Lithium-ion secondary battery

Abstract

To provide a positive electrode active material capable of improving cycle characteristics of a secondary battery.SOLUTION: Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. An inner region is a non-stoichiometric compound containing a transition metal such as titanium, and an outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy. Since these are topotaxy, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since an outer coating layer in contact with an electrolyte is a compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One aspect of the present invention relates to an article, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, a manufacture, or a composition of matter. One aspect of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, or an electronic device, or a manufacturing method thereof. In particular, it relates to a positive electrode active material that can be used in a secondary battery, a secondary battery, and an electronic device having the secondary battery.

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

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

Background Art

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

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

[0006] Therefore, improvements to the cathode active material have been studied with the aim of improving the cycle characteristics and increasing the capacity of lithium-ion secondary batteries. (Patent Documents 1 and 2)

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

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

[0009] 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 high-capacity secondary battery. Or, one aspect of the present invention is to provide a secondary battery with excellent charge-discharge characteristics. Or, one aspect of the present invention is to provide a secondary battery with high safety or reliability. Or, one aspect of the present invention is to provide a secondary battery with high safety or reliability as one of the problems.

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

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

Means for Solving the Problems

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

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

[0014] One aspect of the present invention is a positive electrode active material, which has a first region, a second region, and a third region. The first region exists inside the positive electrode active material, the second region and the third region exist on the surface layer portion of the positive electrode active material, the third region exists in a region closer to the surface of the positive electrode active material than the second region, the first region has an oxide of lithium and a first transition metal, and has a layered rock salt-type crystal structure. The second region has a non-stoichiometric compound containing an oxide of a second transition metal.

[0015] ​​​​​​​​​has, the non-stoichiometric compound has a rock-salt type crystal structure, and the third region has a compound of typical elements, The compound of typical elements is a cathode active material having a rock-salt type crystal structure.

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

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

[0018] In the above, the crystal orientation of the first region and that of the second region partially coincide, and it is preferable that the crystal orientation of the second region and that of the third region partially coincide.

[0019] In the above, the (1-1-4) plane of the layered rock-salt type crystal structure possessed by the first region, or a plane orthogonal to the (1-1-4) plane, and the {100} plane of the rock-salt type crystal structure possessed by the second region have a misorientation degree of 0.12 or less, and the {100} plane of the rock-salt type crystal structure possessed by the second region and the {100} plane of the rock-salt type crystal structure possessed by the third region have a misorientation degree of 0.12 or less. This is preferable.

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

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

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

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

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

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

[0026] Also, by covering the surface of the positive electrode active material with a film to protect the above-described crystal structure, it is possible to suppress a decrease in capacity during charge and discharge cycles. The film covering the surface of the positive electrode active material is a film having carbon (a film containing a graphene compound), or a film having lithium or a decomposition product of the electrolytic solution is used.

[0027] In particular, it is preferable to obtain a powder in which the surface of the positive electrode active material is coated with graphene oxide using a spray drying device. The spray drying device is a manufacturing device using a spray drying method in which hot air is supplied to a suspension to remove the dispersion medium.

[0028] By repeatedly performing charge and discharge cycles, there is a risk that cracks or fractures may occur in the particles of the positive electrode active material. Such a shape change may expose a new surface of the positive electrode active material, and the surface may come into contact with the electrolytic solution to cause a decomposition reaction or the like, and it is said that the cycle characteristics and charge and discharge characteristics of the secondary battery are deteriorated. Therefore, it is preferable to provide a coating film that can prevent shape changes such as cracks or fractures in the particles of the positive electrode active material.

[0029]

[0030] However, in order to coat the surface of the positive electrode active material having a heavy weight per unit volume with relatively light graphene oxide, a suspension was prepared and a revolving mixer was used, but the coating was insufficient.

[0031] Therefore, in order to coat the particle surface of the positive electrode active material with graphene oxide, it is preferable to mix graphene oxide and a polar solvent (such as water), perform ultrasonic treatment, further mix the particles of the positive electrode active material, prepare a suspension, and then produce a dry powder using a spray drying apparatus. The dry powder produced in this way may be referred to as a composite. The size of a single droplet of the spray liquid sprayed from the nozzle of the spray drying apparatus depends on the nozzle diameter. If the particle diameter is smaller than the nozzle diameter, multiple particles will exist within a single droplet of the spray liquid sprayed from the nozzle. When checking the surface of the particles after drying under the condition that the maximum particle diameter is smaller than the nozzle diameter, although some coated portions of graphene oxide can be confirmed, it cannot be said that the coating is sufficient. It is preferable that the nozzle diameter of the spray drying apparatus and the maximum particle diameter of the active material are of the same order, so that the coating property of the active material is good. Furthermore, it is preferable to adjust the size of the maximum particle diameter of the positive electrode active material in the production of the positive electrode active material so that it is of the same order as the nozzle diameter.

[0032] Since graphene oxide is well dispersed in water, a suspension of water and graphene oxide can be prepared by stirring using ultrasonic waves. By adding the positive electrode active material to the suspension and spraying it using a spray drying apparatus, a powder in which the surface of the positive electrode active material is coated with graphene oxide can be obtained.

[0033] Note that the suspension becomes more acidic as the amount of graphene oxide increases. Therefore, the positive electrode active material

[0034]

[0035]

[0036]

[0036]

[0036] There is a risk of etching a part of the surface (for example, LiCoO2 containing Mg or F). Therefore, it is preferable to adjust the hydrogen ion index (pH) of the suspension before spraying to approach about pH 7, that is, to approach neutrality, or to make it pH 8 or higher, that is, alkaline. For this pH adjustment, it is preferable to use an aqueous LiOH solution. Also, for example, when using LiCoO2 as the positive electrode active material, if only pure water is used as the dispersion medium of the suspension, the surface of the positive electrode active material may be damaged. Therefore, by using a mixture of ethanol and water as the dispersion medium of the suspension, damage to the surface of the active material may be reduced.

[0037] By preparing the suspension as described above, a positive electrode active material efficiently coated with graphene oxide on the surface can be prepared. By coating the surface with graphene oxide, it is possible to prevent shape changes such as cracks or fractures in the particles of the positive electrode active material. In addition, the positive electrode active material with a surface coated with graphene oxide can suppress alteration and deterioration even when it comes into contact with the atmosphere or the like after production. Here, after production refers to the period from after the production of the positive electrode active material to the production of a secondary battery using the positive electrode active material, including storage and transportation of the positive electrode active material. Also, by forming the film, it is possible to prevent direct contact and reaction between the positive electrode active material and the electrolyte. Therefore, when a secondary battery is produced, the reliability of the secondary battery is improved.

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

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

[0040] Another aspect of the present invention is a secondary battery having a positive electrode having the above positive electrode active material or the positive electrode active material covered with a film, and a negative electrode.

[0041] In addition, various shapes of secondary batteries can be used according to the device to be used. For example, cylindrical shapes, rectangular shapes, coin-type shapes, laminate (flat plate) shapes, etc. can be mentioned.

Advantages of the Invention

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

Brief Description of the Drawings

[0043]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

Figure 32

Figure 33

Figure 34

Figure 35

Figure 36

Figure 37

Figure 38

Figure 39

Figure 40

Figure 41

Figure 42

Figure 43

Figure 44

Figure 45

Figure 46

Figure 47

Figure 48

Figure 49

Figure 50

Figure 51

Figure 52

Figure 53

Figure 54

Figure 55

Figure 56

Figure 57

Figure 58

Mode for Carrying Out the Invention

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art can easily understand that its form and details can be variously changed. Also, the present invention is not construed as being limited to the description content of the embodiments shown below. In addition, in each of the drawings described in this specification, the size, thickness, etc. of each component such as the positive electrode, negative electrode, active material layer, separator, and exterior body may be exaggerated for the sake of clarity of individual explanations. Therefore, each component is not necessarily limited to its size, and the relative

[0045] between each component is not necessarily limited to its size, and the relative relationship between each component is not necessarily limited to its size, and the relative ​​It is not limited to a relative size.

[0046] In addition, in the configuration of the present invention described in this specification, etc., the same parts or parts having similar functions The same reference numerals are used for the components in different drawings, and the repeated explanations will be omitted. When referring to parts with similar functions, the hatch pattern is the same and no special reference numeral is attached. There may not be.

[0047] In addition, in this specification and the like, Miller indices are used to denote crystal planes and directions. In the notation, a superscript bar is added to the number in crystallography, but in this specification, the crystal plane and Due to limitations on notation, directions are indicated by a - (minus sign) before the number instead of a bar above the number. Also, individual directions that indicate directions within a crystal are expressed in [ ], and equivalent directions are expressed in [ ]. The collective orientation indicating all crystals is indicated by < >, and the individual crystal faces are indicated by ( ), and they have equivalent symmetry. The aggregate planes are represented by {}. Note that the crystal planes and directions in the drawings are The crystallographic notation is given with a bar above the number. Also, 1 Å (angstrom) is 10 -10 m.

[0048] In this specification, segregation refers to a phenomenon in which a solid consisting of multiple elements (e.g., A, B, C) This refers to the phenomenon in which a certain element (such as B) is distributed unevenly.

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

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

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

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

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

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

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

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

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

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

[0059]

[0060]

[0061] <The first region 101> The first region 101 has a composite oxide of lithium and a first transition metal. Also, the first region 101 may be said to have lithium, a first transition metal, and oxygen. It is preferable that the composite oxide of lithium and the first transition metal has a layered rock salt type crystal structure.

[0060]

[0061] ​​ As the first transition metal, only cobalt may be used, or a mixture of cobalt and cobalt may be used as the first transition metal. Two types of cobalt and manganese may be used, or three types of cobalt, manganese, and nickel may be used. good.

[0062] That is, the first region is made up of lithium cobalt oxide, lithium manganese oxide, and lithium nickel oxide. , lithium cobalt oxide in which some of the cobalt is replaced by manganese, nickel-manganese-cobalt oxide, The first region 101 may contain, in addition to the transition metal, lithium valence oxide, etc. It may contain metals other than transition metals, such as aluminum.

[0063] The first region 101 functions as a region that particularly contributes to the charge-discharge reaction in the positive electrode active material 100. In order to increase the capacity when the positive electrode active material 100 is used in a secondary battery, the first region Preferably, the volume of the region 101 is larger than that of the second and third regions.

[0064] Materials with a layered rock salt crystal structure have high discharge capacity and allow lithium to diffuse two-dimensionally. Therefore, it has the advantage of being low in resistance, and is therefore preferable as the first region 101. When the region 101 has a layered rock salt type crystal structure, it is surprisingly possible to Segregation of typical elements is likely to occur.

[0065] The first region 101 may be either single crystal or polycrystalline. The powder 1 may be polycrystalline with an average crystallite size of 280 nm or more and 630 nm or less. In the case of crystals, the grain boundaries can sometimes be observed using a TEM. The average grain size is It can be calculated from the half-width of XRD.

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

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

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

[0069] As the second transition metal, it is preferable to use a metal with non-stoichiometry. It may be said that the second region 102 preferably has a non-stoichiometric compound. For example, at least one of titanium, vanadium, manganese, iron, chromium, niobium, cobalt, zinc, zirconium, nickel, etc. can be used as the second transition metal. However, the second transition metal is preferably an element different from the first transition metal.

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

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

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

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

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

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

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

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

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

[0079] Note that the second region 102 preferably has a rock-salt type crystal structure, but not all of the second region 102 needs to have a rock-salt type crystal structure. For example, the second region 102 may have a spinel type crystal structure, an olivine type crystal structure, a corundum type crystal structure, a rutile type crystal structure, or other crystal structures. 2 may have other crystal structures such as a spinel type crystal structure, an olivine type crystal structure, a corundum type crystal structure, or a rutile type crystal structure. In addition, as long as the structure in which six oxygen atoms are adjacent to the cation is maintained, there may be distortion in the crystal structure. Also, there may be a cation deficiency in a part of the second region 102.

[0080] In addition, a part of the second region 102 may be amorphous. If the second region 102 is too thin, its function as a buffer region will deteriorate, but if it is too thick, there is a risk of causing a decrease in capacity. Therefore, the second region 102 preferably exists from the surface of the positive electrode active material 100 to a depth of 20 nm, more preferably up to 10 nm in the depth direction.

[0081]

[0082] In addition, the second transition metal may have a concentration gradient.

[0083]

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

[0084] The third region 103 is a region that comes into contact with the electrolyte when the positive electrode active material 100 is used in a secondary battery. Therefore, the material used for the third region 103 is preferably a material that undergoes few electrochemical changes during charge and discharge and is not easily altered upon contact with the electrolyte. A compound of typical elements that is a stoichiometric compound and is electrochemically stable is preferable for the third region 103. By having the third region 103 in the surface layer portion of the positive electrode active material 100, the stability of the secondary battery during charge and discharge can be improved. Here, high stability of the secondary battery means, for example, that the crystal structure of the composite oxide containing lithium and the first transition metal possessed by the first region 101 is more stable. Alternatively, it means that the change in the capacity of the secondary battery is small even when charge and discharge are repeated. Alternatively, it means that the valence change of the metal possessed by the positive electrode active material 100 is suppressed even after charge and discharge are repeated.

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

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

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

[0088] Also, it is preferable that the compound of the typical element contained in the third region 103 has a rock-salt type crystal structure. When the third region 103 has a rock-salt type crystal structure, the crystal orientation is likely to match that of the second region 102. When the crystal orientations of the first region 101, the second region 102, and the third region 103 are substantially the same, the second region 102 and the third region 103 can function as a more stable coating layer. However, not all of the third region 103 needs to have a rock-salt type crystal structure. For example, the third region 103 may have other crystal structures such as a spinel type crystal structure, an olivine type crystal structure, a cordierite type crystal structure, and a rutile type crystal structure. It may be.

[0089] Moreover, as long as the structure in which six oxygens are adjacent to the cation is maintained, the crystal structure may have a distortion. Also, there may be a cation deficiency in a part of the third region 103. The third region 103 may have other crystal structures such as a spinel type crystal structure, an olivine type crystal structure, a cordierite type crystal structure, and a rutile type crystal structure. It may be.

[0090] In addition, as long as the structure in which six oxygens are adjacent to the cation is maintained, the crystal structure may have a distortion. Also, there may be a cation deficiency in a part of the third region 103. Moreover, a part of the third region 103 may be amorphous.

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

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

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

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

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

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

[0097] When the crystal orientations from the first region 101 to the third region 103 are substantially the same, the second region 102 and the third region 103 function as a coating layer having a stable bond with the first region 101. Therefore, the

[0098] positive electrode active material 100 having a strong coating layer can be obtained. Since the second region 102 and the third region 103 have a stable bond with the first region 101, when the positive electrode active material 100 is used in a secondary battery, the change in the crystal structure of the first region 101 caused by charge and discharge can be effectively suppressed. Further, even when lithium is removed from the first region 101 during charging, the detachment of cobalt and oxygen from the first region 101 can be suppressed by the coating layer

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

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

[0101]

Equation

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

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

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

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

[0106] Example 1: Lithium cobalt oxide, lithium titanate, and magnesium oxide First, referring to FIGS. 2 and 3, the first transition metal is cobalt, and the first region 101 is a layer The lithium cobalt oxide has a crystalline rock salt structure, and the second transition metal is titanium. The second region 102 has lithium titanate having a rock salt crystal structure, and the third region 1 An example where the compound of the main group element in 03 is magnesium oxide with a rock salt type crystal structure This article explains:

[0107] Figure 2(A) shows the layered rocksalt structure of lithium cobalt oxide (LiCoO2) (space group R-3mH). Crystal structure model of lithium titanate (LiTiO2) rock salt type (space group Fd-3mZ) ) crystal structure model, and crystals of magnesium oxide rock salt type (space group Fd-3mZ) The structural model is shown in Figure 2(A). All the models are viewed from the b-axis direction.

[0108] From the diagram of Figure 2(A) alone, it is not clear that layered rock salt crystals and rock salt crystals can be topotactic. However, here, we can see that the layered rock salt crystals are arranged in different orientations (for example, the arrows in Figure 2(A)). In Figure 2(B), a layered rock salt crystal is viewed from the <1-1-4> plane. Orientation model of rock salt crystals <100> The model shown is viewed from the plane orientation.

[0109] As shown in Figure 2(B), when the layered rock salt crystal is viewed from the <1-1-4> plane orientation, the rock salt Crystals of the type <100> The atomic arrangement is similar to that seen from the plane orientation of the metal. The bare nearest-neighbor distances are also of similar values. For example, in layered rock-salt type lithium cobaltate, the Li-O distance is 2.089 Å and the Co-O distance is 1.925 Å. Also, in rock-salt type lithium titanate, the Li-O distance is 2.138 Å and the Ti-O distance is 2.051 Å. Further, in rock-salt type magnesium oxide, the Mg-O distance is 2.106 Å. Therefore, the Li-O distance between them is 2.089 Å and the Co-O distance is 1.925 Å. Also, in rock-salt type lithium titanate the Li-O distance is 2.138 Å and the Ti-O distance is 2.051 Å. Also, in rock salt type magnesium oxide, the Mg-O distance is 2.106 Å.

[0110] Therefore, using Fig. 3, the mismatch degree between regions when the (1-1-4) crystal plane of the layered rock-salt type crystal and the {1 00} crystal plane of the rock-salt type crystal are in contact will be explained.

[0111] As shown in Fig. 3, the metal-oxygen-metal distance of the (1-1-4) crystal plane 101p(1-1-4) of lithium cobaltate having a layered rock-salt type crystal structure in the first region 101 is 4. 01 Å. Also, the metal-oxygen-metal distance of the { 100} crystal plane 102p{100} of lithium titanate having a rock-salt type crystal structure in the second region 102 is 4.19 Å. Therefore, the mismatch degree f between the crystal plane 101p(1-1-4) and the crystal plane 102p{100} is 0 .04.

[0112] Also, the metal-oxygen-metal distance of the {100} crystal plane 103p{100} of magnesium oxide having a rock-salt type crystal structure in the third region 103 is 4.21 Å. Therefore, the mismatch degree f between the crystal plane 102p{100} and the crystal plane 103p{100} is 0.02.

[0113] [[ID=3,8]]Thus, since the mismatch degree between the first region 101 and the second region 102, and the mismatch degree between the second region 10 2 and the third region 103 are sufficiently small, topotaxy can occur from the first region 101 to the third region 103.

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

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

[0116] ≪Example 2: Lithium Cobalt Oxide, Manganese Oxide, and Calcium Oxide≫ Next, an example will be described in which the first transition metal is cobalt, the first region 101 has lithium cobalt oxide having a layered rock salt type crystal structure, the second transition metal is manganese, the second region 102 has manganese oxide having a rock salt type crystal structure, and the compound of the typical element included in the third region 103 is calcium oxide having a rock salt type crystal structure. In this case as well, similar to FIGS. 2 and 3, when the layered rock salt type crystal of the first region 101 is viewed from the <1-1 -4> plane orientation, the atomic arrangement is similar to that when the rock salt type crystals of the second region 102 and the third region 103 are viewed from the <100> plane orientation.

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

[0118] The crystal plane (1-1-4) of the layered rock salt-type crystal is in contact with the {100} crystal plane of the rock salt-type crystal The mismatch degree between the regions will be described. The crystal plane (1-1-4) of lithium cobaltate with a layered rock salt-type crystal structure in the first region 101 The metal-oxygen-metal distance between the metal-oxygen-metal is 4.01 Å. Also, the metal-oxygen-metal distance between the metal-oxygen-metal of the crystal plane {100} of manganese oxide with a rock salt-type crystal structure in the second region 102 is 4.45 Å. Therefore, the mismatch degree f between the crystal plane (1-1-4) of the first region 101 and the crystal plane {100} of the second region 102 is 0 0.11. 0.11. .11.

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

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

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

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

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

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

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

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

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

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

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

[0130] For example, in TEM images and STEM images, differences in the constituent elements are observed as differences in the brightness of the images. Therefore, it can be observed that the constituent elements of the first region 101, the second region 102, and the third region 103 are different. Also, in the surface analysis of EDX (for example, elemental mapping), it can be observed that the first region 101, the second region 102, and the third region 103 have different elements. region 101, the second region 102, and the third region 103 have different elements.

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

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

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

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

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

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

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

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

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

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

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

[0142] When the surface of the positive electrode active material 100 is analyzed by XPS, when the concentration of the first transition metal is set to 1, the relative value of the concentration of the second transition metal is preferably 0.05 or more and 0.4 or less, and more preferably 0.1 or more and 0. 3 or less. Also, the relative value of the concentration of the typical element is preferably 0.4 or more and 1.5 or less, more preferably 0.45 or more and 1.00 or less. Also, the relative value of the fluorine concentration is preferably 0.05 or more and 1 .5 or less, and more preferably 0.3 or more and 1.00 or less.

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

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

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

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

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

[0148] In order to promote grain growth during firing, it is effective to make the ratio of Li to the first transition metal in the starting material greater than 1, that is, to make lithium slightly excessive. For example, when the ratio of Li to the first transition metal is about 1.06, it is easy to obtain a positive electrode active material with a D50 of 15 μm or more. Note that as will be described later, since lithium may be lost outside the system during the process of producing the positive electrode active material, the ratio of lithium to the first transition metal in the resulting positive electrode active material may not match the ratio of lithium to the first transition metal in the starting material. However, if the amount of lithium becomes excessive in order to make the particle size fall within the preferred range, there is a risk that the capacity retention rate when used in a secondary battery will decrease.

[0149] However, the inventors of the present invention have clarified that by providing the second region 102 having the second transition metal in the surface layer portion, it is possible to make the particle size fall within the preferred range by controlling the ratio of Li to the first transition metal, while producing a positive electrode active material having a high capacity retention rate.

[0150] However, in the case of the positive electrode active material according to one aspect of the present invention in which a region having a second transition metal is provided in the surface layer portion, the ratio of Li to the first transition metal in the starting material is preferably 1.00 or more and 1.07 or less, and 1 .03 or more and 1.06 or less is more preferable. It has been clarified that a positive electrode active material having a high capacity retention rate can be produced.

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

[0152] [Formation of the Second Region] The second region 102 can be formed by coating particles of a composite oxide having lithium and the first transition metal with a material having the second transition metal. When firing, it is necessary to cause grain growth.

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

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

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

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

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

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

[0159] In Fig. 4(A-3), the chemical formula of titanium(IV) isopropoxide (TTIP), which is one of the titanium alkoxides described in the manufacturing method to be described later, is shown. (IV) isopropoxide (TTIP) is shown.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0174] As described above, rock-salt type cobalt oxide exists on the surface of the particles 110. Also, magnesium oxide Umm also has a rock-salt type crystal structure. Therefore, it is presumed that magnesium exists as magnesium oxide on the surface of particle 110 rather than inside particle 110 and is more stable. This is why magnesium segregates on the surface of particle 110 when heated.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0190] When the composite oxide containing lithium and the first transition metal that the first region 101 has has cracks, typical elements may also segregate into the cracks upon heating. In addition to typical elements, the second transition metal may also segregate. The crack portion is a region in contact with the electrolytic solution, similar to the particle surface. Therefore, when typical elements and the second transition metal segregate into the crack portion, the third region 103 and the second region 102 are formed, and the region in contact with the electrolytic solution can be made of a chemically stable material. Therefore, a secondary battery with excellent cycle characteristics can be obtained.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0210] First, an alkoxide of the second transition metal dissolved in alcohol and the composite oxide particles of lithium and the first transition metal are mixed.

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

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

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

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

[0215]

[0216] Next, the recovered residue is dried. In this embodiment, it is dried under vacuum at 70°C for 1 hour. <Step 15: Second Heating> Next, the composite oxide particles coated with the material having the second transition metal produced in Step 14 are heated. This step may be referred to as the second heating. The heating time is preferably set such that the holding time within the specified temperature range is 50 hours or less, more preferably 2 hours or more and 10 hours or less, and even more preferably 1 hour or more and 3 hours or less. If the heating time is too short, segregation of typical elements may not occur, but if it is too long, diffusion of the second transition metal may proceed too far and a good second region 102 may not be formed.​​​​​​​​

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

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

[0219] By heating in step 15, a composite oxide of lithium and a first transition metal is formed, and a coating thereon is formed. The oxide of the second transition metal formed in the first region 101 is topotactic. Region 102 is the topotaxis.

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

[0221] The crystal orientations of the second region 102 and the third region 103 are roughly the same, and the crystal orientations of the first region 101 are When the positive electrode active material 100 is used in a secondary battery, the positive electrode active material 100 exhibits stable bonding with the positive electrode active material 100. This effectively suppresses the change in the crystal structure of the first region 101 that occurs when the first region 101 is charged. Even when lithium has left the first region 101, the surface layer portion having a stable bond can prevent the first transition metal such as cobalt and oxygen from detaching from the first region 101. Furthermore, the region in contact with the electrolyte can be made of a chemically stable material. Therefore, a secondary battery with excellent cycle characteristics can be obtained.

[0222] Note that it is sufficient if a part of the first region 101 and the second region 102 is topotactic, and it is not necessary for all of the first region 101 and the second region 102 to be topotactic. Also, it is sufficient if a part of the second region 102 and the third region 103 is topotactic, and it is not necessary for all of the second region 102 and the third region 103 to be topotactic.

[0223] In addition, when the compound of the representative element included in the starting material contains oxygen, it is preferable to perform the heating in step 15 in an atmosphere containing oxygen. By heating in an atmosphere containing oxygen, the formation of the third region 103 is promoted.

[0224] Furthermore, the segregation of the representative element is promoted by the fluorine contained in the starting material.

[0225] As described above, in the method for producing a positive electrode active material according to one aspect of the present invention, after coating the element that forms the second region 102, heating is performed to form the third region 103, and it is possible to form two types of regions on the surface of the positive electrode active material 100. That is, normally, two coating steps are required to provide two types of regions in the surface layer portion. However, the method for producing a positive electrode active material according to one aspect of the present invention only requires one coating step (sol-gel process), so it is a productive production method.

[0226] ​​​​​​​​​​​<Step 16: Cooling> Next, the particles heated in step 15 are cooled to room temperature. For example, the time required for cooling from the holding temperature to room temperature is the same as the time required for heating. It is preferable to set the time to a time equal to or longer than that, specifically, 10 hours or more and 50 hours or less.

[0227] <Step 17: Recovery> The cooled particles are then collected. Preferably, the particles are then sieved. In this step, a positive electrode active material having a first region 101, a second region 102 and a third region 103 is formed. Substance 100 can be made.

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

[0229] (Embodiment 2) In this embodiment, a secondary battery having the positive electrode active material 100 described in the previous embodiment is used. In this embodiment, the positive electrode, the negative electrode, and the electrolyte solution However, the following description will be given taking as an example a secondary battery enclosed in an exterior body.

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

[0231] <Cathode active material layer> The positive electrode active material layer contains at least a positive electrode active material. In addition, other substances such as a coating on the surface of the active material, a conductive additive, or a binder may be included.

[0232] The positive electrode active material 100 described in the previous embodiment can be used as the positive electrode active material. By using the positive electrode active material 100 described in the previous embodiment, it is possible to achieve high capacity and good cycle characteristics. It can be an excellent secondary battery.

[0233] As the conductive assistant, a carbon material, a metal material, a conductive ceramic material, etc. can be used. Also, a fibrous material may be used as the conductive assistant. The content of the conductive assistant 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.

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

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

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

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

[0238]

[0239] ​​​​​​​​​​​​​​​An example of the cross-sectional structure will be described.

[0240] 7A shows a vertical cross-sectional view of the active material layer 200. The active material layer 200 is made of granular positive electrode active material. 100, a graphene compound 201 as a conductive additive, and a binder (not shown). Here, the graphene compound 201 may be, for example, graphene or multi-graphene. Here, the graphene compound 201 preferably has a sheet shape. In addition, the graphene compound 201 may be a multi-graphene or (and) a plurality of graphenes. The graphene may be partially overlapped to form a sheet.

[0241] In the vertical cross section of the active material layer 200, as shown in FIG. 7(B), In FIG. 7(B), the sheet-like graphene compound 201 is dispersed almost uniformly. The graphene compound 201 is shown schematically in bold, but in reality it is a single layer or multiple layers of carbon molecules. The graphene compounds 201 are thin films having a thickness of 1000 nm. The positive electrode active material 100 is partially covered with the positive electrode active material 100 or adhered to the surface of a plurality of particles of the positive electrode active material 100. Since they are formed as described above, they are in surface contact with each other.

[0242] Here, a plurality of graphene compounds are bonded to each other to form a mesh-like graphene compound. It is possible to form a graphene sheet (hereinafter referred to as a graphene compound net or graphene net). When the active material is covered with a graphene net, the graphene net can connect the active material to each other. It can also function as a binder to bind the particles together. Therefore, the ratio of the active material to the electrode volume or weight can be reduced. The rate can be improved. That is, the capacity of the secondary battery can be increased.

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

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

[0245] Also, it is also possible to cover the entire surface of the active material with the graphene compound in advance using a spray dryer. After that, when manufacturing the positive electrode active material layer, adding more graphene compound can also improve the conductive path between the active materials. After that, when manufacturing the positive electrode active material layer, adding more graphene compound can also improve the conductive path between the active materials.

[0246] As the binder, for example, rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. are preferably used. Also, as the binder, fluororubber can be used. Moreover, as the binder, for example, it is preferable to use water-soluble polymers. As the water-soluble polymers, for example, polysaccharides etc. can be used. As the polysaccharides, carboxymethyl cellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, diacetylcellulose, cellulose derivatives such as regenerated cellulose, starch, etc.

[0247] can be used. Also, it is more preferable to use these water-soluble polymers in combination with the aforementioned rubber materials.

[0248]

[0249]

[0250] The binder may be used in combination of a plurality of the above.For example, a material with particularly excellent viscosity adjustment effect may be used in combination with other materials. For example, rubber materials and the like are excellent in adhesive force and elastic force, but it may be difficult to adjust the viscosity when mixed with a solvent in some cases. In such cases, for example, it is preferable to mix with a material having a particularly excellent viscosity adjustment effect. As the material having a particularly excellent viscosity adjustment effect, for example, a water-soluble polymer may be used. Further, as the water-soluble polymer having a particularly excellent viscosity adjustment effect, the above-mentioned polysaccharides, such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose and diacetyl cellulose, regenerated cellulose and other cellulose derivatives, or starch can be used.

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

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

[0253] When a binder covering or in contact with the surface of the active material forms a film, it is also expected to function as a passivation film and suppress the decomposition of the electrolyte. Here, the passivation film is a film having no electron conductivity or extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, the decomposition of the electrolyte can be suppressed at the battery reaction potential. Further, it is more desirable that the passivation film suppresses electrical conductivity while allowing lithium ions to conduct. Here, the passivation film is a film having no electron conductivity or extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, the decomposition of the electrolyte can be suppressed at the battery reaction potential. Here, the passivation film is a film having no electron conductivity or extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, the decomposition of the electrolyte can be suppressed at the battery reaction potential. Here, the passivation film is a film having no electron conductivity or extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, the decomposition of the electrolyte can be suppressed at the battery reaction potential. Here, the passivation film is a film having no electron conductivity or extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, the decomposition of the electrolyte can be suppressed at the battery reaction potential. It is further desirable that the passivation film suppresses electrical conductivity while allowing lithium ions to conduct.

[0254] <Positive current collector> As the positive current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and alloys thereof, etc., having high conductivity can be used. Further, the material used for the positive current collector is preferably insoluble at the potential of the positive electrode. Also, an aluminum alloy added with an element for improving heat resistance such as silicon, titanium, neodymium, scandium, and molybdenum can be used. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can be appropriately used in shapes such as foil, plate (sheet), net, punched metal, expanded metal, etc. The current collector is preferably one having a thickness of 5 μm or more and 30 μm or less. As the positive current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and alloys thereof, etc., having high conductivity can be used. As the positive current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and alloys thereof, etc., having high conductivity can be used. As the positive current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and alloys thereof, etc., having high conductivity can be used. As the positive current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and alloys thereof, etc., having high conductivity can be used. As the positive current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and alloys thereof, etc., having high conductivity can be used. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector is preferably one having a thickness of 5 μm or more and 30 μm or less.

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

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

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

[0258] In this specification, etc., SiO refers to, for example, silicon monoxide. Alternatively, SiO can be represented 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, more preferably 0.3 or more and 1.2 or less. x

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

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

[0261] Graphite exhibits a potential as low as that of metallic lithium (0.05 V or more and 0.3 V or less vs. Li / Li+) when lithium ions are inserted into graphite (when a lithium-graphite intercalation compound is formed). i + ) As a result, a lithium-ion secondary battery can exhibit a high operating voltage. Furthermore, graphite has advantages such as a relatively high capacity per unit volume, a relatively small volume expansion, low cost, and high safety compared to metallic lithium, and thus is preferable.

[0262] Also, as the negative electrode active material, oxides such as titanium dioxide (TiO2), lithium titanate (Li4Ti5O12), lithium-graphite intercalation compound (LiC6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), etc. can be used. i5O 12 ) x C6)

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

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

[0265] Also, a material that undergoes a conversion reaction can be used as the negative electrode active material. For example, transition metal oxides such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), which do not form an alloy with lithium, may be used as the negative electrode active material. As materials that undergo a conversion reaction, furthermore, oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, sulfides such as CoS 0.89 5]

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

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

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

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

[0270] Further, 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 singly or in any combination and ratio of two or more of these. It is possible.

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

[0272] In addition, the electrolyte contains vinylene carbonate, propane sultone (PS), and tert-butyl ether. Benzene (TBB), Fluoroethylene Carbonate (FEC), LiBOB, and Squishi Additives such as dinitrile compounds such as dibenzonitrile and adiponitrile may also be added. The concentration of the material to be added may be, for example, 0.1 wt% to 5 wt% of the total solvent. .

[0273] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0274] The use of polymer gel electrolytes increases safety against leakage, etc. It is possible to make the device thinner and lighter.

[0275] The polymers that can be gelled include silicone gel, acrylic gel, acrylonitrile gel, Polyethylene oxide gel, polypropylene oxide gel, fluorine polymer Gel or the like can be used.

[0276] Examples of the polymer include polyalkylene oxides such as polyethylene oxide (PEO). Polymers with a hexagonal structure, PVDF, polyacrylonitrile, etc., and their For example, a copolymer containing PVDF and hexafluoropropylene (H PVDF-HFP, a copolymer of PVDF and PVDF, can be used. The mer may have a porous shape.

[0277] In addition, instead of the electrolyte solution, solid electrolytes containing inorganic materials such as sulfides and oxides, and P A solid electrolyte containing a polymer material such as EO (polyethylene oxide) can be used. This is the case. When using a solid electrolyte, it is not necessary to install a separator or a spacer. Also, since the entire battery can be solidified, the risk of leakage is eliminated and the safety is significantly improved.

[0278] [Separator] Also, it is preferable for a secondary battery to have a separator. As the separator, for example, paper, non-woven fabric, glass fiber, ceramics, or synthetic fibers made of nylon (polyamide), vinylon (poly vinyl alcohol-based fiber), polyester, acrylic, polyolefin, polyurethane, etc. can be used. The separator is preferably processed into an envelope shape and arranged to wrap either the positive electrode or the negative electrode.

[0279] The separator may have a multilayer structure. For example, a ceramic-based material, a fluorine-based material, a polyamide-based material, or a mixture thereof can be coated on an organic material film such as polypropylene or polyethylene. As the ceramic-based material, for example, aluminum oxide particles, silicon oxide particles, etc. can be used. As the fluorine-based material, for example, PVDF, polytetrafluoroethylene, etc. can be used. As the polyamide-based material, for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used.

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

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

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

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

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

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

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

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

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

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

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

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

[0292] When the current I flowing through the secondary battery reaches a predetermined current, for example, a current equivalent to 0.01C, When CCCV charging is stopped, all switches are turned off as shown in Figure 9(C). The switch is turned off and the current I becomes 0. Therefore, the voltage V applied to the internal resistance R R becomes 0V However, the voltage V applied to the internal resistance R due to CV charging R is small enough that Even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B hardly descends.

[0293] The secondary battery voltage V during CCCV charging and after CCCV charging is stopped B and An example of the charging current is shown in Figure 9(D). Even if CCCV charging is stopped, the secondary battery voltage V B Gahoton It shows that the aircraft does not descend at all.

[0294] ≪CC discharge≫ Next, we will explain CC discharge, which is one of the discharge methods. CC discharge is a method in which the A constant current flows from the secondary battery, and the secondary battery voltage V B becomes a certain voltage, for example 2.5V. This is a discharge method in which the discharge is stopped when

[0295] The secondary battery voltage V during CC discharge B An example of the discharge current is shown in Figure 10. According to the secondary battery voltage V B is shown to be descending.

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

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

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

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

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

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

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

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

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

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

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

[0307] Fig. 12(B) is a diagram schematically showing a cross-section of the cylindrical secondary battery. Inside the hollow cylindrical battery can 602, a wound battery element is provided with a strip-shaped positive electrode 604 and a negative electrode 606 sandwiching a separator 605 therebetween. Although not shown, the battery element is wound around a center pin. One end of the battery can 602 is closed and the other end is open. For the battery can 602, metals such as nickel, aluminum, and titanium that are corrosion-resistant to the electrolytic solution, or alloys of these or alloys of these and other metals (for example, stainless steel, etc.) can be used. ​。Also, in order to prevent corrosion by the electrolytic solution, it is preferable to coat nickel, aluminum, or the like. Inside the battery can 602, a battery element in which a positive electrode, a negative electrode, and a separator are wound is sandwiched between a pair of opposing insulating plates 608 and 609. Further, 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.

[0308] Since the positive electrode and the negative electrode used in the cylindrical secondary battery are wound, it is preferable to form the active material on both sides of the current collector. A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collecting lead) 607 is connected to the negative electrode 606. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of a metal material such as aluminum. The positive electrode terminal 603 is resistance welded to the safety valve mechanism 612, and the negative electrode terminal 607 is resistance welded to the bottom of the battery can 602, respectively. The safety valve mechanism 612 is electrically connected to the positive electrode cap 601 via a PTC element (Positive Temperature Coefficient) 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 value. The PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises. By increasing the resistance, the current amount is limited to prevent abnormal heat generation. For the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics or the like can be used.

[0309] Also, as shown in FIG. 12(C), a plurality of secondary batteries 600 are connected in series by conductive plates 613 and 614. The module 615 may be configured by sandwiching it therebetween. The plurality of secondary batteries 600 may be connected in parallel, in series, or in 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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0330] Furthermore, the structure of the wound body 950 is shown in FIG. 16. The wound body 950 includes a negative electrode 931 and a positive ​​​​​​​​​​The winding body 950 has a pole 932 and a separator 933. The negative electrode 931 and the positive electrode 932 are stacked one on top of the other, and the laminated sheet is wound to form a wound body. The negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated. You can stack several of them.

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

[0332] By using the positive electrode active material described in the above embodiment for the positive electrode 932, it is possible to achieve high capacity cycling. The secondary battery 913 can have excellent characteristics.

[0333] [Laminated secondary battery] Next, an example of a laminated secondary battery will be described with reference to FIGS. If the laminated secondary battery is made flexible, it will have at least one flexible portion. If the secondary battery is mounted in an electronic device that also has a battery, it can be bent according to the deformation of the electronic device. can.

[0334] A laminated secondary battery 980 will be described with reference to FIG. The battery 980 has a wound body 993 shown in FIG. 16, a positive electrode 995, and a separator 996. Similar to the wound body 950, a negative electrode 994 and a positive electrode 995 are stacked with a separator 996 sandwiched therebetween. The laminated sheet is then wound up.

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

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

[0337] The film 981 and the film 982 having a recess can be made of, for example, a metal material 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 recess, when a force is applied from the outside, the film 981 and the film 98 2 having a recess can be deformed, and a flexible secondary battery can be manufactured.

[0338] In addition, although FIGS. 17(B) and 17(C) show an example using two films, a space may be formed by bending one film, and the winding body 99 3 described above may be housed in the space.

[0339] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, the secondary battery 980 with high capacity and excellent cycle characteristics can be obtained.

[0340] Also, in FIG. 17, the secondary battery 9 having a wound body in the space formed by the film serving as the exterior body has been described in the example of 80. However, for example, as shown in FIG. 18, even a secondary battery having a plurality of strip-shaped positive electrodes, separators, and negative electrodes in the space formed by the film serving as the exterior body is acceptable.

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

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

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

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

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

[0346] Here, examples of the external views of the laminated secondary battery 500 are shown in FIGS. 19 and 20. FIGS. 1 9 and 20 have a positive electrode 503, a negative electrode 506, a separator 507, an exterior body 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511.

[0347] FIG. 21(A) shows the external views of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a positive electrode current collector 50 1, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. Also, the positive electrode ​​​​503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). The negative electrode 506 has a negative electrode current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504 and is present. Also, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, a tab region . The area and shape of the tab regions of the positive electrode and the negative electrode are not limited to the example shown in Fig. 21(A) .

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

[0349] First, the negative electrode 506, the separator 507, and the positive electrode 503 are laminated. Fig. 21(B) shows the laminated negative electrode 506, separator 507, and positive electrode 503 . Here, an example is shown in which 5 sets of negative electrodes and 4 sets of positive electrodes are used. Next, the tab regions of the positive electrode 503 are joined to each other, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode . For the joining, for example, ultrasonic welding or the like can be used . Similarly, the tab regions of the negative electrode 506 are joined to each other, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode .

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

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

[0352] Next, the electrolytic solution 508 is introduced into the inside of the exterior body 509 from the inlet provided in the exterior body 509. This introduction of the electrolytic solution 508 is preferably performed under a reduced-pressure atmosphere or an inert gas atmosphere. Finally, the inlet is joined. In this way, a secondary battery 500 of the laminate type can be fabricated.

[0353] 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.

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

[0355] FIG. 22(A) shows a schematic top view of a bendable secondary battery 50. FIGS. 22(B1), , (B2), and (C) are schematic cross-sectional views taken along cutting lines C1-C2, C3-C 4, and A1-A2 in FIG. 22(A), respectively. The battery 50 has an exterior body 51 and a positive electrode 11a and a negative electrode 11b housed inside the exterior body 5 1. A lead 12a electrically connected to the positive electrode 11a and a lead 12b electrically connected to the negative electrode 11b extend outside the exterior body 5 1. An electrolytic solution (not shown) is sealed in the region surrounded by the exterior body 51 in addition to the positive electrode 11a and the negative electrode 1 1b.

[0356] The positive electrode 11a and the negative electrode 11b of the battery 50 will be described with reference to FIG. 23. FIG. 2 3(A) is a perspective view for explaining the lamination order of the positive electrode 11a, the negative electrode 11b, and the separator 14. FIG. 23(B) shows, in addition to the positive electrode 11a and the negative electrode 11b, the leads 12a and the leads It is a perspective view showing 12b.

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

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

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

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

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

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

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

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

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

[0366]

[0367] ​​​​More specifically, when the total thickness of the stacked positive electrode 11a, negative electrode 11b, and separator (not shown) is defined as thickness t, the distance La is preferably 0.8 times or more and 3.0 times or less, more preferably 0.9 times or more and 2.5 times or less, and even more preferably 1.0 times or more and 2.0 times or less of the thickness t. By setting the distance La within this range, a compact and highly reliable battery with respect to bending can be realized. When the total thickness of the stacked positive electrode 11a, negative electrode 11b, and separator 214 is defined as thickness t, the distance La is 0.8 times or more and 3.0 times or less, preferably 0.9 times or more and 2.5 times or less, and more preferably 1.0 times or more and 2.0 times or less. Preferably, the distance La is within this range. By setting the distance La within this range, a compact and highly reliable battery with respect to bending can be realized.

[0368] Also, when the distance between the pair of seal portions 62 is defined as distance Lb, it is preferable that the distance Lb is sufficiently larger than the width Wb of the negative electrode 11b. Thereby, even when the positive electrode 11a and the negative electrode 11b come into contact with the exterior body 51 when the battery 50 is repeatedly deformed such as bent, a part of the positive electrode 11a and the negative electrode 11b can be displaced in the width direction, so that it is possible to effectively prevent the positive electrode 11a and the negative electrode 11b from rubbing against the exterior body 51. For example, the difference between the distance Lb between the pair of seal portions 62 and the width Wb of the negative electrode 11b 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, and even more preferably 2.0 times or more and 4.0 times or less of the thickness t of the positive electrode 11a and the negative electrode 11b. That is, when the positive electrode 11a and the negative electrode 11b come into contact with the exterior body 51 when the battery 50 is repeatedly deformed such as bent, a part of the positive electrode 11a and the negative electrode 11b can be displaced in the width direction, so that it is possible to effectively prevent the positive electrode 11a and the negative electrode 11b from rubbing against the exterior body 51. For example, the difference between the distance Lb between the pair of seal portions 62 and the width Wb of the negative electrode 11b 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, and even more preferably 2.0 times or more and 4.0 times or less of the thickness t of the positive electrode 11a and the negative electrode 11b. That is, when the positive electrode 11a and the negative electrode 11b come into contact with the exterior body 51 when the battery 50 is repeatedly deformed such as bent, a part of the positive electrode 11a and the negative electrode 11b can be displaced in the width direction, so that it is possible to effectively prevent the positive electrode 11a and the negative electrode 11b from rubbing against the exterior body 51.

[0369] In other words, it is preferable that the distance Lb, width Wb, and thickness t satisfy the relationship of the following mathematical formula 2. Here, a satisfies 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, and more preferably 1.0 or more and 2.0 or less. That is, it is preferable that the distance Lb, width Wb, and thickness t satisfy the relationship of the following mathematical formula 2.

[0370] In other words, it is preferable that the distance Lb, width Wb, and thickness t satisfy the relationship of the following mathematical formula 2.

[0371]

Equation

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

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

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

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

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

[0377] Also, there is a space 73 between the ends of the positive electrode 11a and the negative electrode 11b and the exterior body 51 so that when bent, the ends of the positive electrode 11a and the negative electrode 11b located on the inner side can be displaced relatively without contacting the exterior body 51.

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

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

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

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

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

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

[0384] FIG. 24(D) shows an example of a bangle-type display device. The portable display device 7100 includes a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. Also, FIG. 24(E) shows the state of the bent secondary battery 7104. The secondary battery 7104 is bent. ​​​​​​When worn on the user's arm in the stretched state, the housing deforms and part or all of the curvature of the secondary battery 7104 changes. Note that the degree of bending at any point on the curve is represented by the radius of the corresponding circle, and this value is the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, part or all of the main surface of the housing or the secondary battery 7104 changes within a range where the radius of curvature is 40 mm or more and 150 mm or less. If the radius of curvature on the main surface of the secondary battery 7104 is in the range of 40 mm or more and 150 mm or less, high reliability can be maintained. By using the secondary battery of one aspect of the present invention for the above secondary battery 7104, a lightweight and long-life portable display device can be provided. At any point on the curve, the degree of bending is represented by the value of the radius of the corresponding circle, and this is the radius of curvature. The reciprocal of the radius of curvature is called the curvature. Specifically, Part or all of the main surface of the housing or the secondary battery 7104 changes within a range where the radius of curvature is 40 mm or more and 150 mm or less. If the radius of curvature on the main surface of the secondary battery 7104 is in the range of 40 mm or more and 150 mm or less, high reliability can be maintained. By using the secondary battery of one aspect of the present invention for the above secondary battery 7104, a lightweight and long-life portable display device can be provided. mm or less, high reliability can be maintained. By using the secondary battery of one aspect of the present invention for the above secondary battery 7104, a lightweight and long-life portable display device can be provided. By using the secondary battery of one aspect of the present invention for the above secondary battery 7104, a lightweight and long-life portable display device can be provided.

[0385] Figure 24(F) shows an example of a wristwatch-type portable information terminal. The portable information terminal 7200 contains a housing 7201, a display unit 7202, a band 7203, a buckle 7204, operation buttons 72 05, input / output terminals 7206, etc.

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

[0387] The display surface of the display unit 7202 is provided in a curved shape, and display can be performed along the curved display surface. Further, the display unit 7202 is provided with a touch sensor and can be operated by touching the screen with a finger or a stylus. For example, by touching the icon 72 07 displayed on the display unit 7202, an application can be launched. 07 displayed on the display unit 7202, an application can be launched.

[0388] In addition to time setting, the operation buttons 7205 can turn the power on and off, and turn wireless communication on and off. It can have various functions such as operations, execution and cancellation of the manner mode, execution and cancellation of the power saving mode, etc. For example, the function of the operation button 7205 can also be freely set by the operating system incorporated in the portable information terminal 7200.

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

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

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

[0392] The portable information terminal 7200 preferably has a sensor. Examples of the sensor include human body sensors such as fingerprint sensors, pulse sensors, body temperature sensors, etc., and touch sensors, pressure sensors, acceleration sensors, etc. It is preferably mounted.

[0393] FIG. 24(G) shows an example of a bracelet-type display device. The display device 7300 has a display unit 7 ​​​​​​​​It has 304 and has a secondary battery according to one aspect of the present invention. Further, the display device 7300 can also be provided with a touch sensor in the display unit 7304, and can also function as a portable information terminal .

[0394] The display surface of the display unit 7304 is curved, and display can be performed along the curved display surface . Further, the display device 7300 can change the display state by means of communication-standardized short-range wireless communication or the like .

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

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

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

[0398] By using the secondary battery according to one aspect of the present invention as the secondary battery of a consumer electronic device, a lightweight and long-life product can be provided. For example, consumer electronic devices include electric toothbrushes, electric shavers, electric beauty devices, etc. As the secondary batteries for these products, considering the ease of use by the user, secondary batteries with a stick shape, small size, light weight, and large capacity are desired .

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

[0400] Next, FIGS. 25(A) and 25(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIGS. 25(A) and 25(B) includes a housing 9630 a, a housing 9630b, a movable part 9640 that connects the housing 9630a and the housing 9630b, a display part 9631 that has a display part 9631a and a display part 9631b, a display mode switching switch 9626, a power switch 9627, a power saving mode switching switch 9625, a fastener 96 29, and an operation switch 9628. By using a flexible panel for the display part 9631, a tablet terminal with a wider display part can be obtained. FIG. 25(A shows the open state of the tablet terminal 9600, and FIG. 25(B) shows the closed state of the tablet terminal 9600. ridge 7502 that includes a liquid supply bottle, a sensor, etc. To enhance safety, a protection circuit that prevents overcharging and over

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

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

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

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

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

[0406] In addition, FIG. 25(A) shows an example where the display areas of the display unit 9631b and the display unit 9631a are the same, but it is not particularly limited. One size and the other size may be different, and the quality of the display may also be different. For example, one may be a display panel capable of performing a higher-definition display than the other.

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

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

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

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

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

[0412] First, an example of the operation when power is generated by the solar cell 9633 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 so as to be a voltage for charging the power storage body 9635. Then, 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 required for the display unit 9631. Also, when the display on the display unit 9631 is not performed, SW1 is turned off and SW2 is turned on to charge the power storage body 9635. It may be configured to conduct electricity.

[0413] Although the solar cell 9633 is shown as an example of the power generation means, it is not particularly limited, and charging of the storage body 9635 may be performed by other power generation means such as a piezoelectric element (piezoelectric element) or a thermoelectric conversion element (Peltier element). For example, it may be configured to charge by a contactless power transmission module that wirelessly (non - contact) transmits and receives power, or by combining other charging means. For example, it may be configured to charge by a contactless power transmission module that wirelessly (non - contact) transmits and receives power, or by combining other charging means. For example, it may be configured to charge by a contactless power transmission module that wirelessly (non - contact) transmits and receives power, or by combining other charging means. That is also acceptable.

[0414] FIG. 26 shows an example of another electronic device. In FIG. 26, the display device 8000 is an example of an electronic device using the secondary battery 8004 according to one aspect of the present invention. Specifically, the display device 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, a speaker unit 8003, a secondary battery 8004, etc. The secondary battery 8004 according to one aspect of the present invention is provided inside the housing 8001. The display device 8000 can be supplied with power from a commercial power source, or can use the power stored in the secondary battery 8004. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, the display device 8000 can be used by using the secondary battery 8004 according to one aspect of the present invention as an uninterruptible power supply. The display unit 8002 can use a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc., a semiconductor display device. The display unit 8002 can use a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc., a semiconductor display device. The display unit 8002 can use a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc., a semiconductor display device. The display unit 8002 can use a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc., a semiconductor display device. The display unit 8002 can use a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc., a semiconductor display device. The display unit 8002 can use a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc., a semiconductor display device. The display unit 8002 can use a light - emitting device having a light - emitting element such as a liquid crystal display device, an organic EL element, etc. in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), etc., a semiconductor display device. That is also acceptable.

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

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

[0417] In FIG. 26, the installed lighting device 8100 is an example of an electronic device using the secondary battery 81 03 according to one aspect of the present invention. Specifically, the lighting device 8100 includes a housing 8101, a light source 8102, a secondary battery 8103, etc. In FIG. 26, the case where the secondary battery 8103 is provided inside the ceiling 81 01 and the ceiling 8104 where the light source 8102 is installed is illustrated However, the secondary battery 8103 may be provided inside the housing 8101. The lighting device 8100 can receive power supply from a commercial power source or 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.

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

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

[0420] ​​ In FIG. 26, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is an example of an electronic device using a secondary battery 8203 according to an aspect of the present invention. Specifically, the indoor unit 8200 has a housing 8201, an air outlet 8202, a secondary battery 8203, etc. FIG. 26 illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source, or can use the power stored in the secondary battery 8203. In particular, when the secondary battery 82 03 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the secondary battery 8203 according to an aspect of the present invention as an uninterruptible power supply, the use of the air conditioner becomes possible.

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

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

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

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

[0425] According to one aspect of the present invention, the cycle characteristics of the secondary battery can be improved, and the reliability can be enhanced. Also, according to one aspect of the present invention, a high-capacity secondary battery can be obtained. , the characteristics of the secondary battery can be improved, and thus the secondary battery itself can be made smaller and lighter. Therefore, by mounting the secondary battery, 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.

[0426] (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.

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

[0428] In FIG. 27, a vehicle using the secondary battery, which is one aspect of the present invention, is illustrated. FIG. 27(A) shows an automobile 8400 that is an electric vehicle using an electric motor as a power source for 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 the form of 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 the secondary batteries shown in FIG. 17 may be installed with respect to the floor portion inside the vehicle. The secondary battery can drive not only the electric motor 8406 but also supply power to a light-emitting device such as a headlight 8401 or a room light (not shown).

[0429] In addition, the secondary battery is used to power the speedometer, tachometer, and other displays of the automobile 8400. The secondary battery can supply power to the navigation device of the automobile 8400. The present invention can provide power to semiconductor devices such as mobile terminals.

[0430] The automobile 8500 shown in FIG. 27(B) has a plug-in type secondary battery. It can be charged by receiving power from an external charging facility using a contactless power supply system or other methods. FIG. 27(B) shows a diagram of a charging device 8021 installed on a ground and a charging station 8022 installed on a vehicle 8500. The secondary battery 8024 is shown being charged via a cable 8022. For charging methods and connector specifications, please refer to the specified CHAdeMO (registered trademark) or Combo. The charging device 8021 is a charging station installed in a commercial facility. For example, plug-in technology can be used to The secondary battery 8024 installed in the automobile 8500 can be charged by the power supply. Charging is performed by converting AC power to DC power via a converter such as an AC-DC converter. It is possible.

[0431] Although not shown, a power receiving device is mounted on the vehicle and power is supplied contactlessly from a power transmitting device on the ground. In this case, a power transmission device is installed on the road or exterior wall. By incorporating this technology, charging can be carried out not only when the vehicle is stopped but also while the vehicle is moving. This method may be used to transmit and receive power between vehicles. A solar cell may be provided to charge the secondary battery when the vehicle is stopped or running. The power can be supplied by an electromagnetic induction method or a magnetic resonance method.

[0432] Further, FIG. 27(C) shows an example of a two-wheeled vehicle using a secondary battery according to an aspect of the present invention. FIG. 27 (C) shows a scooter 8600 equipped with 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 .

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

[0434] According to an aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery can be increased . Therefore, the secondary battery itself can be made smaller and lighter. If the secondary battery itself can be made smaller and lighter, it contributes to reducing the weight of the vehicle, so the cruising range can be improved . Also, the secondary battery mounted on the vehicle can 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 peak power demand . If it is possible to avoid using a commercial power supply during peak power demand, it can contribute to energy conservation and reduction of carbon dioxide emissions [[ID=

[34] ] . Also, if the cycle characteristics are good, the secondary battery can be used for a long time, so the amount of rare metals such as cobalt used can be reduced . .

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

[0436] In this example, a positive electrode active material according to one embodiment of the present invention was prepared, and the positive electrode active material was subjected to STE The results of the observations with M, the results of the fast Fourier transform of the TEM image, and the energy dispersive X-ray The results of the analysis (EDX) are explained below. Also, the characteristics of the secondary battery using this positive electrode active material are explained. The results of the evaluation will be explained below.

[0437] [Preparation of positive electrode active material] <Sample 01> In this example, the positive electrode active material of Sample 01 is The composite oxide of lithium and the first transition metal is lithium cobalt oxide, and the second region The second transition metal oxide has lithium titanate, and the third region has As the oxide of a typical element, a material containing magnesium oxide was prepared.

[0438] In this example, lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd., product number 10 ... Therefore, in this example, step 1 described in the first embodiment was used. Steps 2 and 13 were omitted. The lithium cobalt oxide particles had a particle size of about 20 μm. m, and the area that can be analyzed by XPS includes fluorine, magnesium, calcium, sodium, It is a lithium cobalt oxide particle containing silicon, sulfur, and phosphorus.

[0439] Next, in step 14, lithium cobalt oxide particles containing magnesium and fluorine are mixed with sol-gel The titanium-containing material was coated by the coating method. Specifically, TTIP was dissolved in isopropanol. The solution was dissolved in isopropanol to prepare a solution of TTIP. The μ particles were mixed. TTIP was mixed with lithium cobaltate containing magnesium and fluorine so that the amount was 0.01 ml / g.

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

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

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

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

[0444] Next, the heated particles were cooled to room temperature. The temperature drop time from the holding temperature to room temperature was 10 to 1 15 hours. Thereafter, a crushing treatment was performed. The crushing treatment was performed by sieving, and a sieve with an opening of 53 μm was used.

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

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

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

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

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

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

[0451] ≪Sample 03≫ As a comparative example, Sample 03 was prepared by forming a region containing titanium on lithium cobalt oxide particles not containing magnesium by the sol-gel method and then heating them. The lithium cobalt oxide particles were manufactured by Nippon Kagaku Kogyo Co., Ltd. (product name: C-10N). This is lithium cobalt oxide particles in which magnesium is not detected by X

[0452] PS and about 1 atomic% of fluorine is detected. .

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

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

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

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

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

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

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

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

[0461]

Table 1

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

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

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

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

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

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

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

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

[0470] As shown in Fig. 31(B2) and Fig. 31(C2), it was also revealed that magnesium and fluorine were somewhat unevenly distributed near the surface in Sample 05 without heating . .

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

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

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

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

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

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

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

[0478] In addition, the magnesium concentration is more than 1 / 5 of the peak at a distance of 4.42 nm, i.e., the positive electrode The distance was 4.57 nm or more, that is, up to 2.71 nm from the surface of the active material particle. At depths of 2.86 nm or more from the surface of the material particle, the measured value of magnesium is 1 / Therefore, in sample 01, the first peak was observed from the surface to 2.71 nm in the depth direction. It was revealed that it was in the region of 3.

[0479] The titanium concentration is more than half of the peak from the distance of 2.14 nm to the distance of 3.42 nm. In other words, the thickness was 0.43 nm to 1.71 nm from the surface of the positive electrode active material particle. It became clear that range was the second area.

[0480] Next, secondary batteries were fabricated using the positive electrode active materials of Samples 01 to 05 prepared above. The results of evaluation of the charge-discharge characteristics of the secondary battery will be described below.

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

[0482] The positive electrode contains the positive electrode active material (LCO), acetylene black (AB), and polyvinyl fluoride. PVDF was mixed with LCO:AB:PVDF = 95:2.5:2.5 (weight ratio). The resulting slurry was applied to a current collector.

[0483] The counter electrode was made of lithium metal.

[0484] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. We used the following.

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

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

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

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

[0489] [Evaluation of cycle characteristics] ≪Charging 4.4V≫ For the secondary batteries of Sample 01 and Sample 05, the cycle characteristics when charged at 4.4V The properties were evaluated. The cycle characteristic measurement temperature was set at 25°C. Charging was performed at 4.4 V (CCCV, 0. 5C, cut-off current 0.01C), and discharging was performed at 2.5 V (CC, 0.5C).

[0490] Fig. 35 shows a graph of the cycle characteristics when charging at 4.4 V. The solid line in the figure is for Sample 0 1, and the dotted line is a graph of a secondary battery having the positive electrode active material of Sample 05. As shown in Fig. 35 As such, the secondary battery having Sample 01 maintained a 99.5% energy density retention rate even after 50 cycles and showed extremely good cycle characteristics. On the other hand, for the secondary battery having Sample 05 the energy density retention rate at the time of passing 50 cycles was 94.3%.

[0491] ≪Charging at 4.6 V≫ For the secondary batteries of Samples 01 to 04, the cycle characteristics when charging at 4.6 V were evaluated. The measurement temperature was set at 25°C. Charging was performed at 4.6 V (CCCV, 0.5C, cut-off current 0.01C), and discharging was performed at 2.5 V (CC, 0.5C).

[0492] Fig. 36 shows a graph of the cycle characteristics when charging at 4.6 V. As shown in Fig. 36, the secondary battery having Sample 01, which is the positive electrode active material of one aspect of the present invention, maintained a 94.1% energy density retention rate even after 50 cycles of charge and discharge at a high voltage of 4.6 V and showed extremely good cycle characteristics. On the other hand, the secondary batteries having the positive electrode active materials of Comparative Examples 02 to 04 were inferior to Sample 01. For example, in the case of Sample 04, the energy density retention rate at the time of passing 50 cycles was 33.2%.

[0493] Thus, the configuration of the positive electrode active material of one aspect of the present invention enables charging at a high voltage exceeding 4.4 V It has been clarified that a remarkable effect is exhibited when discharging is performed.

Example

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

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

[0496] [Production of positive electrode active material, production of secondary battery] ≪Sample 06, Sample 07≫ In this example, lithium cobaltate particles (manufactured by Nippon Chemical Industry Co., Ltd., product name: C-20F) were used as starting materials.

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

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

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

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

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

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

[0503] Figure 38 shows the TEM-EDX analysis results of sample 07 after heating. The cross-sectional TEM image includes the surface of the substrate and the crack. The HAADF-STEM image of the area including the particle surface is shown in Figure 38(B1), and the Ti mapping image is shown. This is shown in Figure 38(B2). Similarly, the crack area indicated by the circle marked 2 in Figure 38(A) The HAADF-STEM image of the region about 20 nm deep from the surface is shown in Figure 38(C1). The Ti mapping image is shown in Figure 38(C2). Figure 3 shows a HAADF-STEM image of the rack area at a depth of approximately 500 nm from the surface. The Ti mapping image is shown in Figure 38(D1) and the Ti mapping image is shown in Figure 38(D2). The crack area indicated by the circle is approximately 1000 nm deep from the surface. The TEM image is shown in FIG. 38(E1), and the Ti mapping image is shown in FIG. 38(E2).

[0504] As shown in Figures 37 and 38, titanium segregates on the particle surface in sample 06 before heating. Although it was observed that the cracks were discolored, no segregation was observed in the cracks. In sample 07, titanium was observed to segregate both on the particle surface and in the cracks. In other words, it became clear that titanium segregates at the interface of the cracked portion due to heating.

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

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

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

[0508] As shown in FIGS. 39 and 40, magnesium was not observed to segregate on the particle surface or at the crack part in sample 06 before heating. On the other hand, in sample 07 after heating, segregation of magnesium was observed both on the particle surface and at the crack part.

[0509] Next, in order to quantify titanium and magnesium, EDX point analysis was performed on the regions indicated by the circles numbered 1 to 6 in FIG. 37(A), and the regions indicated by the circles numbered 1 to 6 in FIG. 38(A). Two measurements were taken within the range of each region. For the regions indicated by the circles numbered 1 to 6 in FIG. 37(A) and the regions indicated by the circles numbered 1 to 6 in FIG. 38(A), EDX point analysis was carried out. Two measurements were taken within the range of each region.

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

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

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

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

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

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

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

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

[0518] The initial characteristics were measured by charging in CCCV mode at 0.2C, 4.6V, and a cut-off current of 0.05C. Discharging was performed in CC mode at 0.2C and a cut-off voltage of 3.0V. Here, 1C was defined as 160 mA / g, which is the current value per unit weight of the positive electrode active material. The measurement temperature was 25°C. The results of the measurement of the initial characteristics are shown in Table 2. The rate characteristics were measured after the measurement of the initial characteristics. The discharge rate was changed, and except for the discharge rate, the same conditions as those for the measurement of the initial characteristics were used: 0.2C charge / 0.2C discharge, 0.2C charge / 0.5C discharge, 0 .2C charge / 1.0C discharge, 0.2C charge / 2.0C discharge, 0.2C charge / 3.0C discharge

[0519]

Table 2

[0520] After the measurement of the initial characteristics, the rate characteristics were measured. The discharge rate was changed, and except for the discharge rate, the same conditions as those for the measurement of the initial characteristics were used: 0.2C charge / 0.2C discharge, 0.2C charge / 0.5C discharge, 0 .2C charge / 1.0C discharge, 0.2C charge / 2.0C discharge, 0.2C charge / 3.0C discharge .2C charge / 1.0C discharge, 0.2C charge / 2.0C discharge, 0.2C charge / 3.0C discharge 、Measured in the order of 0.2C charge / 4.0C discharge and 0.2C charge / 5.0C discharge. The measurement temperature was set at 25°C.

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

[0522]

Table 3

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

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

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

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

[0527] The tap density of the positive electrode active material of sample 07 was 2.21 g / cm 3 It was. Tap Dense The measurement was performed using a MULTI TESTER MT-1000 (manufactured by Seishin Enterprises). .

[0528] As described above, the positive electrode active material of Sample 07, which is one embodiment of the present invention, has good initial characteristics, laser The results showed that the initial charge / discharge efficiency, cycle efficiency, and temperature characteristics were significantly improved. It was estimated that the rate of side effects was suppressed, at over 98%. The discharge rate also showed a good capacity of 96.1% based on 0.2C. [Example]

[0529] In this example, a positive electrode active material having a region containing titanium and magnesium in the surface layer portion was The results of fabricating and evaluating the properties of the starting materials were shown below, with the ratio of Li to first transition metals being varied.

[0530] [Preparation of positive electrode active material] In this example, samples 11 to 17, which used cobalt as the first transition metal, Positive electrode active materials of Samples 21 to 28 and Samples 31 to 40 were prepared. The sample was prepared by the following method and conditions.

[0531] <Samples 11-17> First, the starting materials, lithium source, cobalt source, magnesium source, and fluorine source were prepared. In this example, lithium carbonate was used as the lithium source, and cobalt oxide was used as the cobalt source. magnesium oxide as a magnesium source, lithium fluoride as a fluorine source and lithium source Thiol was used.

[0532] At this time, Sample 11 was weighed so that the Li / Co ratio of the starting material was 1.00. Sample 12 was weighed so that the Li / Co ratio of the starting material was 1.03. Sample 13 was weighed so that the Li / Co ratio of the starting material was 1.05. Sample 14 was weighed so that the Li / Co ratio of the starting material was 1.06. Sample 15 was weighed so that the Li / Co ratio of the starting material was 1.07. Sample 16 was weighed so that the Li / Co ratio of the starting material was 1.08. Sample 17 was weighed so that the Li / Co ratio of the starting material was 1.13.

[0533] In addition, for samples 11 to 17, the number of cobalt atoms contained in the starting material was When the number of magnesium atoms is 1, the number of fluorine atoms is 0.01 and 0.02. The sea urchin was weighed.

[0534] Next, the weighed starting materials were mixed for each sample using a ball mill.

[0535] Next, the mixed starting materials were calcined at 1000°C for 10 hours with a temperature increase rate of 200°C / h. The flow rate of the dry air was set to 10 L / min.

[0536] In the above process, particles of composite oxide containing lithium, cobalt, fluorine, and magnesium are mixed. Successful.

[0537] Next, to 2-propanol, TTIP was added in an amount of 0.01 ml / g per gram of the positive electrode active material, and mixed to prepare a 2-propanol solution of tetra-i-propoxytitanium. Next, TTIP was added to 2-propanol in an amount of 0.01 ml / g per gram of the positive electrode active material, and mixed to prepare a 2-propanol solution of tetra-i-propoxytitanium. It was prepared.

[0538] To this 2-propanol solution of TTIP, particles of a composite oxide containing lithium, cobalt, fluorine, and magnesium were added and mixed. To this 2-propanol solution of TTIP, particles of a composite oxide containing lithium, cobalt, fluorine, and magnesium were added and mixed.

[0539] The above mixture was stirred with a magnetic stirrer for 4 hours under the conditions of 25 °C and a humidity of 90% RH. By this treatment, hydrolysis and polycondensation reactions were caused by water in the atmosphere and TTIP, and a titanium-containing layer was formed on the surface of the lithium cobalt oxide particles having magnesium and fluorine. The above mixture was stirred with a magnetic stirrer for 4 hours under the conditions of 25 °C and a humidity of 90% RH. By this treatment, hydrolysis and polycondensation reactions were caused by water in the atmosphere and TTIP, and a titanium-containing layer was formed on the surface of the lithium cobalt oxide particles having magnesium and fluorine. The above mixture was stirred with a magnetic stirrer for 4 hours under the conditions of 25 °C and a humidity of 90% RH. By this treatment, hydrolysis and polycondensation reactions were caused by water in the atmosphere and TTIP, and a titanium-containing layer was formed on the surface of the lithium cobalt oxide particles having magnesium and fluorine. It was formed.

[0540] The mixture after the above treatment was filtered, and the residue was collected. As the filter for filtration, Kiriyama filter paper (No. 4) was used. (No. 4) was used.

[0541] The collected residue was vacuum dried at 70 °C for 1 hour.

[0542] The dried powder was heated. The heating was carried out at 800 °C (heating rate: 200 °C / hour) for a holding time of 2 hours in an oxygen atmosphere. It was carried out in an oxygen atmosphere.

[0543] The heated powder was cooled and subjected to a crushing treatment. The crushing treatment was carried out by sieving, and a sieve with an opening size of 53 μm was used. The crushing treatment was carried out by sieving, and a sieve with an opening size of 53 μm was used.

[0544] The particles after the crushing treatment were used as the positive electrode active materials for Samples 11 to 17.

[0545] ≪Samples 21 to 27≫ For Samples 21 to 27, the starting materials were the same as those for Samples 11 to 16. It was. At this time, Sample 21 was weighed so that the Li / Co ratio of the starting materials was 1.00. Sample 22 was weighed so that the Li / Co ratio of the starting materials was 1.03. Sample 23 was weighed so that the Li / Co ratio of the starting materials was 1.05. Sample 24 was weighed so that the Li / Co ratio of the starting materials was 1.06. Sample 25 was weighed so that the Li / Co ratio of the starting materials was 1.07. Sample 26 was weighed so that the Li / Co ratio of the starting materials was 1.08. Sample 27 was weighed so that the Li / Co ratio of the starting materials was 1.13.

[0546] Samples 21 to 27 were prepared in the same manner as Samples 11 to 17, except that the concentration of the TTIP 2-propanol solution was adjusted so that the amount of TTIP per gram of the positive electrode active material was 0.02 ml / g.

[0547] ≪Sample 28≫ Sample 28 had the same Li / Co ratio of the starting materials and the same amount of TTIP as Sample 23. That is, Sample 28 was weighed so that the Li / Co ratio of the starting materials was 1.05, and the amount of TTIP per gram of the positive electrode active material was adjusted to 0.02 ml / g.

[0548]

[0549] However, in Sample 28, after mixing the starting materials, firing was performed at 950°C.

[0550] Except for the firing temperature, it was prepared in the same manner as Sample 23.

[0551] Samples 11 to 17 and Samples 21 to 28 were presumed to be positive electrode active materials having lithium cobaltate inside and having a region containing titanium and magnesium in the surface layer portion. ​​​​≪Samples 31 to 40≫ Samples 31 to 40 were prepared as comparative examples without forming a titanium-containing region.

[0552] Sample 31 was weighed so that the Li / Co ratio of the starting materials was 1.00. Sample 3 2 was weighed so that the Li / Co ratio of the starting materials was 1.01. Sample 33 was the starting materials were weighed so that the Li / Co ratio was 1.02. Sample 34 was the starting materials Li / Co ratio was weighed so that it was 1.03. Sample 35 was the starting materials Li / Co ratio was weighed so that it was 1.035. Sample 36 was the starting materials Li / Co ratio was 1.04 and weighed. Sample 37 was weighed so that the Li / Co ratio of the starting materials was 1.051 Sample 38 was weighed so that the Li / Co ratio of the starting materials was 1.061 Sample 39 was weighed so that the Li / Co ratio of the starting materials was 1.081. Sample 40 was weighed so that the Li / Co ratio of the starting materials was 1.130.

[0553] In addition, when the number of cobalt atoms contained in the starting materials was made 1 in common for Samples 31 to 40, the number of magnesium atoms was 0.01 and the number of fluorine atoms was 0.02 and weighed.

[0554] Next, the weighed starting materials were mixed for each sample using a ball mill.

[0555] Next, the mixed starting materials were fired. The firing was carried out at 1000 °C for 10 hours, the heating rate was 200 °C / h and the flow rate of dry air was 10 L / min.

[0556] In the above process, composite oxide particles containing lithium, cobalt, fluorine, and magnesium were synthesized. ​

[0557] After cooling the synthesized particles, they were heated. The heating was carried out at 800 °C (heating rate 200 °C / hour), holding time 2 hours, in an oxygen atmosphere.

[0558] The heated powder was cooled and subjected to a crushing treatment. The crushing treatment was carried out by sieving, and a sieve with an opening size of 53 μm was used.

[0559] The particles after the crushing treatment were used as the positive electrode active materials for Samples 31 to 40.

[0560] The preparation conditions for Samples 11 to 17, Samples 21 to 28, and Samples 31 to 4 0 are shown in Table 4.

[0561]

Table 4

[0562] [XPS] For the positive electrode active materials of Samples 11 to 17, Samples 21 to 28, and Samples 31 to 4 0, XPS analysis was performed. The results of the XPS analysis of Samples 11 to 17 are shown in Table 5, the results of the XPS analysis of Samples 21 to 28 are shown in Table 6, and the results of the XPS analysis of Samples 31 to 40 are shown in Table 7. In Tables 5 to 7, the relative values when the concentration of each element with cobalt as 1 are shown. ~ Samples 40 are shown. Note that in Tables 5 to 7, the relative values when the concentration of each element with cobalt as 1 are shown. was taken as 1.

[0563]

Table 5

[0564]

Table 6

[0565] [Table 7]

[0566] In addition, from the analysis results in Tables 5 to 7, the graphs extracted for the relative values of magnesium and titanium were The rough outline is shown in Figure 46. Figure 46(A) is a graph of the Li / Co ratio and the relative magnesium value, and Figure 4 6(B) is a graph of the Li / Co ratio and the relative titanium value.

[0567] First, from Samples 31 to 40 in FIG. 46(A), the cases without the titanium-containing coating layer were examined. In this case, the magnesium concentration was high in samples with a Li / Co ratio of 1.00 or more and 1.05 or less. This is because the magnesium contained in the starting material is converted by heating. This is thought to be because the element segregated within the range where the concentration could be detected by XPS. Above 1.06, the magnesium concentration becomes low, and if the lithium becomes too excessive, the magnesium It was speculated that this would make it less likely for sodium to segregate.

[0568] Also, from Samples 11 to 16 and Samples 21 to 26 in Figure 46(A), When there is a region containing titanium in the surface layer, the element concentration can be detected by XPS more easily than when there is no titanium. It was revealed that the magnesium concentration in the feasible range increases.

[0569] Furthermore, when the Li / Co ratio is 1.06, the original structure is not observed by XPS when there is no titanium-containing region. The magnesium concentration is low in the detectable range, while the titanium In the sample with this region, the magnesium concentration is high within the range where the element concentration can be detected by XPS. In other words, by forming a region containing titanium in the surface layer, even when the Li / Co ratio is high, It was also revealed that sufficient segregation of magnesium occurred.

[0570] Even when the region contains titanium, when the Li / Co ratio is 1.07, the magnesium concentration is lower than when the ratio is 1.06. Also, when the Li / Co ratio is 1.08 or more, it is presumed that segregation of magnesium is less likely to occur even when the region contains titanium.

[0571] [Evaluation of cycle characteristics] <<Energy density retention rate>> Next, using the positive electrode active materials of Sample 11 to Sample 14, Sample 16, and Sample 21 to Sample 24, and Sample 26, the cycle characteristics were evaluated in the same manner as in Example 1.

[0572] The shape of the secondary battery, the materials and mixing ratios of the positive electrode active material, conductive assistant, and binder in the positive electrode, the counter electrode, electrolyte, exterior body, conditions of the cycle characteristic test, etc. were the same as those in Example 1.

[0573] Figure 47(A) shows a graph of the energy density retention rate at the time of 4.6 V charging and the number of charge-discharge cycles of the secondary battery using the positive electrode active materials of Sample 11 to Sample 14 and Sample 16 prepared so that TTIP per gram of the positive electrode active material is 0.01 ml / g. Figure 47(B) shows a graph of the energy density retention rate at the time of 4.6 V charging and the number of charge-discharge cycles of the secondary battery using the positive electrode active materials of Sample 21 to Sample 24 and Sample 26 prepared so that TTIP per gram of the positive electrode active material is 0.02 ml / g.

[0574] As is clear from Figure 47(A), when TTIP is 0.01 ml / g, the positive electrode active materials of Sample 11 to Sample 14, that is, those with a Li / Co ratio of 1.00 or more and 1.06 or less, have good cycle characteristics. showed an icicle characteristic. In particular, the cathode active materials of Sample 11 and Sample 12, that is, with a Li / Co ratio of 1 .00 or more and 1.03 or less showed extremely good cycle characteristics. On the other hand, in Sample 16 with a Li / Co ratio of 1.08, the energy density retention rate deteriorated at a relatively early stage .

[0575] Also, as is clear from Fig. 47(B), when TTIP was 0.02 ml / g, the cathode active materials of Sample 2 1 to Sample 24, that is, with a Li / Co ratio of 1.00 or more and 1.06 or less showed good cycle characteristics. In particular, the cathode active materials of Sample 23 and Sample 24, that is, with a Li / Co ratio of 1.05 or more and 1.06 or less showed extremely good cycle characteristics.

[0576] Fig. 48 shows a graph comparing Sample 11, which showed the best cycle characteristics among Samples 11 to 15, with Sample 23, which showed the best cycle characteristics among Samples 21 to 25.

[0577] As is clear from Fig. 48, both showed extremely good cycle characteristics, but Sample 23 with TTIP of 0.02 ml / g had better cycle characteristics.

[0578] ≪Discharge Capacity Retention Rate≫ Next, the results of evaluating the cycle characteristics in terms of the discharge capacity retention rate for Samples 21 to 26 and Sample 28 are shown in Fig. 49.

[0579] The shapes of the secondary batteries of Samples 21 to 26, the cathode active materials, conductive aids, binders in the cathode, the materials and mixing ratios of the anode, the electrolyte, the exterior body, the conditions of the cycle characteristic test, etc. were the same as in Example 1.

[0580] ​​ The secondary battery using Sample 28 used PVDF as a binder, and the positive electrode active material (LCO ), AB, and PVDF were mixed at LCO:AB:PVDF = 95:3:2 (weight ratio). The others were fabricated and evaluated in the same manner as the secondary batteries using Samples 21 to 26.

[0581] As is apparent from FIG. 49, Samples 21 to 24 and Sample 28 exhibited good cycle characteristics. Among them, Sample 28 exhibited extremely good cycle characteristics. For Sa mple 28, the discharge capacity retention rate after 50 cycles was 85% or more.

[0582] On the other hand, Samples 25 and 26 with Li / Co ratios of 1.07 and 1.08 showed a deterioration in the discharge capacity retention rate from a relatively early stage.

[0583] From the above results, when TTIP is 0.02 ml / g per gram of the positive electrode active material, it became clear that the preferable range of the Li / Co ratio is 1.00 or more and less than 1.07. Furthermore, it became clear that when the range of the Li / Co ratio is 1.05 or more and 1.06 or less, extremely good cycle characteristics are exhibited .

[0584] The charge-discharge curves of the secondary batteries using Sample 28, Sample 24, which showed extremely good cycle characteristics in FIG. 49, and Sample 2 5, which showed deterioration at a relatively early stage, are shown in FIG. 50.

[0585] FIG. 50(A) is the charge-discharge curve of the secondary battery using Sample 28, FIG. 50(B) is the charge-discharge curve of the secondary battery using Sample 24, and FIG. 50(C) is the charge-discharge curve of the secondary battery using Sample 2 5. The results of repeating charge and discharge 50 times each are overlapped and shown. As shown by the arrows in the figure, from the first cycle to the 50th cycle, the charge-discharge capacity ​​ The amount is decreasing.

[0586] As shown in FIGS. 50(A) and 50(B), the positive electrode active material of one embodiment of the present invention, Sample 28 and Sample 24 showed high charge-discharge capacity and good charge-discharge characteristics. Compared with sample 25 in Figure 50(C), sample 2 in Figure 50(A) and Figure 50(B) It was revealed that the decrease in charge / discharge capacity was significantly suppressed in Samples 8 and 24. [Example]

[0587] In this example, the positive electrode active material of Sample 24 prepared in Example 2 was observed by SEM and The results of the SEM-EDX analysis are explained below.

[0588] Sample 24 has a Li / Co ratio of 1.06 and a TTIP ratio of 0.02 m per weight of the positive electrode active material. The SEM image of Sample 24 is shown in Figure 51(A). Enlarged images of a portion of Figure 51(A) are shown in Figure 51(B) and Figure 51(C).

[0589] As is clear from FIG. 51, there were many convex regions on the surface layer of the positive electrode active material.

[0590] Next, the results of analyzing the positive electrode active material of Sample 24 using SEM-EDX are shown in Figure 52. Figure 52(A-1) is an SEM image of the surface layer of the positive electrode active material, and Figure 52(A-2) is an SEM image of the titanium Mapping, Figure 52(B-1) is the mapping of magnesium, Figure 52(B-2) is the mapping of oxygen Mapping, Figure 52(C-1) is the mapping of aluminum, Figure 52(C-2) is the mapping of cobalt In the EDX element mapping image in Figure 52, the area below the detection limit is The count is shown in black, and the more the count increases, the closer it gets to white.

[0591] The same regions in the figures of FIGS. 52(A-1), 52(A-2), and 52(B-1) were enclosed by dotted lines. As is clear from comparing the regions enclosed by the dotted lines, titanium and magnesium were distributed in the convex regions on the surface layer part of the positive electrode active material. Therefore, it was confirmed that Sample 24 is a positive electrode active material having a convex fourth region 104 having titanium and magnesium on the third region 103.

[0592] As shown in Example 2, Sample 24 is one of the samples showing extremely good cycle characteristics. Therefore, even if a fourth region exists in the surface layer part, or regardless of the presence or absence of the fourth region, it has become clear that a positive electrode active material showing good cycle characteristics can be obtained.

[0593] As a result of Examples 1 to 3 above, it has become clear that by forming a region containing titanium in the surface layer part, a positive electrode active material showing good cycle characteristics can be obtained. Also, when the Li / Co ratio is increased to increase the particle size of the positive electrode active material, there is a concern that the cycle characteristics may deteriorate. However, it has become clear that by forming a region containing titanium in the surface layer part, the range of the Li / Co ratio in which good cycle characteristics can be obtained can be widened. Also, even if a fourth region having titanium and magnesium exists in the surface layer part of the positive electrode active material, it has become clear that good cycle characteristics are shown.

[0594] From the results of Examples 1 to 3 above, it has become clear that by forming a region containing titanium in the surface layer part, a positive electrode active material showing good cycle characteristics can be obtained. Also, when the Li / Co ratio is increased to increase the particle size of the positive electrode active material, there is a concern that the cycle characteristics may deteriorate. However, it has become clear that by forming a region containing titanium in the surface layer part, the range of the Li / Co ratio in which good cycle characteristics can be obtained can be widened. Also, even if a fourth region having titanium and magnesium exists in the surface layer part of the positive electrode active material, it has become clear that good cycle characteristics are shown.

Example

[0595] In this example, an example of a method for manufacturing a positive electrode active material coated with graphene oxide is shown, and the results of observing the positive electrode active material produced by that method with an electron microscope will be described. ​​​​​​​​​​

[0596] As shown in the process flow diagram of FIG. 53, the process of forming a film on the positive electrode active material includes (S11) weighing graphene oxide, (S12) mixing and stirring graphene oxide and pure water, (S13) controlling the pH, (S14) adding the active material, (S15) completing the suspension, (S16) spray drying the suspension using a spray dryer, and (S17) collecting the powder in a container. In (S12), although pure water is used as the dispersion medium, it is not particularly limited, and ethanol or the like may be used. Also, in (S14), the active material is the positive electrode active material.

[0597]

[0598] A schematic diagram of the spray dryer 280 is shown in FIG. 54. The spray dryer 280 has a chamber 281 and a nozzle 282. The suspension 284 is supplied to the nozzle 282 via a tube 283. The suspension 284 is sprayed from the nozzle 282 into the chamber 281 and dried in the chamber 281. The nozzle 282 may be heated by a heater 285. Here, the region of the chamber 281 close to the nozzle 282, for example, the region surrounded by the dashed two-dot line shown in FIG. 54, is also heated by the heater 285.

[0599] Here, when a suspension containing a positive electrode active material and graphene oxide is used as the suspension 284, the powder of the positive electrode active material covered with graphene oxide is collected into the recovery container 286 through the chamber 281.

[0600] Here, the atmosphere in the chamber 281 may be sucked by an aspirator or the like through the path indicated by the arrow 288.

[0601] An example of the film formation conditions is shown below.

[0602] First, graphene oxide was dispersed in a solvent to prepare a suspension.

[0603] Although pure water has high dispersibility as a dispersion medium for graphene oxide, depending on the active material added later, it may react with the cathode active material, eluting Li, or may damage the surface structure of the cathode active material. Therefore, the ratio of ethanol to pure water was set to 4:6, and graphene oxide was dispersed in the liquid.

[0604] For stirring to disperse in the liquid, a stirrer and an ultrasonic generator were used, and the rotation speed was set to 750 rpm, and ultrasonic waves were irradiated for 2 minutes.

[0605] Next, an aqueous LiOH solution was dropped to adjust the pH to pH 7 (25°C).

[0606] The cathode active material (in this example, lithium cobaltate particles (trade name : C-20F) manufactured by Nippon Chemical Industry Co., Ltd.) was added, and for stirring, a stirrer and an ultrasonic generator were used, and the rotation speed was 750 rpm, and ultrasonic waves were irradiated for 1 minute. A suspension was prepared through the above steps. The above-mentioned lithium cobaltate particles (trade name: C-20F) manufactured by Nippon Chemical Industry Co., Ltd. are lithium cobaltate particles containing at least fluorine, magnesium, calcium, sodium, silicon, sulfur, and phosphorus, and have a particle size of about 20 μm.

[0607] Next, using a spray dryer, the suspension was uniformly sprayed with a spray nozzle (nozzle diameter 20 μm) to obtain a powder. Regarding the hot air temperature of the spray dryer, the inlet temperature was 16 0°C, the outlet temperature was 40°C, and the N2 gas flow rate was 10 L / min.

[0608] The cross-sectional TEM photograph of the obtained powder is shown in Fig. 55. Also, the SEM photograph is shown in Fig. 56. As a comparative example, the same cathode active material (C-20F manufactured by Nippon Chemical Industry Co., Ltd.) as that of the spray-dried product was used as a raw material and mixed with graphene oxide using a rotating and revolving mixer. As a result, the coating was insufficient. The SEM photograph of that comparative example is shown in Fig. 57. It can be seen that the film in Fig. 56 is more uniform on the surface of the powder compared with Fig. 57.

[0609] It can be seen that the film in Fig. 56 is more uniform on the surface of the powder compared with Fig. 57. It can be seen.

[0610] After coating graphene oxide using a spray-drying apparatus, a cross-sectional configuration example in the case of further using a graphene compound as a conductive assistant for the active material layer 200 covered with graphene oxide will be described with reference to Fig. 58. A cross-sectional configuration example in the case of further using a graphene compound as a conductive assistant for the active material layer 200 covered with graphene oxide will be described with reference to Fig. 58. will be described with reference to Fig. 58.

[0611] Fig. 58(A) shows a longitudinal sectional view of the active material layer 200. The active material layer 200 includes granular cathode active material 100 covered with graphene oxide, graphene compound 201 as a conductive assistant, and 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 shape. Here, for example, graphene or multi-graphene may be used as the graphene compound 201. Here, the graphene compound 201 preferably has a sheet shape. Here, for example, graphene or multi-graphene may be used as the graphene compound 201. Here, the graphene compound 201 preferably has a sheet shape. Here, the graphene compound 201 preferably has a sheet shape. Also, the graphene compound 201 may be formed by a plurality of multi-graphenes or (and) a plurality of graphenes partially overlapping to form a sheet shape. Here, the graphene compound 201 preferably has a sheet shape. Also, the graphene compound 201 may be formed by a plurality of multi-graphenes or (and) a plurality of graphenes partially overlapping to form a sheet shape. .

[0612] In the longitudinal section of the active material layer 200, as shown in Fig. 58(B), the cathode active material 100 covered with the film 105 made of graphene oxide is in contact with the graphene compound 201. In the longitudinal section of the active material layer 200, as shown in Fig. 58(B), the cathode active material 100 covered with the film 105 made of graphene oxide is in contact with the graphene compound 201. is represented. A plurality of graphene compounds 201 are in partial contact with the positive electrode active material 10 0 covered by the film 105 and are formed so as to adhere to the film 105 of the adjacent positive electrode active material 100 and are in contact with each other.

[0613] Since the graphene compound 201 and the film 105 are made of the same carbon-based material, an excellent conductive path can be formed.

[0614] The film 105 has the effect of protecting the crystal structure of the positive electrode active material 100 so that the electrolytic solution does not come into contact with it, and has the effect of forming an excellent conductive path. 【Explanation of...

Claims

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

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

3. A lithium-ion secondary battery having a positive electrode and a negative electrode, wherein the positive electrode has positive electrode active material particles containing lithium cobaltate, the positive electrode active material particles contain magnesium, fluorine, and titanium, magnesium and fluorine are unevenly distributed on the surface side and crack portions of the positive electrode active material particles, titanium is further unevenly distributed on the surface side of the positive electrode active material particles, the positive electrode active material particles have a first region containing lithium cobaltate, a second region containing titanium, and a third region containing magnesium oxide and cobalt oxide, at least the third region is on the outermost surface of the positive electrode active material particles, a part of the third region overlaps with a part of the second region, the first region is further inside than the third region and the second region, The crystal orientations from the first region to the third region are substantially the same. A lithium-ion secondary battery. **Claim 4** When a linear analysis is performed on the cross-section of the positive electrode active material particles by EDX, the peak of magnesium is closer to the surface side than the peak of titanium. The lithium-ion secondary battery according to any one of claims 1 to 3. **Claim 5** When XPS analysis is performed on the positive electrode active material particles, the peak position of the binding energy of fluorine is 682 eV or more and 685 eV or less. The lithium-ion secondary battery according to any one of claims 1 to 4. **Claim 6** The crack portion further contains cobalt and oxygen. The lithium-ion secondary battery according to any one of claims 1 to 5. **Claim 7** On the surface side of the positive electrode active material particles, there is a region where the atomic number ratio of magnesium to cobalt (Mg / Co) measured by EDX is 0.15 or more and 0.50 or less. The lithium-ion secondary battery according to any one of claims 1 to 6.

Images