Lithium-ion secondary battery

Abstract

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

Description

[Technical field]

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

[0002] In this specification, the term "electricity storage device" refers to elements and devices having an electricity storage function in general. For example, lithium ion secondary batteries and other storage batteries (also called secondary batteries) These include lithium ion capacitors and electric double layer capacitors.

[0003] In addition, in this specification, the term "electronic device" refers to any device having a power storage device. Electro-optical devices having a power storage device, and information terminal devices having a power storage device are all electronic devices. [Background technology]

[0004] In recent years, various types of storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have become available. The development of lithium-ion batteries, which have high power and high energy density, is particularly Secondary batteries are used in mobile phones, smartphones, tablets, and notebook computers. Mobile information terminals, portable music players, digital cameras, medical equipment, or hybrid vehicles ( HEV), electric vehicle (EV), or plug-in hybrid vehicle (PHEV), etc. Demand is expanding rapidly along with the development of the semiconductor industry, such as next-generation clean energy vehicles. As a source of rechargeable energy, they have become indispensable in today's information society.

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

[0006] Therefore, we developed a positive electrode active material with the aim of improving the cycle characteristics and increasing the capacity of lithium-ion secondary batteries. Improvements to the material are being considered (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-018914 A [Patent Document 2] JP 2015-201432 A Summary of the Invention [Problem to be solved by the invention]

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

[0009] One embodiment of the present invention is to improve the efficiency of charge / discharge cycles by using the same in a lithium ion secondary battery. Another object of the present invention is to provide a positive electrode active material in which the decrease in the amount of the positive electrode active material is suppressed. Another object of the present invention is to provide a high-capacity secondary battery. Another object of the present invention is to provide a secondary battery having excellent charge and discharge characteristics. An object of the present invention is to provide a secondary battery with high safety and reliability.

[0010] Another embodiment of the present invention is a novel substance, active material particles, secondary battery, or a manufacturing method thereof. One of the objectives is to provide the following.

[0011] The description of these problems does not preclude the existence of other problems. It is not necessary for the embodiment to solve all of these problems. It is possible to extract problems other than those mentioned above from the description of the claim. [Means for solving the problem]

[0012] In order to achieve the above object, one aspect of the present invention provides a positive electrode active material having a surface layer having a different structure from an inner region. The inner region is a nonstoichiometric compound, and the outer region is a stoichiometric compound. It is preferable that there is.

[0013] The inner region preferably comprises titanium and the outer region may comprise magnesium. Moreover, these two regions may overlap.

[0014] The inner region is formed through a coating process such as the sol-gel method, and the outer region is formed by segregation caused by heating. Therefore, it is preferable to form the

[0015] One embodiment of the present invention is a positive electrode active material, the positive electrode active material including a first region, a second region, and and a third region, the first region being present inside the positive electrode active material, and the second region and the third region being present inside the positive electrode active material. The first region is present in the surface layer of the positive electrode active material, and the third region is located closer to the surface of the positive electrode active material than the second region. The first region has an oxide of lithium and a first transition metal and is layered. The first region has a rock-salt crystal structure, and the second region has a non-stoichiometric compound having an oxide of a second transition metal. the non-stoichiometric compound has a rock-salt crystal structure; the third region has compounds of main group elements; The compound of a typical element is a positive electrode active material having a rock salt type crystal structure.

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

[0017] In the above, the third region may have fluorine. The region may comprise cobalt.

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

[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) 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 second region has a {100} plane of a rock-salt type crystal structure. The degree of mismatch of the {100} plane of the rock-salt crystal structure of the third region is 0.12 or less. It is preferred.

[0020] Another embodiment of the present invention is a positive electrode active material, the positive electrode active material being a mixture of lithium and titanium. and a surface layer portion of the positive electrode active material, the surface layer portion of the positive electrode active material being formed of cobalt, magnesium, oxygen, and fluorine. When the concentration of cobalt measured by X-ray photoelectron spectroscopy is taken as 1, the titanium concentration is 0.0. 5 or more and 0.4 or less, magnesium concentration is 0.4 or more and 1.5 or less, and fluoride concentration is is 0.05 or more and 1.5 or less.

[0021] Another aspect of the present invention is a method for producing a lithium-based fluorine-containing gas comprising the steps of: and mixing the mixture of a lithium source, a cobalt source, a magnesium source and a fluorine source. , heated at 800℃ to 1100℃ for 2 hours to 20 hours, and lithium and cobalt obtaining particles having magnesium, oxygen, and fluorine; and The step of dissolving titanium alkoxide in alcohol, and adding lithium and Particles containing cobalt, magnesium, oxygen, and fluorine are mixed together, and water vapor is added. a step of stirring the mixture in an atmosphere containing the precipitate; a step of recovering the precipitate from the mixture; , in an oxygen-containing atmosphere at 500°C to 1200°C for a holding time of 50 hours or less. and a step of forming a positive electrode active material.

[0022] In the above-mentioned manufacturing method, the number of lithium atoms contained in the lithium source and the number of cobalt atoms contained in the cobalt source are The ratio of the number of Li and Co atoms to the number of Li and Co atoms is preferably 1.00≦Li / Co<1.07.

[0023] In the above-mentioned preparation method, the number of fluorine atoms contained in the fluorine source and the number of magnesium atoms contained in the magnesium source are The ratio of the number of magnesium atoms contained is Mg:F=1:x (1.5≦x≦4). is preferred.

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

[0025] In the above-mentioned manufacturing method, lithium carbonate is used as the lithium source, and cobalt oxide 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. Um can be used.

[0026] In addition, the surface of the positive electrode active material is covered with a film to protect the above-mentioned crystal structure, thereby improving the charge / discharge resistance. The film that covers the surface of the positive electrode active material can suppress the decrease in capacity during the cycle. Examples of the coating include a carbon-containing film (a film containing a graphene compound) and a lithium or A coating having a decomposition product of the electrolyte is used.

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

[0028] Repeated charge / discharge cycles can cause cracks or fractures in the particles of the positive electrode active material. Such a change in shape may cause the positive electrode active material to be broken. When a new surface of the material is exposed, it comes into contact with the electrolyte and a decomposition reaction occurs, resulting in the formation of a second It is said that the cycle characteristics and charge / discharge characteristics of the battery are deteriorated.

[0029] This prevents the particles of the positive electrode active material from cracking or changing shape, such as by breaking. It is preferable to provide a coating film capable of preventing the adhesion of the resin.

[0030] However, the surface of the positive electrode active material, which has a heavy weight per unit volume, is relatively heavy. To coat the light amount of graphene oxide, a suspension was prepared and mixed with a rotating / revolving mixer. However, the coating was insufficient.

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

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

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

[0034] When the nozzle diameter of the spray dryer is set to be approximately the same as the maximum particle diameter of the active material, This is preferable because the coating of the material is good. Furthermore, the positive electrode is preferably made to have a diameter approximately equal to 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] Graphene oxide disperses well in water, so ultrasonic stirring is used to disperse the water and graphene oxide. A suspension of phenanthrene can be prepared. A positive electrode active material is added to the suspension, and the suspension is used to By spraying the graphene oxide on the surface of the positive electrode active material using a spray dryer, A coated powder can be obtained.

[0036] In addition, the suspension becomes more acidic as the amount of graphene oxide increases. There is a risk of etching part of the surface of the material (e.g., LiCoO2 containing Mg or F). Therefore, the pH of the suspension before spraying is adjusted to approximately pH 7. It is preferable to make the pH close to neutral, or to make the pH 8 or higher, i.e., alkaline. For pH adjustment, it is preferable to use an aqueous LiOH solution. When LiCoO2 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. By using the mixed liquid, damage to the surface of the active material may be reduced.

[0037] By preparing the suspension as described above, the surface is efficiently covered with graphene oxide. By covering the surface with graphene oxide, the positive electrode active material can be prepared. This prevents the particles of the electrode active material from cracking or changing shape, such as by breaking. In addition, the positive electrode active material, whose surface is covered with graphene oxide, can withstand exposure to the atmosphere after production. Here, "after production" refers to, for example, the end of the production of the positive electrode active material. This refers to the period from the completion of storage until the production of a secondary battery using the positive electrode active material. The positive electrode active material and the electrolyte are also bonded to each other by forming a coating. This prevents direct contact and reaction, so when a secondary battery is made, the secondary The reliability of the battery is improved.

[0038] In addition, the spray drying method can be carried out using a known device, for example, a countercurrent type pressurized nozzle. A pressurized spray dryer using a nozzle type spray dryer or a parallel flow nozzle type spray dryer can be used.

[0039] When the active material is used in a secondary battery, the graphene oxide covering the surface of the active material may be reduced. The reduced graphene oxide is called "RGO (Reduced Graphene Oxide)". In addition, some oxygen or oxygen-containing atomic groups in RGO are carbon. For example, RGO may remain bonded to epoxy groups and carboxyl groups. In some cases, the aryl group may have a functional group such as a carbonyl group or a hydroxyl group.

[0040] Another aspect of the present invention is a method for producing the above-mentioned positive electrode active material or the above-mentioned positive electrode active material covered with a coating. The secondary battery has a positive electrode and a negative electrode.

[0041] In addition, secondary batteries can be used in a variety of shapes to suit the device in which they are used. For example, cylindrical shapes, square shapes, coin shapes, laminated (flat) shapes, etc. can be done. Effect of the Invention

[0042] According to one embodiment of the present invention, by using the compound in a lithium ion secondary battery, It is possible to provide a positive electrode active material in which the capacity decrease due to the charge-discharge reaction is suppressed. It is also possible to provide a secondary battery having high safety and reliability. In addition, a novel material, active material particles, secondary battery, and a method for producing the same are provided. It is possible. [Brief description of the drawings]

[0043] [Figure 1] FIG. 1 illustrates an example of a positive electrode active material. [Diagram 2] FIG. 2 is a diagram illustrating a crystal structure of a positive electrode active material. [Diagram 3] FIG. 2 is a diagram illustrating a crystal structure of a positive electrode active material. [Figure 4] FIG. 2 is a diagram illustrating a sol-gel method. [Diagram 5] 1A and 1B are diagrams illustrating a segregation model of elements contained in a positive electrode active material. [Figure 6] 1A and 1B are diagrams illustrating a segregation model of elements contained in a positive electrode active material. [Figure 7] FIG. 13 is a cross-sectional view of an active material layer in the case where a graphene compound is used as a conductive assistant. [Figure 8] FIG. 4 is a diagram illustrating a method of charging a secondary battery. [Figure 9] FIG. 4 is a diagram illustrating a method of charging a secondary battery. [Figure 10] 5A to 5C are diagrams illustrating a method of discharging a secondary battery. [Figure 11] FIG. 2 is a diagram illustrating a coin-type secondary battery. [Figure 12] FIG. 2 is a diagram illustrating a cylindrical secondary battery. [Figure 13] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 14] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 15] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 16] 1A and 1B are diagrams illustrating examples of secondary batteries. [Figure 17] FIG. 1 is a diagram illustrating a laminated secondary battery. [Figure 18] FIG. 1 is a diagram illustrating a laminated secondary battery. [Figure 19] FIG. 2 is a diagram showing the appearance of a secondary battery. [Figure 20] FIG. 2 is a diagram showing the appearance of a secondary battery. [Figure 21] 1A to 1C are diagrams illustrating a method for manufacturing a secondary battery. [Figure 22] 1A and 1B are diagrams illustrating a bendable secondary battery. [Diagram 23] 1A and 1B are diagrams illustrating a bendable secondary battery. [Figure 24] 1A to 1C are diagrams illustrating examples of electronic devices. [Diagram 25] 1A to 1C are diagrams illustrating examples of electronic devices. [Figure 26] 1A to 1C are diagrams illustrating examples of electronic devices. [Figure 27]1A to 1C are diagrams illustrating examples of electronic devices. [Figure 28] 1 is a transmission electron microscope image of the positive electrode active material of Example 1. [Figure 29] 3 is an FFT image of a transmission electron microscope image of the positive electrode active material of Example 1. [Diagram 30] 1 is an elemental mapping image of the positive electrode active material of Example 1. [Diagram 31] 1 is an elemental mapping image of a positive electrode active material of a comparative example of Example 1. [Diagram 32] 3 is a graph showing the results of TEM-EDX linear analysis of the positive electrode active material of Example 1. [Diagram 33] 3 is a graph showing the charge / discharge characteristics of the secondary battery of Example 1. [Diagram 34] 4 is a graph showing charge / discharge characteristics of a secondary battery of a comparative example of Example 1. [Diagram 35] 3 is a graph showing cycle characteristics of the secondary battery of Example 1. [Diagram 36] 3 is a graph showing cycle characteristics of the secondary battery of Example 1. [Figure 37] TEM-EDX area analysis image of a comparative example of Example 2. [Figure 38] TEM-EDX area analysis image of the positive electrode active material of Example 2. [Figure 39] TEM-EDX area analysis image of a comparative example of Example 2. [Diagram 40] TEM-EDX area analysis image of the positive electrode active material of Example 2. [Diagram 41] Graph showing the results of EDX point analysis of Example 2. [Diagram 42] Graph showing the results of EDX point analysis of Example 2. [Diagram 43] 6 is a graph showing the rate characteristics of the secondary battery of Example 2. [Diagram 44] 13 is a graph showing temperature characteristics of the secondary battery of Example 2. [Diagram 45] 1 is a graph showing cycle characteristics of the secondary battery of Example 2. [Diagram 46] 1 is a graph showing the results of XPS analysis of the positive electrode active material of Example 3. [Figure 47] 13 is a graph showing cycle characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 48] 13 is a graph showing cycle characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 49] 13 is a graph showing cycle characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 50] 13 is a graph showing the charge / discharge characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 51] 1 is an SEM image of the positive electrode active material of Example 4. [Figure 52] 1 is a SEM-EDX image of the positive electrode active material of Example 4. [Figure 53] FIG. 1 is a diagram showing the process flow of Example 5. [Figure 54] FIG. 13 is a diagram illustrating a spray drying apparatus according to a fifth embodiment. [Figure 55] 1 is a TEM photograph showing one embodiment of the present invention according to Example 5. [Figure 56] 1 is a SEM photograph showing one embodiment of the present invention according to Example 5. [Figure 57] 11 is a SEM photograph showing a comparative example of Example 5. [Figure 58] FIG. 11 is a cross-sectional view of an active material layer in the case where a graphene compound is used as a conductive assistant in Example 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description, and those skilled in the art will recognize that the present invention may be modified in various ways in form and detail. The present invention is not limited to the description of the following embodiments. It is not something that can be done.

[0045] In each of the drawings described in this specification, the positive electrode, the negative electrode, the active material layer, the separator, the exterior body, etc. The size and thickness of each component may be exaggerated for clarity of description. Therefore, each component is not necessarily limited by its size, and the correlation between each component is not necessarily limited by its size. It is not limited to the relative size.

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

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

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

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

[0050] In the present specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately. The structure may contain a deficiency of cations or anions.

[0051] Layered rock salt crystals and anions in rock salt crystals form a cubic close-packed structure (face-centered cubic lattice structure). When layered rock salt crystals come into contact with each other, the cubic close-packed structure of anions is formed. However, the space group of the layered rock salt crystal 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 the space group is different from that of the rock salt type crystals, which have the simplest symmetry, the above conditions are satisfied. The Miller indices of the crystal planes are different between layered rock-salt crystals and rock-salt crystals. In crystals and rock salt crystals, the cubic close-packed structure formed by anions is oriented in the same direction. When this occurs, it is said that the crystal orientation is roughly the same.

[0052] The alignment of the crystal orientations in the two regions is confirmed by TEM (transmission electron microscope) and STEM (scanning electron microscope) images. High-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image, ) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. X-ray diffraction, electron diffraction, neutron diffraction, etc. can also be used for judgment. TEM image In rocks such as these, the arrangement of cations and anions can be observed as repeated bright and dark lines. When the orientation of the cubic close-packed structure of salt-type crystals and rock salt-type crystals is aligned, bright and dark lines appear between the crystals. It can be observed that the angle between the repeats is 5 degrees or less, and more preferably 2.5 degrees or less. In addition, light elements such as oxygen and fluorine may not be clearly observed in TEM images. In some cases, the alignment of the metal elements can be used to determine whether the orientation is consistent.

[0053] In this specification, the similarity of the structure of a two-dimensional interface is called epitaxy. Crystal growth that resembles the structure of a two-dimensional interface is called epitaxial growth. Topotaxis refers to the fact that two molecules have the same fundamental structural similarity or have the same crystallographic orientation. Therefore, in the case of topotaxis, when a part of a cross section is observed, two regions (for example For example, the crystal orientation of the underlying region and the region that is grown is roughly the same.

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

[0055] As shown in FIG. 1B, the second region 102 does not cover the entire first region 101. Similarly, the third region 103 does not have to cover the entire second region 102. Furthermore, a third region 103 may be present in contact with the first region 101.

[0056] Furthermore, the second region 102 and the third region 103 may have different thicknesses depending on the location. good.

[0057] In addition, a third region 103 may be present inside the positive electrode active material 100. For example, When the region 101 is polycrystalline, a third region 103 may be present near the grain boundaries. The third layer is formed on the portion of the positive electrode active material 100 having the crystal defect, the crack portion, and the vicinity thereof. In FIG. 1(B), a part of the grain boundary is shown by a dotted line. In the literature, crystal defects are defects that can be observed in TEM images, that is, defects caused by the inclusion of other elements in the crystal. The cracked part is, for example, the part shown in Figure 1(C). The term "crack" refers to a crack or fissure that occurs in a particle, such as crack portion 106.

[0058] Similarly, as shown in FIG. 1B, a second region 102 is present inside the positive electrode active material 100. For example, when the first region 101 is polycrystalline, the second region 102 may be present near the grain boundary. In addition, the positive electrode active material 100 may have crystal defects, cracks, and The second region 102 may be present in the vicinity of the positive electrode active material 100. The third region 103 and the second region 102 may overlap each other.

[0059] <First Area 101> The first region 101 includes a composite oxide of lithium and a first transition metal. It may be said that 101 contains lithium, a first transition metal, and oxygen.

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

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

[0062] That is, the first region is made up of lithium cobalt oxide, lithium manganese oxide, and lithium nickel oxide. , lithium cobalt oxide in which some of the cobalt is replaced by manganese, nickel-manganese-cobalt oxide Lithium barium oxide, etc. In addition to the transition metal, the first region 101 may also include Metals other than transition metals, such as aluminum, may also be included.

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

[0064] Materials with a layered rock-salt crystal structure have a high discharge capacity and allow lithium to diffuse two-dimensionally. Therefore, it has a feature that the resistance is low, and is preferable as the first region 101. When the region 101 has a layered rock salt type crystal structure, it is unexpectedly possible to obtain a layer of magnesium, etc., which will be described later. Segregation of typical elements is likely to occur.

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

[0066] Since polycrystals have a clear crystal structure, there are sufficient paths for two-dimensional diffusion of lithium ions. In addition, it is easier to produce than a single crystal, and therefore is preferable for the first region 101. stomach.

[0067] In addition, the entire first region 101 does not have to have a layered rock salt type crystal structure. A portion of the region 101 may be amorphous or have another crystal structure.

[0068] <Second Region 102> The second region 102 comprises an oxide of a second transition metal. It may be said that the metal ions include a transition metal and oxygen.

[0069] It is preferable to use a non-stoichiometric metal as the second transition metal. It may be said that 2 preferably has a non-stoichiometric compound. For example, the second transition metal and Titanium, vanadium, manganese, iron, chromium, niobium, cobalt, zinc, zirconium At least one of the second transition metals, such as nickel, tungsten, and zinc, can be used. It is preferable that the transition metal is an element different from the transition metal of 1.

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

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

[0072] The second area 102 is a buffer area connecting the first area 101 and a third area 103 (described later). The nonstoichiometric compound functions as a region where the valence of the metal in the nonstoichiometric compound changes. The interatomic distances can change. Also, nonstoichiometric compounds often have a cation or anion defect. Therefore, the second region 102 is a buffer region. As a region, the third region 103 can absorb the strain generated between the first region 101 and the third region 103.

[0073] The second region 102 may also include lithium in addition to the second transition metal and oxygen. For example, lithium titanate, lithium manganese oxide, etc. The region 102 may contain the typical element contained in the third region 103 described below. The region 102 contains the elements contained in the first region 101, including lithium, and the elements contained in the third region 102. The region 103 is preferably a buffer region containing the elements.

[0074] That is, the second region 102 is made of lithium titanate, titanium oxide, vanadium oxide, manganese oxide, or the like. It contains cancer, iron oxide, copper oxide, chromium oxide, niobium oxide, cobalt oxide, zinc oxide, etc. This can be done.

[0075] The second region 102 may also include a first transition metal. For example, A second transition metal may be present at some of the first transition metal sites of the composite oxide having the metal. stomach.

[0076] For example, when the second transition metal is titanium, the titanium is converted into titanium oxide in the second region 102. It can exist as tantalum oxide (TiO2) or as lithium titanate (LiTiO2). In the second region 102, a composite oxide having lithium and a first transition metal may be used. A portion of the first transition metal sites of the oxide may be substituted with titanium.

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

[0078] In addition, the second region 102 has the same type of crystal structure as the third region 103 described later. In this case, the crystal orientation of the second region 102 and the third region 103 tend to coincide. .

[0079] It is preferable that the second region 102 has a rock salt type crystal structure. The second region 102 does not necessarily have to have a rock-salt crystal structure. For example, the second region 102 may have a spinel crystal structure. Crystal structure, olivine type crystal structure, corundum type crystal structure, rutile type crystal structure, etc. It may have other crystal structures.

[0080] In addition, if the structure with six oxygen atoms adjacent to the cation is maintained, there will be no distortion in the crystal structure. In addition, a part of the second region 102 may have a cation deficiency.

[0081] A portion of the second region 102 may be amorphous.

[0082] If the second region 102 is too thin, its function as a buffer region is reduced. Therefore, the second region 102 is It is preferable that it exists within a depth of 20 nm, more preferably 10 nm, from the surface in the depth direction. The second transition metal may also have a concentration gradient.

[0083] <Third Area 103> The third region 103 contains a compound of a typical element. The compound of a typical element is a stoichiometric compound. Compounds of typical elements are electrochemically stable compounds made of typical elements. It is preferable to use magnesium oxide, calcium oxide, beryllium oxide, fluorine oxide, etc. At least one of lithium fluoride and sodium fluoride can be used.

[0084] The third region 103 is a region that comes into contact with an electrolyte when the positive electrode active material 100 is used in a secondary battery. Therefore, the material used for the third region 103 is one that does not undergo electrochemical changes during charging and discharging. It is preferable that the material has a low content and is not easily altered by contact with the electrolyte. Therefore, a compound of a typical element that is electrochemically stable is preferable for the third region 103. The substance 100 has the third region 103 in the surface layer portion, and thus the secondary battery is stable during charging and discharging. Here, the high stability of the secondary battery can be achieved by, for example, improving the quality of the secondary battery in the first region. The crystal structure of the composite oxide containing lithium and the first transition metal in 101 is more stable. Alternatively, it means that the capacity of the secondary battery changes little even after repeated charging and discharging. Alternatively, even after repeated charging and discharging, the change in the valence of the metal contained in the positive electrode active material 100 is suppressed. It means to be controlled.

[0085] The third region 103 may contain fluorine. In this case, some of the anions in the compound of the main group element may be substituted with fluorine.

[0086] The anions in compounds of main group elements are partially replaced by fluorine, e.g., lithium Therefore, even if the third region 103 exists, the charge and discharge are not hindered. In addition, the presence of fluorine on the surface layer of the positive electrode active material particles prevents the electrolyte from decomposing. This may improve corrosion resistance against the hydrofluoric acid produced.

[0087] Furthermore, the third region 103 contains lithium, a first transition metal, and a second transition metal. It's fine.

[0088] The compound of the main group element contained in the third region 103 preferably has a rock-salt type crystal structure. It is preferable that the third region 103 has a rock salt type crystal structure, and the crystal alignment with the second region 102 is good. The crystal orientation of the first region 101, the second region 102, and the third region 103 is likely to be the same. When the orientations of the second region 102 and the third region 103 are roughly the same, the coating becomes more stable. It can function as a layer.

[0089] However, the entire third region 103 does not have to have a rock-salt crystal structure. Region 103 is a spinel type crystal structure, an olivine type crystal structure, a corundum type crystal structure, a rutile type crystal structure, It may have other crystal structures including a type crystal structure.

[0090] In addition, if the structure in which six oxygen atoms are adjacent to the cation is maintained, the crystal structure is distorted. Furthermore, a part of the third region 103 may have a cation deficiency.

[0091] A part of the third region 103 may be amorphous.

[0092] If the third region 103 is too thin, the function of improving the stability during charging and discharging is reduced. If the third region 103 is too thick, the capacitance will decrease. Therefore, the thickness of the third region 103 is set to 0.5 nm or less. The thickness is preferably at most 50 nm, and more preferably at least 0.5 nm and at most 2 nm.

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

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

[0095] In general, the positive electrode active material loses manganese, cobalt, nickel, etc. as it is repeatedly charged and discharged. The first transition metal dissolves into the electrolyte, oxygen is released, and the crystal structure becomes unstable. However, the positive electrode active material 100 according to one embodiment of the present invention has the following properties: A second region 102 that functions as a buffer region and a third region 103 that is electrochemically stable. Therefore, the elution of the first transition metal is effectively suppressed, and the first region 101 It is possible to make the crystal structure of the composite oxide containing lithium and transition metals more stable. Therefore, the cycle characteristics of a secondary battery having the positive electrode active material 100 can be significantly improved. Also, 4.3V (vs. Li / Li + ) especially voltages exceeding 4.5V (vs. Li / Li + When charging and discharging is performed at a high voltage of 100 V or higher, the configuration of one embodiment of the present invention is It has a remarkable effect.

[0096] <Heteroepitaxial growth and topotaxis> The second region 102 is formed by heteroepitaxial growth from the first region 101. It is preferable that the third region 103 is heteroepitaxially grown from the second region 102. It is preferable that the region formed by heteroepitaxial growth is In this case, the crystal orientation of the underlying region roughly coincides in three dimensions, resulting in topotaxis. , the first region 101, the second region 102 and the third region 103 are topotaxis. can be done.

[0097] When the crystal orientations of the first region 101 to the third region 103 are roughly aligned, the second region The first region 101 and the third region 103 are formed as a coating layer having a stable bond with each other. 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 generated by charging and discharging In addition, the change in the crystal structure of the first region 101 can be effectively suppressed. Even if the ion is removed, the coating layer has a stable bond and the ion is prevented from being removed from the first region 101. It is possible to suppress the release of cobalt and oxygen from the electrolyte. Therefore, it is possible to make a secondary battery with excellent cycle characteristics. It can be a pond.

[0099] <Inconsistency between areas> In order to achieve heteroepitaxial growth, the crystal in the base region and the crystal to be grown must be aligned in a plane. The degree of inconsistency is important.

[0100] In this specification, the mismatch degree f is defined by the following formula 1. The average closest distance between oxygen and cations in the crystal to be grown is a, and the natural anions and cations in the crystal to be grown are a and b. Let b be the average of the closest distances of the ons.

[0101]

number

[0102] For heteroepitaxial growth, the crystals in the base region and the crystals to be grown must be inconsistent. The degree of matching f must be 0.12 or less. For the sake of length, the mismatch factor f is preferably 0.08 or less, and more preferably 0.04 or less. It is nice.

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

[0104] The second region 102 has a rock salt type crystal structure, and the third region 103 has a rock salt type The second region 102 and the third region 103 are arranged so that the degree of mismatch f of the crystal structure is 0.12 or less. 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 has The degree of mismatch f of the rock-salt type crystal structure is 0.12 or less, and the second region 102 has The degree of mismatch f between the rock-salt type crystal structure of the third region 102 and the rock-salt type crystal structure of the third region 103 is 0 The first area 101, the second area 102, and the third area 103 satisfy the condition that the difference is equal to or less than .12. Examples of materials and crystal planes of region 103 are given below.

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

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

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

[0109] As shown in Figure 2(B), when a layered rock salt crystal is viewed from the <1-1-4> plane orientation, the rock salt Crystal of the type <100> The atomic arrangement is very similar to that seen from the plane orientation of the metal and the acid. The nearest neighbor distances of the elements are similar. For example, in the layered rock-salt lithium cobalt oxide The Li-O distance is 2.089 Å, and the Co-O distance is 1.925 Å. The Li-O distance in lithium is 2.138 Å, and the Ti-O distance is 2.051 Å. The Mg-O distance in magnesium oxide salt 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 The degree of mismatch between the regions when the crystal faces of {00} are in contact will now be described.

[0111] As shown in FIG. 3, the first region 101 is made of lithium cobalt oxide having a layered rock salt type crystal structure. The metal-oxygen-metal distance in the crystal plane 101p(1-1-4) of Zn(1-1-4) is 4. 01 Å. The second region 102 of lithium titanate having a rock-salt crystal structure has a thickness of 100 nm. The metal-oxygen-metal distance in the {100} crystal plane 102p{100} is 4.19 Å. Therefore, the mismatch f between the crystal plane 101p(1-1-4) and the crystal plane 102p{100} is 0 The value is .04.

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

[0113] In this manner, the degree of mismatch between the first region 101 and the second region 102 and the degree of mismatch between the second region 10 Since the degree of mismatch between the first region 101 and the third region 103 is sufficiently small, Topotaxis is possible up to region 103.

[0114] On the other hand, although they are not in contact in FIG. 3, let us suppose that the crystal plane 101p(1-1-4) of the first region 101 When the crystal plane 103p{100} of the third region 103 contacts the first region 103, the degree of mismatch f is 0.05. In other words, the presence of the second region 102 makes it possible to reduce the degree of mismatch. Furthermore, since the second region 102 is a transition metal oxide having non-stoichiometry, The presence of the first region 101 to the third region 103 provides a more stable transition. 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 layered rock-salt type (1-1-4) plane and the rock-salt type {100} plane are in contact with each other. Although the above example has been described, the present invention is not limited to this example. As long as they are in contact with each other, that's fine.

[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. The second transition metal is manganese, and the second region 102 is The third region 103 has manganese oxide having a rock salt type crystal structure, and the third region 103 has a manganese oxide having a main group element. An example will be described in which the compound is calcium oxide having a rock salt type crystal structure.

[0117] In this case, similarly to FIG. 2 and FIG. 3, the layered rock salt type crystal in the first region 101 is <1-1 When 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 seen from the plane orientation.

[0118] The (1-1-4) crystal face of the layered rock salt crystal and the {100} crystal face of the rock salt crystal meet. The degree of inconsistency between the regions when the layered rock-salt crystals in the first region 101 are The metal-oxygen-metal distance of the (1-1-4) crystal plane of lithium cobalt oxide having the structure is The crystal structure of the manganese oxide in the second region 102 is 4.01 Å. The metal-oxygen-metal distance in the {100} crystal plane is 4.45 Å. Therefore, the first region The mismatch f between the crystal plane (1-1-4) of 101 and the crystal plane {100} of the second region 102 is 0 It is .11.

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

[0120] In this manner, the degree of mismatch between the first region 101 and the second region 102 and the degree of mismatch between the second region 10 Since the degree of mismatch between the first region 101 and the third region 103 is sufficiently small, It is possible topotaxis up to region 103.

[0121] On the other hand, suppose that the crystal plane (1-1-4) of the first region 101 and the crystal plane {10 0} contact, the mismatch f is 0.20, making heteroepitaxial growth difficult. In other words, the presence of the second region 102 prevents the heterojunction from extending from the first region to the third region. Therefore, the second region 102 and the third region 103 are epitaxially grown. , it can function as a covering layer having a stable bond with the first region 101.

[0122] <Example 3: Lithium nickel-manganese-cobalt oxide, manganese oxide, calcium oxide> Next, the first transition metal is nickel, manganese and cobalt, and the first region 101 is Lithium nickel-manganese-cobalt oxide (LiNi 0. 33 Co 0.33 Mn 0.33 O2), the second transition metal is manganese, and the second The region 102 has manganese oxide having a rock salt type crystal structure, and the third region 103 has Let us explain an example of a compound of a main group element, calcium oxide, which has a rock salt type crystal structure. do.

[0123] In this case, as shown in Figs. 2 and 3, the layered rock salt crystals are aligned in the <1-1-4> plane direction. From the angle, it looks like a rock salt crystal. <100> The atomic arrangement is very similar to that seen from the plane orientation of The (1-1-4) crystal face of the layered rock salt crystal and the {100} crystal face of the rock salt crystal are The degree of inconsistency between the regions when they are in contact with each other will now be described.

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

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

[0126] In this manner, the degree of mismatch between the first region 101 and the second region 102 and the degree of mismatch between the second region 10 Since the degree of mismatch between the first region 101 and the third region 103 is sufficiently small, It is possible topotaxis up to region 103.

[0127] On the other hand, suppose that the crystal plane (1-1-4) of the first region 101 and the crystal plane {10 0} contact, the mismatch f is 0.18, making heteroepitaxial growth difficult. In other words, the presence of the second region 102 prevents the heterojunction from extending from the first region to the third region. Therefore, the second region 102 and the third region 103 are epitaxially grown. , it can function as a covering layer having a stable bond with the first region 101.

[0128] <Boundaries between each area> As described above, 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. For example, the second transition metal in the second region 102 may have a concentration gradient. In addition, the third region 103 is a region in which typical elements are segregated, as will be described later. Since it is preferable to have a concentration gradient of the main group elements, The border may not be clear.

[0129] The first region 101, the second region 102, and the third region 103 are used for a TEM image, a STEM image, and , FFT (Fast Fourier Transform) analysis, EDX (Energy Dispersive X-ray Analysis), ToF-S Depth analysis by IMS (time-of-flight secondary ion mass spectrometry), XPS (X-ray photoelectron Spectroscopy), Auger electron spectroscopy, TDS (thermal desorption spectroscopy), etc. You can confirm that.

[0130] For example, in TEM and STEM images, differences in the constituent elements appear as differences in the brightness of the images. Therefore, the constituent elements of the first region 101, the second region 102, and the third region 103 In addition, surface analysis by EDX (e.g. element mapping) also reveals that the first It is observed that the first region 101, the second region 102 and the third region 103 have different elements. I can understand.

[0131] In addition, line analysis by EDX and depth direction analysis by ToF-SIMS revealed that the first region 101, the peaks of the concentrations of the elements in the second region 102 and the third region 103 are detected. It is possible.

[0132] However, it is not necessarily the case that the first region 101, the second region 102, and the third region are determined by various analyses. It is not necessary that a clear boundary of the region 103 is observable.

[0133] In this specification, the third region 103 present in the surface layer portion of the positive electrode active material 100 is The concentration of a typical element such as magnesium detected by depth direction analysis from the surface of the substance 100 is The depth direction analysis is performed by the EDX line analysis described above. Analysis using a depth profile and analysis using ToF-SIMS can be used.

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

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

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

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

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

[0139] Therefore, the third region 103 and the second region 102 may overlap. The region 103 is located closer to the surface of the positive electrode active material particle than the second region 102. In addition, the peak of the concentration of the main group element is closer to the positive electrode than the peak of the concentration of the second transition metal. It is preferred that it is present in a region close to the surface of the active material particles.

[0140] The peak of the second transition metal is at a depth of 0.2 nm from the surface to the center of the positive electrode active material 100. and preferably exists at a depth of 0.5 nm to 3 nm. It is more preferable that

[0141] In addition, the measurement range of XPS is about 5 nm from the surface of the particle of the positive electrode active material 100. It is possible to quantitatively analyze the concentration of elements present at a depth of about 5 nm from the surface. The element concentrations of the third region 103 and the second region 102, which are present at a distance of about 5 nm, are quantitatively analyzed. It can be analyzed.

[0142] When the surface of the positive electrode active material 100 was analyzed by XPS, the concentration of the first transition metal was set to 1. The relative value of the concentration of the second transition metal is preferably 0.05 to 0.4, and more preferably 0.1 to 0. The relative concentration of the typical element is preferably 0.4 to 1.5. The relative value of the fluorine concentration is preferably 0.05 to 1.00. 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 described above, the first region 101, the second region 102, and the third region 103 have Since elements may have a concentration gradient, a first region 101 may have a second region, such as fluorine. The third region 102 and the third region 103 may have the same elements. The first region 101 and the second region 102 may contain the same elements. The first region 101, the second region 102 and the third region 103 are made of carbon, sulfur, silicon, , sodium, calcium, chlorine, zirconium, and other elements.

[0144] [Particle size] If the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse, and if it is too small, It becomes difficult to maintain the crystal structure described above. Therefore, the D50 (also called the median diameter) ) is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less. In a later step, a coating is formed on the surface of the positive electrode active material 100 using a spray dryer. In this case, it is preferable that the nozzle diameter and the maximum particle size of the positive electrode active material 100 are almost the same. If the particle size is less than 5 μm, when using a spray dryer with a nozzle diameter of 20 μm, The secondary particles are coated together, resulting in a decrease in coating properties.

[0145] In order to increase the density of the positive electrode active material layer, large particles (the longest part is about 20 μm or more) are required. The larger particles (the longest part is about 1 μm) are mixed with the smaller particles (the longest part is about 40 μm or less). It is also effective to fill the gaps between the particles with small particles. This is also possible.

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

[0147] When the particle size of the starting material is small, the particle size of the positive electrode active material is adjusted to the above-mentioned preferred range by calcination. When the grains are mixed, grain growth is required.

[0148] To promote grain growth during sintering, the ratio of Li to the first transition metal in the starting material should be greater than 1. For example, Li and the first transition metal When the metal ratio is about 1.06, it is easy to obtain a positive electrode active material with a D50 of 15 μm or more. However, as will be described later, lithium may be lost outside the system during the process of producing the positive electrode active material. The ratio of lithium to the first transition metal in the finished positive electrode active material is The ratio of transition metals in the alloy may not match that of the alloy.

[0149] However, if the amount of lithium becomes too excessive in order to set the particle size within the preferred range, the secondary battery When used in a battery, the capacity retention rate may decrease.

[0150] However, the present inventors have provided a second region 102 having a second transition metal in the surface layer portion. By controlling the ratio of Li to the first transition metal, the grain size can be kept within a preferred range. They revealed that it is possible to fabricate a positive electrode 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 in which a region having a second transition metal is provided in a surface layer portion, The ratio of Li to the first transition metal in the raw material is preferably 1.00 to 1.07. It is more preferable that it is greater than or equal to .03 and less than or equal to 1.06.

[0152] [Formation of the second region] The second region 102 is a composite oxide having lithium and a first transition metal, and is provided with a second transition metal. It can be formed by coating a material having a transition metal.

[0153] As a method for coating a material having a second transition metal, a liquid phase method such as a sol-gel method is used. , solid-phase method, sputtering method, deposition method, CVD (chemical vapor deposition) method, PLD (pulse laser deposition) method In the present embodiment, a method such as the deposition method can be applied to achieve a uniform coating. Here, we will explain the case where a sol-gel method, which is expected to be effective and allows processing at atmospheric pressure, is applied.

[0154] <Sol-gel method> The method of coating a material having a second transition metal by the sol-gel method is described with reference to FIG. He explains.

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

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

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

[0158] For example, titanium alkoxides include tetramethoxytitanium, tetraethoxytitanium, and tetraethoxytitanium. tra-n-propoxytitanium, tetra-i-propoxytitanium (tetraisotitanium orthotitanate) isopropyl, titanium(IV) isopropoxide, titanium tetraisop ropoxide(IV), TTIP, etc.) Titanium, tetra-i-butoxy titanium, tetra-sec-butoxy titanium, tetra-t- Butoxytitanium and the like can be used.

[0159] FIG. 4(A-3) shows titanium alkoxide, which is one of the titanium alkoxides described in the production method described later. (IV) The chemical formula of isopropoxide (TTIP) is shown below.

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

[0161] Next, lithium, transition metal, magnesium, and the like are added to an alcohol solution of the alkoxide of the second transition metal. Particles of a composite oxide having aluminum 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 alkoxide were dissolved as shown in Figure 4(B). Hydrolysis of the side occurs. Then, the products in Figure 4(B) undergo dehydration condensation as shown in Figure 4(C). The hydrolysis shown in Figure 4(B) and the condensation reaction shown in Figure 4(C) occur repeatedly. A sol of the oxide of the second transition metal is produced. This reaction is shown in FIG. 4(D-1) and FIG. As shown in (D-2), the second transition also occurs on the surface of the composite oxide particle 110. A layer including a metal is formed.

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

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

[0165] [Segregation in the third region] The third region 103 is a region including a sputtering method, a solid phase method, a liquid phase method such as a sol-gel method, etc. However, the present inventors have found that the method using a source of a typical element such as magnesium When the fluorine source is mixed with the material of the first region 101 and then heated, the typical elements are condensed into the positive electrode active material particles. It was also revealed that the lattice structure segregates to the surface layer of the lattice structure and forms a third region 103. By having the third region 103 formed by the above-mentioned process, the positive electrode active material 100 has excellent cycle characteristics. It became clear that

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

[0167] The segregation model of this typical element will be explained using Figures 5 and 6. Magnesium, etc. The segregation model of the typical elements in the starting materials is based on the ratio of lithium to the first transition metal. It is speculated that the ratio of Li to the first transition metal in the starting material is less than 1.03. The segregation model when the lithium content is low, i.e., when the lithium content is low, is explained using FIG. Segregation model for materials with a ratio of Li to first transition metals of 1.03 or more, i.e., lithium-rich The following will be explained with reference to FIG. 6. In addition, the first transition in FIG. 5 and FIG. 6 For example, the metal is cobalt, the second transition metal is titanium, and the main group element is magnesium. He explains.

[0168] FIG. 5(A) shows a lithium-cobalt alloy produced with a Li:Co ratio of less than 1.03 in the starting materials. 1 is a model diagram of the surface of a composite oxide particle 110 having magnesium and fluorine. In the figure, region 111 contains lithium, cobalt, magnesium, and fluorine. This is the region where lithium cobalt oxide (LiCoO2) is the main component. Um has a layered rock salt type crystal structure.

[0169] Generally, particles of a composite oxide having lithium, cobalt, magnesium and fluorine are used. It is known that during synthesis, some lithium escapes from the system (outside the particles produced). The causes of this are that lithium volatilizes during firing, and lithium dissolves when the starting materials are mixed. Therefore, the ratio of lithium and cobalt is smaller than that of the starting material. The Li and Co ratio in the composite oxide particles 110 containing magnesium and fluorine is It may become smaller.

[0170] When the Li to Co ratio of the starting material is less than 1.03, the surface of the particles 110 is dominated by lithium cobalt oxide. Lithium is easily removed from cobalt oxide, and the resulting mixture is called cobalt oxide. As shown in FIG. 1, the surface of the composite oxide particle 110 is covered with cobalt oxide (CoO X (X>0)) layer 114 It may be covered with

[0171] Cobalt oxide has a rock-salt crystal structure. Therefore, in the particle 110 of FIG. 5(A), the layers On the region 111 having lithium cobalt oxide having a crystalline rock-salt type structure, In some cases, a cobalt oxide layer 114 having a crystal structure is in contact with the cobalt oxide layer 114 .

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

[0173] Next, the particles 110 coated with the titanium-containing layer 112 are heated. As will be described later, for example, the material is heated in an oxygen atmosphere at 800° C. for 2 hours, and the resulting material is one of the materials according to the present invention. The state of the positive electrode active material 100 is shown in FIG. The titanium in the layer 112 having the titanium ions diffuses toward the inside of the grain 110. The magnesium and fluorine contained in 1 segregate to the surface of the particle 110.

[0174] As described above, rock salt type cobalt oxide is present on the surface of the particle 110. Magnesium also has a rock-salt crystal structure. Therefore, magnesium is more easily absorbed from the inside of the particle 110. It is presumed that magnesium oxide on the surface of the particle 110 is more stable than magnesium oxide. This is thought to be the reason why magnesium segregates to the surface of the particle 110 when heated. do.

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

[0176] Fluorine has a higher electronegativity than oxygen. Therefore, it is difficult to form stable compounds such as magnesium oxide. In the case of fluorine, the charge is biased and the relationship between magnesium and oxygen is It is speculated that this weakens the bond. Therefore, oxygen in magnesium oxide is replaced by fluorine. It is speculated that this makes it easier for magnesium to move around the substituted fluorine. do.

[0177] This can also be explained by the phenomenon of the melting point of the mixture dropping. Magnesium oxide (melting point 2852 When magnesium oxide (melting point 848°C) and lithium fluoride (melting point 848°C) are added at the same time, the melting point of magnesium oxide drops. The lowering of the melting point makes it easier for magnesium to move when heated, It is also thought that this makes it easier for aluminum to segregate.

[0178] Finally, the third region 103 is made of cobalt oxide and magnesium oxide having a rock salt type crystal structure. In addition, some of the oxygen in cobalt oxide and magnesium oxide is converted to fluorine. It is thought to be replaced by

[0179] The diffused titanium partly replaces the cobalt sites of the lithium cobalt oxide, and partly dissolves in the titanium. After heating, the second region 102 becomes lithium titanate having a rock salt crystal structure. Contains thium.

[0180] After heating, the first region 101 has lithium cobalt oxide having a layered rock salt type crystal structure. do.

[0181] Next, the case where the Li to Co ratio of the starting material is 1.03 or more will be described with reference to FIG. 6(A) is a lithium-cobalt alloy prepared with a Li:Co ratio of 1.03 or more in the starting materials. 1 is a model diagram of the surface vicinity of a particle 120 of a composite oxide containing magnesium and fluorine. In the figure, region 121 has lithium, cobalt, magnesium, and fluorine. This is an area where

[0182] The particle 120 in FIG. 6(A) has sufficient lithium, so that it is possible to obtain lithium, cobalt, magnesium, and When the composite oxide particles 120 containing lithium and fluorine are calcined, the lithium is added to the particles 12. Even if the particle is released from 0, lithium is diffused from inside the particle 120 to the surface to compensate, so The cobalt oxide layer is unlikely to form.

[0183] FIG. 6B shows a particle 120 of FIG. 6A to which a layer 122 containing titanium is applied by a sol-gel method. At the stage of FIG. 6(B), the titanium-containing layer 122 is a titanium oxide film. Since it is a gel of a fluoride compound, it has low crystallinity.

[0184] FIG. 6C shows the particle 120 after coating with the titanium-containing layer 122 of FIG. 6B by heating. By heating, titanium in the titanium-containing layer 122 is converted into particles 1 The titanium diffuses toward the inside of the region 10. The diffused titanium bonds with the lithium contained in the region 121. The lithium titanate is combined with the lithium oxide to form a layer 125 having lithium titanate.

[0185] Lithium is bonded to titanium to form lithium titanate, so that lithium is present on the surface of the particle 120. Therefore, as shown in FIG. 6(C), the surface of the particle 120 is oxidized. It is believed that a cobalt layer 124 forms temporarily.

[0186] FIG. 6D shows that heating has been sufficiently performed since FIG. 6C, and the positive electrode active material 1 according to one embodiment of the present invention is obtained. 00. A cobalt oxide layer 124 having a rock salt type crystal structure is formed on the surface. By virtue of the presence of magnesium in the particle 120, the magnesium oxide is more likely to form on the surface of the particle 120 than in the interior of the particle 120. It is thought that it is more stable to exist as magnesium. Also, as in the case of Figure 5, Its presence promotes magnesium segregation.

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

[0188] In this way, a third region 103 having magnesium oxide and cobalt oxide, titanate The second region 102 having lithium and the first region 10 having lithium cobalt oxide. A positive electrode active material 100 having a molecular weight of 1 is prepared.

[0189] When the typical element is segregated by heating, the lithium contained in the first region 101 and the first When a complex oxide containing a transition metal is polycrystalline or has crystal defects, the surface layer Typical elements are also observed near the grain boundaries and near crystal defects of composite oxides containing lithium and first transition metals. The typical elements segregated near the grain boundaries or near the crystal defects are effective in the first region 101. This may contribute to further stabilization of the crystal structure of the composite oxide containing lithium and the first transition metal. do.

[0190] In addition, the composite oxide containing lithium and the first transition metal contained in the first region 101 is formed in the crack portion. When the typical elements have the same structure, they can also segregate at cracks due to heating. The cracks are located in the area in contact with the electrolyte, as well as on the particle surface. Therefore, the typical elements and the second transition metal are segregated in the cracks, forming the third region 1. The formation of the first region 103 and the second region 102 makes the region in contact with the electrolyte chemically stable. Therefore, it is possible to obtain a secondary battery having excellent cycle characteristics. do.

[0191] The ratio of the typical element (T) and fluorine (F) in the starting material is T:F=1:x (1.5≦x≦4) (starting material In the range of T:F=, segregation of the typical elements occurs effectively. It is more preferable that the atomic ratio is about 1:2.

[0192] The third region 103 formed by segregation is formed by epitaxial growth. Therefore, the crystal orientations of the second region 102 and the third region 103 may partly roughly coincide with each other. That is, the second region 102 and the third region 103 may be topotaxis. When the crystal orientations of the region 102 and the third region 103 are roughly the same, they are more favorable. It can function as a covering layer.

[0193] However, all of the typical elements such as magnesium added as the starting material are in the third region 10 For example, the first region 101 may not contain a typical element such as magnesium. It may contain small amounts.

[0194] <Fourth Area 104> As shown in FIG. 1C, the positive electrode active material 100 has a fourth region 103 on the third region 103. 04. Furthermore, the positive electrode active material 100 may have defects such as cracks 106. At this time, the fourth region 104 may be present so as to fill in defects such as the crack portion 106. stomach.

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

[0196] The fourth region 104 may be in a convex shape, a strip shape, or a layer shape. The fourth region 104 is preferably a region including the second transition metal and the main group element contained in the starting material. , the second transition metal and the typical metal that are not included in the second region 102 and the third region 103 In other words, the presence of the fourth region 104 makes the second region 102 and the and the second region 103 has a second transition metal and a typical element in an appropriate amount. In some cases, the crystal structure of the second region 102 and the third region 103 can be stabilized. In addition, the presence of the fourth region 104 prevents defects such as cracks 106 in the positive electrode active material 100. It may be possible to repair the defect.

[0197] The presence of the fourth region 104 and the shape of the fourth region 104 are confirmed by SEM (Scanning Electron Microscopy). The elements contained in the fourth region 104 can be observed by a scanning electron microscope (SEM). It can be analyzed using EDX, etc.

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

[0199] <Step 11: Preparation of starting materials> First, a starting material is prepared. The material prepared in this process is finally used to form the first region 10 A first and a third region 103 are formed.

[0200] The first region 101 contains a lithium source and a first transition metal as raw materials. A transition metal source of the above is prepared. Also, as a raw material of a compound of a typical element contained in the third region 103, 1. A source of a typical element is prepared.

[0201] In addition, it is preferable to provide a fluorine source. Fluorine can be added to the raw materials to: In a later process, the typical element contained in the third region 103 segregates on the surface of the positive electrode active material 100. It has the effect of promoting

[0202] The lithium source may be, for example, lithium carbonate or lithium fluoride. As the source of the transition metal, for example, an oxide of the first transition metal can be used. The source may be, for example, an oxide of the typical element contained in the third region, Fluorides of the above can be used.

[0203] The fluorine source may be, for example, lithium fluoride or a fluoride of a typical element in the third region. In other words, lithium fluoride can be used as both a lithium source and a fluorine source. There can be.

[0204] The amount of fluorine contained in the fluorine source is 1.0 to 4 times the amount of typical elements contained in the typical element source. (atomic ratio), and more preferably 1.5 times or more and 3 times or less (atomic ratio). More preferred.

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

[0206] <Step 13: First Heating> Next, the mixed material is heated in step 12. This step is called baking or first heating. Heating is preferably performed at a temperature between 800°C and 1100°C, and above 900°C. It is more preferable to carry out the heating at a temperature of 1000° C. or more and 1000° C. or less. The heating time is 2 hours or more and 20 hours or less. It is preferable to perform the firing in a dry atmosphere such as dry air. The dry atmosphere is preferably one with a dew point of -50°C or less, and more preferably one with a dew point of -100°C or less. In this embodiment, the heating is performed at 1000° C. for 10 hours, and the temperature is increased by 200 ℃ / h, and dry air with a dew point of -109℃ will flow at 10L / min. Cool the mixture to room temperature.

[0207] The heating in step 13 produces a layered rock-salt crystal structure of lithium and the first transition metal. At this stage, the main group elements and fullerenes contained in the starting materials are mixed together to produce a composite oxide. The fluorine is dissolved in the complex oxide. However, some of the main elements are already dissolved in the complex oxide. In some cases, it may be unevenly distributed on the surface.

[0208] In addition, lithium, cobalt, fluorine, magnesium, etc., which are pre-synthesized as starting materials, are used. In this case, steps 12 and 13 may be performed. For example, lithium cobalt oxide particles manufactured by Nippon Chemical Industry Co., Ltd. (Product name: C-20F) can be used as one of the starting materials. This has a particle size of about 20 The area that can be analyzed by XPS is fluorine, magnesium, calcium, and sodium. The lithium cobalt oxide particles contain thorium, silicon, sulfur, and phosphorus.

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

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

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

[0212] Next, the mixture is stirred in an atmosphere containing water vapor. The stirring time is determined based on the reaction time between the water in the atmosphere and TTIP, which is then hydrolyzed and polymerized. Any time sufficient for the condensation reaction to occur is sufficient, for example, 4 hours, 25°C, and 90% RH. This can be done under conditions of Relative Humidity.

[0213] As mentioned above, by reacting TTIP with water in the atmosphere, the reaction is more efficient than when liquid water is added. The sol-gel reaction can be carried out slowly even at room temperature. By reacting, the reaction is more efficient than, for example, heating at a temperature above the boiling point of the alcohol solvent. The sol-gel reaction can be carried out slowly. Thus, a coating layer containing high quality titanium and having a uniform thickness can be formed.

[0214] The precipitate is collected from the mixture after the above treatment. The collection method can be filtration, centrifugation, etc. In this embodiment, the collected material is collected by filtration. A paper filter was used for filtration, and the residue was filtered with the same aluminium as the solvent in which the titanium alkoxide was dissolved. It will be washed with Coal.

[0215] Next, the collected residue is dried. In this embodiment, the residue is dried in vacuum at 70° C. for 1 hour. Let us assume that.

[0216] <Step 15: Second Heating> Next, the composite oxide coated with the material having the second transition metal prepared in step 14 is The particles are heated. This step is sometimes called the second heating. The heating time is determined by the temperature of the particles. The retention time within the range is preferably 50 hours or less, and more preferably 2 hours or more and 10 hours or less. It is more preferable to carry out the heating for 1 hour or more and 3 hours or less. If the time is too short, segregation of the main group elements may not occur, but if it is too long, the diffusion of the second transition metal may occur. There is a risk that the diffusion will proceed too far and a good second region 102 will not be formed.

[0217] The specified temperature is preferably 500°C or higher and 1200°C or lower, and more preferably 800°C or higher and 1000°C or lower. If the specified temperature is too low, segregation of the main group elements and the second transition metals may not occur. However, if the temperature is too high, the first transition metal in the composite oxide particles is reduced, and the composite oxide The layered structure of lithium and the first transition metal in the composite oxide particle is decomposed. There is a risk that the security of the equipment may not be maintained.

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

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

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

[0221] The crystal orientations of the second region 102 and the third region 103 are roughly the same, and the first region 101 Since the positive electrode active material 100 has a stable bond with the positive electrode, when the positive electrode active material 100 is used in a secondary battery, the positive electrode active material 100 is stable with the positive electrode. This effectively suppresses the change in the crystal structure of the first region 101 that occurs when the first region 101 is charged. Even if lithium is removed from the region 101 of FIG. 1, the surface layer portion has stable bonds. This suppresses the release of the first transition metal such as cobalt and oxygen from the first region 101. Furthermore, the area in contact with the electrolyte can be made of a chemically stable material. Therefore, a secondary battery having excellent cycle characteristics can be obtained.

[0222] It is sufficient that the first region 101 and the second region 102 are partially topotaxis. It is not necessary that the entire area 101 and the second area 102 are topotaxis. The second region 102 and the third region 103 may be partially topotaxis. Not all of the regions 103 need to be topotaxis.

[0223] In addition, when the compound of the main group element contained in the third region contains oxygen, the compound is placed in an atmosphere containing oxygen. It is preferable to perform the heating in step 15 in an oxygen-containing atmosphere. This promotes the formation of the region 103.

[0224] Furthermore, the fluorine contained in the starting material promotes the segregation of the typical elements.

[0225] In this manner, in the method for manufacturing the positive electrode active material according to one embodiment of the present invention, the second region 102 is formed. After coating the positive electrode active material 100 with the element, heating is performed to form the third region 103. In other words, it is possible to form two types of regions on the surface of the In order to provide the region, two coating steps are required. The method for producing the material requires only one coating process (sol-gel process), making it a highly productive method. It is.

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

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

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

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

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

[0231] <Cathode active material layer> The positive electrode active material layer includes at least a positive electrode active material. In addition, other substances such as a coating on the surface of the active material, a conductive aid, 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, it is possible to obtain a high capacity and good cycle characteristics. This makes it possible to produce an excellent secondary battery.

[0233] As the conductive assistant, a carbon material, a metal material, a conductive ceramic material, or the like can be used. In addition, a fibrous material may be used as the conductive assistant. The content of the electrical auxiliary agent is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less. is more preferred.

[0234] The conductive assistant can form an electrical conductive network in the active material layer. The conductive agent can maintain the electrical conduction path between the positive electrode active materials. By adding an electrical auxiliary agent, it is possible to realize an active material layer having high electrical conductivity. .

[0235] Examples of the conductive assistant include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon fibers. Examples of carbon fibers that can be used include mesophase pitch carbon fibers. In addition, carbon fibers such as isotropic pitch-based carbon fibers can be used. Carbon nanofibers and carbon nanotubes can be used. The tube can be produced by, for example, a vapor phase growth method. For example, carbon black (acetylene black (AB) etc.), graphite particles Carbon materials such as copper, nickel, and graphene can be used. Nickel, aluminum, silver, gold and other metal powders, metal fibers, conductive ceramic materials, etc. It can be used.

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

[0237] Graphene compounds have excellent electrical properties, such as high electrical conductivity, as well as high flexibility and In addition, graphene may have excellent physical properties such as high mechanical strength. The compound has a planar shape. Graphene compounds enable surface contact with low contact resistance. In addition, even if the material is thin, it can have very high conductivity, and a small amount of the material can be used to efficiently conduct electricity within the active material layer. Therefore, the graphene compound can be used as a conductive additive. This is preferable because it is possible to increase the contact area between the active material and the conductive assistant. By using a laser dryer, the entire surface of the active material is covered with graphene, which is a conductive additive. It is preferable to form the compound as a coating. In addition, electrical resistance may be reduced. Here, the graphene compound is preferably, for example, graphene or multigraphene. It is particularly preferred to use graphene oxide or RGO, where RGO is, for example, This refers to a compound obtained by reducing graphene oxide (GO).

[0238] When using an active material with a small particle size, for example, an active material with a particle size of 1 μm or less, the specific surface area of ​​the active material is Therefore, a large amount of conductive additive is required. This tends to result in a relatively reduced amount of active material carried. If the capacity of the secondary battery decreases, the capacity of the secondary battery decreases. When graphene compounds are used, they efficiently form conductive paths even in small amounts. This is particularly preferable because it is possible to avoid reducing the amount of the active material carried.

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

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

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

[0242] Here, a plurality of graphene compounds are bonded to each other to form a mesh-like graphene compound. The graphene compound is then bonded to the graphene sheet (hereinafter referred to as a graphene compound net or a graphene net). When the active material is covered with a graphene net, the graphene net can bond the active material to each other. It can also function as a binder to bind the material together. This allows the amount of binder to be reduced. The ratio of active material to the electrode volume or weight can be adjusted to suit the application. In other words, the capacity of the secondary battery can be increased.

[0243] Here, graphene oxide is used as the graphene compound 201, and is mixed with an active material to form an active material. After the layer that will become the layer 200 is formed, it is preferable to reduce it. By using graphene oxide, which has extremely high dispersibility in polar solvents, The mixture 201 can be dispersed approximately uniformly inside the active material layer 200. The solvent is removed by evaporation from the dispersion medium containing the dispersed graphene oxide, and the graphene oxide is reduced. Therefore, the graphene compounds 201 remaining in the active material layer 200 are partially overlapped with each other. By dispersing the particles so that they are in surface contact with each other, a three-dimensional conductive path can be formed. The reduction of graphene oxide may be performed, for example, by heat treatment or by using a reducing agent. This is also possible.

[0244] Therefore, unlike granular conductive additives such as acetylene black, which come into point contact with the active material, graphite Since the compound 201 enables surface contact with low contact resistance, it is more effective than ordinary conductive additives. The amount of the positive electrode active material 100 and the graphene compound 201 is reduced, and the electrical conductivity between the positive electrode active material 100 and the graphene compound 201 is improved. Therefore, the ratio of the granular positive electrode active material 100 in the active material layer 200 can be increased. This makes it possible to increase the discharge capacity of the secondary battery.

[0245] In addition, the entire surface of the active material was previously covered with a graphene compound using a spray dryer. Thereafter, when the positive electrode active material layer is produced, a graphene compound may be further added to the positive electrode active material layer. It also allows for a better conductive path between them.

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

[0247] As the binder, it is preferable to use, for example, a water-soluble polymer. As the molecule, for example, polysaccharides can be used. CMC, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose Cellulose derivatives such as cellulose, diacetyl cellulose, regenerated cellulose, and starch These water-soluble polymers can be used in combination with the above-mentioned rubber materials. It is even better if there is a

[0248] Alternatively, the binder may be polystyrene, polymethyl acrylate, or polymethyl methacrylate. Polyvinyl chloride (Polymethyl methacrylate (PMMA)), Sodium polyacrylate, Polyvinyl chloride Polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, Polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene Polyethylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride Polyvinyl chloride (PVdF), polyacrylonitrile (PAN), ethylene propylene diene polymer It is preferable to use materials such as polyvinyl acetate and nitrocellulose.

[0249] The binder may be used in combination of two or more of the above.

[0250] For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with other materials. For example, rubber materials have excellent adhesive strength and elasticity, but it is difficult to adjust the viscosity when mixed with a solvent. In such cases, for example, it is possible to mix the material with a particularly excellent viscosity adjusting effect. As a material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer is preferably used. In addition, examples of water-soluble polymers that are particularly effective in adjusting viscosity include the aforementioned polysaccharides, such as calcium carbonate. Carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxy Cellulose derivatives such as propyl cellulose, diacetyl cellulose, and regenerated cellulose For example, starch or starch can be used.

[0251] In addition, cellulose derivatives such as carboxymethyl cellulose are, for example, carboxymethyl The solubility of cellulose increases when it is converted into a salt such as sodium salt or ammonium salt. It is easy to exert its effect as a viscosity adjuster. The higher the solubility, the easier it is to make the electrode slurry. In the preparation of the electrode, the dispersibility of the electrode with the active material and other components can be improved. In this regard, the cellulose and cellulose derivatives used as the binder for the electrode are as follows: These salts are also included.

[0252] Water-soluble polymers stabilize the viscosity by dissolving in water, and also serve as active materials and binders. Other materials to be combined, such as styrene butadiene rubber, are stable in aqueous solution. In addition, since it has a functional group, it is easy to stably adsorb on the surface of the active material. It is expected that cellulose derivatives such as carboxymethyl cellulose, for example, For example, many materials have functional groups such as hydroxyl groups and carboxyl groups. It is expected that the polymers will interact with each other and widely cover the surface of the active material.

[0253] When the binder that covers or contacts the surface of the active material forms a film, it is called a passive film. It is expected that the passive film will also play a role in preventing the decomposition of the electrolyte. It is a film with no or very low electrical conductivity, for example, on the surface of an active material. When a dynamic membrane is formed, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. In addition, the passive film suppresses electrical conductivity while allowing lithium ions to conduct. And even more desirable.

[0254] <Positive electrode current collector> The positive electrode current collector may be made of metals such as stainless steel, gold, platinum, aluminum, titanium, or the like. In addition, the material used for the positive electrode current collector can be an alloy of these materials, which has high electrical conductivity. It is preferable that the material does not dissolve at the potential of the positive electrode. Aluminum alloys containing elements such as indium and molybdenum that improve heat resistance are used. It can also be formed from a metal element that reacts with silicon to form a silicide. Metal elements that react with silicon to form silicide include zirconium, titanium, and Tantalum, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten , cobalt, nickel, etc. Current collectors are available in foil, plate (sheet), mesh, punched The current collector may be in the form of a metal, an expanded metal, or the like. It is advisable to use one with a thickness of 5 μm or more and 30 μm or less.

[0255] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer contains a conductive assistant and and a binder.

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

[0257] As a negative electrode active material, it is possible to carry out charge / discharge reactions by alloying / de-alloying reactions with lithium. For example, silicon, tin, gallium, aluminum, and Rumanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one of these elements can be used. These elements have a large capacity compared to carbon. Silicon has a high theoretical capacity of 4200mAh / g. It is preferable to use silicon. Compounds containing these elements may also be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V 2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3 Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, I nSb, SbSn, etc. Here, the charge / discharge reaction occurs due to alloying / dealloying reactions with lithium. Elements capable of undergoing a reaction and compounds containing such elements are sometimes called alloy materials. do.

[0258] In this specification, SiO refers to, for example, silicon monoxide. Alternatively, SiO x Here, it is preferable that x has a value close to 1. For example, x is 0 A value between 0.2 and 1.5 is preferred, and a value between 0.3 and 1.2 is more preferred.

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

[0260] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesophase graphite. Carbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. Here, as the artificial graphite, spherical graphite having a spherical shape can be used. For example, the MCMB may have a spherical shape, which is preferred. It is relatively easy to reduce the particle size, which may be preferable. Examples of the graphite include flake graphite and spherical natural graphite.

[0261] When lithium ions are inserted into graphite (when lithium-graphite intercalation compounds are formed), It has a low potential similar to that of lithium metal (0.05V to 0.3V vs. Li / L i + This allows the lithium-ion secondary battery to exhibit a high operating voltage. In addition, graphite has a relatively high capacitance per unit volume, a relatively small volume expansion, and is inexpensive. However, lithium ions are preferred because they have the advantage of being safer than metallic lithium.

[0262] In addition, titanium dioxide (TiO2) and lithium titanium oxide (Li4T 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] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, which has a Li3N structure. Li 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm 3 ) And preferable.

[0264] When a composite nitride of lithium and transition metals is used, the negative electrode active material contains lithium ions, The positive electrode active material is made of V2O5, Cr3O8, etc., which do not contain lithium ions. It is preferable that the positive electrode active material contains lithium ions. The lithium ions contained in the positive electrode active material are first removed to form the negative electrode active material. A complex nitride of lithium and a transition metal can be used.

[0265] In addition, a material that undergoes a conversion reaction can also be used as the negative electrode active material. For example, Lithium oxide (LiO), cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. A transition metal oxide that does not form an alloy with the negative electrode active material may be used. Further materials that are produced include Fe2O3, CuO, Cu2O, RuO2, Cr2O3, etc. oxide, CoS 0.89 , NiS, CuS and other sulfides, Zn3N2, Cu3N, Ge3 Nitrides such as N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. It also occurs with fluoride.

[0266] The conductive assistant and binder that can be contained in the negative electrode active material layer are the same as those that can be contained in the positive electrode active material layer. The conductive additive and binder may be the same as those that 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 lithium.

[0268] [Electrolyte] The electrolytic solution contains a solvent and an electrolyte. The solvent for the electrolytic solution is preferably an aprotic organic solvent. For example, ethylene carbonate (EC), propylene carbonate (PC), ethylene carbonate, chloroethylene carbonate, vinylene carbonate, gamma-butyrolactone lactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate ethyl propionate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1 ,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethylsulfur oxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran One of trihydrofuran, sulfolane, sultone, etc., or two or more of these Combinations and ratios may be used.

[0269] In addition, a flame-retardant and non-volatile ionic liquid (room-temperature molten salt) is used as the solvent for the electrolyte. By using one or more, the internal temperature of the secondary battery increases due to an internal short circuit or overcharging. Even if the battery is heated, it can prevent explosion or fire of the secondary battery. Ionic liquids are made of cations and anions. The electrolyte solution contains an organic cation and an anion. Ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, etc. Aliphatic onium cations such as imidazolium cations and pyridinium cations Aromatic cations are also used as anions in electrolytes. Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkyl Sulfonate anion, tetrafluoroborate anion, perfluoroalkylborate anion, hexafluorophosphate anion, or perfluoroalkyl phosphate anions, etc.

[0270] The electrolyte to be dissolved in the above solvent is, for example, LiPF6, LiClO4, Li AsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4 , Li2B 10 Cl 10 , Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO 3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2) 2. Lithium such as LiN(C4F9SO2)(CF3SO2) and LiN(C2F5SO2)2 Use one or more of these salts in any combination and ratio. can be done.

[0271] The electrolyte used in secondary batteries is free of granular waste and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "inorganic substances"). It is preferable to use a highly purified electrolyte solution with a low content of ruthenium oxide (also called "pure substance"). Specifically, the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less, more preferably It is preferably 0.01% or less.

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

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

[0274] By using a polymer gel electrolyte, safety against leakage etc. is improved. It is possible to reduce the thickness and weight of the device.

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

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

[0277] In addition, instead of the electrolyte, solid electrolytes containing inorganic materials such as sulfides and oxides, and P A solid electrolyte containing a polymer material such as EO (polyethylene oxide) can be used. When a solid electrolyte is used, the installation of a separator or spacer becomes unnecessary. Since the entire pond can be solidified, there is no risk of leakage, and safety is improved dramatically.

[0278] [Separator] The secondary battery preferably has a separator. The separator may be, for example, a paper. , nonwoven fabric, glass fiber, ceramics, or nylon (polyamide), vinylon (poly Vinyl alcohol fiber), polyester, acrylic, polyolefin, polyurethane The separator can be made of synthetic fibers or the like. It is preferable that the separator is processed into a shape such that it envelops either the positive electrode or the negative electrode.

[0279] The separator may have a multi-layer structure. For example, the separator may be made of an organic material such as polypropylene or polyethylene. The material film is made of ceramic, fluorine, polyamide, or a combination of these. The ceramic material can be, for example, arsenic oxide. Aluminum particles, silicon oxide particles, etc. can be used. For example, PVDF, polytetrafluoroethylene, etc. can be used. Polyamide-based materials Examples of materials used include nylon and aramid (meta-aramid and para-aramid). It is possible.

[0280] Coating with ceramic materials improves oxidation resistance, making it ideal for separators during high-voltage charging and discharging. This suppresses the deterioration of the capacitor and improves the reliability of the secondary battery. By coating the electrode, the separator and the electrode are more easily adhered to each other, improving the output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, which contributes to the safety of secondary batteries. This can improve safety.

[0281] For example, a mixture of aluminum oxide and aramid is coated on both sides of a polypropylene film. Alternatively, the surface of the polypropylene film that comes into contact with the positive electrode may be coated with aluminum oxide. Alternatively, the surface in contact with the negative electrode may be coated with a mixed material of rubber and aramid, and a fluorine-based material may be coated on the surface. .

[0282] By using a multi-layered separator, the safety of the secondary battery can be ensured even if the overall thickness of the separator is thin. Since the capacity per unit volume of the secondary battery can be increased, the capacity per unit volume of the secondary battery can be increased.

[0283] [Exterior body] The exterior body of the secondary battery is made of, for example, a metal material such as aluminum or a resin material. Also, a film-like exterior body can be used. For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. On the film made of the material, a flexible metal such as aluminum, stainless steel, copper, nickel, etc. is A thin metal film is then applied, and a polyamide resin or polyester resin is applied to the outer surface of the exterior body on the thin metal film. For example, a three-layer film having an insulating synthetic resin film such as a fluorine-based resin can be used.

[0284] [Charge / discharge method] The secondary battery can be charged and discharged, for example, as follows.

[0285] ≪CC charging≫ First, we will explain CC charging, which is one of the charging methods. CC charging is This is a charging method in which a constant current is passed through the secondary battery and charging is stopped when a specified voltage is reached. The secondary battery is assumed to be an equivalent circuit with internal resistance R and secondary battery capacity C as shown in Figure 8(A). In this case, the secondary battery voltage V B is the voltage V across the internal resistance R R and the secondary battery capacity C Applied voltage V C It is the sum of.

[0286] During CC charging, as shown in Figure 8(A), the switch is turned on and a constant current is applied. Current I flows through the secondary battery. During this time, current I is constant, so V R = R × I Ohm's Law According to the law, the voltage V across the internal resistance R R On the other hand, the voltage applied to the secondary battery capacity C is constant. Pressure V C increases over time. Therefore, the secondary battery voltage V B As time passes, Both rise.

[0287] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, charging is stopped. When CC charging is stopped, the switch is turned off and the current I = 0, as shown in Figure 8(B). Therefore, the voltage V applied to the internal resistance R R Therefore, with the internal resistance R The voltage drop of the secondary battery V B decreases.

[0288] The secondary battery voltage V during CC charging and after CC charging is stopped B and the charging current An example is shown in Figure 8(C). The secondary battery voltage V B But, C C It shows a slight decrease after charging is stopped.

[0289] ≪CCCV charging≫ Next, we will explain CCCV charging, which is a charging method different from the above. First, charge the battery to a specified voltage using CC charging, then use CV (constant voltage) charging to reduce the current flowing. This is a charging method in which charging is continued until the battery becomes low, specifically until the battery reaches a cut-off current value.

[0290] During CC charging, the constant current power supply is switched on and the constant current is The voltage power supply is switched off and a constant current I flows through the secondary battery. During this time, the current I Since it is constant, V R According to Ohm's law, the voltage V across the internal resistance R is R Also On the other hand, the voltage V applied to the secondary battery capacity C is C increases over time. Therefore, the secondary battery voltage V B increases over time.

[0291] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, the CC charge is switched to C During CV charging, the constant voltage power supply is switched to V charging, as shown in Figure 9(B). The switch is turned on, the constant current power supply switch is turned off, and the secondary battery voltage V B becomes constant On the other hand, the voltage V applied to the secondary battery capacity C C V increases over time. B =V R +V C Therefore, the voltage V across the internal resistance R R becomes smaller over time. Voltage V across resistor R R As becomes smaller, V R By Ohm's law, = R × I, The current I flowing to the next battery also becomes smaller.

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

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

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

[0295] The secondary battery voltage V during CC discharge B An example of the discharge current is shown in Fig. 10. According to the secondary battery voltage V B The figure shows how the light descends.

[0296] Next, the discharge rate and the charge rate will be described. It is the relative ratio of the current during discharge and is expressed in units of C. For a battery with a rated capacity of X (Ah), In this case, the current equivalent to 1C is X(A). When discharging with a current of 2X(A), the current is 2C. If it is discharged at a current of X / 5(A), it is said to be discharged at 0.2C. The charging rate is also the same; if you charge with a current of 2X(A), it will be charged at 2C. When the battery was charged with a current of X / 5(A), it was charged at 0.2C. .

[0297] (Embodiment 3) In this embodiment, the shape of a secondary battery having the positive electrode active material 100 described in the previous embodiment is The material used in the secondary battery described in this embodiment is the same as that in the previous embodiment. The description of the form may be taken into consideration.

[0298] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. FIG. 11(A) shows a coin-type (single-layer flat type) 11(A) is a cross-sectional view of the secondary battery shown in FIG.

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

[0300] The positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 are each an active material. The barrier layer need only be formed on one side.

[0301] The positive electrode can 301 and the negative electrode can 302 are made of nickel or aluminum, which is resistant to corrosion by the electrolyte. , titanium, or alloys of these with other metals (e.g. stainless steel In addition, nickel or aluminum can be used to prevent corrosion by the electrolyte. The positive electrode can 301 is for covering the positive electrode 304, and the negative electrode can 302 is for covering the negative electrode 304. 7 and electrically connected to each other.

[0302] The negative electrode 307, the positive electrode 304, and the separator 310 are impregnated with an electrolyte, and the negative electrode 307, the positive electrode 304, and the separator 310 are then impregnated with an electrolyte. As shown in FIG. 1, the positive electrode can 301 is placed downward, and the positive electrode 304, the separator 310, the negative electrode 307, The positive electrode can 301 and the negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are secured together with a gasket 303 interposed therebetween. Then, the laminate is pressed to manufacture a coin-type secondary battery 300.

[0303] By using the positive electrode active material described in the above embodiment for the positive electrode 304, it is possible to achieve high capacity and cycle. The coin-type secondary battery 300 can be made to have excellent characteristics.

[0304] Here, the flow of current during charging of a secondary battery will be explained with reference to FIG. When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of electric current are in the same direction. In secondary batteries that use lithium, the anode and cathode are connected by charging and discharging. The cathode (cathode) is switched, and the oxidation and reduction reactions are switched, so the reaction potential The electrode with the higher reaction potential is called the positive electrode, and the electrode with the lower reaction potential is called the negative electrode. In this case, the charge / discharge current is always the same whether the battery is charging or discharging or a reverse pulse current is applied. Even when an electric current flows through the positive electrode, it is called the "positive electrode" or "+ electrode (plus electrode)" and the negative electrode is called the "negative electrode" or "-electrode (minus electrode)". When the terms anode and cathode are used, the difference between charging and discharging is , which can lead to confusion. The term "cathode" is not used in this specification. When using the terms negative electrode ( ) or cathode ( ), specify whether they are charging or discharging, and positive electrode ( It will also be indicated whether it corresponds to a positive pole or a negative pole.

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

[0306] [Cylindrical secondary battery] Next, an example of a cylindrical secondary battery will be described with reference to FIG. As shown in FIG. 12(A), the battery has a positive electrode cap (battery lid) 601 on the top surface and The positive electrode cap and the battery can (external can) 602 are disposed on the bottom surface of the positive electrode cap and the battery can (external can). It is insulated from 602 by a gasket (insulating packing) 610 .

[0307] Fig. 12(B) is a schematic diagram showing a cross section of a cylindrical secondary battery. Inside the can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are sandwiched between a separator 605. A wound battery element is provided. Although not shown, the battery element is wound around a center pin. The battery can 602 is closed at one end and open at the other end. The material is nickel, aluminum, titanium, or other metals that are resistant to corrosion by the electrolyte. These and their alloys with other metals (e.g., stainless steel, etc.) can be used. In addition, in order to prevent corrosion by the electrolyte, it is preferable to coat the electrode with nickel, aluminum, or the like. A battery element in which a positive electrode, a negative electrode, and a separator are wound inside a battery can 602. The battery element is sandwiched between a pair of opposing insulating plates 608 and 609. A non-aqueous electrolyte (not shown) is poured into the battery can 602. A coin-type secondary battery can be used.

[0308] The positive and negative electrodes used in cylindrical secondary batteries are wound, so active material is formed on both sides of the current collector. A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative A negative electrode terminal (negative electrode current collecting lead) 607 is connected to the positive electrode 606. The positive terminal 607 may be made of a metal material such as aluminum. 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 is a PTC (Positive Temperature Coefficient) The positive electrode cap 601 is electrically connected to the positive electrode cap 601 via a capacitance 611. The safety valve mechanism 612 is a mechanism for releasing the positive electrode cap 601 when the internal pressure of the battery increases beyond a predetermined threshold. The PTC element 611 cuts off the electrical connection between the positive electrode 604 and the positive electrode 604. It is a thermal resistor element whose resistance increases when the temperature rises, and the amount of current is limited by the increase in resistance. It prevents abnormal heat generation. The PTC element is made of barium titanate (BaTiO3) Semiconductor ceramics and the like can be used.

[0309] 12C, a plurality of secondary batteries 600 are mounted on a conductive plate 613 and a conductive plate 614. The secondary batteries 600 may be sandwiched between the secondary batteries 600 to form a module 615. They may be connected in series or in parallel and then in series. By configuring a module 615 having a plurality of secondary batteries 600, It is possible to extract a large amount of power.

[0310] FIG. 12(D) is a top view of module 615. For clarity of illustration, conductive plate 613 is As shown in FIG. 12(D), the module 615 includes a plurality of secondary batteries 600. The conductive plate 613 may be placed on the conductive wire 616. In addition, a temperature control device 617 may be provided between the multiple secondary batteries 600. When the secondary battery 600 is overheated, 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. This makes the performance of the module 615 less susceptible to the effects of outside temperature.

[0311] By using the positive electrode active material described in the above embodiment for the positive electrode 604, it is possible to achieve high capacity and cycle. The cylindrical secondary battery 600 can be made to have excellent characteristics.

[0312] [Example of secondary battery structure] Another structural example of the secondary battery will be described with reference to FIGS.

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

[0314] The circuit board 900 includes a terminal 911 and a circuit 912. The terminal 911 is connected to a terminal 951. , a terminal 952, an antenna 914, an antenna 915, and a circuit 912. A plurality of terminals 911 are provided, and each of the plurality of terminals 911 is used as a control signal input terminal, a power supply terminal, etc. may also be used.

[0315] The circuit 912 may be provided on the back surface of the circuit board 900. The antenna 915 is not limited to a coil shape, but may be, for example, a wire shape or a plate shape. Planar antenna, aperture antenna, traveling wave antenna, EH antenna, magnetic field antenna, dielectric Alternatively, antenna 914 or antenna 915 may be used. The flat conductor may function as one of the conductors for electric field coupling. In other words, the annulus can be used as one of the two conductors of the capacitor. In this way, the electromagnetic field, the magnetic field, and the like can be detected by the antenna 914 or the antenna 915. 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. This allows the amount of power received by the antenna 914 to be increased.

[0317] The secondary battery has a layer 916 between the antenna 914 and the secondary battery 913, and between the antenna 915 and the secondary battery 913. The layer 916 has a function of shielding an electromagnetic field generated by the secondary battery 913, for example. The layer 916 may be made of, for example, a magnetic material.

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

[0319] For example, as shown in FIG. 14(A-1) and FIG. 14(A-2), In the secondary battery 913 shown in (B), an antenna may be provided on each of a pair of opposing surfaces. FIG. 14(A-1) is an external view seen from one side of the pair of faces. FIG. 13(A) and FIG. 13(A-2) are external views seen from the other side of the pair of surfaces. The same parts as those of the secondary battery shown in FIG. 13(B) are shown in FIG. 13(A) and FIG. 13(B). The description of the secondary battery can be used as appropriate.

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

[0321] By adopting the above structure, the size of both the antenna 914 and the antenna 918 can be increased. The antenna 918 can perform data communication with an external device, for example. The antenna 918 has a shape that can be applied to the antenna 914, for example. A communication method between the secondary battery and other devices via the antenna 918. Examples of such methods include NFC and other response methods that can be used between secondary batteries and other devices. can be applied.

[0322] Alternatively, as shown in FIG. 14(B-1), the secondary battery 9 shown in FIG. 13(A) and FIG. 13(B) may be used. A display device 920 may be provided in the display device 13. The display device 920 is electrically connected to the terminal 911. It is not necessary to provide the label 910 in the portion where the display device 920 is provided. 13(A) and 13(B), the same parts as those of the secondary battery shown in FIG. The description of the secondary battery shown in FIG. 13(B) can be used as appropriate.

[0323] The display device 920 displays, for example, an image indicating whether charging is in progress, an image indicating the amount of stored power, etc. The display device 920 may be, for example, an electronic paper, a liquid crystal display device, an electrophotographic display device, or the like. For example, an electroluminescence (EL) display device can be used. By using the par, the power consumption of the display device 920 can be reduced.

[0324] Alternatively, as shown in FIG. 14(B-2), the secondary battery 9 shown in FIG. 13(A) and FIG. 13(B) may be used. A sensor 921 may be provided on the sensor 13. The sensor 921 is connected to the terminal 911 via a terminal 922. Electrically connected to the same part as the secondary battery shown in FIG. 13(A) and FIG. 13(B). In this regard, the description of the secondary battery shown in FIG. 13(A) and FIG. 13(B) can be appropriately applied.

[0325] The sensor 921 may be, for example, a sensor for detecting displacement, position, speed, acceleration, angular velocity, number of rotations, distance, light, etc. , liquid, magnetic, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow It is sufficient if the device has the function of measuring the amount, humidity, gradient, vibration, odor, or infrared rays. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed can be obtained. It is also possible to detect a signal (such as temperature) and store it in memory within the circuit 912.

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

[0327] A secondary battery 913 shown in FIG. 15(A) has a terminal 951 and a terminal 952 provided inside a housing 930. The winding body 950 is impregnated with an electrolyte inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is in contact with the housing by using an insulating material or the like. In FIG. 15A, for convenience, the housing 930 is not in contact with the 9, in reality, the winding body 950 is covered by the housing 930, and the terminals 951 and 95 2 extends outside the housing 930. The housing 930 is made of a metal material (e.g., aluminum). Materials such as rubber or resin materials can be used.

[0328] As shown in FIG. 15B, the housing 930 shown in FIG. 15A is made of a plurality of materials. For example, the secondary battery 913 shown in FIG. The wound body 930b is attached to the housing 930a. 50 are provided.

[0329] The housing 930a can be made of an insulating material such as an organic resin. By using a material such as organic resin on the surface on which the secondary battery 913 is formed, If the shielding of the electric field by the housing 930a is small, the shielding of the housing 930a can be suppressed. Antennas such as antenna 914 and antenna 915 may be provided inside the housing 930b. For example, a metal material can be used.

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

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

[0332] By using the positive electrode active material described in the above embodiment for the positive electrode 932, the battery can be cycled with a high capacity. The secondary battery 913 can have excellent characteristics.

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

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

[0335] The number of layers of the negative electrode 994, the positive electrode 995, and the separator 996 is determined as required. The negative electrode 994 is connected to the lead electrode 997 and the lead The positive electrode 995 is connected to a negative electrode collector (not shown) via one of the lead electrodes 998. The other of the electrode 997 and the lead electrode 998 is connected to a positive electrode current collector (not shown).

[0336] As shown in FIG. 17B, a film 981 that serves as an exterior body and a film 98 having a recess are 2 are bonded together by thermocompression or the like to form a space in which the above-mentioned wound body 993 is housed. In this way, a secondary battery 980 can be manufactured as shown in FIG. 3 has a lead electrode 997 and a lead electrode 998, a film 981, and a recess The inside of the film 982 is impregnated with an electrolyte.

[0337] The film 981 and the film 982 having the recesses are made of a metal material such as aluminum. The film 981 and the film 982 having the recesses can be made of a resin material. If a resin material is used as the material, when an external force is applied, the film 981 and the recessed portion The film 982 having the electrode can be deformed to produce a secondary battery having flexibility. can be done.

[0338] In addition, although an example using two films is shown in FIG. 17(B) and FIG. 17(C), A space is formed by folding one sheet of film, and the above-mentioned wound body 99 is inserted into the space. It may also accommodate 3.

[0339] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, it is possible to achieve high capacity cycling. The secondary battery 980 can have excellent characteristics.

[0340] In addition, in FIG. 17, a secondary battery 9 having a wound body in a space formed by a film serving as an exterior body is shown. We have explained the example of 80, but as shown in Figure 18, the shape is determined by the film that is the exterior body. The space defined by the positive electrode layer can be used as a secondary battery having a plurality of rectangular positive electrodes, separators, and negative electrodes. good.

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

[0342] In the laminated secondary battery 500 shown in FIG. 18(A), a positive electrode current collector 501 and a negative electrode current collector The positive electrode current collector 504 also serves as a terminal for obtaining electrical contact with the outside. A part of the current collector 501 and the negative electrode current collector 504 is exposed to the outside from the exterior body 509. In addition, the positive electrode current collector 501 and the negative electrode current collector 504 may be arranged in a manner similar to that described above. Instead of exposing it to the outside, a lead electrode is used to connect the lead electrode to the positive electrode current collector 501 or the negative electrode The lead electrode may be exposed to the outside by ultrasonic bonding to the current collector 504 .

[0343] In the laminated secondary battery 500, the exterior body 509 is made of, for example, polyethylene, poly A film made of propylene, polycarbonate, ionomer, polyamide, etc. is coated with a A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied. On the metallic thin film, an insulating synthetic resin such as polyamide resin or polyester resin is applied as the outer surface of the exterior body. A laminate film having a three-layer structure with an oil film can be used.

[0344] An example of the cross-sectional structure of a laminated secondary battery 500 is shown in FIG. For simplicity, A) shows an example consisting of two current collectors, but in reality, it is composed of multiple electrode layers. It consists of:

[0345] In FIG. 18B, as an example, the number of electrode layers is 16. However, the secondary battery 500 has flexibility. In FIG. 18(B), the negative electrode current collector 504 has eight layers. The positive electrode current collector 501 has a structure of 8 layers, totaling 16 layers. The cross section of the extraction part is shown, and eight layers of negative electrode current collector 504 are ultrasonically bonded. The number of electrode layers is not limited to 16, and may be more or less. In addition, when the number of electrode layers is small, the secondary battery can have a larger capacity. In this case, a secondary battery can be made thin and has excellent flexibility.

[0346] An example of the external appearance of a laminated secondary battery 500 is shown in FIGS. 19 and 20. 9 and 20 show a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead The positive electrode 510 and the negative electrode 511 are connected to each other.

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

[0348] [Method of manufacturing laminated secondary battery] Here, an example of a method for producing a laminated secondary battery shown in FIG. 19 will be described with reference to FIG. This will be explained using (B) and (C).

[0349] First, the negative electrode 506, the separator 507, and the positive electrode 503 are laminated. The negative electrode 506, the separator 507, and the positive electrode 503 are shown. Next, the bonding of the tab regions of the positive electrode 503 and the bonding of the tabs of the positive electrode on the outermost surface are shown. The positive electrode lead electrode 510 is bonded to the region. For example, ultrasonic welding or the like may be used for bonding. Similarly, the bonding between the tab regions of the negative electrodes 506 and the bonding of the negative electrode leads to the tab region of the outermost negative electrode are preferably performed. Then, the metal layer 511 is bonded.

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

[0351] Next, as shown in FIG. 21(C), the exterior body 509 is folded at the portion indicated by the dashed line. After that, the outer periphery of the exterior body 509 is bonded. For example, thermocompression bonding may be used for bonding. 509, so that the electrolyte 508 can be poured in later. An area that is not joined (hereinafter referred to as an inlet) is provided.

[0352] Next, the electrolyte 508 is introduced into the inside of the exterior body 509 through an inlet provided in the exterior body 509. The electrolyte 508 is preferably introduced under a reduced pressure or an inert gas atmosphere. Finally, the inlet is joined. In this way, a laminated secondary battery is produced. A secondary battery 500 can be fabricated.

[0353] By using the positive electrode active material described in the above embodiment for the positive electrode 503, it is possible to achieve high capacity and cycle. The secondary battery 500 can have excellent characteristics.

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

[0355] Fig. 22(A) shows a schematic top view of a bendable secondary battery 50. , (B2), and (C) are cut along the lines C1-C2 and C3-C in FIG. 22(A), respectively. 4 is a schematic cross-sectional view taken along the line A1-A2. The positive electrode 11a and the negative electrode 11b are electrically connected to the positive electrode 11a. The lead 12a electrically connected to the negative electrode 11b and the lead 12b electrically connected to the negative electrode 11b are disposed in the outer casing 5. In addition, the area surrounded by the exterior body 51 includes the positive electrode 11a and the negative electrode 11b. In addition to 1b, an electrolyte (not shown) is enclosed.

[0356] The positive electrode 11a and the negative electrode 11b of the battery 50 will be described with reference to FIG. 3(A) is a perspective view illustrating the stacking order of the positive electrode 11a, the negative electrode 11b, and the separator 14. FIG. 23(B) shows the positive electrode 11a and the negative electrode 11b, as well as the lead 12a and the lead FIG. 12b is a perspective view showing the same.

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

[0358] The surfaces of the positive electrode 11a on which the positive electrode active material layer is not formed and the surfaces of the negative electrode 11b on which the negative electrode active material layer is not formed are Positive electrode 11a and negative electrode 11b are stacked such that their surfaces without the formation of a dielectric layer are in contact with each other.

[0359] In addition, the surface of the positive electrode 11a on which the positive electrode active material is formed and the surface of the negative electrode 11b on which the negative electrode active material is formed are A separator 14 is provided between the surfaces. In FIG. 23(A), the separator is not shown for ease of viewing. 14 is shown by a dotted line.

[0360] As shown in FIG. 23B, the positive electrodes 11a and the leads 12a are bonded to each other at the joints 15a. The negative electrodes 11b and the leads 12b are electrically connected to each other at the joints 15b. The electrodes are electrically connected to each other.

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

[0362] The exterior body 51 has a film-like shape and is made up of two pieces of material that sandwich the positive electrode 11a and the negative electrode 11b. The exterior body 51 includes a folded portion 61, a pair of seal portions 62, and a seal The pair of seal parts 62 are disposed to sandwich the positive electrode 11a and the negative electrode 11b. The seal portion 63 is also called a side seal. It has a portion that overlaps with the lead 12b and can also be called a top seal.

[0363] The exterior body 51 has ridge lines 71 and valley lines 72 arranged alternately at the portions overlapping the positive electrode 11a and the negative electrode 11b. In addition, the seal portion 62 and the seal portion 63 of the exterior body 51 have a corrugated shape arranged in a straight line. Preferably, 63 is flat.

[0364] FIG. 22(B1) is a cross section cut at the portion overlapping with the ridge line 71, and FIG. 22(B2) is a cross section cut at the portion overlapping with the valley line 72. 22(B1) and (B2) are cross sections taken along the line 72. and corresponds to a 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 defined as La. When the battery 50 is deformed, for example by bending, the positive electrode 11a and the negative electrode 11b are In this case, if the distance La is too short, the exterior body 51 and the The positive electrode 11a and the negative electrode 11b may rub against each other strongly, and the exterior body 51 may be damaged. When the metal film of the exterior body 51 is exposed, the metal film is corroded by the electrolyte. Therefore, it is preferable to set the distance La as long as possible. On the other hand, if the distance La is made too large, the volume of the battery 50 increases.

[0366] In addition, the greater the total thickness of the laminated positive electrode 11a and negative electrode 11b, the greater the It is preferable to increase the distance La between the sealing portion 62 and the recessed portion 63 .

[0367] More specifically, a positive electrode 11a, a negative electrode 11b, and a separator (not shown) are stacked. When the total thickness of 214 is thickness t, the distance La is 0.8 to 3.0 times the thickness t. Preferably, the ratio is 0.9 to 2.5 times, more preferably 1.0 to 2.0 times. By setting the distance La in this range, the device is compact and has good resistance to bending. This makes it possible to realize a highly reliable battery.

[0368] In addition, when the distance between the pair of seal portions 62 is Lb, the distance Lb is the width of the negative electrode 11b. It is preferable that the thickness is sufficiently larger than Wb. This allows the battery 50 to be protected against repeated bending, etc. When the positive electrode 11a and the negative electrode 11b are deformed, even if the positive electrode 11a and the negative electrode 11b come into contact with the exterior body 51, Since a part of the positive electrode 11a and the negative electrode 11b can be shifted in the width direction, This effectively prevents the pole 11b and the exterior body 51 from rubbing against each other.

[0369] For example, the difference between the distance Lb between the pair of seal portions 62 and the width Wb of the negative electrode 11b is a and 1.6 times or more and 6.0 times or less, preferably 1.8 times or more and 5. 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, the width Wb, and the thickness t satisfy the relationship of the following formula 2. It is.

[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, and more preferably is greater than or equal to 1.0 and less than or equal to 2.0.

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

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

[0375] When the battery 50 is bent, the part of the exterior body 51 located on the outside of the bend stretches, and the other part located on the inside stretches. More specifically, the portion located on the outside of the exterior body 51 is deformed so as to shrink. On the other hand, the inside of the exterior body 51 is deformed so that the amplitude of the wave becomes smaller and the wave period becomes larger. The part where the wave is located is deformed so that the amplitude of the wave becomes large and the period of the wave becomes small. As described above, the deformation of the exterior body 51 reduces the stress applied to the exterior body 51 due to bending. Therefore, the material that constitutes the exterior body 51 does not need to expand or contract. The battery 50 can be bent with little force without breaking.

[0376] Furthermore, as shown in FIG. 22(D), when the battery 50 is bent, the positive electrode 11a and the negative electrode 11b are At this time, the multiple stacked positive electrodes 11a and negative electrodes 11b are shifted relative to each other. Since the end of the seal portion 63 is fixed by the fixing member 17, the As a result, the positive electrode 11a and the negative electrode 11 The stress applied to the positive electrode 11a and the negative electrode 11b is relieved, and the positive electrode 11a and the negative electrode 11b themselves do not need 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] In addition, a space 73 is provided between the ends of the positive electrode 11a and the negative electrode 11b and the exterior body 51. As a result, when the battery is bent, the ends of the positive electrode 11a and the negative electrode 11b located on the inside are in contact with the exterior body. 51 can be displaced relative to each other without contacting them.

[0378] The battery 50 shown in FIG. 22 and FIG. 23 does not break the exterior body even when repeatedly bent and stretched. The battery is less susceptible to damage such as loss of the positive electrode 11a and the negative electrode 11b, and the battery characteristics are also less likely to deteriorate. The positive electrode 11a of the battery 50 uses the positive electrode active material described in the previous embodiment. This makes it possible to obtain a battery with even better cycle characteristics.

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

[0380] First, as described in part of the third embodiment, a bendable secondary battery is mounted on an electronic device. Examples are shown in Figures 24(A) to 24(G). Examples of devices include television sets (also called televisions or television receivers); Computer monitors, digital cameras, digital video cameras, digital photos Frame, mobile phone (also called mobile phone or mobile phone device), portable game machine, portable information Examples include terminals, audio playback devices, and large game machines such as pachinko machines.

[0381] In addition, the flexible secondary battery can be mounted on the inner or outer walls of houses or buildings, or on the inside or outside of automobiles. It is also possible to incorporate it along the curved surfaces of the interior or exterior of the vehicle.

[0382] FIG. 24A shows an example of a mobile phone. A mobile phone 7400 includes a housing 7401. In addition to the display unit 7402, operation buttons 7403, an external connection port 7404, The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, etc. The secondary battery 7407 is a secondary battery of one embodiment of the present invention. This makes it possible to provide a lightweight mobile phone with a long life.

[0383] FIG. 24B shows the mobile phone 7400 in a curved state. When the battery is deformed by applying an external force to the battery, the secondary battery installed inside the battery is released. The secondary battery 7407 is also bent. At this time, the state of the bent secondary battery 7407 is shown in FIG. The secondary battery 7407 is a thin storage battery. The secondary battery 7407 is in a bent state. The secondary battery 7407 is fixed in place by a resistor. For example, the current collector 7409 is made of copper foil, some of which is alloyed with gallium. The adhesion between the collector 7409 and the active material layer in contact therewith is improved, and the secondary battery 7407 This structure is highly reliable even when bent.

[0384] FIG. 24D shows an example of a bangle-type display device. The portable display device 7100 is The device includes a housing 7101 , a display unit 7102 , operation buttons 7103 , and a secondary battery 7104 . FIG. 24E shows the bent state of the secondary battery 7104. When the device is attached to the user's arm, the housing may deform and cause damage to part of the secondary battery 7104 or The total curvature changes. Note that the degree of curvature at any point on the curve is expressed as the radius of the corresponding circle. The value expressed is the radius of curvature, and the inverse of the radius of curvature is called the curvature. Within the range of 40 mm to 150 mm, a part of the main surface of the case or the secondary battery 7104 The radius of curvature of the main surface of the secondary battery 7104 is 40 mm or more and 150 mm or less. If the thickness is within the range of 1 mm or less, high reliability can be maintained. By using the secondary battery of one embodiment, a lightweight, long-life portable display device can be provided.

[0385] FIG. 24F shows an example of a wristwatch-type portable information terminal. The portable information terminal 7200 is , a housing 7201, a display unit 7202, a band 7203, a buckle 7204, and an operation button 72 05, input / output terminal 7206, etc.

[0386] The portable information terminal 7200 is capable of carrying out mobile telephone calls, e-mails, viewing and creating documents, playing music, and using the Internet. - It can run various applications such as internet communication and computer games. do.

[0387] The display unit 7202 has a curved display surface, and displays images along the curved display surface. The display portion 7202 is provided with a touch sensor, and can be used to input a touch signal to the screen using a finger or a stylus. For example, the icon 72 displayed on the display unit 7202 can be operated by touching it. You can launch the application by touching 07.

[0388] The operation button 7205 is used to set the time, turn the power on and off, and turn wireless communication on and off. It has various functions such as operation, silent mode activation and deactivation, power saving mode activation and deactivation, etc. For example, an operating system installed in the portable information terminal 7200 can The function of the operation button 7205 can also be freely set using the stem.

[0389] In addition, the mobile information terminal 7200 is capable of performing short-distance wireless communication according to a communication standard. For example, by communicating with a wireless headset, You can also make calls.

[0390] The portable information terminal 7200 also includes an input / output terminal 7206, and a connector for connecting to other information terminals. Data can be exchanged directly through the input / output terminal 7206. The charging operation can be performed by wireless power supply without going through the input / output terminal 7206. This is also possible.

[0391] A display portion 7202 of a portable information terminal 7200 includes a secondary battery of one embodiment of the present invention. By using the secondary battery of one embodiment of the present invention, a lightweight portable information terminal with a long life can be provided. For example, the secondary battery 7104 shown in FIG. 24E is curved inside the housing 7201. or may be incorporated in a bendable state inside the band 7203.

[0392] The portable information terminal 7200 preferably has a sensor. For example, a fingerprint sensor may be used as the sensor. Sensors for human body such as pulse sensors, body temperature sensors, touch sensors, pressure sensors, acceleration sensors It is preferable that the above-mentioned components are mounted on the vehicle.

[0393] FIG. 24G shows an example of a wristband-type display device. The display device 7300 includes a display unit 7 The display device 7300 includes a display 304 and a secondary battery of one embodiment of the present invention. The display unit 7304 may be equipped with a touch sensor, and may function as a portable information terminal. It is also possible.

[0394] The display surface of the display unit 7304 is curved, and the display can be performed along the curved display surface. In addition, the display device 7300 can display a display state by short-distance wireless communication according to a communication standard. The situation can be changed.

[0395] The display device 7300 also has an input / output terminal, and can directly connect to other information terminals via a connector. It is also possible to charge the device via the input / output terminals. The charging operation may be performed by wireless power supply without going through the input / output terminals.

[0396] By using the secondary battery of one embodiment of the present invention as the secondary battery included in the display device 7300, It is possible to provide a display device with a long life and low cost.

[0397] FIG. 1 shows an example in which the secondary battery having excellent cycle characteristics shown in the above embodiment is mounted on an electronic device. 24(H), FIG. 25 and FIG. 26.

[0398] By using the secondary battery of one embodiment of the present invention as a secondary battery in everyday electronic devices, the device can be lightweight and have a long life. For example, we can provide a wide range of products for daily electronic devices, such as electric toothbrushes, electric shavers, These include mobile beauty devices, and the secondary batteries for these products are designed to be easy for users to carry. Therefore, there is a demand for a stick-shaped secondary battery that is small, lightweight, and has a large capacity.

[0399] FIG. 24(H) is a perspective view of a device also called a tobacco-containing smoking device (electronic cigarette). In 24(H), the electronic cigarette 7500 is an atomizer 7501 that includes a heating element and an atomizer A secondary battery 7504 that supplies power to the myza, and a cart including a liquid supply bottle and sensors, etc. The secondary battery 7504 is composed of a ridge 7502. To enhance safety, the secondary battery 7504 is protected from overcharging and overcharging. A protection circuit for preventing discharge may be electrically connected to the secondary battery 7504. The secondary battery 7504 has an external terminal so that it can be connected to a charging device. The 504 is the tip when held, so the total length is short and the weight is light. Since the secondary battery of one embodiment of the present invention has a high capacity and good cycle characteristics, We offer the 7500 electronic cigarette, which is small and lightweight and can be used for long periods of time. Can be provided.

[0400] Next, FIG. 25(A) and FIG. 25(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIG. 25(A) and FIG. 25(B) includes a housing 9630. a, housing 9630b, a movable part 9640 connecting the housing 9630a and the housing 9630b, A display unit 9631 having a display unit 9631a and a display unit 9631b, and a display mode changeover switch 9626, power switch 9627, power saving mode switch 9625, fastener 96 29, and an operation switch 9628. The display unit 9631 has a flexible panel. By using this, a tablet terminal with a larger display area can be created. 25(B) shows the tablet terminal 9600 in an open state, and FIG. 25(C) shows the tablet terminal 9600 in a closed state. The figure shows the 9600 in a closed state.

[0401] The tablet terminal 9600 also includes a battery storage device inside the housing 9630a and the housing 9630b. The power storage unit 9635 is connected to the housing 9630a through the movable portion 9640. It is located across 9630b.

[0402] A part of the display unit 9631a can be used as a touch panel area 9632a. By touching the operation keys 9638, data can be input. In 1a, as an example, half of the area has a display function only, and the other half The display unit 963 has a touch panel function, but is not limited to this. The entire area of ​​the display unit 96 may have a touch panel function. The entire surface of 31a is made to display keyboard buttons to make it a touch panel, and the display part 9631b is displayed It can be used as a screen.

[0403] In addition, in the display unit 9631b, as in the display unit 9631a, The area 9632b of the touch panel can be used as the keyboard of the touch panel. By touching the area where the display switch button 9639 is displayed with your finger or a stylus, A keyboard button can be displayed on the display portion 9631b.

[0404] In addition, the touch panel area 9632a and the touch panel area 9632b can be touched simultaneously. You can also input the character.

[0405] A display mode changeover switch 9626 is used to change the display orientation between portrait and landscape. You can switch between black and white and color display. The touch 9625 detects when in use by an optical sensor built into the tablet terminal 9600. The brightness of the display can be optimized according to the amount of external light. In addition to optical sensors, other sensors such as gyros and acceleration sensors that detect tilt are also available. The device may be built-in.

[0406] FIG. 25A shows an example in which the display area of ​​the display portion 9631b is the same as that of the display portion 9631a. However, there is no particular limitation, and one size may be different from the other size. For example, one display panel may have a higher resolution than the other. It is also possible to use the following.

[0407] FIG. 25B shows the tablet terminal in a closed state. The tablet terminal includes a housing 9630 and a solar cell 96 33, a charge / discharge control circuit 9634 including a DCDC converter 9636. A power storage unit according to one embodiment of the present invention is used as 9635.

[0408] In addition, since the tablet terminal 9600 can be folded in two, when not in use, the housing 9630a and The housing 9630b can be folded so that the housing 9630a and the housing 9630b overlap each other. Since the display unit 9631a and the display unit 9631b can be protected, the durability of the tablet terminal 9600 can be improved. In addition, the power storage unit 9635 using the secondary battery of one embodiment of the present invention can A tablet that can be used for a long period of time due to its high capacity and good cycle characteristics. A mobile terminal 9600 can be provided.

[0409] In addition, the tablet terminals shown in Figs. 25(A) and 25(B) can be used in various Functions that display information (still images, videos, text images, etc.), calendars, dates, or times A function to display information on the display unit, and a function to input or edit information displayed on the display unit. It has input functions, functions to control processing by various software (programs), etc. It is possible.

[0410] The solar cell 9633 attached to the surface of the tablet device supplies power to the touch panel, The solar cell 9633 can be provided to a display unit, a video signal processor, or the like. The structure can be provided on one or both sides of the power storage unit 9630, and can efficiently charge the power storage unit 9635. It is possible to use a lithium ion battery as the power storage unit 9635. This has the advantage of enabling miniaturization.

[0411] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. A block diagram is shown in FIG. 25C. 5, DC-DC converter 9636, converter 9637, switches SW1 to SW3, table The display unit 9631 is shown, which includes a storage battery 9635, a DC-DC converter 9636, and a The inverter 9637 and the switches SW1 to SW3 are connected to the charge / discharge control circuit 96 shown in FIG. This corresponds to 34.

[0412] First, an example of operation in which power is generated by the solar cell 9633 using external light will be described. The power generated by the solar cell is converted to a voltage for charging the storage battery 9635 by the DCDC controller. The voltage is increased or decreased by a inverter 9636. When power from the 9633 is used, switch SW1 is turned on and the converter 9637 The voltage is increased or decreased to a voltage required for the display unit 9631. When not displaying the battery status, turn SW1 off and SW2 on to charge the battery 9635. The configuration may be such that the power supply is electrically connected to the power source.

[0413] The solar cell 9633 is shown as an example of a power generating means, but is not limited thereto. Storage of electricity by other power generation means such as piezoelectric elements and thermoelectric conversion elements For example, the device may be configured to transmit and receive power wirelessly (contactlessly). It is also possible to combine it with a non-contact power transmission module that charges the battery by using other charging methods. This is also fine.

[0414] FIG. 26 shows another example of electronic equipment. In FIG. 26, a display device 8000 according to one embodiment of the present invention is 8 is an example of an electronic device using a secondary battery 8004 according to an embodiment. 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, and a speaker unit. The secondary battery 8004 according to one embodiment of the present invention includes a housing. The display device 8000 is provided inside a body 8001. The display device 8000 receives power from a commercial power source. Alternatively, the power stored in the secondary battery 8004 can be used. Even when power cannot be supplied from a commercial power source due to a power outage or the like, the present invention according to one embodiment of the present invention can be used. By using the secondary battery 8004 as an uninterruptible power supply, the display device 8000 can be used. do.

[0415] The display unit 8002 may be a liquid crystal display device, an emitting device having light emitting elements such as organic EL elements in each pixel, or the like. Device, electrophoretic display device, DMD (Digital Micromirror Devi ce), PDP (Plasma Display Panel), FED (Field A semiconductor display device such as a 3D Emission Display can be used.

[0416] In addition, display devices are used for TV broadcast reception, personal computers, advertising displays, etc. , all display devices for displaying information are included.

[0417] In FIG. 26, a stationary lighting device 8100 includes a secondary battery 81 according to one embodiment of the present invention. 8101, a light source 8102, and a light source 8103 are used. 26, the secondary battery 8103 is disposed in the housing 81. 8102 is installed inside a ceiling 8104. However, the secondary battery 8103 may be provided inside the housing 8101. The device 8100 can receive power from a commercial power source, or store power in a secondary battery 8103. Therefore, when the power supply from the commercial power source is cut off due to a power outage, Even when the electricity cannot be received, the secondary battery 8103 according to one embodiment of the present invention is used as an uninterruptible power source. This enables the lighting device 8100 to be used.

[0418] In addition, FIG. 26 illustrates a lighting device 8100 that is installed on a ceiling 8104. However, in the secondary battery according to one embodiment of the present invention, other than the ceiling 8104, for example, the side wall 8105, the floor 8106, 106, the window 8107, etc., can be used as a fixed lighting device, or a tabletop lighting device. The present invention can also be used in lighting devices of this type.

[0419] In addition, the light source 8102 may be an artificial light source that artificially obtains light using electricity. Specifically, incandescent lamps, fluorescent lamps and other discharge lamps, light emitting diodes (LEDs) and organic electroluminescence (EL) elements The element is an example of the artificial light source.

[0420] In FIG. 26, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is as follows: 8 is an example of an electronic device using a secondary battery 8203 according to one embodiment of the present invention. The device 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, and the like. 8 illustrates an example in which the secondary battery 8203 is provided in the indoor unit 8200. The battery 8203 may be provided in the outdoor unit 8204. A secondary battery 8203 may be provided in both the power source 8202 and the power source 8204. The power supply can be provided from a commercial power source, or the power stored in the secondary battery 8203 can be used. In particular, a secondary battery 82 is provided in both the indoor unit 8200 and the outdoor unit 8204. If 03 is installed, when power cannot be supplied from the commercial power source due to a power outage, etc. In addition, by using the secondary battery 8203 according to one embodiment of the present invention as an uninterruptible power supply, The conditioner can be used.

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

[0422] In FIG. 26, an electric refrigerator-freezer 8300 includes a secondary battery 8304 according to one embodiment of the present invention. Specifically, an electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator It has a storage compartment door 8302, a freezer compartment door 8303, a secondary battery 8304, etc. A secondary battery 8304 is provided inside the housing 8301. The electric refrigerator-freezer 8300 is It can receive power from a commercial power source, or use the power stored in the secondary battery 8304. Therefore, when power cannot be supplied from commercial power sources due to a power outage, etc. However, by using the secondary battery 8304 according to one embodiment of the present invention as an uninterruptible power supply, It will be possible to use the 8300 freezer refrigerator.

[0423] Among the above-mentioned electronic devices, high-frequency heating devices such as microwave ovens, electric rice cookers, etc. The equipment requires high power for a short period of time. Therefore, the equipment supplements the power that cannot be supplied by commercial power sources. By using a secondary battery according to one embodiment of the present invention as an auxiliary power source for It can prevent the commercial power breaker from tripping during use.

[0424] In addition, during periods when electronic devices are not in use, especially during periods when the total amount of power that can be supplied by commercial power suppliers is low, During times when the ratio of electricity actually used (called the electricity usage rate) is low, By storing power in the battery, it is possible to prevent high power usage outside of the above time periods. For example, in the case of the electric refrigerator-freezer 8300, when the temperature is low, the refrigerator compartment door 830 2. During the night when the freezer door 8303 is not opened or closed, the secondary battery 8304 stores electricity. Then, as the temperature rises, the refrigerator door 8302 and the freezer door 8303 are opened and closed. During the daytime, when the vehicle is turned on, the secondary battery 8304 is used as an auxiliary power source, and the daytime power usage rate is can be kept low.

[0425] According to one embodiment of the present invention, the cycle characteristics of a secondary battery are improved, and the reliability is improved. Moreover, according to one aspect of the present invention, a high-capacity secondary battery can be obtained, and therefore This improves the characteristics of the secondary battery, thereby making it possible to reduce the size and weight of the secondary battery itself. Therefore, the secondary battery according to one embodiment of the present invention can be used in the electronic devices described in this embodiment. By incorporating the above, it is possible to provide an electronic device with a longer life and a lighter weight. The embodiment can be implemented in appropriate combination with other embodiments.

[0426] (Embodiment 5) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle will be described.

[0427] When a secondary battery is installed in a vehicle, it becomes a hybrid vehicle (HEV), electric vehicle (EV), or powertrain. This will make it possible to realize next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). .

[0428] FIG. 27 illustrates an example of a vehicle using a secondary battery according to one embodiment of the present invention. The automobile 8400 shown in FIG. 1 is an electric automobile that uses an electric motor as a power source for driving. Alternatively, an electric motor and an engine can be selected as the power source for driving. By using one embodiment of the present invention, the cruising distance can be extended. In addition, the automobile 8400 has a secondary battery. 12(C) and 12(D) are mounted on the floor of the vehicle. In addition, a battery pack using multiple secondary batteries as shown in FIG. The secondary battery may be installed on the floor of the vehicle. In addition, it supplies power to light-emitting devices such as headlights 8401 and room lights (not shown). It can be provided.

[0429] In addition, the secondary battery is used for the display of the speedometer, tachometer, etc. of the automobile 8400. The secondary battery can supply power to the navigation device of the automobile 8400. The present invention can provide power to semiconductor devices such as power distribution systems.

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

[0431] Although not shown, a power receiving device is mounted on the vehicle and receives power from a ground power transmitting device in a non-contact manner. In this non-contact power supply method, a power transmission device is installed on the road or exterior wall. By incorporating this technology, charging can be done not only when the vehicle is stopped but also while it is moving. Using this method, electric power may be transmitted between vehicles. A solar battery may be installed to charge the secondary battery when the vehicle is stopped or running. The power can be supplied using an electromagnetic induction method or a magnetic resonance method.

[0432] FIG 27(C) shows an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. The scooter 8600 shown in (C) has a secondary battery 8602, side mirrors 8601, and a turn signal. The secondary battery 8602 can supply electricity to the direction indicator light 8603. can.

[0433] In addition, the scooter 8600 shown in FIG. 27(C) has a secondary battery 860 in the storage space under the seat 8604. 2 can be stored. The secondary battery 8602 can be stored in the under-seat storage 8604 even if it is small. The secondary battery 8602 can be removed and stored in the under-seat storage 8604. When charging, the secondary battery 8602 is brought indoors, charged, and stored before driving. Just do that.

[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. Therefore, the secondary battery itself can be made smaller and lighter. If the body can be made smaller and lighter, it will contribute to reducing the weight of the vehicle, which will improve the driving range. In addition, the secondary battery installed in the vehicle can be used as a power supply source for other purposes besides the vehicle. In this case, for example, it is possible to avoid using commercial power sources during peak power demand periods. If we can avoid using commercial power sources during peak power demand periods, we can save energy and reduce the This can contribute to reducing carbon dioxide emissions. In addition, if the cycle characteristics are good, Since the batteries can be used for a long period of time, the amount of rare metals used, including cobalt, can be reduced. It is possible.

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

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

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

[0438] In this example, lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd., product number 101102102) were used as the starting material. For this reason, in this embodiment, step 1 described in the first embodiment was used. Steps 2 and 13 were omitted. The lithium cobalt oxide particles had a particle size of about 20 μm. m, and the areas that can be analyzed by XPS include fluorine, magnesium, calcium, sodium, The lithium cobalt oxide particles contain silicon, sulfur, and phosphorus.

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

[0440] The above mixture was stirred with a magnetic stirrer for 4 hours at 25°C and 90% RH. This treatment caused hydrolysis and polycondensation reactions between the water in the atmosphere and TTIP. Then, a layer containing titanium was formed on the surface of the lithium cobalt oxide particles containing magnesium and fluorine. It was formed.

[0441] The mixed solution after the above treatment was filtered, and the residue was collected. (No.4) was used.

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

[0443] The lithium cobalt oxide particles coated with the titanium-containing material were then heated. The flow rate of dry air was set to 10 L / min, and the temperature was kept at 800°C (heating rate: 200°C / hour). The heating time was 2 hours. Dry air with a dew point of -109℃ or less was used.

[0444] The heated particles were then cooled to room temperature. The cooling time from the holding temperature to room temperature was 10 to 1 The time was set to 5 hours. After that, the mixture was crushed by sieving. The sieve used had an opening size of 53 μm.

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

[0446] Sample 02: Sample 02 is a comparative example. It is made of a magnet without being coated with a material containing titanium. The nanoparticles were prepared by heating lithium cobalt oxide particles containing sodium and fluorine.

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

[0448] The lithium cobalt oxide particles containing magnesium and fluorine were heated for 800 ℃ (heating rate 200℃ / hour), holding time 2 hours, oxygen flow rate 10L / min .

[0449] The heated powder was cooled and sieved in the same manner as sample 01, and the sieved powder was then separated into the positive and negative powders of sample 02. It was used as an active material.

[0450] Sample 02 has lithium cobalt oxide inside and a magnesium-containing region on the surface. It was speculated that the positive electrode active material had the above-mentioned structure.

[0451] Sample 03: Sample 03 is a comparative example of magnesium-free lithium cobalt oxide. The titanium particles were fabricated by forming a titanium-containing region on them using a sol-gel method, followed by heating.

[0452] The lithium cobalt oxide particles used were made by Nippon Kagaku Kogyo Co., Ltd. (product name: C-10N). Lithium cobalt oxide in which no magnesium was detected by PS, but fluorine was detected at approximately 1 atomic percent. It is a particle.

[0453] Titanium was added to the lithium cobalt oxide particles by the sol-gel method in the same way as sample 01. A region containing the granules was formed, dried, heated, cooled and sieved. This was the positive result of sample 03. It was used as an active material.

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

[0455] Sample 04: Sample 04 is a comparative example in which lithium cobalt oxide particles are not heated. Used as is.

[0456] The lithium cobalt oxide particles used were manufactured by Nippon Kagaku Kogyo Co., Ltd. (product name: C-10N).

[0457] Sample 04 is a positive electrode active material that does not have a coating layer.

[0458] Sample 05: Sample 05 is a comparative example of cobalt with magnesium and fluorine. The lithium nitrate particles were used as is without heating.

[0459] The lithium cobalt oxide particles containing magnesium and fluorine were manufactured by Nippon Kagaku Kogyo Co., Ltd. (product name: C -20F) was used. In other words, sample 05 was made from the same material as sample 01. It is.

[0460] The conditions for Samples 01 to 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.). The electron microscope image obtained is shown in FIG. As shown in FIG. 28, the positive electrode active material is divided into three distinct regions, a first region 101 and a second region 102. The third region 103 is considered to have a first region 02 and a third region 103. The first region 101 and the second region 102 were observed as brighter regions. The crystal orientation of the second region 102 partially coincides with that of the third region 103. The crystal orientation was partially consistent.

[0463] [STEM-FFT] FFT (Fast Fourier Transform) image of the area indicated by 103FFT in the STEM image shown in Figure 28 This is shown in Figure 29(A1). Figure 29(A2) shows the center point O of Figure 29(A1) with a cross. , the bright points A, B, and C are circled. Similarly, the FF The T image is shown in Figure 29(B1). Figure 29(B2) shows the center point O of Figure 29(B1) drawn with a cross. The figure shows the bright spots A, B, and C surrounded by circles. The T image is shown in Figure 29(C1). Figure 29(C2) shows the center point O of Figure 29(C1) with a cross. The figure shows bright points A, B, and C circled.

[0464] The distance between the bright spot A and the center point O shown in FIG. 29(A2) was d=0.256 nm. The distance between point B and the center point O was d = 0.241 nm. The distance between the bright spot C and the center point O was , d=0.209nm. Also, ∠COA=121°, ∠COB=52°, ∠AO B=69°. From these results, the area shown by 103FFT is magnesium oxide ( It was inferred that the crystals 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. 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°, ∠COB=52 From these results, the area indicated by 102FFT is titanic acid. It was assumed to contain lithium (LiTiO2, cubic crystal).

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

[0467] [EDX] In addition, the positive electrode active material of sample 01 was analyzed by high angle annular dark field scanning transmission microscopy (HAADF- The STEM image and the element mapping image using EDX are shown in FIG. 30. HAADF-STEM image, Fig. 30(A2) is an oxygen atom mapping image, Fig. 30(B1) is a carbon Baltic atom mapping image, Fig. 30(B2) is a fluorine atom mapping image, Fig. 30(C1) is FIG. 30(C2) is a mapping image of titanium atoms, and FIG. 30(C3) is a mapping image of magnesium atoms. 30(A2) to 30(C2) and 31(A2) to 31(C2) In the element mapping image, values ​​below the detection limit are shown in white, and as the count increases, the color approaches black. It is shown as follows.

[0468] As shown in FIG. 30(A2) and FIG. 30(B1), oxygen atoms and cobalt atoms are positively charged. It was revealed that the active material particles were distributed throughout the active material particles. As shown in Fig. 30(C1) and Fig. 30(C2), fluorine atoms, titanium atoms and magnesium atoms It was revealed that the atoms were unevenly distributed in the region close to the surface of the positive electrode active material.

[0469] Next, the comparative positive electrode active material of sample 05 was analyzed using HAADF-STEM images and EDX. The element mapping images are shown in Figure 31. Figure 31(A1) is a HAADF-STEM image, and Figure 31(B1) is a (A2) is an oxygen atom mapping image, (B1) is a cobalt atom mapping image, and (B2) is a cobalt atom mapping image. (B2) is a fluorine atom mapping image, (C1) is a titanium atom mapping image, and (C2) is a titanium atom mapping image. (C2) is a magnesium atomic mapping image.

[0470] As shown in Figure 31(B2) and Figure 31(C2), in sample 05 that was not heated, However, it was found that magnesium and fluorine were distributed unevenly near the surface to some extent. .

[0471] [EDX linear analysis] In addition, a cross section near the surface of the positive electrode active material of sample 01 was subjected to linear analysis using TEM-EDX. The results are shown in Figure 32. The data detected on the line connecting the positive electrode active material and the positive electrode active material are shown in the graph. The distance of 14 nm is inside the particle. Since EDX tends to broaden the analysis area, In some cases, not only the central element but also the surrounding elements may be detected.

[0472] As shown in FIG. 32, magnesium and titanium are present near the surface of the positive electrode active material of sample 01. It is clear that the distribution of magnesium is closer to the surface than the distribution of titanium. In addition, the magnesium peak was closer to the surface than the titanium peak. It was also revealed that cobalt and oxygen exist from the outermost surface of the positive electrode active material particles. was speculated.

[0473] In addition, almost no fluorine was detected in Figure 32. This is because fluorine, which is a light element, was detected by EDX. This was thought to be because fluorine was difficult to detect.

[0474] From the above STEM images, FFT images, elemental mapping images using EDX, and EDX linear analysis Sample 01 has lithium cobalt oxide as the first region, which is one embodiment of the present invention. a second region having lithium, titanium, cobalt, and oxygen; and a third region having It was confirmed that the positive electrode active material contained magnesium and oxygen as the active materials. In sample 01, it became clear that part of the second region overlaps with part of the third region. Ta.

[0475] In addition, in the graph of FIG. 32, the amount of oxygen detected is stable at a distance of 4 nm or more. In this example, the average amount of oxygen detected in this stable region is O ave Calculate the average value O ave 5 of 5 0% value, 0.5O ave The distance x of the measurement point showing the closest measurement value to the particle diameter of the positive electrode active material is It was assumed that the surface of the child was

[0476] In this embodiment, the average amount of oxygen detected in the range of 4 nm to 14 nm is ave teeth The result was 674.2. The closest measurement to 337.1, which is 50% of 674.2, was The x-axis of the fixed point was a distance of 1.71 nm. It was estimated that the distance of 1.71 nm corresponds to the surface of the positive electrode active material particle.

[0477] If the surface of the positive electrode active material particle is 1.71 nm in distance in FIG. 32, then the magnesium The peak is 0.72 nm from the surface of the positive electrode active material particle, and the titanium peak is 1.00 nm from the surface. It was m.

[0478] In addition, the magnesium concentration is more than 1 / 5 of the peak at a distance of 4.42 nm, i.e., the positive electrode The distance was 4.57 nm or more, that is, the positive electrode active material particle surface area. At depths of 2.86 nm or more from the surface of the material particle, the measured magnesium concentration is 1 / Therefore, in sample 01, the first ion was not observed from the surface to a depth of 2.71 nm. It was revealed that the area was 3.

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

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

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

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

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

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

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

[0486] [Evaluation of charge / discharge characteristics] Next, the charge / discharge characteristics of the secondary batteries of Sample 01 and Sample 05 prepared above were evaluated. The measurement temperature was 25°C. Charging was performed at 4.6V (CCCV, 0.5C, cut-off voltage Current 0.01C) and discharge 2.5V (CC, 0.5C), each was charged and discharged 20 times. In this case, 1C is a current value per weight of the positive electrode active material of 137 mA / g. .

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

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

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

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

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

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

[0493] In this way, the configuration of the positive electrode active material according to one embodiment of the present invention can be used with a high voltage of more than 4.4 V. It became clear that a remarkable effect was observed when discharging the material. EXAMPLES

[0494] In this example, a positive electrode active material according to one embodiment of the present invention was prepared and analyzed in a manner different from that in Example 1. The results are described below. In addition, the characteristics of a secondary battery using the positive electrode active material are different from those in Example 1. The results of evaluation under the above conditions will be explained.

[0495] In this embodiment, the positive electrode active material is a composite acid of lithium and a first transition metal contained in the first region. The second region has an oxide of a second transition metal, and the second region has lithium cobalt oxide. The third region has lithium titanate as a typical element oxide, and the third region has magnesium oxide as a typical element oxide. One was made with nesium.

[0496] [Preparation of positive electrode active material, preparation of secondary battery] <Sample 06, Sample 07> In this example, lithium cobalt oxide particles (manufactured by Nippon Chemical Industry Co., Ltd., product number 101102102) were used as the starting material. The model used was C-20F.

[0497] Next, in step 14, the lithium cobalt oxide particles are coated with titanium oxide by the sol-gel method. The mixture was then turned over and dried. TTIP was added to the lithium cobalt oxide at a concentration of 0.004 ml / g. The same procedure as in Example 1 was carried out except that the titanium oxide was mixed in the above mixture. The lithium cobalt oxide particles before this are referred to as Sample 06.

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

[0499] Thereafter, the mixture was cooled and collected in the same manner as in Example 1 to obtain a positive electrode active material. Let's call this sample 07.

[0500] [TEM-EDX] Regarding Sample 06 and Sample 07, especially the cracks in the particles and their surroundings The results were analyzed using TEM-EDX.

[0501] First, the results of TEM-EDX area analysis of titanium are shown in FIG. 37 and FIG.

[0502] FIG. 37 shows the TEM-EDX analysis results of sample 06 before heating. The cross-sectional TEM image shows the surface of the substrate and the crack area. The HAADF-STEM image of the area including the particle surface is shown in Fig. 37(B1), and the Ti mapping image is shown. FIG. 37(B2) shows the crack area shown by the circle marked 2 in FIG. 37(A). The HAADF-STEM image of the region about 20 nm deep from the surface is shown in Figure 37(C1). The Ti mapping image is shown in FIG. 37(C2). Fig. 3 is a HAADF-STEM image of the area of ​​the rack at a depth of about 500 nm from the surface. The Ti mapping image is shown in FIG. 37(D1) and the Ti mapping image is shown in FIG. 37(D2). The crack area indicated by the circle is about 1000 nm deep from the surface. The TEM image is shown in FIG. 37(E1), and the Ti mapping image is shown in FIG. 37(E2). In the EDX element mapping images of FIG. 40, the counts below the detection limit are shown in black. The more the number increases, the closer it gets to white.

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

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

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

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

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

[0508] As shown in Figures 39 and 40, magnesium is distributed on the particle surface, crystallites, and other surfaces of Sample 06 before heating. No segregation was observed in either the rack or the rack section. On the other hand, in sample 07 after heating, magnesium Segregation was observed both on the particle surface and in the cracks.

[0509] Next, in order to quantify titanium and magnesium, the samples shown in circles numbered 1 to 6 in FIG. EDX point analysis was performed on the area and the areas indicated by circles marked 1 to 6 in FIG. Measurements were taken at two locations within each region.

[0510] FIG. 41 shows the results of EDX point analysis in terms of the atomic ratio of titanium and cobalt. The results are for sample 06 before heating. Detection points 1 to 6 in FIG. This is within the area indicated by the circles marked 1 to 6 in FIG. 37(A). FIG. 41(B) shows the sample after heating. The detection points 1 to 6 in FIG. 41(B) are the same as those in FIG. 38( A) is within the area indicated by circles numbered 1 to 6.

[0511] As shown in Figure 41, the crack in sample 06 had a Ti / Co ratio of 0 at all measurement points. On the other hand, there were many areas where titanium had increased in the cracked area of ​​sample 07. In addition, there were also measurement points where the Ti / Co ratio was 0.05 or more. The Ti / Co ratio was in the range of 0.10 to 0.18.

[0512] Next, the results of EDX point analysis are shown in Figure 42, in terms of the ratio of the number of magnesium and cobalt atoms. The location is the same as in Figure 41.

[0513] As shown in Figure 42, in sample 06, Mg / On the other hand, in sample 07, the particle surface and crack area had a magnetron structure. The Mg / Co ratio on the particle surface was 0.15 to 0.50. The range was between 0 and 0.22 at the cracked area.

[0514] Next, the positive electrode active material of sample 07 after heating was used to test a CR2032 type coin-shaped secondary battery. A battery was fabricated. The positive electrode consisted of the positive electrode active material (LCO) of sample 02, AB, and polyfluoride. Polyvinylidene fluoride (PVDF) was mixed in a ratio of LCO:AB:PVDF=95:3:2 (weight ratio). The slurry was applied to a positive electrode current collector. The positive electrode active material layer, which contains the positive electrode active material, AB, and PVDF, was loaded with 7. 6 mg / cm 2 It was decided.

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

[0516] The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC): 1 mol / L LiPF6 was dissolved in the mixture of DEC = 3:7 (volume ratio) and The material used contained 2 wt% nylene carbonate (VC).

[0517] [Initial characteristics, rate characteristics] The initial characteristics and the rating of the secondary battery using the positive electrode active material of sample 07 prepared above were The characteristics of the heat treatment were measured.

[0518] The initial characteristics were measured with CCCV, 0.2C, 4.6V, and a cutoff current of 0.05C. Discharge was performed at CC, 0.2C, and cutoff voltage 3.0V. Note that 1C here is The current value per unit weight of the positive electrode active material was 160 mA / g. The measurement temperature was 25°C. The results of measuring the characteristics are shown in Table 2.

[0519] [Table 2]

[0520] After measuring the initial characteristics, the rate characteristics were measured. The discharge rate was changed, and all other characteristics were the same as the initial characteristics. 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 , 0.2C charge / 4.0C discharge, 0.2C charge / 5.0C discharge. Measurement temperature was set to 25°C.

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

[0522] [Table 3]

[0523] [Temperature characteristics] Next, the amount of the positive electrode active material layer was set to 8.2 mg / cm 2 The rest are the same as the cells where the rates were evaluated. We fabricated cells under the same conditions and evaluated the temperature characteristics. All charging was performed at 25°C, CCCV, 0.2 The discharge was performed at 25°C, 0°C, -10°C, - The temperature was then set to 20℃ and 45℃, with CC, 0.2C, and a cut-off voltage of 3.0V. The results of the measurements are shown in FIG.

[0524] [Cycle characteristics] Next, a cell was fabricated under the same conditions as the cell for which the temperature characteristics were measured, and the cycle characteristics were measured. For cycle characteristics, charging was performed at CCCV, 1.0C, 4.55V, and cutoff current was 0.05C. The discharge was performed at CC, 1.0 C, and the cutoff voltage was 3.0 V. The measurement temperature of the cycle characteristics was The temperature was kept at 45°C and the measurement was performed for 100 cycles. The discharge capacity retention rate after 100 cycles was 86%. The measured cycle characteristics were plotted in terms of discharge capacity retention rate in Figure 45. .

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

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

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

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

[0529] In this example, a positive electrode active material having a region containing titanium and magnesium in a surface layer portion was The results of fabricating the devices with different ratios of Li / first transition metal in the starting materials and evaluating their characteristics are shown below.

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

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

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

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

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

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

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

[0537] Next, 2-propanol was added with TTIP of 0.01 ml / g per weight of the positive electrode active material. Add TTIP and mix to make a 2-propanol solution of tetra-i-propoxytitanium. It was made.

[0538] Lithium, cobalt, fluorine, and magnesium were added to this 2-propanol solution of TTIP. The composite oxide particles containing the metal oxide were added and mixed.

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

[0540] The mixed solution after the above treatment was filtered, and the residue was collected. (No.4) was used.

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

[0542] The dried powder was heated to 800°C (heating rate: 200°C / hour) for 2 hours. , was carried out under an oxygen atmosphere.

[0543] The heated powder was cooled and crushed by sieving. The sieve used had an opening size of 53 μm.

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

[0545] <Sample 21-27> Samples 21 to 27 use the same starting materials as Samples 11 to 16. At this time, Sample 21 was weighed so that the Li / Co ratio of the starting material was 1.00. Sample 22 was weighed so that the Li / Co ratio of the starting material was 1.03. Sample 23 was weighed so that the Li / Co ratio of the starting material was 1.05. Sample 24 was weighed so that the Li / Co ratio of the starting material was 1.06. Sample 25 was weighed so that the starting material had a Li / Co ratio of 1.07. Sample 26 was weighed so that the starting material had a Li / Co ratio of 1.08. Sample 27 was weighed so that the starting material had a Li / Co ratio of 1.13.

[0546] For samples 21 to 27, the concentration of TTIP in 2-propanol solution was adjusted by the weight of the positive electrode active material. The amount of TTIP per unit volume was set to 0.02 ml / g, and the rest of the samples were 17 was prepared in the same manner.

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

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

[0549] Other than the firing temperature, the sample was prepared in the same manner as Sample 23.

[0550] Samples 11 to 17 and samples 21 to 28 have lithium cobalt oxide in the interior and a surface layer It was speculated that the positive electrode active material had a region containing titanium and magnesium.

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

[0552] For sample 31, the starting material was weighed so that the Li / Co ratio was 1.00. Sample 2 was weighed out so that the Li / Co ratio of the starting material was 1.01. The raw materials were weighed so that the Li / Co ratio was 1.02. Sample 34 was made of the starting material Li The Li / Co ratio of the starting material was 1.03. The Li / Co ratio of the starting material was 1.04. Sample 37 was weighed so that the Li / Co ratio of the starting material was 1.051. Sample 38 was weighed so that the Li / Co ratio of the starting material was 1.061. Sample 39 was weighed so that the Li / Co ratio of the starting material was 1.081. Sample 40 was weighed out so that the Li / Co ratio of the starting material was 1.130.

[0553] In addition, for samples 31 to 40, the number of cobalt atoms contained in the starting material was When the number of magnesium atoms is 1, the number of fluorine atoms is 0.01 and 0.02. The sea urchin was weighed.

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

[0555] Next, the mixed starting materials were calcined at 1000°C for 10 hours with a temperature increase of 200°C / h. The flow rate of the dry air was 10 L / min.

[0556] In the above process, particles of a composite oxide containing lithium, cobalt, fluorine, and magnesium are mixed. Successful.

[0557] The synthesized particles were cooled and then heated. The heating was performed at 800°C (heating rate: 200°C / hour), and the temperature was kept constant. The reaction was carried out for 2 hours under an oxygen atmosphere.

[0558] The heated powder was cooled and crushed by sieving. The sieve used had an opening size of 53 μm.

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

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

[0561] [Table 4]

[0562] [XPS] Sample 11~Sample 17, Sample 21~Sample 28, Sample 31~Sample 4 The positive electrode active material of Sample 11 to Sample 17 were subjected to XPS analysis. The results of the XPS analysis of samples 21 to 28 are shown in Table 5, the results of the XPS analysis of samples 21 to 28 in Table 6, and the results of the XPS analysis of sample 31 in Table 7. The results of the XPS analysis of Sample 40 are shown in Table 7. Note that in Tables 5 to 7, the concentration of each element is The values ​​shown are relative values ​​with cobalt taken as 1.

[0563] [Table 5]

[0564] [Table 6]

[0565] [Table 7]

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

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

[0568] Also, from Samples 11 to 16 and Samples 21 to 26 in FIG. 46(A), When the surface layer has a titanium-containing region, the element concentration can be detected by XPS more easily than when the surface layer does not have a titanium-containing region. It became clear that the magnesium concentration within the possible range was increased.

[0569] Furthermore, when the Li / Co ratio was 1.06, the elemental structure was not observed by XPS when there was no region containing titanium. The magnesium concentration in the detectable range is low, whereas the titanium concentration is In the samples with regions, the magnesium concentration is high within the range where the element concentration can be detected by XPS. In other words, by forming a region containing titanium in the surface layer, even when the Li / Co ratio is high, It was also revealed that magnesium segregation occurred sufficiently even at high temperatures.

[0570] Even if there is a region containing titanium, the Li / Co ratio of 1.07 is smaller than that of 1.06. In addition, when the Li / Co ratio was 1.08 or more, the magnesium concentration decreased. It was presumed that even if the region contains magnesium, segregation of magnesium is unlikely to occur.

[0571] [Evaluation of cycle characteristics] <Energy density maintenance rate> Next, samples 11 to 14, sample 16 and samples 21 to 24, The positive electrode active material of Sample 26 was used to evaluate the cycle characteristics in the same manner as in Example 1.

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

[0573] In FIG. 47(A), the amount of TTIP per weight of the positive electrode active material was prepared to be 0.01 ml / g. 4. For secondary batteries using the positive electrode active materials of Samples 11 to 14 and Sample 16 The graph of the energy density retention rate and the number of charge / discharge cycles when charged to 6 V is shown in Figure 47(B). Sample 21 was prepared so that the amount of TTIP per weight of the positive electrode active material was 0.02 ml / g. ~Energy consumption at 4.6V charging of secondary batteries using the positive electrode active materials of Sample 24 and Sample 26 The graph shows the relationship between the energy density maintenance rate and the number of charge / discharge cycles.

[0574] As is clear from FIG. 47(A), when TTIP was 0.01 ml / g, samples 11 to Sample 14, i.e., the positive electrode active material with a Li / Co ratio of 1.00 to 1.06, is a good sample. In particular, samples 11 and 12, which have a Li / Co ratio of 1 The positive electrode active material with a value between 0.00 and 1.03 showed extremely good cycle characteristics. In sample 16 with a / Co ratio of 1.08, the energy density retention rate deteriorated at a relatively early stage. was.

[0575] Also, as is clear from FIG. 47(B), when TTIP was 0.02 ml / g, sample 2 1 to Sample 24, that is, the positive electrode active material with a Li / Co ratio of 1.00 to 1.06, is good. In particular, samples 23 and 24, which have a Li / Co ratio of The positive electrode active materials having a value of 1.05 or more and 1.06 or less showed extremely good cycle characteristics.

[0576] Figure 48 shows the sample that showed the best cycle characteristics among samples 11 to 15. Sample 11 and Sample 21 to Sample 25 showed the best cycle characteristics. A graph comparing 3 is shown below.

[0577] As is clear from FIG. 48, both of them showed very good cycle characteristics, but TTIP Sample 23 at 0.02 ml / g had better cycle characteristics.

[0578] ≪Discharge capacity maintenance rate≫ Next, for Samples 21 to 26 and Sample 28, the cycles were determined based on the discharge capacity retention rate. The results of evaluating the loop characteristics are shown in FIG.

[0579] The shape of the secondary batteries of Samples 21 to 26, the positive electrode active material, the conductive additive, and the The materials and mixing ratio of the indium, the counter electrode, the electrolyte, the exterior body, and the conditions of the cycle characteristic test are given in the examples. Same as 1.

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

[0581] As is clear from FIG. 49, Samples 21 to 24 and Sample 28 have good Among them, sample 28 showed extremely good cycle characteristics. In sample 28, the discharge capacity retention rate after 50 cycles was 85% or more.

[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 deteriorated from a relatively early stage.

[0583] From the above results, it is preferable that the amount of TTIP per weight of the positive electrode active material is 0.02 ml / g. It was revealed that the range of the Li / Co ratio was 1.00 or more and less than 1.07. When the Li / Co ratio is in the range of 1.05 to 1.06, excellent cycle characteristics are observed. It became clear that...

[0584] Samples 28 and 24, which showed extremely good cycle characteristics in FIG. The charge / discharge curves of the secondary battery using sample 25, which showed deterioration at an early stage, are shown in Figure 50. vinegar.

[0585] Figure 50(A) is sample 28, Figure 50(B) is sample 24, Figure 50(C) is sample 2 The charge and discharge curves of the secondary battery using 50 charge and discharge cycles are shown in Fig. 1. As shown by the arrows in the figure, the charge / discharge capacity increases from the 1st cycle to the 50th cycle. The amount is decreasing.

[0586] As shown in FIG. 50(A) and FIG. 50(B), a cathode active material according to one embodiment of the present invention is a sacrificial oxide (SAO). Sample 28 and Sample 24 showed high charge / discharge capacity and good charge / discharge characteristics. Sample 2 in Fig. 50(A) and Fig. 50(B) compared to Sample 25 in Fig. 50(C). It was revealed that the decrease in charge / discharge capacity was significantly suppressed in Sample 8 and Sample 24. EXAMPLES

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

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

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

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

[0591] The same areas in Figures 52(A-1), 52(A-2), and 52(B-1) are surrounded by dotted lines. As is clear from comparing the areas enclosed by dotted lines, the protruding areas on the surface of the positive electrode active material , titanium and magnesium were distributed.

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

[0593] As shown in Example 2, sample 24 was a sample that exhibited extremely good cycle characteristics. Therefore, even if a fourth region exists in the surface layer, or even if a fourth region does not exist, It was revealed that a positive electrode active material exhibiting good cycle characteristics can be obtained by using the above-mentioned method.

[0594] From the results of Examples 1 to 3, it can be seen that by forming a region containing titanium in the surface layer, It was revealed that a positive electrode active material exhibiting good cycle characteristics was obtained. There is a concern that increasing the Li / Co ratio to increase the particle size of the material may result in a deterioration in cycle characteristics. However, by forming a titanium-containing region in the surface layer, good cycle characteristics can be obtained. It was revealed that the range of Li / Co ratios could be widened. Even if the fourth region containing titanium and magnesium exists, good cycle characteristics are observed. It became clear that: EXAMPLES

[0595] In this example, an example of a method for producing a positive electrode active material covered with graphene oxide will be described. The results of observing the positive electrode active material produced by this method with an electron microscope will be described.

[0596] As shown in the process flow diagram of FIG. 53, the process of forming a coating on a positive electrode active material includes (S11) oxidizing grout. Weighing out the graphene, (S12) mixing and stirring the graphene oxide with pure water, (S13) pH (S14) Adding active material (S15) Completing the suspension (S16) Spray drying (S17) spraying the suspension using the device; and (S18) collecting the powder in a container.

[0597] In (S12), pure water is used as the dispersion medium, but there is no particular limitation, and other suitable dispersion medium such as ethanol may be used. Also, in (S14), the active material is a positive electrode active material.

[0598] A schematic diagram of the spray drying apparatus 280 is shown in FIG. The nozzle 282 is connected to the suspension via a tube 283. The liquid 284 is supplied. The suspension 284 is sprayed into the chamber 281 from the nozzle 282. The nozzle 282 is heated by a heater 285. Here, the heater 285 may heat the nozzle 282 in the chamber 281. Areas close to the heater, for example the area surrounded by the two-dot chain line in FIG. 54, are also heated.

[0599] When a suspension containing a positive electrode active material and graphene oxide was used as the suspension 284, the oxidation The graphene-covered positive electrode active material powder is circulated through the chamber 281 to the collection container 286. It will be collected.

[0600] Here, the atmosphere in the chamber 281 is supplied to an aspirator or the like through a path indicated by an arrow 288. It may be more suctioned.

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

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

[0603] Pure water has high dispersibility as a dispersion medium for graphene oxide, but the active material to be added later Depending on the type, it may react with the positive electrode active material, causing Li to dissolve or changing the surface structure of the positive electrode active material. Therefore, the ratio of ethanol to pure water is 4:6. The graphene oxide was dispersed in the liquid.

[0604] A stirrer and ultrasonic generator were used to stir the mixture and disperse it in the liquid. The rotation speed was The rpm was set to 750 and ultrasonic waves were irradiated for 2 minutes.

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

[0606] The positive electrode active material (in this embodiment, lithium cobalt oxide particles (trade name) manufactured by Nippon Chemical Industry Co., Ltd.) : C-20F) was added, and a stirrer and ultrasonic generator were used for stirring at a rotation speed of 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 nitrogen, magnesium, calcium, sodium, silicon, sulfur, and phosphorus The particles are tungsten particles with a particle size of approximately 20 μm.

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

[0608] A cross-sectional TEM photograph of the resulting powder is shown in Figure 55. Also, a SEM photograph is shown in Figure 56. As a comparative example, the same positive electrode active material (Nippon Chemical Industry Co., Ltd.) was spray-dried. The raw material was graphene oxide (C-20F manufactured by the company) and mixed with a rotating / revolving mixer. The SEM photograph of the comparative example is shown in FIG.

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

[0610] After coating with graphene oxide using a spray dryer, FIG. 1 shows an example of a cross-sectional configuration in which a graphene compound is further used as a conductive assistant in the active material layer 200. Explained in Figure 58.

[0611] 58(A) shows a vertical cross-sectional view of the active material layer 200. The active material layer 200 is made of graphene oxide. The graphene compound 201 is a conductive additive. In this case, the graphene compound 201 may be, for example, graphene. Here, the graphene compound 201 may be in the form of a sheet. In addition, the graphene compound 201 preferably has a shape of a plurality of multi-graphs. Alternatively, a plurality of graphenes may be partially overlapped to form a sheet. .

[0612] In the vertical cross section of the active material layer 200, as shown in FIG. 58(B), The graphene compound 201 is in contact with the positive electrode active material 100 covered with the coating 105. The graphene compounds 201 are each formed of a positive electrode active material 10 covered with a coating 105. 0 and is formed so as to be attached to the coating 105 of the adjacent positive electrode active material 100. We are in contact with each of them.

[0613] The graphene compound 201 and the coating 105 are both carbon-based materials, so they form an excellent conductive path. It can be formed.

[0614] The coating 105 has the effect of protecting the crystal structure of the positive electrode active material 100 from contact with the electrolyte, It has the effect of forming an excellent conductive path. [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 body 61 Bending section 62 Seal part 63 Seal part 71 Ridgeline 72 Valley Line 73 Space 100 Cathode active material 101 areas 101p crystal plane 102 areas 102p crystal surface 103 areas 103p crystal plane 104 areas 105 Coating 106 Crack 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 Nozzle 283 Tube 284 Suspension 285 Heater 286 Collection Container 288 Arrow 300 Secondary battery 301 Positive electrode can 302 Anode 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 body 510 Positive lead electrode 511 Negative lead electrode 600 Secondary battery 601 Positive electrode cap 602 Battery Can 603 Positive terminal 604 Positive electrode 605 Separator 606 negative electrode 607 Negative terminal 608 Insulating plate 609 Insulating plate 611 PTC element 612 Safety valve mechanism 613 Conductive plate 614 Conductive plate 615 Module 616 Conductor 617 Temperature Control Device 900 Circuit Board 910 Label 911 Terminal 912 Circuit 913 Secondary battery 914 Antenna 915 Antenna 916 layers 917 layers 918 Antenna 920 Display device 921 Sensor 922 Terminal 930 Case 930a Case 930b Case 931 negative electrode 932 Positive electrode 933 Separator 950 Wound body 951 Terminal 952 Terminal 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 devices 7101 Case 7102 Display section 7103 Operation button 7104 Secondary battery 7200 Portable Information Terminal 7201 Case 7202 Display section 7203 Band 7204 Buckle 7205 Operation button 7206 Input / output terminal 7207 Icon 7300 display device 7304 Display section 7400 Mobile Phone 7401 Case 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Mike 7407 Secondary battery 7408 Lead electrode 7409 Current collector 7500 Electronic Cigarettes 7501 Atomizer 7502 Cartridge 7504 Secondary battery 8000 display device 8001 Case 8002 Display section 8003 Speaker section 8004 Secondary battery 8021 Charging device 8022 Cable 8024 Secondary battery 8100 Lighting equipment 8101 Case 8102 Light source 8103 Secondary battery 8104 Ceiling 8105 Side wall 8106 Bed 8107 Window 8200 indoor unit 8201 Case 8202 Ventilator 8203 Secondary battery 8204 Outdoor unit 8300 Electric refrigerator-freezer 8301 Case 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 PC 9625 Switch 9626 Switch 9627 Power Switch 9628 Operation Switch 9629 Fastener 9630 Case 9630a Case 9630b Case 9631 Display section 9631a Display section 9631b Display section 9632a area 9632b area 9633 Solar Cells 9634 Charge / discharge control circuit 9635 Electric storage unit 9636 DC-DC Converter 9637 Converter 9638 Operation key 9639 Button 9640 Moving parts

Claims

1. A battery comprising a positive electrode and a negative electrode, the positive electrode has a plurality of positive electrode active material particles including lithium cobalt oxide having a layered rock salt crystal structure, the positive electrode active material particles contain magnesium, fluorine, and titanium in a region including a rock-salt type crystal structure that is located on a surface side of the layered rock-salt type crystal structure, In a graph obtained by performing linear analysis of a cross section of the positive electrode active material particle by EDX, the titanium peak is located more inward of the positive electrode active material particle than the magnesium peak, the region having a rock salt type crystal structure contains magnesium oxide, and fluorine is bonded to magnesium in place of oxygen in a part of the magnesium oxide; the orientation of the crystals of the layered rock salt type crystal structure is the same as the orientation of the crystals of the rock salt type crystal structure, magnesium and fluorine are unevenly distributed on the surface side of the positive electrode active material particles, In an XPS analysis of the plurality of positive electrode active material particles, the titanium concentration is 0.05 or more and 0.4 or less when the cobalt concentration is set to 1. Lithium-ion secondary battery.

2. A battery comprising a positive electrode and a negative electrode, the positive electrode has a plurality of positive electrode active material particles including lithium cobalt oxide having a layered rock salt crystal structure, the positive electrode active material particles contain magnesium, fluorine, and titanium in a region including a rock-salt type crystal structure that is located on a surface side of the layered rock-salt type crystal structure, In a graph obtained by performing linear analysis of a cross section of the positive electrode active material particle by EDX, the titanium peak is located more inward of the positive electrode active material particle than the magnesium peak, the region having a rock salt type crystal structure contains magnesium bonded to fluorine, the orientation of the crystals of the layered rock salt type crystal structure is the same as the orientation of the crystals of the rock salt type crystal structure, magnesium and fluorine are unevenly distributed on the surface side of the positive electrode active material particles; Lithium-ion secondary battery.

3. A battery comprising a positive electrode and a negative electrode, the positive electrode has a plurality of positive electrode active material particles including lithium cobalt oxide having a layered rock salt crystal structure, the positive electrode active material particles contain magnesium, fluorine, and titanium in a region including a rock-salt type crystal structure that is located on a surface side of the layered rock-salt type crystal structure, In a graph obtained by performing linear analysis of a cross section of the positive electrode active material particle by EDX, the titanium peak is located more inward of the positive electrode active material particle than the magnesium peak, The crystal orientation of the crystal having the layered rock-salt type crystal structure is consistent with the crystal orientation of the crystal having the rock-salt type crystal structure, Magnesium and fluorine are unevenly distributed on the surface side of the positive electrode active material particles, In the XPS analysis of the plurality of positive electrode active material particles, when the concentration of cobalt is set to 1, the concentration of titanium is 0.05 or more and 0.4 or less, A lithium ion secondary battery.

4. A lithium ion secondary battery having a positive electrode and a negative electrode, The positive electrode has a plurality of positive electrode active material particles containing lithium cobaltate having a layered rock-salt type crystal structure, The positive electrode active material particles have magnesium, fluorine, and titanium in a region containing a rock-salt type crystal structure, which is located on the surface side of the layered rock-salt type crystal structure, In the graph obtained by performing linear analysis of the cross section of the positive electrode active material particles by EDX, the peak of titanium is inside the positive electrode active material particles more than the peak of magnesium, The region having the rock-salt type crystal structure contains magnesium bonded to fluorine, The crystal orientation of the crystal having the layered rock-salt type crystal structure is consistent with the crystal orientation of the crystal having the rock-salt type crystal structure, Magnesium and fluorine are unevenly distributed on the surface side of the positive electrode active material particles, In the XPS analysis of the plurality of positive electrode active material particles, when the concentration of cobalt is set to 1, the concentration of titanium is 0.05 or more and 0.4 or less, A lithium ion secondary battery.

5. A lithium ion secondary battery having a positive electrode and a negative electrode, The positive electrode has a plurality of positive electrode active material particles containing lithium cobaltate having a layered rock-salt type crystal structure, The positive electrode active material particles have magnesium, fluorine, and titanium in a region containing a rock-salt type crystal structure, which is located on the surface side of the layered rock-salt type crystal structure, In the graph obtained by performing linear analysis of the cross section of the positive electrode active material particles by EDX, the peak of titanium is inside the positive electrode active material particles more than the peak of magnesium, The region having the rock-salt type crystal structure contains magnesium oxide, and in a part of the magnesium oxide, fluorine is bonded to magnesium instead of oxygen, The crystal orientation of the crystal having the layered rock-salt type crystal structure is consistent with the crystal orientation of the crystal having the rock-salt type crystal structure, Magnesium and fluorine are unevenly distributed on the surface side and the inner wall of the crack portion of the positive electrode active material particles, In the XPS analysis of the plurality of positive electrode active material particles, when the concentration of cobalt is set to 1, the concentration of titanium is 0.05 or more and 0.4 or less, A lithium ion secondary battery.

6. A lithium ion secondary battery having a positive electrode and a negative electrode, The positive electrode has a plurality of positive electrode active material particles containing lithium cobaltate having a layered rock salt-type crystal structure. The positive electrode active material particles have magnesium, fluorine, and titanium in a region containing a rock salt-type crystal structure, which is located on the surface side rather than the layered rock salt-type crystal structure. In the graph obtained by performing linear analysis of the cross section of the positive electrode active material particles by EDX, the peak of titanium is closer to the inside of the positive electrode active material particles than the peak of magnesium. The region having the rock salt-type crystal structure contains magnesium bonded to fluorine. The crystal orientation of the layered rock salt-type crystal structure is consistent with the crystal orientation of the rock salt-type crystal structure. Magnesium and fluorine are unevenly distributed on the surface side of the positive electrode active material particles and inside the crack inner wall. In the XPS analysis of the plurality of positive electrode active material particles, when the concentration of cobalt is set to 1, the concentration of titanium is 0.05 or more and 0.4 or less. A lithium ion secondary battery.

7. A lithium ion secondary battery having a positive electrode and a negative electrode. The positive electrode has a plurality of positive electrode active material particles containing lithium cobaltate having a layered rock salt-type crystal structure. The positive electrode active material particles have magnesium, fluorine, and titanium in a region containing a rock salt-type crystal structure, which is located on the surface side rather than the layered rock salt-type crystal structure. In the graph obtained by performing linear analysis of the cross section of the positive electrode active material particles by EDX, the peak of titanium is closer to the inside of the positive electrode active material particles than the peak of magnesium. The crystal orientation of the layered rock salt-type crystal structure is consistent with the crystal orientation of the rock salt-type crystal structure. Magnesium and fluorine are unevenly distributed on the surface side of the positive electrode active material particles and inside the crack inner wall. In the XPS analysis of the plurality of positive electrode active material particles, when the concentration of cobalt is set to 1, the concentration of titanium is 0.05 or more and 0.4 or less. A lithium ion secondary battery.

8. A lithium ion secondary battery having a positive electrode and a negative electrode. The positive electrode has a plurality of positive electrode active material particles containing lithium cobaltate having a layered rock salt-type crystal structure. The positive electrode active material particles have magnesium, fluorine, and titanium in a region containing a rock salt-type crystal structure, which is located on the surface side rather than the layered rock salt-type crystal structure. In the graph obtained by performing linear analysis of the cross section of the positive electrode active material particles by EDX, the peak of titanium is closer to the inside of the positive electrode active material particles than the peak of magnesium. The region having the rock-salt type crystal structure contains magnesium oxide, and in a part of the magnesium oxide, fluorine is bonded to magnesium instead of oxygen. The crystal orientation of the crystal having the layered rock-salt type crystal structure is consistent with the crystal orientation of the crystal having the rock-salt type crystal structure. Magnesium and fluorine are unevenly distributed on the surface side of the positive electrode active material particles and inside the interface of the crack. In the XPS analysis of the plurality of positive electrode active material particles, when the concentration of cobalt is set to 1, the concentration of titanium is 0.05 or more and 0.4 or less. Lithium ion secondary battery.

9. A lithium ion secondary battery having a positive electrode and a negative electrode. The positive electrode has a plurality of positive electrode active material particles containing lithium cobaltate having a layered rock-salt type crystal structure. The positive electrode active material particles have magnesium, fluorine, and titanium in a region containing a rock-salt type crystal structure, which is located on the surface side of the layered rock-salt type crystal structure. In the graph obtained by performing linear analysis of the cross section of the positive electrode active material particles by EDX, the peak of titanium is closer to the inside of the positive electrode active material particles than the peak of magnesium. The region having the rock-salt type crystal structure contains magnesium bonded to fluorine. The crystal orientation of the crystal having the layered rock-salt type crystal structure is consistent with the crystal orientation of the crystal having the rock-salt type crystal structure. Magnesium and fluorine are unevenly distributed on the surface side of the positive electrode active material particles and inside the interface of the crack. In the XPS analysis of the plurality of positive electrode active material particles, when the concentration of cobalt is set to 1, the concentration of titanium is 0.05 or more and 0.4 or less. Lithium ion secondary battery.

10. A lithium ion secondary battery having a positive electrode and a negative electrode. The positive electrode has a plurality of positive electrode active material particles containing lithium cobaltate having a layered rock-salt type crystal structure. The positive electrode active material particles have magnesium, fluorine, and titanium in a region containing a rock-salt type crystal structure, which is located on the surface side of the layered rock-salt type crystal structure. In the graph obtained by performing linear analysis of the cross section of the positive electrode active material particles by EDX, the peak of titanium is closer to the inside of the positive electrode active material particles than the peak of magnesium. The crystal orientation of the crystal having the layered rock-salt type crystal structure is consistent with the crystal orientation of the crystal having the rock-salt type crystal structure. Magnesium and fluorine are unevenly distributed on the surface side of the positive electrode active material particles and inside the interface of the crack. In the XPS analysis of the plurality of positive electrode active material particles, when the concentration of cobalt is set to 1, the concentration of titanium is 0.05 or more and 0.4 or less. Lithium ion secondary battery.

11. Fluorine in the region containing the rock-salt type crystal structure exists in a bonding state other than MgF₂. The lithium-ion secondary battery according to any one of Claims 1 to 10.

12. Fluorine in the region containing the rock-salt type crystal structure exists in a bonding state other than LiF. The lithium-ion secondary battery according to any one of Claims 1 to 11.

13. Fluorine in the region containing the rock-salt type crystal structure exists in a bonding state other than CoF₂. The lithium-ion secondary battery according to any one of Claims 1 to 12.

14. When the plurality of positive electrode active material particles are analyzed by XPS, the peak position of the binding energy of fluorine is 682 eV or more and 685 eV or less. The lithium-ion secondary battery according to any one of Claims 1 to 13.

15. The vertical axis of the graph is NET count. The lithium-ion secondary battery according to any one of Claims 1 to 14.

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