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 apparatus. 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] Note that 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] Also, 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 (HEVs), electric vehicles ( EVs), or plug-in hybrid vehicles (PHEVs). Rechargeable energy It has become an essential component in the modern information society as a source of

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

[0006] One way to increase the capacity of a lithium-ion secondary battery is known to be to increase the charging voltage. For example, the capacity of lithium cobaltate, which is commonly 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 increased 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 increased 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 cathode 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 cathode 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 high capacity as one of the problems. Or, one aspect of the present invention is to provide a secondary battery with excellent charge-discharge characteristics as one of the problems. Or, one aspect of the present invention is to provide a secondary battery with high safety or reliability as one of the problems.

[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 as one of the problems.

[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 descriptions 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 cathode active material by segregation.

[0015] One aspect of the present invention is a cathode active material, and the cathode 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, which is a positive electrode active material. Also, one aspect of the present invention is a positive electrode active material, the positive electrode active material having lithium, a transition metal

[0016] , oxygen, magnesium, and fluorine, being present on the surface of the positive electrode active material, and the total amount of atoms including lithium, transition metal, oxygen, fluorine, and magnesium measured by X-ray photoelectron spectroscopy being 100 atomic%, the magnesium concentration measured by X-ray photoelectron spectroscopy on the surface of the positive electrode active material being 1 atomic% or more and 16 atomic% or less, and the fluorine concentration being 0.2 atomic% or more and 4 atomic% or less, which is a positive electrode active material. 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) , which is a 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 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 , which is a positive electrode active material. Also, in the above, the transition metal preferably includes cobalt. Or, in the above

[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 , which is a positive electrode active material. Also, in the above, the transition metal preferably includes cobalt. Or, in the above

[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 has 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, has 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 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, has 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 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 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. 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 higher and 1100°C or lower for 2 hours or more and 20 hours or less, and a step of heating in an atmosphere containing oxygen at 500°C or higher and 1200°C or lower 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). 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). 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). 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). 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). 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 on the positive electrode active material. The first region exists inside the positive electrode active material, and the second region exists on 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, a positive electrode active material that can suppress a decrease in capacity during charge and discharge cycles can be provided by using it in a lithium-ion secondary battery. In addition, a secondary battery with a high capacity can be provided. Also, a secondary battery with excellent charge and discharge characteristics can be provided. In addition, a secondary battery with high safety or reliability can be provided. Also, 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 changed in various ways. Also, the present invention is not to be construed as being limited to the description of the embodiments shown below.

[0027] 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 explanation. Therefore, each component is not necessarily limited to its size, and the relative size between each component is not limited either.

[0028] In the configuration of the present invention described in this specification, etc., 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 particular reference numeral is attached.

[0029] Also, 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, etc., 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 strictly speaking, may be a structure in which the lattice of the rock salt-type crystal is distorted.

[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 formed by the 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 generally 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, and so on.

[0035] The approximate alignment of the crystal orientations of the two regions can be determined from TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. It can also be determined using 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 can be determined from the arrangement of metal elements. In this specification, etc., the similarity in the structure of a two-dimensional interface is called epitaxy. Also, crystal growth having similarity in the structure of a two-dimensional interface is called epitaxial growth. Further, having a three-dimensional structural similarity or having the same crystallographic orientation is called topotaxy.

[0036] ​​​​​That is. Therefore, in the case of topotaxy, when a part of the cross-section is observed, the crystal orientations of the 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 may be said that the second region 102 is on the first region 101, or the second region 102 may be said to cover at least a part of the first region 101.

[0038] 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 concentration of the elements crossing the dotted line is shown in gray scale to indicate the sloping state. In FIGS. 1(B) and later, for convenience, 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 exist 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 to form 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 to form 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, or a structure in which other elements are incorporated into the crystal. This shall include structures in which other elements are incorporated into the crystal.

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

[0041] In other words, the first region 101 exists inside the positive electrode active material 100, and the second region 102 exists in the surface layer portion of the positive electrode active material 100. Further, the second region 102 may also exist inside the positive electrode active material 100. In other words, the first region 101 exists inside the positive electrode active material 100, and the second region 102 exists in the surface layer portion of the positive electrode active material 100. Further, the second region 102 may also exist inside the positive electrode active material 100. That is, the first region 101 exists inside the positive electrode active material 100, and the second region 102 exists in the surface layer portion of the positive electrode active material 100. Further, the second region 102 may also exist inside the positive electrode active material 100.

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

[0043] If the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse, 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 excessive progress of the reaction with the electrolyte also occur. Therefore, it is preferable that the D50 (also referred to as the median diameter) is 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 40 μm or less. That is, if the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse, 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 excessive progress of the reaction with the electrolyte also occur. Therefore, it is preferable that the D50 (also referred to as the median diameter) is 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 40 μm or less. That is, if the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse, 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 excessive progress of the reaction with the electrolyte also occur. Therefore, it is preferable that the D50 (also referred to as the median diameter) is 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 40 μm or less. That is, if the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse, 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 excessive progress of the reaction with the electrolyte also occur. Therefore, it is preferable that the D50 (also referred to as the median diameter) is 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 40 μm or less. That is, if the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse, 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 excessive progress of the reaction with the electrolyte also occur. Therefore, it is preferable that the D50 (also referred to as the median diameter) is 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, For example, among manganese, cobalt, and nickel, One or more of them can be used. That is, the transition metal possessed by the first region 101 and only cobalt may be used, or two kinds of cobalt and manganese may be used, or three kinds of cobalt, manganese, and nickel may 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 with 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-discharge reaction among the positive electrode active materials 100. In order to increase the capacity when the positive electrode active material 100 is used in a secondary battery, it is preferable that the volume of the

[0048] first region 101 is larger than that of the second region 102. The 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, unexpectedly, magnesium tends 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

[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 replaced by 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 102 is an electrochemically stable material, it is suitable as a coating layer because deterioration hardly occurs even when charge and discharge are repeated.

[0051] If the second region 102 is too thin, its function as a coating layer will decrease, but if it becomes 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 can function as a stable coating layer. However, not all of the second region 102 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 is repeatedly charged and discharged, side reactions such as transition metals such as cobalt and manganese eluting into the electrolyte, oxygen being released, and the crystal structure becoming unstable occur, and the deterioration progresses. However, since the positive electrode active material 100 of 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 has the same transition metal as 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 in the first region 101 has more trivalent atoms than atoms of other valences, and it is preferable that the transition metal 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, many metal oxides with a transition metal:oxygen = 1:1 (atomic ratio), such as CoO(II), MnO(II), and Ni( (II), increase. 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, EELS is preferable because it has a high spatial resolution and can analyze even if the second region 102 is a thin layer of several nm.

[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 in the first region 101 is less than 3.8, and the transition metal in the second region 102 has an L3 / L2 that is / L2 is preferably 3.8 or more.

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

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

[0060] In addition, 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, and more preferably about 684.3 eV. This is a binding energy that does not match either of MgF2 and LiF.

[0061] In the present 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 images, STEM images, 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 depth 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 present up to a depth of 1 nm, and even more preferably present 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 production method. In the case of the production 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 region combining 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. Also, 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 interior, 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. Intention 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, the concentrations of magnesium and fluorine in the raw materials are preferably 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, the concentrations of magnesium and fluorine in the second region 102 resulting from segregation are preferably Mg :F = y:1 (3 ≤ y ≤ 5) (atomic ratio), and more preferably about Mg:F = 4:1 .

[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 substantially the same 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 substantially the same, 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, but one aspect of the present invention is not limited to this. For example, as shown in FIG. 1(C), , the positive electrode active material 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 increased. Also, 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 even better 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 producing 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 of forming the second region 102 having magnesium oxide and fluorine due to 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) because of this, 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.

[0086] 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 part of the composite oxide containing lithium and a transition metal. ​​​​​​​​​​At this point, most of the magnesium and fluorine are in the form of complex oxides 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 time is the same as or shorter than the heating time. For example, it is recommended to carry out the test for 10 to 15 hours. After cooling, the synthesized material is preferably sieved. In this embodiment, the mixture is sieved using a 53 μm mesh.

[0088] The starting materials are lithium, cobalt, fluorine, and magnesium, which are synthesized in advance. In this case, steps S12 to S14 may be used. can be omitted.

[0089] Next, the material cooled in S14 is subjected to a second heating (S15). In order to distinguish between the first and second heating, it is sometimes called the second heating or annealing. Optimal conditions for the second heating The particle size and composition of the composite oxide containing lithium, cobalt, fluorine, and magnesium It depends on the temperature, but it is preferable to hold the temperature for 50 hours or less, and 2 hours or more. It is more preferable to perform the treatment for 10 hours or less. The specified temperature is 500°C or higher and 1200°C or lower. Preferably, the temperature is 700° C. or higher and 1000° C. or lower, more preferably, about 800° C. It is also preferable to heat the material in an atmosphere containing oxygen. In this embodiment, the material is heated at 800° C. The heating time was set to 2 hours, with the temperature rising at 200℃ / h and 10L / h of dry air with a dew point of -109℃. It will be run at 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]

[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.

[0097] As the conductive aid, a carbon material, a metal material, a conductive ceramic material, or the like can be used. Also, 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 a 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, isotropic pitch-based carbon fibers, etc. 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, fullerenes, etc. can be used. Also, for example, metal powders, metal fibers, conductive ceramic materials, etc. such as copper, nickel, aluminum, silver, gold, etc. can be used.

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

[0101] The graphene compound has excellent electrical properties of having high electrical conductivity, high flexibility, and high It may have excellent physical properties such as mechanical strength. 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 can efficiently form conductive paths in the active material layer in a small amount. Therefore, using a graphene compound as a conductive assistant is preferable 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 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, for example, graphene oxide (GO).

[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 be large and the relative amount of the supported active material tends to decrease. When the supported amount of the active material decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as the conductive assistant the graphene compound can efficiently form conductive paths even in a small amount so it is not necessary to reduce the supported amount of the active material, which is particularly preferable.

[0103] Hereinafter, as an example, a cross - sectional configuration example when 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 formed by partial overlap of a plurality of multi-graphenes and / or a plurality of graphenes.

[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 to 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 power 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. Therefore, 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. As a result, 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 the binder , fluororubber can be used.

[0110] In addition, as the binder, for example, it is preferable to use a water-soluble polymer. Water-soluble polymers Examples of the base include polysaccharides. Examples of the polysaccharides include cellulose derivatives such as carboxymethyl cellulose (CMC), methylcellulose, ethylcellulose, hydroxypropyl cellulose, diacetylcellulose, regenerated cellulose, and starch etc. can be used. Further, 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 (polymethyl methacrylate (PMMA)), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene lene, isobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride ( PVdF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, nitrocellulose and other materials are preferably used.

[0112] A plurality of the above binders may be used in combination.

[0113] For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with other materials. For example, although 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 a particularly excellent viscosity adjusting effect. As the material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer may be used. Further, as the water-soluble polymer having a particularly excellent viscosity adjusting effect, the above-described polysaccharides, for example, carbo Boxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxy propyl cellulose and cellulose derivatives such as diacetyl cellulose, regenerated cellulose, etc., or starch can be used.

[0114] Note that cellulose derivatives such as carboxymethyl cellulose can be made into salts such as sodium salts and ammonium salts of carboxymethyl cellulose to increase solubility and make it easier to exert the effect as a viscosity modifier. By increasing the solubility, the dispersibility of 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. When water-soluble polymers dissolve in water, they stabilize the viscosity and can stably disperse the active material and other materials combined as binders, such as styrene-butadiene rubber, etc., in an aqueous solution. Also, due to having functional groups, they are expected to be easily adsorbed stably on the surface of the active material. Also, cellulose derivatives such as carboxymethyl cellulose, for example, have many materials with functional groups such as hydroxyl groups and carboxyl groups. Due to having functional groups, it is expected that the polymers interact with each other and exist widely covering 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 without electron conductivity or a film with extremely low electrical conductivity. For example, on the surface of the active material,

[0116] a film with no conductivity or a film with extremely low electrical conductivity. For example, ​When a dynamic film is formed, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. Moreover, 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, materials with high conductivity such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. It can also be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react 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), mesh, 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, at least one of the materials containing them 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, V 2Sn3, 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 example, as graphite, artificial graphite, natural graphite, etc. can be mentioned. As artificial graphite, for example, mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. can be mentioned.

[0123] For example, as graphite, artificial graphite, natural graphite, etc. can be mentioned. As artificial graphite, for example, mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. can 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, and this may be preferable. Examples of natural graphite include scaly graphite, spheroidized natural graphite, and the like.

[0124] Graphite exhibits a potential as low as that of metallic lithium when lithium ions are inserted into the graphite (when forming a lithium-graphite intercalation compound) (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, relatively small volume expansion, low cost, and high safety compared to metallic lithium, and thus is preferable.

[0125] In addition, 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 as the negative electrode active material.

[0126] In addition, Li3N-type structured Li Li 3-x M x N (M = Co, Ni, Cu), which is a complex nitride of lithium and a transition metal, can be used as the negative electrode active material. 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 complex nitride of lithium and a transition metal, since lithium ions are contained in the negative electrode active material, it can be combined with materials such as V2O5 and Cr3O8 that do not contain lithium ions as the positive electrode active material, which is preferable. Even when a material containing lithium ions is used as the positive electrode active material, by previously desorbing the lithium ions contained in the positive electrode active material, a complex nitride of lithium and 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 preferable. such as, 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 the solvent of the electrolytic solution, safety against 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, gels of fluorine-based polymers, 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 the solvent of 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, a quaternary Ammonium cations, tertiary sulfonium cations, quaternary phosphonium cations, etc. include aliphatic onium cations such as , and aromatic cations such as imidazolium cations and pyridinium cations. In addition, as the anion used in the electrolyte, monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkyl sulfonic acid anions, tetrafluoroborate anions, perfluoroalkyl borate anions, hexafluorophosphate anions, or perfluoroalkyl phosphate anions, etc. can be mentioned.

[0134] In addition, as the electrolyte dissolved in the above solvent, 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 in any combination and ratio of two or more of these. It is possible.

[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 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), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), LiBOB, dinitrile compounds such as succinonitrile, adiponitrile, etc. may be added to the electrolytic solution. The concentration of the added material may be, for example, 0.1 wt% or more and 5 wt% or less based on the entire solvent.

[0137] Alternatively, a polymer gel electrolyte obtained by swelling a polymer with an electrolytic solution may be used. By using the polymer gel electrolyte, the safety against liquid leakage and the like is enhanced. In addition, the secondary battery can be made thinner and lighter.

[0138] As the polymer to be gelled, silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide-based gel, polypropylene oxide-based gel, fluorine-based polymer gel, etc. can be used.

[0139] As the polymer, for example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, etc., and copolymers containing them can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. In addition, the formed polymer may have a porous shape.

[0140] Alternatively, instead of the electrolytic solution, a solid electrolyte having an inorganic material such as a sulfide-based or oxide-based material, or a solid electrolyte having a polymer material such as a PEO (polyethylene oxide)-based material can be used. When using a solid electrolyte, it is not necessary to install a separator or a spacer. Also, the electricity ​​​​​​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 the like, non-woven fabrics, glass fibers, ceramics, or synthetic fibers made of nylon (polyamide), vinylon (polyvinyl alcohol-based fibers), polyester, acrylic, 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. Examples of the ceramic-based material include aluminum oxide particles, silicon oxide particles, etc. Examples of the fluorine-based material include PVDF, polytetrafluoroethylene, etc. Examples of the polyamide-based material include nylon, aramid (meta-aramid, para-aramid), etc.

[0143] Coating with a ceramic-based material improves the oxidation resistance, so that deterioration of the separator during high-voltage charge and discharge can be suppressed and the reliability of the secondary battery can be improved. 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, particularly aramid, improves the heat resistance, so that 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. Alternatively, 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 a secondary battery having the positive electrode active material 100 described in the previous embodiment will be described. The materials used for 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 formed 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 electrolytic solution, or alloys of these or alloys of these and other metals (e.g., stainless steel, etc.) can be used. Also, in order to prevent corrosion by the electrolytic solution, it is preferable to coat with nickel, aluminum, etc. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 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, and 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] Figure 5(B) is a diagram schematically showing a cross-section of a cylindrical secondary battery. Inside the hollow cylindrical battery can 602, a battery element is provided in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 interposed therebetween. 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. For the battery can 602, metals such as nickel, aluminum, titanium, etc. that are corrosion-resistant to the electrolytic solution, or alloys of these or alloys of these with other metals (for example, stainless steel, etc.) can be used. Also, in order to prevent corrosion by the electrolytic solution, it is preferable to coat with nickel or 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 and 609. Also, the inside of the battery can 602 where the battery element is provided is filled with a non-aqueous electrolytic solution (not shown). The non-aqueous electrolytic solution can be the same as that used in a coin-type secondary battery. For the positive electrode and negative electrode used in the cylindrical secondary battery, 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 use 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.

[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 use 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. 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 above a predetermined threshold. Also, the PTC element 611 is a thermal sensitive resistance element whose resistance increases when the temperature rises, and limits 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.

[0156] Also, as shown in FIG. 5(C), a module 615 may be configured 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, or may be connected in series, or may be further connected in series after being connected in parallel. By configuring a module 615 having a plurality of secondary batteries 600, a large amount of power can be extracted. By configuring 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 a 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 is overheated, it can be cooled by the temperature control device 617, and when the secondary battery 600 is too cold, it can be heated by the temperature control device 617. Therefore, the performance of the module 615 is less affected by the outside air temperature. Therefore, 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 discharging 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 diagrams showing the external appearance of a battery pack. The battery pack includes 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, or the like.

[0162] The circuit 912 has, for example, a function as a protection circuit that protects the secondary battery 913 from overcharging, over-discharging, and over-current. 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. Further, an antenna such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, or 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 can communicate with an external device 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 being able to shield the electromagnetic field generated by the secondary battery 913, for example. As the layer 916 a magnetic material can be used, for example.

[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), antennas 918 may be provided on a pair of opposite surfaces of the secondary battery 913 shown in FIGS. 6(A) and 6(B). 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 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.

[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 of the pair of surfaces of the secondary battery 913. The layer 917 has a function of being able to shield the electromagnetic field generated by the secondary battery 913, for example. As the layer 917 a magnetic material can be used, for example.

[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 with 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. Note that, for the same parts as those of 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, an electronic paper, a liquid crystal display device, an electroluminescence (also referred to as EL) display device, etc. can be used. For example, by using an 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. Note that, for the same parts as those of 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 capable of measuring displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light , liquid, magnetism, temperature, chemical substances, 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 wound in the same manner as the wound body 950 described in FIG. 9, with the negative electrode 994 and the positive electrode 995 overlapping each other with the separator 996 therebetween, and the laminated sheet is wound.

[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 a film 981 serving as an exterior body and a film 98 2 having a concave portion, whereby the secondary battery 980 shown in FIG. 10(C) can be manufactured. 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 98 2 having a concave portion. The film 981 and the film 982 having a concave portion can be made of a metal material

[0184] such as aluminum or a resin material. If a resin material is used as the material of the film 981 and the film 982 having a concave portion, when a force is applied from the outside, the film 981 and the concave portion will be such that when a force is applied from the outside, the film 981 and the concave portion The film 982 can be deformed to fabricate a flexible secondary battery. This is achievable.

[0185] Also, although FIGS. 10(B) and 10(C) show examples using two films, a space can be formed by bending a single film, and the above-described winding body 99 3 can be housed in the 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 winding 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 electrolytic solution 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 electrolytic solution 508. For the electrolytic solution 508, the electrolytic solution 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 negative electrode current collector 504 also serve as terminals for obtaining electrical contact with the outside. Therefore, the positive electrode

[0189] 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 is exposed to the outside from the exterior body 509. In addition, the positive electrode current collector 501 and the negative electrode current collector 504 may be arranged in a manner similar to that described above. Instead of exposing it to the outside, a lead electrode is used to connect the lead electrode to the positive electrode current collector 501 or the negative electrode The lead electrode may be exposed to the outside by ultrasonic bonding to the current collector 504 .

[0190] In the laminated secondary battery 500, the exterior body 509 is made of, for example, polyethylene, poly A film made of propylene, polycarbonate, ionomer, polyamide, etc. is coated with a A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied. On the metallic thin film, an insulating synthetic resin such as polyamide resin or polyester resin is applied as the outer surface of the exterior body. A laminate film having a three-layer structure with an oil film can be used.

[0191] An example of the cross-sectional structure of a laminated secondary battery 500 is shown in FIG. For simplicity, A) shows an example consisting of two current collectors, but in reality, it is composed of multiple electrode layers. It consists of:

[0192] In FIG. 11B, as an example, the number of electrode layers is 16. In FIG. 11B, the negative electrode current collector 504 has eight layers. The positive electrode current collector 501 has a structure of 8 layers, totaling 16 layers. The cross section of the extraction part is shown, and eight layers of negative electrode current collector 504 are ultrasonically bonded. The number of electrode layers is not limited to 16, and may be more or less. In addition, when the number of electrode layers is small, the secondary battery can have a larger capacity. Combined, it can be 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 bonding, for example, thermocompression bonding or the like may be used. At this time , in order to be able to later put the electrolytic solution 508, provide a non-bonded region (hereinafter referred to as an inlet) on a part (or one side) of the exterior body 509.

[0199] Next, introduce the electrolytic solution 508 from the inlet provided in the exterior body 509 to the inside of 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 cut lines C1-C2, C3-C4 in FIG. 15(A), and cut line A1-A2, 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 enclosed.

[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 the lead 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 so that the surfaces of the positive electrode 211a where the positive electrode active material layer is not formed and the surfaces of the negative electrode 211b where the negative electrode active material layer is not formed are in contact with 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 by a dotted line for easy viewing. rator 214 is shown by a dotted line. ​​

[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 with the leads 212a and the leads 212b and can also be called a top seal.

[0210] The exterior body 251 preferably has a wave shape in which ridge lines 271 and valley lines 2 72 are arranged alternately in a portion overlapping with 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 with the ridge line 271, and FIG. 15(B2) is a cross-section cut at a portion overlapping with 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, the positive electrode 211a and the negative electrode 211b are deformed so as to shift from each other in the longitudinal 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 are strongly rubbed, and the outer body 251 may be damaged. 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.

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

[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. 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 be displaced in the width direction. Therefore, 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). .

[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] Also, 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), in the bent portion 261, it is preferable to have a space 273 between the longitudinal ends of the positive electrode 211a and the negative electrode 211b and the exterior body 251. 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. That is, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following formula (1).

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

[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 of the others are deformed so as to shrink. More specifically, the portion located outside the exterior body 251 is deformed so 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 portion located inside is deformed so that the amplitude of the wave is large and the period of the wave is small . Thus, when the exterior body 251 is deformed, the stress applied to the exterior body 251 due to bending is relaxed, so that the material itself constituting the exterior body 251 does not need to expand and contract. As a result , the exterior body 251 can be bent with a small force without being damaged. As shown in FIG. 15(D), when the battery 250 is bent, the positive electrode 211a and the negative electrode 21

[0223] 1b are displaced relative to each other. At this time, the plurality of stacked positive electrodes 211a and negative electrodes 211b are displaced so that the amount of displacement increases as they approach 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 expand and contract. As a result, the battery 250 can be bent without the positive electrode 211a and the negative electrode 211b being damaged . In addition, 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 displaced relative to each other without contacting the exterior body 251.

[0224] The battery 250 illustrated in FIGS. 15 and 16 is less likely to be damaged, such as damage to the exterior body, the positive electrode 211a, and the negative electrode 211b, even when repeatedly bent and stretched, and the battery characteristics are also less likely to deteriorate .

[0225] . 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 a 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 a 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-mentioned secondary battery 7407, a lightweight and long-life mobile phone can be provided.

[0230] FIG. 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, at that time, the state of the bent secondary battery 7407 is shown in FIG. 17(C ). The secondary battery 7407 is a thin storage battery. The secondary battery 7407 is fixed in the bent state . Incidentally, the secondary battery 7407 has a lead electrode 7408 electrically connected to the current collector 7409 .

[0231] FIG. 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 according to one aspect of the present invention for the above-described secondary battery 7104, a lightweight and long-life portable display device can be provided . . .

[0232] FIG. 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.

[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 equipped with a touch sensor and can be operated by touching the screen with a finger or a stylus. For example, an application can be launched by touching the icon 7207 displayed on the display unit 7202.

[0235] The operation button 7205 can perform various functions such as time setting, power on / off operation, wireless communication on / off operation, execution and cancellation of the silent mode, and execution and cancellation of the power saving mode. For example, the functions 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, it can communicate with a wireless headset capable of wireless communication to make hands-free calls.

[0237] In addition, the mobile information terminal 7200 is equipped 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, body temperature sensors, and touch sensors, pressure sensors, acceleration sensors, etc. It is preferably equipped with such sensors.

[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 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 communication - standard short - range wireless communication or the like.

[0242] The display device 7300 is provided with input / output terminals and can directly exchange data with other information terminals via a connector. It can also be charged 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 9630 a, a housing 9630b, a movable part 9640 connecting the housing 9630a and the housing 9630b, a display unit 9631, a display mode switch 9626, a power switch 9627, a power saving mode switch 9625, a fastener 9629, and an operation switch 9628. The display unit 9631 can be a tablet terminal with a wider display area by using a flexible panel. FIG. 18(A) shows the tablet terminal 9600 in an open state, and FIG. 18(B) shows the tablet terminal 9600 in a closed state.

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

[0246] 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 switch button of the touch panel is displayed with a finger or a stylus, etc., the display unit 9631 can display keyboard buttons. In addition, the display mode 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 switch

[0247] ​​​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 gyroscopes and acceleration sensors.

[0248] Figure 18(B) shows a closed state, and 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 terminals 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] The solar cell 9633 attached to the surface of the tablet terminal supplies power to the touch panel, ​​​​​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 described 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 of 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 obtain a voltage for charging the power storage body 9635. When the power from the solar cell 9633 is used for the operation of the display unit 9631, the switch SW1 is turned on, and the converter 9637 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 other power generation means such as a piezoelectric element (piezoelectric element) or a thermoelectric conversion element (Peltier element) may be used to charge the power storage body 9635. For example, a configuration for wireless (non-contact) power transmission and reception can also be used. ​​​A configuration that combines a contactless power transmission module that charges wirelessly or other charging means may also be used. This is also acceptable.

[0255] FIG. 19 shows an example of another electronic device. In FIG. 19, the display device 8000 is an example of an electronic device using the secondary battery 8004 according to one aspect of the present invention. Specifically, the display device 800 0 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, a speaker unit 8003, a secondary battery 8004, etc. The secondary battery 8004 according to one aspect of the present invention is provided inside the housing 8001. The display device 8000 can be supplied with power from a commercial power source, or can use the power stored in the secondary battery 8004. Therefore even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8004 according to one aspect of the present invention as an uninterruptible power supply, the display device 8000 can be used . The display unit 8002 can be provided with a light-emitting element such as a liquid crystal display device, an organic EL element, etc. at each pixel, a light-emitting device, an electrophoretic display device, a DMD (Digital Micromirror Devi ce), a PDP (Plasma Display Panel), a FED (Field

[0256] Emission Display), etc., and a semiconductor display device can be used. 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. ce), a PDP (Plasma Display Panel), a FED (Field Emission Display), etc.

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

[0258] In FIG. 19, the 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 where 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., and can also be used for tabletop lighting devices.

[0260] Also, as the light source 8102, an artificial light source that artificially obtains light using power can be used. Specifically, incandescent bulbs, discharge lamps such as fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements can be cited as 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 the 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. However, 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 the commercial power supply, and can also use the power stored in the secondary battery 8203. In particular, when the secondary battery 82 03 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when the power supply from the commercial power supply cannot be received due to a power outage or the like, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, the air conditioner can be used.

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

[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 the commercial power supply, and can also use the power stored in the secondary battery 8304. Therefore, even when the power supply from the commercial power supply cannot be received due to a power outage or the like, by using the secondary battery 8304 according to one aspect of the present invention as an uninterruptible power supply, the electric refrigerator 8300 can be used. ​​​​

[0264] Also, during time periods when the electronic device is not in use, especially during time periods when the ratio of the total amount of power that can be supplied by the commercial power supply source to the amount of power actually used (referred to as the power usage rate) is low, by storing power in the secondary battery, it is possible to suppress an increase in the power usage rate outside of the above time periods. For example, in the case of the electric refrigerator 8300, during the night when the temperature is low and the doors 830 2 for the refrigerator compartment and 8303 for the freezer compartment are not opened or closed, power is stored in the secondary battery 8304. Then, during the day when the temperature rises and the doors 8302 for the refrigerator compartment and 8303 for the freezer compartment are opened and closed, by using the secondary battery 8304 as an auxiliary power source, the power usage rate during the day can be kept low.

[0265] In addition to the above-described 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 achieved, and thus the secondary battery itself can be made smaller and lighter. Therefore, by mounting the secondary battery, which is one aspect of the present invention, on the electronic device described in this embodiment, an electronic device with a longer lifespan and lighter weight can be obtained. This embodiment can be implemented in appropriate combination with other embodiments.

[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 (HEVs), electric vehicles (EVs), or plug-in hybrid vehicles (PHEVs) 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 also can 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 The secondary battery can also 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, etc. 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 ones such as CHAdeMO (registered trademark) and Combo ​​​ It may be appropriately performed in any manner. The charging device 8021 may be a charging station installed in a commercial facility or may also be a household power source. For example, by plug-in technology, the secondary battery 8024 mounted on the vehicle 8500 can be charged by external power supply. Charging can be performed by converting AC power into DC power through a conversion device such as an AC-DC converter. This can be done.

[0271] Also, although not shown, a power receiving device can be mounted on the vehicle, and power can be supplied non-contact from a power transmission device on the ground for charging. In the case of this non-contact power supply method, by incorporating a power transmission device into a road or an outer wall it is possible to charge not only while the vehicle is stopped but also while it is running. Also, using this non-contact power supply method, power can be transmitted and received between vehicles. Furthermore, a solar cell can be provided on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped or running. For such non-contact power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0272] Also, Fig. 20(C) shows an example of a two-wheeled vehicle using a secondary battery according to an aspect of the present invention. Fig. 20 (C) shows that the scooter 8600 includes a secondary battery 8602, a side mirror 8601, and a direction indicator light 8603. The secondary battery 8602 can supply electricity to the direction indicator light 8603. This can be done.

[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 It is preferable to carry the secondary battery 8602 indoors for charging during charging, and store it before driving. It is preferable to store it before driving.

[0274] According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery can be increased. Therefore, the secondary battery itself can be reduced in size and weight. If the secondary battery itself can be reduced in size and weight, it contributes to reducing the weight of the vehicle, and thus the cruising range can be improved. In addition, the secondary battery mounted on the vehicle can also be used as a power supply other than the vehicle. In this case, for example, it is possible to avoid using a commercial power supply during the peak of power demand. If it is possible to avoid using a 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 reduced in size and weight, it contributes to reducing the weight of the vehicle, and thus the cruising range can be improved. In addition, the secondary battery mounted on the vehicle can also be used as a power supply other than the vehicle. In this case, for example, it is possible to avoid using a commercial power supply during the peak of power demand. If it is possible to avoid using a 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 reduced in size and weight, it contributes to reducing the weight of the vehicle, and thus the cruising range can be improved. In addition, the secondary battery mounted on the vehicle can also be used as a power supply other than the vehicle. In this case, for example, it is possible to avoid using a commercial power supply during the peak of power demand. If it is possible to avoid using a 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, the secondary battery mounted on the vehicle can also be used as a power supply other than the vehicle. In this case, for example, it is possible to avoid using a commercial power supply during the peak of power demand. If it is possible to avoid using a 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. 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.

[0277] <Preparation of positive electrode active materials of Samples 1 to 6> Positive electrode active materials from Sample 1 to Sample 6 were prepared by changing 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 additional starting materials so that 0.5 atomic% magnesium and 1 atomic% fluorine were contained with respect to the cobalt included in the common starting materials. Hereinafter, Sample 1 will be expressed as using 0.5 mol% MgO and 1 mol% LiF as 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 included in the common starting materials. The same applies to Samples 2 and later.

[0278] For Sample 2, 0.5 mol% MgO and 0.5 mol% LiF with respect to cobalt were used as additional starting materials. For Sample 3, 0.5 mol% MgO and 2 mol% LiF were used as additional starting materials. For Sample 4 as a comparative example, 1 mol% LiF was used as an additional starting material and magnesium was not added. For Sample 5 as a comparative example, 0.5 mol% MgO was used as an additional starting material and fluorine was not added. For Sample 6 as a comparative example, neither magnesium nor fluorine was added. The common starting materials and additional starting materials for each sample are shown in Table 1.

[0279]

[0280]

[0281]

Table 1

[0282] Regarding the above six samples, in the same manner as the production method described in Embodiment 1, 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 steps, and the positive electrode active material after these steps 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 before the second heating 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.

[0284] As shown in Figure 22(B), in Sample 1 containing magnesium and fluorine in the starting material, some magnesium segregation was observed 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 fluorine in the starting material, no segregation of magnesium near the surface was observed.

[0286] As shown in Figure 22(C) and Figure 23(C), almost no fluorine was observed inside the positive electrode active material in both Sample 1 and Sample 5. This was 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: Monochromatized Al (1486.6 eV) Detection area: 100 μm φ Detection depth: Approximately 4 - 5 nm (extraction angle 45°) Measurement spectrum: Wide, Li 1s, Co 2p, Ti 2p, O 1s, C 1s, F 1s, S 2p, Ca 2p, Mg 1s, Na 1s, Zr 3d

[0289] The results of quantifying the concentration 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 ratio 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 the additive starting materials, even before the second heating, magnesium was present near the surface of the positive electrode active material measurable by XPS. After the second heating, the amount of magnesium near the surface of the positive electrode active material further increased. That is, it is considered that the segregation of magnesium to the surface of the positive electrode active material progressed due to the second heating.

[0295] ​ 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 has no 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 has the unexpected effect of segregating magnesium to the surface layer portion of the positive electrode active material.

[0297] <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 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, and the 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 and coated on the current collector.

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

[0300] As the electrolyte contained in the electrolytic solution, 1 mol / L 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] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0302] The measurement temperature for the cycle characteristic test was 25°C. Charging was performed at a current density of 68 The current density was then set at 1.4mA / g, with a constant current of 0.5mA / g and an upper limit voltage of 4.6V. The battery was charged at a constant voltage up to 1000 V. The battery was discharged at a constant voltage of 68.5 mA / g per unit weight of active material. The charge / discharge cycle was performed at a current of 100 mA and a lower limit voltage of 2.5 V. 30 charge / discharge cycles were performed for each battery.

[0303] 25(A) and 25(B) show the results of the first and second heating of sample 1 and the first heating of sample 5. FIG. 25(A) shows a graph of the cycle characteristics of a secondary battery using the positive electrode active material of FIG. 1 before and after heating. ) is the energy density when charged to 4.6V, and Fig. 25(B) is the energy density when charged to 4.6V. 1 is a graph showing the retention rate. The energy density is the product of the discharge capacity and the average discharge voltage.

[0304] As shown in FIG. 25, in sample 1 having magnesium and fluorine in the added starting material, The cycle characteristics were significantly improved by heating the battery in step 2. The energy density was also good. Ta.

[0305] As was made clear from the XPS results mentioned above, the positive This is believed to be due to an increase in the amount of magnesium present near the surface of the electrode active material.

[0306] On the other hand, in sample 5, which has only magnesium in the added starting material, the No significant difference was observed in the cycle characteristics.

[0307] Next, in FIG. 26 and FIG. 27, the positive electrode active materials of Samples 1 to 6 after the second heating are used. The graph showing the cycle characteristics of the secondary battery is shown. FIG. 26 is a graph of the energy density when charged at 4.6V and FIG. 27 is a graph of the energy density retention rate when charged at 4.6V.

[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 clarified 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 clarified 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 Sample 7 and Sample 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, collected, and a positive electrode active material was produced to fabricate a secondary battery.

[0313] The common starting materials and additive starting materials of Samples 1, 7, and 8, where the atomic ratio of magnesium to fluorine in the raw materials is Mg:F = 1:2, and Sample 6 without added magnesium and fluorine as a comparative example are shown in Table 4.

[0314]

Table 4

[0315] <Cycle characteristics> Graphs of the cycle characteristics of secondary batteries using the positive electrode active materials of Samples 1, 7, 8, and Sample 6 (comparative example) are shown in FIGS. 28(A) and 28(B). FIG. 28(A) is a graph of the energy density during charging at 4.6 V, and FIG. 28(B) is a graph of the energy density retention rate during charging at 4.6 V. As shown in FIGS. 28(A) and 28(B), all 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 using 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 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, as a result 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, it is shown. Regarding.

[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.

[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), in which magnesium oxide was coated on lithium cobaltate using a polygonal barrel sputter, were used. Sample 9 (Comparative Example) and the production method of Sample 10 (Comparative Example) will be described below. Regarding.

[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. .

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

[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.

[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 and the like. 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 and the like. 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 and the like. 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 and the like. 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 a 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 a 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 a 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 the 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 the 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 the 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 the secondary batteries using the positive electrode active materials of Sample 7, Sample 9 (comparative example), and Sample 10 (comparative example), respectively.

[0330] A sample having a second region formed by segregation of magnesium, as shown in Fig. 31 Sample 7 had a larger capacity 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 had 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 additive 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 clarified to be an image of

[0011] incidence .

[0340] Figure 34(A) is the same STEM image near the surface of the positive electrode active material as in Figure 33(A), and the FFT image of the region shown by FFT2 in Figure 34( A) is shown in Figure 34(B). Some of the bright spots in the FFT image of Figure 34(B) are named A, B, C, and O as shown in Figure 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 the data of lithium cobaltate (LiCoO2) in the ICDD database ( ICDD50 - 0653), where the d of OA(101) is 0.24 nm, OB( 104) is 0.20 nm, OC(003) is 0.47 nm, ∠AOB = 25°, ∠BOC = 55°, and ∠AOC = 80°. Therefore, the region shown by FFT2 is a region having lithium cobaltate and was clarified to be an image of

[0010] incidence.

[0343] Also, from the STEM images of Figure 33(A) and Figure 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 orientation was consistent between the first region and the second region.

[0344] <stem-edx> Next, the results of analyzing the vicinity of the surface and the vicinity of 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 added with 0.5 mol% MgO and 1 mol% LiF in Example 1 than Sample 1 (FIG. 22), using the starting materials added with 1 mol% MgO and 2 mol% LiF Sample 7 (FIG. 35) has clearer magnesium observed in the vicinity of the surface of the positive electrode active material. This supports the result of Example 1 that the more magnesium there is in the vicinity of 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 crystal defects of the positive electrode active material of Sample 7. In the crystal defect 1001 in the figure, a portion with a different brightness from the others considered to be crystal defects was observed.

[0348] The results of analyzing the portion of 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 portion, 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 defects and their 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 sample. 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 the sample. This was considered to be because fluorine, which is a light element, is difficult to detect by EDX. )

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

[0352] Multiple positive electrode active material particles were used as samples, and ToF-SIMS analysis and sputtering were alternately repeated while performing analysis in the depth direction from the surface of the positive electrode active material. The measuring device 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] Magnesium oxide ions ([MgO2] 2- ) and fluorine ions (F - ) about the intensity of, Fig. 38 shows a graph with the horizontal axis being the number of measurements (number of cycles). In this measurement, since analysis is being performed on negative ions, the distribution of magnesium is evaluated by the intensity of [MgO2] 2- . Each intensity is normalized with the maximum value set to 1. As shown in Fig. 38, in Sample 7 having the second region formed by magnesium segregation, it is clear that the depth direction distributions and peaks of magnesium and fluorine overlap

[0354] . became.

[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 has been removed, so the quantification error is larger than usual.

[0357]

Table 6

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

[0359] As shown in Table 6, in the range from a depth of 4 nm to 5 nm from the surface towards 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 shown are the XPS spectra of standard samples of MgF2 and LiF.

[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. For the fluorine present in the surface layer of the positive electrode active material, LiF was considered to be the main binding state. 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 682 eV or more and less than 685 eV, more precisely 684.3 eV. This did not match 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. .

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 cathode active materials of Samples 11 to 13> Cathode active materials of Samples 11 to 13 were prepared by varying the temperature of the second heating. All the 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.

[0366] The cathode active materials were prepared in the same manner as Sample 7 of Example 1, except that the temperature of the second heating was 700 °C for Sample 11, 900 °C for Sample 12, and 1000 °C for Sample 13. 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 cathode active materials of Sample 7 and Samples 11 to 13, secondary batteries were fabricated in the same manner as in Example 1, and their 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 700 °C and 12 with the second heating temperature of 900 °C showed the next best cycle characteristics. ​ 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. 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

[0370] 00°C or lower, and even more preferably about 800°C.

[0371] ≪Atmosphere of the second heating≫ <Production of the positive electrode active material of Samples 14 to 16> The positive electrode active materials of Samples 14 to 1 6 were produced with the atmosphere of the second heating changed from dry air to 100% oxygen. All starting materials were lithium carbonate and cobalt oxide as the common starting materials, and 1 mol% MgO and 2 mol% LiF as the added starting materials were used. The positive electrode active materials were produced in the same manner as 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 produced 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 of 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) show the case where the temperature of the second heating was 800°C. Sample 14 and Sample 7, Figures 41(B) and 42(B) are for the samples at 900°C Sample 15 and Sample 12, Figures 41(C) and 42(C) are for the samples at 1000°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 second heating for each

[0374]

Table 8

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

Example

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

[0377] ≪Comparison between Fluorine and Chlorine≫ First, the cycle characteristics were compared when magnesium and fluorine were used as the additive starting materials and when chlorine was used instead of fluorine.

[0378] <Preparation of Cathode Active Materials for Samples 17 and 18> For Sample 7, 1 mol% MgO and 2 mol% LiF were used as the additive starting materials with respect to cobalt. 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% 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 any metal, Sample 6 of Example 1 was used.

[0385] For Sample 6, Sample 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 .

[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 to do so.

[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 to be extremely effective.

[0390] From the previous examples, by adding magnesium and fluorine as the starting materials for the positive electrode active material, it was revealed that magnesium segregates on the surface of the positive electrode active material. Also, since 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 was found to be a positive electrode active material with high capacity and excellent cycle characteristics. It was found to be a positive electrode active material with high capacity and excellent cycle characteristics.

[0391] Since the 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, and it can also contribute to energy saving and reduction of carbon dioxide emissions. Since the 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, and it can also contribute to energy saving and reduction of carbon dioxide emissions. Since the 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, and it can also contribute to energy saving and reduction of carbon dioxide emissions. Since the 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, and it can also contribute to energy saving and reduction of carbon dioxide emissions.

Examples

[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. 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. Sample 31 having magnesium and fluorine and Sample 32 having no magnesium and fluorine as a comparative example were prepared.

[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, the starting materials 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, the starting materials 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 for 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 for the added 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 of 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] For Sample 32, each starting material was weighed so as to have an atomic ratio of LiCo 0.333 Mn 0.333 Ni 0.333 O2. Further, firing was performed at 1000 °C. Otherwise, it was produced 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, using the positive electrode active materials of Sample 31 and Sample 32 prepared as described above, coin-type secondary batteries of CR2032 type (diameter 20 mm, height 3.2 mm) were fabricated, and their cycle characteristics were evaluated. coin-type secondary batteries of CR2032 type (diameter 20 mm, height 3.2 mm) were fabricated, and their cycle characteristics were evaluated.

[0408] 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 :2.5 was coated on a current collector of aluminum foil and used. Further, N-methyl-2-pyrrolidone (NMP) was used as the solvent. For the positive electrode, a slurry obtained by mixing the positive electrode active materials of Sample 31 and Sample 32, acetylene black (AB

[0409] Lithium metal was used for the counter electrode.

[0410] As the electrolyte for the electrolyte solution, 1 mol / L of lithium hexafluorophosphate (LiPF6) was used. For the electrolyte solution, ethylene carbonate (EC) and diethyl carbonate (DEC) were used in a mixture of EC:DEC = 3:7 (volume ratio), to which vinylene carbonate (VC) was added at 2 wt%.

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

[0412] The measurement temperature for the cycle characteristic test was 25°C. Charging was carried out 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 carried out until the current density reached 1.4 mA / g. Discharging was carried out at a constant current of 68.5 mA / g per active material weight and a lower limit voltage of 2.5 V.

[0413] The discharge capacity at the time of charging to 4.6 V 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.

[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 characteristics.

[0415] Next, the results of various analyses performed on 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 obtained by enlarging a part of FIG. 44(A).

[0417] As is clear from FIG. 45, a region about 0.5 nm from the surface of the positive electrode active material was observed to have a different brightness from other regions. This was considered to be because there was a large amount of magnesium, an element lighter than the transition metal.

[0418] In addition, a region from about 0.5 nm to about 5 nm from the surface of the positive electrode active material was observed to have different regularity from the internal region. 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.

[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). Part of the bright spots of the FFT1 image is denoted as A, B, C, and O as shown in FIG. 46(B).

[0420] Regarding the bright spots of the FFT image of the region indicated by FFT1, the measured values were d = 0.2 2 nm for OA, d = 0.25 nm for OB, and d = 0.23 nm for OC. 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 became clear that the regions shown by FFT2 and FFT3 have the same layered rock - salt - type crystal structure but different crystal axis directions.

[0429] Also, within the observable ranges in Figs. 45(A), 45(B), and 46(A), even though the brightness is different, it was observed that the crystal orientations were generally consistent.

[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 along with the STEM image. M in Fig. 47 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 to overlap.

[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, the repeating pattern of the oxygen atom layer, the M (any one of nickel, manganese, cobalt) atom layer, and the lithium atom layer can be observed. In the bright-field STEM image, the repeating dark and bright layers are considered to be due to the repeating M layer and the oxygen and lithium layers. That is, FFT3 and FFT2 have the same layered rock salt-type crystal structure, but the directions of the crystal axes are different.

[0433] Moreover, 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 the image of

[0011] incidence.

[0434] <edx> Next, the results of analyzing a cross-section near the surface of the positive electrode active material of Sample 31 using EDX are shown in Figs. 48 and 49.

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

[0436] First, from Fig. 48(B-1), it was observed that magnesium was analyzed in a region about 3 nm from the surface of the positive electrode active material. Also, from the comparison of Fig. 49(A-2), Fig. 49(B-1), and Fig. 49(B -2), it was observed that there is a region in the surface layer part of the positive electrode active material where manganese is less and nickel and cobalt are more than in the interior. This region is about 5 nm from the surface and almost overlaps with the region where different regularities were observed from the interior in the STEM image. Therefore, it was confirmed that Sample 31 is a positive electrode active material having a region containing magnesium in the surface layer part and a region with a low manganese content in a part of the interior.

[0437] Summarizing the above results, the positive electrode active material of Sample 31 prepared by heating at 800 °C with the molar ratio of starting materials as LiNi Mn .

[0438] +1 mol% MgO + 2 mol% LiF was found to have the following characteristics. 1 / 3 Mn 1 / 3 Co 1 / 3 O2

[0439] First, the positive electrode active material of sample 31 has a second region having magnesium oxide in the surface layer. The inner part has a layered rock-salt type crystal structure, and the inner part has LiNi x Mn y Co z O2(x+y+z=1) and layered rock salt type crystals near the surface. LiNi with crystal structure a Mn b Co c O2(a+b+c=1) and a region having do.

[0440] LiNi inside x Mn y Co z O2 and LiNi a Mn b Co c O2 is the same layered salt structure. They have a crystal structure, but the orientation of the crystal axes may differ.

[0441] In addition, the content of each element is y>b, and the sum of nickel, manganese, and cobalt is In contrast, the manganese content may be low in regions close to the surface.

[0442] The positive electrode active material of sample 31 having the above characteristics is extremely suitable for use in secondary batteries. It shows good cycle characteristics. EXAMPLES

[0443] In this example, cobalt is used as the transition metal, and magnesium and fluorine are used as the starting materials. The results of EELS analysis of the positive electrode active material prepared by adding .

[0444] The sample of Example 1 was prepared by adding 1 mol% MgO and 2 mol% LiF as 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 unit 7103 Operation button 7104 Secondary battery 7200 Portable information terminal 7201 Housing 7202 Display unit 7203 Band 7204 Buckle 7205 Operation Button 7206 Input / Output Terminal 7207 Icon 7300 Display Device 7304 Display Unit 7400 Mobile Phone 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 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 DCDC 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, 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 exists in a range where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 of the peak, A lithium ion secondary battery.

3. having 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. A lithium-ion secondary battery.

4. 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 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. A lithium-ion secondary battery.

5. In claim 3 or claim 4, The carbon fiber is carbon nanofiber or carbon nanotube. Lithium-ion secondary battery.

6. having 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 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 line analysis of STEM-EDX is 1 / 5 of the peak, Lithium-ion secondary battery.

7. having 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 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 is present in a range where the concentration of magnesium detected by the line analysis of STEM-EDX is 1 / 5 of the peak. Lithium-ion secondary battery.

8. In claim 6 or claim 7, The crystal defect is observed in a TEM image or a STEM image. Lithium-ion secondary battery.

9. 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 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. 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 electrolyte has vinylene carbonate. 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 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, A lithium-ion secondary battery.

11. In claim 9 or claim 10, the electrolytic solution further has a dinitrile compound, A lithium-ion secondary battery.

12. In claim 11, the dinitrile compound has adiponitrile, A lithium-ion secondary battery.

13. In claim 12, the electrolytic solution has the adiponitrile as an additive, the concentration of the additive is 0.1 wt% or more and 5 wt% or less with respect to the entire solvent of the electrolytic solution. A lithium-ion secondary battery.

14. In claim 11, the dinitrile compound has succinonitrile, A lithium-ion secondary battery.

15. In claim 14, the electrolytic solution has the succinonitrile as an additive, the concentration of the additive is 0.1 wt% or more and 5 wt% or less with respect to the entire solvent of the electrolytic solution. A lithium-ion secondary battery.

16. In any one of claims 9 to 15, the electrolytic solution further has one or more selected from ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, and fluoroethylene carbonate, Lithium-ion secondary battery.

17. In any one of Claims 9 to 16, the electrolyte solution contains LiPF ６ and is a lithium-ion secondary battery.

18. In any one of Claims 9 to 16, the electrolyte solution contains LiBF ４ and is a lithium-ion secondary battery.

19. In any one of Claims 1 to 18, the thickness of the second region is 0.5 nm or more and 50 nm or less, and it is a lithium-ion secondary battery.

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