Lithium-ion rechargeable battery

Abstract

To provide a cathode active material for a lithium ion secondary battery which has a high capacity and is improved in charge / discharge cycle characteristics.SOLUTION: A cathode active material containing lithium, cobalt, oxygen and magnesium includes a compound which is expressed by a layered rock salt structure. In the cathode active material, a space group of the compound is expressed as R-3m. Regarding the compound, in a complex oxide containing lithium and cobalt, magnesium is substituted at a lithium position and a cobalt position. The compound is a particle, the substituted magnesium is present more in a region to 5 nm from a surface of the particle in comparison with a region deeper than the surface by 10 nm or more, and magnesium substituted at the lithium position is more than magnesium substituted at the cobalt position.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One aspect of the present invention relates to a product, a method, or a method of manufacture; or, the present invention relates to a process , relating to machines, manufacturers, or compositions of matter One aspect of the present invention relates to a semiconductor device, display device, light-emitting device, energy storage device, lighting device or electronic The present invention relates to equipment or methods for manufacturing such equipment, particularly positive electrode active materials that can be used in secondary batteries. This relates to quality, secondary batteries, and electronic devices containing secondary batteries.

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

[0003] Furthermore, in this specification, "electronic equipment" refers to all devices that have an energy storage device. Electro-optical devices and information terminal devices with energy storage devices are all electronic devices. [Background technology]

[0004] In recent years, various energy storage technologies have emerged, such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. The development of such devices is thriving, particularly lithium-ion batteries, which offer high power output and high energy density. Rechargeable batteries are used in mobile phones, smartphones, tablets, and laptop computers, etc. Mobile information terminals, portable music players, digital cameras, medical devices, next-generation clean energy Gee Motors (Hybrid Electric Vehicles (HEVs), Electric Vehicles (EVs), Plug-in Hybrids) With the development of the semiconductor industry, demand for electric vehicles (PHEVs, etc.) has expanded rapidly, and rechargeable batteries are becoming increasingly available. As a source of energy, it has become indispensable in today's information society.

[0005] One of the characteristics required of lithium-ion secondary batteries is further increase 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, the positive electrode Improvements to the active material are being considered (Patent Documents 1 and 2). Also, the composition of the positive electrode active material Research on crystal 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 Str) is introduced in Non-Patent Document 5. By using a photo database, we can perform XRD data analysis. It is possible.

[0008] Furthermore, as shown in Non-Patent Documents 6 and 7, first-principles calculations can be used. This allows for the calculation of energy according to the crystalline structure, composition, etc., of a compound. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2002-216760 [Patent Document 2] Japanese Patent Publication No. 2006-261132 [Non-patent literature]

[0010] [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. [Non-Patent Document 6] Dudarev, SL et al, “Electron-energy-loss spectra and the structural stability of nickel oxide: An LSDA1U study”, Physical Review B, 1998, 57(3) 1505. [Non-Patent Document 7] Zhou, F. et al, “First-principles prediction of redox potentials in transition-metal compounds with LDA+U”, Physical Review B, 2004, 70 235121. [Overview of the project] [Problems that the invention aims to solve]

[0011] 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 a positive electrode active material and a method for producing the same. Alternatively, to improve productivity. One objective is to provide a method for producing a positive electrode active material. Alternatively, one aspect of the present invention is: 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 that has high capacity. Alternatively, one aspect of the present invention provides a high capacity two One objective is to provide a next-generation battery. Alternatively, one aspect of the present invention provides a battery with excellent charge-discharge characteristics. One of the objectives is to provide a secondary battery that can maintain a high-voltage charged state for a long 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 when the material is held. 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.

[0012] 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 our objectives is to provide legal frameworks.

[0013] Furthermore, the description of these problems does not preclude the existence of other problems. One embodiment does not need to solve all of these problems. It is possible to extract other problems from the description of the claims. [Means for solving the problem]

[0014] One aspect of the present invention relates to a positive electrode active material having lithium, cobalt, oxygen, and magnesium. It has compounds represented by a layered rock salt structure, and the space group of the compounds is represented by R-3m. The compound is a composite oxide having lithium and cobalt, where the lithium position and cobalt The compound is a compound in which magnesium is substituted at the t position, and the compound is a particle, and the substituted magnesium Gnesium is present in the region from the surface of the particle up to 5 nm, and in the region deeper than 10 nm from the surface. Magnesium, which is present in greater quantities compared to the region and is substituted at the lithium position, is substituted at the cobalt position. It is a positive electrode active material in greater quantities than the magnesium that is replaced.

[0015] Furthermore, in the above configuration, the positive electrode active material may, for example, contain fluorine.

[0016] Furthermore, in the above configuration, for example, the compound is such that the coordinate of cobalt in the unit cell is (0 (0,0,x), where the coordinates of oxygen are (0,0,x) and 0.20≦x≦0.25. The unit has a charging depth, and the volume of the unit cell at the charging depth is the same as the volume at charging depth 0. It has a volume difference of 2.5% or less from the knit cell.

[0017] Alternatively, one aspect of the present invention is a secondary battery having the positive electrode active material described above.

[0018] Alternatively, in one aspect of the present invention, the charging voltage is V, the change in V is dV, and the charging capacity is Q. Let dQ be the change in Q, and the relationship between dQ / dV (the ratio of dQ to dV) and V be... In the dQ / dVvsV curve that represents the curve, the dQ / dVvsV curve is between 0.1C and 1.0C. Measured at the rates below, at temperatures between 10°C and 35°C, using the dQ / dV vs sV curve. The voltage is measured twice in the range of V between 4.54V and 4.58V, and if V is 4.54V or higher... Within the range of 4.58V or less, the second measurement shows a first peak, and the above voltage This is a secondary battery whose voltage is based on the oxidation-reduction potential of lithium metal.

[0019] Furthermore, in the above configuration, for example, the dQ / dV vs V curve is such that V is 4.05V or higher. Measured in the range of 8V or less, and in the range of V between 4.08V and 4.18V, It has two peaks, and a third peak in the range where V is between 4.18V and 4.25V. Furthermore, the above voltage is a voltage based on the oxidation-reduction potential of lithium metal.

[0020] Furthermore, in the above configuration, for example, the secondary battery has a positive electrode, and a second peak is observed during charging. At voltage V, the positive electrode has a crystal structure corresponding to the space group P2 / m, and the first peak is At the observed charging voltage V, the positive electrode has a crystal structure corresponding to the space group R-3m.

[0021] Furthermore, in the above configuration, for example, the secondary battery has a negative electrode, and the negative electrode is made of lithium metal.

[0022] Furthermore, in the above configuration, for example, the positive electrode is taken from the secondary battery, and the dQ / dVvsV curve The positive electrode is measured using lithium metal as the counter electrode.

[0023] Alternatively, in one aspect of the present invention, the charging voltage is V, the change in V is dV, and the charging capacity is Q. Let dQ be the change in Q, and the relationship between dQ / dV (the ratio of dQ to dV) and V be... In the dQ / dVvsV curve that represents the curve, the dQ / dVvsV curve is between 0.1C and 1.0C. Measured at the rates below, at temperatures between 10°C and 35°C, using the dQ / dV vs sV curve. The voltage was repeatedly measured in the range of V from 4.05V to 4.58V, and when V reached 4.54 The first peak is present in the range of V to 4.58V, and V is between 4.08V and 4.18V. There is a second peak in the range below V, and V is in the range of 4.18V to 4.25V. There is a third peak, and the above voltage is a voltage referenced to the oxidation-reduction potential of lithium metal. Yes, the first peak showed an increase in peak intensity from the first to the tenth measurement, and the first The peak intensity decreased from the 30th to the 100th measurement, and the second peak was This is a secondary battery in which the voltage at the peak position increases from the 30th to the 100th measurement.

[0024] Furthermore, in the above configuration, for example, the secondary battery has a positive electrode, and a second peak is observed during charging. At voltage V, the positive electrode has a crystal structure corresponding to the space group P2 / m, and the first peak is At the observed charging voltage V, the positive electrode has a crystal structure corresponding to the space group R-3m.

[0025] Furthermore, in the above configuration, for example, the secondary battery has a negative electrode, and the negative electrode is made of lithium metal.

[0026] Furthermore, in the above configuration, for example, the positive electrode is taken from the secondary battery, and the dQ / dVvsV curve The positive electrode is measured using lithium metal as the counter electrode.

[0027] Alternatively, one aspect of the present invention comprises a secondary battery as described in any one of the above, and a display unit. It is an electronic device.

[0028] Alternatively, one aspect of the present invention comprises a secondary battery as described in any one of the above, an electric motor, It is a vehicle that possesses [a certain feature]. [Effects of the Invention]

[0029] 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 invention provides a positive electrode active material for ponds and a method for producing the same. Furthermore, it provides a positive electrode with high productivity. We can provide a method for producing active materials. Furthermore, we can provide a method for use in lithium-ion secondary batteries. Therefore, it is possible to provide a positive electrode active material in which the decrease in capacity during charge-discharge cycles is suppressed. Furthermore, it can provide high-capacity secondary batteries. It can also provide secondary batteries with excellent charge / discharge characteristics. It can provide this. Also, even when the high-voltage charge state is maintained for a long time, cobal This provides a positive electrode active material in which the elution of transition metals such as t is suppressed. Furthermore, it is safe and This can provide highly reliable secondary batteries. Furthermore, it can utilize novel materials, active material particles, and energy storage solutions. We can provide apparatus or methods for manufacturing them. [Brief explanation of the drawing]

[0030] [Figure 1] Figure 1 is a diagram illustrating the charge depth and crystal structure of a positive electrode active material according to one embodiment of the present invention. [Figure 2] Figure 2 illustrates the charge depth and crystal structure of a conventional positive electrode active material. [Figure 3] Figure 3 shows the XRD pattern calculated from the crystal structure. [Figure 4] Figure 4A is a diagram illustrating the crystal structure of a positive electrode active material according to one embodiment of the present invention. Figure 4B is a diagram illustrating the magnetism of a positive electrode active material according to one embodiment of the present invention. [Figure 5] Figure 5A is a diagram illustrating the crystal structure of a conventional positive electrode active material. Figure 5B is a diagram illustrating the magnetism of a conventional positive electrode active material. [Figure 6] Figure 6A is a diagram illustrating the crystal structure. Figure 6B is a diagram illustrating the crystal structure. Figure 6C is a diagram illustrating the crystal structure. [Figure 7] Figure 7A is a diagram illustrating the crystal structure. Figure 7B is a diagram illustrating the crystal structure. [Figure 8] Figure 8A is a diagram illustrating the crystal structure. Figure 8B is a diagram illustrating the crystal structure. [Figure 9] Figure 9A is a diagram illustrating the crystal structure. Figure 9B is a diagram illustrating the crystal structure. Figure 9C is a diagram illustrating the crystal structure. [Figure 10] Figure 10A is a diagram illustrating the crystal structure. Figure 10B is a diagram illustrating the crystal structure. [Figure 11] Figure 11A is a diagram illustrating the crystal structure. Figure 11B is a diagram illustrating the crystal structure. Figure 11C is a diagram illustrating the crystal structure. [Figure 12] Figure 12 illustrates an example of a method for producing a positive electrode active material according to one aspect of the present invention. [Figure 13] Figure 13 illustrates another example of a method for producing a positive electrode active material according to one embodiment of the present invention. [Figure 14] Figure 14A is a cross-sectional view of the active material layer when a graphene compound is used as a conductive additive. Figure 14B is a cross-sectional view of the active material layer when a graphene compound is used as a conductive additive. [Figure 15] Figure 15A is a diagram illustrating the charging method of a secondary battery. Figure 15B is a diagram illustrating the charging method of a secondary battery. Figure 15C is a diagram illustrating an example of secondary battery voltage and charging current. [Figure 16]Figure 16A is a diagram illustrating the charging method of a secondary battery. Figure 16B is a diagram illustrating the charging method of a secondary battery. Figure 16C is a diagram illustrating the charging method of a secondary battery. Figure 16D is a diagram illustrating an example of secondary battery voltage and charging current. [Figure 17] Figure 17 shows an example of secondary battery voltage and discharge current. [Figure 18] Figure 18A is a diagram illustrating a coin-type rechargeable battery. Figure 18B is a diagram illustrating a coin-type rechargeable battery. Figure 18C is a diagram illustrating the charging of a rechargeable battery. [Figure 19] Figure 19A is a diagram illustrating a cylindrical secondary battery. Figure 19B is a diagram illustrating a cylindrical secondary battery. Figure 19C is a diagram illustrating multiple secondary batteries. Figure 19D is a diagram illustrating multiple secondary batteries. [Figure 20] Figure 20A is a diagram illustrating an example of a battery pack. Figure 20B is a diagram illustrating an example of a battery pack. [Figure 21] Figure 21A is a diagram illustrating an example of a battery pack. Figure 21B is a diagram illustrating an example of a battery pack. Figure 21C is a diagram illustrating an example of a battery pack. Figure 21D is a diagram illustrating an example of a battery pack. [Figure 22] Figure 22A is a diagram illustrating an example of a secondary battery. Figure 22B is a diagram illustrating an example of a secondary battery. [Figure 23] Figure 23 illustrates an example of a wound body. [Figure 24] Figure 24A is a diagram illustrating the configuration of a laminated secondary battery. Figure 24B is a diagram illustrating a laminated secondary battery. Figure 24C is a diagram illustrating a laminated secondary battery. [Figure 25] Figure 25A is a diagram illustrating a laminated rechargeable battery. Figure 25B is a diagram illustrating a laminated rechargeable battery. [Figure 26] Figure 26 shows the external appearance of a secondary battery. [Figure 27] Figure 27 shows the external appearance of a secondary battery. [Figure 28]Figure 28A shows an example of a positive electrode and an example of a negative electrode. Figure 28B is a diagram illustrating the method of manufacturing a secondary battery. Figure 28C is a diagram illustrating the method of manufacturing a secondary battery. [Figure 29] Figure 29A illustrates a bendable secondary battery. Figure 29B illustrates a bendable secondary battery. Figure 29C illustrates a bendable secondary battery. Figure 29D illustrates a bendable secondary battery. Figure 29E illustrates a bendable secondary battery. [Figure 30] Figure 30A is a diagram illustrating a bendable secondary battery. Figure 30B is a diagram illustrating a bendable secondary battery. [Figure 31] Figure 31A illustrates an example of an electronic device. Figure 31B illustrates an example of an electronic device. Figure 31C illustrates an example of an electronic device. Figure 31D illustrates an example of an electronic device. Figure 31E illustrates an example of a secondary battery. Figure 31F illustrates an example of an electronic device. Figure 31G illustrates an example of an electronic device. Figure 31H illustrates an example of an electronic device. [Figure 32] Figure 32A illustrates an example of an electronic device. Figure 32B illustrates an example of an electronic device. Figure 32C illustrates a charging control circuit. [Figure 33] Figure 33 illustrates an example of an electronic device. [Figure 34] Figure 34A is a diagram illustrating an example of a vehicle. Figure 34B is a diagram illustrating an example of a vehicle. Figure 34C is a diagram illustrating an example of a vehicle. [Figure 35] Figure 35A shows the dQ / dV vs V curve. Figure 35B shows the dQ / dV vs V curve. [Figure 36] Figure 36A shows the charge-discharge curve. Figure 36B shows the charge-discharge curve. [Figure 37] Figure 37A shows the charge-discharge curve. Figure 37B shows the cycle characteristics. [Figure 38] Figure 38 shows the results of XRD. [Figure 39] Figure 39 shows the results of XRD. [Figure 40] Figure 40A shows the XRD results. Figure 40B shows the XRD results. [Figure 41] Figure 41 shows the results of XRD. [Figure 42] Figure 42 shows the dQ / dV vs V curve. [Figure 43] Figure 43A shows the dQ / dV vs V curve. Figure 43B shows the dQ / dV vs V curve. [Modes for carrying out the invention]

[0031] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention This is not limited to the description below, and its form and details can be changed in various ways, as is the case for those skilled in the art. This will be easily understood. Furthermore, the present invention shall be interpreted as being limited to the contents of the embodiments described below. It is not something that should be done.

[0032] Furthermore, in this specification, crystal planes and directions are indicated by Miller indices. In crystallography, numbers are represented with a superscript bar, but in this specification, due to limitations on patent application notation, the numbers are represented as follows: Sometimes, instead of placing a bar above a letter, 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 < > represents individual crystal planes ( ), and sets of planes with equivalent symmetry are {}. They express each other.

[0033] In this specification, segregation refers to the process of a solid composed of multiple elements (e.g., A, B, C). This refers to the phenomenon in which a certain element (for example, B) is distributed non-uniformly in space.

[0034] In this specification, the surface layer of particles such as active materials refers to the region from the surface up to approximately 10 nm. This refers to the surface. Surfaces created by cracks or fissures can also be called the surface. Furthermore, the area deeper than the surface layer is also called the surface. , internally.

[0035] In this specification, etc., layered rock salt-type crystals of composite oxides containing lithium and transition metals The structure has a rock salt-type ionic arrangement in which cations and anions are arranged alternately, and transition metals Because lithium is arranged in a regular pattern to form a two-dimensional plane, two-dimensional diffusion of lithium is possible. This refers to a crystal structure. It may also have defects such as vacancies in cations or anions. Strictly speaking, a layered rock salt crystal structure is a structure in which the lattice of rock salt crystals is distorted. There is.

[0036] Furthermore, in this specification and elsewhere, 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 is characterized by the presence of a cation or anion. A deficiency in either a cation or anion is also acceptable.

[0037] Furthermore, in this specification, etc., the pseudo-spinel type of composite oxide containing lithium and a transition metal The crystal structure of cobalt is space group R-3m, and although it is not a spinel-type crystal structure, it is 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 possesses symmetry. Note that pseudo-spinel crystal structures are found in light elements such as lithium. The element may occupy the oxygen 4-coordinate position, and in this case as well, the ion arrangement is similar to that of the spinel type. It has symmetry.

[0038] Furthermore, the pseudo-spinel type crystal structure, although having Li randomly between layers, is a CdCl2 type. It can also be said that it is a crystal structure similar to the crystal structure. The crystal structure is when lithium nickelate is charged to a depth of charge of 0.94 (Li 0.06 Ni It has a crystal structure similar to that of O2, but is pure lithium cobaltate or a layered structure containing a large amount of cobalt. It is known that rock salt-type cathode active materials do not usually adopt this crystal structure.

[0039] Layered rock salt crystals, and the anions of rock salt crystals, have a cubic close-packed structure (face-centered cubic lattice structure). ) takes this form. It is also presumed that pseudo-spinel crystals adopt a cubic close-packed structure for anions. 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 The space groups of type crystals are Fm-3m (the space group of a typical rock salt type crystal) and Fd-3m (the simplest). Because it is different from the space group of rock salt crystals that have symmetry, the crystal planes that satisfy the above conditions The Lars 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, anions When the orientations of the cubic close-packed structures that are formed are aligned, we say that the crystal orientations are roughly the same. There is.

[0040] The approximate agreement of the crystal orientation in the two regions can be seen in TEM (transmission electron microscope) images and STE (spherical spectroscopy) images. M (Scanning Transmission Electron Microscope) image, HAADF-STEM (High-angle scattering annular dark-field scanning transmission electron microscope) image. The determination should be made based on images from a microscope, ABF-STEM (annular bright-field scanning transmission electron microscope), etc. This can be done. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as criteria for judgment. Yes, it is possible. In TEM images, the arrangement of cations and anions can be observed as a repetition of bright and dark lines. It can be inferred. When the orientation of the cubic close-packed structure is aligned in layered rock salt crystals and rock salt crystals, the crystal In between, the angle between the repetition of bright and dark lines is 5 degrees or less, more preferably 2.5 degrees or less. The condition can be observed. Furthermore, light elements such as oxygen and fluorine are clearly visible in TEM images, etc. In some cases, it may not be possible to discern this, but in such cases, the alignment of the metal elements can be determined by their arrangement. ru.

[0041] Furthermore, in this specification, the theoretical capacity of the positive electrode active material refers to the insertion and removal capacity of the positive electrode active material. This refers to the amount of electricity that would be generated if all the lithium were to be desorbed. For example, the theoretical capacity of LiCoO2 is 27 The theoretical capacity of LiNiO2 is 274mAh / g, and the theoretical capacity of LiMn2O4 is 4mAh / g. The capacity is 148mAh / g.

[0042] Furthermore, in this specification, etc., the charging depth when all insertable and removable lithium is inserted. The degree is 0, and the charge depth when all the insertable and detachable lithium in the positive electrode active material has been detached is 1. Let's assume that's the case.

[0043] Furthermore, in this specification, charging means moving lithium ions from the positive electrode to the negative electrode within the battery. This refers to the movement of electrons, specifically from the negative electrode to the positive electrode in an external circuit. Therefore, the process of releasing lithium ions is called charging. Also, the charging depth is 0.74 or higher. Positive electrode active material with a charge depth of 0.9 or less, more specifically 0.8 to 0.83, is subjected to high voltage. This refers to a charged positive electrode active material. Therefore, for example, in LiCoO2, 219 If it is charged at 0.2mAh / g, it is a positive electrode active material that has been charged at a high voltage. In O2, 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 Um, constant current charging is performed, and then the current value is 0.01C, or the constant current charging value. The positive electrode active material, after being charged at a constant voltage until the current value is reduced to about 1 / 5 to 1 / 100, is also subjected to high voltage. This refers to a positive electrode active material that has been charged.

[0044] Similarly, discharge is the movement of lithium ions from the negative electrode to the positive electrode within a battery, and externally... This refers to the movement of electrons from the positive electrode to the negative electrode in a circuit. The positive electrode active material is lithium. The insertion of ions is called discharge. Also, the positive electrode active material has a charge depth of 0.06 or less, The positive electrode active material, which has been discharged to more than 90% of its charge capacity from a state of being charged at high voltage, This refers to the positive electrode active material that has been discharged for 2 minutes. For example, in LiCoO2, the charge capacity is 2 19.2mAh / g indicates a high-voltage charging state, and from here, 90% of the charge capacity... A positive electrode active material that has been discharged to a certain level of 197.3 mAh / g or more is a positive electrode active material that has been sufficiently discharged. It is of quality. Also, in LiCoO2, the battery voltage is 3V or less in a 25°C environment (counter electrode lithium In the case of Um, the positive electrode active material after constant current discharge until it reaches a certain state is also the positive electrode active material that has been sufficiently discharged. Let's assume that's the case.

[0045] 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 this is the case. For example, it can be obtained by differentiating capacitance (Q) with respect to voltage (V) (dQ / dV). Around the peaks in the dQ / dV curve, non-equilibrium phase transitions occur, and the crystal structure changes significantly. It is thought that they understand.

[0046] (Embodiment 1)

[0047] This embodiment describes a positive electrode active material according to one aspect of the present invention.

[0048] [Structure of the positive electrode active material] Using Figures 1 and 2, a positive electrode active material 100 according to one aspect of the present invention and a conventional positive electrode active material The quality will be explained, and these differences will be discussed. Figures 1 and 2 show the positive electrode active material. This section describes the case where cobalt is used as the transition metal. It also discusses the conventional cathode shown in Figure 2. Active material refers to a material in which elements other than lithium, cobalt, and oxygen are added internally or to the surface layer. This is simple lithium cobalt oxide (LiCoO2) that has not undergone any processing such as coating. be.

[0049] <Conventional positive electrode active material> Lithium cobalt oxide (LiCoO2), one of the conventional positive electrode active materials, is mentioned in Non-Patent Document 1 and Non-Patent Document 2. As described in reference 2, etc., the crystal structure changes depending on the depth of charge. Cobalt acid A typical crystal structure of lithium is shown in Figure 2.

[0050] As shown in Figure 2, lithium cobalt oxide at charge depth 0 (discharge state) has space group R- It has a region with a 3m crystal structure, and there are three CoO2 layers in the unit cell. Therefore, this crystal structure is sometimes called the O3 type crystal structure. Note that the CoO2 layer is cobalt This refers to an octahedral structure in which oxygen atoms are coordinated in six positions, and which is continuous on a plane in a state of shared edges. .

[0051] Furthermore, when the charging depth is 1, it has a crystal structure of space group P-3m1, and the unit cell contains Co One O2 layer is present. Therefore, this crystal structure is sometimes called an O1 type crystal structure.

[0052] 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. This structure has a CoO2 structure like P-3m1(O1) and R-3m(O 3) It can also be described as a structure in which LiCoO2 structures like this are alternately stacked. The crystal structure is sometimes called the H1-3 type crystal structure. In this structure, the number of cobalt atoms per unit cell is twice that of other structures. However, Figure 2 In this specification, and in order to facilitate comparison with other structures, the c-axis of the H1-3 type crystal structure is defined as follows: This will be shown as a diagram that is half the size of a knit cell.

[0053] The process involves repeatedly charging and discharging at a high voltage, such as when the charge depth reaches approximately 0.88 or higher. In contrast, lithium cobalt oxide has an H1-3 type crystal structure and a R-3m(O3) structure in its discharge state. Between the two phases, the crystal structure undergoes repeated changes (i.e., non-equilibrium phase transitions).

[0054] However, these two crystal structures have a large displacement of the CoO2 layer. (See dotted line in Figure 2) As indicated by the arrows, in the H1-3 type crystal structure, the CoO2 layer is large from R-3m(O3) It is collapsing. Such dynamic structural changes negatively affect the stability of the crystal structure. Eur.

[0055] Furthermore, the volume difference is also large. When comparing per the same number of cobalt atoms, H1-3 type crystal The difference in volume between the O3-type crystal structure in its structure and discharge state is 3.5% or more.

[0056] In addition, the H1-3 type crystal structure has a continuous CoO2 layer, such as P-3m1(O1). The resulting structure is likely to be unstable.

[0057] 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 properties. This reduces the number of sites where lithium can exist stably, and also makes lithium insertion and removal more difficult. This is likely the reason.

[0058] <Positive electrode active material according to one aspect of the present invention> ≪Inside≫ In contrast, the positive electrode active material 100 of one aspect of the present invention has a fully discharged state and a high-voltage state. The changes in crystal structure under pressure and the same number of transition metal atoms are compared. The difference in volume in that case is small.

[0059] Figure 1 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 magnesium, cobalt, and oxygen. In addition to the above, it contains magnesium. It is preferable that it contains halogens such as fluorine and chlorine.

[0060] The crystal structure of the charge depth 0 (discharge state) in Figure 1 is R-3m(O3), the same as in Figure 2. On the other hand, the positive electrode active material 100 of one aspect of the present invention is in a state where it is sufficiently charged to a charge depth of about 0.88. In addition, it has a crystal structure different from that of Figure 2. The crystal structure of this space group R-3m is described herein, etc. This will be referred to as a pseudo-spinel crystal structure. The pseudo-spinel crystal shown in Figure 1 is also shown. In the structural diagram, to explain the symmetry of the cobalt atom and the oxygen atom, lithium is used. Although the "um" is omitted from the notation, in reality, there is approximately 12 atomic percent of cobalt between the CoO2 layers. Lithium exists in both O3-type and pseudo-spinel-type crystal structures. Furthermore, it is preferable for magnesium to be present in a dilute manner between the CoO2 layers, i.e., at the lithium sites. It seems that halogens such as fluorine are present randomly and dilutely at the oxygen site. It is preferable.

[0061] In the positive electrode active material 100, when charged at high voltage and a large amount of lithium is released, the crystal structure The changes are more suppressed than with conventional LiCoO2. For example, as shown by the dotted line in Figure 1. In these crystal structures, there is almost no displacement of the CoO2 layer.

[0062] Furthermore, the positive electrode active material 100 has an O3-type crystal structure with a charging depth of 0 and a pseudo-crystal structure with a charging depth of 0.88. The volume difference per unit cell in spinel-type crystal structures is less than 2.5%, or more specifically, 2. It is less than 2%.

[0063] Therefore, the crystal structure is less likely to collapse even when repeatedly charged and discharged at high voltage.

[0064] In the pseudo-spinel crystal structure, the coordinates of cobalt and oxygen in the unit cell are Co( This can be shown within the range 0,0,0.5, O(0,0,x), and 0.20≦x≦0.25. Cut.

[0065] Magnesium, which is randomly and dilutely present between the CoO2 layers, that is, at the lithium sites, It has the effect of suppressing the displacement of the CoO2 layer. Therefore, magnesium is present between the CoO2 layers. This makes it easy to form a pseudo-spinel crystal structure. Therefore, magnesium is a positive electrode active material of 100. It is preferable that the magnesium is distributed throughout the entire particle. Furthermore, it is preferable to perform a heat treatment in the process of manufacturing the positive electrode active material 100.

[0066] However, if the heat treatment temperature is too high, cation mixing occurs and magnesium The likelihood of magnesium entering the cobalt site increases. Furthermore, if the heat treatment temperature is too high, the effect of maintaining the structure of R-3m will be lost. There are concerns about adverse effects such as the reduction of cobalt to its divalent state and the evaporation of lithium. It can be done.

[0067] Therefore, prior to the heat treatment to distribute magnesium throughout the particles, cobalt acid It is preferable to add halogen compounds such as fluorine compounds to lithium. Adding a substance causes a decrease in the melting point of lithium cobalt oxide. By lowering the melting point, the At temperatures where on-mixing is unlikely to occur, it is easy to distribute magnesium throughout the particles. It is. Furthermore, if a fluorine compound is present, it provides corrosion resistance to hydrofluoric acid produced by the decomposition of the electrolyte. It can be expected that this will improve.

[0068] Furthermore, until now, the positive electrode active material 100 has been a composite acid having lithium, cobalt, and oxygen. While we have described the case where it is a monoxide, 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 is less than 0.075. The following is more preferable:

[0069] When a high-voltage charge is maintained for a long period of time, transition metals dissolve from the positive electrode active material into the electrolyte. This may cause the crystal structure to collapse. However, by having nickel in the above proportion, the positive electrode activity In some cases, it may be possible to suppress the leaching of transition metals from substance 100.

[0070] By adding nickel, the charge and discharge voltage decreases, so for the same capacity, the voltage is lowered. Because this can be achieved, it may be possible to suppress the leaching of transition metals and the decomposition of the electrolyte. Here, charge / discharge voltage refers to, for example, the voltage within the range from zero charge depth to a predetermined charge depth. .

[0071] ≪Surface layer≫ It is preferable that magnesium is distributed throughout the particles of the positive electrode active material 100, but 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 set of particles. The particle surface is In other words, they are all crystal defects, and during charging, lithium leaks out from the surface, so the inside This region tends to have a lower lithium concentration. Therefore, it is prone to instability and the crystal structure This is a part where the structure is easily broken down. If the magnesium concentration in the surface layer is high, it can cause changes in the crystal structure. It can be effectively suppressed. Also, if the magnesium concentration in the surface layer is high, the electrolyte will It can also be expected that the corrosion resistance to hydrofluoric acid produced by the dissolution process will improve.

[0072] Furthermore, the concentration of halogens such as fluorine in the surface layer of the positive electrode active material 100 is higher than the average concentration of the entire particle. It is also preferable that the halogen is present in the surface layer, which is the region in contact with the electrolyte. This can effectively improve corrosion resistance to hydrofluoric acid.

[0073] Thus, the surface layer of the positive electrode active material 100 has a higher concentration of magnesium and fluorine than the interior. It is preferable that the composition is high and different from the internal composition. Furthermore, it is preferable that the composition is a crystal that is stable at room temperature. It is preferable to have a structure. Therefore, the surface layer may have a different crystal structure from the interior. For example, at least a portion of the surface layer of the positive electrode active material 100 has a rock salt type crystalline structure. It may be. Also, if the surface and interior have different crystal structures, the arrangement of the crystals in the surface and interior It is preferable that the directions are roughly the same.

[0074] However, if the surface layer consists only of MgO, or only of a solid solution of MgO and CoO(II), The insertion and removal of lithium becomes difficult. Therefore, the surface layer contains at least cobalt. In the discharge state, it also contains lithium and must have a path for lithium insertion and removal. Furthermore, it is preferable that the concentration of cobalt is higher than that of magnesium.

[0075] ≪Grain boundary≫ The magnesium or halogen contained in the positive electrode active material 100 is randomly and dilutely present inside. While some segregation is acceptable, it is more preferable that some of the segregation is located at the grain boundaries.

[0076] In other words, the magnesium concentration at and near the grain boundaries of the positive electrode active material 100 is also internal. It is preferable that the halogen concentration is higher than in other regions. Also, the halogen concentration at and near the grain boundaries is also preferable. It is preferable that it be higher than other areas of the part.

[0077] Similar to particle surfaces, grain boundaries are also surface defects. Therefore, they are prone to instability and can alter the crystal structure. Cementation is likely to begin. Therefore, if the magnesium concentration is high at and near the grain boundaries, This allows for more effective suppression of changes in crystal structure.

[0078] Furthermore, if the magnesium and halogen concentrations at and near the grain boundaries are high, the positive electrode activity Even if a crack occurs along the grain boundary of 100 particles of material, the crack will Magnesium and halogen concentrations are high near the surface. Therefore, after cracks occur... This also improves the corrosion resistance to hydrofluoric acid in the positive electrode active material.

[0079] In this specification, the vicinity of a grain boundary refers to the region extending approximately 10 nm from the grain boundary. Let's do that.

[0080] ≪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, Problems include difficulty in supporting the active material layer during coating onto the electrolytic body, and excessive reaction with the electrolyte. This also occurs. Therefore, D50 is preferably 1 μm or more and 100 μm or less, and 2 μm or more and 40 It is more preferable that the particle size be μm or less, and even more preferable that it be between 5 μm and 30 μm.

[0081] <Analysis method> One aspect of the present invention is that a certain positive electrode active material exhibits a pseudo-spinel crystal structure when charged at a high voltage. Whether or not the positive electrode active material 100 is of a certain type can be determined by XRD and electron diffraction of the positive electrode charged with high voltage. Analysis is performed using methods such as neutron diffraction, electron spin resonance (ESR), and nuclear magnetic resonance (NMR). This can be determined by the symmetry of the transition metal such as cobalt in the positive electrode active material. High-resolution analysis is possible, allowing for comparison of crystallinity and crystal orientation, and enabling analysis of lattice periodic strain. It is possible to analyze the crystallite size and other properties by directly measuring the positive electrode obtained by disassembling a secondary battery. It is preferable in that it can achieve sufficient accuracy, among other things.

[0082] The positive electrode active material 100 in one aspect of the present invention is in a state where it is charged with a high voltage as described above. A key feature is that the crystal structure changes little when discharged. Materials in which 50 wt% or more of the crystalline structure exhibits significant changes in state can withstand high-voltage charging and discharging. This is undesirable because it cannot be achieved. Furthermore, simply adding impurity elements does not result in the desired crystal structure. It is important to note that this is not always the case. For example, Coba containing magnesium and fluorine Although they share the common characteristic of being lithium luteate, when charged at high voltage, they form pseudo-spinel crystals. Cases where the structure accounts for 60 wt% or more, and where the H1-3 type crystal structure accounts for 50 wt% or more. And, there is. Also, at a given voltage, the pseudo-spinel crystal structure becomes approximately 100 wt%, and Furthermore, increasing the specified voltage may result in the formation of an H1-3 type crystal structure. To determine whether or not it is a positive electrode active material 100 of a specific type, crystals such as XRD are used. An analysis of the structure is necessary.

[0083] However, when the positive electrode active material is in a high-voltage charged or discharged state, its crystalline structure changes when exposed to the air. Changes in structure can occur. For example, a change from a pseudo-spinel type crystal structure to an H1-3 type crystal structure. It may change. Therefore, all samples should be handled in an inert atmosphere such as an argon atmosphere. It is preferable to drink.

[0084] ≪Charging method≫ For determining whether a certain composite oxide is a positive electrode active material 100 according to one aspect of the present invention High-voltage charging, for example, uses a coin cell (CR2032 type, 20mm diameter) with a lithium counter electrode. It can be made (3.2mm in diameter) and charged.

[0085] More specifically, the positive electrode consists of a slurry mixed with positive electrode active material, a conductive additive, and a binder. A positive electrode current collector made of aluminum foil can be used, coated with this material.

[0086] 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 occurs, the potential of the secondary battery and the potential of the positive electrode are different. Voltage and potential in this specification, etc. Unless otherwise specified, this represents the potential of the positive electrode.

[0087] The electrolyte in the electrolyte solution contains 1 mol / L lithium hexafluoride phosphate (LiPF6). The electrolyte used is ethylene carbonate (EC) and diethyl carbonate (DEC). EC:DEC = 3:7 (volume ratio), vinylene carbonate (VC) is mixed at 2 wt%. You can use the one that you have.

[0088] Polypropylene with a thickness of 25 μm can be used for the separator.

[0089] The positive electrode and negative electrode cans can be made of stainless steel (SUS). Cut.

[0090] The coin cell manufactured under the above conditions was charged with a constant current of 4.6V and 0.5C, and then the current value was measured. Charge at a constant voltage until the current reaches 0.01C. Here, 1C is defined as 137mA / g. The temperature should be set to 25°C. After charging in this manner, the coin cell is subjected to an argon atmosphere glow. By disassembling the device in a box and removing the positive electrode, a positive electrode active material charged with high voltage can be obtained. To suppress reactions with external components when performing various analyses afterward, the area is sealed in an argon atmosphere. It is preferable to do so. For example, XRD can be performed by sealing the sample in a sealed container under an argon atmosphere. can.

[0091] Furthermore, the above is the charging voltage when lithium metal is used as the counter electrode. (Negative electrode of a secondary battery) For example, when charging using graphite, when lithium metal is used as the negative electrode... Charging can be performed using a value obtained by subtracting 0.1V from the charging voltage as a guideline.

[0092] In this specification, when lithium metal is used as the counter electrode, the charging voltage is, for example, when the graphite negative electrode is used. For the secondary battery used, the value obtained by subtracting 0.05V to 0.3V from that value is preferable. The value can be calculated by subtracting 0.1V.

[0093] ≪XRD≫ CuKα1 line calculated from pseudo-spinel crystal structure and H1-3 type crystal structure models. Figure 3 shows the ideal powder XRD pattern obtained by [the test]. For comparison, LiCo[0] is also shown. The ideal XR calculated from the crystal structures of O2(O3) and CoO2(O1) at a charge depth of 1. Pattern D is also shown. Note that the patterns for LiCoO2(O3) and CoO2(O1) are shown in I. CSD (Inorganic Crystal Structure Database) (See Non-Patent Document 5) From the crystal structure information obtained, Materials Studio Reflex Powder Diff is one of the modules in o(BIOVIA). Created using raction. The range of 2θ is set to 15° to 75°, and Step si ze=0.01, wavelength λ1=1.540562×10 -10 m, λ2 not set, Mon The ochromator was set to single. The pattern of the H1-3 type crystal structure is not patented. It was similarly prepared from the crystal structure information described in Reference 3. The pseudo-spinel pattern is one embodiment of the present invention. The crystal structure was estimated from the XRD pattern of the positive electrode active material, and TOPAS ver.3 (Bru The crystal structure was fitted using Ker's crystal structure analysis software, and the XRD process was performed as before. I created a turn.

[0094] As shown in Figure 3, in the pseudo-spinel crystal structure, 2θ = 19.30 ± 0.20° (19 (0.10° to 19.50°), and 2θ = 45.55 ± 0.10° (45.45°) Diffraction peaks appear at angles above 45.65°. More specifically, 2θ = 19.3 0 ± 0.10° (between 19.20° and 19.40°), and 2θ = 45.55 ± 0. A sharp diffraction peak appears at 05° (between 45.50° and 45.60°). However, H1- In the type 3 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 = The appearance of a peak at 45.55±0.10° indicates that the positive electrode active material 100 of one embodiment of the present invention This can be considered a characteristic of [the product / service].

[0095] 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 locations where the peaks appear are close together. More specifically, the main diffraction peaks of both. 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 2θ = 0.7 or less, and more preferably 2θ = 0.5 or less.

[0096] In one embodiment of the present invention, the positive electrode active material 100, when charged with high voltage, forms a pseudo-spinel type crystal. Although it has a structure, not all particles have to have a pseudo-spinel type crystal structure. Other crystal structures It may contain or be partially amorphous. However, regarding the XRD pattern... When Rietveld analysis is performed, it is preferable that the pseudo-spinel crystal structure is 50 wt% or more. It is preferable that the content be 60 wt% or more, and even more preferable that it be 66 wt% or more. Preferably, the pseudo-spinel crystal structure is 50 wt% or more, more preferably 60 wt% or more. More preferably, if the content is 66 wt% or more, it will be a positive electrode active material with sufficiently excellent cycle characteristics. It is possible.

[0097] Furthermore, Rietveld analysis was performed even after more than 100 charge-discharge cycles from the start of measurement. When the pseudo-spinel crystal structure is present, it is preferable that it is 35 wt% or more, and 40 wt% or more. It is more preferable that it be 43 wt% or more, and even more preferable that it be 43 wt% or more.

[0098] 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 LiC in the discharged state. It only decreases to about 1 / 10 of oO2(O3). Therefore, the X value is the same as the positive electrode before charging and discharging. Even under RD measurement conditions, a clear peak of a pseudo-spinel crystal structure was observed after high-voltage charging. Yes, it is possible. On the other hand, in simple LiCoO2, some parts can 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 determined from the full width at half maximum of the XRD peak.

[0099] 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. In situations where a different element is substituted at the um position, or where cobalt enters the oxygen 4-coordinate position (A site), It becomes larger in total. Therefore, first, the amount of Co3O4 with heteroatomic substitution and spinel-type crystal structure is small. They create a composite oxide that has no defects, that is, a layered rock salt type crystal structure with few defects, and then magnesium When magnesium is mixed with a fluorine source and magnesium is inserted into the lithium position, good It is believed that this will enable the fabrication of cathode active materials that exhibit cycle characteristics.

[0100] The lattice constant of the c-axis in the crystal structure of the positive electrode active material in the discharged state is preferably 14.06 0×10 -10 m or less, more preferably 14.055×10 -10 m or less, and even more preferably 1 4.051×10 -10 m or less. The lattice constant of the c-axis after annealing is preferably 14 .065×10 -10 m or less.

[0101] To make the lattice constant of the c-axis within the above range, it is preferable that there be less impurities, and in particular, it is preferable that there be less addition of transition metals other than cobalt, manganese, and nickel. Specifically, it is preferably 30<​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Since the volume of the surface layer is extremely small when compared, even if the surface layer of the positive electrode active material 100 has a crystal structure different from that of the inside, it is highly likely that it will not appear in the XRD pattern. When the XRD of the charged positive electrode has a peak at 2θ = 18.70 ± 0.20°, the full width at half maximum is 10 times or less, preferably 5 times or less, more preferably

[0106] 4.3 times or less, and even more preferably 3.8 times or less, compared to the full width at half maximum before charging or when discharging to 2.5 V. When the XRD of the charged positive electrode has a peak at 2θ = 45.2 ± 0.30°, the full width at half maximum is 4 times or less, more preferably 3.3 times or less, and even more preferably 2.8 times or less, compared to the full width at half maximum before charging or when discharging to 2.5 V. The peak at 2θ = 18.70 ± 0.20° is considered to correspond to the (0 0 3) plane of the O3-type crystal structure, and the peak at 2θ = 45.2 ± 0.30° is considered to correspond to the (1 0 4) plane of the O3-type crystal structure, respectively. In addition, in the above, based on the voltage of lithium metal, it is preferable that the full width at half maximum is within the range shown above even when the charging voltage is 4.5V or higher, more preferably 4.45V or higher.

[0107]

[0108] When the XRD of the charged positive electrode has a peak at 2θ = 19.30 ± 0.20°, the full width at half maximum is 10 times or less, preferably 5 times or less, more preferably 4.3 times or less, and even more preferably 3.8 times or less, compared to the full width at half maximum of the peak that appears at 2θ = 18.70 ± 0.20° before charging or when discharging to 2.5 V. When charging, the XRD of the positive electrode ​​If the positive electrode and XRD have a peak at 2θ = 45.55 ± 0.10°, then the full width at half maximum is Before charging, or after discharging to 2.5V, the voltage is 2θ = 45.2 ± 0.30°. Compared to the full width at half maximum of the peak, it is 5 times or less, more preferably 4.3 times or less, even more preferably The ratio is 3.8 times or less.

[0109] Furthermore, in the above, the charging voltage is 4.5V or higher, based on the voltage of lithium metal. Preferably 4.55V or higher, and even more preferably 4.6V or higher, but the full width at half maximum is as above. It is preferable that the range is as indicated.

[0110] Furthermore, the XRD of the charged positive electrode is, for example, 2θ = 19.28 ± 0.6°, or 2 The peak is located at θ = 19.32 ± 0.4°.

[0111] The small increase in the full width at half maximum is due to lithium being released during charging. This demonstrates that the disorder in the crystal structure can be suppressed to a small extent. Therefore, for example, the positive electrode activity of one embodiment of the present invention In the charge-discharge cycle characteristics of secondary batteries using materials, the decrease in discharge capacity is suppressed.

[0112] Furthermore, as will be described in the later embodiments, in a positive electrode using a positive electrode active material according to one embodiment of the present invention, If the charge depth is deep, for example, around 4.5V based on lithium metal voltage, after discharge For example, the lattice constant of the a-axis becomes smaller compared to the value when discharged to 2.5V. After that, As the charging depth increases further, the lattice constant of the a-axis increases. At this time, for example, a It is preferable that the lattice constant of the axis be as close as possible to the value after discharge.

[0113] The change in the lattice constant along the a-axis is thought to correspond, for example, to a Co-O bond. The bond is considered to have a high covalent nature. When the depth of charge is deep, the lattice constant of the a-axis approaches the value after discharge, and it is considered that charging is performed while maintaining a stable crystal structure.

[0114] In charging, when the voltage based on lithium metal is 4.55 V or more, the lattice constant of the a-axis is For example, it is preferably 2.813×10 -10 m or more.

[0115] Note that in the positive electrode active material, the desorption and insertion of carrier ions, here for example lithium ions, are repeated by several charge-discharge cycles. By repeating the desorption and insertion of carrier ions [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​4+ no Ko It may also be balt. This paramagnetic cobalt is Co 2+ and Co 4+ In either case Although they cannot be distinguished by ESR because they have only one electron pair, the valence of the surrounding elements can be determined. Either valency is acceptable.

[0117] On the other hand, conventional positive electrode active materials have a lithium-free spinel on the surface when charged. Some sources state that it can have a crystal structure of the type shown. In this case, spinel is shown in Figure 5A. It will have the Co3O4 crystal structure.

[0118] When spinel is described by the general formula A[B2]O4, element A is oxygen in 4-coordinate state, and element B is oxygen. This results in 6-coordinate oxygen. Therefore, in this specification, sites with 4-coordinate oxygen are referred to as site A, and sites with 6-coordinate oxygen are referred to as site A. Site B is sometimes referred to as Site Ito.

[0119] In Co3O4 with a spinel-type crystal structure, not only is there an oxygen 6-coordinate B site, but also an oxygen 4-coordinate site. Cobalt is also present at site A. As shown in Figure 5B, in oxygen 4-coordinate cobalt, torn e g orbit and t 2g Of the orbits, e g The orbital energy is low. Therefore, oxygen 4 coordination Co 2+ Co 3+ and Co 4+ All of them have unpaired electrons and are paramagnetic. If particles containing sufficient spinel-type Co3O4 are analyzed by ESR, etc., then Co3O4 will be found to be oxygen-4 coordinated. 2 + Co 3+ or Co 4+ A peak originating from paramagnetic cobalt should be detected. .

[0120] However, in one embodiment of the present invention, the positive electrode active material 100 is oxygen 4-coordinate paramagnetic cobalt The originating peaks are so few that they cannot be identified. Therefore, the pseudo-spinels referred to in this specification, etc., are Unlike positive 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 detection capability that can be detected by ESR, etc. In some cases, the peaks originating from Pinel-type CO3O4 are small or too few 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 it exists.

[0121] ≪XPS≫ X-ray photoelectron spectroscopy (XPS) can detect depths of approximately 2 to 8 nm (usually around 5 nm) from the surface. Since analysis of the region up to that point is possible, the concentration of each element can be determined for approximately half of the surface layer. It can be analyzed quantitatively. Furthermore, narrow-scan analysis can analyze the bonding state of elements. It is possible. Note that the quantitative accuracy of XPS is often around ±1 atomic percent, and the detection limit is for elements. It varies, but it is approximately 1 atomic percent.

[0122] When XPS analysis was performed on positive electrode active material 100, with the cobalt concentration set to 1, The relative concentration of magnesium is preferably 0.4 to 1.5, and preferably 0.45 to 1.00. Less than is preferable. Also, the relative value of the halogen concentration, such as fluorine, should be between 0.05 and 1.5. Preferably, 0.3 or more and more preferably 1.00 or less.

[0123] Furthermore, when the positive electrode active material 100 was analyzed using XPS, the bonding energy between fluorine and other elements was observed. The peak indicating ghee is preferably between 682eV and 685eV, and is also 684.3eV. It is even more preferable that it be around V. This is because the binding energy of lithium fluoride is 6. It is different from both 85 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 It is preferable that the bond is something other than magnesium fluoride.

[0124] Furthermore, when XPS analysis was performed on the positive electrode active material 100, the bonding of magnesium with other elements was observed. The peak indicating the total energy is preferably between 1302 eV and less than 1304 eV. It is even more preferable that the voltage be around 1303 eV. This is because of the bonding of magnesium fluoride. This value is different from the energy of 1305 eV, and is close to the bond energy of magnesium oxide. It is a high value. In other words, if the positive electrode active material 100 contains magnesium, magnesium fluoride It is preferable that the bond is something other than mu.

[0125] ≪EDX≫ EDX measurement is a method of measuring while scanning within a region and evaluating that region in two dimensions. This is sometimes called DX surface analysis. Furthermore, data from linear regions can be extracted from EDX surface analysis. The process of evaluating the distribution of atomic concentrations within positive electrode active material particles is sometimes called line analysis.

[0126] EDX surface analysis (e.g., elemental mapping) can be used to analyze the interior, surface, and vicinity of grain boundaries. Furthermore, the concentrations of magnesium and fluorine can be quantitatively analyzed. Also, EDX Linear analysis allows for the analysis of peak concentrations of magnesium and fluorine.

[0127] When EDX radiation analysis was performed on positive electrode active material 100, the magnesium concentration in the surface layer was P. The 'k' is preferably present in the positive electrode active material 100 from the surface toward the center to a depth of 3 nm. Furthermore, it is more preferable that they exist up to a depth of 1 nm, and more preferably up to a depth of 0.5 nm. And is even more preferable.

[0128] Furthermore, the distribution of fluorine in the positive electrode active material 100 can be superimposed on the distribution of magnesium. This is preferable. Therefore, when EDX radiation analysis is performed, the peak of fluorine concentration in the surface layer indicates the positive electrode active material. Preferably, it exists from the surface of quality 100 to a depth of 3 nm toward the center, and to a depth of 1 nm It is more preferable that they be present up to m, and even more preferable that they be present up to a depth of 0.5 nm. It's nice.

[0129] Furthermore, when line analysis or surface analysis was performed on the positive electrode active material 100, near the grain boundaries The ratio of magnesium to cobalt atoms (Mg / Co) is between 0.020 and 0.50. Preferred. More preferably 0.025 or more and 0.30 or less. More preferably 0.030 or more and 0 A value of 0.20 or less is preferable.

[0130] ≪dQ / dVvsV curve≫ Furthermore, the positive electrode active material according to one aspect of the present invention, after being charged at a high voltage, is subjected to, for example, a low voltage of 0.2C or less. When discharging at a high rate, a characteristic voltage change may appear near the end of the discharge. The transformation is in the dQ / dVvsV curve obtained from the discharge curve, with lithium metal as the counter electrode. In total, the presence of at least one peak in the range of 3.5V to 3.9V clearly indicates a certain level of accuracy. It can be chewed.

[0131] Furthermore, the positive electrode active material according to one embodiment of the present invention exhibits a charge dQ / dVvsV curve of 4.0 The first peak in the range of 5V to less than 4.15V, and the range of 4.15V to less than 4.25V A second peak in the range, and a third peak in the range of 4.5V to 4.58V. And, it may have.

[0132] Furthermore, the positive electrode active material according to one aspect of the present invention has a rate of 0.1C to 1.0C, more specifically For example, 0.5C, the measurement temperature is, for example, between 10°C and 35°C, more specifically, for example When charged at 25°C, the dQ / dVvsV curve shows that the charging voltage with lithium metal as the counter electrode... The first peak in the voltage range of 4.08V to 4.18V, and 4.18V to 4.2 A second peak occurs in the range of 5V or less, and in the range of 4.54V to 4.58V. It is preferable to have a total of three peaks, including a third peak.

[0133] Alternatively, in the above, a rate of 0.01 or more and less than 0.1C, more specifically, for example A rate of 0.05C, with a measurement temperature of, for example, between 10°C and 35°C, or more specifically, 2 When charged at 5°C, the charging voltage with lithium metal as the counter electrode is shown in the dQ / dVvsV curve. The first peak is in the range of 4.03V to 4.13V, and the second peak is in the range of 4.14V to 4.21V. The second peak in the range of V or less, and in the range of 4.50V to 4.60V It is preferable to have a total of three peaks, including a third peak.

[0134] Furthermore, at the charging voltage in which the first peak described above is observed, the positive electrode active material is in space group P2 / It is preferable that the crystal structure is represented by m. Furthermore, the third peak is observed in the following case. In terms of voltage, the positive electrode active material preferably has a crystal structure corresponding to the space group R-3m. It's nice.

[0135] Furthermore, the third peak described above has a shape in which the top of the peak is flattened compared to the Lorentz function. Alternatively, it can be expressed as the sum of two or more Lorentz functions with the same peak height but different peak positions. It is preferable that it has a shape that is such that the third peak has the shape described above. For example, the factors that cause the third peak to have this shape are: It is possible that both O3-type and pseudo-spinel-type crystal structures coexist.

[0136] Furthermore, in a secondary battery having a positive electrode having a positive electrode active material according to one aspect of the present invention and a negative electrode, The negative electrode has graphite, and the dQ / dV vs sV curve of the secondary battery is as shown above for lithium metal. In the voltage range obtained by subtracting 0.1V from the voltage, at least the first to third peaks It is preferable to have two. In such a case, the charge-discharge cycle is repeated and the charge The dQ / dVvsV curve was obtained from the curve, and measurements were taken from the 1st to the 10th charge-discharge cycle. In the case of a secondary battery, if the dQ / dV vs V curve has a third peak, the peak strength of that peak is... An increase in degree is preferable, and in measurements taken from the 30th to the 100th charge-discharge cycle. For example, if the dQ / dV vs V curve of a secondary battery has a third peak, then that peak... If the intensity decreases and the dQ / dVvsV curve of the secondary battery has a first peak, for example Then, the voltage at that peak position increases.

[0137] [An example of the structure of a positive electrode active material] LiCoO2 is a LiCoO2 in which magnesium is substituted at the positions of lithium atoms and cobalt atoms. An example of case 2 is explained below.

[0138] <First principles calculation> LiC in which magnesium is substituted at the position of a lithium atom or a cobalt atom. For oO2, using first-principles calculations, the stabilization energy before substitution and the stabilization energy after substitution were determined. We will determine the energy content and consider the effect of magnesium.

[0139] The crystal structure is assumed to be a layered rock-salt structure, the space group is R-3m, and the lattice is determined using first-principles calculations. The positions of the atoms are optimized, and each energy is determined.

[0140] Below is an example of the results of a first-principles calculation.

[0141] As software, VASP (The Vienna Ab initio simu The lation package was used. Additionally, the functional was GGA (Generali The zed-gradient-approximation (U) was used. Cobalt U The potential was set to 4.91. The pseudopotential of the electronic state was calculated using PAW (Project). The potential generated by the (or Augmented Wave) method was used. The to-off energy was set to 520 eV. For the U potential, see Non-Patent Document 6. See also Non-Patent Document 7.

[0142] In this specification, the energy obtained in this manner is referred to as the stabilization energy.

[0143] First, a 4x4x1 supercell was fabricated, and the crystal structure of LiCoO2 was optimized. The stabilization energy was determined. At this time, the lattice constant was optimized. k-points were used. The structure was 3x3x3. The number of atoms was 48 lithium atoms, 48 ​​cobalt atoms, and 48 oxygen atoms. I set it to 96.

[0144] Next, one lithium atom or one cobalt atom is replaced with a magnesium atom. Then, without changing the lattice constant, optimization was performed and the stabilization energy was determined.

[0145] Next, for each structure whose stabilization energy was determined, one lithium atom was removed. The structural stabilization energy is determined, and the difference ΔE between the stabilization energy before and after lithium desorption is calculated. We calculated ΔE. ΔE can be expressed by the following formula. Note that the following applies to LiCoO2 ( The difference between the energy after detaching 48-x lithium atoms and the energy before detachment is To represent. E total (Li 48 Co 48 O 96 ) is the stabilization energy of LiCoO2, E total (Li x Co 48 O 96 ) extracts (48-x) lithium atoms from LiCoO2 Stabilization energy after desorption, E metal (Li) is the stabilizing energy of lithium atoms It is ghee. The stabilization energy of the lithium atom was calculated using a body-centered cubic structure.

[0146]

number

[0147] Also, similar to LiCoO2, Li 48 Co 48 O 96 In this case, one lithium atom , a structure in which (48-x) lithium atoms are removed in a structure substituted with magnesium (Li (x-1) Mg1Co 48 O 96 ) and one cobalt atom is replaced with magnesium. A structure in which (48-x) lithium atoms have been removed in the structure (Li x Mg1Co 47 O96 ) For each of the above, the difference in stabilization energy before and after lithium desorption is calculated as follows: I requested it.

[0148] Next, the voltage Va after desorption was determined. The voltage Va was calculated using the following formula. It can be calculated as follows: Here, n is the number of moles of lithium removed, and F is the Faraday constant. be.

[0149]

number

[0150] Here, if we use the difference in stabilization energies ΔE as the Gibbs free energy ΔG, then The following equation is obtained.

[0151]

number

[0152] The voltage Va calculated from the above formula is shown in the table below. Note that in the table, ortho refers to ol This indicates that lithium at the t position was removed, and para (para) indicates that lithium at the para position was removed. The term "meta" indicates that the lithium atom at the meta position was detached.

[0153] [Table 1]

[0154] Figure 6A shows the crystal structure of LiCoO2 viewed from the a-axis direction, and Figure 6B shows the crystal structure viewed from the c-axis direction. The crystal structures are shown below.

[0155] Figure 6C shows the crystal structure obtained by removing one lithium atom from the crystal structure shown in Figure 6A.

[0156] Figure 7A shows the crystal structure shown in Figure 6A, but with a single magnesium atom substituted at the lithium position. Figure 7B shows the crystal structure as viewed from the a-axis direction, and Figure 7B shows it as viewed from the c-axis direction. vinegar.

[0157] Figure 8A shows the crystal structure in which one lithium atom has been removed from the crystal structure shown in Figure 7A. Figure 8B shows Figure 8A viewed from the c-axis direction.

[0158] Figure 9A shows two lithium atoms corresponding to the ortho position in the crystal structure shown in Figure 7B. Figure 9B shows the extracted crystal structure, with two lithium atoms corresponding to the para position extracted. Figure 9C shows the crystal structure with three lithium atoms extracted corresponding to the meta positions. Each will be shown.

[0159] Figure 10A shows the crystal structure shown in Figure 6A, with one magnesium atom placed at the cobalt position. Figure 10B shows the altered crystal structure viewed from the a-axis direction, and Figure 10B shows the structure viewed from the c-axis direction. To show

[0160] Figure 11A shows the crystal structure obtained by removing one lithium atom from the crystal structure shown in Figure 10A. Figure 11B shows Figure 11A viewed from the c-axis direction.

[0161] Figure 11C shows the crystal structure in which two lithium atoms have been removed from the crystal structure shown in Figure 10B. show.

[0162] When magnesium atoms are substituted for cobalt atoms, Va becomes a value of 3.7V or higher. The value was approximately 0.5V lower compared to the case where magnesium atoms were not substituted. On the other hand, When lithium was substituted, Va became an even lower value.

[0163] From this, we can determine whether to substitute the magnesium atom at the lithium position or the cobalt position. In this case, a voltage drop was observed, suggesting that it could be a factor in the bump on the discharge curve. Furthermore, when the cobalt position is replaced, the voltage difference compared to when it is not replaced is proportional. A relatively small, lithium-based substitution may result in a more clearly observable bump. On the other hand, if the voltage is too low, the lithium that has been released will need to be re-inserted during discharge. It is also possible that um is not inserted during the discharge.

[0164] Below, as a positive electrode active material in one embodiment of the present invention, lithium, magnesium, cobalt, acid dQ / obtained from the discharge curve of a secondary battery using a positive electrode active material containing element and fluorine as the positive electrode An example of a dV vs V curve is shown. Lithium metal was used as the counter electrode. Charge-discharge cycle measurements were performed. The discharge curves for cycles 1, 2, 3, 5, and 10 were then analyzed using the dQ / dV vs V curve. The results were calculated and are shown in Figure 43A. A magnified view of the range from 3.4V to 4.0V is also shown in Figure 43A. As shown in Figure 43B, a downward-convex peak is observed, as is clear from Figures 43A and 43B. The largest peak was at approximately 3.9V. Also, as shown in the figure, 3.5V At least one peak was present in the range of 3.9V.

[0165] Thus, the positive electrode active material according to one aspect of the present invention, after being charged at a high voltage, is, for example, 0.2C or It has become clear that when discharging at the lower rate, a characteristic voltage change appears near the end of the discharge. This change occurred in the dQ / dVvsV curve, ranging from 3.5V to 3.9V. This can be clearly confirmed by the presence of at least one peak.

[0166] The results in Table 1 show that, although there are slight differences in voltage values, they fall within the range of 3.5V to 3.9V. The peak is due to magnesium being substituted at the cobalt or lithium position. This suggests a possibility.

[0167] This embodiment can be implemented in appropriate combination with other embodiments.

[0168] (Embodiment 2) This embodiment shows an example of a method for producing a positive electrode active material according to one aspect of the present invention.

[0169] [Method for preparing positive electrode active material] First, using Figure 12, we will show an example of a method for producing a positive electrode active material 100, which is one aspect of the present invention. I will explain this further. Figure 13 also shows another example of a specific manufacturing method.

[0170] <Step S11> As shown in step S11 of Figure 12, first, as the material for the first mixture, a fluorine source and salt Prepare halogen sources and magnesium sources such as elemental sources. Also prepare a lithium source. preferable.

[0171] For example, lithium fluoride and magnesium fluoride can be used as fluorine sources. In particular, lithium fluoride has a relatively low melting point of 848°C, and in the annealing process described later... It is preferable because it melts easily. Examples of chlorine sources include lithium chloride and magnesium chloride. Magnesium sources can be used, for example, magnesium fluoride, magnesium oxide. Lithium, magnesium hydroxide, magnesium carbonate, etc. can be used. For example, lithium fluoride and lithium carbonate can be used. Lithium can be used as both a lithium source and a fluorine source. Cium can be used as both a fluorine source and a magnesium source.

[0172] In this embodiment, lithium fluoride (LiF) is prepared as the fluorine source and lithium source. Magnesium fluoride (MgF2) will be prepared as the fluorine source and magnesium source. (Step S11 in Figure 13). Lithium fluoride (LiF) and magnesium fluoride (MgF2) are Mixing LiF:MgF2 in a molar ratio of approximately 65:35 yields the highest effect in lowering the melting point. (Non-patent document 4). On the other hand, if the amount of lithium fluoride increases, there will be an excess of lithium. There are concerns that the cycle characteristics will deteriorate. Therefore, lithium fluoride (LiF) and magnesium fluoride The molar ratio of um-MgF2 is preferably LiF:MgF2=x:1 (0≦x≦1.9). Furthermore, LiF:MgF2=x:1 (0.1≦x≦0.5) is more preferable, and LiF:M gF2 = x:1 (near x = 0.33) is even more preferable. Note that in this specification, the term "nearby" is used. This value is set to be greater than 0.9 times that value and less than 1.1 times that value.

[0173] Furthermore, if the following mixing and grinding steps are to be performed wet, a solvent will be prepared. The solvent will be A Ketones such as cetone, alcohols such as ethanol and isopropanol, ethers, and dio Xane, 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 this embodiment, acetone is used (see step S11 in Figure 13).

[0174] <Step S12> Next, the materials for the first mixture described above are mixed and ground (steps shown in Figures 12 and 13). (P S12). Mixing can be done dry or wet, but wet mixing allows for finer grinding. This is preferable because it allows for mixing. For mixing, for example, a ball mill, a bead mill, etc. can be used. When using a ball mill, for example, zirconia balls can be used as the media. Preferably, this mixing and grinding process is carried out thoroughly to finely pulverize the first mixture. It's nice.

[0175] <Step S13, Step S14> The mixed and crushed material is collected (step S13 in Figures 12 and 13), and the first The mixture is obtained (step S14 in Figures 12 and 13).

[0176] The first mixture, for example, has an average particle size (D50: also called median diameter) of 600 nm. It is preferable that the thickness is 20 μm or less, and more preferably 1 μm or more and 10 μm or less. It is fine. With this first mixture that has been finely pulverized, lithium, transition metals and When mixed with a complex oxide containing oxygen, the first mixture forms on the surface of the complex oxide particles. It is easy to apply uniformly. When the first mixture is uniformly applied to the surface of the composite oxide particles... After heating, halogens and magnesium are distributed evenly across the surface layer of the composite oxide particles. It is preferable to have a region on the surface that does not contain halogens and magnesium. In the electrochemical state, it may become difficult to form the pseudo-spinel crystal structure described later.

[0177] <Step S21> Next, as shown in step S21 of Figure 12, having lithium, a transition metal and oxygen A lithium source and a transition metal source are prepared as materials for the composite oxide.

[0178] For example, lithium carbonate, lithium fluoride, etc., can be used as lithium sources.

[0179] As the transition metal, at least one of cobalt, manganese, and nickel can be used. The composite oxide containing lithium, transition metals, and oxygen has a layered rock salt-type crystalline structure. Since this is preferable, the mixing ratio of cobalt, manganese, and nickel is such that it can take the form of layered rock salt. It is preferable to do so. Furthermore, to the extent that these transition metals can take on a layered rock salt type crystal structure, Aluminum may be added.

[0180] As the transition metal source, oxides, hydroxides, etc. of the above-mentioned transition metals can be used. As a source of oxal, for example, cobalt oxide, cobalt hydroxide, etc. can be used. As a nickel source, manganese oxide, manganese hydroxide, etc. can be used. For example, nickel oxide, nickel hydroxide, etc. can be used as an aluminum source. Aluminum oxide, aluminum hydroxide, etc., can be used.

[0181] <Step S22> Next, the lithium source and transition metal source are mixed (step S22 in Figure 12). Mixing can be carried out dry or wet. For mixing, for example, a ball mill or bead mill can be used. It is possible. When using a ball mill, for example, zirconia balls can be used as the media. It is preferable to use [this].

[0182] <Step S23> Next, the mixture of ingredients described above is heated. This step is called baking to distinguish it from the subsequent heating step. This may be referred to as the first heating stage. Heating should be carried out at a temperature between 800°C and 1100°C. Preferably, the process is carried out at 900°C to 1000°C, more preferably 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, it can lead to excessive reduction of transition metals and evaporation of lithium. This could lead to defects. For example, a defect where cobalt becomes divalent could occur.

[0183] The heating time is preferably between 2 hours and 20 hours. The firing process involves using dry air or other moisture-free materials. This process should be carried out in an atmosphere with low humidity (for example, a dew point of -50°C or lower, more preferably -100°C or lower). Preferably, heating at 1000°C for 10 hours, with the temperature increase at 200°C / h, and drying The atmosphere flow rate is preferably 10 L / min. After that, the heated material is cooled to room temperature. It can be rejected. For example, if the cooling time from the specified temperature to room temperature is 10 hours or more and 50 hours or more It is preferable to place it at the bottom.

[0184] However, cooling to room temperature in step S23 is not mandatory. 24. There is a problem in performing steps S25 and S31 to S34. If not available, cooling may be limited to a temperature higher than room temperature.

[0185] <Step S24, Step S25> The material fired above is recovered (step S24 in Figure 12), and lithium, transition metals and A complex oxide containing oxygen is obtained (step S25 in Figure 12). Specifically, cobalt oxide is obtained. Lithium, lithium manganese, lithium nickelate, and cobalt are partially replaced by manganese. To obtain lithium cobaltate or lithium nickel-manganese-cobaltate.

[0186] Furthermore, step S25 includes pre-synthesized lithium, transition metals, and oxygen. A composite oxide may be used (see Figure 13). In this case, steps S21 to step S24 can be omitted.

[0187] 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, The composite oxide containing oxygen, and the positive electrode active material, have lithium, cobalt, as the main components. The main components are nickel, manganese, aluminum, and oxygen, with elements other than those listed above considered impurities. For example, when analyzed by glow discharge mass spectrometry, the total impurity concentration is 10,000 p. It is preferable that it is 5000 ppm wt or less, and more preferably 5000 ppm wt or less. The combined impurity concentrations of titanium and transition metals such as arsenic are 3000 ppm wt or less. It is preferable that the concentration be 1500 ppm wt or less.

[0188] For example, as pre-synthesized lithium cobalt oxide, manufactured by Nippon Chemical Industrial Co., Ltd. Lithium cobalt oxide particles (product name: Cellseed C-10N) can be used. The average particle size (D50) is approximately 12 μm, and by glow discharge mass spectrometry (GD-MS)... In the impurity analysis, the magnesium concentration and fluorine concentration were 50 ppm wt or less. Calcium, aluminum, and silicon concentrations are 100 ppm wt or less, nickel Sulfur concentration is 150 ppm wt or less, sulfur concentration is 500 ppm wt or less, arsenic concentration is 11 00 ppm wt or less, and the concentration of other elements other than lithium, cobalt, and oxygen is 150 This is lithium cobalt oxide with a concentration of less than ppm wt.

[0189] Alternatively, lithium cobalt oxide particles manufactured by Nippon Chemical Industrial Co., Ltd. (product name: Cellseed C- 5H) 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- This is lithium cobalt oxide, equivalent to or less than 10N.

[0190] In this embodiment, cobalt is used as the transition metal, and pre-synthesized cobalt acid We will use lithium particles (Cellseed C-10N manufactured by Nippon Chemical Industrial Co., Ltd.) (Figure) (See 13).

[0191] The composite oxide having lithium, transition metal, and oxygen in step S25 has defects and strain. It is preferable to have a layered rock salt type crystal structure with few impurities. It is preferable that it be a composite oxide. A composite oxide having lithium, a transition metal and oxygen is preferable. A high concentration of pure substances increases the likelihood of a crystal structure with many defects or distortions.

[0192] <Step S31> Next, the first mixture is mixed with a composite oxide having lithium, a transition metal, and oxygen. (Step S31 in Figures 12 and 13) Having lithium, transition metals and oxygen The transition metal TM in the composite oxide and the magnesium Mg present in the first mixture Mix1 Mix The atomic ratio of 1 is TM:Mg Mix1 =1: y(0.0005≦y≦0.03) Preferably, TM:Mg Mix1 The condition is that =1:y(0.001≦y≦0.01) More preferably, TM:Mg Mix1 A ratio of approximately 1:0.005 is even more preferable.

[0193] The mixing in step S31 is performed in order to avoid destroying the composite oxide particles, as is the case with the mixing in step S12. It is preferable to use milder conditions. For example, a higher rotational speed than the mixing in step S12. It is preferable to have conditions with less or shorter duration. Also, dry processing is gentler than wet processing. It can be said that these are favorable conditions. For mixing, for example, a ball mill or bead mill can be used. To do so. When using a ball mill, for example, zirconia balls can be used as the media. It is preferable.

[0194] <Step S32, Step S33> The materials mixed above are collected (step S32 in Figures 12 and 13), and the second mixture This is obtained (step S33 in Figures 12 and 13).

[0195] In this embodiment, the mixture of lithium fluoride and magnesium fluoride is treated as an impurity. Although a method of adding to lithium cobalt oxide with low concentration is described, one aspect of the present invention is This is not the only option. Instead of the second mixture in step S33, lithium cobalt oxide is used as the starting material. You may also use materials that have been calcined with added magnesium and fluorine sources. This includes the processes of steps S11 to S14 and steps S21 to S25. Because there is no need to separate the processes, it is simple and highly productive.

[0196] Alternatively, lithium cobalt oxide with pre-added magnesium and fluorine can be used. It may also be used. If lithium cobalt oxide with magnesium and fluorine added is used, Steps up to S32 can be omitted, making the process simpler.

[0197] Furthermore, lithium cobalt oxide, which has magnesium and fluorine added to it beforehand, Furthermore, a magnesium source and a fluorine source may be added.

[0198] <Step S34> Next, the second mixture is heated. This step is annealed to distinguish it from the previous heating step. Alternatively, it may involve a second heating process.

[0199] Annealing is preferably carried out at an appropriate temperature and time. The particle size of the composite oxide having lithium, transition metal and oxygen in step S25 It varies depending on conditions such as composition. If the particles are small, a lower temperature or Shorter durations may be preferable in some cases.

[0200] For example, if the average particle size (D50) of the particles in step S25 is about 12 μm, annealing The temperature is preferably between 600°C and 950°C. The annealing time is, for example, 3 hours or more. Preferably, 10 hours or more is preferred, more preferably 60 hours or more.

[0201] On the other hand, if the average particle size (D50) of the particles in step S25 is about 5 μm, the annealing temperature The temperature is preferably between 600°C and 950°C. The annealing time is, for example, between 1 hour and 10 hours. Less than 1 hour is preferable, and around 2 hours is more preferable.

[0202] The cooling time after annealing is preferably, for example, 10 hours or more and 50 hours or less.

[0203] When the second mixture is annealed, first the material with the lower melting point from the first mixture (for example, fluorine) It is thought that lithium oxide (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 a complex oxide occurs. It is thought to be distributed on the surface layer of the particles.

[0204] The elements present in the first mixture distributed in the surface layer are lithium, transition metals, and oxygen. It is thought to form a solid solution in a composite oxide containing [the specified element].

[0205] The diffusion of elements in this first mixture is more pronounced in the surface and within the composite oxide particles than within them. The reaction is faster near grain boundaries. Therefore, magnesium and halogens are concentrated in the surface layer and near grain boundaries. As described later, the magnesium concentration in the surface layer and near the grain boundaries is higher than in the interior. When the value is high, changes in the crystal structure can be suppressed more effectively.

[0206] <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.

[0207] When fabricated using the methods shown in Figures 12 and 13, fewer defects are produced when charged at high voltage. It is possible to fabricate a cathode active material that adopts a pseudo-spinel crystal structure. When Rietveld analysis was performed, the pseudo-spinel structure was observed. Cathode active materials with a Nell-type crystal structure of 50% or more exhibit excellent cycle characteristics and rate characteristics. It is a positive electrode active material.

[0208] To produce a positive electrode active material having a pseudo-spinel crystal structure after high-voltage charging, It has magnesium and fluorine, and is annealed at an appropriate temperature and time. It is effective to manufacture them. Magnesium and fluorine sources are used as starting materials for the composite oxide. It may be added. However, when added to the starting material of a composite oxide, the magnesium source and If the melting point of the fluorine source is higher than the firing temperature, the magnesium source and fluorine source will not melt and will not diffuse. This may result in insufficient processing. If this occurs, the layered rock salt crystal structure will have many defects or strains. Therefore, defects are likely to occur in the pseudo-spinel crystal structure after high-voltage charging. This may cause distortion.

[0209] 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 The source and fluorine source are mixed and annealed to form a composite oxide with magnesium and fluorine on the surface. It is preferable to solid-solve the material. By manufacturing in this manner, defects can be removed after high-voltage charging. Alternatively, it is possible to fabricate a positive electrode active material that adopts a pseudo-spinel structure with low strain.

[0210] Furthermore, the positive electrode active material 100 produced in the above process is further coated with other materials. This may be done. Further heating may also be performed.

[0211] For example, the positive electrode active material 100 and a compound containing phosphoric acid can be mixed. Furthermore, it can be heated after mixing. By mixing a compound containing phosphoric acid, high voltage The positive electrode exhibits suppressed leaching of transition metals such as cobalt, even when kept charged for extended periods. It can be converted into active material 100. Furthermore, heating after mixing makes the phosphoric acid more uniform. It can be covered.

[0212] Examples of compounds containing phosphoric acid include lithium phosphate and ammonium dihydrogen phosphate. It can be used. Mixing can be done, for example, by a solid-phase method. Heating can be done, for example, at 800°C. This can be done at temperatures above ℃ for 2 hours.

[0213] This embodiment can be implemented in appropriate combination with other embodiments.

[0214] (Embodiment 3) In this embodiment, a secondary battery having the positive electrode active material 100 described in the previous embodiment is used Examples of materials that can be used will be described. In this embodiment, the positive electrode, negative electrode and electrolytic Let's take a secondary battery, in which the liquid is enclosed in an outer casing, as an example.

[0215] [Positive electrode] The positive electrode comprises a positive electrode active material layer and a positive electrode current collector.

[0216] <Cathode active material layer> The positive electrode active material layer has at least positive electrode active material. In addition, it may include other substances such as a coating on the surface of the active material, a conductive additive, or a binder.

[0217] 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 as a secondary battery with excellent performance.

[0218] As a conductive additive, carbon materials, metal materials, or conductive ceramic materials can be used. This is possible. In addition, fibrous materials may be used as conductive additives. The content of the conductive additive is preferably 1 wt% to 10 wt%, and preferably 1 wt% to 5 wt%. The bottom one is preferable.

[0219] Conductive additives can be used to form an electrical conduction network within the active material layer. The auxiliary agent can maintain the electrical conduction pathways between the positive electrode active materials. By adding a conductive additive, it is possible to realize an active material layer with high electrical conductivity. ru.

[0220] Examples of conductive additives include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon. Fibers can be used. For example, mesophase pitch carbon fibers can be used. Carbon fibers such as fiber and isotropic pitch carbon fibers can be used. Carbon nanofibers and carbon nanotubes can be used. Notubes can be fabricated, for example, by vapor phase growth. Also, as a conductive additive, For example, carbon black (acetylene black (AB), etc.), graphite particles. Carbon materials such as ions, graphene, and fullerenes can be used. Also, for example, copper, Metal powders and fibers such as nickel, aluminum, silver, and gold, and conductive ceramic materials, etc. You can use it.

[0221] Furthermore, graphene compounds may be used as conductive additives.

[0222] Graphene compounds possess excellent electrical properties, including high conductivity, and high flexibility. It may possess excellent physical properties such as high mechanical strength. The compound has a planar shape. The graphene compound enables surface contact with low contact resistance. Furthermore, even thin materials can have very high conductivity, allowing for efficient use within the active material layer in small quantities. A conductive path can be formed. Therefore, graphene compounds are used as conductive additives. This is preferable because it increases the contact area between the active material and the conductive additive. By using a plate-drying device, the entire surface of the active material is covered with graphene, which is a conductive additive. It is preferable to form the compound as a coating. Furthermore, it may be possible to reduce electrical resistance. Therefore, it is preferable. Here, as graphene compounds, for example, graphene, multigraphene , or it is particularly preferable to use RGO. Here, RGO is, for example, graphene oxide ( This refers to compounds obtained by reducing graphene oxide (GO).

[0223] 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 The coefficient of conductivity is large, requiring more conductive paths to connect the active materials. Therefore, the amount of conductive additive is large. This tends to happen, and relatively, the amount of active material carried decreases. If the amount decreases, the capacity of the secondary battery will decrease. 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.

[0224] In the following example, a graphene compound is used as a conductive additive in the active material layer 200. An example of a cross-sectional configuration will be explained.

[0225] Figure 14A 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.

[0226] In the longitudinal section of the active material layer 200, as shown in Figure 14B, the interior of the active material layer 200 In Figure 14B, the graphene compound 201 is dispersed in a roughly uniform sheet-like manner. Although the rafen compound 201 is schematically represented by a thick line, it is actually a single or multilayer carbon molecule. It is a thin film having a thickness of [a certain thickness]. Multiple graphene compounds 201 are multiple granular positive electrode active materials. It partially covers 100, or adheres to the surface of multiple granular positive electrode active material 100. Because they are formed in a uniform manner, they are in surface contact with each other.

[0227] Here, multiple graphene compounds bond together to form a network of graphene compounds. Forming a material sheet (hereinafter referred to as graphene compound net or graphene net) This is possible. When the active material is covered with a graphene net, the graphene net interacts with the active material. It can also function as a binder to combine them. Therefore, the amount of binder can be reduced. Because it is possible or not to use the active material in relation to the electrode volume and electrode weight The ratio can be improved. In other words, the capacity of the secondary battery can be increased.

[0228] Here, graphene oxide is used as graphene compound 201 and mixed with the active material to produce the active material It is preferable to form a layer that will become the 200th layer and then reduce it. Formation of graphene compound 201 Furthermore, by using graphene oxide, which has extremely high dispersibility in polar solvents, graphene 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 returned. Therefore, the graphene compound 201 remaining in the active material layer 200 partially overlaps, By being dispersed to the extent that they are in surface contact with each other, a three-dimensional conductive path can be formed. Furthermore, the reduction of graphene oxide may be carried out, for example, by heat treatment, or by using a reducing agent. You may go.

[0229] Therefore, unlike granular conductive additives such as acetylene black that make point contact with the active material, the graph Since compound 201 enables surface contact with low contact resistance, it is not a typical conductive additive. This method improves the electrical conductivity between granular positive electrode active material 100 and graphene compound 201 using a smaller amount. This can be done. 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.

[0230] 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 the spaces between the active materials are further separated by the graphene compound. It is also possible to form conductive paths.

[0231] Examples of binders include styrene-butadiene rubber (SBR) and styrene-isopropyl alcohol. Lenyl-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene- It is preferable to use a rubber material such as a propylene-diene copolymer as a binder. Therefore, fluororubber can be used.

[0232] Furthermore, it is preferable to use a water-soluble polymer as the binder. As molecules, for example, polysaccharides can be used. As for polysaccharides, carboxymethyl Cholecellulose (CMC), methylcellulose, ethylcellulose, hydroxypropyl Cellulose derivatives such as cellulose, diacetylcellulose, and regenerated cellulose, and starch These can be used. In addition, these water-soluble polymers can be used in combination with the aforementioned rubber material. It is even preferable if used.

[0233] Alternatively, the binder could be polystyrene, methyl polyacrylate, or polymethacrylic acid. Methyl (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl Polyalcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, Polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene Polyethylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer It is preferable to use materials such as polyvinyl acetate and nitrocellulose.

[0234] You may use a combination of several of the binders mentioned above.

[0235] 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 when mixed with a solvent, it is difficult to adjust their viscosity. In such cases, for example, mixing with a material that has particularly excellent viscosity-modifying effects may be necessary. This is preferable. As a material with particularly excellent viscosity adjustment effect, for example, a water-soluble polymer can be used. Good. Also, as water-soluble polymers that are particularly excellent in viscosity adjustment, the aforementioned polysaccharides, for example, Boxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydrox Cellulose inducers such as cypropylcellulose, diacetylcellulose, and regenerated cellulose Conductors and starch can be used.

[0236] Furthermore, cellulose derivatives such as carboxymethylcellulose are, for example, carboxymethyl Solubility increases when cellulose is converted into salts such as sodium salts or ammonium salts. This makes it easier for the viscosity modifier to exert its effect. The increased solubility makes it easier for the electrode slurry to When preparing the Lee, it is also possible to improve the dispersibility of the active material and other components. In this case, the cellulose and cellulose derivatives used as electrode binders are: These salts shall also be included.

[0237] Fluorine-based resins have advantages such as excellent mechanical strength, high chemical resistance, and high heat resistance. PVDF, a type of fluoropolymer resin, possesses extremely superior properties among fluoropolymer resins. It possesses mechanical strength, excellent processability, and high heat resistance.

[0238] On the other hand, with PVDF, when the slurry produced during the coating of the active material layer becomes alkaline... It may gel, or it may become insoluble. This can sometimes lead to a decrease in the adhesion between the current collector and the active material layer. Positive electrode of one aspect of the present invention By using an active material, the pH of the slurry can be lowered, suppressing gelation and insolubilization. It is desirable that it is compatible.

[0239] The thickness of the positive electrode active material layer is, for example, 10 μm to 200 μm, or 50 μm. The thickness is between m and 150 μm. The amount of support in the positive electrode active material layer is, for example, the amount of cobalt in the positive electrode active material. When the material has a layered rock salt type crystalline structure, 1 mg / cm³ 2 50mg / cm 2 The following: Alternatively, 5 mg / cm³ 2 More than 30mg / cm 2 The following applies: Positive electrode activity The density of the material layer is, for example, that the positive electrode active material has a layered rock salt type crystalline structure containing cobalt. If it contains 2.2 g / cm³ 3 More than 4.9g / cm 3 The following: Alternatively, 3.8 g / cm 3 More than 4.5g / cm 3 The following applies:

[0240] <Positive electrode current collector> As the positive electrode current collector, metals such as stainless steel, gold, platinum, aluminum, and titanium, and Highly conductive materials such as these 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, and Aluminum alloys to which elements that improve heat resistance, such as candium and molybdenum, have been added. It can be used. Furthermore, it can be formed with a metallic element that reacts with silicon to form a silicide. It may also be the case that, as a metallic element that reacts with silicon to form a silicide, zirconium, Titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten Examples include cellulose, cobalt, and nickel. Current collectors come in foil, plate (sheet), mesh, and perforated forms. Shapes such as metal-like or expanded metal-like can be used as appropriate. The current collector has a thickness It is best to use particles that are between 5 μm and 30 μm in size.

[0241] [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. It may have a binder.

[0242] <Negative electrode active material> For example, alloy materials or carbon-based materials can be used as the negative electrode active material.

[0243] As a negative electrode active material, the charge-discharge reaction is carried out by alloying and dealloying reactions with lithium. Any possible element can be used. For example, silicon, tin, gallium, aluminum, Germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one of these elements can be used. Such elements have a capacity compared to carbon. Larger, and especially silicon, has a high theoretical capacity of 4200 mAh / g. Therefore, the negative electrode active material Silicon is preferred. Compounds containing these elements may also be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag 3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, Examples include InSb and SbSn. Here, charging and discharging occur through alloying and dealloying reactions with lithium. In some cases, elements capable of carrying out reactions, and compounds containing such elements, are referred to as alloying materials. be.

[0244] In this specification, SiO refers to silicon monoxide, for example. Alternatively, SiO refers to Si O x It can also be expressed as follows. Here, it is preferable that x has one neighboring value. For example, x is A value of 0.2 to 1.5 is preferred, and a value of 0.3 to 1.2 is more preferred.

[0245] Examples of carbon-based materials include graphite, easily graphitizable carbon (soft carbon), and poorly graphitizable carbon (hard carbon). Using carbon fiber, carbon nanotubes, graphene, carbon black, etc. stomach.

[0246] Examples of graphite include artificial graphite and natural graphite. For example, meso Examples include carbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spheroidal graphite, which has a spherical shape, can be used as artificial graphite. For example, MCMB may have a spherical shape, which is preferable. Also, the surface of MCMB Reducing the product is relatively easy and sometimes preferable. Examples of natural graphite include Examples include flaky graphite and spheroidized natural graphite.

[0247] Graphite is formed when lithium ions are inserted into it (during the formation of lithium-graphite intercalation compounds). ) exhibits a potential as low as lithium metal (0.05V to 0.3V vs. Li / Li + This allows lithium-ion rechargeable batteries to exhibit a high operating voltage. Furthermore, graphite has a relatively high capacity per unit volume, relatively small volume expansion, and is inexpensive. It is preferable because it has advantages such as higher safety compared to lithium metal.

[0248] Furthermore, titanium dioxide (TiO2) and lithium titanium oxide (Li4) are used as negative electrode active materials. Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5) ), use oxides such as tungsten oxide (WO2) and molybdenum oxide (MoO2). It is possible.

[0249] Furthermore, as the negative electrode active material, a Li3N type structure, which is a lithium and transition metal binitride, is also used. TsuLi 3-x M x N (M = Co, Ni, Cu) can be used. For example, Li 2. 6Co 0.4 The N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm²). 3 )of This is preferable.

[0250] When using a lithium-transition metal binitride, lithium ions are included in the negative electrode active material. In combination with materials such as V2O5 and Cr3O8 that do not contain lithium ions as the positive electrode active material. It is preferable that this be done. Furthermore, when using a material containing lithium ions as the positive electrode active material, Also, by pre-desorbing the lithium ions contained in the positive electrode active material, the negative electrode active material and Therefore, a lithium-transition metal composite can be used.

[0251] Furthermore, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example For example, lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO). Transition metal oxides that do not form alloys with mu may be used as the negative electrode active material. Conversion reaction Materials that produce this include Fe2O3, CuO, Cu2O, RuO2, and Cr2O3. Oxides such as CoS 0.89 , sulfides such as NiS and CuS, Zn3N2, Cu3N, Ge Nitrides such as 3N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. This also occurs with fluorides.

[0252] The conductive additives and binders that the negative electrode active material layer may have are, for example, the positive electrode active material layer Materials similar to those used for conductive additives and binders can be used.

[0253] <Negative electrode current collector> The negative electrode current collector can be made of the same material as the positive electrode current collector. It is preferable to use a material that does not alloy with carrier ions such as lithium.

[0254] [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), br Tylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyro Lactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate Tyl, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-Dioxane, 1,4-Dioxane, Dimethoxyethane (DME), Dimethyl Sulfane Hoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetra One of the following, or two or more of these: trahydrofuran, sulfolane, sultone, etc. It can be used in combinations and ratios.

[0255] 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 these devices, the internal temperature of the secondary battery may rise due to internal short circuits or overcharging. However, this can prevent secondary batteries from rupturing or catching fire. Ionic liquids are composed of cations and anions. It consists of and contains organic cations and anions. As organic cations used in the electrolyte, four quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations Aliphatic onium cations such as imidazolium cations and pyridinium cations, etc. Aromatic cations are an example. In addition, monovalent amides are used as anions in the electrolyte. Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkyl Anions of tetrafluoroborate, perfluoroalkyl volate Toanions, hexafluorophosphate anions, or perfluoroalkyl phosphates Examples include ether anions.

[0256] Furthermore, examples of electrolytes to be dissolved in the above solvent include LiPF6, LiClO4, and L. iAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO 4. Li2B 10 Cl 10 Li2B 12 Cl 12 LiCF3SO3, LiC4F9S O3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2 LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. Using one type of thium salt, or two or more of these in any combination and ratio. It is possible.

[0257] The electrolyte used in secondary batteries contains particulate matter and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as " It is preferable to use a highly purified electrolyte with a low content of impurities (also called "foulings"). Specifically, the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less. Preferably, the amount is 0.01% or less.

[0258] Furthermore, the electrolyte contains vinylene carbonate, propanesultone (PS), and tert-butyl. Benzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxa) LiBOB (Lithium-Borate), as well as dinitriles such as succinonitrile and adiponitrile. Additives such as solvent 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%.

[0259] Alternatively, a polymer gel electrolyte, obtained by swelling a polymer with an electrolyte solution, may be used.

[0260] Using polymer gel electrolytes enhances safety against leakage and other issues. The pond can be made thinner and lighter.

[0261] Examples of polymers that can be gelled include silicone gel, acrylic gel, and acrylonitrile gel. Polyethylene oxide gel, polypropylene oxide gel, fluorine polymer Gels and the like can be used.

[0262] Examples of polymers include polyalkylene oxides such as polyethylene oxide (PEO). Polymers having a side structure, PVDF, polyacrylonitrile, etc., and those Copolymers containing the above can be used. For example, PVDF and hexafluoropropylene ( PVDF-HFP, a copolymer of HFP, can be used. The rimer may have a porous structure.

[0263] In addition, instead of an electrolyte, a solid electrolyte containing inorganic materials such as sulfide-based or oxide-based materials may be used. Solid electrolytes containing polymer materials such as PEO (polyethylene oxide) can be used. It is possible. When using a solid electrolyte, the installation of separators and spacers becomes unnecessary. Also, Because the entire battery can be made solid, the risk of leakage is eliminated, dramatically improving safety.

[0264] [Separator] Furthermore, it is preferable that the secondary battery has a separator. Examples of separators include: Paper, nonwoven fabric, glass fiber, ceramics, or nylon (polyamide), vinylon (poly (vinyl alcohol-based fibers), polyester, acrylic, polyolefin, polyurethane A separator made of synthetic fibers or the like can be used. It is preferable to process it into a shape and arrange it so as to enclose either the positive or negative electrode.

[0265] The separator may have a multilayer structure. For example, an organic material such as polypropylene or polyethylene. The material film contains ceramic-based materials, fluorine-based materials, polyamide-based materials, or a combination thereof. Mixtures and other materials can be coated onto it. Examples of ceramic materials include aluminum oxide. Aluminum particles, silicon oxide particles, etc. can be used. Examples of fluorine-based materials include PVDF, polytetrafluoroethylene, etc. can be used. Polyamide materials and For example, nylon, aramid (meta-aramid, para-aramid), etc. can be used. It is possible.

[0266] Coating with ceramic materials improves oxidation resistance, thus preventing separation during high-voltage charging and discharging. This can suppress the degradation of the data and improve the reliability of secondary batteries. Furthermore, fluorine-based materials... Coating the electrode makes it easier for the separator and electrode to adhere to each other, which can improve the output characteristics. Coating with polyamide materials, especially aramid, improves heat resistance, thus improving the heat resistance of secondary batteries. Safety can be improved.

[0267] For example, a mixture of aluminum oxide and aramid material is applied to both sides of a polypropylene film. It may also be done by applying aluminum oxide to the surface of the polypropylene film that is in contact with the positive electrode. A mixed material of um and aramid may be coated, and a fluorine-based material may be coated on the surface in contact with the negative electrode. .

[0268] Using a multilayer separator ensures the safety of secondary batteries even with a thin overall separator. Because this can be maintained, the capacity per unit volume of the secondary battery can be increased.

[0269] [Exterior] For the casing of a secondary battery, metal materials such as aluminum or resin materials are used. It is possible to have it. Also, a film-like outer covering can be used. For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide On a film made of materials such as aluminum, stainless steel, copper, nickel, etc., which have excellent flexibility A thin metal film is provided, and on the thin metal film, a polyamide resin, polyester resin, etc. are used as the outer surface of the exterior body. A three-layer film with an insulating synthetic resin film, such as a tellate resin, can be used.

[0270] [Charge / discharge method] The charging and discharging of a secondary battery can be performed, for example, as follows.

[0271] ≪CC charging≫ First, let's explain CC charging as one of the charging methods. CC charging is a method that covers 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. Yes, it exists. We assume that the secondary battery is an equivalent circuit of its internal resistance R and secondary battery capacity C, as shown in Figure 15A. 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.

[0272] While CC charging is in progress, the switch turns on as shown in Figure 15A, 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 both rise.

[0273] And the secondary battery voltage V B When the voltage reaches a predetermined level, for example 4.3V, charging stops. When CC charging is stopped, the switch turns off, as shown in Figure 15B, 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.

[0274] The secondary battery voltage V during CC charging and after CC charging has stopped. B and charging current An example is shown in Figure 15C. 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.

[0275] ≪CCCV charging≫ Next, we will explain CCCV charging, which is a different charging method from the one described above. CCCV charging is, First, charge until a predetermined voltage is reached by CC charging, and then charge until the current flowing during CV (constant voltage) charging decreases, specifically until it reaches the termination current value. This is a charging method.

[0276] While CC charging is being performed, as shown in FIG. 16A, the switch of the constant current power supply is on, and the switch of the constant voltage power supply is off, and a constant current I flows into the secondary battery. During this period, since the current I is constant, according to Ohm's law of V R = R×I, the voltage V R applied to the internal resistance R is also constant. On the other hand, the voltage V C applied to the secondary battery capacity C increases with the passage of time. Therefore, the secondary battery voltage V increases with the passage of time. B

[0277] And when the secondary battery voltage V B reaches a predetermined voltage, for example, 4.3V, switch from CC charging to CV charging. While CV charging is being performed, as shown in FIG. 16B, the switch of the constant voltage power supply is on, the switch of the constant current power supply is off, and the secondary battery voltage V B becomes constant . On the other hand, the voltage V C applied to the secondary battery capacity C increases with the passage of time. V B = V R + V C Therefore, the voltage V R applied to the internal resistance R decreases with the passage of time. As the voltage V applied to the internal resistance R decreases, according to Ohm's law of V R = R×I, the current I flowing into the secondary battery also decreases. R

[0278] And when the current I flowing into the secondary battery reaches a predetermined current, for example, a current equivalent to 0.01C Next, stop charging. When CCCV charging is stopped, all switches will turn off as shown in Figure 16C. The switch turns off, and the current I becomes 0. Therefore, the voltage V across the internal resistance R is lost. R The voltage becomes 0V. However, the voltage V across the internal resistance R due to CV charging R Because it has become small enough Even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B It hardly descends at all.

[0279] The secondary battery voltage V during CCCV charging and after CCCV charging has stopped. B and An example of the charging current is shown in Figure 16D. Even when CCCV charging is stopped, the secondary battery voltage V B Mostly It appears that it is not descending at all.

[0280] ≪CC discharge≫ Next, we will explain CC discharge, one of the discharge methods. CC discharge is a discharge method that is used throughout the entire discharge period. A constant current is drawn from the secondary battery, and the secondary battery voltage V B when the voltage reaches a predetermined voltage, for example, 2.5V This is a discharge method that stops the discharge when it reaches a certain point.

[0281] The secondary battery voltage V during CC discharge B Figure 17 shows an example of the discharge current. According to this, the secondary battery voltage V B The image shows it descending.

[0282] Next, we will explain the discharge rate and charge rate. The discharge rate is the rate at which the battery capacity is charged relative to the battery capacity. This is the relative ratio of the current during discharge, and is expressed in units of C. In this case, the current equivalent to 1C is X(A). If discharged with a current of 2X(A), then 2 If the discharge was performed with a current of C, and the discharge was performed with a current of X / 5(A), then the discharge was performed with 0.2C. That is to say. Also, the charging rate is the same; if charged with a current of 2X(A), then 2C. If you say you charged it, and you charged it with a current of X / 5(A), then you can say you charged it at 0.2C. cormorant.

[0283] The previous embodiment showed the charging voltage when lithium metal is used as the counter electrode. Secondary When charging a battery using graphite as the negative electrode, for example, lithium metal is used as the negative electrode. Charging can be performed using a value obtained by subtracting 0.1V from the charging voltage when the battery is in use.

[0284] In this specification, when lithium metal is used as the counter electrode, the charging voltage is, for example, when the graphite negative electrode is used. For the secondary battery used, the value obtained by subtracting 0.05V to 0.3V from that value is preferable. The value can be calculated by subtracting 0.1V.

[0285] ≪Charge / Discharge Cycle Characteristics≫ A secondary battery according to one aspect of the present invention suppresses the decrease in discharge capacity associated with charge-discharge cycles. Yes, it is possible. In particular, a secondary battery according to one aspect of the present invention can perform charge-discharge cycles at a high charging voltage. However, this can suppress the decrease in discharge capacity.

[0286] In one aspect of the present invention, the positive electrode is subjected to repeated CCCV charging and CC discharging with lithium metal as the counter electrode. In the charge-discharge cycle performed, the upper limit voltage for charging is preferably 4.4V or higher, more preferably The upper limit voltage is 4.5V or more and 5V or less, more preferably 4.6V or more and 5V or less. This is the voltage with lithium metal as the counter electrode, and the rate in CC charging is, for example, 0.05C or higher. The current is 3C or less, more preferably 0.1C to 2C, and the termination current in CV charging is For example, the temperature is between 0.001C and 0.05C, and the rate in CC discharge is, for example, 0.0 The temperature range is between 1°C and 3°C, the measurement temperature is between 10°C and 50°C, and the measurement is performed 30 to 150 times. Performing the following charge-discharge cycles will result in a discharge capacity of 75% or more compared to the first charge-discharge cycle. More preferably 80% or more, even more preferably 85% or more, and even more preferably 90% or more It is above.

[0287] Alternatively, a secondary battery according to one aspect of the present invention has a positive electrode and a negative electrode according to one aspect of the present invention, The negative electrode has graphite, and in a charge-discharge cycle in which CCCV charging and CC discharge are repeatedly performed, The upper limit voltage of the electric current is preferably 4.3V or higher, more preferably 4.4V or higher and 4.9V or lower. More preferably, the voltage is 4.5V or more and 4.9V or less, and this upper limit voltage is when lithium metal is used as the counter electrode. The voltage is such that the rate in CC charging is, for example, 0.05C or more and 3C or less, more preferably. The current is between 0.1C and 2C, and the termination current in CV charging is, for example, between 0.001C and 0 The temperature is 0.05C or less, and the rate in CC discharge is, for example, 0.01C or more and 3C or less. The measurement temperature is between 10°C and 50°C, and the charge-discharge cycle is performed between 30 and 150 times. Therefore, the discharge capacity is 75% or more, more preferably 80% or more, compared to the first charge-discharge cycle. More preferably, it is 85% or more, and even more preferably 90% or more.

[0288] Furthermore, in the above, after 30 to 150 charge-discharge cycles, the discharge capacity The positive electrode active material is 1.3 times or more than that of a comparative secondary battery having a conventional material, and more preferably. It is 1.45 times or more, and more preferably 1.6 times or more.

[0289] This embodiment can be implemented in appropriate combination with other embodiments.

[0290] (Embodiment 4) In this embodiment, the form of a secondary battery having the positive electrode active material 100 described in the previous embodiment Let me explain an example of the shape. The material used in the secondary battery described in this embodiment is the same as in the previous embodiment. The description of the form can be taken into consideration.

[0291] [Coin-type rechargeable battery] First, let's describe an example of a coin-type rechargeable battery. Figure 18A shows a coin-type (single-layer flattened) battery. Figure 18B is an external view of the secondary battery, and Figure 18B is a cross-sectional view thereof.

[0292] The coin-type rechargeable battery 300 consists of a positive electrode casing 301 which also serves as the positive electrode terminal and a negative electrode casing which also serves as the negative electrode terminal. The can 302 is insulated and sealed with 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 30 provided in contact with it. It is formed by 6. The negative electrode 307 is provided with the negative electrode current collector 308 and is set to be in contact with it. It is formed by the kerned negative electrode active material layer 309.

[0293] Furthermore, the positive electrode 304 and negative electrode 307 used in the coin-type secondary battery 300 are each active The material layer only needs to be formed on one side.

[0294] The positive electrode can 301 and negative electrode can 302 contain nickel and aluminum, which are corrosion-resistant to the electrolyte. Metals such as titanium, or alloys of these or alloys of these with other metals (for example, stainless steel) Steel, etc. can be used. In addition, nickel or aluminum can be used to prevent corrosion by the electrolyte. It is preferable to coat with aluminum or the like. Positive electrode can 301 is positive electrode 304, and negative electrode can 302 is negative electrode 3 Connect each of them electrically to 07.

[0295] These negative electrode 307, positive electrode 304, and separator 310 are impregnated with an electrolyte, as shown in Figure 18B. As shown, with the positive electrode can 301 at the bottom, the positive electrode 304, separator 310, negative electrode 307, and negative The electrode cans 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are connected via a gasket 303. The coin-shaped rechargeable battery 300 is manufactured by crimping the parts together.

[0296] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, high capacity cycling is achieved. This allows for the creation of a coin-type secondary battery 300 with excellent performance characteristics.

[0297] Here, we will use Figure 18C to explain the current flow during the charging of a secondary battery. 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. Yes. 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, so the reaction potential changes. The electrode with the higher potential is called the positive electrode, and the electrode with the lower reaction potential is called the negative electrode. Therefore, in this specification Therefore, 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 (plus electrode)," and the negative electrode is called the "negative electrode." We will refer to this as the "negative electrode" or "- electrode (minus electrode)." In relation to oxidation and reduction reactions... If we use the terms anode and cathode, then during charging and discharging, This could be reversed and cause confusion. Therefore, the anode and cathode The term (cathode) will not be used in this specification. When using the terms cathode, specify whether it is during charging or discharging, and indicate the positive electrode ( We will also indicate whether it corresponds to the negative (last) or last (minus) pole.

[0298] The charger is connected to the two terminals shown in Figure 18C, and the secondary battery 300 is charged. As the 300 battery charges, the potential difference between the electrodes increases.

[0299] [Cylindrical rechargeable battery] Next, refer to Figures 19A, 19B, 19C, and 19D for an example of a cylindrical secondary battery. Let me explain. Figure 19A shows the external view of the cylindrical secondary battery 600. Figure 19B shows the cylindrical This is a schematic diagram showing a cross-section of a type 600 secondary battery. As shown in Figure 19B, it is cylindrical. The secondary battery 600 has a positive electrode cap (battery cover) 601 on its top surface, and on its sides and bottom It has a battery container (outer container) 602. These positive electrode cap and battery container (outer container) 602 are It is insulated by a gasket (insulating packing) 610.

[0300] Inside the hollow cylindrical battery can 602, there is a separator between the strip-shaped positive electrode 604 and the negative electrode 606. A battery element is provided, wound with a 605 in between. Although not shown in the diagram, the battery element is It is wound around the center pin. The battery can 602 is closed at one end and open at the other end. The battery can 602 contains nickel, aluminum, and titanium, which are corrosion-resistant to the electrolyte. Metals such as these, or alloys thereof, or alloys of these with other metals (for example, stainless steel, etc.) It can be used. In addition, nickel, aluminum, etc. can be used to prevent corrosion by the electrolyte. It is preferable to cover the battery can 602. Inside the battery can 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 injected. The non-aqueous electrolyte can be the same as that used in coin-type rechargeable batteries. ru.

[0301] 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 to do so. The positive electrode 604 is connected to the positive electrode terminal (positive electrode current collector lead) 603, and the negative The negative terminal (negative current collector lead) 607 is connected to pole 606. The positive terminal 603 and the negative Both electrode terminals 607 can be made of metal materials such as aluminum. Positive electrode terminal 6 Terminal 03 is resistance-welded to the safety valve mechanism 612, and the negative terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 uses a PTC element (Positive Temperature C It is electrically connected to the positive electrode cap 601 via the efficient)611. The safety valve mechanism 612 activates the positive electrode cap 601 when the internal pressure of the battery rises above a predetermined threshold. This disconnects the electrical connection between the positive electrode 604 and the positive electrode 611. Also, the PTC element 611 is at a certain temperature. This is a thermal resistance element whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current. This prevents abnormal heat generation. The PTC element uses barium titanate (BaTiO3) Semiconductor ceramics and the like can be used.

[0302] Furthermore, as shown in Figure 19C, multiple secondary batteries 600 are connected to conductive plates 613 and 614. Module 615 may be configured by inserting it in between. Multiple secondary batteries 600 are connected in parallel. They may be connected in series, or they may be connected in parallel and then further connected in series. It may be. By configuring a module 615 having multiple secondary batteries 600, It can extract a large amount of electricity.

[0303] Figure 19D is a top view of module 615. To make the diagram clearer, the conductive plate 613 is pointed. As shown by the lines, module 615 electrically powers multiple secondary batteries 600 as shown in Figure 19D. It may have a conductor 616 connected to it. A conductive plate may be superimposed on the conductor 616. This is possible. Furthermore, a temperature control device 617 may be provided between multiple secondary batteries 600. When the secondary battery 600 overheats, the temperature control device 617 cools it down, and the secondary battery 600 When it gets too cold, it can be heated by the temperature control device 617. The performance of the 615 becomes less affected by the ambient temperature. The heat transfer medium of the temperature control device 617 is It is preferable that the material has insulating and non-flammable properties.

[0304] By using the positive electrode active material described in the previous embodiment for the positive electrode 604, high capacity cycling is achieved. This allows for the creation of a cylindrical secondary battery 600 with excellent performance characteristics.

[0305] [Example of a secondary battery structure] Another example of a secondary battery structure will be explained using Figures 20 to 24.

[0306] Figures 20A and 20B show the external view of the battery pack. The battery pack is a circuit base It has a plate 900 and a secondary battery 913. A label 910 is attached to the secondary battery 913. Furthermore, as shown in Figure 20B, the secondary battery 913 has terminal 951 and terminal 9 It has 52.

[0307] The circuit board 900 has a circuit 912. Terminal 911 is connected to the circuit board 900. The child 951, terminal 952, antenna 914, antenna 915, and circuit 912 are connected. Furthermore, multiple terminals 911 are provided, and each of the multiple terminals 911 is designated as a control signal input terminal. It can also be used as a power terminal, etc.

[0308] Circuit 912 may be provided on the back surface of circuit board 900. Note that antenna 914 Furthermore, the antenna 915 is not limited to a coil shape, but may be, for example, linear or plate-shaped. Planar antenna, aperture antenna, traveling wave antenna, EH antenna, magnetic field antenna, dielectric Body antennas or other types of antennas may be used.

[0309] Alternatively, antenna 914 may be a flat conductor. This flat conductor is a conductor for electric field coupling. It can function as one of the components. That is, one of the two conductors that a capacitor has. Antenna 914 may function as a single conductor. This allows only electromagnetic and magnetic fields to be generated. Alternatively, power can be exchanged using an electric field. .

[0310] The battery pack has a layer 916 between the antenna 914 and the secondary battery 913. Layer 6 has the function of shielding electromagnetic fields, for example, from secondary batteries 913. For example, a magnetic material can be used as the sixth element.

[0311] Note that the structure of the secondary battery is not limited to Figure 20A or Figure 20B.

[0312] For example, as shown in Figures 21A and 21B, the battery pack shown in Figures 20A and 20B In this case, antennas may be provided on each of the opposing pair of surfaces. Figure 21A shows the above-mentioned Figure 21B is an external view showing one of the paired faces, and Figure 21B is an external view showing the other of the paired faces. Yes. Furthermore, for the same parts as the battery pack shown in Figures 20A and 20B, Figures 20A and 20B are shown. The explanation of the battery pack shown in Figure 20B can be used as appropriate.

[0313] As shown in Figure 21A, an antenna is formed by sandwiching a layer 916 between one of the pair of surfaces of the secondary battery 913. A layer 917 is provided on the other side of the pair of sides of the secondary battery 913, as shown in Figure 21B. An antenna 918 is provided on either side of it. Layer 917 is an electromagnetic field, for example, from a secondary battery 913. It has the function of being able to shield. For layer 917, for example, a magnetic material can be used. can.

[0314] By adopting the above structure, the size of both antenna 914 and antenna 918 can be increased. It can be done. Antenna 918 can, for example, perform data communication with external devices. It has the ability to do so. Antenna 918 has a shape that can be applied to, for example, antenna 914. An antenna can be applied. Communication method between the secondary battery and other devices via antenna 918. In terms of the formula, it is used between a rechargeable battery and other devices, such as NFC (Near Field Communication). A variety of response methods can be applied.

[0315] Alternatively, as shown in Figure 21C, the battery pack shown in Figures 20A and 20B may have a display device 92 A value of 0 may be provided. The display device 920 is electrically connected to terminal 911. Labels 910 do not need to be provided in the area where the 920 is provided. (See Figures 20A and 2) For the same part as the battery pack shown in Figure 0B, see the battery pack shown in Figures 20A and 20B. Explanations can be used as appropriate.

[0316] The display device 920 may display, for example, an image indicating whether or not it is charging, an image indicating the amount of stored power, etc. It may be displayed. The display device 920 may be, for example, electronic paper, liquid crystal display device, etc. A trollescent (also known as EL) display device can be used. For example, an electronic paper By using a supercharger, the power consumption of the display device 920 can be reduced.

[0317] Alternatively, as shown in Figure 21D, the battery pack shown in Figures 20A and 20B may be connected to the sensor 921 A terminal 921 may be provided. The sensor 921 is electrically connected to terminal 911 via terminal 922. Note that the same parts as the secondary battery shown in Figures 20A and 20B are shown in Figures 20A and 20B. The explanation of the battery pack shown in 0B can be used as appropriate.

[0318] Sensor 921 can measure, for example, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, Light, liquid, magnetism, temperature, chemicals, sound, time, hardness, electric field, electric current, voltage, power, radiation, It should have the ability to measure flow rate, humidity, gradient, vibration, odor, or infrared radiation. i. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed can be obtained. It can also detect parameters (such as temperature) and store them in the memory within circuit 912.

[0319] Furthermore, an example of the structure of the secondary battery 913 will be explained using Figures 22 and 23.

[0320] The secondary battery 913 shown in Figure 22A 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 an insulating material or the like. It is not in contact with 930. Note that in Figure 22A, for convenience, the housing 930 is shown separately. However, in reality, the wound body 950 is covered by the housing 930, and terminals 951 and 952 are covered by the housing. It extends outside the body 930. The housing 930 is made of a metal material (for example, aluminum). ) or resin materials can be used.

[0321] Furthermore, as shown in Figure 22B, the housing 930 shown in Figure 22A is formed from multiple materials. This is also possible. For example, the secondary battery 913 shown in Figure 22B has housings 930a and 930b attached to it. The components are joined together, and the winding body 950 is provided in the area enclosed by the housing 930a and housing 930b. It is being done.

[0322] For the enclosure 930a, insulating materials such as organic resins can be used. In particular, the antenna By using a material such as organic resin on the surface where the na is formed, the electric field produced by the secondary battery 913 is created. This can suppress shielding. 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 the enclosure 930b. For example, metal materials can be used.

[0323] Furthermore, the structure of the wound body 950 is shown in Figure 23. The wound body 950 consists of a negative electrode 931 and It has a positive electrode 932 and a separator 933. The wound body 950 sandwiches the separator 933. Then the negative electrode 931 and the positive electrode 932 are stacked on top of each other, and the stacked sheet is wound up. It is a body. Furthermore, the stacking of the negative electrode 931, the positive electrode 932, and the separator 933 is further Multiple layers can be stacked.

[0324] The negative electrode 931 is connected to terminal 911 shown in Figure 20 via either terminal 951 or terminal 952. The positive terminal 932 is connected to terminal 951 and the other terminal of terminal 952, as shown in Figure 20. It connects to 11.

[0325] By using the positive electrode active material described in the previous embodiment for the positive electrode 932, high capacity cycling is achieved. This allows for the creation of a secondary battery 913 with excellent performance characteristics.

[0326] [Laminated rechargeable battery] Next, examples of laminate-type secondary batteries will be explained with reference to Figures 24 to 30. 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 will also bend in accordance with the deformation of the electronic device. It's also possible.

[0327] Using Figure 24, we will explain the laminated type secondary battery 980. The next battery 980 has a wound body 993 as shown in Figure 24A. The wound body 993 is connected to the negative electrode 994 and It has a positive electrode 995 and a separator 996. The winding body 993 is a winding as explained in Figure 23. Similar to the rotating body 950, the negative electrode 994 and the positive electrode 995 overlap with the separator 996 in between. These are laminated sheets, and the laminated sheets are then rolled up.

[0328] The number of layers in the stack consisting of the negative electrode 994, positive electrode 995, and separator 996 is required. The design should be appropriate depending on the capacitance and element volume. The negative electrode 994 is connected to the lead electrode 997 and One end of electrode 998 is connected to a negative electrode current collector (not shown), and positive electrode 995 is connected to a lead The electrode 997 and the other lead electrode 998 are connected to a positive electrode current collector (not shown). .

[0329] As shown in Figure 24B, there is a film 981 that forms the outer casing and a film 982 having a recess. The aforementioned coiled body 993 is housed in a space formed by bonding the two together by heat pressing or the like. Thus, a secondary battery 980 can be manufactured as shown in Figure 24C. The wound body 993 is It has lead electrodes 997 and lead electrodes 998, and a film 981 and a film having a recess It is impregnated with electrolyte inside the Rum 982.

[0330] Film 981 and film 982 having a recess are made of a metal material such as aluminum. Materials and resins 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 be affected. The film 982 having the property can be deformed, and a flexible storage battery can be manufactured. It is possible.

[0331] Furthermore, Figures 24B and 24C show examples using two films, but one film is also available. A space is formed by folding the film, and the aforementioned wound body 993 is housed in that space. You may submit it.

[0332] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, high capacity cycling is achieved. This allows for the creation of a secondary battery 980 with excellent performance characteristics.

[0333] Furthermore, in Figures 24B and 24C, the winding body is in the space formed by the film that serves as the outer casing. An example of a secondary battery 980 having the following characteristics has been described, for example, as shown in Figures 25A and 25B. In the space formed by the outer film, there are multiple strip-shaped positive electrodes and separators. It may also be a secondary battery having a negative electrode.

[0334] The laminate-type secondary battery 500 shown in Figure 25A consists of a positive electrode current collector 501 and a positive electrode active material. A positive electrode 503 having a layer 502, and a negative electrode having a current collector 504 and a negative electrode active material layer 505. It has an 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 509. Furthermore, the inside of the outer casing 509 is filled with electrolyte 508. The electrolyte 508 contains the following: The electrolyte shown in Form 2 can be used.

[0335] In the laminate-type secondary battery 500 shown in Figure 25A, the positive electrode current collector 501 and the negative electrode The current collector 504 also serves as a terminal for obtaining electrical contact with the outside. Therefore, the positive electrode is concentrated A portion of the current collector 501 and the negative electrode current collector 504 is arranged to be exposed to the outside from the outer casing 509. It may also be placed outside the casing 509. Without exposing the side, lead electrodes are used to connect the lead electrodes to the positive electrode current collector 501, or the negative electrode current collector. The lead electrodes may be exposed to the outside by ultrasonic bonding with the electrostatic body 504.

[0336] In the laminated secondary battery 500, the outer casing 509 is made of, for example, polyethylene, On a film made of materials such as polypropylene, polycarbonate, ionomer, and polyamide, A thin film of a highly flexible metal such as aluminum, stainless steel, copper, or nickel is provided, and further, An insulating synthetic material such as polyamide resin or polyester resin is used as the outer surface of the exterior body on a thin metal film. A three-layer laminate film with a resin film can be used.

[0337] Furthermore, an example of the cross-sectional structure of the laminate-type secondary battery 500 is shown in Figure 25B. For simplicity, the example shown consists of two current collectors, but in reality, as shown in Figure 25B... It is composed of multiple electrode layers.

[0338] In Figure 25B, the number of electrode layers is set to 16 as an example. The secondary battery 500 is also flexible. In Figure 25B, the negative electrode current collector 504 has 8 layers, and the positive electrode current collector The electrode 501 has a structure of 16 layers in total, consisting of 8 layers. Figure 25B shows the negative electrode extraction section. This shows a cross-section, where eight layers of negative electrode current collectors 504 are ultrasonically bonded. Of course, the number of electrode layers The number is not limited to 16; it can be more or less. If the number of electrode layers is large, It can be made into a secondary battery with a large capacity. Also, if the number of electrode layers is small, it can be made thin. This allows for the creation of a rechargeable battery that can be molded and possesses excellent flexibility.

[0339] Here, an example of the external view of the laminate-type secondary battery 500 is shown in Figures 26 and 27. Figures 26 and 27 show the positive electrode 503, negative electrode 506, separator 507, casing 509, and positive electrode ri It has a lead electrode 510 and a negative lead electrode 511.

[0340] Figure 28A shows the external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is the positive electrode current collector 501 The positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. 03 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). Negative electrode 5 06 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 the following characteristics. The area and shape of the tab regions of the positive and negative electrodes are not limited to the example shown in Figure 28A. stomach.

[0341] [Method for manufacturing laminated rechargeable batteries] Here, an example of a method for manufacturing a laminate-type secondary battery, whose external view is shown in Figure 26, is shown in Figure 2. This will be explained using 8B and Figure 28C.

[0342] First, the negative electrode 506, separator 507, and positive electrode 503 are stacked. (As shown in Figure 28B) The negative electrode 506, separator 507, and positive electrode 503 are shown. Here, there are 5 sets of negative electrodes and 4 sets of positive electrodes. An example of how to use them together is shown. Next, the joining of the tab regions of the positive electrode 503 and the tab region of the outermost positive electrode. The positive lead electrode 510 is joined to the region. For joining, ultrasonic welding or the like can be used. Similarly, the bonding of the tab regions of the negative electrode 506 and the negative electrode lead to the tab region of the outermost negative electrode. The electrode 511 is joined.

[0343] Next, the negative electrode 506, separator 507, and positive electrode 503 are placed on the outer casing 509.

[0344] Next, as shown in Figure 28C, fold the outer casing 509 at the part indicated by the dashed line. The outer periphery of the exterior body 509 is joined. For joining, for example, heat compression bonding may be used. At this time, To allow the electrolyte 508 to be added later, a part (or one side) of the outer casing 509 is made in contact with the surface. A non-connected area (hereinafter referred to as the inlet) is provided.

[0345] Next, the electrolyte 508 (not shown) is introduced through the inlet provided in the outer casing 509. Introduce into the inside of 509. 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 It is possible to manufacture a secondary battery of type 500.

[0346] By using the positive electrode active material described in the previous embodiment for the positive electrode 503, high capacity cycling is achieved. This allows for the creation of a secondary battery 500 with excellent performance characteristics.

[0347] [Bendable rechargeable battery] Next, an example of a bendable secondary battery will be described with reference to Figures 29 and 30. ru.

[0348] Figure 29A shows a schematic top view of a bendable secondary battery 250. Figures 29B and 2 Figures 9C and 29D show the cutting lines C1-C2, C3-C4, and cutting lines in Figure 29A, respectively. This is a schematic cross-sectional view along line A1-A2. The secondary battery 250 consists of an outer casing 251 and an outer casing 2 It has a positive electrode 211a and a negative electrode 211b housed inside 51. The positive electrode 211a and electricity Lead 212a is electrically connected to the negative electrode 211b, and lead 212 is electrically connected to the negative electrode 211b. b extends to the outside of the outer casing 251. The region enclosed by the outer casing 251 contains the positive electrode. In addition to 211a and the negative electrode 211b, an electrolyte (not shown) is sealed inside.

[0349] The positive electrode 211a and negative electrode 211b of the secondary battery 250 will be explained using Figure 30. Figure 30A explains the stacking order of the positive electrode 211a, the negative electrode 211b, and the separator 214. This is a perspective view. Figure 30B shows the positive electrode 211a and the negative electrode 211b, as well as the lead 21 This is a perspective view showing lead 2a and lead 212b.

[0350] As shown in Figure 30A, the secondary battery 250 has multiple strip-shaped positive electrodes 211a, multiple strips It has a negative electrode 211b and a plurality of separators 214. Positive electrode 211a and negative electrode 21 Each 1b has a protruding tab portion and a portion other than the tab. One side of the positive electrode 211a A positive electrode active material layer is formed on the part other than the tab of the negative electrode 211b, and on the part other than the tab on one side of the negative electrode 211b A negative electrode active material layer is formed.

[0351] The sides of the positive electrode 211a that do not have a positive electrode active material layer formed on them, and the negative electrode active The positive electrode 211a and the negative electrode 211b are stacked so that their surfaces, which do not have any material formed on them, are in contact with each other. It will be done.

[0352] 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 30, the separator is shown for clarity. Route 214 is indicated by a dotted line.

[0353] Also, as shown in Figure 30B, the multiple positive electrodes 211a and leads 212a are connected at the joint 215a They are electrically connected at the joint 21. Electrically connected at 5b.

[0354] Next, the outer casing 251 will be explained using Figures 29B, 29C, (D), and (E).

[0355] The outer casing 251 has a film-like shape and sandwiches the positive electrode 211a and the negative electrode 211b. It is folded in half. The outer casing 251 has a folded portion 261 and a pair of sealing portions It has a 262 and a sealing portion 263. The pair of sealing portions 262 are positive electrode 211a and It is provided on either side of the negative electrode 211b and can also be called a side seal. Also, seal portion 2 Section 63 has a portion that overlaps with leads 212a and 212b, and is also called the top seal. It is possible.

[0356] The outer casing 251 has ridges 271 and valleys in the portion that overlaps with the positive electrode 211a and the negative electrode 211b. It is preferable that the 272 have a wave shape arranged alternately. Also, the sealing portion 2 of the outer casing 251 It is preferable that 62 and the sealing portion 263 are flat.

[0357] Figure 29B shows a cross-section cut at the point where it overlaps with ridge line 271, and Figure 29C shows the valley line 272 Figures 29B and 29C both show the secondary battery 250 and the positive This corresponds to the cross-section in the width direction of pole 211a and negative pole 211b.

[0358] Here, the ends in the width direction of the positive electrode 211a and the negative electrode 211b, that is, 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 25 When deformation such as bending is applied, the positive electrode 211a and the negative electrode 211b are as described later. They deform so that they are offset from each other in the longitudinal direction. In this case, if the distance La is too short, the outer casing 251 In some cases, the positive electrode 211a and the negative electrode 211b rub strongly against each other, causing damage to the outer casing 251. Yes. In particular, when the metal film of the outer casing 251 is exposed, the metal film is affected by the electrolyte. There is a risk of corrosion. Therefore, it is preferable to set the distance La as long as possible. That's true. On the other hand, if the distance La is made too large, the volume of the secondary battery 250 will increase. .

[0359] Furthermore, the thicker the combined thickness of the stacked positive electrode 211a and negative electrode 211b, the greater the positive electrode 21 It is preferable to increase the distance La between 1a and the negative electrode 211b and the seal portion 262. stomach.

[0360] More specifically, stacked positive electrode 211a and negative electrode 211b and (not shown) separate When the total thickness of 214 is t, the distance La is between 0.8 and 3.0 times the thickness t. Preferably, the ratio is 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.

[0361] Furthermore, when the distance between the pair of sealing portions 262 is denoted as distance Lb, distance Lb is set to the positive electrode 211 Make it sufficiently larger than the width of a and the negative electrode 211b (here, the width Wb of the negative electrode 211b). This is preferable. This allows the secondary battery 250 to be subjected to repeated bending or 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 Because a portion of the negative electrode 211b can be shifted in the width direction, the positive electrode 211a and the negative electrode 211 This effectively prevents friction between b and the outer casing 251.

[0362] 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 positive. The thickness t of electrode 211a and negative electrode 211b is 1.6 times or more and 6.0 times or less, preferably 1.8 It is preferable that the ratio be between 2.0 and 4.0 times, and more preferably between 2.0 and 4.0 times. stomach.

[0363] In other words, it is preferable that the distance Lb, width Wb, and thickness t satisfy the relationship shown in the following formula. It's nice.

[0364]

number

[0365] Here, a is 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, more preferably The value of 'k' satisfies 1.0 or greater and 2.0 or less.

[0366] Furthermore, Figure 29D is a cross-section including lead 212a, and the secondary battery 250, positive electrode 211a This corresponds to the longitudinal cross-section of the negative electrode 211b. As shown in Figure 29D, the bent portion 26 In 1, between 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.

[0367] Figure 29E shows a schematic cross-sectional view of the secondary battery 250 when it is bent. Figure 29D is a diagram. This corresponds to the cross-section at the cutting line B1-B2 in 29A.

[0368] When the secondary battery 250 is bent, a portion of the outer casing 251 located on the outside of the bend stretches inwards. Other parts located there 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. On the other hand, the outer body The portion located inside 251 is modified so that the wave amplitude is large and the wave period is small. Shape. In this way, the outer casing 251 deforms, and as it bends, the outer casing 251 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 does not get damaged, and the secondary battery 250 can be bent with a small force. can.

[0369] Also, as shown in Figure 29E, when the secondary battery 250 is bent, the positive electrode 211a and the negative electrode 2 11b and the other are relatively shifted. At this time, multiple stacked positive electrodes 211a and negative electrodes are shifted. Since one end of pole 211b on the sealing portion 263 side is fixed by the fixing member 217, it is not foldable. Each part shifts such that the amount of shift increases the closer it is to the recessed part 261. As a result, the positive electrode 2 The stress on 11a and the negative electrode 211b is relieved, and the positive electrode 211a and the negative electrode 211b themselves The body does not need to expand or contract. As a result, the positive electrode 211a and the negative electrode 211b are not damaged. The 250 secondary battery can be bent.

[0370] Furthermore, there is a space 273 between the positive electrode 211a and the negative electrode 211b and the outer casing 251. By doing so, the positive electrode 211a and negative electrode 211b, which are located on the inside when bent, are positioned within the outer casing 25 It can shift relative to point 1 without making contact.

[0371] The secondary battery 250 illustrated in Figures 29 and 30 can withstand repeated bending and straightening, and the external Damage to the casing, damage to the positive electrode 211a and negative electrode 211b are less likely to occur, and battery characteristics do not deteriorate. It is a battery that is difficult to use. 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.

[0372] This embodiment can be implemented in appropriate combination with other embodiments.

[0373] (Embodiment 5) This embodiment describes an example of mounting a secondary battery, which is one aspect of the present invention, into an electronic device. I will reveal it.

[0374] First, as explained in part of Embodiment 3, a bendable secondary battery is mounted in an electronic device. Examples are shown in Figures 31A to 31G. Electronic devices using a bendable secondary battery and For example, television equipment (also called television or television receiver), computer Monitors for use with computers, digital cameras, digital video cameras, digital photo frames, etc. M, mobile phone (also called mobile phone or mobile phone device), portable game console, personal digital assistant, Examples include sound reproduction devices and large game machines such as pachinko machines.

[0375] Furthermore, rechargeable batteries with flexible shapes can be attached to the interior or exterior walls of houses and buildings, or to automatic It can also be integrated to conform to the curved surfaces of the car's interior or exterior.

[0376] Figure 31A shows an example of a mobile phone. The mobile phone 7400 is housed in a casing 7401. In addition to the built-in display unit 7402, there are operation buttons 7403, an external connection port 7404, and a speaker. It is equipped with a microphone 7405, microphone 7406, etc. Note that the mobile phone 7400 is a secondary battery It has a battery 7407. A secondary battery according to one embodiment of the present invention is used for the above secondary battery 7407. This allows us to provide lightweight and long-lasting mobile phones.

[0377] Figure 31B shows the mobile phone 7400 in a curved state. Mobile phone 7400 When the entire structure is bent by an external force, the secondary battery 7 located inside it is revealed. The 407 is also bent. Figure 31C shows the state of the bent secondary battery 7407 at that time. The 7407 secondary battery is a thin rechargeable battery. The 7407 secondary battery is fixed in a bent state. It is done. Furthermore, the secondary battery 7407 has lead electrodes electrically connected to the current collector. Yes, for example, the current collector is made of copper foil, and part of it is alloyed with gallium, and the active material that comes into contact with the current collector This improves adhesion to the structural layer, resulting in a configuration that ensures high reliability even when the secondary battery 7407 is bent. It is.

[0378] Figure 31D shows an example of a bangle-type display device. The portable display device 7100 is housed in a casing. It comprises a body 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. Figure 31E shows the state of the bent secondary battery 7104. The secondary battery 7104 is bent. When worn on the user's arm in this state, the casing deforms, causing part or all of the secondary battery 7104 to be damaged. The curvature changes. The degree of curvature at any point on the curve can be expressed using the radius of the corresponding circle. The resulting value is called the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, if the radius of curvature is 40 Within a range of 150 mm or more, a portion or all of the main surface of the housing or secondary battery 7104 The part changes. The radius of curvature on the main surface of secondary battery 7104 is 40 mm or more and 150 mm or less. Within the following range, high reliability can be maintained. The above secondary battery 7104 is an embodiment of the present invention. By using a rechargeable battery, a lightweight and long-lasting portable display device can be provided.

[0379] Figure 31F 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 720 5. It is equipped with input / output terminals 7206, etc.

[0380] The 7200 mobile information terminal offers mobile phone calls, email, document viewing and creation, music playback, and more. It can run various applications such as internet communication and computer games. Cut.

[0381] The display unit 7202 has a curved display surface, and displays information along the curved surface. It is possible to do so. In addition, the display unit 7202 is equipped with a touch sensor, and the screen can be touched with a finger or stylus. It can be operated by touching it. For example, icon 7 displayed on the display unit 7202 Touching 207 will launch the application.

[0382] The 7205 control button is used for time setting, as well as power on / off, wireless communication on, and more. Various functions such as operation, activation and deactivation of silent mode, and activation and deactivation of power saving mode. It can be made to hold. For example, the operating system built into the personal digital assistant 7200 The system also allows you to freely configure the function of the control button 7205.

[0383] Furthermore, the 7200 portable information terminal is capable of performing standardized short-range wireless communication. For example, by communicating with a wireless headset, hands-free operation is possible. You can also make calls.

[0384] Furthermore, the portable information terminal 7200 is equipped with an input / output terminal 7206, and can connect to other information terminals. Data can be exchanged directly via this. Also, charging is possible via input / output terminal 7206. It can also perform electrical operations. Note that charging is done wirelessly without using input / output terminal 7206. You may go.

[0385] The display unit 7202 of the portable information terminal 7200 has a secondary battery according to one aspect 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 31E is placed inside the housing 7201 in a curved state. Alternatively, it can be incorporated into the band 7203 in a flexible state.

[0386] 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 accelerometers. It is preferable that sensors, etc., be installed.

[0387] Figure 31G shows an example of an armband-type display device. The display device 7300 has a display unit 73 The present invention has a secondary battery having 04. The display device 7300 also has a display Part 7304 can also be equipped with a touch sensor, and it can also function as a portable information terminal. It can also be done this way.

[0388] The display unit 7304 has a curved display surface, and displays are performed along the curved display surface. This is possible. In addition, the display device 7300 can display information via standardized short-range wireless communication. The situation can be changed.

[0389] 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 its input / output terminals. Furthermore, charging may be performed wirelessly without using input / output terminals.

[0390] 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 lightweight and long-lasting display devices.

[0391] Furthermore, an example of mounting the secondary battery with good cycle characteristics shown in the previous embodiment into an electronic device is provided. This will be explained using Figures 31H, 32, and 33.

[0392] 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 essential products. For example, everyday electronic devices such as electric toothbrushes and electric shavers. Examples include electric beauty devices, and the rechargeable batteries for these products are designed to be easy for the user to hold. The idea is to create a rechargeable battery that is small, lightweight, and high-capacity, with a stick-like shape.

[0393] Figure 31H is a perspective view of a device also known as a tobacco-containing smoking device (electronic cigarette). In 1H, the e-cigarette 7500 includes an atomizer 7501 containing a heating element, and an atomizer The rechargeable battery 7504 that supplies power, and a cartridge containing a liquid supply bottle and sensors, etc. It consists of 7502. To enhance safety, overcharging and over-discharging of the secondary battery 7504 are controlled. A protective circuit to prevent this may be electrically connected to the secondary battery 7504. (Secondary battery shown in Figure 31H) The 7504 has an external terminal so that it can be connected to a charging device. The rechargeable battery 7504 has Since this will be the tip in that case, it is desirable that the total length be short and the weight be light. i. A secondary battery according to one aspect of the present invention has high capacity and good cycle characteristics, and therefore can be used over a long period of time. This allows us to offer the 7500, a small and lightweight e-cigarette that can be used for extended periods.

[0394] Next, Figures 32A and 32B show an example of a foldable tablet device. The tablet terminal 9600 shown in 32A and 32B consists of a housing 9630a and a housing 963 0b, movable part 9640 connecting housing 9630a and housing 9630b, display unit 9631a and Display unit 9631 having display unit 9631b, switches 9625 to 9627, retainer It has a fastener 9629 and an operating switch 9628. The display unit 9631 has flexibility By using a panel, a tablet device with a larger display area can be created. (Figure) Figure 32A shows the tablet terminal 9600 in an open state, and Figure 32B shows the tablet terminal This shows the state with the last 9600 closed.

[0395] Furthermore, the tablet terminal 9600 stores inside the housings 9630a and 9630b. It has an electric body 9635. The electric body 9635 passes through the movable part 9640 and the housing 9630a and the housing It is provided across body 9630b.

[0396] 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 collected. Input can be made. For example, keys can be placed on the entire surface of the display unit 9631a on the housing 9630a. The board buttons are displayed, and information such as text and images is shown on the display unit 9631b on the chassis 9630b. It may also be used to display information.

[0397] Furthermore, the keyboard is displayed on the display unit 9631b on the chassis 9630b side, and the chassis 9630 The display unit 9631a on side a may be used to display information such as characters and images. The touch panel keyboard display switching button is displayed in section 9631, By touching the button with a finger or stylus, the keyboard will be displayed on the display unit 9631. You can do that.

[0398] 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 input to the touch panel area of ​​the display unit 9631b.

[0399] Furthermore, switches 9625 to 9627 are used to operate the tablet terminal 9600. It not only provides an interface for doing so, but also an interface that allows switching between various functions. It may also be used as a surface. For example, at least switch 9625 to switch 9627 It also functions as a switch to turn the tablet device 9600 on and off. It is also permissible to do so. Furthermore, for example, at least one of switches 9625 to 9627 may be A function to switch the display orientation, such as portrait or landscape, or to switch between black and white and color display. It may have a function to change. Also, for example, a small number of switches 9625 to 9627 At the very least, one may have a function to adjust the brightness of the display unit 9631. Also, the display unit 96 The brightness level of 31 is detected by the light sensor built into the tablet device 9600 during use. The optimal setting can be determined according to the amount of ambient light. Note that the tablet device uses a light sensor. In addition, it incorporates other detection devices such as gyroscopes, accelerometers, and other sensors that detect tilt. It's okay to store it.

[0400] Also, in Figure 32A, the display unit 9631a on the housing 9630a side and the display unit on the housing 9630b side The example shows that the display area of ​​9631b is almost the same as that of display unit 9631a and display unit 96 The display area of ​​each of the 31b is not particularly limited, and the size of one and the size of the other may differ. They may be present, 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 various operations.

[0401] Figure 32B shows the tablet terminal 9600 in a folded state. The terminal 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 the energy storage body 9635, according to one aspect of the present invention Use an energy storage device.

[0402] 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. Durability can be improved. Furthermore, the energy storage body 9635 using a secondary battery according to one aspect of the present invention is Due to its high capacity and good cycle characteristics, this tablet can be used for extended periods of time. We can provide the 9600 type terminal.

[0403] In addition, the tablet terminal 9600 shown in Figures 32A and 32B has various other features. Features that display information (still images, videos, text images, etc.), calendar, date or time. Functions that display such information on the display unit, and touch input operations or editing of the information displayed on the display unit. It has features such as input functionality and the ability to control processing through various software (programs). It is possible.

[0404] The solar cell 9633 attached to the surface of the tablet device 9600 provides power to the tablet. It can be supplied to the control panel, display unit, or video signal processing unit, etc. Note that the solar cell 96 33 can be provided on one or both sides of the housing 9630, and efficiently charges the energy storage unit 9635. This configuration can be implemented in a specific way. Note that the energy storage unit 9635 is a lithium-ion battery. Using it offers advantages such as enabling miniaturization.

[0405] Furthermore, the configuration and operation of the charge / discharge control circuit 9634 shown in Figure 32B are shown in Figure 32C. A block diagram will be shown and explained. Figure 32C shows the solar cell 9633, the energy storage unit 9635, and the DCD. C converter 9636, converter 9637, switches SW1 to SW3, display unit 963 Regarding 1, it shows the energy storage unit 9635, the DC-DC converter 9636, and the converter 96 37. Switches SW1 to SW3 correspond to the charge / discharge control circuit 9634 shown in Figure 32B. This will be the location.

[0406] First, let's explain an example of how the solar cell 9633 operates when generating electricity using ambient light. The electricity generated by the solar cells is converted into a DC-DC converter to provide the voltage necessary to charge the 9635 energy storage unit. The converter 9636 performs voltage boosting or bucking. Then, the solar power is used to control the operation of the display unit 9631. When power from pond 9633 is used, switch SW1 is turned ON, and converter 963 In step 7, the voltage is increased or decreased to the required voltage for the display unit 9631. Also, the display unit 963 If you do not want to display in step 1, turn SW1 off and turn SW2 on to enable the storage unit 9635. The configuration should include charging capabilities.

[0407] While solar cell 9633 is shown as an example of a power generation method, it is not particularly limited to this method. Storage using other power generation methods such as piezoelectric elements (piezo elements) and thermoelectric elements (Peltier elements) The configuration may also involve charging the battery 9635. For example, power may be transmitted and received wirelessly (contactlessly). This includes contactless power transmission modules that charge via this method, as well as configurations that combine this with other charging methods. You may do so.

[0408] Figure 33 shows an example of another electronic device. In Figure 33, the display device 8000 is the present invention. This is an example of an electronic device using a secondary battery 8004 according to one embodiment. Specifically, the display device 80 00 corresponds to a display device for receiving TV broadcasts, and consists of a housing 8001, a display unit 8002, and a speaker. It has a part 8003, a secondary battery 8004, etc. A secondary battery 8004 according to one aspect of the present invention is It is located inside the enclosure 8001. The display device 8000 receives power from the commercial power supply. You can receive power from it, or you can use the power stored in the secondary battery 8004. Therefore, even when power cannot be supplied from the commercial power source due to a power outage or the like, 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. Yes.

[0409] The display unit 8002 has light-emitting elements such as liquid crystal display devices and organic EL elements in each pixel. Optical devices, electrophoresis display devices, DMDs (Digital Micromirror Dev ice), PDP (Plasma Display Panel), FED (Field Semiconductor display devices such as Emission Displays can be used.

[0410] In addition to being used for receiving TV broadcasts, the display devices are also used for personal computers and for displaying advertisements. This includes all information display devices.

[0411] In Figure 33, the fixed lighting device 8100 is a secondary battery 8 according to one aspect of the present invention. This is an example of an electronic device using 103. Specifically, the lighting device 8100 has a housing 8101, It has a light source 8102, a secondary battery 8103, etc. In Figure 33, the secondary battery 8103 is located in the housing 8 For example, consider the case where 101 and the light source 8102 are installed inside the ceiling 8104. Although shown, the secondary battery 8103 may also be located inside the housing 8101. The device 8100 can receive power from a commercial power source, or from a secondary battery 8103. It is also possible to use stored power. Therefore, in the event of a power outage, etc., power supply from commercial power source 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.

[0412] In Figure 33, a fixed lighting device 8100 installed on the ceiling 8104 is shown as an example. However, in one aspect of the present invention, the secondary battery is located on the side wall 8105, floor, and other surfaces besides the ceiling 8104. It can also be used in fixed lighting devices installed in windows such as 8106 and 8107, and also in tables It can also be used in overhead lighting fixtures and other applications.

[0413] Furthermore, the light source 8102 can use an artificial light source that artificially obtains light using electricity. Yes, it is possible. Specifically, this includes discharge lamps such as incandescent light bulbs and fluorescent lamps, and LEDs and organic EL elements. Optical elements are an example of the artificial light sources mentioned above.

[0414] In Figure 33, the air conditioner having an indoor unit 8200 and an outdoor unit 8204 is This is an example of an electronic device using a secondary battery 8203 according to one aspect of the present invention. Specifically, the room The internal unit 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, etc. (Figure 33) The example given is that the secondary battery 8203 is installed in the indoor unit 8200, but The next battery 8203 may be located in the outdoor unit 8204. Alternatively, it may be located in the indoor unit 8200 and the room The secondary battery 8203 may be provided on both sides of the outdoor unit 8204. - It can also receive power from the commercial power supply, or stored in the secondary battery 8203 Electricity can also be used. In particular, both the indoor unit 8200 and the outdoor unit 8204 can use secondary batteries 8 If 203 is installed, when power cannot be supplied from the commercial power source due to a power outage, etc. However, by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply, Conditioner can be used.

[0415] Figure 33 shows a separate-type air conditioner consisting of an indoor unit and an outdoor unit. The example shown is an integrated air conditioner that 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.

[0416] In Figure 33, the electric refrigerator 8300 is a secondary battery 8304 according to one aspect of the present invention. This is an example of an electronic device using [a specific component]. Specifically, the electric refrigerator 8300 has a casing 8301, It has a refrigerator door 8302, a freezer door 8303, a secondary battery 8304, etc. In Figure 33, The secondary battery 8304 is located inside the casing 8301. The electric refrigerator 8300 is It can also receive power from the commercial power supply, or power stored in the secondary battery 8304 It is also possible to use this. Therefore, if power cannot be supplied from the commercial power source due to a power outage, etc. Even at times, by using the secondary battery 8304 according to one aspect of the present invention as an uninterruptible power supply, The 8300 refrigerator / freezer will become available for use.

[0417] Of the electronic devices mentioned above, high-frequency heating devices such as microwave ovens and electric rice cookers are included. Sub-devices require high power for short periods. Therefore, they need 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 to assist, electronic devices This prevents the commercial power circuit breaker from tripping when using it.

[0418] 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 the time periods when the proportion of electricity actually used (called the electricity usage rate) is low, By storing power in the secondary 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 83 02. At night when the freezer door 8303 is not opened or closed, power is supplied to the secondary battery 8304. Store. Then, 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, daytime electricity usage The rate can be kept low.

[0419] According to one aspect of the present invention, the cycle characteristics of a secondary battery are improved, thereby enhancing reliability. This can be done. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be made, and thus This improves the characteristics of secondary batteries, and therefore makes the secondary batteries themselves smaller and lighter. 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, it becomes possible to create electronic devices with a longer lifespan and lighter weight.

[0420] This embodiment can be implemented in appropriate combination with other embodiments.

[0421] (Embodiment 6) This embodiment shows an example in which a secondary battery according to one aspect of the present invention is mounted on a vehicle.

[0422] When a secondary battery is installed in a vehicle, it can become a hybrid electric vehicle (HEV), an electric vehicle (EV), or This enables the realization of next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). ru.

[0423] Figure 34 illustrates a vehicle using a secondary battery, which is one embodiment of the present invention. Figure 34A shows The vehicle shown, model 8400, is an electric vehicle that uses an electric motor as its power source for driving. Alternatively, an electric motor and an engine may be appropriately selected and used as the power source for propulsion. This is a hybrid vehicle capable of [something]. By using one aspect of the present invention, a long driving range is achieved. A vehicle can be realized. Furthermore, the 8400 automobile has a secondary battery. The secondary battery is, The secondary battery modules shown in Figures 19C and 19D are arranged on the floor of the vehicle. You can use it. Also, a battery pack made by combining multiple secondary batteries as shown in Figure 22 can be placed on the floor inside the vehicle. It may be installed in part. The secondary battery not only drives the electric motor 8406, To supply power to light-emitting devices such as headlights 8401 and interior lights (not shown). It is possible.

[0424] Furthermore, the secondary battery is used in the speedometer, tachometer, and other displays of the 8400 automobile. It can supply power to the display device. Furthermore, the secondary battery powers the navigation system of the 8400 automobile. It can supply power to semiconductor devices such as gate systems.

[0425] The automobile 8500 shown in Figure 34B has a plug-in type secondary battery. It can be charged by receiving power from an external charging facility using methods such as contactless power supply. Figure 34B shows the secondary battery installed in the automobile 8500, powered by the ground-mounted charging device 8021. 8024 indicates that charging is taking place via cable 8022. During charging, Charging methods and connector specifications are determined by the specified methods such as CHAdeMO® or Combo. It can be done as appropriate. The charging device 8021 may also be a charging station installed in a commercial facility. It may also be a household power supply. For example, by plug-in technology, external power supply The power supply can charge the secondary battery 8024 installed in the vehicle 8500. This can be done by converting AC power to DC power via a conversion device such as an AC / DC converter. can.

[0426] 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 supplying power. In this contactless power supply method, the power transmission equipment is installed on the road or exterior wall. By incorporating this, charging can be performed not only when the vehicle is stopped but also while it is in motion. The electric system 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 while the vehicle is stopped or in motion. Electromagnetic induction and magnetic resonance methods can be used to supply power in this environment.

[0427] Furthermore, Figure 34C shows an example of a two-wheeled vehicle using a secondary battery according to one embodiment of the present invention. The scooter 8600 shown includes a secondary battery 8602, side mirrors 8601, and turn signals 86 It is equipped with 03. The secondary battery 8602 can supply power to the turn signal light 8603. .

[0428] Furthermore, the scooter 8600 shown in Figure 34C has a secondary battery 8602 in the under-seat storage compartment 8604. It can store the secondary battery 8602 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. Therefore, when charging, the 8602 secondary battery is carried indoors, charged, and stored before driving. That's all you need to do.

[0429] 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 allows for miniaturization and weight reduction of the secondary battery itself. Secondary battery Making the unit itself smaller and lighter would contribute to reducing the vehicle's weight, thus improving its range. Yes, 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. Therefore, if we can avoid using commercial power during peak electricity demand, we can save energy and It can contribute to reducing carbon dioxide emissions. Also, if the cycle characteristics are good, two Because the next battery can be used for a long period of time, the amount of rare metals used, including cobalt, can be reduced. It is possible.

[0430] This embodiment can be implemented in appropriate combination with other embodiments. [Examples]

[0431] In this embodiment, 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 We evaluated the cycle characteristics during voltage charging. Furthermore, we analyzed the characteristics using XRD.

[0432] [Fabrication of positive electrode active material] ≪Sample 1≫ In Sample 1, the fabrication method shown in Figure 13 of Embodiment 1 was used, with the transition metal being . A positive electrode active material containing balt was fabricated. First, the molar ratio of LiF to MgF2 was LiF:Mg Weigh the materials so that F2 = 1:3, add acetone as the solvent, and mix and grind in a wet process. Mixing and grinding were performed using a ball mill with zirconia balls at 150 rpm, 1 hour. The process was carried out. The processed material was recovered and used as the first mixture (steps S11 to S in Figure 13). Step S14).

[0433] In Sample 1, the pre-synthesized lithium cobalt oxide was supplied by Nippon Chemical Industries, Ltd. We used the company's CellSeed C-10N (step S25 in Figure 13). CellSeed C-1 As described in Embodiment 1, 0N is cobalt with a D50 of about 12 μm and low impurity content. It is lithium trioxide.

[0434] Next, the amount of magnesium in the first mixture relative to the molecular weight of lithium cobaltate The particles were weighed to a concentration 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 the second mixing was performed. This was done (steps S31 to S33 in Figure 13).

[0435] Next, the second mixture is placed in an alumina crucible and heated in an oxygen atmosphere muffle furnace at 850°C for 6 minutes. The material was annealed for 0 hours. The alumina crucible was covered during annealing. The oxygen flow rate was 10. The flow rate was set to L / min. The heating was performed at 200°C / hr, and the cooling was carried out over a period of 10 hours or more. The processed material was used as the positive electrode active material for Sample 1 (step S34 in Figure 13, step S34). (S35)

[0436] [Manufacturing of secondary batteries] Next, using Sample 1 prepared above, we will create a CR2032 type (20mm diameter) A coin-shaped rechargeable battery with a height of 3.2 mm was fabricated.

[0437] The positive electrode contains the positive electrode active material prepared above, acetylene black (AB), and polyfluoride. Vinylidene (PVDF) is mixed with the positive electrode active material in a ratio of AB:PVDF = 95:3:2 (by weight). A mixture of slurry was applied to a current collector. The amount of positive electrode active material supported was 8.2 mg / cm 2 That was the case.

[0438] Lithium metal was used for the counter electrode.

[0439] The electrolyte in the electrolyte solution contains 1 mol / L lithium hexafluoride phosphate (LiPF6). The electrolyte used is ethylene carbonate (EC) and diethyl carbonate (DEC). EC:DEC = 3:7 (volume ratio), vinylene carbonate (VC) is mixed at 2 wt%. I used that.

[0440] A 25 μm thick polypropylene was used for the separator.

[0441] The positive electrode and negative electrode cans were made of stainless steel (SUS).

[0442] The positive electrode of the secondary battery was pressed. Specifically, after applying pressure at 210 kN / m, it was pressed at 1467 k The pressure was increased to N / m.

[0443] [Cycle characteristics and dQ / dVvsV curves] A secondary battery using Sample 1 is charged using CCCV (0.05C, 4.5V or 4.6V, cutoff current 0.005C), discharge at CC (0.05C, 2.5V) at 25℃ Two cycles were measured.

[0444] Subsequently, we began measuring the cycle characteristics. Specifically, we used Sample 1 for secondary cycles. Charge the battery at 25°C using CCCV (0.2C, 4.5V or 4.6V, then terminate the charge) The battery is repeatedly charged and discharged at CC (0.2C, 2.5V) with a current of 0.02C, and the cycle is performed. The characteristics were evaluated.

[0445] Figure 35 shows the results obtained by deriving the dQ / dV vs V curve from the charging curve of each cycle. 5A is the dQ / dV vs V curve in cycles 1, 3, 4, 5, and 10. Figure 35B shows the results for 10, 30, 50, 70 and 100 cycles. The dQ / dV vs V curve is shown.

[0446] Furthermore, Figure 36A shows the first cycle, Figure 36B shows the third cycle, and Figure 37A shows the fifth cycle. The charge-discharge curves for each cycle are shown. Figure 37B shows the discharge capacity for each cycle.

[0447] As shown in Figures 35A and 35B, in the range of 4.08V to 4.18V The first peak, the second peak in the range of 4.18V to 4.25V, and 4. A third peak was observed in the range of 54V to 4.58V.

[0448] As shown in Figure 35A, the third peak is from the 1st to the 10th cycle. A tendency was observed for peak intensity to increase with increasing number of pulses.

[0449] As shown in Figure 35B, after 30 cycles, the first peak increases with the number of cycles. The curve shifted to the right, and there was a tendency for the voltage value corresponding to the peak to increase. Also, the third The peak intensity decreases with increasing cycle count, and at 100 cycles, the peak is almost gone. I hardly ever see it anymore. [Examples]

[0450] In this example, Sample 1, which was prepared in the previous example, was evaluated using XRD.

[0451] [XRD(1)] Powder XRD analysis of the positive electrode before charging using Sample 1 with CuKα1 radiation. The XRD measurements were taken in air, and the electrodes were attached to a glass plate to maintain flatness. The XRD device was set up for powder samples, but the sample height was as required by the device. It was adjusted to the measurement surface.

[0452] The obtained XRD pattern is DIFFRAC.EVA (Bruker XRD data). Using analysis software, background removal and Kα2 removal were performed. This resulted in conductivity Signals originating from auxiliary agents, binders, and sealed containers have also been removed.

[0453] 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), The determined crystallite size and lattice constants for the a-axis and c-axis were found.

[0454] Next, multiple secondary batteries were fabricated using Sample 1 and charged using CCCV. A positive electrode was fabricated using mple 1 as the positive electrode active material. The amount of mple 1 used in the positive electrode was approximately 7 mg. / cm 2 The charging voltage was 4.5V, 4.525V, 4.55V, 4.575V, and We used five conditions: 4.6V and 4.6V. A secondary battery was fabricated and evaluated for each condition. Specifically... The typical charging conditions are to charge with a constant current of 0.5C until each charging voltage is reached, and then the current value becomes 0.01C. It was charged at a constant voltage until it reached the charge level. Here, 1C was defined as 137mA / g. Each secondary 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. Figures 38 and 39 show the respective charging voltages. The XRD patterns of the positive electrode under these conditions are shown. Figures 38 and 39 show different ranges of 2θ. For comparison, the pseudo-spinel crystal structure, the H1-3 type crystal structure, and Li 0.35 OO The crystal structure pattern of 2 (space group R-3m, O3) is also shown. 0.35 CoO2 corresponds to the crystal structure at a charge depth of 0.65.

[0455] Furthermore, using a secondary battery different from the secondary battery used for the charging conditions, the charge and discharge cycle was performed 10 times. After going to Ikuru, I disassembled it in the glove box, removed the positive electrode, cleaned it with DMC, and then electrolyzed it. The liquid was removed, the sample was sealed in a sealed container under an argon atmosphere, and XRD analysis was performed. The charging conditions were: After charging with a constant current of 0.5C until the voltage reaches 4.6V, charge with a constant voltage until the current value becomes 0.01C. The discharge conditions were CC discharge at 0.2C and 2.5V.

[0456] Tables 2 through 5 show the values ​​analyzed using XRD. For XRD before charging, see below. It is labeled "Before charging" and the charging is done at 4.5V, 4.525V, 4.55V, 4.575V and For the XRD after reaching 4.6V, the values ​​were "4.5V" and "4.525V," respectively. It is labeled "4.55V", "4.575V", and "4.6V", and then discharged. Furthermore, regarding the XRD after 9 charge / discharge cycles, i.e., the XRD after 10 cycles: This should be described as "after 10cy discharge".

[0457] Table 2 shows the crystallite size and volume ratio when fitting is performed assuming an O3 type crystal structure. And the lattice constants are shown in Table 3 when fitted assuming a pseudo-spinel type crystal structure. Table 4 shows the crystallite size, volume ratio, and lattice constant, assuming an H1-3 type crystal structure. The crystallite size, volume ratio, and lattice constant after the ting process are shown, respectively. Each table also shows the GOF (Good of Fitness) score.

[0458] [Table 2]

[0459] [Table 3]

[0460] [Table 4]

[0461] Furthermore, Table 5 shows two peaks (Peak 1 and Peak 2) that are thought to correspond to the O3 type crystal structure. Table 6 shows the peak value and full width at half maximum of Peak 2), which are considered to correspond to the pseudo-spinel crystal structure. The peak values ​​and full width at half maximum (FWHM) of the two peaks (peak 3 and peak 4): The full width (at half maximum) is shown for each. Peak value FWHM was calculated using TOPAS. Also, L in the table is the Lorentz function. This value indicates the degree of fit.

[0462] [Table 5]

[0463] [Table 6]

[0464] At 4.55V, it was suggested that O3-type crystal structures and pseudo-spinel-type crystal structures coexist. Above 4.575, the pseudo-spinel crystal structure became dominant.

[0465] The lattice constant of the a-axis was compared to the value before charging or after discharging when the charging voltage was 4.5V and 4. At 0.525V, the lattice constant decreases to 2.81 × 10⁻⁶. -10 m or more 2.83×10 -10 m The range was as follows: As the charging voltage increased, i.e., the charging depth increased, the grid The constant tended to increase, approaching its value before charging or after discharging.

[0466] Compared to the values ​​before charging or after discharging, the increase in the full width at half maximum was limited to a maximum of approximately 3.4 times. Ta.

[0467] [XRD(2)] The charge-discharge cycle was performed using the conditions described in the previous example, and 1, 3, 10, 20, and 30 cycles were performed. XRD was evaluated over 50 cycles. In each cycle, last CCCV charging is performed during charging, the charging voltage is set to 4.6V, and no discharge is performed after charging. Disassemble it inside the glove box, remove the positive electrode, clean it with DMC to remove the electrolyte, and The samples were sealed in a rougone atmosphere and XRD analysis was performed. Figures 40A, 40B, and 4 Figure 1 shows the XRD spectrum. Figures 40A, 40B, and 41 are shown respectively. The range of the angle 2θ is different. Also, Table 7 shows three peaks (Peak 3, Peak 4 and P). The peak value, FWHM, and L values ​​for step 5) are shown.

[0468] [Table 7]

[0469] The peak observed at 2θ = 19.30 ± 0.20° increases as the number of cycles increases. A tendency was observed where a larger peak value indicated a greater amount of lithium ions being released. This suggests that the discharge capacity may increase. [Examples]

[0470] In this embodiment, a secondary battery is fabricated using a positive electrode active material according to one aspect of the present invention, and the dQ / dVv The sV curve was calculated.

[0471] The secondary battery using Sample 1 is charged using CCCV (0.05C, 4.5V, terminated). With a current of 0.005C and discharge at CC (0.05C, 2.5V) at 25°C, 2 cycles I measured the crunch.

[0472] Subsequently, charging was performed at 25°C using CCCV (0.05C, 4.9V, termination current 0.00). The charging curve was measured using 5C (1C = 200mA / g). Next, the measured charging car... The dQ / dV vs V curve was derived from the value of B. The results are shown in Figure 42.

[0473] From Figure 42, the first maximum peak is at approximately 4.08V, the second maximum peak is at approximately 4.19V, and approximately A third maximum peak was observed at 4.56V, and a fourth maximum peak was observed at approximately 4.65V.

[0474] Comparing Figure 35A and Figure 42, the charging rate is smaller (the charging speed is slower). A tendency was observed for the peak to shift to a value approximately 0.2V smaller. [Explanation of Symbols]

[0475] 100: Positive electrode active material

Claims

1. A lithium-ion secondary battery having a positive electrode, The positive electrode has a positive electrode active material containing lithium cobalt oxide, The positive electrode active material is magnesium, and the lithium-ion secondary battery. However, the positive electrode is Multiple batteries are manufactured, each having the aforementioned positive electrode, a counter electrode made of lithium metal, an electrolyte, and a separator made of polypropylene (wherein the electrolyte of the electrolyte is lithium hexafluoride phosphate at a concentration of 1 mol / L, and the electrolyte is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of EC:DEC = 3:7, and vinylene carbonate (VC) at 2 wt%)). Of the aforementioned multiple batteries, the first battery is defined as one that is charged with a constant current of 0.5C up to 4.55V in a 25°C environment, and then charged with a constant voltage of 4.55V until the current reaches 0.01C, also in a 25°C environment. Of the aforementioned multiple batteries, the second battery is defined as one that was charged with a constant current of 0.5C up to 4.575V in a 25°C environment, and then charged with a constant voltage of 4.575V until the current value reached 0.01C, also in a 25°C environment. Of the aforementioned multiple batteries, the third battery is defined as one that is charged with a constant current of 0.5C up to 4.6V in a 25°C environment, and then charged with a constant voltage of 4.6V until the current reaches 0.01C, also in a 25°C environment. In a glove box under an argon atmosphere, the positive electrodes of the first to third batteries are removed and sealed in the first to third sealed containers, respectively. Subsequently, the positive electrodes of the first to third batteries, which are sealed in the first to third sealed containers, are each subjected to powder XRD analysis using CuKα1 radiation. When the XRD pattern obtained by powder XRD analysis of the positive electrode of the first battery was fitted using models of O3-type crystal structure, pseudo-spinel-type crystal structure, and H1-3-type crystal structure, the result showed that the positive electrode of the first battery has an O3-type crystal structure and a pseudo-spinel-type crystal structure. When the XRD pattern obtained by powder XRD analysis of the positive electrode of the third battery was fitted using models of O3-type crystal structure, pseudo-spinel-type crystal structure, and H1-3-type crystal structure, the positive electrode of the third battery was found to have both a pseudo-spinel-type crystal structure and an H1-3 crystal structure, with the pseudo-spinel-type crystal structure being more abundant than the H1-3 crystal structure. When the XRD pattern obtained by powder XRD analysis of the positive electrode of the second battery is fitted using models of O3-type crystal structure, pseudo-spinel-type crystal structure, and H1-3-type crystal structure, the pseudo-spinel-type crystal structure observed in the positive electrode of the second battery is found to be more numerous than the pseudo-spinel-type crystal structure observed in the positive electrode of the first battery. Lithium-ion rechargeable battery.

2. In claim 1, The XRD patterns obtained by powder XRD analysis of the positive electrodes of the first to third batteries are lithium-ion secondary batteries, after background removal and Kα2 removal using DIFFRAC.EVA (XRD data analysis software manufactured by Bruker).

3. In claim 1 or claim 2, The aforementioned magnesium concentration peak is present in the lithium-ion secondary battery, at a depth of 3 nm from the surface of the positive electrode active material, as determined by EDX radiation analysis.

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