Lithium-ion rechargeable battery

Abstract

In all-solid-state rechargeable batteries, the conductive path is maintained when the volume of the active material changes during charging and discharging. It may become more difficult. [Solution] A positive electrode in an all-solid-state secondary battery that exhibits minimal volume change between the charging and discharging states. An active material is used. For example, it has a layered rock salt type crystalline structure in the discharge state and a charge depth of 0.8 A positive electrode active material having a crystal structure similar to that of cadmium chloride at a certain charge level. In terms of quality, it exhibits less change in volume and crystal structure before and after charging and discharging compared to known positive electrode active materials.

Description

Technical Field

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

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

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

Background Art

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

[0005] Among them, attention has been focused on all-solid-state lithium ion secondary batteries that use solid electrolytes instead of the combination of organic electrolytes and lithium salts. All-solid-state lithium ion secondary batteries use non-flammable solid electrolytes instead of flammable organic electrolytes, so they have high safety. They also have advantages such as being easy to increase energy density and size.

[0006] Therefore, research on solid electrolytes is being actively conducted aiming at the practical application of all-solid-state lithium ion secondary batteries (Patent Documents 1 to Patent Document 3).

[0007] In addition, lithium cobaltate, which is widely used as a positive electrode active material for secondary batteries not only in all-solid-state batteries, has had detailed research on its crystal structure (Non-Patent Documents 1 to Non-Patent Documents 3).

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0009]

Non-Patent Document 1

[0010] One of the challenges of all-solid-state secondary batteries is that when the volume of the active material changes during charging and discharging, lithium There is a problem in that the conductive pathways of ions become difficult to maintain.

[0011] In conventional secondary batteries using organic electrolytes, the electrolyte enters the voids within the active material layer, causing lithium to... This forms the conductive pathway for ions. Therefore, even if the volume of the active material changes and the size of the voids changes, Because the electrolyte is liquid, the conductive pathway of lithium ions is maintained without any problems.

[0012] However, in all-solid-state secondary batteries, when the volume of the active material changes, the voids in the active material increase. In some cases, physical contact between the part and the solid electrolyte may be lost, and the conductive path of lithium ions may be affected. It is difficult to maintain capacity. Therefore, the capacity tends to decrease significantly with each charge-discharge cycle.

[0013] Therefore, one aspect of the present invention relates to an all-solid-state lithium-ion battery in which the decrease in capacity during charge-discharge cycles is suppressed. One of our objectives is to provide a ion rechargeable battery. Alternatively, we aim to provide a high-capacity, safe, and all-in-one battery. One of the objectives is to provide a solid-state lithium-ion secondary battery and a method for manufacturing the same. Alternatively, one of the objectives is to provide a method for manufacturing highly productive all-solid-state lithium-ion secondary batteries. Alternatively, one of the objectives is to provide a high-capacity all-solid-state lithium-ion secondary battery. To provide safe or reliable all-solid-state lithium-ion secondary batteries. This is one of the objectives.

[0014] Alternatively, one aspect of the present invention provides novel materials, active materials, energy storage devices, or methods for producing them. One of the objectives is to provide it.

[0015] Furthermore, the description of these problems does not preclude the existence of other problems. The embodiments do not need to solve all of these problems. It is possible to extract other issues from the description of the requested terms. [Means for solving the problem]

[0016] To achieve the above objective, a secondary battery according to one aspect of the present invention is provided in a charged state and a discharged state. It is characterized by using a positive electrode active material that undergoes little change in volume. For example, in the discharge state, It has a rock salt-type crystalline structure, with a charge depth of approximately 0.8, specifically between 0.77 and 0.84. A positive electrode active material having a crystal structure similar to that of a CdCl2 type crystal structure in the charged state is already Compared to conventional cathode active materials, it exhibits less change in volume and crystal structure before and after charging and discharging.

[0017] One aspect of the present invention relates to a two-way electrode comprising a positive electrode, a negative electrode, and a solid electrolyte layer between the positive and negative electrodes. A secondary battery in which the positive electrode has a crystal structure similar to that of a CdCl2 type crystal structure. be.

[0018] Another aspect of the present invention comprises a positive electrode, a negative electrode, and a solid electrolyte layer between the positive and negative electrodes. A secondary battery having the following characteristics, wherein the depth of charge of the secondary battery is 0.77 or more and 0.84 or less. When the positive electrode was analyzed by powder X-ray diffraction using CuKα1 rays, θ = 19.30 ± 0. This is a secondary battery with diffraction peaks at 20° and 2θ = 45.55 ± 0.10°.

[0019] Furthermore, in the above, it is preferable that the solid electrolyte layer has an oxide-based solid electrolyte.

[0020] Furthermore, in the above, the oxide-based solid electrolyte has a NASICON-type crystal structure. preferable. [Effects of the Invention]

[0021] According to one aspect of the present invention, all-solid-state lithium is provided in which the decrease in capacity during charge-discharge cycles is suppressed. We can provide ion-based secondary batteries, or high-capacity, safe all-solid-state lithium batteries. We can provide a mu-ion secondary battery and a method for manufacturing the same. Or, a highly productive method. We can provide a method for manufacturing all-solid-state lithium-ion secondary batteries. Alternatively, we can provide a method for manufacturing high-capacity all-solid-state lithium-ion secondary batteries. We can provide solid-state lithium-ion secondary batteries. Or, high safety or reliability An all-solid-state lithium-ion secondary battery can be provided. Alternatively, one aspect of the present invention is: This invention can provide novel materials, active materials, energy storage devices, or methods for producing them. [Brief explanation of the drawing]

[0022] [Figure 1] A diagram illustrating the charge depth and crystal structure of a positive electrode active material according to one embodiment of the present invention. [Figure 2] A diagram illustrating the charge depth and crystal structure of conventional cathode active materials. [Figure 3] XRD pattern calculated from crystal structure. [Figure 4] A diagram illustrating the crystal structure and magnetism of a positive electrode active material used in a secondary battery according to one embodiment of the present invention. [Figure 5] A diagram illustrating the crystal structure and magnetism of conventional positive electrode active materials. [Figure 6] A diagram illustrating an example of a method for producing a positive electrode active material used in a secondary battery according to one embodiment of the present invention. [Figure 7] A diagram illustrating another example of a method for producing a positive electrode active material used in a secondary battery according to one aspect of the present invention. [Figure 8] A diagram illustrating an example of a secondary battery according to one aspect of the present invention. [Figure 9] A diagram illustrating an example of a secondary battery according to one aspect of the present invention. [Figure 10] A diagram illustrating an example of a method for producing a solid electrolyte used in a secondary battery according to one aspect of the present invention. [Figure 11] A diagram illustrating an example of a secondary battery according to one aspect of the present invention. [Figure 12] A diagram illustrating an example of a secondary battery according to one aspect of the present invention. [Figure 13] A diagram illustrating an example of a secondary battery and a method for manufacturing the same according to one aspect of the present invention. [Figure 14] A diagram illustrating an example of a secondary battery and a method for manufacturing the same according to one aspect of the present invention. [Figure 15]A diagram illustrating an example of a small electronic device and a vehicle having a secondary battery according to one aspect of the present invention. [Figure 16] A diagram illustrating an example of a vehicle and a house having a secondary battery according to one aspect of the present invention. [Modes for carrying out the invention]

[0023] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is... Not limited to the following description, the form and details can be modified in various ways, as any person skilled in the art would know. This is easily understood. Furthermore, the present invention shall be interpreted as being limited to the contents of the embodiments described below. It's not something that can be done.

[0024] Furthermore, in this specification, crystal planes and directions are indicated by Miller indices. Table of crystal planes and directions In crystallography, numbers are preceded by a superscript bar, but in this specification, due to limitations on patent application notation, numbers are not preceded by a superscript bar. Sometimes, instead of placing a bar above the number, a minus sign (-) is placed before the number to represent it. Furthermore, the individual orientations indicating directions within a crystal are [ ], and the collective orientation showing all equivalent directions is < >The individual planes that represent crystal planes are ( ), and the set of planes with equivalent symmetry are {}. This is how it is expressed. Also, 1 Å is 10 -10 It is m.

[0025] In this specification, the surface layer of particles such as active material refers to the region from the surface up to approximately 10 nm. It can also be said that surfaces created by cracks or fissures are considered surfaces. Furthermore, the region deeper than the surface layer is called a surface. It's called the interior.

[0026] In this specification, etc., the layered rock salt type crystal structure of a composite oxide containing lithium and a transition metal This structure has a rock salt-type ionic arrangement in which cations and anions are arranged alternately, and it contains transition metals and Because lithium is arranged in a regular pattern to form a two-dimensional plane, two-dimensional diffusion of lithium is possible. This refers to the crystal structure. It may contain defects such as vacancies in cations or anions. Also, layers... Strictly speaking, the rock salt crystal structure is a structure in which the lattice of the rock salt crystal is distorted. be.

[0027] Furthermore, in this specification, a rock salt-type crystal structure is defined as a structure in which cations and anions are arranged alternately. This refers to a structure that contains certain elements. It is also acceptable for there to be deficiencies in cations or anions.

[0028] Furthermore, in this specification, a crystal structure similar to a CdCl2-type crystal structure refers to a space group R-3 Taking the case where m is present and cobalt is the transition metal as an example, cobalt is in an oxygen 6-coordinate state. It has a two-dimensional structure in which cobalt forms a triangular lattice, with random arrangement between the CoO2 layers. This refers to a crystal structure that contains Li. Also, in crystal structures similar to the CdCl2 type crystal structure, acid The element has a cubic close-packed structure, and the oxygen layers are repeated in a pattern of three types of layers, such as ABCABC. This crystal structure, similar to the CdCl2 type, is found in lithium nickelate with a charging depth of 0.9 When charged to 4 (Li 0.06 Its crystal structure is similar to that of NiO2, but it is a pure cobalt oxide. In layered rock salt type cathode active materials containing a large amount of thium or cobalt, this crystal structure is usually taken It is known that this is not the case.

[0029] Crystal structures similar to the CdCl2 type crystal structure have a symmetry in the arrangement of cations similar to that of the spinel type. Because it possesses this characteristic, it can be described as a pseudo-spinel type crystal structure.

[0030] Layered rock salt crystals, rock salt crystals, and anions with crystal structures similar to the CdCl2 type crystal structure The cubic structure is a close-packed cubic structure (face-centered cubic lattice structure). When these come into contact, anions... There are crystal planes in which the orientation of the cubic close-packed structure is aligned. However, layered rock salt type crystals The space group of crystals similar to CdCl2-type crystals is R-3m, and the space group of rock salt-type crystals is R-3m. Fm-3m (space group of typical rock salt crystals) and Fd-3m (space group with the simplest symmetry) Because it is different from the space group of rock salt crystals, the Miller indices of crystal planes that satisfy the above conditions are layered Rock salt crystals and crystals similar to CdCl2-type crystals are different from rock salt crystals. In layered rock salt crystals, crystals similar to CdCl2-type crystals, and rock salt crystals, When the orientations of the cubic close-packed structure composed of anions are aligned, the orientation of the crystal is approximately consistent. There are times when you might say, "ru."

[0031] The approximate agreement of the crystal orientation in the two regions can be seen in TEM (transmission electron microscope) images and STEM images. (Scanning transmission electron microscope) image, HAADF-STEM (High-angle scattering annular dark-field scanning transmission electron microscope) This can be determined from images such as microscopic images and ABF-STEM (annular bright-field scanning transmission electron microscope) images. Yes, it is possible. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc., can also be used as criteria for judgment. In TEM images, the arrangement of cations and anions can be observed as a repetition of bright and dark lines. Yes, it is possible. When the orientation of the cubic close-packed structure is aligned in layered rock salt crystals and rock salt crystals, intercrystalline The angle between the repeating bright and dark lines is 5 degrees or less, more preferably 2.5 degrees or less. The child can be observed. Furthermore, light elements such as oxygen and fluorine can be clearly observed in TEM images, etc. In some cases, this is not possible, but in such cases, the alignment of the metal elements can be determined by their arrangement. .

[0032] Furthermore, in this specification, the theoretical capacity of the positive electrode active material refers to the insertable and removable capacity of the positive electrode active material. This refers to the amount of electricity that would be generated if all lithium were to be desorbed. For example, the theoretical capacity of LiCoO2 is 27 The theoretical capacity of LiNiO2 is 274mAh / g, and the theoretical capacity of LiMn2O4 is 4mAh / g. The capacity is 148mAh / g.

[0033] Furthermore, in this specification, etc., the charging depth when all insertable and removable lithium is inserted. Let 0 be the charge depth when all the insertable and detachable lithium in the positive electrode active material has been detached, and 1 be the charge depth when 0 is the charge depth when 1 is the charge depth when all the insertable and detachable lithium in the positive electrode active material has been detached. Let's leave it at that.

[0034] Furthermore, in this specification, charging refers to the transfer of lithium ions from the positive electrode to the negative electrode within the battery. This refers to the movement of electrons from the negative electrode to the positive electrode in an external circuit. In this case, the process of releasing lithium ions is called charging. Also, the charging depth is 0.74 or higher. Positive electrode active material with a charge depth of 0.9 or less, more specifically 0.77 to 0.84, is subjected to high voltage. This refers to a charged positive electrode active material. For example, in LiCoO2, 212mAh / If it is charged to g or more, it is a positive electrode active material that has been charged at a high voltage. Also, LiCoO2 Furthermore, in a 25°C environment, the charging voltage should be between 4.55V and 4.63V (in the case of lithium counter electrode). The positive electrode is charged with a constant current, and then with a constant voltage until the current value becomes 0.01C. The material in question is a positive electrode active material that has been charged with high voltage.

[0035] Similarly, discharge is the movement of lithium ions from the negative electrode to the positive electrode within a battery, and external circuits This refers to the transfer of electrons from the positive electrode to the negative electrode. The positive electrode active material is lithium. The insertion of ions is called discharge. Also, a positive electrode active material with a charge depth of 0.06 or less, A positive electrode active material that has been discharged to more than 90% of its charge capacity from a high-voltage charged state is sufficiently... This refers to the positive electrode active material that has been discharged. For example, in LiCoO2, the charge capacity is 2 If the charge level is 12mAh / g or higher, it is charged at a high voltage, and from here, it will reach 90% of its capacity. A positive electrode active material that has been discharged to 190.8 mAh / g or more is a positive electrode active material that has been sufficiently discharged. It is of quality. Also, in LiCoO2, the battery voltage is 3V or less in a 25°C environment (counter electrode lithium In the case of Um, the positive electrode active material after constant current discharge until it reaches a certain state is also the positive electrode active material that has been sufficiently discharged. Let's assume that's the case.

[0036] Furthermore, in this specification, a non-equilibrium phase change refers to a phenomenon that causes a nonlinear change in a physical quantity. This is what we will do. For example, by differentiating capacitance (Q) with respect to voltage (V) (dQ / dV) Around the peaks in the dQ / dV curve, non-equilibrium phase transitions occur, and the crystal structure changes significantly. It is thought that they understand.

[0037] (Embodiment 1) In this embodiment, a positive electrode active material 1 that can be used in a secondary battery 100 according to one aspect of the present invention Let me explain point 11.

[0038] [Structure of the positive electrode active material] First, using Figures 1 and 2, we will explain the positive electrode active material used in a secondary battery 100 according to one embodiment of the present invention. 11 and conventional positive electrode active materials will be explained, and the differences between them will be discussed. The positive electrode active material is one in which elements other than lithium, cobalt, and oxygen are added internally or on the surface. A simple lithium cobalt oxide (LiCoO) that has not been coated or otherwise processed in any way. 2) is the answer.

[0039] <Conventional positive electrode active material> Lithium cobaltate is used as described in Non-Patent Documents 1 and 2, etc. The crystal structure changes depending on the electron depth. A typical crystal structure is shown in Figure 2.

[0040] As shown in Figure 2, LiCoO2 at charge depth 0 (discharge state) is connected to the space group R-3m. It has a crystalline structure, with three CoO2 layers present in the unit cell. This crystalline structure is called O3 type. It is sometimes called a crystal structure. Note that the CoO2 layer is an octahedral structure in which oxygen atoms are coordinated to cobalt in a 6-coordinate manner. However, this refers to a structure that is continuous in a plane while sharing edges.

[0041] Furthermore, lithium cobalt oxide at a charging depth of 1 has a crystal structure of space group P-3m1, A single CoO2 layer exists within the nit cell. Therefore, this crystal structure is considered to be an O1 type crystal structure. They may call.

[0042] Furthermore, lithium cobalt oxide at a charge depth of approximately 0.88 has a crystal structure of space group R-3m. It has a structure like CoO2, such as P-3m1(O1), and R-3m(O3 This can be described as a structure in which the structure of LiCoO2, like the one shown above, and are alternately stacked. This is sometimes called the H1-3 type crystal structure. However, in reality, the H1-3 type crystal structure is a unit The number of cobalt atoms per cell is twice that of other structures. However, as shown in Figure 2, In the specification, the c-axis of the H1-3 type crystal structure is defined as a unit to facilitate comparison with other crystal structures. This will be shown using a diagram that is half the size of a cell.

[0043] Repeated high-voltage charging and discharging, resulting in a charge depth of approximately 0.88 or higher. Therefore, lithium cobalt oxide has an H1-3 type crystal structure and a R-3m(O3) structure in its discharged state. Between these two points, the crystal structure undergoes repeated changes (i.e., non-equilibrium phase transitions).

[0044] However, these two crystal structures have a large displacement of the CoO2 layer. (See dotted line in Figure 2) As indicated by the arrows, in the H1-3 type crystal structure, the CoO2 layer is larger than R-3m(O3). It's collapsing. Such dynamic structural changes negatively affect the stability of the crystal structure. Shut up.

[0045] Furthermore, the volume difference is also large. When comparing per the same number of cobalt atoms, the H1-3 type crystal structure The volume difference between the O3-type crystal structure in the formation state and the discharge state is 3.5% or more.

[0046] In addition, the H1-3 type crystal structure has continuous CoO2 layers such as P-3m1(O1) Such a structure is likely to be unstable.

[0047] Therefore, repeated high-voltage charging and discharging causes the crystalline structure of lithium cobalt oxide to break down. The breakdown of the crystal structure causes a deterioration in cycle characteristics. This is because the breakdown of the crystal structure leads to... The number of sites where lithium can exist stably decreases, and the insertion and removal of lithium becomes more difficult. It is considered a sting.

[0048] <Positive electrode active material that can be used in a secondary battery according to one aspect of the present invention> ≪Inside≫ In contrast, the positive electrode active material 111 of one aspect of the present invention is in a fully discharged state and a high voltage In the charged state, the difference in volume and crystal structure is small.

[0049] Figure 1 shows the crystal structure of the positive electrode active material 111 before and after charging and discharging. The positive electrode active material 111 is lithium It is a composite oxide containing cobalt and oxygen. In addition to the above, it contains magnesium. It is preferable that it has halogens such as fluorine and chlorine.

[0050] The crystal structure of the charge depth 0 (discharge state) in Figure 1 is R-3m(O3), the same as in Figure 2. In one aspect of the present invention, the positive electrode active material 111 is such that when the charge depth is 0.77 or more and 0.84 or less, It has a different crystal structure from Figure 2. This crystal structure of space group R-3m is referred to as Cd in this specification, etc. This crystal structure will be referred to as a crystal structure similar to the Cl2 type crystal structure. In the diagram of a crystal structure similar to the one shown, the symmetry of the cobalt atom and the oxygen atom are explained. Therefore, the lithium is omitted from the display, but in reality, between the CoO2 layers, there is cobalt Lithium is present in concentrations of 16 to 23 atoms. Furthermore, it exhibits an O3-type crystal structure and Cd In any crystal structure similar to the Cl2 type crystal structure, the space between the CoO2 layers, i.e., lithium It is preferable that a dilute amount of magnesium be present at the site. Also, at the oxygen site, It is preferable that a halogen such as fluorine is present in a thin and dilute manner.

[0051] In the positive electrode active material 111, when charged at high voltage and a large amount of lithium is released, the crystal structure changes. The chemical reaction is suppressed compared to conventional LiCoO2. For example, as shown by the dotted line in Figure 1, In these crystal structures, there is almost no displacement of the CoO2 layer. That is, a lot of lithium is desorbed. Even in this state, the symmetry of the crystal structure remains unchanged.

[0052] Furthermore, the positive electrode active material 111 has an O3-type crystal structure with a charging depth of 0 and a Cd structure with a charging depth of 0.88. The difference in volume per unit cell for crystal structures similar to the Cl2 type crystal structure is 2.5% or less. More specifically, it is less than 2.2%.

[0053] Therefore, the crystal structure is less likely to collapse even when repeatedly charged and discharged at high voltage. The symmetry of the crystal does not change. Therefore, the interface with the solid electrolyte is easily maintained. Also, because there is little volume change, it is an all-solid-state battery. Even when used in this way, it is easy to maintain physical contact with the solid electrolyte. Therefore, charge-discharge cycle This allows for the creation of an all-solid-state secondary battery in which the decrease in capacity is suppressed.

[0054] Furthermore, crystal structures similar to the CdCl2 type crystal structure are found in the unit cell, where cobalt and oxygen The coordinates are Co(0,0,0.5), O(0,0,x), and within the range of 0.20≦x≦0.25. It can be shown internally.

[0055] Magnesium, which is randomly and dilutely present between the CoO2 layers, i.e., at the lithium sites, is C It has the effect of suppressing the displacement of the oO2 layer. Therefore, magnesium is present between the CoO2 layers. Therefore, magnesium tends to form a crystal structure similar to the CdCl2 type crystal structure. It is preferable that magnesium is distributed throughout the particles of the highly active material 111. In order to distribute it, it is preferable to perform a heat treatment in the manufacturing process of the positive electrode active material 111. It's nice.

[0056] However, if the heat treatment temperature is too high, cation mixing occurs and magnesium The likelihood of it entering the cobalt site increases. If magnesium is present in the cobalt site, The effect of maintaining the structure of R-3m is lost. Furthermore, if the heat treatment temperature is too high, There are concerns about adverse effects such as the reduction of cobalt to its divalent state and the evaporation of lithium. ru.

[0057] Therefore, prior to the heat treatment to distribute magnesium throughout the particles, cobalt oxide is used. It is preferable to add halogen compounds such as fluorine compounds to the thium. Adding this causes a melting point depression of lithium cobalt oxide. By causing a melting point depression, catho At temperatures where mixing is less likely to occur, it becomes easier to distribute magnesium throughout the particles. ru.

[0058] ≪Surface layer≫ It is preferable that magnesium is distributed throughout the particles of the positive electrode active material 111, but in addition to this, Furthermore, it is more preferable that the magnesium concentration on the surface of the particle is higher than the average concentration of the entire particle. The surface of the particles is, so to speak, entirely composed of crystal defects, and during charging, lithium is released from the surface. Therefore, this area tends to have a lower lithium concentration than the interior. As a result, it becomes unstable. This is a region where changes in the crystal structure are likely to begin easily. This allows for more effective suppression of changes in the crystal structure.

[0059] Furthermore, the concentration of halogens such as fluorine in the surface layer of the positive electrode active material 111 is higher than the average concentration of the entire particle. A higher value is preferable.

[0060] Thus, the surface layer of the positive electrode active material 111 has a higher concentration of magnesium and fluorine than the interior. It is preferable that the composition is high and different from the internal composition. Furthermore, the composition should be stable at room temperature. It is preferable to adopt this structure. Therefore, the surface layer may have a different crystalline structure from the interior. For example, at least a portion of the surface layer of the positive electrode active material 111 has a rock salt type crystalline structure. It may be. Also, if the surface and interior have different crystal structures, the arrangement of the crystals in the surface and interior It is preferable that the directions are roughly the same.

[0061] However, if the surface layer consists only of MgO, or only of a solid solution of MgO and CoO(II), The insertion and removal of thium becomes difficult. Therefore, the surface layer contains at least cobalt. In the discharge state, it must also contain lithium and have a pathway for lithium insertion and removal. Furthermore, a higher concentration of cobalt than magnesium is preferable.

[0062] Furthermore, the positive electrode active material 111 may have a solid electrolyte in its surface layer. For example, sulfide-based solid electrolytes, oxide-based solid electrolytes, halide-based solid electrolytes, and These combinations can be used. Solid electrolytes containing aluminum have a high potential. However, it can be stable and preferable as the surface layer of the positive electrode active material 111.

[0063] Furthermore, the positive electrode active material 111 has a surface layer containing lithium niobate and other solid electrolytes, which loosely interacts with the surface. It may have a buffer layer. The buffer layer is located between the lithium cobalt oxide and the solid electrolyte. It is preferable to do so.

[0064] Furthermore, the positive electrode active material 111 comprises a solid electrolyte or buffer layer as described above, and lithium cobalt oxide. It may have a region where M and are mixed.

[0065] ≪Grain boundary≫ Furthermore, the magnesium concentration at and near the grain boundaries of the positive electrode active material 111 is also within the interior of other It is preferable that the halogen concentration is higher than the region. Furthermore, the halogen concentration at and near the grain boundaries should also be high. Preferably, one of titanium and aluminum is present at the grain boundary and in its vicinity. They may have a method.

[0066] Similar to particle surfaces, grain boundaries are also surface defects. Therefore, they are prone to instability and changes in crystal structure. This process is likely to begin. Therefore, if the magnesium concentration at and near the grain boundaries is high, This allows for more effective suppression of changes in the crystal structure.

[0067] Furthermore, if the magnesium and halogen concentrations at and near the grain boundaries are high, the positive electrode active material Even if a crack occurs along the grain boundary of a particle of quality 111, the surface created by the crack will not be Magnesium and halogen concentrations are higher near the surface. Therefore, after cracks occur... This also improves the corrosion resistance of the positive electrode active material to hydrofluoric acid.

[0068] In this specification, the vicinity of a grain boundary refers to the region extending approximately 10 nm from the grain boundary. Let's do it this way.

[0069] <Analysis method> A certain material exhibits a crystal structure similar to the CdCl2 type when charged at high voltage. Whether or not a positive electrode active material 111 is one aspect of the invention is determined by the positive electrode charged with high voltage, XRD, Using electron diffraction, neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. This can be determined by analyzing it. In particular, XRD can determine the transition metals such as cobalt present in the positive electrode active material. The symmetry can be analyzed with high resolution, and even if the positive electrode obtained by disassembling a secondary battery is measured directly, it will still be possible to analyze it with high resolution. It is preferable in that it can achieve sufficient accuracy, among other things.

[0070] The positive electrode active material 111 in one aspect of the present invention, as described above, is in a high-voltage charging state and a discharge state A characteristic feature is that there is little change in volume and crystal structure. In a high-voltage charging state, in a discharge state Materials with a large crystal structure that exhibits significant changes are not suitable because they cannot withstand high-voltage charging and discharging. That's not good. And simply adding impurity elements may not result in the desired crystal structure. It is important to note that, for example, lithium cobaltate containing magnesium and fluorine Even though they share the characteristic of being "mu," crystals with a structure similar to the CdCl2 type crystal structure under high-voltage charging conditions... There are cases where the structural component accounts for 60 wt% or more, and cases where the H1-3 type crystal structure makes up the majority. Therefore, in order to determine whether or not it is a positive electrode active material 111 according to one aspect of the present invention, XRD is used. Analysis of the crystal structure, including the initial structure, is necessary.

[0071] However, the positive electrode active material in a charged or discharged state undergoes a change in its crystal structure when exposed to the atmosphere. In some cases, a crystal structure similar to the CdCl2 type crystal structure may be converted to an H1-3 type crystal structure. The structure may change. Therefore, the sample should be handled in an inert atmosphere such as an argon atmosphere. It is preferable to drink.

[0072] ≪Charging method≫ A certain composite oxide can be used as a positive electrode active material 1 in a secondary battery 100 according to one aspect of the present invention. High-voltage charging to determine whether or not it is 11 is performed in a secondary battery where the counter electrode is lithium metal. It is preferable to do so. If a material other than lithium metal is used for the counter electrode, the potential of the secondary battery and the positive electrode This is because the potentials are different, making it difficult to measure the potential of the positive electrode. The voltage and potential shown are those of the positive electrode unless otherwise specified.

[0073] Materials other than lithium metal, such as graphite, silicon, and lithium titanium oxide, were used for the negative electrode. When analyzing an all-solid-state secondary battery, the cell is disassembled, the negative electrode is removed, and then the counter electrode is examined. It is preferable to reassemble it into a lithium cell. Methods for removing the negative electrode include shearing it. Possible methods include scraping and polishing.

[0074] A secondary battery with a lithium metal counter electrode is charged with a constant current under charging conditions of 4.6V and 0.5C. After that, constant voltage charging is performed until the current value reaches 0.01C. Here, 1C is equivalent to 137mA. Let's assume the charge level is / g. The temperature is 25°C. After charging in this way, the coin cell is charged with argon. If you disassemble it inside the glove compartment and take out the positive electrode, you can obtain a positive electrode that has been charged with high voltage. It is preferable to handle the samples in an argon atmosphere when performing various analyses afterward. For example, XRD can be performed by sealing the sample in a sealed container under an argon atmosphere.

[0075] ≪XRD≫ The crystal structure is similar to that of the CdCl2 type, and it was calculated from the H1-3 type crystal structure model. Figure 3 shows an ideal powder XRD pattern using CuKα1 line. Also, for comparison, a charged The crystal structures of LiCoO2(O3) at depth 0 and CoO2(O1) at charging depth 1 were calculated. The ideal XRD pattern is also shown. Note that LiCoO2(O3) and CoO2(O1 The pattern is ICSD (Inorganic Crystal Structure) From the crystal structure information obtained from the Database, Materials Studio ( Reflex Powder Diffra Created using ction. The range of 2θ is from 15° to 75°, and the step size =0.01, wavelength λ1=1.540562Å, λ2 is not set, Monochromat "or" was interpreted as "single". The H1-3 type crystal structure pattern is the crystal described in Non-Patent Document 3. It was similarly created from structural information. The crystal structure pattern similar to the CdCl2 type crystal structure is this The crystal structure of the positive electrode active material of one embodiment of the invention was estimated from the XRD pattern, and TOPAS ver The structure was fitted using .3 (Bruker's crystal structure analysis software), and the same as the others. I created an XRD pattern as shown.

[0076] As shown in Figure 3, in a crystal structure similar to the CdCl2 type crystal structure, 2θ = 19.30 ± 0.20° (between 19.10° and 19.50°), and 2θ = 45.55 ± 0.10 Diffraction peaks appear at an angle between 45.45° and 45.65°. To be more precise... , 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less), and 2θ = A sharp diffraction peak appears at 45.55±0.05° (between 45.50° and 45.60°). However, in the H1-3 type crystal structure and CoO2 (P-3m1, O1), these positions No peak appears. Therefore, when charged at high voltage, 2θ = 19.30 ± 0.2 The appearance of peaks at 0° and 2θ = 45.55 ± 0.10° is one aspect of the present invention. This can be considered a characteristic of the positive electrode active material 111.

[0077] This shows the crystal structure at a charging depth of 0 and the crystal structure when charged at high voltage, and the XRD diffraction peak It can also be said that the positions where the 'k' appears are close together. More specifically, the main diffraction peaks of both are In two or more of these, more preferably three or more, the difference in the position where the peak appears is 2θ = It can be said that the value is 0.7 or less, and more preferably 2θ = 0.5 or less.

[0078] Furthermore, in one aspect of the present invention, the positive electrode active material 111 has a CdCl2-type crystal structure when charged with a high voltage. It has a crystal structure similar to that of CdCl2, but all the particles have a crystal structure similar to that of CdCl2. It does not have to be a crystalline structure. It may contain other crystalline structures, or part of it may be amorphous. However, when Rietveld analysis was performed on the XRD pattern, the CdCl2 type crystal structure was found. Preferably, the crystal structure similar to the above is present in 50 wt% or more, and 60 wt% or more. More preferably, and even more preferably 66 wt% or more. Similar crystal structures make up 50 wt% or more, more preferably 60 wt% or more, and even more preferably 60 wt% or more. If the content is 66 wt% or more, it can be used as a cathode active material with sufficiently excellent cycle characteristics.

[0079] Furthermore, the crystallite size of the CdCl2-like crystals present in the positive electrode active material particles is related to the discharge state. The concentration only drops to about 1 / 10th of that of LiCoO2(O3). Therefore, the positive electrode before charging and discharging. Even under the same XRD measurement conditions, a clear CdCl2-type crystal structure similar to that observed after high-voltage charging was observed. The peaks of the crystal structure can be observed. On the other hand, in simple LiCoO2, some of it is CdCl2 Even if it can adopt a structure similar to a crystal structure similar to the type crystal structure, the crystallite size will be small. The peaks become broader and smaller. The crystallite size is determined from the full width at half maximum of the XRD peak. It is possible.

[0080] Furthermore, the layered rock salt type of particles in the positive electrode active material during discharge can be estimated from the XRD pattern. In the crystal structure, it is preferable that the lattice constant of the c axis is small. When a different element is substituted at the 'm' position, such as when cobalt enters the oxygen 4-coordinate position (A site) It becomes larger. Therefore, first, the amount of Co3O4 with heteroatomic substitution and spinel-type crystal structure decreases. In other words, a complex oxide is created that takes on a layered rock salt type crystal structure with few defects, and then magnesium is added. When a mixture of a zinc source and a halogen source is used and magnesium is inserted in the lithium position, a good result is obtained. It is believed that this will enable the fabrication of cathode active materials that exhibit cycle characteristics.

[0081] The lattice constant of the c axis in the crystal structure of the positive electrode active material in the discharge state is determined in the fabrication process described later. Before annealing, a depth of 14.060 Å or less is preferred, and a depth of 14.055 Å or less is more preferred. A value of 4.051 Å or less is even more preferable. The lattice constant of the c axis after annealing should be 14.060 Å or less. The bottom is preferable.

[0082] In order to keep the lattice constant of the c axis within the above range, it is preferable to have fewer impurities, especially cobalt. It is preferable to add fewer transition metals other than manganese and nickel, specifically 300 It is preferable that the concentration be 0 ppm or less, and more preferably 1500 ppm or less. It is preferable to have less cation mixing between lithium and cobalt, manganese, and nickel. stomach.

[0083] Furthermore, the features revealed by the XRD pattern are characteristics of the internal structure of the positive electrode active material. Therefore, for positive electrode active materials with a particle size (D50) of approximately 1 μm to 100 μm, the internal structure is as follows: Because the volume of the surface layer is very small, the surface layer of the positive electrode active material 111 has a different crystal structure from the interior. Even if a structure exists, it is highly likely that it will not be reflected in the XRD pattern.

[0084] ≪ESR≫ Here, using Figures 4 and 5, we will compare crystal structures similar to the CdCl2 type crystal structure with other crystal structures. This section explains how to determine the difference from the crystal structure using ESR. In a crystal structure similar to the above, as shown in Figures 1 and 4(A), cobalt is oxygen-6 coordinated. It exists at the site. As shown in Figure 4(B), in oxygen-6 coordinated cobalt, the 3d orbital is e g orbit and t 2gThe orbit that splits into orbits and avoids the direction where oxygen exists is t 2g The energy of the orbit is low. Some of the cobalt present at the oxygen 6 - coordination site is t 2g with all t - orbits filled and is diamagnetic Co 3+ However, other parts of the cobalt present at the oxygen 6 - coordination site may be paramagnetic Co 2+ or Co 4+ Even if it is cobalt of this paramagnetic Co In both cases of Co 2+ and Co 4+ Since there is one unpaired electron in both cases, it cannot be distinguished by ESR, but it can take either valence depending on the valence of the elements present around it. On the other hand, in the conventional cathode active material, there is a description that it may have a spinel - type crystal structure that does not contain lithium in the surface layer in the charged state. In this case, it will have Co3O4 with the spinel - type crystal structure shown in Fig. 5(A).

[0085] When spinel is described by the general formula A[B2]O4, element A is coordinated with oxygen 4, and element B is coordinated with oxygen 6 Therefore, in this specification etc., the site with oxygen 4 - coordination may be called the A - site, and the site with oxygen 6 - coordination may be called the B - site. In Co3O4 with a spinel - type crystal structure, cobalt exists not only at the oxygen 6 - coordination B - site but also at the oxygen 4 - coordination

[0086] A - site. As shown in Fig. 5(B), for cobalt with oxygen 4 - coordination Among the split e - orbits and t - orbits, the energy of the e - orbit is low. Therefore, cobalt with oxygen 4 - coordination Co

[0087] Co Co split e g orbit and t 2g Among the orbits, the energy of the e g orbit is low. Therefore, cobalt with oxygen 4 - coordination Co 2+ Co 3+ and Co 4+All of them have unpaired electrons and are paramagnetic. If particles containing sufficient spinel-type Co3O4 are analyzed by ESR, etc., then Co3O4 will be found to be oxygen-4 coordinated. 2+ Co 3+ or Co 4+ A peak originating from paramagnetic cobalt should be detected. ru.

[0088] However, in one embodiment of the present invention, the positive electrode active material 111 is made of oxygen-4 coordinated paramagnetic cobalt. The resulting peak is too small to be observed. Therefore, the CdCl2 type crystal structure as referred to in this specification, etc. Unlike orthogonal spinel, crystal structures similar to this one contain oxygen 4-coordinates in amounts detectable by ESR. It does not contain cobalt. Therefore, compared to conventional examples, the positive electrode active material of one embodiment of the present invention This indicates that the peak originating from spinel-type Co3O4, which can be detected by ESR, etc., is small or can be confirmed. In some cases, it is so small that it does not contribute to the charge-discharge reaction. The less Nell-type Co3O4 there is, the better. Thus, from ESR analysis, the positive electrode active material 11 Case 1 can be judged to be different from previous examples.

[0089] ≪XPS≫ X-ray photoelectron spectroscopy (XPS) can detect depths from the surface up to approximately 2 nm to 8 nm (usually around 5 nm). Because analysis of this region is possible, the concentration of each element can be quantitatively determined for approximately half of the surface layer. It can be analyzed in this way. Furthermore, narrow scan analysis can analyze the bonding state of elements. It is possible. However, the quantitative accuracy of XPS is often around ±1 atomic percent, and the detection limit is also limited by element. The amount is approximately 1 atomic percent.

[0090] When XPS analysis was performed on the positive electrode active material 111, the concentration of cobalt was set to 1, The relative concentration of magnesium is preferably between 0.4 and 1.5, and between 0.45 and 1.00. A full concentration is preferable. Furthermore, the relative concentration of halogens such as fluorine should be between 0.05 and 1.5. Ideally, the value should be between 0.3 and 1.00.

[0091] Furthermore, when the positive electrode active material 111 was analyzed using XPS, the bonding energy between fluorine and other elements was determined. The peak showing - is preferably 682eV or higher and less than 685eV, and 684.3eV It is even more preferable that it be of a certain degree. This is because the binding energy of LiF is 685 eV. This value is different from both the bond energy of MgF2, which is 686 eV. If the positive electrode active material 111 contains fluorine, the bond must be other than LiF and MgF2. It is preferable.

[0092] Furthermore, when the positive electrode active material 111 was analyzed using XPS, the bonding between magnesium and other elements was observed. The peak indicating energy is preferably between 1302 eV and less than 1304 eV. It is even more preferable that it be around 1303 eV. This is the bond energy of MgF2. This value is different from 1305 eV and is close to the bond energy of MgO. In other words, positive If the highly active material 111 contains magnesium, it is preferable that the bond is other than MgF2. .

[0093] ≪EDX≫ EDX measurement is a method of measuring while scanning within a region and evaluating that region in two dimensions. It is sometimes called X-plane analysis. Also, data from linear regions is extracted from EDX plane analysis, and atoms The process of evaluating the distribution of concentration within positive electrode active material particles is sometimes called line analysis.

[0094] EDX surface analysis (e.g., elemental mapping) can be used to analyze the interior, surface, and vicinity of grain boundaries. Furthermore, the concentrations of magnesium and fluorine can be quantitatively analyzed. Also, EDX Linear analysis allows for the analysis of peak concentrations of magnesium and fluorine.

[0095] When EDX radiation analysis was performed on the positive electrode active material 111, the magnesium concentration peak in the surface layer was observed. It is preferable that it exists from the surface of the positive electrode active material 111 to a depth of 3 nm towards the center. It is more preferable that it exists up to a depth of 1 nm, and more preferably up to a depth of 0.5 nm. That is even more preferable.

[0096] Furthermore, it is preferable that the distribution of fluorine in the positive electrode active material 111 overlaps with the distribution of magnesium. Therefore, when EDX radiation analysis was performed, the peak in fluorine concentration at the surface was in the positive electrode active material. Preferably, it exists from the surface of 111 to a depth of 3 nm toward the center, and to a depth of 1 nm It is more preferable that it be present up to a certain depth, and even more preferable that it be present up to a depth of 0.5 nm. stomach.

[0097] Furthermore, when line analysis or surface analysis was performed on the positive electrode active material 111, the near grain boundaries were observed. The ratio of magnesium to cobalt atoms (Mg / Co) should ideally be between 0.020 and 0.50. It is preferable that it be between 0.025 and 0.30. Furthermore, a value between 0.030 and 0. A value of 20 or less is preferable.

[0098] ≪dQ / dVvsV curve≫ Furthermore, the positive electrode active material according to one aspect of the present invention, after being charged at a high voltage, is subjected to, for example, a low voltage of 0.2C or less. When discharging at a high rate, a characteristic voltage change may appear near the end of the discharge. The voltage is calculated from the discharge curve, specifically the dQ / dVvsV, where a peak appears around 3.9V. It is clear that at a constant voltage, there is at least one peak within the range up to 3.5V. It can be verified.

[0099] [Method for preparing positive electrode active material] Next, using Figure 6, we will show a positive electrode activity that can be used in a secondary battery 100, which is one embodiment of the present invention. An example of a method for preparing substance 111 will be described. Figure 7 also shows other specific preparation methods. Here is an example.

[0100] <s11> As shown in S11 of Figure 6, the materials for the first mixture include a halogen source such as fluorine and a Prepare a magnesium source. Also, prepare a lithium source.

[0101] For example, lithium fluoride and magnesium fluoride can be used as halogen sources. In particular, lithium fluoride has a relatively low melting point of 848°C, and in the annealing process described later... It is preferable because it melts easily. Examples of halogen sources include lithium chloride and magnesium chloride. Magnesium can be used, for example, magnesium fluoride, or oxide. Magnesium, magnesium hydroxide, magnesium carbonate, etc. can be used. For example, lithium fluoride and lithium carbonate can be used as the fluorine source. Lithium fluoride can be used as both a lithium source and a halogen source. Magnesium can be used as both a halogen source and a magnesium source.

[0102] In this embodiment, lithium fluoride is prepared as the halogen source and lithium source, and Magnesium fluoride will be prepared as the source of ions and magnesium (Figure 7S11). ). Lithium fluoride (LiF) and magnesium fluoride (MgF2) have a ratio of LiF:MgF2 = 65: Mixing at a molar ratio of approximately 35 yields the greatest effect in lowering the melting point. On the other hand, lithium fluoride If the amount of 'mu' increases, there is a concern that the lithium will become excessive and the cycle characteristics will deteriorate. Therefore, the molar ratio of lithium fluoride (LiF) to magnesium fluoride (MgF2) is LiF:MgF2 It is preferable that =x:1 (0≦x≦1.9), and LiF:MgF2=x:1 (0.1 (≤x ≤ 0.5) is more preferable, and LiF:MgF2=x:1 (near x=0.33) is even more preferable. Preferably. In this specification, "nearby" means greater than 0.9 times the value and greater than 1.1 times the value. Set the range to the smallest possible values.

[0103] Furthermore, if the following mixing and grinding steps are performed wet, a solvent must be prepared. The solvent is acetone. Ketones such as ethanol, alcohols such as ethanol and isopropanol, ethers, dioxides Sun, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc. can be used. It is more preferable to use an aprotic solvent that does not react easily with lithium. In terms of application method, acetone will be used (see Figure 7S11).

[0104] <s12> Next, the materials for the first mixture described above are mixed and ground (S12 in Figures 6 and 7). Grinding can be done dry or wet, but wet grinding allows for finer pulverization. Therefore, it is preferable. For mixing, for example, a ball mill, a bead mill, etc. can be used. When using Lumil, it is preferable to use zirconia balls as the medium, for example. It is preferable to carry out this mixing and grinding process thoroughly to finely pulverize the first mixture.

[0105] <S13、S14> The mixed and ground materials described above are collected (S13 in Figures 6 and 7) to obtain the first mixture. S14 in Figures 6 and 7).

[0106] The first mixture, for example, has an average particle size (D50) of 600 nm or more and 20 μm or less. It is preferable that the particle size is 1 μm or more and 10 μm or less. If the first mixture is obtained, a composite oxide having lithium, a transition metal and oxygen can be obtained in a later step. When mixed with the first mixture, it is easier to uniformly adhere the first mixture to the surface of the composite oxide particles. When the first mixture is uniformly attached to the composite oxide particles, the surface layer of the composite oxide particles after heating It is preferable because it is easy to distribute halogens and magnesium evenly throughout the part. If there are regions that do not contain ions and magnesium, a CdCl2-type crystal will form in the charged state. This may make it difficult to form crystal structures similar to the original structure.

[0107] <s21> Next, as shown in S21 of Figure 6, a composite oxide having lithium, a transition metal, and oxygen A lithium source and a transition metal source are prepared as materials.

[0108] For example, lithium carbonate, lithium fluoride, etc., can be used as lithium sources.

[0109] As the transition metal, at least one of cobalt, manganese, and nickel can be used. Oxides containing lithium, transition metals, and oxygen have a layered rock salt-type crystalline structure. Because it is preferable, cobalt, manganese, and nickel can take on a layered rock salt type crystalline structure. It is preferable that the mixing ratio of Kell is such that it can take on a layered rock salt type crystalline structure. Aluminum may be added to these transition metals.

[0110] As a transition metal source, oxides, hydroxides, etc. of the above-mentioned transition metals can be used. As a source, for example, cobalt oxide, cobalt hydroxide, etc. can be used. As a source, manganese oxide, manganese hydroxide, etc. can be used. Nickel oxide, nickel hydroxide, etc. can be used as the aluminum source. Aluminum hydroxide, aluminum oxide, etc., can be used.

[0111] <s22> Next, the lithium source and transition metal source are mixed (S22). The mixing is done dry or wet. This can be done using a ball mill, bead mill, etc., for mixing. When using a ball mill, it is preferable to use zirconia balls as the media, for example. It seems so.

[0112] <s23> Next, heat the materials mixed above. This step may be referred to as firing or the first heating for the purpose of distinguishing it from subsequent heating steps. The heating is preferably carried out at 800 °C or higher and lower than 1100 °C, more preferably at 900 °C or higher and 1000 °C or lower, and even more preferably about 950 °C. If the temperature is too low, there is a risk that the decomposition and melting of the starting materials will be insufficient. On the other hand, if the temperature is too high, defects may occur due to excessive reduction of transition metals, evaporation of lithium, etc. For example, defects may occur where cobalt becomes divalent. The heating is preferably carried out at 800 °C or higher and lower than 1100 °C, more preferably at 900 °C or higher and 1000 °C or lower, and even more preferably about 950 °C. If the temperature is too low, there is a risk that the decomposition and melting of the starting materials will be insufficient. On the other hand, if the temperature is too high, defects may occur due to excessive reduction of transition metals, evaporation of lithium, etc. For example, defects may occur where cobalt becomes divalent. The heating time is preferably 2 hours or more and 20 hours or less. The firing is preferably carried out in an atmosphere with little water such as dry air (for example, dew point -50 °C or lower, more preferably -100 °C or lower). For example, heating is carried out at 1000 °C for 10 hours, the temperature rise is 200 °C / h, and the flow rate of the dry atmosphere is preferably 10 L / min. Subsequently, cool the heated material to room temperature. For example, the temperature drop time from the specified temperature to room temperature is preferably 10 hours or more and 50 hours or less. The heated material is recovered (S24), and a composite oxide containing lithium, a transition metal, and oxygen is obtained (S25). Specifically, lithium cobalt oxide, lithium manganate, lithium nickelate, lithium cobalt oxide in which part of cobalt is substituted with manganese, or lithium nickel-manganese-cobalt oxide is obtained.

[0113] The heating time is preferably 2 hours or more and 20 hours or less. The firing is preferably carried out in an atmosphere with little water such as dry air (for example, dew point -50 °C or lower, more preferably -100 °C or lower). For example, heating is carried out at 1000 °C for 10 hours, the temperature rise is 200 °C / h, and the flow rate of the dry atmosphere is preferably 10 L / min. Subsequently, cool the heated material to room temperature. For example, the temperature drop time from the specified temperature to room temperature is preferably 10 hours or more and 50 hours or less. The heating time is preferably 2 hours or more and 20 hours or less. The firing is preferably carried out in an atmosphere with little water such as dry air (for example, dew point -50 °C or lower, more preferably -100 °C or lower). For example, heating is carried out at 1000 °C for 10 hours, the temperature rise is 200 °C / h, and the flow rate of the dry atmosphere is preferably 10 L / min. Subsequently, cool the heated material to room temperature. For example, the temperature drop time from the specified temperature to room temperature is preferably 10 hours or more and 50 hours or less. The heating time is preferably 2 hours or more and 20 hours or less. The firing is preferably carried out in an atmosphere with little water such as dry air (for example, dew point -50 °C or lower, more preferably -100 °C or lower). For example, heating is carried out at 1000 °C for 10 hours, the temperature rise is 200 °C / h, and the flow rate of the dry atmosphere is preferably 10 L / min. Subsequently, cool the heated material to room temperature. For example, the temperature drop time from the specified temperature to room temperature is preferably 10 hours or more and 50 hours or less.

[0114] <S24, S25> The material fired above is recovered (S24), and a composite oxide containing lithium, a transition metal, and oxygen is obtained (S25). Specifically, lithium cobalt oxide, lithium manganate, lithium nickelate, lithium cobalt oxide in which part of cobalt is substituted with manganese, or lithium nickel-manganese-cobalt oxide is obtained. The material fired above is recovered (S24), and a composite oxide containing lithium, a transition metal, and oxygen is obtained (S25). Specifically, lithium cobalt oxide, lithium manganate, lithium nickelate, lithium cobalt oxide in which part of cobalt is substituted with manganese, or lithium nickel-manganese-cobalt oxide is obtained. In addition, a composite oxide containing lithium, a transition metal, and oxygen synthesized in advance in S25 may be used (see Fig. 7). In this case, S21 to S24 can be omitted. In addition, a composite oxide containing lithium, a transition metal, and oxygen synthesized in advance in S25 may be used (see Fig. 7). In this case, S21 to S24 can be omitted.

[0115] In addition, a composite oxide containing lithium, a transition metal, and oxygen synthesized in advance in S25 may be used (see Fig. 7). In this case, S21 to S24 can be omitted. In addition, a composite oxide containing lithium, a transition metal, and oxygen synthesized in advance in S25 may be used (see Fig. 7). In this case, S21 to S24 can be omitted. It is carried out.

[0116] When using a composite oxide having lithium, a transition metal and oxygen synthesized in advance, it is preferable to use one with few impurities. Here, the main components are lithium, a transition metal ( cobalt, nickel, manganese), aluminum and oxygen, and elements other than the above main components are regarded as impurities. For example, when analyzed by glow discharge mass spectrometry, the concentration of impurity elements is preferably 10,000 ppm wt or less in total, and more preferably 5000 ppm wt or less In particular, the total impurity concentration of transition metals such as titanium and arsenic is preferably 3000 ppm or less, and more preferably 1500 ppm or less.

[0117] The composite oxide having lithium, a transition metal and oxygen of S25 preferably has a layered rock salt-type crystal structure with few defects and strains. Therefore, it is preferable that the composite oxide has few impurities. If the composite oxide having lithium, a transition metal and oxygen contains a large amount of impurities, it is likely to have a crystal structure with many defects or strains.

[0118] <s31> Next, the first mixture is mixed with a composite oxide having lithium, a transition metal, and oxygen. (S31). Transition metal TM in a composite oxide having lithium, transition metal and oxygen, The number of atoms of magnesium in the first mixture Mix1 is Mg Mix1 The ratio is TM:Mg Mix1 It is preferable that =1:y(0.0005≦y≦0.03), and TM:Mg M ix1 It is more preferable that =1:y(0.001≦y≦0.01), and TM:Mg M ix1 A ratio of approximately 1:0.005 is even more preferable.

[0119] The S31 mixing process uses milder conditions than the S12 mixing process to avoid destroying the composite oxide particles. It is preferable to do so. Mixing can be done dry or wet. Mixing can be done, for example, with a bo Lumil, bead mill, etc. can be used. When using a ball mill, for example, It is preferable to use zirconia balls as the base.

[0120] <S32、S33> The materials mixed above are collected (S32) to obtain a second mixture (S33).

[0121] In this embodiment, a mixture of lithium fluoride and magnesium fluoride is used to remove impurities. Although a method of adding to a small amount of lithium cobalt oxide is described, one aspect of the present invention is This is not limited to that. Instead of the second mixture of S33, magnesium is used as the starting material for lithium cobalt oxide. A product that has been calcined with the addition of a nesium source and a halogen source may also be used. In this case, S1 Because there is no need to separate processes 1 through S14 and processes S21 through S25, it is simple and productive. expensive.

[0122] Alternatively, using lithium cobalt oxide to which magnesium and fluorine have been pre-added. This is also acceptable. If lithium cobalt oxide with added magnesium and fluorine is used, S32 This process can be simplified by omitting the steps up to that point.

[0123] Furthermore, lithium cobalt oxide, which has magnesium and fluorine added to it beforehand, A magnesium source and a halogen source may be added to it.

[0124] <s34> Next, heat the second mixture. This step may be referred to as annealing or the second heating for the purpose of distinguishing it from the previous heating step.

[0125] Annealing is preferably carried out at an appropriate temperature and time. The appropriate temperature and time vary depending on conditions such as the size and composition of the composite oxide particles having lithium, transition metal, and oxygen of S 25. When the particles are small, a lower temperature or a shorter time may be more preferable than when they are large.

[0126] For example, when the average particle diameter (D50) of the S25 particles is about 12 μm, the annealing temperature is preferably, for example, 600°C or higher and 950°C or lower. The annealing time is preferably, for example, 3 hours or longer, more preferably 10 hours or longer, and even more preferably 60 hours or longer.

[0127] On the other hand, when the average particle diameter (D50) of the S25 particles is about 5 μm, the annealing temperature is preferably, for example, 600°C or higher and 950°C or lower. The annealing time is preferably, for example, 1 hour or longer and 10 hours or shorter, and more preferably about 2 hours.

[0128] The temperature drop time after annealing is preferably, for example, 10 hours or longer and 50 hours or shorter.

[0129] When the second mixture is annealed, first, the material with a low melting point (for example, lithium fluoride, melting point 848°C) in the first mixture melts and is considered to be distributed on the surface layer of the composite oxide particles. Next, due to the presence of this melted material, the melting point of other materials drops, and it is presumed that other materials melt. For example, magnesium fluoride (melting point 1263°C) melts and is considered to be distributed on the surface layer of the composite oxide particles.

[0130] The elements present in the first mixture distributed on the surface are lithium, transition metals, and oxygen. It is thought to form a solid solution within the composite oxide it contains.

[0131] Elemental diffusion in this first mixture occurs more at the surface and grain boundaries than within the composite oxide particles. This is faster. Therefore, magnesium and halogens are more efficient at the surface and grain boundaries than internally. The concentration will be even higher. As will be discussed later, if the magnesium concentration at the surface and grain boundaries is high, the crystal structure will be This allows for more effective suppression of change.

[0132] <s35> The annealed material described above is recovered to obtain a positive electrode active material 111, which is one embodiment of the present invention.

[0133] When fabricated using the methods shown in Figures 6 and 7, CdC with fewer defects is produced when charged at high voltage. A positive electrode active material with a crystal structure similar to the L2 type crystal structure can be fabricated. Rietveld analysis is performed. When this happens, the positive electrode active material in which 50% or more of the crystal structure is similar to that of the CdCl2 type crystal structure is, This is a positive electrode active material with excellent coolant properties and rate properties.

[0134] A positive electrode active material having a crystal structure similar to that of the CdCl2 type is fabricated after high-voltage charging. This includes the positive electrode active material having magnesium and fluorine, and appropriate temperature and time. Annealing between the two is an effective method for production. Magnesium and fluorine are complex oxides. It may be added to the starting material. However, when added to the starting material of a composite oxide, magnesium If the melting points of the magnesium source and halogen source are higher than the firing temperature, the magnesium source and halogen source There is a risk that it will not melt and diffusion will be insufficient. As a result, many of the layered rock salt crystal structures will be formed. Defects or strains are likely to occur. Therefore, the CdCl2 type crystal structure after high-voltage charging Crystal structures similar to the one described may also be susceptible to defects or distortions.

[0135] Therefore, first we look for a layered rock salt type crystal structure with few impurities and few defects or strains. It is preferable to obtain a composite oxide. Then, in a subsequent step, the composite oxide and magnesium source The halogen source is mixed and annealed to form a composite oxide with magnesium and fluorine on the surface. It is preferable to solid-solve the material. By manufacturing in this manner, defects can be removed after high-voltage charging. Alternatively, to fabricate a positive electrode active material that adopts a crystal structure similar to a CdCl2-type crystal structure with low strain. It is possible.

[0136] (Embodiment 2) In this embodiment, an embodiment that can be used in a secondary battery 100 according to one aspect of the present invention This section will explain the materials other than the positive electrode active material 111 described in section 1, and the configuration of the secondary battery 100. ru.

[0137] <Configuration of a secondary battery> As shown in Figure 8(A), a secondary battery 100 according to one embodiment of the present invention comprises a positive electrode 110 and a solid electrolyte. It has a layer 120 and a negative electrode 130.

[0138] The positive electrode 110 has a positive electrode current collector 113 and a positive electrode active material layer 114. It has a positive electrode active material 111 and a solid electrolyte 121. The positive electrode active material layer 114 is conductive It may contain auxiliary agents and binders.

[0139] The solid electrolyte layer 120 has a solid electrolyte 121. The solid electrolyte layer 120 has a positive electrode 110 and It is located between the negative electrodes 130 and does not have either the positive electrode active material 111 or the negative electrode active material 131. It is a domain.

[0140] The negative electrode 130 has a negative electrode current collector 133 and a negative electrode active material layer 134. It has a negative electrode active material 131 and a solid electrolyte 121. The negative electrode active material layer 134 is conductive It may contain auxiliary agents and binders. Note that when metallic lithium is used for the negative electrode 130. As shown in Figure 8(B), the negative electrode 130 can be made without a solid electrolyte 121. Using metallic lithium in the negative electrode 130 improves the energy density of the secondary battery 100. This is desirable.

[0141] Furthermore, as shown in Figure 9(A), the set consists of a positive electrode 110, a solid electrolyte layer 120, and a negative electrode 130. A secondary battery may be formed by stacking multiple positive electrodes 110 and solid electrolyte layers 120. By stacking the negative electrode 130, the voltage of the secondary battery can be increased. Figure 9(A) When a combination of positive electrode 110, solid electrolyte layer 120, and negative electrode 130 is stacked in four layers: This is a schematic diagram.

[0142] Furthermore, the secondary battery 100 in one aspect of the present invention may be a thin-film type all-solid-state battery. Body batteries are created using vapor phase methods (vacuum deposition, pulsed laser deposition, aerosol deposition, spa Positive electrodes, solid electrolytes, negative electrodes, wiring electrodes, etc., can be fabricated by depositing films using the (Tatta) method. For example, as shown in Figure 9(B), wiring electrodes 141 and 142 are placed on the substrate 140. After formation, a positive electrode 110 is formed on the wiring electrode 141, and a solid electrolyte layer 12 is placed on the positive electrode 110. A 0 is formed, and a negative electrode 130 is formed on the solid electrolyte layer 120 and the wiring electrode 142 to form a secondary electrode A pond 100 can be fabricated. The substrate 140 can be a ceramic substrate or a glass substrate. Plastic substrates, metal substrates, etc., can be used.

[0143] <Positive electrode> The positive electrode active material 111 of the positive electrode 110 is the positive electrode active material 111 described in Embodiment 1. It is preferable to use it. The positive electrode active material 111 described in Embodiment 1 has a volume that increases with charging and discharging. Because the change is reduced, the lithium ion conduction pathway is maintained even when used in all-solid-state secondary batteries. It's easy to drip, which is desirable.

[0144] The positive electrode current collector 113 can be made from metals such as stainless steel, silver, gold, platinum, aluminum, or titanium. Highly conductive materials such as alloys thereof can be used. Also, the positive electrode current collector The materials used should preferably not dissolve at the positive electrode potential. Also, silicon, titanium, and neoplastic materials are preferable. Aluminum with added elements that improve heat resistance, such as zinc, scandium, and molybdenum. A metal alloy can be used. Additionally, a metal element that reacts with silicon to form a silicide can be used. It may be formed by zirconium. Metal elements that react with silicon to form silicides include zirconium. Titanium, Titanium, Hafnium, Vanadium, Niobium, Tantalum, Chromium, Molybdenum, Examples include sten, cobalt, and nickel. Current collectors can be foil-shaped, plate-shaped (sheet-shaped), or mesh-shaped. Shapes such as perforated metal or expanded metal can be used as appropriate.

[0145] Furthermore, the positive electrode current collector 113 can be made of, for example, silver paste, gold paste, platinum paste, etc. A conductive layer formed by applying a metal paste or metal nano-ink may also be used. In addition, conductive layers formed by sputtering, CVD, vapor deposition, etc., may be used.

[0146] As conductive additives, carbon materials, metal materials, or conductive ceramic materials can be used. Yes, it is possible. Additionally, fibrous materials may be used as conductive additives. The conductive additive allows for the active material layer to function properly. An electrical conduction network can be formed inside. With a conductive additive, the positive electrode active material The electrical conduction pathway can be maintained. By adding a conductive additive to the active material layer, This makes it possible to create an active material layer with high electrical conductivity.

[0147] Furthermore, conductive additives include, for example, natural graphite, artificial graphite such as mesocarbon microbeads, and carbon. Fibers can be used. For example, mesophase pitch carbon fibers can be used. Carbon fibers such as fiber and isotropic pitch carbon fibers can be used. Carbon nanofibers and carbon nanotubes can be used. Notubes can be fabricated, for example, by vapor phase growth. Also, as a conductive additive, For example, carbon black (acetylene black (AB), etc.), graphite particles. Carbon materials such as ions, graphene, and fullerenes can be used. Also, for example, copper, Metal powders and fibers such as nickel, aluminum, silver, and gold, and conductive ceramic materials, etc. You can use it.

[0148] Furthermore, graphene compounds may be used as conductive additives.

[0149] Graphene compounds possess excellent electrical properties, including high conductivity, as well as high flexibility and high It possesses excellent physical properties, such as high mechanical strength, and may also have other properties. The compound has a planar shape. Graphene compounds enable surface contact with low contact resistance. Furthermore, even thin materials can have very high conductivity, allowing for efficient conduction within the active material layer with only a small amount. An electric current can be formed. Therefore, graphene compounds can be used as conductive additives. This is preferable because it increases the contact area between the active material and the conductive additive. By using a laser dryer, the entire surface of the active material is covered and converted into graphene, which is a conductive additive. It is preferable to form the composite as a coating. Furthermore, it may be possible to reduce electrical resistance. Therefore, it is preferable. Here, as the graphene compound, for example, graphene or multigraphe It is particularly preferable to use graphene or RGO. Here, RGO is, for example, graphene oxide. This refers to the compound obtained by reducing graphene oxide (GO).

[0150] When using active materials with small particle sizes, for example, active materials with a particle size of 1 μm or less, the specific surface area of ​​the active material is Larger materials require more conductive paths to connect the active materials. Therefore, a larger amount of conductive additive is needed. This tends to happen, and relatively, the amount of active material carried decreases. When this decreases, the capacity of the secondary battery decreases. In such cases, a conductive additive is used. When graphene compounds are used, even small amounts of graphene compounds efficiently form conductive paths. This is particularly preferable because it does not require reducing the amount of active material supported.

[0151] Examples of binders include styrene-butadiene rubber (SBR) and styrene-isoprene rubber. N-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene- It is preferable to use a rubber material such as a propylene-diene copolymer. Fluororubber can be used.

[0152] Furthermore, it is preferable to use a water-soluble polymer as the binder. For example, polysaccharides can be used as the derivative. Cellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose Cellulose derivatives such as lurose, diacetylcellulose, and regenerated cellulose, as well as starch, etc. These can be used. Furthermore, these water-soluble polymers can be used in combination with the aforementioned rubber materials. It would be even better if they were there.

[0153] Alternatively, as a binder, polystyrene, polymethyl acrylate, polymethyl methacrylate can be used. Chill (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), poly Ethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, Polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, poly Ethylene terephthalate, nylon, polyvinylidene fluoride (PVdF), polyacrylo Nitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, nitrocellulose It is preferable to use ingredients such as loin.

[0154] You may use a combination of several of the binders mentioned above.

[0155] For example, a material with particularly excellent viscosity-modifying properties may be used in combination with other materials. For example, rubber materials have excellent adhesive and elastic properties, but their viscosity is difficult to adjust when mixed with a solvent. In such cases, for example, mixing with a material that has particularly excellent viscosity-modifying effects may be used. This is preferable. As a material with particularly excellent viscosity adjustment effect, for example, a water-soluble polymer can be used. Furthermore, water-soluble polymers that are particularly excellent in viscosity adjustment include the aforementioned polysaccharides, for example, calcium carbonate. Voxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxy Cellulose derivatives such as propylcellulose, diacetylcellulose, and regenerated cellulose. Body or starch can be used.

[0156] Furthermore, cellulose derivatives such as carboxymethylcellulose are, for example, carboxymethyl By using salts such as sodium salts or ammonium salts of cellulose, the solubility increases. It becomes easier to exert its effect as a viscosity modifier. The increased solubility makes the electrode slurry - When manufacturing, it is also possible to improve the dispersibility with the active material and other components. As for cellulose and cellulose derivatives used as electrode binders, This also includes salt.

[0157] Water-soluble polymers stabilize viscosity by dissolving in water, and also function as active materials and binders. Other materials to be combined with it, such as styrene-butadiene rubber, are stably separated in an aqueous solution. It can be dispersed. Furthermore, because it has functional groups, it is easily and stably adsorbed onto the surface of the active material. This is expected. Also, cellulose derivatives such as carboxymethylcellulose, For example, many materials have functional groups such as hydroxyl groups and carboxyl groups, and because they have functional groups It is expected that the polymers will interact with each other and exist to broadly cover the surface of the active material.

[0158] <Negative electrode> The negative electrode active material 131 of the negative electrode 130 may be, for example, lithium metal, alloy material, or carbon material. Fees and other charges may be used.

[0159] Using lithium metal as the negative electrode active material 131 significantly increases the energy density of the secondary battery. It is preferable to be able to do so.

[0160] Furthermore, the charge-discharge reaction is carried out by alloying and dealloying reactions with lithium as the negative electrode active material. Elements that can be used include silicon, tin, gallium, and aluminum. Germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one of these elements can be used. Such elements have a capacity compared to carbon. The capacity is large, and silicon in particular has a high theoretical capacity of 4200 mAh / g. Therefore, negative electrode active material It is preferable to use silicon. Alternatively, compounds containing these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2 , V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, A g3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3 Examples include InSb and SbSn. Here, filling and discharging occur through alloying and dealloying reactions with lithium. When elements capable of undergoing electrochemical reactions, and compounds containing such elements, are referred to as alloying materials. There is.

[0161] In this specification, SiO refers to silicon monoxide, for example. Alternatively, SiO refers to SiO x It can also be expressed as follows. Here, it is preferable that x has one neighboring value. For example, x is 0 A value of 0.2 to 1.5 is preferred, and a value of 0.3 to 1.2 is more preferred.

[0162] Carbon-based materials include graphite, easily graphitizable carbon (soft carbon), and poorly graphitizable carbon (hard carbon). Carbon, carbon nanotubes, graphene, carbon black, etc. can be used. .

[0163] Examples of graphite include synthetic graphite and natural graphite. An example of synthetic graphite is Mesoca. Examples include carbon microbeads (MCMB), coke-based synthetic graphite, and pitch-based synthetic graphite. Here, spheroidal graphite, which has a spherical shape, can be used as artificial graphite. Furthermore, MCMB may have a spherical shape, which is preferable. Also, the surface area of ​​MCMB Reducing the size is relatively easy and sometimes preferable. Examples of natural graphite include, Examples include flaky graphite and spheroidized natural graphite.

[0164] Graphite is formed when lithium ions are inserted into it (during the formation of lithium-graphite intercalation compounds). It exhibits a low potential, similar to lithium metal (0.05V to 0.3V vs. Li / L). i + This allows lithium-ion secondary batteries to exhibit a high operating voltage. Furthermore, graphite has a relatively high capacity per unit volume, relatively small volume expansion, and is inexpensive. It is preferable because it has advantages such as higher safety compared to lithium metal.

[0165] Furthermore, titanium dioxide (TiO2) and lithium titanium oxide (Li4T) are used as negative electrode active materials. i5O 12 ), lithium-graphite intercalation compound (Li x C6), Niobium pentoxide (Nb2O5) Oxides such as tungsten oxide (WO2) and molybdenum oxide (MoO2) can be used. can.

[0166] Furthermore, the negative electrode active material has a Li3N-type structure, which is a lithium and transition metal binitride. Li 3-x M x N (M = Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 The N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm²). 3 ) indicates And it is preferable.

[0167] When a lithium-transition metal binitride is used, lithium ions are included in the negative electrode active material, Combined with lithium-ion-free materials such as V2O5 and Cr3O8 as positive electrode active materials. This is preferable. By pre-desorbing the lithium ions contained in the positive electrode active material, the negative electrode active material is used. A lithium-transition metal composite can be used.

[0168] Furthermore, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example, Lithium oxide, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO). Transition metal oxides that do not form alloys with the negative electrode active material may be used. The resulting materials include Fe2O3, CuO, Cu2O, RuO2, Cr2O3, etc. CoS oxides 0.89 , sulfides such as NiS and CuS, Zn3N2, Cu3N, Ge3 Nitrides such as N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. It can also occur with fluoride.

[0169] Alternatively, the surface layer of the negative electrode active material may be coated with a solid electrolyte. For example, the surface layer of the negative electrode active material The part may be coated with an oxide-based solid electrolyte and a sulfide-based electrolyte.

[0170] The conductive additives and binders that the negative electrode active material layer may have include the positive electrode active material layer Materials similar to conductive additives and binders can be used.

[0171] The negative electrode current collector 133 uses the same materials as the positive electrode current collector, in addition to copper foil, copper paste, etc. This is possible. Furthermore, the negative electrode current collector uses a material that does not alloy with carrier ions such as lithium. It is preferable that they be present.

[0172] <Solid electrolyte layer> The solid electrolyte 121 in the solid electrolyte layer 120 may be, for example, a sulfide-based solid electrolyte or an acid Compound-based solid electrolytes, halogenated solid electrolytes, etc., can be used.

[0173] Sulfide-based solid electrolytes include thiosilicon-based (Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, etc.), sulfide glass (70Li2S・30P2S5, 30Li2 S·26B2S3·44LiI, 63Li2S·38SiS2·1Li3PO4, 57L i2S・38SiS2・5Li4SiO4, 50Li2S・50GeS2, etc.), sulfide crystals Crystallized glass (Li7P3S 11 Li 3.25 P 0.95 Contains S4, etc. Sulfide-based Solid electrolytes include materials with high conductivity, can be synthesized at low temperatures, and are relatively soft. It has advantages such as the conductivity path being easily maintained even after repeated charging and discharging.

[0174] Oxide-based solid electrolytes include materials having a perovskite-type crystal structure (La 2 / 3-x Li 3x Materials having a NASICON-type crystal structure (Li 1-X Al X Ti 2- X (PO4)3 etc.) Materials having a garnet-type crystal structure (Li7La3Zr2O 12 etc. ), materials having a LISICON-type crystal structure (Li 14 ZnGe4O 16 etc.), LLZO (Li7La3Zr2O 12 ), oxide glass (Li3PO4-Li4SiO4, 50L i4SiO4·50Li3BO3 etc.), oxide crystallized glass (Li 1.07 Al 0.69 Ti 1.46 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (including (PO4)3, etc.) The oxide-based solid electrolyte has advantages such as being stable in the atmosphere.

[0175] Halide-based solid electrolytes include LiAlCl4, Li3InBr6, LiF, LiCl , LiBr, LiI, etc. Also, composite materials obtained by filling the pores of porous alumina or porous silica with these halide-based solid electrolytes can also be used as solid electrolytes. This is possible.

[0176] Also, different solid electrolytes may be mixed and used.

[0177] ≪LATP≫ Among them, Li 1+x Al x Ti 2-x (PO4)3( 0 < x < 1) (hereinafter referred to as LATP) contains aluminum and titanium, which are elements that the positive electrode active material 111 used in the secondary battery 100 of one embodiment of the present invention may have. Therefore, a synergistic effect can be expected for improving the cycle characteristics, which is preferable. Also, an improvement in productivity due to reduction of processes can be expected. In this specification, etc., the NASICON-type crystal structure refers to a compound represented by M2(XO4)3( M: transition metal, X: S, P, As, Mo, W, etc.), and has a structure in which MO6 octahedrons and XO4 tetrahedrons share vertices and are three-dimensionally arranged.

[0178] An example of the method for producing LATP will be described using FIG. 10.

[0179] ≪S51≫ ​​​First, as materials for LATP, we have a lithium source, an aluminum source, a titanium source, and a phosphorus source. Prepare. In S51 of Figure 10, lithium carbonate is used as the lithium source, and aluminum is used as the aluminum source. Aluminum oxide, titanium oxide as a titanium source, and ammonium dihydrogen phosphate as a phosphorus source. We will use this.

[0180] Furthermore, if the following mixing and grinding steps are performed wet, a solvent must be prepared. (Aprotic solvent) It is preferable to use [a specific solvent]. In S51 of Figure 10, acetone is used as the solvent.

[0181] ≪S52≫ Next, the above materials are mixed and ground (S52 in Figure 10). Mixing can be done dry or wet. It is possible to do this, but the wet method is preferred because it can grind the material to a finer size. For example, mixing Ball mills, bead mills, etc. can be used. When using a ball mill, even It is preferable to use zirconia balls as the medium. For example, zirconia balls This wet ball mill, using a special mechanism, can perform ball milling at 300 rpm for 2 hours. .

[0182] ≪S53≫ Next, the mixed and ground materials are heated (S53 in Figure 10). This step is used for subsequent processing. To distinguish it from the heating process, it is sometimes referred to as calcination or first heating. Heating is performed at 170°C or higher. It is preferable to carry out the process at a temperature below 500°C, and more preferably at a temperature between 350°C and 450°C. The heating temperature needs to be higher than the decomposition temperature of the material used as the phosphorus source, but on the other hand, heating If the temperature is too high, titanium dioxide may undergo a transformation to a rutile-type crystal structure, for example. It can be heated in a nitrogen atmosphere at 400°C for 10 hours. The heating rate is 200°C / hour. It is possible.

[0183] ≪S54≫ Next, the heated ingredients are crushed in a mortar (S54 in Figure 10).

[0184] ≪S55≫ Furthermore, the mixture is mixed and ground using a ball mill, bead mill, etc. (S55 in Figure 10). The mixing can be carried out dry or wet; if carried out wet, a solvent is added. Furthermore, thorough grinding is preferable as it allows for the synthesis of LATP with fewer impurities. For example, using a wet ball mill with acetone as the solvent, the ball mill treatment is performed at 400 rpm for 20 hours. It is possible to perform the necessary actions.

[0185] ≪S56≫ Next, the mixed and ground materials described above are heated (S56 in Figure 10). This step is performed in the previous step To distinguish it from the heating process, it is sometimes referred to as the main firing or second heating. Heating is performed at 723°C or higher. It is preferable to perform the process at temperatures above 1000°C, and more preferably between 800°C and 950°C. This is preferable. If the temperature is too low, lithium carbonate will not decompose, and LATP synthesis will not proceed sufficiently. There is a risk. On the other hand, if the temperature is too high, there is a risk that lithium may evaporate. If a dry air atmosphere (dew point below -50°C) is used, it can be heated at 900°C for 2 hours. The temperature can be increased to 200°C / hour.

[0186] The main firing of S56 is, for example, annealing in the manufacturing process of the positive electrode active material 111 (Figure 6 and This may be carried out in conjunction with S34) in Figure 7. S56 is the main firing process and the process of manufacturing the positive electrode active material 111. By combining this process with annealing, the heating process can be reduced, and productivity can be improved. ru.

[0187] ≪S57≫ Next, the material heated above may be ground (S57 in Figure 10). Grinding can be done, for example, using a mortar and pestle. After crushing, it is processed in a ball mill at 300 rpm for 6 hours. Then, a mesh opening of 32 μm is used. You can bet on it.

[0188] LATP can be obtained through the process described above.

[0189] <Shape of the outer casing and secondary battery> In one aspect of the present invention, the outer casing of the secondary battery 100 can be made of various materials and shapes. While this is possible, it is preferable that the positive electrode, solid electrolyte layer, and negative electrode have the function of pressurizing them.

[0190] For example, Figure 11 shows an example of a cell used to evaluate the materials of an all-solid-state battery.

[0191] Figure 11(A) is a schematic cross-sectional view of the evaluation cell, which consists of a lower member 261 and an upper member 262 and fixing screws and wing nuts 264 that secure them, and a retaining screw 263 The electrode plate 253 is pressed down by the rotation to secure the evaluation material. (Stainless steel material) An insulator 266 is provided between the lower member 261, which is made of material, and the upper member 262. There is also an O-ring 2 for sealing between the upper member 262 and the retaining screw 263. 65 is provided.

[0192] The evaluation material is placed on an electrode plate 251, surrounded by an insulating tube 252, and subjected to electrical stimulation from above. The material is being pressed by the polarity plate 253. This is a magnified, oblique view of the area around the evaluation material. The figure is shown in Figure 11(B).

[0193] As an example of the evaluation material, we show a stacked structure consisting of a positive electrode 250a, a solid electrolyte layer 250b, and a negative electrode 250c. The cross-sectional view is shown in Figure 11(C). Note that in Figures 11(A), (B), and (C) The same symbol is used for the same location.

[0194] The electrode plate 251 and lower member 261, which are electrically connected to the positive electrode 250a, are the positive electrode It can be said that this corresponds to a terminal. It is an electrode plate electrically connected to the negative electrode 250c. 253 and the upper member 262 can be said to correspond to the negative electrode terminal. Electrode plate While applying pressure to the evaluation material via plate 251 and electrode plate 253, electrical resistance and other parameters are measured. It can be measured.

[0195] Furthermore, the outer casing of the secondary battery according to one aspect of the present invention uses a package with excellent airtightness. This is preferable. For example, ceramic packages or resin packages can be used. Furthermore, when sealing the outer casing, it is necessary to block out outside air and seal it in a tightly sealed atmosphere, for example, a glove box. It is preferable to perform this within the premises.

[0196] Figure 12(A) shows a secondary battery according to one embodiment of the present invention, having an exterior and shape different from that of Figure 11. A perspective view is shown. The secondary battery in Figure 12(A) has external electrodes 271 and 272 and multiple packs. It is sealed with an outer casing that includes a cage member.

[0197] Figure 12(B) shows an example of a cross-section cut along the dashed line in Figure 12(A). Positive electrode 250a, A laminate having a solid electrolyte layer 250b and a negative electrode 250c has an electrode layer 273a provided on a flat plate. A package member 270a, a frame-shaped package member 270b, and an electrode layer 2 on a flat plate. The package member 270c, which has 73b provided, is enclosed and sealed by the structure. The package components 270a, 270b, and 270c contain insulating materials, such as resin materials and ceramics. Mick can be used.

[0198] The external electrode 271 is electrically connected to the positive electrode 250a via the electrode layer 273a. It functions as a positive terminal. In addition, the external electrode 272 is electrically negative via the electrode layer 273b. It is electrically connected to the 250c pole and functions as a negative terminal.

[0199] Furthermore, Figure 13 shows a laminate-type secondary battery according to one embodiment of the present invention, which differs from the above, and an example of its manufacture. And as shown in Figure 14.

[0200] Figure 13(A) is an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is the positive electrode current collector 50 The positive electrode has a positive electrode active material layer 502 formed on the surface of the positive electrode current collector 501. 503 has a region at its end where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). The negative electrode 506 has a negative electrode current collector 504, and the negative electrode active material layer 505 is on the surface of the negative electrode current collector 504. It is formed on a surface. Also, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed at its end. , that is, it has a tab region. Note that the area of ​​the tab region of the positive electrode 503 and the negative electrode 506 is The shape is not limited to the example shown in Figure 13(A).

[0201] Then, the negative electrode 506, the solid electrolyte layer 507, and the positive electrode 503 are stacked. (See Figure 13(B) for stacking.) The negative electrode 506, solid electrolyte layer 507, and positive electrode 503 are shown. Here, five sets of negative electrodes are used, and the positive electrode is also shown. An example using four sets of poles is shown. Next, the joining of the tab regions of the positive pole 503 and the outermost positive pole The positive lead electrode 510 is joined to the tab region. For joining, for example, ultrasonic welding is used. This is sufficient. Similarly, the joining of the tab regions of the negative electrode 506 and the negative contact of the tab region of the outermost negative electrode The electrode lead 511 is joined.

[0202] Next, as shown in Figure 13(C), the negative electrode 506, the solid electrolyte layer 507 and The laminated body of the positive electrode 503 is placed, and the outer casing 509 is bent at the part indicated by the dashed line. The outer periphery of the exterior body 509 is joined. The exterior body 509 is made of laminated metal foil and organic resin film. Laminated film, for example, aluminum foil or stainless steel foil, is used for bonding, for example For example, heat sealing or similar methods can be used. In this way, the secondary laminate type shown in Figure 13(D) is formed. A 500-cell battery can be manufactured. Furthermore, using a single sheet of laminate film... The example shown involves joining two laminate films together and sealing them by bonding the edges. It can also be used as a composition.

[0203] Multiple laminated rechargeable batteries (500) are used as a single battery module for electric vehicles. It can be mounted anywhere.

[0204] Figure 14(A) shows three laminated rechargeable batteries 500 arranged on a first plate 521 and a second plate 521. This is a perspective view showing how it is sandwiched and fixed between plates 524. As shown in Figure 14(B) The first plate 521 and the second plate are attached using fixing devices 525a and 525b. By fixing the distance between the terminal 524 and the other terminal, it is possible to pressurize three secondary batteries 500. ru.

[0205] Figures 14(A) and 14(B) show an example using three laminated 500 rechargeable batteries. As shown, it is not particularly limited, and it is also possible to use four or more 500 rechargeable batteries, or ten or more. If used, it can be used as a power source for small vehicles, and if 100 or more are used, it can be used for vehicle-mounted power supplies. It can also be used as a large-scale power supply. Furthermore, it includes protection circuits to prevent overcharging and temperature rise. A temperature sensor for monitoring the temperature may be provided on the laminated secondary battery 500.

[0206] In all-solid-state batteries, by applying a predetermined pressure in the stacking direction of the stacked positive and negative electrodes, internal pressure is applied. The contact state of the interface in the part can be kept good. A predetermined pressure is applied in the stacking direction of the positive and negative electrodes. By applying force, it is possible to suppress the expansion in the stacking direction caused by charging and discharging of all-solid-state batteries. This can improve the reliability of all-solid-state batteries.

[0207] This embodiment can be used in appropriate combination with other embodiments.

[0208] (Embodiment 3) In this embodiment, using Figures 15 and 16, the secondary battery described in the previous embodiment is used This section will explain an example of its implementation in electronic devices.

[0209] [Small electronic equipment] First, using Figures 15(A) to 15(C), we will show an all-solid-state secondary battery, which is one embodiment of the present invention. This section describes an example of implementation in electronic devices.

[0210] Figure 15(A) shows an example of a mobile phone. The mobile phone 2100 has a housing 2101 In addition to the display unit 2102 incorporated into it, there are operation buttons 2103, an external connection port 2104, and It is equipped with a speaker 2105, a microphone 2106, etc. Note that the mobile phone 2100 is secondary It has a battery 2107. The above secondary battery 2107 is an all-solid-state secondary battery according to one embodiment of the present invention By using this technology, we can provide mobile phones that are highly safe, lightweight, and have a long lifespan.

[0211] The 2100 mobile phone offers mobile phone calls, email, document viewing and creation, music playback, and internet connectivity. It can run various applications such as internet communication and computer games. .

[0212] The operation button 2103 is used for setting the time, as well as turning the power on and off, and turning wireless communication on and off. It has various functions such as operation, silent mode activation and deactivation, and power saving mode activation and deactivation. This can be done. For example, the operating system built into the mobile phone 2100 The system also allows you to freely configure the function of the operation button 2103.

[0213] Furthermore, the mobile phone 2100 is capable of performing standardized short-range wireless communication. For example, by communicating with a wireless headset, hands-free communication is possible. They can also talk.

[0214] Furthermore, the mobile phone 2100 is equipped with an external connection port 2104, and can connect to other information terminals. Data can be exchanged directly via this. Also, via external connection port 2104... It can also be charged wirelessly. Note that the charging operation is performed wirelessly without going through the external connection port 2104. It may also be done by electricity.

[0215] The mobile phone 2100 preferably has a sensor. For example, a fingerprint sensor. Human body sensors such as pulse sensors and body temperature sensors, as well as touch sensors, pressure sensors, and acceleration sensors. It is preferable that the following are installed:

[0216] Figure 15(B) is a perspective view of a device also known as a tobacco-containing smoking device (electronic cigarette). In 15(B), the electronic cigarette 2200 includes a heating element 2201 and an electric heater that supplies power to the heating element 2201. It has a secondary battery 2204 that supplies power. When the stick 2202 is inserted into it, The wick 2202 is heated by the heating element 2201. To enhance safety, a secondary battery 2 A protection circuit to prevent overcharging and over-discharging of battery 204 may be electrically connected to the secondary battery 2204. The secondary battery 2204 shown in Figure 15(B) has external terminals so that it can be connected to a charging device. The 2204 secondary battery is the tip when held, so the total length is short. Furthermore, it is desirable that the weight be light. One embodiment of the present invention is an all-solid-state secondary battery which is highly safe and high Due to its capacity and good cycle characteristics, it is small and can be used for long periods of time. Furthermore, we can offer the lightweight e-cigarette 2200.

[0217] Figure 15(C) shows an unmanned aerial vehicle 2300 having multiple rotors 2302. 2300 is a secondary battery 2301, a camera 2303, and an antenna ( (Not shown) The unmanned aerial vehicle 2300 can be remotely controlled via an antenna. One embodiment of the present invention provides an all-solid-state secondary battery that is highly safe, has high capacity, and good cycle characteristics. Therefore, it is suitable as an all-solid-state secondary battery to be mounted on the unmanned aerial vehicle 2300.

[0218] [vehicle] Next, using Figures 15(D), 15(E), and 16, a secondary battery according to one embodiment of the present invention will be shown. This section describes an example of implementing this in a vehicle.

[0219] Figure 15(D) shows an electric motorcycle 2400 using an all-solid-state secondary battery according to one embodiment of the present invention. The motorized motorcycle 2400 is a secondary battery 2401, a display unit 2402, and a hand, which are all according to one aspect of the present invention. It is equipped with the 2403. The secondary battery 2401 supplies electricity to the motor that provides power. Yes, it is possible. The display unit 2402 shows the remaining charge of the secondary battery 2401, the speed of the electric motorcycle 2400, and the horizontal. Status and other information can be displayed.

[0220] Figure 15(E) shows an example of an electric bicycle using a secondary battery according to one embodiment of the present invention. The 2500 includes a battery pack 2502. The battery pack 2502 is an all-in-one unit of one aspect of the present invention. It has a solid-state rechargeable battery.

[0221] The battery pack 2502 can supply power to the motor that assists the driver. Also, the battery pack 2502 can be removed from the bicycle 2500 and carried around. Pack 2502 and electric bicycle 2500 have a display unit that can show the battery level, etc. It's okay to be there.

[0222] Furthermore, as shown in Figure 16(A), a secondary battery having a plurality of secondary batteries 2601 according to one embodiment of the present invention The 2602 pond module is for hybrid electric vehicles (HEVs), electric vehicles (EVs), or plug-in applications. It may be installed in hybrid electric vehicles (PHEVs) and other electronic devices.

[0223] Figure 16(B) shows an example of a vehicle equipped with a secondary battery module 2602. 03 is an electric vehicle that uses an electric motor as the power source for driving. High-performance vehicles can use electric motors and engines as power sources for operation, with the appropriate selection available. It is a hybrid automobile. By using one aspect of the present invention, a vehicle with high safety and long driving range is obtained. It is possible to realize a vehicle.

[0224] The rechargeable battery not only powers the electric motor (not shown), but also the headlights and interior lights. It can supply power to light-emitting devices such as lights. Additionally, the vehicle 2603 has a secondary battery. Display devices such as speedometers, tachometers, navigation systems, and semiconductors It can supply power to conductive devices.

[0225] Vehicle 2603 uses a plug-in or wireless connection to the secondary battery of the secondary battery module 2602. It can be charged by receiving power from an external charging facility using a contact-to-charge method or the like.

[0226] Figure 16(C) shows charging from a ground-mounted charging device 2604 to the vehicle 2603 via a cable. This indicates that the device is powered. For charging, please refer to the charging method and connector specifications. This can be done as appropriate using the prescribed methods such as deMO(registered trademark) or combos. For example, plug-in techniques By means of this technique, the secondary battery module 2 mounted on vehicle 2603 is powered by an external power supply. The 602 can be charged. Charging is done via a conversion device such as an AC / DC converter. This can be done by converting current power to direct current power. The charging device 2604 is as shown in Figure 16(C). This could be a charging station installed in a residential building or a charging station located in a commercial facility. That's good too.

[0227] Although not shown in the diagram, a power receiving device is mounted on the vehicle, and power is supplied wirelessly from a ground-based power transmission device. It can also be charged by doing so. In this contactless power supply method, power transmission equipment is installed in roads or exterior walls. By incorporating this, charging can be performed not only when the vehicle is stopped but also while it is in motion. Furthermore, this contactless power supply... This method may be used to transmit and receive power between vehicles. Furthermore, the exterior of the vehicle Solar panels may be installed to charge the secondary battery when the vehicle is stopped or in motion. Electromagnetic induction or magnetic resonance methods can be used to supply power to it.

[0228] Furthermore, the house shown in Figure 16(C) is an energy storage system having an all-solid-state secondary battery, which is one embodiment of the present invention. It has a system 2612 and a solar panel 2610. The energy storage system 2612 is solar Panel 2610 and wiring 2611 are electrically connected. Also, the energy storage system 2 612 and the ground-mounted charging device 2604 may be electrically connected. The electricity obtained from the 2610 can be used to charge the energy storage system 2612. The power stored in the TEM 2612 is supplied to the vehicle 2603 via the charging device 2604. The battery module 2602 can be charged.

[0229] The electricity stored in the energy storage system 2612 can also supply power to other electronic devices in the house. This is possible. Therefore, even when power cannot be supplied from the commercial power source due to a power outage, etc., this By using the energy storage system 2612 according to one aspect of the invention as an uninterruptible power supply, electronic devices It will become available for use.

[0230] This embodiment can be used in appropriate combination with other embodiments. [Explanation of symbols]

[0231] 100: Secondary battery, 110: Positive electrode, 111: Positive electrode active material, 113: Positive electrode current collector, 114: Positive electrode active material layer, 120: Solid electrolyte layer, 121: Solid electrolyte, 130: Negative electrode, 131: Negative Electrode active material, 133: Negative electrode current collector, 134: Negative electrode active material layer, 140: Substrate, 141: Wiring current Pole, 142: Wiring electrode, 250a: Positive electrode, 250b: Solid electrolyte layer, 250c: Negative electrode, 2 51: Electrode plate, 252: Insulating tube, 253: Plate for electrode, 261: Lower member, 2 62: Upper component, 264: Wing nut, 265: O-ring, 266: Insulator, 270a: Package component, 270b: Package component, 270c: Package component, 271: External power Pole, 272: External electrode, 273a: Electrode layer, 273b: Electrode layer, 500: Secondary battery, 50 1: Positive electrode current collector, 502: Positive electrode active material layer, 503: Positive electrode, 504: Negative electrode current collector, 505: 506: Negative electrode active material layer, 507: Negative electrode, 509: Solid electrolyte layer, 509: Outer casing, 510: Positive electrode Lead electrode, 511: Negative lead electrode, 521: First plate, 524: Second plate , 525a: Fixing device, 525b: Fixing device, 2100: Mobile phone, 2101: Housing, 2102: Display unit, 2103: Operation buttons, 2104: External connection port, 2105: Speaker -Ka, 2106: Microphone, 2107: Rechargeable battery, 2200: Electronic cigarette, 2201: Heating Element, 2202: Stick, 2204: Secondary battery, 2300: Unmanned aerial vehicle, 2301: Secondary battery, 2302: rotor, 2303: camera, 2400: electric motorcycle, 2401: Rechargeable battery, 2402: display unit, 2403: handlebars, 2500: bicycle, 2500: electric Bicycle, 2502: Battery pack, 2601: Rechargeable battery, 2602: Rechargeable battery module, 2603: Vehicle, 2604: Charging device, 2610: Solar panel, 2611: Wiring, 2 612: Energy storage system ​​

Claims

1. A lithium-ion secondary battery having a positive electrode, a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode, The positive electrode has a positive electrode active material, The positive electrode active material comprises lithium, cobalt, magnesium, and fluorine. The space group of the positive electrode active material has a crystal structure of R-3m, In the crystal structure of R-3m, CoO ２ The lithium sites between the layers have the magnesium, In the aforementioned positive electrode active material, the magnesium concentration in the surface layer is higher than the magnesium concentration in the interior. A lithium-ion secondary battery in which, when the battery using the lithium metal positive electrode and counter electrode is charged to 4.6V, and the positive electrode removed from the battery after charging is analyzed by powder X-ray diffraction using CuKα1 rays, the battery has diffraction peaks at least at 2θ = 19.30 ± 0.20° and 2θ = 45.55 ± 0.10°.

2. A lithium-ion secondary battery having a positive electrode, a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode, The positive electrode has a positive electrode active material, The positive electrode active material comprises lithium, cobalt, magnesium, and fluorine. The space group of the positive electrode active material has a crystal structure of R-3m, In the crystal structure of R-3m, CoO ２ The lithium sites between the layers have the magnesium, In the aforementioned positive electrode active material, the magnesium concentration in the surface layer is higher than the magnesium concentration in the interior. A lithium-ion secondary battery in which, when the positive electrode is subjected to XRD measurement under the following XRD measurement conditions, the measured XRD pattern has diffraction peaks at 2θ = 19.30 ± 0.20° and 2θ = 45.55 ± 0.10°. XRD measurement conditions: A secondary battery is fabricated using the positive electrode and lithium metal as the counter electrode. The secondary battery with lithium metal as the counter electrode is charged with a constant current of 0.5C (1C is the current value per positive electrode active material, which is assumed to be 137mA / g) up to 4.6V, and then charged with a constant voltage until the current value becomes 0.01C. The secondary battery with lithium metal as the counter electrode is disassembled in an argon atmosphere to remove the positive electrode, and the positive electrode is measured by XRD using CuKα1 radiation.

3. In claim 1 or claim 2, The solid electrolyte layer is a lithium-ion secondary battery having an oxide-based solid electrolyte.

4. In claim 1 or claim 2, The solid electrolyte layer is a lithium-ion secondary battery having a sulfide-based solid electrolyte.

5. In claim 1 or claim 2, The solid electrolyte layer is a lithium-ion secondary battery having a halide-based solid electrolyte.

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