroepitaxial Growth and Topotaxy> The second region 102 is formed by heteroepitaxial growth from the first region 101. This is preferable. Further, the third region 103 is preferably formed by heteroepitaxial growth from the second region 102. The region formed by heteroepitaxial growth becomes topotactic, in which the crystal orientation is three-dimensionally substantially consistent with that of the underlying region. Therefore, the first region 101, the second region 102, and the third region 103 can be

[0097] made topotactic. When the crystal orientations of the crystals from the first region 101 to the third region 103 are substantially consistent, the second region 102 and the

[0098] third region 103 function as a coating layer having a stable bond with the first region 101. Therefore, the positive electrode active material 100 having a strong coating layer can be obtained. Since the second region 102 and the third region 103 have a stable bond with the first region 101, when the positive electrode active material 100 is used in a secondary battery, the change in the crystal structure of the first region 101 caused by charge and discharge can be effectively suppressed. Also,

[0099] <Degree of Inconsistency between Regions> For heteroepitaxial growth, the degree of inconsistency between the crystal of the underlying region and the crystal to be grown is important.

[0100] In this specification and the like, the degree of mismatch f is defined by the following Equation 1. In the crystal of the underlying region, let a be the average of the nearest-neighbor distances between oxygen and cations, and let b be the average of the nearest-neighbor distances between the natural anions and cations of the crystal to be grown.

[0101]

Equation

[0102] For heteroepitaxial growth, the degree of mismatch f between the crystal of the underlying region and the crystal to be grown needs to be 0.12 or less. For more stable layer-by-layer heteroepitaxial growth, the degree of mismatch f is preferably 0.08 or less, and more preferably 0.04 or less.

[0103] Therefore, it is preferable to select the materials for the first region 101 and the second region 102 such that the degree of mismatch f between the layered rock-salt-type crystal structure of the first region 101 and the rock-salt-type crystal structure of the second region 102 is 0.12 or less.

[0104] Also, it is preferable to select the materials for the second region 102 and the third region 103 such that the degree of mismatch f between the rock-salt-type crystal structure of the second region 102 and the rock-salt-type crystal structure of the third region 103 is 0.12 or less.

[0105] As described above, the degree of mismatch f between the layered rock-salt-type crystal structure of the first region 101 and the rock-salt-type crystal structure of the second region 102 is 0.12 or less, and the degree of mismatch f between the rock-salt-type crystal structure of the second region 102 and the rock-salt-type crystal structure of the third region 103 is 0.12 or less, and ​​​​​​​​The materials and crystal planes of the first region 101, the second region 102, and the third region 103 that satisfy the condition of being 0.12 or less are exemplified below. The materials and crystal planes of the first region 101, the second region 102, and the third region 103 are exemplified below.

[0106] ≪Example 1: Lithium cobaltate, lithium titanate, and magnesium oxide≫ First, using FIGS. 2 and 3, an example will be described in which the first transition metal is cobalt, the first region 101 has lithium cobaltate having a layered rock-salt-type crystal structure, the second transition metal is titanium, the second region 102 has lithium titanate having a rock-salt-type crystal structure, and the compound of typical elements that the third region 103 has is magnesium oxide having a rock-salt-type crystal structure. The second region 102 has lithium titanate having a rock-salt-type crystal structure, and the third region 103 has magnesium oxide having a rock-salt-type crystal structure as the compound of typical elements. For the example where the compound of typical elements that the third region 103 has is magnesium oxide having a rock-salt-type crystal structure, it will be described. will be described.

[0107] In FIG. 2(A), models of the crystal structures of layered rock-salt-type (space group R-3mH) lithium cobaltate (LiCoO2), rock-salt-type (space group Fd-3mZ ) of lithium titanate (LiTiO2), and rock-salt-type (space group Fd-3mZ) of magnesium oxide are shown. FIG. 2(A) is a model when viewed from the b-axis direction in all cases. ) of lithium titanate (LiTiO2), and a model of the crystal structure of rock-salt-type (space group Fd-3mZ) of magnesium oxide are shown. FIG. 2(A) is a model when viewed from the b-axis direction in all cases.

[0108] Just from the figure of FIG. 2(A), it is not visible that the layered rock-salt-type crystal and the rock-salt-type crystal are topotactic. However, here, assume that the layered rock-salt-type crystal is viewed from different orientations (for example, the orientation including the arrow in FIG. 2(A)). In FIG. 2(B), a model of the layered rock-salt-type crystal viewed from the <1-1-4> plane orientation and a model of the rock-salt-type crystal viewed from the <100> plane orientation are shown. orientation). In FIG. 2(B), a model of the layered rock-salt-type crystal viewed from the <1-1-4> plane orientation and a model of the rock-salt-type crystal viewed from the <100> plane orientation are shown. orientation).

[0109] As shown in FIG. 2(B), when the layered rock-salt-type crystal is viewed from the <1-1-4> plane orientation, the atomic arrangement becomes very similar to that when the rock-salt-type crystal is viewed from the <100> plane orientation. Also, the metal and the acid type crystal, when viewed from the <100> plane orientation, the atomic arrangement becomes very similar. Also, the metal and the acid The bare nearest distances also take on similar values. For example, in layered rock salt-type lithium cobaltate, the Li-O distance is 2.089 Å and the Co-O distance is 1.925 Å. Also, in rock salt-type lithium titanate, the Li-O distance is 2.138 Å and the Ti-O distance is 2.051 Å. Further, in rock salt-type magnesium oxide, the Mg-O distance is 2.106 Å. Therefore, using Figure 3, the mismatch degree between regions when the (1-1-4) crystal plane of the layered rock salt-type crystal and the {100} crystal plane of the rock salt-type crystal are in contact will be explained. As shown in Figure 3, the metal-oxygen-metal distance of the (1-1-4) crystal plane 101p(1-1-4) of lithium cobaltate having a layered rock salt-type crystal structure in the first region 101 is 4.01 Å. Also, the metal-oxygen-metal distance of the {100} crystal plane 102p{100} of lithium titanate having a rock salt-type crystal structure in the second region 102 is 4.19 Å. Therefore, the mismatch degree f between the crystal plane 101p(1-1-4) and the crystal plane 102p{100} is 0.04.

[0110] Moreover, the metal-oxygen-metal distance of the {100} crystal plane 103p{100} of magnesium oxide having a rock salt-type crystal structure in the third region 103 is 4.21 Å. Therefore, the mismatch degree f between the crystal plane 102p{100} and the crystal plane 103p{100} is 0.02. Thus, since the mismatch degree between the first region 101 and the second region 102, and the mismatch degree between the second region 102 and the third region 103 are sufficiently small, topotaxy can occur from the first region 101 to the third region 103.

[0111] As shown in Figure 3, the metal-oxygen-metal distance of the (1-1-4) crystal plane 101p(1-1-4) of lithium cobaltate having a layered rock salt-type crystal structure in the first region 101 is 4.01 Å. Also, the metal-oxygen-metal distance of the {100} crystal plane 102p{100} of lithium titanate having a rock salt-type crystal structure in the second region 102 is 4.19 Å. Therefore, the mismatch degree f between the crystal plane 101p(1-1-4) and the crystal plane 102p{100} is 0.04. Moreover, the metal-oxygen-metal distance of the {100} crystal plane 103p{100} of magnesium oxide having a rock salt-type crystal structure in the third region 103 is 4.21 Å. Therefore, the mismatch degree f between the crystal plane 102p{100} and the crystal plane 103p{100} is 0.02. Thus, since the mismatch degree between the first region 101 and the second region 102, and the mismatch degree between the second region 102 and the third region 103 are sufficiently small, topotaxy can occur from the first region 101 to the third region 103.

[0112] Moreover, the metal-oxygen-metal distance of the {100} crystal plane 103p{100} of magnesium oxide having a rock salt-type crystal structure in the third region 103 is 4.21 Å. Therefore, the mismatch degree f between the crystal plane 102p{100} and the crystal plane 103p{100} is 0.02. Thus, since the mismatch degree between the first region 101 and the second region 102, and the mismatch degree between the second region 102 and the third region 103 are sufficiently small, topotaxy can occur from the first region 101 to the third region 103.

[0113] As shown in Figure 3, the metal-oxygen-metal distance of the (1-1-4) crystal plane 101p(1-1-4) of lithium cobaltate having a layered rock salt-type crystal structure in the first region 101 is 4.01 Å. Also, the metal-oxygen-metal distance of the {100} crystal plane 102p{100} of lithium titanate having a rock salt-type crystal structure in the second region 102 is 4.19 Å. Therefore, the mismatch degree f between the crystal plane 101p(1-1-4) and the crystal plane 102p{100} is 0.04.

[0114] On the other hand, although not in contact in FIG. 3, if the crystal plane 101p(1-1-4) of the first region 101 contacts the crystal plane 103p{100} of the third region 103, the degree of mismatch f is 0.05, and it becomes so. That is, due to the presence of the second region 102, the degree of mismatch can be reduced, and it is possible. Furthermore, since the second region 102 is a transition metal oxide having non-stoichiometry, the presence of the second region 102 allows the first region 101 to the third region 103 to become a more stable topotaxy. Therefore, the second region 102 and the third region 103 can function as a coating layer having a stable bond with the first region 101.

[0115] In this embodiment, although the example in which the (1-1-4) plane of the layered rock salt type contacts the {100} plane of the rock salt type has been described, one aspect of the present invention is not limited to this. It is only necessary that crystal planes that can become topotaxy contact each other.

[0116] ≪Example 2: Lithium Cobalt Oxide, Manganese Oxide, and Calcium Oxide≫ Next, an example will be described in which the first transition metal is cobalt, the first region 101 has lithium cobalt oxide having a layered rock salt type crystal structure, the second transition metal is manganese, the second region 102 has manganese oxide having a rock salt type crystal structure, and the compound of the typical element included in the third region 103 is calcium oxide having a rock salt type crystal structure. In this case as well, similar to FIGS. 2 and 3, when the layered rock salt type crystal of the first region 101 is viewed from the <1-1

[0117] -4> plane orientation, the atomic arrangement is very similar to the case when the rock salt type crystals of the second region 102 and the third region 103 are viewed from the <100> plane orientation.

[0118] The crystal plane (1-1-4) of the layered rock salt-type crystal is in contact with the {100} crystal plane of the rock salt-type crystal The mismatch degree between each region will be described when this occurs. The crystal plane (1-1-4) of lithium cobaltate having a layered rock salt-type crystal structure in the first region 101 The metal-oxygen-metal distance between is 4.01 Å. Also, the metal-oxygen-metal distance between the crystal plane {100} of manganese oxide having a rock salt-type crystal structure in the second region 102 is 4.45 Å. Therefore, the mismatch degree f between the crystal plane (1-1-4) of the first region 101 and the crystal plane {100} of the second region 102 is 0 .11.

[0119] Also, the metal-oxygen-metal distance between the crystal plane {100} of calcium oxide having a rock salt-type crystal structure in the third region 103 is 4.82. Therefore, the mismatch degree f between the crystal plane {1 00} of the second region 102 and the crystal plane {100} of the third region 103 is 0.08.

[0120] Thus, since the mismatch degree between the first region 101 and the second region 102, and the mismatch degree between the second region 10 2 and the third region 103 are sufficiently small, topotaxy can be achieved from the first region 101 to the third region 103.

[0121] On the other hand, if the crystal plane (1-1-4) of the first region 101 and the crystal plane {10 0} of the third region 103 are in contact, the mismatch degree f becomes 0.20, so heteroepitaxial growth is difficult . That is, due to the presence of the second region 102, hetero epitaxial growth from the first region to the third region becomes possible. Therefore, the second region 102 and the third region 103 can be functioned as a coating layer having a stable bond with the first region 101.

[0122] ​ ≪Example 3: Lithium Nickel Manganese Cobalt Oxide, Manganese Oxide, Calcium Oxide≫ Next, the first transition metal is nickel, manganese, and cobalt, and the first region 101 is lithium nickel manganese cobalt oxide (LiNi 0. 33 Co 0.33 Mn 0.33 O2) having a layered rock salt-type crystal structure, the second transition metal is manganese, and the second region 102 has manganese oxide having a rock salt-type crystal structure, and the third region 103 has an example in which the compound of the typical element is calcium oxide having a rock salt-type crystal structure will be described. will be described.

[0123] Also in this case, as shown in FIGS. 2 and 3, when viewing the layered rock salt-type crystal from the <1-1-4> plane direction position, the atomic arrangement is very similar to that when viewing the rock salt-type crystal from the <100> plane orientation. The degree of mismatch between the (1-1-4) crystal plane of the layered rock salt-type crystal and the {100} crystal plane of the rock salt-type crystal when they are in contact will be described.

[0124] The metal-oxygen-metal distance of the crystal plane (1-1-4) of lithium nickel manganese cobalt oxide having a layered rock salt-type crystal structure in the first region 101 is 4.07 Å. Also, the second The metal-oxygen-metal distance of the crystal plane {100} of manganese oxide having a rock salt-type crystal structure in the region 102 is 4.45 Å. Therefore, the degree of mismatch f between the crystal plane (1-1-4 ) of the first region 101 and the crystal plane {100} of the second region 102 is 0.09. ) and the crystal plane {100} of the second region 102 is 0.09.

[0125] Also, the crystal plane {100} of calcium oxide having a rock salt-type crystal structure in the third region 103 The metal-oxygen-metal distance is 4.82. Therefore, the mismatch degree f between the crystal plane {1 00} of the second region 102 and the crystal plane {100} of the third region 103 is 0.08.

[0126] Thus, since the mismatch degree between the first region 101 and the second region 102, and the mismatch degree between the second region 10 2 and the third region 103 are sufficiently small, topotaxy can be achieved from the first region 101 to the third region 103.

[0127] On the other hand, if the crystal plane (1-1-4) of the first region 101 and the crystal plane {10 0} of the third region 103 are in contact, the mismatch degree f becomes 0.18, making heteroepitaxial growth difficult. That is, the presence of the second region 102 enables heteroepitaxial growth from the first region to the third region. Therefore, the second region 102 and the third region 103 can function as a coating layer having a stable bond with the first region 101.

[0128] <Boundary between each region> As described above, the first region 101, the second region 102, and the third region 103 are regions having different compositions. However, the elements contained in each region may have a concentration gradient. For example, the second transition metal contained in the second region 102 may have a concentration gradient. In addition, since the third region 103 is preferably a region where typical elements are segregated, as will be described later, it may have a concentration gradient of typical elements. Therefore, the boundaries of each region may not be clear.

[0129] The first region 101, the second region 102, and the third region 103 are observed by TEM images, STEM images , FFT (Fast Fourier Transform) analysis, EDX (Energy Dispersive X-ray Analysis), ToF-S Depth direction analysis by IMS (Time-of-Flight Secondary Ion Mass Spectrometry), XPS (X-ray Photoelectron Spectroscopy), Auger electron spectroscopy, TDS (Temperature Programmed Desorption Gas Analysis), etc. can confirm that they have different compositions .

[0130] For example, in TEM images and STEM images, since the differences in the constituent elements appear as differences in the brightness of the images, it can be observed that the constituent elements of the first region 101, the second region 102, and the third region 103 are different. Also, in the surface analysis of EDX (for example, elemental mapping), it can be observed that the first region 101, the second region 102, and the third region 103 have different elements . Also, in the line analysis of EDX and the depth direction analysis using ToF-SIMS, the peaks of the concentrations of the respective elements possessed by the first region 101, the second region 102, and the third region 103 can be detected .

[0131] Also, in the line analysis of EDX and the depth direction analysis using ToF-SIMS, the peaks of the concentrations of the respective elements possessed by the first region 101, the second region 102, and the third region 103 can be detected .

[0132] However, it is not always necessary to be able to observe clear boundaries between the first region 101, the second region 102, and the third region 103 by various analyses .

[0133] In this specification, etc., the third region 103 present in the surface layer portion of the positive electrode active material 100 refers to the depth from the surface of the positive electrode active material 100 until the concentration of typical elements such as magnesium detected by depth direction analysis becomes 1 / 5 of the peak . As the depth direction analysis, the above-mentioned line analysis of EDX and the depth direction analysis using ToF-SIMS, etc. can be used . .

[0134] The peak of the concentration of the typical elements is at a depth of 3 nm from the surface of the positive electrode active material 100 toward the center. Preferably, the ions are present up to a depth of 1 nm, more preferably up to a depth of 0 It is more preferred that it be present up to 0.5 nm.

[0135] The depth at which the concentration of the typical element becomes 1 / 5 of the peak varies depending on the fabrication method, but will be described later. In the case of the manufacturing method, the depth is generally about 2 nm to 5 nm from the surface of the positive electrode active material.

[0136] Regarding the third region 103 existing inside the first region 101, such as near the grain boundary or near the crystal defect, However, the concentration of the typical elements detected by the depth profile analysis is 1 / 5 or more of the peak. We will do so.

[0137] The distribution of fluorine contained in the positive electrode active material 100 preferably overlaps with the distribution of the above-mentioned typical elements. Therefore, fluorine also has a concentration gradient, and the peak of the fluorine concentration is on the surface of the positive electrode active material 100. It is preferable that the particles exist within a depth of 3 nm from the surface toward the center, and that the particles exist within a depth of 1 nm. It is more preferable that the thickness of the pores is 0.5 nm, and it is even more preferable that the thickness of the pores is 0.5 nm.

[0138] In this specification, the second region 102 present in the surface layer portion of the positive electrode active material 100 is The region where the concentration of the second transition metal detected by depth analysis is more than half of the peak. The second region existing inside the first region 101, such as near the grain boundary or near the crystal defect, For 102, the concentration of the second transition metal detected by depth profile analysis was half of the peak. The analytical method is the above-mentioned EDX line analysis and T Depth direction analysis using oF-SIMS can be used.

[0139] Therefore, the third region 103 and the second region 102 may overlap. However, the third region 103 is preferably present in a region closer to the surface of the positive electrode active material particles than the second region 102. Also, the peak of the concentration of the typical element is preferably present in a region closer to the surface of the positive electrode active material particles than the peak of the concentration of the second transition metal.

[0140] The peak of the second transition metal is preferably present at a depth of 0.2 nm or more and 10 nm or less from the surface of the positive electrode active material 100 toward the center, and more preferably present at a depth of 0.5 nm or more and 3 nm or less.

[0141] Note that XPS has a measurement range of about 5 nm from the surface of the particles of the positive electrode active material 100. Therefore, it is possible to quantitatively analyze the element concentration present about 5 nm from the surface. Therefore, the element concentrations of the third region 103 and the second region 102 present about 5 nm from the surface can be quantitatively analyzed.

[0142] When the surface of the positive electrode active material 100 is analyzed by XPS, when the concentration of the first transition metal is set to 1, the relative value of the concentration of the second transition metal is preferably 0.05 or more and 0.4 or less, and more preferably 0.1 or more and 0.3 or less. Also, the relative value of the concentration of the typical element is preferably 0.4 or more and 1.5 or less, and more preferably 0.45 or more and 1.00 or less. Also, the relative value of the fluorine concentration is preferably 0.05 or more and 1.5 or less, and more preferably 0.3 or more and 1.00 or less.

[0143] Note that as described above, since the elements possessed by the first region 101, the second region 102, and the third region 103 may have a concentration gradient, the first region 101 may contain a second region such as fluorine. ​​​​​​​​​It may also have elements possessed by the first region 102 and the third region 103. Similarly, the third region 1 03 may have elements possessed by the first region 101 and the second region 102. Also the first region 101, the second region 102, and the third region 103 may have other elements such as carbon, sulfur, silicon , sodium, calcium, chlorine, zirconium, etc.

[0144] [Particle size] If the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse, and if it is too small, it becomes difficult to maintain the crystal structure described later. Therefore, the D50 (also referred to as the median diameter ) is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less. Also, when forming a film on the surface of the positive electrode active material 100 in a later process using a spray dryer device , it is preferable that the nozzle diameter is substantially the same as the maximum particle size of the positive electrode active material 100. When the particle size is less than 5 μm and a spray dryer device with a nozzle diameter of 20 μm is used , the secondary particles will be coated together, resulting in a decrease in the coating property.

[0145] Also, in order to increase the density of the positive electrode active material layer, it is effective to mix large particles (the longest part is about 20 μm or more and 40 μm or less) and small particles (the longest part is about 1 μm), and fill the gaps between the large particles with the small particles. Therefore, there may be two or more peaks in the particle size distribution.

[0146] Note that the particle size of the positive electrode active material is affected not only by the particle size of the starting material but also by the ratio of lithium contained in the starting material to the first transition metal (hereinafter referred to as the ratio of Li to the first transition metal).

[0147] When the particle size of the starting material is small, in order to make the particle size of the positive electrode active material fall within the above-preferred range, it is necessary to cause grain growth during firing. During firing, it is necessary to cause grain growth.

[0148] In order to promote grain growth during firing, it is effective to make the ratio of Li to the first transition metal in the starting material greater than 1, that is, to make lithium slightly excessive. For example, when the ratio of Li to the first transition metal is about 1.06, it is easy to obtain a positive electrode active material with a D50 of 15 μm or more. Note that as will be described later, since lithium may be lost outside the system during the process of producing the positive electrode active material, the ratio of lithium to the first transition metal in the resulting positive electrode active material may not match the ratio of lithium to the first transition metal in the starting material.

[0149] However, if the amount of lithium becomes excessive in order to make the particle size fall within the preferred range, there is a risk that the capacity retention rate when used in a secondary battery will decrease.

[0150] However, the present inventors have clarified that by providing a second region 102 having a second transition metal in the surface layer portion, it is possible to produce a positive electrode active material having a high capacity retention rate while controlling the ratio of Li to the first transition metal so that the particle size falls within the preferred range.

[0151] In the case of the positive electrode active material according to one aspect of the present invention in which a region having a second transition metal is provided in the surface layer portion, the ratio of Li to the first transition metal in the starting material is preferably 1.00 or more and 1.07 or less, and 1 .03 or more and 1.06 or less is more preferable.

[0152] [Formation of Second Region] The second region 102 can be formed by coating particles of a composite oxide having lithium and a first transition metal with a material having a second transition metal. ​

[0153] As a method for coating a material having a second transition metal, liquid phase methods such as the sol-gel method , solid phase methods, sputtering methods, vapor deposition methods, CVD (chemical vapor deposition) methods, PLD (pulse laser deposition) methods, and the like can be applied. In this embodiment, a case where the sol-gel method, which can be expected to provide a uniform coating and can be processed at atmospheric pressure, is applied will be described.

[0154] <Sol-gel method> A method for coating a material having a second transition metal by applying the sol-gel method will be described with reference to FIG. 4.

[0155] First, an alkoxide of the second transition metal is dissolved in alcohol.

[0156] FIG. 4(A-1) shows the general formula of the alkoxide of the second transition metal. In the formula of FIG. 4(A-1), M2 represents the alkoxide of the second transition metal. R represents an alkyl group having 1 to 18 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 13 carbon atoms. Further, FIG. 4(A -1) shows the general formula in the case where the second transition metal is tetravalent, but one aspect of the present invention is not limited thereto. The second transition metal may be divalent, trivalent, pentavalent, hexavalent or heptavalent. In this case, the alkoxide of the second transition metal has an alkoxy group corresponding to the valence of the second transition metal.

[0157] FIG. 4(A-2) shows the general formula of titanium alkoxide used when titanium is applied as the second transition metal. In FIG. 4(A-2), R represents an alkyl group having 1 to 18 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 13 carbon atoms.

[0158] ​​​​​​​​​For example, as the titanium alkoxide, tetramethoxy titanium, tetraethoxy titanium, te tra-n-propoxy titanium, tetra-i-propoxy titanium (orthotitanic acid tetrai sopropyl, titanium(IV) isopropoxide, Titanium tetraisop ropoxide(IV), TTIP, etc. may also be denoted), tetra-n-butoxy titanium, tetra-i-butoxy titanium, tetra-sec-butoxy titanium, tetra-t- butoxy titanium, etc. can be used.

[0159] Figure 4(A-3) shows the chemical formula of titanium(IV) isopropoxide (TTIP), which is one kind of titanium alkoxide described in the production method to be described later.

[0160] As the solvent for dissolving the alkoxide of the second transition metal, alcohols are preferred. For example, methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol, etc. can be used.

[0161] Next, particles of a composite oxide containing lithium, a transition metal, magnesium, and fluorine are mixed into an alcohol solution of the alkoxide of the second transition metal, and stirred in an atmosphere containing water vapor.

[0162] By placing it in an atmosphere containing H2O, hydrolysis of water and the alkoxide of the second transition metal occurs as shown in Figure 4(B). Subsequently, dehydration condensation occurs between the products shown in Figure 4(B) as shown in Figure 4(C). The hydrolysis shown in Figure 4(B) and the condensation reaction shown in Figure 4(C) repeatedly occur, and a sol of the oxide of the second transition metal is formed. This reaction also occurs on the particles 110 of the composite oxide as shown in Figures 4(D-1) and 4 (D-2), and the second transition is formed on the surface of the particles 110. metal A layer comprising a metal is formed.

[0163] Thereafter, the particles 110 are collected and the alcohol is evaporated. do.

[0164] In this embodiment, a composite material containing lithium, a first transition metal, a main group element, and fluorine is used. Before coating the oxide particles on the positive electrode current collector, a material containing a second transition metal is coated on the oxide particles. However, one embodiment of the present invention is not limited thereto. A positive electrode active material layer containing particles of a composite oxide having a transition metal, a typical element, and fluorine is formed. Then, the positive electrode current collector and the positive electrode active material layer are both immersed in an alkoxide solution of a second transition metal, The material having the second transition metal may be coated.

[0165] [Segregation in the third region] The third area 103 is a method using a liquid phase method such as a sputtering method, a solid phase method, or a sol-gel method. However, the present inventors have found that the method using a source of a main group element such as magnesium When the fluorine source is mixed with the material of the first region 101 and then heated, the main group elements are condensed into the positive electrode active material particles. It was also revealed that the particles segregate to the surface layer of the particles, forming a third region 103. The positive electrode active material 100 has excellent cycle characteristics. It was revealed that it would be.

[0166] When the third region 103 is formed through heating as described above, the heating is conducted to the composite oxide particles. It is preferable to carry out this step after coating the material containing the second transition metal. Even after coating with a material containing magnesium, when heated, the typical elements such as magnesium tend to be concentrated on the surface of the particles. This is to analyze the

[0167] Using FIGS. 5 and 6, the segregation model of this typical element will be described. For typical elements such as magnesium the segregation model is presumed to be slightly different depending on the ratio of lithium to the first transition metal contained in the starting material. Therefore, the segregation model when the ratio of Li to the first transition metal in the starting material is less than 1.03, that is, when lithium is scarce, will be described using FIG. 5. And the segregation model when the ratio of Li to the first transition metal in the starting material is 1.03 or more, that is, when lithium is abundant, will be described using FIG. 6. Also, in these segregation models, and FIGS. 5 and 6, the case where the first transition metal is cobalt, the second transition metal is titanium, and the typical element is magnesium will be taken as an example for explanation. will be described using FIG. 6. Also, in these segregation models, and FIGS. 5 and 6, the case where the first transition metal is cobalt, the second transition metal is titanium, and the typical element is magnesium will be taken as an example for explanation. will be described.

[0168] FIG. 5(A) is a model diagram of the vicinity of the surface of the composite oxide particles 110 having lithium, cobalt, magnesium, and fluorine, which were produced with the Li to Co ratio of the starting material being less than 1.03. Region 111 in the figure is a region having lithium, cobalt, magnesium, and fluorine, and lithium cobaltate (LiCoO2) is the main component. Lithium cobaltate has a layered rock salt type crystal structure. has a layered rock salt type crystal structure. has a layered rock salt type crystal structure.

[0169] Generally, when synthesizing composite oxide particles having lithium, cobalt, magnesium, and fluorine, it is known that lithium partially goes outside the system (outside the particles to be produced). The reasons for this include lithium volatilizing during firing, and lithium eluting into the solvent when mixing the starting materials. Therefore, the Li to Co ratio in the composite oxide particles 110 having lithium, cobalt, magnesium, and fluorine may be smaller than the Li to Co ratio of the starting material. magnesium, and fluorine may be smaller than the Li to Co ratio of the starting material. magnesium, and fluorine may be smaller than the Li to Co ratio of the starting material. becomes smaller.​

[0170] When the Li to Co ratio of the starting materials is less than 1.03, on the surface of the particles 110, lithium is likely to be detached from lithium cobaltate to form cobalt oxide. Therefore, as shown in Fig. 5(A), the surface of the composite oxide particles 110 may be covered with a cobalt oxide (CoO X (X>0)) layer 114 .

[0171] Cobalt oxide has a rock-salt crystal structure. Therefore, in the particles 110 of Fig. 5(A), on the region 111 having lithium cobaltate with a layered rock-salt crystal structure, a cobalt oxide layer 114 having a rock-salt crystal structure may be in contact.

[0172] Such particles 110 are coated with a material containing titanium by a sol-gel method or the like. Fig. 5(B ) shows a state where the particles 110 are coated with a layer 112 containing titanium by the sol-gel method. At the stage of Fig. 5(B), since the layer 112 containing titanium is a gel of titanium oxide, its crystallinity is low.

[0173] Next, the particles 110 after being coated with the layer 112 containing titanium are heated. Although the details of the heating conditions will be described later, for example, they are heated at 800°C for 2 hours in an oxygen atmosphere to prepare the positive electrode active material 100 which is one embodiment of the present invention, and the state is shown in Fig. 5(C). By heating, titanium in the layer 112 containing titanium diffuses toward the inside of the particles 110. At the same time, magnesium and fluorine contained in the region 11 1 segregate on the surface of the particles 110.

[0174] As described above, rock-salt type cobalt oxide exists on the surface of the particles 110. Also, magnesium oxide ​​​Uum also has a rock-salt type crystal structure. Therefore, it is speculated that magnesium exists more stably as magnesium oxide on the surface of particle 110 than inside particle 110. This is considered to be the reason why magnesium segregates on the surface of particle 110 when heated.

[0175] Furthermore, it is considered that fluorine contained in the starting material promotes the segregation of magnesium.

[0176] Fluorine has a higher electronegativity than oxygen. Therefore, even in a stable compound such as magnesium oxide, adding fluorine causes a charge bias and is speculated to weaken the bond between magnesium and oxygen. Therefore, it is speculated that when oxygen in magnesium oxide is replaced by fluorine, magnesium becomes more likely to move around the substituted fluorine.

[0177] This can also be explained by the phenomenon of the melting point of the mixture decreasing. When magnesium oxide (melting point 2852 °C) and lithium fluoride (melting point 848 °C) are added simultaneously, the melting point of magnesium oxide decreases. The decrease in the melting point makes it easier for magnesium to move during heating, and it is also considered that magnesium segregation is more likely to occur.

[0178] Finally, the third region 103 becomes a solid solution of cobalt oxide and magnesium oxide having a rock-salt type crystal structure. Also, it is considered that a part of the oxygen possessed by cobalt oxide and magnesium oxide is replaced by fluorine.

[0179] The diffused titanium partly substitutes for the cobalt site of lithium cobaltate, and partly titanium ​​​​​​​​​It becomes lithium acid. The second region 102 after heating has a rock-salt type crystal structure of lithium titanate and has titanium.

[0180] The first region 101 after heating has lithium cobaltate having a layered rock-salt type crystal structure .

[0181] Next, the case where the Li to Co ratio of the starting material is 1.03 or more will be described with reference to FIG. 6. FIG. 6(A) is a model diagram near the surface of the particles 120 of the composite oxide having lithium, cobalt , magnesium and fluorine, which are produced with the Li to Co ratio of the starting material being 1.03 or more. Region 121 in the figure is a region having lithium, cobalt, magnesium and fluorine.

[0182] Since the particles 120 in FIG. 6(A) have sufficient lithium, when the particles 120 of the composite oxide having lithium, cobalt, magnesium and fluorine are fired, etc., even if lithium detaches from the particles 12 0, lithium diffuses from the inside to the surface of the particles 120 and is supplemented, so it is difficult to form a cobalt oxide layer on the surface.

[0183] FIG. 6(B) shows a state in which the particles 120 in FIG. 6(A) are coated with a layer 122 having titanium by the sol-gel method. At the stage of FIG. 6(B), since the layer 122 having titanium is a gel of titanium oxide, the crystallinity is low.

[0184] FIG. 6(C) shows a state in which the particles 120 after coating the layer 122 having titanium in FIG. 6(B) have started to be heated. By heating, titanium in the layer 122 having titanium diffuses toward the inside of the particles 1 10. The diffused titanium combines with lithium contained in the region 121 They combine to form lithium titanate, and a layer 125 having lithium titanate is formed.

[0185] Since lithium combines with titanium to form lithium titanate, lithium is relatively deficient on the surface of the particles 120. Therefore, as shown in FIG. 6(C), it is presumed that a cobalt oxide layer 124 is temporarily formed on the surface of the particles 120. Since lithium combines with titanium to form lithium titanate, lithium is relatively deficient on the surface of the particles 120. Therefore, as shown in FIG. 6(C), it is presumed that a cobalt oxide layer 124 is temporarily formed on the surface of the particles 120. Since lithium combines with titanium to form lithium titanate, lithium is relatively deficient on the surface of the particles 120. Therefore, as shown in FIG. 6(C), it is presumed that a cobalt oxide layer 124 is temporarily formed on the surface of the particles 120.

[0186] FIG. 6(D) shows a state in which heating has been sufficiently performed from FIG. 6(C) and the positive electrode active material 100 which is one embodiment of the present invention is obtained. The presence of the cobalt oxide layer 124 having a rock salt-type crystal structure on the surface makes it considered that magnesium exists more stably as magnesium oxide on the surface of the particles 120 than inside the particles 120. Also, as in the case of FIG. 5, the presence of fluorine promotes the segregation of magnesium. FIG. 6(D) shows a state in which heating has been sufficiently performed from FIG. 6(C) and the positive electrode active material 100 which is one embodiment of the present invention is obtained. The presence of the cobalt oxide layer 124 having a rock salt-type crystal structure on the surface makes it considered that magnesium exists more stably as magnesium oxide on the surface of the particles 120 than inside the particles 120. Also, as in the case of FIG. 5, the presence of fluorine promotes the segregation of magnesium. FIG. 6(D) shows a state in which heating has been sufficiently performed from FIG. 6(C) and the positive electrode active material 100 which is one embodiment of the present invention is obtained. The presence of the cobalt oxide layer 124 having a rock salt-type crystal structure on the surface makes it considered that magnesium exists more stably as magnesium oxide on the surface of the particles 120 than inside the particles 120. Also, as in the case of FIG. 5, the presence of fluorine promotes the segregation of magnesium. FIG. 6(D) shows a state in which heating has been sufficiently performed from FIG. 6(C) and the positive electrode active material 100 which is one embodiment of the present invention is obtained. The presence of the cobalt oxide layer 124 having a rock salt-type crystal structure on the surface makes it considered that magnesium exists more stably as magnesium oxide on the surface of the particles 120 than inside the particles 120. Also, as in the case of FIG. 5, the presence of fluorine promotes the segregation of magnesium. FIG. 6(D) shows a state in which heating has been sufficiently performed from FIG. 6(C) and the positive electrode active material 100 which is one embodiment of the present invention is obtained. The presence of the cobalt oxide layer 124 having a rock salt-type crystal structure on the surface makes it considered that magnesium exists more stably as magnesium oxide on the surface of the particles 120 than inside the particles 120. Also, as in the case of FIG. 5, the presence of fluorine promotes the segregation of magnesium.

[0187] Therefore, as shown in FIG. 6(D), magnesium and fluorine contained in the region 121 segregate to the surface and together with cobalt oxide form a third region 103. Therefore, as shown in FIG. 6(D), magnesium and fluorine contained in the region 121 segregate to the surface and together with cobalt oxide form a third region 103.

[0188] In this way, a positive electrode active material 100 having a third region 103 having magnesium oxide and cobalt oxide, a second region 102 having lithium titanate, and a first region 101 having lithium cobaltate is produced. In this way, a positive electrode active material 100 having a third region 103 having magnesium oxide and cobalt oxide, a second region 102 having lithium titanate, and a first region 101 having lithium cobaltate is produced. In this way, a positive electrode active material 100 having a third region 103 having magnesium oxide and cobalt oxide, a second region 102 having lithium titanate, and a first region 101 having lithium cobaltate is produced.

[0189] When segregating typical elements by heating, when the composite oxide containing lithium and the first transition metal in the first region 101 is polycrystalline or when crystal defects are present, not only in the surface layer portion but also in the vicinity of grain boundaries or crystal defects of the composite oxide containing lithium and the first transition metal, typical elements are also segregated. When segregating typical elements by heating, when the composite oxide containing lithium and the first transition metal in the first region 101 is polycrystalline or when crystal defects are present, not only in the surface layer portion but also in the vicinity of grain boundaries or crystal defects of the composite oxide containing lithium and the first transition metal, typical elements are also segregated. When segregating typical elements by heating, when the composite oxide containing lithium and the first transition metal in the first region 101 is polycrystalline or when crystal defects are present, not only in the surface layer portion but also in the vicinity of grain boundaries or crystal defects of the composite oxide containing lithium and the first transition metal, typical elements are also segregated. Elements may segregate. Typical elements segregated near grain boundaries or crystal defects may contribute to further stabilization of the crystal structure of the composite oxide containing lithium and the first transition metal that the first region 101 has.

[0190] When the composite oxide containing lithium and the first transition metal that the first region 101 has has a crack part, typical elements may also segregate to the crack part by heating. Also, not only typical elements but also the second transition metal may segregate. The crack part is a region in contact with the electrolyte, like the particle surface. Therefore, when typical elements and the second transition metal segregate to the crack part and the third region 103 and the second region 102 are formed, the region in contact with the electrolyte can be made of a chemically stable material. Therefore, a secondary battery with excellent cycle characteristics can be obtained.

[0191] When the ratio of the typical element (T) to fluorine (F) in the starting material is in the range of T:F = 1:x (1.5 ≤ x ≤ 4) (atomic ratio), segregation of the typical element occurs effectively, which is preferable. Also, it is more preferable that T:F is about 1:2 (atomic ratio).

[0192] Since the third region 103 formed by segregation is formed by epitaxial growth, the crystal orientations of the second region 102 and the third region 103 may be generally in agreement in part. That is, the second region 102 and the third region 103 may be topotactic. When the crystal orientations of the second region 102 and the third region 103 are generally in agreement, they can function as a better coating layer.

[0193] However, all of the typical elements such as magnesium added as the starting material are in the third region 10 ​​​​​​​​​​​​​It does not have to be segregated to 3. For example, the first region 101 may slightly contain typical elements such as magnesium. It may contain a small amount.

[0194] <The fourth region 104> Also, as shown in FIG. 1(C), the positive electrode active material 100 may have a fourth region 1 04 on the third region 103. Further, when the positive electrode active material 100 has defects such as a crack portion 106, the fourth region 104 may exist so as to fill the defects such as the crack portion 106. It may be.

[0195] The fourth region 104 has a part of the elements included in the second region 102 and the third region 103. For example, the fourth region 104 has a second transition metal and a typical element.

[0196] The fourth region 104 may be convex, strip-shaped, or layered. The fourth region 104 is formed from the second transition metal and the typical element that are included in the starting material or the like and are not included in the second region 102 and the third region 103. That is, the presence of the fourth region 104 can maintain the second transition metal and the typical element included in the second region 102 and the third region 103 in an appropriate amount, and may stabilize the crystal structure of the second region 102 and the third region 103. Further, the presence of the fourth region 104 may repair defects such as the crack portion 106 that the positive electrode active material 100 has. The presence of the fourth region 104 and the shape of the fourth region 104 can be observed by SEM (scanning electron microscope) or the like. In addition, the elements included in the fourth region 104 are SEM- The presence of the fourth region 104 and the shape of the fourth region 104 can be observed by SEM (scanning electron microscope) or the like. Also, the elements included in the fourth region 104 are SEM- It may be possible to repair defects such as the crack portion 106 that the positive electrode active material 100 has.

[0197] The presence of the fourth region 104 and the shape of the fourth region 104 can be observed by SEM (scanning electron microscope) or the like. Also, the elements included in the fourth region 104 are SEM- microscope) or the like. Also, the elements included in the fourth region 104 are SEM- It can be analyzed by EDX or the like.

[0198] [Method for producing a positive electrode active material] Next, an example of a method for producing the positive electrode active material 100 according to one aspect of the present invention will be described.

[0199] <Step 11: Preparation of starting materials> First, starting materials are prepared. From the materials prepared in this step, finally, the first region 10 1 and the third region 103 are formed.

[0200] As a lithium source and a raw material of the first transition metal included in the first region 101, a lithium source and a first transition metal source are prepared. Further, as a raw material of the compound of the typical element included in the third region 103 , a typical element source is prepared.

[0201] In addition to these, it is preferable to prepare a fluorine source. By adding fluorine to the raw materials, it has the effect of promoting the segregation of the typical element included in the third region 103 on the surface of the positive electrode active material 100 in a later step .

[0202] As the lithium source, for example, lithium carbonate or lithium fluoride can be used. As the first transition metal source, for example, an oxide of the first transition metal can be used. As the typical element source, for example, an oxide of the typical element included in the third region, a fluoride of the typical element included in the third region etc. can be used.

[0203] As the fluorine source, for example, lithium fluoride, a fluoride of the typical element included in the third region, etc. can be used. That is, lithium fluoride can be used as both a lithium source and a fluorine source.

[0204] The fluorine contained in the fluorine source is 1.0 times or more and 4 times or less (atomic ratio) of the typical element contained in the typical element source, preferably 1.5 times or more and 3 times or less (atomic ratio), and more preferably so. (atomic ratio), and more preferably 1.5 times or more and 3 times or less (atomic ratio). Furthermore, it is more preferable.

[0205] <Step 12: Mixing of starting materials> Next, a lithium source, a first transition metal source, and a typical element source are mixed. It is preferable to further add a fluorine source. For mixing, for example, a ball mill or a bead mill can be used.

[0206] <Step 13: First heating> Next, the material mixed in Step 12 is heated. This step may be called firing or first heating. The heating is preferably performed at 800 °C or higher and 1100 °C or lower, more preferably 900 °C or higher and 1000 °C or lower. The heating time is preferably 2 hours or more and 20 hours or less. Firing is preferably performed in a dry atmosphere such as dry air. The dry atmosphere preferably has a dew point of -50 °C or lower, more preferably an atmosphere of -100 °C or lower. In this embodiment, heating is performed at 1000 °C for 10 hours, and the temperature is raised at 200 °C / h, and dry air with a dew point of -109 °C is flowed at 10 L / min. Then, the heated material is cooled to room temperature.

[0207] By the heating in Step 13, a composite oxide of lithium and the first transition metal having a layered rock salt-type crystal structure can be synthesized. At this point, the typical element and fluorine contained in the starting material are dissolved in the composite oxide. However, in some cases, a part of the typical element may be unevenly distributed on the surface of the composite oxide. composite oxide of lithium and the first transition metal having a layered rock salt-type crystal structure can be synthesized. At this point, the typical element and fluorine contained in the starting material are dissolved in the composite oxide. However, in some cases, a part of the typical element may be unevenly distributed on the surface of the composite oxide. fluorine are dissolved in the composite oxide. However, in some cases, a part of the typical element may already be unevenly distributed on the surface of the composite oxide. surface.

[0208] Alternatively, particles of a composite oxide containing lithium, cobalt, fluorine, and magnesium, which have been synthesized in advance as starting materials, may be used. In this case, Steps 12 and 13 can be omitted. For example, lithium cobaltate particles (trade name: C-20F) manufactured by Nippon Chemical Industry Co., Ltd. can be used as one of the starting materials. These have a particle size of about 20 μm and are lithium cobaltate particles containing fluorine, magnesium, calcium, sodium, silicon, sulfur, and phosphorus in a region analyzable by XPS from the surface. can be used. In this case, Steps 12 and 13 can be omitted. For example, lithium cobaltate particles (trade name: C-20F) manufactured by Nippon Chemical Industry Co., Ltd. can be used as one of the starting materials. These have a particle size of about 20 μm and are lithium cobaltate particles containing fluorine, magnesium, calcium, sodium, thorium, silicon, sulfur, and phosphorus in a region analyzable by XPS from the surface.

[0209] <Step 14: Coating with a second transition metal> Next, the composite oxide of lithium and the first transition metal is cooled to room temperature. Then, the surface of the composite oxide particles of lithium and the first transition metal is coated with a material having the second transition metal. In this manufacturing method example, the sol-gel method is applied. First, an alkoxide of the second transition metal dissolved in alcohol and the composite oxide particles of lithium and the first transition metal are mixed. In this manufacturing method example, the sol-gel method is applied.

[0210] First, an alkoxide of the second transition metal dissolved in alcohol and the composite oxide particles of lithium and the first transition metal are mixed. For example, when titanium is used as the second transition metal, TTIP can be used as the alkoxide of the second transition metal. Also, for example, isopropanol can be used as the alcohol.

[0211] For example, when titanium is used as the second transition metal, TTIP can be used as the alkoxide of the second transition metal. Also, for example, isopropanol can be used as the alcohol. For example, when titanium is used as the second transition metal, TTIP can be used as the alkoxide of the second transition metal. Also, for example, isopropanol can be used as the alcohol. For example, when titanium is used as the second transition metal, TTIP can be used as the alkoxide of the second transition metal. Also, for example, isopropanol can be used as the alcohol.

[0212] Next, the above mixture is stirred in an atmosphere containing water vapor. The stirring can be performed, for example, with a magnetic stirrer. The stirring time should be sufficient for water and TTIP in the atmosphere to undergo hydrolysis and polycondensation reactions. For example, 4 hours, 25°C, and 90%RH humidity. Next, the above mixture is stirred in an atmosphere containing water vapor. The stirring can be performed, for example, with a magnetic stirrer. The stirring time should be sufficient for water and TTIP in the atmosphere to undergo hydrolysis and polycondensation reactions. For example, 4 hours, 25°C, and 90%RH humidity. Next, the above mixture is stirred in an atmosphere containing water vapor. The stirring can be performed, for example, with a magnetic stirrer. The stirring time should be sufficient for water and TTIP in the atmosphere to undergo hydrolysis and polycondensation reactions. For example, 4 hours, 25°C, and 90%RH humidity. The stirring time should be sufficient for water and TTIP in the atmosphere to undergo hydrolysis and polycondensation reactions. For example, 4 hours, 25°C, and 90%RH humidity. It can be carried out under the condition of (Relative Humidity, relative humidity).

[0213] As described above, by reacting water in the atmosphere with TTIP, the sol-gel reaction can proceed more slowly than when adding liquid water. Also, by reacting titanium alkoxide with water at room temperature, the sol-gel reaction can proceed more slowly than when heating, for example, at a temperature exceeding the boiling point of the alcohol solvent. By reacting titanium alkoxide with water, the sol-gel reaction can proceed more slowly than when heating, for example, at a temperature exceeding the boiling point of the alcohol solvent. By proceeding with the sol-gel reaction slowly, a coating layer containing titanium with a uniform thickness and good quality can be formed. By proceeding with the sol-gel reaction slowly, a coating layer containing titanium with a uniform thickness and good quality can be formed.

[0214] Precipitates are recovered from the mixed solution after the above treatment. As the recovery method, filtration, centrifugation , evaporation to dryness, etc. can be applied. In this embodiment, recovery is performed by filtration . A paper filter is used for filtration, and the residue is washed with the same alcohol as the solvent in which the titanium alkoxide is dissolved .

[0215] Next, the recovered residue is dried. In this embodiment, vacuum drying is performed at 70°C for 1 hour .

[0216] <Step 15: Second Heating> Next, the composite oxide particles coated with the material having the second transition metal produced in Step 14 are heated. This step may be referred to as the second heating. The heating time is preferably set such that the holding time within the specified temperature range is 50 hours or less, more preferably 2 hours or more and 10 hours or less , and even more preferably 1 hour or more and 3 hours or less. If the heating time is too short, segregation of typical elements may not occur, but if it is too long, diffusion of the second transition metal may proceed too far and a good second region 102 may not be formed . too short, segregation of typical elements may not occur, but if it is too long, diffusion of the second transition metal may proceed too far and a good second region 102 may not be formed .

[0217] The specified temperature is preferably 500°C or higher and 1200°C or lower, and more preferably 800°C or higher and 1000°C or lower. If the specified temperature is too low, segregation of the main group elements and second transition metals will not occur. However, if the temperature is too high, the first transition metal in the composite oxide particles will be reduced, and the composite oxide The layer structure of lithium and the first transition metal in the composite oxide particle is broken down. There is a risk that it may not be possible to maintain the quality.

[0218] In this embodiment, the specified temperature is set to 800°C and is maintained for 2 hours, and the temperature is increased by 200°C. / h, and the flow rate of dry air is 10 L / min.

[0219] By heating in step 15, a composite oxide of lithium and a first transition metal is formed, and a coating thereon is formed. The oxide of the second transition metal is topotactic. Region 102 is the topotaxis.

[0220] Furthermore, by heating in step 15, the inside of the composite oxide particles of lithium and the first transition metal is The typical elements that were in solid solution become unevenly distributed on the surface, that is, segregate, and become compounds of the typical elements. The third region 103 is formed. At this time, the compound of the main group element is transferred from the second region 102 to the hetero That is, the second region 102 and the third region 103 grow epitaxially. become.

[0221] The crystal orientations of the second region 102 and the third region 103 are roughly the same, and the crystal orientations of the first region 101 are When the positive electrode active material 100 is used in a secondary battery, the positive electrode active material 100 exhibits stable bonding with the positive electrode active material 100. This effectively suppresses the change in the crystal structure of the first region 101 that occurs when the first region 101 is charged. Even when lithium has left the first region 101, the surface layer portion having a stable bond can prevent the first transition metal such as cobalt and oxygen from detaching from the first region 101. Furthermore, the region in contact with the electrolytic solution can be made of a chemically stable material. Therefore, a secondary battery with excellent cycle characteristics can be obtained. Note that it is sufficient if a part of the first region 101 and the second region 102 is topotactic, and it is not necessary for all of the first region 101 and the second region 102 to be topotactic. Also, it is sufficient if a part of the second region 102 and the third region 103 is topotactic, and it is not necessary for all of the second region 102 and the third region 103 to be topotactic.

[0222] In addition, when the compound of the representative element included in the third region contains oxygen, it is preferable to perform the heating in step 15 in an atmosphere containing oxygen. By heating in an atmosphere containing oxygen, the formation of the third region 103 is promoted. Also, segregation of the representative element is promoted by the fluorine contained in the starting material. In this way, in the method for producing a positive electrode active material according to one aspect of the present invention, after coating the element for forming the second region 102, heating is performed to form the third region 103, and it becomes possible to form two types of regions on the surface of the positive electrode active material 100. That is, normally, two coating steps are required to provide two types of regions in the surface layer portion, but the method for producing a positive electrode active material according to one aspect of the present invention only requires one coating step (sol-gel step), so it is a production method with good productivity.

[0223]

[0224]

[0225]

[0226] <Step 16: Cooling> Next, the particles heated in Step 15 are cooled to room temperature. If the temperature drop time is long, it is preferable because it is easy to make them topotactic. For example, the temperature drop time from the holding temperature to room temperature is preferably the same or longer than the temperature rise time, specifically 10 hours or more and 50 hours or less.

[0227] <Step 17: Recovery> Next, the cooled particles are recovered. Further, it is preferable to sieve the particles. In the above process, the positive electrode active material 100 having the first region 101, the second region 102, and the third region 103 can be produced.

[0228] This embodiment can be implemented in appropriate combination with other embodiments.

[0229] (Embodiment 2) In this embodiment, examples of materials that can be used for the secondary battery having the positive electrode active material 100 described in the previous embodiment will be described. In this embodiment, a secondary battery in which the positive electrode, the negative electrode, and the electrolyte are wrapped in an exterior body will be described as an example.

[0230] [Positive Electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector. [[ID=۳۸]]

[0231] [Positive Electrode Active Material Layer] The positive electrode active material layer has at least a positive electrode active material. Further, the positive electrode active material layer may contain other substances such as a film on the surface of the active material, a conductive assistant, or a binder in addition to the positive electrode active material.

[0232] As the positive electrode active material, the positive electrode active material 100 described in the previous embodiment can be used. By using the positive electrode active material 100 described in the previous embodiment, high capacity and cycle characteristics ​​​​It can be an excellent secondary battery.

[0233] As the conductive assistant, a carbon material, a metal material, a conductive ceramic material, etc. can be used. Also, a fibrous material may be used as the conductive assistant. The content of the conductive assistant relative to the total amount of the active material layer is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less.

[0234] The conductive assistant can form an electric conduction network in the active material layer. The conductive assistant can maintain the electric conduction path between the positive electrode active materials. By adding the conductive assistant to the active material layer, an active material layer having high electric conductivity can be realized.

[0235] As the conductive assistant, for example, natural graphite, artificial graphite such as mesocarbon microbeads, carbon fibers, etc. can be used. As the carbon fibers, for example, carbon fibers such as mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers can be used. Also, as the carbon fibers, carbon nanofibers, carbon nanotubes, etc. can be used. The carbon nanotubes can be produced, for example, by a vapor growth method. Also, as the conductive assistant, for example, carbon materials such as carbon black (such as acetylene black (AB)), graphite (black lead) particles, graphene, fullerene, etc. can be used. Also, for example, metal powders, metal fibers, conductive ceramic materials, etc. such as copper, nickel, aluminum, silver, gold can be used.

[0236] Also, a graphene compound may be used as the conductive assistant.

[0237] ​Graphene compounds may have excellent electrical properties such as high conductivity, and excellent physical properties such as high flexibility and high mechanical strength. In addition, graphene compounds have a planar shape. Graphene compounds enable surface contact with low contact resistance. In addition, they may have very high conductivity even when thin, and can efficiently form conductive paths in the active material layer in a small amount. Therefore, it is preferable to use a graphene compound as a conductive aid because the contact area between the active material and the conductive aid can be increased. By using a spray dryer, it is preferable to form a coating of the graphene compound, which is a conductive aid, covering the entire surface of the active material. In addition, it may be preferable because the electrical resistance can be reduced. Here, as the graphene compound, it is particularly preferable to use, for example, graphene or multi-graphene or RGO. Here, RGO refers to a compound obtained by reducing graphene oxide (GO), for example. When using an active material with a small particle size, for example, an active material of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive aid tends to increase, and the relative amount of the active material supported tends to decrease. When the supported amount of the active material decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as a conductive aid, since the graphene compound can efficiently form conductive paths even in a small amount, it is not necessary to reduce the supported amount of the active material, which is particularly preferable. Hereinafter, as an example, when a graphene compound is used as a conductive aid in the active material layer 200

[0238] When using an active material with a small particle size, for example, an active material of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive aid tends to increase, and the relative amount of the active material supported tends to decrease. When the supported amount of the active material decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as a conductive aid, since the graphene compound can efficiently form conductive paths even in a small amount, it is not necessary to reduce the supported amount of the active material, which is particularly preferable. When the supported amount of the active material decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as a conductive aid, since the graphene compound can efficiently form conductive paths even in a small amount, it is not necessary to reduce the supported amount of the active material, which is particularly preferable. the graphene compound can efficiently form conductive paths even in a small amount, so it is not necessary to reduce the supported amount of the active material, which is particularly preferable.

[0239] Hereinafter, as an example, when a graphene compound is used as a conductive aid in the active material layer 200 An example of the cross-sectional structure will be described.

[0240] FIG. 7(A) shows a longitudinal sectional view of the active material layer 200. The active material layer 200 includes granular positive electrode active material 100, a graphene compound 201 as a conductive assistant, and a binder (not shown). Here, for example, graphene or multi-graphene may be used as the graphene compound 201. Here, the graphene compound 201 preferably has a sheet-like shape. Also, the graphene compound 201 may be a sheet formed by partial overlap of a plurality of multi-graphenes and / or a plurality of graphenes.

[0241] In the longitudinal section of the active material layer 200, as shown in FIG. 7(B), the sheet-like graphene compound 201 is dispersed substantially uniformly inside the active material layer 200. In FIG. 7(B), the graphene compound 201 is schematically represented by a thick line, but actually it is a thin film having a thickness of a single layer or multiple layers of carbon molecules. A plurality of graphene compounds 201 are formed so as to partially cover a plurality of granular positive electrode active materials 100 or to adhere onto the surfaces of a plurality of granular positive electrode active materials 100, so they are in surface contact with each other.

[0242] Here, by bonding a plurality of graphene compounds to each other, a network-like graphene compound sheet (hereinafter referred to as a graphene compound net or graphene net) can be formed. When the active material is covered with the graphene net, the graphene net can also function as a binder that binds the active materials together. Therefore, the amount of the binder can be reduced or it can be not used, so the ratio of the active material in the electrode volume and electrode weight ​​​​​​​The rate can be improved. That is, the capacity of the secondary battery can be increased.

[0243] Here, it is preferable to use graphene oxide as the graphene compound 201, mix it with the active material, and then reduce it after forming the layer that becomes the active material layer 200. By using graphene oxide, which has extremely high dispersibility in a polar solvent, for the formation of the graphene compound 201, the graphene compound 201 can be dispersed approximately uniformly inside the active material layer 200. After removing the solvent by volatilization from the dispersion medium containing uniformly dispersed graphene oxide and reducing the graphene oxide, the graphene compounds 201 remaining in the active material layer 200 partially overlap each other and are dispersed to the extent of surface contact with each other, so that a three-dimensional conductive path can be formed. Here, it is preferable to use graphene oxide as the graphene compound 201, mix it with the active material, and then reduce it after forming the layer that becomes the active material layer 200. By using graphene oxide, which has extremely high dispersibility in a polar solvent, for the formation of the graphene compound 201, the graphene compound 201 can be dispersed approximately uniformly inside the active material layer 200. After removing the solvent by volatilization from the dispersion medium containing uniformly dispersed graphene oxide and reducing the graphene oxide, the graphene compounds 201 remaining in the active material layer 200 partially overlap each other and are dispersed to the extent of surface contact with each other, so that a three-dimensional conductive path can be formed. After removing the solvent by volatilization from the dispersion medium containing uniformly dispersed graphene oxide and reducing the graphene oxide, the graphene compounds 201 remaining in the active material layer 200 partially overlap each other and are dispersed to the extent of surface contact with each other, so that a three-dimensional conductive path can be formed. After removing the solvent by volatilization from the dispersion medium containing uniformly dispersed graphene oxide and reducing the graphene oxide, the graphene compounds 201 remaining in the active material layer 200 partially overlap each other and are dispersed to the extent of surface contact with each other, so that a three-dimensional conductive path can be formed. After removing the solvent by volatilization from the dispersion medium containing uniformly dispersed graphene oxide and reducing the graphene oxide, the graphene compounds 201 remaining in the active material layer 200 partially overlap each other and are dispersed to the extent of surface contact with each other, so that a three-dimensional conductive path can be formed. The reduction of graphene oxide may be performed, for example, by heat treatment or by using a reducing agent. The reduction of graphene oxide may be performed, for example, by heat treatment or by using a reducing agent.

[0244] Therefore, unlike granular conductive aids such as acetylene black that make point contact with the active material, the graphene compound 201 enables surface contact with low contact resistance. Thus, it can improve the electrical conductivity between the granular positive electrode active material 100 and the graphene compound 201 with a smaller amount than ordinary conductive aids. Therefore, unlike granular conductive aids such as acetylene black that make point contact with the active material, the graphene compound 201 enables surface contact with low contact resistance. Thus, it can improve the electrical conductivity between the granular positive electrode active material 100 and the graphene compound 201 with a smaller amount than ordinary conductive aids. Therefore, unlike granular conductive aids such as acetylene black that make point contact with the active material, the graphene compound 201 enables surface contact with low contact resistance. Thus, it can improve the electrical conductivity between the granular positive electrode active material 100 and the graphene compound 201 with a smaller amount than ordinary conductive aids. Therefore, unlike granular conductive aids such as acetylene black that make point contact with the active material, the graphene compound 201 enables surface contact with low contact resistance. Thus, it can improve the electrical conductivity between the granular positive electrode active material 100 and the graphene compound 201 with a smaller amount than ordinary conductive aids. Therefore, the ratio of the granular positive electrode active material 100 in the active material layer 200 can be increased. As a result, the discharge capacity of the secondary battery can be increased.

[0245] Also, it is possible to cover the entire surface of the active material with the graphene compound in advance using a spray drying device. Then, when producing the positive electrode active material layer, adding more graphene compound can further improve the conductive path between the active materials. Also, it is possible to cover the entire surface of the active material with the graphene compound in advance using a spray drying device. Then, when producing the positive electrode active material layer, adding more graphene compound can further improve the conductive path between the active materials. Also, it is possible to cover the entire surface of the active material with the graphene compound in advance using a spray drying device. Then, when producing the positive electrode active material layer, adding more graphene compound can further improve the conductive path between the active materials.

[0246] As the binder, for example, rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. are preferably used. Also, fluororubber can be used as the binder.

[0247] Also, as the binder, for example, water-soluble polymers are preferably used. As the water-soluble polymer, for example, polysaccharides can be used. As the polysaccharide, carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, cellulose derivatives such as diacetyl cellulose, regenerated cellulose, starch, etc. can be used. Also, using these water-soluble polymers in combination with the aforementioned rubber materials is even more preferable.

[0248]

[0249] The binder may be used in combination of a plurality of the above.

[0250] ​​​​​​​​​​​​​​​For example, a material with particularly excellent viscosity adjustment effect may be used in combination with other materials. For example, rubber materials and the like are excellent in adhesive force and elastic force, but it may be difficult to adjust the viscosity when mixed with a solvent. In such a case, for example, it is preferable to mix with a material having a particularly excellent viscosity adjustment effect. As the material having a particularly excellent viscosity adjustment effect, for example, a water-soluble polymer may be used. In addition, as the water-soluble polymer having a particularly excellent viscosity adjustment effect, the polysaccharides described above, for example, carbo xymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxy propyl cellulose and diacetyl cellulose, cellulose derivatives such as regenerated cellulose, or starch can be used.

[0251] Note that cellulose derivatives such as carboxymethyl cellulose can be made into salts such as sodium salts and ammonium salts of carboxymethyl cellulose, so that the solubility increases, and it becomes easier to exhibit the effect as a viscosity modifier. By increasing the solubility, the dispersibility with the active material and other components can also be enhanced when preparing the electrode slurry. In this specification, the cellulose and cellulose derivatives used as the electrode binder shall include those salts.

[0252] The water-soluble polymer stabilizes the viscosity by dissolving in water, and can also stably disperse the active material and other materials combined as a binder, for example, styrene-butadiene rubber, in an aqueous solution. In addition, since it has a functional group, it is expected to be easily adsorbed stably on the surface of the active material. In addition, cellulose derivatives such as carboxymethyl cellulose have many functional groups such as hydroxyl groups and carboxyl groups, and because they have functional groups, It is expected that polymers interact with each other and widely cover the surface of the active material.

[0253] When a binder that covers or contacts the surface of the active material forms a film, it is also expected to serve as a passivation film and suppress the decomposition of the electrolyte. Here, the passivation film is a film with no electron conductivity or extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. In addition, it is more desirable that the passivation film suppresses electrical conductivity while allowing lithium ions to conduct. A film with no electron conductivity or extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. In addition, it is more desirable that the passivation film suppresses electrical conductivity while allowing lithium ions to conduct. A film with no electron conductivity or extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. In addition, it is more desirable that the passivation film suppresses electrical conductivity while allowing lithium ions to conduct.

[0254] <Positive current collector> As the positive current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and alloys thereof, which have high conductivity, can be used. Also, the material used for the positive current collector preferably does not elute at the potential of the positive electrode. In addition, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, and molybdenum to improve heat resistance can be used. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector preferably has a thickness of 5 μm or more and 30 μm or less. As the positive current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and alloys thereof, which have high conductivity, can be used. Also, the material used for the positive current collector preferably does not elute at the potential of the positive electrode. In addition, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, and molybdenum to improve heat resistance can be used. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector preferably has a thickness of 5 μm or more and 30 μm or less. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector preferably has a thickness of 5 μm or more and 30 μm or less. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector preferably has a thickness of 5 μm or more and 30 μm or less. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector preferably has a thickness of 5 μm or more and 30 μm or less. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector preferably has a thickness of 5 μm or more and 30 μm or less. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector preferably has a thickness of 5 μm or more and 30 μm or less. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector preferably has a thickness of 5 μm or more and 30 μm or less.

[0255] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. Further, the negative electrode active material layer may have a conductive assistant and a binder.

[0256] <Negative electrode active material> As the negative electrode active material, for example, an alloy-based material, a carbon-based material, or the like can be used.

[0257] As the negative electrode active material, an element capable of performing a charge-discharge reaction by an alloying / dealloying reaction with lithium can be used. For example, at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used. Such an element has a larger capacity than carbon, and particularly silicon has a high theoretical capacity of 4200 mAh / g. Therefore, it is preferable to use silicon as the negative electrode active material. Further, a compound having these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, SbSn, etc. are available. Here, an element capable of performing a charge-discharge reaction by an alloying / dealloying reaction with lithium, and a compound having the element, etc. may be referred to as an alloy-based material in some cases.

[0258] In this specification, etc., SiO refers to, for example, silicon monoxide. Alternatively, SiO can be expressed as SiO x . Here, x preferably has a value in the vicinity of 1. For example, x is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less. x

[0259] As the carbon-based material, graphite, graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, carbon black, etc. may be used. .

[0260] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. Here, spherical graphite having a spherical shape can be used as the artificial graphite. For example, MCMB may have a spherical shape, which is preferable. Also, it is relatively easy to reduce the surface area of MCMB, which may be preferable. Examples of natural graphite include flake graphite, spheroidized natural graphite, etc.

[0261] Graphite exhibits a potential as low as that of lithium metal (0.05 V or more and 0.3 V or less vs. Li / Li) when lithium ions are inserted into the graphite (when a lithium-graphite intercalation compound is formed). i +

[0262] Also, as the negative electrode active material, oxides such as titanium dioxide (TiO2), lithium titanate (Li4Ti5O12), lithium-graphite intercalation compound (LiC6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2) can be used. i5O 12 x

[0263] Also, as the negative electrode active material, a Li3N-type structure, which is a complex nitride of lithium and a transition metal, can be used. Li 3-x M x N (M = Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 exhibits a large charge-discharge capacity (900 mAh / g, 1890 mAh / cm 3 ) and is preferable. and is preferable.

[0264] When using a complex nitride of lithium and a transition metal, since the negative electrode active material contains lithium ions, it can be preferably combined with materials such as V2O5 and Cr3O8 that do not contain lithium ions as the positive electrode active material. Even when using a material containing lithium ions for the positive electrode active material, by previously desorbing the lithium ions contained in the positive electrode active material, a complex nitride of lithium and a transition metal can be used as the negative electrode active material. it can be preferably combined with materials such as V2O5 and Cr3O8 that do not contain lithium ions as the positive electrode active material. Even when using a material containing lithium ions for the positive electrode active material, by previously desorbing the lithium ions contained in the positive electrode active material, a complex nitride of lithium and a transition metal can be used as the negative electrode active material.

[0265] Also, a material that undergoes a conversion reaction can be used as the negative electrode active material. For example, transition metal oxides such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), which do not form alloys with lithium, may be used as the negative electrode active material. As materials that undergo a conversion reaction, furthermore, oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, sulfides such as CoS, NiS, and CuS, 0.89 nitrides such as Zn3N2, Cu3N, and Ge3 N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3 also undergo the reaction.

[0266] As the conductive assistant and binder that the negative electrode active material layer can have, those that the positive electrode active material layer has Conductive aids that can be used and materials similar to binders can be used.

[0267] <Negative electrode current collector> For the negative electrode current collector, the same materials as those for the positive electrode current collector can be used. Note that the negative electrode current collector preferably uses a material that does not alloy with carrier ions such as lithium. It is preferable to use a material that does not alloy with carrier ions such as lithium.

[0268] [Electrolyte solution] The electrolyte solution has a solvent and an electrolyte. As the solvent of the electrolyte solution, an aprotic organic solvent is preferred. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., one kind, or two or more of these can be used in any combination and ratio. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. tetrahydrofuran, sulfolane, sultone, etc., one kind, or two or more of these can be used in any combination and ratio. tetrahydrofuran, sulfolane, sultone, etc., one kind, or two or more of these can be used in any combination and ratio.

[0269] In addition, by using one or more ionic liquids (room temperature molten salts) that are flame-retardant and have low volatility as the solvent of the electrolyte solution, even if the internal temperature rises due to internal short circuit or overcharging of the secondary battery, etc., rupture or ignition of the secondary battery can be prevented. The ionic liquid consists of a cation and an anion and contains an organic cation and an anion. As the organic cation used in the electrolyte solution, quaternary even if the internal temperature rises due to internal short circuit or overcharging of the secondary battery, etc., rupture or ignition of the secondary battery can be prevented. The ionic liquid consists of a cation and an anion and contains an organic cation and an anion. even if the internal temperature rises due to internal short circuit or overcharging of the secondary battery, etc., rupture or ignition of the secondary battery can be prevented. The ionic liquid consists of a cation and an anion and contains an organic cation and an anion. The ionic liquid consists of a cation and an anion and contains an organic cation and an anion. As the organic cation used in the electrolyte solution, quaternary Ammonium cations, tertiary sulfonium cations, quaternary phosphonium cations, etc. such as aliphatic onium cations, imidazolium cations, pyridinium cations, etc. Aromatic cations can be mentioned. Also, as anions used in the electrolyte, monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkyl sulfonic acid anions, tetrafluoroborate anions, perfluoroalkyl borate anions, hexafluorophosphate anions, or perfluoroalkyl phosphate anions, etc. can be mentioned.

[0270] Also, as electrolytes dissolved in the above solvents, 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, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. of lithium salts can be used alone, or two or more of these can be used in any combination and ratio. It is possible.

[0271] For the electrolyte used in the secondary battery, it is preferable to use a highly purified electrolyte with a low content of particulate dust and elements other than the constituent elements of the electrolyte (hereinafter, simply referred to as "impurities"). Specifically, the weight ratio of impurities to the electrolyte is preferably 1% or less, more preferably 0.1% or less, and even more preferably 0.01% or less. It is also simply referred to as "impurities".) Specifically, the weight ratio of impurities to the electrolyte is preferably 1% or less, more preferably 0.1% or less, and even more preferably 0.01% or less. It is preferable to set it as such.

[0272] In addition, additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), LiBOB, and dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolytic solution. The concentration of the additive material may be, for example, 0.1 wt% or more and 5 wt% or less based on the entire solvent. In addition, polymer gel electrolytes in which the polymer is swollen with an electrolytic solution may be used. Using the polymer gel electrolyte enhances the safety against liquid leakage and the like. In addition, the secondary battery can be made thinner and lighter. As the polymer to be gelled, silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide-based gel, polypropylene oxide-based gel, fluorine-based polymer gel, etc. can be used.

[0273] As the polymer, for example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, etc., and copolymers containing them can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. In addition, the formed polymer may have a porous shape.

[0274] In addition, instead of the electrolytic solution, solid electrolytes having inorganic materials such as sulfide-based and oxide-based materials, and solid electrolytes having polymer materials such as PEO (polyethylene oxide)-based materials can be used.

[0275]

[0276]

[0277] When using a solid electrolyte, it is not necessary to install a separator or a spacer. Also, since the entire battery can be solidified, the risk of leakage is eliminated and the safety is significantly improved. Moreover, it is preferable for a secondary battery to have a separator. As the separator, for example, paper,

[0278] [Separator] non-woven fabric, glass fiber, ceramics, or a synthetic fiber formed using nylon (polyamide), vinylon (poly vinyl alcohol-based fiber), polyester, acrylic, polyolefin, polyurethane, etc. can be used. The separator is preferably processed into an envelope shape and arranged to wrap either the positive electrode or the negative electrode. Moreover, the separator may have a multilayer structure. For example, a ceramic-based material, a fluorine-based material, a polyamide-based material, or a mixture thereof can be coated on an organic material film such as polypropylene or polyethylene. As the ceramic-based material, for example, aluminum oxide particles, silicon oxide particles, etc. can be used. As the fluorine-based material, for example, PVDF, polytetrafluoroethylene, etc. can be used. As the polyamide-based material, for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used.

[0279] Coating with a ceramic-based material improves oxidation resistance, so it is possible to suppress deterioration of the separator during high-voltage charge and discharge and improve the reliability of the secondary battery. Also, coating with a fluorine-based material makes it easier for the separator and the electrode to adhere, and it is possible to improve the output characteristics. Coating with a polyamide-based material, particularly aramid, improves heat resistance, so the safety of the secondary battery When coating with a ceramic-based material, the oxidation resistance is improved, so deterioration of the separator during high-voltage charge and discharge can be suppressed, and the reliability of the secondary battery can be improved. Also, when coating with a fluorine-based material, the separator and the electrode are likely to adhere, and the output characteristics can be improved. When coating with a polyamide-based material, particularly aramid, the heat resistance is improved, so the safety of the secondary battery For example, PVDF, polytetrafluoroethylene, etc. can be used as the fluorine-based material. For the polyamide-based material, for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used. For example, aluminum oxide particles, silicon oxide particles, etc. can be used as the ceramic-based material. can be improved.

[0280] Coating with a ceramic-based material improves oxidation resistance, so it is possible to suppress deterioration of the separator during high-voltage charge and discharge and improve the reliability of the secondary battery. Also, coating with a fluorine-based material makes it easier for the separator and the electrode to adhere, and it is possible to improve the output characteristics. Moreover, coating with a polyamide-based material, particularly aramid, improves heat resistance, so the safety of the secondary battery can be improved. can be improved. The safety can be improved.

[0281] For example, a mixed material of aluminum oxide and aramid may be coated on both sides of a polypropylene film. Also, a mixed material of aluminum oxide and aramid may be coated on the surface of the polypropylene film that contacts the positive electrode, and a fluorine-based material may be coated on the surface that contacts the negative electrode. .

[0282] When using a separator with a multilayer structure, even if the overall thickness of the separator is thin, the safety of the secondary battery can be maintained, so the capacity per unit volume of the secondary battery can be increased.

[0283] [Outer package] As the outer package of the secondary battery, for example, a metal material such as aluminum or a resin material can be used. Also, a film-shaped outer package can be used. As the film, for example, a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, with a flexible metal thin film such as aluminum, stainless steel, copper, or nickel provided on it, and further with an insulating synthetic resin film such as a polyamide-based resin or a polyester-based resin provided as the outer surface of the outer package on the metal thin film, a three-layer structure film can be used.

[0284] [Charging and discharging method] The charging and discharging of the secondary battery can be performed, for example, as follows.

[0285] ≪CC charging≫ First, as one of the charging methods, CC charging will be described. CC charging is a charging method in which a constant current is passed through the secondary battery throughout the charging period, and the charging is stopped when a predetermined voltage is reached. Assume the secondary battery to have an equivalent circuit of internal resistance R and secondary battery capacity C as shown in Fig. 8(A). In this case, the secondary battery voltage V B is the sum of the voltage V R across the internal resistance R and the voltage V across the secondary battery capacity C C .

[0286] While CC charging is being performed, as shown in Fig. 8(A), the switch is turned on and a constant current I flows into the secondary battery. During this period, since the current I is constant, according to Ohm's law V R =R×I, the voltage V across the internal resistance R is also constant. On the other hand, the voltage V R across the secondary battery capacity C rises with the passage of time. Therefore, the secondary battery voltage V C rises with the passage of time B as well.

[0287] And when the secondary battery voltage V B reaches a predetermined voltage, for example, 4.3V, the charging is stopped . When the CC charging is stopped, as shown in Fig. 8(B), the switch is turned off and the current I = 0 . Therefore, the voltage V R across the internal resistance R becomes 0V. Therefore, due to the elimination of the voltage drop across the internal resistance R , the secondary battery voltage V B drops.

[0288] Examples of the secondary battery voltage V B and the charging current during CC charging and after CC charging is stopped are shown in Fig. 8(C). The secondary battery voltage V which was rising during CC charging B is shown to slightly decrease after CC charging is stopped.

[0289] ≪CCCV Charging≫ ​​Next, CCCV charging, which is a charging method different from the above, will be described. CCCV charging first charges up to a predetermined voltage by CC charging, and then charges until the current flowing during CV (constant voltage) charging decreases, specifically until it reaches the termination current value.

[0290] While CC charging is being performed, as shown in Fig. 9(A), the switch of the constant current power supply is on, and the switch of the constant voltage power supply is off, and a constant current I flows into the secondary battery. During this period, since the current I is constant, according to Ohm's law of V R =R×I, the voltage V R across the internal resistance R is also constant. On the other hand, the voltage V C across the secondary battery capacity C increases with the passage of time. Therefore, the secondary battery voltage V increases with the passage of time. B

[0291] When the secondary battery voltage V B reaches a predetermined voltage, for example, 4.3V, the charging is switched from CC charging to C V charging. While CV charging is being performed, as shown in Fig. 9(B), the switch of the constant voltage power supply is on, the switch of the constant current power supply is off, and the secondary battery voltage V B becomes constant . On the other hand, the voltage V C across the secondary battery capacity C increases with the passage of time. Since V B =V R +V C , the voltage V R across the internal resistance R decreases with the passage of time. As the voltage V across the internal resistance R decreases, according to Ohm's law of V R =R×I, the current I flowing into the secondary battery also decreases. R

[0292] When the current I flowing through the secondary battery reaches a predetermined current, for example, a current equivalent to 0.01C , charging is stopped. When CCCV charging is stopped, as shown in Fig. 9(C), all switches turn off and the current I = 0. Therefore, the voltage V R across the internal resistance R becomes 0V . However, since the voltage V R across the internal resistance R has become sufficiently small due to CV charging , even when the voltage drop across the internal resistance R disappears, the secondary battery voltage V B hardly drops.

[0293] Examples of the secondary battery voltage V B and the charging current during CCCV charging and after CCCV charging is stopped are shown in Fig. 9(D). It shows that even when CCCV charging is stopped, the secondary battery voltage V B hardly drops.

[0294] ≪CC Discharge≫ Next, CC discharge, which is one of the discharge methods, will be described. CC discharge is a discharge method in which a constant current flows from the secondary battery throughout the discharge period, and the discharge is stopped when the secondary battery voltage V B reaches a predetermined voltage, for example, 2.5V.

[0295] Examples of the secondary battery voltage V B and the discharge current during CC discharge are shown in Fig. 10. It shows that as the discharge progresses , the secondary battery voltage V B ave

[0296] Next, the discharge rate and the charging rate will be described. The discharge rate is the relative ratio of the current during discharge to the battery capacity, and is expressed in units of C. In a battery with a rated capacity of X (Ah), a current equivalent to 1C is X (A). When discharging with a current of 2X (A), it is 2C It is said that discharging is performed, and when discharging is performed at a current of X / 5 (A), it is said that discharging is performed at 0.2C. The same applies to the charging rate. When charging is performed at a current of 2X (A), it is said that charging is performed at 2C. When charging is performed at a current of X / 5 (A), it is said that charging is performed at 0.2C. .

[0297] (Embodiment 3) In this embodiment, an example of the shape of the secondary battery having the positive electrode active material 100 described in the previous embodiment will be described. The materials used in the secondary battery described in this embodiment can refer to the description of the previous embodiment. .

[0298] [Coin-shaped secondary battery] First, an example of a coin-shaped secondary battery will be described. FIG. 11(A) is an external view of a coin-shaped (single-layer flat type ) secondary battery, and FIG. 11(B) is a cross-sectional view thereof.

[0299] The coin-shaped secondary battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal, which are insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact therewith. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact therewith.

[0300] Note that for the positive electrode 304 and the negative electrode 307 used in the coin-shaped secondary battery 300, the active material layers may be formed only on one side.

[0301] The positive electrode can 301 and the negative electrode can 302 are made of nickel or aluminum that is corrosion-resistant to the electrolytic solution. , metals such as titanium, or alloys thereof, or alloys of these with other metals (e.g., stainless steel etc.) can be used. Further, in order to prevent corrosion by the electrolytic solution, it is preferable to coat with nickel, aluminum etc. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 30 7 respectively.

[0302] These negative electrode 307, positive electrode 304 and separator 310 are impregnated with an electrolyte, and as shown in Fig. 11(B ), with the positive electrode can 301 facing downwards, the positive electrode 304, separator 310, negative electrode 307, negative electrode can 302 are laminated in this order, and the positive electrode can 301 and the negative electrode can 302 are crimped via a gasket 303 to manufacture a coin-shaped secondary battery 300.

[0303] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, a coin-type secondary battery 300 with high capacity and excellent cycle characteristics can be obtained.

[0304] Here, the flow of current during charging of the secondary battery will be described with reference to Fig. 11(C). When a secondary battery using lithium is regarded as a single closed circuit, the movement of lithium ions and the flow of current are in the same direction . In a secondary battery using lithium, the anode (positive electrode) and cathode (negative electrode) are reversed during charging and discharging, and the oxidation reaction and reduction reaction are reversed. Therefore, 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. Therefore, in this specification , whether during charging, discharging, when a reverse pulse current is flowing, or when a charging current is flowing, the positive electrode is called the "positive electrode" or the "+ electrode (plus electrode)", and the negative electrode is called the "negative electrode" or the "- electrode (minus electrode)". Related to oxidation reactions and reduction reactions ​​​If terms such as the following anode and cathode are used, they will be reversed during charging and discharging, which may cause confusion. Therefore, the terms anode and cathode shall not be used in this specification. If the terms anode and cathode are used, it shall be specified whether it is during charging or discharging, and it shall also be noted which corresponds to the positive electrode ( plus electrode) and the negative electrode (minus electrode).

[0305] A charger is connected to the two terminals shown in Fig. 11(C), and the secondary battery 300 is charged. As the charging of the secondary battery 300 progresses, the potential difference between the electrodes increases.

[0306] [Cylindrical Secondary Battery] Next, an example of a cylindrical secondary battery will be described with reference to Fig. 12. As shown in Fig. 12(A), the cylindrical secondary battery 600 has a positive electrode cap (battery lid) 601 on the upper surface and a battery can (outer can) 602 on the side surface and the bottom surface. The positive electrode cap and the battery can (outer can) 602 are insulated by a gasket (insulating packing) 610.

[0307] Fig. 12(B) is a diagram schematically showing a cross section of the cylindrical secondary battery. Inside the hollow cylindrical battery can 602, a wound battery element is provided in which a strip-shaped positive electrode 604 and a negative electrode 606 are sandwiched by a separator 605. Although not shown, the battery element is wound around a center pin. One end of the battery can 602 is closed and the other end is open. For the battery can 602, metals such as nickel, aluminum, and titanium that are corrosion-resistant to the electrolytic solution, or alloys thereof or alloys of these with other metals (for example, stainless steel, etc.) can be used. 。Also, in order to prevent corrosion by the electrolytic solution, it is preferable to coat nickel, aluminum, or the like. Inside the battery can 602, a battery element in which a positive electrode, a negative electrode, and a separator are wound is sandwiched between a pair of opposing insulating plates 608 and 609. Also, the inside of the battery can 602 where the battery element is provided is filled with a non-aqueous electrolytic solution (not shown). The non-aqueous electrolytic solution can be the same as that used in a coin-type secondary battery. For the positive electrode and negative electrode used in a cylindrical secondary battery, it is preferable to form active materials on both sides of the current collector in order to be wound. A positive electrode terminal (positive current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative current collector lead) 607 is connected to the negative electrode 606. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of a metal material such as aluminum. The positive electrode terminal 603 is resistance-welded to the safety valve mechanism 612, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602.

[0308] The safety valve mechanism 612 is electrically connected to the positive electrode cap 601 via a PTC element (Positive Temperature Coefficient) 611. When the internal pressure of the battery rises above a predetermined threshold value, the safety valve mechanism 612 cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604. The PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises. By increasing the resistance, the current amount is limited to prevent abnormal heat generation. For the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics or the like can be used. Also, as shown in FIG. 12(C), a plurality of secondary batteries 600 are connected in parallel by a conductive plate 613 and a conductive plate 614. The positive electrode terminal 603 and the negative electrode terminal 607 can both be made of a metal material such as aluminum. The positive electrode terminal 603 is resistance-welded to the safety valve mechanism 612, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 is electrically connected to the positive electrode cap 601 via a PTC element (Positive Temperature Coefficient) 611. When the internal pressure of the battery rises above a predetermined threshold value, the safety valve mechanism 612 cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604. The safety valve mechanism 612 is a device that cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the internal pressure of the battery rises above a predetermined threshold value. The PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises, and it limits the current amount to prevent abnormal heat generation by increasing the resistance. For the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics or the like can be used. The safety valve mechanism 612 is a device that cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the internal pressure of the battery rises above a predetermined threshold value. The PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises, and it limits the current amount to prevent abnormal heat generation by increasing the resistance. For the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics or the like can be used. The PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises, and it limits the current amount to prevent abnormal heat generation by increasing the resistance. For the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics or the like can be used. For the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics or the like can be used. For the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics or the like can be used.

[0309] Also, as shown in FIG. 12(C), a plurality of secondary batteries 600 are connected in parallel by a conductive plate 613 and a conductive plate 614. The module 615 may be configured by sandwiching it therebetween. The plurality of secondary batteries 600 may be connected in parallel, in series, or in parallel and then further in series. By configuring a module 615 having a plurality of secondary batteries 600, a large amount of power can be extracted.

[0310] FIG. 12(D) is a top view of the module 615. The conductive plate 613 is shown by a dotted line for clarity of the figure. As shown in FIG. 12(D), the module 615 may have wires 616 for electrically connecting a plurality of secondary batteries 600. The conductive plate 613 can be provided so as to overlap on the wire 616. Further, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 is overheated, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Therefore, the performance of the module 615 is less likely to be affected by the outside air temperature.

[0311] By using the positive electrode active material described in the previous embodiment for the positive electrode 604, a cylindrical secondary battery 600 with high capacity and excellent cycle characteristics can be obtained.

[0312] [Structural Example of Secondary Battery] Another structural example of the secondary battery will be described with reference to FIGS. 13 to 17.

[0313] FIGS. 13(A) and 13(B) are views showing the external appearance of the secondary battery. The secondary battery has a circuit board 900 and a secondary battery 913. A label 910 is attached to the secondary battery 913. Further, as shown in FIG. 13(B), the secondary battery has a terminal 951, a terminal 952, an antenna 914, and an antenna 915. ​​​​​​​​​​​

[0314] The circuit board 900 has a terminal 911 and a circuit 912. The terminal 911 is connected to the terminal 951 , the terminal 952, the antennas 914 and 915, and the circuit 912. Note that a plurality of terminals 911 may be provided, and each of the plurality of terminals 911 may be used as a control signal input terminal, a power supply terminal and so on.

[0315] The circuit 912 may be provided on the back surface of the circuit board 900. Note that the antennas 914 and 915 are not limited to a coil shape, and may be, for example, linear or plate-shaped. Also, a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, a dielectric antenna or other antennas may be used. Alternatively, the antenna 914 or the antenna 915 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling . That is, the antenna 914 or the antenna 915 may function as one of the two conductors of the capacitor. Thereby, power can be exchanged not only by electromagnetic fields and magnetic fields but also by electric fields.

[0316] The line width of the antenna 914 is preferably larger than the line width of the antenna 915. Thereby , the amount of power received by the antenna 914 can be increased.

[0317] The secondary battery has a layer 916 between the antennas 914 and 915 and the secondary battery 913. The layer 916 has a function of, for example, shielding the electromagnetic field generated by the secondary battery 913. As the layer 916, for example, a magnetic material can be used.

[0318] Note that the structure of the secondary battery is not limited to that shown in FIG. 13.

[0319] For example, as shown in FIGS. 14(A-1) and 14(A-2), among the secondary batteries 913 shown in FIGS. 13(A) and 13 (B), antennas may be provided on each of a pair of opposing surfaces. FIG. 14(A-1) is an external view seen from one side direction of the pair of surfaces, and FIG. 14( A-2) is an external view seen from the other side direction of the pair of surfaces. For the same parts as the secondary battery shown in FIGS. 13(A) and 13(B), the description of the secondary battery shown in FIGS. 13(A) and 13(B) can be appropriately incorporated.

[0320] As shown in FIG. 14(A-1), an antenna 914 is provided with a layer 916 sandwiched between one of a pair of surfaces of the secondary battery 913, and as shown in FIG. 14(A-2), an antenna 918 is provided with a layer 917 sandwiched between the other of a pair of surfaces of the secondary battery 913. The layer 917 has a function of being able to shield the electromagnetic field caused by the secondary battery 91 3. As the layer 917, for example, a magnetic material can be used.

[0321] By adopting the above structure, the sizes of both the antenna 914 and the antenna 918 can be increased . The antenna 918 has a function of being able to perform data communication with an external device, for example. For the antenna 918, an antenna having a shape applicable to the antenna 914, for example, can be applied. As the communication method between the secondary battery and another device via the antenna 918, response methods such as NFC that can be used between the secondary battery and another device can be applied.

[0322] Alternatively, as shown in FIG. 14(B-1), among the secondary batteries 9 shown in FIGS. 13(A) and 13(B) ​​​​​​A display device 920 may be provided at 13. The display device 920 is electrically connected to a terminal 911. Note that a label 910 does not have to be provided at the portion where the display device 920 is provided. Note that, for the same portions as the secondary battery shown in FIGS. 13(A) and 13(B), the description of the secondary battery shown in FIGS. 13(A) and 13(B) can be appropriately incorporated.

[0323] The display device 920 may display, for example, an image indicating whether charging is in progress, an image indicating the stored power amount, etc. As the display device 920, for example, electronic paper, a liquid crystal display device, an electroluminescence (also referred to as EL) display device, etc. can be used. For example, by using electronic paper, the power consumption of the display device 920 can be reduced.

[0324] Alternatively, as shown in FIG. 14(B-2), a sensor 921 may be provided in the secondary battery 913 shown in FIGS. 13(A) and 13(B). The sensor 921 is electrically connected to the terminal 911 via a terminal 922. Note that, for the same portions as the secondary battery shown in FIGS. 13(A) and 13(B), the description of the secondary battery shown in FIGS. 13(A) and 13(B) can be appropriately incorporated.

[0325] As the sensor 921, for example, it may have a function capable of measuring displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, inclination, vibration, odor, or infrared rays. By providing the sensor 921, for example, data indicating the environment where the secondary battery is placed (such as temperature) can be detected and stored in the memory in the circuit 912.

[0326] Furthermore, a structural example of the secondary battery 913 will be described with reference to FIGS. 15 and 16.

[0327] The secondary battery 913 shown in FIG. 15(A) has a wound body 950 provided with a terminal 951 and a terminal 952 inside a housing 930. The wound body 950 is impregnated with an electrolytic solution inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like. In FIG. 15(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered with the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used. In FIG. 15(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered with the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used. In FIG. 15(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered with the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used. In FIG. 15(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered with the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used. In FIG. 15(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered with the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum) or a resin material can be used.

[0328] As shown in FIG. 15(B), the housing 930 shown in FIG. 15(A) may be formed of a plurality of materials. For example, the secondary battery 913 shown in FIG. 15(B) has a housing 930a and a housing 930b bonded together, and a wound body 950 is provided in a region surrounded by the housing 930a and the housing 930b. As shown in FIG. 15(B), the housing 930 shown in FIG. 15(A) may be formed of a plurality of materials. For example, the secondary battery 913 shown in FIG. 15(B) has a housing 930a and a housing 930b bonded together, and a wound body 950 is provided in a region surrounded by the housing 930a and the housing 930b. As shown in FIG. 15(B), the housing 930 shown in FIG. 15(A) may be formed of a plurality of materials. For example, the secondary battery 913 shown in FIG. 15(B) has a housing 930a and a housing 930b bonded together, and a wound body 950 is provided in a region surrounded by the housing 930a and the housing 930b. As shown in FIG. 15(B), the housing 930 shown in FIG. 15(A) may be formed of a plurality of materials. For example, the secondary battery 913 shown in FIG. 15(B) has a housing 930a and a housing 930b bonded together, and a wound body 950 is provided in a region surrounded by the housing 930a and the housing 930b.

[0329] As the housing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by the housing 930a is small, antennas such as an antenna 914 and an antenna 915 may be provided inside the housing 930a. As the housing 930b, for example, a metal material can be used. As the housing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by the housing 930a is small, antennas such as an antenna 914 and an antenna 915 may be provided inside the housing 930a. As the housing 930b, for example, a metal material can be used. As the housing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by the housing 930a is small, antennas such as an antenna 914 and an antenna 915 may be provided inside the housing 930a. As the housing 930b, for example, a metal material can be used. As the housing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by the housing 930a is small, antennas such as an antenna 914 and an antenna 915 may be provided inside the housing 930a. As the housing 930b, for example, a metal material can be used. As the housing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by the housing 930a is small, antennas such as an antenna 914 and an antenna 915 may be provided inside the housing 930a. As the housing 930b, for example, a metal material can be used.

[0330] Furthermore, the structure of the wound body 950 is shown in FIG. 16. The wound body 950 includes a negative electrode 931 and a positive It has a negative electrode 931 and a positive electrode 932, and a separator 933. The wound body 950 sandwiches the separator 933 such that the negative electrode 931 and the positive electrode 932 overlap and are laminated, and the laminated sheet is wound to form a wound body That is. Note that the lamination of the negative electrode 931, the positive electrode 932, and the separator 933 may be further stacked multiple times.

[0331] The negative electrode 931 is connected to the terminal 911 shown in FIG. 13 via one of the terminals 951 and 952 The positive electrode 932 is connected to the terminal 91 1 shown in FIG. 13 via the other of the terminals 951 and 952.

[0332] By using the positive electrode active material described in the previous embodiment for the positive electrode 932, a secondary battery 913 with high capacity and excellent cycle characteristics can be obtained.

[0333] [Laminated secondary battery] Next, an example of a laminated secondary battery will be described with reference to FIGS. 17 to 23. If the laminated secondary battery has a flexible configuration, when it is mounted on an electronic device having at least a part of a flexible portion, the secondary battery can also be bent in accordance with the deformation of the electronic device

[0334] The laminated secondary battery 980 will be described with reference to FIG. 17. The laminated secondary battery 980 has a wound body 993 shown in FIG. 17(A). The wound body 993 has a negative electrode 994 a positive electrode 995, and a separator 996. Similar to the wound body 950 described in FIG. 16, the wound body 993 sandwiches the separator 996 such that the negative electrode 994 and the positive electrode 995 overlap and are laminated, and the laminated sheet is wound.

[0335] ​​​Note that the number of laminations of the laminate composed of the negative electrode 994, the positive electrode 995, and the separator 996 may be appropriately designed according to the required capacity and the element volume. The negative electrode 994 is connected to a negative electrode current collector (not shown) via one of the lead electrodes 997 and the lead electrode 998, and the positive electrode 995 is connected to a positive electrode current collector (not shown) via the other of the lead electrode 997 and the lead electrode 998.

[0336] As shown in FIG. 17(B), the winding body 993 described above is housed in a space formed by thermocompression bonding or the like the film 981 serving as the exterior body and the film 98 2 having a concave portion, whereby a secondary battery 980 as shown in FIG. 17(C) can be manufactured. The winding body 99 3 has the lead electrodes 997 and 998 and is impregnated with the electrolytic solution inside the film 981 and the film 98 2 having a concave portion. As the material of the film 981 and the film 982 having a concave portion, a metal material

[0337] such as aluminum or a resin material can be used. If a resin material is used as the material of the film 981 and the film 982 having a concave portion, when a force is applied from the outside, the film 981 and the film 98 2 having a concave portion can be deformed, and a flexible secondary battery can be manufactured. Moreover, although FIGS. 17(B) and 17(C) show an example using two films, a space may be formed by bending one film, and the winding body 99 3 described above may be housed in the space.

[0338] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, a secondary battery 980 with high capacity and excellent cycle characteristics can be obtained.

[0339] characteristics can be obtained. characteristics can be obtained.

[0340] Also, in FIG. 17, a secondary battery 9 having a winding body in a space formed by a film serving as an exterior body has been described with reference to the example of 80. However, for example, as shown in FIG. 18, a secondary battery having a plurality of strip-shaped positive electrodes, separators, and negative electrodes in a space formed by a film serving as an exterior body may also be used. is fine.

[0341] The laminated secondary battery 500 shown in FIG. 18(A) includes a positive electrode 503 having a positive electrode current collector 501 and a positive electrode active material layer 502, a negative electrode 506 having a negative electrode current collector 504 and a negative electrode active material layer 505, a separator 507, an electrolytic solution 508, and an exterior body 509. A separator 507 is disposed between the positive electrode 503 and the negative electrode 506 provided in the exterior body 509. Further, the interior of the exterior body 509 is filled with the electrolytic solution 508. As the electrolytic solution 508, the electrolytic solution shown in Embodiment 2 can be used.

[0342] In the laminated secondary battery 500 shown in FIG. 18(A), the positive electrode current collector 501 and the negative electrode current collector 504 also serve as terminals for obtaining electrical contact with the outside. Therefore, a part of the positive electrode current collector 501 and the negative electrode current collector 504 may be arranged to be exposed to the outside from the exterior body 509. Alternatively, the positive electrode current collector 501 and the negative electrode current collector 504 may not be exposed to the outside from the exterior body 509, and a lead electrode may be ultrasonically bonded to the lead electrode and the positive electrode current collector 501 or the negative electrode current collector 504 so that the lead electrode is exposed to the outside.

[0343] In the laminated secondary battery 500, the exterior body 509 is, for example, a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and on the film, an ​​​​​​​​​​​ A metal thin film with excellent flexibility such as aluminum, stainless steel, copper, nickel, etc. is provided, and further, an insulating synthetic resin film such as a polyamide-based resin or a polyester-based resin is provided on the metal thin film as the outer surface of the exterior body. A three-layer laminated film can be used.

[0344] In addition, an example of the cross-sectional structure of the laminated secondary battery 500 is shown in FIG. 18(B). In FIG. 18(A), for simplicity, an example composed of two current collectors is shown, but actually, it is composed of a plurality of electrode layers.

[0345] In FIG. 18(B), as an example, the number of electrode layers is 16. Note that even when the number of electrode layers is 16, the secondary battery 500 has flexibility. In FIG. 18(B), the negative electrode current collector 504 has 8 layers, and the positive electrode current collector 501 has a total of 16 layers with 8 layers. Note that FIG. 18(B) shows the cross-section of the extraction part of the negative electrode, and the 8-layer negative electrode current collector 504 is ultrasonically bonded. Of course, the number of electrode layers is not limited to 16, and it may be more or less. When the number of electrode layers is large, a secondary battery with a larger capacity can be obtained. Also, when the number of electrode layers is small, it can be thinned and a secondary battery with excellent flexibility can be obtained.

[0346] Here, an example of the external view of the laminated secondary battery 500 is shown in FIGS. 19 and 20. FIGS. 19 and 20 have a positive electrode 503, a negative electrode 506, a separator 507, an exterior body 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511.

[0347] FIG. 21(A) shows the external views of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a positive electrode current collector 501, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. Also, the positive electrode ​​​​​​​​​​​​​503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). The negative electrode 506 has a negative electrode current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504 Moreover, 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 the negative electrode are not limited to the example shown in FIG. 21(A).

[0348] [Method for manufacturing a laminated secondary battery] Here, an example of a method for manufacturing a laminated secondary battery whose external view is shown in FIG. 19 will be described with reference to FIGS. 21 (B) and (C).

[0349] First, the negative electrode 506, the separator 507, and the positive electrode 503 are laminated. FIG. 21(B) shows the laminated negative electrode 506, separator 507, and positive electrode 503. Here, an example is shown in which five negative electrodes and four positive electrodes are used. Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For the joining, for example, ultrasonic welding or the like can be used. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode. [[ID=Twenty-two]]Here, an example is shown in which five negative electrodes and four positive electrodes are used. Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode lead electrode 4 sets are used. Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For the joining, for example, ultrasonic welding or the like can be used. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead For the joining, for example, ultrasonic welding or the like can be used. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead region of the outermost negative electrode. z

[0350] Next, the negative electrode 506, the separator 507, and the positive electrode 503 are arranged on the exterior body 509.

[0351] Next, as shown in FIG. 21(C), the exterior body 509 is bent at the portion indicated by the broken line. Then, the outer peripheral portion of the exterior body 509 is joined. For the joining, for example, thermocompression bonding or the like can be used. At this time, a region that is not joined (hereinafter referred to as the inlet) is provided in a part (or one side) of the exterior body 509 so that the electrolytic solution 508 can be introduced later. After that, the outer peripheral portion of the exterior body 509 is joined. For the joining, for example, thermocompression bonding or the like can be used. At this time In order to be able to put the electrolytic solution 508 later, a region that is not joined (hereinafter referred to as the inlet) is provided in a part (or one side) of the exterior body 509.

[0352] ​​ Next, the electrolytic solution 508 is introduced into the inside of the exterior body 509 from the inlet provided in the exterior body 509. This introduction of the electrolytic solution 508 is preferably carried out under a reduced pressure atmosphere or an inert gas atmosphere. Finally, the inlet is joined. In this way, a secondary battery 500 of the laminate type can be manufactured. By using the positive electrode active material described in the previous embodiment for the positive electrode 503, a secondary battery 500 with high capacity and excellent cycle characteristics can be obtained.

[0353]

[0354] [Bendable Secondary Battery] Next, an example of a bendable secondary battery will be described with reference to FIGS. 22 and 23. .

[0355] FIG. 22(A) shows a schematic top view of a bendable secondary battery 50. FIGS. 22(B1), (B2), and (C) are schematic cross-sectional views taken along the cutting lines C1 - C2, C3 - C4, and A1 - A2 in FIG. 22(A), respectively. The battery 50 has an exterior body 51 and a positive electrode 11a and a negative electrode 11b housed inside the exterior body 51. A lead 12a electrically connected to the positive electrode 11a and a lead 12b electrically connected to the negative electrode 11b extend outside the exterior body 51. Also, an electrolytic solution (not shown) is enclosed in the region surrounded by the exterior body 51 in addition to the positive electrode 11a and the negative electrode 11b.

[0356] The positive electrode 11a and the negative electrode 11b of the battery 50 will be described with reference to FIG. 23. FIG. 23(A) is a perspective view for explaining the lamination order of the positive electrode 11a, the negative electrode 11b, and the separator 14. FIG. 23(B) shows, in addition to the positive electrode 11a and the negative electrode 11b, the leads 12a and the leads​​​​​​​​ It is a perspective view showing 12b.

[0357] As shown in Fig. 23(A), the battery 50 has a plurality of strip-shaped positive electrodes 11a, a plurality of strip-shaped negative electrodes 11b, and a plurality of separators 14. The positive electrode 11a and the negative electrode 11b each have a protruding tab portion and a portion other than the tab. A positive electrode active material layer is formed on the portion other than the tab on one surface of the positive electrode 11a, and a negative electrode active material layer is formed on the portion other than the tab on one surface of the negative electrode 11b.

[0358] The positive electrodes 11a and the negative electrodes 11b are laminated so that the surfaces of the positive electrode 11a where the positive electrode active material layer is not formed are in contact with each other, and the surfaces of the negative electrode 11b where the negative electrode active material layer is not formed are in contact with each other.

[0359] Also, a separator 14 is provided between the surface of the positive electrode 11a where the positive electrode active material is formed and the surface of the negative electrode 11b where the negative electrode active material is formed. In Fig. 23(A), the separator 14 is shown by a dotted line for easy viewing.

[0360] As shown in Fig. 23(B), a plurality of positive electrodes 11a and the lead 12a are electrically connected at the joint portion 15a. Also, a plurality of negative electrodes 11b and the lead 12b are electrically connected at the joint portion 15b.

[0361] Next, the exterior body 51 will be described with reference to Figs. 22(B1), (B2), (C), and (D).

[0362] The exterior body 51 has a film-like shape and is bent in two so as to sandwich the positive electrode 11a and the negative electrode 11b. The exterior body 51 has a bent portion 61, a pair of seal portions 62, and a seal portion 63. The pair of seal portions 62 are provided sandwiching the positive electrode 11a and the negative electrode 11b. ​ It is formed and can also be called a side seal. Further, the seal portion 63 has a portion overlapping with the lead 12a and the lead 12b, and can also be called a top seal.

[0363] The exterior body 51 preferably has a corrugated shape in which ridge lines 71 and valley lines 72 are arranged alternately in a portion overlapping with the positive electrode 11a and the negative electrode 11b. Also, the seal portions 62 and 63 of the exterior body 51 are preferably flat.

[0364] FIG. 22(B1) is a cross-section cut at a portion overlapping with the ridge line 71, and FIG. 22(B2) is a cross-section cut at a portion overlapping with the valley line 72. Both FIGS. 22(B1) and (B2) correspond to a cross-section in the width direction of the battery 50, the positive electrode 11a, and the negative electrode 11b.

[0365] Here, let the distance between the end portion of the negative electrode 11b in the width direction and the seal portion 62 be the distance La. When the battery 50 is deformed such as being bent, as will be described later, the positive electrode 11a and the negative electrode 11b are deformed so as to shift from each other in the length direction. At that time, if the distance La is too short, the exterior body 51 and the positive electrode 11a and the negative electrode 11b may rub strongly, and the exterior body 51 may be damaged. In particular, when the metal film of the exterior body 51 is exposed, the metal film may be corroded by the electrolytic solution. Therefore, it is preferable to set the distance La as long as possible. On the other hand, if the distance La is made too large, the volume of the battery 50 will increase.

[0366] Further, the thicker the total thickness of the stacked positive electrode 11a and negative electrode 11b, the more preferably the distance La between the end portion of the negative electrode 11b and the seal portion 62 is increased.

[0367] More specifically, when the total thickness of the stacked positive electrode 11a, negative electrode 11b, and separator (not shown) is defined as thickness t, the distance La should be 0.8 times or more and 3.0 times or less, preferably 0.9 times or more and 2.5 times or less, more preferably 1.0 times or more and 2.0 times or less of the thickness t. When the total thickness of the stacked positive electrode 11a, negative electrode 11b, and separator (not shown) is defined as thickness t, the distance La should be 0.8 times or more and 3.0 times or less, preferably 0.9 times or more and 2.5 times or less, more preferably 1.0 times or more and 2.0 times or less of the thickness t. When the total thickness of the stacked positive electrode 11a, negative electrode 11b, and separator (not shown) is defined as thickness t, the distance La should be 0.8 times or more and 3.0 times or less, preferably 0.9 times or more and 2.5 times or less, more preferably 1.0 times or more and 2.0 times or less of the thickness t. By setting the distance La within this range, a compact and highly reliable battery with respect to bending can be realized. By setting the distance La within this range, a compact and highly reliable battery with respect to bending can be realized.

[0368] Also, when the distance between the pair of seal portions 62 is defined as distance Lb, it is preferable that the distance Lb is sufficiently larger than the width Wb of the negative electrode 11b. This can effectively prevent the positive electrode 11a and the negative electrode 11b from rubbing against the exterior body 51 when the battery 50 is repeatedly deformed, such as being bent, because even if the positive electrode 11a and the negative electrode 11b come into contact with the exterior body 51, a part of the positive electrode 11a and the negative electrode 11b can shift in the width direction. This can effectively prevent the positive electrode 11a and the negative electrode 11b from rubbing against the exterior body 51 when the battery 50 is repeatedly deformed, such as being bent, because even if the positive electrode 11a and the negative electrode 11b come into contact with the exterior body 51, a part of the positive electrode 11a and the negative electrode 11b can shift in the width direction. This can effectively prevent the positive electrode 11a and the negative electrode 11b from rubbing against the exterior body 51 when the battery 50 is repeatedly deformed, such as being bent, because even if the positive electrode 11a and the negative electrode 11b come into contact with the exterior body 51, a part of the positive electrode 11a and the negative electrode 11b can shift in the width direction. This can effectively prevent the positive electrode 11a and the negative electrode 11b from rubbing against the exterior body 51 when the battery 50 is repeatedly deformed, such as being bent, because even if the positive electrode 11a and the negative electrode 11b come into contact with the exterior body 51, a part of the positive electrode 11a and the negative electrode 11b can shift in the width direction.

[0369]

[0370]

[0371] In other words, it is preferable that the distance Lb, width Wb, and thickness t satisfy the relationship of the following formula (2).

Equation

[0372] Here, a satisfies 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, more preferably 1.0 or more and 2.0 or less. Here, a satisfies 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, more preferably 1.0 or more and 2.0 or less.

[0373] Further, FIG. 22(C) is a cross-section including the lead 12a, corresponding to the longitudinal cross-section of the battery 50, the positive electrode 11a, and the negative electrode 11b. As shown in FIG. 22(C), it is preferable to have a space 73 between the longitudinal ends of the positive electrode 11a and the negative electrode 11b and the exterior body 51 at the bending portion 61 . .

[0374] FIG. 22(D) shows a schematic cross-sectional view when the battery 50 is bent. FIG. 22(D) corresponds to the cross-section at the cutting line B1-B2 in FIG. 22(A). .

[0375] When the battery 50 is bent, a part of the exterior body 51 located on the outer side of the bend stretches, and the other part located on the inner side deforms to shrink. More specifically, the part located on the outer side of the exterior body 51 deforms such that the amplitude of the wave is small and the period of the wave is large. On the other hand, the part located on the inner side of the exterior body 51 deforms such that the amplitude of the wave is large and the period of the wave is small. In this way, when the exterior body 51 deforms, the stress applied to the exterior body 51 due to bending is relaxed, so it is not necessary for the material itself constituting the exterior body 51 to stretch and contract. As a result, the battery 50 can be bent with a small force without the exterior body 51 being damaged. . . . . . .

[0376] Also, as shown in FIG. 22(D), when the battery 50 is bent, the positive electrode 11a and the negative electrode 11b shift relative to each other. At this time, since one end on the seal portion 63 side of the plurality of stacked positive electrodes 11a and negative electrodes 11b is fixed by the fixing member 17, they shift such that the shift amount becomes larger closer to the bending portion 61. As a result, the positive electrode 11a and the negative electrode 11 . . The stress applied to b is relaxed, and it is not necessary for the positive electrode 11a and the negative electrode 11b themselves to expand and contract. Thus, the battery 50 can be bent without damaging the positive electrode 11a and the negative electrode 11b. .

[0377] Also, there is a space 73 between the ends of the positive electrode 11a and the negative electrode 11b and the exterior body 51. As a result, when bent, the ends of the positive electrode 11a and the negative electrode 11b located on the inner side can shift relative to each other without contacting the exterior body 51.

[0378] The battery 50 illustrated in FIGS. 22 and 23 is a battery in which damage to the exterior body, damage to the positive electrode 11a and the negative electrode 11b, etc. are less likely to occur even when repeatedly bent and stretched, and the battery characteristics are also less likely to deteriorate. By using the positive electrode active material described in the previous embodiment for the positive electrode 11a included in the battery 50, a battery with even better cycle characteristics can be obtained.

[0379] (Embodiment 4) In this embodiment, an example of mounting a secondary battery, which is one aspect of the present invention, on an electronic device will be described. .

[0380] First, examples of mounting a bendable secondary battery, which was partially described in Embodiment 3, on an electronic device are shown in FIGS. 24(A) to 24(G). Examples of electronic devices to which a bendable secondary battery is applied include, for example, a television device (also referred to as a television or a television receiver), a monitor for a computer, a digital camera, a digital video camera, a digital photo frame, a mobile phone (also referred to as a mobile phone or a mobile phone device), a portable game machine, a portable information terminal, an audio playback device, a large game machine such as a pachinko machine, and the like.

[0381] In addition, a secondary battery having a flexible shape can be incorporated along the inner wall or outer wall of a house or building, or along the curved surface of the interior or exterior of an automobile. It is also possible to incorporate it along the curved surface of the interior or exterior of an automobile.

[0382] FIG. 24(A) shows an example of a mobile phone. The mobile phone 7400 includes a display unit 7402 incorporated in a housing 7401, in addition to operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like. The mobile phone 7400 also has a secondary battery 7407. By using the secondary battery of one aspect of the present invention for the above-mentioned secondary battery 7407, a lightweight and long-life mobile phone can be provided. By using the secondary battery of one aspect of the present invention for the secondary battery 7407, a lightweight and long-life mobile phone can be provided.

[0383] FIG. 24(B) shows a state in which the mobile phone 7400 is bent. When the mobile phone 7400 is deformed by an external force to be bent as a whole, the secondary battery 7407 provided inside it is also bent. Also, at that time, the state of the bent secondary battery 7407 is shown in FIG. 24(C). The secondary battery 7407 is a thin rechargeable battery. The secondary battery 7407 is fixed in a bent state. The secondary battery 7407 is a thin rechargeable battery. The secondary battery 7407 is fixed in a bent state. The secondary battery 7407 has a lead electrode 7408 electrically connected to a current collector 7409. For example, the current collector 7409 is a copper foil, and a part of it is alloyed with gallium to improve the adhesion to the active material layer in contact with the current collector 7409, so that the secondary battery 7407 has a high reliability in a bent state. The secondary battery 7407 has a lead electrode 7408 electrically connected to a current collector 7409. For example, the current collector 7409 is a copper foil, and a part of it is alloyed with gallium to improve the adhesion to the active material layer in contact with the current collector 7409, so that the secondary battery 7407 has a high reliability in a bent state.

[0384] FIG. 24(D) shows an example of a bangle-type display device. The portable display device 7100 includes a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. Also, FIG. 24(E) shows the state of the bent secondary battery 7104. The secondary battery 7104 is bent. ​​​​​​When worn on the user's arm in the deformed state, the housing deforms and part or all of the curvature of the secondary battery 7104 changes. Note that the degree of bending at any point on the curve is represented by the radius of the corresponding circle, and the reciprocal of the radius of curvature is called the curvature. Specifically, part or all of the main surface of the housing or the secondary battery 7104 changes within the range of 40 mm or more and 150 mm or less. If the radius of curvature on the main surface of the secondary battery 7104 is in the range of 40 mm or more and 150

[0385] mm or less, high reliability can be maintained. By using the secondary battery of one aspect of the present invention for the secondary battery 7104, a lightweight and long- life portable display device can be provided.

[0386] FIG. 24(F) shows an example of a wristwatch-type portable information terminal. The portable information terminal 7200 includes a housing 7201, a display unit 7202, a band 7203, a buckle 7204, operation buttons 72

[0387] 05, input / output terminals 7206, and the like.

[0386] The portable information terminal 7200 can execute various applications such as a mobile phone, e-mail, text viewing and creation, music playback, Internet communication, and computer games.

[0387] The display unit 7202 is provided with a curved display surface, and can perform display along the curved display surface. Further, the display unit 7202 includes a touch sensor, and can be operated by touching the screen with a finger or a stylus. For example, an application can be launched by touching the icon 72

[0388] 07 displayed on the display unit 7202. The operation buttons 7205 can be used not only for time setting but also for powerIt can have various functions such as operations, execution and cancellation of the manner mode, execution and cancellation of the power saving mode, etc. For example, the function of the operation button 7205 can also be freely set by the operating system incorporated in the portable information terminal 7200.

[0389] In addition, the portable information terminal 7200 can execute communication-standardized short-range wireless communication. For example, it can communicate hands-free by communicating with a wireless headset.

[0390] In addition, the portable information terminal 7200 is provided with an input / output terminal 7206 and can directly exchange data with other information terminals via a connector. It can also be charged via the input / output terminal 7206. Note that the charging operation may be performed by wireless power supply without passing through the input / output terminal 7206.

[0391] The display unit 7202 of the portable information terminal 7200 has a secondary battery according to one aspect of the present invention. By using the secondary battery according to one aspect of the present invention, a lightweight and long-life portable information terminal can be provided. For example, the secondary battery 7104 shown in FIG. 24(E) can be incorporated in a curved state inside the housing 7201 or in a state where it can be curved inside the band 7203.

[0392] The portable information terminal 7200 preferably has a sensor. As the sensor, for example, human body sensors such as fingerprint sensors, pulse sensors, body temperature sensors, etc., touch sensors, pressure sensors, acceleration sensors, etc. are preferably mounted.

[0393] FIG. 24(G) shows an example of a bracelet-type display device. The display device 7300 has a display unit 7 ​​​​​​​​It has 304 and has a secondary battery according to one aspect of the present invention. Further, the display device 7300 may include a touch sensor in the display unit 7304, and may also function as a portable information terminal. The display surface of the display unit 7304 is curved, and display can be performed along the curved display surface. In addition, the display device 7300 can change the display state by means of communication-standardized short-range wireless communication or the like.

[0394] The display surface of the display unit 7304 is curved, and display can be performed along the curved display surface. In addition, the display device 7300 can change the display situation by means of communication-standardized short-range wireless communication or the like. In addition, the display device 7300 is provided with input / output terminals and can directly exchange data with other information terminals via a connector. Charging can also be performed via the input / output terminals.

[0395] In addition, the display device 7300 is provided with input / output terminals and can directly exchange data with other information terminals via a connector. Charging can also be performed via the input / output terminals. Note that the charging operation may be performed by wireless power supply without passing through the input / output terminals. Note that the charging operation may be performed by wireless power supply without passing through the input / output terminals.

[0396] By using the secondary battery according to one aspect of the present invention as the secondary battery of the display device 7300, a lightweight and long-life display device can be provided. By using the secondary battery according to one aspect of the present invention as the secondary battery of the display device 7300, a lightweight and long-life display device can be provided.

[0397] In addition, an example of mounting the secondary battery with good cycle characteristics shown in the previous embodiment on an electronic device will be described with reference to FIGS. 24(H), 25, and 26. In addition, an example of mounting the secondary battery with good cycle characteristics shown in the previous embodiment on an electronic device will be described with reference to FIGS. 24(H), 25, and 26.

[0398] By using the secondary battery according to one aspect of the present invention as the secondary battery of consumer electronic devices, lightweight and long-life products can be provided. For example, consumer electronic devices include electric toothbrushes, electric shavers, electric beauty devices, etc. As the secondary batteries of these products, considering the ease of use by the user, a secondary battery with a stick shape, small size, light weight, and large capacity is desired. By using the secondary battery according to one aspect of the present invention as the secondary battery of consumer electronic devices, lightweight and long-life products can be provided. For example, consumer electronic devices include electric toothbrushes, electric shavers, electric beauty devices, etc. As the secondary batteries of these products, considering the ease of use by the user, a secondary battery with a stick shape, small size, light weight, and large capacity is desired. FIG. 24(H) is a perspective view of a device also called a tobacco storage smoking device (electronic cigarette). FIG. By using the secondary battery according to one aspect of the present invention as the secondary battery of consumer electronic devices, lightweight and long-life products can be provided. For example, consumer electronic devices include electric toothbrushes, electric shavers, electric beauty devices, etc. As the secondary batteries of these products, considering the ease of use by the user, a secondary battery with a stick shape, small size, light weight, and large capacity is desired.

[0399] FIG. 24(H) is a perspective view of a device also called a tobacco storage smoking device (electronic cigarette). FIG. In 24(H), the electronic cigarette 7500 includes an atomizer 7501 containing a heating element, and an atom izer is supplied with power by a secondary battery 7504, and a cartridge including a liquid supply bottle, a sensor, etc. 7502. To enhance safety, a protection circuit for preventing overcharging and over discharging of the secondary battery 7504 may be electrically connected to the secondary battery 7504. The secondary battery 7504 shown in Fig. 24(H) has external terminals so that it can be connected to a charging device. Since the secondary battery 7 504 becomes the tip portion when held, it is desirable that the total length is short and the weight is light. Since the secondary battery according to one aspect of the present invention has a high capacity and good cycle characteristics, it can provide a small and lightweight electronic cigarette 7500 that can be used for a long time over a long period.

[0400] Next, Figs. 25(A) and 25(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in Figs. 25(A) and 25(B) includes a housing 9630 a, a housing 9630b, a movable part 9640 connecting the housing 9630a and the housing 9630b, a display unit 9631 having a display unit 9631a and a display unit 9631b, a display mode switching switch 9626, a power switch 9627, a power saving mode switching switch 9625, a fastener 96 29, and an operation switch 9628. By using a flexible panel for the display unit 9631, a tablet terminal having a wider display unit can be obtained. Fig. 25(A ) shows the open state of the tablet terminal 9600, and Fig. 25(B) shows the closed state of the tablet terminal 9600.

[0401] In addition, the tablet terminal 9600 stores electricity inside the housing 9630a and the housing 9630b. ​​It has a power storage body 9635. The power storage body 9635 passes through the movable part 9640 and is provided across the housing 9630a and the housing 9630b.

[0402] The display unit 9631a can have a part as the touch panel area 9632a, and data can be input by touching the displayed operation key 9638. Note that in the display unit 963 1a, as an example, a configuration in which half of the area has only a display function and the other half has a touch panel function is shown, but it is not limited to this configuration. All areas of the display unit 963 1a may also have a touch panel function. For example, the entire surface of the display unit 96 31a can be made to display keyboard buttons as a touch panel, and the display unit 9631b can be used as a display screen.

[0403] Also, in the display unit 9631b, similar to the display unit 9631a, a part of the display unit 9631b can be made the touch panel area 9632b. Also, by touching the position where the keyboard display switching button 9639 of the touch panel is displayed with a finger or a stylus, etc., keyboard buttons can be displayed on the display unit 9631b.

[0404] Also, simultaneous touch input can be performed on the touch panel area 9632a and the touch panel area 9632b.

[0405] Also, the display mode switching switch 9626 can select switching of the display orientation such as vertical display or horizontal display, switching between black and white display and color display, etc. The power saving mode switching switch 9625 is detected by the optical sensor built in the tablet terminal 9600 during use The brightness of the display can be optimized according to the amount of external light. The tablet-type terminal is not only equipped with a light sensor, but may also incorporate other detection devices such as sensors for detecting inclination, such as gyroscopes and acceleration sensors.

[0406] Also, in FIG. 25(A), an example is shown where the display areas of the display unit 9631b and the display unit 9631a are the same, but it is not particularly limited, and the size of one may be different from that of the other, and the quality of the display may also be different. For example, one may be a display panel that can perform a higher-definition display than the other.

[0407] FIG. 25(B) shows a closed state, and the tablet-type terminal includes a housing 9630, a solar cell 96 33, and a charge / discharge control circuit 9634 including a DCDC converter 9636. Also, as the power storage body 9635, a power storage body according to one aspect of the present invention is used.

[0408] Note that since the tablet-type terminal 9600 is foldable in two, when not in use, the housing 9630a and the housing 9630b can be folded so as to overlap each other. By folding, the display unit 9631a and the display unit 9631b can be protected, thus enhancing the durability of the tablet-type terminal 9600. Also, since the power storage body 9635 using the secondary battery according to one aspect of the present invention has a high capacity and good cycle characteristics, a tablet-type terminal 9600 that can be used for a long time over a long period can be provided.

[0409] In addition, the tablet-type terminals shown in FIGS. 25(A) and 25(B) also have functions for displaying various information (such as still images, moving images, text images), a function for displaying a calendar, date, or time on the display unit, and a touch input operation or editing function for the information displayed on the display unit.​​​ It has an input function, a function of controlling processing by various software (programs), etc. It can be done.

[0410] Power can be supplied to the touch panel, display unit, or video signal processing unit, etc. by the solar cell 9633 mounted on the surface of the tablet-type terminal. Note that the solar cell 9633 can be provided on one side or both sides of the housing 9630, and can be configured to efficiently charge the power storage body 9635. Note that when a lithium-ion battery is used as the power storage body 9635, there are advantages such as size reduction.

[0411] Also, the configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 25(B) will be described with reference to the block diagram in FIG. 25( C). FIG. 25(C) shows the solar cell 9633, the power storage body 963 5, the DCDC converter 9636, the converter 9637, the switches SW1 to SW3, and the display unit 9631. The power storage body 9635, the DCDC converter 9636, the con verter 9637, and the switches SW1 to SW3 correspond to the parts of the charge / discharge control circuit 96 34 shown in FIG. 25(B).

[0412] First, an example of the operation when power is generated by the solar cell 9633 by external light will be described. The power generated by the solar cell is stepped up or down by the DCDC con verter 9636 to become a voltage for charging the power storage body 9635. When the power from the solar cell 9633 is used for the operation of the display unit 9631, the switch SW1 is turned on, and the converter 9637 steps up or down the voltage to the voltage required for the display unit 9631. Also, when the display on the display unit 9631 is not performed, SW1 is turned off and SW2 is turned on to charge the power storage body 9635. It may be configured to conduct electricity.

[0413] The solar cell 9633 has been shown as an example of the power generation means, but it is not particularly limited, and charging of the storage body 9635 may be performed by other power generation means such as piezoelectric elements (piezoelectric devices) and thermoelectric conversion elements (Peltier devices). For example, it may be configured to charge by transmitting and receiving power wirelessly (non - contact), or by combining other charging means. For example, it may be a configuration that charges by transmitting and receiving power wirelessly (non - contact), or a configuration that combines other charging means. For example, it may be a contactless power transmission module that charges by wireless (non - contact) power transmission and reception, or a configuration that combines other charging means. It may also be so.

[0414] Fig. 26 shows an example of another electronic device. In Fig. 26, the display device 8000 is an example of an electronic device using the secondary battery 8004 according to one embodiment of the present invention. Specifically, the display device 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, a speaker unit 8003, a secondary battery 8004, etc. The secondary battery 8004 according to one embodiment of the present invention is provided inside the housing 8001. The display device 8000 can be supplied with power from a commercial power source, or can use the power stored in the secondary battery 8004. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, the display device 8000 can be used by using the secondary battery 8004 according to one embodiment of the present invention as an uninterruptible power supply. The display device 8000 can be supplied with power from a commercial power source, or can use the power stored in the secondary battery 8004. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, the display device 8000 can be used by using the secondary battery 8004 according to one embodiment of the present invention as an uninterruptible power supply. The display device 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, a speaker unit 8003, a secondary battery 8004, etc. The secondary battery 8004 according to one embodiment of the present invention is provided inside the housing 8001. The display device 8000 can be supplied with power from a commercial power source, or can use the power stored in the secondary battery 8004. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, the display device 8000 can be used by using the secondary battery 8004 according to one embodiment of the present invention as an uninterruptible power supply. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, the display device 8000 can be used by using the secondary battery 8004 according to one embodiment of the present invention as an uninterruptible power supply. The display device 8000 can be supplied with power from a commercial power source, or can use the power stored in the secondary battery 8004. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, the display device 8000 can be used by using the secondary battery 8004 according to one embodiment of the present invention as an uninterruptible power supply.

[0415] The display unit 8002 can use a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc., a semiconductor display device. The display unit 8002 can use a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc., a semiconductor display device. The display unit 8002 can use a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc., a semiconductor display device. For the display unit 8002, a semiconductor display device such as a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc. can be used.

[0416] In addition to being used for receiving TV broadcasts, the display device includes display devices for personal computers, advertising displays, etc. for all information display purposes. All information display purpose display devices are included.

[0417] In FIG. 26, the installed lighting device 8100 is an example of an electronic device using the secondary battery 81 03 according to one aspect of the present invention. Specifically, the lighting device 8100 includes a housing 8101, a light source 8102, a secondary battery 8103, etc. In FIG. 26, the case where the secondary battery 8103 is provided inside the ceiling 81 01 and the ceiling 8104 where the light source 8102 is installed is illustrated as an example However, the secondary battery 8103 may be provided inside the housing 8101. The lighting device 8100 can receive power supply from a commercial power source, or can use the power stored in the secondary battery 8103. Therefore, even when the power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8103 according to one aspect of the present invention as an uninterruptible power supply the lighting device 8100 can be used. Even when the power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8103 according to one aspect of the present invention as an uninterruptible power supply the lighting device 8100 can be used.

[0418] In addition, in FIG. 26, the installed lighting device 8100 provided on the ceiling 8104 is illustrated as an example However, the secondary battery according to one aspect of the present invention can be used not only for the ceiling 8104 but also for installed lighting devices provided on, for example, side walls 8105, floors 8 106, windows 8107, etc., and can also be used for tabletop type lighting devices and the like.

[0419] In addition, as the light source 8102, an artificial light source that artificially obtains light using power can be used. Specifically, incandescent bulbs, discharge lamps such as fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements can be cited as examples of the above artificial light sources.

[0420] In FIG. 26, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is an example of an electronic device using a secondary battery 8203 according to one aspect of the present invention. Specifically, the indoor unit 8200 has a housing 8201, an air outlet 8202, a secondary battery 8203, etc. FIG. 26 illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used. In FIG. 26, an electric refrigerator 8300 is an example of an electronic device using a secondary battery 8304 according to one aspect of the present invention. Specifically, the electric refrigerator 8300 has a housing 8301, a door for the refrigerating compartment 8302, a door for the freezing compartment 8303, a secondary battery 8304, etc. In FIG. 26, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator 8300 has a housing 8201, an air outlet 8202, a secondary battery 8203, etc. In FIG. 26, it illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 820, and the air conditioner can receive power supply from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used. illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used. illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used. illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used. illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used. illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used. illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used. illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used. illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source or use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used.

[0421] Note that in FIG. 26, a separate-type air conditioner composed of an indoor unit and an outdoor unit is illustrated, but a secondary battery according to one aspect of the present invention can also be used in an integrated-type air conditioner having the functions of the indoor unit and the outdoor unit in one housing. Note that in FIG. 26, a separate-type air conditioner composed of an indoor unit and an outdoor unit is illustrated, but a secondary battery according to one aspect of the present invention can also be used in an integrated-type air conditioner having the functions of the indoor unit and the outdoor unit in one housing. Note that in FIG. 26, a separate-type air conditioner composed of an indoor unit and an outdoor unit is illustrated, but a secondary battery according to one aspect of the present invention can also be used in an integrated-type air conditioner having the functions of the indoor unit and the outdoor unit in one housing.

[0422] In FIG. 26, an electric refrigerator 8300 is an example of an electronic device using a secondary battery 8304 according to one aspect of the present invention. Specifically, the electric refrigerator 8300 has a housing 8301, a door for the refrigerating compartment 8302, a door for the freezing compartment 8303, a secondary battery 8304, etc. In FIG. 26, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator 8300 has a housing 8301, a door for the refrigerating compartment 8302, a door for the freezing compartment 8303, a secondary battery 8304, etc. In FIG. 26, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator 8300 has a housing 8301, a door for the refrigerating compartment 8302, a door for the freezing compartment 8303, a secondary battery 8304, etc. In FIG. 26, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator 8300 has a housing 8301, a door for the refrigerating compartment 8302, a door for the freezing compartment 8303, a secondary battery 8304, etc. In FIG. 26, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator 8300 It can also receive power supply from a commercial power source, or use the power stored in the secondary battery 8304. Therefore, when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8304 according to one aspect of the present invention as an uninterruptible power supply, the electric refrigerator 8300 can be used. Moreover, among the above-described electronic devices, high-frequency heating devices such as microwave ovens and electronic devices such as electric rice cookers require high power in a short time. Therefore, by using the secondary battery according to one aspect of the present invention as an auxiliary power supply to supplement the power that cannot be covered by the commercial power source, it is possible to prevent the breaker of the commercial power source from tripping during the use of the electronic device. In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low. According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the reliability can be enhanced. Also, according to one aspect of the present invention, a high-capacity secondary battery can be obtained.

[0423] Among the above-described electronic devices, high-frequency heating devices such as microwave ovens and electronic devices such as electric rice cookers require high power in a short time. Therefore, by using the secondary battery according to one aspect of the present invention as an auxiliary power supply to supplement the power that cannot be covered by the commercial power source, it is possible to prevent the breaker of the commercial power source from tripping during the use of the electronic device. Moreover, among the above-described electronic devices, high-frequency heating devices such as microwave ovens and electronic devices such as electric rice cookers require high power in a short time. Therefore, by using the secondary battery according to one aspect of the present invention as an auxiliary power supply to supplement the power that cannot be covered by the commercial power source, it is possible to prevent the breaker of the commercial power source from tripping during the use of the electronic device. In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low. In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low.

[0424] In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low. In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low. In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low. In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low. In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low. In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low. In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low. In addition, during the time when the electronic device is not in use, particularly during the time when the ratio of the actually used power amount to the total power amount that can be supplied by the commercial power source (referred to as the power utilization rate) is low, by storing power in the secondary battery, it is possible to suppress the increase in the power utilization rate outside the above time range. For example, in the case of the electric refrigerator 8300, at night when the temperature is low and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are not performed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the opening and closing of the refrigerator door 8302 and the freezer door 8303 are performed, by using the secondary battery 8304 as an auxiliary power supply, the power utilization rate during the day can be kept low.

[0425] According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the reliability can be enhanced. Moreover, according to one aspect of the present invention, a high-capacity secondary battery can be obtained. , the characteristics of the secondary battery can be improved, and thus the secondary battery itself can be made smaller and lighter. Therefore, by mounting the secondary battery according to one aspect of the present invention on the electronic device described in this embodiment, an electronic device with a longer lifespan and lighter weight can be obtained. This embodiment can be implemented in appropriate combination with other embodiments.

[0426] (Embodiment 5) In this embodiment, an example of mounting the secondary battery according to one aspect of the present invention on a vehicle is shown.

[0427] When the secondary battery is mounted on a vehicle, next-generation clean energy vehicles such as hybrid electric vehicles (HEVs), electric vehicles (EVs), or plug-in hybrid electric vehicles (PHEVs) can be realized.

[0428] In FIG. 27, a vehicle using the secondary battery according to one aspect of the present invention is illustrated. FIG. 27(A) shows an automobile 8400 that is an electric vehicle using an electric motor as a power source for driving. Or, it is a hybrid vehicle that can appropriately select and use an electric motor and an engine as power sources for driving. By using one aspect of the present invention, a vehicle with a long endurance can be realized. Further, the automobile 8400 has a secondary battery. The secondary battery may be arranged and used in parallel with the modules of the secondary battery shown in FIGS. 12(C) and 12(D) with respect to the floor portion inside the vehicle. Also, a battery pack combining a plurality of the secondary batteries shown in FIG. 17 may be installed with respect to the floor portion inside the vehicle. The secondary battery can not only drive the electric motor 8406 but also supply power to light-emitting devices such as headlight 8401 and room light (not shown).

[0429] In addition, the secondary battery can supply power to displays such as the speedometer and tachometer of the vehicle 8400. In addition, the secondary battery can supply power to semiconductor devices such as the navigation system of the vehicle 8400.

[0430] The vehicle 8500 shown in FIG. 27(B) can be charged by receiving power supply from an external charging facility by a plug-in method, a non-contact power supply method, or the like to the secondary battery of the vehicle 8500. FIG. 27(B) shows a state where charging is being performed from the ground-mounted charging device 8021 to the secondary battery 8024 mounted on the vehicle 8500 via the cable 8022. When charging, the charging method, the connector standard, etc. may be appropriately performed in a predetermined manner such as CHAdeMO (registered trademark) or Combo. The charging device 8021 may be a charging station provided in a commercial facility, or may also be a household power source. For example, by plug-in technology, the secondary battery 8024 mounted on the vehicle 8500 can be charged by external power supply. Charging can be performed by converting AC power into DC power via a conversion device such as an AC-DC converter.

[0431] Although not shown, a power receiving device can be mounted on the vehicle, and power can be supplied non-contact from a ground power transmission device for charging. In the case of this non-contact power supply method, by incorporating the power transmission device into a road or an outer wall, charging can be performed not only while the vehicle is stopped but also while it is running. In addition, power can be transmitted and received between vehicles using this non-contact power supply method. Furthermore, a solar cell may be provided on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped or running. For such non-contact power supply, an electromagnetic induction method or a magnetic field resonance method can be used. ​

[0432] In addition, FIG. 27(C) shows an example of a two-wheeled vehicle using a secondary battery according to an aspect of the present invention. In FIG. 27 (C), the scooter 8600 shown includes a secondary battery 8602, a side mirror 8601, and a direction indicator light 8603. The secondary battery 8602 can supply electricity to the direction indicator light 8603. It can be done.

[0433] In addition, the scooter 8600 shown in FIG. 27(C) can store the secondary battery 860 2 in the under-seat storage 8604. Even if the under-seat storage 8604 is small, the secondary battery 8602 can be stored in the under-seat storage 8604. The secondary battery 8602 is removable and can be carried indoors for charging during charging, and stored before driving. That's all.

[0434] According to an aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery can be increased. Therefore, the secondary battery itself can be made smaller and lighter. If the secondary battery itself can be made smaller and lighter, it contributes to reducing the weight of the vehicle, so the cruising range can be improved. In addition, the secondary battery mounted on the vehicle can also be used as a power supply other than the vehicle. In this case, for example, it is possible to avoid using a commercial power source during the peak period of power demand. If it is possible to avoid using a commercial power source during the peak period of power demand, it can contribute to energy conservation and reduction of carbon dioxide emissions. In addition, if the cycle characteristics are good, the secondary battery can be used for a long time, so the amount of use of rare metals such as cobalt can be reduced. It can be done. In addition, if the cycle characteristics are good, the secondary battery can be used for a long time, so the amount of use of rare metals such as cobalt can be reduced. It can be done.

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

Example

[0436] In this example, a cathode active material, which is one aspect of the present invention, was prepared, and the STE M observation results, the results of performing a fast Fourier transform on the TEM image, and the results of energy-dispersive X-ray analysis (EDX) will be described. In addition, the results of evaluating the characteristics of a secondary battery using the cathode active material will be described.

[0437] [Preparation of cathode active material] ≪Sample 01≫ In this example, as the cathode active material of Sample 01, it has lithium cobaltate as a composite oxide of lithium and a first transition metal in the first region, and the second region has lithium titanate as an oxide of a second transition metal, and has magnesium oxide as an oxide of a typical element in the third region. A product having these was prepared.

[0438] In this example, lithium cobaltate particles (manufactured by Nippon Chemical Industry Co., Ltd., product name: C-20F) were used as starting materials. Therefore, in this example, Steps 1 2 and Step 13 described in Embodiment 1 were omitted. The above lithium cobaltate particles have a particle size of about 20 μ m and are lithium cobaltate particles containing fluorine, magnesium, calcium, sodium, silicon, sulfur, and phosphorus in a region analyzable by XPS.

[0439] Next, as Step 14, a material containing titanium was coated on the lithium cobaltate particles containing magnesium and fluorine by the sol-gel method. Specifically, TTIP was dissolved in isopropanol to prepare an isopropanol solution of TTIP. Then, to this solution, lithium cobaltate ​ The μ particles were mixed. TTIP was mixed with lithium cobaltate containing magnesium and fluorine so that the amount was 0.01 ml / g.

[0440] The above mixture was stirred with a magnetic stirrer for 4 hours under the conditions of 25 °C and a humidity of 90% RH. By this treatment, hydrolysis and polycondensation reactions were caused by water in the atmosphere and TTIP, and a titanium-containing layer was formed on the surface of the lithium cobaltate particles having magnesium and fluorine.

[0441] The mixture after the above treatment was filtered, and the residue was recovered. For the filter for filtration, Kiriyama filter paper (No. 4) was used.

[0442] The recovered residue was vacuum dried at 70 °C for 1 hour.

[0443] Next, the lithium cobaltate particles coated with the titanium-containing material were heated. Using a muffle furnace the flow rate of dry air was 10 L / min, and heating was performed at 800 °C (heating rate 200 °C / hour) for a holding time of 2 hours. Dry air with a dew point of -109 °C or lower was used.

[0444] Next, the heated particles were cooled to room temperature. The temperature reduction time from the holding temperature to room temperature was set to 10 to 1 5 hours. Then, a crushing treatment was performed. The crushing treatment was carried out by sieving, and a sieve with an opening of 53 μm was used.

[0445] Finally, the cooled particles were recovered to obtain the positive electrode active material of Sample 01.

[0446] ≪Sample 02≫ Sample 02 was prepared as a comparative example by heating lithium cobaltate particles having magnesium and fluorine without coating with a titanium-containing material. ​​​

[0447] Lithium cobalt oxide particles containing magnesium and fluorine were manufactured by Nippon Kagaku Kogyo Co., Ltd. (product name: C -20F).

[0448] These lithium cobalt oxide particles containing magnesium and fluorine were heated. The heating was carried out at 800 °C (heating rate: 200°C / hour), holding time: 2 hours, and oxygen flow rate: 10 L / min. .

[0449] The heated powder was cooled in the same manner as Sample 01 and sieved, and the resulting product was used as the positive electrode active material of Sample 02. .

[0450] Sample 02 was presumed to be a positive electrode active material having lithium cobalt oxide inside and a region containing magnesium in the surface layer part. .

[0451] ≪Sample 03≫ Sample 03 was prepared as a comparative example by forming a region containing titanium by the sol-gel method on lithium cobalt oxide particles not containing magnesium and then heating them. .

[0452] Lithium cobalt oxide particles manufactured by Nippon Kagaku Kogyo Co., Ltd. (product name: C-10N) were used. These are lithium cobalt oxide particles in which magnesium is not detected by X PS and about 1 atomic% of fluorine is detected. .

[0453] For these lithium cobalt oxide particles, a region containing titanium was formed by the sol-gel method in the same manner as Sample 01, dried, heated, cooled, and sieved. This was used as the positive electrode active material of Sample 03. . .

[0454] Sample 03 has lithium cobalt oxide inside and a region containing titanium in the surface layer part. It was presumed to be the positive electrode active material.

[0455] ≪Sample 04≫ As a comparative example, the lithium cobaltate particles were used as they were without heating. They were used as they were.

[0456] The lithium cobaltate particles used were those manufactured by Nippon Chemical Industry Co., Ltd. (product name: C-10N).

[0457] Sample 04 is a positive electrode active material without a coating layer.

[0458] ≪Sample 05≫ As a comparative example, the lithium cobaltate particles having magnesium and fluorine were used as they were without heating. They were used as they were.

[0459] The lithium cobaltate particles having magnesium and fluorine used were those manufactured by Nippon Chemical Industry Co., Ltd. (product name: C -20F). That is, Sample 05 is the same as that used as the starting material in Sample 01. It is.

[0460] The conditions from Sample 01 to Sample 05 are shown in Table 1.

[0461]

Table 1

[0462] [STEM] The positive electrode active material of the obtained Sample 01 was observed with an electron microscope (JEM-ARM 200F manufactured by JEOL Ltd., acceleration voltage 200 kV). The obtained electron microscope image is shown in Fig. 28. As shown in Fig. 28, the positive electrode active material was considered to have three different regions, a first region 101, a second region 1 02, and a third region 103. The third region 103 was observed as a brighter region than the first region 101 and the second region 102. Also, the first region 101 and The crystal orientations of the second region 102 partially match, and those of the second region 102 and the third region 103 partially match.

[0463] [STEM-FFT] The FFT (Fast Fourier Transform) image of the region indicated by 103FFT in the STEM image shown in FIG. 28 is shown in FIG. 29(A1). FIG. 29(A2) shows the center point O of FIG. 29(A1) with a cross and shows the bright spots A, B, and C surrounded by circles. Similarly, the FF T image of the region indicated by 102FFT is shown in FIG. 29(B1). FIG. 29(B2) shows the center point O of FIG. 29(B1) with a cross and shows the bright spots A, B, and C surrounded by circles. Also, the FF T image of the region indicated by 101FFT is shown in FIG. 29(C1). FIG. 29(C2) shows the center point O of FIG. 29(C1) with a cross and shows the bright spots A, B, and C surrounded by circles.

[0464] The distance between the bright spot A and the center point O shown in FIG. 29(A2) was d = 0.256 nm. The distance between the bright spot B and the center point O was d = 0.241 nm. The distance between the bright spot C and the center point O was d = 0.209 nm. Also, ∠COA = 121°, ∠COB = 52°, ∠AO B = 69°. From these results, it was inferred that the region indicated by 103FFT contains magnesium oxide ( MgO, cubic crystal).

[0465] Similarly, the distance between the bright spot A and the center point O shown in FIG. 29(B2) was d = 0.238 nm . The distance between the bright spot B and the center point O was d = 0.225 nm. The distance between the bright spot C and the center point O was d = 0.198 nm. Also, ∠COA = 123°, ∠COB = 52 °, ∠AOB = 71°. From these results, it was inferred that the region indicated by 102FFT contains titanic acid It was speculated that it contained lithium (LiTiO2, cubic crystal).

[0466] The distance between the bright spot A and the center point O shown in Fig. 29 (C2) was d = 0.240 nm. The distance between the bright spot B and the center point O was d = 0.235 nm. The distance between the bright spot C and the center point O was , d = 0.196 nm. Also, ∠COA = 126°, ∠COB = 52°, ∠AO B = 74°. From these results, it was speculated that the region shown by the 101 FFT contained lithium cobaltate (LiCoO2, Rhombohedral).

[0467] [EDX] Moreover, the high-angle annular dark-field scanning transmission electron microscopy (HAADF- STEM) image and the elemental mapping image using EDX of the positive electrode active material of Sample 01 are shown in Fig. 30. Fig. 30 (A1) is the HAADF-STEM image, Fig. 30 (A2) is the oxygen atom mapping image, Fig. 30 (B1) is the cobalt atom mapping image, Fig. 30 (B2) is the fluorine atom mapping image, Fig. 30 (C1) is the titanium atom mapping image, and Fig. 30 (C2) is the magnesium atom mapping image. Note that , in the EDX elemental mapping images of Fig. 30 (A2) to Fig. 30 (C2) and Fig. 31 (A2) to Fig. 31 (C2), when it is below the detection limit, it is shown in white, and it is shown so that it approaches black as the count increases .

[0468] As shown in Fig. 30 (A2) and Fig. 30 (B1), it became clear that oxygen atoms and cobalt atoms were distributed throughout the positive electrode active material particles. On the other hand, as shown in Fig. 30 (B2), Fig. 30 ( C1) and Fig. 30 (C2), it became clear that fluorine atoms, titanium atoms and magnesium atoms were unevenly distributed in the region close to the surface of the positive electrode active material.

[0469] Next, using the HAADF-STEM image and EDX of the positive electrode active material of the comparative example of Sample 05 The elemental mapping images are shown in Fig. 31. Fig. 31(A1) is the HAADF-STEM image, Fig. 31 (A2) is the oxygen atom mapping image, Fig. 31(B1) is the cobalt atom mapping image, Fig. 31 (B2) is the fluorine atom mapping image, Fig. 31(C1) is the titanium atom mapping image, Fig. 31 (C2) is the magnesium atom mapping image.

[0470] As shown in Fig. 31(B2) and Fig. 31(C2), it was also revealed that magnesium and fluorine were somewhat unevenly distributed near the surface even in Sample 05 that had not been heated . .

[0471] [EDX Line Analysis] In addition, the results of linear analysis by TEM-EDX for the cross-section near the surface of the positive electrode active material of Sample 01 are shown in Fig. 32. Fig. 32 is a graph of the data detected on the line connecting the outside and the inside of the positive electrode active material of Sample 01 . The distance of 0 nm is the outside of the positive electrode active material, and the distance of 14 nm is inside the particle. Since EDX tends to have a wide analysis region, elements around the center of the electron beam irradiation may also be detected . .

[0472] As shown in Fig. 32, there are peaks of magnesium and titanium near the surface of the positive electrode active material of Sample 01, and it became clear that the distribution of magnesium is closer to the surface than that of titanium . Also, it became clear that the peak of magnesium is closer to the surface than the peak of titanium . In addition, it was speculated that cobalt and oxygen are present from the outermost surface of the positive electrode active material particles . .

[0473] In Fig. 32, almost no fluorine was detected. This is presumably because fluorine, being a light element, is difficult to detect by EDX.

[0474] From the above STEM image, FFT image, elemental mapping image using EDX, and EDX line analysis, it was confirmed that sample 01 is a positive electrode active material having lithium cobaltate as the first region, which is an aspect of the present invention, and having lithium, titanium, cobalt, and oxygen as the second region, and having magnesium and oxygen as the third region. Also, in sample 01, it became clear that a part of the second region and a part of the third region overlap.

[0475] Also, in the graph of Fig. 32, the detected amount of oxygen is stable at a distance of 4 nm or more. Therefore, in this example, the average value O of the detected amount of oxygen in this stable region was obtained, and the distance x of the measurement point showing the measured value closest to 50% of the average value O ave ave was estimated to be the surface of the particles of the positive electrode active material. ave

[0476] In this example, the average O of the detected amount of oxygen in the range of 4 nm or more and 14 nm or less was ave 674.2. The x-axis of the measurement point showing the measured value closest to 337.1, which is 50% of 674.2, was 1.71 nm. Therefore, in this example, it was estimated that the distance of 1.71 nm in the graph of Fig. 32 is the surface of the particles of the positive electrode active material.

[0477] Assuming that the surface of the positive electrode active material particles is at a distance of 1.71 nm in Fig. 32, the peak of magnesium is 0.72 nm from the surface of the positive electrode active material particles, and the peak of titanium is 1.00 n from the surface. ​​​​​​​​​​​​​​ was m.

[0478] Also, the magnesium concentration was 1 / 5 or more of the peak at a distance of 4.42 nm, that is, from the surface of the positive electrode active material particles to 2.71 nm. At a distance of 4.57 nm or more, that is, at a depth of 2.86 nm or more from the surface of the positive electrode active material particles, the measured value of magnesium was less than 1 / 5 of the peak. Therefore, it was revealed that Sample 01 was in the region of No. 3 up to 2.71 nm in the depth direction from the surface. [[ID=1)]]

[0479] Also, the titanium concentration was 1 / 2 or more of the peak from a distance of 2.14 nm to a distance of 3.42 n m. That is, it was revealed that the range from 0.43 nm or more to 1.71 nm or less from the surface of the positive electrode active material particles was the second region.

[0480]

[0481] Next, a secondary battery using the positive electrode active materials of Samples 01 to 05 prepared above will be manufactured and the results of evaluating the charge and discharge characteristics of the secondary battery will be described.

[0481] [Manufacture of Secondary Battery] A coin-type secondary battery of CR2032 type (diameter 20 mm, height 3.2 mm) using the positive electrode active materials of Samples 01 to 05 prepared above was manufactured. (diameter 20 mm height 3.2 mm) was manufactured.

[0482] For the positive electrode, a slurry obtained by mixing a positive electrode active material (LCO), acetylene black (AB), and polyvinylidene fluoride (PVDF) at LCO:AB:PVDF = 95:2.5:2.5 (weight ratio) was applied to a current collector. was used.

[0483] Lithium metal was used for the counter electrode.

[0484] 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%. We used the following.

[0485] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0486] [Charge / discharge characteristics evaluation] Next, the charge-discharge characteristics of the secondary batteries of Sample 01 and Sample 05 prepared above were evaluated. The measurement temperature was 25°C. Charging was performed at a cutoff voltage of 4.6V (CCCV, 0.5C). Current 0.01C), discharge 2.5V (CC, 0.5C), and 20 charge / discharge cycles. Here, 1C is a current value per weight of the positive electrode active material of 137 mA / g. .

[0487] FIG. 33 shows a graph of the charge-discharge characteristics of a secondary battery using the positive electrode active material of Sample 01. As shown in Figure 33, the charge-discharge characteristics were good with a broad plateau. The charge / discharge graphs almost overlapped, and the cycle characteristics were good.

[0488] FIG. 34 shows a graph of the charge-discharge characteristics of the secondary battery of Sample 05 of the comparative example. Although the battery showed good charge-discharge characteristics in the first cycle, as shown by the arrows in the figure, the charge-discharge characteristics decreased with the number of cycles. The charge / discharge capacity decreased.

[0489] [Evaluation of cycle characteristics] ≪Charging 4.4V≫ For the secondary batteries of Sample 01 and Sample 05, the cycle characteristics when charged at 4.4V The cycle characteristics were evaluated at a temperature of 25°C. Charging was performed at 4.4 V (CCCV, 0. The battery was charged at 2.5V (CC, 0.5C, cut-off current 0.01C) and discharged at 2.5V (CC, 0.5C).

[0490] Figure 35 shows a graph of the cycle characteristics when charging at 4.4 V. The solid line in the figure indicates sample 0. The dotted line is the graph for the secondary battery having the positive electrode active material of Sample 05. As shown, the secondary battery containing sample 01 maintained the energy density even after 50 cycles. The cycle life was 99.5%, demonstrating excellent cycle characteristics. The secondary battery maintained an energy density of 94.3% after 50 cycles.

[0491] ≪Charging 4.6V≫ For the secondary batteries of Sample 01 to Sample 04, the cycle characteristics when charged at 4.6V are The measurement temperature was 25°C. The charge was 4.6V (CCCV, 0.5C, cutoff The current was 0.01 C, and the discharge was 2.5 V (CC, 0.5 C).

[0492] Figure 36 shows a graph of the cycle characteristics when charging at 4.6V. The secondary battery having Sample 01, which is a positive electrode active material according to one embodiment of the present invention, exhibited a high voltage of 4.6 V. Even after 50 cycles of voltage charging and discharging, the energy density is maintained at 94.1%, which is extremely On the other hand, the positive electrode active materials of Samples 02 to 04 of the comparative examples showed good cycle characteristics. The secondary battery with the quality is inferior to Sample 01. For example, in the case of Sample 04, The energy density retention rate after the test was 33.2%.

[0493] As described above, the positive electrode active material according to one embodiment of the present invention can be charged at a high voltage exceeding 4.4 V. It has been revealed that a remarkable effect is exhibited when discharging is performed.

Example

[0494] In this example, a positive electrode active material which is an aspect of the present invention was produced, and analysis different from that of Example 1 was performed and the results will be described. Also, the characteristics of the secondary battery using the positive electrode active material will be described for the results evaluated under conditions different from those of Example 1.

[0495] In this example, as the positive electrode active material, it has lithium cobalt oxide as a composite oxide of lithium and a first transition metal in the first region, and lithium titanate as an oxide of a second transition metal in the second region, and magnesium oxide as an oxide of a typical element in the third region, and a product having the same was produced.

[0496] [Production of Positive Electrode Active Material, Production of Secondary Battery] ≪Sample 06, Sample 07≫ In this example, lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd., product name: C-20F) were used as the starting material.

[0497] Next, as step 14, titanium oxide was coated on the lithium cobalt oxide particles by the sol-gel method and dried. It was carried out in the same manner as in Example 1 except that TTIP was mixed with the lithium cobalt oxide so as to be 0.004 ml / g. After being coated with this titanium oxide, the lithium cobalt oxide particles before heating were designated as Sample 06.

[0498] Next, the lithium cobalt oxide particles coated with titanium oxide of Sample 06 were heated. Using a muffle furnace, heating was carried out in an oxygen atmosphere at 800 ° C. for a holding time of 2 hours, and the oxygen flow rate was 10 L / min.

[0499] Thereafter, cooling and recovery were carried out in the same manner as in Example 1 to obtain a positive electrode active material. The positive electrode active material after heating was designated as Sample 07.

[0500] [TEM-EDX] Regarding Sample 06 and Sample 07, particularly regarding the cracks generated in the particles and the vicinity thereof, analysis was performed using TEM-EDX.

[0501] First, the results of TEM-EDX surface analysis for titanium are shown in FIGS. 37 and 38.

[0502] FIG. 37 shows the TEM-EDX analysis results of Sample 06 before heating. FIG. 37(A) is a cross-sectional TEM image including the particle surface and the crack part. The HAADF-STEM image of the region including the particle surface, indicated by the circle labeled 1 in FIG. 37(A), is shown in FIG. 37(B1), and the Ti mapping image is shown in FIG. 37(B2). Similarly, the HAADF-STEM image of the region with a depth of about 20 nm from the surface in the crack part, indicated by the circle labeled 2 in FIG. 37(A), is shown in FIG. 37(C1), and the Ti mapping image is shown in FIG. 37(C2). The HAADF-STEM image of the region with a depth of about 500 nm from the surface in the crack part, indicated by the circle labeled 3 in FIG. 37(A), is shown in FIG. 3 7(D1), and the Ti mapping image is shown in FIG. 37(D2). The HAADF-STEM image of the region with a depth of about 1000 nm from the surface in the crack part, indicated by the circle labeled 4 in FIG. 37(A), is shown in FIG. 3 7(E1), and the Ti mapping image is shown in FIG. 37(E2). In the EDX elemental mapping images of FIGS. 37 to 40, cases below the detection limit are shown in black, and it is shown such that the closer the count is to increasing, the closer it is to white. 7(D1), and the Ti mapping image is shown in FIG. 37(D2). The HAADF-STEM image of the region with a depth of about 1000 nm from the surface in the crack part, indicated by the circle labeled 4 in FIG. 37(A), is shown in FIG. 3 7(E1), and the Ti mapping image is shown in FIG. 37(E2). Note that in the EDX elemental mapping images from FIGS. 37 to 40, cases below the detection limit are shown in black, and it is shown such that the closer the count is to increasing, the closer it is to white. TEM image is shown in FIG. 37(E1), and the Ti mapping image is shown in FIG. 37(E2). Note that in the EDX elemental mapping images of FIGS. 37 to 40, cases below the detection limit are shown in black, and it is shown such that the closer the count is to increasing, the closer it is to white. The more the count increases, the closer it is shown to white.

[0503] Figure 38 shows the TEM-EDX analysis results of sample 07 after heating. Figure 38(A) is a cross-sectional TEM image including the particle surface and the crack part. The region including the particle surface, indicated by the circle marked 1 in Figure 38(A), has its HAADF-STEM image shown in Figure 38(B1) and its Ti mapping image shown in Figure 38(B2). Similarly, the region of the crack part with a depth of about 20 nm from the surface, indicated by the circle marked 2 in Figure 38(A), has its HAADF-STEM image shown in Figure 38(C1) and its Ti mapping image shown in Figure 38(C2). The region of the crack part with a depth of about 500 nm from the surface, indicated by the circle marked 3 in Figure 38(A), has its HAADF-STEM image shown in Figure 38(D1) and its Ti mapping image shown in Figure 38(D2). The region of the crack part with a depth of about 1000 nm from the surface, indicated by the circle marked 4 in Figure 38(A), has its HAADF-STEM image shown in Figure 38(E1) and its Ti mapping image shown in Figure 38(E2). It is a cross-sectional TEM image including the particle surface and the crack part. The HAADF-STEM image of the region including the particle surface, indicated by the circle marked 1 in Figure 38(A), is shown in Figure 38(B1), and the Ti mapping image is shown in Figure 38(B2). Similarly, the HAADF-STEM image of the region of the crack part with a depth of about 20 nm from the surface, indicated by the circle marked 2 in Figure 38(A), is shown in Figure 38(C1), and the Ti mapping image is shown in Figure 38(C2). The HAADF-STEM image of the region of the crack part with a depth of about 500 nm from the surface, indicated by the circle marked 3 in Figure 38(A), is shown in Figure 38(D1), and the Ti mapping image is shown in Figure 38(D2). The HAADF-STEM image of the region of the crack part with a depth of about 1000 nm from the surface, indicated by the circle marked 4 in Figure 38(A), is shown in Figure 38(E1), and the Ti mapping image is shown in Figure 38(E2).

[0504] As shown in Figures 37 and 38, although titanium was observed to segregate on the particle surface in sample 06 before heating, no segregation was confirmed in the crack part. On the other hand, in sample 07 after heating, titanium segregation was observed both on the particle surface and in the crack part. That is, it became clear that titanium segregates at the interface of the crack part by heating.

[0505] Next, the results of TEM-EDX surface analysis for magnesium are shown in Figures 39 and 40.

[0506] Figure 39(A) is a cross-sectional TEM image of the same sample 06 as Figure 37(A). Figures 39(B1 ), Figure 39(C1), Figure 39(D1) and Figure 39(E1) are the same as Figures ​​​​​​​(C1), the same HAADF-STEM images as those in FIGS. 37(D1) and 37(E1). The Mg mapping image of the same region as in FIG. 39(B1) is shown in FIG. 39(B2). FIG. 39(C1) The Mg mapping image of the same region as in FIG. 39(C1) is shown in FIG. 39(C2). The Mg mapping image of the same region as in FIG. 39(D1) is shown in FIG. 39(D2). The Mg mapping image of the same region as in FIG. 39(E1) is shown in FIG. 39(E2).

[0507] FIG. 40(A) is a cross-sectional TEM image of the same sample 07 as in FIG. 38(A). FIGS. 40(B1 ), FIG. 40(C1), FIG. 40(D1) and FIG. 40(E1) are the same HAADF-STEM images as those in FIGS. 38(B1), FIGS. 38 (C1), FIGS. 38(D1) and FIGS. 38(E1). The Mg mapping image of the same region as in FIG. 40(B1) is shown in FIG. 40(B2). FIG. 40(C1) The Mg mapping image of the same region as in FIG. 40(C1) is shown in FIG. 40(C2). The Mg mapping image of the same region as in FIG. 40(D1) is shown in FIG. 40(D2). The Mg mapping image of the same region as in FIG. 40(E1) is shown in FIG. 40(E2).

[0508] As shown in FIGS. 39 and 40, in sample 06 before heating, no segregation was confirmed on the particle surface or at the crack part for magnesium. On the other hand, in sample 07 after heating, segregation of magnesium was observed both on the particle surface and at the crack part. Next, in order to quantify titanium and magnesium, EDX point analysis was performed on the regions indicated by circles numbered 1 to 6 in FIG. 37(A), and the regions indicated by circles numbered 1 to 6 in FIG. 38(A). Two measurements were taken within the range of each region.

[0509]

[0510]

[0510] Figure 41 shows the results of EDX point analysis in terms of the atomic number ratio of titanium to cobalt. Figure 41(A) is the result of sample 06 before heating. The detection points 1 to 6 in Figure 41(A) are respectively within the regions indicated by the circles labeled 1 to 6 in Figure 37(A). Figure 41(B) is the result of the sample 07 after heating. The detection points 1 to 6 in Figure 41(B) are respectively within the regions indicated by the circles labeled 1 to 6 in Figure 38( A).

[0511] As shown in Figure 41, for the crack part of sample 06, Ti / Co was 0 .01 or less at any measurement point. On the other hand, in the crack part of sample 07, there were many places where titanium increased, and there were also measurement points where Ti / Co was 0.05 or more. Also, on the particle surface of sample 07, Ti / Co was between 0.10 and 0.18.

[0512] Next, Figure 42 shows the results of EDX point analysis in terms of the atomic number ratio of magnesium to cobalt. The detection points are the same as those in Figure 41.

[0513] As shown in Figure 42, for sample 06, Mg / Co was 0.03 or less both on the particle surface and in the crack part. On the other hand, for sample 07, there were many places where magnesium increased both on the particle surface and in the crack part. Mg / Co on the particle surface was between 0.15 and 0.50, and in the crack part, it was in the range of 0 to 0.22.

[0514] Next, a CR2032 type coin-shaped secondary battery was fabricated using the cathode active material of sample 07 after heating. For the cathode, the cathode active material (LCO) of sample 02, AB, and polyvinylidene fluoride (PVDF) were mixed at LCO:AB:PVDF = 95:3:2 (by weight) ​​A slurry applied to the positive current collector was used. As the positive current collector, an aluminum foil with a thickness of 20 μm was used. The loading amount of the positive electrode active material layer containing the positive electrode active material, AB, and PVDF was 7. 6 mg / cm 2 was used.

[0515] Lithium metal was used as the counter electrode.

[0516] In the electrolyte, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of EC: DEC = 3:7, and 1 mol / L of LiPF6 was dissolved therein, and vinylene carbonate (VC) was added at 2 wt%. was used.

[0517] [Initial characteristics, rate characteristics] Regarding the secondary battery using the positive electrode active material of Sample 07 prepared above, the initial characteristics and rate characteristics were measured.

[0518] For the measurement of the initial characteristics, charging was performed in CCCV mode at 0.2C, 4.6V, and a cut-off current of 0.05C. Discharging was performed in CC mode at 0.2C and a cut-off voltage of 3.0V. Here, 1C was defined as 160 mA / g based on the current value per unit weight of the positive electrode active material. The measurement temperature was set at 25°C. The results of the measurement of the initial characteristics are shown in Table 2. The rate characteristics were measured after the measurement of the initial characteristics. By changing the discharge rate, under the same conditions as the measurement of the initial

[0519]

Table 2

[0520] characteristics except for the discharge rate, 0.2C charge / 0.2C discharge, 0.2C charge / 0.5C discharge, 0 .2C charge / 1.0C discharge, 0.2C charge / 2.0C discharge, 0.2C charge / 3.0C discharge were performed. 、Measured in the order of 0.2C charge / 4.0C discharge and 0.2C charge / 5.0C discharge. The measurement temperature was set at 25°C.

[0521] Table 3 shows the results of measuring the initial characteristics and rate characteristics. The discharge curves at each rate are shown in Figure 43.

[0522]

Table 3

[0523] [Temperature characteristics] Next, a cell with the same conditions as the cell whose rate was evaluated was fabricated, except that the loading amount of the positive electrode active material layer was 8.2 mg / cm 2 , and its temperature characteristics were evaluated. All charging was performed at 25°C, CCCV, 0.2 C, 4.6V, and a cut-off current of 0.05C. Discharging was performed in the order of 25°C, 0°C, -10°C, - 20°C, 45°C, CC, 0.2C, and a cut-off voltage of 3.0V. The measurement results of the temperature characteristics are shown in Figure 44.

[0524] [Cycle characteristics] Next, a cell with the same conditions as the cell whose temperature characteristics were measured was fabricated, and its cycle characteristics were measured. For the cycle characteristics, charging was performed at CCCV, 1.0C, 4.55V, and a cut-off current of 0.05C , and discharging was performed at CC, 1.0C, and a cut-off voltage of 3.0V. The measurement temperature of the cycle characteristics was set at 45°C, and 100 cycles were measured. The discharge capacity retention rate after 100 cycles was 86%. Figure 45 shows a graph of the measured cycle characteristics in terms of the discharge capacity retention rate.

[0525] . Also, the measured specific surface area of the positive electrode active material of Sample 07 was 0.13 m 2 / g.

[0526] In addition, as a result of measuring the particle size distribution of the positive electrode active material of Sample 07, the average particle size was 21.5 μm, 10%D was 13.1 μm, 50%D was 22.0 μm, and 90%D was 34.4 μm.

[0527] In addition, the tap density of the positive electrode active material of Sample 07 was 2.21 g / cm 3 . The tap density was measured using MULTI TESTER MT-1000 (manufactured by Seishin Enterprise Co., Ltd). .

[0528] As describe...

Claims

1. A lithium-ion secondary battery having a positive electrode and a negative electrode, wherein the positive electrode has positive electrode active material particles containing lithium cobaltate, the positive electrode active material particles contain magnesium, fluorine, and titanium, the positive electrode active material particles have a first region containing lithium cobaltate, a second region containing titanium, and a third region containing magnesium oxide and cobalt oxide, at least the third region is on the outermost surface of the positive electrode active material particles, a part of the third region overlaps with a part of the second region, the first region is further inside than the third region and the second region, the crystal orientations from the first region to the third region are substantially the same, the third region contains magnesium, cobalt, oxygen, and fluorine, a lithium-ion secondary battery.

2. The first region has a layered rock salt-type crystal structure, the second region has a rock salt-type crystal structure, the third region has a rock salt-type crystal structure, the lithium-ion secondary battery according to Claim 1.

3. the positive electrode active material particles contain magnesium bonded to oxygen and fluorine, the lithium-ion secondary battery according to Claim 1 or 2.

4. When a linear analysis is performed on a cross section of the positive electrode active material particles by EDX, the peak of magnesium is closer to the surface side than the peak of titanium, the lithium-ion secondary battery according to any one of Claims 1 to 3.

5. A lithium-ion secondary battery having a positive electrode and a negative electrode, wherein the positive electrode has positive electrode active material particles containing lithium cobaltate, the positive electrode active material particles contain magnesium, fluorine, and titanium, the positive electrode active material particles have a first region containing lithium cobaltate, a second region containing titanium, and a third region containing magnesium oxide and cobalt oxide, at least the third region is on the outermost surface of the positive electrode active material particles, a part of the third region overlaps with a part of the second region, the first region is further inside than the third region and the second region, the crystal orientations from the first region to the third region are substantially the same, the third region contains magnesium bonded to oxygen and fluorine, a lithium-ion secondary battery.

6. The first region has a layered rock salt-type crystal structure, the second region has a rock salt-type crystal structure, the third region has a rock salt-type crystal structure, the lithium-ion secondary battery according to Claim 5.

7. When performing a linear analysis of the cross-section of the positive electrode active material particles by EDX, the peak of magnesium is closer to the surface side than the peak of titanium, The lithium ion secondary battery according to claim 5 or 6.

8. The fluorine in the third region exists in a bonding state other than MgF ２ ​ The lithium ion secondary battery according to any one of claims 1 to 7.

9. Fluorine in the third region exists in a bonding state other than LiF. The lithium ion secondary battery according to any one of claims 1 to 8.

10. The fluorine in the third region exists in a bonding state other than CoF ２ and The lithium ion secondary battery according to any one of claims 1 to 9.

11. When the positive electrode active material particles are analyzed by XPS, the peak position of the binding energy of fluorine is 682 eV or more and 685 eV or less. The lithium ion secondary battery according to any one of claims 1 to 10.

12. On the surface side of the positive electrode active material particles, there is a region where the atomic number ratio of magnesium to cobalt (Mg / Co) measured by EDX is 0.15 or more and 0.50 or less. The lithium ion secondary battery according to any one of claims 1 to 11.

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