Lithium-ion secondary battery

Abstract

To provide a positive electrode active material which can improve 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. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the 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 the crystal structure and the two kinds of regions 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 the outer coating layer in contact with an electrolyte is the compound of representative elements which is chemically stable, a 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 device. 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 "power storage device" refers to elements and devices in general that have a power storage function. For example, lithium-ion secondary batteries and other storage batteries (also called secondary batteries) This includes silicon ion capacitors and electric double layer capacitors.

[0003] In addition, in this specification, the term "electronic device" refers to a device in general that has 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 energy storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have become available. In particular, lithium-ion batteries, which have high output and high energy density, are being developed. The secondary battery is used in mobile phones, smartphones, tablets, or laptop computers. Portable 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, including 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 aimed to improve the cycle characteristics and capacity of lithium-ion secondary batteries by developing a positive electrode active material. Improvements to the material are being investigated (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-018914 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-201432 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 present invention 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-discharge characteristics. One of the objects 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, a secondary battery, or a manufacturing method thereof. One of our goals 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 embodiments to solve all of these problems. It is possible to extract other problems 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 is to provide a cathode active material having a surface layer portion different from an inner region. The inner region is a non-stoichiometric compound, and the outer region is a stoichiometric compound. It is preferable that there is.

[0013] Preferably, the inner region comprises titanium and the outer region comprises magnesium. Furthermore, 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 same.

[0015] One aspect 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, wherein the first region is present inside the positive electrode active material, and the second region and the third region are 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 the second region has a layered structure. The first region has a rock salt crystal structure, and the second region contains a non-stoichiometric compound having an oxide of a second transition metal. The non-stoichiometric compounds have a rock salt crystal structure, and 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 contain 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 mismatch is 0.12 or less, and the second region has a {100} plane of a rock-salt type crystal structure. The third region has a rock salt type crystal structure with a {100} plane mismatch of 0.12 or less. It is preferable.

[0020] Another embodiment of the present invention is a positive electrode active material, the positive electrode active material comprising lithium and titanium. , cobalt, magnesium, oxygen, and fluorine, and is present in the surface layer of the positive electrode active material. When the cobalt concentration measured by X-ray photoelectron spectroscopy is set to 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 fluorine-containing ion exchange catalyst comprising: a lithium source, a cobalt source, a magnesium source, and a fluorine source; and mixing a mixture of a lithium source, a cobalt source, a magnesium source and a fluorine source. , heated at 800°C to 1100°C for 2 hours to 20 hours, and obtaining particles having magnesium, oxygen, and fluorine; and and dissolving titanium alkoxide in alcohol. 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; , heated in an oxygen-containing atmosphere at 500°C to 1200°C for a holding time of 50 hours or less. and a step of:

[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 cobalt atoms to the number of Li / Co atoms is preferably 1.00≦Li / Co<1.07.

[0023] In the above-mentioned production 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 production method, the number of magnesium atoms contained in the magnesium source is It is preferable that the cobalt content is 0.5 atomic % or more and 1.5 atomic % or less of the number of cobalt atoms contained in the cobalt source. It's 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 crystalline structure, thereby improving the charge / discharge characteristics. The film covering the surface of the positive electrode active material can suppress the decrease in capacity during the cycle. Examples of the film include a carbon-containing film (a film containing a graphene compound), or a film containing 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 remove the 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, causing a decomposition reaction and 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 breaking. It is preferable to provide a coating film that can

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

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

[0032] The size of a droplet of sprayed liquid 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 sprayed liquid. The particle surface after drying is determined under the condition that the maximum particle diameter is smaller than the nozzle diameter. Upon inspection, some areas were found to be coated with graphene oxide, but it was unclear whether the coating 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, the active material can be easily dispersed. This is preferable because the coating of the material is good. 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. By spraying the graphene oxide onto the surface of the positive electrode active material using a spray dryer, A coated powder can be obtained.

[0036] Note that the suspension becomes more acidic as the amount of graphene oxide increases. There is a risk of etching part of the surface (for example, LiCoO2 containing Mg or F). Therefore, the hydrogen ion exponent (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, that is, 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 a mixed liquid, damage to the surface of the active material may be reduced.

[0037] By preparing the suspension as described above, the surface can be efficiently coated with graphene oxide. By covering the surface with graphene oxide, it is possible to prepare a positive electrode active material. This prevents cracks or breakage of the particles of the electrode active material. 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 time after the production of the positive electrode active material is completed. This refers to the period from the completion of storage until the production of a secondary battery using the positive electrode active material. The formation of a coating also allows the positive electrode active material and the electrolyte to adhere to each other. This prevents direct contact and reaction, so when a secondary battery is made, the secondary Battery reliability is improved.

[0038] In addition, a known device can be used for the spray-drying method, for example, a countercurrent pressure nozzle. A nozzle-type spray dryer, a parallel counterflow nozzle-type pressurized spray dryer, or the like can be used.

[0039] When 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 atoms or atomic groups containing oxygen atoms are carbon atoms. For example, RGO may contain epoxy groups and carboxyl groups. In some cases, the alkyl 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 manufacturing a cathode active material, comprising: The secondary battery has a positive electrode and a negative electrode.

[0041] Secondary batteries can be used in a variety of shapes to suit the device they are used in. For example, cylindrical shapes, square shapes, coin shapes, laminated (flat) shapes, etc. can be done. [Effects 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 decrease in capacity due to the charge-discharge reaction is suppressed. It is also possible to provide a secondary battery that is safe and highly reliable. Furthermore, the present invention provides a novel material, active material particles, a secondary battery, and a method for producing the same. It is possible. [Brief explanation of the drawings]

[0043] [Figure 1] 1A to 1C illustrate an example of a positive electrode active material. [Figure 2] 1A and 1B are diagrams illustrating the crystal structure of a positive electrode active material. [Figure 3] 1A and 1B are diagrams illustrating the crystal structure of a positive electrode active material. [Figure 4] FIG. 1 is a diagram illustrating a sol-gel method. [Figure 5] FIG. 10 is a diagram illustrating a segregation model of elements contained in a positive electrode active material. [Figure 6] FIG. 10 is a diagram illustrating a segregation model of elements contained in a positive electrode active material. [Figure 7] FIG. 10 is a cross-sectional view of an active material layer in the case where a graphene compound is used as a conductive additive. [Figure 8] FIG. 2 is a diagram illustrating a method for charging a secondary battery. [Figure 9] FIG. 2 is a diagram illustrating a method for charging a secondary battery. [Figure 10] FIG. 2 is a diagram 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. [Figure 23] 1A and 1B are diagrams illustrating a bendable secondary battery. [Figure 24] 1A to 1C illustrate examples of electronic devices. [Figure 25] 1A to 1C illustrate examples of electronic devices. [Figure 26] 1A to 1C illustrate examples of electronic devices. [Figure 27]1A to 1C illustrate examples of electronic devices. [Figure 28] 1 is a transmission electron microscope image of the positive electrode active material of Example 1. [Figure 29] 1 is an FFT image of a transmission electron microscope image of the positive electrode active material of Example 1. [Figure 30] 1 is an elemental mapping image of the positive electrode active material of Example 1. [Figure 31] 1 is an elemental mapping image of a positive electrode active material of a comparative example of Example 1. [Figure 32] 3 is a graph showing the results of TEM-EDX linear analysis of the positive electrode active material of Example 1. [Figure 33] 2 is a graph showing the charge / discharge characteristics of the secondary battery of Example 1. [Figure 34] 1 is a graph showing charge / discharge characteristics of a secondary battery of a comparative example of Example 1. [Figure 35] 3 is a graph showing the cycle characteristics of the secondary battery of Example 1. [Figure 36] 3 is a graph showing the 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. [Figure 40] TEM-EDX area analysis image of the positive electrode active material of Example 2. [Figure 41] Graph showing the results of EDX point analysis in Example 2. [Figure 42] Graph showing the results of EDX point analysis in Example 2. [Figure 43] 10 is a graph showing the rate characteristics of the secondary battery of Example 2. [Figure 44] 10 is a graph showing the temperature characteristics of the secondary battery of Example 2. [Figure 45] 10 is a graph showing the cycle characteristics of the secondary battery of Example 2. [Figure 46] 1 is a graph showing the results of XPS analysis of the positive electrode active material of Example 3. [Figure 47] 10 is a graph showing the cycle characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 48] 10 is a graph showing the cycle characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 49] 10 is a graph showing the cycle characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 50] 10 is a graph showing the charge-discharge characteristics of a secondary battery using the positive electrode active material of Example 3. [Figure 51] 10 is an SEM image of the positive electrode active material of Example 4. [Figure 52] 1 is an 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. 10 is a diagram illustrating a spray drying apparatus according to a fifth embodiment. [Figure 55] 1 is a TEM photograph showing an embodiment of the present invention according to Example 5. [Figure 56] 10 is an SEM photograph showing an embodiment of the present invention according to Example 5. [Figure 57] 10 is an SEM photograph showing a comparative example of Example 5. [Figure 58] FIG. 10 is a cross-sectional view of an active material layer in the case where a graphene compound is used as a conductive additive in Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and various modifications in form and details are possible by those skilled in the art. Furthermore, the present invention should not be construed as being limited to the description of the following embodiments. It is not something that can be done.

[0045] In each drawing described in this specification, the positive electrode, negative electrode, active material layer, separator, outer casing, 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 a relative size.

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

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

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

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

[0050] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately. It is possible for there to be a deficiency of cations or anions.

[0051] The anions of layered rock salt crystals and 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 closest packing composed of anions However, the space group of the layered rock salt crystal is R-3m. The rock salt crystal space group Fm-3m (the general rock salt crystal space group) and Fd-3m ( Since the space group is different from that of rock salt crystals, which have the simplest symmetry, the results satisfying the above conditions 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 composed of anions is aligned When this occurs, the crystal orientation is said to be 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 as materials for judgment. TEM image In layers 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 formed by the repetition of the above is 5 degrees or less, and more preferably 2.5 degrees or less. However, in TEM images, light elements such as oxygen and fluorine may not be clearly observed. In this case, the alignment of the orientation can be determined by the arrangement of the metal elements.

[0053] In this specification, the similarity of the structure of a two-dimensional interface is referred to as epitaxy. Crystal growth that resembles the structure of a two-dimensional interface is called epitaxial growth. Topotaxis refers to the fact that the two molecules have similar fundamental structures or have the same crystallographic orientation. Therefore, in the case of topotaxis, when a part of the cross section is observed, two regions (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 substance 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. 1(B), 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. Also, 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] Furthermore, 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 boundary. The third layer is applied to the portion of the positive electrode active material 100 having the crystal defects, the crack portion, and the vicinity thereof. A region 103 may exist. 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. 1(B), a second region 102 exists 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, portions with 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 can 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 cobalt may be used as the first transition metal. Two types of cobalt and manganese may be used, or three types of cobalt, manganese, and nickel may be used. good.

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

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

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

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

[0066] Since 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, so it is preferable for the first region 101. stomach.

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

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

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

[0071] 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). Non-stoichiometric compounds function as a region where the valence of the metal in the non-stoichiometric compound changes. Interatomic distances can change, and nonstoichiometric compounds often lack cations or anions. Therefore, the second region 102 is a buffer region. As a region, the strain occurring between the first region 101 and the third region 103 can be absorbed.

[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. may be used. The region 102 may contain the same main group element as 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 preferably contains the elements contained therein as a buffer region.

[0074] That is, the second region 102 is made of lithium titanate, titanium oxide, vanadium oxide, manganese oxide, or the like. 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 may exist as titanium dioxide (TiO2) or as lithium titanate (LiTiO2). In the second region 102, a composite acid having lithium and a first transition metal may be used. Some of the first transition metal sites of the oxide may be substituted with titanium.

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

[0078] The second region 102 may have the same type of crystal structure as the third region 103 described later. In this case, the crystal orientations of the second region 102 and the third region 103 tend to match. .

[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 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 is 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, it will not function as a buffer region. Therefore, the second region 102 is formed by It is preferable that it exists within 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 main group element. The compound of a main group element is a stoichiometric compound. The compounds of typical elements are electrochemically stable compounds made of typical elements. It is preferable to use magnesium oxide, calcium oxide, beryllium oxide, fluorine, 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 undergoes electrochemical changes during charging and discharging. It is preferable that the material has a low content and is resistant to deterioration when in 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, which improves stability during charging and discharging of the secondary battery. Here, the high stability of the secondary battery can be achieved by, for example, The crystalline structure of the composite oxide containing lithium and first transition metals in 101 is more stable. Alternatively, it refers to the fact that the capacity of a secondary battery changes little even after repeated charging and discharging. Alternatively, even after repeated charge and discharge, 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, charge and discharge are not hindered. In addition, the presence of fluorine in 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 and third regions 102 and 103 are roughly the same, the second and third regions 102 and 103 form a more stable coating. It can function as a layer.

[0089] However, the third region 103 does not necessarily 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 the above-mentioned crystal structure.

[0090] In addition, if the structure in which six oxygen atoms are adjacent to the cation is maintained, there is no distortion in the crystal structure. 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 thickness is too large, 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 vicinity of the surface of the positive electrode active material 100 is analyzed by XPS, The peak position of the fluorine binding 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 binding energy that does not match any of the above.

[0094] In this specification, the peak position of the binding 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 binding energy of the element. This refers to the value of the bond energy such that

[0095] Generally, the positive electrode active material, such as manganese, cobalt, and nickel, degrades as the charge and discharge cycle is repeated. The first transition metal dissolves in 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 are performed at a high voltage of 1000 V or higher, the structure 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. The third region 103 is preferably formed by heteroepitaxial growth from the second region 102. It is preferable that the region formed by heteroepitaxial growth is 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 from the first region 101 to the third region 103 are roughly the same, The third region 103 and the first region 101 are coated with a stable bond. Therefore, the positive electrode active material 100 can have a strong coating layer.

[0098] The second region 102 and the third region 103 have stable bonds 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 by charging. Even if the silicon is removed, the coating layer with stable bonding prevents the silicon from being absorbed from the first region 101. Furthermore, the area in contact with the electrolyte can be prevented from releasing cobalt and oxygen. Therefore, it is possible to make a secondary battery with excellent cycle characteristics. It can be a pond.

[0099] <Inconsistency between areas> For heteroepitaxial growth, the crystal in the base region and the crystal you want to grow must be The degree of inconsistency is important.

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

[0101]

number

[0102] For heteroepitaxial growth, the crystal in the base region and the crystal 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's 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 mismatch f of the rock salt type crystal structure is 0.12 or less. It is preferable to select the material of the region 102 as follows.

[0104] The rock salt type crystal structure of the second region 102 and the rock salt type crystal structure of the third region 103 are 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] 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 as described above. 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 ratio is 0.12 or less. Examples of materials and crystal planes of the region 103 are listed below.

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

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

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

[0109] As shown in Figure 2(B), when the layered rock salt crystal is viewed from the <1-1-4> plane orientation, the rock salt Crystals of the type <100> The atomic arrangement is similar to that seen from the plane orientation of the metal. The nearest neighbor distances of the elements also have similar values. For example, in the layered rock salt lithium cobalt oxide The distance between Li and O is 2.089 Å, and the distance between Co and O is 1.925 Å. The distance between Li and O in lithium is 2.138 Å, and the distance between Ti and O is 2.051 Å. The Mg-O distance in 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 planes {00} contact each other will be explained below.

[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 the (1-1-4) of the ruthenium is 4. 01 Å. In addition, the second region 102 of lithium titanate having a rock salt crystal structure has a thickness of { 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 It 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 f between the plane 102p{100} and the crystal plane 103p{100} is 0.02.

[0113] In this way, the mismatch between the first region 101 and the second region 102 and the The mismatch between the first region 101 and the third region 103 is sufficiently small, so that the first region 101 to the third region 103 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 That is, the presence of the second region 102 makes it possible to reduce the degree of mismatch. Furthermore, since the second region 102 is a non-stoichiometric transition metal oxide, The presence of the first region 101 to the third region 103 allows a more stable transition. Therefore, the second region 102 and the third region 103 are It can function as a coating layer with a stable bond to 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, one embodiment of the present invention is not limited to this. 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 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, as in FIGS. 2 and 3, the layered rock salt crystals in the first region 101 are formed at a density of <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 layered rock salt crystals in the first region 101 are as follows: The metal-oxygen-metal distance of the (1-1-4) crystal plane of lithium cobalt oxide with 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. The mismatch f between the crystal plane (1-1-4) of the first region 101 and the crystal plane {100} of the second region 102 is 0. It is .11.

[0119] The third region 103 has a rock salt type crystal structure and has a crystal plane {100} The metal-oxygen-metal distance is 4.82. Therefore, the crystal plane {1 The mismatch f between the {00} crystal plane of the third region 103 and the {100} crystal plane of the third region 103 is 0.08.

[0120] In this way, the mismatch between the first region 101 and the second region 102 and the The mismatch between the first region 101 and the third region 103 is sufficiently small, so that the first region 101 to the third region 103 Topotaxis is possible up to region 103.

[0121] On the other hand, if the crystal plane (1-1-4) of the first region 101 and the crystal plane {10 0} contact, the mismatch f is 0.20, making heteroepitaxial growth difficult. In other words, the presence of the second region 102 allows the heterojunction from the first region to the third region to be formed. Therefore, the second region 102 and the third region 103 are formed by epitaxial growth. , can function as a coating layer having a stable bond with the first region 101.

[0122] <Example 3: Lithium nickel-manganese-cobalt oxide, manganese oxide, calcium oxide> Next, the first transition metal is nickel, manganese, and cobalt, and the first region 101 is Lithium nickel-manganese-cobalt oxide (LiNi) with a layered rock-salt type crystal structure 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 consider an example where the compound of a main group element is calcium oxide, which has a rock salt type crystal structure. do.

[0123] In this case, as shown in Figures 2 and 3, the layered rock salt crystals are aligned in the <1-1-4> plane direction. From the perspective of the crystals, it is a rock salt type. <100> The atomic arrangement is very similar to that seen from the plane orientation of the The (1-1-4) crystal plane of the layered rock salt crystal and the {100} crystal plane of the rock salt crystal are The degree of inconsistency between the regions when they are in contact 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 of the crystal plane (1-1-4) of aluminum is 4.07 Å. The metal-oxygen bond of the {100} crystal plane of manganese oxide with a rock-salt crystal structure in the region 102 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 101 and the crystal plane {100} of the second region 102 is 0.09.

[0125] The third region 103 has a rock salt type crystal structure and has a crystal plane {100} The metal-oxygen-metal distance is 4.82. Therefore, the crystal plane {1 The mismatch f between the {00} crystal plane of the third region 103 and the {100} crystal plane of the third region 103 is 0.08.

[0126] In this way, the mismatch between the first region 101 and the second region 102 and the The mismatch between the first region 101 and the third region 103 is sufficiently small, so that the first region 101 to the third region 103 Topotaxis is possible up to region 103.

[0127] On the other hand, if the crystal plane (1-1-4) of the first region 101 and the crystal plane {10 0} contact, the mismatch f is 0.18, making heteroepitaxial growth difficult. In other words, the presence of the second region 102 allows the heterojunction from the first region to the third region to be formed. Therefore, the second region 102 and the third region 103 are formed by epitaxial growth. , can function as a coating 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 However, the elements in each region have a concentration gradient. For example, the second transition metal contained in the second region 102 may have a concentration gradient. The third region 103 is a region where the typical elements are segregated, as will be described later. Therefore, there may be 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 TEM images, STEM images, 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 constituent elements appear as differences in image brightness. Therefore, the constituent elements of the first region 101, the second region 102, and the third region 103 In addition, area analysis by EDX (e.g., elemental 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, EDX line analysis and depth direction analysis using ToF-SIMS revealed that the first region 101, the second region 102, and the third region 103 detect the peaks of the concentrations of the elements. 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 identified 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 mentioned above. Analysis in the depth direction using ToF-SIMS and other techniques can be used.

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

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

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

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

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

[0139] Therefore, the third area 103 and the second area 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 preferable that the active material particles are present in a region close to the surface.

[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. Preferably, the thickness is between 0.5 nm and 3 nm, and the thickness is between 0.5 nm and 3 nm. It is more preferable that

[0141] 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 in the area of ​​about 5 nm from the surface. The element concentrations in 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 or more and 0.4 or less, and more preferably 0.1 or more and 0. The relative concentration of the typical element is preferably 0.4 or more and 1.5 or less. The relative value of the fluorine concentration is more preferably 0.45 or more and 1.00 or less. 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, the first region 101 may be 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, and the like. It may also contain other elements such as sodium, calcium, chlorine, zirconium, etc.

[0144] [Particle size] If the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse, and if it is too small, it becomes difficult to disperse lithium later. Therefore, it becomes difficult to maintain the crystal structure described above. ) 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 substantially 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, which reduces the 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) 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. It 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 affected 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 can be adjusted to the above-mentioned preferred range by calcination. When this is done, 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, a mixture of 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. As will be described later, lithium may be lost outside the system during the process of preparing 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 may not match the ratio of the transition metals in 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 particle size can be kept within a preferred range. It was revealed that a positive electrode active material with a high capacity retention rate could be produced.

[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 or more and 1.07 or less, and 1 It is more preferable that it is greater than 0.03 and less than 1.06.

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

[0153] As a method for coating a material containing a second transition metal, a liquid phase method such as a sol-gel method is used. , solid phase method, sputtering method, evaporation method, CVD (chemical vapor deposition) method, PLD (pulse laser In this embodiment, a method such as the deposition method can be applied. The application of the sol-gel method, which is expected to be effective and allows processing at atmospheric pressure, will be described.

[0154] <Sol-gel method> The method of coating a material containing a second transition metal using the sol-gel method is shown in FIG. I will explain.

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

[0156] Figure 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, and R represents an alkyl group having 1 to 18 carbon atoms. aryl group, or a substituted or unsubstituted aryl group having 6 to 13 carbon atoms. In the above-1), the general formula is shown for the case where the second transition metal is tetravalent, 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- Page 10 10 used when titanium is used as the second transition metal. In Figure 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-butoxytitanium, tetra-sec-butoxytitanium, 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 below. (IV) The chemical formula of isopropoxide (TTIP) is shown below.

[0160] The solvent for dissolving the alkoxide of the second transition metal is preferably an alcohol. For example, methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol A roller or the like can be used.

[0161] Next, lithium, transition metal, magnesium, and the like are added to an alcohol solution of the second transition metal alkoxide. Particles of a composite oxide containing 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 are separated 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. This reaction produces a sol of the oxide of the second transition metal. This reaction is shown in Figure 4(D-1) and Figure 4 As shown in (D-2), the second transition also occurs on the surface of the composite oxide particle 110. A layer comprising a metal is formed.

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

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

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

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

[0167] The segregation model of this typical element will be explained using Figures 5 and 6. Magnesium, etc. The segregation model of the typical elements is based on the ratio of lithium to the first transition metal in the starting material. Therefore, 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 will be explained using Figure 5. Segregation model when the ratio of Li to first transition metals in the material is 1.03 or more, i.e., when there is a lot of lithium. The following will be explained using FIG. 6. In addition, these segregation models and the first transition in FIG. 5 and FIG. 6 For example, if the metal is cobalt, the second transition metal is titanium, and the main group element is magnesium, He explains.

[0168] Figure 5(A) shows the lithium-cobalt zeolite prepared with a Li:Co ratio of the starting materials of less than 1.03. 110. The surface of the composite oxide particle 110 is shown in Fig. 11. The region 111 in the figure 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 containing 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 higher 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 covered with lithium cobalt oxide. Lithium is easily released from cobalt oxide, forming cobalt oxide, as shown in Figure 5(A). 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 type crystal structure. Therefore, in the particle 110 of FIG. 5(A), the layer On the region 111 having lithium cobalt oxide with a rock-salt crystal 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 titanium-containing material by a sol-gel method or the like. ) shows a state in which a particle 110 is coated with a titanium-containing layer 112 by a sol-gel method. 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 of the present invention. The state of the positive electrode active material 100 produced in this embodiment is shown in FIG. The titanium in the layer 112 diffuses toward the inside of the grain 110. The magnesium and fluorine contained in 1 segregate on the surface of the particles 110 .

[0174] As described above, rock salt type cobalt oxide is present on the surface of the particles 110. Magnesium also has a rock-salt type crystal structure. Therefore, magnesium is more easily absorbed into the grain 110 than into the interior of the grain. 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, so it is difficult to form stable compounds such as magnesium oxide. In the case of magnesium and oxygen, the addition of fluorine causes a bias in the charge. It is thought that this weakens the bond. Therefore, oxygen in magnesium oxide is replaced with 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 decreasing. 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 decreases. The lower 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, part 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 substitutes for the cobalt site of the lithium cobalt oxide, and partly replaces 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 contains 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 to Co ratio of 1.03 or more in the starting materials. 1 is a model diagram of the vicinity of the surface of a particle 120 of a composite oxide containing magnesium and fluorine. The region 121 in the figure contains lithium, cobalt, magnesium, and fluorine. This is an area where

[0182] The particle 120 in FIG. 6(A) has sufficient lithium, so that it can be easily mixed with lithium, cobalt, magnesium, and the like. When the particles 120 of the composite oxide having lithium and fluorine are calcined, lithium is added to the particles 12. Even if the particle leaves the 0, lithium diffuses from inside the particle 120 to the surface to compensate, 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 hydrochloride gel, it has low crystallinity.

[0184] FIG. 6C shows the particle 120 after being coated with the titanium-containing layer 122 of FIG. 6B by heating. By heating, the 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 resulting mixture becomes lithium titanate, forming a layer 125 containing 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 temporary cobalt layer 124 forms.

[0186] FIG. 6D shows the state where heating is sufficiently performed from 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. The presence of magnesium in the particles 120 allows the magnesium to be oxidized on the surface of the particles 120 rather than inside the particles 120. It is thought that magnesium is more stable than fluorine. 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 found near the grain boundaries and 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 composite oxides containing lithium and first transition metals. 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 are present, they can also segregate in cracked areas 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 segregate in the crack area, forming the third region 1. The formation of the second 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 with excellent cycle characteristics. do.

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

[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 partially coincide with each other. That is, the second region 102 and the third region 103 may be topotaxis. If the crystal orientations of the region 102 and the third region 103 are roughly the same, they will have better 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 contain a typical element such as magnesium. It may contain a small amount.

[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. 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 defects such as cracks 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 includes 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 formed by 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 That is, the fourth region 104 is formed from the second region 102 and the and the second region 103 has a second transition metal and a main group element in an appropriate amount. The crystal structure of the second region 102 and the third region 103 may be stabilized. Furthermore, the presence of the fourth region 104 prevents defects such as cracks 106 that the positive electrode active material 100 has. 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 Microscope). The elements contained in the fourth region 104 can be observed using a scanning electron microscope (SEM). It can be analyzed using EDX, etc.

[0198] [Method for 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, starting materials are prepared. The materials prepared in this step are finally used to form the first region 10 The first and third regions 103 are formed.

[0200] The first region 101 contains a lithium source and a first transition metal as raw materials. The transition metal source is prepared as follows. , a source of main group elements is prepared.

[0201] In addition to these, it is preferable to prepare a fluorine source. Fluorine can be added to the raw materials to In a later step, 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] As the lithium source, for example, lithium carbonate or lithium fluoride can be used. 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, or a cation 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 contained in the third region. In other words, lithium fluoride can be used as both a lithium source and a fluorine source. You can be there.

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

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

[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 carried out 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. A dry atmosphere is preferably one with a dew point of -50°C or less, and more preferably -100°C or less. In this embodiment, the heating is performed at 1000° C. for 10 hours, and the temperature is increased by 200° C. °C / h, and dry air with a dew point of -109°C is to be flowed at 10 L / min. Cool the mixture to room temperature.

[0207] The heating in step 13 produces a layered rock-salt-type crystal structure of lithium and the first transition metal. At this stage, the main group elements and fluorine atoms contained in the starting materials are separated. The fluorine is dissolved in the composite oxide. However, some of the main elements are already dissolved in the composite oxide. It may be unevenly distributed on the surface.

[0208] In addition, lithium, cobalt, fluorine, and magnesium are synthesized as starting materials. In this case, steps 12 and 13 may be performed. For example, lithium cobalt oxide particles manufactured by Nippon Chemical Industry Co., Ltd. (trade name: C-20F) can be used as one of the starting materials. The area that can be analyzed by XPS from the surface is fluorine, magnesium, calcium, and sodium. It is a lithium cobalt oxide particle containing 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 metal composite oxide particles.

[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 amount of water in the atmosphere and the amount of TTIP that is hydrolyzed and polymerized. The time may be long enough to cause a condensation reaction, 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 solvent alcohol. The sol-gel reaction can be carried out slowly. This allows the formation of a coating layer containing titanium of uniform thickness and high quality.

[0214] After the above treatment, the precipitate is collected from the mixture. The collection method can be filtration, centrifugation, etc. In this embodiment, the collected material is recovered by filtration. A paper filter was used for filtration, and the residue was collected in the same alcoholic solvent as that used to dissolve the titanium alkoxide. It will be washed with coke.

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

[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, and it is even 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 dispersion will proceed too much 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 second transition metals will not occur. However, if the temperature is too high, the first transition metal in the composite oxide particles will be reduced, and the composite oxide The layer structure of lithium and the first transition metal in the composite oxide particle is broken down. There is a risk that it may not be possible to maintain the quality.

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

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

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

[0221] The crystal orientations of the second region 102 and the third region 103 are roughly the same, and the crystal orientations of the first region 101 are When the positive electrode active material 100 is used in a secondary battery, the positive electrode active material 100 exhibits stable bonding with the positive electrode active material 100. This effectively suppresses the change in the crystal structure of the first region 101 that occurs when the first region 101 is charged. Even if lithium is removed from the region 101 of the first electrode, the surface layer portion has stable bonds. This prevents the first transition metal such as cobalt and oxygen from being released 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 with 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 first region 101 and the second region 102 are all topotaxis. The second region 102 and the third region 103 may be partially topotaxis. Not all of the region 103 needs to be topotaxis.

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

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

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

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

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

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

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

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

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

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

[0233] As the conductive additive, a carbon material, a metal material, a conductive ceramic material, or the like can be used. A fibrous material may also be used as the conductive additive. 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 additive can form an electrically 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 with high electrical conductivity. .

[0235] Examples of the conductive additive include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon fiber. Examples of carbon fibers that can be used include mesophase pitch carbon fibers. 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, vapor phase growth method. For example, carbon black (acetylene black (AB) etc.), graphite particles Carbon materials such as graphene and fullerene can be used. Metal powders and fibers such as nickel, aluminum, silver, and gold, as well as conductive ceramic materials, etc. It can be used.

[0236] A graphene compound may also be used as the conductive additive.

[0237] Graphene compounds have excellent electrical properties, such as high conductivity, as well as high flexibility and high In addition, graphene may have excellent physical properties such as high mechanical strength. The graphene compound has a planar shape, which allows for surface contact with low contact resistance. In addition, even if they are thin, they can have very high conductivity, and even a small amount 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 additive. 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. Here, RGO is, for example, graphene oxide. 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 relative decrease in the amount of active material carried. If the amount of the conductive additive decreases, the capacity of the secondary battery will decrease. 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] As an example, in the case where a graphene compound is used as a conductive additive 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 additive, and a binder (not shown). Here, the graphene compound 201 may be, for example, graphene or multi-graphene. Here, the graphene compound 201 preferably has a sheet shape. In addition, the graphene compound 201 may be a multi-graphene or (and) a multi-graphene. The graphene may be partially overlapped to form a sheet.

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

[0242] Here, a plurality of graphene compounds are bonded to each other to form a mesh-like graphene compound. It is possible to form a graphene sheet (hereinafter referred to as a graphene compound net or graphene net). When the active material is covered with a graphene net, the graphene net can connect the active material to each other. It can also function as a binder to bind the particles together. Therefore, the ratio of the active material to the electrode volume or weight can be reduced. 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 forming the layer that will become the layer 200, 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 by, for example, heat treatment or by using a reducing agent. It 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 granular positive electrode active material 100 and the graphene compound 201 is small, and the electrical conductivity between the granular 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 a 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, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene 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. cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose Cellulose derivatives such as cellulose, diacetyl cellulose, and regenerated cellulose, as well as starch These water-soluble polymers can be used in combination with the rubber materials described above. It is even better if there is one.

[0248] Alternatively, the binder may be polystyrene, polymethyl acrylate, or polymethyl methacrylate. Polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl Polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, Polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene Polyethylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride Polyvinyl fluoride (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 with 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, mixing with a material that has a particularly excellent viscosity adjusting effect can As a material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer is preferably used. Furthermore, examples of water-soluble polymers that are particularly effective in adjusting viscosity include the aforementioned polysaccharides, such as carbohydrates. Carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxy Cellulose derivatives such as propyl cellulose, diacetyl cellulose, and regenerated cellulose Carbohydrates and starches can be used.

[0251] The cellulose derivatives such as carboxymethyl cellulose are, for example, By converting cellulose into salts such as sodium salts or ammonium salts, the solubility increases, It is easier to exert its effect as a viscosity adjuster. The increased solubility makes it easier to make electrode slurry. When preparing a substrate, it is also possible to improve the dispersibility of the active material and other components. In this case, the cellulose and cellulose derivatives used as binders for electrodes include These salts are also included.

[0252] Water-soluble polymers stabilize viscosity by dissolving in water, and also act as active materials and binders. Other materials to be combined, such as styrene butadiene rubber, are stably dispersed in aqueous solution. In addition, since it has functional groups, it can be easily and stably adsorbed onto the surface of the active material. It is expected that cellulose derivatives such as carboxymethyl cellulose will 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 suppressing the decomposition of the electrolyte. It is a film with no or very low electrical conductivity, and for example, it is 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. Highly conductive materials such as alloys of these can be used. It is preferable that silicon, titanium, neodymium, scavenger, etc. are not eluted 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 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, and punched shapes. The current collector may be in the form of a metal, an expanded metal, or the like. It is recommended to use 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 additive 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 and dealloying reactions with lithium. Any suitable element can be used, such as silicon, tin, gallium, aluminum, 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 particularly high theoretical capacity of 4200mAh / g. It is preferable to use silicon. Alternatively, compounds containing these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V 2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3 Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, I nSb, SbSn, etc. Here, the charge / discharge reaction occurs due to alloying and 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 and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO refers to 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 materials include graphite, easily 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 include carbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. 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 preferable. It is relatively easy to reduce the particle size, which is sometimes preferable. Examples include flake graphite and spherical natural graphite.

[0261] When lithium ions are inserted into graphite (when lithium-graphite intercalation compounds are formed), It exhibits 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 capacity per unit volume, a relatively small volume expansion, and is inexpensive. It is preferable because it has advantages such as higher safety compared to lithium metal.

[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 a transition metal is used, the negative electrode active material contains lithium ions, The positive electrode active material is a combination of materials such as V2O5 and Cr3O8 that do not contain lithium ions. It is preferable that a material containing lithium ions is used as the positive electrode active material. By first removing the lithium ions contained in the positive 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. , cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. A transition metal oxide that does not form an alloy with the metal may be used as the negative electrode active material. Further materials that can be 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 additive 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 same materials as the conductive additive and binder 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 methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1 ,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfone oxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran One of tetrahydrofuran, 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 batteries, the internal temperature of the secondary battery can be increased due to an internal short circuit or overcharging. Even if the battery is not fully charged, it can prevent the secondary battery from exploding or catching fire. Ionic liquids are made up of cations and anions. The organic cations used in the electrolyte include quaternary cations. 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 perfluoroalkylphosphate anions, etc.

[0270] The electrolyte to be dissolved in the 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 ammonium salts in any combination and ratio. can be done.

[0271] The electrolyte used in secondary batteries is free from granular dust and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). It is preferable to use a highly purified electrolyte solution with a low content of ammonium hydroxide. 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, the electrolyte contains vinylene carbonate, propane sultone (PS), and tert-butyl ether. Benzene (TBB), Fluoroethylene Carbonate (FEC), LiBOB, and Squishi Additives such as dinitrile compounds such as dibenzonitrile and adiponitrile may also be added. The concentration of the material to be added may be, for example, 0.1 wt% to 5 wt% of the total solvent. .

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

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

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

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

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

[0278] [Separator] The secondary battery preferably has a separator. The separator may be made of, for example, 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 electrode be processed into a shape such that it wraps around 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 material, fluorine material, polyamide material, or a combination of these. The ceramic material can be, for example, aluminum oxide. Aluminum particles, silicon oxide particles, etc. can be used. For example, PVDF, polytetrafluoroethylene, etc. can be used. Polyamide-based materials Materials used include nylon, aramid (meta-aramid, para-aramid), etc. It is possible.

[0280] Coating with ceramic materials improves oxidation resistance, making it suitable for separators during high-voltage charging and discharging. This can suppress the deterioration of the battery and improve the reliability of the secondary battery. By coating, the separator and electrodes can be more easily attached to each other, improving output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, which contributes to the safety of secondary batteries. Safety can be improved.

[0281] For example, a mixture of aluminum oxide and aramid is coated on both sides of a polypropylene film. Alternatively, aluminum oxide may be applied to the surface of the polypropylene film that comes into contact with the positive electrode. The surface that comes into 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 that comes into contact with the negative electrode. .

[0282] By using a multilayer separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin. Since the temperature can be maintained, the capacity per volume of the secondary battery can be increased.

[0283] [Exterior body] The exterior of the secondary battery is made of a metal material such as aluminum or a resin material. Also, a film-like outer casing can be used. For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. On the film made of the material, a highly flexible metal such as aluminum, stainless steel, copper, or nickel is A metal thin film is then formed on the metal thin film, and the outer surface of the exterior body is made of a polyamide resin or polyester. A three-layer film having an insulating synthetic resin film such as a vinyl 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 as one of the charging methods. CC charging is a method in which the battery is constantly charged for the entire charging period. This is a charging method in which a constant current flows through the secondary battery and charging stops when the voltage reaches a specified level. Assuming that the secondary battery is 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, the switch is turned on and a constant voltage is applied, as shown in Figure 8(A). 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 also 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 stops. 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, the internal resistance R The voltage drop of the secondary battery V B is decreasing.

[0288] The secondary battery voltage V during CC charging and after CC charging is stopped B and 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 up to a specified voltage using CC charging, then use CV (constant voltage) charging to reduce the current that flows. This is a charging method in which charging is continued until the current becomes low, specifically until the end current value is reached.

[0290] During CC charging, as shown in Figure 9(A), the constant current power supply is switched on and the constant 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 applied to 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 the internal resistance R R As becomes smaller, V R By Ohm's law, = R × I, The current I flowing through the battery also becomes smaller.

[0292] When the current I flowing through the secondary battery reaches a predetermined current, for example, a current equivalent to 0.01C, When CCCV charging is stopped, all switches are turned off as shown in Figure 9(C). The switch is turned off and the current I becomes 0. Therefore, the voltage V applied to the internal resistance R R becomes 0V However, the voltage V applied to the internal resistance R due to CV charging R is small enough that Even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B hardly descends 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 CCCV charging is stopped, the secondary battery voltage V B Gahoton It shows that the aircraft does not descend at all.

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

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

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

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

[0298] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. 11(B) 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 a negative electrode current collector 308 and a The negative electrode active material layer 309 is formed by bonding the negative electrode active material layer 309 to the negative electrode active material layer 309 .

[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 and aluminum, which are corrosion-resistant to the electrolyte. , titanium, or alloys thereof 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 preferably coated with a positive electrode 304, and the negative electrode can 302 is preferably coated with a negative electrode 304. 7 and electrically connect to each other.

[0302] The negative electrode 307, the positive electrode 304, and the separator 310 are impregnated with an electrolyte, and the resulting structure is shown in FIG. ) the positive electrode can 301 is placed downward, and the positive electrode 304, separator 310, 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 form a coin-type secondary battery 300.

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

[0304] Here, the flow of current during charging of the secondary battery will be explained using FIG. 11(C). When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In secondary batteries that use lithium, the anode and cathode are connected by charging and discharging. The cathode (electrode) is switched, and the oxidation reaction and reduction reaction are switched. The electrode with a higher reaction potential is called the positive electrode, and the electrode with a lower reaction potential is called the negative electrode. In this case, even during charging, discharging, or when 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 (positive electrode) and cathode (negative electrode) are used, the difference between charging and discharging is Therefore, the anode and cathode are often used interchangeably. The term "anode" (negative electrode) is not used in this specification. When using the terms "positive electrode" or "cathode," specify whether it is charging or discharging, and It will also be noted whether it corresponds to a positive pole (positive electrode) or a negative pole (negative electrode).

[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. 12. Cylindrical secondary battery 600 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 attached to the bottom surface. It is insulated from 602 by a gasket (insulating packing) 610 .

[0307] Fig. 12(B) is a schematic diagram showing the cross section of a cylindrical secondary battery. Inside the can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are placed with a separator 605 sandwiched between them. The battery element is wound around a center pin (not shown). 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 corrosion-resistant to the electrolyte, or Alloys of these and other metals (e.g., stainless steel) can be used. In addition, it is preferable to coat the electrode with nickel, aluminum, etc. to prevent corrosion by the electrolyte. 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. The inside of the battery can 602 is filled with a non-aqueous electrolyte (not shown). 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 603. The positive electrode terminal 607 can be made of a metal material such as aluminum. 603 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) element. The positive electrode cap 601 is electrically connected to the positive electrode cap 601 via a positive electrode coefficient 611. The safety valve mechanism 612 releases the positive electrode cap 601 when the internal pressure of the battery exceeds 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 whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current. It prevents abnormal heat generation. The PTC element is made of barium titanate (BaTiO3) Semiconductor ceramics and the like can be used.

[0309] 12(C), a plurality of secondary batteries 600 are mounted on conductive plates 613 and 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 may be connected in parallel and then connected in series. By configuring a module 615 having a plurality of secondary batteries 600, It can extract a large amount of power.

[0310] FIG. 12(D) is a top view of the module 615. For clarity of illustration, the 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 plurality of secondary batteries 600. When the secondary battery 600 is overheated, it is cooled by the temperature control device 617. If the battery 600 is too cold, it can be heated by the temperature control device 617. This makes the performance of the module 615 less susceptible to the 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 cycling. 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. 13(B), the secondary battery has a terminal 951 and a terminal 952. , antenna 914, and antenna 915.

[0314] The circuit board 900 has a terminal 911 and a circuit 912. The terminal 911 is connected to a terminal 951. , terminal 952, antenna 914, antenna 915, and 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 capacitor has two conductors, one of which is an annulus. The antenna 914 or the antenna 915 may be activated. Instead, 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 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 FIGS. 14(A-1) and 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 surfaces. A-2) is an external view 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 FIGS. 13(A) and 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 the two surfaces of a secondary battery 913. As shown in FIG. 14(A-2), an antenna 914 is provided, and the pair of surfaces of the secondary battery 913 On the other hand, an antenna 918 is provided across a layer 917. The layer 917 is, for example, a secondary battery 91 The layer 917 has a function of shielding 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 can be applied. Examples include response methods such as NFC 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) 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 area where the display device 920 is provided. 13(A) and 13(B), the same parts as those of the secondary battery shown in FIG. 13(A) and The explanation 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 or not, an image indicating the amount of stored power, etc. The display device 920 may be, for example, an electronic paper, a liquid crystal display, an electrophotographic display, 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) 13 may be provided with a sensor 921. The sensor 921 is connected to the terminal 911 via a terminal 922. It is 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 FIGS. 13(A) and 13(B) can be used as appropriate.

[0325] The sensor 921 may be, for example, a sensor for detecting displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, etc. , liquid, magnetic, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow It is sufficient if it has the function of measuring volume, humidity, gradient, vibration, odor, or infrared. 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] Furthermore, an example of the structure of the secondary battery 913 will be described with reference to FIGS.

[0327] The 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. 15A, the housing 930 is not in contact with the housing 930. For convenience, the housing 930 is shown separated. Although the figure shows the winding body 950, in reality, the winding body 950 is covered by the housing 930, and the terminals 951 and 955 are 2 extends outside the housing 930. The housing 930 is made of a metal material (e.g., aluminum Rubber or resin materials can be used.

[0328] As shown in FIG. 15(B), the housing 930 shown in FIG. 15(A) is made of a plurality of materials. For example, the secondary battery 913 shown in FIG. 15B may be formed by a housing 930a and a housing 930b. The wound body 930 is located in the area surrounded by the housing 930a and the housing 930b. 50 are provided.

[0329] The housing 930a can be made of an insulating material such as 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 electric field by 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] Furthermore, the structure of the wound body 950 is shown in Fig. 16. The wound body 950 is made up of a negative electrode 931 and a positive electrode 932. The winding body 950 has a pole 932 and a separator 933. The negative electrode 931 and the positive electrode 932 are stacked one on top of the other, and the laminated sheet is wound to form a wound body. The negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated. You can stack several of them.

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

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

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

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

[0335] 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 current collector (not shown) via one of the lead electrodes 998. The positive electrode 997 and the lead electrode 998 are connected to a positive electrode current collector (not shown).

[0336] As shown in FIG. 17(B), 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, and the above-mentioned wound body 993 is housed in the space formed. In this way, a secondary battery 980 can be fabricated as shown in FIG. 3 has lead electrodes 997 and 998, and is connected to a film 981 and a recessed portion. 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 material such as a resin. If a resin material is used as the material, when external force is applied, the film 981 and the recessed portion The film 982 can be deformed to produce a flexible secondary battery. can be done.

[0338] In addition, although Fig. 17(B) and Fig. 17(C) show examples using two films, 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 that serves as an exterior body is shown. For example, as shown in Figure 18, the shape of the outer film is It can also be used as a secondary battery having a plurality of rectangular positive electrodes, separators, and negative electrodes in the space formed. 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 electrode current collector 504 also serves as a terminal for 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 outer casing 509. In addition, the positive electrode current collector 501 and the negative electrode current collector 504 may be disposed in the outer casing 509. The lead electrode is not exposed to the outside, and the lead electrode is connected 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 an A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied, and the metal is further 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 three-layer laminate film provided 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. A) shows an example of a structure consisting of two current collectors for simplicity, but in reality, it is composed of multiple electrode layers. It consists of:

[0345] In FIG. 18(B), as an example, the number of electrode layers is set to 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 eight layers, making a total of 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 this case, a secondary battery having a larger capacity can be obtained. In this case, a secondary battery can be made thin and highly flexible.

[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 provided.

[0347] 21(A) shows an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is connected to the 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 the 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 negative electrode are not limited to the example shown in FIG. I can't.

[0348] [Method for manufacturing laminated secondary batteries] Here, an example of a method for manufacturing the 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 stacked. The figure shows five pairs of negative electrodes 506, separators 507, and positive electrodes 503. 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 can be used for bonding. Similarly, the bonding of the tab regions of the negative electrodes 506 to each other and the bonding of the negative electrode leads to the tab region of the negative electrode on the outermost surface are also preferable. Then, the bonded electrode 511 is formed.

[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 broken line. After that, the outer periphery of the exterior body 509 is bonded. For example, thermocompression bonding may be used for bonding. , so that the electrolyte 508 can be poured later, An area that is not bonded (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 introduction of the electrolytic solution 508 is preferably carried out under a reduced pressure atmosphere or an inert gas atmosphere. Finally, the inlet is joined. In this way, a laminated secondary battery is completed. 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 cycling. 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 cutting 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 battery 50 is made up of an exterior body 51 and an exterior body 52. The positive electrode 11a and the negative electrode 11b are housed inside the battery 1. The positive electrode 11a is electrically connected to the negative electrode 11b. The lead 12a electrically connected to the negative electrode 11b and the lead 12b electrically connected to the negative electrode 11b are 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 includes a plurality of strip-shaped positive electrodes 11a, a plurality of strip-shaped negative electrodes 11b, and a plurality of strip-shaped negative electrodes 11c. 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 The positive electrode 11a and the negative electrode 11b are stacked so that the surfaces on which no film is formed 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. 23(B), the positive electrodes 11a and the leads 12a are connected to each other at the joints 15a. The negative electrodes 11b and the leads 12b are electrically connected at the joints 15b. are electrically connected.

[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 sandwiching the positive electrode 11a and the negative electrode 11b. The exterior body 51 includes a bent portion 61, a pair of seal portions 62, and a seal The pair of sealing portions 62 are set 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. It is preferable that the seal portion 62 and the seal portion 63 of the exterior body 51 have a wave shape arranged in a line. Preferably, 63 is flat.

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

[0365] Here, the distance between the end of the negative electrode 11b in the width direction and the seal portion 62 is defined as La. When the battery 50 is deformed by bending or the like, the positive electrode 11a and the negative electrode 11b are If the distance La is too short, the outer casing 51 and the outer casing 52 may deform. The positive electrode 11a and the negative electrode 11b may rub against each other so strongly that 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 stacked 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 sealing portion 62.

[0367] More specifically, the stacked positive electrode 11a, negative electrode 11b, and separator (not shown) are When the total thickness of 214 is thickness t, the distance La is between 0.8 and 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, it is possible to make the device compact and resistant 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 a distance Lb, the distance Lb is It is preferable that the thickness is sufficiently larger than Wb. This allows the battery 50 to withstand repeated bending, etc. When the positive electrode 11a and the negative electrode 11b are deformed, even if they come into contact with the exterior body 51, the positive electrode 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 the thickness t of the negative electrode 11b are 1.6 times or more and 6.0 times or less, preferably 1.8 times or more and 5.0 times or less, 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's nice.

[0371]

number

[0372] Here, a is 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, and more preferably is between 1.0 and 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 formed between the end portions of the positive electrode 11a and the negative electrode 11b in the length direction and the outer casing 51. It is preferable to do so.

[0374] FIG. 22(D) shows a schematic cross-sectional view of the battery 50 when bent. This corresponds to the cross section taken along the 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 outside 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 relieves the stress applied to the exterior body 51 due to bending. Therefore, the material that constitutes the exterior body 51 does not need to stretch. 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 bent. At this time, the stacked positive electrodes 11a and negative electrodes 11b are 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 11b are shifted so that the amount of shift becomes larger. The stress acting on the positive electrode 11a and the negative electrode 11b is alleviated, 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 formed between the ends of the positive electrode 11a and the negative electrode 11b and the outer casing 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 FIGS. 22 and 23 does not break the exterior body even when repeatedly bent and stretched. The battery is less likely to suffer damage, breakage of the positive electrode 11a and the negative electrode 11b, and the battery characteristics are 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] (Fourth embodiment) 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 explained 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 wall of a house or building, or on the inside or outside of a car. It is also possible to incorporate it along the curved surface of the interior or exterior of the vehicle.

[0382] FIG. 24A shows an example of a mobile phone. The mobile phone 7400 has a housing 7401. In addition to the display unit 7402 incorporated in the 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, long-lasting mobile phone.

[0383] FIG. 24B shows the mobile phone 7400 in a bent state. When the entire device is deformed by an external force and curved, the secondary battery inside 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 shown in the bent state. The secondary battery 7407 is fixed in place by a lead wire electrically connected to the current collector 7409. For example, the current collector 7409 is made of copper foil, and is partially mixed with gallium. The adhesion between the current collector 7409 and the active material layer in contact therewith is improved, and the secondary battery 7407 This configuration is highly reliable even when bent.

[0384] FIG. 24(D) shows an example of a bangle-type display device. The portable display device 7100 includes: The device includes a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. 24(E) shows the state of the bent secondary battery 7104. The secondary battery 7104 is bent. When the device is worn on the user's arm with the device attached, the housing may deform and cause damage to part of the secondary battery 7104 or The total curvature changes. 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 reciprocal of the radius of curvature is called the curvature. Specifically, the radius of curvature is The area is within the range of 40 mm to 150 mm, and the area is part of the main surface of the casing 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. 24(F) 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 phone calls, e-mails, viewing and creating documents, playing music, and internet access. - It can run various applications such as internet communication and computer games. do.

[0387] The display surface of the display unit 7202 is curved, and the display is performed along the curved display surface. The display portion 7202 is provided with a touch sensor, and can be touched with 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 standardized short-range wireless communication. For example, by communicating with a wireless headset, hands-free operation is possible. You can also make calls.

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

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

[0392] The mobile information terminal 7200 preferably has a sensor. For example, a fingerprint sensor may be used as the sensor. Human body sensors such as pulse sensors and body temperature sensors, as well as touch sensors, pressure sensors, and acceleration sensors It is preferable that a sensor, etc. be installed.

[0393] FIG. 24G shows an example of a wristband-type display device. The display device 7300 includes a display unit 7 304 and includes the secondary battery of one embodiment of the present invention. The display unit 7304 may be provided 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 images can be displayed along the curved display surface. The display device 7300 can also communicate with the display device 7300 by short-distance wireless communication according to a communication standard. The situation can be changed.

[0395] The display device 7300 is also equipped with an input / output terminal, and can be directly connected 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 using 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, This makes it possible to provide a display device with a long life at a low cost.

[0397] In addition, an example in which the secondary battery with good cycle characteristics shown in the above embodiment is mounted on an electronic device is shown in FIG. 24(H), 25 and 26.

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

[0399] FIG. 24(H) is a perspective view of a device also called a tobacco-containing smoking device (electronic cigarette). 24(H), the electronic cigarette 7500 is an atomizer 7501 containing a heating element and an atomizer A secondary battery 7504 that supplies power to the MYZA, and a cart containing a liquid supply bottle, sensors, etc. 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 a compact and lightweight e-cigarette 7500 that 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, a housing 9630b, a movable part 9640 connecting the housings 9630a and 9630b, and a display a display unit 9631 having a display unit 9631a and a display unit 9631b; a display mode changeover switch; 9626, power switch 9627, power saving mode switch 9625, fastener 96 29, an operation switch 9628, and a display unit 9631. By using this, it is possible to create a tablet terminal with a larger display area. 25(B) shows the tablet terminal 9600 in an open state, and FIG. 25(C) shows the tablet terminal 9600 in an open state. The figure shows the 9600 closed.

[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, for 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 displayed as a keyboard button to serve as 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, a part of the display unit 9631b 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 can be displayed on the display portion 9631b.

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

[0405] A display mode changeover switch 9626 changes the display orientation between portrait and landscape. You can select between black and white and color display. The touch 9625 detects when in use by the light sensor built into the tablet terminal 9600. The display brightness 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, and the display For example, one display panel may be capable of displaying images with higher resolution than the other. It may also be possible to use the following.

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

[0408] In addition, since the tablet terminal 9600 can be folded in half, 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 units 9631a and 9631b can be protected, the durability of the tablet terminal 9600 can be improved. Furthermore, the power storage unit 9635 using the secondary battery of one embodiment of the present invention can With its high capacity and good cycle characteristics, this tablet can be used for a long period of time. A mobile terminal 9600 can be provided.

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

[0410] The solar cell 9633 attached to the surface of the tablet terminal supplies power to the touch panel, The solar cell 9633 can be supplied 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. When a lithium-ion battery is used 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. 25(B) are shown in FIG. A block diagram is shown in FIG. 25(C) and will be explained. In FIG. 25(C), a solar cell 9633, a power storage unit 963 5, DC-DC converter 9636, converter 9637, switches SW1 to SW3, table The display unit 9631 is shown, and the storage battery 9635, the DC-DC converter 9636, 25B. This corresponds to 34.

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

[0413] The solar cell 9633 is shown as an example of a power generating means, but is not particularly limited thereto. Power storage using other power generation methods such as piezoelectric elements and thermoelectric conversion elements For example, the power may be transmitted and received wirelessly (contactlessly). It is also possible to combine it with a contactless power transmission module that charges the battery, or other charging means. That's fine.

[0414] Another example of electronic equipment is shown in FIG. 26. In FIG. 26, a display device 8000 is a display device according to one embodiment of the present invention. 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 8003 and a secondary battery 8004. 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 The display device 8000 can be used by using the secondary battery 8004 as an uninterruptible power supply. do.

[0415] The display unit 8002 includes a liquid crystal display device, an emitting device having a light emitting element such as an organic EL element in each pixel, and Device, electrophoretic display device, DMD (Digital Micromirror Device) ce), PDP (Plasma Display Panel), FED (Field A semiconductor display device such as a reflective LED (emission display) can be used.

[0416] In addition to TV broadcast reception, display devices are also used for personal computers and advertising displays. , including all display devices for displaying information.

[0417] In FIG. 26, a stationary lighting device 8100 includes a secondary battery 81 according to one embodiment of the present invention. 8101, a housing 8102, a light source 8103, and a light source 8104. 26, the secondary battery 8103 is mounted in the housing 81. 8101 and a light source 8102 are 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 can store power in a secondary battery 8103. Therefore, if the power supply from the commercial power source is interrupted due to a power outage, etc., Even when the power is not available, the secondary battery 8103 according to one embodiment of the present invention can be used as an uninterruptible power supply. This allows the lighting device 8100 to be used.

[0418] 26 shows an example of a fixed lighting device 8100 provided on a ceiling 8104. However, the secondary battery according to one embodiment of the present invention is not limited to the ceiling 8104, but may be installed on other parts such as the side wall 8105 and the floor 8106. 106, it can be used for a fixed lighting device provided in a window 8107, etc., or it can be used for a tabletop lighting device. It can also be used in lighting devices of this type.

[0419] 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, and light-emitting devices such as LEDs and organic 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 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. Both the power supply 8201 and the power supply 8204 may be provided with a secondary battery 8203. The power supply can be supplied from a commercial power source, or the power stored in the secondary battery 8203 can be used. In particular, both the indoor unit 8200 and the outdoor unit 8204 may be equipped with secondary batteries 82 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 of 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, it is an all-in-one air conditioner that has the functions of both the indoor unit and the outdoor unit in a single housing. The secondary battery according to one embodiment of the present invention can also be used in 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 the commercial power source due to a power outage, etc. However, by using the secondary battery 8304 of one embodiment of the present invention as an uninterruptible power supply, It will be possible to use the 8300-capacity refrigerator.

[0423] Among the above-mentioned electronic devices, high-frequency heating devices such as microwave ovens and electric rice cookers are Equipment requires high power for a short period of time, so it supplements the power that cannot be supplied by commercial power. By using a secondary battery according to one embodiment of the present invention as an auxiliary power source for This prevents the commercial power breaker from tripping during use.

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

[0425] According to one embodiment of the present invention, the cycle characteristics of the secondary battery are improved, and the reliability is improved. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be obtained. 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 make the electronic device lighter and with a longer life span. The present 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), an electric vehicle (EV), or a powertrain. This will enable the realization of next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). .

[0428] 27A and 27B illustrate 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 aspect of the present invention, it is possible to extend the driving range. Furthermore, 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 a combination of 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). can be provided.

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

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

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

[0432] 27C 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 even if the under-seat storage 8604 is small. The secondary battery 8602 can be 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. 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 This can contribute to reducing carbon dioxide emissions. Since the battery 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. [Example]

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

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

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

[0439] Next, in step 14, lithium cobalt oxide particles containing magnesium and fluorine are mixed with sol-gel The titanium-containing material was coated by the coating method. Specifically, TTIP was dissolved in isopropanol. The solution was dissolved in isopropanol to prepare a solution of TTIP. TTIP reacts 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 prevented the hydrolysis and polycondensation reactions between the water in the atmosphere and TTIP. Then, a layer containing titanium was formed on the surface of 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 under vacuum at 70°C for 1 hour.

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

[0444] Next, the heated particles were cooled to room temperature. The cooling time from the holding temperature to room temperature was 10 to 1 The mixture was left for 5 hours. After that, it was crushed by sieving. The sieve used had an opening 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, and is made of a material containing titanium without coating it. The particles were prepared by heating lithium cobalt oxide particles containing sodium and fluorine.

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

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

[0449] The heated powder was cooled in the same way as sample 01, sieved, and then added to the positive electrode of sample 02. The electrode active material was

[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

[0451] <<Sample 03>> Sample 03 is a comparative example of lithium cobalt oxide without magnesium. The titanium-containing region was formed on the titanium particles by the sol-gel method, and then the particles were heated.

[0452] The lithium cobalt oxide particles used were manufactured by Nippon Chemical Industry Co., Ltd. (product name: C-10N). Lithium cobalt oxide in which magnesium is not detected in PS, but fluorine is detected at approximately 1 atomic % It is a particle.

[0453] Titanium was added to these lithium cobalt oxide particles by the sol-gel method in the same way as sample 01. A region containing the sample was formed, dried, heated, cooled and sieved. The electrode active material was

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

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

[0456] The lithium cobalt oxide particles used were manufactured by Nippon Chemical Industry 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 containing magnesium and fluorine. The lithium titanate particles were used as is without heating.

[0459] Lithium cobalt oxide particles containing magnesium and fluorine were manufactured by Nippon Chemical Industry Co., Ltd. (product name: C -20F) was used. In other words, Sample 05 was made from the same material as Sample 01. 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 observed under an electron microscope (JEM-ARM manufactured by JEOL Ltd.). The electron microscope image obtained is shown in Figure 28. As shown in FIG. 28, the cathode 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, and the second region 102 and 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 of the area indicated by 102FFT 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 circled. The T image is shown in Figure 29(C1). Figure 29(C2) shows the center point O of Figure 29(C1) drawn with a cross. The figure shows the bright spots 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 bright point C and the center point O was , d=0.209nm. Also, ∠COA=121°, ∠COB=52°, ∠AO B=69°. From these results, the region shown by 103FFT is magnesium oxide ( It was inferred that it contained MgO (cubic crystal).

[0465] Similarly, the distance between the bright spot A and the center point O shown in Figure 29(B2) is d = 0.238 nm. 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 region indicated by 102FFT is titanic acid. It was speculated 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 bright point 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. It was speculated that it contained (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 element mapping image using EDX are shown in Figure 30. Figure 30(A1) shows HAADF-STEM image, Fig. 30(A2) is an oxygen atom mapping image, Fig. 30(B1) is a Baltic atom mapping image, Figure 30(B2) is a fluorine atom mapping image, Figure 30(C1) is FIG. 30(C2) is a titanium atom mapping image, and FIG. 30(C3) is a magnesium atom mapping image. 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 Figure 30(A2) and Figure 30(B1), oxygen atoms and cobalt atoms are positive electrodes. It was clear that the active material particles were distributed throughout the entire active material particles. Fluorine atoms, titanium atoms, and magnesium atoms as shown in Figure 30(C1) and Figure 30(C2). It was revealed that the molecules were unevenly distributed in the region close to the surface of the positive electrode active material.

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

[0470] As shown in Figure 31(B2) and Figure 31(C2), Sample 05, which was not heated, It was also revealed 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 analyzed by TEM-EDX. The results are shown in Figure 32. Figure 32 shows the outside and inside of the positive electrode active material of Sample 01. The data detected on the line connecting the positive electrode active material and the positive electrode active material are plotted on a graph. The distance of 14 nm is inside the particle. Since EDX tends to broaden the analysis area, electron beam irradiation In some cases, not only the central element but also the surrounding elements may be detected.

[0472] As shown in FIG. 32, the positive electrode active material of Sample 01 has magnesium and titanium in the vicinity of its surface. It is clear that the distribution of magnesium is closer to the surface than the distribution of titanium. It was also found that 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 Figure 32, almost no fluorine was detected, but this is because fluorine, a light element, was detected by EDX. This was thought to be because fluorine was difficult to detect.

[0474] The above STEM image, FFT image, elemental mapping image using EDX, and EDX linear analysis Therefore, Sample 01 has lithium cobalt oxide as the first region, which is one embodiment of the present invention. The second region has lithium, titanium, cobalt, and oxygen, and the third region has It was confirmed that the cathode 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, the graph in Figure 32 shows that the amount of oxygen detected is stable at a distance of 4 nm or more. In this example, the average detected amount of oxygen 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

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

[0477] If the surface of the positive electrode active material particle is 1.71 nm in distance in Figure 32, 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, up to 2.71 nm from the surface of the active material particle. At depths of 2.86 nm or more from the surface of the material particle, the measured value of magnesium is 1 / Therefore, in sample 01, the first peak was observed from the surface to 2.71 nm in the depth direction. It was revealed that it was in the region of 3.

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

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

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

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

[0483] 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 wt%. We used the following.

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

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

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

[0488] FIG. 34 shows a graph of the charge-discharge characteristics of the secondary battery of Sample 05 of the comparative example. However, as shown by the arrows in the figure, the charge-discharge characteristics deteriorated as the cycles progressed. The charge / discharge capacity decreased.

[0489] [Evaluation of cycle characteristics] ≪Charging 4.4V≫ For the secondary batteries of 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. The battery was charged at 2.5V (CC, 0.5C, cut-off current 0.01C) and discharged at 2.5V (CC, 0.5C).

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

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

[0492] Figure 36 shows a graph of the cycle characteristics when charging at 4.6V. The secondary battery having Sample 01, which is a positive electrode active material according to one embodiment of the present invention, exhibited a high voltage of 4.6 V. Even after 50 cycles of voltage charging and discharging, the energy density is 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 with the quality is inferior to Sample 01. For example, in the case of Sample 04, The energy density retention rate after the test was 33.2%.

[0493] As described above, the positive electrode active material according to one embodiment of the present invention can be charged at a high voltage exceeding 4.4 V. It was found that a significant effect was achieved when discharge was performed. [Example]

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

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

[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 10 ... The model number: C-20F was used.

[0497] Next, in step 14, the lithium cobalt oxide particles are coated with titanium oxide by the sol-gel method. The solution 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 sample was heated in an oxygen atmosphere at 800°C for 2 hours using a furnace. The oxygen flow rate was 10 L / min.

[0499] Thereafter, the cathode active material was obtained by cooling and recovering in the same manner as in Example 1. , let's call it sample 07.

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

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

[0502] Figure 37 shows the TEM-EDX analysis results of sample 06 before heating. The cross-sectional TEM image includes the surface of the substrate and the crack. The HAADF-STEM image of the area including the particle surface is shown in Figure 37(B1), and the Ti mapping image is shown. This is shown in Figure 37(B2). Similarly, the crack area indicated by the circle marked 2 in Figure 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). Figure 3 shows a HAADF-STEM image of the rack area at a depth of approximately 500 nm from the surface. 37(D1) and Ti mapping image is shown in FIG. 37(D2). The crack area indicated by the circle is approximately 1000 nm deep from the surface. The TEM image is shown in Figure 37(E1), and the Ti mapping image is shown in Figure 37(E2). In the EDX element mapping images of Figures 40 and 41, values ​​below the detection limit are shown in black, and counts The more the number increases, the closer it gets to white.

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

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

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

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

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

[0508] As shown in Figures 39 and 40, magnesium is present on the particle surface and in the crystallites of Sample 06 before heating. On the other hand, in sample 07 after heating, magnesium segregation was observed. Segregation was observed both on the particle surface and in cracks.

[0509] Next, to quantify titanium and magnesium, the samples were analyzed using the circles labeled 1 to 6 in FIG. 37(A). EDX point analysis was performed on the area and the areas indicated by circles 1 to 6 in Figure 38(A). Measurements were taken at two locations within each area.

[0510] Figure 41 shows the results of EDX point analysis in terms of the atomic ratio of titanium to cobalt. This is the result for sample 06 before heating. Detection points 1 to 6 in Figure 41(A) are This is within the area indicated by the circles marked 1 to 6 in Figure 37(A). The results are for sample 07. The detection points 1 to 6 in Figure 41(B) are the same as those in Figure 38( A) is within the area indicated by the circles numbered 1 to 6.

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

[0512] Next, Figure 42 shows the results of EDX point analysis 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 both had magnetite. 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. 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 coated on 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 of LiPF6 was dissolved in a mixture of DEC = 3:7 (volume ratio) and The material used contained 2 wt% of nylene carbonate (VC).

[0517] [Initial characteristics, rate characteristics] The secondary battery using the positive electrode active material of Sample 07 prepared above was evaluated for initial characteristics and The properties of the coating were measured.

[0518] The initial characteristics were measured with CCCV charging at 0.2C, 4.6V, and a cutoff current of 0.05C. Discharge was performed at CC, 0.2C, and a cutoff voltage of 3.0V. The current value per weight of the positive electrode active material was 160 mA / g. The measurement temperature was 25°C. The results of measuring the properties 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 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 43.

[0522] [Table 3]

[0523] [Temperature characteristics] Next, the amount of the positive electrode active material layer was increased to 8.2 mg / cm 2 The rest are the same as the cells where the rate was evaluated. The cells were fabricated under the same conditions and the temperature characteristics were evaluated. All charging was performed at 25°C, CCCV, 0.2 The discharge was performed at 25°C, 0°C, -10°C, and - The temperature was 20℃ and 45℃, and the temperature was CC, 0.2C, and the cut-off voltage was 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 a cutoff current of 0.05C. The discharge was performed at CC, 1.0 C, and a cutoff voltage of 3.0 V. The measurement temperature for the cycle characteristics was The temperature was kept at 45°C and the measurement was carried out for 100 cycles. The discharge capacity retention rate after 100 cycles was 86%. The measured cycle characteristics were plotted as a graph of the discharge capacity retention rate in Figure 45. .

[0525] 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 was 2.21 g / cm 3 It was. Tap Dense The measurement was performed using a MULTI TESTER MT-1000 (manufactured by Seishin Enterprises). .

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

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

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

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

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

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

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

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

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

[0537] Next, 2-propanol was added to the positive electrode active material at a concentration of 0.01 ml / g of TTIP. 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. Particles of a composite oxide containing the compound 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 under 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 of 53 μm.

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

[0545] <Samples 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 Li / Co ratio of the starting material was 1.07. Sample 26 was weighed so that the Li / Co ratio of the starting material was 1.08. Sample 27 was weighed so that the Li / Co ratio of the starting material was 1.13.

[0546] Samples 21 to 27 were prepared by varying the concentration of TTIP in 2-propanol solution relative to the weight of the positive electrode active material. The TTIP per 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 weight of the active material was set to 0.02 ml / g.

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

[0549] 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 cathode active material had a region containing titanium and magnesium.

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

[0552] Sample 31 was weighed so that the Li / Co ratio of the starting material was 1.00. Sample 2 was weighed 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. 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 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 rate of 200°C / h. The flow rate of the dry air was set to 10 L / min.

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

[0557] The synthesized particles were cooled and then heated to 800°C (heating rate: 200°C / hour). 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 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 was 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 are shown in Table 6, and the results of the XPS analysis of Sample 31 are shown in Table 7. The results of the XPS analysis of Sample 40 are shown in Table 7. In Tables 5 to 7, the concentration of each element is The values ​​are relative to cobalt, which is set to 1.

[0563] [Table 5]

[0564] [Table 6]

[0565] [Table 7]

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

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

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

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

[0570] Even if there is a region containing titanium, when the Li / Co ratio is 1.07, the In addition, when the Li / Co ratio was 1.08 or more, the magnesium concentration decreased. It was speculated that even if there is a region containing 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, Using the positive electrode active material of Sample 26, the cycle characteristics were evaluated 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 mixing ratio, The electrodes, electrolyte, exterior body, conditions for the cycle characteristic test, etc. were the same as 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. The 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 6V 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 retention 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] As is clear from Figure 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 or more and 1.06 or less, is good. In particular, Samples 23 and 24, which have a Li / Co ratio of The positive electrode active materials with 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. 11 and Sample 2, which showed the best cycle characteristics among Samples 21 to 25. A graph comparing 3 is shown below.

[0577] As is clear from Figure 48, both showed extremely good cycle characteristics, but TTIP Sample 23 with 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 Figure 49.

[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 inductor, counter electrode, electrolyte, exterior body, and cycle characteristic test conditions are examples. Same as 1.

[0580] The secondary battery using Sample 28 used PVDF as a binder and a positive electrode active material (LCO ), AB, and PVDF were mixed in a weight ratio of LCO:AB:PVDF=95:3:2. The other secondary batteries 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 exhibited 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, respectively, The discharge capacity retention rate deteriorated from a relatively early stage.

[0583] From the above results, it is found that the preferable 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. 49, and Figure 50 shows the charge / discharge curve of the secondary battery using sample 25, which showed deterioration at an early stage. vinegar.

[0585] Figure 50(A) is sample 28, Figure 50(B) is sample 24, Figure 50(C) is sample 2 The charge and discharge curves of the secondary battery using 5 are shown in Fig. 1. The results of 50 charge and discharge cycles are shown. 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 FIGS. 50(A) and 50(B), the positive electrode active material of one embodiment of the present invention, Sample 28 and Sample 24 showed high charge-discharge capacity and good charge-discharge characteristics. Compared with sample 25 in Figure 50(C), sample 2 in Figure 50(A) and Figure 50(B) It was revealed that the decrease in charge / discharge capacity was significantly suppressed in Samples 8 and 24. [Example]

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

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

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

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

[0591] The same areas in Figures 52(A-1), 52(A-2), and 52(B-1) are surrounded by dotted lines. As is clear from comparing the area surrounded by the dotted line, the convex area 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 the fourth convex regions 104.

[0593] As shown in Example 2, Sample 24 was one of the samples 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 found that a positive electrode active material exhibiting good cycle characteristics can be obtained by this 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 portion, It was found that a positive electrode active material exhibiting good cycle characteristics could be 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 the Li / Co ratio can be widened. Even if the fourth region containing titanium and magnesium exists, good cycle characteristics are exhibited. It became clear that: [Example]

[0595] In this example, an example of a method for manufacturing a positive electrode active material coated 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 below.

[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 graphene, (S12) mixing and stirring graphene oxide with pure water, (S13) pH (S14) Adding active material (S15) Completing 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 mediums such as ethanol may also be used. In addition, in (S14), the active material is a positive electrode active material.

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

[0599] When a suspension containing a positive electrode active material and graphene oxide is used as the suspension 284, the oxidation The graphene-covered positive electrode active material powder is circulated through the chamber 281 into 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 the path indicated by the 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 material, 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 an ultrasonic generator were used to stir the mixture and disperse it in the liquid. The rotation speed was set to 750 rpm, 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 example, lithium cobalt oxide particles (trade name) manufactured by Nippon Chemical Industry Co., Ltd.) :C-20F)) was added, and a stirrer and an ultrasonic generator were used for stirring, and the rotation speed was 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 silicon, magnesium, calcium, sodium, silicon, sulfur, and phosphorus The particles are titanium particles with a particle size of approximately 20 μm.

[0607] Next, the suspension was sprayed using a spray-drying device with a spray nozzle (nozzle diameter 20 μm). The powder was obtained by uniformly spraying. The hot air temperature at the inlet 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, and an 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 graphene oxide using a planetary mixer. The SEM photograph of the comparative example is shown in Figure 57.

[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, 1 shows an example of a cross-sectional configuration in which a graphene compound is further used as a conductive additive in the active material layer 200. This is 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 a sheet-like graphene or a multi-graphene. In addition, the graphene compound 201 preferably has a shape of a plurality of multigraphs. 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 active material layer 200 is made of graphene oxide. The graphene compound 201 is in contact with the positive electrode active material 100 covered with the coating 105. The plurality of graphene compounds 201 are formed by depositing the positive electrode active material 10 covered with the coating 105. 0 and is formed so as to be in contact with 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, and 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 face 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 tubes 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 board 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 circuits 913 Secondary battery 914 Antenna 915 Antenna 916 layers 917 layers 918 Antenna 920 Display device 921 Sensor 922 terminal 930 chassis 930a housing 930b housing 931 negative electrode 932 Positive electrode 933 Separator 950 Wound body 951 terminal 952 terminals 980 Secondary battery 981 Film 982 Film 993 Wound body 994 negative electrode 995 positive electrode 996 Separator 997 Lead Electrode 998 Lead electrode 7100 Portable display devices 7101 Housing 7102 Display section 7103 Operation button 7104 Secondary battery 7200 Personal Digital Assistant 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 Housing 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Microphone 7407 Secondary battery 7408 Lead electrode 7409 Current collector 7500 e-cigarettes 7501 Atomizer 7502 Cartridge 7504 Secondary battery 8000 display device 8001 Case 8002 Display section 8003 Speaker section 8004 Secondary battery 8021 Charging device 8022 cable 8024 Secondary battery 8100 Lighting equipment 8101 Housing 8102 Light source 8103 Secondary battery 8104 Ceiling 8105 Side wall 8106 beds 8107 Window 8200 indoor unit 8201 Housing 8202 Ventilation outlet 8203 Secondary battery 8204 Outdoor unit 8300 Electric refrigerator-freezer 8301 Housing 8302 Refrigerator door 8303 Freezer door 8304 Secondary battery 8400 Automobiles 8401 Headlight 8406 Electric motor 8500 cars 8600 Scooter 8601 Side mirror 8602 Secondary battery 8603 Turn signal light 8604 Under-seat storage 9600 tablet device 9625 Switch 9626 Switch 9627 Power Switch 9628 Operation Switch 9629 Fasteners 9630 chassis 9630a housing 9630b housing 9631 Display section 9631a Display section 9631b Display section 9632a area 9632b area 9633 Solar Cells 9634 Charge / Discharge Control Circuit 9635 Electricity storage unit 9636 DC / DC Converter 9637 Converter 9638 Operation key 9639 Button 9640 Moving parts

Claims

1. A lithium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte solution, the positive electrode has positive electrode active material particles containing lithium cobalt oxide, The positive electrode active material particles have an interior and a surface layer portion, The interior has a layered rock salt type crystal structure, the surface layer portion has a rock salt type crystal structure, the surface layer portion is present in a region closer to the surface of the positive electrode active material particle than the interior portion, the positive electrode active material particles have titanium, magnesium, fluorine, and oxygen in the surface layer portion, an EDX ray analysis of the positive electrode active material particles shows that a magnesium peak and a titanium peak exist in the surface layer portion, and the magnesium peak exists in a region closer to the surface of the positive electrode active material particles than the titanium peak; the orientation of the crystals of the layered rock salt type crystal structure in the interior roughly coincides with the orientation of the crystals of the rock salt type crystal structure in the surface layer portion; The electrolyte solution contains vinylene carbonate. Lithium-ion secondary battery.

2. A lithium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte solution, the positive electrode has positive electrode active material particles containing lithium cobalt oxide, The positive electrode active material particles have an interior and a surface layer portion, The interior has a layered rock salt type crystal structure, the surface layer portion has a rock salt type crystal structure, the surface layer portion is present in a region closer to the surface of the positive electrode active material particle than the interior portion, the positive electrode active material particles have titanium, magnesium, fluorine, and oxygen in the surface layer portion, an EDX ray analysis of the positive electrode active material particles reveals that a magnesium concentration peak and a titanium concentration peak exist in the surface layer portion, and the magnesium concentration peak exists in a region closer to the surface of the positive electrode active material particles than the titanium concentration peak; the surface layer portion has a region where the magnesium concentration detected in the depth direction from the surface of the positive electrode active material particle by the EDX ray analysis is ⅕ or more of the peak, and a region where the titanium concentration detected in the depth direction from the surface of the positive electrode active material particle is ½ or more of the peak, the orientation of the crystals of the layered rock salt type crystal structure in the interior roughly coincides with the orientation of the crystals of the rock salt type crystal structure in the surface layer portion; The electrolyte solution contains vinylene carbonate. Lithium-ion secondary battery.

3. A lithium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte solution, the positive electrode has positive electrode active material particles containing lithium cobalt oxide, The positive electrode active material particles have an interior and a surface layer portion, The interior has a layered rock salt type crystal structure, the surface layer portion has a rock salt type crystal structure, the surface layer portion is present in a region closer to the surface of the positive electrode active material particle than the interior portion, the positive electrode active material particles have titanium, magnesium, fluorine, and oxygen in the surface layer portion, an EDX ray analysis of the positive electrode active material particles shows that a magnesium peak and a titanium peak exist in the surface layer portion, and the magnesium peak exists in a region closer to the surface of the positive electrode active material particles than the titanium peak; the orientation of the crystals of the layered rock salt type crystal structure in the interior roughly coincides with the orientation of the crystals of the rock salt type crystal structure in the surface layer portion; The electrolyte contained in the electrolytic solution contains lithium hexafluorophosphate, The electrolyte solution contains ethylene carbonate, diethyl carbonate, and vinylene carbonate. Lithium-ion secondary battery.

4. A lithium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte solution, the positive electrode has positive electrode active material particles containing lithium cobalt oxide, The positive electrode active material particles have an interior and a surface layer portion, The interior has a layered rock salt type crystal structure, the surface layer portion has a rock salt type crystal structure, the surface layer portion is present in a region closer to the surface of the positive electrode active material particle than the interior portion, the positive electrode active material particles have titanium, magnesium, fluorine, and oxygen in the surface layer portion, an EDX ray analysis of the positive electrode active material particles reveals that a magnesium concentration peak and a titanium concentration peak exist in the surface layer portion, and the magnesium concentration peak exists in a region closer to the surface of the positive electrode active material particles than the titanium concentration peak; the surface layer portion has a region where the magnesium concentration detected in the depth direction from the surface of the positive electrode active material particle by the EDX ray analysis is ⅕ or more of the peak, and a region where the titanium concentration detected in the depth direction from the surface of the positive electrode active material particle is ½ or more of the peak, the orientation of the crystals of the layered rock salt type crystal structure in the interior roughly coincides with the orientation of the crystals of the rock salt type crystal structure in the surface layer portion; The electrolyte contained in the electrolytic solution contains lithium hexafluorophosphate, The electrolyte solution contains ethylene carbonate, diethyl carbonate, and vinylene carbonate. Lithium-ion secondary battery.

5. A lithium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte solution, the positive electrode has positive electrode active material particles containing lithium cobalt oxide, The positive electrode active material particles have an interior and a surface layer portion, The interior has a layered rock salt type crystal structure, the surface layer portion has a rock salt type crystal structure, the surface layer portion is present in a region closer to the surface of the positive electrode active material particle than the interior portion, the positive electrode active material particles have titanium, magnesium, fluorine, and oxygen in the surface layer portion, an EDX ray analysis of the positive electrode active material particles shows that a magnesium peak and a titanium peak exist in the surface layer portion, and the magnesium peak exists in a region closer to the surface of the positive electrode active material particles than the titanium peak; the orientation of the crystals of the layered rock salt type crystal structure in the interior roughly coincides with the orientation of the crystals of the rock salt type crystal structure in the surface layer portion; The electrolyte contained in the electrolytic solution contains lithium hexafluorophosphate, The electrolyte solution contains vinylene carbonate and propane sultone. Lithium-ion secondary battery.

6. A lithium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte solution, the positive electrode has positive electrode active material particles containing lithium cobalt oxide, The positive electrode active material particles have an interior and a surface layer portion, The interior has a layered rock salt type crystal structure, the surface layer portion has a rock salt type crystal structure, the surface layer portion is present in a region closer to the surface of the positive electrode active material particle than the interior portion, the positive electrode active material particles have titanium, magnesium, fluorine, and oxygen in the surface layer portion, an EDX ray analysis of the positive electrode active material particles reveals that a magnesium concentration peak and a titanium concentration peak exist in the surface layer portion, and the magnesium concentration peak exists in a region closer to the surface of the positive electrode active material particles than the titanium concentration peak; the surface layer portion has a region where the magnesium concentration detected in the depth direction from the surface of the positive electrode active material particle by the EDX ray analysis is ⅕ or more of the peak, and a region where the titanium concentration detected in the depth direction from the surface of the positive electrode active material particle is ½ or more of the peak, the orientation of the crystals of the layered rock salt type crystal structure in the interior roughly coincides with the orientation of the crystals of the rock salt type crystal structure in the surface layer portion; The electrolyte contained in the electrolytic solution contains lithium hexafluorophosphate, The electrolyte solution contains vinylene carbonate and propane sultone. Lithium-ion secondary battery.

7. In any one of claims 1 to 6, The electrolyte further contains adiponitrile. Lithium-ion secondary battery.

8. In any one of claims 1 to 7, In X-ray photoelectron spectroscopy, when the concentration of cobalt is taken as 1, the relative value of the concentration of titanium is 0.05 or more and 0.4 or less. Lithium-ion secondary battery.

9. In any one of claims 1 to 8, In X-ray photoelectron spectroscopy, when the concentration of cobalt is taken as 1, the relative value of the concentration of magnesium is 0.4 or more and 1.5 or less. Lithium-ion secondary battery.

10. In any one of claims 1 to 9, The positive electrode further contains a conductive additive, The conductive additive contains carbon fiber or graphene. Lithium-ion secondary battery.

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