Method for preparing positive electrode active material

Abstract

A positive electrode active material for lithium-ion secondary batteries that offers high capacity and excellent charge-discharge cycle characteristics. provide. [Solution] The positive electrode active material is designed to show little change in its crystal structure between the charging and discharging states. For example, in the discharged state, it has a layered rock salt-type crystalline structure, and when charged with a high voltage of about 4.6V... In its state, the positive electrode active material having a pseudo-spinel type crystal structure is more responsive than known positive electrode active materials. There is little change in crystal structure and volume before and after discharge. In the charged state, it is a pseudo-spinel type crystal. To produce a cathode active material with a structure, lithium cobalt oxide is synthesized, and then fluorine is added. Add lithium fluoride and magnesium fluoride and mix, then heat at the appropriate temperature and time. It is preferable.

Description

[Technical Field]

[0001] One aspect of the present invention relates to a product, a method, or a method of manufacture. Alternatively, the present invention relates to a process. This relates to machines, manufacturers, or compositions of matter. One aspect of the present invention relates to semiconductor devices, display devices, light-emitting devices, energy storage devices, lighting devices, or electronic devices. The present invention relates to a device or a method for manufacturing such a device. In particular, to a positive electrode active material that can be used in a secondary battery. This relates to secondary batteries and electronic devices having secondary batteries.

[0002] In this specification, the term "energy storage device" refers to all elements and devices that have an energy storage function. For example, lithium-ion secondary batteries and other rechargeable batteries (also called secondary batteries) This includes muon capacitors and electric double-layer capacitors.

[0003] Furthermore, in this specification, "electronic equipment" refers to all devices that have an energy storage device, and the energy storage device is All electronic devices, including electro-optical devices and information terminal devices with energy storage systems, are considered electronic equipment. [Background technology]

[0004] In recent years, various energy storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have been developed. Development of new devices is actively underway. In particular, lithium-ion batteries, which have high power output and high energy density, are being developed. The next battery is used in mobile phones, smartphones, tablets, or laptop computers, etc. Personal digital assistants, portable music players, digital cameras, medical devices, next-generation clean energy - Automobiles (Hybrid electric vehicles (HEV), electric vehicles (EV), plug-in hybrid vehicles) (PHEV, etc.) Along with the development of the semiconductor industry, demand for rechargeable vehicles is rapidly expanding. As a source of energy, it has become indispensable in today's information society.

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

[0006] Therefore, in order to improve the cycle characteristics and increase the capacity of lithium-ion secondary batteries, positive electrode activity Improvements to the material are being considered (Patent Documents 1 and 2). Also, the crystal of the positive electrode active material. Research on the structure has also been conducted (Non-Patent Documents 1 to 3).

[0007] X-ray diffraction (XRD) is one of the techniques used to analyze the crystal structure of positive electrode active materials. ICSD (Inorganic Crystal Structural Impulse) is introduced in Patent Document 5. By using a photodata database, it is possible to analyze XRD data. can. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2002-216760 [Patent Document 2] Japanese Patent Publication No. 2006-261132 [Non-patent literature]

[0009] [Non-Patent Document 1] Toyoki Okumura et al, “Correlation of lithium ion distribution and X-ray absorption near-edge structure in O3-and O2-lithium cobalt oxides from first-principle calculation”, Journal of Materials Chemistry, 2012, 22, p.17340-17348 [Non-Patent Document 2] Motohashi, T. et al, “Electronic phase diagram of the layered cobalt oxide system LixCoO2 (0.0≦x≦1.0)”, Physical Review B, 80(16);165114 [Non-Patent Document 3] Zhaohui Chen et al, “Staging Phase Transitions in LixCoO2”, Journal of The Electrochemical Society, 2002, 149(12) A1604-A1609 [Non-Patent Document 4] WE Counts et al, Journal of the American Ceramic Society,(1953) 36 [1] 12-17. Fig.01471 [Non-Patent Document 5] Belsky, A. et al., “New developments in the Inorganic Crystal Structure Database (ICSD): accessibility in support of materials research and design”, Acta Cryst., (2002) B58 364-369. [Overview of the project] [Problems that the invention aims to solve]

[0010] One aspect of the present invention relates to a lithium-ion secondary battery with high capacity and excellent charge-discharge cycle characteristics. One of the objectives is to provide highly active materials and methods for producing them. Alternatively, to provide a highly productive method. One objective is to provide a method for producing a positive electrode active material. Alternatively, one aspect of the present invention is to provide a method for producing a positive electrode active material. When used in lithium-ion secondary batteries, the decrease in capacity during charge-discharge cycles is suppressed. One objective of the present invention is to provide a positive electrode active material. Alternatively, one aspect of the present invention relates to a high-capacity secondary One objective of this invention is to provide a battery. Alternatively, one aspect of this invention provides a battery with excellent charge-discharge characteristics. One of the objectives is to provide a rechargeable battery, or to maintain a high-voltage charged state for an extended period of time. The objective is to provide a positive electrode active material in which the elution of transition metals such as cobalt is suppressed even in such cases. This is one aspect of the present invention. Alternatively, one aspect of the present invention provides a safe or reliable secondary battery. This will be one of the challenges.

[0011] Alternatively, one aspect of the present invention relates to a novel substance, active material particles, energy storage device, or a method for producing the same. One of the objectives is to provide [this].

[0012] 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]

[0013] To achieve the above objectives, a positive electrode active material according to one aspect of the present invention is provided in both a charged state and a discharged state. Furthermore, it is characterized by little change in crystal structure. For example, in the discharge state, layered rock salt type crystals It has a crystalline structure, and when charged with a high voltage of about 4.6V, it exhibits a pseudo-spinel type crystalline structure. The positive electrode active material exhibits changes in crystal structure and volume before and after charging and discharging compared to known positive electrode active materials. There are few.

[0014] In order to create a positive electrode active material that has a pseudo-spinel type crystal structure in the charged state, lithium After synthesizing particles of a composite oxide containing um, a transition metal, and oxygen, a fluorine source and salt Add a halogen source such as an elemental source and a magnesium source and mix, then further at an appropriate temperature and time. It is preferable to heat it in this way.

[0015] Halogens and magnesium are impurities for the layered rock salt crystal structure. First, by synthesizing composite oxide particles with few impurities, a layered rock salt-type crystal structure with few defects is created. The particles can have a structure. The material may contain a halogen source such as a fluorine source or a chlorine source and By adding a magnesium source and heating at the appropriate temperature and time, a product with fewer defects and sufficient capacity is produced. A positive electrode active material having a pseudo-spinel-type crystal structure in the electrostatic state can be fabricated.

[0016] One aspect of the present invention involves mixing a lithium source, a fluorine source, and a magnesium source to produce a first mixture. A process for manufacturing a material, a composite oxide having lithium, a transition metal, and oxygen, and a first The process involves mixing a mixture and a second mixture to produce a second mixture, and heating the second mixture. This is a method for producing a positive electrode active material.

[0017] Furthermore, in the above, the composite oxide having lithium, a transition metal, and oxygen emits glow-like light. When analyzed by electromass spectrometry, the concentrations of elements other than lithium, transition metals, and oxygen were 500. It is preferable that the concentration is 0 ppm wt or less.

[0018] Furthermore, in the above, the first mixture contains lithium fluoride L as the lithium source and fluorine source. It is preferable to have iF.

[0019] Furthermore, in the above, magnesium fluoride (MgF2) is used as the fluorine source and magnesium source. The molar ratio of lithium fluoride (LiF) to magnesium fluoride (MgF2) is LiF:MgF It is preferable that 2 = x: 1 (0.1 ≤ x ≤ 0.5).

[0020] Furthermore, the second mixture has lithium, a transition metal, and oxygen. The transition metal TM present in the composite oxide and the magnesium Mg present in the first mixture Mix1 M ix1 The atomic ratio is TM:Mg Mix1 =1:y(0.001≦y≦0.01) It is preferable to do so.

[0021] Furthermore, in the above, the heating temperature in the step of heating the second mixture is 600°C or higher and 95°C or higher. It is preferable that the temperature be 0°C or lower.

[0022] Furthermore, in the above, the heating time in the step of heating the second mixture is 2 hours or more. It is preferable that the duration be 60 hours or longer.

[0023] Another aspect of the present invention provides a positive electrode having a positive electrode active material prepared by the above method, and a negative electrode, It is a rechargeable battery. [Effects of the Invention]

[0024] According to one aspect of the present invention, a lithium-ion secondary battery with high capacity and excellent charge-discharge cycle characteristics is provided. This can provide a positive electrode active material and a method for producing the same. Furthermore, it can provide a positive electrode active material with high productivity. We can provide a method for producing the material. Furthermore, by using it in lithium-ion secondary batteries... This provides a positive electrode active material that suppresses capacity degradation during charge-discharge cycles. Furthermore, it is possible to provide high-capacity secondary batteries. Additionally, secondary batteries with excellent charge / discharge characteristics are available. It can be provided. Also, even if the cobalt is kept in a high-voltage charged state for a long time, This provides a positive electrode active material in which the elution of transition metals such as [other metals] is suppressed. Furthermore, it can provide safety or We can provide highly reliable secondary batteries. Furthermore, we can develop novel materials, active material particles, and energy storage devices. We can provide a solution or a method for producing them. [Brief explanation of the drawing]

[0025] [Figure 1] A diagram illustrating an example of a method for producing a positive electrode active material according to one aspect of the present invention. [Figure 2] A diagram illustrating another example of a method for producing a positive electrode active material according to one aspect of the present invention. [Figure 3] A diagram illustrating the charge depth and crystal structure of a positive electrode active material according to one embodiment of the present invention. [Figure 4] A diagram illustrating the charge depth and crystal structure of conventional cathode active materials. [Figure 5] XRD pattern calculated from crystal structure. [Figure 6] A diagram illustrating the crystal structure and magnetism of a positive electrode active material according to one embodiment of the present invention. [Figure 7] A diagram illustrating the crystal structure and magnetism of conventional positive electrode active materials. [Figure 8] Cross-sectional view of the active material layer when a graphene compound is used as a conductive additive. [Figure 9] A diagram illustrating how to charge a rechargeable battery. [Figure 10] A diagram illustrating how to charge a rechargeable battery. [Figure 11]A diagram illustrating the discharge method of a secondary battery. [Figure 12] A diagram illustrating a coin-type rechargeable battery. [Figure 13] A diagram illustrating a cylindrical rechargeable battery. [Figure 14] A diagram illustrating an example of a secondary battery. [Figure 15] A diagram illustrating an example of a secondary battery. [Figure 16] A diagram illustrating an example of a secondary battery. [Figure 17] A diagram illustrating an example of a secondary battery. [Figure 18] A diagram illustrating a laminated rechargeable battery. [Figure 19] A diagram illustrating a laminated rechargeable battery. [Figure 20] A diagram showing the external appearance of a secondary battery. [Figure 21] A diagram showing the external appearance of a secondary battery. [Figure 22] A diagram illustrating the method for manufacturing a secondary battery. [Figure 23] A diagram illustrating a rechargeable battery that can be bent. [Figure 24] A diagram illustrating a rechargeable battery that can be bent. [Figure 25] A diagram illustrating an example of an electronic device. [Figure 26] A diagram illustrating an example of an electronic device. [Figure 27] A diagram illustrating an example of an electronic device. [Figure 28] A diagram illustrating an example of a vehicle. [Figure 29] Graph of particle size distribution of LiF, MgF2, and the first mixture in Example 1. [Figure 30] A graph illustrating the XPS analysis of the positive electrode active material in Example 1, and a diagram illustrating the particles. [Figure 31] Graph of the XPS analysis of the positive electrode active material in Example 1. [Figure 32] SEM image of the positive electrode active material of Example 1. [Figure 33] XRD pattern of the positive electrode active material of Example 1. [Figure 34]XRD pattern of the positive electrode active material of Example 1. [Figure 35] XRD pattern of the positive electrode active material of Example 1. [Figure 36] XRD pattern of the positive electrode active material of Example 1. [Figure 37] XRD pattern of the positive electrode active material of Example 1. [Figure 38] Cycle characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 39] Cycle characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 40] Cycle characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 41] Cycle characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 42] Rate characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 43] Rate characteristics of a secondary battery using the positive electrode active material of Example 1. [Figure 44] Graphs showing the charging capacity and voltage of Sample 1 and Sample 15 in Example 1. [Figure 45] Graphs of dQ / dV vs V for Sample 1 and Sample 15 of Example 1. [Figure 46] Graph of dQ / dV vs V for Sample 1 of Example 1. [Figure 47] Graph of dQ / dV vs V for Sample 1 of Example 1. [Figure 48] Graphs showing the discharge capacity and voltage of Sample 1 and Sample 4 in Example 1. [Figure 49] Graphs of dQ / dV vs V for Sample 1 and Sample 4 of Example 1. [Figure 50] XRD patterns of Sample 21 and Sample 22 from Example 2. [Figure 51] XRD patterns of Sample 21 and Sample 22 from Example 2. [Figure 52] XRD patterns of Sample 23 and Sample 24 from Example 2. [Figure 53] XRD patterns of Sample 25 and Sample 26 from Example 2. [Figure 54] Charge / discharge cycle characteristics. [Figure 55] DSC evaluation results. [Figure 56] XRD pattern. [Figure 57] XRD pattern. [Figure 58] Charge / discharge cycle characteristics. [Modes for carrying out the invention]

[0026] 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.

[0027] 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 {}. To express

[0028] In this specification, segregation refers to the segregation of a solid composed of multiple elements (e.g., A, B, C). This refers to the phenomenon in which a certain element (for example, B) is distributed non-uniformly in space.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] Furthermore, in this specification, etc., the pseudo-spinel type of composite oxide containing lithium and a transition metal The crystal structure is R-3m, and although it is not a spinel-type crystal structure, cobalt, Magnesium and other ions occupy the 6-coordinate position of oxygen, and the arrangement of cations is similar to that of a spinel. This refers to a crystal structure that exhibits symmetry. Note that pseudo-spinel crystal structures are found in light elements such as lithium. It can occupy the oxygen 4-coordinate position, and in this case as well, the ion arrangement is symmetrical, similar to the spinel type. It has a sexual nature.

[0033] Furthermore, the pseudo-spinel type crystal structure has Li randomly placed between the layers, but is a CdCl2 type structure. It can also be said that it is a crystal structure similar to the crystal structure. This is a crystal similar to the CdCl2 type. The structure is such that when lithium nickelate is charged to a charging depth of 0.94 (Li 0.06 NiO 2) A layered rock with a crystal structure similar to that of pure lithium cobaltate, or rich in cobalt. It is known that salt-type cathode active materials do not usually adopt this crystal structure.

[0034] Layered rock salt crystals, and the anions of rock salt crystals, have a cubic close-packed structure (face-centered cubic lattice structure). It takes this form. It is also presumed that in pseudo-spinel crystals, the anions adopt a cubic close-packed structure. When they come into contact, there exists a crystal plane in which the orientation of the cubic close-packed structure composed of anions is aligned. However, the space group of layered rock salt crystals and pseudo-spinel crystals is R-3m, and rock salt crystals The space groups of crystals Fm-3m (the space group of typical rock salt crystals) and Fd-3m (the simplest space group) Because it is different from the space group of rock salt crystals with symmetry, the mirror of the crystal plane that satisfies the above conditions The index differs between layered rock salt crystals, pseudo-spinel crystals, and rock salt crystals. In layered rock salt crystals, pseudo-spinel crystals, and rock salt crystals, the structure is composed of anions. When the orientations of the resulting cubic close-packed structure are aligned, it can be said that the crystal orientations are roughly the same. be.

[0035] 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. .

[0036] 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 274. In mAh / g, the theoretical capacity of LiNiO2 is 274mAh / g, and the theoretical capacity of LiMn2O4 is It is 148mAh / g.

[0037] 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.

[0038] 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. A positive electrode active material with a charge depth of 0.9 or less, more specifically between 0.8 and 0.83, is charged at high voltage. This refers to the electrolyzed positive electrode active material. Therefore, for example, in LiCoO2, 219. If it is charged at 2mAh / g, it is a positive electrode active material that has been charged at a high voltage. In step 2, under a 25°C environment, the charging voltage is set to 4.525V or higher and 4.65V or lower (counter electrode lithium (In the case of M) constant current charging is performed, and then the current value is 0.01C, or the current during constant current charging. The positive electrode active material, after being charged at a constant voltage until the current value is about 1 / 5 to 1 / 100, is also subjected to high voltage. This refers to a charged positive electrode active material.

[0039] 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 21 9.2mAh / g indicates a state of high-voltage charging, and from here, 90% of the charging capacity... The positive electrode active material after discharging to 197.3 mAh / g or more is a sufficiently discharged positive electrode active material. Furthermore, in LiCoO2, the battery voltage is 3V or less in a 25°C environment (counter electrode lithium In the case of M), the positive electrode active material after constant current discharge until it reaches a certain state is also considered to be a sufficiently discharged positive electrode active material. Let's leave it at that.

[0040] Furthermore, in this specification, a non-equilibrium phase change refers to a phenomenon that causes a nonlinear change in a physical quantity. Let's assume that... For example, by differentiating capacitance (Q) with respect to voltage (V) (dQ / dV), we can obtain... Around the peak in the Q / dV curve, a non-equilibrium phase transition occurs, and the crystal structure changes significantly. It is thought that this is the case.

[0041] (Embodiment 1) [Method for preparing positive electrode active material] First, using Figure 1, an example of a method for producing a positive electrode active material 100, which is one aspect of the present invention, will be described. I will explain. Figure 2 also shows another example of a specific manufacturing method.

[0042] <Step S11> As shown in step S11 of Figure 1, first, as materials for the first mixture, a fluorine source and a chlorine source Prepare halogen sources and magnesium sources. It is also preferable to provide a lithium source. It's nice.

[0043] For example, lithium fluoride, magnesium fluoride, etc., can be used as fluorine sources. In particular, lithium fluoride has a relatively low melting point of 848°C and can be dissolved in the annealing process described later. It is preferable because it melts easily. As a chlorine source, for example, lithium chloride, magnesium chloride, etc. It can be used. Examples of magnesium sources include magnesium fluoride and magnesium oxide. Lithium, magnesium hydroxide, magnesium carbonate, etc. can be used as a lithium source. For example, lithium fluoride and lithium carbonate can be used. Tium can be used as both a lithium source and a fluorine source. Um can be used as both a fluorine source and a magnesium source.

[0044] In this embodiment, lithium fluoride (LiF) is prepared as the fluorine source and lithium source, We will prepare magnesium fluoride (MgF2) as the source of fluorine and magnesium. Step S11 in Figure 2). Lithium fluoride (LiF) and magnesium fluoride (MgF2) are Li Mixing F:MgF2 in a molar ratio of approximately 65:35 yields the greatest effect in lowering the melting point. (Non-patent document 4). On the other hand, if the amount of lithium fluoride increases, the lithium becomes excessive. There are concerns that the characteristics will deteriorate. Therefore, lithium fluoride (LiF) and magnesium fluoride The molar ratio of MgF2 is preferably LiF:MgF2=x:1 (0≦x≦1.9). LiF:MgF2=x:1 (0.1≦x≦0.5) is more preferable. 2=x:1 (neighborhood of x=0.33) is even more preferable. In this specification, neighborhood means The value should be greater than 0.9 times that value and less than 1.1 times that value.

[0045] Furthermore, if the following mixing and grinding steps are to be performed wet, a solvent will be prepared. The solvent will be 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 step S11 in Figure 2).

[0046] <Step S12> Next, the materials of the first mixture described above are mixed and ground (step S1 in Figures 1 and 2). 2) Mixing can be done dry or wet, but wet mixing allows for finer grinding. This is preferable for mixing. For mixing, for example, a ball mill, bead mill, etc. can be used. When using a quartz mill, it is preferable to use zirconia balls as the media, for example. It is preferable to carry out this mixing and grinding process thoroughly to finely pulverize the first mixture.

[0047] <Step S13, Step S14> The mixed and ground materials described above are collected (step S13 in Figures 1 and 2), and the first mixture This is obtained (step S14 in Figures 1 and 2).

[0048] The first mixture, for example, has an average particle size (D50: also called median diameter) of 600 nm or less. It is preferable that the particle size is 20 μm or less, and more preferably 1 μm or more and 10 μm or less. i. If the first mixture is pulverized in this way, then lithium, transition metals and When mixed with an oxygen-containing composite oxide, the first mixture is evenly distributed on the surface of the composite oxide particles. It is easy to adhere to the first. When the first mixture is uniformly attached to the surface of the composite oxide particles, This makes it easier to distribute halogens and magnesium evenly across the surface layer of composite oxide particles after heating. It is preferable to sauté. If there is an area on the surface that does not contain halogen and magnesium, charging In this state, it may become difficult to form the pseudo-spinel crystal structure described later.

[0049] <Step S21> Next, as shown in step S21 of Figure 1, a composite having lithium, a transition metal and oxygen A lithium source and a transition metal source are prepared as materials for the oxide.

[0050] For example, lithium carbonate, lithium fluoride, etc., can be used as lithium sources.

[0051] As the transition metal, at least one of cobalt, manganese, and nickel can be used. Composite oxides containing lithium, transition metals, and oxygen have a layered rock salt-type crystalline structure. Therefore, the mixing ratio of cobalt, manganese, and nickel that can take the form of layered rock salt is preferable. It is preferable that these transition metals be used within the range in which they can take on a layered rock salt type crystal structure. Luminium may be added.

[0052] 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 oxide, aluminum hydroxide, etc., can be used.

[0053] <Step S22> Next, the lithium source and transition metal source are mixed (step S22 in Figure 1). This can be done dry or wet. For mixing, for example, a ball mill or bead mill can be used. This is possible. When using a ball mill, for example, zirconia balls can be used as the media. It is preferable that they be present.

[0054] <Step S23> Next, the mixture of materials described above is heated. This step is called a baking step to distinguish it from the subsequent heating step. Alternatively, this may be referred to as the first heating stage. Heating is preferably carried out at a temperature between 800°C and 1100°C. It is preferable to perform the process at a temperature between 900°C and 1000°C, and even more preferable at around 950°C. This is preferable. If the temperature is too low, the decomposition and melting of the starting material may be insufficient. On the other hand, if the temperature is too high, the transition metals may be excessively reduced, lithium may evaporate, etc. Defects may occur. For example, a defect in which cobalt becomes divalent may occur.

[0055] The heating time is preferably between 2 hours and 20 hours. The firing process involves using dry air or other moisture-free materials. This can be done in a low-temperature environment (for example, with a dew point of -50°C or lower, more preferably -100°C or lower). Preferably, heating at 1000°C for 10 hours, with a heating rate of 200°C / h and a dry atmosphere. The ambient airflow rate is preferably 10 L / min. After that, the heated material is cooled to room temperature. It is possible to do so. For example, the cooling time from a specified temperature to room temperature can be between 10 hours and 50 hours. It is preferable to do so.

[0056] However, cooling to room temperature in step S23 is not mandatory. 4. If there are no problems in performing steps S25 and steps S31 to S34 If necessary, cooling may be limited to a temperature higher than room temperature.

[0057] <Step S24, Step S25> The calcined material is recovered (step S24 in Figure 1), and lithium, transition metals and oxygen A composite oxide having the above is obtained (step S25 in Figure 1). Specifically, lithium cobaltate. Lithium manganese, lithium nickelate, and cobalt in which part of the cobalt is replaced by manganese. Lithium baltate or lithium nickel-manganese-cobaltate is obtained.

[0058] Furthermore, step S25 includes pre-synthesized lithium, transition metals, and oxygen. A composite oxide may also be used (see Figure 2). In this case, steps S21 to S2 The number 4 can be omitted.

[0059] When using a pre-synthesized composite oxide containing lithium, a transition metal, and oxygen, It is preferable to use materials with few impurities. In this specification, lithium, transition metals and For complex oxides containing oxygen and positive electrode active materials, the main components are lithium, cobalt, and nickel. The main components are oxal, manganese, aluminum, and oxygen, with elements other than those listed above being considered impurities. For example, when analyzed by glow discharge mass spectrometry, the total impurity concentration was 10,000 pp. It is preferable that the m wt is less than or equal to 5000 ppm wt, and more preferably less than or equal to 5000 ppm wt. In particular, The combined impurity concentration of titanium and transition metals such as arsenic is 3000 ppm wt or less. It is preferable that the concentration be 1500 ppm wt or less.

[0060] For example, as pre-synthesized lithium cobalt oxide, a cobalt oxide manufactured by Nippon Chemical Industrial Co., Ltd. Lithium baltate particles (product name: Cellseed C-10N) can be used. The average particle size (D50) is approximately 12 μm, and the results were obtained by glow discharge mass spectrometry (GD-MS). In impurity analysis, magnesium and fluorine concentrations were 50 ppm wt or less. Cium, aluminum, and silicon concentrations are 100 ppm wt or less, nickel The concentration is 150 ppm wt or less, the sulfur concentration is 500 ppm wt or less, and the arsenic concentration is 110 0 ppm wt or less, and the concentration of other elements other than lithium, cobalt, and oxygen is 150 ppm. This is lithium cobalt oxide with a weight of less than or equal to pm wt.

[0061] Alternatively, lithium cobalt oxide particles manufactured by Nippon Chemical Industrial Co., Ltd. (product name: Cellseed C-5) H) can also be used. This has an average particle size (D50) of approximately 6.5 μm, and GD- In impurity analysis by MS, the concentrations of elements other than lithium, cobalt, and oxygen were C-1 This is lithium cobalt oxide, which is equivalent to or less than 0N.

[0062] In this embodiment, cobalt is used as the transition metal, and pre-synthesized cobalt oxide is used. We will use thium particles (Cellseed C-10N manufactured by Nippon Chemical Industrial Co., Ltd.) (Figure 2) reference).

[0063] The composite oxide having lithium, transition metal and oxygen in step S25 has defects and strains. It is preferable to have a layered rock salt type crystalline structure with few impurities. It is preferable that it be an oxide. A composite oxide having lithium, a transition metal and oxygen is preferable to an impurity. When a material contains many substances, it is highly likely to result in a crystal structure with many defects or strains.

[0064] <Step S31> Next, the first mixture is mixed with a composite oxide having lithium, a transition metal, and oxygen. (Step S31 in Figures 1 and 2). A composite acid having lithium, a transition metal, and oxygen. The transition metal TM in the compound and the magnesium Mg present in the first mixture Mix1 Mix1 The original The ratio of offspring is TM:Mg Mix1 It is preferable that =1:y(0.0005≦y≦0.03) Mashiku, TM:Mg Mix1 It is preferable that =1:y(0.001≦y≦0.01) Mashiku, TM:Mg Mix1 A ratio of approximately 1:0.005 is even more preferable.

[0065] The mixing in step S31 is performed in a way that does not destroy the composite oxide particles, similar to the mixing in step S12. It is preferable to use milder conditions. For example, the rotation speed may be higher than that of the mixing in step S12. It is preferable to use conditions with fewer or shorter durations. Also, dry processes are gentler than wet processes. It can be said that these are reasonable conditions. For mixing, for example, a ball mill or bead mill can be used. When using a ball mill, for example, zirconia balls can be used as the media. preferable.

[0066] <Step S32, Step S33> The materials mixed above are collected (step S32 in Figures 1 and 2) to obtain a second mixture. (Step S33 in Figures 1 and 2).

[0067] 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 this. Instead of the second mixture in step S33, lithium cobalt oxide starting material A material may be used that has been calcined with a magnesium source and a fluorine source added to it. , the process of steps S11 to S14 and the process of steps S21 to S25 Because there is no need to divide it into sections, it is simple and highly productive.

[0068] Alternatively, using lithium cobalt oxide to which magnesium and fluorine have been pre-added. This is also fine. If lithium cobalt oxide with added magnesium and fluorine is used, step Steps up to S32 can be omitted, making the process simpler.

[0069] Furthermore, lithium cobalt oxide, which has magnesium and fluorine added to it beforehand, A magnesium source and a fluorine source may be added to it.

[0070] <Step S34> Next, the second mixture is heated. This step is distinguished from the previous heating step by annealing. In some cases, this is referred to as a second heating process.

[0071] Annealing is preferably carried out at the appropriate temperature and time. The appropriate temperature and time are The particle size of composite oxides having lithium, transition metals and oxygen in TEP S25 and It varies depending on conditions such as composition. Smaller particles require a lower temperature or shorter duration than larger particles. There are times when a shorter time is preferable.

[0072] For example, if the average particle size (D50) of the particles in step S25 is about 12 μm, the annealing temperature The temperature is preferably between 600°C and 950°C. The annealing time is preferably 3 hours or more. More preferably 10 hours or more, and even more preferably 60 hours or more.

[0073] On the other hand, if the average particle size (D50) of the particles in step S25 is about 5 μm, the annealing temperature For example, a temperature of 600°C to 950°C is preferred. The annealing time is, for example, 1 hour to 10 hours. Less than two hours is preferable, and about two hours is more preferable.

[0074] The cooling time after annealing is preferably, for example, 10 hours or more and 50 hours or less.

[0075] When the second mixture is annealed, first the material with the lower melting point from the first mixture (e.g., fluoride) It is thought that lithium (melting point 848°C) melts and is distributed on the surface of the composite oxide particles. Next, the presence of this molten material causes a decrease in the melting point of other materials, which in turn causes the other materials to melt. It is presumed that, for example, magnesium fluoride (melting point 1263°C) melts and complex oxide particles form. It is thought to be distributed in the surface layer of the egg.

[0076] 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.

[0077] The elemental diffusion in this first mixture is more pronounced in the surface and grain layers than in the interior of the composite oxide particles. The rate is faster near the boundary. Therefore, magnesium and halogens are more efficient in the surface layer and near the grain boundaries. As described later, the magnesium concentration in the surface layer and near the grain boundaries is higher than in the interior. Higher levels can more effectively suppress changes in crystal structure.

[0078] <Step S35> The annealed material described above is recovered to obtain a positive electrode active material 100, which is one embodiment of the present invention.

[0079] When fabricated using the methods shown in Figures 1 and 2, pseudospeakers with fewer defects are produced when charged at high voltage. It is possible to fabricate a cathode active material that adopts a Nell-type crystal structure. When Rietveld analysis is performed, it is a pseudo-spinel type. A cathode active material with a crystalline structure of 50% or more exhibits excellent cycle characteristics and rate characteristics. It is the active material.

[0080] To produce a positive electrode active material having a pseudo-spinel crystal structure after high-voltage charging, the positive electrode active material is It contains magnesium and fluorine, and is made by annealing at an appropriate temperature and time. It is effective to manufacture them. Magnesium and fluorine sources are added to the starting material of the composite oxide. It may be added. However, when added to the starting material of a composite oxide, the magnesium source and f If the melting point of the fluorine source is higher than the firing temperature, the magnesium and fluorine sources will not melt, and diffusion will occur. This may result in insufficient growth. This would lead to many defects or strains in the layered rock salt crystal structure. It is highly likely that defects or There is a risk of distortion occurring.

[0081] 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 fluorine source is mixed and annealed to deposit magnesium and fluorine on the surface layer of the composite oxide. It is preferable to use solid solution. By manufacturing in this manner, defects and This allows for the fabrication of a positive electrode active material that adopts a pseudo-spinel structure with minimal strain.

[0082] Furthermore, the positive electrode active material 100 produced in the above process is further coated with other materials. This is also acceptable. Furthermore, further heating may be performed.

[0083] For example, the positive electrode active material 100 can be mixed with a compound containing phosphoric acid. The mixture can be heated after mixing. By mixing a compound containing phosphoric acid, high voltage can be used. Even when kept charged for a long period of time, the leaching of transition metals such as cobalt is suppressed in the positive electrode activity. It can be made into substance 100. Also, by heating after mixing, the phosphoric acid can be coated more uniformly. It can be overturned.

[0084] Examples of compounds containing phosphoric acid include lithium phosphate and ammonium dihydrogen phosphate. It can be done. Mixing can be done, for example, by a solid-phase method. Heating can be done, for example, at 800°C. This can be done in 2 hours.

[0085] [Structure of the positive electrode active material] Next, using Figures 3 and 4, we will show a positive electrode, which is one embodiment of the present invention that can be manufactured by the method described above. This section describes the active material 100 and conventional positive electrode active materials, and explains the differences between them. (Figure 3) Figure 4 describes the case where cobalt is used as the transition metal in the positive electrode active material. Furthermore, the conventional positive electrode active material described in Figure 4 contains elements other than lithium, cobalt, and oxygen. Simple cobalt that has not been processed by adding to the part or coating the surface. It is lithium trioxide (LiCoO2).

[0086] <Conventional positive electrode active material> Lithium cobalt oxide (LiCoO2), a conventional positive electrode active material, is mentioned in Non-Patent Document 1 and Non-Patent Document 1. As described in reference 2, the crystal structure changes depending on the depth of charge. A typical crystal structure of thium is shown in Figure 4.

[0087] As shown in Figure 4, lithium cobalt oxide at charge depth 0 (discharge state) is in space group R-3 It has a region with a crystalline structure of m, and there are three CoO2 layers in the unit cell. This crystal structure is sometimes called an O3 type crystal structure. Note that the CoO2 layer is cobalt. This refers to a structure in which an octahedron structure, in which oxygen atoms are coordinated in six positions, is continuous on a plane through the sharing of edges.

[0088] Furthermore, when the charging depth is 1, it has a crystal structure of space group P-3m1, and the unit cell contains CoO Two layers are present, but only one layer exists. Therefore, this crystal structure is sometimes called an O1 type crystal structure.

[0089] 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 It can also be described as a structure in which the LiCoO2 structure, like the one shown above, is alternately stacked. The crystal structure is sometimes called the H1-3 type crystal structure. However, in reality, the H1-3 type crystal structure is The number of cobalt atoms per unit cell is twice that of other structures. However, see Figure 4. Initially, in this specification, to facilitate comparison with other structures, the c-axis of the H1-3 type crystal structure is considered unified. This will be shown using a diagram that is half the size of a net cell.

[0090] 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).

[0091] However, these two crystal structures have a large displacement of the CoO2 layer. (See dotted line in Figure 4) 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] <Positive electrode active material according to one aspect of the present invention> ≪Inside≫ In contrast, in one aspect of the present invention, the positive electrode active material 100 is in a fully discharged state and a high voltage The changes in crystal structure and the values ​​per equal number of transition metal atoms were compared in the charged state. The difference in volume between the two cases is small.

[0096] Figure 3 shows the crystal structure of the positive electrode active material 100 before and after charging and discharging. The positive electrode active material 100 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.

[0097] The crystal structure of the charge depth 0 (discharge state) in Figure 3 is R-3m(O3), the same as in Figure 4. In one embodiment of the present invention, the positive electrode active material 100 is fully charged to a charge depth of approximately 0.88. It has a crystal structure different from that shown in Figure 4. The crystal structure of this space group R-3m is described in this specification, etc. This will be referred to as a pseudo-spinel crystal structure. The pseudo-spinel crystal structure shown in Figure 3 is... In the diagram, to explain the symmetry of the cobalt atom and the oxygen atom, lithium Although the "mu" is omitted from the display, in reality, there is about 12 atomic percent of cobalt between the CoO2 layers. Lithium is present. Also, in both the O3 type crystal structure and the pseudo-spinel type crystal structure. It is preferable that a dilute amount of magnesium be present between the CoO2 layers, i.e., at the lithium sites. Furthermore, halogens such as fluorine are present randomly and dilutely at the oxygen site. preferable.

[0098] In the positive electrode active material 100, 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 3, In these crystal structures, there is almost no displacement of the CoO2 layer.

[0099] Furthermore, the positive electrode active material 100 has an O3-type crystal structure with a charging depth of 0 and a pseudo-slide with a charging depth of 0.88. The volume difference per unit cell in the Pinel-type crystal structure is less than 2.5%, or more specifically, 2.2%. It is less than %.

[0100] Therefore, even if high voltage charge and discharge are repeated, the crystal structure is difficult to collapse.

[0101] The pseudo-spinel type crystal structure can be represented by the coordinates of cobalt and oxygen in the unit cell, Co(0 ,0,0.5), O(0,0,x), within the range of 0.20 ≦ x ≦ 0.25 .

[0102] Magnesium, which is randomly and thinly present in the CoO2 layer, that is, the lithium site, has the effect of suppressing the shift of the CoO2 layer. Therefore, when magnesium is present between the CoO2 layers , it is likely to form a pseudo-spinel type crystal structure. Therefore, it is preferable that magnesium is distributed throughout the particles of the positive electrode active material 100. Also, in order to distribute magnesium throughout the particles , it is preferable to perform heat treatment in the manufacturing process of the positive electrode active material 100. However, if the temperature of the heat treatment is too high, cation mixing may occur and magnesium is likely to enter the cobalt site. When magnesium is present in the cobalt site,

[0103] the effect of maintaining the R-3m structure is lost. Furthermore, if the temperature of the heat treatment is too high, there are also concerns about adverse effects such as cobalt being reduced to divalent and lithium evaporating. Therefore, it is preferable to add a halogen compound such as a fluorine compound to lithium cobaltate before the heat treatment for distributing magnesium throughout the particles. By adding the halogen compound , the melting point of lithium cobaltate drops. By lowering the melting point, it becomes easier to distribute magnesium throughout the particles at a temperature where cation mixing is less likely to occur.

[0104] Therefore, it is preferable to add a halogen compound such as a fluorine compound to lithium cobaltate before the heat treatment for distributing magnesium throughout the particles. By adding the halogen compound , the melting point of lithium cobaltate drops. By lowering the melting point, it becomes easier to distribute magnesium throughout the particles at a temperature where cation mixing is less likely to occur. mixing is less likely to occur. Furthermore, if fluorine compounds are present, the corrosion resistance to hydrofluoric acid produced by the decomposition of the electrolyte will be improved. Improvement can be expected.

[0105] Furthermore, the positive electrode active material 100 has been a composite oxide having lithium, cobalt, and oxygen. While I have described the case where it is a material, it may also contain nickel in addition to cobalt. In this case, the number of nickel atoms in the sum of the number of cobalt and nickel atoms (Co+Ni) The ratio of Ni (Ni / (Co+Ni)) is preferably less than 0.1, and preferably 0.075 or less. It is preferable to be lower.

[0106] If a high-voltage charge is maintained for a long period of time, transition metals will dissolve from the positive electrode active material into the electrolyte. There is a risk that the crystal structure will collapse. However, by having nickel in the above proportion, the positive electrode active material In some cases, it may be possible to suppress the leaching of transition metals from quality 100.

[0107] Adding nickel lowers the charge and discharge voltage, so for the same capacity, the voltage is lowered. Because this can be achieved, it may be possible to suppress the elution of transition metals and the decomposition of the electrolyte. In this context, charge / discharge voltage refers to, for example, the voltage within the range from zero charge depth to a predetermined charge depth.

[0108] ≪Surface layer≫ It is preferable that magnesium is distributed throughout the particles of the positive electrode active material 100, but in addition 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. In other words, the magnesium concentration in the particle surface layer, measured by XPS, etc., is measured by ICP-MS, etc. It is more preferable that the magnesium concentration is higher than the average magnesium concentration of the entire particle. If it hums, it's all a crystal defect, and during charging, lithium leaks out from the surface, so the inside... This is a part where the lithium concentration tends to be low. Therefore, it is a part that tends to be unstable and whose crystal structure is liable to collapse. If the magnesium concentration in the surface layer is high, the change in the crystal structure can be more effectively suppressed. Also, if the magnesium concentration in the surface layer is high, it can be expected that the corrosion resistance against hydrofluoric acid generated by the decomposition of the electrolyte will be improved.

[0109] Also, for halogens such as fluorine, it is preferable that the concentration in the surface layer of the positive electrode active material 100 is higher than the average of the whole particle. The presence of halogen in the surface layer, which is the region in contact with the electrolyte, can effectively improve the corrosion resistance against hydrofluoric acid.

[0110] Thus, it is preferable that the surface layer of the positive electrode active material 100 has a different composition with higher concentrations of magnesium and fluorine than the inside. Also, as the composition, it is preferable to have a crystal structure that is stable at room temperature. Therefore, the surface layer may have a different crystal structure from the inside and. For example, at least a part of the surface layer of the positive electrode active material 100 may have a rock-salt-type crystal structure . Also, when the surface layer and the inside have different crystal structures, it is preferable that the orientations of the crystals in the surface layer and the inside are substantially the same.

[0111] However, if the surface layer is only MgO or only a structure in which MgO and CoO(II) are solid-solved, the insertion and extraction of lithium will become difficult. Therefore, the surface layer must have at least cobalt and also have lithium in the discharged state and have a path for the insertion and extraction of lithium. Also, it is preferable that the concentration of cobalt is higher than that of magnesium.

[0112] ≪Grain boundary≫ ​​​​The magnesium or halogen contained in the positive electrode active material 100 is present randomly and dilutely within it. While this is acceptable, it is more preferable that some of the segregation occurs at the grain boundaries.

[0113] In other words, the magnesium concentration at and near the grain boundaries of the positive electrode active material 100 is also within the interior. It is preferable that the halogen concentration in the grain boundaries and their vicinity is higher than in other regions. It is preferable that the region is higher than other regions.

[0114] 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.

[0115] 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 with quality 100, the surface created by the crack... 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.

[0116] 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.

[0117] ≪Particle size≫ The particle size of the positive electrode active material 100 is important; if it is too large, lithium diffusion becomes difficult, and it is coated onto the current collector. When this happens, there are problems such as the surface of the active material layer becoming too rough. On the other hand, if it is too small, current collection... Problems include difficulty in supporting the active material layer during coating onto the body, and excessive reaction with the electrolyte. Therefore, D50 is preferably 1 μm to 100 μm, and 2 μm to 40 μm. It is more preferable that the particle size is less than or equal to m, and even more preferable that it is between 5 μm and 30 μm.

[0118] <Analysis method> One embodiment of the present invention in which a positive electrode active material exhibits a pseudo-spinel crystal structure when charged at a high voltage. Whether or not it is positive electrode active material 100 is determined by XRD, electron diffraction, and the positive electrode charged with high voltage. Analysis is performed using neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. This can be determined by the following. In particular, XRD enhances the symmetry of transition metals such as cobalt in the positive electrode active material. It can analyze with high resolution, compare the crystallinity and crystal orientation, and analyze the periodic strain of the lattice. Furthermore, even if the positive electrode obtained by disassembling a secondary battery is measured directly, it is possible to analyze the crystallite size. It is preferable in that it can achieve sufficient accuracy, among other things.

[0119] The positive electrode active material 100 in one aspect of the present invention is charged with a high voltage and discharged as described above. A key feature is that the crystal structure changes little depending on the state. When charged at high voltage, the discharge state... Materials in which 50 wt% or more of the crystalline structure exhibits significant changes from its state can withstand high-voltage charging and discharging. This is undesirable because it does not result in the desired crystal structure. Furthermore, simply adding impurity elements does not guarantee the formation of the desired crystal structure. It is important to note that there are cases where this is not the case. For example, cobalt containing magnesium and fluorine Although they share the common characteristic of being lithium trioxide, when charged at high voltage, they exhibit a pseudo-spinel crystal structure. When the structure accounts for 60 wt% or more, and when the H1-3 type crystal structure accounts for 50 wt% or more. , and at a given voltage, the pseudo-spinel crystal structure becomes approximately 100 wt%, and further When the predetermined voltage is increased, an H1-3 type crystal structure may be formed. Therefore, the present invention To determine whether or not a positive electrode active material 100 is one aspect of a particular material, the crystal structure, including XRD, is used. An analysis of the structure is necessary.

[0120] However, when the positive electrode active material is in a high-voltage charged or discharged state, its crystalline structure changes when exposed to air. This can sometimes cause changes. For example, a change from a pseudo-spinel type crystal structure to an H1-3 type crystal structure. This can sometimes happen. Therefore, all samples should be handled in an inert atmosphere such as an argon atmosphere. It is preferable to ring it.

[0121] ≪Charging method≫ A high level of precision for determining whether a certain composite oxide is a positive electrode active material 100 according to one aspect of the present invention. Voltage charging is, for example, a coin cell (CR2032 type, 20mm diameter, height) with a lithium counter electrode. It can be made (3.2mm) and charged.

[0122] More specifically, the positive electrode is made of a slurry containing a positive electrode active material, a conductive additive, and a binder. Alternatively, a positive electrode current collector made of aluminum foil coated with aluminum foil can be used.

[0123] Lithium metal can be used as the counter electrode. However, if a material other than lithium metal is used as the counter electrode... When this happens, the potential of the secondary battery and the potential of the positive electrode are different. The voltage and potential in this specification are Unless otherwise specified, this is the potential of the positive electrode.

[0124] The electrolyte in the electrolyte solution is 1 mol / L lithium hexafluoride phosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), with vinylene carbonate (VC) mixed in at 2 wt%. It is possible to use things.

[0125] Polypropylene with a thickness of 25 μm can be used for the separator.

[0126] For the positive electrode can and the negative electrode can, those made of stainless steel (SUS) can be used. .

[0127] The coin cell prepared under the above conditions is charged at a constant current of 4.6 V and 0.5 C, and then charged at a constant voltage until the current value becomes 0.01 C. Here, 1 C is taken as 137 mA / g. The temperature is 25°C. After charging in this way, if the coin cell is disassembled in a glove box under an argon atmosphere to take out the positive electrode, a positive electrode active material charged at a high voltage can be obtained. After that, when performing various analyses, in order to suppress the reaction with external components, it is preferable to seal it in an argon atmosphere. For example, XRD can be performed by enclosing it in a sealed container under an argon atmosphere. .

[0128] ≪XRD≫ The ideal powder XRD patterns calculated from the models of the pseudo-spinel crystal structure and the H1-3 crystal structure for CuKα1 line are shown in Fig. 5. For comparison, the ideal XRD patterns calculated from the crystal structures of LiCoO 2(O3) with a charge depth of 0 and CoO2(O1) with a charge depth of 1 are also shown. The patterns of LiCoO2(O3) and CoO2(O1) are from the crystal structure information obtained from the Inorganic Crystal Structure Database (ICSD) (see Non-Patent Document 5) and created using the Reflex Powder Diffraction, which is one of the modules of Materials Studio (BIOVIA). The range of 2θ is from 15° to 75°, Step size = 0.01, wavelength λ1 = 1.540562×10 m, λ2 has no setting, Mono -10 . ​The chromator was set to single. The pattern of the H1-3 type crystal structure is from non-patent literature. It was similarly prepared from the crystal structure information described in 3. The pseudo-spinel pattern is one aspect of the present invention. The crystal structure was estimated from the XRD pattern of the positive electrode active material, and TOPAS ver.3 (Bruk The crystal structure was fitted using ER Corporation's crystal structure analysis software, and the XRD pattern was analyzed as before. I created a line.

[0129] As shown in Figure 5, in the pseudo-spinel crystal structure, 2θ = 19.30 ± 0.20° (19. (10° to 19.50°), and 2θ = 45.55 ± 0.10° (45.45° or less) Diffraction peaks appear above 45.65°. More specifically, 2θ = 19.30 ±0.10° (between 19.20° and 19.40°), and 2θ = 45.55 ± 0.0 A sharp diffraction peak appears at 5° (between 45.50° and 45.60°). However, H1-3 In the type crystal structure and CoO2(P-3m1,O1), peaks do not appear at these positions. Therefore, when charged at high voltage, 2θ = 19.30 ± 0.20° and 2θ = 4 The appearance of a peak of 5.55±0.10° indicates that the positive electrode active material 100 of one embodiment of the present invention It can be said to be a characteristic feature.

[0130] 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.

[0131] Furthermore, in one embodiment of the present invention, the positive electrode active material 100, when charged with high voltage, exhibits a pseudo-spinel type crystal structure. Although it has a structure, not all particles have to have a pseudo-spinel type crystal structure. It may contain some amorphous material, or part of it may be amorphous. However, regarding the XRD pattern, When performing vertex analysis, it is preferable that the pseudo-spinel crystal structure accounts for 50 wt% or more. It is more preferable that it be 60 wt% or more, and even more preferable that it be 66 wt% or more. It is desirable that the pseudo-spinel crystal structure be 50 wt% or more, more preferably 60 wt% or more, Preferably, if the amount is 66 wt% or more, it will be a positive electrode active material with sufficiently excellent cycle characteristics. It is possible.

[0132] Furthermore, even after more than 100 charge-discharge cycles from the start of measurement, Rietveld analysis was performed. Preferably, the pseudo-spinel crystal structure is 35 wt% or more, and 40 wt% or more. It is more preferable that the amount be 43 wt% or more, and even more preferable that it be 43 wt% or more.

[0133] Furthermore, the crystallite size of the pseudo-spinel structure possessed by the particles of the positive electrode active material is the same as that of LiCo in the discharged state. It only drops to about 1 / 10th of O2(O3). Therefore, it has the same XR as the positive electrode before charging and discharging. Even under measurement conditions D, a clear peak of a pseudo-spinel crystal structure was observed after high-voltage charging. On the other hand, in simple LiCoO2, some parts could adopt a structure similar to a pseudo-spinel crystal structure. Even so, the crystallite size becomes smaller, and the peaks become broader and smaller. This can be calculated from the full width at half maximum of the XRD peak.

[0134] 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 fluorine source and a magnesium source is inserted into the lithium position, a good solution is obtained. It is believed that this method can be used to create positive electrode active materials that exhibit cyclic properties.

[0135] The lattice constant of the c-axis in the crystal structure of the positive electrode active material in the discharge state is 14.060 before annealing. ×10 -10 m or less is preferred, 14.055 × 10 -10 m or less is more preferable, 14 .051×10 -10 A value of m or less is even more preferable. The lattice constant of the c-axis after annealing is 14. 060×10 -10 m or less is preferable.

[0136] 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 is 0 ppm wt or less, and more preferably 1500 ppm wt or less. It is preferable. Also, cation mixing of lithium with cobalt, manganese, and nickel is minimal. It is preferable to do so.

[0137] 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 an average particle size (D50) of about 1 μm to 100 μm, the internal and relative In comparison, the volume of the surface layer is very small, so the surface layer of the positive electrode active material 100 is different from the interior. Even if a crystal structure exists, it is highly likely that it will not be reflected in the XRD pattern.

[0138] ≪ESR≫ Here, using Figures 6 and 7, we will illustrate the differences between the pseudo-spinel crystal structure and other crystal structures. We will now explain how to make a determination using ESR. In the pseudo-spinel type crystal structure, see Figure 3 and As shown in Figure 6(A), cobalt is present at the oxygen 6-coordinate site. Figure 6(B) Thus, in oxygen-6 coordinated cobalt, the 3d orbital is e g orbit and t 2g The orbit splits, and oxygen remains t is a trajectory that avoids the direction in which it is located. 2g It has low orbital energy. It is located at the oxygen 6-coordinate site. Some of the cobalt that does this is t 2g Diamagnetic Co with all orbits filled 3+ It is cobalt. However, some of the cobalt present at the oxygen 6-coordinate site is paramagnetic Co 2+ or Co 4 + It may also be cobalt. This paramagnetic cobalt is Co 2+ and Co 4+ In either place Although the ESR cannot distinguish between the two because they both have one unpaired electron, the valence of the surrounding elements determines their distinguishing properties. Either valency is acceptable.

[0139] On the other hand, conventional positive electrode active materials are spinel-type materials that do not contain lithium in the surface layer when charged. Some sources state that it may have the following crystal structure. In this case, the spine shown in Figure 7(A) It will have a Co3O4 crystal structure, which is of the r-type crystal structure.

[0140] When spinel is represented by the general formula A[B2]O4, element A is oxygen in 4-coordinate state, and element B is oxygen in 6-coordinate state. This results in coordination. Therefore, in this specification, sites with 4 oxygen coordination are referred to as sites A, and sites with 6 oxygen coordination are referred to as sites A. Site B is sometimes referred to as Site T.

[0141] In Co3O4 with a spinel-type crystal structure, not only the B site with 6 oxygen coordinates, but also the 4 oxygen coordinates... Cobalt is also present at site A. As shown in Figure 7(B), in oxygen 4-coordinate cobalt Split e g orbit and t 2g Of the orbits, e g The orbital energy is low. Therefore, oxygen is supplied in four parts. 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.

[0142] However, in one embodiment of the present invention, the positive electrode active material 100 is made of oxygen-4 coordinated paramagnetic cobalt. The resulting peaks are so few that they cannot be observed. Therefore, the pseudo-spinels referred to in this specification are not true Unlike spinel, it does not contain oxygen-four coordinated cobalt in amounts detectable by ESR. Therefore, compared to conventional examples, the positive electrode active material of one aspect of the present invention has a speed that can be detected by ESR, etc. In some cases, the peaks originating from Nell-type CO3O4 may be small or too small to be detected. Since spinel-type Co3O4 does not contribute to the charge-discharge reaction, the less spinel-type Co3O4 there is, the better. This is preferable. Thus, as can be seen from the ESR analysis, the positive electrode active material 100 is different from conventional examples. It can be determined that...

[0143] ≪XPS≫ X-ray photoelectron spectroscopy (XPS) can analyze depths of approximately 2 to 8 nm (usually around 5 nm) from the surface. Because analysis of the region is possible, the concentration of each element can be quantified in approximately half of the surface region. It can be analyzed precisely. Furthermore, narrow-scan analysis can analyze the bonding state of elements. This is possible. Note that the quantitative accuracy of XPS is often around ±1 atomic percent, and the detection limit is limited to the element. It varies, but it is approximately 1 atomic percent.

[0144] When XPS analysis was performed on positive electrode active material 100, 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.

[0145] Furthermore, when the positive electrode active material 100 was analyzed using XPS, the bond 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 to a certain degree. This is because the binding energy of lithium fluoride is 68. It is different from both 5 eV and the bond energy of magnesium fluoride, which is 686 eV. This is the value. In other words, if the positive electrode active material 100 contains fluorine, lithium fluoride and fluorine It is preferable that the bond is something other than magnesium oxide.

[0146] Furthermore, when XPS analysis was performed on the positive electrode active material 100, 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 the energy is around 1303 eV. This is because the binding energy of magnesium fluoride This value is different from the energy of 1305 eV and is close to the bond energy of magnesium oxide. This is the value. In other words, if the positive electrode active material 100 contains magnesium, then magnesium fluoride Other types of bonding are preferred.

[0147] ≪EDX≫ EDX measurement is a method of measuring while scanning within a region and evaluating that region in two dimensions. This is sometimes called X-plane analysis. Furthermore, data from linear regions is extracted from EDX plane analysis, and the original The process of evaluating the distribution of particle concentration within the positive electrode active material particles is sometimes called linear analysis.

[0148] EDX surface analysis (e.g., elemental mapping) reveals the interior, surface, and vicinity of grain boundaries. Furthermore, the concentrations of magnesium and fluorine can be quantitatively analyzed. The analysis allows for the identification of peaks in magnesium and fluorine concentrations.

[0149] When EDX radiation analysis was performed on positive electrode active material 100, the magnesium concentration peak in the surface layer was observed. It is preferable that it exists within a depth of 3 nm from the surface toward the center of the positive electrode active material 100. 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.

[0150] Furthermore, it is preferable that the distribution of fluorine in the positive electrode active material 100 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 towards the center to a depth of 3 nm, 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.

[0151] Furthermore, when line analysis or surface analysis was performed on the positive electrode active material 100, 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.

[0152] ≪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 a low voltage of, for example, 0.2C or less. When discharging at a rate, a characteristic voltage change may appear near the end of the discharge. In the dQ / dV vs V curve obtained from the discharge curve, the range is from 3.5V to 3.9V. This can be clearly confirmed by the presence of at least one peak.

[0153] (Embodiment 2) In this embodiment, it is used in a secondary battery having the positive electrode active material 100 described in the previous embodiment. Examples of materials that can be used will be described. In this embodiment, the positive electrode, negative electrode and electrolyte However, let's take a secondary battery, which is enclosed in an outer casing, as an example to explain.

[0154] [Positive electrode] The positive electrode comprises a positive electrode active material layer and a positive electrode current collector.

[0155] <Cathode active material layer> The positive electrode active material layer contains at least positive electrode active material. Furthermore, the positive electrode active material layer contains positive electrode active material In addition, other substances such as a coating on the surface of the active material, a conductive additive, or a binder may be included.

[0156] As the positive electrode active material, the positive electrode active material 100 described in the previous embodiment can be used. By using the positive electrode active material 100 described in the previous embodiment, high capacity and cycle characteristics can be achieved. It can be used to create an excellent rechargeable battery.

[0157] As conductive additives, carbon materials, metal materials, or conductive ceramic materials can be used. Yes, it is possible. Additionally, fibrous materials may be used as conductive additives. The conductivity relative to the total amount of the active material layer... The content of the electrolytic agent is preferably 1 wt% to 10 wt%, and preferably 1 wt% to 5 wt%. This is preferable.

[0158] Conductive additives can be used to form an electrical conduction network within the active material layer. The agent can maintain the electrical conduction pathway between the positive electrode active materials. By adding an electro-enhancing agent, it is possible to create an active material layer with high electrical conductivity. .

[0159] Examples of conductive additives include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon fibers. Fibers can be used. For example, mesophase pitch carbon fibers can be used. Carbon fibers such as isotropic pitch carbon fibers can be used. Carbon nanofibers and carbon nanotubes can be used. The tubes can be fabricated, for example, by vapor phase growth. Also, as a conductive additive, for example... Examples include carbon black (acetylene black (AB), etc.) and graphite particles. Carbon materials such as graphene and fullerene can be used. Also, for example, copper, nickel Metal powders such as oxal, aluminum, silver, and gold, as well as metal fibers and conductive ceramic materials. It can be used.

[0160] Furthermore, graphene compounds may be used as conductive additives.

[0161] 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 graphene compounds, for example, graphene, multigraphene, Alternatively, it is particularly preferable to use RGO. Here, RGO is, for example, graphene oxide (g This refers to the compound obtained by reducing raphene oxide (GO).

[0162] 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.

[0163] In the following example, a graphene compound is used as a conductive additive in the active material layer 200. An example of the cross-sectional configuration will be explained.

[0164] Figure 8(A) shows a longitudinal cross-sectional view of the active material layer 200. The active material layer 200 consists of granular positive electrode active material. It contains 100, a graphene compound 201 as a conductive additive, and a binder (not shown). Hmm. Here, as graphene compound 201, for example, graphene or multigraphene It is fine to use it. Here, it is preferable that the graphene compound 201 has a sheet-like shape. Furthermore, graphene compound 201 is a multigraphene, or (and) multiple graphenes. The graphene may be partially overlapping and form a sheet.

[0165] In the longitudinal section of the active material layer 200, as shown in Figure 8(B), the interior of the active material layer 200 In Figure 8(B), the graphene compound 201 is dispersed in a generally uniform sheet-like manner. Graphene compound 201 is schematically represented by a thick line, but in reality it is a single or multiple layer of carbon molecules. It is a thin film with a layer thickness. Multiple graphene compounds 201 are multiple granular cathode active materials The material 100 is partially covered, or adheres to the surface of multiple granular positive electrode active materials 100. Because they are formed in such a way, they are in surface contact with each other.

[0166] Here, multiple graphene compounds bond together to form a network of graphene compounds. Forming a sheet (hereinafter referred to as graphene compound net or graphene net) Yes, it is possible. When the active material is covered with a graphene net, the graphene net connects the active materials to each other. It can also function as a binder. Therefore, it reduces the amount of binder needed. Because it is possible to do so or not to use it, the ratio of active material to electrode volume or electrode weight The efficiency can be improved. In other words, the capacity of the secondary battery can be increased.

[0167] Here, graphene oxide is used as graphene compound 201 and mixed with the active material to form the active material It is preferable to reduce the layer after forming the layer that will become layer 200. By using graphene oxide, which has extremely high dispersibility in polar solvents, graphene formation can be achieved. The compound 201 can be dispersed approximately uniformly within the active material layer 200. The solvent is volatilized and removed from the dispersion medium containing dispersed graphene oxide, and the graphene oxide is reduced. Therefore, the graphene compound 201 remaining in the active material layer 200 partially overlaps, and By being dispersed to the extent that they are in surface contact, a three-dimensional conductive path can be formed. The reduction of graphene oxide may be carried out, for example, by heat treatment or by using a reducing agent. That's fine.

[0168] Therefore, unlike granular conductive additives such as acetylene black that make point contact with the active material, graph Compound 201 enables surface contact with low contact resistance, unlike conventional conductive additives. It improves the electrical conductivity between the granular positive electrode active material 100 and the graphene compound 201 using only a small amount. Therefore, the ratio of positive electrode active material 100 in the active material layer 200 can be increased. This allows for an increase in the discharge capacity of the secondary battery.

[0169] Furthermore, by using a spray drying device beforehand, the entire surface of the active material is covered with a conductive additive. A graphene compound is formed as a coating, and then the graphene compound is used to guide the active materials together. It can also be used to create an electric pass.

[0170] 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.

[0171] 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.

[0172] Alternatively, as a binder, polystyrene, polymethyl acrylate, polymethyl methacrylate can be used. Chill (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl Alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, Liimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene Polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, It is preferable to use materials such as polyvinyl acetate or nitrocellulose.

[0173] You may use a combination of several of the binders mentioned above.

[0174] 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.

[0175] Furthermore, cellulose derivatives such as carboxymethylcellulose are, for example, carboxymethyl By using salts such as sodium salts or ammonium salts of cellulose, the solubility increases. It becomes easier to exert its effect as a viscosity modifier. The increased solubility makes the electrode slurry - When manufacturing, it is also possible to improve the dispersibility with the active material and other components. As for cellulose and cellulose derivatives used as electrode binders, This shall also include salt.

[0176] 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.

[0177] When a binder covering or in contact with the surface of the active material forms a film, it is considered a passivation film. It is also expected to play a role in suppressing the decomposition of the electrolyte. Here, the passive film is an electrolytic film. A film that does not conduct air, or a film with extremely low electrical conductivity, for example, on the surface of an active material When a dynamic film is formed, the decomposition of the electrolyte can be suppressed at the battery reaction potential. It can. Furthermore, the passivation film suppresses electrical conductivity, while lithium ions can conduct electricity. And even better.

[0178] <Positive electrode current collector> As the positive electrode current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and this Highly conductive materials such as alloys can be used. Also, materials used for the positive electrode current collector It is preferable that the material does not dissolve at the positive electrode potential. Also, silicon, titanium, neodymium, sucrose Aluminum alloys with added elements that improve heat resistance, such as valdium and molybdenum, are used. It can be formed by metal elements that react with silicon to form silicides. This is also good. Examples of metallic elements that react with silicon to form silicides include zirconium and thi. Tan, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten These include cobalt, nickel, etc. Current collectors come in foil, plate (sheet), mesh, and perforated forms. Shapes such as metallic or expanded metal can be used as appropriate. The thickness of the current collector is It is best to use particles between 5 μm and 30 μm in size.

[0179] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer also contains a conductive additive and It may have a binder.

[0180] <Negative electrode active material> For example, alloy materials or carbon-based materials can be used as the negative electrode active material.

[0181] As a negative electrode active material, it is possible to perform charge and discharge reactions through alloying and dealloying reactions with lithium. Any suitable element can be used. For example, silicon, tin, gallium, aluminum, galvanic acid. Among the following, a small amount is found in luminum, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one element can be used. Such elements have a larger capacity compared to carbon. In particular, silicon has a high theoretical capacity of 4200 mAh / g. Therefore, silicon is used as the negative electrode active material. It is preferable to use lycon. Alternatively, compounds containing these elements may be used. Example For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V 2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3 Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, I Examples include nSb and SbSn. Here, the charge-discharge reaction occurs through alloying and dealloying reactions with lithium. Elements capable of performing this action, and compounds containing such elements, are sometimes referred to as alloying materials. ru.

[0182] 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.

[0183] 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. .

[0184] 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.

[0185] Graphite is formed when lithium ions are inserted into it (during the formation of lithium-graphite intercalation compounds). It exhibits a potential as low as lithium metal (0.05V to 0.3V vs. Li / Li + This allows lithium-ion secondary batteries to exhibit a high operating voltage. Furthermore, graphite has a relatively high volume per unit volume, relatively small volume expansion, and is inexpensive. It is preferable because it has advantages such as higher safety compared to lithium metal.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] <Negative electrode current collector> The negative electrode current collector can be made of the same material as the positive electrode current collector. It is preferable to use a material that does not alloy with carrier ions such as thium.

[0192] [Electrolyte] An electrolyte solution contains a solvent and an electrolyte. A non-protic organic solvent is preferred as the solvent for the electrolyte solution. For example, ethylene carbonate (EC), propylene carbonate (PC), and buty Lenyl carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolane Chtone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate Methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1 ,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfone Hoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetra One of the following: lahydrofuran, sulfolane, sultone, or two or more of these. It can be used in combinations and ratios.

[0193] Furthermore, as the solvent for the electrolyte, an ionic liquid (a room-temperature molten salt) that is flame-retardant and non-volatile is used. By using one or more of them, the internal temperature of the secondary battery rises due to internal short circuits or overcharging. This can also prevent secondary batteries from rupturing or catching fire. Ionic liquids contain cations and anions. It consists of organic cations and anions. As organic cations used in the electrolyte, quaternary cations are used. Ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, etc. aliphatic onium cations, imidazolium cations, pyridinium cations, etc. Aromatic cations are one example. Also, monovalent amide-based anions are used as anions in the electrolyte. Nions, monovalent methide anions, fluorosulfonate anions, perfluoroalkyl Sulfonate anions, tetrafluoroborate anions, perfluoroalkyl borates Anions, hexafluorophosphate anions, or perfluoroalkyl phosphates Examples include anions.

[0194] Furthermore, examples of electrolytes to be dissolved in the above solvent include LiPF6, LiClO4, and Li AsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4 Li2B 10 Cl 10 Li2B 12 Cl 12 LiCF3SO3, LiC4F9SO 3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2) 2. Lithium compounds such as LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. Using one type of um salt, or two or more of these salts in any combination and ratio. It is possible.

[0195] The electrolyte used in secondary batteries contains particulate matter and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "non-contaminated"). It is preferable to use a highly purified electrolyte with a low content of (also called "pure substance"). Specifically, the weight ratio of impurities to the electrolyte should be 1% or less, preferably 0.1% or less, more preferably It is preferable that the amount be 0.01% or less.

[0196] Furthermore, the electrolyte contains vinylene carbonate, propanesultone (PS), and tert-butylbe. TBB (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate) LiBOB (Lithium-Borate), as well as dinitriles such as succinonitrile and adiponitrile. Additives such as compounds may be added. The concentration of the added material should be, for example, relative to the total solvent. The concentration should be between 0.1 wt% and 5 wt%.

[0197] Alternatively, a polymer gel electrolyte, obtained by swelling a polymer with an electrolyte solution, may be used.

[0198] Using polymer gel electrolytes enhances safety against leakage and other issues. Furthermore, secondary batteries... It is possible to make it thinner and lighter.

[0199] Examples of polymers that can be gelled include silicone gel, acrylic gel, and acrylonitrile gel. Polyethylene oxide gels, polypropylene oxide gels, fluorine polymers Gels or similar materials can be used.

[0200] Examples of polymers include polyalkylene oxides such as polyethylene oxide (PEO). Polymers having a denture structure, PVDF, polyacrylonitrile, etc., and those Copolymers containing PVDF and hexafluoropropylene (H) can be used. For example, PVDF and hexafluoropropylene (H) PVDF-HFP, a copolymer of FP, can be used. The material may have a porous structure.

[0201] In addition, instead of an electrolyte, a solid electrolyte containing inorganic materials such as sulfide-based or oxide-based materials, or P Solid electrolytes containing polymer materials such as EO (polyethylene oxide) can be used. When using a solid electrolyte, the installation of separators and spacers becomes unnecessary. Because the entire pond can be solidified, the risk of leakage is eliminated, dramatically improving safety.

[0202] [Separator] Furthermore, it is preferable that the secondary battery has a separator. The separator can be, for example, paper. Nonwoven fabrics, glass fibers, ceramics, or nylon (polyamide), vinylon (poly Vinyl alcohol-based fibers, polyester, acrylic, polyolefin, polyurethane Materials made from synthetic fibers, etc., can be used. The separator is envelope-shaped. It is preferable to process it in such a way that it encloses either the positive or negative electrode.

[0203] The separator may have a multilayer structure. For example, organic materials such as polypropylene and polyethylene. The material film contains ceramic-based materials, fluorine-based materials, polyamide-based materials, or a mixture thereof. A combination of these materials can be used as a coating. Examples of ceramic materials include aluminum oxide. Examples of fluorine-based materials include nium particles, silicon oxide particles, etc. PVDF, polytetrafluoroethylene, etc. can be used as polyamide materials. For example, nylon, aramid (meta-aramid, para-aramid), etc. can be used. can.

[0204] Coating with ceramic materials improves oxidation resistance, thus preventing separation during high-voltage charging and discharging. This can suppress degradation of the battery and improve the reliability of secondary batteries. Furthermore, by using fluorine-based materials... This allows the separator and electrodes to adhere more closely, improving the output characteristics. Coating with polyamide materials, especially aramid, improves heat resistance, thus increasing the safety of secondary batteries. It can improve overall health.

[0205] For example, a mixture of aluminum oxide and aramid material is coated on both sides of a polypropylene film. It may also be done by using aluminum oxide on the surface of the polypropylene film that is in contact with the positive electrode. A mixed material of aramid may be coated, and a fluorine-based material may be coated on the surface in contact with the negative electrode.

[0206] Using a multilayer separator ensures the safety of the secondary battery even if the overall thickness of the separator is thin. Because it can maintain this state, the capacity per unit volume of a secondary battery can be increased.

[0207] [Exterior] For the casing of a secondary battery, metal materials such as aluminum or resin materials are used. It is possible to use a film-like outer covering. As for the film, For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. A film made of the following materials, with highly flexible gold such as aluminum, stainless steel, copper, and nickel. A thin metal film is provided, and on the metal thin film, a polyamide resin and polyester resin are used as the outer surface of the exterior body. A three-layer film with an insulating synthetic resin film, such as a ru-based resin, can be used.

[0208] [Charge / discharge method] The charging and discharging of a secondary battery can be performed, for example, as follows.

[0209] ≪CC charging≫ First, let's explain CC charging as one of the charging methods. CC charging is used throughout the entire charging period. This charging method involves supplying a constant current to the secondary battery and stopping the charging process when a predetermined voltage is reached. The secondary battery is assumed to be an equivalent circuit of internal resistance R and secondary battery capacity C, as shown in Figure 9(A). In this case, the secondary battery voltage V B This is the voltage V across the internal resistance R. R and secondary battery capacity C The voltage V C It is the sum of.

[0210] While CC charging is in progress, the switch turns on, as shown in Figure 9(A), and a certain amount of power is supplied. Current I flows through the secondary battery. During this time, since the current I is constant, V R Ohm's law = R × I According to the law, the voltage V across the internal resistance R is R It is also constant. On the other hand, the electricity applied to the secondary battery capacity C Pressure V C The voltage increases over time. Therefore, the secondary battery voltage V B The passage of time and They will both rise.

[0211] And the secondary battery voltage V B Charging stops when the voltage reaches a predetermined level, for example, 4.3V. When CC charging is stopped, the switch turns off as shown in Figure 9(B), and the current I=0 Therefore, the voltage V across the internal resistance R is... R The voltage becomes 0V. Therefore, the secondary battery voltage V B It will decline.

[0212] The secondary battery voltage V during CC charging and after CC charging has stopped. B and charging current An example is shown in Figure 9(C). The secondary battery voltage V was rising while CC charging was being performed. B However, C The image shows a slight decrease after C charging is stopped.

[0213] ≪CCCV charging≫ Next, we will explain CCCV charging, which is a different charging method from the one described above. CCCV charging is First, the battery is charged to a predetermined voltage using CC charging, and then the current that flows through it is charged using CV (constant voltage) charging. This charging method continues until the current level drops to a minimum, specifically until it reaches the cutoff current value.

[0214] While CC charging is in progress, the constant current power supply switch is turned on, as shown in Figure 10(A). The constant voltage power supply is switched off, and a constant current I flows to the secondary battery. During this time, current I Since V is constant, R According to Ohm's law, =R × I, the voltage across the internal resistance R is V. R too It remains constant. On the other hand, the voltage V across the secondary battery capacity C is constant. C It increases over time. Therefore, the secondary battery voltage V B It increases over time.

[0215] And the secondary battery voltage V B When the voltage reaches a predetermined level, for example 4.3V, CC charging is switched to C Switch to V charging. While CV charging is being performed, constant voltage charge as shown in Figure 10(B) The power switch is turned on, the constant current power supply switch is turned off, and the secondary battery voltage V B It remains constant On the other hand, the voltage V across the secondary battery capacity C C It increases over time. B =V R +V C Therefore, the voltage V across the internal resistance R R It decreases over time. Voltage V across internal resistance R R As V decreases, R According to Ohm's law, =R × I, The current I flowing through the secondary battery also decreases.

[0216] And when the current I flowing through the secondary battery becomes a predetermined current, for example, a current equivalent to 0.01C... , stop charging. When CCCV charging is stopped, all switches will be affected, as shown in Figure 10(C). The switch turns off, and the current I becomes 0. Therefore, the voltage V across the internal resistance R remains. R and 0V Yes. However, the voltage V across the internal resistance R due to CV charging R Because it has become small enough Therefore, even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B It hardly descends at all.

[0217] The secondary battery voltage V during CCCV charging and after CCCV charging has stopped. B and An example of electric current is shown in Figure 10(D). Even when CCCV charging is stopped, the secondary battery voltage V B almost It appears that it hardly descends at all.

[0218] ≪CC discharge≫ Next, we will explain CC discharge, one of the discharge methods. CC discharge is used throughout the entire discharge period. A constant current is drawn from the secondary battery, and the secondary battery voltage V B When it reaches a predetermined voltage, for example 2.5V This is a discharge method that stops the discharge when it reaches a certain point.

[0219] The secondary battery voltage V during CC discharge B Figure 11 shows an example of the discharge current. According to this, secondary battery voltage V B The image shows it descending.

[0220] Next, we will explain the discharge rate and charge rate. The discharge rate is the ratio of the battery capacity to the charge rate. This is the relative ratio of the current during discharge, and is expressed in units of cubic centimeters (C). Therefore, the current equivalent to 1C is X(A). If discharged with a current of 2X(A), then 2C If it was discharged with a current of X / 5(A), then it was discharged at 0.2C. It is said that the charging rate is also similar; if charged with a current of 2X(A), it will charge at 2C. They said they charged it, and if they charged it with a current of X / 5(A), they said they charged it at 0.2C. .

[0221] (Embodiment 3) In this embodiment, the shape of the secondary battery having the positive electrode active material 100 described in the previous embodiment is Let's explain an example. The material used in the secondary battery described in this embodiment is the same as in the previous embodiment. The description of the state can be taken into consideration.

[0222] [Coin-type rechargeable battery] First, let's explain an example of a coin-type rechargeable battery. Figure 12(A) shows a coin-type (single-layer flat type) Figure 12(B) is an external view of the secondary battery, and Figure 12(B) is a cross-sectional view thereof.

[0223] The coin-type rechargeable battery 300 consists of a positive electrode casing 301, which also serves as the positive terminal, and a negative electrode casing, which also serves as the negative terminal. 302 is insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 consists of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with it. It is formed by the following. Furthermore, the negative electrode 307 is provided in contact with the negative electrode current collector 308. It is formed by a negative electrode active material layer 309.

[0224] Furthermore, the positive electrode 304 and negative electrode 307 used in the coin-type secondary battery 300 are each active materials The layer only needs to be formed on one side.

[0225] The positive electrode container 301 and the negative electrode container 302 are made of nickel and aluminum, which are corrosion-resistant to the electrolyte. , metals such as titanium, or alloys thereof, or alloys of these with other metals (e.g., stainless steel) (etc.) can be used. In addition, nickel and aluminum can be used to prevent corrosion by the electrolyte. It is preferable to cover it with a material such as a nut. The positive electrode can 301 is the positive electrode 304, and the negative electrode can 302 is the negative electrode 30 Connect each of the 7s electrically.

[0226] These negative electrode 307, positive electrode 304, and separator 310 are impregnated with the electrolyte, as shown in Figure 12(B As shown in the image, with the positive electrode can 301 at the bottom, the positive electrode 304, separator 310, and negative electrode 307, The negative electrode cans 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are connected by a gasket 303. The coin-type secondary battery 300 is manufactured by crimping the parts together.

[0227] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, high capacity cycle This allows for the creation of a coin-type secondary battery 300 with superior characteristics.

[0228] Here, we will use Figure 12(C) to explain the current flow during the charging of a secondary battery. Using lithium When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In addition, in lithium-ion secondary batteries, the anode and cathode are used during charging and discharging. The cathode is swapped, and the oxidation and reduction reactions are reversed, thus changing the reaction potential. The electrode with a high reaction potential is called the positive electrode, and the electrode with a low reaction potential is called the negative electrode. Therefore, in this specification... In this case, whether charging or discharging, or even when applying a reverse pulse current, Even when an electric current is flowing, the positive electrode is called the "positive electrode" or "+ electrode (positive pole)," and the negative electrode is called the "positive pole." This will be referred to as the "negative electrode" or "- electrode (minus electrode)". Related to oxidation and reduction reactions. Using the terms anode and cathode, the difference between charging and discharging is significant. This could be reversed and cause confusion. Therefore, the anode and cathode The term cathode will not be used in this specification. When using terms such as positive electrode () or cathode, specify whether it is during charging or discharging, and the positive electrode ( The corresponding polarity (positive or negative) should also be indicated.

[0229] The charger is connected to the two terminals shown in Figure 12(C), and the secondary battery 300 is charged. As the charging of the next battery 300 progresses, the potential difference between the electrodes will increase.

[0230] [Cylindrical rechargeable battery] Next, an example of a cylindrical secondary battery will be explained with reference to Figure 13. Cylindrical secondary battery 600 The external view is shown in Figure 13(A). Figure 13(B) schematically shows a cross-section of the cylindrical secondary battery 600. This is a diagram showing the exact configuration. As shown in Figure 13(B), the cylindrical secondary battery 600 has a top surface It has a positive electrode cap (battery cover) 601 and a battery can (outer casing) 602 on its side and bottom. These positive electrode caps and battery can (outer can) 602 are connected by a gasket (insulating packing). It is insulated by 610.

[0231] Inside the hollow cylindrical battery can 602, there is a strip-shaped positive electrode 604 and a negative electrode 606 separated by a separator 6 A battery element is provided wound with 05 sandwiched in between. Although not shown in the diagram, the battery element is a sensor It is wound around the turpin. Battery can 602 is closed at one end and open at the other. The battery can 602 contains nickel, aluminum, titanium, etc., which are corrosion-resistant to the electrolyte. Using metals, or alloys thereof, or alloys of these with other metals (for example, stainless steel, etc.) It is possible to do so. Also, to prevent corrosion by the electrolyte, nickel, aluminum, etc. are used. It is preferable to cover the battery container 602. Inside the battery container 602, the positive electrode, the negative electrode and The battery element, around which the separator is wound, is sandwiched between a pair of opposing insulating plates 608 and 609. Furthermore, the inside of the battery can 602, which is equipped with the battery element, contains a non-aqueous electrolyte (not shown). It is being injected. A non-aqueous electrolyte similar to that used in coin-type rechargeable batteries can be used. .

[0232] Since the positive and negative electrodes used in cylindrical storage batteries are wound, active material is formed on both sides of the current collector. It is preferable that the positive electrode 604 is connected to the positive electrode terminal (positive electrode current collector lead) 603, and the negative electrode The negative terminal (negative current collector lead) 607 is connected to 606. Positive terminal 603 and negative terminal Terminals 607 can both be made of metal materials such as aluminum. Positive terminal 60 Terminal 3 is resistance-welded to the safety valve mechanism 612, and the negative terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 is a PTC element (Positive Temperature Coefficient). It is electrically connected to the positive electrode cap 601 via the efficient 611. The valve mechanism 612, when the rise in the internal pressure of the battery exceeds a predetermined threshold, and the positive electrode cap 601 and This disconnects the electrical connection with the positive electrode 604. Also, the PTC element 611 is at a higher temperature. This is a thermal resistance element whose resistance increases when the temperature rises, and by increasing the resistance, it limits the amount of current. This prevents overheating. The PTC element uses a barium titanate (BaTiO3) semiconductor. Conductive ceramics and the like can be used.

[0233] Furthermore, as shown in Figure 13(C), multiple secondary batteries 600 are connected to conductive plates 613 and 614 Module 615 may be configured by sandwiching it between them. Multiple secondary batteries 600 are connected in parallel. They may be connected in series, or connected in parallel and then further connected in series. It may be done. By configuring a module 615 having multiple secondary batteries 600, It can extract a large amount of power.

[0234] Figure 13(D) is a top view of module 615. The conductive plate 613 is shown in the diagram for clarity. This is shown by the dotted line. As shown in Figure 13(D), module 615 has multiple secondary batteries 600 It may have electrically connected conductors 616. A conductive plate may be superimposed on the conductors 616. It is possible to have a temperature control device 617 between multiple secondary batteries 600. i. When the secondary battery 600 overheats, the temperature control device 617 cools it down, and the secondary battery 6 When 00 is too cold, it can be heated by the temperature control device 617. The performance of module 615 becomes less affected by ambient temperature. The heat of the temperature control device 617 The medium preferably has insulating and non-flammable properties.

[0235] By using the positive electrode active material described in the previous embodiment for the positive electrode 604, high capacity cycle This allows for the creation of a cylindrical secondary battery 600 with superior characteristics.

[0236] [Example of a secondary battery structure] Another example of a secondary battery structure will be explained using Figures 14 to 18.

[0237] Figures 14(A) and 14(B) show the external view of the secondary battery. The secondary battery 913 is It is connected to antennas 914 and 915 via circuit board 900. Furthermore, label 910 is attached to the secondary battery 913. In addition, as shown in Figure 14(B)... The secondary battery 913 is connected to terminals 951 and 952.

[0238] The circuit board 900 has terminal 911 and circuit 912. Terminal 911 is connected to terminal 951 It is connected to terminal 952, antenna 914, antenna 915, and circuit 912. Multiple terminals 911 are provided, and each of the multiple terminals 911 is designated as a control signal input terminal and a power supply terminal. You could also do this.

[0239] The circuit 912 may be provided on the back surface of the circuit board 900. Furthermore, the antenna 914 and The antenna 915 is not limited to a coil shape, but may also be linear, plate-shaped, etc. Planar antenna, aperture antenna, traveling wave antenna, EH antenna, magnetic field antenna, dielectric Antennas such as antennas may be used. Alternatively, antenna 914 or antenna 915 may be used. Alternatively, a flat conductor may be used. This flat conductor functions as one of the conductors for electric field coupling. This is possible. In other words, as one of the two conductors of the capacitor, You may activate antenna 914 or antenna 915. This will allow only electromagnetic and magnetic fields to be generated. Alternatively, power can be exchanged using an electric field.

[0240] The line width of antenna 914 is preferably larger than the line width of antenna 915. Furthermore, the amount of power received can be increased by antenna 914.

[0241] The secondary battery has a layer 916 between antennas 914 and 915 and the secondary battery 913. It has the function of shielding electromagnetic fields, for example, from secondary batteries 913. It has. For layer 916, for example, a magnetic material can be used.

[0242] Note that the structure of the secondary battery is not limited to that shown in Figure 14.

[0243] For example, as shown in Figures 15(A-1) and 15(A-2), Figures 14(A) and 14 Even if an antenna is provided on each of the opposing pairs of surfaces of the secondary battery 913 shown in (B) Good. Figure 15(A-1) is an external view showing one of the pair of surfaces mentioned above, and Figure 15(A-2) Figure 14(A) and Figure 14(B) are external views showing the other side of the pair of faces described above. For the same parts as the secondary battery shown, see Figure 14(A) and Figure 14(B) Explanations can be used as appropriate.

[0244] As shown in Figure 15(A-1), a layer 916 is sandwiched between one of the pair of surfaces of the secondary battery 913. An inlet 914 is provided, and as shown in Figure 15(A-2), a pair of sides of the secondary battery 913 On the other side, an antenna 918 is provided with a layer 917 in between. Layer 917 is, for example, a secondary battery 91 It has the function of shielding the electromagnetic field caused by 3. For layer 917, for example, a magnetic material. You can use it.

[0245] By adopting the above structure, the size of both antenna 914 and antenna 918 can be increased. It is possible. Antenna 918 can, for example, perform data communication with external devices. It has the function of being able to do so. Antenna 918 has an antenna shape that can be applied to, for example, antenna 914. An antenna can be applied. This is a communication method between a secondary battery and other devices via antenna 918. For example, it can be used between a rechargeable battery and other devices, such as NFC (Near Field Communication). A response method that can be applied can be used.

[0246] Alternatively, as shown in Figure 15(B-1), the secondary battery 9 shown in Figures 14(A) and 14(B) A display device 920 may be provided at 13. The display device 920 is electrically connected to terminal 911. It is not necessary to provide a label 910 in the area where the display device 920 is provided. For the same parts as the secondary battery shown in Figures 14(A) and 14(B), see Figure 14(A) and The explanation of secondary batteries shown in Figure 14(B) can be used as appropriate.

[0247] The display device 920 displays, for example, an image indicating whether or not it is charging, an image indicating the amount of stored power, etc. It may be shown. The display device 920 may be, for example, electronic paper, liquid crystal display device, or electronic A luminescent (also known as EL) display device can be used. For example, an electronic paper By using this method, the power consumption of the display device 920 can be reduced.

[0248] Alternatively, as shown in Figure 15(B-2), the secondary battery 9 shown in Figures 14(A) and 14(B) A sensor 921 may be provided at 13. The sensor 921 is connected to terminal 911 via terminal 922. It is electrically connected. Note that it is located in the same part as the secondary battery shown in Figures 14(A) and 14(B). Accordingly, the explanation of secondary batteries shown in Figures 14(A) and 14(B) can be appropriately referenced.

[0249] Examples of sensors 921 include displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, and light. Liquid, magnetism, temperature, chemicals, sound, time, hardness, electric field, electric current, voltage, power, radiation, flow It should have the ability to measure quantity, humidity, gradient, vibration, odor, or infrared radiation. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed can be collected. It can also detect (temperature, etc.) and store it in the memory within circuit 912.

[0250] Furthermore, an example of the structure of the secondary battery 913 will be explained using Figures 16 and 17.

[0251] The secondary battery 913 shown in Figure 16(A) has terminals 951 and 952 inside the housing 930. It has a wound body 950. The wound body 950 is impregnated with an electrolyte inside the housing 930. Terminal 952 is in contact with the housing 930, and terminal 951 is in contact with the housing by using insulating material, etc. It is not in contact with the body 930. Note that in Figure 16(A), for convenience, the housing 930 is separated. As shown in the diagram, in reality the wound body 950 is covered by the housing 930, and terminals 951 and 95 2 extends outside the casing 930. The casing 930 is made of a metal material (e.g., aluminum). Materials such as lum or resin can be used.

[0252] Furthermore, as shown in Figure 16(B), the housing 930 shown in Figure 16(A) is made of multiple materials. They may be formed. For example, the secondary battery 913 shown in Figure 16(B) has a housing 930a and a housing 9 30b is bonded together, and the area enclosed by the housing 930a and housing 930b is wound up 9 50 is provided.

[0253] For the casing 930a, insulating materials such as organic resin can be used. In particular, the antenna By using a material such as organic resin on the surface where the electric field of the secondary battery 913 is formed, Shielding can be suppressed. Furthermore, if the shielding of the electric field by the housing 930a is small, the housing 930a Antennas such as antenna 914 and antenna 915 may be installed inside. For example, metal materials can be used.

[0254] Furthermore, the structure of the wound body 950 is shown in Figure 17. The wound body 950 consists of a negative electrode 931 and a positive electrode. It has poles 932 and separators 933. The coiled body 950 sandwiches the separators 933. The negative electrode 931 and the positive electrode 932 are stacked on top of each other, and the stacked sheet is wound up to form a wound body. Furthermore, the stacking of the negative electrode 931, the positive electrode 932, and the separator 933 is further multiplied. You can do it multiple times.

[0255] The negative electrode 931 is connected to terminal 911 shown in Figure 14 via either terminal 951 or terminal 952. The positive terminal 932 is connected to terminal 91 shown in Figure 14 via terminal 951 and the other terminal 952. It connects to 1.

[0256] By using the positive electrode active material described in the previous embodiment for the positive electrode 932, high capacity cycle This allows for the creation of a secondary battery 913 with superior characteristics.

[0257] [Laminated rechargeable battery] Next, an example of a laminate-type secondary battery will be explained with reference to Figures 18 to 24. If a laminate-type secondary battery has a flexible structure, the number of flexible parts can be reduced. If implemented in electronic devices that also possess some of these features, the secondary battery can also be bent in accordance with the deformation of the electronic device. can.

[0258] Using Figure 18, we will explain the laminated secondary battery 980. The battery 980 has a wound body 993 as shown in Figure 18(A). The wound body 993 has a negative electrode 994 It has a positive electrode 995 and a separator 996. The wound body 993 is explained in Figure 17. Similar to the wound body 950, the negative electrode 994 and the positive electrode 995 overlap with the separator 996 in between. The sheets are joined together and laminated, and then the laminated sheets are rolled up.

[0259] The number of layers in the stack consisting of the negative electrode 994, positive electrode 995, and separator 996 is the required number of layers. The design should be appropriate depending on the capacitance and element volume. The negative electrode 994 is connected to the lead electrode 997 and the lead One side of the electrode 998 is connected to the negative electrode current collector (not shown), and the positive electrode 995 is connected to the lead electrode It is connected to a positive electrode current collector (not shown) via pole 997 and the other of lead electrode 998.

[0260] As shown in Figure 18(B), there is a film 981 which will be the outer casing and a film 98 which has a recess. The aforementioned coiled body 993 is housed in the space formed by bonding 2 together by heat pressing or the like. As a result, a secondary battery 980 can be manufactured as shown in Figure 18(C). (Winding body 99) 3 has lead electrodes 997 and 998, a film 981 and a recess The film 982 is impregnated with an electrolyte solution inside it.

[0261] Film 981 and film 982 having a recess are made of a metal material such as aluminum. or resin materials can be used. Film 981 and film 982 having recesses If a resin material is used as the material, when an external force is applied, the film 981 and the recess will The film 982 can be deformed, and a flexible storage battery can be manufactured. can.

[0262] Furthermore, Figures 18(B) and 18(C) show examples using two films, A space is formed by folding a single film, and the aforementioned wound body 99 is placed in that space. You may store 3.

[0263] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, high capacity cycle This allows for the creation of a secondary battery 980 with superior characteristics.

[0264] Figure 18 also shows a secondary battery 9 having a wound body in a space formed by a film that serves as the outer casing. We have described 80 examples, but for example, as shown in Figure 19, it is formed by a film that forms the outer casing. In the space provided, it can also be used as a secondary battery having multiple strip-shaped positive electrodes, separators, and negative electrodes. stomach.

[0265] The laminated secondary battery 500 shown in Figure 19(A) consists of a positive electrode current collector 501 and a positive electrode active material The positive electrode 503 has a solid layer 502, and the negative electrode has a current collector 504 and a negative electrode active material layer 505. It has a negative electrode 506, a separator 507, an electrolyte 508, and an outer casing 509. A separator 507 is installed between the positive electrode 503 and the negative electrode 506 located within the body 509. It is. Also, the inside of the outer casing 509 is filled with electrolyte 508. The electrolyte 508 contains actual The electrolyte shown in Form 2 of the application can be used.

[0266] In the laminate-type secondary battery 500 shown in Figure 19(A), the positive electrode current collector 501 and the negative electrode current collector are... The polar current collector 504 also serves as a terminal for obtaining electrical contact with the outside. Therefore, it is the positive electrode. Parts of the current collector 501 and the negative electrode current collector 504 are exposed to the outside from the outer casing 509. They may also be arranged in this manner. Furthermore, the positive electrode current collector 501 and the negative electrode current collector 504 may be separated from the outer casing 509. Without exposing it to the outside, lead electrodes are used to connect the lead electrodes to the positive electrode current collector 501, or to the negative electrode. The lead electrodes may be exposed to the outside by ultrasonic bonding with the current collector 504.

[0267] In the laminated secondary battery 500, the outer casing 509 is made of, for example, polyethylene, poly On a film made of materials such as propylene, polycarbonate, ionomer, and polyamide, A highly flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided, and further, the metal An insulating synthetic resin such as polyamide resin or polyester resin is used as the outer surface of the outer casing on a thin film. A three-layer laminate film with a lipid film can be used.

[0268] Furthermore, an example of the cross-sectional structure of the laminate-type secondary battery 500 is shown in Figure 19(B). A) shows an example consisting of two current collectors for simplicity, but in reality, see Figure 19(B). As shown, it is composed of multiple electrode layers.

[0269] In Figure 19(B), the number of electrode layers is set to 16 as an example. However, the secondary battery 500 is flexible. In Figure 19(B), the negative electrode current collector 504 has 8 layers, The positive electrode current collector 501 has a structure of 8 layers, for a total of 16 layers. Figure 19(B) shows the negative electrode. This shows a cross-section of the extraction section, where eight layers of negative electrode current collectors 504 are ultrasonically bonded. The number of electrode layers is not limited to 16; it can be more or fewer. This allows for the creation of a secondary battery with a larger capacity. Also, in cases where the number of electrode layers is small... In combination, it is possible to create a rechargeable battery that is thin and highly flexible.

[0270] Here, an example of the external view of the laminate-type secondary battery 500 is shown in Figures 20 and 21. Figure 2 Figures 0 and 21 show the positive electrode 503, negative electrode 506, separator 507, casing 509, and positive electrode lead. It has a lead electrode 510 and a negative lead electrode 511.

[0271] Figure 22(A) shows the external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is the positive electrode current collector 50 The positive electrode has a positive electrode active material layer 502 formed on the surface of the positive electrode current collector 501. 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). Negative electrode 506 has a negative electrode current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. Furthermore, the negative electrode 506 is the region where the negative electrode current collector 504 is partially exposed, i.e., the tab region. It has a tab region. The area and shape of the tab regions of the positive and negative electrodes are not limited to the example shown in Figure 22(A). I can't.

[0272] [Method for manufacturing laminated rechargeable batteries] Here, an example of a method for manufacturing a laminate-type secondary battery, as shown in Figure 20, is presented in Figure 22. We will explain using (B) and (C).

[0273] First, the negative electrode 506, separator 507, and positive electrode 503 are stacked. (See Figure 22(B) for details.) The negative electrode 506, separator 507, and positive electrode 503 are shown. Here, there are 5 sets of negative electrodes and 5 sets of positive electrodes. An example of using four sets is shown. Next, the joining of the tab regions of the positive electrode 503 and the tab of the outermost positive electrode. The positive lead electrode 510 is joined to the region. For joining, for example, ultrasonic welding can be used. Good. Similarly, the bonding of the tab regions of the negative electrode 506 and the negative electrode connection to the tab region of the outermost negative electrode The electrode 511 is joined.

[0274] Next, the negative electrode 506, separator 507, and positive electrode 503 are placed on the outer casing 509.

[0275] Next, as shown in Figure 22(C), the outer casing 509 is folded at the part indicated by the dashed line. Next, the outer perimeter of the exterior body 509 is joined. For joining, for example, heat compression bonding may be used. In order to allow the electrolyte 508 to be added later, a part (or one side) of the outer casing 509 A region that is not connected (hereinafter referred to as the inlet) is provided.

[0276] Next, the electrolyte 508 (not shown) is introduced into the outer casing 509 through the inlet provided in the outer casing 5 Introduce into the inside of 09. Introduce electrolyte 508 under reduced pressure or inert atmosphere. It is preferable to do so. And finally, the inlet is joined. In this way, the laminate type A secondary battery 500 can be manufactured.

[0277] By using the positive electrode active material described in the previous embodiment for the positive electrode 503, high capacity cycle This allows for the creation of a secondary battery 500 with superior characteristics.

[0278] [Bendable rechargeable battery] Next, an example of a bendable secondary battery will be described with reference to Figures 23 and 24. .

[0279] Figure 23(A) shows a schematic top view of a bendable secondary battery 250. Figure 23(B1 ), (B2), and (C) respectively correspond to the cutting lines C1-C2 and C3- in Figure 23(A). C4 is a schematic cross-sectional view at the cutting line A1-A2. The secondary battery 250 is connected to the outer casing 251 and It has a positive electrode 211a and a negative electrode 211b housed inside the outer casing 251. Lead 212a is electrically connected to 1a, and lead 211b is electrically connected to the negative electrode. Code 212b extends to the outside of the outer casing 251. Also, the area enclosed by the outer casing 251 In addition to the positive electrode 211a and the negative electrode 211b, an electrolyte (not shown) is sealed inside. .

[0280] The positive electrode 211a and negative electrode 211b of the secondary battery 250 will be explained using Figure 24. Figure 24(A) shows the stacking order of the positive electrode 211a, negative electrode 211b, and separator 214. This is an explanatory perspective view. Figure 24(B) shows the positive electrode 211a and the negative electrode 211b, as well as the Lee This is a perspective view showing lead 212a and lead 212b.

[0281] As shown in Figure 24(A), the secondary battery 250 has multiple strip-shaped positive electrodes 211a, multiple short It has a booklet-shaped negative electrode 211b and a plurality of separators 214. Positive electrode 211a and negative electrode 2 Each of the 11b has a protruding tab portion and a portion other than the tab. One of the positive electrodes 211a A positive electrode active material layer is formed on the part of the surface other than the tab, and on the part of one side of the negative electrode 211b other than the tab A negative electrode active material layer is formed in minutes.

[0282] The sides of the positive electrode 211a where the positive electrode active material layer is not formed, and the negative electrode active material of the negative electrode 211b The positive electrode 211a and the negative electrode 211b are stacked so that surfaces without a formed surface are in contact with each other. It can be done.

[0283] Furthermore, the surface on which the positive electrode active material of the positive electrode 211a is formed and the surface on which the negative electrode active material of the negative electrode 211b is formed A separator 214 is provided between the surfaces. In Figure 24, the separator is shown for clarity. The number 214 is shown with a dotted line.

[0284] Also, as shown in Figure 24(B), the multiple positive electrodes 211a and leads 212a are connected at the joint 215 They are electrically connected at a. The multiple negative electrodes 211b and leads 212b are connected at joint 2 Electrically connected at 15b.

[0285] Next, the exterior body 251 will be explained using Figures 23(B1), (B2), (C), and (D). ru.

[0286] The outer casing 251 has a film-like shape and sandwiches the positive electrode 211a and the negative electrode 211b. It is folded in two. The outer casing 251 has a folded portion 261 and a pair of sealing portions 2 It has 62 and a sealing portion 263. The pair of sealing portions 262 are positive electrode 211a and negative electrode It is provided on either side of pole 211b and can also be called a side seal. Also, seal portion 26 3 has a portion that overlaps with leads 212a and 212b, and is also called the top seal. It is possible.

[0287] The outer casing 251 has a ridge line 271 and a valley line 2 in the portion that overlaps with the positive electrode 211a and the negative electrode 211b. It is preferable that the 72 have a wave shape arranged alternately. Also, the sealing portion 26 of the outer casing 251 2 and the sealing portion 263 are preferably flat.

[0288] Figure 23(B1) shows a cross-section cut at the point where it overlaps with ridge line 271, and Figure 23(B2) shows... This is a cross-section taken at the point where it overlaps with valley line 272. Figures 23(B1) and (B2) are both secondary. This corresponds to the cross-section in the width direction of the battery 250 and the positive electrode 211a and negative electrode 211b.

[0289] Here, the ends in the width direction of the positive electrode 211a and the negative electrode 211b, i.e., the positive electrode 211a and The distance La is defined as the distance between the end of the negative electrode 211b and the seal portion 262. (Secondary battery 250) When deformation such as bending is applied, the positive electrode 211a and the negative electrode 211b become longer, as will be described later. They deform so that they are offset from each other in the opposite direction. In this case, if the distance La is too short, the outer casing 251 and The positive electrode 211a and the negative electrode 211b rub against each other strongly, which can damage the outer casing 251. In particular, when the metal film of the outer casing 251 is exposed, the metal film corrodes due to the electrolyte. There is a risk of being eaten. Therefore, it is preferable to set the distance La as long as possible. However, if the distance La is made too large, the volume of the secondary battery 250 will increase.

[0290] Furthermore, the thicker the combined thickness of the stacked positive electrode 211a and negative electrode 211b, the greater the positive electrode 211 It is preferable to increase the distance La between a and the negative electrode 211b and the seal portion 262. .

[0291] More specifically, stacked positive electrode 211a and negative electrode 211b and separate (not shown) When the total thickness of -214 is t, the distance La is between 0.8 and 3.0 times the thickness t. Preferably, 0.9 times or more and 2.5 times or less, more preferably 1.0 times or more and 2.0 times or less. It is preferable that the distance La is within this range, making it compact and resistant to bending. This enables the creation of highly reliable batteries.

[0292] Furthermore, when the distance between the pair of sealing portions 262 is denoted as distance Lb, distance Lb is set to the positive electrode 211a and to be sufficiently larger than the width of the negative electrode 211b (here, the width Wb of the negative electrode 211b). This is preferable. This allows the secondary battery 250 to withstand repeated bending and other deformations. Even if the positive electrode 211a and the negative electrode 211b come into contact with the outer casing 251, the positive electrode 211a and the negative electrode Because a portion of the pole 211b can be shifted in the width direction, the positive pole 211a and the negative pole 211b This effectively prevents the outer casing 251 from rubbing against each other.

[0293] For example, the difference between the distance Lb between the pair of sealing portions 262 and the width Wb of the negative electrode 211b is the positive electrode The thickness t of 211a and the negative electrode 211b is 1.6 times or more and 6.0 times or less, preferably 1.8 times. It is preferable that the ratio is 5.0 times or less, and more preferably 2.0 times or more and 4.0 times or less. .

[0294] In other words, it is preferable that the distance Lb, width Wb, and thickness t satisfy the relationship shown in Equation 1 below. It's nice.

[0295]

number

[0296] Here, a is 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, more preferably It satisfies the condition of being between 1.0 and 2.0.

[0297] Figure 23(C) shows a cross-section including lead 212a, secondary battery 250, and positive electrode 211a. And it corresponds to the longitudinal cross-section of the negative electrode 211b. As shown in Figure 23(C), it is bent. In section 261, the longitudinal ends of the positive electrode 211a and the negative electrode 211b, and the outer casing 251 It is preferable to have a space 273 between it and the other.

[0298] Figure 23(D) shows a schematic cross-sectional view of the secondary battery 250 when bent. This corresponds to the cross-section at the cutting line B1-B2 in Figure 23(A).

[0299] When the secondary battery 250 is bent, a portion of the outer casing 251 located on the outside of the bend stretches, and a portion located on the inside stretches. Other parts that are placed will deform to shrink. More specifically, the parts located on the outside of the outer casing 251 The part deforms so that the wave amplitude is small and the wave period is large. Meanwhile, the outer casing 2 The portion located inside 51 is deformed so that the wave amplitude is large and the wave period is small. In this way, the exterior body 251 deforms, and as it bends, the exterior body 251 is affected. Because the stress is relieved, the material that makes up the exterior 251 does not need to expand or contract. As a result, the outer casing 251 was not damaged, and the secondary battery 250 could be bent with little force. Cut.

[0300] Furthermore, as shown in Figure 23(D), when the secondary battery 250 is bent, the positive electrode 211a and the negative electrode 211b and the other are relatively shifted. At this time, multiple stacked positive electrodes 211a and Since one end of the negative electrode 211b on the sealing portion 263 side is fixed by the fixing member 217, Each component shifts such that the amount of displacement increases the closer it is to the bent portion 261. This causes the positive electrode The stress on 211a and the negative electrode 211b is relieved, and the positive electrode 211a and the negative electrode 211b The device itself does not need to expand or contract. As a result, the positive electrode 211a and the negative electrode 211b are not damaged. It can bend a 250-cell secondary battery without any problems.

[0301] Furthermore, there is a space 273 between the positive electrode 211a and the negative electrode 211b and the outer casing 251. As a result, the positive electrode 211a and the negative electrode 211b, which are located on the inside when bent, are positioned within the outer casing 251 It can shift relative to each other without making contact.

[0302] The secondary battery 250 illustrated in Figures 23 and 24 can withstand repeated bending and stretching, and the outer casing remains intact. Damage to the body, damage to the positive electrode 211a and negative electrode 211b are less likely to occur, and the battery characteristics do not deteriorate. It is a difficult battery. The positive electrode 211a of the secondary battery 250 is as described in the previous embodiment. By using a positive electrode active material, it is possible to create a battery with even better cycle characteristics.

[0303] (Embodiment 4) This embodiment describes an example in which a secondary battery, which is one aspect of the present invention, is mounted in an electronic device. do.

[0304] First, as described in part of Embodiment 3, a bendable secondary battery is mounted in an electronic device. Examples are shown in Figures 25(A) to 25(G). An electronic device using a bendable secondary battery. As equipment, for example, television equipment (also called television or television receiver), Computer monitors, digital cameras, digital video cameras, digital photo Frame, mobile phone (also called mobile phone or mobile phone device), portable game console, mobile information Examples include terminals, audio playback devices, and large game machines such as pachinko machines.

[0305] Furthermore, rechargeable batteries with flexible shapes can be installed in the interior or exterior walls of houses and buildings, or in automobiles. It can also be incorporated along the curved surfaces of the interior or exterior.

[0306] Figure 25(A) shows an example of a mobile phone. Mobile phone 7400 has a housing 7401 In addition to the display unit 7402 incorporated into it, there are operation buttons 7403, an external connection port 7404, and It is equipped with a speaker 7405, a microphone 7406, etc. Note that the mobile phone 7400 is secondary. It has a battery 7407. The secondary battery 7407 of the present invention is used This allows us to provide lightweight and long-lasting mobile phones.

[0307] Figure 25(B) shows the mobile phone 7400 in a curved state. When the 0 is deformed by an external force and the whole thing is bent, the secondary battery located inside is revealed. The 7407 is also bent. Figure 25(C) shows the state of the bent secondary battery 7407 at that time. As shown in the diagram, the 7407 secondary battery is a thin rechargeable battery. The 7407 secondary battery is in a bent state. It is fixed in place. Furthermore, the secondary battery 7407 has lead electrodes electrically connected to the current collector. It has. For example, the current collector is made of copper foil, and a portion of it is alloyed with gallium to make contact with the current collector. The adhesion with the active material layer is improved, resulting in a highly reliable structure for the secondary battery 7407 even when it is bent. It is complete.

[0308] Figure 25(D) shows an example of a bangle-type display device. The portable display device 7100 is The device comprises a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. Figure 25(E) also shows the state of the bent secondary battery 7104. The secondary battery 7104 is bent. When worn on the user's arm in a distorted state, the casing deforms, causing part of the secondary battery 7104 or All curvatures change. Note that the degree of curvature at any point in the curve is equal to the radius of the corresponding circle. The value expressed is called the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, the radius of curvature Within a range of 40mm to 150mm, a portion of the main surface of the housing or secondary battery 7104 The whole thing changes. The radius of curvature on the main surface of secondary battery 7104 is 40 mm or more and 150 High reliability can be maintained within a range of mm or less. The present invention applies to the secondary battery 7104 described above. By using one embodiment of a secondary battery, a lightweight and long-lasting portable display device can be provided.

[0309] Figure 25(F) shows an example of a wristwatch-type personal information terminal. The personal information terminal 7200 is , housing 7201, display unit 7202, band 7203, buckle 7204, operation button 72 05. It is equipped with input / output terminals 7206, etc.

[0310] The 7200 mobile information terminal offers mobile phone, email, document viewing and creation, music playback, and internet connectivity. - It can run various applications such as network communication and computer games. ru.

[0311] The display unit 7202 has a curved display surface, and displays are made along the curved display surface. It can do this. In addition, the display unit 7202 is equipped with a touch sensor, allowing you to touch the screen with your finger or stylus. It can be operated by touching it. For example, the icon 72 displayed on the display unit 7202 Touching 07 will launch the application.

[0312] The 7205 control button is used for setting the time, turning the power on and off, and turning wireless communication on and off. It has various functions such as operation, silent mode activation and deactivation, and power saving mode activation and deactivation. This can be done. For example, the operating system built into the mobile information terminal 7200 The stem also allows you to freely configure the function of the control button 7205.

[0313] Furthermore, the personal information terminal 7200 is capable of performing standardized short-range wireless communication. Yes, for example, by communicating with a wireless headset, hands-free operation is possible. You can also make phone calls.

[0314] Furthermore, the portable information terminal 7200 is equipped with an input / output terminal 7206, and connects to other information terminals via a connector. It can directly exchange data via this. It can also be charged via input / output terminal 7206. It is also possible to perform this operation. Note that charging is performed wirelessly without using input / output terminal 7206. That's fine.

[0315] The display unit 7202 of the portable information terminal 7200 has a secondary battery according to one embodiment of the present invention. By using a secondary battery according to one aspect of the present invention, a lightweight and long-lasting portable information terminal can be provided. For example, the secondary battery 7104 shown in Figure 25(E) is placed inside the housing 7201 in a curved state. Alternatively, it can be incorporated into the band 7203 in a flexible state.

[0316] The personal information terminal 7200 preferably has a sensor. For example, a fingerprint sensor. Human body sensors such as pulse sensors and body temperature sensors, as well as touch sensors, pressure sensors, and acceleration sensors. It is preferable that the following are installed:

[0317] Figure 25(G) shows an example of an armband-type display device. The display device 7300 consists of a display unit 7 The present invention has a secondary battery having 304. The display device 7300 is a table The display unit 7304 can also be equipped with a touch sensor, and can function as a portable information terminal. It is also possible.

[0318] The display unit 7304 has a curved display surface, and displays are made along the curved display surface. Yes, it is possible. Furthermore, the display device 7300 can communicate via standardized short-range wireless communication, etc. The situation can be changed.

[0319] Furthermore, the display device 7300 is equipped with input / output terminals and can be directly connected to other information terminals via connectors. It can exchange data. It can also be charged via input / output terminals. Furthermore, charging may be performed wirelessly without using input / output terminals.

[0320] By using a secondary battery according to one aspect of the present invention as the secondary battery of the display device 7300, We can provide display devices with a long lifespan in large quantities.

[0321] Furthermore, the figure shows an example of mounting the secondary battery with good cycle characteristics shown in the previous embodiment into an electronic device. This will be explained using Figures 25(H), 26 and 27.

[0322] By using a secondary battery according to one aspect of the present invention as a secondary battery in everyday electronic devices, a lightweight and long-lasting battery can be achieved. We can provide a variety of products. For example, as everyday electronic devices, electric toothbrushes, electric shavers, etc. Examples include mobile beauty devices, and the rechargeable batteries for these products are designed with ease of handling by the user in mind. What is desired is a rechargeable battery that is stick-shaped, small, lightweight, and has a large capacity.

[0323] Figure 25(H) is a perspective view of a device also known as a tobacco-containing smoking device (electronic cigarette). In 25(H), the electronic cigarette 7500 includes an atomizer 7501 containing a heating element, and The cart contains the 7504 rechargeable battery that powers the Myza, as well as liquid supply bottles, sensors, and other components. It consists of Ridge 7502. To enhance safety, overcharging of the secondary battery 7504 and over A protective circuit to prevent discharge may be electrically connected to the secondary battery 7504. (See Figure 25(H)) The secondary battery 7504 has external terminals so that it can be connected to a charging device. The 504 is the tip when held, so the overall length is short and the weight is light. This is desirable. A secondary battery according to one aspect of the present invention has high capacity and good cycle characteristics, We offer the 7500, a small and lightweight e-cigarette that can be used for extended periods of time. It can be used.

[0324] Next, Figures 26(A) and 26(B) show an example of a foldable tablet device. The tablet terminal 9600 shown in Figures 26(A) and 26(B) has a housing 9630. a, housing 9630b, movable part 9640 connecting housing 9630a and housing 9630b, display A display unit 9631 having section 9631a and display unit 9631b, switches 9625 to switches It has a 9627, a fastener 9629, and an operating switch 9628. The display unit 9631 has, By using a flexible panel, a tablet terminal with a larger display area can be created. This is possible. Figure 26(A) shows the tablet terminal 9600 in an open state, and Figure 26( B) shows the tablet device 9600 in the closed position.

[0325] Furthermore, the tablet terminal 9600 stores energy inside the housings 9630a and 9630b. It has a body 9635. The energy storage body 9635 passes through the movable part 9640 and the housing 9630a and housing It is provided over 9630b.

[0326] The display unit 9631 can have all or part of its area designated as a touch panel area, and By touching the image, text, input form, etc., including the icon displayed in that area, data can be accessed. Input is possible. For example, the entire surface of the display unit 9631a on the chassis 9630a can be used for keyboard input. The access buttons are displayed, and information such as text and images is shown on the display unit 9631b on the housing 9630b. You may also use it by displaying it.

[0327] Furthermore, the keyboard is displayed on the display unit 9631b on the chassis 9630b side, and the chassis 9630a The side display unit 9631a may be used to display information such as characters and images. Display a touch panel keyboard display switch button on 9631, and By touching the tongue with a finger or stylus, the keyboard will be displayed on the display unit 9631. You may do so.

[0328] Furthermore, the touch panel area of ​​the display unit 9631a on the housing 9630a side and the housing 9630b side It is also possible to simultaneously input touch data to the touch panel area of ​​the display unit 9631b.

[0329] Furthermore, switches 9625 to 9627 are used to operate the tablet terminal 9600. It's not just an interface for doing that, but also an interface that allows you to switch between various functions. - It may also be a face. For example, at least of switch 9625 to switch 9627 One of them functions as a switch to turn the power of the tablet device 9600 on and off. It is also possible that, for example, at least one of switches 9625 to 9627 is vertical A function to switch the display orientation, such as horizontal or horizontal display, or to switch between black and white and color display. It may also have a function to enable. Also, for example, at least one of switches 9625 to 9627 Furthermore, the display unit 963 may have a function to adjust the brightness of the display unit 9631. The brightness of 1 is detected by the light sensor built into the tablet device 9600 during use. It can be optimized according to the amount of light. Note that tablet devices use light sensors. In addition, it incorporates other detection devices such as gyroscopes, accelerometers, and other sensors that detect tilt. You may allow it.

[0330] Also, in Figure 26(A), the display unit 9631a on the housing 9630a side and the display on the housing 9630b side The example shows that the display area of ​​section 9631b is almost the same as that of display section 9631a and display section 9 The display area of ​​each 631b is not particularly limited, and if one size is different from the other... They may be different, and the display quality may also differ. For example, one may have a higher resolution display than the other. It may also be used as a display panel that can perform the following actions.

[0331] Figure 26(B) shows the tablet terminal 9600 in a folded state. The terminal type 9600 includes a housing 9630, a solar cell 9633, and a DC-DC converter 9636. It has a charge / discharge control circuit 9634. Furthermore, as an energy storage body 9635, according to one aspect of the present invention A power storage device is used.

[0332] As mentioned above, the 9600 tablet can be folded in half, so when not in use... The casings 9630a and 9630b can be folded so that they overlap. By folding it, the display unit 9631 can be protected, thus improving the durability of the tablet terminal 9600. It can improve performance. Furthermore, the energy storage body 9635 using a secondary battery according to one aspect of the present invention is high Because it has a large capacity and good cycle characteristics, it is a tablet that can be used for long periods of time over an extended period. We can provide the T-type terminal 9600.

[0333] In addition, the tablet terminal 9600 shown in Figures 26(A) and 26(B) is Features that display various information (still images, videos, text images, etc.), calendar, date or It has the function of displaying the time and other information on the display unit, and the ability to perform touch input operations or edit the information displayed on the display unit. Features such as touch input functionality, the ability to control processing through various software (programs), etc. It can have.

[0334] Power is supplied by a solar cell 9633 mounted on the surface of the tablet device 9600. It can be supplied to a panel, display unit, or video signal processing unit, etc. Note: Solar cell 963 3 can be provided on one or both sides of the housing 9630, and efficiently charges the energy storage unit 9635. This configuration can be used. Note that a lithium-ion battery can be used as the energy storage unit 9635. Having it offers advantages such as enabling miniaturization.

[0335] Furthermore, the configuration and operation of the charge / discharge control circuit 9634 shown in Figure 26(B) are shown in Figure 26( A block diagram is shown and explained in C). Figure 26(C) shows the solar cell 9633 and the energy storage unit 963. 5. DC-DC converter 9636, converter 9637, switch SW1 to SW3, table The diagram shows the section 9631, and includes the energy storage unit 9635, the DC-DC converter 9636, and the capacitor. The converter 9637 and switches SW1 to SW3 are connected to the charge / discharge control circuit 96 shown in Figure 26(B). This corresponds to section 34.

[0336] First, let's explain an example of operation when electricity is generated by the solar cell 9633 using ambient light. The electricity generated by the solar panel is converted to a DC-DC converter to provide the voltage needed to charge the 9635 energy storage unit. The converter 9636 performs voltage boosting or de-voltage adjustment. Then, the solar cell controls the operation of the display unit 9631. When power from 9633 is used, switch SW1 is turned ON, and converter 9637 The voltage is then boosted or lowered to the voltage required for the display unit 9631. If you do not want the display to appear, turn SW1 off and SW2 on to charge the battery 9635. The configuration should be designed to handle electricity.

[0337] The solar cell 9633 is shown as an example of a power generation method, but it is not particularly limited to this method. Energy storage using other power generation methods such as electrical elements (piezo elements) and thermoelectric conversion elements (Peltier elements) The configuration may also involve charging the body 9635. For example, power may be transmitted and received wirelessly (contactlessly). This configuration uses a contactless power transmission module for charging, or a combination of other charging methods. That's fine.

[0338] Figure 27 shows an example of another electronic device. In Figure 27, the display device 8000 is part of the present invention. This is an example of an electronic device using a secondary battery 8004 according to the embodiment. Specifically, the display device 800 0 corresponds to a display device for receiving TV broadcasts, and consists of a housing 8001, a display unit 8002, and a speaker unit. The invention includes 8003, a secondary battery 8004, etc. A secondary battery 8004 according to one aspect of the present invention has a housing It is located inside the body 8001. The display device 8000 receives power from the commercial power supply. It can be used to power the device, or it can use the power stored in the secondary battery 8004. Even when power cannot be supplied from the commercial power source due to a power outage, etc., according to one aspect of the present invention By using the secondary battery 8004 as an uninterruptible power supply, the display device 8000 can be used. ru.

[0339] The display unit 8002 has light-emitting elements such as liquid crystal display devices and organic EL elements in each pixel. Equipment, electrophoresis display device, DMD (Digital Micromirror Display) ce), PDP (Plasma Display Panel), FED (Field Semiconductor display devices such as Emission Displays can be used.

[0340] In addition to being used for receiving TV broadcasts, display devices are also used for personal computers, advertising displays, and more. This includes all information display devices.

[0341] In Figure 27, the fixed lighting device 8100 is a secondary battery 81 according to one aspect of the present invention. This is an example of an electronic device using 03. Specifically, the lighting device 8100 has a housing 8101 and light It has a power source 8102, a secondary battery 8103, etc. In Figure 27, the secondary battery 8103 is located in the housing 81 An example is provided where 01 and the light source 8102 are installed inside the ceiling 8104. However, the secondary battery 8103 may also be located inside the housing 8101. The 8100 can receive power from the commercial power supply, or it can store power in the secondary battery 8103. It is also possible to use the accumulated power. Therefore, if power is not supplied from the commercial power source due to a power outage, etc. Even when it is not possible to receive a power supply, the secondary battery 8103 according to one aspect of the present invention can be used as an uninterruptible power supply. This makes it possible to use the lighting device 8100.

[0342] Figure 27 illustrates a fixed lighting device 8100 installed on the ceiling 8104. However, in one aspect of the present invention, the secondary battery is located in a location other than the ceiling 8104, for example, the side wall 8105, the floor 8 106, It can also be used in fixed lighting devices installed in windows 8107, etc., and on a tabletop It can also be used in lighting fixtures and other similar devices.

[0343] Furthermore, the light source 8102 can be an artificial light source that uses electricity to artificially produce light. Specifically, this includes incandescent light bulbs, discharge lamps such as fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements. The element is an example of the artificial light source mentioned above.

[0344] In Figure 27, an air conditioner having an indoor unit 8200 and an outdoor unit 8204, This is an example of an electronic device using a secondary battery 8203 according to one aspect of the present invention. Specifically, indoor The unit 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, etc. (See Figure 27) This example illustrates the case where the secondary battery 8203 is provided in the indoor unit 8200, but Battery 8203 may be located in the outdoor unit 8204. Alternatively, it may be located in the indoor unit 8200 and the outdoor unit. The secondary battery 8203 may be provided on both sides of the unit 8204. (Air conditioner) It can receive power from the commercial power supply, or from the electricity stored in the secondary battery 8203. It can also use force. In particular, both the indoor unit 8200 and the outdoor unit 8204 can use secondary batteries 82 If 03 is provided, when power cannot be supplied from the commercial power source due to a power outage, etc. Furthermore, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, an air conditioner can be used. Conditioner can be used.

[0345] Note that Figure 27 shows a separate-type air conditioner consisting of an indoor unit and an outdoor unit. As an example, an integrated air conditioner has both the indoor and outdoor unit functions in a single housing. A secondary battery according to one aspect of the present invention can also be used in the conditioner.

[0346] In Figure 27, the electric refrigerator 8300 is powered by a secondary battery 8304 according to one aspect of the present invention. This is an example of the electronic equipment used. Specifically, the electric refrigerator 8300 consists of a casing 8301 and a refrigerator. It has a storage room door 8302, a freezer room door 8303, a secondary battery 8304, etc. In Figure 27, two The next battery 8304 is located inside the casing 8301. The electric refrigerator 8300 is, It can receive power from the commercial power supply, or it can use the power stored in the secondary battery 8304. It can also be used. Therefore, when power cannot be supplied from the commercial power source due to a power outage, etc. However, by using the secondary battery 8304 according to one aspect of the present invention as an uninterruptible power supply, electric cooling The 8300 freezer / refrigerator will become available for use.

[0347] Of the electronic devices mentioned above, high-frequency heating devices such as microwave ovens and electric rice cookers are also included. The equipment requires high power in a short period of time. Therefore, it needs to supplement the power that cannot be supplied by the commercial power supply. By using a secondary battery according to one aspect of the present invention as an auxiliary power source for electronic devices, This prevents the commercial power circuit breaker from tripping during use.

[0348] Furthermore, during periods when electronic devices are not in use, especially the total amount of electricity that can be supplied by the commercial power source... Of these, during periods when the proportion of electricity actually used (called the electricity usage rate) is low, secondary By storing power in the battery, the rate of power consumption outside of the above-mentioned time period is suppressed. It is possible. For example, in the case of the electric refrigerator 8300, when the temperature is low, the refrigerator door 830 2. At night when the freezer door 8303 is not opened or closed, power is stored in the secondary battery 8304. And as the temperature rises, the refrigerator door 8302 and the freezer door 8303 are opened and closed. During the daytime, by using the secondary battery 8304 as an auxiliary power source, the daytime power usage rate It can be kept low.

[0349] According to one aspect of the present invention, the cycle characteristics of a secondary battery are improved, and its reliability is enhanced. This is possible. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be made, and therefore This allows for improved characteristics of secondary batteries, and therefore, the secondary batteries themselves can be made smaller and lighter. Yes, it is possible. Therefore, a secondary battery, which is one aspect of the present invention, can be used in the electronic device described in this embodiment. By incorporating this technology, electronic devices can be made longer-lasting and lighter. This can be implemented in appropriate combination with other embodiments.

[0350] (Embodiment 5) This embodiment shows an example in which a secondary battery, which is one aspect of the present invention, is mounted on a vehicle.

[0351] When a secondary battery is installed in a vehicle, it becomes a hybrid electric vehicle (HEV), an electric vehicle (EV), or a hybrid electric vehicle. This will enable the realization of next-generation clean energy vehicles such as plug-in hybrid electric vehicles (PHEVs). .

[0352] Figure 28 illustrates a vehicle using a secondary battery, which is one embodiment of the present invention. Figure 28(A) The automobile 8400 shown is an electric vehicle that uses an electric motor as a power source for driving. Yes. Alternatively, an electric motor and an engine can be appropriately selected and used as the power source for propulsion. This is a hybrid vehicle that can achieve the following: By using one aspect of the present invention, the driving range can be extended. This makes it possible to realize a vehicle. In addition, the 8400 automobile has a secondary battery. The secondary battery is The secondary battery modules shown in Figures 13(C) and 13(D) are positioned on the floor portion of the vehicle. You can use them by arranging them side by side. Also, a battery pack made by combining multiple secondary batteries as shown in Figure 16. It may be installed on the floor inside the vehicle. The secondary battery drives the electric motor 8406. In addition, it supplies power to light-emitting devices such as headlights 8401 and interior lights (not shown). They can provide it.

[0353] Furthermore, the secondary battery is used for the speedometer, tachometer, and other displays in the 8400 automobile. It can supply power to the device. In addition, the secondary battery is the navigation system of the 8400 automobile. It can supply power to semiconductor devices such as ignition systems.

[0354] The automobile 8500 shown in Figure 28(B) is a secondary battery that the automobile 8500 has plug-in type It can be charged by receiving power from an external charging facility using methods such as contactless power supply. Figure 28(B) shows the two devices mounted on the automobile 8500, connected to the ground-mounted charging device 8021. The next diagram shows the state in which the battery 8024 is being charged via cable 8022. Therefore, charging methods and connector standards are specified by CHAdeMO (registered trademark) and Combo, etc. The method can be carried out as appropriate. The charging device 8021 is installed at a charging station in a commercial facility. It is also fine to use a household power supply. For example, plug-in technology allows for external power supply. The power supply can charge the secondary battery 8024 installed in the 8500 vehicle. Charging is performed by converting AC power to DC power via a conversion device such as an AC / DC converter. It is possible.

[0355] 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.

[0356] Furthermore, Figure 28(C) shows an example of a two-wheeled vehicle using a secondary battery according to one embodiment of the present invention. Figure 28 The scooter 8600 shown in (C) includes a secondary battery 8602, side mirrors 8601, and turn signals. It is equipped with a light 8603. The secondary battery 8602 supplies electricity to the turn signal light 8603. can.

[0357] Furthermore, the scooter 8600 shown in Figure 28(C) has a secondary battery 860 in the under-seat storage 8604. It can store 2. The secondary battery 8602 can be stored even if the under-seat storage 8604 is small. It can be stored in the under-seat storage compartment 8604. The secondary battery 8602 is removable. When charging, the 8602 secondary battery is carried indoors, charged, and stored before driving. That's all you need to do.

[0358] According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery is increased. This makes it possible to make the secondary battery itself smaller and lighter. Making the body smaller and lighter contributes to reducing the vehicle's weight, thus improving its driving range. It is possible. Furthermore, the secondary battery installed in the vehicle can also be used as a power source for purposes other than the vehicle itself. In this case, for example, it is possible to avoid using commercial power during peak electricity demand. If the use of commercial power can be avoided during peak electricity demand, energy conservation and two It can contribute to reducing carbon dioxide emissions. Furthermore, if the cycle characteristics are good, secondary... Because batteries can be used for extended periods, the amount of rare metals used, including cobalt, can be reduced. It is possible.

[0359] This embodiment can be implemented in appropriate combination with other embodiments. [Examples]

[0360] In this example, a positive electrode active material according to one aspect of the present invention and a positive electrode active material of a comparative example were prepared, and XP Features were analyzed using S, SEM, and XRD. Furthermore, cycle characteristics during high-voltage charging were analyzed. Sex was evaluated.

[0361] [Fabrication of positive electrode active material] ≪Sample 1≫ In Sample 1, the manufacturing method shown in Figure 2 of Embodiment 1 uses cobalt as the transition metal. A positive electrode active material was fabricated. First, the molar ratio of LiF to MgF2 was set to LiF:MgF2=1: The mixture was weighed to a value of 3, acetone was added as a solvent, and the mixture was mixed and ground using a wet process. The grinding was performed using a ball mill with zirconia balls at 150 rpm for 1 hour. The processed material was recovered and used as the first mixture (steps S11 to S14 in Figure 2). ).

[0362] Figure 29 shows the particle size distribution of LiF and MgF2 before mixing, and the first mixture after mixing. The particle size distribution is measured using a laser diffraction particle size distribution analyzer, SALD-2200 (Shimadzu Corporation). The experiment was conducted using (manufacturing). The D50 of the first mixture was 3.561 μm, and the mode diameter was 4.008 μm. Yes. Figure 29 and these results confirm that the first mixture was sufficiently pulverized. It was done.

[0363] In Sample 1, lithium cobalt oxide was pre-synthesized by Nippon Chemical Industries, Ltd. We used CellSeed C-10N manufactured by our company (step S25 in Figure 2). CellSeed C-10N As described in Embodiment 1, this is a cobalt acid with a D50 of about 12 μm and few impurities. It is lithium.

[0364] Next, the amount of magnesium atoms in the first mixture relative to the molecular weight of lithium cobalt oxide The ingredients were weighed to a quantity of 0.5 atomic percent and mixed by dry mixing. Zirconia balls were used for mixing. The process was carried out using a ball mill at 150 rpm for 1 hour. The processed material was collected and used for the second mixture. This was done (steps S31 to S33 in Figure 2).

[0365] Next, the second mixture is placed in an alumina crucible and heated in an oxygen-filled muffle furnace at 850°C for 60 minutes. The alumina crucible was annealed for 2 hours. During annealing, the crucible was covered. The oxygen flow rate was 10 L. The rate was set to / min. The heating rate was set to 200°C / hr, and the cooling rate was reduced over a period of 10 hours or more. The processed material was used as the positive electrode active material for Sample 1 (Steps S34 and S35 in Figure 2). ).

[0366] ≪Sample 2≫ Except for setting the annealing time to 2 hours in step S34 of Figure 2, the process was carried out in the same manner as in Sample 1. The prepared sample was designated as Sample 2 (comparative example).

[0367] ≪Sample 3≫ Except for not performing annealing in step S34 in Figure 2, the sample was prepared in the same manner as Sample 1. The result was designated as Sample 3 (Comparative Example).

[0368] ≪Sample 4≫ Cobalt acid without any special treatment (steps S31 to S35 in Figure 2 are not performed) Lithium (Cellseed C-10N) was used as Sample 4 (Comparative Example).

[0369] ≪Sample 5≫ In Sample 5, lithium cobalt oxide was pre-synthesized by Nippon Chemical Industries, Ltd. We used Cellseed C-5H manufactured by our company (step S25 in Figure 2). Also, step S in Figure 2 In sample 34, annealing was performed at 900°C for 2 hours. Other conditions were the same as for sample 1. It was made.

[0370] ≪Sample 6≫ Lithium cobaltate without any special processing (steps S31 to S35 are not performed) Cellseed C-5H was designated as Sample 6 (Comparative Example).

[0371] ≪Sample 7≫ In Sample 7, a magnesium source and a fluorine source were added to the lithium cobalt oxide starting material. It was then calcined to synthesize lithium cobalt oxide containing magnesium and fluorine. After that, an We performed the procedure.

[0372] Specifically, lithium carbonate is used as the lithium source, and cobalt oxide and magnesium are used as the cobalt source. Magnesium oxide is used as the um source and lithium fluoride as the fluorine source, with an atomic ratio of Li Co 0.99 Mg 0.01 O 1.98 F 0.02 Weigh the ingredients to achieve the desired result and mix in a ball mill. did.

[0373] Next, the mixture is placed in an alumina crucible, covered, and heated in a muffle furnace under a dry air atmosphere for 95 minutes. The product was fired at 0°C for 10 hours. The dry air flow rate was 10 L / min. The heating rate was 200°C / h. The temperature was set to r, and the cooling process was carried out for more than 10 hours. The materials after heat treatment were treated with magnesium and fluorine. It was formulated as lithium cobaltate containing [the specified compound].

[0374] Next, place lithium cobaltate, which contains magnesium and fluorine, into an alumina crucible and close the lid. The material was then annealed in an oxygen-filled muffle furnace at 800°C for 2 hours. The oxygen flow rate was 10 L. The rate was set to / min. The heating rate was set to 200°C / hr, and the cooling rate was reduced over a period of 10 hours or more. The material after processing was designated as Sample 7.

[0375] ≪Sample 8≫ Lithium cobalt oxide (commercially available) containing magnesium and fluorine (Nippon Chemical Industries) Place the commercially manufactured Cellseed C-20F in an alumina crucible, cover it, and place it in an oxygen atmosphere. The material was annealed in a furnace at 800°C for 2 hours. The oxygen flow rate was 10 L / min. The temperature was set to 0°C / hr, and the cooling process was carried out for more than 10 hours. The material after heat treatment was used for sample 8. That's what I decided.

[0376] ≪Sample 9≫ No special processing is performed (steps S31 to S35 are not performed), magnesium And lithium cobalt oxide containing fluorine (Cellseed C-20F manufactured by Nippon Chemical Industries, Ltd.) This was designated as pull 9 (comparative example).

[0377] ≪Sample 10≫ In Sample 10, the pre-synthesized lithium cobalt oxide was Aldrich Co Lithium baltate (catalog No. 442704, D50 is approximately 11 μm) was used (Figure) Step S25 of Figure 2). Also, in step S34 of Figure 2, annealing is performed at 850°C for 20 minutes. Time was used. Other conditions were the same as for Sample 1.

[0378] ≪Sample 11≫ Lithium cobaltate without any special processing (steps S31 to S35 are not performed) Sample 11 (comparative example) was selected from MU (Aldrich No. 442704).

[0379] ≪Sample 12≫ In Sample 12 (Comparative Example), lithium cobalt oxide was synthesized in advance, and Nippon Chemical We used CellSeed C-5hV manufactured by Gaku Kogyo Co., Ltd. (D50 is approximately 6 μm) (Step S2 in Figure 2). 5) This is lithium cobalt oxide containing approximately 5100 ppm wt of titanium as an impurity. Furthermore, in step S34 of Figure 2, annealing was performed at 800°C for 2 hours. The conditions were the same as for Sample 1.

[0380] ≪Sample 13≫ Sample 13 (comparative example) under annealing conditions of 850°C and 6°C in step S34 of Figure 2. Aside from setting the time to 0 hours, it was prepared in the same way as Sample 12.

[0381] ≪Sample 14≫ Lithium cobaltate without any special processing (steps S31 to S35 are not performed) Sample 14 (comparative example) was selected from M (Cellseed C-5hV, manufactured by Nippon Chemical Industrial Co., Ltd.).

[0382] ≪Sample 15≫ Sample 15 (comparative example) used pre-synthesized lithium cobalt oxide (Nippon Chemical Industries). A layer containing aluminum was applied to the surface of Cellseed C-5H (manufactured by [company name]) using the sol-gel method. After formation, the material was annealed at 500°C for 2 hours.

[0383] Specifically, aluminum isopropoxide and 2-propanol are mixed, and cobalt is added to it. Lithium cobalt oxide (C-5H) was added. At this time, aluminum relative to lithium cobalt oxide The weight of muisopropoxide was reduced to 0.0092 times. This mixture was left to stand for 8 hours. Stirring in a constant temperature bath with 90% humidity, the H2O in the atmosphere and aluminum isopropoxide The two substances were reacted to form an aluminum-containing layer on the surface of the lithium cobalt oxide. Then, the two substances were filtered. The material was recovered and dried under reduced pressure at 70°C for 1 hour.

[0384] The lithium cobalt oxide, which has been dried as described above and has an aluminum layer formed on its surface, is then processed using alumina It was placed in a crucible, covered, and annealed. The annealing was done at 500°C (heating increase of 200°C / hour). The procedure was performed with a holding time of 2 hours and an oxygen flow rate of 10 L / min. After that, it was allowed to return to room temperature for 10 hours. The sample was cooled for 15 hours or less and collected, which was designated as Sample 15.

[0385] Table 1 shows the preparation conditions for Sample 1 through Sample 15.

[0386] [Table 1]

[0387] [XPS] Surface XPS analysis was performed on samples 1 through 4 prepared as described above. The concentrations (atomic %) of the elements are shown in Table 2.

[0388] [Table 2]

[0389] Figure 30(A) shows a graph extracted from Table 2 containing data on magnesium and fluorine. This shows that in sample 4, which did not contain lithium fluoride and magnesium fluoride, fluor The concentrations of lithium and magnesium were low. Also, particulate lithium fluoride and fluoride Even in Sample 3, which had magnesium oxide added but was not annealed, fluorine and magnesium The concentration of citric acid did not become very high. This is due to the nature of surface XPS analysis, as shown in Figure 30 (B1 ) on top of particles 1001 that do not contain a certain element, fine particles 100 that contain a certain element at a high concentration If 2 is present, a region 100 containing the element with a large area, as shown in Figure 30(B2) This is thought to be because certain elements are less likely to be detected from the detection region 1010 than when there is 3. It can be done.

[0390] Furthermore, lithium fluoride and magnesium fluoride were added to the sample, and it was annealed for 2 hours. In case 2, the fluorine concentration had increased significantly. Furthermore, lithium fluoride and magnesium fluoride... In Sample 1, which was annealed for 60 hours with the addition of um, the magnesium concentration also increased significantly. there was.

[0391] From a comparison of Sample 2 and Sample 1, it was found that when annealing is performed, lithium fluoride, which has a lower melting point, is the first to melt. It was hypothesized that the lithium cobalt oxide (melting point 848°C) would melt and be distributed on the surface of the lithium cobalt oxide particles. Furthermore, if the annealing time is extended, the presence of molten lithium fluoride will cause magnesium fluoride to... The melting point of sium (melting point 1263°C) decreases, causing magnesium fluoride to melt and cobalt to form. It was hypothesized that the lithium oxide particles were distributed on the surface.

[0392] Next, Figure 31 shows the region representing the carbon bonding state in the XPS narrow scan analysis. In unannealed sample 3, the CO3 bond peak was high. In contrast, 2 In sample 2, which was annealed for a certain time, the CO3 bond decreased, while in sample 1, which was annealed for 60 hours... Then it decreased even further. The CO3 bond in the surface layer of lithium cobalt oxide was lithium carbonate (Li Since it is highly likely to be 2CO3, annealing will result in an excess of lithium. It is believed that this process suppressed the process and allowed for the production of superior lithium cobalt oxide.

[0393] [SEM] Next, SEM images of samples 1 to 4 are shown in Figure 32. Figure 32(A1) shows sample 1 Figure 32(A2) is a magnified view of the SEM image of sample 2. Figure 32(B1) is the SEM image of sample 2. Figure 32(B2) is a magnified view of the image. Figure 32(C1) is an SEM image of sample 3. 3(C2) is a magnified view of it. Figure 32(D1) is an SEM image of sample 4, Figure 32(D2 ) is a magnified view of it.

[0394] Sample 4, which is lithium cobalt oxide that has not undergone any special treatment, has numerous irregularities on its surface. Observed. Also, in sample 3, what appeared to be lithium fluoride and magnesium fluoride were found. The presence of fine particles was observed.

[0395] In contrast, the surfaces of Sample 2 and Sample 1, which were annealed, were smooth and not uneven. The number of irregularities had decreased. Sample 1, which was annealed for a longer period than Sample 2, had fewer irregularities. There was a tendency for this not to be the case.

[0396] [Manufacturing of secondary batteries] Next, using Sample 1, Sample 2, Sample 4 through Sample 15 prepared above, I fabricated a coin-type rechargeable battery of the CR2032 type (20mm in diameter, 3.2mm in height).

[0397] The positive electrode contains the positive electrode active material prepared above, acetylene black (AB), and polyfluoride. Nylidene (PVDF) is mixed with the positive electrode active material in a ratio of AB:PVDF = 95:3:2 (by weight). A slurry was used, which was then coated onto the current collector.

[0398] Lithium metal was used for the counter electrode.

[0399] The electrolyte in the electrolyte solution is 1 mol / L lithium hexafluoride phosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), with vinylene carbonate (VC) mixed in at 2 wt%. They used something.

[0400] A 25 μm thick polypropylene was used for the separator.

[0401] The positive electrode and negative electrode cans were made of stainless steel (SUS).

[0402] The positive electrode of the secondary battery using sample 7 was pressurized to 210 kN. No pressure was applied to the positive electrode of the next battery.

[0403] [Calculate lattice constant from XRD before charging] Before charging using Sample 1, Sample 4, Sample 5 through Sample 12, Sample 14 Powder XRD analysis using CuKα1 radiation was performed on the positive electrode. XRD was measured in air. The electrodes were attached to a glass plate to maintain flatness. The XRD apparatus was set for powder samples. Although it was a wing, the height of the sample was adjusted to match the measurement surface required by the device.

[0404] The obtained XRD pattern is DIFFRAC.EVA (Bruker XRD data solution). Background removal and Kα2 removal were performed using analysis software. This resulted in the reduction of conductive interference. Signals originating from the agent, binder, and sealed container have also been removed.

[0405] Subsequently, lattice constants were calculated using TOPAS. At this time, no optimization of atomic positions, etc., was performed. Only the lattice constant was fitted. GOF (good of fitness), estimated. Table 3 shows the crystallite size and the lattice constants for the a-axis and c-axis, respectively.

[0406] [Table 3]

[0407] Samples 12 and 14, which contain approximately 5100 ppm wt of titanium as an impurity, The c-axis tended to be larger than the others.

[0408] [XRD after initial charge] The secondary batteries using Sample 1, Sample 2, Sample 7, and Sample 9 were measured at 4.6V. CCCV charging was performed. Specifically, constant current charging was performed at 0.5C until the voltage reached 4.6V, after which the current value was reduced to 0. The battery was charged at a constant voltage until it reached 01C. Here, 1C is defined as 137mA / g. The rechargeable battery was disassembled in a glove box under an argon atmosphere, and the positive electrode was removed. The electrolyte was removed by washing with MC (dimethyl carbonate). Then, under an argon atmosphere... The samples were sealed in airtight containers and subjected to XRD analysis.

[0409] Figure 33 shows four secondary batteries using Sample 1, Sample 2, Sample 7, and Sample 9. The XRD pattern of the positive electrode after charging at 0.6V is shown. For comparison, the pseudo-spinel crystal structure is also shown. The pattern of the H1-3 type crystal structure is also shown.

[0410] Samples 1 and 7, after being charged at 4.6V, exhibited a pseudo-spinel crystal structure. This became clear. Furthermore, from Sample 7, in which a magnesium source and a fluorine source were added to the starting material... However, sample 1, which was a mixture of lithium cobalt oxide with a magnesium source and a fluorine source, The sharper pattern suggested higher crystallinity.

[0411] On the other hand, sample 2, which was insufficiently annealed, and sample 9, which was not annealed at all, It was revealed that the sample has an H1-3 type crystal structure after being charged to 4.6V. Pattern 2 was clearly broader than that of sample 1, suggesting lower crystallinity.

[0412] [XRD after initial charge, by charging depth] Next, using the positive electrode active materials of Sample 1 and Sample 2, the voltage was charged from 4.5V to 4.65V. We performed XRD analysis of the charge state of secondary batteries that were charged by precisely varying the voltage.

[0413] Figure 34 shows the positive electrode active material of Sample 1, at 4.5V, 4.525V, 4.55V, and 4. The XRD pattern of the positive electrode after one CCCV charge at 575V, 4.6V, and 4.65V. For comparison, the pseudo-spinel crystal structure, the H1-3 type crystal structure, and Li 0.35 Co The crystal structure pattern (space group R-3m, O3) for O2 (charge depth 0.65) is shown below. To show.

[0414] From Figure 34, the positive electrode active material of Sample 1 was L when charged at 4.5V and 4.525V. i 0.35 It was revealed that it has a CoO2(O3) crystal structure.

[0415] Also, when charged at 4.55V, Li 0.35 Crystal structure of CoO2(O3) and pseudospinel Since peaks were observed in both types of crystal structures, it is believed that these two crystal structures coexist. This was speculated.

[0416] Furthermore, when charged at 4.575V, a peak in the pseudo-spinel crystal structure was observed.

[0417] Furthermore, when charged at 4.6V, in addition to the peak of the pseudo-spinel crystal structure, a slight H The presence of peaks in the 1-3 type crystal structure indicates that these two crystal structures coexist. This was speculated.

[0418] When charged at 4.65V, peaks mainly of the H1-3 type crystal structure were observed. The resulting peak was slender, suggesting a decrease in crystallinity.

[0419] Thus, in the well-annealed sample 1, at a charging voltage of around 4.55V, Li0 .35 The CoO2(O3) crystal structure changes to a pseudo-spinel crystal structure, and the charging voltage 4 It was found that the pseudo-spinel crystal structure is maintained down to approximately 0.6V. The change was in the charging voltage, which was around 4.65V.

[0420] Figure 35 shows the positive electrode active material of Sample 2, at 4.5V, 4.55V, 4.6V, or 4. The XRD pattern of the positive electrode after one CCCV charge at 65V is shown. For comparison, a pseudo-spindle is shown. Li-type crystal structure, H1-3 type crystal structure, Li 0.35 The crystal structure of CoO2(O3) The pattern and the pattern of the CoO2(O1) type crystal structure are shown together.

[0421] From Figure 35, the positive electrode active material of Sample 2, when charged at 4.5V, behaves similarly to that of Sample 1. Li 0.35 It was revealed that it has a CoO2(O3) crystal structure.

[0422] However, when charged at 4.55 V, unlike Sample 1, Li 0.35 CoO2(O3) Both peaks of the crystal structure and the H1-3 type crystal structure were observed.

[0423] Furthermore, when charged at 4.6 V, unlike Sample 1, mainly the peak of the H1-3 type crystal structure was observed.

[0424] When charged at 4.65 V, peaks of the CoO2(O1) type crystal structure were observed together with the H1-3 type crystal structure. Also, it became a fairly broad peak, and it was speculated that the crystallinity had greatly decreased. It was speculated that the crystallinity had greatly decreased.

[0425] Thus, in Sample 2 where the annealing was insufficient, before and after the charging voltage of 4.55 V, early also Li 0.35 underwent a phase change from the crystal structure of CoO2(O3) to the H1-3 type crystal structure.

[0426] As described in Embodiment 1, the H1-3 type crystal structure is a structure in which the CoO2 layer is greatly displaced from the crystal structure in the discharged state, and since the volume difference is also large, it is considered that the crystal structure collapses by repeating the change to the H1-3 type crystal structure. Therefore, when used in an actual product, it is necessary to determine the upper limit of the charging voltage so as not to change to the H1-3 type crystal structure. Therefore, for a positive electrode active material that undergoes a phase change to the H1-3 type crystal structure around a charging voltage of 4.55 V like Sample 2, the upper limit of the charging voltage is 4.55 V or less, for example, 4.5 V.

[0427] Therefore, for a positive electrode active material like Sample 1 that maintains the spinel-like crystal structure even at a charging voltage of 4.6 V, the upper limit of the charging voltage can be set to 4.6 V. If the charging voltage can be increased,

[0428] On the other hand, for a positive electrode active material like Sample 1 that maintains the spinel-like crystal structure even at a charging voltage of 4.6 V, the upper limit of the charging voltage can be set to 4.6 V. If the charging voltage can be increased, This allows for a higher capacity per unit weight of positive electrode active material, resulting in a high-capacity secondary battery. can.

[0429] [XRD after 10 charge / discharge cycles (discharged state)] Next, the secondary batteries using Sample 1 and Sample 2 were charged and discharged 10 times at high voltage. In terms of operation, the charge-discharge cycle, which involves CCCV charging (4.6V) followed by CC discharge (2.5V), is repeated 10 times. After returning the battery, we disassembled the discharged secondary battery, extracted the positive electrode, and performed XRD analysis.

[0430] Figure 36 shows the positive electrode of secondary batteries using Sample 1 and Sample 2 after 10 charge-discharge cycles. The XRD pattern is shown. For comparison, the pattern of the ideal crystal structure of lithium cobalt oxide is also shown. This will also be shown.

[0431] The pattern of sample 2, which has insufficient annealing and adopts an H1-3 type crystal structure during high-voltage charging, is It is brighter than Sample 1, which is well annealed and adopts a pseudo-spinel crystal structure when charged at high voltage. It was found to be quite broad, suggesting low crystallinity.

[0432] [XRD after 100 charge / discharge cycles (charged state)] Next, the secondary batteries using Sample 1 and Sample 2 were charged via CCCV (4.45V) After repeating CC discharge (2.5V) 100 times, charge at 4.6V and then charge The rechargeable battery was disassembled, the positive electrode was removed, and XRD analysis was performed.

[0433] Figure 37 shows the high power output after 100 charge-discharge cycles of secondary batteries using Sample 1 and Sample 2. The XRD pattern of the positive electrode charged by pressure is shown. For comparison, the pseudo-spinel crystal structure and The H1-3 type crystal structure pattern is also shown.

[0434] As shown in Figure 37, even after 100 cycles, the positive electrode active material of sample 1 is still pseudos It had a Pinel-type crystal structure. Rietveld analysis revealed a pseudo-spinel-type crystal structure. The proportion was 43.6 wt%, and the proportion of H1-3 type crystal structure was 56.4 wt%.

[0435] On the other hand, almost all of the positive electrode active material in Sample 2 had an H1-3 type crystal structure. The peak was quite broad, suggesting a significant decrease in crystallinity.

[0436] [Cycle Characteristics] Next, sample 1, sample 2, sample 4, sample 5, sample 7, sample 10, The cycle characteristics of secondary batteries using Sample 12 and Sample 13 were evaluated. The results are shown in Figures 38 and 39. Note that the secondary battery evaluated here is defined as the amount of active material supported in the positive electrode layer. 7 mg / cm³ 2 8 mg / cm³ or more 2 The following are the items.

[0437] Figure 38 shows Sample 1, Sample 2, Sample 4, Sample 10, Sample 12 and Regarding Sample 13, at 25℃, charging is CCCV (0.5C, 4.6V, cutoff current 0.0 The results of 50 cycles of discharge (1C, CC: 0.5C, 2.5V) are shown in the figure. Figure 38(A) shows the discharge capacity, and Figure 38(B) shows the discharge capacity retention rate. Note that in Figure 38, 1C is positive. The current value per unit weight of the extremely active material was set to 137 mA / g.

[0438] Sample 1, which has a pseudo-spinel crystal structure after 60 hours of annealing and high-voltage charging, is extremely It exhibited excellent cycle characteristics. The discharge capacity retention rate after 50 cycles was 96.1%. .

[0439] On the other hand, sample 4, which was not treated in any way, and sample 4, which was annealed for 2 hours and then high-voltage charged, were subjected to H Sample 2, which has a 1-3 type crystal structure, was significantly degraded. Discharge capacity after 50 cycles. The maintenance rate was below 60% in all cases.

[0440] Aldrich No. 442704 was used as the pre-synthesized lithium cobaltate. Sample 10, which was annealed after being mixed with a magnesium source and a fluorine source, showed good results. The cycle characteristics were observed. The discharge capacity retention rate after 50 cycles was 79.8%.

[0441] On the other hand, lithium cobalt oxide containing approximately 5100 ppm wt of titanium as an impurity was used. For samples 12 and 13, after mixing with the magnesium source and fluorine source... Despite being annealed, the degradation was significant. This is because the annealing time was short. The same was true for sample 12 and the longer sample 13.

[0442] Figure 39 shows the results for Sample 1, Sample 5, and Sample 7 after 100 cycles at 45°C. The measurement results are shown. Figure 39(A) shows the discharge capacity, and Figure 39(B) shows the discharge capacity retention rate. In Figure 39, 1C is the current value per unit weight of positive electrode active material, which was set to 160 mA / g. The measurement conditions were: Charging is CCCV (1.0C, 4.55V, cutoff current 0.05C), discharging is CC (1.0C) (3.0V)

[0443] Even when measured at 45°C, Sample 1 showed extremely good cycle characteristics. The discharge capacity retention rate after the cycle was 93.3%. Furthermore, the lithium cobalt oxide with small particle size was also found. Sample 5, which was prepared in the same way as Sample 1 except that it used the same method and the annealing time was set to 2 hours, was also extremely It showed excellent cycle characteristics for the first time.

[0444] Furthermore, after adding a magnesium source and a fluorine source to the starting material and firing it, annealing is performed. Sample 7 also showed good cycle characteristics.

[0445] Furthermore, for Sample 1 and Sample 4, see Figures 38 and 39 and the amount of positive electrode active material supported. Figure 40 and the results of evaluating the cycle characteristics by changing the electrolyte and charging voltage are shown below. This is shown in Figure 41.

[0446] All secondary batteries used in this evaluation had a positive electrode active material load of 20 mg / cm³. 2 That's all. Furthermore, the electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). ) is mixed in an EC:DEC ratio of 3:7 (by volume), and vinylene carbonate is added to it. Two types were used, one with an additional 2 wt% of (VC) added. The charging voltage was 4.5V. The voltage was set to 4.6V.

[0447] Figure 40 shows a sample using an electrolyte solution mixed with EC:DEC = 3:7 (volume ratio). The cycle characteristics of pull 1 and sample 4 are shown. Figure 40(A) shows the charging voltage at 4.5V. Figure 40(B) shows the cycle characteristics when the charging voltage is 4.6V.

[0448] Also, in Figure 41, vinylene carbonate is used as the electrolyte in a ratio of EC:DEC = 3:7 (by volume). The cycle characteristics of Sample 1 and Sample 4, using a mixture with an additional 2 wt% of VC added, were examined. Figure 41(A) shows the case when the charging voltage is 4.5V, and Figure 41(B) shows the case when the charging voltage is 4. This shows the cycle characteristics when the voltage is set to 6V.

[0449] As is clear from Figures 40 and 41, the amount of positive electrode active material layer, electrolyte, and charging voltage Even after making changes, Sample 1 showed extremely good cycle characteristics.

[0450] From the various analysis results above, when charged at a high voltage of 4.6V, a pseudo-spinel type crystal structure was observed. It was revealed that the positive electrode active material possessing [this characteristic] exhibits extremely good cycle characteristics. In order to adopt a pseudo-spinel crystal structure after high-voltage charging, magnesium and fluorine are required. It has become clear that annealing at the appropriate temperature and time is effective. Furthermore, the appropriate annealing time depends on the size or composition of the lithium cobalt oxide particles. It was inferred that they were different.

[0451] Furthermore, lithium cobalt oxide, which is calcined with magnesium and fluorine added to the starting material, It may be annealed, but lithium cobalt oxide with fewer impurities contains magnesium and fluorine. It has become clear that mixing and annealing is more effective.

[0452] Furthermore, from a comparison of the lattice constant and cycle characteristics, the lattice constant of the c-axis is 14.060 × 10⁻⁶. -10 m The following lithium cobalt oxide is used to mix a magnesium source and a fluorine source and anneal. This revealed a tendency for the cathode active material to exhibit good cycle characteristics. Firstly, it is a layered rock salt type crystal with little heteroatomic substitution and spinel-type Co3O4 crystal structure. A complex oxide is created to form a structure, and then a magnesium source and a fluorine source are mixed together to form a magnesium By inserting cium at the lithium position, a cathode active material exhibiting good cycle characteristics can be fabricated. That was the conclusion.

[0453] [Rate Characteristics] Next, for a secondary battery using Sample 1, which exhibits extremely good cycle characteristics as described above, and Sample 4, which is a comparative example without mixing a magnesium source and a fluorine source, the rate characteristics were evaluated, and the results are shown in FIGS. 42 and 43. The coin cells for rate characteristic evaluation were fabricated in the same manner as the coin cells for XRD measurement described above, except that the loading amount of the positive electrode active material layer was set to 20.8 mg / cm² or more and 1.0 mg / cm² or less. For the first charge, the upper limit was set to 4.5 V or 4.6 V, and it was performed under CCCV, 0.2 C, 4.6 V, and a cut-off current of 0.05 C. For the first discharge, it was performed under CC, 0.2 C, and a cut-off voltage of 3.0 V. Here, 1 C was defined as a current value of 200 mA / g per unit weight of the positive electrode active material.

[0454] For the charge-discharge cycles after the first cycle, only the discharge rate was changed, and measurements were carried out in the order of 0.2 C charge / 0.2 C discharge, 0.2 C charge / 0.5 C discharge, 0.2 C charge / 1.0 C discharge, and 0.2 C charge / 2.0 C discharge. The measurement temperature was set to 25°C. 2 or more 1.0 mg / cm² 2 or less. For the first charge, the upper limit was set to 4.5 V or 4.6 V, and it was performed under CCCV, 0.2 C, 4.6 V, and a cut-off current of 0.05 C. For the first discharge, it was performed under CC, 0.2 C, and a cut-off voltage of 3.0 V. Here, 1 C was defined as a current value of 200 mA / g per unit weight of the positive electrode active material. For the first charge, the upper limit was set to 4.5 V or 4.6 V, and it was performed under CCCV, 0.2 C, 4.6 V, and a cut-off current of 0.05 C. For the first discharge, it was performed under CC, 0.2 C, and a cut-off voltage of 3.0 V. Here, 1 C was defined as a current value of 200 mA / g per unit weight of the positive electrode active material. For the first charge, the upper limit was set to 4.5 V or 4.6 V, and it was performed under CCCV, 0.2 C, 4.6 V, and a cut-off current of 0.05 C. For the first discharge, it was performed under CC, 0.2 C, and a cut-off voltage of 3.0 V. Here, 1 C was defined as a current value of 200 mA / g per unit weight of the positive electrode active material. For the charge-discharge cycles after the first cycle, only the discharge rate was changed, and measurements were carried out in the order of 0.2 C charge / 0.2 C discharge, 0.2 C charge / 0.5 C discharge, 0.2 C charge / 1.0 C discharge, and 0.2 C charge / 2.0 C discharge. The measurement temperature was set to 25°C. For the charge-discharge cycles after the first cycle, only the discharge rate was changed, and measurements were carried out in the order of 0.2 C charge / 0.2 C discharge, 0.2 C charge / 0.5 C discharge, 0.2 C charge / 1.0 C discharge, and 0.2 C charge / 2.0 C discharge. The measurement temperature was set to 25°C. For the charge-discharge cycles after the first cycle, only the discharge rate was changed, and measurements were carried out in the order of 0.2 C charge / 0.2 C discharge, 0.2 C charge / 0.5 C discharge, 0.2 C charge / 1.0 C discharge, and 0.2 C charge / 2.0 C discharge. The measurement temperature was set to 25°C.

[0455] FIG. 42(A) shows the discharge curves of Sample 1 at each rate when the charging voltage is 4.5 V, and FIG. 42(B) shows the discharge curves of Sample 1 at each rate when the charging voltage is 4.6 V. FIG. 43(A) shows the discharge curves of Sample 4 at each rate when the charging voltage is 4.5 V, and FIG. 43(B) shows the discharge curves of Sample 4 at each rate when the charging voltage is 4.6 V. FIG. 42(A) shows the discharge curves of Sample 1 at each rate when the charging voltage is 4.5 V, and FIG. 42(B) shows the discharge curves of Sample 1 at each rate when the charging voltage is 4.6 V. FIG. 43(A) shows the discharge curves of Sample 4 at each rate when the charging voltage is 4.5 V, and FIG. 43(B) shows the discharge curves of Sample 4 at each rate when the charging voltage is 4.6 V. FIG. 42(A) shows the discharge curves of Sample 1 at each rate when the charging voltage is 4.5 V, and FIG. 42(B) shows the discharge curves of Sample 1 at each rate when the charging voltage is 4.6 V. FIG. 43(A) shows the discharge curves of Sample 4 at each rate when the charging voltage is 4.5 V, and FIG. 43(B) shows the discharge curves of Sample 4 at each rate when the charging voltage is 4.6 V. FIG. 42(A) shows the discharge curves of Sample 1 at each rate when the charging voltage is 4.5 V, and FIG. 42(B) shows the discharge curves of Sample 1 at each rate when the charging voltage is 4.6 V. FIG. 43(A) shows the discharge curves of Sample 4 at each rate when the charging voltage is 4.5 V, and FIG. 43(B) shows the discharge curves of Sample 4 at each rate when the charging voltage is 4.6 V.

[0456] As is clear from FIGS. 42 and 43, the secondary battery using Sample 1 exhibited better rate characteristics when charged at a high voltage compared to Sample 4, and this tendency became more prominent at higher rates. As is clear from FIGS. 42 and 43, the secondary battery using Sample 1 exhibited better rate characteristics when charged at a high voltage compared to Sample 4, and this tendency became more prominent at higher rates. As is clear from FIGS. 42 and 43, the secondary battery using Sample 1 exhibited better rate characteristics when charged at a high voltage compared to Sample

[0457] Furthermore, in the secondary battery using Sample 1, at low discharge rates such as 0.2C, the discharge termination occurred. It became clear that there is a characteristic voltage change near the end of the process.

[0458] [Charging curve and dQ / dVvsV curve] Next, sample 1, which is one embodiment of the present invention, and after forming an aluminum-containing layer on the surface, For a secondary battery using sample 15 annealed at 500°C for 2 hours, the charging curve and dQ are described. The results of comparing the / dV vs V curves are shown.

[0459] The secondary batteries using Sample 1 and Sample 15 were tested at 25°C until they reached 4.9V with a capacity of 10mAh / g. Figure 44 shows the charging curves during charging. The solid line represents Sample 1, and the dashed line represents Sample 15. Two rechargeable batteries were measured using each sample.

[0460] The dQ / dVvsV curve, which represents the change in voltage with respect to charging capacity, was obtained from the data in Figure 44. This is shown in Figure 45. Figure 45(A) shows d for sample 1, and Figure 45(B) shows d for sample 15. This is the Q / dV vs V curve.

[0461] As is clear from Figures 45(A) and 45(B), both Sample 1 and Sample 15 In this case as well, peaks were observed at voltages of approximately 4.06V and 4.18V, and in relation to voltage... The capacity change was nonlinear. Between these two peaks, the current state at a charge depth of 0.5 It is thought to have a crystal structure (space group P2 / m). The space group P2 / m at a charging depth of 0.5 is shown in Figure As shown in 4, the lithium is aligned. Energy is used for this alignment of lithium. Therefore, it is thought that the change in capacitance with respect to voltage has become nonlinear.

[0462] Furthermore, in comparative example sample 15, a large peak was observed at approximately 4.54V and 4.61V. A peak was observed. The area between these two peaks is thought to represent the H1-3 phase crystal structure. .

[0463] On the other hand, Sample 1, which exhibits extremely good cycle characteristics, shows a small peak of about 4.55V. Although some was observed, it was not clear. Therefore, dQ / d was obtained from more detailed measurement results. The VvsV curves are shown in Figures 46 and 47. Figure 47 is an enlarged view of Figure 46.

[0464] As shown in Figure 47, detailed measurements revealed peaks at approximately 4.55V and 4.63V. This was observed. The area between these two peaks is thought to represent a pseudo-spinel crystal structure. The peak between approximately 4.63V and 4.64V is thought to represent an H1-3 type crystal structure. It is possible.

[0465] Thus, in the dQ / dVvsV curve of Sample 1, some peaks are extremely broad, In some cases, the crystal structure may be small. In such cases, it is possible that two crystal structures coexist. For example, the coexistence of two phases: O3 and pseudospinel, or pseudospinel and H1-3. There is a possibility that this is the case.

[0466] [Discharge curves and dQ / dVvsV curves] Next, a secondary battery using Sample 1, which is one embodiment of the present invention, and Sample 4, which is a comparative example. The following shows the results of comparing the discharge curve and the dQ / dV vs V curve.

[0467] Figure 48(A) shows the discharge curve for sample 1, and Figure 48(B) shows the discharge curve for sample 4. The discrepancy is due to discharge after CCCV charging at 4.6V. Discharge is CC discharge down to 2.5V. The following was performed. The discharge rate was set to 0.05C (1C = 200mA / g).

[0468] As shown in Figure 48(A), in Sample 1, near the end of the discharge (the area enclosed by the dashed line in the figure) A characteristic voltage change was observed. This is the voltage observed in the low-rate discharge shown in Figure 40. It is similar to change.

[0469] The dQ / dVvsV curve, representing the change in voltage with respect to discharge capacity, was obtained from the data in Figure 48. Figure 49 shows the dQ / dVv for sample 1 (A) and sample 4 (B). This is an sV curve. The graph was created for the region with a voltage of 3.5V or higher to clearly depict the peak.

[0470] As shown in Figure 49(B), Sample 4 does not contain a mixture of magnesium and fluorine sources. Then, two large downward-convex peaks were observed at approximately 4.37V and 3.87V, It became clear that the discharge curve of Sample 4 has two inflection points.

[0471] On the other hand, as is clear from Figure 49(A), sample 1 has even more downward-convex peaks. The following was observed. The largest peak was at approximately 3.9V. Also, as indicated by the arrows in the figure... There was at least one peak in the range of 3.5V to 3.9V. The peaks represent the voltage changes in the area enclosed by the dashed lines in Figure 48(A).

[0472] Thus, as explained in Figures 40, 48, and 49, one aspect of the present invention is Sun The positive electrode active material of pull-1 is charged at a high voltage and then discharged at a low rate, for example, 0.2C or less. It became clear that a characteristic voltage change appears near the end of the discharge. This change is, In the dQ / dVvsV curve, there is at least one peak in the range of 3.5V to 3.9V. Its existence makes this clearly verifiable. [Examples]

[0473] In this embodiment, a positive electrode active material having cobalt and nickel as transition metals is prepared, X We used RD to analyze the features.

[0474] [Fabrication of positive electrode active material] ≪Sample 21≫ As Sample 21, the raw materials of cobalt and nickel were prepared using the manufacturing method shown in Figure 1 of Embodiment 1. The ratio of nickel atoms (Ni) to the sum of atoms (Co+Ni): Ni / (Co+Ni ) fabricated a positive electrode active material with a coefficient of 0.01.

[0475] First, in the same manner as steps S11 to S14 of Embodiment 1 and Embodiment 1, LiF A first mixture was prepared in which the molar ratio of LiF to MgF2 was LiF:MgF2 = 1:3.

[0476] Next, as in steps S21 and S22 of Embodiment 1, Li:Ni:Co =1:0.01:0.99 atomic ratio (Ni / (Co+Ni)=0.01) The materials were weighed and mixed. Lithium carbonate was used as the lithium source, and cobalt oxide was used as the cobalt source. For the nickel source, nickel hydroxide was used. The mixture was heated at 300 rpm for 20 hours. Seton was added and the process was carried out in a wet manner.

[0477] Next, as in steps S23 to S25 of Embodiment 1, a dry air atmosphere is created. After being fired in a flue furnace at 900°C for 10 hours, it was recovered and contained lithium, cobalt, nickel, and A composite oxide containing oxygen was obtained. The flow rate of dry air was set to 10 L / min. The temperature was raised to 20°C. The temperature was set to 0°C / hr, and the cooling process was carried out over a period of more than 10 hours.

[0478] Next, as in steps S31 to S33 of Embodiment 1, the first mixture and lith A second mixture is prepared by mixing a composite oxide containing um, cobalt, nickel, and oxygen. The magnesium contained in the first mixture was found to be equal to the sum of the number of atoms of cobalt and nickel. The mixture was prepared so that the atomic weight of the element was 0.5 atomic percent.

[0479] Next, as in steps S34 and S35 of Embodiment 1, the second mixture is prepared The material was annealed in an oxygen-atmosphere muffle furnace at 850°C for 2 hours, then recovered to obtain the cathode active material. The oxygen flow rate was set to 10 L / min. The heating rate was set to 200°C / hr, and the cooling rate was set to 10 hours or more. The process was carried out. The positive electrode active material obtained in this way was designated as Sample 21.

[0480] ≪Sample 22≫ In step S11, LiF and MgF2 are not added, and in step S34, The positive electrode active material, prepared in the same way as Sample 21 except that Neale was not performed, was used for Sample 22. This was designated as a comparative example.

[0481] ≪Sample 23≫ In step S21, the raw materials were weighed so that Ni / (Co+Ni) = 0.075. Sample 23 was a positive electrode active material prepared in the same manner as Sample 21.

[0482] ≪Sample 24≫ In step S11, LiF and MgF2 are not added, and in step S34, The positive electrode active material, prepared in the same way as sample 23 except that Neale was not performed, was used for sample 24. This was designated as a comparative example.

[0483] ≪Sample 25≫ In step S21, the raw materials were weighed so that Ni / (Co+Ni)=0.1, and other than that, Sample 25 was a positive electrode active material prepared in the same manner as Sample 21.

[0484] ≪Sample 26≫ In step S11, LiF and MgF2 are not added, and in step S34, The positive electrode active material, prepared in the same manner as Sample 25 except that Neale was not performed, was used for Sample 26. This was designated as a comparative example.

[0485] The preparation conditions for Samples 21 to 26 are shown in Table 4.

[0486] [Table 4]

[0487] [Manufacturing of secondary batteries] Next, using samples 21 to 26 prepared above, coins were made in the same manner as in Example 1. A rechargeable battery of type [type] was manufactured.

[0488] [XRD after initial charge] The secondary batteries using Samples 21 to 26 were subjected to CC at 4.6V, similar to Example 1. After CV charging, the positive electrode was removed and XRD analysis was performed.

[0489] Figures 50 and 51 show secondary batteries using samples 21 and 22 at 4.6V. The XRD pattern of the positive electrode after charging is shown in Figure 51(A), starting from 2θ=18° in Figure 50. This shows an enlarged view of the section where 2θ = 20°. Figure 51(B) shows the section from 2θ = 43° in Figure 50. A magnified view of the region where 2θ=46° is shown. For comparison, a pseudo-spinel crystal structure, H1- Type 3 crystal structure and Li 0.35 The crystal structure pattern of CoO2 (charge depth 0.65) The crystalline structure is also shown. Note that the pseudo-spinel type crystal structure and H1-3 type crystal structure shown in this embodiment are also shown. Yobi Li 0.35 The comparison patterns of the crystal structure in the case of CoO2 all use CoB as a transition metal. This calculation is based on a structure that contains only bolts and does not include nickel.

[0490] In sample 21, which underwent addition of Mg and F sources and annealing, a pseudo-spinel-type crystal structure was observed. A peak was observed. Also, the H1-3 type crystal structure and Li 0.35 Crystals when CoO2 is used Structural peaks were also observed. Furthermore, some peaks were shifted from the comparison pattern. This was thought to be due to the presence of nickel.

[0491] On the other hand, in sample 22, which did not undergo the addition of Mg and F sources and annealing, pseudospinel was observed. No peaks were observed in the H1-3 type crystal structure. However, the peaks in the H1-3 type crystal structure and Li 0.35 The peaks in the crystal structure for CoO2 were observed.

[0492] Figure 52 shows the secondary batteries using samples 23 and 24 after being charged to 4.6V. The XRD pattern of the positive electrode is shown. For comparison, the pseudo-spinel type crystal structure and the H1-3 type crystal structure are also shown. and Li 0.35 Also include the crystal structure pattern for CoO2 (charge depth 0.65). To show.

[0493] In sample 23, which underwent addition of Mg and F sources and annealing, a pseudo-spinel crystal structure was observed. While peaks in the H1-3 type crystal structure were observed, peaks in the pseudo-spinel type crystal structure were more dominant. That was the case.

[0494] On the other hand, in sample 24, where Mg and F sources were not added and annealing was not performed, H1-3 type Crystal structure and Li 0.35 The peaks in the crystal structure for CoO2 were observed. The presence of many smears and the broad peaks suggested a decrease in crystallinity.

[0495] Figure 53 shows the secondary batteries using samples 25 and 26 after being charged to 4.6V. The XRD pattern of the positive electrode is shown. For comparison, the pseudo-spinel type crystal structure and the H1-3 type crystal structure are also shown. and Li 0.35 Also include the crystal structure pattern for CoO2 (charge depth 0.65). To show.

[0496] In samples 25 and 26, where Ni / (Co+Ni) was set to 0.1, the crystal structure was No significant differences were observed. Furthermore, this crystal structure is a pseudo-spinel type crystal structure, H1-3 Crystal structure and Li 0.35 It was inferred that it was neither of the CoO2 types.

[0497] From Figures 50 to 53, the positive electrode active material having lithium, a transition metal, and oxygen is the main component When cobalt and nickel are present as transition metals, Ni / (Co+Ni) is less than 0.1. It was found that, more specifically, a value of 0.075 or less is preferable. Ni / ( If Co+Ni is within the above range, then by adding and annealing the Mg source and F source... This is because it has a pseudo-spinel crystal structure when charged at 4.6V. In the state, the positive electrode active material having a pseudo-spinel type crystal structure is, as described in the previous example, good It exhibits favorable cycle characteristics. [Examples]

[0498] In this embodiment, a secondary battery using a positive electrode active material according to one aspect of the present invention is fabricated, and differential scanning heat Quantitative measurement (Differential scanning calorimetry: DS) C) and charge tolerance tests were performed.

[0499] ≪Sample 27≫ Lithium phosphate was ground using a zirconia mortar.

[0500] To Sample 1 prepared in the previous example, lithium phosphate that had been ground in a mortar was mixed. The amount of lithium phosphate mixed corresponds to 0.04 mol per 1 mol of sample 1. The amount was such that mixing was performed using a ball mill with zirconia balls at 150 rpm. The mixture was left for a certain amount of time. After mixing, it was sieved through a 300 μm diameter sieve. Then, the resulting mixture was sieved through an aluminum sieve. It was placed in a crucible, covered, and annealed at 850°C for 2 hours in an oxygen atmosphere. After that, 5 The sample was passed through a 3 μm diameter sieve to obtain sample 27.

[0501] ≪Sample 28≫ Lithium phosphate was ground. The grinding was performed using a ball mill with zirconia balls, 4 The process was run at 00 rpm for 60 hours. After grinding, the material was sieved through a 300 μm diameter sieve.

[0502] The sample 1 prepared in the previous example was mixed with pulverized lithium phosphate. The combined amount of lithium phosphate is equivalent to 0.06 mol per 1 mol of sample 1. The quantity was measured. Mixing was performed using a ball mill with zirconia balls at 150 rpm for 1 hour. The mixture was then passed through a 300 μm diameter sieve. After that, the resulting mixture was placed in an alumina crucible. It was placed in a cauldron, covered, and annealed at 750°C for 20 hours in an oxygen atmosphere. After that, 53 The sample was sieved through a μmφ sieve to obtain sample 28.

[0503] [Manufacturing of secondary batteries] Next, we have Sample 27 and Sample 28 prepared above, and Sample 1 shown in the previous example. Using the above, a CR2032 type coin-type rechargeable battery was fabricated.

[0504] For the positive electrode, use sample 1, sample 27, or sample 28 as the active material, and AB, A slurry mixed with PVDF in a ratio of active material:AB:PVDF = 95:3:2 (by weight). - was used as a coating for the current collector.

[0505] Lithium metal was used for the counter electrode.

[0506] The electrolyte in the electrolyte solution is 1 mol / L lithium hexafluoride phosphate (LiPF6). The electrolyte used in the secondary battery whose charge-discharge characteristics were evaluated later is ethylene carbonate (E C) and diethyl carbonate (DEC) were mixed in a volume ratio of EC:DEC = 3:7. The secondary batteries whose cycle characteristics were evaluated later contain ethylene carbonate (EC) and Diethyl carbonate (DEC) has an EC:DEC ratio of 3:7 (by volume), vinylene carbonate A mixture containing 2 wt% of hydroxypropyl alcohol (VC) was used.

[0507] A 25 μm thick polypropylene was used for the separator.

[0508] The positive electrode and negative electrode cans were made of stainless steel (SUS).

[0509] The positive electrode of the secondary battery was pressurized with 210 kN / m, and then further pressurized with 1467 kN / m. The following procedure was performed. The loading amount of the positive electrode using Sample 1 was approximately 21 mg / cm³. 2 , the electrode density is approximately 3.9 g / cm³ 3 The amount of material loaded onto the positive electrode using sample 28 was approximately 20 mg / C. m 2 The electrode density is approximately 3.7 g / cm³. 3 That was the case.

[0510] [Charge / discharge characteristics] The secondary batteries using Sample 1 and Sample 28 were charged using CCCV (0.05C, 4. Discharge at 5V or 4.6V (cutoff current 0.005C), and CC (0.5C, 2.5V). The initial charge capacity, discharge capacity, and Coulomb efficiency are shown in Table 5. Coulomb efficiency is... This value is obtained by normalizing the discharge capacity by the charge capacity and expressing it as a percentage. As shown in Table 5, excellent cool Ron efficiency was achieved.

[0511] [Table 5]

[0512] [Cycle Characteristics] The secondary batteries using Sample 1 and Sample 28 were charged using CCCV (0.05C, 4. 5V or 4.6V, cutoff current 0.005C), discharge CC (0.05C, 2.5V) The measurement was performed over two cycles at 25°C.

[0513] Subsequently, the secondary batteries using Sample 1 and Sample 28 were charged at 25°C. CCV (0.2C, 4.5V or 4.6V, cutoff current 0.02C), discharge CC (0. The cycle characteristics were evaluated by repeatedly charging and discharging the battery at 2C, 2.5V. After 25 cycles... The capacity retention rate in Sample 1 was 99.0% under the condition of a charging voltage of 4.5V, and under the condition of a charging voltage of 4.6V. Under the V condition, the success rate was 96.1%, and in sample 28, under the charging voltage condition of 4.5V, the success rate was 99.0%. The capacitance retention rate was 97.8% under the condition of a voltage of 4.6V. The capacitance retention rate after 50 cycles was for sample 1. So, under a charging voltage of 4.5V, it was 97.3%, and under a charging voltage of 4.6V, it was 80.0%. In Sample 28, the battery life was 96.6% under a charging voltage of 4.5V and 93% under a charging voltage of 4.6V. It was 0.5%. Figure 54(A) shows the change in discharge capacity for a charging voltage of 4.5V, and Figure 5 4(B) shows the changes in discharge capacity under the condition of a charging voltage of 4.6V. The horizontal axis of this graph represents the number of cycles, and the vertical axis represents the discharge capacity. Lithium phosphate coated sump In the 28, although the charge / discharge capacity decreases by the weight of lithium phosphate, the cycle characteristics are... Furthermore, it improves. This is because the lithium phosphate coating removes metals such as cobalt from the positive electrode active material. This is thought to be a result of suppressed ion elution and reduced electrolyte decomposition.

[0514] [Differential Scanning Calorimetry] The secondary batteries using Sample 1, Sample 27, and Sample 28 were charged using CCCV(0 0.05C, 4.5V or 4.6V, cutoff current 0.005C), discharge CC (0.05C) The measurement was taken over two cycles at 25°C with a voltage of 2.5V.

[0515] Subsequently, the secondary batteries using Sample 1, Sample 27, and Sample 28 were charged using CC. The test was performed using CV (0.05C, 4.5V or 4.6V, cutoff current 0.005C). The rechargeable battery was disassembled in a glove box under an argon atmosphere, and the positive electrode was removed. Then, it was cleaned with DMC to remove the electrolyte. After that, it was punched out to a 3mm diameter.

[0516] 1 μL of electrolyte was dropped onto the punched-out positive electrode and placed in a sealed container made of stainless steel. The electrolyte contains For the electrolyte, 1 mol / L lithium hexafluoride phosphate (LiPF6) was used, and the electrolyte solution was Ethylene carbonate (EC) and diethyl carbonate (DEC) have a ratio of EC:DEC = 3 A mixture in a volume ratio of 7 was used.

[0517] DSC evaluation was performed. The measurement was taken using a Rigaku high-sensitivity differential scanning calorimeter Thermo p The lus EV02 DSC8231 was used. The measurement conditions were in a temperature range from room temperature to 400°C. The heating rate was set to 5°C / min.

[0518] Figure 55 shows the results of the DSC measurement. The horizontal axis is Temperature, and the vertical axis is This shows the heat flow. Figure 55(A) compares sample 1 and sample 27. Figure 55(B) shows a comparison between Sample 1 and Sample 28, respectively.

[0519] Figure 55(A) shows that in sample 1, peaks were observed near 171°C and near 251°C. In sample 27, the temperature rose to approximately 188°C and approximately 252°C, respectively, and also The area intensity representing heat quantity decreased. Also, as shown in Figure 55(B), in sample 28 as well, An increase in saturation and a decrease in area intensity were observed, particularly in the range of 150°C to 200°C. A significant decrease in area intensity was observed. Therefore, the presence of phosphoric acid in the manufacturing process of the positive electrode active material suggests that The study suggested that mixing the compound with the other compound improved its thermal stability.

[0520] [Charge endurance test] The secondary batteries using Sample 1 and Sample 28 were charged using CCCV (0.05C, 4. 5V or 4.6V, cutoff current 0.005C), discharge CC (0.05C, 2.5V) The measurement was performed over two cycles at 25°C.

[0521] Subsequently, charging was performed at 60°C using CCCV (0.05C). The upper voltage limit was 4.55V. The voltage is set to 4.65V, and the termination condition is when the voltage of the secondary battery is 0.01V less than the upper limit voltage. The time it took for the voltage to drop below 4.54V (for example, 4.55V) was measured. (Rechargeable battery voltage) If the voltage falls below the upper limit, it may indicate that a short circuit or other problem is occurring. 1C was defined as 200mA / g.

[0522] Table 6 shows the time measured for each secondary battery.

[0523] [Table 6]

[0524] In sample 28, the time it took for the secondary battery voltage to drop was long, and the process of fabricating the positive electrode active material was The study suggested that mixing the compound with phosphoric acid improved its charge resistance. [Examples]

[0525] In this embodiment, a secondary battery using a positive electrode active material according to one aspect of the present invention was fabricated, and atomic absorption spectroscopy was performed. The leaching of metals was evaluated according to the specified method.

[0526] [Manufacturing of secondary batteries] First, using sample 27 prepared above and sample 1 shown in the previous example, A laminate-type rechargeable battery was fabricated.

[0527] For the positive electrode, use either Sample 1 or Sample 27 as the active material, and combine it with AB and PVDF. A slurry of active material AB:PVDF = 95:3:2 (by weight) is applied to one side of the current collector. A coated version was used.

[0528] The negative electrode uses graphite as the active material, along with VGCF(registered trademark), CMC-Na, and SBR. Composition of active ingredients: VGCF(registered trademark):CMC-Na:SBR=96:1:1:2 (by weight) A slurry is mixed in a ratio (of 1, 2, 3) and its viscosity adjusted with pure water. This slurry is then coated onto one side of the current collector, dried, and then coated with pure water. A volatile substance was used. 18 μm thick copper foil was used as the current collector. The load was approximately 14 mg / cm 2 That was the case.

[0529] The electrolyte in the electrolyte solution is 1 mol / L lithium hexafluoride phosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). C:DEC = 3:7 (volume ratio), with vinylene carbonate (VC) mixed in at 2 wt%. They used something.

[0530] A 25 μm thick polypropylene was used for the separator.

[0531] The fabricated secondary battery undergoes a process of charging and discharging at a low rate to remove gas, for the purpose of aging. I went several times.

[0532] A positive electrode having sample 1 or sample 27 and a negative electrode having graphite are combined to create After aging the manufactured secondary battery, charging was performed at 25°C using CCCV (0.05C, 4.4°C). The discharge was performed at CC (0.05C, 2.5V) with a termination current of 0.005C. 1C was... I assumed approximately 200mA / g.

[0533] Subsequently, charging was performed using CCCV (0.05C, 4.45V, cutoff current 0.005C). The rechargeable batteries were then stored at 60°C for 14 days.

[0534] Subsequently, discharge was performed at 25°C using CC (0.05C, 2.5V). 1C is 200 The value was set to mA / g.

[0535] [Atomic absorption measurement] Next, the secondary battery was disassembled in a glove box under an argon atmosphere to remove the negative electrode, and then DM The electrolyte was removed by washing with C. Then, the current collector was removed. The active material layer powder was mixed. Then, approximately 0.1 mg was extracted and atomic absorption spectrometry was performed.

[0536] The amount of cobalt was measured using furnace atomic absorption spectrometry. The measurement was performed using Analytik J. ContrAA 600 continuous light source atomic absorption spectrometry from ena (Analytic Jena) The apparatus was used. In the measurement, cobalt was atomized at 2500°C, and the wavelength was 235.8183 nm. The light was irradiated onto the sample. Two secondary battery cells were fabricated for each of Sample 1 and Sample 27. The average value was then calculated. Measurements were taken 20 times per cell, and the average value was calculated.

[0537] The amount of cobalt obtained was 9722 ppm in sample 1 and 597 ppm in sample 27. The cobalt content was 1 ppm. The amount of cobalt was normalized by the amount of cobalt present in the positive electrode active material layer. Yes, it is possible. Specifically, the amount of cobalt contained in the entire negative electrode of the secondary battery can be calculated from the obtained measurements. The amount of cobalt contained in the entire positive electrode of the secondary battery was used for normalization. In Sample 27, The amount of balt decreased. It was mixed with a phosphate-containing compound during the process of preparing the positive electrode active material. As a result, the leaching of cobalt from the positive electrode active material was suppressed, and the amount deposited on the negative electrode was also reduced. This suggests that... [Examples]

[0538] In this example, a positive electrode active material according to one aspect of the present invention is prepared and its characteristics are analyzed using XRD. Furthermore, the cycle characteristics during high-voltage charging were evaluated.

[0539] ≪Sample 51≫ Except for setting the annealing time to 8 hours in step S34 of Figure 2, the same procedure was followed as in Example 1. Sample 51 was prepared in the same way as Pull 1.

[0540] ≪Sample 52≫ Except for setting the annealing time to 30 hours in step S34 of Figure 2, the same procedure as in Example 1 was followed. Sample 52 was prepared in the same manner as Sample 1.

[0541] [XRD after initial charge] Similar to Example 1, secondary batteries were prepared using samples 51 and 52, and the first charge was performed. We performed an electric charge and evaluated the XRD after the initial charge.

[0542] Figure 56 shows the positive voltage after charging secondary batteries using samples 51 and 52 to 4.6V. The XRD pattern of the poles is shown.

[0543] Sample 52, after being charged at 4.6V, was found to have a pseudo-spinel crystal structure. On the other hand, sample 51 suggested an H1-3 type crystal structure. From this, during annealing... The results suggest that a 30-hour interval yields superior cathode active material compared to an 8-hour interval. It was suggested that an annealing time longer than 8 hours is preferable.

[0544] [Cycle Characteristics] Similar to Example 1, the secondary batteries using Sample 51 and Sample 52 were cycled We evaluated the characteristics.

[0545] At 25℃, charging is CCCV (1C, 4.6V, cutoff current 0.01C), and discharging is CC (0. The cycle characteristics were evaluated at 5C, 2.5V. At 1C, the current is approximately 137mA / g. The discharge capacity retention rate after 40 charge-discharge cycles was 47.8% in sample 28. The percentages were 98.4% for sample 29 and 97.6% for sample 1 prepared in Example 1. Ta.

[0546] At 45℃, charging is CCCV (1C, 4.55V, cutoff current 0.05C), and discharging is CC(1 The cycle characteristics were evaluated with C (3.0V). 1C is approximately 160mA / g. The discharge capacity retention rate after 100 charge-discharge cycles was 39% in sample 51. The figure was 4%, and 78.4% in a sample of 52.

[0547] Sample 52 demonstrated excellent cycling characteristics at both 25°C and 45°C. This indicates that a superior cathode active material can be obtained by annealing for 30 hours. I was instigated. [Examples]

[0548] In this example, a positive electrode active material according to one aspect of the present invention is prepared and its characteristics are analyzed using XRD. Furthermore, the cycle characteristics during high-voltage charging were evaluated.

[0549] ≪Sample 61≫ In step S11 of Figure 2, MgF2 is not added, and the other conditions are the same as in Example 1. Sample 61 was prepared in the same manner as Sample 1. Molecular weight of lithium cobalt oxide. For the first mixture, weigh it out so that the atomic amount of lithium it contains is 1.17 atomic percent. It was mixed using a dry method.

[0550] ≪Sample 62≫ In step S11 of Figure 2, LiF and MgF2 are not added, and instead Mg(OH) Adding 2, and using the same conditions as Sample 1 shown in Example 1, the sample was prepared as follows: The ratio was set to 62. The magnesium content of the first mixture relative to the molecular weight of lithium cobalt oxide was determined. The um was weighed to an atomic weight of 0.5 atomic percent and mixed by dry mixing.

[0551] [XRD after initial charge] Similar to Example 1, secondary batteries were prepared using samples 61 and 62, and the initial charge was performed. We performed an electric charge and evaluated the XRD after the initial charge.

[0552] Figure 57 shows the positive voltage after charging secondary batteries using samples 61 and 62 at 4.6V. The XRD pattern of the poles is shown.

[0553] Both sample 61 and sample 62, after charging at 4.6V, showed H1- The results suggest a type 3 crystal structure. Therefore, in the process of step S11, When using compounds containing lithium and compounds containing fluorine, a better positive result can be obtained. This suggests that a highly active material can be obtained.

[0554] [Cycle Characteristics] Similar to Example 1, the secondary batteries using Sample 61 and Sample 62 were cycled The characteristics were evaluated. Figure 58(A) shows the results of cycle measurements at 25°C with a charging voltage of 4.6V. Figure 58(B) shows the results of charging at 45°C with a charging voltage of 4.55V. Both Sample 61 and Sample 62 were cycled compared to Sample 1 shown in Example 1. The resulting decrease in capacity was more pronounced. A pseudo-spinel crystal structure was clearly observed after high-voltage charging. This is likely because it was not measured. [Explanation of symbols]

[0555] 100 Cathode active material 1001 particles 1002 Fine particles 1003 area 1010 Detection area

Claims

[Claim 1] A step of mixing a lithium source, a fluorine source, and a magnesium source to produce a first mixture, A step of mixing a composite oxide having lithium, a transition metal, and oxygen with the first mixture to produce a second mixture, The steps include heating the second mixture and A method for producing a positive electrode active material having [a certain characteristic].

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