Lithium-ion rechargeable 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 appliance, 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 the present specification, the power storage device refers to all elements and devices having a power storage function. For example, it includes storage batteries (also referred to as secondary batteries) such as lithium-ion secondary batteries, lithium-ion capacitors, and electric double layer capacitors.

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

Background Art

[0004] In recent years, various power storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have been actively developed. In particular, lithium-ion secondary batteries with high output and high energy density are 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 vehicles (HEV), electric vehicles (EV), or plug-in hybrid vehicles (PHEV). Along with the development of the semiconductor industry, the demand for them has rapidly expanded. , as a source of rechargeable energy, has become essential in modern information society.

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

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

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] There is 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. Another aspect of the present invention is to provide a high-capacity secondary battery. Another aspect of the present invention is to provide a secondary battery with excellent charge-discharge characteristics. Another aspect of the present invention is to provide a secondary battery with high safety or reliability.

[0010] Alternatively, one aspect of the present invention relates to a novel substance, active material particles, secondary battery, or method for producing the same. One of the objectives is to provide [this].

[0011] Furthermore, the description of these problems does not preclude the existence of other problems. The embodiments do not need to solve all of these problems. It is possible to extract other issues from the description of the requested terms. [Means for solving the problem]

[0012] To achieve the above objective, one aspect of the present invention provides a surface layer of the positive electrode active material that differs from the internal region. Two types of regions are established. The inner region is a non-stoichiometric compound, and the outer region is a stoichiometric compound. It is preferable to have one.

[0013] Furthermore, the inner region preferably contains titanium, and the outer region preferably contains magnesium. This is preferable. Furthermore, these two types of regions may overlap.

[0014] Furthermore, the inner region is formed through a coating process such as the sol-gel method, while the outer region undergoes segregation due to heating. Therefore, it is preferable to form it this way.

[0015] One aspect of the present invention is a positive electrode active material, wherein the positive electrode active material comprises a first region and a second region. It has a third region, the first region is located inside the positive electrode active material, and the second and third regions The first region is located on the surface of the positive electrode active material, and the third region is located further away from the second region of the positive electrode active material. It exists in a region close to the surface, and the first region has an oxide of lithium and a first transition metal, and is layered. It has a rock salt-type crystal structure, and the second region is an unstoichiometric compound having an oxide of the second transition metal. The non-stoichiometric compounds have a rock salt-type crystal structure, and the third region contains compounds of main group elements. Compounds of main group elements are cathode active materials that have 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 is a main group element. It is preferably magnesium oxide.

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

[0018] In the above, the crystal orientations of the first region and the second region partially coincide, and the second region and It is preferable that the crystal orientations of the third region coincide in part.

[0019] In the above, the (1-1-4) plane of the layered rock salt type crystal structure of the first region, or ( 1-1-4) The plane perpendicular to the plane and the {100} plane of the rock salt type crystal structure of the second region The degree of mismatch is 0.12 or less, and the {100} plane of the rock salt type crystal structure of the second region and The degree of misconformity of the {100} plane of the rock salt-type crystal structure in the third region is 0.12 or less. It is preferable.

[0020] Another aspect of the present invention is a positive electrode active material comprising lithium and titanium. It contains cobalt, magnesium, oxygen, and fluorine, and is present on the surface layer of the positive electrode active material. In a sample, when the cobalt concentration measured by X-ray photoelectron spectroscopy is set to 1, the titanium concentration is 0.0 The magnesium concentration is between 0.4 and 1.5, and the fluorine concentration is between 5 and 0.4. The positive electrode active material has a value between 0.05 and 1.5.

[0021] Another aspect of the present invention relates to a lithium source, a cobalt source, a magnesium source and a fluorine source. The process of mixing the lithium source, cobalt source, magnesium source and fluorine source Heat at 800°C to 1100°C for 2 to 20 hours, and then add lithium and cobalt. The process involves obtaining particles containing magnesium, oxygen, and fluorine, and titanium alkoxy. The process involves dissolving the alkoxide in alcohol, and then adding lithium to the alcohol solution of titanium alkoxide. A mixture of particles containing cobalt, magnesium, oxygen, and fluorine, and water vapor is added. The process involves stirring in a humid atmosphere, recovering the precipitate from the mixture, and processing the recovered precipitate. Heat in an oxygen-containing atmosphere at a temperature between 500°C and 1200°C for a holding time of 50 hours or less. This is a method for producing a positive electrode active material, comprising the steps described above.

[0022] Furthermore, in the above manufacturing method, the number of lithium atoms in the lithium source and the number of lithium atoms in the cobalt source It is preferable that the ratio of the number of cobalt atoms is 1.00 ≤ Li / Co < 1.07.

[0023] Furthermore, in the above manufacturing method, the number of fluorine atoms contained in the fluorine source and the magnesium source The ratio of magnesium atoms present is Mg:F = 1:x (1.5 ≤ x ≤ 4). It is preferable.

[0024] Furthermore, in the above manufacturing method, the number of magnesium atoms contained in the magnesium source is cobalt The cobalt content in the source should preferably be between 0.5 atomic percent and 1.5 atomic percent. It's nice.

[0025] Furthermore, in the above manufacturing method, lithium carbonate is used as the lithium source, and oxidation is used as the cobalt source. Cobalt is used, magnesium oxide is used as the magnesium source, and lithium fluoride is used as the fluorine source. You can use Um.

[0026] Furthermore, by covering the surface of the positive electrode active material with a coating and protecting the aforementioned crystal structure, the charge and discharge process is improved. This enables the suppression of capacity degradation in the cycle. Examples include a carbon-containing coating (a film containing a graphene compound), or lithium or A coating containing decomposition products of the electrolyte is used.

[0027] In particular, powders in which the surface of the positive electrode active material is coated with graphene oxide using a spray drying device It is preferable to obtain the following. The spray drying apparatus supplies hot air to the suspension and the dispersion medium This is a manufacturing apparatus that uses a spray-drying method for removal.

[0028] Repeated charge-discharge cycles can cause cracks or fractures in the particles of the positive electrode active material. Shape changes such as becoming bloated may occur. If such shape changes occur, the positive electrode active material A new surface of the material is exposed, and when that surface comes into contact with the electrolyte, decomposition reactions occur, and It is said that the cycle characteristics and charge / discharge characteristics of the next battery will be reduced.

[0029] Therefore, it prevents changes in shape such as cracking or splitting of the positive electrode active material particles. It is preferable to provide a coating film.

[0030] However, compared to the surface of the positive electrode active material, which has a heavy weight per unit volume, To coat a small amount of graphene oxide, a suspension was prepared and a rotation-orbit mixer was used. However, the covering was insufficient.

[0031] Therefore, in order to coat the particle surface of the positive electrode active material with graphene oxide, Fen and a polar solvent (such as water) are mixed and subjected to sonication, and then the particles of the positive electrode active material are mixed in. A preferred method involves preparing a suspension and then using a spray-drying device to produce a dried powder. The dried powder produced in this manner is sometimes called a composite.

[0032] The size of a single droplet of spray liquid emitted from the nozzle of a spray drying device depends on the nozzle diameter.

[0033] If the particle size is smaller than the nozzle diameter, multiple particles will be contained within a single drop of spray liquid emitted from the nozzle. It will exist. The particle surface after drying under the condition that the maximum particle diameter is smaller than the nozzle diameter. Upon inspection, some areas coated with graphene oxide can be seen, but it cannot be said that the coating is sufficient. I couldn't say it.

[0034] When the nozzle diameter of the spray drying device and the maximum particle size of the active material are made to be approximately the same, This is preferable because it results in good coating of the material. Furthermore, the positive electrode should be approximately the same size as the nozzle diameter. In the production of the active material, it is preferable to adjust the maximum particle size of the positive electrode active material.

[0035] Since graphene oxide disperses well in water, stirring with ultrasound allows the water and graphene oxide to disperse. A suspension of fen can be prepared. A positive electrode active material is added to the suspension, and the suspension is used By spraying with a spray-drying device, the surface of the positive electrode active material is coated with graphene oxide. A covered powder can be obtained.

[0036] Furthermore, the acidity of the suspension increases as the amount of graphene oxide increases. Therefore, the positive electrode active material There is a risk of etching a portion of the surface (for example, LiCoO2 containing Mg or F). Therefore, the pH of the suspension before spraying is adjusted to approach approximately pH 7. It is preferable to make it as close to neutral as possible, or to make it alkaline, with a pH of 8 or higher. For pH adjustment, it is preferable to use an aqueous LiOH solution. Also, for example, as a positive electrode active material... When using LiCoO2, if only pure water is used as the dispersion medium for the suspension, the positive electrode active material The surface may be damaged. Therefore, a mixture of ethanol and water is used as the dispersion medium for the suspension. Using a combined solution may reduce damage to the surface of the active material.

[0037] By preparing the suspension as described above, the surface can be efficiently coated with graphene oxide. A positive electrode active material can be prepared. By coating the surface with graphene oxide, the positive electrode active material can be prepared. This prevents changes in shape, such as cracking or breaking, in the particles of the highly active material. It can. Also, positive electrode active materials whose surfaces are coated with graphene oxide can withstand exposure to the atmosphere after manufacturing. This can suppress alteration and deterioration. Here, "after manufacturing" refers to, for example, the end of manufacturing of the positive electrode active material. This refers to the period from the end of production until a secondary battery using the positive electrode active material is manufactured, and the storage of the positive electrode active material. This includes tubing and transport, etc. Furthermore, by forming a coating, the positive electrode active material and the electrolyte... Because it prevents direct contact and reaction, when a secondary battery is manufactured, the secondary Battery reliability will improve.

[0038] Furthermore, known equipment can be used in the spray drying method, for example, a counterflow type pressurized nozzle A spray drying apparatus of the L-type, a parallel flow nozzle type pressurized spray drying apparatus, etc., can be used.

[0039] Furthermore, when used in secondary batteries, the graphene oxide covering the surface of the active material may be reduced. Reduced graphene oxide is called "RGO (Reduced Graphene Oxide) It is sometimes called "de)". Note that RGO contains some oxygen or oxygen-containing atomic groups. In some cases, they may remain in a bonded state. For example, RGO has epoxy groups and carboxyl groups. They may have functional groups such as carbonyl groups or hydroxyl groups.

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

[0041] Furthermore, rechargeable batteries can be used in a variety of shapes to suit the device they are used in. Examples include cylindrical, rectangular, coin-shaped, and laminated (flat) shapes. It is possible. [Effects of the Invention]

[0042] According to one aspect of the present invention, by using it in a lithium-ion secondary battery, during the charge-discharge cycle This provides a positive electrode active material in which the decrease in capacity is suppressed. Furthermore, it offers excellent charge and discharge characteristics. We can provide a secondary battery. We can also provide a secondary battery that is safe or highly reliable. It is possible to provide novel materials, active material particles, secondary batteries, or methods for producing them. It is possible. [Brief explanation of the drawing]

[0043] [Figure 1] A diagram illustrating an example of a positive electrode active material. [Figure 2] A diagram illustrating the crystal structure of the positive electrode active material. [Figure 3] A diagram illustrating the crystal structure of the positive electrode active material. [Figure 4] A diagram illustrating the sol-gel method. [Figure 5] A diagram illustrating the elemental segregation model of the positive electrode active material. [Figure 6] A diagram illustrating the elemental segregation model of the positive electrode active material. [Figure 7] Cross-sectional view of the active material layer when a graphene compound is used as a conductive additive. [Figure 8] A diagram illustrating how to charge a rechargeable battery. [Figure 9] A diagram illustrating how to charge a rechargeable battery. [Figure 10] A diagram illustrating the discharge method of a secondary battery. [Figure 11] A diagram illustrating a coin-type rechargeable battery. [Figure 12] A diagram illustrating a cylindrical rechargeable battery. [Figure 13] A diagram illustrating an example of a secondary battery. [Figure 14] A diagram illustrating an example of a secondary battery. [Figure 15] A diagram illustrating an example of a secondary battery. [Figure 16] A diagram illustrating an example of a secondary battery. [Figure 17] A diagram illustrating a laminated rechargeable battery. [Figure 18] A diagram illustrating a laminated rechargeable battery. [Figure 19] A diagram showing the external appearance of a secondary battery. [Figure 20] A diagram showing the external appearance of a secondary battery. [Figure 21] A diagram illustrating the method for manufacturing a secondary battery. [Figure 22] A diagram illustrating a rechargeable battery that can be bent. [Figure 23] A diagram illustrating a rechargeable battery that can be bent. [Figure 24] A diagram illustrating an example of an electronic device. [Figure 25] A diagram illustrating an example of an electronic device. [Figure 26] A diagram illustrating an example of an electronic device. [Figure 27]A diagram illustrating an example of an electronic device. [Figure 28] Transmission electron microscope image of the positive electrode active material of Example 1. [Figure 29] FFT image of the transmission electron microscope image of the positive electrode active material of Example 1. [Figure 30] Elemental mapping image of the positive electrode active material in Example 1. [Figure 31] Elemental mapping image of the positive electrode active material of the comparative example of Example 1. [Figure 32] Graph showing the TEM-EDX linear analysis results of the positive electrode active material in Example 1. [Figure 33] Graph showing the charge and discharge characteristics of the secondary battery in Example 1. [Figure 34] Graph showing the charge and discharge characteristics of the secondary battery in the comparative example of Example 1. [Figure 35] Graph of the cycle characteristics of the secondary battery in Example 1. [Figure 36] Graph of the cycle characteristics of the secondary battery in Example 1. [Figure 37] TEM-EDX surface analysis image of the comparative example of Example 2. [Figure 38] TEM-EDX surface analysis image of the positive electrode active material of Example 2. [Figure 39] TEM-EDX surface analysis image of the comparative example of Example 2. [Figure 40] TEM-EDX surface analysis image of the positive electrode active material of Example 2. [Figure 41] Graph showing the EDX point analysis results for Example 2. [Figure 42] Graph showing the EDX point analysis results for Example 2. [Figure 43] Graph of the rate characteristics of the secondary battery in Example 2. [Figure 44] Graph showing the temperature characteristics of the secondary battery in Example 2. [Figure 45] Graph showing the cycle characteristics of the secondary battery in Example 2. [Figure 46] Graph showing the XPS analysis results of the positive electrode active material in Example 3. [Figure 47] A graph showing the cycle characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 48] A graph showing the cycle characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 49] A graph showing the cycle characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 50] A graph showing the charge and discharge characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 51] SEM image of the positive electrode active material in Example 4. [Figure 52] SEM-EDX image of the cathode active material in Example 4. [Figure 53] This diagram shows the process flow of Example 5. [Figure 54] A diagram illustrating the spray drying apparatus of Example 5. [Figure 55] This is a TEM photograph showing one embodiment of the present invention in Example 5. [Figure 56] This is an SEM image showing one embodiment of the present invention in Example 5. [Figure 57] This is an SEM image showing a comparative example of Example 5. [Figure 58] Cross-sectional view of the active material layer when a graphene compound is used as a conductive additive in Example 5. [Modes for carrying out the invention]

[0044] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is... Not limited to the following description, the form and details can be modified in various ways, as any person skilled in the art would know. This is easily understood. Furthermore, the present invention shall be interpreted as being limited to the contents of the embodiments described below. It's not something that can be done.

[0045] In the figures described herein, the positive electrode, negative electrode, active material layer, separator, and outer casing are shown separately. The size, thickness, etc., of each individual component may be exaggerated for the sake of clarity in the explanation. Yes. Therefore, each component is not necessarily limited to its size, nor is the relationship between each component limited. It is not limited to relative size.

[0046] Furthermore, in the configuration of the present invention as described herein, parts that are the same or have similar functions The same symbols are used consistently across different drawings, and explanations of their repetition are omitted. When referring to parts with similar functions, the hatch pattern is the same, and no special designation is given. There are cases where this is not the case.

[0047] Furthermore, Miller indices are used to express crystal planes and directions in this specification. In this notation, a superscript bar is placed over the number in crystallography, but in this specification and elsewhere, the crystal plane and Due to notation constraints, instead of placing a bar above the number to indicate direction, a minus sign (-) is placed before the number. The symbol is used to indicate the direction within the crystal. Additionally, individual orientations indicating directions within the crystal are indicated by [ ], and equivalent directions are shown. The collective orientation that shows all is < >, and the individual planes that show crystal planes are ( ), and they have equivalent symmetry. The set of planes is represented by {}. Note that the notation of crystal planes and directions in the drawings is as follows: The original notation, with a bar above the crystallographic number, will be used. Also, 1 Å (angstrom) is 10 -10 It is m.

[0048] In this specification, segregation refers to the process of a solid composed of multiple elements (e.g., A, B, C) This refers to the phenomenon where a certain element (for example, B) is distributed unevenly.

[0049] In this specification, etc., the layered rock salt type crystal structure of a composite oxide containing lithium and a transition metal This structure has a rock salt-type ionic arrangement in which cations and anions are arranged alternately, and it contains transition metals and Because lithium is arranged in a regular pattern to form a two-dimensional plane, two-dimensional diffusion of lithium is possible. This refers to the crystal structure. It may contain defects such as vacancies in cations or anions. Also, layers... Strictly speaking, the rock salt crystal structure is a structure in which the lattice of the rock salt crystal is distorted. be.

[0050] Furthermore, in this specification, a rock salt-type crystal structure is defined as a structure in which cations and anions are arranged alternately. This refers to a structure that contains certain elements. It is also acceptable for there to be deficiencies in cations or anions.

[0051] Layered rock salt crystals and the anions of rock salt crystals form a cubic close-packed structure (face-centered cubic lattice structure). When layered rock salt crystals and rock salt crystals come into contact, cubic close-packed formation is created by anions. There are crystal planes where the orientation of the packing structure is aligned. However, the space group of layered rock salt crystals is R-3m. The space groups of rock salt crystals are Fm-3m (the general space group of rock salt crystals) and Fd-3m ( Since it is different from the space group of rock salt crystals with the simplest symmetry, the above conditions are satisfied The Miller indices of the crystal planes differ between layered rock salt crystals and rock salt crystals. In this specification, layered rock salt crystals are used. In crystals and rock salt-type crystals, the orientation of the cubic close-packed structure composed of anions is aligned. In this case, we can say that the orientation of the crystals is roughly consistent.

[0052] The coincidence of crystal orientation in two regions is evident in TEM (transmission electron microscope) images and STEM (transmission electron microscope) images. (Transmission electron microscope) image, HAADF-STEM (High-angle scattering annular dark-field scanning transmission electron microscope) This can be determined from images such as ) images and ABF-STEM (annular bright-field scanning transmission electron microscope) images. X-ray diffraction, electron diffraction, neutron diffraction, etc., can also be used as criteria for judgment. TEM image In layers of rock, the arrangement of cations and anions can be observed as a repetition of bright and dark lines. When the orientation of the cubic close-packed structure is aligned in salt-type and rock-type crystals, bright and dark lines appear between the crystals. It can be observed that the angle formed by the repetition of this pattern is 5 degrees or less, more preferably 2.5 degrees or less. Note that light elements such as oxygen and fluorine may not be clearly visible in TEM images, etc. Yes, but in that case, the alignment of the metal elements can be determined by their arrangement.

[0053] In this specification, the similarity in the structure of a two-dimensional interface is referred to as epitaxy. Crystal growth that has similarities to the structure of a two-dimensional interface is called epitaxial growth. Topotaxis refers to having fundamental structural similarities or having the same crystallographic orientation. Therefore, if it is topotaxis, when you observe a part of the cross-section, you will see two regions (even The orientation of the crystals in the underlying region and the region formed by growth is roughly consistent.

[0054] (Embodiment 1) [Structure of the positive electrode active material] First, using Figure 1, a positive electrode active material 100, which is one embodiment of the present invention, will be described. Quality 100 is a substance containing a transition metal capable of electrochemically intercalating or releasing lithium ions. As shown in Figure 1(A), the positive electrode active material 100 has a first region 101 inside, The surface portion has a second region 102 and a third region 103.

[0055] As shown in Figure 1(B), the second region 102 does not cover the entirety of the first region 101. It is not necessary. Similarly, the third region 103 does not cover the entirety of the second region 102. Alternatively, a third region 103 may exist adjacent to the first region 101.

[0056] Furthermore, even if the thickness of the second region 102 and the third region 103 differs from place to place good.

[0057] Furthermore, a third region 103 may exist inside the positive electrode active material 100. For example, the first region When region 101 is polycrystalline, a third region 103 may exist near the grain boundary. In the areas of the positive electrode active material 100 with crystal defects, cracks, and their vicinity, a third Region 103 may exist. In Figure 1(B), a portion of the grain boundary is shown by a dotted line. In texts and other documents, a crystal defect is defined as a defect observable by TEM imaging, i.e., the inclusion of other elements in the crystal. This refers to embedded structures, cavities, etc. Furthermore, a crack is, for example, shown in Figure 1(C). This refers to cracks and fissures that occur in particles, such as in the crack section 106.

[0058] Similarly, as shown in Figure 1(B), a second region 102 exists inside the positive electrode active material 100. This is also possible. For example, when the first region 101 is polycrystalline, the second region 102 may be located near the grain boundary. The positive electrode active material 100 may have crystal defects, cracks and A second region 102 may exist in the vicinity of those regions. Also, inside the positive electrode active material 100 The third region 103 and the second region 102 may overlap.

[0059] <First Domain 101> The first region 101 has a composite oxide of lithium and a first transition metal. It can also be said that 101 contains lithium, a first transition metal, and oxygen.

[0060] Composite oxides of lithium and the first transition metal are preferably found to have a layered rock salt-type crystalline structure. stomach.

[0061] As the first transition metal, only cobalt may be used, or cobalt may be used as the first transition metal. You can use two types, tho and manganese, or you can use three types, cobalt, manganese, and nickel. good.

[0062] In other words, the first region consists of lithium cobaltate, lithium manganeseate, and lithium nickelate. Lithium cobaltate, in which some of the cobalt is replaced by manganese, nickel-manganese-cobalt oxide It may contain lithium baltate, etc. In addition, the first region 101 may contain, It may contain metals other than transition metals, such as aluminum.

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

[0064] Materials with a layered rock salt crystal structure have high discharge capacity and lithium can diffuse two-dimensionally. It has features such as low resistance, and is therefore preferred as the first region 101. If region 101 has a layered rock salt type crystal structure, surprisingly, magnesium, etc., as will be described later. Segregation of typical elements is likely to occur.

[0065] The first region 101 may be a single crystal or a polycrystalline material. For example, the first region 10 Material 1 may be a polycrystalline material with an average crystallite size of 280 nm or more and 630 nm or less. In the case of crystals, grain boundaries can sometimes be observed using TEM, etc. Also, the average grain size is... It can be calculated from the half-width of the XRD.

[0066] Because polycrystalline materials have a distinct crystal structure, the two-dimensional diffusion paths of lithium ions are sufficiently clear. It is secured. In addition, it is easier to produce than single crystals, so it is preferred as the first region 101. stomach.

[0067] Furthermore, not all of the first region 101 has to be of the layered rock salt type crystalline structure. For example, the first A portion of region 101 may be amorphous or have other crystalline structures.

[0068] <Second Domain 102> The second region 102 has an oxide of the second transition metal. It can be said that it contains a transferring metal and oxygen.

[0069] As the second transition metal, it is preferable to use a metal with non-stoichiometric properties. Second region 10 It can be said that it is preferable for 2 to have an unstoichiometric compound. For example, a second transition metal and Titanium, vanadium, manganese, iron, chromium, niobium, cobalt, zinc, zirconium At least one of the following can be used: 1.5, 2.5, 3.5, 4 It is preferable that the element is different from the transition metal in 1.

[0070] In this specification, a metal with non-stoichiometric properties refers to a metal that can have multiple valencies. A non-stoichiometric compound is a compound of a metal that can have multiple valencies and another element.

[0071] Furthermore, it is preferable that the second region 102 has a rock salt-type crystalline structure.

[0072] The second region 102 is a buffer region connecting the first region 101 and the third region 103, which will be described later. It functions as a domain. Unstoichiometric compounds change depending on the valence of the metal they contain. Interatomic distances can change. Also, non-stoichiometric compounds often have deficiencies in cations or anions. Alternatively, dislocations (so-called Magnelis phases) are formed. Therefore, the second region 102 is a buffer region. As a region, it can absorb the strain generated between the first region 101 and the third region 103.

[0073] Furthermore, the second region 102 may contain lithium in addition to the second transition metal and oxygen. For example, it may have lithium titanate, lithium manganeseate, etc. Furthermore, the second Region 102 may contain the same main group elements as the third region 103, which will be described later. Region 102 contains elements such as lithium that are present in the first region 101, and the third region It is preferable for region 103 to contain the elements present in the buffer region.

[0074] In other words, the second region 102 consists of lithium titanate, titanium oxide, vanadium oxide, and man oxide. This includes cancer, iron oxide, copper oxide, chromium oxide, niobium oxide, cobalt oxide, zinc oxide, etc. It is possible.

[0075] The second region 102 may also have a first transition metal. For example, the first transition metal A second transition metal may be present at a portion of the first transition metal site of a composite oxide containing the group. stomach.

[0076] For example, if the second transition metal is titanium, then in the second region 102, titanium oxide It may exist as (TiO2) or as lithium titanate (LiTiO2). It may also be done. In addition, in the second region 102, a composite acid having lithium and a first transition metal Some of the first transition metal sites of the ion may be substituted with titanium.

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

[0078] Furthermore, the second region 102 has the same type of crystal structure as the third region 103, which will be described later. This is preferable. In this case, the crystal orientations of the second region 102 and the third region 103 tend to coincide. .

[0079] Furthermore, it is preferable that the second region 102 has a rock salt type crystal structure, but the second region 10 Not all of region 2 has to be of the rock salt type crystal structure. For example, region 2 102 is of the spinel type. Crystal structures, including olivine-type crystal structures, corundum-type crystal structures, and rutile-type crystal structures. It may have other crystalline structures.

[0080] Furthermore, if the structure in which six oxygen atoms are adjacent to the cation is maintained, the crystal structure will be strained. It is also possible that there are cation deficiencies in a portion of the second region 102.

[0081] Furthermore, a portion of the second region 102 may be amorphous.

[0082] The second region 102, if too thin, will have reduced functionality as a buffer region, but if too thick... However, this may lead to a decrease in capacity. Therefore, the second region 102 is the positive electrode active material 100 It is preferable that it exists within 20 nm, more preferably 10 nm, in the depth direction from the surface. Furthermore, the second transition metal may have a concentration gradient.

[0083] <Third Domain 103> The third region 103 contains compounds of main group elements. Compounds of main group elements are stoichiometric compounds. It is a substance. As a compound of typical elements, it is a compound consisting of electrochemically stable typical elements. It is preferable to use magnesium oxide, calcium oxide, beryllium oxide, fluorine, etc. At least one of lithium fluoride or sodium fluoride can be used.

[0084] The third region 103 is the 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 in the third region 103 undergoes electrochemical changes during the charging and discharging process. It is preferable that the material has low ions and is not easily altered by contact with the electrolyte. Therefore, electrochemically stable compounds of typical elements are preferred as the third region 103. Material 100 has a third region 103 on its surface, which ensures safety during charging and discharging of secondary batteries. Qualitative performance can be improved. Here, high stability of a secondary battery means, for example, in the first region. The crystal structure of the composite oxide containing lithium and the first transition metal that 101 possesses is more stable. This refers to the fact that the capacity of a secondary battery does not change significantly even after repeated charging and discharging. Alternatively, even after repeated charging and discharging, the change in the valence state of the metal in the positive electrode active material 100 is suppressed. It means to be controlled or restrained.

[0085] Furthermore, the third region 103 may contain fluorine. In this case, some of the anions in the compound of typical elements may be substituted with fluorine.

[0086] When anions in compounds of typical elements are partially substituted with fluorine, for example, lithium The diffusion of the substance can be increased. Therefore, even if a third region 103 is present, it does not hinder charging and discharging. It becomes more difficult. Also, the presence of fluorine on the surface of the positive electrode active material particles causes the electrolyte to decompose. This can improve corrosion resistance to hydrofluoric acid produced.

[0087] Furthermore, the third region 103 has lithium, a first transition metal and a second transition metal. It's okay to be there.

[0088] Furthermore, compounds of main group elements in the third region 103 preferably have a rock salt-type crystal structure. It seems that the third region 103 has a rock salt-type crystal structure, and the arrangement of the crystals with the second region 102 The orientations tend to coincide. Crystals of the first region 101, the second region 102, and the third region 103. When the orientations are roughly aligned, the second region 102 and the third region 103 provide more stable coverage. It can function as a layer.

[0089] However, not all of the third region 103 has to be a rock salt type crystal structure. For example, the third Region 103 contains spinel-type crystal structures, olivine-type crystal structures, corundum-type crystal structures, and rutile. It may have other crystal structures, including a type crystal structure.

[0090] Furthermore, if the structure in which six oxygen atoms are adjacent to the cation is maintained, then the crystal structure will not be strained. This is also acceptable. Furthermore, a portion of the third region 103 may contain a cation deficiency.

[0091] Furthermore, a portion of the third region 103 may be amorphous.

[0092] The third region 103, if too thin, will have reduced function in improving stability during charging and discharging. If it becomes too thick, it will lead to a decrease in capacity. Therefore, the thickness of the third region 103 should be 0.5 nm or less. A wavelength of 50 nm or less is preferred, and 0.5 nm to 2 nm is more preferred.

[0093] Furthermore, if the third region 103 contains fluorine, the fluorine is magnesium fluoride (MgF2). It exists in bonding states other than lithium fluoride (LiF) and cobalt fluoride (CoF2). It is preferable that... Specifically, when the vicinity of the surface of the positive electrode active material 100 is analyzed by XPS, The peak position of the oxy-bond energy is preferably between 682 eV and 685 eV. It is more preferable that the voltage be around 684.3 eV. This is because MgF2, LiF, and CoF2 This is a bond energy that does not coincide with any of the others.

[0094] In this specification, the peak position of the binding energy of a certain element when analyzed by XPS. This refers to the range in which the intensity of the energy spectrum is maximum, corresponding to the bond energy of that element. This refers to the value of the bond energy that results in [the specified value].

[0095] Generally, the positive electrode active material undergoes repeated charging and discharging, and as a result, manganese, cobalt, nickel, etc. The first transition metal dissolves into the electrolyte, oxygen is released, and the crystal structure becomes unstable. A side reaction occurs, and degradation progresses. However, the positive electrode active material 100, which is one embodiment of the present invention, A second region 102 that functions as a buffer region, and a third region 103 that is electrochemically stable. It has both. Therefore, it effectively suppresses the elution of the first transition metal and the first region 101 It is possible to make the crystal structure of the lithium-transition metal composite oxide more stable. Therefore, it is possible to significantly improve the cycle characteristics of a secondary battery having positive electrode active material 100. This is possible. Also, 4.3V (vs. Li / Li + Voltages exceeding 4.5V, especially 4.5V (vs. Li / Li + When charging and discharging are performed at a high voltage of ) or higher, the configuration of one aspect of the present invention is It produces remarkable results.

[0096] <Heteroepitaxial growth and topotaxy> The second region 102 is formed by heteroepitaxial growth from the first region 101. This is preferable. Furthermore, the third region 103 is heteroepitaxial from the second region 102. It is preferable that it is formed by growth. The region formed by heteroepitaxial growth Therefore, the underlying region and the crystal orientation roughly coincide in three dimensions, resulting in a topotaxis. The first region 101, the second region 102, and the third region 103 are topotaxi. It is possible.

[0097] When the crystal orientations from the first region 101 to the third region 103 are roughly coincide, the second region Regions 102 and the third region 103 are coating layers that have a stable bond with the first region 101. Therefore, the positive electrode active material 100 can have a strong coating layer.

[0098] The second region 102 and the third region 103 have a stable bond with the first region 101. Therefore, when the positive electrode active material 100 is used in a secondary battery, the first region 101 is created by charging and discharging. This effectively suppresses changes in the crystal structure. Also, charging allows lithium to be released from the first region 101. Even if the um is removed, the first region 101 is maintained by the coating layer which has a stable bond. Furthermore, the release of cobalt and oxygen can be suppressed. This allows for the creation of chemically stable materials. Therefore, secondary electric power plants with excellent cycle characteristics can be produced. It can be used as a pond.

[0099] <Degree of inconsistency between domains> To perform heteroepitaxial growth, you need a base region crystal and the crystal you want to grow. The degree of inconsistency is important.

[0100] In this specification, the degree of mismatch f is defined by the following formula 1. a is the average nearest distance between oxygen and cations, and the natural anions and cations of the crystal you want to grow Let b be the average of the closest distances to ON.

[0101]

number

[0102] For heteroepitaxial growth, the underlying crystal region and the desired crystal are necessary. The degree of conformation f must be 0.12 or less. Layered, more stable heteroepitaxial formation For optimal performance, the mismatch degree f is preferably 0.08 or less, and even more preferably 0.04 or less. It's nice.

[0103] Therefore, the layered rock salt type crystal structure of the first region 101 and the second region 102 The degree of mismatch f of the rock salt-type crystal structure is 0.12 or less, the first region 101 and the second region It is preferable to select a material from region 102.

[0104] Furthermore, the rock salt type crystal structure of the second region 102 and the rock salt type crystal structure of the third region 103 The degree of mismatch f in the crystal structure is 0.12 or less, so the second region 102 and the third region 1 It is preferable to select material 03.

[0105] As described above, the first region 101 has a layered rock salt type crystal structure, and the second region 102 is The degree of misconformity f of the rock salt type crystal structure is 0.12 or less, and the second region 102 is present. The degree of mismatch f between the rock salt-type crystal structure and the rock salt-type crystal structure of the third region 103 is 0 The first region 101, the second region 102, and the third region satisfy the condition that they are 0.12 or less. Examples of materials and crystal planes in region 103 are shown below.

[0106] ≪Example 1: Lithium cobaltate, lithium titanate, and magnesium oxide≫ First, using Figures 2 and 3, the first transition metal is cobalt, and the first region 101 is a layer. It has lithium cobalt oxide with a rock salt-type crystalline structure, and the second transition metal is titanium. The second region 102 has lithium titanate having a rock salt-type crystal structure, and the third region 1 An example where the compound of the main group element present in 03 is magnesium oxide, which has a rock salt-type crystal structure. I will explain this.

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

[0108] Based solely on Figure 2(A), it is not possible to determine that layered rock salt crystals and rock salt crystals become topotaxis. It's not visible. However, here, we can see layered rock salt crystals in different orientations (for example, the arrows in Figure 2(A)). We will view it from the direction that includes it. Figure 2(B) shows layered rock salt type crystals in the plane of <1-1-4>. A model viewed from a directional perspective, a rock salt-type crystal <100> This shows a model viewed from the plane orientation.

[0109] As shown in Figure 2(B), when layered rock salt crystals are viewed from the <1-1-4> plane orientation, rock salt Crystal of the type <100> The atomic arrangement is very similar to that when viewed from a specific plane orientation. Also, metals and acids The prime nearest proximity distance also takes a similar value. For example, in layered rock salt type lithium cobalt oxide The Li-O junction is 2.089 Å, and the Co-O junction is 1.925 Å. Also, rock salt type titanate The distance between Li and O in lithium is 2.138 Å, and the distance between Ti and O is 2.051 Å. The Mg-O distance in salt-type magnesium oxide is 2.106 Å.

[0110] Therefore, using Figure 3, the (1-1-4) crystal plane of the layered rock salt type crystal and the {1} of the rock salt type crystal This section explains the degree of mismatch between regions when the crystal planes of {00} are in contact.

[0111] As shown in Figure 3, the first region 101 has a layered rock salt type crystalline structure of lithium cobalt acid. The distance between metal-oxygen-metal atoms on crystal plane 101p(1-1-4) of the atom is 4. It is 01Å. Also, lithium titanate having a rock salt type crystal structure in the second region 102 { The metal-oxygen-metal distance on the crystal plane 102p{100} is 4.19 Å. Therefore, the degree of mismatch f between crystal plane 101p(1-1-4) and crystal plane 102p{100} is 0 It is 0.04.

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

[0113] Thus, the degree of inconsistency between the first region 101 and the second region 102, and the second region 10 Since the degree of inconsistency between region 2 and the third region 103 is sufficiently small, from the first region 101 to the third region Topotaxy can occur up to region 103.

[0114] On the other hand, although they are not in contact in Figure 3, if we assume that the crystal plane 101p(1-1-4) of the first region 101 The degree of mismatch f when the crystal plane 103p{100} of the third region 103 is in contact with it is 0.05. Therefore, the existence of the second region 102 makes it possible to reduce the degree of inconsistency. Furthermore, since the second region 102 is a transition metal oxide having non-stoichiometric properties, the second region The presence of 102 makes the first region 101 to the third region 103 more stable. It may become a potax. Therefore, the second region 102 and the third region 103 are the first region It can function as a coating layer having a stable bond with 101.

[0115] In this embodiment, the (1-1-4) surface of the layered rock salt type and the {100} surface of the rock salt type are in contact. Examples have been given, but the present invention is not limited to these. Crystal planes that can become topotaxy It's enough if they are in contact with each other.

[0116] ≪Example 2: Lithium cobalt oxide, manganese oxide, and calcium oxide≫ Next, the first transition metal is cobalt, and the first region 101 has a layered rock salt type crystal structure. It has lithium cobaltate, the second transition metal is manganese, and the second region 102 is It has manganese oxide with a rock salt-type crystal structure, and the third region 103 has a chemical reaction of main group elements. An example is given where the compound is calcium oxide having a rock salt-type crystalline structure.

[0117] In this case as well, similar to Figures 2 and 3, the layered rock salt type crystals of the first region 101 are <1-1 Viewed from the plane orientation of -4>, the rock salt type crystals of the second region 102 and the third region 103 are <100> The atomic arrangement is very similar to that when viewed from that plane orientation.

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

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

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

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

[0122] ​ ≪Example 3: Lithium nickel-manganese-cobaltate, manganese oxide, calcium oxide≫ Next, the first transition metals are nickel, manganese, and cobalt, and the first region 101 is Lithium nickel-manganese-cobalt oxide (LiNi) has a layered rock salt-type crystalline structure. 0. 33 Co 0.33 Mn 0.33 It has O2), and the second transition metal is manganese, and the second Region 102 contains manganese oxide having a rock salt-type crystal structure, and the third region 103 contains This section describes an example where a compound of a typical element is calcium oxide, which has a rock salt-type crystal structure. ru.

[0123] In this case as well, as shown in Figures 2 and 3, layered rock salt type crystals are arranged in the <1-1-4> plane. From this perspective, the rock salt-type crystals <100> The atomic arrangement is very similar to that when viewed from that plane orientation. The (1-1-4) crystal plane of the layered rock salt crystal and the {100} crystal plane of the rock salt crystal are This section explains the degree of inconsistency between regions when they are in contact.

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

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

[0126] Thus, the degree of inconsistency between the first region 101 and the second region 102, and the second region 10 Since the degree of inconsistency between region 2 and the third region 103 is sufficiently small, from the first region 101 to the third region Topotaxy can be performed up to region 103.

[0127] On the other hand, if we assume that the crystal plane (1-1-4) of the first region 101 and the crystal plane {10} of the third region 103 When {0} is in contact, the degree of mismatch f becomes 0.18, making heteroepitaxial growth difficult. In other words, the existence of a second region 102 means that the heterogeneity from the first region to the third region is Epitaxial growth becomes possible. Therefore, the second region 102 and the third region 103 This allows it to function as a coating layer having a stable bond with the first region 101.

[0128] <Boundaries between each region> As previously stated, the first region 101, the second region 102, and the third region 103 are These are regions with different compositions. However, the elements in each region have a concentration gradient. This can happen. For example, the second transition metal in the second region 102 may have a concentration gradient. Furthermore, the third region 103 is a region where typical elements are segregated, as will be described later. Because this is preferable, there may be a concentration gradient of typical elements in each region. The boundaries may not be clear.

[0129] The first region 101, the second region 102, and the third region 103 are TEM images, STEM images. , FFT (Fast Fourier Transform) analysis, EDX (Energy Dispersive X-ray Analysis), ToF-S IMS (Time-of-Flight Secondary Ion Mass Spectrometry) analysis in the depth direction, XPS (X-ray Photoelectron spectroscopy), Auger electron spectroscopy, TDS (Temperature Programmed Desorption Spectroscopy), 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 (e.g., elemental mapping), it can be observed that the first region 101, the second region 102, and the third region 103 have different elements . Also, in the line analysis of EDX and the depth direction analysis using ToF-SIMS, the peak concentrations of each element possessed by the first region 101, the second region 102, and the third region 103 can be detected .

[0131] However, it is not always necessary to observe clear boundaries between the first region 101, the second region 102, and the third region 103 by various analyses .

[0132] In this specification, etc., the third region 103 existing 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

[0133] .

[0134] ​​​​Furthermore, the peak concentration of typical elements is located at a depth of 3 nm, radiating from the surface towards the center of the positive electrode active material 100. It is preferable that it exists up to a depth of 1 nm, more preferably to a depth of 0 It is even more preferable that it be present up to 0.5 nm.

[0135] Furthermore, the depth at which the concentration of typical elements becomes 1 / 5 of the peak varies depending on the preparation method, as will be discussed later. In the case of the fabrication method, the distance from the surface of the positive electrode active material is generally about 2 nm to 5 nm.

[0136] Regarding the third region 103 located inside the first region 101, such as near grain boundaries or crystal defects: However, if the concentration of typical elements detected by depth profiling is 1 / 5 or more of the peak in that region, Let's do that.

[0137] It is preferable that the distribution of fluorine in the positive electrode active material 100 overlaps with the distribution of the above-mentioned main group elements. Therefore, fluorine also has a concentration gradient, and the peak of fluorine concentration is in the table of positive electrode active material 100. Preferably, it exists up to a depth of 3 nm from the surface toward the center, and preferably up to a depth of 1 nm. It is more preferable that it be present up to a depth of 0.5 nm.

[0138] Furthermore, in this specification, the second region 102 present on the surface of the positive electrode active material 100 is deep This refers to the region where the concentration of the second transition metal detected by directional analysis is 1 / 2 or more of the peak. This shall be the case. The second region is located inside the first region 101, such as near grain boundaries or near crystal defects. For 102 as well, the concentration of the second transition metal detected by depth profiling is half of the peak. The above refers to the region. The analytical methods used are the EDX line analysis and T2. Depth analysis using oF-SIMS can be utilized.

[0139] Therefore, the third region 103 and the second region 102 may overlap. However, the third region Region 103 is located closer to the surface of the positive electrode active material particles than the second region 102. This is preferable. Also, the peak concentration of the main group element is higher than the peak concentration of the second transition metal at the positive electrode. It is preferable that the active material particles are located in a region close to the surface.

[0140] The second transition metal peak is located at a depth of 0.2 nm, extending from the surface to the center of the positive electrode active material 100. Preferably, they exist at a depth of 10 nm or less, and at a depth of 0.5 nm to 3 nm. It is preferable to do so.

[0141] Furthermore, XPS has a measurement range of approximately 5 nm from the surface of the positive electrode active material 100 particles. Therefore, it is possible to quantitatively analyze the elemental concentration present at about 5 nm from the surface. The elemental concentrations of the third region 103 and the second region 102, which are located at approximately 5 nm, were quantitatively determined. It can be analyzed.

[0142] When the surface of the positive electrode active material 100 was analyzed using XPS, the concentration of the first transition metal was set to 1. The relative concentration of the second transition metal is preferably 0.05 or more and 0.4 or less, and preferably 0.1 or more. A value of 3 or less is more preferable. Furthermore, the relative concentration of the main group elements is preferably between 0.4 and 1.5. A value of 0.45 to 1.00 is more preferable. Furthermore, the relative value of the fluorine concentration should be 0.05 to 1. A value of 0.5 or less is preferred, and a value of 0.3 or more and 1.00 or less is more preferred.

[0143] As mentioned above, the first region 101, the second region 102, and the third region 103 have Since elements may have concentration gradients, the first region 101 is a second region such as fluorine. Region 102 and the third region 103 may have elements. Similarly, the third region 1 03 may contain elements present in the first region 101 and the second region 102. The first region 101, the second region 102, and the third region 103 are carbon, sulfur, and silicon. It may also contain other elements such as sodium, calcium, chlorine, and zirconium.

[0144] [Particle size] The particle size of the positive electrode active material 100 is important; if it is too large, lithium diffusion becomes difficult, and if it is too small, the particle size is also important. It becomes difficult to maintain the described crystal structure. Therefore, D50 (also called the median diameter) ) is preferably 5 μm to 100 μm, and preferably 10 μm to 70 μm. It is preferable. Furthermore, in a later process, a coating is formed on the surface of the positive electrode active material 100 using a spray-drying device. In this case, it is preferable that the nozzle diameter and the maximum particle size of the positive electrode active material 100 are approximately the same. i. When the particle size is less than 5 μm, if a spray drying device with a nozzle diameter of 20 μm is used, The secondary particles become clustered together and cover the surface, resulting in reduced coverage.

[0145] Furthermore, in order to increase the density of the positive electrode active material layer, large particles (with the longest part being approximately 20 μm or less) are required. Mixing large particles (approximately 40 μm or less) with small particles (the longest part is approximately 1 μm), Filling the gaps with small particles is also effective. Therefore, there are two or more peaks in the particle size distribution. That's fine.

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

[0147] If the particle size of the starting material is small, in order to bring the particle size of the positive electrode active material into the above preferred range, firing It is necessary to allow the grains to grow during this process.

[0148] To promote grain growth during firing, the ratio of Li to the first transition metal in the starting material should be greater than 1. In other words, it is effective to have a slight excess of lithium. For example, Li and the first transition gold If the genus ratio is set to approximately 1.06, it is easier to obtain a positive electrode active material with a D50 of 15 μm or more. As will be discussed later, lithium may be lost from the system during the process of manufacturing the positive electrode active material. The ratio of lithium to the first transition metal in the resulting positive electrode active material is the ratio of lithium to the first transition metal in the starting material. This may not match the ratio of transition metals.

[0149] However, if the amount of lithium becomes excessive in order to bring the particle size within a desirable range, the secondary battery When used in this manner, there is a risk that the capacity retention rate will decrease.

[0150] However, the present inventors have provided a second region 102 having a second transition metal in the surface layer. By controlling the ratio of Li to the first transition metal, the particle size can be kept within a desirable range. We demonstrated that it is possible to produce a cathode active material with a high capacity retention rate.

[0151] In the case of a positive electrode active material according to one embodiment of the present invention, which provides a region having a second transition metal in its surface layer, The ratio of the raw material Li to the first transition metal is preferably 1.00 or more and 1.07 or less. A value between 0.03 and 1.06 is more preferable.

[0152] [Formation of the second region] The second region 102 consists of particles of a composite oxide having lithium and a first transition metal, and the second transition It can be formed by coating it with a material that has a transferable metal.

[0153] Methods for coating a material containing a second transition metal include liquid phase methods such as the sol-gel method. Solid-phase method, sputtering method, vapor deposition method, CVD (chemical vapor deposition), PLD (pulsed laser) method Methods such as the deposition method can be applied. In this embodiment, a uniform coating is achieved. We will now explain the case where the sol-gel method, which is promising and can be processed at atmospheric pressure, is applied.

[0154] <Sol-gel method> Figure 4 illustrates a method for coating a material containing a second transition metal using the sol-gel method. I will explain.

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

[0156] Figure 4(A-1) shows the general formula for the alkoxide of the second transition metal. Equation in Figure 4(A-1) The M2 in the expression indicates an alkoxide of the second transition metal. R is an alkyl group with 1 to 18 carbon atoms. This represents an aryl group, or a substituted or unsubstituted group with 6 to 13 carbon atoms. Also, Figure 4(A -1) showed the general formula when the second transition metal is tetravalent, but one aspect of the present invention is not limited thereto. The second transition metal may be divalent, trivalent, pentavalent, hexavalent, or heptavalent. In addition, the alkoxide of the second transition metal has an alkoxy group corresponding to the valence of the second transition metal. ru.

[0157] Figure 4(A-2) shows the titanium alcohol used when titanium is applied as the second transition metal. The general formula for hydroxide is shown. In Figure 4(A-2), R is an alkyl group having 1 to 18 carbon atoms, or This represents a substituted or unsubstituted aryl group with 6 to 13 carbon atoms.

[0158] For example, as titanium alkoxides, tetramethoxytitanium, tetraethoxytitanium, Tra-n-propoxytitanium, tetra-i-propoxytitanium (tetra-i orthotitanium) Sopropyl, Titanium(IV) Isopropoxide, Titanium tetraisop rop oxide(IV), sometimes written as TTIP, etc., tetra-n-butoxy Titanium, tetra-i-butoxytitanium, tetra-sec-butoxytitanium, tetra-t- Butoxytitanium and the like can be used.

[0159] Figure 4(A-3) shows titanium, a type of titanium alkoxide, which will be described later in the manufacturing method. (IV) The chemical formula for isopropoxide (TTIP) is shown.

[0160] Alcohols are preferred as solvents for dissolving the alkoxide of the second transition metal, for example methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol You can use things like slack.

[0161] Next, lithium, transition metal, and magnesium are added to an alcoholic solution of the second transition metal alkoxide. Particles of a composite oxide containing um and fluorine are mixed and stirred in an atmosphere containing water vapor. .

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

[0163] Subsequently, particle 110 is collected and the alcohol is vaporized. Details of the preparation method will be described later. do.

[0164] In this embodiment, a composite comprising lithium, a first transition metal, a main group element, and fluorine is used. An example of coating the positive electrode current collector with a material containing a second transition metal before coating it with oxide particles. The present invention will be explained below, but is not limited to this aspect. On the positive electrode current collector, lithium, first A positive electrode active material layer is formed containing particles of a composite oxide having transition metals, main elements, and fluorine. Then, the positive electrode current collector and the positive electrode active material layer are both immersed in a second transition metal alkoxide solution. A material having a second transition metal may be used as a coating.

[0165] [Segregation of the third domain] The third area 103 includes liquid phase methods such as sputtering, solid phase, and sol-gel methods, etc. It can also be formed by the method described above. However, the inventors of this invention use a typical element source such as magnesium and When the fluorine source is mixed with the material in the first region 101 and then heated, the typical elements are converted into positive electrode active material particles. It was revealed that it segregates in the surface layer of the child and forms a third region 103. Having a third region 103 formed in this way, the positive electrode active material 100 has excellent cycle characteristics. It became clear that this would happen.

[0166] When the third region 103 is formed by heating as described above, the heating affects the particles of the composite oxide. It is preferable to perform this after coating with a material containing a second transition metal. Surprisingly, the second transition metal Even after coating with a material containing these elements, heating causes typical elements such as magnesium to shift to the surface of the particles. This is for the purpose of analysis.

[0167] Figures 5 and 6 illustrate this segregation model of typical elements, such as magnesium. The segregation model of typical elements is determined by the ratio of lithium to the first transition metal in the starting material. It is suspected that they are slightly different. Therefore, the ratio of the starting material Li to the first transition metal is 1.03. The segregation model when lithium is low, i.e., full, is explained using Figure 5. Then, the starting point Segregation model when the ratio of Li to the first transition metal is 1.03 or higher, i.e., lithium is abundant. This will be explained using Figure 6. Furthermore, these segregation models, and the first transition in Figures 5 and 6, Let's take the example where the metal is cobalt, the second transition metal is titanium, and the main element is magnesium. That's how I explain it.

[0168] Figure 5(A) shows lithium and cobalt produced with a starting material Li-to-Co ratio of less than 1.03. In a model diagram of the vicinity of the surface of particles 110 of a composite oxide having magnesium and fluorine. There is. Region 111 in the figure contains lithium, cobalt, magnesium, and fluorine. This region is characterized by lithium cobalt oxide (LiCoO2) as its main component. Um has a layered rock salt-type crystalline structure.

[0169] Generally, particles of a composite oxide containing lithium, cobalt, magnesium, and fluorine It is known that during synthesis, some lithium escapes from the system (outside the resulting particles). The causes include lithium volatilization during firing and lithium dissolving when mixing the starting materials. This includes leaching into the medium, etc. Therefore, compared to the Li-Co ratio of the starting materials, lithium and cobalt The ratio of Li to Co in the composite oxide particles 110 having magnesium and fluorine is It may become smaller.

[0170] If the Li-Co ratio of the starting materials is less than 1.03, cobalt oxide is present on the surface of particle 110. Lithium readily detaches from thium to form cobalt oxide. Therefore, as shown in Figure 5(A)... The surface of the composite oxide particles 110 of the sea urchin is made of cobalt oxide (CoO X (X>0)) layer 114 It may be covered.

[0171] Cobalt oxide has a rock salt-type crystalline structure. Therefore, in particle 110 in Figure 5(A), layers On a region 111 having lithium cobalt oxide having a rock salt-type crystal structure, A cobalt oxide layer 114 having a crystalline structure may be in contact with it.

[0172] A titanium-containing material is coated onto these particles 110 by a sol-gel method or the like. Figure 5(B ) shows a state in which a titanium layer 112 is coated on particle 110 by the sol-gel method. At the stage shown in Figure 5(B), the layer 112 containing titanium is a titanium oxide gel, It has low crystallinity.

[0173] Next, the particles 110, after being coated with the titanium layer 112, are heated. Details of the heating conditions are as follows: As will be described later, for example, heating at 800°C for 2 hours in an oxygen atmosphere, the first of the present invention Figure 5(C) shows the state in which the positive electrode active material 100, which is the embodiment, has been prepared. By heating, titanium The titanium in layer 112 diffuses toward the interior of particle 110. At the same time, region 11 The magnesium and fluorine contained in 1 segregate onto the surface of particle 110.

[0174] As mentioned above, rock salt-type cobalt oxide is present on the surface of particle 110. Also, magnesium oxide Um also has a rock salt-type crystalline structure. Therefore, magnesium is located inside particle 110. Furthermore, it is presumed that it is more stable to exist as magnesium oxide on the surface of particle 110. This is thought to be the reason why magnesium segregates onto the surface of particle 110 when heated. ru.

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

[0176] Fluorine has a higher electronegativity than oxygen. Therefore, stable compounds like magnesium oxide... In materials, adding fluorine causes an imbalance in charge, affecting magnesium and oxygen. It is presumed that this weakens the bond. Therefore, oxygen in magnesium oxide is replaced by fluorine. This is presumed to make it easier for magnesium to migrate around the substituted fluorine. ru.

[0177] This can also be explained by the phenomenon of the melting point of the mixture decreasing. Magnesium oxide (melting point 285°C) When magnesium oxide (°C) and lithium fluoride (melting point 848°C) are added simultaneously, the melting point of magnesium oxide decreases. This lowers the melting point, making it easier for magnesium to move when heated, and thus the magnesium melts. It is also thought that this may make um segregation more likely to occur.

[0178] Finally, the third region 103 has a rock salt-type crystalline structure, containing cobalt oxide and magnesium oxide. It forms a solid solution of um. Also, some of the oxygen contained in cobalt oxide and magnesium oxide is fluorine. It is thought to be replaced by

[0179] The diffused titanium partially replaces the cobalt site of lithium cobalt oxide, and partially replaces titanium It becomes lithium oxide. The second region 102 after heating has a rock salt-type crystalline structure of lithium titanate. It contains lithium.

[0180] The first region 101 after heating contains lithium cobalt oxide having a layered rock salt-type crystalline structure. ru.

[0181] Next, we will explain the case where the Li-Co ratio of the starting materials is 1.03 or higher, using Figure 6. 6(A) is lithium, cobalt, produced with a starting material Li-to-Co ratio of 1.03 or higher. This is a model diagram of the vicinity of the surface of particles 120 of a composite oxide having magnesium and fluorine. Region 121 in the figure contains lithium, cobalt, magnesium, and fluorine. It is a domain.

[0182] Particle 120 in Figure 6(A) contains sufficient lithium, therefore lithium, cobalt, magnesium When firing the composite oxide particles 120 containing um and fluorine, lithium is released into the particles 12 Even if lithium detaches from particle 0, it is replenished by diffusing from inside particle 120 to the surface, so the surface The cobalt oxide layer is less likely to form.

[0183] Figure 6(B) shows a layer 122 containing titanium added to the particle 120 of Figure 6(A) by the sol-gel method. This shows the coated state. At the stage shown in Figure 6(B), the titanium-containing layer 122 is titanium acid Because it is a monoxide gel, its crystallinity is low.

[0184] Figure 6(C) shows the particles 120 after being coated with the titanium layer 122 shown in Figure 6(B), and then heated. This shows the state in which heating has begun. Due to heating, the titanium in the titanium-containing layer 122 becomes particles 1 It diffuses inward towards region 10. The diffused titanium bonds with the lithium contained in region 121. They combine to form lithium titanate, and a layer 125 containing lithium titanate is formed.

[0185] Lithium combines with titanium to form lithium titanate, so on the surface of particle 120, There is a relative deficiency of um. Therefore, as shown in Figure 6(C), oxidation occurs on the surface of particle 120. It is presumed that a cobalt layer 124 is temporarily formed.

[0186] Figure 6(D) shows that the positive electrode active material 1 of the present invention has been sufficiently heated, as seen from Figure 6(C). This shows the state where it is 00. The cobalt oxide layer 124, which has a rock salt-type crystalline structure, is on the surface. By being present, magnesium oxide forms on the surface of particle 120 rather than inside particle 120. It is thought that it is more stable to exist as magnesium. Also, as in the case of Figure 5, fluorine Its presence promotes magnesium segregation.

[0187] Therefore, as shown in Figure 6(D), the magnesium and fluorine contained in region 121 are on the surface It segregates and, together with cobalt oxide, forms a third region, 103.

[0188] In this way, a third region 103 having magnesium oxide and cobalt oxide, titanic acid A second region 102 having lithium, and a first region 10 having lithium cobaltate A positive electrode active material 100 having 1 is produced.

[0189] Furthermore, when typical elements are segregated by heating, lithium and the first region 101 When a complex oxide containing a transition metal is polycrystalline or has crystal defects, only the surface layer is affected. Furthermore, typical elements are not found near grain boundaries or crystal defects in composite oxides containing lithium and the first transition metal. Elements can segregate. Typical elements that segregate near grain boundaries or crystal defects have a first region 10¹. This contributes to further stabilization of the crystal structure of composite oxides containing lithium and a first transition metal. ru.

[0190] Furthermore, the composite oxide containing lithium and the first transition metal in the first region 101 is in the crack area When this is present, heating can cause segregation of main group elements into the crack area. Furthermore, not only main group elements but also Furthermore, a second transition metal may also segregate. The cracked area is the region in contact with the electrolyte, similar to the particle surface. Therefore, typical elements and the second transition metal segregate in the crack area, forming the third region 1. The formation of region 03 and the second region 102 makes the region in contact with the electrolyte chemically stable. It can be made into a material. Therefore, it can be made into a secondary battery with excellent cycle characteristics. ru.

[0191] The ratio of typical elements (T) to fluorine (F) in the starting materials is T:F = 1:x (1.5 ≤ x ≤ 4) (original Within the range of the number of elements ratio, segregation of main group elements occurs effectively, which is preferable. Also, T:F = A ratio of approximately 1:2 (atomic ratio) is even more preferable.

[0192] The third region 103, formed by segregation, was formed by epitaxial growth. Therefore, the crystal orientations of the second region 102 and the third region 103 are partially identical. Therefore, the second region 102 and the third region 103 can become topotaxi. If the crystal orientations of region 102 and the third region 103 are roughly the same, these are better. It can function as a coating layer.

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

[0194] <The fourth domain 104> Furthermore, as shown in Figure 1(C), the positive electrode active material 100 is located on the third region 103 and the fourth region 1 It may also have 04. Furthermore, the positive electrode active material 100 may have defects such as cracks 106. Even if a fourth region 104 exists to fill defects such as the crack portion 106, stomach.

[0195] The fourth region 104 contains some of the elements present in the second region 102 and the third region 103. For example, the fourth region 104 contains a second transition metal and a main group element.

[0196] The fourth region 104 may be convex, strip-shaped, or layered. Good. The fourth region 104 is among the second transition metals and main group elements contained in the starting material, etc. , second transition metals and typical types not included in the second region 102 and the third region 103 It is formed from elements. In other words, the existence of the fourth region 104 means that the second region 102 and And the second transition metal and main group elements in the third region 103 are kept in appropriate amounts, and the second region In some cases, the crystal structure of region 102 and the third region 103 can be stabilized. Furthermore, the presence of the fourth region 104 causes defects such as cracks 106 in the positive electrode active material 100. It may be possible to repair the damage.

[0197] The existence of a fourth region 104, and the shape of the fourth region 104, are determined by SEM (Scanning Electron Microscope). It can be observed with a microscope, etc. Furthermore, the elements in the fourth region 104 are SEM- It can be analyzed using EDX, etc.

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

[0199] <Step 11: Preparation of starting materials> First, the starting materials are prepared. From the materials prepared in this process, the final product will be the first region 10 Regions 1 and 3, 103 are formed.

[0200] The first region 101 contains lithium and the first transition metal as raw materials, a lithium source and the first Prepare a transition metal source. Also, as a raw material for compounds of main group elements that are present in the third region 103 Prepare a source of typical elements.

[0201] In addition to these, it is preferable to provide a fluorine source. Fluorine, when added to the raw materials, In a later step, the typical elements present in the third region 103 segregate onto the surface of the positive electrode active material 100. It has the effect of promoting [something].

[0202] For example, lithium carbonate and lithium fluoride can be used as lithium sources. For example, an oxide of the first transition metal can be used as the transition metal source. Main group elements Sources include, for example, oxides of typical elements found in the third region, and typical elements found in the third region. Fluorides and the like can be used.

[0203] As a fluorine source, for example, lithium fluoride, fluorides of typical elements in the third region, etc. It can be used. In other words, lithium fluoride can be used as both a lithium source and a fluorine source. It is possible to be there.

[0204] The amount of fluorine in the fluorine source is between 1.0 and 4 times the amount of typical elements in the typical element source. It is preferable that the ratio is (atomic ratio), and that it is between 1.5 and 3 times (atomic ratio). It is preferable.

[0205] <Step 12: Mixing the starting materials> Next, the lithium source, the first transition metal source, and the main group element source are mixed. Then, the fluorine source is added. Preferably, a ball mill or a bead mill can be used for mixing.

[0206] <Step 13: First heating> Next, the mixture from step 12 is heated. This step is called baking, or first heating. In some cases, heating is preferably carried out at 800°C to 1100°C, and 900°C. It is more preferable to perform the process at a temperature of 1000°C or lower. The heating time should be between 2 hours and 20 hours. It is preferable to do so. Firing is preferably carried out in a dry atmosphere such as dry air. A dry atmosphere is preferable, for example, one with a dew point of -50°C or lower, and an atmosphere with a dew point of -100°C or lower. Even more preferable. In this embodiment, heating is performed at 1000°C for 10 hours, and the temperature rise is 200 Dry air with a temperature of °C / h and a dew point of -109°C will be flowed at a rate of 10 L / min. Then, heating will be performed. Cool the materials to room temperature.

[0207] Heating in step 13 brings lithium and the first transition metal having a layered rock salt-type crystalline structure. A complex oxide can be synthesized. At this point, the main group elements contained in the starting material and the f Electron is dissolved in the complex oxide. However, some of the main group elements are already in the complex oxide. They may also be concentrated on the surface.

[0208] Furthermore, lithium, cobalt, fluorine, and magnesium were pre-synthesized as starting materials. Particles of a composite oxide containing the may be used. In this case, steps 12 and 13 are This can be omitted. For example, lithium cobalt oxide particles manufactured by Nippon Chemical Industrial Co., Ltd. (Product name: C-20F) can be used as one of the starting materials. This has a particle size of approximately 20 The region is μm in size, and fluorine, magnesium, calcium, and na are present in the area that can be analyzed from the surface by XPS. These are lithium cobalt oxide particles containing thorium, silicon, sulfur, and phosphorus.

[0209] <Step 14: Coat with a second transition metal> Next, the lithium-first transition metal composite oxide is cooled to room temperature. Then lithium and the first The surface of a composite oxide particle of a transition metal (1) is coated with a material containing a second transition metal. In the example manufacturing method, the sol-gel method will be applied.

[0210] First, the alkoxide of the second transition metal dissolved in alcohol, and lithium and the first transition metal Mix the composite oxide particles of the genus with [another substance].

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

[0212] Next, the above mixture is stirred in an atmosphere containing water vapor. Stirring is done, for example, by magnetics. This can be done with a thaler. The stirring time is necessary for the water and TTIP in the atmosphere to hydrolyze and hemolybdenum. Any time sufficient for the condensation reaction to occur is acceptable, for example, 4 hours at 25°C and 90% RH. This can be done under relative humidity conditions.

[0213] As described above, by reacting TTIP with water in the atmosphere, it is possible to achieve a better result than when adding liquid water. This also allows the sol-gel reaction to proceed slowly. Furthermore, titanium alkoxide and water can be reacted at room temperature. By reacting, for example, heating at a temperature exceeding the boiling point of the solvent alcohol is possible. This allows the sol-gel reaction to proceed slowly. This allows for the formation of a coating layer containing high-quality titanium with a uniform thickness.

[0214] After the above processing is complete, the precipitate is recovered from the mixture. Recovery methods include filtration and centrifugation. Evaporation to dryness or the like can be applied. In this embodiment, recovery will be carried out by filtration. A paper filter was used for filtration, and the residue was filtered using the same solvent as the titanium alkoxide solution. We will clean it using a call system.

[0215] Next, the recovered residue is dried. In this embodiment, it is vacuum dried at 70°C for 1 hour. Let's assume that.

[0216] <Step 15: Second heating> Next, the composite oxide coated with the material having the second transition metal, which was prepared in step 14, Heat the particles. This step may be referred to as the second heating step. The heating time is until the specified temperature is reached. The holding time within the range is preferably 50 hours or less, and is preferably 2 hours or more and 10 hours or less. It is more preferable to do so, and even more preferable to do so for 1 hour or more but 3 hours or less. If the interval is too short, segregation of main group elements may not occur, but if it is too long, the expansion of the second transition metal may occur. There is a risk that the dispersion will progress too far, preventing the formation of a healthy second region 102.

[0217] The specified temperature is preferably between 500°C and 1200°C, and between 800°C and 1000°C. This is more preferable. If the specified temperature is too low, segregation of main group elements and secondary transition metals will not occur. There is a risk of this happening. However, if the level is too high, the first transition metal in the composite oxide particles will be reduced, and the composite acid The layered structure of lithium and the first transition metal in the composite oxide particles, which causes the oxide particles to decompose. There is a risk that it may not be able to be maintained.

[0218] In this embodiment, the specified temperature is set to 800°C and maintained for 2 hours, with the heating rate increasing by 200°C. The dry air flow rate is set to 10 L / min per hour.

[0219] The heating in step 15 generates a composite oxide of lithium and the first transition metal, and a coating thereon. The oxide of the second transition metal that is obtained becomes topotaxis. In other words, the first region 101 and the second region Region 102 becomes topotaxy.

[0220] Furthermore, the heating in step 15 causes the lithium and first transition metal composite oxide particles to form inside the interior. The main group elements that were in solid solution become unevenly distributed on the surface, resulting in solid solution, or segregation, and form compounds of the main group elements. A third region 103 is formed. At this time, compounds of main group elements move from the second region 102 to the left. It grows loepitaxially. That is, the second region 102 and the third region 103 are topotaxy. Yes.

[0221] The crystal orientations of the second region 102 and the third region 103 are roughly coincided, and the first region 101 Because it has a stable bond, when the positive electrode active material 100 is used in a secondary battery, charging and discharging The resulting change in the crystal structure of the first region 101 can be effectively suppressed. Furthermore, the charging process can also be used to control the second region. Even if lithium is removed from region 101, the surface layer, which has stable bonds, This suppresses the departure of the first transition metal, such as cobalt, and oxygen from the first region 101. This can be achieved. Furthermore, the area in contact with the electrolyte can be made of a chemically stable material. Therefore, it can be used to create a secondary battery with excellent cycle characteristics.

[0222] Furthermore, the first region 101 and the second region 102 only need to be partially topotaxis, and the first region It is not necessary for all of region 101 and the second region 102 to be topotaxi. Also, the second region Regions 102 and the third region 103 only need to be partially topotaxy, and the second region 102 and the third region Not all of region 103 needs to be topotaxis.

[0223] Furthermore, if the compound of a main group element in the third region contains oxygen, an oxygen-containing atmosphere is used. It is preferable to perform the heating in step 15 in an oxygen-containing atmosphere. The formation of region 103 is promoted.

[0224] Furthermore, the fluorine contained in the starting materials promotes the segregation of main group elements.

[0225] Thus, in a method for producing a positive electrode active material according to one aspect of the present invention, a second region 102 is formed. After coating with the element, heating is performed to form a third region 103, and the positive electrode active material 100 It becomes possible to form two types of regions on the surface. In other words, normally, two types of regions on the surface In order to create the region, two coating processes are required, but in one aspect of the present invention, positive electrode active material The preparation method requires only one coating step (sol-gel step), making it a highly productive method. That is the case.

[0226] <Step 16: Cooling> Next, the particles heated in step 15 are cooled to room temperature. If the cooling time is long, the topography will be It is preferable as it is easy to induce taxi. For example, the time required to cool from the holding temperature to room temperature is the same as the time required to cool down. It is preferable to use a period of time equal to or longer than that, specifically between 10 and 50 hours.

[0227] <Step 17: Recovery> Next, the cooled particles are collected. Furthermore, it is preferable to sift the particles. In the process, a positive electrode activity having a first region 101, a second region 102, and a third region 103 It is possible to produce substance 100.

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

[0229] (Embodiment 2) In this embodiment, it is used in a secondary battery having the positive electrode active material 100 described in the previous embodiment. Examples of materials that can be used will be described. In this embodiment, the positive electrode, negative electrode and electrolyte However, let's take a secondary battery, which is enclosed in an outer casing, as an example to explain.

[0230] [Positive electrode] The positive electrode comprises 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 positive electrode active material. Furthermore, the positive electrode active material layer contains 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] As the positive electrode active material, the positive electrode active material 100 described in the previous embodiment can be used. By using the positive electrode active material 100 described in the previous embodiment, high capacity and cycle characteristics can be achieved. It can be used to create an excellent rechargeable battery.

[0233] As conductive additives, carbon materials, metal materials, or conductive ceramic materials can be used. Yes, it is possible. Additionally, fibrous materials may be used as conductive additives. The conductivity relative to the total amount of the active material layer... The content of the electrolytic agent is preferably 1 wt% to 10 wt%, and preferably 1 wt% to 5 wt%. This is preferable.

[0234] Conductive additives can be used to form an electrical conduction network within the active material layer. The agent can maintain the electrical conduction pathway between the positive electrode active materials. By adding an electro-enhancing agent, it is possible to create an active material layer with high electrical conductivity. .

[0235] Examples of conductive additives include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon fibers. Fibers can be used. For example, mesophase pitch carbon fibers can be used. Carbon fibers such as isotropic pitch carbon fibers can be used. Carbon nanofibers and carbon nanotubes can be used. The tubes can be fabricated, for example, by vapor phase growth. Also, as a conductive additive, for example... Examples include carbon black (acetylene black (AB), etc.) and graphite particles. Carbon materials such as graphene and fullerene can be used. Also, for example, copper, nickel Metal powders such as oxal, aluminum, silver, and gold, as well as metal fibers and conductive ceramic materials. It can be used.

[0236] Furthermore, graphene compounds may be used as conductive additives.

[0237] Graphene compounds possess excellent electrical properties, including high conductivity, as well as high flexibility and high It possesses excellent physical properties, such as high mechanical strength, and may also have other properties. The compound has a planar shape. Graphene compounds enable surface contact with low contact resistance. Furthermore, even thin materials can have very high conductivity, allowing for efficient conduction within the active material layer with only a small amount. An electric current can be formed. Therefore, graphene compounds can be used as conductive additives. This is preferable because it increases the contact area between the active material and the conductive additive. By using a laser dryer, the entire surface of the active material is covered and converted into graphene, which is a conductive additive. It is preferable to form the composite as a coating. Furthermore, it may be possible to reduce electrical resistance. Therefore, it is preferable. Here, as the graphene compound, for example, graphene or multigraphe It is particularly preferable to use graphene or RGO. Here, RGO is, for example, graphene oxide. This refers to the compound obtained by reducing graphene oxide (GO).

[0238] When using active materials with small particle sizes, for example, active materials with a particle size of 1 μm or less, the specific surface area of ​​the active material is Larger materials require more conductive paths to connect the active materials. Therefore, a larger amount of conductive additive is needed. This tends to happen, and relatively, the amount of active material carried decreases. When this decreases, the capacity of the secondary battery decreases. In such cases, a conductive additive is used. When graphene compounds are used, even small amounts of graphene compounds efficiently form conductive paths. This is particularly preferable because it does not require reducing the amount of active material supported.

[0239] In the following example, a graphene compound is used as a conductive additive in the active material layer 200. An example of the cross-sectional configuration will be explained.

[0240] Figure 7(A) shows a longitudinal cross-sectional view of the active material layer 200. The active material layer 200 consists of granular positive electrode active material. It contains 100, a graphene compound 201 as a conductive additive, and a binder (not shown). Hmm. Here, as graphene compound 201, for example, graphene or multigraphene It is fine to use it. Here, it is preferable that the graphene compound 201 has a sheet-like shape. Furthermore, graphene compound 201 is a multigraphene, or (and) multiple graphenes. The graphene may be partially overlapping and form a sheet.

[0241] In the longitudinal section of the active material layer 200, as shown in Figure 7(B), the interior of the active material layer 200 In Figure 7(B), the graphene compound 201 is dispersed in a generally uniform sheet-like manner. Graphene compound 201 is schematically represented by a thick line, but in reality it is a single or multiple layer of carbon molecules. It is a thin film with a layer thickness. Multiple graphene compounds 201 are multiple granular cathode active materials The material 100 is partially covered, or adheres to the surface of multiple granular positive electrode active materials 100. Because they are formed in such a way, they are in surface contact with each other.

[0242] Here, multiple graphene compounds bond together to form a network of graphene compounds. Forming a sheet (hereinafter referred to as graphene compound net or graphene net) Yes, it is possible. When the active material is covered with a graphene net, the graphene net connects the active materials to each other. It can also function as a binder. Therefore, it reduces the amount of binder needed. Because it is possible to do so or not to use it, the ratio of active material to electrode volume or electrode weight The efficiency can be improved. In other words, the capacity of the secondary battery can be increased.

[0243] Here, graphene oxide is used as graphene compound 201 and mixed with the active material to form the active material It is preferable to reduce the layer after forming the layer that will become layer 200. By using graphene oxide, which has extremely high dispersibility in polar solvents, graphene formation can be achieved. The compound 201 can be dispersed approximately uniformly within the active material layer 200. The solvent is volatilized and removed from the dispersion medium containing dispersed graphene oxide, and the graphene oxide is reduced. Therefore, the graphene compound 201 remaining in the active material layer 200 partially overlaps, and By being dispersed to the extent that they are in surface contact, a three-dimensional conductive path can be formed. The reduction of graphene oxide may be carried out, for example, by heat treatment or by using a reducing agent. That's fine.

[0244] Therefore, unlike granular conductive additives such as acetylene black that make point contact with the active material, graph Compound 201 enables surface contact with low contact resistance, unlike conventional conductive additives. It improves the electrical conductivity between the granular positive electrode active material 100 and the graphene compound 201 using only a small amount. Therefore, the ratio of granular positive electrode active material 100 in the active material layer 200 can be increased. This can be done. This allows for an increase in the discharge capacity of the secondary battery.

[0245] Furthermore, the entire surface of the active material is previously covered with a graphene compound using a spray-drying device. Alternatively, when fabricating the positive electrode active material layer, a graphene compound may be added to further enhance the active material. This can also improve the conductive paths between components.

[0246] Examples of binders include styrene-butadiene rubber (SBR) and styrene-isoprene rubber. N-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene- It is preferable to use a rubber material such as a propylene-diene copolymer. Fluororubber can be used.

[0247] Furthermore, it is preferable to use a water-soluble polymer as the binder. For example, polysaccharides can be used as the derivative. Cellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose Cellulose derivatives such as lurose, diacetylcellulose, and regenerated cellulose, as well as starch, etc. These can be used. Furthermore, these water-soluble polymers can be used in combination with the aforementioned rubber materials. It would be even better if they were there.

[0248] Alternatively, as a binder, polystyrene, polymethyl acrylate, polymethyl methacrylate can be used. Chill (polymethyl methacrylate (PMMA)), sodium polyacrylate, polyvinyl Polyalcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, Polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene Polyethylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), ethylene propylene diene polymer It is preferable to use materials such as polyvinyl acetate and nitrocellulose.

[0249] You may use a combination of several of the binders mentioned above.

[0250] For example, a material with particularly excellent viscosity-modifying properties may be used in combination with other materials. For example, rubber materials have excellent adhesive and elastic properties, but their viscosity is difficult to adjust when mixed with a solvent. In such cases, for example, mixing with a material that has particularly excellent viscosity-modifying effects may be used. This is preferable. As a material with particularly excellent viscosity adjustment effect, for example, a water-soluble polymer can be used. Furthermore, water-soluble polymers that are particularly excellent in viscosity adjustment include the aforementioned polysaccharides, for example, calcium carbonate. Voxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxy Cellulose derivatives such as propylcellulose, diacetylcellulose, and regenerated cellulose. Body or starch can be used.

[0251] Furthermore, cellulose derivatives such as carboxymethylcellulose are, for example, carboxymethyl By using salts such as sodium salts or ammonium salts of cellulose, the solubility increases. It becomes easier to exert its effect as a viscosity modifier. The increased solubility makes the electrode slurry - When manufacturing, it is also possible to improve the dispersibility with the active material and other components. As for cellulose and cellulose derivatives used as electrode binders, This shall also include salt.

[0252] Water-soluble polymers stabilize viscosity by dissolving in water, and also function as active materials and binders. Other materials to be combined with it, such as styrene-butadiene rubber, are stably separated in an aqueous solution. It can be dispersed. Furthermore, because it has functional groups, it is easily and stably adsorbed onto the surface of the active material. This is expected. Also, cellulose derivatives such as carboxymethylcellulose, For example, many materials have functional groups such as hydroxyl groups and carboxyl groups, and because they have functional groups It is expected that the polymers will interact with each other and exist to broadly 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 considered a passivation film. It is also expected to play a role in suppressing the decomposition of the electrolyte. Here, the passive film is an electrolytic film. This is a non-conductive film, or a film with extremely low electrical conductivity, for example, on the surface of an active material. When a dynamic film is formed, the decomposition of the electrolyte can be suppressed at the battery reaction potential. It can. Furthermore, the passivation film suppresses electrical conductivity, while lithium ions can conduct electricity. And even better.

[0254] <Positive electrode current collector> As the positive electrode current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and this Highly conductive materials such as alloys can be used. Also, materials used for the positive electrode current collector It is preferable that the material does not dissolve at the positive electrode potential. Also, silicon, titanium, neodymium, sucrose Aluminum alloys with added elements that improve heat resistance, such as valdium and molybdenum, are used. It can be formed by metal elements that react with silicon to form silicides. This is also good. Examples of metallic elements that react with silicon to form silicides include zirconium and thi. Tan, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten These include cobalt, nickel, etc. Current collectors come in foil, plate (sheet), mesh, and perforated forms. Shapes such as metallic or expanded metal can be used as appropriate. The thickness of the current collector is It is best to use particles between 5 μm and 30 μm in size.

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

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

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

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

[0259] Carbon-based materials include graphite, easily graphitizable carbon (soft carbon), and poorly graphitizable carbon (hard carbon). Carbon, carbon nanotubes, graphene, carbon black, etc. can be used. .

[0260] Examples of graphite include synthetic graphite and natural graphite. An example of synthetic graphite is Mesoca. Examples include carbon microbeads (MCMB), coke-based synthetic graphite, and pitch-based synthetic graphite. Here, spheroidal graphite, which has a spherical shape, can be used as artificial graphite. Furthermore, MCMB may have a spherical shape, which is preferable. Also, the surface area of ​​MCMB Reducing the size is relatively easy and sometimes preferable. Examples of natural graphite include, Examples include flaky graphite and spheroidized natural graphite.

[0261] Graphite is formed when lithium ions are inserted into it (during the formation of lithium-graphite intercalation compounds). It exhibits a low potential, similar to lithium metal (0.05V to 0.3V vs. Li / L). i + This allows lithium-ion secondary batteries to exhibit a high operating voltage. Furthermore, graphite has a relatively high volume per unit volume, relatively small volume expansion, and is inexpensive. It is preferable because it has advantages such as higher safety compared to lithium metal.

[0262] Furthermore, titanium dioxide (TiO2) and lithium titanium oxide (Li4T) are used as negative electrode active materials. i5O 12 ), lithium-graphite intercalation compound (Li x C6), Niobium pentoxide (Nb2O5) Oxides such as tungsten oxide (WO2) and molybdenum oxide (MoO2) can be used. can.

[0263] Furthermore, the negative electrode active material has a Li3N-type structure, which is a lithium and transition metal binitride. Li 3-x M x N (M = Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 The N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm²). 3 ) indicates And it is preferable.

[0264] When a lithium-transition metal binitride is used, lithium ions are included in the negative electrode active material, Combined with lithium-ion-free materials such as V2O5 and Cr3O8 as positive electrode active materials. This is preferable. By pre-desorbing the lithium ions contained in the positive electrode active material, the negative electrode active material is used. A lithium-transition metal composite can be used.

[0265] Furthermore, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example, Lithium oxide, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO). Transition metal oxides that do not form alloys with the negative electrode active material may be used. The resulting materials include Fe2O3, CuO, Cu2O, RuO2, Cr2O3, etc. CoS oxides 0.89 , sulfides such as NiS and CuS, Zn3N2, Cu3N, Ge3 Nitrides such as N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. It can also occur with fluoride.

[0266] The conductive additives and binders that the negative electrode active material layer may have include the positive electrode active material layer Materials similar to conductive additives and binders can be used.

[0267] <Negative electrode current collector> The negative electrode current collector can be made of the same material as the positive electrode current collector. It is preferable to use a material that does not alloy with carrier ions such as thium.

[0268] [Electrolyte] An electrolyte solution contains a solvent and an electrolyte. A non-protic organic solvent is preferred as the solvent for the electrolyte solution. For example, ethylene carbonate (EC), propylene carbonate (PC), and buty Lenyl carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolane Chtone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate Methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1 ,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfone Hoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetra One of the following: lahydrofuran, sulfolane, sultone, or two or more of these. It can be used in combinations and ratios.

[0269] Furthermore, as the solvent for the electrolyte, an ionic liquid (a room-temperature molten salt) that is flame-retardant and non-volatile is used. By using one or more of them, the internal temperature of the secondary battery rises due to internal short circuits or overcharging. This can also prevent secondary batteries from rupturing or catching fire. Ionic liquids contain cations and anions. It consists of organic cations and anions. As organic cations used in the electrolyte, quaternary cations are used. Ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, etc. aliphatic onium cations, imidazolium cations, pyridinium cations, etc. Aromatic cations are one example. Also, monovalent amide-based anions are used as anions in the electrolyte. Nions, monovalent methide anions, fluorosulfonate anions, perfluoroalkyl Sulfonate anions, tetrafluoroborate anions, perfluoroalkyl borates Anions, hexafluorophosphate anions, or perfluoroalkyl phosphates Examples include anions.

[0270] Furthermore, examples of electrolytes to be dissolved in the above solvent include LiPF6, LiClO4, and Li AsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4 Li2B 10 Cl 10 Li2B 12 Cl 12 LiCF3SO3, LiC4F9SO 3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2) 2. Lithium compounds such as LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. Using one type of um salt, or two or more of these salts in any combination and ratio. It is possible.

[0271] The electrolyte used in secondary batteries contains particulate matter and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "non-contaminated"). It is preferable to use a highly purified electrolyte with a low content of (also called "pure substance"). Specifically, the weight ratio of impurities to the electrolyte should be 1% or less, preferably 0.1% or less, more preferably It is preferable that the amount be 0.01% or less.

[0272] Furthermore, the electrolyte contains vinylene carbonate, propanesultone (PS), and tert-butylbe. TBB, fluoroethylene carbonate (FEC), LiBOB, and also succinyl Additives such as dinitrile compounds like notrilate and adiponitrile may be added. The concentration of the material should be, for example, between 0.1 wt% and 5 wt% relative to the total solvent. .

[0273] Alternatively, a polymer gel electrolyte, obtained by swelling a polymer with an electrolyte solution, may be used.

[0274] Using polymer gel electrolytes enhances safety against leakage and other issues. Furthermore, secondary batteries... It is possible to make it thinner and lighter.

[0275] Examples of polymers that can be gelled include silicone gel, acrylic gel, and acrylonitrile gel. Polyethylene oxide gels, polypropylene oxide gels, fluorine polymers Gels or similar materials can be used.

[0276] Examples of polymers include polyalkylene oxides such as polyethylene oxide (PEO). Polymers having a denture structure, PVDF, polyacrylonitrile, etc., and those Copolymers containing PVDF and hexafluoropropylene (H) can be used. For example, PVDF and hexafluoropropylene (H) PVDF-HFP, a copolymer of FP, can be used. The material may have a porous structure.

[0277] In addition, instead of an electrolyte, a solid electrolyte containing inorganic materials such as sulfide-based or oxide-based materials, or P Solid electrolytes containing polymer materials such as EO (polyethylene oxide) can be used. When using a solid electrolyte, the installation of separators and spacers becomes unnecessary. Because the entire pond can be solidified, the risk of leakage is eliminated, dramatically improving safety.

[0278] [Separator] Furthermore, it is preferable that the secondary battery has a separator. The separator can be, for example, paper. Nonwoven fabrics, glass fibers, ceramics, or nylon (polyamide), vinylon (poly Vinyl alcohol-based fibers, polyester, acrylic, polyolefin, polyurethane Materials made from synthetic fibers, etc., can be used. The separator is envelope-shaped. It is preferable to process it in such a way that it encloses either the positive or negative electrode.

[0279] The separator may have a multilayer structure. For example, an organic material such as polypropylene or polyethylene. The material film contains ceramic-based materials, fluorine-based materials, polyamide-based materials, or a combination thereof. Mixtures and other materials can be coated onto it. Examples of ceramic materials include aluminium oxide. Aluminum particles, silicon oxide particles, etc. can be used. As for fluorine-based materials, For example, PVDF, polytetrafluoroethylene, etc. can be used. Polyamide materials Materials used include, for example, nylon and aramid (meta-aramid, para-aramid). It is possible.

[0280] Coating with ceramic materials improves oxidation resistance, thus preventing separation during high-voltage charging and discharging. This can suppress degradation of the battery and improve the reliability of secondary batteries. Furthermore, by using fluorine-based materials... This allows the separator and electrodes to adhere more closely, improving the output characteristics. Coating with polyamide materials, especially aramid, improves heat resistance, thus increasing the safety of secondary batteries. It can improve overall health.

[0281] For example, a mixture of aluminum oxide and aramid material is applied to both sides of a polypropylene film. It may also be done by applying aluminum oxide to the surface of the polypropylene film that is in contact with the positive electrode. A mixed material of um and aramid may be coated, and a fluorine-based material may be coated on the surface in contact with the negative electrode. .

[0282] Using a multilayer separator ensures the safety of the secondary battery even if the overall thickness of the separator is thin. Because it can maintain this state, the capacity per unit volume of a secondary battery can be increased.

[0283] [Exterior] For the casing of a secondary battery, metal materials such as aluminum or resin materials are used. It is possible to use a film-like outer covering. As for the film, For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. A film made of the following materials, with highly flexible gold such as aluminum, stainless steel, copper, and nickel. A thin metal film is provided, and on the metal thin film, a polyamide resin and polyester resin are used as the outer surface of the exterior body. A three-layer film with an insulating synthetic resin film, such as a ru-based resin, can be used.

[0284] [Charge / discharge method] The charging and discharging of a secondary battery can be performed, for example, as follows.

[0285] ≪CC charging≫ First, let's explain CC charging as one of the charging methods. CC charging is used throughout the entire charging period. This charging method involves supplying a constant current to the secondary battery and stopping the charging process when a predetermined voltage is reached. The secondary battery is assumed to be an equivalent circuit of internal resistance R and secondary battery capacity C, as shown in Figure 8(A). In this case, the secondary battery voltage V B This is the voltage V across the internal resistance R. R and secondary battery capacity C The voltage V C It is the sum of.

[0286] While CC charging is in progress, the switch turns on as shown in Figure 8(A), and a certain amount of power is supplied. Current I flows through the secondary battery. During this time, since the current I is constant, V R Ohm's law = R × I According to the law, the voltage V across the internal resistance R is R It is also constant. On the other hand, the electricity applied to the secondary battery capacity C Pressure V C The voltage increases over time. Therefore, the secondary battery voltage V B The passage of time and They will both rise.

[0287] And the secondary battery voltage V B Charging stops when the voltage reaches a predetermined level, for example, 4.3V. When CC charging is stopped, the switch turns off as shown in Figure 8(B), and the current I=0 Therefore, the voltage V across the internal resistance R is... R The voltage becomes 0V. Therefore, the internal resistance R The voltage drop is eliminated, and the secondary battery voltage V B It will decline.

[0288] The secondary battery voltage V during CC charging and after CC charging has stopped. B and charging current An example is shown in Figure 8(C). The secondary battery voltage V was rising while CC charging was being performed. B However, C The image shows a slight decrease after C charging is stopped.

[0289] ≪CCCV charging≫ Next, we will explain CCCV charging, which is a different charging method from the one described above. CCCV charging is First, the battery is charged to a predetermined voltage using CC charging, and then the current that flows through it is charged using CV (constant voltage) charging. This charging method continues until the current level drops to a minimum, specifically until it reaches the cutoff current value.

[0290] While CC charging is in progress, the constant current power supply switch is turned on, as shown in Figure 9(A). The voltage power supply switch is turned off, and a constant current I flows to the secondary battery. During this time, the current I Since it is constant, V R According to Ohm's law, =R × I, the voltage across the internal resistance R is V. R one It is constant. On the other hand, the voltage V across the secondary battery capacity C C It increases over time. Therefore, the secondary battery voltage V B It increases over time.

[0291] And the secondary battery voltage V B When the voltage reaches a predetermined level, for example 4.3V, CC charging is switched to C Switch to V charging. While CV charging is being performed, a constant voltage power supply is used as shown in Figure 9(B). The switch for the constant current power supply is turned on, and the secondary battery voltage V B It becomes constant On the other hand, the voltage V across the secondary battery capacity C... C It increases over time. B =V R +V C Therefore, the voltage V across the internal resistance R R It decreases over time. Voltage V across resistor R R As V decreases, R According to Ohm's law, =R × I, two The current I flowing through the next battery will also decrease.

[0292] And when the current I flowing through the secondary battery becomes a predetermined current, for example, a current equivalent to 0.01C... , stop charging. When CCCV charging is stopped, all switches will turn off as shown in Figure 9(C). The switch turns off, and the current I becomes 0. Therefore, the voltage V across the internal resistance R is lost. R The voltage becomes 0V. However, the voltage V across the internal resistance R due to CV charging R Because it has become small enough Even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B It hardly descends at all.

[0293] The secondary battery voltage V during CCCV charging and after CCCV charging has stopped. B and An example of electric current is shown in Figure 9(D). Even when CCCV charging is stopped, the secondary battery voltage V B Mostly It appears that it is not descending at all.

[0294] ≪CC discharge≫ Next, we will explain CC discharge, one of the discharge methods. CC discharge is used throughout the entire discharge period. A constant current is drawn from the secondary battery, and the secondary battery voltage V B When it reaches a predetermined voltage, for example 2.5V This is a discharge method that stops the discharge when it reaches a certain point.

[0295] The secondary battery voltage V during CC discharge B Figure 10 shows an example of the discharge current. According to this, secondary battery voltage V B The image shows it descending.

[0296] Next, we will explain the discharge rate and charge rate. The discharge rate is the ratio of the battery capacity to the charge rate. This is the relative ratio of the current during discharge, and is expressed in units of cubic centimeters (C). Therefore, the current equivalent to 1C is X(A). If discharged with a current of 2X(A), then 2C If it was discharged with a current of X / 5(A), then it was discharged at 0.2C. It is said that the charging rate is also similar; if charged with a current of 2X(A), it will charge at 2C. They said they charged it, and if they charged it with a current of X / 5(A), they said they charged it at 0.2C. .

[0297] (Embodiment 3) In this embodiment, the shape of the secondary battery having the positive electrode active material 100 described in the previous embodiment is Let's explain an example. The material used in the secondary battery described in this embodiment is the same as in the previous embodiment. The description of the state can be taken into consideration.

[0298] [Coin-type rechargeable battery] First, let's describe an example of a coin-type rechargeable battery. Figure 11(A) shows a coin-type (single-layer flat type) Figure 11(B) is an external view of the secondary battery, and Figure 11(B) is a cross-sectional view thereof.

[0299] The coin-type rechargeable battery 300 consists of a positive electrode casing 301, which also serves as the positive terminal, and a negative electrode casing, which also serves as the negative terminal. 302 is insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 consists of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with it. It is formed by the following. The negative electrode 307 is provided in contact with the negative electrode current collector 308. It is formed by a negative electrode active material layer 309.

[0300] Furthermore, the positive electrode 304 and negative electrode 307 used in the coin-type secondary battery 300 are each made of live metal The layer only needs to be formed on one side.

[0301] The positive electrode container 301 and the negative electrode container 302 are made of nickel and aluminum, which are corrosion-resistant to the electrolyte. , metals such as titanium, or alloys thereof, or alloys of these with other metals (e.g., stainless steel) (etc.) can be used. In addition, nickel and aluminum can be used to prevent corrosion by the electrolyte. It is preferable to cover it with a material such as a nut. The positive electrode can 301 is the positive electrode 304, and the negative electrode can 302 is the negative electrode 30 Connect each of the 7s electrically.

[0302] These negative electrode 307, positive electrode 304, and separator 310 are impregnated with the electrolyte, as shown in Figure 11(B As shown in the image, with the positive electrode can 301 at the bottom, the positive electrode 304, separator 310, and negative electrode 307, The negative electrode cans 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are connected by a gasket 303. The coin-type secondary battery 300 is manufactured by crimping the parts together.

[0303] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, high capacity cycle This allows for the creation of a coin-type secondary battery 300 with superior characteristics.

[0304] Here, we will use Figure 11(C) to explain the current flow during the charging of a secondary battery. Using lithium When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In addition, in lithium-ion secondary batteries, the anode and cathode are used during charging and discharging. The cathode is swapped, and the oxidation and reduction reactions are reversed, thus changing the reaction potential. The electrode with a high reaction potential is called the positive electrode, and the electrode with a low reaction potential is called the negative electrode. Therefore, in this specification... In this case, whether charging or discharging, or even when applying a reverse pulse current, Even when an electric current is flowing, the positive electrode is called the "positive electrode" or "+ electrode (positive pole)," and the negative electrode is called the "positive pole." This will be referred to as the "negative electrode" or "- electrode (minus electrode)". Related to oxidation and reduction reactions. Using the terms anode and cathode, the difference between charging and discharging is significant. This could be reversed and cause confusion. Therefore, the anode and cathode The term cathode will not be used in this specification. When using terms such as positive electrode () or cathode, specify whether it is during charging or discharging, and the positive electrode ( The corresponding polarity (positive or negative) should also be indicated.

[0305] The charger is connected to the two terminals shown in Figure 11(C), and the secondary battery 300 is charged. As the charging of the next battery 300 progresses, the potential difference between the electrodes will increase.

[0306] [Cylindrical rechargeable battery] Next, an example of a cylindrical secondary battery will be explained with reference to Figure 12. Cylindrical secondary battery 600 As shown in Figure 12(A), it has a positive electrode cap (battery cover) 601 on the top surface, and the sides and The bottom surface has a battery can (outer casing) 602. These positive electrode cap and battery can (outer casing) 602 is insulated by gasket (insulating packing) 610.

[0307] Figure 12(B) is a schematic diagram showing a cross-section of a cylindrical secondary battery. Inside can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are separated by a separator 605. A wound battery element is provided. Although not shown in the diagram, the battery element is centered around the center pin. It is wound up. Battery can 602 is closed at one end and open at the other end. This is a metal such as nickel, aluminum, or titanium that is corrosion-resistant to the electrolyte, or this These alloys or alloys of these with other metals (for example, stainless steel) can be used. Furthermore, to prevent corrosion from the electrolyte, it is preferable to coat the components with nickel, aluminum, etc. Inside the battery can 602, the positive electrode, negative electrode, and separator are wound together to form a battery element. It is sandwiched between a pair of opposing insulating plates 608 and 609. Furthermore, a battery element is provided. The inside of the battery can 602 is filled with a non-aqueous electrolyte (not shown). The non-aqueous electrolyte is A battery similar to a coin-type rechargeable battery can be used.

[0308] Since the positive and negative electrodes used in cylindrical secondary batteries are wound, active material is formed on both sides of the current collector. It is preferable to do so. The positive electrode 604 is connected to the positive electrode terminal (positive electrode current collector lead) 603, and the negative The negative terminal (negative current collector lead) 607 is connected to pole 606. The positive terminal 603 and the negative Both electrode terminals 607 can be made of metal materials such as aluminum. Positive electrode terminal 6 Terminal 03 is resistance-welded to the safety valve mechanism 612, and the negative terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 uses a PTC element (Positive Temperature C It is electrically connected to the positive electrode cap 601 via the efficient)611. The safety valve mechanism 612 activates the positive electrode cap 601 when the internal pressure of the battery rises above a predetermined threshold. This disconnects the electrical connection between the positive electrode 604 and the positive electrode 611. Also, the PTC element 611 is at a certain temperature. This is a thermal resistance element whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current. This prevents abnormal heat generation. The PTC element uses barium titanate (BaTiO3) Semiconductor ceramics and the like can be used.

[0309] Furthermore, as shown in Figure 12(C), multiple secondary batteries 600 are connected to conductive plates 613 and 614 Module 615 may be configured by sandwiching it between them. Multiple secondary batteries 600 are connected in parallel. They may be connected in series, or connected in parallel and then further connected in series. It may be done. By configuring a module 615 having multiple secondary batteries 600, It can extract a large amount of power.

[0310] Figure 12(D) is a top view of module 615. The conductive plate 613 is shown in the diagram for clarity. This is shown by the dotted line. As shown in Figure 12(D), module 615 has multiple secondary batteries 600 It may have electrically connected conductors 616. A conductive plate 613 is superimposed on the conductors 616. It can be provided as follows. Furthermore, a temperature control device 617 is provided between multiple secondary batteries 600. It is also possible. When the secondary battery 600 overheats, it is cooled by the temperature control device 617. If the battery 600 becomes too cold, it can be heated by the temperature control device 617. Therefore, the performance of module 615 is less affected by ambient temperature.

[0311] By using the positive electrode active material described in the previous embodiment for the positive electrode 604, high capacity cycle This allows for the creation of a cylindrical secondary battery 600 with superior characteristics.

[0312] [Example of a secondary battery structure] Another example of a secondary battery structure will be explained using Figures 13 to 17.

[0313] Figures 13(A) and 13(B) show the external view of a secondary battery. A secondary battery is a circuit It has a circuit board 900 and a secondary battery 913. A label 910 is attached to the secondary battery 913. Furthermore, as shown in Figure 13(B), the secondary battery has terminal 951 and terminal 952 It also has antenna 914 and antenna 915.

[0314] The circuit board 900 has terminal 911 and circuit 912. Terminal 911 is connected to terminal 951 It is connected to terminal 952, antenna 914, antenna 915, and circuit 912. Multiple terminals 911 are provided, and each of the multiple terminals 911 is designated as a control signal input terminal and a power supply terminal. You could also do this.

[0315] The circuit 912 may be provided on the back surface of the circuit board 900. Furthermore, the antenna 914 and The antenna 915 is not limited to a coil shape, but may also be linear, plate-shaped, etc. Planar antenna, aperture antenna, traveling wave antenna, EH antenna, magnetic field antenna, dielectric Antennas such as antennas may be used. Alternatively, antenna 914 or antenna 915 may be used. Alternatively, a flat conductor may be used. This flat conductor functions as one of the conductors for electric field coupling. This is possible. In other words, as one of the two conductors of the capacitor, You may activate antenna 914 or antenna 915. This will allow only electromagnetic and magnetic fields to be generated. Alternatively, power can be exchanged using an electric field.

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

[0317] The secondary battery has a layer 916 between antennas 914 and 915 and the secondary battery 913. It has the function of shielding electromagnetic fields, for example, from secondary batteries 913. It has. For 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 Figure 13.

[0319] For example, as shown in Figures 14(A-1) and 14(A-2), Figures 13(A) and 13 Even if an antenna is provided on each of the opposing pairs of surfaces of the secondary battery 913 shown in (B) Good. Figure 14(A-1) is an external view of the pair of surfaces as seen from one side, and Figure 14( A-2) is an external view of the pair of surfaces as seen from the other side. Note that Figure 13(A) and The same parts as the secondary battery shown in Figure 13(B) are shown in Figures 13(A) and 13(B). The explanation of secondary batteries can be used as appropriate.

[0320] As shown in Figure 14(A-1), a layer 916 is sandwiched between one of the pair of surfaces of the secondary battery 913. An inlet 914 is provided, and as shown in Figure 14(A-2), a pair of sides of the secondary battery 913 On the other side, an antenna 918 is provided with a layer 917 in between. Layer 917 is, for example, a secondary battery 91 It has the function of shielding the electromagnetic field caused by 3. For layer 917, for example, a magnetic material. You can use it.

[0321] By adopting the above structure, the size of both antenna 914 and antenna 918 can be increased. It is possible. Antenna 918 can, for example, perform data communication with external devices. It has the function of being able to do so. Antenna 918 has an antenna shape that can be applied to, for example, antenna 914. An antenna can be applied. This is a communication method between a secondary battery and other devices via antenna 918. Examples include response methods that can be used between rechargeable batteries and other devices, such as NFC. It can be applied.

[0322] Alternatively, as shown in Figure 14(B-1), the secondary battery 9 shown in Figures 13(A) and 13(B) A display device 920 may be provided at 13. The display device 920 is electrically connected to terminal 911. It is not necessary to provide a label 910 in the area where the display device 920 is provided. For the same parts as the secondary battery shown in Figures 13(A) and 13(B), see Figure 13(A) and The explanation of secondary batteries shown in Figure 13(B) can be used as appropriate.

[0323] The display device 920 displays, for example, an image indicating whether or not it is charging, an image indicating the amount of stored power, etc. It may be shown. The display device 920 may be, for example, electronic paper, liquid crystal display device, or electronic A luminescent (also known as EL) display device can be used. For example, an electronic paper By using this method, the power consumption of the display device 920 can be reduced.

[0324] Alternatively, as shown in Figure 14(B-2), the secondary battery 9 shown in Figures 13(A) and 13(B) A sensor 921 may be provided at 13. The sensor 921 is connected to terminal 911 via terminal 922. It is electrically connected. Note that it is located in the same part as the secondary battery shown in Figures 13(A) and 13(B). Accordingly, the explanation of secondary batteries shown in Figures 13(A) and 13(B) can be appropriately referenced.

[0325] Examples of sensors 921 include displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, and light. Liquid, magnetism, temperature, chemicals, sound, time, hardness, electric field, electric current, voltage, power, radiation, flow It should have the ability to measure quantity, humidity, gradient, vibration, odor, or infrared radiation. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed can be collected. It can also detect (temperature, etc.) and store it in the memory within circuit 912.

[0326] Furthermore, an example of the structure of the secondary battery 913 will be explained using Figures 15 and 16.

[0327] The secondary battery 913 shown in Figure 15(A) has terminals 951 and 952 inside the housing 930. It has a wound body 950. The wound body 950 is impregnated with an electrolyte inside the housing 930. Terminal 952 is in contact with the housing 930, and terminal 951 is in contact with the housing by using insulating material, etc. It is not in contact with the body 930. Note that in Figure 15(A), for convenience, the housing 930 is separated. As shown in the diagram, in reality the wound body 950 is covered by the housing 930, and terminals 951 and 95 2 extends outside the casing 930. The casing 930 is made of a metal material (e.g., aluminum). Materials such as lum or resin can be used.

[0328] Furthermore, as shown in Figure 15(B), the housing 930 shown in Figure 15(A) is made of multiple materials. They may be formed. For example, the secondary battery 913 shown in Figure 15(B) has a housing 930a and a housing 9 30b is bonded together, and the area enclosed by the housing 930a and housing 930b is wound up 9 50 is provided.

[0329] For the casing 930a, insulating materials such as organic resin can be used. In particular, the antenna By using a material such as organic resin on the surface where the electric field of the secondary battery 913 is formed, Shielding can be suppressed. Furthermore, if the shielding of the electric field by the housing 930a is small, the housing 930a Antennas such as antenna 914 and antenna 915 may be installed inside. For example, metal materials can be used.

[0330] Furthermore, the structure of the wound body 950 is shown in Figure 16. The wound body 950 consists of a negative electrode 931 and a positive electrode. It has poles 932 and separators 933. The coiled body 950 sandwiches the separators 933. The negative electrode 931 and the positive electrode 932 are stacked on top of each other, and the stacked sheet is wound up to form a wound body. Furthermore, the stacking of the negative electrode 931, the positive electrode 932, and the separator 933 is further multiplied. You can do it multiple times.

[0331] The negative electrode 931 is connected to terminal 911 shown in Figure 13 via either terminal 951 or terminal 952. The positive terminal 932 is connected to terminal 91 shown in Figure 13 via terminal 951 and the other terminal 952. It connects to 1.

[0332] By using the positive electrode active material described in the previous embodiment for the positive electrode 932, high capacity cycle This allows for the creation of a secondary battery 913 with superior characteristics.

[0333] [Laminated rechargeable battery] Next, an example of a laminate-type secondary battery will be explained with reference to Figures 17 to 23. If a laminate-type secondary battery has a flexible structure, the number of flexible parts can be reduced. If implemented in electronic devices that also possess some of these features, the secondary battery can also be bent in accordance with the deformation of the electronic device. can.

[0334] Using Figure 17, we will explain the laminated secondary battery 980. The battery 980 has a wound body 993 as shown in Figure 17(A). The wound body 993 has a negative electrode 994 It has a positive electrode 995 and a separator 996. The wound body 993 is explained in Figure 16. Similar to the wound body 950, the negative electrode 994 and the positive electrode 995 overlap with the separator 996 in between. The sheets are joined together and laminated, and then the laminated sheets are rolled up.

[0335] The number of layers in the stack consisting of the negative electrode 994, positive electrode 995, and separator 996 is the required number of layers. The design should be appropriate depending on the capacitance and element volume. The negative electrode 994 is connected to the lead electrode 997 and the lead One side of the electrode 998 is connected to the negative electrode current collector (not shown), and the positive electrode 995 is connected to the lead electrode It is connected to a positive electrode current collector (not shown) via pole 997 and the other of lead electrode 998.

[0336] As shown in Figure 17(B), there is a film 981 which will be the outer casing and a film 98 which has a recess. The aforementioned coiled body 993 is housed in the space formed by bonding 2 together by heat pressing or the like. As a result, a secondary battery 980 can be manufactured as shown in Figure 17(C). (Winding body 99) 3 has lead electrodes 997 and 998, a film 981 and a recess The film 982 is impregnated with an electrolyte solution inside it.

[0337] Film 981 and film 982 having a recess are made of a metal material such as aluminum. or resin materials can be used. Film 981 and film 982 having recesses If a resin material is used as the material, when an external force is applied, the film 981 and the recess will To create a rechargeable battery in which the film 982 can be deformed and is flexible. It is possible.

[0338] Furthermore, Figures 17(B) and 17(C) show examples using two films, A space is formed by folding a single film, and the aforementioned wound body 99 is placed in that space. You may store 3.

[0339] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, high capacity cycle This allows for the creation of a secondary battery 980 with superior characteristics.

[0340] Figure 17 also shows a secondary battery 9 having a wound body in a space formed by a film that serves as the outer casing. I have explained 80 examples, but for example, as shown in Figure 18, the shape is formed by the film that forms the outer casing. In the resulting space, it can also be used as a secondary battery having multiple strip-shaped positive electrodes, separators, and negative electrodes. good.

[0341] The laminated secondary battery 500 shown in Figure 18(A) consists of a positive electrode current collector 501 and a positive electrode active material The positive electrode 503 has a solid layer 502, and the negative electrode has a current collector 504 and a negative electrode active material layer 505. It has a negative electrode 506, a separator 507, an electrolyte 508, and an outer casing 509. A separator 507 is installed between the positive electrode 503 and the negative electrode 506 located within the body 509. It is. Also, the inside of the outer casing 509 is filled with electrolyte 508. The electrolyte 508 contains actual The electrolyte shown in Form 2 of the application can be used.

[0342] In the laminate-type secondary battery 500 shown in Figure 18(A), the positive electrode current collector 501 and the negative electrode current collector are... The polar current collector 504 also serves as a terminal for obtaining electrical contact with the outside. Therefore, it is the positive electrode. Parts of the current collector 501 and the negative electrode current collector 504 are exposed to the outside from the outer casing 509. They may also be arranged in this manner. Furthermore, the positive electrode current collector 501 and the negative electrode current collector 504 may be separated from the outer casing 509. Without exposing it to the outside, lead electrodes are used to connect the lead electrodes to the positive electrode current collector 501, or to the negative electrode. The lead electrodes may be exposed to the outside by ultrasonic bonding with the current collector 504.

[0343] In the laminated secondary battery 500, the outer casing 509 is made of, for example, polyethylene, poly On a film made of materials such as propylene, polycarbonate, ionomer, and polyamide, A highly flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided, and further, the metal An insulating synthetic resin such as polyamide resin or polyester resin is used as the outer surface of the outer casing on a thin film. A three-layer laminate film with a lipid film can be used.

[0344] Furthermore, an example of the cross-sectional structure of the laminate-type secondary battery 500 is shown in Figure 18(B). In A), for simplicity, an example consisting of two current collectors is shown, but in reality, multiple electrode layers are used. It consists of:

[0345] In Figure 18(B), the number of electrode layers is set to 16 as an example. However, the secondary battery 500 is flexible. In Figure 18(B), the negative electrode current collector 504 has 8 layers, The positive electrode current collector 501 has a structure of 8 layers, for a total of 16 layers. Figure 18(B) shows the negative electrode This shows a cross-section of the extraction section, where eight layers of negative electrode current collectors 504 are ultrasonically bonded. The number of electrode layers is not limited to 16; it can be more or fewer. This allows for the creation of a secondary battery with a larger capacity. Also, in cases where the number of electrode layers is small... In combination, it is possible to create a rechargeable battery that is thin and highly flexible.

[0346] Here, an example of the external view of the laminate-type secondary battery 500 is shown in Figures 19 and 20. Figure 1 Figures 9 and 20 show the positive electrode 503, negative electrode 506, separator 507, casing 509, and positive electrode lead. It has a lead electrode 510 and a negative lead electrode 511.

[0347] Figure 21(A) shows the external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is the positive electrode current collector 50 The positive electrode has a positive electrode active material layer 502 formed on the surface of the positive electrode current collector 501. 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). 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. Furthermore, the negative electrode 506 is the region where the negative electrode current collector 504 is partially exposed, i.e., the tab region. It has a tab region. The area and shape of the tab regions of the positive and negative electrodes are not limited to the example shown in Figure 21(A). I can't.

[0348] [Method for manufacturing laminated rechargeable batteries] Here, an example of a method for manufacturing a laminate-type secondary battery, as shown in Figure 19, is presented in Figure 21. We will explain using (B) and (C).

[0349] First, the negative electrode 506, separator 507, and positive electrode 503 are stacked. (See Figure 21(B) for details.) The negative electrode 506, separator 507, and positive electrode 503 are shown. Here, there are 5 sets of negative electrodes and 5 sets of positive electrodes. An example of using four sets is shown. Next, the joining of the tab regions of the positive electrode 503 and the tab of the outermost positive electrode. The positive lead electrode 510 is joined to the region. For joining, for example, ultrasonic welding can be used. Good. Similarly, the bonding of the tab regions of the negative electrode 506 and the negative electrode connection to the tab region of the outermost negative electrode The electrode 511 is joined.

[0350] Next, the negative electrode 506, separator 507, and positive electrode 503 are placed on the outer casing 509.

[0351] Next, as shown in Figure 21(C), the outer casing 509 is folded at the part indicated by the dashed line. Next, the outer perimeter of the exterior body 509 is joined. For joining, for example, heat compression bonding may be used. In order to allow the electrolyte 508 to be added later, a part (or one side) of the outer casing 509 A region that is not connected (hereinafter referred to as the inlet) is provided.

[0352] Next, the electrolyte 508 is introduced into the inside of the outer casing 509 through the inlet provided in the outer casing 509. The introduction of electrolyte 508 is preferably carried out under a reduced pressure atmosphere or an inert gas atmosphere. And finally, the inlet is joined. In this way, the laminated secondary battery A certain secondary battery 500 can be manufactured.

[0353] By using the positive electrode active material described in the previous embodiment for the positive electrode 503, high capacity cycle This allows for the creation of a secondary battery 500 with superior characteristics.

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

[0355] Figure 22(A) shows a schematic top view of a bendable secondary battery 50. Figure 22(B1) (B2) and (C) correspond to the cutting lines C1-C2 and C3-C in Figure 22(A), respectively. 4. This is a schematic cross-sectional view at the cutting line A1-A2. The battery 50 consists of the outer casing 51 and the outer casing 5 It has a positive electrode 11a and a negative electrode 11b housed inside 1. The positive electrode 11a is electrically connected The lead 12a, and the lead 12b electrically connected to the negative electrode 11b, are connected to the outer casing 5. It extends to the outside of 1. Also, the region enclosed by the outer casing 51 contains the positive electrode 11a and the negative electrode 1 In addition to 1b, an electrolyte solution (not shown) is sealed inside.

[0356] The positive electrode 11a and negative electrode 11b of the battery 50 will be explained using Figure 23. Figure 2 3(A) is a perspective view illustrating the stacking order of the positive electrode 11a, the negative electrode 11b, and the separator 14. Yes. Figure 23(B) shows the positive electrode 11a and the negative electrode 11b, as well as the lead 12a and lead This is a perspective view of 12b.

[0357] As shown in Figure 23(A), the battery 50 has multiple strip-shaped positive electrodes 11a and multiple strip-shaped negative electrodes It has an electrode 11b and a plurality of separators 14. The positive electrode 11a and the negative electrode 11b are respectively It has a protruding tab portion and a portion other than the tab. The portion other than the tab on one side of the positive electrode 11a A positive electrode active material layer is formed on the positive electrode, and a negative electrode active material layer is formed on the part of one side of the negative electrode 11b other than the tab. It will be accomplished.

[0358] The surfaces of the positive electrode 11a that do not have a positive electrode active material layer formed on them, and the negative electrode active material layer of the negative electrode 11b. The positive electrode 11a and the negative electrode 11b are stacked so that their surfaces, which do not have a surface formed on them, are in contact with each other.

[0359] Furthermore, the positive electrode active material formed on the positive electrode 11a and the negative electrode active material formed on the negative electrode 11b A separator 14 is provided between the surfaces. In Figure 23(A), the separator is shown for clarity. The number 14 is shown with a dotted line.

[0360] Also, as shown in Figure 23(B), the multiple positive electrodes 11a and leads 12a are connected at the joint 15a. They are electrically connected at the joint 15b. They are electrically connected.

[0361] Next, the exterior body 51 will be explained using Figures 22(B1), (B2), (C), and (D). .

[0362] The outer casing 51 has a film-like shape and consists of two parts that sandwich the positive electrode 11a and the negative electrode 11b. It is bent in that way. The outer casing 51 has a bent part 61, a pair of sealing parts 62, and It has a seal portion 63 and a pair of seal portions 62 sandwiching the positive electrode 11a and the negative electrode 11b. It can also be called a side seal. The seal portion 63 is connected to the lead 12a and It has a portion that overlaps with lead 12b and can also be called a top seal.

[0363] The outer casing 51 has alternating ridges 71 and valleys 72 in the portion that overlaps with the positive electrode 11a and the negative electrode 11b. It is preferable that the casing body 51 has a wave shape arranged in a row. Also, the sealing portion 62 and the sealing portion 63 is preferably flat.

[0364] Figure 22(B1) shows a cross-section cut at the point where it overlaps with ridge line 71, and Figure 22(B2) shows a valley. This is a cross-section taken at the point where it overlaps with line 72. Figures 22(B1) and (B2) both show battery 50 This corresponds to the cross-section in the width direction of the positive electrode 11a and the negative electrode 11b.

[0365] Here, the distance between the end of the negative electrode 11b in the width direction and the seal portion 62 is denoted as distance La. When the pond 50 is subjected to deformation such as bending, the positive electrode 11a and the negative electrode 11b, as described later, They deform so that they are offset from each other in the longitudinal direction. In this case, if the distance La is too short, the outer casing 51 and The positive electrode 11a and the negative electrode 11b may rub against each other strongly, potentially damaging the outer casing 51. When the metal film of the outer casing 51 is exposed, the metal film is corroded by the electrolyte. There is a risk of this happening. 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 battery 50 will increase.

[0366] Furthermore, the thicker the combined thickness of the stacked positive electrode 11a and negative electrode 11b, the more the edges of the negative electrode 11b It is preferable to increase the distance La between the part and the sealing part 62.

[0367] More specifically, stacked positive electrode 11a and negative electrode 11b and a separator (not shown) When the total thickness of 214 is denoted as thickness t, the distance La is between 0.8 and 3.0 times the thickness t. Preferably, 0.9 times or more and 2.5 times or less, more preferably 1.0 times or more and 2.0 times or less. It is preferable that the distance La is within this range, making it compact and resistant to bending. This enables the creation of highly reliable batteries.

[0368] Furthermore, when the distance between the pair of sealing portions 62 is denoted as distance Lb, the distance Lb is the width of the negative electrode 11b. It is preferable to make it sufficiently larger than Wb. This allows the battery 50 to be repeatedly bent, etc. Even when deformation is applied, the positive electrode 11a and negative electrode 11b come into contact with the outer casing 51, Since a portion of 11a and the negative electrode 11b can be shifted in the width direction, the positive electrode 11a and the negative This effectively prevents friction between the pole 11b and the outer casing 51.

[0369] For example, the difference between the distance Lb between the pair of sealing portions 62 and the width Wb of the negative electrode 11b is the same as the positive electrode 11 The thickness t of a and the negative electrode 11b is 1.6 times or more and 6.0 times or less, preferably 1.8 times or more. It is preferable that the ratio is 0 times or less, and more preferably 2.0 times or more and 4.0 times or less.

[0370] In other words, it is preferable that the distance Lb, width Wb, and thickness t satisfy the relationship shown in equation 2 below. It's nice.

[0371]

number

[0372] Here, a is 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, more preferably It satisfies the condition of being between 1.0 and 2.0.

[0373] Furthermore, Figure 22(C) shows a cross-section including lead 12a, battery 50, positive electrode 11a, and negative electrode. This corresponds to the longitudinal cross-section of 11b. As shown in Figure 22(C), the bent portion 61 There is a space 73 between the longitudinal ends of the positive electrode 11a and the negative electrode 11b and the outer casing 51. It is preferable to do so.

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

[0375] When the battery 50 is bent, a portion of the outer casing 51 located on the outside of the bend stretches, while the other portions located on the inside stretch. A portion of it deforms in a way that causes it to shrink. More specifically, the part located on the outside of the outer casing 51 becomes wave-shaped. The amplitude is reduced and the wave period is increased as it deforms. Meanwhile, inside the outer casing 51 The area in question is deformed such that the wave amplitude is large and the wave period is small. As the outer casing 51 deforms, the stress on the outer casing 51 due to bending is relieved. Therefore, the material that makes up the exterior body 51 does not need to expand or contract. As a result, the exterior body 51 It can bend a 50-cell battery with minimal force without damaging it.

[0376] Furthermore, as shown in Figure 22(D), when the battery 50 is bent, the positive electrode 11a and the negative electrode 11b and These are each shifted relative to each other. At this time, the multiple stacked positive electrodes 11a and negative electrodes 11b Since one end of the seal portion 63 is fixed by the fixing member 17, the closer to the bent portion 61 They shift so that the amount of displacement increases. As a result, the positive electrode 11a and the negative electrode 11 The stress on b is relieved, and there is no need for the positive electrode 11a and negative electrode 11b themselves to expand or contract. As a result, the battery 50 can be bent without damaging the positive electrode 11a and the negative electrode 11b. .

[0377] Furthermore, there is a space 73 between the ends of the positive electrode 11a and the negative electrode 11b and the outer casing 51. As a result, when bent, the ends of the positive electrode 11a and negative electrode 11b located on the inside become attached to the outer casing. It can shift relative to 51 without making contact.

[0378] The battery 50 illustrated in Figures 22 and 23 can withstand repeated bending and straightening without damaging its outer casing. A battery that is less prone to damage, such as breakage of the positive electrode 11a and negative electrode 11b, and whose battery characteristics do not deteriorate easily. The positive electrode 11a of the battery 50 is made using the positive electrode active material described in the previous embodiment. This allows for the creation of batteries with even better cycle characteristics.

[0379] (Embodiment 4) This embodiment describes an example in which a secondary battery, which is one aspect of the present invention, is mounted in an electronic device. do.

[0380] First, as described in part of Embodiment 3, a bendable secondary battery is mounted in an electronic device. Examples are shown in Figures 24(A) to 24(G). An electronic device using a bendable secondary battery. As equipment, for example, television equipment (also called television or television receiver), Computer monitors, digital cameras, digital video cameras, digital photo Frame, mobile phone (also called mobile phone or mobile phone device), portable game console, mobile information Examples include terminals, audio playback devices, and large game machines such as pachinko machines.

[0381] Furthermore, rechargeable batteries with flexible shapes can be installed in the interior or exterior walls of houses and buildings, or in automobiles. It can also be incorporated along the curved surfaces of the interior or exterior.

[0382] Figure 24(A) shows an example of a mobile phone. Mobile phone 7400 has a housing 7401 In addition to the display unit 7402 incorporated into it, there are operation buttons 7403, an external connection port 7404, and It is equipped with a speaker 7405, a microphone 7406, etc. Note that the mobile phone 7400 is secondary. It has a battery 7407. The secondary battery 7407 of the present invention is used This allows us to provide lightweight and long-lasting mobile phones.

[0383] Figure 24(B) shows the mobile phone 7400 in a curved state. When the 0 is deformed by an external force and the whole thing is bent, the secondary battery located inside is revealed. The 7407 is also bent. Figure 24(C) shows the state of the bent secondary battery 7407 at that time. As shown in the diagram, the 7407 secondary battery is a thin rechargeable battery. The 7407 secondary battery is in a bent state. It is fixed in place. Furthermore, the secondary battery 7407 is electrically connected to the current collector 7409. It has an electrode 7408. For example, the current collector 7409 is copper foil and partially gallium compounded. By gold-plating the active material layer that comes into contact with the current collector 7409, the adhesion between the active material layer and the secondary battery 7407 is improved. This design ensures high reliability even when bent.

[0384] Figure 24(D) shows an example of a bangle-type display device. The portable display device 7100 is The device comprises a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. Figure 24(E) also shows the state of the bent secondary battery 7104. The secondary battery 7104 is bent. When worn on the user's arm in a distorted state, the casing deforms, causing part of the secondary battery 7104 or All curvatures change. Note that the degree of curvature at any point in the curve is equal to the radius of the corresponding circle. The value expressed as such is the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, the radius of curvature Within a range of 40mm to 150mm, a portion of the main surface of the housing or secondary battery 7104 The whole thing changes. The radius of curvature on the main surface of secondary battery 7104 is 40 mm or more and 150 High reliability can be maintained within a range of mm or less. The present invention applies to the secondary battery 7104 described above. By using one embodiment of a secondary battery, a lightweight and long-lasting portable display device can be provided.

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

[0386] The 7200 mobile information terminal offers mobile phone, email, document viewing and creation, music playback, and internet connectivity. - It can run various applications such as network communication and computer games. ru.

[0387] The display unit 7202 has a curved display surface, and displays are made along the curved display surface. It can do this. In addition, the display unit 7202 is equipped with a touch sensor, allowing you to touch the screen with your finger or stylus. It can be operated by touching it. For example, the icon 72 displayed on the display unit 7202 Touching 07 will launch the application.

[0388] The 7205 control button is used for setting the time, turning the power on and off, and turning wireless communication on and off. It has various functions such as operation, silent mode activation and deactivation, and power saving mode activation and deactivation. This can be done. For example, the operating system built into the mobile information terminal 7200 The stem also allows you to freely configure the function of the control button 7205.

[0389] Furthermore, the personal information terminal 7200 is capable of performing standardized short-range wireless communication. Yes, for example, by communicating with a wireless headset, hands-free operation is possible. You can also make phone calls.

[0390] Furthermore, the portable information terminal 7200 is equipped with an input / output terminal 7206, and connects to other information terminals via a connector. It can directly exchange data via this. It can also be charged via input / output terminal 7206. It is also possible to perform this operation. Note that charging is performed wirelessly without using input / output terminal 7206. That's fine.

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

[0392] The personal information terminal 7200 preferably has a sensor. For example, a fingerprint sensor. Human body sensors such as pulse sensors and body temperature sensors, as well as touch sensors, pressure sensors, and acceleration sensors. It is preferable that the following are installed:

[0393] Figure 24(G) shows an example of an armband-type display device. The display device 7300 consists of a display unit 7 The present invention has a secondary battery having 304. The display device 7300 is a table The display unit 7304 can also be equipped with a touch sensor, and can function as a portable information terminal. It is also possible.

[0394] The display unit 7304 has a curved display surface, and displays are made along the curved display surface. Yes, it is possible. Furthermore, the display device 7300 can communicate via standardized short-range wireless communication, etc. The situation can be changed.

[0395] Furthermore, the display device 7300 is equipped with input / output terminals and can be directly connected to other information terminals via connectors. It can exchange data. It can also be charged via input / output terminals. Furthermore, charging may be performed wirelessly without using input / output terminals.

[0396] By using a secondary battery according to one aspect of the present invention as the secondary battery of the display device 7300, We can provide display devices with a long lifespan in large quantities.

[0397] Furthermore, the figure shows an example of mounting the secondary battery with good cycle characteristics shown in the previous embodiment into an electronic device. This will be explained using Figures 24(H), 25, and 26.

[0398] By using a secondary battery according to one aspect of the present invention as a secondary battery in everyday electronic devices, a lightweight and long-lasting battery can be achieved. We can provide a variety of products. For example, as everyday electronic devices, electric toothbrushes, electric shavers, etc. Examples include mobile beauty devices, and the rechargeable batteries for these products are designed with ease of handling by the user in mind. What is desired is a rechargeable battery that is stick-shaped, small, lightweight, and has a large capacity.

[0399] Figure 24(H) is a perspective view of a device also known as a tobacco-containing smoking device (electronic cigarette). In 24(H), the electronic cigarette 7500 includes an atomizer 7501 containing a heating element, and The cart contains the 7504 rechargeable battery that powers the Myza, as well as liquid supply bottles, sensors, and other components. It consists of Ridge 7502. To enhance safety, overcharging of the secondary battery 7504 and over A protective circuit to prevent discharge may be electrically connected to the secondary battery 7504. (See Figure 24(H)) The secondary battery 7504 has external terminals so that it can be connected to a charging device. The 504 is the tip when held, so the overall length is short and the weight is light. This is desirable. A secondary battery according to one aspect of the present invention has high capacity and good cycle characteristics, We offer the 7500, a small and lightweight e-cigarette that can be used for extended periods of time. It can be used.

[0400] Next, Figures 25(A) and 25(B) show an example of a foldable tablet device. The tablet terminal 9600 shown in Figures 25(A) and 25(B) has a housing 9630. a, housing 9630b, movable part 9640 connecting housing 9630a and housing 9630b, display Display unit 9631 having section 9631a and display unit 9631b, display mode switching switch 9626, Power switch 9627, Power saving mode switch 9625, Fastener 96 29, it has an operating switch 9628. The display unit 9631 has a flexible panel. By using this, a tablet device with a larger display area can be created. Figure 25(A Figure 25(B) shows the tablet terminal 9600 in an open state. This shows the state with the last 9600 closed.

[0401] Furthermore, the tablet terminal 9600 stores energy inside the housings 9630a and 9630b. It has a body 9635. The energy storage body 9635 passes through the movable part 9640 and the housing 9630a and housing It is located across 9630b.

[0402] The display unit 9631a can be partially designated as a touch panel area 9632a, and the display will be Data can be entered by touching the operation key 9638. Note that the display unit 963 In 1a, as an example, one half of the area has a display-only function, and the other half of the area The diagram shows a configuration that includes touch panel functionality, but is not limited to this configuration. Display unit 963 The entire area of ​​1a may also be configured to have touch panel functionality. For example, the display unit 96 The entire surface of 31a is used as a touch panel with keyboard buttons, and the display unit 9631b is displayed. It can be used as a screen.

[0403] Furthermore, in the display unit 9631b, similar to the display unit 9631a, a part of the display unit 9631b This can be designated as the touch panel area 9632b. Also, the touch panel keyboard... By touching the location where the display switch button 9639 is displayed with your finger or stylus, Keyboard buttons can be displayed on the display unit 9631b.

[0404] Furthermore, touch panel area 9632a and touch panel area 9632b can be touched simultaneously. You can also input text.

[0405] Additionally, the display mode switch 9626 switches the display orientation, such as portrait or landscape. You can switch between black and white and color displays. Power saving mode switch. The 9625 is detected by the light sensor built into the tablet terminal 9600 when in use. The display brightness can be optimized according to the amount of ambient light. In addition to optical sensors, other detection sensors such as gyroscopes and accelerometers that detect tilt are also used. The device may be built-in.

[0406] Furthermore, Figure 25(A) shows an example where the display area of ​​display unit 9631b and display unit 9631a are the same. However, this is not particularly limited, and one size may be different from the other. The quality of these components may also differ. For example, one display panel may be capable of displaying higher resolution than the other. That is also acceptable.

[0407] Figure 25(B) shows the closed state, and the tablet terminal consists of a housing 9630 and a solar cell 96 33. It has a charge / discharge control circuit 9634 including a DC-DC converter 9636. Also, an energy storage unit As 9635, a power storage body according to one aspect of the present invention is used.

[0408] Furthermore, since the tablet device 9600 is foldable, when not in use, the casing 9630a and The casing 9630b can be folded so that it overlaps with the other casing. By folding it, Because the display units 9631a and 9631b are protected, the tablet terminal 9600 has a durable Durability can be improved. Furthermore, the energy storage body 9635 using a secondary battery according to one aspect of the present invention is Due to its high capacity and good cycle characteristics, this tablet can be used for extended periods of time. We can provide the 9600 type terminal.

[0409] In addition, the tablet devices shown in Figures 25(A) and 25(B) are also available in various forms. Functions to display information (still images, videos, text images, etc.), calendar, date or time, etc. A function that displays information on the display unit, and a touch input operation or editing of the information displayed on the display unit. It has input capabilities, and functions to control processing through various software (programs), etc. It is possible.

[0410] The solar cell 9633 mounted on the surface of the tablet device powers the touch panel. It can be supplied to the display unit or the video signal processing unit, etc. Note that the solar cell 9633 is housed in a casing. A structure that can be provided on one or both sides of the body 9630 and efficiently charges the energy storage body 9635. It can be made to be a complete product. Furthermore, if a lithium-ion battery is used as the energy storage body 9635, It has advantages such as being able to be miniaturized.

[0411] Furthermore, the configuration and operation of the charge / discharge control circuit 9634 shown in Figure 25(B) are shown in Figure 25( A block diagram is shown and explained in C). Figure 25(C) shows the solar cell 9633 and the energy storage unit 963. 5. DC-DC converter 9636, converter 9637, switch SW1 to SW3, table The diagram shows the section 9631, and includes the energy storage unit 9635, the DC-DC converter 9636, and the capacitor. The converter 9637 and switches SW1 to SW3 are connected to the charge / discharge control circuit 96 shown in Figure 25(B). This corresponds to section 34.

[0412] First, let's explain an example of operation when electricity is generated by the solar cell 9633 using ambient light. The electricity generated by the solar panel is converted to a DC-DC converter to provide the voltage needed to charge the 9635 energy storage unit. The converter 9636 performs voltage boosting or de-voltage adjustment. Then, the solar cell controls the operation of the display unit 9631. When power from 9633 is used, switch SW1 is turned ON, and converter 9637 The voltage is then boosted or lowered to the voltage required for the display unit 9631. If you do not want the display to appear, turn SW1 off and SW2 on to charge the battery 9635. The configuration should be designed to handle electricity.

[0413] The solar cell 9633 is shown as an example of a power generation method, but it is not particularly limited to this method. Energy storage using other power generation methods such as electrical elements (piezo elements) and thermoelectric conversion elements (Peltier elements) The configuration may also involve charging the body 9635. For example, power may be transmitted and received wirelessly (contactlessly). This configuration uses a contactless power transmission module for charging, or a combination of other charging methods. That's fine.

[0414] Figure 26 shows an example of another electronic device. In Figure 26, the display device 8000 is one of the present inventions. This is an example of an electronic device using a secondary battery 8004 according to the embodiment. Specifically, the display device 800 0 corresponds to a display device for receiving TV broadcasts, and consists of a housing 8001, a display unit 8002, and a speaker unit. The invention includes 8003, a secondary battery 8004, etc. A secondary battery 8004 according to one aspect of the present invention has a housing It is located inside the body 8001. The display device 8000 receives power from the commercial power supply. It can be used to power the device, or it can use the power stored in the secondary battery 8004. Even when power cannot be supplied from the commercial power source due to a power outage, etc., according to one aspect of the present invention By using the secondary battery 8004 as an uninterruptible power supply, the display device 8000 can be used. ru.

[0415] The display unit 8002 has light-emitting elements such as liquid crystal display devices and organic EL elements in each pixel. Equipment, electrophoresis display device, DMD (Digital Micromirror Display) ce), PDP (Plasma Display Panel), FED (Field Semiconductor display devices such as Emission Displays can be used.

[0416] In addition to being used for receiving TV broadcasts, display devices are also used for personal computers, advertising displays, and more. This includes all information display devices.

[0417] In Figure 26, the fixed lighting device 8100 is a secondary battery 81 according to one aspect of the present invention. This is an example of an electronic device using 03. Specifically, the lighting device 8100 has a housing 8101 and light It has a power source 8102, a secondary battery 8103, etc. In Figure 26, the secondary battery 8103 is located in the housing 81 An example is provided where 01 and the light source 8102 are installed inside the ceiling 8104. However, the secondary battery 8103 may also be located inside the housing 8101. The 8100 can receive power from the commercial power supply, or it can store power in the secondary battery 8103. It is also possible to use the accumulated power. Therefore, if power is not supplied from the commercial power source due to a power outage, etc. Even when it is not possible to receive a power supply, the secondary battery 8103 according to one aspect of the present invention can be used as an uninterruptible power supply. This makes it possible to use the lighting device 8100.

[0418] Note that Figure 26 illustrates a fixed lighting device 8100 installed on the ceiling 8104. However, in one aspect of the present invention, the secondary battery is located in a location other than the ceiling 8104, for example, the side wall 8105, the floor 8 106, It can also be used in fixed lighting devices installed in windows 8107, etc., and on a tabletop It can also be used in lighting fixtures and other similar devices.

[0419] Furthermore, the light source 8102 can be an artificial light source that uses electricity to artificially produce light. Specifically, this includes incandescent light bulbs, discharge lamps such as fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements. The element is an example of the artificial light source mentioned above.

[0420] In Figure 26, the air conditioner having an indoor unit 8200 and an outdoor unit 8204 is, This is an example of an electronic device using a secondary battery 8203 according to one aspect of the present invention. Specifically, indoor The unit 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, etc. (See Figure 26) This example illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but Battery 8203 may be located in the outdoor unit 8204. Alternatively, it may be located in the indoor unit 8200 and the outdoor unit. The secondary battery 8203 may be provided on both sides of the unit 8204. (Air conditioner) It can receive power from the commercial power supply, or from the electricity stored in the secondary battery 8203. It can also use force. In particular, both the indoor unit 8200 and the outdoor unit 8204 can use secondary batteries 82 If 03 is provided, when power cannot be supplied from the commercial power source due to a power outage, etc. Furthermore, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, an air conditioner can be used. Conditioner can be used.

[0421] Note that in Figure 26, a separate-type air conditioner consisting of an indoor unit and an outdoor unit is shown. As an example, an integrated air conditioner has both the indoor and outdoor unit functions in a single housing. A secondary battery according to one aspect of the present invention can also be used in the conditioner.

[0422] In Figure 26, the electric refrigerator 8300 is powered by a secondary battery 8304 according to one aspect of the present invention. This is an example of the electronic equipment used. Specifically, the electric refrigerator 8300 consists of a casing 8301 and a refrigerator. It has a storage room door 8302, a freezer room door 8303, a secondary battery 8304, etc. In Figure 26, two The next battery 8304 is located inside the casing 8301. The electric refrigerator 8300 is, It can receive power from the commercial power supply, or it can use the power stored in the secondary battery 8304. It can also be used. Therefore, when power cannot be supplied from the commercial power source due to a power outage, etc. However, by using the secondary battery 8304 according to one aspect of the present invention as an uninterruptible power supply, electric cooling The 8300 freezer / refrigerator will become available for use.

[0423] Of the electronic devices mentioned above, high-frequency heating devices such as microwave ovens and electric rice cookers are not included. The equipment requires high power in a short period of time. Therefore, it needs to supplement the power that cannot be supplied by the commercial power supply. By using a secondary battery according to one aspect of the present invention as an auxiliary power source for electronic devices, This prevents the commercial power circuit breaker from tripping during use.

[0424] Furthermore, during periods when electronic devices are not in use, especially the total amount of electricity that can be supplied by the commercial power source... Of these, during periods when the proportion of electricity actually used (called the electricity usage rate) is low, secondary By storing power in the battery, the rate of power consumption outside of the above-mentioned time period is suppressed. It is possible. For example, in the case of the electric refrigerator 8300, when the temperature is low, the refrigerator door 830 2. At night when the freezer door 8303 is not opened or closed, power is stored in the secondary battery 8304. And as the temperature rises, the refrigerator door 8302 and the freezer door 8303 are opened and closed. During the daytime, by using the secondary battery 8304 as an auxiliary power source, the daytime power usage rate It can be kept low.

[0425] According to one aspect of the present invention, the cycle characteristics of a secondary battery are improved, and its reliability is enhanced. This is possible. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be made, and therefore This allows for improved characteristics of secondary batteries, and therefore, the secondary batteries themselves can be made smaller and lighter. Yes, it is possible. Therefore, a secondary battery, which is one aspect of the present invention, can be used in the electronic device described in this embodiment. By incorporating this technology, electronic devices can be made longer-lasting and lighter. This can be implemented in appropriate combination with other embodiments.

[0426] (Embodiment 5) This embodiment shows an example in which a secondary battery according to one aspect of the present invention is mounted on a vehicle.

[0427] When a secondary battery is installed in a vehicle, it becomes a hybrid electric vehicle (HEV), an electric vehicle (EV), or a hybrid electric vehicle. This will enable the realization of next-generation clean energy vehicles such as plug-in hybrid electric vehicles (PHEVs). .

[0428] Figure 27 illustrates a vehicle using a secondary battery, which is one embodiment of the present invention. Figure 27(A) The automobile 8400 shown is an electric vehicle that uses an electric motor as a power source for driving. Yes. Alternatively, an electric motor and an engine can be appropriately selected and used as the power source for propulsion. This is a hybrid vehicle that can achieve the following: By using one aspect of the present invention, the driving range can be extended. This makes it possible to realize a vehicle. In addition, the 8400 automobile has a secondary battery. The secondary battery is The secondary battery modules shown in Figures 12(C) and 12(D) are positioned on the floor portion of the vehicle. You can use them by arranging them side by side. Also, a battery pack made by combining multiple secondary batteries as shown in Figure 17. It may be installed on the floor inside the vehicle. The secondary battery drives the electric motor 8406. In addition, it supplies power to light-emitting devices such as headlights 8401 and interior lights (not shown). They can provide it.

[0429] Furthermore, the secondary battery is used for the speedometer, tachometer, and other displays in the 8400 automobile. It can supply power to the device. In addition, the secondary battery is the navigation system of the 8400 automobile. It can supply power to semiconductor devices such as ignition systems.

[0430] The automobile 8500 shown in Figure 27(B) is a secondary battery that plugs into the automobile 8500. It can be charged by receiving power from an external charging facility using methods such as contactless power supply. Figure 27(B) shows the two devices mounted on the automobile 8500, connected to the ground-mounted charging device 8021. The next diagram shows the state in which the battery 8024 is being charged via cable 8022. Therefore, charging methods and connector specifications are subject to the standards of CHAdeMO (registered trademark) and Combo, etc. The method can be carried out as appropriate. The charging device 8021 is installed at a charging station in a commercial facility. It is also fine to use a household power supply. For example, plug-in technology allows for external power supply. The power supply can charge the secondary battery 8024 installed in the 8500 vehicle. Charging is performed by converting AC power to DC power via a conversion device such as an AC / DC converter. It is possible.

[0431] Although not shown in the diagram, a power receiving device is mounted on the vehicle, and power is supplied wirelessly from a ground-based power transmission device. It can also be charged by doing so. In this contactless power supply method, power transmission equipment is installed in roads or exterior walls. By incorporating this, charging can be performed not only when the vehicle is stopped but also while it is in motion. Furthermore, this contactless power supply... This method may be used to transmit and receive power between vehicles. Furthermore, the exterior of the vehicle Solar panels may be installed to charge the secondary battery when the vehicle is stopped or in motion. Electromagnetic induction or magnetic resonance methods can be used to supply power to it.

[0432] Furthermore, Figure 27(C) shows an example of a motorcycle using a secondary battery according to one embodiment of the present invention. Figure 27 The scooter 8600 shown in (C) includes a secondary battery 8602, side mirrors 8601, and turn signals. It is equipped with a light 8603. The secondary battery 8602 supplies electricity to the turn signal light 8603. can.

[0433] Furthermore, the scooter 8600 shown in Figure 27(C) has a secondary battery 860 in the under-seat storage 8604. It can store 2. The secondary battery 8602 can be stored even if the under-seat storage 8604 is small. It can be stored in the under-seat storage compartment 8604. The secondary battery 8602 is removable. When charging, the 8602 secondary battery must be carried indoors, charged, and stored before driving. That's all you need to do.

[0434] According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery is increased. This makes it possible to make the secondary battery itself smaller and lighter. Making the body smaller and lighter contributes to reducing the vehicle's weight, which in turn improves its driving range. It is possible. Furthermore, the secondary battery installed in the vehicle can also be used as a power source for purposes other than the vehicle itself. In this case, for example, it is possible to avoid using commercial power during peak electricity demand. If the use of commercial power can be avoided during peak electricity demand, energy conservation and two It can contribute to reducing carbon dioxide emissions. Furthermore, if the cycle characteristics are good, secondary... Because batteries can be used for extended periods, the amount of rare metals used, including cobalt, can be reduced. It is possible.

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

[0436] In this embodiment, a positive electrode active material according to one aspect of the present invention is prepared, and the positive electrode active material is subjected to STE The results of observations with M, the fast Fourier transform of the TEM images, and energy-dispersive X-rays were obtained. This section explains the results of the analysis (EDX). It also describes the characteristics of a secondary battery using the positive electrode active material. We will explain the results of the evaluation.

[0437] [Fabrication of positive electrode active material] ≪Sample 01≫ In this embodiment, the positive electrode active material of Sample 01 is the first region having It has lithium cobaltate as a composite oxide of lithium and a first transition metal, and the second region It has lithium titanate as the second transition metal oxide, and the third region has Furthermore, a material containing magnesium oxide was prepared as an oxide of a typical element.

[0438] In this embodiment, lithium cobalt oxide particles (manufactured by Nippon Chemical Industrial Co., Ltd., commercial product) were used as the starting material. (Name: C-20F) was used. Therefore, in this embodiment, step 1 described in Embodiment 1 was used. Steps 2 and 13 were omitted. The lithium cobalt oxide particles mentioned above have a particle size of approximately 20 μm. m is the region analyzable by XPS, containing fluorine, magnesium, calcium, sodium, These are lithium cobalt oxide particles containing silicon, sulfur, and phosphorus.

[0439] Next, as step 14, solge to lithium cobalt oxide particles containing magnesium and fluorine. The titanium-containing material was coated using the TTIP method. Specifically, TTIP was dissolved in isopropanol. A solution of TTIP in isopropanol was prepared. Then, lithium cobaltate was added to the solution. The particles were mixed. TTIP is compared to lithium cobalt oxide containing magnesium and fluorine. The mixture was prepared to a concentration of 0.01 ml / g.

[0440] The above mixture was stirred with a magnetic stirrer for 4 hours under conditions of 25°C and 90% RH humidity. Mixed. This process causes hydrolysis and polycondensation reactions to occur between the water in the atmosphere and TTIP. Therefore, a titanium-containing layer is applied to the surface of lithium cobalt oxide particles that contain magnesium and fluorine. It was formed.

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

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

[0443] Next, lithium cobalt oxide particles coated with a titanium-containing material were heated in a muffle furnace. Using this method, the flow rate of dry air is set to 10 L / min, and the temperature is increased to 800°C (heating up at 200°C / hour), and the temperature is maintained. The heating was performed for a duration of 2 hours. Dry air with a dew point of -109°C or lower was used.

[0444] Next, the heated particles were cooled to room temperature. The cooling time from the holding temperature to room temperature was 10 to 1 The process was left for 5 hours. After that, crushing was performed. The crushing was done by sieving. A sieve with a mesh size of 53 μm was used.

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

[0446] ≪Sample 02≫ Sample 02 is a comparative example in which a magnesium-containing material is not coated. Lithium cobalt oxide particles containing cilium and fluorine were prepared by heating them.

[0447] Lithium cobalt oxide particles containing magnesium and fluorine are manufactured by Nippon Chemical Industrial Co., Ltd. (product name; C (-20F) was used.

[0448] These lithium cobalt oxide particles containing magnesium and fluorine were heated. The heating was performed at 800°C. The experiment was conducted using a heating rate of 200°C / hour, a holding time of 2 hours, and an oxygen flow rate of 10 L / min. .

[0449] The heated powder was cooled in the same way as sample 01, and the resulting mixture was sieved. It was used as the most active material.

[0450] Sample 02 has lithium cobalt oxide internally and a region containing magnesium on its surface. It was presumed to be the positive electrode active material.

[0451] ≪Sample 03≫ Sample 03 is a comparative example of a magnesium-free cobalt acid. The material was fabricated by forming a titanium-containing region on thium particles using the sol-gel method, followed by heating.

[0452] Lithium cobalt oxide particles were manufactured by Nippon Chemical Industrial Co., Ltd. (product name: C-10N). This is X Lithium cobalt oxide, in which magnesium is not detected by PS, and fluorine is detected at approximately 1 atomic percent. It is a particle.

[0453] For these lithium cobalt oxide particles, titanium was added using the sol-gel method, similar to Sample 01. The containing region was formed, dried, heated, cooled, and sieved. This was the correct sample for sample 03. It was used as the most active material.

[0454] Sample 03 has lithium cobalt oxide internally and a region containing titanium on its surface. It was presumed to be the positive electrode active material.

[0455] ≪Sample 04≫ Sample 04 is used as a comparative example, and lithium cobalt oxide particles are used without heating. I used it as is.

[0456] Lithium cobalt oxide particles were manufactured by Nippon Chemical Industrial Co., Ltd. (product name: C-10N).

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

[0458] ≪Sample 05≫ Sample 05 is a comparative example of cobalt containing magnesium and fluorine. Lithium trioxide particles were used without heating.

[0459] Lithium cobalt oxide particles containing magnesium and fluorine are manufactured by Nippon Chemical Industrial Co., Ltd. (product name; C -20F) was used. In other words, sample 05 is the same as the starting material used in sample 01. That is the case.

[0460] The conditions for 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 examined using an electron microscope (JEM-ARM, manufactured by JEOL Ltd.). Observations were made at 200F (acceleration voltage 200kV). The obtained electron microscope image is shown in Figure 28. As shown in 28, the positive electrode active material has three different regions: the first region 101 and the second region 1 It was thought to have region 02 and a third region 103. The third region 103 is the first region It was observed as a brighter region than region 101 and the second region 102. Also, the first region 101 and The crystal orientation of the second region 102 partially coincides, and the second region 102 and the third region 103 The crystal orientations were partially identical.

[0463] [STEM-FFT] The region indicated by 103FFT in the STEM image shown in Figure 28 is an FFT (Fast Fourier Transform) image. This is shown in Figure 29(A1). Figure 29(A2) shows the center point O of Figure 29(A1) as a cross. This is a diagram showing bright spots A, B, and C circled. Similarly, the FF region shown by 10²FFT. The T-image is shown in Figure 29(B1). Figure 29(B2) shows the center point O of Figure 29(B1) with a cross shape. This is a diagram showing the bright spots A, B, and C circled. It also shows the FF region in the 10¹FFT. The T-image is shown in Figure 29(C1). Figure 29(C2) shows the center point O of Figure 29(C1) with a cross shape. This diagram shows the bright spots A, B, and C circled in the image.

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

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

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

[0467] [EDX] Furthermore, the positive electrode active material of sample 01 was analyzed using high-angle scattering annular dark-field scanning transmission microscopy (HAADF- Figure 30 shows STEM images and elemental mapping images using EDX. Figure 30(A1) HAADF-STEM image, Figure 30(A2) is an oxygen atom mapping image, Figure 30(B1) is a co Figure 30(B2) is a Baltic atom mapping image, Figure 30(C1) is a fluorine atom mapping image. Figure 30(C2) shows a titanium atom mapping image, while Figure 30(C2) shows a magnesium atom mapping image. EDX in Figures 30(A2) to 30(C2) and Figures 31(A2) to 31(C2) In elemental mapping images, values ​​below the detection limit are shown in white, and the image becomes closer to black as the count increases. It indicates that...

[0468] As shown in Figures 30(A2) and 30(B1), the oxygen atom and cobalt atom are at the positive electrode. It was revealed that it is distributed throughout the active material particles. On the other hand, Figure 30(B2), Figure 30( As shown in C1) and Figure 30(C2), fluorine atoms, titanium atoms and magnesium atoms It was revealed that the microorganisms are predominantly located in areas 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. The elemental mapping images are shown in Figure 31. Figure 31(A1) is the HAADF-STEM image, Figure 31 (A2) is an oxygen atom mapping image, Figure 31(B1) is a cobalt atom mapping image, Figure 31 (B2) is a fluorine atom mapping image, Figure 31(C1) is a titanium atom mapping image, Figure 31 (C2) is a magnesium atom mapping image.

[0470] As shown in Figures 31(B2) and 31(C2), in sample 05 which has not been heated... However, it became clear that magnesium and fluorine were somewhat concentrated near the surface. .

[0471] [EDX linear analysis] Furthermore, a linear analysis of the cross-section near the surface of the positive electrode active material of sample 01 was performed using TEM-EDX. The results are shown in Figure 32. Figure 32 shows the outside and inside of the positive electrode active material of sample 01. This graph shows the data detected along the line connecting the parts, with a distance of 0 nm being outside the positive electrode active material. A distance of 14 nm is inside the particle. EDX tends to have a wide analytical area, so electron beam irradiation In some cases, elements can be detected not only in the center but also in the surrounding area.

[0472] As shown in Figure 32, magnesium and titanium are present near the surface of the positive electrode active material of sample 01. A peak exists, and it is clear that the magnesium distribution is closer to the surface than the titanium distribution. It turned out that the magnesium peak was closer to the surface than the titanium peak. It became clear that cobalt and oxygen are present from the outermost surface of the positive electrode active material particles. This was speculated.

[0473] Note that in Figure 32, fluorine was hardly detected, which is because fluorine is a light element in EDX. This was thought to be because tx is difficult to detect.

[0474] The above STEM images, FFT images, and elemental mapping images using EDX, and EDX linear analysis... Sample 01 is an embodiment of the present invention, having lithium cobalt oxide as the first region. The second region contains lithium, titanium, cobalt, and oxygen, and the third region It was confirmed that the positive electrode active material contains magnesium and oxygen. In Sample 01, it became clear that a portion of the second region and a portion of the third region overlapped. Ta.

[0475] Furthermore, in the graph in Figure 32, the oxygen detection amount is stable at a distance of 4 nm or more. Therefore, in this case... In this example, the average value of the oxygen detected in this stable region is O ave Find the mean O ave 5 0% value, 0.50 ave The distance x of the measurement point that showed the closest measurement value is the particle size of the positive electrode active material. We decided to assume that it was the surface of the child.

[0476] In this embodiment, the average amount of oxygen detected in the range of 4 nm to 14 nm is O ave teeth The value was 674.2. The measurement closest to 337.1, which is 50% of 674.2, was measured. The x-axis of the fixed point was at a distance of 1.71 nm. Therefore, in this embodiment, in the graph of Figure 32... We assumed that the distance of 1.71 nm represents the surface of the particles of the positive electrode active material.

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

[0478] Furthermore, the magnesium concentration is greater than 1 / 5 of the peak at a distance of 4.42 nm, i.e., the positive electrode. The distance was 2.71 nm from the surface of the active material particles. Distances of 4.57 nm or more, i.e., positive electrode active At depths greater than 2.86 nm from the surface of the material particles, the magnesium measurement is 1 / of the peak. The result was less than 5. Therefore, sample 01 was found to have a depth of 2.71 nm from the surface. It was revealed that it was in the region of 3.

[0479] Furthermore, the titanium concentration is greater than half of the peak from a distance of 2.14 nm to a distance of 3.42 nm. It was up to m. In other words, from the surface of the positive electrode active material particles, it was between 0.43 nm and 1.71 nm. It became clear that the range was the second region.

[0480] Next, a secondary battery was fabricated using the positive electrode active materials of Samples 01 to 05 prepared above. Next, we will explain the results of our evaluation of the charge and discharge characteristics of the secondary battery.

[0481] [Manufacturing of secondary batteries] Using the positive electrode active materials of Samples 01 to 05 prepared above, a CR2032 type A coin-shaped rechargeable battery with dimensions of 20mm in diameter and 3.2mm in height was fabricated.

[0482] The positive electrode contains positive electrode active material (LCO), acetylene black (AB), and polyvinyl fluoride. Den (PVDF) is mixed in LCO:AB:PVDF = 95:2.5:2.5 (by weight ratio) A slurry was used, which was coated onto the current collector.

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

[0484] The electrolyte in the electrolyte solution is 1 mol / L lithium hexafluoride phosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), with vinylene carbonate (VC) mixed at 2% by weight. They used something.

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

[0486] [Evaluation of charge / discharge characteristics] Next, we will evaluate the charge and discharge characteristics of the secondary batteries of Sample 01 and Sample 05 prepared above. The measurement was performed. The measurement temperature was set to 25℃. Charging was performed at 4.6V (CCCV, 0.5C, cutoff voltage). The current was 0.01C, and the discharge was 2.5V (CC, 0.5C), with each undergoing 20 charge-discharge cycles. I did it. Note that 1C here refers to the current value per unit weight of positive electrode active material, which is 137 mA / g. .

[0487] Figure 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 33, it exhibited good charge-discharge characteristics with a wide plateau. Also, 20 cycles The charge and discharge graphs almost overlapped, indicating good cycle characteristics.

[0488] Figure 34 shows a graph of the charge-discharge characteristics of the secondary battery of comparative example sample 05. In the first cycle, it showed good charge / discharge characteristics, but as the arrows in the figure indicate, The charge / discharge capacity has 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 are as follows: The performance was evaluated. The cycle characteristic measurement temperature was set to 25°C. Charging was performed at 4.4V (CCCV, 0. Discharge was performed at 2.5V (CC, 0.5C) with a cutoff current of 0.01C.

[0490] Figure 35 shows a graph of the cycle characteristics when charged at 4.4V. The solid line in the figure represents sample 0 1. The dotted line is a graph of a secondary battery with the positive electrode active material of sample 05. As shown in Figure 35. The secondary battery containing sample 01 maintained its energy density even after 50 cycles. The figure was 99.5%, indicating extremely good cycle characteristics. On the other hand, sample 05 had The rechargeable battery maintained an energy density of 94.3% after 50 cycles.

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

[0492] Figure 36 shows a graph of the cycle characteristics when charged at 4.6V. As shown in Figure 36, A secondary battery having sample 01, which is a positive electrode active material according to one aspect of the invention, has a high voltage of 4.6V. Even after 50 cycles of voltage charging and discharging, the energy density retention rate is 94.1%, which is extremely impressive. It showed good cycle characteristics. On the other hand, the positive electrode active material of comparative examples Samples 02 to 04 The quality of the secondary battery was inferior to that of sample 01, for example, in the case of sample 04, 50 cycles The energy density maintenance rate after the test was 33.2%.

[0493] Thus, the configuration of the positive electrode active material in one aspect of the present invention is charged at a high voltage exceeding 4.4V. It was found that the device exhibits a remarkable effect when discharged. [Examples]

[0494] In this embodiment, a positive electrode active material according to one aspect of the present invention was prepared and subjected to a different analysis than in Example 1. The results will be explained. Furthermore, the characteristics of the secondary battery using the positive electrode active material will be described in a manner different from that of Example 1. We will now explain the results of the evaluation under these conditions.

[0495] In this embodiment, the positive electrode active material is a composite acid of lithium and a first transition metal having a first region. It has lithium cobalt oxide as an oxide, and the second region has a second transition metal oxide and Furthermore, it contains lithium titanate, and as an oxide of a typical element in the third region, magnesium oxide. We created a material containing nesium.

[0496] [Fabrication of positive electrode active material, fabrication of secondary batteries] ≪Sample 06, Sample 07≫ In this embodiment, lithium cobalt oxide particles (manufactured by Nippon Chemical Industrial Co., Ltd., commercial product) were used as the starting material. (Name: C-20F) was used.

[0497] Next, in step 14, the lithium cobalt oxide particles are coated with titanium oxide by the sol-gel method. Turn over and dry. Add TTIP to lithium cobalt oxide at a concentration of 0.004 ml / g. The procedure was the same as in Example 1, except that it was mixed with the other material. After coating with titanium oxide, heating Let's refer to the lithium cobalt oxide particles before processing as Sample 06.

[0498] Next, the lithium cobalt oxide particles coated with titanium oxide from sample 06 were heated. Using a flue furnace, the sample was heated in an oxygen atmosphere at 800°C for 2 hours, with an oxygen flow rate of 10 Set to L / min.

[0499] The positive electrode active material was then cooled and recovered in the same manner as in Example 1 to obtain the positive electrode active material. Let's call this sample 07.

[0500] [TEM-EDX] Regarding samples 06 and 07, in particular, cracks that occurred in the particles and around them Therefore, we performed the analysis using TEM-EDX.

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

[0502] Figure 37 shows the TEM-EDX analysis results of sample 06 before heating. Figure 37(A) shows the grains. This is a cross-sectional TEM image including the subsurface and the crack. It is indicated by the circle labeled 1 in Figure 37(A). Figure 37(B1) shows the HAADF-STEM image of the region including the particle surface, and the Ti mapping image. This is shown in Figure 37(B2). Similarly, the crack portion indicated by the circle labeled 2 in Figure 37(A) Figure 37(C1) shows a HAADF-STEM image of the region with a depth of approximately 20 nm from the surface. The Ti mapping image is shown in Figure 37(C2). The circle labeled 3 in Figure 37(A) is the one shown. Figure 3 shows a HAADF-STEM image of the rack region at a depth of approximately 500 nm from the surface. In Figure 37(D2), the Ti mapping image is shown in Figure 37(D1). The part labeled 4 in Figure 37(A) is shown. The circled area shows the HAADF-S region within the crack, with a depth of approximately 1000 nm from the surface. The TEM image is shown in Figure 37(E1), and the Ti mapping image is shown in Figure 37(E2). In the EDX elemental mapping image in Figure 40, values ​​below the detection limit are shown in black, and the count is The more there is, the closer it gets to white.

[0503] Figure 38 shows the TEM-EDX analysis results of sample 07 after heating. Figure 38(A) shows the grains. This is a cross-sectional TEM image including the subsurface and the crack. It is indicated by the circle labeled 1 in Figure 38(A). Figure 38(B1) shows the HAADF-STEM image of the region including the particle surface, and the Ti mapping image. This is shown in Figure 38(B2). Similarly, the crack portion indicated by the circle labeled 2 in Figure 38(A) Figure 38(C1) shows a HAADF-STEM image of the region with a depth of approximately 20 nm from the surface. The Ti mapping image is shown in Figure 38(C2). The circle labeled 3 in Figure 38(A) is the one shown. Figure 3 shows a HAADF-STEM image of the rack region at a depth of approximately 500 nm from the surface. In Figure 38(D2), the Ti mapping image is shown in Figure 38(D1). The part labeled 4 in Figure 38(A) is shown. The circled area shows the HAADF-S region within the crack, with a depth of approximately 1000 nm from the surface. The TEM image is shown in Figure 38(E1), and the Ti mapping image is shown in Figure 38(E2).

[0504] As shown in Figures 37 and 38, titanium is segregated on the particle surface in sample 06 before heating. Although some signs of segregation were observed, no segregation was confirmed in the cracked areas. On the other hand, after heating... In sample 07, segregation was observed in titanium both on the particle surface and in the cracked areas. In other words, it became clear that heating causes titanium to segregate at the interface of the crack.

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

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

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

[0508] As shown in Figures 39 and 40, magnesium was present on the particle surface of sample 06 before heating. No segregation was observed in either the rack or the sample. On the other hand, in sample 07 after heating, magnesium Segregation was observed in both the particle surface and the cracked areas.

[0509] Next, to quantify titanium and magnesium, we will use the circles labeled 1 to 6 in Figure 37(A). EDX point analysis was performed on the region and the regions indicated by circles labeled 1 to 6 in Figure 38(A). Measurements were taken at two locations within each region.

[0510] Figure 41 shows the results of the EDX point analysis, expressed as the atomic ratio of titanium to cobalt. Figure 41(A) This is the result for sample 06 before heating. The detection locations 1 to 6 in Figure 41(A) are respectively This is the area indicated by the circles labeled 1 to 6 in Figure 37(A). Figure 41(B) shows the results after heating. This is the result of Sample 07. The detection locations 1 to 6 in Figure 41(B) correspond to Figure 38( A) Within the area indicated by the circles labeled 1 to 6.

[0511] As shown in Figure 41, the Ti / Co ratio was 0 at all measurement points in the crack area of ​​sample 06. It was less than 0.01. On the other hand, in the cracked area of ​​sample 07, there were many areas where the amount of titanium increased. Furthermore, there were measurement points where the Ti / Co ratio was 0.05 or higher. Also, on the particle surface of sample 07 The Ti / Co ratio was between 0.10 and 0.18.

[0512] Next, Figure 42 shows the results of the EDX point analysis, expressed as the atomic ratio of magnesium to cobalt. The location is the same as in Figure 41.

[0513] As shown in Figure 42, in sample 06, Mg / was present in both the particle surface and the cracked area. The Co content was 0.03 or less. On the other hand, in sample 07, both the particle surface and the crack area contained magnesium. There were many areas where the amount of cium had increased. The Mg / Co ratio on the particle surface was 0.15-0.50. The values ​​were in between, and in the cracked areas, they ranged from 0 to 0.22.

[0514] Next, using the positive electrode active material of sample 07 after heating, a CR2032 type coin-type secondary electrode is used. A battery was fabricated. The positive electrode used the positive electrode active material (LCO) from sample 02, along with AB and polyfluorine. Mix vinylidene ferric acid (PVDF) in a ratio of LCO:AB:PVDF = 95:3:2 (by weight). A slurry was used, coated onto the positive electrode current collector. The positive electrode current collector was made of aluminum with a thickness of 20 μm. A nium foil was used. The amount of positive electrode active material, AB, and PVDF supporting the positive electrode active material layer was 7. 6 mg / cm³ 2 That's what I decided.

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

[0516] The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC) at EC: A mixture of DEC=3:7 (volume ratio) was prepared by dissolving 1 mol / L of LiPF6 in it. A solution containing 2 wt% nylene carbonate (VC) 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 The performance characteristics were measured.

[0518] Initial characteristics were measured under CCCV, 0.2C, 4.6V, and a cutoff current of 0.05C. I did it. The discharge was performed with CC, 0.2C, and a cutoff voltage of 3.0V. Note that 1C here is The current value per unit weight of positive electrode active material was set to 160 mA / g. The measurement temperature was 25°C. Initial The results of the characteristic measurements are shown in Table 2.

[0519] [Table 2]

[0520] After initial characteristic measurements, rate characteristics were measured. The discharge rate was varied, and all other characteristics were measured as they were initially. Under the same conditions as the characteristic measurement, 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 Measurements were taken in the following order: 0.2C charge / 4.0C discharge, and 0.2C charge / 5.0C discharge. Measurement temperature The temperature was set to 25℃.

[0521] The results of the initial characteristics and rate characteristics measurements are shown in Table 3. The discharge curves for each rate are also shown in Figure 3. This is shown in section 43.

[0522] [Table 3]

[0523] [Temperature characteristics] Next, the amount of positive electrode active material supported is 8.2 mg / cm³. 2 Other than that, the cells that evaluated the rate were the same. Cells were fabricated under various conditions, and their temperature characteristics were evaluated. All charging was performed at 25°C, using CCCV, 0.2 Discharge was performed at C, 4.6V, and a cutoff current of 0.05C. Discharge was performed at 25℃, 0℃, -10℃, and - The tests were conducted at 20°C and then 45°C, using CC, 0.2C, and a cutoff voltage of 3.0V. Temperature characteristics... The results of the sex measurement are shown in Figure 44.

[0524] [Cycle Characteristics] Next, a cell was created under the same conditions as the cell whose temperature characteristics were measured, and its cycle characteristics were measured. In terms of cycle characteristics, the charge was CCCV, 1.0C, 4.55V, and the cutoff current was 0.05C. The discharge was performed at CC, 1.0C, and a cutoff voltage of 3.0V. The temperature at which the cycle characteristics were measured was The temperature was set to 45°C, and measurements were taken over 100 cycles. The discharge capacity retention rate after 100 cycles was 86%. The measured cycle characteristics are shown in a graph of discharge capacity retention rate in Figure 45. .

[0525] Furthermore, the specific surface area of ​​the positive electrode active material of sample 07 was measured and found to be 0.13 m². 2 / g Ta.

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

[0527] Furthermore, the tap density of the positive electrode active material in sample 07 was 2.21 g / cm³. 3 That was it. Tap close For temperature measurement, a MULTI TESTER MT-1000 (manufactured by Seishin Corporation) was used. .

[0528] As described above, the positive electrode active material of Sample 07, which is one embodiment of the present invention, exhibits good initial characteristics and It was revealed that the initial charge-discharge efficiency is particularly important. The high percentage of over 98% suggested that side effects were suppressed. Furthermore, the high 2C value was also observed. In terms of discharge rate, it showed excellent capacity, achieving 96.1% of the 0.2C standard. [Examples]

[0529] In this embodiment, regarding a positive electrode active material having a region containing titanium and magnesium in its surface layer, The following shows the results of evaluating the properties of samples prepared by varying the ratio of Li / first transition metal in the starting material.

[0530] [Fabrication of positive electrode active material] In this example, cobalt was used as the first transition metal in samples 11 to 17. We prepared positive electrode active materials for samples 21-28 and 31-40. The sample preparation method and conditions were as follows:

[0531] ≪Samples 11-17≫ First, the starting materials are lithium, cobalt, magnesium, and fluorine sources. The weights were then weighed. In this embodiment, lithium carbonate was used as the lithium source and cobalt oxide as the cobalt source. Magnesium oxide is used as the magnesium source, and fluoride is used as the fluorine and lithium source. They used lithium.

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

[0533] Also, common to samples 11 to 17 is the number of cobalt atoms contained in the starting material. When the ratio is set to 1, the number of magnesium atoms becomes 0.01 and the number of fluorine atoms becomes 0.02. The sea urchins were weighed.

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

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

[0536] In the above process, particles of a composite oxide containing lithium, cobalt, fluorine, and magnesium are combined. I did it.

[0537] Next, 2-propanol has a TTIP of 0.01 ml / g per unit weight of positive electrode active material. Add TTIP and mix to make a 2-propanol solution of tetra-i-propoxytitanium. I made it.

[0538] In this 2-propanol solution of TTIP, lithium, cobalt, fluorine, and magnesium are added. Particles of the composite oxide were added and mixed.

[0539] The above mixture was stirred with a magnetic stirrer for 4 hours under conditions of 25°C and 90% RH humidity. The mixture was stirred. This process caused hydrolysis and polycondensation reactions between the water in the atmosphere and TTIP. A layer containing titanium is formed on the surface of lithium cobalt oxide particles that have magnesium and fluorine. This formed.

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

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

[0542] The dried powder was heated. Heating was performed at 800°C (increase of temperature by 200°C per hour), and the holding time was 2 hours. The procedure was performed under an oxygen atmosphere.

[0543] The heated powder was cooled and then crushed. The crushing process was carried out by sieving. A sieve with a mesh size of 53 μm was used.

[0544] The particles that had undergone the crushing process were used as the positive electrode active material for samples 11 to 17.

[0545] Samples 21-27 Samples 21-27 use the same starting materials as samples 11-16. There he 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 21-27 show the concentration of the 2-propanol solution of TTIP as the positive electrode active material weight. Aside from ensuring the TTIP per unit volume was 0.02 ml / g, the rest of the sample was from Sample 11 to Sample It was made in the same way as item 17.

[0547] ≪Sample 28≫ Sample 28 used the same Li / Co ratio and TTIP amount for the starting materials as Sample 23. In other words, sample 28 was weighed so that the Li / Co ratio of the starting materials was 1.05, and the positive electrode The TTIP per unit weight of active material was set to 0.02 ml / g.

[0548] However, in sample 28, the starting materials were mixed and then fired at 950°C.

[0549] Aside from the firing temperature, it was prepared in the same manner as Sample 23.

[0550] Samples 11-17 and 21-28 have lithium cobalt oxide inside, and the surface layer It was inferred that the positive electrode active material has regions containing titanium and magnesium.

[0551] ≪Samples 31-40≫ Samples 31 to 40 were prepared without forming a titanium-containing region as comparative examples.

[0552] Sample 31 was weighed so that the Li / Co ratio of the starting materials was 1.00. Sample 3 Sample 2 was weighed so that the Li / Co ratio of the starting material was 1.01. Sample 33 was the starting material. The raw materials were weighed so that the Li / Co ratio was 1.02. Sample 34 was made from the starting material Li The weight was measured so that the Li / Co ratio was 1.03. Sample 35 had a Li / Co ratio of starting material. The weight was measured to achieve 1.035. Sample 36 had a Li / Co ratio of 1.04 in its starting material. The weight was measured to achieve the following. Sample 37 has a Li / Co ratio of 1.051 in its starting materials. The sea urchins were weighed. 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] Furthermore, common to samples 31 to 40 is the number of cobalt atoms contained in the starting material. When the ratio is set to 1, the number of magnesium atoms becomes 0.01 and the number of fluorine atoms becomes 0.02. The sea urchins were weighed.

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

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

[0556] In the above process, particles of a composite oxide containing lithium, cobalt, fluorine, and magnesium are combined. I did it.

[0557] The synthesized particles were cooled and then heated. The heating was at 800°C (200°C / hour), and then maintained. The exercise was conducted under an oxygen atmosphere with a time limit of 2 hours.

[0558] The heated powder was cooled and then crushed. The crushing process was carried out by sieving. A sieve with a mesh size of 53 μm was used.

[0559] The particles that had undergone the crushing process were used as the positive electrode active material for samples 31 to 40.

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

[0561] [Table 4]

[0562] [XPS] Samples 11-17, 21-28, 31-4 XPS analysis was performed on the positive electrode active material of sample 0. XPS analysis of samples 11 to 17 Table 5 shows the results of the analysis, Table 6 shows the results of the XPS analysis of samples 21 to 28, and Table 6 shows the results of sample 31 The results of the XPS analysis of sample 40 are shown in Table 7. Note that in Tables 5-7, the concentrations of each element are shown. The relative values ​​are shown with cobalt set to 1.

[0563] [Table 5]

[0564] [Table 6]

[0565] [Table 7]

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

[0567] First, looking at samples 31 to 40 in Figure 46(A), we can see the case where there is no coating layer containing titanium. In addition, magnesium concentration was high in samples with a Li / Co ratio of 1.00 to 1.05. It became clear that heating causes the magnesium contained in the starting material to This is thought to be because the elemental concentrations were segregated to a range detectable by XPS. On the other hand, the Li / Co ratio If the ratio is 1.06 or higher, the magnesium concentration will be low, and if lithium becomes excessive, the magnesium will be too high. It was hypothesized that this would make segregation of cium less likely to occur.

[0568] Also, from samples 11 to 16 and samples 21 to 26 in Figure 46(A) If the surface layer contains a region with titanium, the elemental concentration can be detected by XPS more easily than if it does not. It became clear that magnesium concentrations were elevated within a certain range.

[0569] Furthermore, if the Li / Co ratio is 1.06 and there is no region containing titanium, the original XPS will be used. While the magnesium concentration within the detectable range is low, the concentration of titanium is low. In samples with a region, the magnesium concentration in the range detectable by XPS is high. In other words, by forming a region containing titanium in the surface layer, when the Li / Co ratio is high... However, it became clear that sufficient segregation of magnesium occurred.

[0570] Even if it contains a region with titanium, if the Li / Co ratio is 1.07, it is different from when it is 1.06. The magnesium concentration also decreased. Furthermore, if the Li / Co ratio is 1.08 or higher, titanium is used. It was hypothesized that even if a region containing magnesium is present, magnesium segregation would be less likely to occur.

[0571] [Evaluation of cycle characteristics] Energy density maintenance rate Next, samples 11-14, sample 16, and samples 21-24, The cycle characteristics were evaluated using the positive electrode active material of Sample 26 in the same manner as in Example 1.

[0572] The shape of the secondary battery, the positive electrode active material in the positive electrode, the conductive additive, the binder material and mixing ratio, The electrodes, electrolyte, casing, and cycle characteristic test conditions were the same as in Example 1.

[0573] Figure 47(A) shows the preparation so that the TTIP per unit weight of positive electrode active material is 0.01 ml / g. The secondary battery using the positive electrode active materials of samples 11-14 and 16 was described in section 4. Figure 47(B) shows a graph of the energy density retention rate and the number of charge / discharge cycles when charging at 6V. Sample 21 was prepared so that the TTIP per unit weight of positive electrode active material was 0.02 ml / g. ~Energy of secondary batteries using the positive electrode active materials of Sample 24 and Sample 26 when charged at 4.6V The graph shows the energy density maintenance rate and the number of charge / discharge cycles.

[0574] As is clear from Figure 47(A), when TTIP is 0.01 ml / g, sample 11~ Sample 14, that is, the positive electrode active material with a Li / Co ratio of 1.00 to 1.06, is a good sample. The characteristics were observed, particularly in samples 11 and 12, i.e., when the Li / Co ratio was 1. Positive electrode active materials with a capacitance between 0.00 and 1.03 showed extremely good cycle characteristics. On the other hand, Li In sample 16, where the / Co ratio was 1.08, the energy density maintenance rate deteriorated relatively early. He was.

[0575] Furthermore, as is clear from Figure 47(B), when TTIP is 0.02 ml / g, Sample 2 Samples 1 through 24, i.e., positive electrode active materials with a Li / Co ratio between 1.00 and 1.06, are good. It showed excellent cycle characteristics, particularly in samples 23 and 24, i.e., Li / Co ratio. Positive electrode active materials with a coefficient between 1.05 and 1.06 showed extremely good cycle characteristics.

[0576] Figure 48 shows the sample that exhibited the best cycle characteristics among samples 11 to 15. Sample 11 and Sample 2, which showed the best cycle characteristics among Samples 21-25. A graph comparing option 3 is shown.

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

[0578] ≪Discharge capacity maintenance rate≫ Next, for samples 21 to 26 and sample 28, the discharge capacity retention rate was measured by s The results of the evaluation of the cruising characteristics are shown in Figure 49.

[0579] The shape of secondary batteries in samples 21 to 26, the positive electrode active material, conductive additive, and The materials and mixing ratios of the industrial components, counter electrode, electrolyte, casing, and cycle performance test conditions are described in the examples. It was treated the same as 1.

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

[0581] As is clear from Figure 49, samples 21-24 and sample 28 are good. The cycle characteristics were shown. In particular, sample 28 showed extremely good cycle characteristics. In Sample 28, the discharge capacity retention rate after 50 cycles was 85% or higher.

[0582] On the other hand, samples 25 and 26, which have Li / Co ratios of 1.07 and 1.08, The discharge capacity retention rate began to deteriorate relatively early on.

[0583] Based on the above results, a TTIP of 0.02 ml / g per unit weight of positive electrode active material is preferable. It was revealed that the Li / Co ratio range is between 1.00 and less than 1.07. Furthermore, A Li / Co ratio in the range of 1.05 to 1.06 exhibits extremely good cycle characteristics. It became clear that...

[0584] Figure 49 shows that samples 28 and 24, and relatively, exhibited extremely good cycle characteristics. Figure 50 shows the charge-discharge curve of a secondary battery using sample 25, which showed deterioration at an early stage. vinegar.

[0585] Figure 50(A) is sample 28, Figure 50(B) is sample 24, and Figure 50(C) is sample 2 This is the charge-discharge curve of a secondary battery using 5. The results of 50 charge-discharge cycles are shown. As shown by the arrows in the diagram, the charge and discharge capacity increases from the 1st cycle to the 50th cycle. The quantity is decreasing.

[0586] As shown in Figures 50(A) and 50(B), the positive electrode active material of one embodiment of the present invention is Sun Pull 28 and Sample 24 showed high charge / discharge capacity and good charge / discharge characteristics. Compared to sample 25 in Figure 50(C), sample 2 in Figures 50(A) and 50(B) Samples 8 and 24 showed a significant reduction in the decrease in charge / discharge capacity. [Examples]

[0587] In this example, the cathode active material of sample 24 prepared in Example 2 was observed using SEM and This section explains the results of the SEM-EDX analysis.

[0588] Sample 24 has a Li / Co ratio of 1.06 and a TTIP of 0.02 m³ per unit weight of positive electrode active material. This sample was prepared to achieve a concentration of l / g. The SEM image of sample 24 is shown in Figure 51(A). Figures 51(B) and 51(C) show enlarged images of a portion of Figure 51(A).

[0589] As is clear from Figure 51, numerous convex regions were present on the surface of the positive electrode active material.

[0590] Next, Figure 52 shows the results of analyzing the positive electrode active material of sample 24 using SEM-EDX. As shown below. 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 titanium. Mapping, Figure 52(B-1) shows the mapping of magnesium, Figure 52(B-2) shows the mapping of oxygen Mapping, Figure 52(C-1) shows the mapping of aluminum, Figure 52(C-2) shows the mapping of cobalt This is a mapping of elements. Note that in the EDX elemental mapping image in Figure 52, elements below the detection limit are... The combined pieces are indicated by black, and the more the count increases, the closer they are to white.

[0591] The same area in Figures 52(A-1), 52(A-2), and 52(B-1) is enclosed by a dotted line. As is clear from comparing the areas enclosed by the dotted lines, the convex region on the surface of the positive electrode active material has Titanium and magnesium were distributed in the area.

[0592] Therefore, sample 24 has titanium and magnesium on the third region 103. It was confirmed that the positive electrode active material has a convex fourth region 104.

[0593] As shown in Example 2, Sample 24 exhibited extremely good cycle characteristics. There is one. Therefore, even if a fourth region exists in the surface layer, or if a fourth region exists This revealed that a positive electrode active material exhibiting good cycle characteristics can be obtained.

[0594] From the results of Examples 1 to 3 above, by forming a region containing titanium in the surface layer, It was revealed that a positive electrode active material exhibiting good cycle characteristics can be obtained. Increasing the Li / Co ratio to improve particle size quality raises concerns about degraded cycle characteristics. However, by forming a titanium-containing region on the surface, good cycle characteristics can be obtained. It was revealed that the range of the Li / Co ratio can be widened. In addition, the surface layer of the positive electrode active material was found to be Even with the presence of a fourth region containing tan and magnesium, it exhibits good cycle characteristics. This became clear. [Examples]

[0595] This example shows an example of a method for producing a positive electrode active material coated with graphene oxide. This section describes the results of observing the positive electrode active material, fabricated by the method, using an electron microscope.

[0596] As shown in the process flow diagram in Figure 53, the process of forming a film on the positive electrode active material is (S11) oxide Weighing of graphene, (S12) mixing and stirring of graphene oxide and pure water, (S13) pH Control, (S14) Addition of active material, (S15) Completion of suspension, (S16) Spray drying This includes (S17) spraying the suspension using the apparatus and recovering the powder into a container.

[0597] In (S12), pure water is used as the dispersion medium, but it is not particularly limited and ethanol can be used. Any of these may be used. Also, in (S14), the active material shall be the positive electrode active material.

[0598] A schematic diagram of the spray drying apparatus 280 is shown in Figure 54. The spray drying apparatus 280 is a chang It has a bar 281 and a nozzle 282. The nozzle 282 is supplied with a suspension via a tube 283. Liquid 284 is supplied. The suspension 284 is sprayed from the nozzle 282 into the chamber 281. It is supplied and dried in chamber 281. The nozzle 282 is heated by heater 285. It may be heated. Here, the heater 285 heats the nozzle 282 out of the chamber 281. Regions close to the heating element, such as the area enclosed by the dashed line in Figure 54, are also heated.

[0599] Here, if a suspension containing the positive electrode active material and graphene oxide is used as suspension 284, oxidation The graphene-coated positive electrode active material powder is returned to the recovery container 286 via the chamber 281. It will be collected.

[0600] Here, the atmosphere inside chamber 281 is directed to the aspirator, etc., via the path shown by arrow 288. It may be better to use more suction.

[0601] The following is an example of film formation conditions.

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

[0603] Pure water has high dispersibility as a dispersion medium for graphene oxide, but the active material that will be added later... Depending on the material, it may react with the positive electrode active material, causing Li to leach out or altering the surface structure of the positive electrode active material. There is a risk of causing damage. Therefore, the ratio of ethanol to pure water should be 4:6. Then, graphene oxide was dispersed in the liquid.

[0604] For stirring to disperse in the liquid, a stirrer and an ultrasonic generator are used, and the rotation speed is The ultrasonic wave was applied at 750 rpm for 2 minutes.

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

[0606] Positive electrode active material (In this example, lithium cobalt oxide particles manufactured by Nippon Chemical Industrial Co., Ltd. (product name) Add :C-20F)) and stir using a stirrer and ultrasonic generator, rotation speed The suspension was prepared by the above process. Lithium cobalt oxide particles (product name: C-20F) manufactured by Chemical Industry Co., Ltd. contain at least fluorine Cobalt oxide containing ammonium compounds, magnesium, calcium, sodium, silicon, sulfur, and phosphorus. These are thium particles with a particle size of approximately 20 μm.

[0607] Next, using a spray drying device, the suspension is sprayed with a spray nozzle (nozzle diameter 20 μm). The powder was obtained by uniform spraying. The hot air temperature of the spray dryer was 16 degrees Celsius at the inlet. The temperature was set to 0°C, the outlet temperature to 40°C, and the N2 gas flow rate to 10 L / min.

[0608] Figure 55 shows a cross-sectional TEM image of the resulting powder. Figure 56 shows an SEM image. This will be shown. Also, as a comparative example, the same cathode active material as that spray-dried (Nippon Chemical Industries, Ltd.) will be shown. Using C-20F manufactured by Co., Ltd. as a raw material, it is mixed with graphene oxide using a rotation-orbit mixer. The coating was found to be insufficient. A SEM image of the comparative example is shown in Figure 57.

[0609] Compared to Figure 57, Figure 56 shows that the coating on the surface of the powder is more uniform. I understand.

[0610] After coating with graphene oxide using a spray drying device, the graphene oxide-covered An example of a cross-sectional configuration when a graphene compound is further used as a conductive additive in the active material layer 200. This is explained in Figure 58.

[0611] Figure 58(A) shows a longitudinal cross-sectional view of the active material layer 200. The active material layer 200 is graphene oxide. A granular positive electrode active material 100 covered with a material, a graphene compound 201 as a conductive additive, and It includes inda (not shown) and, where graphene compound 201 is, for example, graphene You can use either graphene or multigraphene. Here, graphene compound 201 is in sheet form. It is preferable that the graphene compound 201 has the shape of multiple multigraphs. Graphene, or / or multiple graphenes, may be partially overlapping to form a sheet. .

[0612] In the longitudinal section of the active material layer 200, as shown in Figure 58(B), it is made of graphene oxide. The image shows the positive electrode active material 100, covered with a coating 105, in contact with the graphene compound 201. This represents the multiple graphene compounds 201 covering the positive electrode active material 10 with a coating 105. It is formed to be in partial contact with 0 and to adhere to the coating 105 of the adjacent positive electrode active material 100. And they are in contact with each of them.

[0613] Since graphene compound 201 and coating 105 are both carbon-based materials, they provide excellent conductive paths. It can be formed.

[0614] The coating 105 has the effect of protecting the crystal structure of the positive electrode active material 100 so that it does not come into contact with the electrolyte, It has the effect of forming excellent conductive paths. [Explanation of Symbols]

[0615] 11a positive electrode 11b negative electrode 12a Lead 12b Lead 14 Separator 15a Joint 15b Joint 17 Fixing member 50 Secondary battery 51 Exterior 61 Folding section 62 Seal part 63 Seal part 71 Ridge 72 Valley Line 73 Space 100 Cathode active material 101 areas 101p crystal plane 102 areas 102p crystal face 103 areas 103p crystal plane 104 areas 105 Coating 106 Crack section 110 particles 111 areas 112 layers 114 Cobalt Oxide Layer 120 particles 121 areas 122 layers 124 Cobalt Oxide Layer 125 layers 200 Active material layer 201 Graphene Compounds 214 Separator 280 Spray Drying Equipment 281 Chamber 282 nozzles 283 Tube 284 suspension 285 Heater 286 Collection containers 288 Arrows 300 Secondary battery 301 Positive electrode can 302 Negative electrode can 303 Gasket 304 Positive electrode 305 Positive electrode current collector 306 Positive electrode active material layer 307 Negative electrode 308 Negative electrode current collector 309 Negative electrode active material layer 310 Separator 500 secondary battery 501 Positive electrode current collector 502 Positive electrode active material layer 503 Positive electrode 504 Negative electrode current collector 505 Negative electrode active material layer 506 negative electrode 507 Separator 508 Electrolyte 509 Exterior 510 Positive lead electrode 511 Negative lead electrode 600 Secondary battery 601 Positive Cap 602 Battery Can 603 Positive terminal 604 Positive electrode 605 Separator 606 negative electrode 607 Negative terminal 608 Insulating board 609 Insulating board 611 PTC element 612 Safety valve mechanism 613 Conductive plate 614 Conductive plate 615 modules 616 Conductor 617 Temperature control device 900 Circuit Boards 910 Labels 911 terminal 912 Circuit 913 Secondary battery 914 Antenna 915 Antenna 916 layers 917 layers 918 Antenna 920 Display device 921 Sensor 922 terminals 930 cabinets 930a enclosure 930b enclosure 931 negative electrode 932 Positive electrode 933 Separator 950 Wound body 951 terminal 952 terminals 980 Secondary battery 981 film 982 film 993 Wound body 994 negative electrode 995 positive electrode 996 Separator 997 Lead Electrode 998 Lead Electrode 7100 Portable Display Device 7101 enclosure 7102 Display section 7103 Operation Buttons 7104 Secondary battery 7200 Mobile Information Terminal 7201 enclosure 7202 Display section 7203 Band 7204 Buckle 7205 Operation Buttons 7206 Input / output terminal 7207 Icons 7300 display device 7304 Display section 7400 mobile phones 7401 enclosure 7402 Display section 7403 Operation Buttons 7404 External connection port 7405 Speaker 7406 Microphone 7407 Secondary battery 7408 Lead Electrode 7409 Current collector 7500 e-cigarettes 7501 Atomizer 7502 Cartridge 7504 Secondary battery 8000 display device 8001 enclosure 8002 Display section 8003 Speaker section 8004 Secondary battery 8021 Charging device 8022 Cable 8024 Secondary battery 8100 Lighting device 8101 enclosure 8102 Light source 8103 Secondary battery 8104 Ceiling 8105 Side wall 8106 floor 8107 Window 8200 indoor unit 8201 enclosure 8202 Air vent 8203 Secondary battery 8204 Outdoor unit 8300 Electric Refrigerator / Freezer 8301 enclosure 8302 Refrigerator door 8303 Freezer door 8304 Secondary battery 8400 automobiles 8401 Headlight 8406 Electric motor 8500 automobiles 8600 Scooter 8601 Side Mirror 8602 Secondary battery 8603 Turn signal light 8604 Under-seat storage 9600 Tablet devices 9625 Switch 9626 Switch 9627 Power switch 9628 Operation switch 9629 Fastener 9630 cabinet 9630a enclosure 9630b enclosure 9631 Display section 9631a Display section 9631b Display section 9632a area 9632b area 9633 Solar Cell 9634 Charge / Discharge Control Circuit 9635 Energy Storage Unit 9636 DC-DC converter 9637 Converter 9638 Operation Keys 9639 button 9640 Moving parts

Claims

1. The positive electrode comprises multiple positive electrode active material particles and a conductive additive. The positive electrode active material particles have lithium cobalt oxide, The positive electrode active material particles have magnesium, titanium, and fluorine in their surface layer. The positive electrode active material particles have a rock salt-type crystalline structure in the surface layer and a layered rock salt-type crystalline structure in the interior. The positive electrode active material particles have a region in which the orientation of the crystals having the rock salt type crystal structure in the surface layer and the orientation of the crystals having the layered rock salt type crystal structure in the interior are substantially the same. The conductive additive comprises a graphene compound, A lithium-ion secondary battery wherein a portion of the graphene compound is provided to cover the surface of the positive electrode active material particles.

2. The positive electrode comprises multiple positive electrode active material particles and a conductive additive. The positive electrode active material particles have lithium cobalt oxide, The positive electrode active material particles have magnesium, titanium, and fluorine in their surface layer. The positive electrode active material particles have a rock salt-type crystalline structure in the surface layer and a layered rock salt-type crystalline structure in the interior. The positive electrode active material particles have a region in which the orientation of the crystals having the rock salt type crystal structure in the surface layer and the orientation of the crystals having the layered rock salt type crystal structure in the interior are roughly coincide. The conductive additive comprises a graphene compound, A lithium-ion secondary battery in which a portion of the graphene compound is provided so as to adhere to the surface of the positive electrode active material particles.

3. In claim 1 or claim 2, The graphene compound is a lithium-ion secondary battery having graphene.

4. In any one of claims 1 to 3, A lithium-ion secondary battery in which a portion of the graphene compound is in surface contact with the positive electrode active material particles.

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