Lithium-ion secondary battery

Abstract

When used in lithium-ion secondary batteries, the capacity declines during charge / discharge cycles. To provide a positive electrode active material that suppresses A coating layer is formed by segregation on the surface of a positive electrode active material. The first region is located inside, and the second region is located between the surface and one of the interior regions. The first region has lithium, a transition metal, and oxygen, and the second region has magnesium. The positive electrode active material contains neodymium, fluorine, and oxygen.

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 method for manufacturing a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, or an electronic device. In particular, it relates to a positive electrode active material that can be used in a secondary battery, a secondary battery, and an electronic device having 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 capacity are rapidly expanding in demand along with the development of the semiconductor industry, for portable information terminals such as mobile phones, smartphones, or notebook computers, portable music players, digital cameras, medical devices, or next-generation clean energy automobiles such as hybrid vehicles (HEV), electric vehicles ( EV), or plug-in hybrid vehicles (PHEV). The demand for rechargeable energy is expanding rapidly, It has become an essential element in the modern information society as a source.

[0005] The characteristics currently required for lithium-ion secondary batteries include further increased capacity, improved cycle characteristics, enhanced safety in various operating environments, and improved long-term reliability.

[0006] One method of increasing the capacity of a lithium-ion secondary battery is known to be increasing the charging voltage. For example, the capacity of lithium cobaltate, which is often used as the positive electrode active material of a lithium-ion secondary battery, is generally 155 mAh / g when the charging voltage is 4.3 V, but it becomes 220 mAh / g when the charging voltage is raised to 4.6 V (see Fig. 21(A)).

[0007] However, it is also known that increasing the charging voltage deteriorates the cycle characteristics. For example, for general lithium cobaltate, the capacity retention rate after 30 cycles when the charging voltage is 4.4 V is 95% or more, but when the charging voltage is raised to 4.6 V, the capacity retention rate after 30 cycles drops to 50% or less (see Fig. 21(B)).

[0008] Therefore, in order to improve the cycle characteristics and increase the capacity of lithium-ion secondary batteries, the improvement of the positive electrode active material is being studied (Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] Thus, there is still room for improvement in lithium ion secondary batteries and the positive electrode active materials used therein in various aspects such as capacity, size cycle characteristics, charge / discharge characteristics, reliability, safety, or cost.

[0011] 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 secondary battery with a high capacity. 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.

[0012] Or, one aspect of the present invention is to provide a novel substance, active material, power storage device, or a method for producing them.

[0013] Note that the description of these problems does not prevent the existence of other problems. Note that one aspect of the present invention is not required to solve all of these problems. Note that it is possible to extract other problems from the description of the specification, drawings, and claims.

Means for Solving the Problems

[0014] To achieve the above object, one aspect of the present invention is characterized in that a covering layer is formed on the surface layer portion of the positive electrode active material by segregation.

[0015] One aspect of the present invention is a positive electrode active material, wherein the positive electrode active material includes a first region, a second region, ​​​​​having a first region present inside the positive electrode active material and a second region present in a surface layer portion and a part of the inside of the positive electrode active material, the first region having lithium, a transition metal, and oxygen, and the second region having magnesium, fluorine, and oxygen, is a positive electrode active material.

[0016] Also, one aspect of the present invention is a positive electrode active material, the positive electrode active material having lithium, a transition metal , oxygen, magnesium, and fluorine, being present on the surface of the positive electrode active material, and having, with the total amount of atoms including lithium, transition metal, oxygen, fluorine, and magnesium measured by X-ray photoelectron spectroscopy being 100 atomic%, a magnesium concentration of 1 atomic% or more and 16 atomic% or less, and a fluorine concentration of 0.2 atomic% or more and 4 atomic% or less, measured by X-ray photoelectron spectroscopy, on the surface of the positive electrode active material.

[0017] Also, one aspect of the present invention is a positive electrode active material, the positive electrode active material having lithium, a transition metal , oxygen, magnesium, and fluorine, and the ratio of the magnesium concentration to the fluorine concentration on the surface of the positive electrode active material measured by X-ray photoelectron spectroscopy being Mg:F = y:1 (3 ≤ y ≤ 5) , is a positive electrode active material.

[0018] Also, one aspect of the present invention is a positive electrode active material, the positive electrode active material having lithium, a transition metal , oxygen, magnesium, and fluorine, and the peak position of the binding energy of fluorine on the surface of the positive electrode active material measured by X-ray photoelectron spectroscopy being 682 eV or more and less than 685 eV , is a positive electrode active material.

[0019] Also, in the above, the transition metal preferably contains cobalt. Or, in the above ​​​​​, the transition metal preferably includes manganese, cobalt, and nickel.

[0020] Also, one aspect of the present invention is a positive electrode active material, which has a first region and a second region. The first region exists inside and contains lithium, a transition metal, and oxygen, and has a layered rock salt-type crystal structure. The second region exists in the surface layer part and a part of the inside, contains magnesium, fluorine, and oxygen, and has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same, and the ratio of the magnesium concentration to the fluorine concentration on the surface of the positive electrode active material measured by X-ray photoelectron spectroscopy is Mg:F = y:1 (3 ≤ y ≤ 5). The first region exists inside and has a layered rock salt-type crystal structure with lithium, a transition metal, and oxygen. The second region exists in the surface layer part and a part of the inside and has a rock salt-type crystal structure with magnesium, fluorine, and oxygen. The crystal orientations of the first region and the second region are the same, and the ratio of the magnesium concentration to the fluorine concentration on the surface of the positive electrode active material measured by X-ray photoelectron spectroscopy is Mg:F = y:1 (3 ≤ y ≤ 5). The first region exists inside and has a layered rock salt-type crystal structure with lithium, a transition metal, and oxygen. The second region exists in the surface layer part and a part of the inside and has a rock salt-type crystal structure with magnesium, fluorine, and oxygen. The crystal orientations of the first region and the second region are the same, and the ratio of the magnesium concentration to the fluorine concentration on the surface of the positive electrode active material measured by X-ray photoelectron spectroscopy is Mg:F = y:1 (3 ≤ y ≤ 5). The first region exists inside and has a layered rock salt-type crystal structure with lithium, a transition metal, and oxygen. The second region exists in the surface layer part and a part of the inside and has a rock salt-type crystal structure with magnesium, fluorine, and oxygen. The crystal orientations of the first region and the second region are the same, and the ratio of the magnesium concentration to the fluorine concentration on the surface of the positive electrode active material measured by X-ray photoelectron spectroscopy is Mg:F = y:1 (3 ≤ y ≤ 5). The first region exists inside and has a layered rock salt-type crystal structure with lithium, a transition metal, and oxygen. The second region exists in the surface layer part and a part of the inside and has a rock salt-type crystal structure with magnesium, fluorine, and oxygen. The crystal orientations of the first region and the second region are the same, and the ratio of the magnesium concentration to the fluorine concentration on the surface of the positive electrode active material measured by X-ray photoelectron spectroscopy is Mg:F = y:1 (3 ≤ y ≤ 5). The first region exists inside and has a layered rock salt-type crystal structure with lithium, a transition metal, and oxygen. The second region exists in the surface layer part and a part of the inside and has a rock salt-type crystal structure with magnesium, fluorine, and oxygen. The crystal orientations of the first region and the second region are the same, and the ratio of the magnesium concentration to the fluorine concentration on the surface of the positive electrode active material measured by X-ray photoelectron spectroscopy is Mg:F = y:1 (3 ≤ y ≤ 5).

[0021] Also, in the above, the peak position of the binding energy of fluorine on the surface of the positive electrode active material measured by X-ray photoelectron spectroscopy is preferably 682 eV or more and less than 685 eV. Also, in the above, the peak position of the binding energy of fluorine on the surface of the positive electrode active material measured by X-ray photoelectron spectroscopy is preferably 682 eV or more and less than 685 eV.

[0022] Also, one aspect of the present invention is a method for producing a positive electrode active material, which includes a step of mixing a lithium source, a transition metal source, a magnesium source, and a fluorine source, a step of heating at 800 °C or more and 1100 °C or less for 2 hours or more and 20 hours or less, and a step of heating in an atmosphere containing oxygen at 500 °C or more and 1200 °C or less for a holding time of 50 hours or less. The atomic ratio of fluorine contained in the fluorine source to magnesium contained in the magnesium source is Mg:F = 1:x (1.5 ≤ x ≤ 4). Also, one aspect of the present invention is a method for producing a positive electrode active material, which includes a step of mixing a lithium source, a transition metal source, a magnesium source, and a fluorine source, a step of heating at 800 °C or more and 1100 °C or less for 2 hours or more and 20 hours or less, and a step of heating in an atmosphere containing oxygen at 500 °C or more and 1200 °C or less for a holding time of 50 hours or less. The atomic ratio of fluorine contained in the fluorine source to magnesium contained in the magnesium source is Mg:F = 1:x (1.5 ≤ x ≤ 4). Also, one aspect of the present invention is a method for producing a positive electrode active material, which includes a step of mixing a lithium source, a transition metal source, a magnesium source, and a fluorine source, a step of heating at 800 °C or more and 1100 °C or less for 2 hours or more and 20 hours or less, and a step of heating in an atmosphere containing oxygen at 500 °C or more and 1200 °C or less for a holding time of 50 hours or less. The atomic ratio of fluorine contained in the fluorine source to magnesium contained in the magnesium source is Mg:F = 1:x (1.5 ≤ x ≤ 4). Also, one aspect of the present invention is a method for producing a positive electrode active material, which includes a step of mixing a lithium source, a transition metal source, a magnesium source, and a fluorine source, a step of heating at 800 °C or more and 1100 °C or less for 2 hours or more and 20 hours or less, and a step of heating in an atmosphere containing oxygen at 500 °C or more and 1200 °C or less for a holding time of 50 hours or less. The atomic ratio of fluorine contained in the fluorine source to magnesium contained in the magnesium source is Mg:F = 1:x (1.5 ≤ x ≤ 4). Also, one aspect of the present invention is a method for producing a positive electrode active material, which includes a step of mixing a lithium source, a transition metal source, a magnesium source, and a fluorine source, a step of heating at 800 °C or more and 1100 °C or less for 2 hours or more and 20 hours or less, and a step of heating in an atmosphere containing oxygen at 500 °C or more and 1200 °C or less for a holding time of 50 hours or less. The atomic ratio of fluorine contained in the fluorine source to magnesium contained in the magnesium source is Mg:F = 1:x (1.5 ≤ x ≤ 4). Also, one aspect of the present invention is a method for producing a positive electrode active material, which includes a step of mixing a lithium source, a transition metal source, a magnesium source, and a fluorine source, a step of heating at 800 °C or more and 1100 °C or less for 2 hours or more and 20 hours or less, and a step of heating in an atmosphere containing oxygen at 500 °C or more and 1200 °C or less for a holding time of 50 hours or less. The atomic ratio of fluorine contained in the fluorine source to magnesium contained in the magnesium source is Mg:F = 1:x (1.5 ≤ x ≤ 4).

[0023] Or, one aspect of the present invention is a positive electrode active material, which has a first region and a second region. The first region exists inside the positive electrode active material, and the second region exists in the positive electrode active material. Or, one aspect of the present invention is a positive electrode active material, which has a first region and a second region. The first region exists inside the positive electrode active material, and the second region exists in the positive electrode active material. It exists in the surface part and a part of the interior, and the first region has lithium, cobalt, and oxygen. The second region has cobalt, magnesium, fluorine, and oxygen, and is a positive electrode active material. When the positive electrode active material is analyzed by electron energy loss spectroscopy, the L3 / L of cobalt in the first region is less than 3.8. The L3 / L of cobalt in the second region is 3.8 or more. It is a positive electrode active material.

Advantages of the Invention

[0024] According to one aspect of the present invention, by using it in a lithium-ion secondary battery, a positive electrode active material can be provided that suppresses a decrease in capacity during charge and discharge cycles. Also, a secondary battery with a high capacity can be provided. Further, a secondary battery with excellent charge and discharge characteristics can be provided. Also, a secondary battery with high safety or reliability can be provided. In addition, a novel substance, active material, power storage device, or a method for producing them can be provided.

Brief Description of the Drawings

[0025]

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Best Mode for Carrying Out the Invention

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art can easily understand that its form and details can be variously changed. Also, the present invention is not construed as being limited to the description of the embodiments shown below. Moreover, 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 clarity of individual explanations. Therefore, each component is not necessarily limited to its size, nor is it limited to the relative size between each component.

[0027] In addition, in the configuration of the present invention described in this specification and the like, the same part or parts having the same function are commonly used with the same reference numeral among different drawings, and the repeated description thereof is omitted. Also, when referring to parts having the same function, the hatch pattern is the same, and there may be cases where no reference numeral is particularly assigned.

[0028] Also, in the configuration of the present invention described in this specification and the like, for the same part or parts having the same function, the same reference numeral is commonly used among different drawings, and the repeated description thereof is omitted. Also, when referring to parts having the same function, the hatch pattern is the same, and there may be cases where no reference numeral is particularly assigned. Moreover, when referring to parts having the same function, the hatch pattern is the same, and there may be cases where no reference numeral is particularly assigned.

[0029] In addition, Miller indices are used for the notation of crystal planes and directions. In the notation of Miller indices, in crystallography, a bar is attached above the number, but in this specification and the like, due to the constraints of the application notation, a -(minus sign) is attached before the number. Also, the individual orientation indicating the direction within the crystal is represented by [], the set orientation indicating all equivalent directions is represented by <>, the individual plane indicating the crystal plane is represented by (), and the set plane having equivalent symmetry is represented by {} respectively.

[0030] ​​​​​​​​​​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.

[0031] In this specification and the like, the layered rock salt-type crystal structure of a composite oxide containing lithium and a transition metal means a crystal structure having a rock salt-type ion arrangement in which cations and anions are alternately arranged, and the transition metal and lithium are regularly arranged to form a two-dimensional plane, so that two-dimensional diffusion of lithium is possible. Note that there may be defects such as cation or anion deficiencies. Also, the layered rock salt-type crystal structure is, strictly speaking, a structure in which the lattice of the rock salt-type crystal is distorted in some cases.

[0032] The rock salt-type crystal structure means a structure in which cations and anions are alternately arranged. Note that there may be cation or anion deficiencies.

[0033] The anions of the layered rock salt-type crystal and the rock salt-type crystal take 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 cubic close-packed structure composed of anions coincides. However, since the space group of the layered rock salt-type crystal is R-3m and different from the space group Fm-3m of the rock salt-type, the indices of the crystal planes satisfying the above conditions are different between the layered rock salt-type crystal and the rock salt-type crystal. In this specification, in 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 can be said that the crystal orientations are substantially identical.

[0034] For example, lithium cobaltate having a layered rock salt-type crystal structure and When in contact with magnesium oxide, the crystal orientations are approximately the same for lithium cobaltate when the (1-1-4) plane of lithium cobaltate contacts the {001} plane of magnesium oxide, for lithium cobaltate when the (104) plane of lithium cobaltate contacts the {001} plane of magnesium oxide, for lithium cobaltate when the (0-14) plane of lithium cobaltate contacts the {001} plane of magnesium oxide, for lithium cobaltate when the (001) plane of lithium cobaltate contacts the {111} plane of magnesium oxide, for the (012) plane of lithium cobaltate when it contacts the {111} plane of magnesium oxide, etc.

[0035] The approximate alignment of the crystal orientations in 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) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. It can also be determined from X-ray diffraction, electron beam diffraction, neutron beam diffraction, etc. In TEM images, etc., the arrangement of cations and anions can be observed as a repetition of bright and dark lines. When the orientations of the cubic close-packed structures are aligned in layered rock-salt type crystals and rock-salt type crystals, it can be observed that the angle formed by the repetition of bright and dark lines between the crystals is 5 degrees or less, more preferably 2.5 degrees or less. Note that in some cases, light elements such as oxygen and fluorine cannot be clearly observed in TEM images, etc., but in such cases, the alignment of the metal elements can be used to determine the orientation agreement. In this specification, etc., the similarity in the structure of the two-dimensional interface is called epitaxy. Also, crystal growth having similarity in the structure of the two-dimensional interface is called epitaxial growth. Further, having a three-dimensional structural similarity or having the same crystallographic orientation is called topotaxy When the orientations of the cubic close-packed structures are aligned in layered rock-salt type crystals and rock-salt type crystals, it can be observed that the angle formed by the repetition of bright and dark lines between the crystals is 5 degrees or less, more preferably 2.5 degrees or less. In TEM images, etc., the arrangement of cations and anions can be observed as a repetition of bright and dark lines. When the orientations of the cubic close-packed structures are aligned in layered rock-salt type crystals and rock-salt type crystals, it can be observed that the angle formed by the repetition of bright and dark lines between the crystals is 5 degrees or less, more preferably 2.5 degrees or less. Note that in some cases, light elements such as oxygen and fluorine cannot be clearly observed in TEM images, etc., but in such cases, the alignment of the metal elements can be used to determine the orientation agreement. In this specification, etc., the similarity in the structure of the two-dimensional interface is called epitaxy. Also, crystal growth having similarity in the structure of the two-dimensional interface is called epitaxial growth. Further, having a three-dimensional structural similarity or having the same crystallographic orientation is called topotaxy

[0036] Also, in this specification, etc., the similarity in the structure of the two-dimensional interface is called epitaxy. Also, crystal growth having similarity in the structure of the two-dimensional interface is called epitaxial growth. Further, having a three-dimensional structural similarity or having the same crystallographic orientation is called topotaxy Also, crystal growth having similarity in the structure of the two-dimensional interface is called epitaxial growth. Further, having a three-dimensional structural similarity or having the same crystallographic orientation is called topotaxy Having a three-dimensional structural similarity or having the same crystallographic orientation is called topotaxy That is. 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 approximately the same.

[0037] (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. As shown in FIG. 1(A ), the positive electrode active material 100 has a first region 101 and a second region 102. It can also be said that the second region 102 is on the first region 101, or the second region 102

[0038] may be said to cover at least a part of the first region 101. The first region 101 and the second region 102 are regions having different compositions. However, since the second region 102 is preferably a region where specific elements are segregated, as will be described later, the boundary between the two regions may not be clear. In FIG. 1(A), the first region 101 and the second region 102 are separated by a dotted line, and the gradient of the concentration of the elements crossing the dotted line is shown in varying shades of gray. For convenience, from FIG. 1(B) onwards, the boundary between the first region 101 and the second region 102 will be shown only by a dotted line. Details of the boundary between the first region 101 and the second region 102 will be described later.

[0039] Also, as shown in FIG. 1(B), the second region 102 may be present inside the positive electrode active material. For example, when the first region 101 is polycrystalline, specific elements may segregate at grain boundaries and in the vicinity thereof, forming the second region 102. Also, specific elements may segregate at and in the vicinity of the crystal defect portions of the positive electrode active material, forming the second region 102. Note that this In the specification and the like, a crystal defect refers to a defect observable in a TEM image or the like, a structure in which other elements are incorporated into the crystal, and the like. shall be as defined.

[0040] Also, as shown in FIG. 1(B), the second region 102 does not have to cover all of the first region 101. That is, the first region 101 is present inside the positive electrode active material 100, and the second region 102 is present in the surface layer portion of the positive electrode active material 100. Further, the second region 102 may be present inside the positive electrode active material 100.

[0041] In other words, the first region 101 is present inside the positive electrode active material 100, and the second region 102 is present in the surface layer portion of the positive electrode active material 100. Further, the second region 102 may be present inside the positive electrode active material 100. In other words, the first region 101 is present inside the positive electrode active material 100, and the second region 102 is present in the surface layer portion of the positive electrode active material 100. Further, the second region 102 may be present inside the positive electrode active material 100. That is, the first region 101 may be referred to as, for example, solid phase A. Also, the second region 102 may be referred to as, for example, solid phase B.

[0042] That is, the first region 101 may be referred to as, for example, solid phase A. Also, the second region 102 may be referred to as, for example, solid phase B. That is, the first region 101 may be referred to as, for example, solid phase A. Also, the second region 102 may be referred to as, for example, solid phase B.

[0043] If the particle size of the positive electrode active material 100 is too large, lithium diffusion becomes difficult, and when coated on the current collector, the surface of the active material layer becomes too rough, etc. On the other hand, if it is too small, it becomes difficult to support the active material layer during coating on the current collector, and problems such as an excessive reaction with the electrolytic solution occur. Therefore, the D50 (also referred to as the median diameter) is preferably 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 40 μm or less. If the particle size of the positive electrode active material 100 is too large, lithium diffusion becomes difficult, and when coated on the current collector, the surface of the active material layer becomes too rough, etc. On the other hand, if it is too small, it becomes difficult to support the active material layer during coating on the current collector, and problems such as an excessive reaction with the electrolytic solution occur. Therefore, the D50 (also referred to as the median diameter) is preferably 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 40 μm or less. If the particle size of the positive electrode active material 100 is too large, lithium diffusion becomes difficult, and when coated on the current collector, the surface of the active material layer becomes too rough, etc. On the other hand, if it is too small, it becomes difficult to support the active material layer during coating on the current collector, and problems such as an excessive reaction with the electrolytic solution occur. Therefore, the D50 (also referred to as the median diameter) is preferably 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 40 μm or less. If the particle size of the positive electrode active material 100 is too large, lithium diffusion becomes difficult, and when coated on the current collector, the surface of the active material layer becomes too rough, etc. On the other hand, if it is too small, it becomes difficult to support the active material layer during coating on the current collector, and problems such as an excessive reaction with the electrolytic solution occur. Therefore, the D50 (also referred to as the median diameter) is preferably 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 40 μm or less. If the particle size of the positive electrode active material 100 is too large, lithium diffusion becomes difficult, and when coated on the current collector, the surface of the active material layer becomes too rough, etc. On the other hand, if it is too small, it becomes difficult to support the active material layer during coating on the current collector, and problems such as an excessive reaction with the electrolytic solution occur. Therefore, the D50 (also referred to as the median diameter) is preferably 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 40 μm or less.

[0044] <First Region 101> The first region 101 contains lithium, a transition metal, and oxygen. The first region 101 may be said to have a composite oxide containing lithium and a transition metal. The first region 101 contains lithium, a transition metal, and oxygen. The first region 101 may be said to have a composite oxide containing lithium and a transition metal.

[0045] As the transition metal included in the first region 101, it is preferable to use a metal that can form a layered rock salt type composite oxide together with lithium. For example, among manganese, cobalt, and nickel, one or more can be used. One or more of them can be used. That is, the transition metal contained in the first region 101 and only cobalt can be used, or two types of cobalt and manganese can be used, or three types of cobalt, manganese, and nickel can be used. Further, in addition to the transition metal, the first region 101 may have a metal other than the transition metal such as aluminum.

[0046] That is, the first region 101 can have a composite oxide containing lithium and a transition metal, such as lithium cobaltate, lithium nickelate, lithium cobaltate in which part of cobalt is replaced by manganese, lithium nickel-manganese-cobaltate, lithium nickel-cobalt-aluminate, etc.

[0047] The first region 101 functions as a region that particularly contributes to the charge and discharge reactions 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

[0048] volume of the first region 101 is larger than that of the second region 102. A layered rock salt type crystal structure is preferable as the first region 101 because lithium diffuses two-dimensionally easily. Further, when the first region 101 has a layered rock salt type crystal structure, magnesium is likely to segregate as described later. However, not all of the first region 101 needs to have a layered rock salt type crystal structure. For example, even if there are crystal defects in a part of the first region 101, it is acceptable, or a part of the first

[0049] <The second region 102> The second region 102 contains magnesium, fluorine, and oxygen. For example, it can be said that the second region 102 contains magnesium oxide and part of the oxygen is substituted with fluorine.

[0050] The second region 102 covers at least a part of the first region 101. Since the magnesium oxide contained in the second region 1 02 is an electrochemically stable material, it is suitable as a coating layer because deterioration is less likely to occur even when charge and discharge are repeated.

[0051] If the second region 102 is too thin, the function as a coating layer will deteriorate, but if it is too thick, it will cause a decrease in capacity. Therefore, the thickness of the second region is preferably 0.5 nm or more and 50 nm or less, and more preferably 0.5 nm or more and 3 nm or less.

[0052] If the second region 102 has a rock-salt type crystal structure, it is preferable because the crystal orientation is likely to be consistent with that of the first region 101 and it is likely to function as a stable coating layer. However, not all of the second region 10 2 needs to have a rock-salt type crystal structure. For example, a part of the second region 102 may be amorphous, or may have another crystal structure.

[0053] Generally, as the positive electrode active material repeats charge and discharge, side reactions such as transition metals such as cobalt and manganese eluting into the electrolyte, oxygen detaching, and the crystal structure becoming unstable occur, and the deterioration progresses. However, since the positive electrode active material 100 according to one aspect of the present invention has the second region 102 in the surface layer portion, it is possible to make the crystal structure of the composite oxide containing lithium and transition metals contained in the first region 101 more stable.

[0054] ​​​​​​​Further, the second region 102 has magnesium, fluorine, and oxygen, and preferably further has the same transition metal as that of the first region 101. When the first region 101 and the second region 102 have the same transition metal, it is preferable that the valence of the transition metal is different in these two regions. More specifically, it is preferable that the transition metal included in the first region 101 has more trivalent atoms than atoms of other valences, and it is preferable that the transition metal included in the second region 102 has more divalent atoms than atoms of other valences.

[0055] When there are many divalent transition metals in the second region 102, there are many metal oxides in which the transition metal:oxygen = 1:1 (atomic ratio), such as CoO(II), MnO(II), and Ni( (II). These metal oxides easily form a stable solid solution with magnesium oxide, which is also an oxide of a divalent metal. Therefore, the second region 102 can become a more stable and better coating layer.

[0056] The valence of the transition metal can be analyzed by EELS (electron energy loss spectroscopy), XAFS (X-ray absorption fine structure analysis), XPS (X-ray photoelectron spectroscopy), ESR (electron spin resonance), Mössbauer spectroscopy, etc. Among these, since EELS has a high spatial resolution, it can analyze even if the second region 102 is a thin layer of several nm, which is preferable.

[0057] When analyzing the valence of the transition metal by EELS, the valence can be determined by the ratio of L3 / L2. The higher the L3 / L2, the higher the proportion of the divalent transition metal. For example, when analyzing the transition metals in the first region 101 and the second region 102 by EELS, the L3 / L2 of the transition metal included in the first region 101 is less than 3.8, and the L3 of the transition metal included in the second region 102 is / L2 is preferably 3.8 or more.

[0058] In addition, the second region 102 may also contain lithium.

[0059] Also, as shown in Fig. 1(B), if the second region 102 also exists inside the first region 101 , it is preferable because it may further stabilize the crystal structure of the composite oxide containing lithium and transition metal in the first region 101.

[0060] The fluorine in the second region 102 is preferably present in a bonding state other than MgF2 and LiF. Specifically, when the surface of the positive electrode active material 100 is analyzed by XPS, the peak position of the binding energy between fluorine and other elements is preferably 682 eV or more and less than 685 eV, more preferably about 684.3 eV. This is a binding energy that does not match either of MgF2 and LiF.

[0061] 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.

[0062] <Boundary between the first region 101 and the second region 102> The first region 101 and the second region 102 can be confirmed to have different compositions by TEM image, STEM image, FFT (Fast Fourier Transform) analysis, EDX (Energy Dispersive X-ray Analysis), depth direction analysis by ToF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry), XPS (X-ray Photoelectron Spectroscopy), Auger electron spectroscopy, TDS (Temperature Programmed Desorption Gas Analysis), etc. For example, in the cross-sectional TEM image and STEM image of the positive electrode active material 100, the difference in the constituent elements is observed as the difference in the brightness of the image. Therefore, it can be observed that the constituent elements of the first region 101 and the second region 102 are different. Also, in the elemental distribution image of EDX, it can be observed that the first region 101 and the second region 102 have different elements. However, it is not always necessary to be able to observe a clear boundary between the first region 101 and the second region 102 by various analyses.

[0063] In this specification and the like, the range of the second region 102 present in the surface layer portion of the positive electrode active material 100 refers to the range from the outermost surface of the positive electrode active material 100 until the concentration of magnesium detected by depth direction analysis becomes 1 / 5 of the peak. As the depth direction analysis, the above-described line analysis of EDX, and depth direction analysis using ToF-SIMS and the like can be used. The peak of the magnesium concentration is preferably present up to a depth of 2 nm from the surface of the positive electrode active material 100 toward the center, more preferably up to a depth of 1 nm, and even more preferably up to a depth of 0.5 nm. The depth at which the magnesium concentration becomes 1 / 5 of the peak, that is, the range of the second region 102, varies depending on the manufacturing method. In the case of the manufacturing method described later, it is approximately from 2 nm or more to about 5 nm from the surface of the positive electrode active material.

[0064] Regarding the second region 102 present inside the first region 101, it refers to a region where the concentration of magnesium detected by depth direction analysis is 1 / 5 or more of the peak.

[0065] The distribution of fluorine in the positive electrode active material 100 preferably overlaps with the distribution of magnesium. Therefore, the peak of the fluorine concentration is at a depth from the surface of the positive electrode active material 100 toward the center ​​​​​​​​​​​​​​ It is preferably present up to 2 nm, more preferably present up to 1 nm in depth, and even more preferably present up to 0.5 nm in depth.

[0066] Thus, it can also be said that the second region 102 is a concentration gradient region where the concentrations of magnesium and fluorine decrease from the surface of the positive electrode active material 100 toward the inside.

[0067] The concentrations of magnesium and fluorine can be analyzed by ToF-SIMS, XPS, Auger electron spectroscopy, TDS, etc.

[0068] Note that the measurement range of XPS is about 5 nm from the surface of the positive electrode active material 100. Therefore, the elemental concentration existing about 5 nm from the surface can be quantitatively analyzed. Therefore, when the thickness of the second region 10 2 is less than 5 nm, the combined region of the second region 102 and a part of the first region 101, when the thickness of the second region 102 is 5 nm or more from the surface, the elemental concentration of the second region 102 can be quantitatively analyzed. By performing XPS analysis on the surface of the positive electrode active material 100, when the total amount of atoms including lithium, transition metals, oxygen, fluorine, and magnesium contained in the first region 101 is 100 atomic%, the magnesium concentration is 1 atomic% or more and 16 atomic% or less, and the fluorine concentration is 0.2 atomic% or more and 4 atomic % or less. Further, the ratio of the concentrations of magnesium and fluorine is preferably Mg:F = y: 1 (3 ≤ y ≤ 5) (atomic ratio), and more preferably about Mg:F = 4:1. When the magnesium concentration and the fluorine concentration are within these ranges, the positive electrode active material 100 can exhibit extremely good cycle characteristics when used in a secondary battery.

[0069] As described above, the concentrations of magnesium and fluorine gradually decrease from the surface toward the inside, so the first region 101 may have elements that the second region 102 such as magnesium has. Similarly, the second region 102 may have elements that the first region 101 has. Also, the first region 101 may have other elements such as carbon, sulfur, silicon, sodium, calcium, chlorine, zirconium, etc. The second region 102 may have other elements such as carbon, sulfur, silicon, sodium, calcium, chlorine, zirconium, etc.

[0070] [Segregation] The second region 102 can also be formed by methods such as sputtering, solid-phase method, liquid-phase methods including sol-gel method, etc. However, the inventors of the present invention have clarified that after mixing a magnesium source and a fluorine source with a starting material and then heating, magnesium can be segregated to form the second region 102. Furthermore, it has been clarified that the positive electrode active material having the second region 102 formed in this way has extremely excellent characteristics.

[0071] For example, in Example 4 of Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2016-076454), after synthesizing a composite oxide containing magnesium, the powder of the composite oxide and lithium fluoride are mixed and heated to form a surface oxide fluorinated and lithiated on the surface of the composite oxide. It is described that magnesium was not detected from the surface oxide by this method.

[0072] However, the inventors of the present invention simultaneously mix a magnesium source and a fluorine source as starting materials. As a result, magnesium oxide could be segregated to the surface layer of the positive electrode active material 100. Mean Surprisingly, the inventors have revealed that fluorine added to the starting materials has the effect of segregating magnesium.

[0073] To form the second region 102 by segregation of magnesium, magnesium can be segregated not only to the surface layer of the positive electrode active material 100, but also to grain boundaries and their vicinity, crystal defects and their vicinity. The second region 102 formed in grain boundaries and their vicinity or crystal defects and their vicinity can contribute to further stabilization of the crystal structure of the composite oxide containing lithium and transition metal that the first region 101 has.

[0074] To effectively perform the segregation of the second region 102, it is preferable that the concentrations of magnesium and fluorine in the raw materials are Mg:F = 1:x (1.5 ≤ x ≤ 4) (atomic ratio), and more preferably about Mg:F = 1:2 (atomic ratio).

[0075] On the other hand, it is preferable that the concentrations of magnesium and fluorine in the second region 102 formed as a result of segregation are Mg:F = y:1 (3 ≤ y ≤ 5) (atomic ratio), and more preferably about Mg:F = 4:1 (atomic ratio).

[0076] Since the second region 102 formed by segregation is formed by epitaxial growth, the crystal orientations of the first region 101 and the second region 102 may be generally in agreement in part. That is, the first region 101 and the second region 102 may be topotactic. When the crystal orientations of the first region 101 and the second region 102 are generally in agreement, the second region 102 can function as a better coating layer.

[0077] ​​​​​​​​​​​​ <Third region 103> So far, an example in which the positive electrode active material 100 has the first region 101 and the second region 102 has been described. However, one aspect of the present invention is not limited to this. For example, as shown in Fig. 1(C), , the positive electrode active material 100 may have a third region 103. The third region 103 can be provided, for example, so as to be in contact with at least a part of the second region 102. The third region 103 may be a film having carbon such as a graphene compound, or may be a film having lithium or a decomposition product of the electrolytic solution. When the third region 103 is a film having carbon , the conductivity between the positive electrode active materials 100 and between the positive electrode active material 100 and the current collector can be enhanced. When the third region 103 is a film having lithium or a decomposition product of the electrolytic solution , an excessive reaction with the electrolytic solution can be suppressed, and the cycle characteristics can be improved when used in a secondary battery.

[0078] Furthermore, a buffer region may be provided between the first region 101 and the second region 102. The buffer region preferably has metals such as titanium, aluminum, zirconium, and vanadium in addition to lithium, transition metals, and oxygen. The buffer region may overlap with the first region 101 and the second region 102. When the positive electrode active material 100 has a buffer region , the crystal structures of the first region 101 and the second region 102 can be further stabilized, and a positive electrode active material with excellent cycle characteristics can be obtained, which is preferable.

[0079] [Manufacturing method] Having the first region 101 and the second region 102, and forming the second region 102 by segregation The method for preparing the positive electrode active material 100 in the case will be described with reference to FIG. 2. In the present embodiment, when the transition metal included in the first region 101 is cobalt, that is, when the first region 101 has lithium cobaltate, it will be described. Further, the case where the second region 102 having magnesium oxide and fluorine is formed by segregation will be described.

[0080] First, starting materials are prepared (S11). Specifically, a lithium source, a cobalt source, a magnesium source, and a fluorine source are weighed respectively. As the lithium source, for example, lithium carbonate, lithium fluoride, lithium hydroxide, etc. can be used. As the cobalt source, for example, cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide, cobalt carbonate, cobalt oxalate, cobalt sulfate, etc. can be used. As the magnesium source, for example, magnesium oxide, magnesium fluoride, etc. can be used. As the fluorine source, for example, lithium fluoride, magnesium fluoride, etc. can be used. That is, lithium fluoride can be used as both a lithium source and a fluorine source, and magnesium fluoride can be used as both a magnesium source and a fluorine source. In the present embodiment, lithium carbonate (Li2CO3) is used as the lithium source,

[0081] cobalt oxide (Co3O4) is used as the cobalt source, magnesium oxide (MgO) is used as the magnesium source, and lithium fluoride (LiF) is used as the lithium source and the fluorine source. The atomic ratio of magnesium to fluorine in the raw materials is preferably Mg:F = 1:x (1.5 ≤ x ≤ 4) (atomic

[0082] ratio), and more preferably about Mg:F = 1:2 (atomic ratio). Therefore, The ratio of magnesium oxide to lithium fluoride is preferably MgO:LiF = 1:x (1.5 ≤ x ≤ 4) ( molar ratio), and more preferably about MgO:LiF = 1:2 (molar ratio).

[0083] The molar ratio of each raw material can be, for example, as follows. 1 / 2·Li2CO3 + ((1 - z) / 3)·Co3O4 + z·MgO + 2z·LiF (z = 0.01)

[0084] Next, the weighed starting materials are mixed (S12). For mixing, for example, a ball mill, a bead mill, etc. can be used.

[0085] Next, the material mixed in S12 is heated (S13). This step may be referred to as the first heating or firing for the purpose of distinction from the subsequent heating step. The first heating is preferably carried out at 800°C or higher and 1050°C or lower, and more preferably at 900°C or higher and 1000°C or lower. The heating time is preferably 2 hours or more and 20 hours or less. The first heating is preferably carried out in a dried atmosphere such as dry air. The dried atmosphere preferably has a dew point of -50°C or lower, and more preferably -100°C or lower. In this embodiment, heating is carried out at 1000°C for 10 hours, the temperature is raised at 200°C / h, and dry air with a dew point of -109°C is flowed at 10 L / min. By the first heating in S13, a composite oxide containing lithium and a transition metal in the first region 101 can be synthesized. Also, by this first heating, a part of the magnesium and fluorine contained in the starting materials segregates to the surface layer portion of the composite oxide containing lithium and a transition metal. However

[0086] ​​​​​​​​​​At this point, most of the magnesium and fluorine are in a state of being dissolved in the composite oxide containing lithium and transition metals. It is in a solid solution state.

[0087] Next, the material heated in S13 is cooled to room temperature (S14). The cooling is preferably carried out over the same or more time as the heating up. For example, it can be carried out over a time of 10 hours or more and 15 hours or less. It can be carried out over a time of 10 hours or more and 15 hours or less. After cooling, it is preferable to sieve the synthesized material. In this embodiment, it is sieved using a 53 μm mesh. It can be carried out over a time of 10 hours or more and 15 hours or less. After cooling, it is preferable to sieve the synthesized material. In this embodiment, it is sieved using a 53 μm mesh. In this embodiment, it is sieved using a 53 μm mesh.

[0088] In addition, particles of a composite oxide containing lithium, cobalt, fluorine, and magnesium synthesized in advance as starting materials may be used. In this case, steps S12 to S14 can be omitted. In this case, steps S12 to S14 can be omitted. In this case, steps S12 to S14 can be omitted.

[0089] Next, a second heating is performed on the material cooled in S14 (S15). This step may be referred to as the second heating or annealing for the purpose of distinguishing it from the previous heating step. The optimal conditions for the second heating vary depending on the particle size and composition of the composite oxide containing lithium, cobalt, fluorine, and magnesium, etc., but it is preferable to carry out the holding time at a specified temperature for 50 hours or less, and more preferably 2 hours or more and 10 hours or less. The specified temperature is preferably 500°C or more and 1200°C or less, more preferably 700°C or more and 1000°C or less, and even more preferably about 800°C. Also, it is preferable to heat in an atmosphere containing oxygen. In this embodiment, it is heated at 800°C for 2 hours, the temperature increase is 200°C / h, and dry air with a dew point of -109°C is flowed at 10 L / min. In this case, steps S12 to S14 can be omitted. The optimal conditions for the second heating vary depending on the particle size and composition of the composite oxide containing lithium, cobalt, fluorine, and magnesium, etc., but it is preferable to carry out the holding time at a specified temperature for 50 hours or less, and more preferably 2 hours or more and 10 hours or less. The optimal conditions for the second heating vary depending on the particle size and composition of the composite oxide containing lithium, cobalt, fluorine, and magnesium, etc., but it is preferable to carry out the holding time at a specified temperature for 50 hours or less, and more preferably 2 hours or more and 10 hours or less. The optimal conditions for the second heating vary depending on the particle size and composition of the composite oxide containing lithium, cobalt, fluorine, and magnesium, etc., but it is preferable to carry out the holding time at a specified temperature for 50 hours or less, and more preferably 2 hours or more and 10 hours or less. The specified temperature is preferably 500°C or more and 1200°C or less, more preferably 700°C or more and 1000°C or less, and even more preferably about 800°C. The specified temperature is preferably 500°C or more and 1200°C or less, more preferably 700°C or more and 1000°C or less, and even more preferably about 800°C. In this embodiment, it is heated at 800°C for 2 hours, the temperature increase is 200°C / h, and dry air with a dew point of -109°C is flowed at 10 L / min. In this embodiment, it is heated at 800°C for 2 hours, the temperature increase is 200°C / h, and dry air with a dew point of -109°C is flowed at 10 L / min.

[0090] By performing the second heating in S15, it is possible to promote the segregation of magnesium and fluorine contained in the starting materials to the surface layer of the composite oxide containing lithium, lithium, and transition metals.

[0091] Finally, the material heated in S15 is cooled to room temperature. The cooling is preferably performed over the same or a longer time as the heating. Then, the cooled material is recovered (S16), and the positive electrode active material 100 having the first region 101 and the second region 102 can be obtained. By using the positive electrode active material described in this embodiment, a secondary battery with high capacity and good cycle characteristics can be obtained. This embodiment can be used in appropriate combination with other embodiments.

[0092] By using the positive electrode active material described in this embodiment, a secondary battery with high capacity and good cycle characteristics can be obtained. This embodiment can be used in appropriate combination with other embodiments. This embodiment can be used in appropriate combination with other embodiments.

[0093] (Embodiment 2) In this embodiment, examples of other materials that can be used in 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, negative electrode, and electrolyte are wrapped in an exterior body will be described as an example.

[0094] [Positive Electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector.

[0095] [Positive Electrode Active Material Layer] The positive electrode active material layer has a positive electrode active material. Further, the positive electrode active material layer may have a conductive assistant and a binder.

[0096] 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, a secondary battery with high capacity and excellent cycle characteristics can be obtained. By using the positive electrode active material 100 described in the previous embodiment, a secondary battery with high capacity and excellent cycle characteristics can be obtained.

[0097] ​​​​​​ As the conductive aid, a carbon material, a metal material, a conductive ceramic material, or the like can be used. Further, a fibrous material may be used as the conductive aid. The content of the conductive aid with respect to the total amount of the active material layer is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less.

[0098] The conductive aid can form an electrical conduction network in the electrode. By the conductive aid, the electrical conduction path between the positive electrode active materials can be maintained. By adding the conductive aid to the active material layer, an active material layer having high electrical conductivity can be realized.

[0099] As the conductive aid, 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. Carbon nanotubes can be produced, for example, by a vapor phase growth method. Further, as the conductive aid, 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 such as copper, nickel, aluminum, silver, gold, metal fibers, conductive ceramic materials, etc. can be used.

[0100] Further, a graphene compound may be used as the conductive aid.

[0101] The graphene compound has excellent electrical properties such as high electrical conductivity, and high flexibility and high It may have excellent physical properties such as mechanical strength, and also graphene compounds have a planar shape. Graphene compounds enable surface contact with low contact resistance. Also, even if it is thin, it may have very high conductivity, and it can efficiently form conductive paths in the active material layer with a small amount. Therefore, it is preferable to use a graphene compound as a conductive assistant because it can increase the contact area between the active material and the conductive assistant. Also it is preferable because it may be able to reduce the electrical resistance. Here, as an example of the graphene compound for example, it is particularly preferable to use graphene or multi - graphene or reduced Graphene O xide (hereinafter, RGO). Here, RGO refers to a compound obtained by reducing graphene oxide (GO), for example.

[0102] 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 assistant tends to increase relatively, and the loading amount of the active material tends to decrease. When the loading 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 assistant the graphene compound can efficiently form conductive paths even with a small amount, so it is not necessary to reduce the loading amount of the active material, which is particularly preferable.

[0103] Hereinafter, as an example, a cross - sectional configuration example of using a graphene compound as a conductive assistant in the active material layer 200 will be described.

[0104] Fig. 3(A) shows a longitudinal sectional view of the active material layer 200. The active material layer 200 is a granular positive electrode active material It includes 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 - like structure in which a plurality of multi - graphenes and / or a plurality of graphenes partially overlap.

[0105] In the longitudinal section of the active material layer 200, as shown in Fig. 3(A), the sheet - like graphene compound 201 is dispersed substantially uniformly inside the active material layer 200. In Fig. 3(A), the graphene compound 201 is schematically represented by a thick line, but actually it is a thin film having a thickness of a single layer or multiple layers of carbon molecules. A plurality of graphene compounds 201 are formed so as to wrap, cover, or adhere onto the surfaces of a plurality of granular positive - electrode active materials 100, so they are in surface contact with each other.

[0106] 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 a graphene net) can be formed. When the active material is covered by the graphene net, the graphene net can also function as a binder that binds the active materials to each other. Therefore, the amount of the binder can be reduced or the binder can be not used, so that the ratio of the active material in the electrode volume and the electrode weight can be improved. That is, the capacity of the energy storage device can be increased.

[0107] Here, graphene oxide is used as the graphene compound 201 and mixed with the active material to form the active material​​​​​​ After forming the layer to be layer 200, it is preferably reduced. In the formation of the graphene compound 201 , by using graphene oxide with extremely high dispersibility in a polar solvent, the graphene compound 201 can be dispersed approximately uniformly inside the active material layer 200. Uniformly Remove the solvent by volatilization from the dispersion medium containing uniformly dispersed graphene oxide, and reduce the graphene oxide Therefore, the graphene compounds 201 remaining in the active material layer 200 partially overlap with each other and are dispersed to the extent of surface contact with each other, so that a three-dimensional conductive path can be formed. Note that the reduction of graphene oxide may be performed, for example, by heat treatment or using a reducing agent.

[0108] 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, so 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 in the active material layer 200 of the positive electrode active material 100 can be increased. Thereby, the discharge capacity of the power storage device can be increased.

[0109] As the binder, for example, it is preferable to use rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene -styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene-propylene-diene copolymer. Also as a binder , fluororubber can be used.

[0110] In addition, as the binder, it is preferable to use, for example, a water-soluble polymer. Water-soluble polymer Examples of the base material include polysaccharides. Examples of polysaccharides include cellulose derivatives such as carboxymethyl cellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, diacetylcellulose, and regenerated cellulose, and starch. It is more preferable to use these water-soluble polymers in combination with the above-described rubber material.

[0111] Alternatively, examples of the binder include polystyrene, polymethyl acrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, isobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose. It is preferable to use materials such as these. The binder may be used in combination of two or more of the above.

[0112]

[0113] For example, a material having an especially excellent viscosity adjusting effect may be used in combination with other materials. For example, while rubber materials and the like are excellent in adhesive force and elastic force, 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 an especially excellent viscosity adjusting effect. As the material having an especially excellent viscosity adjusting effect, for example, a water-soluble polymer may be used. As the water-soluble polymer having an especially excellent viscosity adjusting effect, the above-described polysaccharides, for example, carboxymethyl cellulose (CMC), may be used. Carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxy propyl cellulose and cellulose derivatives such as diacetyl cellulose, regenerated cellulose, etc., and starches can be used.

[0114] In addition, cellulose derivatives such as carboxymethyl cellulose can be made into salts such as sodium salts and ammonium salts of carboxymethyl cellulose, which increases solubility and makes it easier to exhibit the effect as a viscosity modifier. By increasing solubility, the dispersibility with the active material and other components can also be enhanced when preparing the electrode slurry. In this specification, cellulose and cellulose derivatives used as the electrode binder shall include those salts. Water-soluble polymers stabilize the viscosity by dissolving in water, and can stably disperse the active material and other materials combined as a binder, such as styrene-butadiene rubber, etc. in an aqueous solution. Also, due to having functional groups, it is expected to be easily and stably adsorbed on the surface of the active material. In addition, cellulose derivatives such as carboxymethyl cellulose have many materials with functional groups such as hydroxyl groups and carboxyl groups, and due to having functional groups, it is expected that the polymers interact with each other and widely cover the surface of the active material.

[0115] When the binder covering the surface of the active material or in contact with the surface forms a film, it is also expected to play a role as a passive film and suppress the decomposition of the electrolyte. Here, the passive film is a film having no electron conductivity or having extremely low electrical conductivity. For example, on the surface of the active material

[0116] ​When a dynamic film is formed, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. In addition, the passive film preferably suppresses electrical conductivity while allowing lithium ions to conduct. Furthermore, it is more desirable.

[0117] <Positive current collector> As the positive current collector, metals such as stainless steel, gold, platinum, aluminum, titanium, and alloys thereof can be used, which are materials with high conductivity. Also, the material used for the positive current collector is preferably one that does not dissolve at the potential of the positive electrode. In addition, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum, etc., which 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 is preferably one with a thickness of 5 μm or more and 30 μm or less.

[0118] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. Also, the negative electrode active material layer may have a conductive assistant and a binder.

[0119] <Negative electrode active material> As the negative electrode active material, for example, alloy-based materials, carbon-based materials, etc. can be used.

[0120] As the negative electrode active material, it is possible to perform charge and discharge reactions through alloying and dealloying reactions with lithium. ​​​​​​​Capable elements 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 elements have a larger capacity compared to carbon. In particular, silicon has a high theoretical capacity of 4200 mAh / g. Therefore, it is preferable to use silicon as the negative electrode active material. Also, compounds containing these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, SbSn, etc. exist. Here, elements capable of performing charge and discharge reactions through alloying and dealloying reactions with lithium, and compounds containing such elements, etc. may be referred to as alloy-based materials. Among them, materials containing at least one can be used. Such elements have a larger capacity compared to carbon. In particular, silicon has a high theoretical capacity of 4200 mAh / g. Therefore, it is preferable to use silicon as the negative electrode active material. Also, compounds containing these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3 Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, I nSb, SbSn, etc. exist. Here, elements capable of performing charge and discharge reactions through alloying and dealloying reactions with lithium, and compounds containing such elements, etc. may be referred to as alloy-based materials.

[0121] In this specification, etc., SiO refers to, for example, silicon monoxide. Alternatively, SiO can also be expressed as SiO x . Here, x preferably has a value near 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 Here, x preferably has a value near 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.

[0122] As the carbon-based material, graphite, graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, carbon black, etc. may be used. For graphite, artificial graphite, natural graphite, etc. may be mentioned. As artificial graphite, for example, mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. may be mentioned.

[0123] For graphite, artificial graphite, natural graphite, etc. may be mentioned. As artificial graphite, for example, mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. may be mentioned.​​ This is possible. Here, spherical graphite having a spherical shape can be used as 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 scaly graphite, spheroidized natural graphite, and the like.

[0124] When lithium ions are inserted into graphite (when forming a lithium-graphite intercalation compound), graphite exhibits a potential as low as that of metallic lithium (0.05 V or more and 0.3 V or less vs. Li / L i + ). As a result, a lithium-ion secondary battery can exhibit a high operating voltage. Furthermore , graphite has advantages such as a relatively high capacity per unit volume, a relatively small volume expansion, low cost, and high safety compared to metallic lithium, and thus is preferable.

[0125] Also, as the negative electrode active material, oxides such as titanium dioxide (TiO2), lithium titanate (Li4T i5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5) , tungsten oxide (WO2), molybdenum oxide (MoO2), etc. can be used.

[0126] Also, as the negative electrode active material, Li3N-type structured Li 3-x M x N (M = Co, Ni, Cu), which is a complex nitride of lithium and a transition metal, 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.

[0127] When using a double nitride of lithium and a transition metal, since lithium ions are contained in the negative electrode active material, it can be preferably combined with materials such as V2O5 and Cr3O8 that do not contain lithium ions as the positive electrode active material. Even when using a material containing lithium ions for the positive electrode active material, by previously desorbing the lithium ions contained in the positive electrode active material, a double nitride of lithium and a transition metal can be used as the negative electrode active material.

[0128] In addition, a material in which a conversion reaction occurs can also 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 an alloy with lithium, may be used as the negative electrode active material. As materials in which a conversion reaction occurs, furthermore, oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, sulfides such as CoS, NiS, and CuS, nitrides such as Zn3N2, Cu3N, and Ge3 0.89 N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3 also cause a reaction.

[0129] As the conductive assistant and binder that the negative electrode active material layer can have, the same materials as those that the positive electrode active material layer can have can be used.

[0130] <Negative electrode current collector> For the negative electrode current collector, the same materials as those for the positive electrode current collector can be used. It is preferable to use a material that does not alloy with carrier ions such as lithium for the negative electrode current collector.

[0131] [Electrolyte solution] The electrolyte solution has a solvent and an electrolyte. As the solvent of the electrolyte solution, an aprotic organic solvent is preferred. and, for example, ethylene carbonate (EC), propylene carbonate (PC), butyl ene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrola ctone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate l, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1 ,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfone xide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tet rahydrofuran, sulfolane, sultone, etc., can be used alone or in any combination and ratio of two or more of these.

[0132] In addition, by using a polymer material that is gelled as a solvent for the electrolytic solution, safety against liquid leakage and the like is enhanced. Also, the secondary battery can be made thinner and lighter. Representative examples of the gelled polymer material include silicone gel, acrylic gel, acrylonitrile gel, polyeth ylene oxide-based gel, polypropylene oxide-based gel, fluorine-based polymer gel, etc. There are.

[0133] In addition, by using one or more ionic liquids (room temperature molten salts) that are flame retardant and hardly volatile as a solvent for the electrolytic solution, even if the internal temperature rises due to an internal short circuit or overcharging of the power storage device, rupture or ignition of the power storage device can be prevented. An ionic liquid consists of a cation and an anion and contains an organic cation and an anion. As the organic cation used in the electrolytic solution, quaternary Ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, etc. include aliphatic onium cations such as , and aromatic cations such as imidazolium cations and pyridinium cations. Examples of the anion used in the electrolyte include monovalent amide-based anions, monovalent methide-based anions, fluorosulfonic acid anions, perfluoroalkyl sulfonic acid anions, tetrafluoroborate anions, perfluoroalkyl borate anions, hexafluorophosphate anions, or perfluoroalkyl phosphate anions, etc.

[0134] Examples of the electrolyte dissolved in the above solvent include, 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.

[0135] 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 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.

[0136] In addition, vinylene carbonate, propane sultone (PS), and tert-butyl ether were used in the electrolyte. Benzene (TBB), Fluoroethylene Carbonate (FEC), LiBOB, and Squishi Dinitrile compounds such as diisopropylnitrile and adiponitrile may also be added. The concentration of may be, for example, 0.1 wt % or more and 5 wt % or less with respect to the entire solvent.

[0137] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution. By using electrolytes, safety against leakage etc. is improved. It is possible to reduce the weight.

[0138] The polymers that can be gelled include silicone gel, acrylic gel, acrylonitrile gel, Polyethylene oxide gel, polypropylene oxide gel, fluorine-based polymer A gel or the like can be used.

[0139] Examples of the polymer include polyalkylene oxides such as polyethylene oxide (PEO). Polymers with a fluororesin structure, PVDF, polyacrylonitrile, etc., and their combinations For example, a copolymer containing PVDF and hexafluoropropylene (H PVDF-HFP, a copolymer of PVDF and PVDF, can be used. The mer may have a porous shape.

[0140] In addition, instead of the electrolyte, solid electrolytes containing inorganic materials such as sulfides and oxides, and P A solid electrolyte containing a polymer material such as EO (polyethylene oxide) can be used. When a solid electrolyte is used, the installation of a separator or spacer becomes unnecessary. Since the entire battery can be solidified, the risk of liquid leakage is eliminated and the safety is significantly improved.

[0141] [Separator] Moreover, the secondary battery preferably has a separator. Examples of the separator include fibers having cellulose such as paper and non-woven fabrics, glass fibers, ceramics, or synthetic fibers made of nylon (polyamide), vinylon (polyvinyl alcohol-based fibers), polyester, acrylonitrile, polyolefin, polyurethane, etc. can be used. The separator is preferably processed into a bag shape and arranged to wrap either the positive electrode or the negative electrode.

[0142] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic-based material, a fluorine-based material, a polyamide-based material, or a mixture thereof. As the ceramic-based material, for example, aluminum oxide particles, silicon oxide particles, etc. can be used. As the fluorine-based material, for example, PVDF, polytetrafluoroethylene, etc. can be used. As the polyamide-based material, for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used.

[0143] Coating with a ceramic-based material improves the oxidation resistance, so it is possible to suppress the 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 the output characteristics can be improved. Coating with a polyamide-based material, especially aramid, improves the heat resistance, so the safety of the secondary battery The safety can be improved.

[0144] For example, a mixed material of aluminum oxide and aramid may be coated on both sides of a polypropylene film. Further, 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.

[0145] When using a separator with a multilayer structure, even if the overall thickness of the separator is thin, the safety of the secondary battery can be maintained, so that the capacity per unit volume of the secondary battery can be increased.

[0146] (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.

[0147] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. FIG. 4(A) is an external view of a coin-type (single-layer flat-type) secondary battery, and FIG. 4(B) is a cross-sectional view thereof.

[0148] The coin-type secondary battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal, which are insulated and sealed by a gasket 303 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. Further, 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.

[0149] 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 on only one side.

[0150] For the positive electrode can 301 and the negative electrode can 302, metals such as nickel, aluminum, titanium, etc. that are corrosion-resistant to the electrolyte, or alloys of these or alloys of these and other metals (such as stainless steel etc.) can be used. Also, in order to prevent corrosion by the electrolyte, 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 307 respectively.

[0151] These negative electrode 307, positive electrode 304 and separator 310 are impregnated with the electrolyte, and as shown in Fig. 4(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 the gasket 303 to manufacture the coin-shaped secondary battery 300.

[0152] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, a coin-shaped secondary battery 300 with high capacity and excellent cycle characteristics can be obtained.

[0153] [Cylindrical secondary battery] Next, an example of a cylindrical secondary battery will be described with reference to Fig. 5. As shown in Fig. 5(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. These positive electrode cap and battery can (outer can) 602 are insulated by a gasket (insulating packing) 610.

[0154] FIG. 5(B) is a diagram schematically showing a cross section of a cylindrical secondary battery. A hollow cylindrical battery can inside 602, a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 interposed therebetween to form a battery element. Although not shown, the battery element is wound around a center pin The battery can 602 has one end closed and the other end open. The battery can 602 is made of a metal such as nickel, aluminum, titanium, etc. that is corrosion-resistant to the electrolytic solution, or an alloy of these or an alloy of these and other metals (for example, stainless steel, etc.) can be used. Also, in order to prevent corrosion by the electrolytic solution, it is preferable to coat with nickel, aluminum, etc. Inside the battery can 602, the battery element around which the positive electrode, negative electrode, and separator are wound is sandwiched between a pair of opposing insulating plates 608, 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 coaxial type secondary battery.

[0155] Since the positive electrode and negative electrode used in the cylindrical secondary battery are wound, it is preferable to form the active material on both sides of the current collector. A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collecting 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 6 03 is resistance welded to the safety valve mechanism 612, and the negative electrode terminal 607 is resistance welded to the bottom of the battery can 602 respectively . The safety valve mechanism 612 is electrically connected to the positive electrode cap 601 via a PTC element (Positive Temperature C oefficient) 611. ​The safety valve mechanism 612 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the internal pressure of the battery rises beyond a predetermined threshold value. Also, the PTC element 611 is a thermosensitive resistance element whose resistance increases when the temperature rises, and it restricts the current flow due to the increase in resistance 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. 5(C), a module 615 may be formed by sandwiching a plurality of secondary batteries 600 between a conductive plate 613 and a conductive plate 614. The plurality of secondary batteries 600 may be connected in parallel, may be connected in series, or may be connected in parallel and then further connected in series. By forming a module 615 having a plurality of secondary batteries 600, a large amount of power can be extracted. Fig. 5(D) is a top view of the module 615. For clarity, the conductive plate 613 is shown by a dotted line. As shown in Fig. 5(D), the module 615 may have a conducting wire 616 that electrically connects the plurality of secondary batteries 600. The conductive plate 613 can be superimposed on the conducting wire 616. Also, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 overheats, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Thus, the performance of the module 615 is less affected by the outside air temperature. By using the positive electrode active material 100 described in the previous embodiment for the positive electrode 604, high capacity and so on can be achieved.

[0156] Also, as shown in Fig. 5(C), a module 615 may be formed by sandwiching a plurality of secondary batteries 600 between a conductive plate 613 and a conductive plate 614. The plurality of secondary batteries 600 may be connected in parallel, may be connected in series, or may be connected in parallel and then further connected in series. By forming a module 615 having a plurality of secondary batteries 600, a large amount of power can be extracted. Also, as shown in Fig. 5(C), a module 615 may be formed by sandwiching a plurality of secondary batteries 600 between a conductive plate 613 and a conductive plate 614. The plurality of secondary batteries 600 may be connected in parallel, may be connected in series, or may be connected in parallel and then further connected in series. By forming a module 615 having a plurality of secondary batteries 600, a large amount of power can be extracted. Also, as shown in Fig. 5(C), a module 615 may be formed by sandwiching a plurality of secondary batteries 600 between a conductive plate 613 and a conductive plate 614. The plurality of secondary batteries 600 may be connected in parallel, may be connected in series, or may be connected in parallel and then further connected in series. By forming a module 615 having a plurality of secondary batteries 600, a large amount of power can be extracted. Also, as shown in Fig. 5(C), a module 615 may be formed by sandwiching a plurality of secondary batteries 600 between a conductive plate 613 and a conductive plate 614. The plurality of secondary batteries 600 may be connected in parallel, may be connected in series, or may be connected in parallel and then further connected in series. By forming a module 615 having a plurality of secondary batteries 600, a large amount of power can be extracted. Also, as shown in Fig. 5(C), a module 615 may be formed by sandwiching a plurality of secondary batteries 600 between a conductive plate 613 and a conductive plate 614. The plurality of secondary batteries 600 may be connected in parallel, may be connected in series, or may be connected in parallel and then further connected in series. By forming a module 615 having a plurality of secondary batteries 600, a large amount of power can be extracted.

[0157] Fig. 5(D) is a top view of the module 615. For clarity, the conductive plate 613 is shown by a dotted line. As shown in Fig. 5(D), the module 615 may have a conducting wire 616 that electrically connects the plurality of secondary batteries 600. The conductive plate 613 can be superimposed on the conducting wire 616. Also, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 overheats, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Thus, the performance of the module 615 is less affected by the outside air temperature. Fig. 5(D) is a top view of the module 615. For clarity, the conductive plate 613 is shown by a dotted line. As shown in Fig. 5(D), the module 615 may have a conducting wire 616 that electrically connects the plurality of secondary batteries 600. The conductive plate 613 can be superimposed on the conducting wire 616. Also, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 overheats, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Thus, the performance of the module 615 is less affected by the outside air temperature. Fig. 5(D) is a top view of the module 615. For clarity, the conductive plate 613 is shown by a dotted line. As shown in Fig. 5(D), the module 615 may have a conducting wire 616 that electrically connects the plurality of secondary batteries 600. The conductive plate 613 can be superimposed on the conducting wire 616. Also, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 overheats, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Thus, the performance of the module 615 is less affected by the outside air temperature. Fig. 5(D) is a top view of the module 615. For clarity, the conductive plate 613 is shown by a dotted line. As shown in Fig. 5(D), the module 615 may have a conducting wire 616 that electrically connects the plurality of secondary batteries 600. The conductive plate 613 can be superimposed on the conducting wire 616. Also, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 overheats, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Thus, the performance of the module 615 is less affected by the outside air temperature. Fig. 5(D) is a top view of the module 615. For clarity, the conductive plate 613 is shown by a dotted line. As shown in Fig. 5(D), the module 615 may have a conducting wire 616 that electrically connects the plurality of secondary batteries 600. The conductive plate 613 can be superimposed on the conducting wire 616. Also, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 overheats, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Thus, the performance of the module 615 is less affected by the outside air temperature. Fig. 5(D) is a top view of the module 615. For clarity, the conductive plate 613 is shown by a dotted line. As shown in Fig. 5(D), the module 615 may have a conducting wire 616 that electrically connects the plurality of secondary batteries 600. The conductive plate 613 can be superimposed on the conducting wire 616. Also, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 overheats, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Thus, the performance of the module 615 is less affected by the outside air temperature. Fig. 5(D) is a top view of the module 615. For clarity, the conductive plate 613 is shown by a dotted line. As shown in Fig. 5(D), the module 615 may have a conducting wire 616 that electrically connects the plurality of secondary batteries 600. The conductive plate 613 can be superimposed on the conducting wire 616. Also, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 overheats, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Thus, the performance of the module 615 is less affected by the outside air temperature.

[0158] By using the positive electrode active material 100 described in the previous embodiment for the positive electrode 604, high capacity and It is possible to obtain a cylindrical secondary battery 600 having excellent cycle characteristics.

[0159] [Structural Example of Secondary Battery] Another structural example of the secondary battery will be described with reference to FIGS. 6 to 9.

[0160] FIGS. 6(A) and 6(B) are views showing the external appearance of a battery pack. The battery pack has a circuit substrate 900 and a secondary battery 913. The secondary battery 913 has a terminal 951 and a terminal 9 52 and is covered with a label 910. The battery pack may also have an antenna 914.

[0161] The circuit substrate 900 is fixed with a seal 915. The circuit substrate 900 has a circuit 912. The terminal 911 is electrically connected to the terminals 951 and 952 of the secondary battery 913 via the circuit substrate 900. The terminal 911 is also electrically connected to the antenna 914 and the circuit 912 via the circuit substrate 900. 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, etc.

[0162] The circuit 912 has, for example, a function as a protection circuit that protects the secondary battery 913 from overcharging, over-discharging, and overcurrent. The circuit 912 may be provided on the back surface of the circuit substrate 900. Note that the antenna 914 is not limited to a coil shape and may be, for example, linear or plate-shaped. Also, antennas such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, and a dielectric antenna may be used. The antenna 914 has a function capable of performing data communication with an external device, for example. The battery pack and via the antenna 914 ​​​As a communication method with other devices, a response method that can be used between the battery pack and other devices, such as NFC, can be applied.

[0163] The battery pack has a layer 916 between the antenna 914 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.

[0164] Note that the structure of the battery pack is not limited to that shown in FIG. 6.

[0165] For example, as shown in FIGS. 7(A-1) and 7(A-2), among the secondary batteries 913 shown in FIGS. 6(A) and 6(B), antennas 918 may be provided on a pair of opposite surfaces. FIG. 7(A-1) is an external view seen from one side direction of the pair of surfaces, and FIG. 7(A-2) is an external view seen from the other side direction of the pair of surfaces. For the same parts as those shown in FIGS. 6(A) and 6(B), the description of the battery pack shown in FIGS. 6(A) and 6(B) can be appropriately incorporated.

[0166] As shown in FIG. 7(A-1), the antenna 914 is provided with the layer 916 sandwiched between a pair of surfaces of the secondary battery 913, and as shown in FIG. 7(A-2), the antenna 918 is provided with the layer 917 sandwiched between the other pair of surfaces of the secondary battery 913. The layer 917 has a function of, for example, shielding the electromagnetic field generated by the secondary battery 913. As the layer 917, for example, a magnetic material can be used.

[0167] With the above structure, two antennas can be provided in the battery pack, and the sizes of both the antenna 914 and the antenna 918 can be increased.

[0168] Antenna 918 can apply an antenna having a shape applicable to antenna 914. . Further, antenna 918 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. That is, antenna 914 may be made to function as one of the two conductors of the capacitor. Thereby, power can be exchanged not only by an electromagnetic field and a magnetic field, but also by an electric field.

[0169] Alternatively, as shown in Fig. 7(B-1), a display device 920 may be provided in the battery pack shown in Figs. 6(A) and 6(B). The display device 920 is electrically connected to terminal 911. For the same parts as the battery pack shown in Figs. 6(A) and 6(B), the description of the battery pack shown in Figs. 6(A) and 6(B) can be appropriately incorporated.

[0170] The display device 920 may display, for example, an image indicating whether it is being charged or not, an image indicating the power storage 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.

[0171] Alternatively, as shown in Fig. 7(B-2), a sensor 921 may be provided in the secondary battery 913 shown in Figs. 6(A) and 6(B). The sensor 921 is electrically connected to terminal 911 via terminal 922 and circuit board 900. For the same parts as the power storage device shown in Figs. 6(A) and 6(B), the description of the power storage device shown in Figs. 6(A) and 6(B) can be appropriately incorporated. . ​​​​​​​​​​​​

[0172] As the sensor 921, for example, it may have a function of measuring displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light , liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays. By providing the sensor 921, for example, data indicating the environment where the power storage device is placed (such as temperature) can be detected and stored in the memory in the circuit 912.

[0173] Furthermore, a structural example of the secondary battery 913 will be described with reference to FIGS. 8 and 9.

[0174] The secondary battery 913 shown in FIG. 8(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. 8(A), for the sake of convenience, the housing 930 is shown separately, but actually, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum or the like) or a resin material can be used.

[0175] Note that, as shown in FIG. 8(B), the housing 930 shown in FIG. 8(A) may be formed of a plurality of materials. For example, the secondary battery 913 shown in FIG. 8(B) has a housing 930a and a housing 930b bonded together, and a wound body 950 is provided in the region surrounded by the housing 930a and the housing 930b.

[0176] The housing 930a can be made of an insulating material such as an organic resin. By using a material such as organic resin on the surface on which the secondary battery 913 is formed, If the shielding of the electric field by the housing 930a is small, the shielding of the housing 930a can be suppressed. Antennas such as antenna 914 and antenna 918 may be provided inside the housing 930b. For example, a metal material can be used.

[0177] The structure of the wound body 950 is shown in FIG. The winding body 950 has a separator 933 sandwiched therebetween. A negative electrode 931 and a positive electrode 932 are stacked on top of each other, and the laminated sheet is wound to form a wound body. In addition, the negative electrode 931, the positive electrode 932, and the separator 933 may be laminated in a plurality of layers. May be layered.

[0178] The negative electrode 931 is connected to the terminal 911 shown in FIG. 6 via one of the terminals 951 and 952. The positive electrode 932 is connected to the terminal 911 shown in FIG. Connected.

[0179] By using the positive electrode active material described in the above embodiment for the positive electrode 932, the battery can be cycled with a high capacity. The secondary battery 913 can have excellent characteristics.

[0180] [Laminated secondary battery] Next, an example of a laminated secondary battery will be described with reference to FIGS. If the laminated secondary battery is made flexible, the flexible portion is at least If the secondary battery is mounted on an electronic device that also has a battery, the secondary battery can be bent according to the deformation of the electronic device. can.

[0181] With reference to FIG. 10, the laminated secondary battery 980 will be described. The laminated secondary battery 980 has a wound body 993 shown in FIG. 10(A). The wound body 993 includes a negative electrode 994 , a positive electrode 995, and a separator 996. The wound body 993 is similar to the wound body 950 described in FIG. 9, in which the negative electrode 994 and the positive electrode 995 overlap with each other with the separator 996 interposed therebetween, and the laminated sheet is wound up.

[0182] 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 a lead electrode 997 and a 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.

[0183] As shown in FIG. 10(B), the wound body 993 described above is housed in a space formed by thermocompression bonding or the like of a film 981 serving as an exterior body and a film 98 2 having a recess, whereby the secondary battery 980 can be manufactured as shown in FIG. 10(C). The wound body 99 3 has a lead electrode 997 and a lead electrode 998, and is impregnated with an electrolytic solution inside the film 981 and the film 982 having a recess.

[0184] For the film 981 and the film 982 having a recess, a metal material 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 recess, when an external force is applied, the film 981 and the recess will... The film 982 can be deformed, and a flexible secondary battery can be manufactured. This is achievable.

[0185] Also, although FIGS. 10(B) and 10(C) show examples using two films, a space can be formed by folding a single film, and the above-described wound body 99 3 can be housed in that space.

[0186] 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.

[0187] Also, in FIG. 10, an example of a secondary battery 9 80 having a wound body in a space formed by a film serving as an exterior body was described. However, for example, as shown in FIG. 11, 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. This is acceptable.

[0188] The laminated secondary battery 500 shown in FIG. 11(A) includes a positive electrode 503 having a positive electrode current collector 501 and a positive electrode active material layer 502, a negative electrode 506 having a negative electrode current collector 504 and a negative electrode active material layer 505, a separator 507, an electrolyte 508, and an exterior body 509. A separator 507 is installed between the positive electrode 503 and the negative electrode 506 provided in the exterior body 509. Also, the interior of the exterior body 509 is filled with the electrolyte 508. As the electrolyte 508, the electrolyte shown in Embodiment 2 can be used. In the laminated secondary battery 500 shown in FIG. 11(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, the positive electrode

[0189] In the laminated secondary battery 500 shown in FIG. 11(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, the positive electrode A part of the current collector 501 and the negative electrode current collector 504 may be arranged to be exposed to the outside from the exterior body 509. Alternatively, the positive electrode current collector 501 and the negative electrode current collector 504 may not be exposed to the outside from the exterior body 509, and the lead electrode may be ultrasonically bonded to the lead electrode and the positive electrode current collector 501 or the negative electrode current collector 504 so that the lead electrode is exposed to the outside. In the laminated secondary battery 500, the exterior body 509 may be provided with a flexible metal thin film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. on a film, and further on the metal thin film, an insulating synthetic resin film such as a polyamide-based resin or a polyester-based resin may be provided as the outer surface of the exterior body. A three-layer laminated film can be used. In addition, an example of the cross-sectional structure of the laminated secondary battery 500 is shown in FIG. 11(B). In FIG. 11(A), for simplicity, an example composed of two current collectors is shown, but actually, it is composed of a plurality of electrode layers.

[0190] In FIG. 11(B), as an example, the number of electrode layers is set to 16. Even when the number of electrode layers is 16, the secondary battery 500 has flexibility. FIG. 11(B) shows a structure of a total of 16 layers with 8 layers of the negative electrode current collector 504 and 8 layers of the positive electrode current collector 501. Note that FIG. 11(B) shows the cross-section of the extraction part of the negative electrode, and 8 layers of the negative electrode current collector 504 are 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,

[0191]

[0192] ​​​​​​​​​​​​​Collectively, it can be made into a secondary battery that can be thinned and has excellent flexibility.

[0193] Here, an example of the external view of the laminated secondary battery 500 is shown in FIGS. 12 and 13. FIG. 1 2 and FIG. 13 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.

[0194] FIG. 14(A) shows an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a positive electrode current collector 50 1, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. Further, the positive electrode 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as a 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 and is formed. Further, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, a tab region 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. 14(A).

[0195] [Manufacturing method of laminated secondary battery] Here, an example of the manufacturing method of the laminated secondary battery whose external view is shown in FIG. 12 will be described with reference to FIGS. 14 (B) and (C).

[0196] First, the negative electrode 506, the separator 507, and the positive electrode 503 are laminated. FIG. 14(B) shows the laminated negative electrode 506, separator 507, and positive electrode 503. Here, an example of using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. Next, the joining of the tab regions of the positive electrode 503 to each other and the joining of the positive electrode lead electrode 510 to the tab region of the outermost positive electrode are performed. For the joining, for example, ultrasonic welding or the like can be used. Similarly, the joining of the tab regions of the negative electrode 506 to each other and the joining of the negative electrode lead to the tab region of the outermost negative electrode are performed. ​Perform the bonding of the anode electrode 511.

[0197] Next, arrange the negative electrode 506, the separator 507, and the positive electrode 503 on the exterior body 509.

[0198] Next, as shown in FIG. 14(C), bend the exterior body 509 at the portion indicated by the dashed line. After that, bond the outer peripheral portion of the exterior body 509. For the bonding, for example, thermocompression bonding or the like may be used. At this time , in order to be able to later insert the electrolytic solution 508, provide a region (hereinafter referred to as the inlet) that is not bonded to a part (or one side) of the exterior body 509.

[0199] Next, introduce the electrolytic solution 508 into the interior of the exterior body 509 through the inlet provided in the exterior body 509. The introduction of the electrolytic solution 508 is preferably performed under a reduced-pressure atmosphere or an inert gas atmosphere. And finally, bond the inlet. In this way, a secondary battery 500, which is a laminated secondary battery, can be manufactured.

[0200] 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.

[0201] [Bendable secondary battery] Next, an example of a bendable secondary battery will be described with reference to FIGS. 15 and 16. .

[0202] FIG. 15(A) shows a schematic top view of a bendable battery 250. FIGS. 15(B1), (B2), and (C) are schematic cross-sectional views taken along the cutting lines C1-C2, C3-C4 and A1-A2 in FIG. 15(A), respectively. The battery 250 includes an exterior body 251 and an exterior body It has a positive electrode 211a and a negative electrode 211b housed inside 251. The positive electrode 211a and the electrically connected lead 212a, and the negative electrode 211b and the electrically connected lead 21 2b extend outside the exterior body 251. Also, in the region surrounded by the exterior body 251, in addition to the positive electrode 211a and the negative electrode 211b, an electrolytic solution (not shown) is encapsulated.

[0203] The positive electrode 211a and the negative electrode 211b of the battery 250 will be described with reference to FIG. 16. FIG. 16(A) is a perspective view for explaining the stacking order of the positive electrode 211a, the negative electrode 211b, and the separator 214. FIG. 16(B) is a perspective view showing the leads 2 12a and 212b in addition to the positive electrode 211a and the negative electrode 211b.

[0204] As shown in FIG. 16(A), the battery 250 has a plurality of strip-shaped positive electrodes 211a, a plurality of strip-shaped negative electrodes 211b, and a plurality of separators 214. The positive electrode 211a and the negative electrode 211 b each have a protruding tab portion and a portion other than the tab. A positive electrode active material layer is formed on the portion other than the tab on one surface of the positive electrode 211a, and a negative electrode active material layer is formed on the portion other than the tab on one surface of the negative electrode 211b.

[0205] The positive electrode 211a and the negative electrode 211b are stacked such that the surfaces of the positive electrode 211a where the positive electrode active material layer is not formed face each other, and the surfaces of the negative electrode 211b where the negative electrode active material layer is not formed face each other. are stacked.

[0206] Also, a separator 214 is provided between the surface of the positive electrode 211a where the positive electrode active material is formed and the surface of the negative electrode 211b where the negative electrode active material is formed. In FIG. 16(A), the separator 214 is shown as a dotted line for easy viewing. ​​​

[0207] Also, as shown in FIG. 16(B), the plurality of positive electrodes 211a and the leads 212a are electrically connected at the joint 215 a. Also, the plurality of negative electrodes 211b and the leads 212b are electrically connected at the joint 2 15b.

[0208] Next, the exterior body 251 will be described with reference to FIGS. 15(B1), (B2), (C), and (D).

[0209] The exterior body 251 has a film-like shape and is bent into two parts so as to sandwich the positive electrode 211a and the negative electrode 211b. The exterior body 251 has a bent portion 261, a pair of seal portions 2 62, and a seal portion 263. The pair of seal portions 262 are provided with the positive electrode 211a and the negative electrode 211b interposed therebetween and can also be called side seals. Also, the seal portion 26 3 has a portion overlapping the leads 212a and the leads 212b and can also be called a top seal.

[0210] The exterior body 251 preferably has a wavy shape in which ridge lines 271 and valley lines 2 72 are arranged alternately in a portion overlapping the positive electrode 211a and the negative electrode 211b. Also, the seal portions 26 2 and the seal portion 263 of the exterior body 251 are preferably flat.

[0211] FIG. 15(B1) is a cross section cut at a portion overlapping the ridge line 271, and FIG. 15(B2) is a cross section cut at a portion overlapping the valley line 272. FIGS. 15(B1) and (B2) both correspond to a cross section in the width direction of the battery 250 and the positive electrode 211a and the negative electrode 211b.

[0212] Here, let the distance between the end portion in the width direction of the negative electrode 211b and the seal portion 262 be the distance La. ​​​. When the battery 250 is deformed such as being bent, as will be described later, the positive electrode 211a and the negative electrode 211b are deformed so as to shift from each other in the length direction. At this time, if the distance La is too short, the outer body 251 and the positive electrode 211a and the negative electrode 211b rub strongly, and the outer body 251 may be damaged and break. In particular, when the metal film of the outer body 251 is exposed, the metal film may be corroded by the electrolyte. Therefore, it is preferable to set the distance La as long as possible. On the other hand, if the distance La is made too large, the volume of the battery 250 increases and it becomes.

[0213] Also, the thicker the total thickness of the stacked positive electrode 211a and negative electrode 211b, the more preferably the distance La between the negative electrode 211 b and the seal portion 262 is increased.

[0214] More specifically, when the total thickness of the stacked positive electrode 211a, negative electrode 211b, and separator 214 (not shown) is defined as thickness t, the distance La is 0.8 times or more and 3.0 times or less of the thickness t, 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 It is preferably the following. By setting the distance La within this range, a compact and highly reliable battery against bending can be realized.

[0215] Also, when the distance between the pair of seal portions 262 is defined as distance Lb, it is preferable to make the distance Lb sufficiently larger than the width Wb of the negative electrode 211b. Thereby, when the battery 250 is repeatedly deformed such as being bent even if the positive electrode 211a and the negative electrode 211b come into contact with the outer body 251, a part of the positive electrode 211a and the negative electrode 211b can shift in the width direction. Therefore, the positive ​​​​​Effectively prevent the positive electrode 211a and the negative electrode 211b from rubbing against the exterior body 251 This can be achieved.

[0216] For example, the difference between the distance Lb between the pair of seal portions 262 and the width Wb of the negative electrode 211b is preferably 1.6 times or more and 6.0 times or less, more preferably 1.8 times or more and 5.0 times or less, still more preferably 2.0 times or more and 4.0 times or less the thickness t of the positive electrode 211a and the negative electrode 211b. That is, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following formula (1). 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. .

[0217] In other words, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following formula (1). That is, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following formula (1).

[0218]

Equation

[0219] 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. That is, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following formula (1).

[0220] Further, FIG. 15(C) is a cross section including the lead 212a and corresponds to a cross section in the longitudinal direction of the battery 250, the positive electrode 211a, and the negative electrode 211b. As shown in FIG. 15(C), it is preferable that a space 273 is provided between the longitudinal ends of the positive electrode 211a and the negative electrode 211b and the exterior body 251 at the bent portion 261. That is, it is preferable that a space 273 is provided between the longitudinal ends of the positive electrode 211a and the negative electrode 211b and the exterior body 251 at the bent portion 261. That is, it is preferable that a space 273 is provided between the longitudinal ends of the positive electrode 211a and the negative electrode 211b and the exterior body 251 at the bent portion 261. That is, it is preferable that a space 273 is provided between the longitudinal ends of the positive electrode 211a and the negative electrode 211b and the exterior body 251 at the bent portion 261.

[0221] FIG. 15(D) shows a schematic cross-sectional view when the battery 250 is bent. FIG. 15(D) corresponds to the cross section taken along the cutting line B1 - B2 in FIG. 15(A). That is, FIG. 15(D) corresponds to the cross section taken along the cutting line B1 - B2 in FIG. 15(A).

[0222] When the battery 250 is bent, a part of the exterior body 251 located on the outer side of the bend extends, and a part located on the inner side Some other parts are deformed to shrink. More specifically, the part located outside the exterior body 251 is deformed such that the amplitude of the wave is small and the period of the wave is large. On the other hand, the exterior body 251 The part located inside is deformed such that the amplitude of the wave is large and the period of the wave is small. In this way, when the exterior body 251 is deformed, the stress applied to the exterior body 251 due to bending is relaxed, so the material itself constituting the exterior body 251 does not need to stretch or contract. As a result, the exterior body 251 can be bent with a small force without being damaged.

[0223] Also, as shown in FIG. 15(D), when the battery 250 is bent, the positive electrode 211a and the negative electrode 21 1b are relatively displaced from each other. At this time, the plurality of stacked positive electrodes 211a and negative electrodes 211b are displaced such that the amount of displacement increases as they are closer to the bent portion 261 because one end on the seal portion 263 side is fixed by the fixing member 217. As a result, the stress applied to the positive electrode 21 1a and the negative electrode 211b is relaxed, and the positive electrode 211a and the negative electrode 211b themselves do not need to stretch or contract. As a result, the battery 250 can be bent without the positive electrode 211a and the negative electrode 211b being damaged.

[0224] Also, since there is a space 273 between the ends of the positive electrode 211a and the negative electrode 211b and the exterior body 251, when bent, the ends of the positive electrode 211a and the negative electrode 211b located inside can be relatively displaced without contacting the exterior body 251.

[0225] The battery 250 illustrated in FIGS. 15 and 16 is less likely to suffer damage to the exterior body, damage to the positive electrode 211a and the negative electrode 211b, etc., even when repeatedly bent and stretched, and the battery characteristics are also less likely to deteriorate. ​​​​It is a battery. By using the positive electrode active material described in the previous embodiment for the positive electrode 211a of the battery 250, a battery with a higher capacity and excellent cycle characteristics can be obtained.

[0226] (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.

[0227] First, an example of mounting the bendable secondary battery, which was partially described in Embodiment 3, on an electronic device is shown in FIG. 17. As an electronic device to which the bendable secondary battery is applied, for example, a television set (also referred to as a TV or a television receiver), a monitor for a computer, a digital camera, a digital video camera, a digital photo frame, a mobile phone ( also referred to as a cellular phone or a mobile phone device), a portable game machine, a portable information terminal, an audio playback device, a large game machine such as a pachinko machine, etc. can be mentioned.

[0228] In addition, it is also possible to incorporate a secondary battery having a flexible shape along the inner wall or outer wall of a house or building, or along the curved surface of the interior or exterior of an automobile.

[0229] FIG. 17(A) shows an example of a mobile phone. The mobile phone 7400 includes a display unit 7402 incorporated in a housing 7401, as well as operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, etc. Note that the mobile phone 7400 has a secondary battery 7407. By using the secondary battery of one aspect of the present invention for the above secondary battery 7407, a lightweight and long-life mobile phone can be provided.

[0230] ​​​​​​​​​Figure 17(B) shows the state in which the mobile phone 7400 is bent. When the mobile phone 740 0 is deformed by an external force and the whole is bent, the secondary battery 7407 provided inside it is also bent. Also, the state of the bent secondary battery 7407 at that time is shown in FIG. 17(C ). The secondary battery 7407 is a thin battery. The secondary battery 7407 is fixed in a bent state . Incidentally, the secondary battery 7407 has a lead electrode 7408 electrically connected to the current collector 7409.

[0231] Figure 17(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. 17(E) shows the state of the bent secondary battery 7104. When the secondary battery 7104 is bent and worn on the user's arm, the housing deforms and the curvature of part or all of the secondary battery 7104 changes. Incidentally, the degree of bending at an arbitrary point on the curve represented by the value of the radius of the corresponding circle is the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, when the radius of curvature is in the range of 40 mm or more and 150 mm or less, part or all of the main surface of the housing or the secondary battery 7104 changes. If the radius of curvature of the main surface of the secondary battery 7104 is in the range of 40 mm or more and 150 mm or less, high reliability can be maintained. By using the secondary battery of one aspect of the present invention for the secondary battery 7104 described above, a lightweight and long-life portable display device can be provided.

[0232] Figure 17(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 05, input / output terminals 7206, etc.​​​

[0233] The mobile information terminal 7200 can execute various applications such as mobile phones, e-mails, text viewing and creation, music playback, Internet communication, and computer games. It can be done.

[0234] The display unit 7202 is provided with a curved display surface and can perform display along the curved display surface. In addition, the display unit 7202 is provided with a touch sensor and can be operated by touching the screen with a finger or a stylus. For example, by touching the icon 7207 displayed on the display unit 7202, an application can be launched.

[0235] In addition to time setting, the operation button 7205 can perform various functions such as turning on and off the power, turning on and off wireless communication, executing and canceling the silent mode, and executing and canceling the power saving mode. For example, the function of the operation button 7205 can also be freely set by the operating system incorporated in the mobile information terminal 7200.

[0236] In addition, the mobile information terminal 7200 can perform communication-standardized short-range wireless communication. For example, by communicating with a wireless headset, it is possible to make hands-free calls.

[0237] In addition, the mobile information terminal 7200 is provided with an input / output terminal 7206 and can directly exchange data with other information terminals via a connector. In addition, charging can also be performed 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.

[0238] The display unit 7202 of the mobile 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 mobile information terminal can be provided. For example, the secondary battery 7104 shown in Fig. 17(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.

[0239] The mobile information terminal 7200 preferably has a sensor. Examples of the sensor include human body sensors such as fingerprint sensors, pulse sensors, and body temperature sensors, and touch sensors, pressure sensors, acceleration sensors, etc. are preferably mounted.

[0240] Fig. 17(G) shows an example of a bracelet-type display device. The display device 7300 has a display unit 7 304 and has a secondary battery according to one aspect of the present invention. Further, the display device 7300 can also be provided with a touch sensor on the display unit 7304, and can also function as a mobile information terminal.

[0241] The display surface of the display unit 7304 is curved, and display can be performed along the curved display surface. In addition, the display device 7300 can change the display state by means of short-range wireless communication conforming to a communication standard, etc.

[0242] 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.

[0243] By using the secondary battery according to one aspect of the present invention as the secondary battery of the display device 7300, light ​​​A display device with a long lifespan can be provided in terms of quantity.

[0244] Next, FIGS. 18(A) and 18(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIGS. 18(A) and 18(B) includes a housing 9630a, a housing 9630b, a movable part 9640 connecting the housing 9630a and the housing 9630b, a display unit 9631, a display mode switching switch 9626, a power switch 9627, a power saving mode switch 9625, a fastener 9629, and an operation switch 9628. By using a flexible panel for the display unit 9631, a tablet terminal with a wider display unit can be achieved. FIG. 18(A) shows the state where the tablet terminal 9600 is opened, and FIG. 18(B) shows the state where the tablet terminal 9600 is closed.

[0245] Also, the tablet terminal 9600 has a power storage body 9635 inside the housing 9630a and the housing 9630b. The power storage body 9635 is provided through the movable part 9640 and extends across the housing 9630a and the housing 9630b.

[0246] A part of the display unit 9631 can be a touch panel area, and data can be input by touching the displayed operation keys. Also, by touching the position where the keyboard display switching button of the touch panel is displayed with a finger or a stylus, etc., the keyboard buttons can be displayed on the display unit 9631.

[0247] Also, the display mode switching switch 9626 can select switching of the display orientation such as vertical display or horizontal display, and switching between black and white display and color display. The power saving mode switching switch The touch 9625 can optimize the display brightness according to the amount of external light detected by the optical sensor built into the tablet terminal 9600 during use. The tablet terminal can incorporate not only an optical sensor but also other detection devices such as sensors for detecting inclination, such as a gyro and an acceleration sensor.

[0248] Figure 18(B) shows the closed state. The tablet terminal includes a housing 9630, a solar cell 96 33, and a charge / discharge control circuit 9634 including a DCDC converter 9636. Also, as the power storage body 9635, a secondary battery according to an aspect of the present invention is used.

[0249] Since the tablet terminal 9600 is foldable in two, it can be folded so that the housing 9630a and the housing 9630b overlap each other when not in use. By folding, the display unit 9631 can be protected, thus enhancing the durability of the tablet terminal 9600. Also, the power storage body 9635 using the secondary battery according to an aspect of the present invention has high capacity and good cycle characteristics, so a tablet terminal that can be used for a long time over a long period can be provided.

[0250] In addition, the tablet terminal shown in FIGS. 18(A) and 18(B) can have functions such as displaying various information (still images, moving images, text images, etc.), displaying a calendar, date, or time on the display unit, a touch input function for touch input operation or editing of the information displayed on the display unit, a function for controlling processing by various software (programs), etc.

[0251] Power is supplied to the touch panel by the solar cell 9633 mounted on the surface of the tablet terminal. ​​​​​It can be supplied to a display unit, a video signal processing unit, etc. 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.

[0252] Also, the configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 18(B) will be illustrated with reference to the block diagram in FIG. 18( C). FIG. 18(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 locations in the charge / discharge control circuit 96 34 shown in FIG. 18(B).

[0253] First, an example of the operation when power is generated by the solar cell 9633 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC 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 required voltage for the display unit 9631. When the display on the display unit 9631 is not performed, SW1 can be turned off and SW2 can be turned on to charge the power storage body 9635.

[0254] Note that the solar cell 9633 is shown as an example of a power generation means, but is not particularly limited, and power storage by other power generation means such as a piezoelectric element (piezoelectric element) or a thermoelectric conversion element (Peltier element) of the body 9635 may be performed. For example, power can be wirelessly (contactlessly) transmitted and received ​​​A configuration may be adopted in which a contactless power transmission module that performs charging or other charging means are combined. This may also be done.

[0255] FIG. 19 shows an example of another electronic device. In FIG. 19, a display device 8000 is an example of an electronic device using a secondary battery 8004 according to one aspect of the present invention. Specifically, the display device 800 0 corresponds to a display device for receiving TV broadcasts and includes a housing 8001, a display unit 8002, a speaker unit 8003, a secondary battery 8004, and the like. The secondary battery 8004 according to one aspect of the present invention is provided inside the housing 8001. The display device 8000 can be supplied with power from a commercial power source or can use the power stored in the secondary battery 8004. Therefore even when power supply from the commercial power source cannot be received due to a power outage or the like, the display device 8000 can be used by using the secondary battery 8004 according to one aspect of the present invention as an uninterruptible power supply

[0256] The display unit 8002 may include a light-emitting device having a light-emitting element such as a liquid crystal display device or an organic EL element in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Devi ce), a PDP (Plasma Display Panel), an FED (Field Emission Display), or the like, and a semiconductor display device can be used.

[0257] In addition to being used for receiving TV broadcasts, the display device includes all display devices for information display, such as those for personal computers and advertising displays.

[0258] In FIG. 19, a stationary lighting device 8100 is a secondary battery 81 according to one aspect of the present invention. ​​​​​​This is an example of an electronic device using 03. Specifically, the lighting device 8100 includes a housing 8101, a light source 8102, a secondary battery 8103, etc. In FIG. 19, the case where the secondary battery 8103 is provided inside the ceiling 81 04 on which the housing 8101 and the light source 8102 are installed is illustrated as an example, but 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.

[0259] In addition, in FIG. 19, the installed lighting device 8100 provided on the ceiling 8104 is illustrated as an example, but 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., or for tabletop lighting devices.

[0260] 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.

[0261] In FIG. 19, 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 includes a housing 8201, an air outlet 8202, a secondary battery 8203, etc. In FIG. 19 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 can use the power stored in the secondary battery 8203. In particular, when the secondary battery 82 03 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the use of the air conditioner becomes possible.

[0262] Note that in FIG. 19, a separate type air conditioner composed of an indoor unit and an outdoor unit is illustrated, but the secondary battery according to one aspect of the present invention can also be used for an integrated type air conditioner having the functions of the indoor unit and the outdoor unit in one housing.

[0263] In FIG. 19, the electric refrigerator 8300 is an example of an electronic device using the secondary battery 8304 according to one aspect of the present invention. Specifically, the electric refrigerator 8300 includes a housing 8301, a door 8302 for the storage compartment, a door 8303 for the freezer compartment, a secondary battery 8304, and the like. In FIG. 19, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator 8300 can receive power supply from a commercial power source, or can use the power stored in the secondary battery 8304. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8304 according to one aspect of the present invention as an uninterruptible power supply, the use of the electric refrigerator 8300 becomes possible. ​​​

[0264] Also, during periods when the electronic device is not in use, especially during periods when the ratio of the actual power consumption to the total power 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 of the above-mentioned periods. For example, in the case of the electric refrigerator 8300, during the night when the temperature is low and the doors 8302 for the refrigerator compartment and 8303 for the freezer compartment are not opened or closed, power is stored in the secondary battery 8304. And during the day when the temperature rises and the doors 8302 for the refrigerator compartment and 8303 for the freezer compartment are opened or closed, by using the secondary battery 8304 as an auxiliary power source, the power utilization rate during the day can be kept low. In addition to the above-mentioned electronic devices, the secondary battery according to one aspect of the present invention can be mounted on any electronic device. According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved. Also, according to one aspect of the present invention, a high-capacity secondary battery can be obtained, and thus the secondary battery itself can be made smaller and lighter.

[0265] Therefore, by mounting the secondary battery, which is one aspect of the present invention, on the electronic devices 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.

[0266] (Embodiment 5) In this embodiment, an example of mounting the secondary battery, which is one aspect of the present invention, on a vehicle is shown.

[0267] When the secondary battery is mounted on a vehicle, next-generation clean energy vehicles such as hybrid electric vehicles (HEV), electric vehicles (EV), or plug-in hybrid electric vehicles (PHEV) can be realized. 。

[0268] In FIG. 20, a vehicle using a secondary battery, which is one aspect of the present invention, is illustrated. FIG. 20(A) The automobile 8400 shown is an electric vehicle that uses an electric motor as a power source for running Or it is a hybrid vehicle that can appropriately select and use an electric motor and an engine as power sources for running By using one aspect of the present invention, a vehicle with a long cruising range can be realized In addition, 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 Alternatively, a battery pack combining a plurality of secondary batteries shown in FIG. 17 may be installed with respect to the floor portion inside the vehicle The secondary battery not only drives the electric motor 8406 But can also supply power to light emitting devices such as headlight 8401 and room light (not shown)

[0269] In addition, the secondary battery can supply power to display devices such as a speedometer and a tachometer that the automobile 8400 has In addition, the secondary battery can supply power to semiconductor devices such as a navigation system that the automobile 8400 has

[0270] The automobile 8500 shown in FIG. 20(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 that the automobile 8500 has FIG. 20(B) shows a state in which charging is being performed from a ground-mounted charging device 8021 to a secondary battery 8024 mounted on the automobile 8500 via a cable 8022 When charging The charging method, the specifications of the connector, etc. are predetermined such as CHAdeMO (registered trademark) and Combo ​​​ It may be appropriately performed in this manner. 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 means of 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 can be done.

[0271] Also, although not shown, a power receiving device may be mounted on the vehicle, and power may be supplied to the vehicle non-contact from a power transmission device on the ground for charging. In the case of this non-contact power supply method, by incorporating the power transmission device into a road or an outer wall charging can be performed not only while the vehicle is stopped but also while it is running. Also, using this non-contact power supply method, power may be transmitted and received between vehicles. 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.

[0272] Also, FIG. 20(C) is an example of a two-wheeled vehicle using a secondary battery according to an aspect of the present invention. FIG. 20 (C) shows a scooter 8600 equipped with a secondary battery 8602, side mirrors 8601, and a direction indicator light 8603. The secondary battery 8602 can supply electricity to the direction indicator light 8603 can.

[0273] Also, the scooter 8600 shown in FIG. 20(C) can store the secondary battery 860 2 in the under-seat storage 8604. The secondary battery 8602 can be stored in the under-seat storage 8604 even if the under-seat storage 8604 is small The secondary battery 8602 can be removable Preferably, during charging, the secondary battery 8602 is carried indoors for charging and stored before driving. Preferably, it is stored before driving.

[0274] According to one aspect of the present invention, the cycle characteristics of the secondary battery can be 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, thereby improving the cruising range. 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 the commercial power supply during the peak of power demand. If it is possible to avoid using the commercial power supply during the peak of power demand, it can contribute to energy saving 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. If the secondary battery itself can be made smaller and lighter, it contributes to reducing the weight of the vehicle, thereby improving the cruising range. If the secondary battery itself can be made smaller and lighter, it contributes to reducing the weight of the vehicle, thereby improving the cruising range. 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 the commercial power supply during the peak of power demand. If it is possible to avoid using the commercial power supply during the peak of power demand, it can contribute to energy saving 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. 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. 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.

[0275] This embodiment can be implemented in appropriate combination with other embodiments.

Example

[0276] In this example, cobalt was applied as the transition metal in the first region of the positive electrode active material. Then, a positive electrode active material prepared by adding magnesium and fluorine to the starting material, and a positive electrode active material prepared without adding magnesium and fluorine as a comparative example were prepared and their characteristics were analyzed. In addition, the cycle characteristics were evaluated by changing the concentrations of magnesium and fluorine added to the starting material. In addition, the cycle characteristics were evaluated by changing the concentrations of magnesium and fluorine added to the starting material. In addition, the cycle characteristics were evaluated by changing the concentrations of magnesium and fluorine added to the starting material.

[0277] <Preparation of Positive Electrode Active Materials of Samples 1 to 6> Cathode active materials from Sample 1 to Sample 6 were prepared by varying the concentrations of the magnesium source and the fluorine source. Lithium carbonate and cobalt oxide were used as common starting materials. Magnesium oxide and lithium fluoride were used as different additional starting materials for each sample. For Sample 1, magnesium oxide and lithium fluoride were used as the additional starting materials such that 0.5 atomic% of magnesium and 1 atomic% of fluorine were included with respect to the cobalt contained in the common starting materials. Hereinafter, Sample 1 will be denoted as using 0.5 mol% MgO and 1 mol% LiF as the additional starting materials. As described above in this specification etc., the amount of the additional starting materials will be indicated by atomic% or mol% with respect to the transition metal contained in the common starting materials. The same notation will be used for Samples 2 and later.

[0278] For Sample 2, 0.5 mol% MgO and 0.5 mol% LiF were used as the additional starting materials with respect to cobalt. For Sample 3, 0.5 mol% MgO and 2 mol% LiF were used as the additional starting materials. For Sample 4 as a comparative example, 1 mol% LiF was used as the additional starting material and no magnesium was added. For Sample 5 as a comparative example, 0.5 mol% MgO was used as the additional starting material and no fluorine was added. For Sample 6 as a comparative example, neither magnesium nor fluorine was added. The common starting materials and the additional starting materials for each sample are shown in Table 1.

[0279]

[0280]

[0281]

Table 1

[0282] For each of the above six samples, in the same manner as the production method described in Embodiment 1, the starting materials were mixed, first heating was performed, after cooling, sieving was carried out, second heating was performed, cooled, recovered, and a positive electrode active material was obtained. The particles during these processes and the positive electrode active material after these processes were analyzed as follows.

[0283] <stem-edx> For Sample 1 and Sample 5 (comparative example), the cross-section near the surface of the particles before the second heating was analyzed using STEM-EDX. Figures 22 and 23 show the STEM-EDX images of Sample 1 and Sample 5 (comparative example) before the second heating, respectively. Figure 22(A) and Figure 23(A) are STEM images, Figure 22(B) and Figure 23(B) are magnesium mappings, and Figure 22(C) and Figure 23(C) are fluorine mappings. As shown in Figure 22(B), in Sample 1 containing magnesium and fluorine in the starting material,

[0284] it was observed that magnesium was segregated to some extent near the surface of the particles even before the second heating. The segregated region was about 1 nm to 2 nm from the surface of the particles.

[0285] On the other hand, as shown in the EDX mapping of Figure 23(B), in Sample 5 containing magnesium but not containing fluorine in the starting material, segregation of magnesium to the vicinity of the surface was not observed.

[0286] As shown in Figures 22(C) and 23(C), almost no fluorine was observed inside the positive electrode active material in both Sample 1 and Sample 5. This is considered to be because fluorine, which is a light element, is difficult to detect by EDX.

[0287] <X-ray Photoelectron Spectroscopy (XPS)> Next, for Sample 1 and Sample 5 (comparative example), the amount of magnesium near the surface of the positive electrode active material before and after the second heating was analyzed.

[0288] The conditions for XPS analysis were as follows. Measuring device: QuanteraII manufactured by PHI ​​X-ray source: Monochromatic Al (1486.6 eV) Detection area: 100 μmφ Detection depth: Approximately 4 - 5 nm (Take-out angle 45°) Measurement spectrum: Wide, Li1s, Co2p, Ti2p, O1s, C1s, F1s, S 2p, Ca2p, Mg1s, Na1s, Zr3d

[0289] The results of quantifying the concentrations of each element using XPS are shown in Table 2. The quantification accuracy is about ±1 atomo mic%, and the detection limit is about 1 atomic% depending on the element. Also, for Ca, since the Mg Auger peak separated by the waveform is removed, the quantification error is larger than usual.

[0290] Also, the results of calculating the abundance ratios of each element when cobalt is set to 1 are shown in Table 3.

[0291]

Table 2

[0292]

Table 3

[0293] Among the abundance ratios of the elements shown in Table 3, the one plotted for magnesium is shown in Figure 2 4.

[0294] As shown in Table 2, Table 3, and Figure 24, in Sample 1 having magnesium and fluorine as additive starting materials, even before the second heating, magnesium was present near the surface of the cathode active material measurable by XPS. After the second heating, the amount of magnesium near the surface of the cathode active material further increased. That is, it is considered that segregation of magnesium to the surface of the cathode active material progressed due to the second heating. increased.

[0295] That is, it is considered that segregation of magnesium to the surface of the cathode active material progressed due to the second heating. Thus, the positive electrode active material of Sample 1 has a first region inside and a second region in the surface layer portion. The first region has lithium cobaltate, and the second region has magnesium. It was confirmed that it is a positive electrode active material.

[0296] On the other hand, in Sample 5 which does not have fluorine as an additive starting material and has only magnesium, magnesium near the surface of the positive electrode active material was below the detection limit both before and after the second heating. Thus, it was revealed that fluorine contained in the starting material unexpectedly has the effect of segregating magnesium to the surface layer portion of the positive electrode active material.

[0297] <Cycle characteristics> Next, using the positive electrode active materials of Sample 1 before and after the second heating, Sample 5 before and after the first heating, and Samples 2, Sample 3, Sample 4, and Sample 6, coin-type secondary batteries of CR2032 type (diameter 2 0 mm, height 3.2 mm) were fabricated, and their cycle characteristics were evaluated.

[0298] For the positive electrode, a slurry obtained by mixing the positive electrode active material prepared above, acetylene black (AB), and polyvinylidene fluoride (PVDF) at a weight ratio of positive electrode active material:AB:PVDF = 95:2.5:2.5 was used, which was coated on a current collector.

[0299] Lithium metal was used for the counter electrode.

[0300] As the electrolyte in the electrolytic solution, 1 mol / L of lithium hexafluorophosphate (LiPF6) was used. In the electrolytic solution, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of EC:DEC = 3:7, and vinylene carbonate (VC) was mixed at 2 wt%. This mixture was used.

[0301] For the positive electrode can and the negative electrode can, those made of stainless steel (SUS) were used.

[0302] The measurement temperature for the cycle performance test was set at 25°C. Charging was carried out at a constant current density of 68 .5 mA / g and an upper limit voltage of 4.6 V, and then constant voltage charging was performed until the current density reached 1.4 mA / g. Discharging was carried out at a constant current density of 68.5 mA / g per active material weight and a lower limit voltage of 2.5 V. Charge-discharge cycles were performed 30 times each.

[0303] Figures 25(A) and 25(B) show graphs of the cycle performance of secondary batteries using the positive electrode active material before and after the second heating of Sample 1 and before and after the first heating of Sample 5. Figure 25(A ) is a graph of the energy density during charging at 4.6 V, and Figure 25(B) is a graph of the energy density retention rate during charging at 4.6 V. The energy density is the product of the discharge capacity and the average discharge voltage.

[0304] As shown in Figure 25, in Sample 1 having magnesium and fluorine in the added starting material, the cycle performance was significantly improved by performing the second heating. Also, the energy density was good.

[0305] As is also clear from the above XPS results, it is considered that this is because the amount of magnesium present near the surface of the positive electrode active material increased by performing the second heating.

[0306] On the other hand, in Sample 5 having only magnesium in the added starting material, no significant difference in cycle performance was observed before and after the second heating.

[0307] Next, Figures 26 and 27 show the positive electrode active materials of Samples 1 to 6 after the second heating. The graph of the cycle characteristics of the secondary battery thus obtained is shown. Fig. 26 is a graph of the energy density during charging at 4.6 V and Fig. 27 is a graph of the energy density retention rate during charging at 4.6 V.

[0308] As shown in Figs. 26 and 27, Sample 4 (comparative example) in which only fluorine was added to the starting material, Sample 5 (comparative example) in which only magnesium was added showed inferior cycle characteristics compared to Sample 6 (comparative example) in which neither magnesium nor fluorine was added. On the other hand, Samples 1 to 3 in which magnesium and fluorine were added to the starting material showed good

[0309] cycle characteristics. The best cycle characteristics were shown by Sample 1 in which the atomic ratio of magnesium to fluorine was 1:2. Next, Sample 2 in which the content ratio of magnesium to fluorine was 1:4 showed good cycle characteristics. Also, as is clear from Fig. 26 not only the cycle characteristics but also the energy density was good. Thus, it was revealed that by adding magnesium and fluorine to the starting material, a positive electrode active material showing good cycle characteristics can be obtained. Also, the atomic ratio of magnesium and fluorine contained in the starting material is preferably Mg:F = 1:x (1.5 ≤ x ≤ 4), and it was revealed that Mg:F =

[0310] about 1:2 is most preferable. <Production of positive electrode active materials for Samples 7 and 8> Next, while keeping the ratio of magnesium to fluorine constant (Mg:F = 1:2), the addition amount was changed to produce positive electrode active materials for Samples 7 and 8.

[0311]

[0312] ​​​Sample 7 used 1 mol% MgO and 2 mol% LiF as the additive starting materials. Sample 8 used 2 mol% MgO and 4 mol% LiF as the additive starting materials. For Samples 7 and 8, the starting materials were mixed in the same manner as the production method described in Embodiment 1, heated for the first time, cooled, sieved, heated for the second time, cooled, and recovered to produce a positive electrode active material and a secondary battery. After that, the starting materials were mixed, heated for the first time, cooled, sieved, heated for the second time, cooled, and recovered to produce a positive electrode active material and a secondary battery. After cooling and collecting, a positive electrode active material was produced and a secondary battery was produced.

[0313] The common starting materials and additive starting materials of Samples 1, 7, and 8, for which the atomic ratio of magnesium to fluorine in the raw materials is Mg:F = 1:2, and Sample 6, which has no added magnesium and fluorine as a comparative example, are shown in Table 4. Samples 1, 7, and 8, for which the atomic ratio of magnesium to fluorine in the raw materials is Mg:F = 1:2, and Sample 6, which has no added magnesium and fluorine as a comparative example, are shown in Table 4. Table 4 shows the common starting materials and additive starting materials of Samples 1, 7, and 8, for which the atomic ratio of magnesium to fluorine in the raw materials is Mg:F = 1:2, and Sample 6, which has no added magnesium and fluorine as a comparative example.

[0314] [Table 4]

[0315] <Cycle characteristics> Figures 28(A) and 28(B) show graphs of the cycle characteristics of secondary batteries using the positive electrode active materials of Samples 1, 7, 8, and Sample 6 (comparative example). Figure 28(A) is a graph of the energy density during charging at 4.6 V, and Figure 28(B) is a graph of the energy density retention rate during charging at 4.6 V. Figures 28(A) and 28(B) show graphs of the cycle characteristics of secondary batteries using the positive electrode active materials of Samples 1, 7, 8, and Sample 6 (comparative example). Figure 28(A) is a graph of the energy density during charging at 4.6 V, and Figure 28(B) is a graph of the energy density retention rate during charging at 4.6 V. As shown in Figures 28(A) and 28(B), all the samples with an atomic ratio of magnesium to fluorine in the raw materials of Mg:F = 1:2 showed good cycle characteristics. Among them, Sample 7, which used 1 mol% MgO and 2 mol% LiF as the additive starting materials, showed the best cycle characteristics, and the energy density retention rate after 30 cycles was 93%. As shown in Figures 28(A) and 28(B), all the samples with an atomic ratio of magnesium to fluorine in the raw materials of Mg:F = 1:2 showed good cycle characteristics. Among them, Sample 7, which used 1 mol% MgO and 2 mol% LiF as the additive starting materials, showed the best cycle characteristics, and the energy density retention rate after 30 cycles was 93%.

[0316] As shown in Figures 28(A) and 28(B), all the samples with an atomic ratio of magnesium to fluorine in the raw materials of Mg:F = 1:2 showed good cycle characteristics. Among them, Sample 7, which used 1 mol% MgO and 2 mol% LiF as the additive starting materials, showed the best cycle characteristics, and the energy density retention rate after 30 cycles was 93%. As shown in Figures 28(A) and 28(B), all the samples with an atomic ratio of magnesium to fluorine in the raw materials of Mg:F = 1:2 showed good cycle characteristics. Among them, Sample 7, which used 1 mol% MgO and 2 mol% LiF as the additive starting materials, showed the best cycle characteristics, and the energy density retention rate after 30 cycles was 93%. As shown in Figures 28(A) and 28(B), all the samples with an atomic ratio of magnesium to fluorine in the raw materials of Mg:F = 1:2 showed good cycle characteristics. Among them, Sample 7, which used 1 mol% MgO and 2 mol% LiF as the additive starting materials, showed the best cycle characteristics, and the energy density retention rate after 30 cycles was 93%. As shown in Figures 28(A) and 28(B), all the samples with an atomic ratio of magnesium to fluorine in the raw materials of Mg:F = 1:2 showed good cycle characteristics. Among them, Sample 7, which used 1 mol% MgO and 2 mol% LiF as the additive starting materials, showed the best cycle characteristics, and the energy density retention rate after 30 cycles was 93%. As is also clear from Fig. 28(A), not only the cycle characteristics but also the energy density were good. There was.

Example

[0317] In this example, the results of comparing a positive electrode active material having a second region formed by segregation of magnesium with a positive electrode active material having a magnesium oxide layer formed by external coating are shown. As the positive electrode active material having a second region formed by segregation of magnesium, Sample 7 of Example 1 using 1 mol% MgO and 2 mol% LiF as starting materials was used. Used.

[0318] <Positive electrode active material having a second region formed by segregation> As the positive electrode active material having a second region formed by segregation of magnesium, Sample 7 of Example 1 using 1 mol% MgO and 2 mol% LiF as starting materials was used. Used. Used.

[0319] <Positive electrode active material having external coating MgO> As the positive electrode active material having a magnesium oxide layer formed by external coating, the positive electrode active materials of Sample 9 (comparative example) and Sample 10 (comparative example) obtained by coating magnesium oxide on lithium cobaltate using a polygonal barrel sputter were used. The production methods of Sample 9 (comparative example) and Sample 10 (comparative example) are described below. Lithium cobaltate manufactured by Nippon Chemical Industry Co., Ltd. (product name: C-10N) was used. For the polygonal barrel sputter, magnesium oxide was used as the target, and film formation was performed using 450 W of power and Ar and O2 as sputtering gases. The partial pressures of Ar and O2 were 0.6 Pa and 0.5 Pa, respectively. The treatment time was 36 minutes for Sample 9 and 180 minutes for Sample 10. (Comparative example) and Sample 10 (comparative example) were used. And the production methods of Sample 9 (comparative example) and Sample 10 (comparative example) are described below.

[0320] Lithium cobaltate manufactured by Nippon Chemical Industry Co., Ltd. (product name: C-10N) was used. For the polygonal barrel sputter, magnesium oxide was used as the target, and film formation was performed using 450 W of power and Ar and O2 as sputtering gases. The partial pressures of Ar and O2 were 0.6 Pa and 0.5 Pa, respectively. The treatment time was 36 minutes for Sample 9 and 180 minutes for Sample 10. As sputtering gases, Ar and O2 were used for film formation. .5 Pa. The treatment time was 36 minutes for Sample 9 and 180 minutes for Sample 10. .

[0321] After STEM observation was performed after the multi-angle barrel sputtering process, in Sample 9, a magnesium oxide layer of about 1 nm to 3 nm adhered to the surface of the positive electrode active material. Also, in Sample 10 a magnesium oxide layer of about 6 nm to 8 nm adhered to the surface of the positive electrode active material.

[0322] Thereafter, Samples 9 and 10 were heated at 800 °C for 2 hours in the same manner as the second heating described in Embodiment 1. The temperature was raised at 200 °C / h, and dry air with a dew point of -109 °C was flowed at 10 L / min. L / min was flowed.

[0323] The conditions of Sample 7, Sample 9 (comparative example), and Sample 10 (comparative example) to be compared in this example are shown in Table 5. are shown in Table 5.

[0324]

Table 5

[0325] <stem> The cross-sections of the positive electrode active materials of Sample 7 and Sample 10 (comparative example) were observed using STEM. The STEM images of Sample 7 having a second region formed by segregation are shown in FIGS. 29(A) and 29(B). The STEM images of Sample 10 (comparative example) having a magnesium oxide layer formed by external coating are shown in FIGS. 30(A) and 30(B). In Sample 7, it was possible to observe that the first region and the second region were different regions from the difference in image brightness. As shown in FIG. 29, in Sample 7 having a second region formed by segregation, a second region of about 1 nm to 2 nm was observed.

[0326] In Sample 7, it was possible to observe that the first region and the second region were different regions from the difference in image brightness. As shown in FIG. 29, in Sample 7 having a second region formed by segregation, a second region of about 1 nm to 2 nm was observed. In Sample 7 having a second region formed by segregation, a second region of about 1 nm to 2 nm was observed. In Sample 7 having a second region formed by segregation, a second region of about 1 nm to 2 nm was observed.

[0327] Also in Sample 10 (comparative example), as shown in FIG. 30, it was possible to observe that a magnesium oxide layer was formed on lithium cobaltate from the difference in image brightness. In Sample 10 (comparative example), a magnesium oxide layer of about 8 nm was observed. Also in Sample 10 (comparative example), as shown in FIG. 30, it was possible to observe that a magnesium oxide layer was formed on lithium cobaltate from the difference in image brightness. In Sample 10 (comparative example), a magnesium oxide layer of about 8 nm was observed. In Sample 10 (comparative example), a magnesium oxide layer of about 8 nm was observed.

[0328] In both Sample 7 and Sample 10 (comparative example), at least part of the arrangement of cations and anions between different layers was aligned, and it was observed that the crystal orientations of the first region and the second region were consistent. In both Sample 7 and Sample 10 (comparative example), at least part of the arrangement of cations and anions between different layers was aligned, and it was observed that the crystal orientations of the first region and the second region were consistent. In both Sample 7 and Sample 10 (comparative example), at least part of the arrangement of cations and anions between different layers was aligned, and it was observed that the crystal orientations of the first region and the second region were consistent.

[0329] <Charge and Discharge Characteristics> Using the positive electrode active materials of Sample 7, Sample 9 (comparative example), and Sample 10 (comparative example), secondary batteries were fabricated in the same manner as in Example 1, and the charge and discharge characteristics were evaluated. FIGS. 31(A), 31(B), and 31(C) show graphs of the charge and discharge characteristics of secondary batteries using the positive electrode active materials of Sample 7, Sample 9 (comparative example), and Sample 10 (comparative example), respectively. Using the positive electrode active materials of Sample 7, Sample 9 (comparative example), and Sample 10 (comparative example), secondary batteries were fabricated in the same manner as in Example 1, and the charge and discharge characteristics were evaluated. FIGS. 31(A), 31(B), and 31(C) show graphs of the charge and discharge characteristics of secondary batteries using the positive electrode active materials of Sample 7, Sample 9 (comparative example), and Sample 10 (comparative example), respectively. Using the positive electrode active materials of Sample 7, Sample 9 (comparative example), and Sample 10 (comparative example), secondary batteries were fabricated in the same manner as in Example 1, and the charge and discharge characteristics were evaluated. FIGS. 31(A), 31(B), and 31(C) show graphs of the charge and discharge characteristics of secondary batteries using the positive electrode active materials of Sample 7, Sample 9 (comparative example), and Sample 10 (comparative example), respectively. Using the positive electrode active materials of Sample 7, Sample 9 (comparative example), and Sample 10 (comparative example), secondary batteries were fabricated in the same manner as in Example 1, and the charge and discharge characteristics were evaluated. FIGS. 31(A), 31(B), and 31(C) show graphs of the charge and discharge characteristics of secondary batteries using the positive electrode active materials of Sample 7, Sample 9 (comparative example), and Sample 10 (comparative example), respectively.

[0330] As shown in FIG. 31, a sample having a second region formed by segregation of magnesium Sample 7 had a larger capacitance and better charge-discharge characteristics than sample 9 having a magnesium oxide layer formed by polygonal barrel sputtering and sample 10.

[0331] <Cycle characteristics> Next, the results of evaluating the cycle characteristics of secondary batteries using the positive electrode active materials of sample 7, sample 9 (comparative example), and sample 10 (comparative example) are shown in FIGS. 32(A) and 32(B). The cycle characteristic test was conducted in the same manner as in Example 1.

[0332] FIG. 32(A) is a graph of the energy density during charging at 4.6 V, and FIG. 32(B) is a graph of the energy density retention rate during charging at 4.6 V. As shown in FIG. 32(B), sample 7 having the second region formed by segregation showed extremely better cycle characteristics than sample 9 and sample 10 having a magnesium oxide layer formed by polygonal barrel sputtering. Also, as shown in FIG. 32(A), the energy density was also better for sample 7.

[0333] Thus, it was revealed that the second region formed by segregation of magnesium contributes to better charge-discharge characteristics and cycle characteristics than the magnesium oxide layer formed by polygonal barrel sputtering.

[0334] From these results, it was speculated that the region containing magnesium formed as a result of segregation of magnesium originally contained in the starting material to the surface contributes more to the stabilization of the crystal structure of lithium cobaltate than the magnesium oxide layer coated from the outside of the lithium cobaltate particles. ​​​​​​​​

Example

[0335] In this example, the characteristics of the positive electrode active material having the second region formed by the segregation of magnesium were clarified by various analyses.

[0336] <Positive electrode active material analyzed> Sample 7 of Example 1 using 1 mol% MgO and 2 mol% LiF as the added starting materials was used as the analysis sample of this example.

[0337] <STEM, FFT> The STEM-FFT images of the cross-section near the surface of the positive electrode active material of Sample 7 having the second region formed by segregation are shown in FIGS. 33 and 34. FIG. 33(A) is the STEM image near the surface of the positive electrode active material, and the FFT (Fast Fourier Transform ) image of the region indicated by FFT1 in FIG. 33(A) is FIG. 33(B). A part of the bright spots of the FFT image in FIG. 33(B) is shown in FIG. 33(C) and is referred to as A, B, C, and O.

[0338] Regarding the bright spots of the FFT image of the region indicated by FFT1, the measured values were OA with d = 0.2 0 nm, OB with d = 0.24 nm, and OC with d = 0.25 nm. Also, ∠AOB = 5 3°, ∠BOC = 74°, and ∠AOC = 127°.

[0339] This is from the data of magnesium oxide (MgO) in the ICDD (International Centre for Diffra ction Data) database (ICDD45-0945), where the d of OA (200) is 0.21 nm, the d of OB (1 -11) is 0.24 nm, the d of OC (-1-11) is 0.24 nm, and ∠AOB = 55 °. °, ∠BOC = 70°, and ∠AOC = 125°. Therefore, the region shown by FFT1 is a region having a rock-salt type crystal structure and was revealed to be an image of

[0011] incidence .

[0340] Fig. 34(A) is the same STEM image near the surface of the positive electrode active material as Fig. 33(A), and the FFT image of the region shown by FFT2 in Fig. 34( A) is Fig. 34(B). Some of the bright spots in the FFT image of Fig. 34(B) were named A, B, C, and O as shown in Fig. 34(C).

[0341] Regarding the bright spots in the FFT image of the region shown by FFT2, the measured values were, respectively, OA with d = 0.2 4 nm, OB with d = 0.20 nm, and OC with d = 0.45 nm. Also, ∠AOB = 2 5°, ∠BOC = 53°, and ∠AOC = 78°.

[0342] This is close to d = 0.24 nm for OA (101), d = 0.20 nm for OB ( 104), d = 0.47 nm for OC (003), ∠AOB = 25°, ∠BOC = 55°, and ∠AOC = 80° obtained from the data of lithium cobalt oxide (LiCoO2) in the ICDD database ( ICDD50 - 0653). Therefore, the region shown by FFT2 is a region having lithium cobalt oxide and was revealed to be an image of

[0010] incidence.

[0343] Also, from the STEM images of Fig. 33(A) and Fig. 34(A), it was observed that the brightness of the image was different between the first region and the second region, and furthermore, it was observed that the crystal orientations were consistent in the first region and the second region.

[0344] <stem-edx> Next, the results of analyzing the vicinity of the surface and crystal defects of Sample 7 using STEM-EDX are shown in FIGS. 35 to 37. The results are shown in FIGS. 35 to 37.

[0345] FIG. 35 shows the STEM-EDX analysis results of the vicinity of the surface of the positive electrode active material of Sample 7. FIG. 35 (A) is a STEM image, FIG. 35(B) is a mapping of magnesium, and FIG. 35(C) is a mapping of fluorine. is a mapping of fluorine.

[0346] Using the starting materials with 0.5 mol% MgO and 1 mol% LiF added in Example 1 than Sample 1 (FIG. 22), Sample 7 (FIG. 35) using the starting materials with 1 mol% MgO and 2 mol% LiF added showed clearer magnesium near the surface of the positive electrode active material. This supports the results of Example 1 that the more magnesium there is near the surface of the positive electrode active material, the better the cycle characteristics. are.

[0347] FIG. 36 is a cross-sectional TEM image of the vicinity of the crystal defect of the positive electrode active material of Sample 7. In the crystal defect 1001 in the figure, parts with different brightness from others regarded as crystal defects were observed.

[0348] The results of analyzing the part of the crystal defect 1001 in FIG. 36 using STEM-EDX are shown in FIG. 37. are shown.

[0349] FIG. 37(A-1) is a STEM image of the crystal defect 1001 part, FIG. 37(A-2) is a mapping of magnesium, FIG. 37(B-1) is a mapping of fluorine, and FIG. 37(B-2) is a mapping of zirconium. is a mapping of zirconium.

[0350] As shown in FIG. 37(A-2), in the crystal defect and its vicinity of the positive electrode active material of Sample 7, , segregation of magnesium was observed. Therefore, it was shown that Sample 7 is a positive electrode active material having a second region not only near the surface but also inside the sample. Also, as shown in Fig. 37(B-2), a large amount of segregation of zirconium was also observed in the second region inside. The process of mixing the starting materials is carried out by a ball mill, and since zirconium is used as the material of the ball mill, there is a possibility that zirconium has been mixed into Sample 7. Also, as shown in Fig. 37(B-1 ), almost no fluorine was detected in the second region inside, which was considered to be because fluorine, which is a light element, is difficult to detect by EDX. )

[0351] <tof-sims> Next, regarding the positive electrode active material of Sample 7 having the second region formed by segregation, mag To examine the depth direction distributions of nesium and fluorine, analysis was performed using ToF-SIMS and the results are shown in Fig. 38.

[0352] Multiple particles of the positive electrode active material were used as samples, and analysis was performed in the depth direction from the surface of the positive electrode active material while alternately repeating ToF-SIMS analysis and sputtering. The measuring device used was TOF.S IMS5-300 (manufactured by ION-TOF), and Cs was used as the ion source for sputtering. The analysis was also performed in a range of about 50 μm square.

[0353] Fig. 38 shows a graph with the horizontal axis being the number of measurements (number of cycles) for the intensities of magnesium oxide ions ([MgO2] 2- ) and fluorine ions (F - ). In this measurement, since analysis is being performed on negative ions, the distribution of magnesium is evaluated by the intensity of [MgO2]

[0354] 2- . Each intensity is normalized with the maximum value being 1.

[0355] As shown in Fig. 38, in Sample 7 having the second region formed by the segregation of magnesium, it is clear that the depth direction distributions and peaks of magnesium and fluorine overlap.

[0355] <xps> Next, regarding the positive electrode active material of Sample 7, the results of analysis using XPS before and after the second heating are shown in Table 6 and FIG. 39. The XPS analysis was performed in the same manner as in Example 1.

[0356] The results of quantifying the concentration of each element in Sample 7 using XPS are shown in Table 6. The quantification accuracy is about ±1 atomic%, and the detection limit is about 1 atomic% depending on the element. Also, for Ca, the Mg Auger peak separated by waveform is removed, so the quantification error is larger than usual.

[0357]

Table 6

[0358] The quantified values in Table 6 are the values when the total amount of lithium, cobalt, titanium, oxygen, carbon, fluorine, sulfur, calcium, magnesium, sodium, and zirconium is 100 atomic% in the range from a depth of 4 nm to 5 nm from the surface to the center of the positive electrode active material where XPS analysis is possible. c%.

[0359] As shown in Table 6, in the range from a depth of 4 nm to 5 nm from the surface to the center of Sample 7 having the second region formed by segregation after the second heating, when the total amount of lithium, cobalt, titanium, oxygen, carbon, fluorine, sulfur, calcium, magnesium, sodium, and zirconium is 100%, the magnesium concentration is 5.5 atomic %, and the fluorine concentration is 1.4 atomic%.

[0360] In addition, when the total amount of lithium, cobalt, oxygen, fluorine, and magnesium is 100%, ​​​​​​​​The calculated concentration of magnesium was 6.7% and that of fluorine was 1.7%. .

[0361] Also, the ratio of the concentrations of magnesium and fluorine was within the range of Mg:F = y:1 (3 ≤ y ≤ 5), and more precisely, it was about Mg:F = 3.9:1.

[0362] Next, the binding state of fluorine in Sample 7 after the second heating was analyzed by surface XPS analysis. The results are shown in Fig. 39. As a comparative example, the results of a sample prepared in the same manner as Sample 7 except that 10 mol% LiF was used as the additive starting material and magnesium was not added are shown. Also, the XPS spectra of standard samples of MgF2 and LiF are shown together.

[0363] As shown in Fig. 39, in the sample using 10 mol% LiF as the additive starting material and not adding magnesium, the peak of the binding energy of fluorine was about 685 eV, which coincides with that of LiF, and it was considered that LiF was the main binding state of fluorine present in the surface layer of the positive electrode active material. On the other hand, in Sample 7 using 1 mol% MgO and 2 mol% LiF as the additive starting material and having the second region, the peak of the binding energy of fluorine present in the surface layer of the positive electrode active material was above 682 eV and less than 685 eV, more precisely 684.3 eV, which did not coincide with either MgF2 or LiF. That is, it was inferred that the fluorine in the second region of the positive electrode active material existed in a binding state other than MgF2 and LiF.

[0364]

Example

[0364] In this example, when producing a positive electrode active material having a second region formed by segregation, the first The results of the study on the temperature of the second heating and the atmosphere during the second heating will be described. .

[0365] ≪Temperature of the second heating≫ <Preparation of the positive electrode active materials of Samples 11 to 13> Positive electrode active materials of Samples 11 to 13 were prepared by changing the temperature of the second heating. All starting materials were lithium carbonate and cobalt oxide as common starting materials, and 1 mol% MgO and 2 mol% LiF were used as additional starting materials.

[0366] For Sample 11, the temperature of the second heating was 700 °C, for Sample 12 it was 900 °C, and for Sample 13 it was 1000 °C. Otherwise, the positive electrode active materials were prepared in the same manner as Sample 7 of Example 1. The temperature of the second heating of Sample 7 is 800 °C. The temperature of the second heating of each sample is shown in Table 7.

[0367]

Table 7

[0368] Using the positive electrode active materials of Sample 7 and Samples 11 to 13, secondary batteries were prepared in the same manner as in Example 1, and the cycle characteristics were evaluated. The cycle characteristics of Sample 7 and Samples 11 to 13 are shown in Fig. 40. The charge / discharge conditions were the same as in Example 1.

[0369] Fig. 40(A) is a graph of the energy density during charging at 4.6 V, and Fig. 40(B) is a graph of the energy density retention rate during charging at 4.6 V. As shown in Fig. 40(B), Sample 7 with the second heating temperature of 800 °C showed the best cycle characteristics. Samples 11 with the second heating temperature of 70 0 °C and Sample 12 with the second heating temperature of 900 °C had the next best cycle This was the characteristic. Even for Sample 13 with the second heating temperature set at 1000 °C, after 20 cycles the energy density retention rate was 76%. This is compared with Sample 6 without the added starting material shown in Fig. 26 where the energy density retention rate after 20 cycles was 63%. It can be said that good cycle characteristics were shown.

[0370] From this, it became clear that the temperature of the second heating is preferably 700 °C or higher and 1000 °C or lower, more preferably 700 °C or higher and 9 00 °C or lower, and even more preferably about 800 °C.

[0371] ≪Atmosphere of the second heating≫ <Preparation of the positive electrode active material for Samples 14 to 16> The positive electrode active materials for Samples 14 to 1 6 were prepared with the atmosphere of the second heating changed from dry air to 100% oxygen. All starting materials were lithium carbonate and cobalt oxide as common starting materials, and 1 mol% MgO and 2 mol% LiF as added starting materials were used. The positive electrode active materials were prepared in the same manner as in Samples 7, 12, and 13, except that the second heating was changed to an oxygen atmosphere.

[0372] Using the positive electrode active materials of Samples 14 to 16, secondary batteries were fabricated in the same manner as in Example 1, and the cycle characteristics were evaluated together with Samples 7, 12, and 13.

[0373] Graphs of the energy density and cycle characteristics for Samples 7, 12 to 16 are shown in Figs. 41 and 42. Fig. 41 shows the energy density, and Fig. 42 shows the cycle characteristics graph. Figs. 41(A) and 42(A) are for the case where the temperature of the second heating was set at 800 °C ​​Sample 14 and Sample 7, Figures 41(B) and 42(B) are for the samples heated to 900 °C. Sample 15 and Sample 12, Figures 41(C) and 42(C) show the cycle characteristics of Sample 16 and Sample 13. Also, Table 8 shows the atmosphere of the second heating and the temperature of the

[0374]

Table 8

[0375] As shown in Figure 41, when the second heating is carried out at 800 °C, 900 °C and 1000 °C, the second heating shows better cycle characteristics when carried out in an oxygen atmosphere than in dry air.

[0376] In this example, the cycle characteristics were compared when magnesium and fluorine were used as the additive starting materials and

[0377] when elements other than magnesium and fluorine were used. ≪Comparison between fluorine and chlorine≫ First, the cycle characteristics were compared when magnesium and

[0378] <Preparation of the positive electrode active material of Samples 17 and 18> For Sample 7, 1 mol% MgO and 2 mol% LiF were used with respect to cobalt as the additive starting materials. For Sample 17, 1 mol% MgO, 1 mol% LiF and 1 mol% LiCl were used. For Sample 18, as a comparative example, 1 mol% MgO and 2 mol% LiCl were used. For No additives were added.

[0379] Samples 7, 17, 18, and 6 were treated in the same manner as in Example 2. Positive electrode active materials were prepared in the same manner, secondary batteries were fabricated using them, and the cycle characteristics were evaluated. The cycle characteristic test was carried out in the same manner as in Example 1.

[0380] <Cycle characteristics> Table 9 shows the starting materials added to each sample and the energy density retention after 20 cycles. Shows the rate.

[0381] [Table 9]

[0382] As shown in Table 9, when chlorine is added instead of fluorine, the cycle characteristics tend to decrease. However, sample 17, which contains 1% each of fluorine and chlorine, showed a The energy density retention rate was over 80%. This was due to the presence of magnesium, fluorine, and chlorine. Compared with sample 6 which did not have either of these, the cycle characteristics were good.

[0383] <Comparison between magnesium and other metals> Next, we used magnesium and fluorine as starting materials, and replaced magnesium with other materials. The cycle characteristics when metals were used were compared.

[0384] <Preparation of Positive Electrode Active Materials for Samples 19 to 29> As a sample using magnesium and fluorine as the added starting material, Sample 7 of Example 1 Sample 19 is a comparative example, and contains 1 mol% MgO, 1 mol% TiO2 and 2mol% LiF were used. Sample 20 is a comparative example. ol% ZrO2 and 2 mol% LiF were used. As a comparative example, Sample 21 used 1 mo l% TiO2 and 2 mol% LiF. As a comparative example, Sample 22 used 1 mol % V2O5 and 2 mol% LiF. As a comparative example, Sample 23 used 1 mol% ZnO and 2 mol% LiF. As a comparative example, Sample 24 used 1 mol% C aO and 2 mol% LiF. As a comparative example, Sample 25 used 1 mol% Al2 O3 and 2 mol% LiF. As a comparative example, Sample 26 used 1 mol% MoO 2 and 2 mol% LiF. As a comparative example, Sample 27 used 1 mol% SrO, 2 mol% LiF. As a comparative example, Sample 28 used 1 mol% NaF, 1 m ol% LiF. As a comparative example, Sample 29 used 1 mol% BaO, 2 mol % LiF. Also, as a comparative example without adding any fluorine or metal, Sample 6 of Example 1 was used.

[0385] For Samples 6, 7, and Samples 19 to 29, the positive electrode active materials were prepared in the same manner as in Example 1, and secondary batteries using them were fabricated and their cycle characteristics were evaluated .

[0386] <Cycle Characteristics> Table 10 shows the added starting materials of each sample and the energy density retention rates after 20 cycles for each of them.

[0387]

Table 10

[0388] As shown in Table 10, when other metals are added instead of magnesium, the cycle characteristics deteriorate. There was a tendency.

[0389] From these results, it became clear that it is extremely effective to use a combination of magnesium and fluorine as the additive starting materials. It was found that this is extremely effective.

[0390] From the previous examples, by adding magnesium and fluorine as the starting materials for the positive electrode active material, it became clear that magnesium segregates on the surface of the positive electrode active material. Also, because it has a good coating layer formed by segregation, it became clear that it becomes a positive electrode active material with high capacity and excellent cycle characteristics. It became clear that this is the case.

[0391] Since a secondary battery having such a positive electrode active material has high capacity and long life, it is suitable for portable electronic devices. Furthermore, if it is applied to vehicles such as automobiles, it is also possible to avoid using commercial power sources during peak power demand times, and it can also contribute to energy conservation and reduction of carbon dioxide emissions. This can also contribute to reducing carbon dioxide emissions.

Example

[0392] In this example, a positive electrode active material to which nickel, manganese, and cobalt were applied as transition metals in the first region was prepared, and the evaluation results will be described.

[0393] <Sample 31, Sample 32> Sample 31 having magnesium and fluorine and Sample 32 having no magnesium and fluorine as a comparative example were prepared. This was done.

[0394] Sample 31 was a sample in which 1 atomic% of magnesium and 2 atomic% of fluorine were added to the sum of nickel, manganese, and cobalt as starting materials. Also, as the starting materials, this was the case. The atomic ratio of nickel, manganese, and cobalt was set to Ni:Mn:Co = 1:1:1.

[0395] First, lithium carbonate (Li2CO3) was used as the lithium source of the common starting materials. Nickel oxide (NiO) was used as the nickel source. Manganese dioxide (MnO2) was used as the manganese source. Cobalt oxide (Co3O4) was used as the cobalt source. Magnesium oxide (MgO) was used as the magnesium source of the additional starting materials. Lithium fluoride (LiF) was used as the fluorine source.

[0396] Each starting material was weighed so as to have an atomic ratio of LiCo 0.323 Mn 0.333 Ni 0.333 O2+MgO 0.01 LiF 0.02 .

[0397] Next, the weighed starting materials were mixed using a ball mill.

[0398] Next, the mixed starting materials were fired. The firing was carried out at 950 °C for 10 hours, with a heating rate of 200 °C / h, and a flow rate of 10 L / min in a dry atmosphere.

[0399] In the above process, composite oxide particles containing lithium, nickel, manganese, cobalt, magnesium, and fluorine were synthesized.

[0400] The synthesized composite oxide particles were cooled to room temperature.

[0401] Next, the composite oxide particles were heated. The heating was carried out at 800 °C (heating rate 200 °C / hour) for 2 hours in a dry air atmosphere.

[0402] The heated powder was cooled to room temperature and subjected to a crushing process. The crushing process was carried out by sieving, and a sieve with a mesh opening of 53 μm was used. The particles obtained after the crushing process were used as the positive electrode active material of Sample 31.

[0403] The particles obtained after the crushing process were used as the positive electrode active material of Sample 31.

[0404] Sample 32 was weighed so that the atomic ratio of each starting material was LiCo 0.333 Mn 0.333 Ni 0.333 O2. Further, firing was carried out at 1000 °C. Otherwise, it was prepared in the same manner as Sample 31. The preparation conditions of Sample 31 and Sample 32 are shown in Table 11. The preparation conditions of Sample 31 and Sample 32 are shown in Table 11.

[0405] The preparation conditions of Sample 31 and Sample 32 are shown in Table 11.

[0406]

Table 11

[0407] <Cycle characteristics> Next, CR2032 type (diameter 20 mm, height 3.2 mm) coin-type secondary batteries were fabricated using the positive electrode active materials of Sample 31 and Sample 32 prepared as described above, and their cycle characteristics were evaluated. For the positive electrode, a slurry obtained by mixing the positive electrode active materials of Sample 31 and Sample 32, acetylene black (AB ) and polyvinylidene fluoride (PVDF) at a weight ratio of positive electrode active material: AB: PVDF = 95: 2.5

[0408] : 2.5 was applied to a current collector of aluminum foil. N-methyl-2-pyrrolidone (NMP) was used as the solvent. For the counter electrode, lithium metal was used. For the counter electrode, lithium metal was used. For the counter electrode, lithium metal was used.

[0409] For the counter electrode, lithium metal was used.

[0410] The electrolyte used contains 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of EC:DEC = 3:7, to which vinylene carbonate (VC) is added at 2% by weight. C:DEC = 3:7 (volume ratio), to which vinylene carbonate (VC) is added at 2% by weight. was used.

[0411] The positive electrode can and the negative electrode can used were made of stainless steel (SUS).

[0412] The measurement temperature for the cycle performance test was 25°C. Charging was performed at a constant current of 68.5 mA / g per active material weight and an upper limit voltage of 4.6 V, and then constant voltage charging was performed until the current density reached 1.4 mA / g. Discharging was performed at a constant current of 68.5 mA / g per active material weight and a lower limit voltage of 2.5 V. .5 mA / g at a constant current and an upper limit voltage of 4.6 V, and then constant voltage charging was performed until the current density reached 1.4 mA / g. Discharging was performed at a constant current of 68.5 mA / g per active material weight and a lower limit voltage of 2.5 V. was performed.

[0413] The discharge capacity at 4.6 V charging and the discharge capacity retention rate of the secondary battery using the positive electrode active materials of Sample 31 and Sample 32 are shown in Fig. 43(A) and Fig. 43(B), respectively. are shown in Fig. 43(A) for the discharge capacity during charging at 4.6 V and in Fig. 43(B) for the discharge capacity retention rate.

[0414] Compared with Sample 32 to which magnesium and fluorine were not added, Sample 31 to which magnesium and fluorine were added showed extremely good cycle performance. showed extremely good cycle performance.

[0415] Next, the results of various analyses of Sample 31 are shown below.

[0416] <stem-fft> STEM images of the cross-section near the surface of the positive electrode active material of Sample 31 are shown in FIGS. 44 and 45. FIG. 44(B) is an enlarged STEM image of a part of FIG. 44(A). FIGS. 45(A) and 45(B) are HAADF-STEM images of a part of FIG. 44(A) enlarged.

[0417] As is clear from FIG. 45, in the region about 0.5 nm from the surface of the positive electrode active material, a state where the brightness is different from other regions was observed. This was considered to be because there was a lot of magnesium, an element lighter than the transition metal. Also, in the region from about 0.5 nm to about 5 nm from the surface of the positive electrode active material, a state where the regularity was different from the internal region was observed. This was considered to be because the crystal orientation was different between the region from about 0.5 nm to about 5 nm from the surface and the region inside it.

[0418]

[0419] FIG. 46(A) is a bright-field STEM image of the same range as FIG. 45(B). The FFT (Fast Fourier Transform) image of the region indicated by FFT1 in FIG. 46(A) is FIG. 46(B). As shown in FIG. 46(B) for some of the bright spots of the FFT1 image, they were named A, B, C, and O.

[0420] Regarding the bright spots of the FFT image of the region indicated by FFT1, the measured values were respectively, OA was d = 0.2 2 nm, OB was d = 0.25 nm, and OC was d = 0.23 nm. Also, ∠AOB = 5 8°, ∠BOC = 69°, and ∠AOC = 127°.

[0421] This is the data of magnesium oxide (MgO) in the ICDD (International Centre for Diffra ction Data) database (I ​​​​​Obtained from CDD45 - 0945), for OA(200), d = 0.21nm, for OB(1 -11), d = 0.24nm, for OC(-1 - 11), d = 0.24nm, ∠AOB = 55 °, ∠BOC = 70°, ∠AOC = 125° are close. Therefore, the region shown by FFT1 is a region with a rock - salt - type crystal structure and is presumed to be the image of

[0011] incidence.

[0422] Also, the FFT image of the region shown by FFT2 in Fig. 46(A) is Fig. 46(C). Some of the bright spots in the FFT 2 image are denoted as A, B, C, and O as shown in Fig. 46(C).

[0423] Regarding the bright spots in the FFT image of the region shown by FFT2, the measured values are respectively, for OA, d = 0.2 5nm, for OB, d = 0.21nm, for OC, d = 0.49nm. Also, ∠AOB = 2 6°, ∠BOC = 57°, ∠AOC = 83°.

[0424] This is close to the data of lithium cobalt oxide (LiCoO2) in the ICDD database ( ICDD50 - 0653), for OA(10 - 11), d = 0.24nm, O B(10 - 14), d = 0.20nm, OC(0003), d = 0.47nm, ∠AOB = 25°, ∠BOC = 55°, ∠AOC = 80°. Therefore, the region shown by FFT2 is a region with a layered rock - salt - type crystal structure and is presumed to be the image of [-12 - 10] incidence.

[0425] Also, the FFT image of the region shown by FFT3 in Fig. 46(A) is Fig. 46(D). Some of the bright spots in the FFT3 image are denoted as A, B, C, and O as shown in Fig. 46(D). .

[0426] ​Regarding the bright spots in the FFT image of the region shown by FFT3, the measured values were as follows: for OA, d = 0.2 1 nm, for OB, d = 0.26 nm, and for OC, d = 0.24 nm. Also, ∠AOB = 5 6°, ∠BOC = 72°, and ∠AOC = 128°.

[0427] This is close to the values obtained from the data of lithium cobalt oxide (LiCoO2) in the ICDD database ( ICDD50 - 0653): for OA (01 - 14), d = 0.20 nm, for O B (10 - 1 - 2), d = 0.23 nm, for OC (1 - 102), d = 0.23 nm, ∠A OB = 55°, ∠BOC = 70°, and ∠AOC = 125°. Therefore, the region shown by FFT2 is inferred to be a region with a layered rock - salt - type crystal structure and is the image of [02 - 21] incidence.

[0428] That is, it was clarified that the regions shown by FFT2 and FFT3 have the same layered rock - salt - type crystal structure but different crystal axis directions.

[0429] Also, in the observable ranges of FIGS. 45(A), 45(B), and 46(A), it was observed that the crystal orientations were approximately the same even though the brightness was different.

[0430] Fig. 47 shows the STEM image of the structure near the surface of the positive electrode active material inferred from the results of STEM - FFT together. In Fig. 47, M represents either nickel, manganese, or cobalt.

[0431] FFT3, which is the region inside the positive electrode active material, has a layered rock - salt - type crystal structure. Also, it is the image of [02 - 21] incidence where lithium and M atoms are observed overlapping.

[0432] ​​In addition, FFT2, which is the region of the surface layer of the positive electrode active material, has a layered rock salt-type crystal structure. Also, in the image of [-12-10] incidence, it is possible to observe the repetition of the layer of oxygen atoms, the layer of M (any one of nickel, manganese, and cobalt) atoms, and the layer of lithium atoms. In the bright-field STEM image, the repetition of the dark and bright layers is considered to be due to the repetition of the layer of M and the layers of oxygen and lithium. That is, FFT3 and FFT2 have the same layered rock salt-type crystal structure, but the directions of the crystal axes are different.

[0433] In addition, FFT1, which is a region closer to the surface than FFT2 in the region of the surface layer of the positive electrode active material, has a rock salt-type crystal structure and is an image of

[0011] incidence.

[0434] <edx> Next, the cross section near the surface of the positive electrode active material of sample 31 was analyzed using EDX. 48 and 49.

[0435] Fig. 48(A-1) is a HAADF-STEM image, Fig. 48(A-2) is an oxygen mapping. 48(B-1) is the mapping of magnesium, and 48(B-2) is the mapping of fluorine. Also, Figure 49(A-1) is the same HAADF-STEM image as Figure 48(A-1), and Figure 49 (A-2) is the mapping of manganese, Fig. 49 (B-1) is the mapping of nickel, Fig. 49 (B-2) is the mapping of cobalt.

[0436] First, from Figure 48(B-1), magnesium is concentrated in a region of about 3 nm from the surface of the positive electrode active material. It was observed that the ion exchange reaction was being analyzed. From the comparison of -2), it can be seen that there is less manganese in the surface layer of the positive electrode active material than in the interior, and It was observed that there was a region with a high concentration of cobalt and Cr. This region was about 5 nm from the surface. This region almost overlaps with the region in which a different regularity from the interior was observed in the STEM image.

[0437] Therefore, in sample 31, the positive electrode active material has a region having magnesium in the surface layer portion, and It was confirmed that the positive electrode active material had a region with a low manganese content in a part of the .

[0438] Considering the above results, the molar ratio of the starting material is LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2 A sample made by heating at 800℃ with +1mol%MgO+2mol%LiF It was revealed that the positive electrode active material No. 31 has the following characteristics.

[0439] First, in the positive electrode active material of Sample 31, there exists a second region having magnesium oxide in the surface layer part. Inside, there is a region having LiNi x Mn y Co z O2 (x + y + z = 1) with a layered rock salt-type crystal structure in a part closer to the center, and a region having LiNi with a layered rock salt-type crystal structure in a part closer to the surface. a Mn b Co c O2 (a + b + c = 1). It has these.

[0440] The internal LiNi x Mn y Co z O2 and LiNi a Mn b Co c O2 have the same layered rock salt-type crystal structure, but the directions of the crystal axes may be different.

[0441] Also, regarding the content ratios of the respective elements, y > b, and the content ratio of manganese to the sum of nickel, manganese, and cobalt may be low in the region closer to the surface. When the positive electrode active material of Sample 31 having the above characteristics is used in a secondary battery, it exhibits extremely good

[0442] cycle characteristics.

Example

Example

[0443] In this example, the results of analyzing the positive electrode active material prepared by applying cobalt as a transition metal and adding magnesium and fluorine to the starting materials using EELS will be described. For the positive electrode active material prepared by using 1 mol% MgO and 2 mol% LiF as the additive starting materials in Example 1, it will be described.

[0444] Sample 1 of Example 1 using 1 mol% MgO and 2 mol% LiF as the additive starting materials Ple 7 was used as the analytical sample in this example.

[0445] The state of cobalt at six analysis points, *1 to *6, in the cross section of sample 7 was analyzed by EELS. FIG. 50 shows the vicinity of the surface of the positive electrode active material of sample 7 used in the EELS analysis. The cross-sectional STEM image is shown with *1 (depth of about 1 nm from the surface) and *2 (depth of about 2.5 nm from the surface). The analysis points are shown at *3 (approximately 5 nm) and *4 (approximately 10 nm from the surface of the positive electrode active material). m, *5 is approximately 100 nm from the surface of the positive electrode active material, *6 is near the center of the particle of the positive electrode active material .

[0446] The EELS spectrum intensity ratios of the cobalt L2 and L3 levels at each analysis point are shown in Table 1. 2 and Figure 51. The higher the L3 / L2 ratio, the lower the valence of cobalt.

[0447] [Table 12]

[0448] As is clear from Table 12 and FIG. 51, the L3 of the analysis point *1 closest to the surface of the positive electrode active material The highest L3 / L2 was 4.6. Also, the L3 / L2 from analysis point *2 to analysis point *6 was 4.6. *It was lower than 1 and in the range of 2.9 to 3.2, so no significant difference was observed.

[0449] From these results, it is clear that at the analysis point*1, cobalt exists in the divalent form as cobalt oxide (CoO). It was estimated that there was a lot of cobalt. In addition, from analysis point *2 to analysis point *6, lithium cobalt oxide It was speculated that most of the cobalt exists in trivalent form as lithium (LiCoO2). [Explanation of symbols]

[0450] 100 Cathode active material 101 First region 102 Second region 103 Third region 200 Active material layer 201 Graphene compound 211a Positive electrode 211b Negative electrode 212a Lead 212b Lead 214 Separator 215a Junction 215b Junction 217 Fixing member 250 Battery 251 Outer package 261 Bending part 262 Sealing part 263 Sealing part 271 Ridge line 272 Valley line 273 Space 300 Secondary battery 301 Positive electrode can 302 Negative electrode can 303 Gasket 304 Positive electrode 305 Positive electrode current collector 306 Positive electrode active material layer 307 Negative electrode 308 Negative electrode current collector 309 Negative electrode active material layer 310 Separator 500 Secondary battery 501 Positive electrode current collector 502 Positive electrode active material layer 503 Positive electrode 504 Negative electrode current collector 505 Negative electrode active material layer 506 Negative electrode 507 Separator 508 Electrolyte 509 Outer package 510 Positive electrode lead electrode 511 Negative electrode lead electrode 600 Secondary battery 601 Positive electrode cap 602 Battery can 603 Positive terminal 604 Positive electrode 605 Separator 606 Negative electrode 607 Negative terminal 608 Insulating plate 609 Insulating plate 611 PTC element 612 Safety valve mechanism 900 Circuit board 910 Label 911 Terminal 912 Circuit 913 Secondary battery 914 Antenna 915 Seal 916 Layer 917 Layer 918 Antenna 920 Display device 921 Sensor 922 Terminal 930 Housing 930a Housing 930b Housing 931 Negative electrode 932 Positive electrode 933 Separator 950 Wound body 951 Terminal 952 Terminal 980 Secondary battery 993 Wound body 994 Negative electrode 995 Positive electrode 996 Separator 997 Lead electrode 998 Lead electrode 1001 Crystal defect 7100 Portable display device 7101 Housing 7102 Display section 7103 Operation button 7104 Secondary battery 7200 Portable information terminal 7201 Housing 7202 Display section 7203 Band 7204 Buckle 7205 Operation Button 7206 Input / Output Terminal 7207 Icon 7300 Display Device 7304 Display Unit 7400 Mobile Phone 7401 Housing 7402 Display Unit 7403 Operation Button 7404 External Connection Port 7405 Speaker 7406 Microphone 7407 Secondary Battery 7408 Lead Electrode 7409 Current Collector 8000 Display Device 8001 Housing 8002 Display Unit 8003 Speaker Unit 8004 Secondary Battery 8021 Charging Device 8022 Cable 8024 Secondary Battery 8100 Lighting Device 8101 Housing 8102 Light Source 8103 Secondary Battery 8104 Ceiling 8105 Side Wall 8106 Floor 8107 Window 8200 Indoor Unit 8201 Housing 8202 Air Outlet 8203 Secondary Battery 8204 Outdoor Unit 8300 Electric Refrigerator 8301 Housing 8302 Refrigerator Door 8303 Freezer Door 8304 Secondary Battery 8400 Automobile 8401 Headlight 8406 Electric Motor 8500 Automobile 8600 Scooter 8601 Side Mirror 8602 Secondary Battery 8603 Direction Indicator 8604 Under-seat Storage 9600 Tablet-type Terminal 9625 Switch 9626 Switch 9627 Power Switch 9628 Operation Switch 9629 Fastener 9630 Housing 9630a Housing 9630b Housing 9631 Display Unit 9633 Solar Cell 9634 Charge and Discharge Control Circuit 9635 Energy Storage Element 9636 DC-DC Converter 9637 Converter 9640 Movable Part< / edx> < / xps> ​​ ​​ < / stem>

Claims

1. having a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode having a positive electrode active material containing lithium cobaltate, the negative electrode having a negative electrode active material containing carbon, the positive electrode active material having a first region and a second region outside the first region, the first region having lithium, cobalt, and oxygen, the second region having magnesium, fluorine, and oxygen, the peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, the second region exists in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak, When a coin-type secondary battery produced using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium-ion secondary battery.

2. having a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode having a positive electrode active material containing lithium cobaltate, the negative electrode having a negative electrode active material containing carbon, the positive electrode active material having a first region existing inside and a second region existing in the surface layer portion, the first region having lithium, cobalt, and oxygen, the second region having magnesium, fluorine, and oxygen, the peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, The second region is present in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged up to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then by constant voltage charging, and then discharged down to a lower limit voltage of 2.5 V by constant current discharging, and the charge-discharge cycle is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium ion secondary battery.

3. A positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region and a second region outside the first region. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by the line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region is present in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged up to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then by constant voltage charging, and then discharged down to a lower limit voltage of 2.5 V by constant current discharging, and the charge-discharge cycle is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. A lithium ion secondary battery.

4. A positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the magnesium concentration detected by line analysis of STEM-EDX for the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the magnesium concentration detected by the line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the 1st cycle. A lithium-ion secondary battery.

5. It has a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region and a second region outside the first region. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the magnesium concentration detected by line analysis of STEM-EDX for the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the magnesium concentration detected by the line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the above-mentioned positive electrode and lithium metal is charged at a temperature of 25°C by constant current charging up to an upper limit voltage of 4.6 V and then by constant voltage charging, and then discharged by constant current discharging down to a lower limit voltage of 2.5 V, and the charge-discharge cycle is repeated, the energy density in the first cycle is 800 mWh / g or more per unit weight of the active material, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle. Lithium-ion secondary battery.

6. A lithium-ion secondary battery comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion. The first region contains lithium, cobalt, and oxygen. The second region contains magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the above-mentioned positive electrode and lithium metal is charged at a temperature of 25°C by constant current charging up to an upper limit voltage of 4.6 V and then by constant voltage charging, and then discharged by constant current discharging down to a lower limit voltage of 2.5 V, and the charge-discharge cycle is repeated, the energy density in the first cycle is 800 mWh / g or more per unit weight of the active material, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle. Lithium-ion secondary battery.

7. A lithium-ion secondary battery comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon, The positive electrode active material has a first region and a second region outside the first region, The first region has lithium, cobalt, and oxygen, The second region has magnesium, fluorine, and oxygen, The peak of the concentration of magnesium detected by line analysis of STEM-EDX for the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, The second region exists in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak, The first region has a layered rock salt-type crystal structure, The second region has a rock salt-type crystal structure, The crystal orientations of the first region and the second region are the same or approximately the same as each other, When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less, A lithium ion secondary battery.

8. A positive electrode, a negative electrode, and an electrolytic solution, The positive electrode has a positive electrode active material containing lithium cobaltate, The negative electrode has a negative electrode active material containing carbon, The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion, The first region has lithium, cobalt, and oxygen, The second region has magnesium, fluorine, and oxygen, The peak of the concentration of magnesium detected by line analysis of STEM-EDX for the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, The second region is present in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same or substantially the same as each other. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current up to an upper limit voltage of 4.6 V and then charged at a constant voltage at a temperature of 25°C, and a charge-discharge cycle of discharging at a constant current down to a lower limit voltage of 2.5 V is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium-ion secondary battery.

9. A positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region and a second region outside the first region. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by the line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region is present in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same or substantially the same as each other. When a coin-type secondary battery manufactured using the positive electrode and lithium metal is charged at a temperature of 25°C by constant current charging up to an upper limit voltage of 4.6 V and then by constant voltage charging, and discharged by constant current discharging down to a lower limit voltage of 2.5 V, and the charge-discharge cycle is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the 1st cycle. Lithium ion secondary battery.

10. It has a positive electrode, a negative electrode, and an electrolyte. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same or substantially the same as each other. When a coin-type secondary battery manufactured using the positive electrode and lithium metal is charged at a temperature of 25°C by constant current charging up to an upper limit voltage of 4.6 V and then by constant voltage charging, and discharged by constant current discharging down to a lower limit voltage of 2.5 V, and the charge-discharge cycle is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the 1st cycle. Lithium ion secondary battery.

11. It has a positive electrode, a negative electrode, and an electrolyte. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region and a second region outside the first region. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same or substantially the same as each other. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current up to an upper limit voltage of 4.6 V and then charged at a constant voltage at a temperature of 25°C, and then discharged at a constant current down to a lower limit voltage of 2.5 V, and the charge-discharge cycle is repeated, the energy density in the first cycle is 800 mWh / g or more per active material weight, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle. A lithium-ion secondary battery.

12. It has a positive electrode, a negative electrode, and an electrolyte. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX on the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, The second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak, The first region has a layered rock salt-type crystal structure, The second region has a rock salt-type crystal structure, The crystal orientations of the first region and the second region are the same or substantially the same as each other, When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and the charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density in the first cycle is 800 mWh / g or more per unit weight of the active material, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle, A lithium-ion secondary battery.

13. A positive electrode, a negative electrode, and an electrolytic solution, The positive electrode includes a positive electrode active material containing lithium cobaltate and a conductive assistant containing carbon fibers, The negative electrode includes a negative electrode active material containing carbon, The positive electrode active material has a first region and a second region outside the first region, The first region contains lithium, cobalt, and oxygen, The second region contains magnesium, fluorine, and oxygen, The peak of the concentration of magnesium detected by line analysis of STEM-EDX on the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, The second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak, When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current to a lower limit voltage of 2.5 V is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium-ion secondary battery.

14. comprising a positive electrode, a negative electrode, and an electrolytic solution; the positive electrode comprising a positive electrode active material containing lithium cobaltate and a conductive assistant containing carbon fiber; the negative electrode comprising a negative electrode active material containing carbon; the positive electrode active material having a first region present inside and a second region present in a surface layer portion; the first region containing lithium, cobalt, and oxygen; the second region containing magnesium, fluorine, and oxygen; a peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to a cross-section of the positive electrode active material is present from the surface of the positive electrode active material to a depth of 2 nm; the second region is present in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak; When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current to a lower limit voltage of 2.5 V is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium-ion secondary battery.

15. comprising a positive electrode, a negative electrode, and an electrolytic solution; the positive electrode comprising a positive electrode active material containing lithium cobaltate and a conductive assistant containing carbon fiber; the negative electrode comprising a negative electrode active material containing carbon; the positive electrode active material having a first region and a second region outside the first region; The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX for the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25 °C and then charged at a constant voltage, and then discharged to a lower limit voltage of 2.5 V by constant current discharge, and the charge-discharge cycle is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. A lithium-ion secondary battery.

16. It has a positive electrode, a negative electrode, and an electrolyte. The positive electrode has a positive electrode active material containing lithium cobaltate and a conductive aid containing carbon fibers. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region existing inside and a second region existing in the surface layer part. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX for the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle in which it is discharged to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the 1st cycle. Lithium ion secondary battery.

17. A positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material containing lithium cobaltate and a conductive auxiliary agent containing carbon fiber. The negative electrode includes a negative electrode active material containing carbon. The positive electrode active material has a first region and a second region outside the first region. The first region contains lithium, cobalt, and oxygen. The second region contains magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle in which it is discharged to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density at the 1st cycle is 800 mWh / g or more per unit weight of the active material, and the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the 1st cycle. Lithium ion secondary battery.

18. A positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material containing lithium cobaltate and a conductive auxiliary agent containing carbon fiber. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery manufactured using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density in the first cycle is 800 mWh / g or more per active material weight, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle. A lithium ion secondary battery.

19. It has a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate and a conductive auxiliary agent containing carbon fibers. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region and a second region outside the first region. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region is present in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same or substantially the same as each other. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged up to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and the charge-discharge cycle of discharging by constant current down to a lower limit voltage of 2.5 V is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium ion secondary battery.

20. A positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material containing lithium cobaltate and a conductive auxiliary agent containing carbon fiber. The negative electrode includes a negative electrode active material containing carbon. The positive electrode active material has a first region present inside and a second region present in the surface layer portion. The first region contains lithium, cobalt, and oxygen. The second region contains magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by the line analysis of STEM-EDX with respect to the cross section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region is present in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same or substantially the same as each other. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then by constant voltage charging, and then discharged to a lower limit voltage of 2.5 V by constant current discharging, and the charge-discharge cycle is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. Lithium ion secondary battery.

21. It has a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate and a conductive assistant containing carbon fiber. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region and a second region outside the first region. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same or approximately the same as each other. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then by constant voltage charging, and then discharged to a lower limit voltage of 2.5 V by constant current discharging, and the charge-discharge cycle is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. Lithium ion secondary battery.

22. It has a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate and a conductive auxiliary agent containing carbon fiber. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region present inside and a second region present in the surface layer portion. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same or substantially the same as each other. When a coin-type secondary battery manufactured using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. A lithium-ion secondary battery.

23. It has a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate and a conductive auxiliary agent containing carbon fiber. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region and a second region outside the first region. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the magnesium concentration detected by STEM-EDX line analysis with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, the second region exists in a range where the magnesium concentration detected by the STEM-EDX line analysis is 1 / 5 of the peak, the first region has a layered rock salt-type crystal structure, the second region has a rock salt-type crystal structure, the crystal orientations of the first region and the second region coincide or are substantially coincident with each other, when a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V and then charged at a constant voltage at a temperature of 25 °C, and a charge-discharge cycle of discharging at a constant current to a lower limit voltage of 2.5 V is repeated, the energy density in the first cycle is 800 mWh / g or more per active material weight, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle, A lithium ion secondary battery.

24. A positive electrode, a negative electrode, and an electrolytic solution, the positive electrode includes a positive electrode active material containing lithium cobaltate and a conductive assistant containing carbon fiber, the negative electrode includes a negative electrode active material containing carbon, the positive electrode active material has a first region existing inside and a second region existing in a surface layer portion, the first region contains lithium, cobalt, and oxygen, the second region contains magnesium, fluorine, and oxygen, the peak of the magnesium concentration detected by STEM-EDX line analysis with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, the second region exists in a range where the magnesium concentration detected by the STEM-EDX line analysis is 1 / 5 of the peak, the first region has a layered rock salt-type crystal structure, The second region has a rock-salt crystal structure, the crystal orientations of the first region and the second region coincide or substantially coincide with each other, when a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current to a lower limit voltage of 2.5 V is repeated, the energy density in the first cycle is 800 mWh / g or more per active material weight, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle, a lithium-ion secondary battery.

25. In any one of Claims 13 to 24, the carbon fiber is carbon nanofiber or carbon nanotube, a lithium-ion secondary battery.

26. comprising a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode having a positive electrode active material containing lithium cobaltate, the negative electrode having a negative electrode active material containing carbon, the positive electrode active material having a first region and a second region outside the first region, the first region having lithium, cobalt, and oxygen, the second region having magnesium, fluorine, and oxygen, the positive electrode active material having crystal defects, the positive electrode active material having magnesium segregated in the vicinity of the crystal defects, the peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, the second region exists in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak, When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current to a lower limit voltage of 2.5 V is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium-ion secondary battery.

27. comprising a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode having a positive electrode active material containing lithium cobaltate, the negative electrode having a negative electrode active material containing carbon, the positive electrode active material having a first region present inside and a second region present in a surface layer portion, the first region having lithium, cobalt, and oxygen, the second region having magnesium, fluorine, and oxygen, the positive electrode active material having crystal defects, the positive electrode active material having magnesium segregated in the vicinity of the crystal defects, The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material is present from the surface of the positive electrode active material to a depth of 2 nm, the second region being present in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak, When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current to a lower limit voltage of 2.5 V is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium-ion secondary battery.

28. comprising a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode having a positive electrode active material containing lithium cobaltate, the negative electrode having a negative electrode active material containing carbon, The positive electrode active material has a first region and a second region outside the first region. The first region contains lithium, cobalt, and oxygen. The second region contains magnesium, fluorine, and oxygen. The positive electrode active material has crystal defects. The positive electrode active material has magnesium segregated in the vicinity of the crystal defects. The peak of the magnesium concentration detected by line analysis of STEM-EDX on the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the magnesium concentration detected by line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V and then charged at a constant voltage at a temperature of 25°C, and the charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. A lithium-ion secondary battery.

29. It has a positive electrode, a negative electrode, and an electrolyte. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion. The first region contains lithium, cobalt, and oxygen. The second region contains magnesium, fluorine, and oxygen. The positive electrode active material has crystal defects. The positive electrode active material has magnesium segregated in the vicinity of the crystal defects. The peak of the magnesium concentration detected by line analysis of STEM-EDX on the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region is present in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current to a lower limit voltage of 2.5 V is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the 1st cycle. A lithium-ion secondary battery.

30. A positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region and a second region outside the first region. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The positive electrode active material has crystal defects. The positive electrode active material has magnesium segregated in the vicinity of the crystal defects. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region is present in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current to a lower limit voltage of 2.5 V is repeated, the energy density at the 1st cycle is 800 mWh / g or more per active material weight, and the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the 1st cycle. A lithium-ion secondary battery.

31. having a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode having a positive electrode active material containing lithium cobaltate, the negative electrode having a negative electrode active material containing carbon, the positive electrode active material having a first region present inside and a second region present in the surface layer portion, the first region having lithium, cobalt, and oxygen, the second region having magnesium, fluorine, and oxygen, the positive electrode active material having crystal defects, the positive electrode active material having magnesium segregated in the vicinity of the crystal defects, the peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross section of the positive electrode active material is present from the surface of the positive electrode active material to a depth of 2 nm, the second region is present in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak, When a coin-type secondary battery produced using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25 °C and then charged at a constant voltage, and the charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density in the first cycle is 800 mWh / g or more per active material weight, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle, A lithium-ion secondary battery.

32. having a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode having a positive electrode active material containing lithium cobaltate, the negative electrode having a negative electrode active material containing carbon, the positive electrode active material having a first region and a second region outside the first region, the first region having lithium, cobalt, and oxygen, The second region has magnesium, fluorine, and oxygen. The positive electrode active material has crystal defects. The positive electrode active material has magnesium segregated in the vicinity of the crystal defects. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region coincide or are substantially coincident with each other. When a coin-type secondary battery manufactured using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and the charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium-ion secondary battery.

33. It has a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The positive electrode active material has crystal defects. The positive electrode active material has magnesium segregated in the vicinity of the crystal defects. The peak of the concentration of magnesium detected by STEM-EDX line analysis with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, The second region exists in a range where the concentration of magnesium detected by the STEM-EDX line analysis is 1 / 5 of the peak, The first region has a layered rock salt-type crystal structure, The second region has a rock salt-type crystal structure, The crystal orientations of the first region and the second region are the same or substantially the same as each other, When a coin-type secondary battery manufactured using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25 °C and then charged at a constant voltage, and the charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium-ion secondary battery.

34. It has a positive electrode, a negative electrode, and an electrolytic solution, The positive electrode has a positive electrode active material containing lithium cobaltate, The negative electrode has a negative electrode active material containing carbon, The positive electrode active material has a first region and a second region outside the first region, The first region has lithium, cobalt, and oxygen, The second region has magnesium, fluorine, and oxygen, The positive electrode active material has crystal defects, The positive electrode active material has magnesium segregated in the vicinity of the crystal defects, The peak of the concentration of magnesium detected by STEM-EDX line analysis with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, The second region exists in a range where the concentration of magnesium detected by the STEM-EDX line analysis is 1 / 5 of the peak, The first region has a layered rock salt-type crystal structure, The second region has a rock-salt type crystal structure, The crystal orientations of the first region and the second region coincide or approximately coincide with each other, When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged by constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged by constant voltage, and a charge-discharge cycle of discharging by constant current to a lower limit voltage of 2.5 V is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. A lithium-ion secondary battery.

35. It has a positive electrode, a negative electrode, and an electrolyte, The positive electrode has a positive electrode active material containing lithium cobaltate, The negative electrode has a negative electrode active material containing carbon, The positive electrode active material has a first region present inside and a second region present in the surface layer portion, The first region has lithium, cobalt, and oxygen, The second region has magnesium, fluorine, and oxygen, The positive electrode active material has crystal defects, The positive electrode active material has magnesium segregated in the vicinity of the crystal defects, The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, The second region exists in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak, The first region has a layered rock-salt type crystal structure, The second region has a rock-salt type crystal structure, The crystal orientations of the first region and the second region coincide or approximately coincide with each other, When a coin-type secondary battery fabricated using the above-mentioned positive electrode and lithium metal is charged at a constant current up to an upper limit voltage of 4.6 V and then charged at a constant voltage at a temperature of 25°C, and a charge-discharge cycle of discharging by constant current down to a lower limit voltage of 2.5 V is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. A lithium-ion secondary battery.

36. comprising a positive electrode, a negative electrode, and an electrolytic solution; the positive electrode having a positive electrode active material containing lithium cobaltate; the negative electrode having a negative electrode active material containing carbon; the positive electrode active material having a first region and a second region outside the first region; the first region having lithium, cobalt, and oxygen; the second region having magnesium, fluorine, and oxygen; the positive electrode active material having crystal defects; the positive electrode active material having magnesium segregated in the vicinity of the crystal defects; the peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists within a depth of 2 nm from the surface of the positive electrode active material; the second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak; the first region having a layered rock-salt type crystal structure; the second region having a rock-salt type crystal structure; the crystal orientations of the first region and the second region are the same or substantially the same as each other; When a coin-type secondary battery fabricated using the above-mentioned positive electrode and lithium metal is charged at a constant current up to an upper limit voltage of 4.6 V at a temperature of 25 °C and then charged at a constant voltage, and a charge-discharge cycle in which it is discharged at a constant current down to a lower limit voltage of 2.5 V is repeated, the energy density in the first cycle is 800 mWh / g or more per unit weight of the active material, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle. A lithium-ion secondary battery.

37. having a positive electrode, a negative electrode, and an electrolytic solution; the positive electrode having a positive electrode active material containing lithium cobaltate; the negative electrode having a negative electrode active material containing carbon; the positive electrode active material having a first region present inside and a second region present in a surface layer portion; the first region having lithium, cobalt, and oxygen; the second region having magnesium, fluorine, and oxygen; the positive electrode active material having crystal defects; the positive electrode active material having magnesium segregated in the vicinity of the crystal defects; the peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists within a depth of 2 nm from the surface of the positive electrode active material; the second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak; the first region having a layered rock-salt type crystal structure; the second region having a rock-salt type crystal structure; the crystal orientations of the first region and the second region are the same or substantially the same as each other; When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current to a lower limit voltage of 2.5 V is repeated, the energy density in the first cycle is 800 mWh / g or more per unit weight of the active material, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle. Lithium ion secondary battery.

38. In any one of Claims 26 to 37, the crystal defect is observed in a TEM image or a STEM image. Lithium ion secondary battery.

39. comprising a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode having a positive electrode active material containing lithium cobaltate, the negative electrode having a negative electrode active material containing carbon, the electrolytic solution having vinylene carbonate, the positive electrode active material having a first region and a second region outside the first region, the first region having lithium, cobalt, and oxygen, the second region having magnesium, fluorine, and oxygen, the peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, the second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak, When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current to a lower limit voltage of 2.5 V is repeated, the energy density retention rate in the 30th cycle is 84% or more and 93% or less. Lithium ion secondary battery.

40. A lithium ion secondary battery comprising a positive electrode, a negative electrode, and an electrolytic solution, wherein the positive electrode has a positive electrode active material containing lithium cobaltate, the negative electrode has a negative electrode active material containing carbon, the electrolytic solution has vinylene carbonate, the positive electrode active material has a first region present inside and a second region present in a surface layer portion, the first region has lithium, cobalt, and oxygen, the second region has magnesium, fluorine, and oxygen, a peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to a cross section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, the second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak, when a coin-type secondary battery manufactured using the positive electrode and lithium metal is charged up to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less, A lithium ion secondary battery.

41. A lithium ion secondary battery comprising a positive electrode, a negative electrode, and an electrolytic solution, wherein the positive electrode has a positive electrode active material containing lithium cobaltate, the negative electrode has a negative electrode active material containing carbon, the electrolytic solution has vinylene carbonate, the positive electrode active material has a first region and a second region outside the first region, the first region has lithium, cobalt, and oxygen, the second region has magnesium, fluorine, and oxygen, The peak of the magnesium concentration detected by STEM-EDX line analysis with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the magnesium concentration detected by the STEM-EDX line analysis is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V and then at a constant voltage, and then discharged at a constant current to a lower limit voltage of 2.5 V, and the charge-discharge cycle is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. A lithium-ion secondary battery.

42. A positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The electrolytic solution has vinylene carbonate. The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the magnesium concentration detected by STEM-EDX line analysis with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the magnesium concentration detected by the STEM-EDX line analysis is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V and then at a constant voltage, and then discharged at a constant current to a lower limit voltage of 2.5 V, and the charge-discharge cycle is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. A lithium-ion secondary battery.

43. It has a positive electrode, a negative electrode, and an electrolytic solution, The positive electrode has a positive electrode active material containing lithium cobaltate, The negative electrode has a negative electrode active material containing carbon, The electrolytic solution has vinylene carbonate, The positive electrode active material has a first region and a second region outside the first region, The first region has lithium, cobalt, and oxygen, The second region has magnesium, fluorine, and oxygen, The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, The second region exists in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak, When a coin-type secondary battery manufactured using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density in the first cycle is 800 mWh / g or more per active material weight, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle, A lithium-ion secondary battery.

44. It has a positive electrode, a negative electrode, and an electrolytic solution, The positive electrode has a positive electrode active material containing lithium cobaltate, The negative electrode has a negative electrode active material containing carbon, The electrolytic solution has vinylene carbonate, The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion, The first region has lithium, cobalt, and oxygen, The second region contains magnesium, fluorine, and oxygen. The peak of the magnesium concentration detected by line analysis of STEM-EDX on the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the magnesium concentration detected by the line analysis of STEM-EDX is 1 / 5 of the peak. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V and then charged at a constant voltage at a temperature of 25°C, and then discharged at a constant current to a lower limit voltage of 2.5 V, and the charge-discharge cycle is repeated, the energy density in the first cycle is 800 mWh / g or more per active material weight, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle. A lithium-ion secondary battery.

45. It has a positive electrode, a negative electrode, and an electrolyte. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The electrolyte has vinylene carbonate. The positive electrode active material has a first region and a second region outside the first region. The first region contains lithium, cobalt, and oxygen. The second region contains magnesium, fluorine, and oxygen. The peak of the magnesium concentration detected by line analysis of STEM-EDX on the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the magnesium concentration detected by the line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The first region and the second region have crystal orientations that are the same as or approximately the same as each other. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current up to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current down to a lower limit voltage of 2.5 V is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium-ion secondary battery.

46. A positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The electrolytic solution has vinylene carbonate. The positive electrode active material has a first region existing inside and a second region existing in the surface layer portion. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the magnesium concentration detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the magnesium concentration detected by the line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The first region and the second region have crystal orientations that are the same as or approximately the same as each other. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current up to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging at a constant current down to a lower limit voltage of 2.5 V is repeated, the energy density retention rate at the 30th cycle is 84% or more and 93% or less. A lithium-ion secondary battery.

47. having a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode having a positive electrode active material containing lithium cobaltate, the negative electrode having a negative electrode active material containing carbon, the electrolytic solution having vinylene carbonate, the positive electrode active material having a first region and a second region outside the first region, the first region having lithium, cobalt, and oxygen, the second region having magnesium, fluorine, and oxygen, the peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm, the second region exists in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak, the first region has a layered rock salt-type crystal structure, the second region has a rock salt-type crystal structure, the first region and the second region have crystal orientations that coincide or are substantially coincident with each other, When a coin-type secondary battery produced using the positive electrode and lithium metal is charged to an upper limit voltage of 4.6 V by constant current charging at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. A lithium-ion secondary battery.

48. having a positive electrode, a negative electrode, and an electrolytic solution, the positive electrode having a positive electrode active material containing lithium cobaltate, the negative electrode having a negative electrode active material containing carbon, the electrolytic solution having vinylene carbonate, the positive electrode active material having a first region existing inside and a second region existing in the surface layer portion, The first region contains lithium, cobalt, and oxygen. The second region contains magnesium, fluorine, and oxygen. The peak of the magnesium concentration detected by STEM-EDX line analysis of the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region exists in a range where the magnesium concentration detected by the STEM-EDX line analysis is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same or approximately the same as each other. When a coin-type secondary battery fabricated using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V and then charged at a constant voltage at a temperature of 25°C, and then discharged at a constant current to a lower limit voltage of 2.5 V, and the charge-discharge cycle is repeated, the energy density at the 30th cycle is 84% or more and 93% or less of the energy density at the first cycle. A lithium-ion secondary battery.

49. It has a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The electrolytic solution contains vinylene carbonate. The positive electrode active material has a first region and a second region outside the first region. The first region contains lithium, cobalt, and oxygen. The second region contains magnesium, fluorine, and oxygen. The peak of the magnesium concentration detected by STEM-EDX line analysis of the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region is present in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The crystal orientations of the first region and the second region are the same or substantially the same as each other. When a coin-type secondary battery manufactured using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging to a lower limit voltage of 2.5 V by constant current discharge is repeated, the energy density in the first cycle is 800 mWh / g or more per unit weight of the active material, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle. A lithium ion secondary battery.

50. It has a positive electrode, a negative electrode, and an electrolyte. The positive electrode has a positive electrode active material containing lithium cobaltate. The negative electrode has a negative electrode active material containing carbon. The electrolyte has vinylene carbonate. The positive electrode active material has a first region present inside and a second region present in the surface layer portion. The first region has lithium, cobalt, and oxygen. The second region has magnesium, fluorine, and oxygen. The peak of the concentration of magnesium detected by line analysis of STEM-EDX with respect to the cross-section of the positive electrode active material exists from the surface of the positive electrode active material to a depth of 2 nm. The second region is present in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak. The first region has a layered rock salt-type crystal structure. The second region has a rock salt-type crystal structure. The first region and the second region have crystal orientations that are the same as or approximately the same as each other. When a coin-type secondary battery manufactured using the positive electrode and lithium metal is charged at a constant current to an upper limit voltage of 4.6 V at a temperature of 25°C and then charged at a constant voltage, and a charge-discharge cycle of discharging by constant current to a lower limit voltage of 2.5 V is repeated, the energy density in the first cycle is 800 mWh / g or more per active material weight, and the energy density in the 30th cycle is 84% or more and 93% or less of the energy density in the first cycle. A lithium-ion secondary battery.

51. In any one of Claims 39 to 50, the electrolytic solution further contains a dinitrile compound. A lithium-ion secondary battery.

52. In Claim 51, the dinitrile compound contains succinonitrile or adiponitrile. A lithium-ion secondary battery.

53. In any one of Claims 1 to 52, the thickness of the second region is 0.5 nm or more and 50 nm or less. A lithium-ion secondary battery.

54. In any one of Claims 1 to 53, the first region contains aluminum. A lithium-ion secondary battery.

55. In any one of Claims 1 to 54, during the constant current charging, the current density per weight of the positive electrode active material is set to 68.5 mA / g. A lithium-ion secondary battery.

56. In any one of Claims 1 to 55, The constant voltage charging was performed until the current density per weight of the positive electrode active material reached 1.4 mA / g. Lithium ion secondary battery.

57. In any one of Claims 1 to 56, the constant current discharge was performed such that the current density per weight of the positive electrode active material became 68.5 mA / g. Lithium ion secondary battery.

58. In any one of Claims 1 to 57, the coin-type secondary battery has a second electrolyte, and the second electrolyte used is one in which 2 wt% of vinylene carbonate is mixed with 1 mol / L of lithium hexafluorophosphate, ethylene carbonate, and diethyl carbonate. Lithium ion secondary battery.

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