Lithium ion secondary battery

Abstract

To provide a positive electrode active material for a secondary battery having high capacity and excellent charge / discharge cycle characteristics. To provide a positive electrode active material in which reduction in capacity in a charge / discharge cycle is suppressed. To provide a secondary battery with high capacity. To provide a secondary battery excellent in charge and discharge characteristics. To provide a secondary battery with high safety and reliability.SOLUTION: The positive electrode active material has a crystalline structure having an R-space group when Rietveld analysis is performed on a pattern obtained by powder X-ray diffraction, and the number of atoms of aluminum is 0.2 times or less the number of atoms of cobalt in X-ray photoelectron spectroscopy analysis. 3m.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

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

[0004] In recent years, various types of energy storage devices have become available, including lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. The development of lithium-ion batteries, which have high output and high energy density, is particularly active. Secondary batteries are used in mobile phones, smartphones, tablets, or laptops. mobile information terminals, portable music players, digital cameras, medical equipment, next-generation clean energy Hybrid vehicles (HEVs), electric vehicles (EVs), plug-in hybrids Demand for rechargeable vehicles (PHEVs, etc.) is rapidly expanding along with the development of the semiconductor industry. As a source of energy, it has become indispensable in today's information society.

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

[0006] Therefore, we developed a positive electrode with the aim of improving the cycle characteristics and increasing the capacity of lithium-ion secondary batteries. Improvements to the active material have been investigated (Patent Documents 1 and 2). Research into the crystal structure is also being conducted (Non-Patent Documents 1 to 3).

[0007] X-ray diffraction (XRD) is one of the techniques used to analyze the crystalline structure of positive electrode active materials. ICSD (Inorganic Crystal Streptavidin) introduced in Non-Patent Document 5 Analysis of XRD data using the Structure Database can be done.

[0008] In addition, as shown in Non-Patent Documents 6 and 7, first-principles calculations can be used. This allows the calculation of energy according to the crystal structure, composition, etc. of the compound.

[0009] Patent document 3 uses first-principles calculations to calculate LiNi 1-x M x Calculate the interatomic distance of O2 Patent Document 4 also shows an example of the properties of silicon oxide compounds calculated by first-principles calculations. The energy of formation is described. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Special Announcement No. 2002-216760 [License 2] Special Announcement No. 2006-261132 [License 3] Special Announcement No. 2016-91633 [License 4] International Publication No. 2011 / 077654 [Non-licensed literature]

[0011] [Non-licensed 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-licensed 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), 2009, 165114 [Non-licensed Document 3] Zhaohui Chen et al, “Staging Phase Transitions in LixCoO2”, Journal of The Electrochemical Society, 2002, 149(12) A1604-A1609 [Non-licensed Document 4] WE Counts et al, Journal of the American Ceramic Society, 1953, 36[1] 12-17. Fig.01471 [Non-licensed 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. Summary of the Invention [Problem to be solved by the invention]

[0012] One aspect of the present invention provides a positive electrode active material for a secondary battery, which has high capacity and excellent charge-discharge cycle characteristics. Another object of the present invention is to provide a method for manufacturing a positive electrode active material with high productivity. Another object of one embodiment of the present invention is to improve the charge / discharge cycle by using a semiconductor device in a secondary battery. Another object of the present invention is to provide a positive electrode active material that suppresses a decrease in capacity during charging. An object of one embodiment of the present invention is to provide a high-capacity secondary battery. An object of one embodiment of the present invention is to provide a secondary battery with excellent charge-discharge characteristics. An object of one embodiment of the present invention is to provide a secondary battery with high safety or reliability. .

[0013] Another embodiment of the present invention is a novel substance, active material particles, a power storage device, or a manufacturing method thereof. One of our goals is to provide a method for

[0014] The description of these problems does not preclude the existence of other problems. It is not necessary for one embodiment to solve all of these problems. It is possible to extract other problems from the claims. [Means for solving the problem]

[0015] One embodiment of the present invention is a CuKα1 When Rietveld analysis was performed on the pattern obtained by powder X-ray diffraction using the It has a crystal structure with the space group R-3m, and in X-ray photoelectron spectroscopy analysis, it is found that aluminum The number of atoms of is 0.2 times or less the number of cobalt atoms.

[0016] In the above configuration, the take-off angle in X-ray photoelectron spectroscopy is 40° or more and 50° or less. It is preferable.

[0017] In the above-mentioned configuration, when the particle is included and the cross section of the particle is analyzed by TEM-EDX, In this case, in the first region where the distance from the surface of the particle is 20 nm or more and 200 nm or less, In TEM-EDX analysis, the number of aluminum atoms is 0.0 of the number of cobalt atoms. The second one is 4 times or more but less than 1.6 times, and the distance from the particle surface is 1 μm or more but 3 μm or less. In the region, the number of aluminum atoms is 1 / 100 of the number of cobalt atoms in the TEM-EDX analysis. It is preferable that the number is less than 0.03 times the number.

[0018] In the above configuration, the cross section of the particle is processed by a focused ion beam processing and observation device. It is preferable that the surface is exposed to the outside.

[0019] In the above-mentioned structure, the positive electrode active material has a coating in contact with the surface of the particle, and the coating contains carbon. The number of cobalt atoms in the coating is less than 0.05 times the number of carbon atoms in the coating. It is preferable that there is.

[0020] In the above-mentioned configuration, the material contains magnesium, and in an analysis by X-ray photoelectron spectroscopy, The number of sodium atoms is preferably 0.4 to 1.5 times the number of cobalt atoms.

[0021] Alternatively, one embodiment of the present invention is a method for producing a semiconductor containing lithium, cobalt, oxygen, nickel, and aluminum. The Rietveld solution was used to calculate the pattern obtained by powder X-ray diffraction using CuKα1 radiation. When analyzed by X-ray photoelectron spectroscopy, it was found to have a crystalline structure with the space group R-3m. In this regard, aluminum is a positive electrode active material having a lower atomic number than cobalt and a higher atomic number than nickel.

[0022] In the above configuration, the take-off angle in X-ray photoelectron spectroscopy is 40° or more and 50° or less. It is preferable.

[0023] In the above-mentioned configuration, when the particle is included and the cross section of the particle is analyzed by TEM-EDX, In this case, in the first region where the distance from the surface of the particle is 20 nm or more and 200 nm or less, In TEM-EDX analysis, the number of aluminum atoms is 0.0 of the number of cobalt atoms. The second one is 4 times or more but less than 1.6 times, and the distance from the particle surface is 1 μm or more but 3 μm or less. In the region, the number of aluminum atoms is 1 / 100 of the number of cobalt atoms in the TEM-EDX analysis. It is preferable that the number is less than 0.03 times the number.

[0024] In the above configuration, in the first region, nickel is detected in the TEM-EDX analysis. The number of atoms is preferably less than 0.5 times the number of aluminum atoms.

[0025] In the above configuration, the cross section of the particle is processed by a focused ion beam processing and observation device. It is preferable that the surface is exposed to the outside.

[0026] In the above-mentioned structure, the positive electrode active material has a coating in contact with the surface of the particle, and the coating contains carbon. The number of cobalt atoms in the coating is less than 0.05 times the number of carbon atoms in the coating. It is preferable that there is.

[0027] In the above configuration, the sulfur concentration measured by glow discharge mass spectrometry is 150 ppm It is preferably m wt or more and 2000 ppm wt or less.

[0028] In the above configuration, the titanium concentration measured by glow discharge mass spectrometry is 300p It is preferably pm wt or less.

[0029] Another embodiment of the present invention is a particle aggregate having a first particle group and a second particle group. It contains lithium, cobalt, oxygen, and aluminum, and is powder X-ray diffracted using CuKα1 radiation. When Rietveld analysis was performed on the patterns obtained by folding, the space group of R-3m was The crystal structure has been confirmed to be mag- netic by elemental analysis using ICP-MS, GD-MS or atomic absorption spectroscopy. The number of atoms of nesium is Mg1, the number of atoms of cobalt is Co1, and Mg1 / Co1 is The particle size distribution of the first particle group has a first maximum peak. The particle size distribution of the second particle group has a second maximum peak, and the first maximum peak is 9 μm or less. The maximum value is at or below 25 μm, and the second maximum peak is at or above 0.1 μm and below 9 μm. The positive electrode active material has the following structure.

[0030] In the above configuration, the intensity of the maximum value of the first maximum peak is I1, and the intensity of the maximum value of the second maximum peak is I2. The intensity of the maximum value of the crack is I2, and I1 / I2 is preferably 0.01 or more and 0.6 or less. stomach.

[0031] In the above-mentioned configuration, the aggregate of particles contains magnesium, and the aggregate of particles is The number of magnesium atoms is between 0.4 and 1.5 times the number of cobalt atoms. is preferred.

[0032] In the above configuration, the particle size distribution is measured using a laser diffraction particle size distribution measuring device. It is preferable that

[0033] In the above configuration, the take-off angle in X-ray photoelectron spectroscopy is 40° or more and 50° or less. It is preferable.

[0034] Another embodiment of the present invention is a cathode including any one of the above cathode active materials and a cathode including a negative electrode. and an electrolyte, and performing one charge and one discharge, and determining a first discharge capacity from the discharge, After that, charge and discharge are alternately performed 50 times, and the second discharge capacity is calculated from the last discharge. The discharge capacity of the second secondary battery is 90% or more of the discharge capacity of the first secondary battery.

[0035] In the above configuration, charging is performed under CCCV conditions, and the CC charging current is 0.01C or less. The upper limit of CC charging is Li / Li + The standard is 4.55V or higher. The termination current of CV charging is 0.001C or more, and discharging is performed under CC conditions. The current must be between 0.05C and 2.0C, and the measurement temperature must be between 15°C and 55°C. is preferred.

[0036] Another embodiment of the present invention includes a positive electrode including any one of the above positive electrode active materials, Metallic lithium was used as the counter electrode, and the battery was charged and discharged once. Then, charge and discharge are alternately performed 50 times, and the second discharge capacity is calculated from the last discharge. The second discharge capacity is 90% or more of the first discharge capacity, and charging is performed under CCCV conditions. The CC charging current is between 0.01C and 1.0C, and the upper limit voltage of CC charging is Li / L. i + The standard is 4.55V or higher, and the CV charge end current is 0.001C or higher, and the discharge The measurement was performed under CC conditions, with the CC discharge current being between 0.05C and 2.0C. It is a secondary battery whose temperature is between 15°C and 55°C.

[0037] Alternatively, one embodiment of the present invention is a composite oxide containing lithium and cobalt and an aluminum oxide. A first step of mixing the ammonium hydroxide and the ammonium hydroxide to form a first mixture, and a second step of heating the first mixture. and a second step, wherein in the first step, the first mixture contains aluminum. The atomic ratio of aluminum to cobalt in the composite oxide is C_a:1. and C_a is 0.0005 or more and 0.02 or less.

[0038] In the above configuration, the heating temperature in the second step is 700°C or higher and 920°C or lower. It is preferable that:

[0039] Alternatively, one embodiment of the present invention is a composite oxide containing lithium and cobalt, and a magnesium oxide. A first step of mixing ammonium and fluorine to form a first mixture; a second step of heating to form a second mixture, the second mixture, aluminum, and a third step of mixing the above to form a third mixture, and a fourth step of heating the third mixture. and in the third step, the third mixture contains aluminum and the first The atomic ratio of aluminum to cobalt in the composite oxide in the step is =C_a:1, where C_a is 0.0005 or more and 0.02 or less. It is a method.

[0040] In the above configuration, the magnesium contained in the first mixture in the first step The atomic ratio of magnesium to cobalt in the composite oxide is C_m:1. It is preferable that C_m is 0.001 or more and 0.06 or less.

[0041] In the above configuration, the heating temperature in the fourth step is 700°C or higher and 920°C or lower. It is preferable that:

[0042] Alternatively, one embodiment of the present invention is a composite oxide containing lithium and cobalt, and a magnesium oxide. A first step of mixing ammonium and fluorine to form a first mixture; a second step of heating to form a second mixture, the second mixture, aluminum, and a third step of mixing nickel and the third mixture to form a third mixture; and heating the third mixture. and a fourth step of adding aluminum to the third mixture in the third step. The atomic ratio of aluminum to cobalt contained in the composite oxide in the first step is It is expressed as cobalt:C_a:1, where C_a is 0.0005 or more and 0.02 or less. The nickel contained in the third mixture in the third step and the complex acid in the first step The atomic ratio of nickel to cobalt in the compound is expressed as nickel:cobalt = C_n:1, and C_ The method for producing the positive electrode active material is such that n is 0.0005 or more and 0.02 or less.

[0043] In the above configuration, the magnesium contained in the first mixture in the first step The atomic ratio of magnesium to cobalt in the composite oxide is C_m:1. It is preferable that C_m is 0.001 or more and 0.06 or less.

[0044] In the above configuration, the heating temperature in the fourth step is 700°C or higher and 920°C or lower. It is preferable that: [Effects of the Invention]

[0045] According to one embodiment of the present invention, a positive electrode active material for a secondary battery has high capacity and excellent charge-discharge cycle characteristics. Also, a method for producing a positive electrode active material with high productivity can be provided. Furthermore, by using it in a secondary battery, it is possible to improve the capacity in the charge / discharge cycle. It is possible to provide a positive electrode active material in which the decrease in the capacity of the positive electrode is suppressed. It is also possible to provide a secondary battery with excellent charge / discharge characteristics. In addition, a novel material, an active material, can be used to provide a secondary battery having high safety and reliability. Particles, power storage devices, or methods for manufacturing the same can be provided. [Brief explanation of the drawings]

[0046] [Figure 1] 1A and 1B are diagrams illustrating an example of a cross section of a positive electrode active material according to one embodiment of the present invention. [Figure 2] 2A and 2B are diagrams illustrating an example of a cross section of a positive electrode active material according to one embodiment of the present invention. [Figure 3] FIG. 3 illustrates an example of a cross section of a positive electrode of one embodiment of the present invention. [Figure 4] FIG. 4 is a diagram illustrating the depth of charge and the crystal structure of a positive electrode active material according to one embodiment of the present invention. [Figure 5] FIG. 5 is a diagram illustrating the state of charge and the crystal structure of a conventional positive electrode active material. [Figure 6] Figure 6 shows the XRD pattern calculated from the crystal structure. [Figure 7] 7A and 7B show the calculation results of the relationship between the occupancy rate of lithium sites and energy. [Figure 8] Figure 8 shows the calculation results for the relationship between the occupancy rate of lithium sites and the c-axis. [Figure 9] FIG. 9 is a diagram showing the relationship between the occupancy rate of lithium sites and the c-axis. [Figure 10] 10A to 10C illustrate an example of a method for manufacturing a positive electrode active material of one embodiment of the present invention. [Figure 11] 11A and 11B are cross-sectional views of an active material layer in which a graphene compound is used as a conductive additive. [Figure 12] 12A and 12B illustrate an example of a secondary battery of one embodiment of the present invention. [Figure 13] 13A and 13B illustrate an example of a secondary battery of one embodiment of the present invention. [Figure 14] 14A to 14C illustrate an example of a secondary battery of one embodiment of the present invention. [Figure 15] 15A and 15B illustrate an example of a secondary battery of one embodiment of the present invention. [Figure 16]16A and 16B are diagrams illustrating a coin-type secondary battery, and Fig. 16C is a diagram illustrating the flow of electricity in the secondary battery. [Figure 17] Figures 17A and 17B are diagrams illustrating a cylindrical secondary battery, and Figures 17C and 17D are diagrams illustrating a module having a plurality of cylindrical secondary batteries. [Figure 18] 18A and 18B are diagrams illustrating an example of a secondary battery. [Figure 19] 19A to 19D are diagrams illustrating an example of a secondary battery. [Figure 20] 20A and 20B are diagrams illustrating an example of a secondary battery. [Figure 21] FIG. 21 is a diagram illustrating an example of a secondary battery. [Figure 22] 22A to 22C are diagrams illustrating a laminated secondary battery. [Figure 23] 23A and 23B are diagrams illustrating a laminated secondary battery. [Figure 24] FIG. 24 is a diagram showing the appearance of a secondary battery. [Figure 25] FIG. 25 is a diagram showing the appearance of a secondary battery. [Figure 26] 26A to 26C are diagrams for explaining a method for manufacturing a secondary battery. [Figure 27] 27A to 27E are diagrams illustrating a bendable secondary battery. [Figure 28] 28A and 28B are diagrams illustrating a bendable secondary battery. [Figure 29] 29A and 29B illustrate an example of a secondary battery and a manufacturing method thereof according to one embodiment of the present invention. [Figure 30] 30A to 30H are diagrams illustrating an example of an electronic device. [Figure 31] 31A to 31C are diagrams illustrating an example of an electronic device. [Figure 32] FIG. 32 is a diagram illustrating an example of an electronic device. [Figure 33]33A to 33C are diagrams illustrating an example of a vehicle. [Figure 34] FIG. 34 is a diagram showing the relationship between the discharge capacity retention rate and the discharge energy of a battery. [Figure 35] FIG. 35 is a diagram showing the relationship between the discharge capacity retention rate and the discharge energy of a battery. [Figure 36] FIG. 36 is a diagram showing the relationship between the discharge capacity retention rate and the discharge energy of a battery. [Figure 37] FIG. 37 is a diagram showing the relationship between the discharge capacity retention rate and the discharge energy of a battery. [Figure 38] 38A and 38B show the results of a continuous charging test of the battery. [Figure 39] FIG. 39 shows the results of XRD evaluation. [Figure 40] FIG. 40 shows the results of XRD evaluation. [Figure 41] FIG. 41 shows the evaluation results of particle size distribution. [Figure 42] FIG. 42 shows the cycle characteristics. [Figure 43] FIG. 43 shows the cycle characteristics results. [Figure 44] Figure 44 shows the evaluation results of particle size distribution. [Figure 45] FIG. 45 shows the cycle characteristics results. [Figure 46] FIG. 46 shows the evaluation results of particle size distribution. [Figure 47] FIG. 47 shows the evaluation results of particle size distribution. [Figure 48] FIG. 48 shows the cycle characteristics of the secondary battery. DETAILED DESCRIPTION OF THE INVENTION

[0047] Hereinafter, embodiments will be described with reference to the drawings. It is possible to implement the present invention in various ways without departing from the spirit and scope of the present invention. It will be readily apparent to those skilled in the art that various modifications may be made to the details of the present invention. However, the present invention should not be construed as being limited to the description of the following embodiments.

[0048] In this specification, the ordinal numbers "first," "second," and "third" refer to the constituent elements. The numbers are added to avoid confusion and do not limit the number of components. The order of the components is not limited. The element referred to as "first" in one embodiment may be used in other embodiments or in the claims. In addition, for example, the second component may be the component referred to as "second" in the specification. A component referred to as "first" in one embodiment may be used in other embodiments, or It may be omitted in the claims.

[0049] In the drawings, elements that are the same or have similar functions, elements that are made of the same material, or In some cases, the same reference numerals may be used to designate elements that are formed at the same time, and repeated explanations thereof will be omitted. It may be omitted.

[0050] In this specification, crystal planes and directions are expressed in Miller indices. In crystallography, numbers are usually marked with a superscript bar, but in this specification and other documents, due to limitations on the notation used in the application, numbers are marked with a superscript bar. Instead of putting a bar above the letter, a number may be expressed by putting a - (minus sign) before it. Also, individual orientations that indicate directions within a crystal are [ ], and collective orientations that indicate all equivalent directions are The symbols are < >, individual crystal faces are ( ), and collective faces with equivalent symmetry are {}. Each one expresses something.

[0051] In this specification, segregation refers to a phenomenon in which a solid consisting of multiple elements (e.g., A, B, C) This refers to the phenomenon in which a certain element (e.g., B) is distributed spatially non-uniformly.

[0052] In this specification, the surface layer of particles of active material or the like refers to the region from the surface to about 10 nm. The surface caused by cracks or fractures can also be called the surface. , called the inside.

[0053] In the present specification and the like, the layered rock salt type crystals of the composite oxide containing lithium and a transition metal The structure is a rock salt type ion arrangement in which cations and anions are arranged alternately, and The lithium atoms are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. It is possible for defects such as cation or anion deficiencies to exist. Strictly speaking, the layered rock salt crystal structure is a case where the lattice of the rock salt crystal is distorted. There is.

[0054] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately. It is possible for there to be a deficiency of cations or anions.

[0055] In the present specification and the like, the pseudospinel type of the composite oxide containing lithium and a transition metal The crystal structure of this is in the space group R-3m, and is not a spinel-type crystal structure, but it is a cobalt-based Ions such as magnesium ions occupy the oxygen hexacoordinated positions, and the arrangement of cations is similar to that of spinel. It refers to a crystalline structure with symmetry. The pseudospinel type crystalline structure is characterized by the absence of light elements such as lithium. The atoms may occupy the oxygen tetracoordinate positions, and in this case the ionic arrangement is similar to that of the spinel type. It has symmetry.

[0056] The pseudospinel crystal structure has random Li between layers, but the CdCl2 type It can be said that this CdCl2-type similar crystal structure is The crystal structure is shown in Fig. 1 when lithium nickel oxide is charged to a charge depth of 0.94 (Li 0.06 Ni O2), but pure lithium cobaltate or cobalt-rich layered It is known that rock salt type positive electrode active materials do not usually have this crystal structure.

[0057] Layered rock salt crystals and the anions of rock salt crystals are in a cubic close-packed structure (face-centered cubic lattice structure) ) It is assumed that the anions in pseudospinel crystals also have a cubic close-packed structure. When they contact, there exists a crystal plane where the orientation of the cubic close-packed structure formed by the anions is aligned. However, the space group of layered rock salt crystals and pseudospinel crystals is R-3m, and The space groups of the rock salt crystals are Fm-3m (the common rock salt crystal space group) and Fd-3m (the simplest Since the space group is different from that of rock salt crystals, which have a perfect symmetry, the crystal plane must be The Lahr index is different between layered rock salt crystals and pseudospinel crystals and between rock salt crystals. In the layered rock salt crystal, pseudospinel crystal, and rock salt crystal, When the orientation of the cubic close-packed structure is aligned, the crystal orientation is roughly the same. There is.

[0058] The crystal orientation of the two regions roughly coincides with each other, as can be seen from TEM (transmission electron microscope) images and STE M (scanning transmission electron microscope) image, HAADF-STEM (high angle annular dark field scanning transmission electron microscope) image This should be judged from images such as annular bright-field scanning transmission electron microscope (ABF-STEM) images. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as a basis for judgment. In TEM images, the arrangement of cations and anions is observed as repeated bright and dark lines. When the orientation of the cubic close-packed structure in the layered rock salt crystal and the rock salt crystal is aligned, the crystal The angle between the repeated bright and dark lines is 5 degrees or less, preferably 2.5 degrees or less. In addition, light elements such as oxygen and fluorine can be clearly observed in TEM images. In some cases, it may not be possible to determine the alignment of the metal elements. do.

[0059] In this specification, the theoretical capacity of the positive electrode active material is the capacity of the positive electrode active material that can be inserted and removed. The theoretical capacity of LiCoO2 is 27 4mAh / g, the theoretical capacity of LiNiO2 is 274mAh / g, the theoretical capacity of LiMn2O4 is 148mAh / g.

[0060] In this specification, the depth of charge when all intercalable and detachable lithium is intercalated is The depth of charge when all the intercalable lithium in the positive electrode active material is deintercalated is 0, and the depth of charge when all the intercalable lithium in the positive electrode active material is deintercalated is 1. Let's assume that this is the case.

[0061] In this specification, charging refers to transferring lithium ions from the positive electrode to the negative electrode in the battery. The positive electrode active material moves electrons from the negative electrode to the positive electrode in an external circuit. In this case, the process of releasing lithium ions is called charging. Also, when the charge depth is 0.74 or more, 0.9 or less, more specifically, a positive electrode active material with a charge depth of 0.8 to 0.83, This refers to the charged positive electrode active material. For example, in LiCoO2, 219 If the charge is 0.2mAh / g, the positive electrode active material is charged at a high voltage. In O2, under a 25°C environment, the charging voltage is set to 4.525V or more and 4.65V or less (opposite electrode lithium After that, the current value is 0.01C, or The positive electrode active material after constant voltage charging until the current value is about 1 / 5 to 1 / 100 of the high voltage This refers to the positive electrode active material charged with

[0062] Similarly, discharging involves transferring lithium ions from the negative electrode to the positive electrode within the battery and discharging them into the external circuit. The positive electrode active material is lithium. The insertion of ions is called discharging. The positive electrode active material is fully discharged from a high voltage charged state to 90% or more of its charge capacity. For example, in the case of LiCoO2, the charge capacity is 2 If it is 19.2mAh / g, it is charged at a high voltage, and from here it is 90% of the charge capacity. The positive electrode active material after discharging 197.3mAh / g or more is a fully discharged positive electrode active material. In addition, in the case of LiCoO2, the battery voltage is 3V or less (counter electrode lithium) in a 25°C environment. The positive electrode active material after constant current discharge until it becomes Let's assume that this is the case.

[0063] In this specification, a non-equilibrium phase change refers to a phenomenon that causes a non-linear change in a physical quantity. For example, the capacitance (Q) can be obtained by differentiating it with respect to the voltage (V) (dQ / dV). A non-equilibrium phase change occurs before and after the peak in the dQ / dV curve, and the crystal structure changes significantly. It is believed that this is the case.

[0064] (Embodiment 1) In this embodiment, a positive electrode active material and the like according to one embodiment of the present invention will be described.

[0065] [Cathode active material] By increasing the charging voltage of the secondary battery, the discharge capacity can be increased. When the active material has a crystalline structure, the crystalline structure may change when the charging voltage is increased. There is a match.

[0066] If the change in crystal structure caused by charging is irreversible, the positive electrode active material will deteriorate due to repeated charging and discharging. There is a concern that the crystalline structure of the battery will be destroyed and the discharge capacity will decrease.

[0067] As the charging voltage of the secondary battery increases, the voltage of the positive electrode generally increases. The positive electrode active material has a stable crystal structure even at high voltages. The stable crystal structure helps prevent the capacity from decreasing with repeated charging and discharging. can.

[0068] In addition, a short circuit in the secondary battery can cause problems with the charging and discharging operations of the secondary battery. Not only this, but it may also lead to heat generation and fire. It is preferable that the short circuit current is suppressed even at a high charging voltage. The electrode active material suppresses short circuit current even at high charging voltages, providing high capacity and safety. Both can be achieved.

[0069] A secondary battery using the positive electrode active material of one embodiment of the present invention has high capacity and excellent charge-discharge cycle characteristics. It is preferable to simultaneously satisfy both the requirements for efficiency and safety.

[0070] Lithium cobalt oxide, Lithium nickel-cobalt-manganese oxide, Nickel-cobalt -Positive electrode active materials with layered structures, such as lithium aluminate, are used in secondary batteries. The amount of lithium per volume and weight of the positive electrode active material that is inserted and removed during charging and discharging is Therefore, secondary batteries using these positive electrode active materials have the advantage of high capacity. There is.

[0071] On the other hand, the layered structure of the positive electrode active material is gradually converted into carrier ions as the charging voltage increases. More specifically, when lithium is released, the lattice constant changes. Or, the layers may become misaligned, and the crystal structure may easily collapse. When a metal is located between layers, the lattice constant changes in the direction perpendicular to the layers due to the desorption of the metal. may occur significantly.

[0072] The positive electrode active material of one embodiment of the present invention comprises a first metal (hereinafter, metal A), a second metal (hereinafter, gold In addition to metal M and oxygen, it is preferred that the metal A contains magnesium. Metal M is one or more metals that are involved in the redox reaction. The inventors have also applied the positive electrode active material containing magnesium. Adding aluminum increases the secondary resistance at higher voltages compared to adding other elements. It was found that short circuits in the battery were suppressed.

[0073] While preventing short circuits is desirable from a safety perspective, it also reduces the discharge capacity. For example, aluminum is effective in suppressing short circuit current, but If the concentration is too high, there is a concern that the capacity may decrease. and aluminum, by further adding nickel, Compared to the case where other elements are added, the decrease in discharge capacity of the secondary battery is more effectively suppressed. I found that...

[0074] When the positive electrode active material according to one embodiment of the present invention has particles, the particles may contain magnesium. It is preferable that the sodium, aluminum and nickel each have a concentration gradient. For example, it is preferable that the concentration near the surface is high. The concentration of nickel in the particles can be higher than that of nickel. Compared to the surface, the concentration gradient of magnesium and aluminum is biased toward the surface, resulting in a steeper profile. may have a profile.

[0075] Here, a high charging voltage is, for example, 4.55V (vs Li / Li + ) More preferable Approximately 4.6V (vs Li / Li + ) or more, more preferably 4.65V (vs Li / Li + )That's all.

[0076] Metal A is, for example, an alkali metal such as lithium, sodium, or potassium, or calcium. The metal A can be lithium, beryllium, magnesium, or other group 2 elements. The metal M is preferably selected from the group consisting of cobalt, manganese, and iron. It is preferable that the metal M contains cobalt. The metal M may be one or more selected from nickel and manganese.

[0077] The positive electrode active material may have a crystalline structure such as a layered rock salt crystalline structure or a spinel crystalline structure. Among these, the positive electrode active material of one embodiment of the present invention has a crystal structure of olivine type. The crystal structure of the layered rock salt type is preferably a layered rock salt type. It may be expressed as the intermediate group R-3m.

[0078] Consider a case where a positive electrode active material 100 has particles 101. The particles 101 are made of metal A, metal M, and and oxygen. Preferably, the particles 101 contain magnesium and aluminum. In the particle 101, magnesium and aluminum preferably have a concentration gradient. For example, it is preferable that the concentration near the surface of the particle 101 is high. It is preferable that the concentration of the surface layer is high.

[0079] For example, in particle 101, magnesium and aluminum are measured by XPS etc. The concentration of the compounds was measured by ICP-MS (inductively coupled plasma mass spectrometry) or GD-MS (glow discharge mass spectrometry). It is preferable that the concentration is higher than the concentration measured by electron transport mass spectrometry or the like.

[0080] For example, in the particle 101, magnesium and aluminum are processed to When the cross section is exposed and analyzed using TEM-EDX, the concentration of the surface layer is It is preferable that the concentration is higher than that of the region deeper than the surface. can be done.

[0081] The particles 101 preferably contain nickel. In the particles 101, nickel has a concentration It is preferable to have a gradient, and for example, the concentration near the surface of the particle 101 may be high. Alternatively, the concentration may be high in the surface layer of the particle 101.

[0082] For example, in particle 101, the concentration of nickel is higher by ICP than by XPS or the like. In some cases, the concentrations measured by HCl-MS or GD-MS may be higher.

[0083] For example, in the particle 101, the nickel is processed to expose its cross section, and the cross section is T When analyzing using EM-EDX, the concentration in the surface layer is higher than the concentration in the deeper region. In some cases, the cost may be too high.

[0084] The magnesium, aluminum, and nickel contained in the positive electrode active material 100 are, for example, Some of the particles may not be incorporated into the crystal structure. For example, the positive electrode active material 100 has a crystalline structure containing a metal A, a metal M, and oxygen, and the crystalline In the structure, some of the elements contained in the crystal structure are magnesium, aluminum, and nickel. Alternatively, magnesium, or magnesium is present between the lattices of the crystal structure. One or more of aluminum and nickel may be present.

[0085] The magnesium, aluminum, and nickel contained in the positive electrode active material 100 are partially in the crystal structure. The positive electrode active material 100 may not be incorporated into the structure. The particles 102 may have one or more of aluminum and nickel as the main component. For example, particle 102 may contact the surface of particle 101 .

[0086] The particles 102 are, for example, at least one of magnesium, aluminum, and nickel. The concentration of one metal is higher than the concentration of the second metal.

[0087] FIG. 1A shows an example of a cross section of a particle 101 contained in a positive electrode active material 100. The particle 101 has the following structure: It has an area 111 and an area 112.

[0088] As shown in FIG. 1B, the distance x1 from the surface of the particle 101 to the region 111 is is smaller than the distance x2 from the surface of the region 112 to the region 112.

[0089] For example, the distance from the particle surface is calculated by taking the distance perpendicular to the tangent of the cross-sectional surface of the particle. Alternatively, a line can be drawn from the surface of the particle cross section to the center of the particle cross section or the center of gravity. The distance in the selected direction can be used.

[0090] FIG. 2A shows an example in which distances in a different direction from those in FIG. 1B are used.

[0091] When a secondary battery has a positive electrode, a negative electrode, and an electrolyte, the secondary battery is charged and discharged by electrolysis. The liquid decomposes, and the decomposition products are converted into the components of the electrode, such as the particles 101 and particles of the active material. A coating 103 may be deposited on the surface of particle 102. FIG. An example of deposition of 3 is shown below.

[0092] Fig. 3 shows an example of a cross section of a positive electrode. An example in which an active material layer 109 is formed on a current collector 108 is shown. This will be explained in more detail later.

[0093] When the number of cobalt atoms in the positive electrode active material 100 is 1, the number of magnesium atoms is The relative value is preferably, for example, 0.001 or more and 0.06 or less, and 0.003 or more and 0.03 or less. It is more preferable. When the number of cobalt atoms is 1, the relative value of the number of aluminum atoms is For example, 0.0005 or more and 0.02 or less is preferable, and 0.001 or more and 0.015 or less is more preferable. The number of cobalt atoms is preferably 0.001 or more and 0.009 or less, and more preferably 0.001 or more and 0.009 or less. In this case, the relative value of the number of nickel atoms is preferably, for example, 0.0005 or more and 0.02 or less, and 0. More preferably, the ratio is 0.001 or more and 0.015 or less, and even more preferably, the ratio is 0.001 or more and 0.009 or less. The number of cobalt atoms, the number of magnesium atoms, the number of aluminum atoms, and the number of nickel atoms The number of atoms can be evaluated, for example, by ICP-MS.

[0094] The particle size distribution of the positive electrode active material 100 has a maximum peak in the range of 9 μm or more and 25 μm or less. Alternatively, in the particle size distribution of the positive electrode active material according to one embodiment of the present invention, it is preferable that the average particle size is The diameter (D50) is preferably 9 μm or more and 25 μm or less.

[0095] The particle diameter of the particles of the positive electrode active material 100 can be determined by, for example, surface observation using an SEM or by TEM. The particle size of the particles of the positive electrode active material 100 can be evaluated by cross-sectional observation, etc. The particle size distribution of the positive electrode active material 100 can be evaluated by, for example, laser diffraction. The measurement can be performed using a folding particle size distribution measuring device or the like.

[0096] In addition, when the maximum peak of the particle size distribution of the positive electrode active material 100 is 9 μm or more and 25 μm or less, When the number of cobalt atoms in the positive electrode active material 100 is 1, the number of magnesium atoms is The relative value of is preferably, for example, 0.001 or more and 0.06 or less, and more preferably 0.003 or more and 0.03 or less. The number of cobalt atoms is more preferably 0.007 or more and 0.025 or less. The number of atoms of magnesium and arsenic can be evaluated by, for example, ICP-MS.

[0097] The positive electrode active material 100 preferably contains a halogen such as fluorine.

[0098] In the positive electrode active material 100, the number of titanium atoms is, for example, 300 ppm wt or less.

[0099] The positive electrode active material 100 has sulfur of 150 ppm wt or more and 2000 ppm wt or less. This may be the case.

[0100] The number of titanium atoms and the number of sulfur atoms in the positive electrode active material 100 are measured by, for example, GD-MS. It can be determined.

[0101] The positive electrode active material 100 is preferably an aggregate of a plurality of particle groups having different particle size distributions. For details of each particle, see, for example, the description of particle 101 and particle 102 described above. It is possible.

[0102] When the positive electrode active material 100 is an aggregate of a plurality of particle groups having different particle size distributions, the particle size distribution is It is preferable that the first maximum peak and the second maximum peak are present. The value is preferably, for example, 9 μm or more and 25 μm or less. Preferably, the thickness is 0.1 μm or more and less than 9 μm. and a second particle group, and in the particle size distribution of the first particle group, the average particle diameter ( D50) is preferably 9 μm or more and 25 μm or less, and in the particle size distribution of the second particle group, In this case, the average particle size (D50) is preferably 0.1 μm or more and less than 9 μm.

[0103] If the first and second maximum peaks overlap, the peaks are separated using a function. Separation may be performed and the intensity and half width of each peak may be analyzed.

[0104] The positive electrode active material 100 has a plurality of particle groups with different particle size distributions, 00 may increase the density of the positive electrode active material layer. This allows the amount of active material per volume of the secondary battery to be increased. On the other hand, if the density of the positive electrode active material is high, However, there is a concern that the electrolyte may not easily penetrate between the particles of the active material layer. However, there is a concern that the output characteristics of the secondary battery may be reduced.

[0105] The positive electrode active material of one embodiment of the present invention is stable even at a high charging voltage, and therefore, the charging capacity can be increased. As a result, the discharge capacity of the secondary battery can be increased. When the capacity per volume of the secondary battery is sufficiently high without excessively increasing the density of the positive electrode active material There is.

[0106] In addition, in the positive electrode active material layer, materials other than the positive electrode active material, such as a conductive additive, a binder, etc. By reducing the proportion, the density of the positive electrode active material layer can be increased.

[0107] The thickness of the positive electrode active material layer is, for example, 10 μm or more and 200 μm or less. The amount of the positive electrode active material layer is, for example, 100 μm or more and 150 μm or less. In the case of a material having a layered rock salt crystal structure, 2 More than 50mg / cm 2 or less than 5 mg / cm 2 More than 30mg / cm 2 The positive electrode active The density of the material layer is, for example, a material having a layered rock salt crystal structure containing cobalt as the positive electrode active material. 2.2 g / cm 3 More than 4.9g / cm 3 or less. Or 3.8 g / cm3 More than 4.5g / cm 3 Here, the amount of support is, for example, the positive electrode This is the value for the active material layer.

[0108] <xps> X-ray photoelectron spectroscopy (XPS) measures the surface to a depth of approximately 2 to 8 nm (usually approximately 5 nm). Since it is possible to analyze the area up to the surface, the concentration of each element can be determined for about half of the surface area. It is possible to quantitatively analyze the element bonding state by narrow scan analysis. The quantitative accuracy of XPS is usually about ±1 atomic %, and the lower limit of detection is The concentration in XPS is measured in atomic percent, for example.

[0109] When the positive electrode active material 100 has a first particle group and a second particle group, The number of magnesium atoms is higher than the number of magnesium atoms in the second particle group. There is.

[0110] The positive electrode active material 100 was subjected to elemental analysis by ICP-MS, GD-MS or atomic absorption. When the number of cobalt atoms (Co1) is 1, the number of magnesium atoms (Mg1) is The relative value is preferably 0.4 or more and 1.5 or less, and more preferably 0.5 or more and 1.1 or less. The Mg1 / Co1 ratio is preferably 0.001 or more and 0.06 or less.

[0111] The relative value of the number of atoms of halogen such as fluorine is preferably 0.05 or more and 1.5 or less, and more preferably 0.3 More preferably, it is 1.00 or less.

[0112] In addition, when the positive electrode active material 100 was analyzed by XPS, the bond energy between fluorine and other elements was The peak showing the energy is preferably 682 eV or more and less than 685 eV, and more preferably 684.8 e It is more preferable that the bond energy is about 500 V, which is the bond energy of magnesium fluoride. That is, when the positive electrode active material 100 contains fluorine, the fluorine Bonds other than magnesium fluoride are preferred.

[0113] Furthermore, when the positive electrode active material 100 was analyzed by XPS, the bonds between magnesium and other elements were The peak showing the combined energy is preferably 1302 eV or more and less than 1304 eV. More preferably, it is about 1303 eV. This is because the bond energy of magnesium fluoride is This is a different value from the 1305 eV, which is the binding energy of magnesium oxide. In other words, when the positive electrode active material 100 contains magnesium, magnesium fluoride Preferably, the bond is other than .

[0114] The number of aluminum atoms evaluated by XPS in the positive electrode active material 100 is In addition, the positive electrode active material 100 was detected by XPS. When the number of cobalt atoms is 1, the relative value of the number of aluminum atoms is, for example, 0.2. Nickel is heat treated in the manufacturing method described later. After that, they may not be detected by XPS.

[0115] In addition, in the positive electrode active material of one embodiment of the present invention, by performing the manufacturing method described below, In some cases, the number of bonds containing carbonate may be reduced compared to the composite oxide used in Step S24.

[0116] <edx> Among EDX measurements, the measurement is performed while scanning the area, and the area is evaluated two-dimensionally. It is sometimes called DX area analysis. Also, data on linear areas is extracted from EDX area analysis, Evaluating the distribution of atomic concentrations within positive electrode active material particles is sometimes called line analysis.

[0117] EDX surface analysis (e.g., elemental mapping) revealed that the The concentrations of magnesium and fluorine can be quantitatively analyzed. Line analysis allows for the analysis of magnesium and fluorine concentration peaks. The concentration of X is expressed in atomic percent, for example.

[0118] When EDX analysis was performed on the particles 101 contained in the positive electrode active material 100, In the first region, which is 20 nm or more and 200 nm or less from the surface, EDX analysis The number of aluminum atoms is preferably 0.04 times or more and less than 1.6 times the number of cobalt atoms. In addition, in the second region where the distance from the surface of the particle 101 is 1 μm or more and 3 μm or less, EDX analysis shows that the number of aluminum atoms is less than 0.03 times the number of cobalt atoms. preferable.

[0119] A more specific method of EDX analysis is to use FIB to process and expose the cross section of the particle. An example of such a method is to extract the SiO2 and analyze it by TEM-EDX analysis.

[0120] [Example of the structure of the positive electrode active material] The positive electrode active material will be described with reference to Figs. 4 and 5. The case where cobalt is used as the transition metal in the substance will be described.

[0121] The positive electrode active material shown in FIG. 5 is prepared by the method described below, to which halogen and magnesium are added. The lithium cobalt oxide shown in Figure 5 is lithium cobalt oxide (LiCoO2). As described in Non-Patent Documents 1 and 2, the crystal structure changes depending on the charge depth. changes.

[0122] As shown in Figure 5, lithium cobalt oxide at a charge depth of 0 (discharged state) is in the 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 an O3 type crystal structure. The term "octahedral structure" refers to a structure in which six oxygen atoms are coordinated to form a single octahedron, which is connected to the plane by edge-sharing. .

[0123] At a charge depth of 1, the crystal structure has the space group P-3m1, and there is Co in the unit cell. There is one O2 layer, so this crystal structure is sometimes called an O1-type crystal structure.

[0124] In addition, when the charge depth is about 0.88, lithium cobalt oxide has a crystal structure of the space group R-3m. This structure is similar to the structure of CoO2, such as P-3m1(O1), and R-3m(O 3) and the structure of LiCoO2, and the structure of The crystal structure is sometimes called the H1-3 type crystal structure. has twice the number of cobalt atoms per unit cell as the other structures. In this specification, the c-axis of the H1-3 type crystal structure is used as a unit to facilitate comparison with other structures. This will be shown in a diagram of half the size of a knit cell.

[0125] As an example, the H1-3 type crystal structure has a unit cell as described in Non-Patent Document 3. The coordinates of cobalt and oxygen in 1(0, 0, 0.27671±0.00045), O2(0, 0, 0.11535±0. 00045), where O1 and O2 are oxygen atoms. The H1-3 crystal structure is formed by a unit cell with one cobalt and two oxygen atoms. On the other hand, as will be described later, the pseudospinel crystal structure of one embodiment of the present invention is preferably is represented by a unit cell with one cobalt and one oxygen. The symmetry between cobalt and oxygen is different between the spinel structure and the H1-3 structure. The pseudospinel structure is less different from the O3 structure than the H1-3 type structure. It is more preferable to use any one of the unit cells to represent the crystal structure of the positive electrode active material. For example, the selection of GOF (good of field) in Rietveld analysis of XRD is fitness) should be selected to be smaller.

[0126] High-voltage charging where the charging voltage is 4.6V or higher based on the oxidation-reduction potential of lithium metal When the battery is repeatedly charged or discharged to a deep depth of charge of 0.8 or more, Lithium cobalt oxide has a H1-3 type crystal structure and a R-3m(O3) structure in the discharged state. The crystal structure changes (i.e., non-equilibrium phase changes) between these two states.

[0127] However, these two crystal structures have a large misalignment of the CoO2 layers. As shown by the arrows and the lines, in the H1-3 type crystal structure, the CoO2 layer is larger than the R-3m(O3) layer. Such dynamic structural changes have a negative effect on the stability of the crystal structure. Yes.

[0128] Furthermore, the difference in volume is large. When comparing the same number of cobalt atoms, the H1-3 type crystal The difference in volume between the structure and the O3-type crystal structure in the discharged state is more than 3.0%.

[0129] In addition, the H1-3 type crystal structure has continuous CoO2 layers such as P-3m1(O1). The resulting structure is likely to be unstable.

[0130] Therefore, repeated high-voltage charging and discharging causes the crystal structure of lithium cobalt oxide to collapse. The breakdown of the crystal structure causes a deterioration in cycle characteristics. , the number of sites where lithium can exist stably decreases, and lithium insertion and desorption becomes difficult. This is thought to be the reason.

[0131] In the positive electrode active material of one embodiment of the present invention, the CoO2 layer is displaced during repeated high-voltage charge and discharge. Furthermore, the change in volume can be reduced. The positive electrode active material of one embodiment of the present invention can achieve excellent cycle characteristics. The positive electrode active material according to one embodiment of the present invention can have a stable crystal structure in a charged state at a high voltage. Therefore, the positive electrode active material of one embodiment of the present invention has a short circuit resistance when maintained in a charged state at a high voltage. In such cases, safety is improved, making it preferable. .

[0132] The positive electrode active material of one embodiment of the present invention has a sufficient discharge state and a high voltage charged state. The change in the crystal structure and the difference in volume when compared per the same number of transition metal atoms in small.

[0133] FIG. 4 shows an example of the crystal structure of the positive electrode active material 100 before and after charge and discharge.

[0134] The crystal structure at charge depth 0 (discharged state) in Figure 4 is the same as that in Figure 5, R-3m(O3). On the other hand, when the positive electrode active material 100 is fully charged, it has a crystal structure different from the H1-3 type. This structure is in the space group R-3m, and is not a spinel-type crystal structure. However, ions such as cobalt and magnesium occupy the oxygen hexacoordinate positions, and the arrangement of cations has a symmetry similar to that of the spinel type. Therefore, this structure is referred to as a pseudo-spinel type crystal in this specification. In the diagram of the pseudospinel crystal structure shown in Figure 4, the cobalt atoms The lithium atom is omitted to illustrate the symmetry of the electrons and the symmetry of the oxygen atoms. However, in reality, there is lithium between the CoO2 layers, for example, at a ratio of 20 atomic % or less to cobalt. In addition, in both the O3 type crystal structure and the pseudospinel type crystal structure, the CoO2 layer It is preferable that magnesium is present in a dilute state between the two, i.e., at the lithium site. It is preferable that halogen such as fluorine is present randomly and dilutely at the oxygen sites.

[0135] In addition, in the pseudospinel crystal structure, light elements such as lithium occupy the four oxygen coordination positions. In this case, the ion arrangement also has a symmetry similar to that of the spinel type.

[0136] The pseudospinel crystal structure has random Li between layers, but the CdCl2 type It can be said that this CdCl2-type similar crystal structure is The crystal structure is shown in Fig. 1 when lithium nickel oxide is charged to a charge depth of 0.94 (Li 0.06 Ni O2), but pure lithium cobaltate or cobalt-rich layered It is known that rock salt type positive electrode active materials do not usually have this crystal structure.

[0137] Layered rock salt crystals and the anions of rock salt crystals are in a cubic close-packed structure (face-centered cubic lattice structure) ) It is assumed that the anions in pseudospinel crystals also have a cubic close-packed structure. When they contact, there exists a crystal plane where the orientation of the cubic close-packed structure formed by the anions is aligned. However, the space group of layered rock salt crystals and pseudospinel crystals is R-3m, and The space groups of the rock salt crystals are Fm-3m (the common rock salt crystal space group) and Fd-3m (the simplest Since the space group is different from that of rock salt crystals, which have a perfect symmetry, the crystal plane must be The Lahr index is different between layered rock salt crystals and pseudospinel crystals and between rock salt crystals. In the layered rock salt crystal, pseudospinel crystal, and rock salt crystal, When the orientation of the cubic close-packed structure is aligned, the crystal orientation is roughly the same. There is.

[0138] In the positive electrode active material 100, when a large amount of lithium is released by charging at a high voltage, the crystal structure The change is suppressed more than that of the conventional positive electrode active material. For example, as shown by the dotted line in Figure 4, These crystal structures have almost no misalignment of the CoO2 layers.

[0139] More specifically, the positive electrode active material 100 has a stable structure even when the charging voltage is high. For example, in the conventional positive electrode active material shown in Figure 5, the charging voltage is For example, even at a voltage of about 4.6 V based on the potential of lithium metal, R-3m(O 3) There exists a region of charging voltage where the crystal structure of For example, the pseudo-stable state is observed even at a voltage of about 4.65 V to 4.7 V based on the potential of lithium metal. There is a region where the pinel type crystal structure can be formed. In some cases, 1-3 type crystals are observed. When graphite is used, for example, even when the voltage of the secondary battery is between 4.3V and 4.5V, R There is a region of charging voltage where the crystal structure of -3m(O3) can be maintained, and if the charging voltage is further increased, For example, in the region between 4.35V and 4.55V based on the potential of lithium metal There is a region in which the pseudospinel type crystal structure can be formed.

[0140] Therefore, the crystalline structure of the positive electrode active material 100 does not collapse even when it is repeatedly charged and discharged at a high voltage. It is difficult to get rid of.

[0141] The pseudospinel crystal structure has the coordinates of cobalt and oxygen in the unit cell as follows: Co (0,0,0.5), O(0,0,x), 0.20≦x≦0.25 can.

[0142] Magnesium exists randomly and dilutely between the CoO2 layers, i.e., at the lithium sites. This has the effect of suppressing the displacement of the CoO2 layers. Therefore, magnesium is a positive electrode active material 100% It is preferable that magnesium is distributed throughout the particles. Therefore, it is preferable to perform heat treatment in the process of manufacturing the positive electrode active material 100.

[0143] However, if the heat treatment temperature is too high, cation mixing occurs and magnesium When magnesium is present in the cobalt site, If the temperature of the heat treatment is too high, the effect of maintaining the structure of R-3m will be lost. However, there are concerns about adverse effects such as cobalt being reduced to a divalent state and lithium evaporating. can be.

[0144] Therefore, before the heat treatment to distribute magnesium throughout the particles, cobalt oxide It is preferable to add a halogen compound such as a fluorine compound to lithium. Adding substances to lithium cobalt oxide lowers its melting point. At a temperature where on-mixing is unlikely to occur, it is easy to distribute magnesium throughout the particles. Furthermore, if a fluorine compound is present, the electrolyte will have corrosion resistance to the hydrofluoric acid produced by decomposition. can be expected to improve.

[0145] If the magnesium concentration is increased above a desired value, the effect on stabilizing the crystal structure is reduced. In addition to the lithium site, magnesium may also be present at the cobalt site. This is thought to be because it will also be included in the

[0146] <Charging method> In order to determine whether a certain composite oxide is the positive electrode active material 100 of one embodiment of the present invention, High voltage charging is performed using a coin cell (CR2032 type, 20mm diameter, high) with a lithium counter electrode. It is possible to create a battery (thickness 3.2mm) and charge it.

[0147] More specifically, the positive electrode is formed by mixing a positive electrode active material, a conductive additive, and a binder in a slurry. The above may be applied to a positive electrode current collector made of aluminum foil and used.

[0148] Lithium metal can be used for the counter electrode. When the secondary battery is in a charged state, the potential of the secondary battery is different from the potential of the positive electrode. is the potential of the positive electrode unless otherwise specified.

[0149] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). EC:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. The above can be used.

[0150] The separator can be made of polypropylene with a thickness of 25 μm.

[0151] The positive and negative electrode cans can be made of stainless steel (SUS). Cut.

[0152] The coin cell prepared under the above conditions was charged at a constant current of 4.6 V and 0.5 C, and then the current value The battery is charged at a constant voltage until the temperature reaches 0.01C. Here, 1C is 137mA / g. After charging in this way, place the coin cell in a glow By disassembling it in the box and removing the positive electrode, the positive electrode active material charged at high voltage can be obtained. When various analyses are carried out after this, the container is sealed in an argon atmosphere to prevent reactions with external components. For example, XRD can be performed in a sealed container in an argon atmosphere. can.

[0153] <xrd> CuKα1 calculated from the pseudospinel crystal structure and H1-3 crystal structure model An ideal powder XRD pattern using the line is shown in Figure 6. For comparison, the LiC at a charge depth of 0 The ideal X calculated from the crystal structure of oO2(O3) and CoO2(O1) at charge depth 1 The RD patterns are also shown. The patterns of LiCoO2(O3) and CoO2(O1) are ICSD(Inorganic Crystal Structure Database) e) (see Non-Patent Document 5) Reflex Powder Dif, one of the modules of io (BIOVIA) The 2θ range was from 15° to 75°, and Step s ize=0.01, wavelength λ1=1.540562×10 -10 m, λ2 are not set, Mo The nochromator was single. The H1-3 type crystal structure pattern is non-patentable. It was similarly created from the crystal structure information described in Reference 3. The pseudospinel crystal structure pattern is The crystal structure of the positive electrode active material according to one embodiment of the present invention was estimated from the XRD pattern, and the TOPAS ve r.3 (crystal structure analysis software manufactured by Bruker) was used for fitting and comparison with other Similarly, XRD patterns were generated.

[0154] As shown in Figure 6, in the pseudospinel crystal structure, 2θ = 19.30 ± 0.20° (1 9.10° to 19.50°), and 2θ = 45.55 ± 0.10° (45.45 Diffraction peaks appear at 2θ = 19. 30±0.10° (19.20° or more and 19.40° or less), and 2θ=45.55±0 A sharp diffraction peak appears at 0.05° (45.50° to 45.60°). No peaks appear at these positions in the 1-3 type crystal structure and CoO2 (P-3m1, O1). Therefore, when charged at high voltage, 2θ=19.30±0.20° and 2 The appearance of a peak at θ=45.55±0.10° indicates that the positive electrode active material 1 according to one embodiment of the present invention This can be said to be a characteristic of 00.

[0155] This shows the crystal structure at charge depth 0 and the crystal structure when charged at high voltage, and the diffraction peaks of the XRD More specifically, the positions where the main diffraction peaks of both are close to each other. The difference in the positions at which peaks appear is 2θ = 0.7 or less, and more preferably 2θ = 0.5 or less.

[0156] The positive electrode active material 100 according to one embodiment of the present invention is a pseudospinel crystal when charged at a high voltage. However, not all of the particles need to have a pseudospinel crystal structure. However, the XRD pattern may be When Rietveld analysis was performed, it was found that the pseudospinel crystal structure was 50 wt% or more. It is preferable that the content is 60 wt% or more, more preferable that the content is 66 wt% or more. It is preferable that the pseudo-spinel type crystal structure is 50 wt% or more, more preferably 60 wt% or more. More preferably, if the content is 66 wt % or more, the positive electrode active material will have sufficiently excellent cycle characteristics. It is possible.

[0157] In addition, even after more than 100 charge / discharge cycles from the start of measurement, Rietveld analysis was performed. Preferably, the pseudo-spinel crystal structure is 35 wt% or more, more preferably 40 wt% or more, and even more preferably 43 wt% or more.

[0158] In addition, the crystallite size of the pseudo-spinel crystal structure of the positive electrode active material particles only decreases to about 1 / 10 of that of LiCoO2(O3) in the discharged state. Therefore, even under the same XRD measurement conditions as those of the positive electrode before charge and discharge, a clear peak of the pseudo-spinel crystal structure can be confirmed after high-voltage charging. On the other hand, in the case of simple LiCoO2, even if a part has a structure similar to the pseudo-spinel crystal structure, the crystallite size becomes small and the peak becomes broad and small. The crystallite size can be determined from the half-value width of the XRD peak.

[0159] <dQ / dV vs V curve> In addition, when the positive electrode active material according to one aspect of the present invention is discharged at a low rate of, for example, 0.2C or less after charging at a high voltage, a characteristic voltage change may appear near the end of discharge. This change can be clearly confirmed by the presence of at least one peak in the range of 3.5V to 3.9V in the dQ / dV vs V curve obtained from the discharge curve.

[0160] [First-principles calculation] Next, in the positive electrode active material according to one aspect of the present invention, the change in the stability of the crystal structure due to the addition of magnesium was estimated by first-principles calculation.

[0161] In the above-mentioned O3-type crystal structure and H1-3-type crystal structure, the change in energy when lithium is desorbed was calculated using first-principles calculation. Also, for each crystal In the structure, when 2% of the lithium on the lithium site is replaced with magnesium was also calculated.

[0162] The lattice and atomic positions were optimized using first-principles calculations, and the energy was calculated. VASP (The Vienna Ab initio simulation software) n package was used. LDA (Local Density Approximation) was used as the functional. density approximation)) + U was used. U potential of cobalt The electron state pseudopotential is PAW (Projector Au The potential generated by the Modified Wave method was used. The energy was set to 600 eV. The k-points were sampled using a 1 × 1 × 1 mesh. For details about the U potential, see Non-Patent Documents 6 and 7. .

[0163] The number of atoms used in the calculation is (48-x) lithium atoms without magnesium addition, Cobalt is 48, oxygen is 96, and when magnesium is added, lithium is (47- x), 1 magnesium, 48 cobalt, and 96 oxygen. x is the atom that has been eliminated. is the number of lithium atoms.

[0164] In this specification, the energy obtained in this manner is referred to as stabilization energy. There is.

[0165] x lithium atoms are removed from a crystal structure model in which one magnesium atom is substituted at the lithium site The energy difference ΔE of the crystal structure model can be calculated using the following formula 1. .

[0166]

number

[0167] Here, E total (Li 47 Mg1Co 48 O 96 ) is Li 48 Co 48 O 96 Rich The energy of the structure in which one Mg atom is substituted for another Mg atom, E total (Li 47-x Mg1C o 48 O 96 ) is Li 48 Co 48 O 96 One lithium atom is replaced with Mg, and Energy of the structure with x atoms removed, E atom (Li) is the energy of one lithium atom Lugie, E. atom (Co) is the energy of one cobalt atom, E atom (Mg) is Ma The energy of one magnesium atom is also calculated by the formula 1 above. This is a crystal structure model in which lithium atoms are replaced with magnesium atoms. The same calculations were performed for the model without the

[0168] The calculation results are shown in Figures 7 and 8.

[0169] In FIG. 7A, the horizontal axis represents the occupancy rate of the lithium site, and the vertical axis represents the energy difference ΔE. The energy difference ΔE is 6 eV when the occupancy rate of the lithium site is 0%, as shown by the dashed line in Figure 7A. The difference between the calculated result and the straight line that represents the positive The lithium in the electrode active material is released. By calculating the energy, we can consider the state in which lithium is released by charging. .

[0170] As shown in Figures 7A and 7B, the energy difference As can be seen from Figure 7B, the O3 type crystal structure It is suggested that the energy of the H1-3 crystal structure intersects with that of the H1-3 crystal structure, and a phase change occurs at this intersection. In the structure with one magnesium atom substituted, the O3 type crystal structure and the H1-3 type crystal structure are The occupancy of the lithium sites where the intersection of the structures is observed is different from that of the structure without magnesium substitution. This means that more lithium can be released without a phase change occurring. This suggests that...

[0171] From the calculation results shown in Figures 7A and 7B, it can be seen that adding magnesium increases the charging efficiency. This means that the charging of the positive electrode active material at a given voltage becomes stable.

[0172] In Fig. 8, the horizontal axis represents the occupancy rate of the lithium site, and the vertical axis represents the lattice constant of the c-axis. As the occupancy rate of SiO_2 decreased, the lattice constant of the c-axis increased and then decreased.

[0173] FIG. 9 shows the c-axis values ​​calculated from the measured values ​​of XRD for the positive electrode active material of one embodiment of the present invention. The relationship between the occupancy rate of the lithium site and the theoretical capacity of lithium cobalt oxide is shown here. The energy density was set at 4mAh / g. Figure 9 shows that the phenomenon matches the calculated results.

[0174] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0175] (Embodiment 2) In this embodiment, an example of a method for manufacturing a positive electrode active material of one embodiment of the present invention will be described.

[0176] [Example of a method for producing a positive electrode active material] Next, an example of a method for manufacturing a positive electrode active material of one embodiment of the present invention will be described with reference to FIG. do.

[0177] <Step S11> In step S11, first, a halogen source such as a fluorine source or a chlorine source, which is a material for the mixture 902, is selected. In addition, a lithium source may be provided.

[0178] As the fluorine source, for example, lithium fluoride, magnesium fluoride, etc. can be used. Among these, lithium fluoride has a relatively low melting point of 848°C, and the annealing process described below It is preferable because it is easily melted. Examples of the chlorine source include lithium chloride, magnesium chloride, etc. Examples of magnesium sources that can be used include magnesium fluoride and magnesium oxide. The lithium source may be cadmium, magnesium hydroxide, magnesium carbonate, etc. For example, lithium fluoride and lithium carbonate can be used as the catalyst. Lithium can be used as both a lithium source and a fluorine source. Sium can be used as both a fluorine source and a magnesium source.

[0179] In this embodiment, lithium fluoride (LiF) is prepared as a fluorine source. Magnesium fluoride (MgF2) will be prepared as the magnesium source. Lithium fluoride LiF and magnesium fluoride MgF2 are LiF:MgF2 = 65:35 (molar ratio) The effect of lowering the melting point is greatest when mixed with lithium fluoride (Non-Patent Document 4). If the amount of lithium is too large, there is a concern that the cycle characteristics may deteriorate. The molar ratio of lithium fluoride LiF and magnesium fluoride MgF2 is LiF:MgF2 = x:1 (0≦x≦1.9), and LiF:MgF2=x:1 (0.1≦ x≦0.5) is more preferable, and LiF:MgF2=x:1 (x=near 0.33) is even more preferable. In this specification, the term "near" means more than 0.9 times and less than 1.1 times the value. Set to a small value.

[0180] If the subsequent mixing and grinding steps are to be carried out wet, a solvent is prepared. ketones such as acetone, alcohols such as ethanol and isopropanol, ethers, di- Xanthan Gum, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc. can be used. It is more preferable to use an aprotic solvent that is less likely to react with lithium. In this embodiment, acetone is used.

[0181] <Step S12> Next, in step S12, the materials of the mixture 902 are mixed and crushed. The process can be carried out by either a dry method or a wet method, but the wet method is preferred because it allows for finer pulverization. For mixing, a ball mill, a bead mill, etc. can be used. When using zirconia balls as media, it is preferable to use zirconia balls as media. It is preferable to carry out the blending and grinding steps sufficiently to pulverize the mixture 902 into fine powder.

[0182] <Step S13> Next, in step S13, the mixed and crushed materials are collected and the mixture 902 is obtain.

[0183] The mixture 902 has, for example, an average particle diameter (D50) of 600 nm or more and 20 μm or less. It is preferable that the particle size is 1 μm or more and 10 μm or less. If the resulting mixture 902 is used, it can be used in a later step to produce a composite oxide containing lithium, a transition metal, and oxygen. When mixed with the composite oxide particles, the mixture 902 can be easily adhered uniformly to the surface of the composite oxide particles. If the mixture 902 is uniformly attached to the surface of the composite oxide particles, the composite oxide particles This is preferable because it is easy to distribute halogen and magnesium thoroughly in the surface layer portion. If there is a region in which halogen and magnesium are not contained, the pseudo-saturation There is a risk that it is difficult to form a Pinel type crystal structure.

[0184] Next, through steps S21 to S24, a metal A, a metal M, and a metal oxide having oxygen are formed. A composite oxide is obtained.

[0185] <Step S21> First, in step S21, a composite oxide material containing metal A, metal M, and oxygen is prepared. A metal A source and a metal M source are prepared.

[0186] An example will be described in which lithium is used as metal A. The lithium source is, for example, carbonate. Lithium, lithium fluoride, etc. can be used.

[0187] As the metal M, for example, at least one of cobalt, manganese, and nickel can be used. can.

[0188] When a layered rock salt type crystal structure is used as the positive electrode active material, the ratio of the materials is The mixture ratio of cobalt, manganese, and nickel is as follows. Also, the layered rock salt type crystal structure Aluminum may be added to these transition metals within the range of .beta..

[0189] As the metal M source, oxides, hydroxides, etc. of the metals exemplified above as the metal M may be used. As the cobalt source, for example, cobalt oxide, cobalt hydroxide, etc. can be used. As the manganese source, manganese oxide, manganese hydroxide, etc. can be used. As the nickel source, nickel oxide, nickel hydroxide, etc. can be used. The aluminum source may be aluminum oxide, aluminum hydroxide, or the like.

[0190] <Step S22> Next, in step S22, the metal A source and the metal M source are mixed. For example, a ball mill, a bead mill, etc. may be used for mixing. When using a ball mill, for example, zirconia balls can be used as the media. It is preferable that:

[0191] <Step S23> Next, in step S23, the mixed material is heated. To distinguish it from the first heating, it is sometimes called firing or first heating. Heating is performed at temperatures above 800°C and It is preferably carried out at a temperature below 0°C, and more preferably at a temperature of 900°C or higher and 1000°C or lower. If the temperature is too low, the decomposition and melting of the starting materials will be insufficient. On the other hand, if the temperature is too high, the oxidation-reduction reaction of the metal M may be activated. There is a risk of defects occurring due to excessive reduction of the metal to be treated or evaporation of metal A. For example, when cobalt is used as the metal M, defects can occur in which the cobalt becomes divalent.

[0192] The heating time is preferably 2 hours or more and 20 hours or less. The temperature should be kept low (for example, a dew point of -50°C or less, preferably -100°C or less). For example, it is preferable to heat at 1000°C for 10 hours, increase the temperature by 200°C / h, and dry The flow rate of the atmosphere is preferably 10 L / min. After that, the heated material is cooled to room temperature. For example, the temperature can be lowered from a specified temperature to room temperature in 10 to 50 hours. It is preferable to set it to below.

[0193] However, cooling to room temperature in step S23 is not essential. If there is no problem in carrying out the steps S24 and S31 to S33, the cooling Temperatures up to above room temperature may also be used.

[0194] The metal contained in the positive electrode active material is Some of the metals may be introduced in steps S41 to S43 described later. It can also be introduced in step S44. More specifically, in steps S22 and S44, In step S23, metal M1 (M1 is cobalt, manganese, nickel, and aluminum) In steps S41 to S44, a metal M2 is introduced. (M2 is, for example, one or more selected from manganese nickel and aluminum) In this way, by separating the steps of introducing metal M1 and metal M2, For example, it may be possible to change the depth profile of the particle compared to the inside of the particle. The concentration of metal M2 in the surface layer can be increased by using the number of atoms of metal M1 as a reference. The ratio of the number of atoms of the metal M2 to the standard is made higher in the surface layer than in the interior. can be done.

[0195] In the positive electrode active material according to one embodiment of the present invention, preferably, cobalt is selected as the metal M1, Nickel and aluminum are selected as the metal M2.

[0196] <Step S24> Next, in step S24, the sintered material is recovered, and the metal A, the metal M, and the oxygen are separated. Specifically, a composite oxide having lithium cobalt oxide, lithium manganese oxide, lithium nickelate, lithium cobaltate in which some of the cobalt is replaced by manganese, or This produces lithium nickel-manganese-cobalt oxide, etc.

[0197] In step S24, a metal A, a metal M, and oxygen are synthesized in advance. A composite oxide may be used. In this case, steps S21 to S23 may be omitted. This can be done.

[0198] For example, a pre-synthesized composite oxide is a cobalt oxide manufactured by Nippon Chemical Industry Co., Ltd. Lithium oxide particles (product name: Cellseed C-10N) can be used. The particle diameter (D50) is approximately 12 μm, and impurities are detected by glow discharge mass spectrometry (GD-MS). Analysis revealed that magnesium and fluorine concentrations were 50 ppm wt or less, and calcium The concentration of aluminum and silicon is 100 ppm wt or less, and the concentration of nickel is 150 ppm wt or less, sulfur concentration 500 ppm wt or less, arsenic concentration 1100 ppm m wt or less, and the concentration of elements other than lithium, cobalt, and oxygen is 150 ppm wt or less, and lithium cobalt oxide.

[0199] Alternatively, lithium cobalt oxide particles (product name: Cellseed C- 5H) can also be used. This has an average particle size (D50) of about 6.5 μm and is In the impurity analysis by -MS, the concentration of elements other than lithium, cobalt, and oxygen was C- It is lithium cobalt oxide, which is about the same as or less than 10N.

[0200] In this embodiment, cobalt is used as the metal M, and pre-synthesized lithium cobaltate is used. The ion beam will be used in this experiment.

[0201] <Step S31> Next, in step S31, the mixture 902 and the composite oxide obtained in step S24 are mixed. The number of transition metal atoms in the composite oxide containing lithium, transition metal, and oxygen is The ratio of TM to the number of magnesium atoms MgMix1 in the mixture 902 is TM:Mg Mix1=1:y (0.001≦y≦0.06) is preferred, and TM:MgMi It is more preferable that x1=1:y (0.003≦y≦0.03).

[0202] The mixing in step S31 is carried out after the mixing in step S12 in order not to destroy the particles of the composite oxide. For example, it is preferable to set the rotation speed to be milder than that of the mixing in step S12. It is preferable to use conditions with less heat or shorter time. For mixing, a ball mill, a bead mill, etc. can be used. When using a ball mill, for example, zirconia balls should be used as the media. is preferred.

[0203] <Step S32> Next, in step S32, the mixed materials are collected to obtain a mixture 903.

[0204] In this embodiment, the mixture of lithium fluoride and magnesium fluoride is treated with an impurity Although the present invention has been described as a method of adding lithium cobalt oxide with low Instead of the mixture 903 in step S33, a starting material of lithium cobalt oxide may be used. A material containing a magnesium source and a fluorine source and then calcined may be used. The process includes steps S11 to S14 and steps S21 to S24. Since there is no need to separate the processes, it is simple and highly productive.

[0205] Alternatively, lithium cobalt oxide pre-doped with magnesium and fluorine is used. Magnesium and fluorine doped lithium cobalt oxide can be used to This is simpler and allows the steps up to step S32 to be omitted.

[0206] Furthermore, lithium cobalt oxide, to which magnesium and fluorine have been added in advance, In addition, a magnesium source and a fluorine source may be added.

[0207] <Step S33> Next, in step S33, the mixture 903 is heated. Alternatively, this may be referred to as annealing or second heating.

[0208] The annealing is preferably carried out at a suitable temperature and time. The particle size and the size of the composite oxide having lithium, a transition metal, and oxygen in step S24 The temperature and composition of the particles vary depending on the conditions. Small particles require lower temperatures or Shorter times may be more preferable.

[0209] For example, if the average particle diameter (D50) of the particles in step S24 is about 12 μm, annealing The temperature is preferably, for example, 600° C. or higher and 950° C. or lower. The annealing time is, for example, 3 hours or longer. It is preferable that the heating time is 10 hours or more, more preferable that the heating time is 60 hours or more.

[0210] On the other hand, when the average particle diameter (D50) of the particles in step S24 is about 5 μm, the annealing temperature The annealing temperature is preferably, for example, 600° C. or higher and 950° C. or lower. The annealing time is, for example, 1 hour or higher and 10 Preferably, it is less than 1 hour, and more preferably about 2 hours.

[0211] The temperature drop time after annealing is preferably, for example, 10 hours or more and 50 hours or less.

[0212] If the annealing temperature in step S33 is too high, the particles may sinter.

[0213] When the mixture 903 is annealed, the material with a low melting point (e.g., fluorine) in the mixture 902 is first annealed. It is thought that the lithium ion (lithium chloride, melting point 848°C) melts and is distributed in the surface layer of the composite oxide particles. The presence of this molten material then lowers the melting point of other materials, causing them to melt. For example, magnesium fluoride (melting point 1263°C) melts and turns into a composite oxide. It is thought to be distributed in the surface layer of the particles.

[0214] The elements contained in the mixture 902 distributed in the surface layer are lithium, transition metals, and oxygen. It is believed that the metal is dissolved in the composite oxide having the formula

[0215] The elements contained in the mixture 902 are diffused in the surface and the inside of the composite oxide particles rather than in the inside. Therefore, magnesium and halogens are more likely to dissolve in the surface layer and near the grain boundaries. As will be described later, the magnesium concentration in the surface layer and near the grain boundaries is higher than that in the interior. When the temperature is high, the change in the crystal structure can be more effectively suppressed.

[0216] <Step S34> Next, in step S34, the annealed material is recovered to obtain a second composite oxide. .

[0217] Next, in step S34, the resulting composite oxide is subjected to further processing. A process for adding the group M2 is performed after step S24. The concentration of the metal M2 in the particle surface layer of the positive electrode active material can be made higher than that in the interior. In some cases, this is preferable.

[0218] The metal M2 is added, for example, in step S31 by adding the metal M2 together with the mixture 902 etc. It may be possible to perform the process by mixing materials having M2. In this case, the number of steps can be reduced and the process can be simplified. This is preferable because it can be easily converted into a

[0219] Alternatively, as will be described later, after steps S31 to S33, An addition step may be carried out. In this case, for example, the formation of a compound of magnesium with metal M2 may be able to suppress it.

[0220] Through steps S41 to S43 described below, a positive electrode active material according to one embodiment of the present invention is obtained. The metal M2 is added in the above process. The metal M2 is added, for example, by a liquid method such as a sol-gel method. Phase method, solid phase method, sputtering method, evaporation method, CVD (chemical vapor deposition) method, PLD (pulse Laser deposition method or the like can be applied.

[0221] <Step S41> First, in step S41, a metal source is prepared. The solvent used in the sol-gel method is prepared. Metal sources include metal alkoxides and metal hydrates. For example, when the metal M2 is aluminum, For example, the number of cobalt atoms in lithium cobalt oxide is 1, and the number of aluminum atoms in the metal source is 1. The relative value of the number of atoms of the metal M2 is 0.005 or more and 0.02 or less. For example, when nickel is contained in addition to cobalt, the cobalt element contained in lithium cobalt oxide is The relative value of the number of nickel atoms in the metal source is 0.0005 or more and 0.02 or less, where the number of nickel atoms in the metal source is 1. It should be below.

[0222] As an example, the sol-gel method is applied to aluminum isopropanol as a metal source. An example in which isopropanol is used as a solvent is shown (step S41 in FIG. 10).

[0223] <Step S42> Next, in step S42, aluminum alkoxide is dissolved in alcohol, and Lithium cobalt oxide particles are mixed into the mixture.

[0224] Next, the mixture of the alcohol solution of metal alkoxide and the lithium cobalt oxide particles was added to water. Stirring is performed in a steam-containing atmosphere. Stirring can be performed, for example, with a magnetic stirrer. The stirring time is determined based on the time it takes for the water in the atmosphere and the metal alkoxide to undergo hydrolysis and polycondensation reactions. For example, 4 hours, 25°C, 90% RH (relative humidity). It can be done under conditions of humidity (relative humidity). and in an atmosphere that is not temperature controlled, such as the atmospheric atmosphere in a draft chamber. In such a case, it is preferable to carry out the stirring for a longer period of time. For example, it may be left at room temperature for 12 hours or more.

[0225] By reacting water vapor in the atmosphere with metal alkoxide, the reaction is more efficient than when liquid water is added. The sol-gel reaction can be carried out slowly even at room temperature. By reacting, the reaction is more efficient than, for example, heating at a temperature above the boiling point of the solvent alcohol. The sol-gel reaction can be carried out slowly. This allows the formation of a coating layer of uniform thickness and high quality.

[0226] For example, when aluminum is added as metal M2, the relative value of the number of atoms of metal M2 is is preferably 0.0005 or more and 0.02 or less with respect to the sum of metal M1 and metal M2, More preferably, it is 0.001 or more and 0.015 or less, and even more preferably, it is 0.001 or more and 0.009 or less. When nickel is added as the metal M2, the relative value of the number of atoms of the metal M2 is, for example, For example, the ratio of the sum of metal M1 and metal M2 is preferably 0.0005 or more and 0.02 or less, and more preferably 0.0 0.01 or more and 0.015 or less is more preferable, and 0.001 or more and 0.009 or less is even more preferable. .

[0227] <Step S43> Next, in step S43, the precipitate is collected from the mixed solution after the above treatment. The resulting residue is dried to obtain a mixture 904. The precipitate can be recovered by filtration, centrifugation, or Evaporation to dryness can be applied. The precipitate is the same as the solvent in which the metal alkoxide was dissolved. It can be washed with alcohol. The drying process is, for example, at 80°C for 1 to 4 hours. In addition, when evaporation to dryness is applied, this step In this step, separation of the solvent and the precipitate is not necessary, and for example, In the calcination step S44), the precipitate can be collected.

[0228] <Step S44> Next, in step S44, the resulting mixture 904 is fired.

[0229] The firing time is preferably 1 hour to 50 hours within the specified temperature range. If the baking time is too short, the surface layer may be damaged. The crystallinity of the compound containing the metal M2 may be low. Alternatively, the diffusion of the metal M2 may be poor. In some cases, the baking time is sufficient, or organic matter may remain on the surface. If the time is too long, the diffusion of metal M2 may proceed too much, resulting in a low concentration in the surface layer and near the grain boundaries. In addition, productivity decreases.

[0230] The specified temperature is preferably 500°C or higher and 1200°C or lower, and more preferably 700°C or higher and 920°C or lower. It is more preferable that the temperature is 800°C or higher and 900°C or lower, and it is even more preferable that the temperature is 800°C or higher and 900°C or lower. The crystallinity of the compound having the metal M2 formed in the layer portion may be low. The diffusion of 2 may be insufficient, or organic matter may remain on the surface.

[0231] It is also preferable that the firing is carried out in an atmosphere containing oxygen. When the oxygen partial pressure is low, the firing temperature If the temperature is not lowered, there is a risk that Co will be reduced.

[0232] In this embodiment, the specified temperature is set to 850° C. and is maintained for 2 hours. °C / h, and the oxygen flow rate is 10 L / min.

[0233] Regarding cooling after firing, it is preferable to take a long cooling time, as this makes it easier to stabilize the crystal structure. For example, it is preferable that the time required for the temperature to drop from the specified temperature to room temperature is 10 hours or more and 50 hours or less. Here, the baking temperature in step S44 is set to be lower than the baking temperature in step S33. Preferably, it is low.

[0234] <Step S45> Next, in step S45, the cooled particles are collected to obtain the positive electrode active material 1 according to one embodiment of the present invention. 00 can be produced. At this time, the collected particles can be further sieved. is preferred.

[0235] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0236] (Embodiment 3) In this embodiment, the positive electrode active material described in the previous embodiment is used in a secondary battery. Examples of materials that can be used will be described below.

[0237] <Configuration example 1 of secondary battery> The following explanation will be given using a secondary battery in which the positive electrode, negative electrode, and electrolyte are enclosed in an outer casing. do.

[0238] [Positive electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector.

[0239] <Cathode active material layer> The positive electrode active material layer contains at least a positive electrode active material. In addition, other substances such as a coating on the surface of the active material, a conductive additive, or a binder may be included.

[0240] As the positive electrode active material, the positive electrode active material 100 described in the previous embodiment can be used. By using the positive electrode active material 100 described in the previous embodiment, it is possible to achieve high capacity and cycle characteristics. Therefore, a secondary battery having excellent properties can be obtained.

[0241] As the conductive additive, a carbon material, a metal material, a conductive ceramic material, or the like may be used. Furthermore, a fibrous material may be used as the conductive additive. The content of the conductive additive is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less. Below is more preferable.

[0242] The conductive additive can form an electrically conductive network in the active material layer. The auxiliary agent can maintain the electrical conduction path between the positive electrode active materials. By adding a conductive additive, it is possible to realize an active material layer with high electrical conductivity. do.

[0243] Examples of the conductive additive include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon. Examples of carbon fibers include mesophase pitch carbon fibers. Carbon fibers such as carbon fibers, isotropic pitch-based carbon fibers, etc. can be used. Carbon nanofibers, carbon nanotubes, etc. can be used. The nanotubes can be produced by, for example, a vapor phase growth method. For example, carbon black (acetylene black (AB) etc.), graphite particles Carbon materials such as silicon, graphene, and fullerene can be used. Metal powders and fibers such as nickel, aluminum, silver, and gold, as well as conductive ceramic materials can be used.

[0244] A graphene compound may also be used as the conductive additive.

[0245] Graphene compounds have excellent electrical properties, such as high conductivity, as well as high flexibility and In some cases, the graphene has excellent physical properties, such as high mechanical strength. Graphene compounds have a planar shape. Graphene compounds enable surface contact with low contact resistance. In addition, even if the material is thin, it can have very high conductivity, and a small amount can be used efficiently in the active material layer. Therefore, graphene compounds are used as conductive additives. This is preferable because it is possible to increase the contact area between the active material and the conductive additive. By using a spray-drying device, the entire surface of the active material is covered with graphene, a conductive additive. It is preferable to form the compound as a coating. In addition, electrical resistance may be reduced. Here, examples of the graphene compound include graphene, multigraphene, and the like. It is particularly preferable to use RGO, which may be, for example, graphene oxide ( This refers to a compound obtained by reducing graphene oxide (GO).

[0246] When using an active material with a small particle size, for example, an active material with a particle size of 1 μm or less, the specific surface area of ​​the active material Therefore, a large amount of conductive additive is required. This tends to result in a relatively reduced amount of active material carried. If the amount of the conductive additive decreases, the capacity of the secondary battery will decrease. When graphene compounds are used, they can efficiently form conductive paths even in small amounts. This is particularly preferable because it is possible to avoid reducing the amount of the active material carried.

[0247] In the following, as an example, a graphene compound is used as a conductive additive in the active material layer 200. An example of the cross-sectional configuration in this case will be described.

[0248] 11A shows a vertical cross-sectional view of the active material layer 200. The active material layer 200 is made of granular positive electrode active material. 100, a graphene compound 201 as a conductive additive, and a binder (not shown). Here, the graphene compound 201 may be, for example, graphene or multi-graphene. Here, the graphene compound 201 preferably has a sheet shape. In addition, the graphene compound 201 may be a multi-graphene or (and) a multi-graphene. The graphene may be partially overlapped to form a sheet.

[0249] In the vertical cross section of the active material layer 200, as shown in FIG. 11B, In FIG. 11B, the sheet-like graphene compound 201 is dispersed almost uniformly. The laphene compound 201 is shown schematically by a thick line, but in reality it is composed of a single layer or multiple layers of carbon molecules. The plurality of graphene compounds 201 are thin films each having a thickness of 1000 . The positive electrode active material 100 is partially covered with the positive electrode active material 100 or adhered to the surface of the positive electrode active material 100. Since they are formed as shown in FIG.

[0250] Here, a plurality of graphene compounds are bonded to each other to form a mesh-like graphene compound. forming a graphene compound net or graphene net. When the active material is covered with a graphene net, the graphene net can Therefore, the amount of binder can be reduced. This allows for the active material to be used in a smaller amount or not in a larger amount, reducing the proportion of the active material in the electrode volume or weight. The ratio can be improved, that is, the capacity of the secondary battery can be increased.

[0251] Here, graphene oxide is used as the graphene compound 201, and is mixed with an active material to form an active material. After forming the layer that will become the graphene compound layer 200, it is preferable to reduce the layer. By using graphene oxide, which has extremely high dispersibility in polar solvents, The compound 201 can be dispersed approximately uniformly inside the active material layer 200. The solvent is evaporated from the dispersion medium containing the graphene oxide dispersed in the solution, and the graphene oxide is reduced. Therefore, the graphene compound 201 remaining in the active material layer 200 partially overlaps with each other. By dispersing the particles so that they come into surface contact with each other, a three-dimensional conductive path can be formed. The reduction of graphene oxide may be carried out by, for example, heat treatment or by using a reducing agent. You may go.

[0252] Therefore, unlike granular conductive additives such as acetylene black, which come into point contact with the active material, Since the phenyl compound 201 enables surface contact with low contact resistance, it is not necessary to use a conventional conductive additive. The electrical conductivity between the granular positive electrode active material 100 and the graphene compound 201 can be improved with a smaller amount than that of the graphene compound 201. Therefore, the ratio of the positive electrode active material 100 in the active material layer 200 can be increased. This makes it possible to increase the discharge capacity of the secondary battery.

[0253] In addition, by using a spray dryer in advance, the entire surface of the active material is covered with the conductive additive. The graphene compound is formed as a coating, and the active material is further bonded to the graphene compound. A conductive path can also be formed.

[0254] Examples of binders include styrene-butadiene rubber (SBR) and styrene-isopropyl Ethylene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene- It is preferable to use a rubber material such as a propylene-diene copolymer. For this purpose, fluororubber can be used.

[0255] As the binder, it is preferable to use, for example, a water-soluble polymer. As the molecule, for example, polysaccharides can be used. cellulose (CMC), methylcellulose, ethylcellulose, hydroxypropyl Cellulose, diacetyl cellulose, regenerated cellulose and other cellulose derivatives, as well as starch In addition, these water-soluble polymers can be used in combination with the above-mentioned rubber materials. It is more preferable to use

[0256] Alternatively, the binder may be polystyrene, polymethyl acrylate, or polymethacrylic acid. Methyl (Polymethyl methacrylate, PMMA), Sodium polyacrylate, Polyvinyl Polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, Polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene Polyethylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride Polyvinyl chloride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer It is preferable to use materials such as polyvinyl acetate and nitrocellulose.

[0257] The binder may be used in combination with two or more of the above.

[0258] For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with other materials. For example, rubber materials have excellent adhesive strength and elasticity, but it is difficult to adjust the viscosity when mixed with a solvent. In such cases, for example, mixing with a material that has a particularly excellent viscosity adjusting effect can be As a material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer is preferably used. Furthermore, examples of water-soluble polymers that are particularly effective in adjusting viscosity include the aforementioned polysaccharides, such as cellulose, cellulose acetate, and the like. Carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxymethylcellulose Cellulose derivatives such as hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose Conductive materials and starch can be used.

[0259] The cellulose derivatives such as carboxymethyl cellulose are, for example, The solubility increases when cellulose is converted into salts such as sodium salts or ammonium salts. The increased solubility of the solubility of the electrode makes it easier to achieve the desired viscosity. It is also possible to improve the dispersibility of the active material and other components when preparing the battery. In the present invention, the cellulose and cellulose derivatives used as binders for the electrodes include: The salts thereof are also included.

[0260] Fluorine-based resins have advantages such as excellent mechanical strength, high chemical resistance, and high heat resistance. PVDF, a type of fluororesin, has extremely excellent properties among fluororesins, It has mechanical strength, excellent processability, and high heat resistance.

[0261] On the other hand, when the slurry produced when coating the active material layer becomes alkaline, PVDF If the binder gels or becomes insoluble, As a result, the adhesion between the current collector and the active material layer may be reduced. By using an active material, the pH of the slurry can be lowered and gelation and insolubilization can be suppressed. This is preferable.

[0262] <Positive electrode current collector> The positive electrode current collector may be made of metals such as stainless steel, gold, platinum, aluminum, titanium, etc. Highly conductive materials such as these alloys can be used. It is preferable that the material does not dissolve at the potential of the positive electrode. Aluminum alloys with added elements such as candium and molybdenum that improve heat resistance It can also be formed from a metal element that reacts with silicon to form silicide. Metal elements that react with silicon to form silicide include zirconium, Titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungste The current collectors are available in foil, plate (sheet), mesh, punched, etc. The current collector may be in the form of a metal, an expanded metal, or the like. It is preferable to use one with a thickness of 5 μm or more and 30 μm or less.

[0263] [How to make the positive electrode] As an example of a method for producing a positive electrode having a positive electrode active material according to one embodiment of the present invention, a slurry is prepared. The slurry can be applied to prepare an electrode. An example of a method for producing a lye will be described.

[0264] Here, the solvent used to prepare the slurry is preferably a polar solvent. For example, water , methanol, ethanol, acetone, tetrahydrofuran (THF), dimethylform amide (DMF), N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMS O) can be used alone or in a mixture of two or more thereof.

[0265] When the positive electrode active material according to one embodiment of the present invention has a first particle group and a second particle group, the first particle The first particle group and the second particle group are mixed in a desired ratio. When the weight ratio of group is 1:w, w is preferably 0.01 or more and 0.6 or less, more preferably Preferably, the ratio is 0.03 or more and 0.6 or less, more preferably 0.04 or more and 0.5 or less, and even more preferably The value is between 0.09 and 0.3.

[0266] The positive electrode active material of one embodiment of the present invention has a particle size according to the mixing ratio of the first particle group and the second particle group. In addition, depending on the proportion of each particle group, The intensity or area of ​​the corresponding maximum peak has a value corresponding to the ratio of the proportions. In addition, one particle group may have one maximum peak, or two or more. When there are two or more peaks, it may be sufficient to use the sum of the areas of the multiple maximum peaks.

[0267] a positive electrode active material in which a first particle group and a second particle group are mixed, a conductive additive, and a binder; The solvent is mixed to prepare a mixture J. The mixing may be carried out under normal pressure or under reduced pressure. In the mixing step, for example, a kneader can be used.

[0268] Next, the viscosity of mixture J is measured. After that, a solvent is added as necessary to adjust the viscosity. Through the above steps, a slurry for coating the active material layer is obtained.

[0269] Here, for example, the higher the viscosity of the mixture J, the more the active material, binder, In addition, the dispersibility of the conductive additive may be excellent (they may be well mixed with each other). It is preferable that the viscosity of mixture J is higher. On the other hand, if the viscosity of mixture J is too high, For example, the coating speed of the electrode may be slowed down, which may be undesirable from the viewpoint of productivity. .

[0270] Next, a method for forming an active material layer on a current collector using the prepared slurry will be described. do.

[0271] First, the slurry is applied onto the current collector. The surface treatment may be, for example, a corona discharge treatment, a plasma treatment, or Here, undercoating is a process in which a slurry is applied to the current collector. Before coating, the active material layer is coated with a film to reduce the interface resistance between the active material layer and the current collector, and to improve the interface resistance between the active material layer and the current collector. It refers to a film formed on the current collector to improve adhesion. It is not necessary to form a film, but it may be formed in an island shape. The capacity can be expressed by using a carbon material as the undercoat. Examples of carbon materials include graphite, acetylene black, and ketjen black. (registered trademark) and other carbon blacks, carbon nanotubes, etc. can be used.

[0272] The slurry can be applied by the slot die method, gravure method, blade method, or a combination of these methods. A continuous coating machine or the like may also be used for coating.

[0273] Next, the solvent of the slurry is evaporated to form the active material layer.

[0274] The evaporation process of the solvent of the slurry is carried out at a temperature of 50°C to 200°C, preferably 60°C to 90°C. The evaporation may be carried out in the following temperature range: The evaporation time may be shortened by carrying out the evaporation under a reduced pressure atmosphere. Alternatively, the evaporation temperature may be lowered.

[0275] The evaporation step can be carried out using a hot plate, a drying oven, or the like.

[0276] The active material layer may be formed on both sides of the current collector, or on only one side. Alternatively, there may be regions where the active material layer is partially formed on both sides.

[0277] After the solvent has evaporated from the active material layer, the active material is compressed by a compression method such as a roll press or a flat press. It is preferable to perform pressing.

[0278] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. and a binder.

[0279] <Negative electrode active material> As the negative electrode active material, for example, an alloy-based material or a carbon-based material can be used.

[0280] As a negative electrode active material, it can carry out charge-discharge reactions by alloying and dealloying reactions with lithium. Any element can be used, such as silicon, tin, gallium, aluminum, Germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one of these elements can be used. These elements have a higher capacity than carbon. Silicon has a particularly high theoretical capacity of 4200mAh / g. Silicon is preferably used, and 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 occurs through alloying and dealloying reactions with lithium. Elements that can undergo a reaction and compounds containing such elements are sometimes called alloy materials. be.

[0281] In this specification, SiO refers to, for example, silicon monoxide. Alternatively, SiO refers to Si O x Here, it is preferable that x has a value close to 1. For example, x can be expressed as The ratio is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0282] Carbon materials include graphite, easily graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). carbon nanotubes, graphene, carbon black, etc. stomach.

[0283] Examples of graphite include artificial graphite and natural graphite. Examples include carbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spherical graphite having a spherical shape can be used as the artificial graphite. For example, the MCMB may have a spherical shape, which is preferable. It is relatively easy to reduce the product, which is sometimes preferable. , flake graphite, and spherical natural graphite.

[0284] When lithium ions are inserted into graphite (the formation of lithium-graphite intercalation compounds), ) shows a low potential similar to that of lithium metal (0.05V to 0.3V vs.Li / Li + This allows lithium-ion secondary batteries to exhibit high operating voltages. Furthermore, graphite has a relatively high capacity per unit volume, a relatively small volume expansion, and is inexpensive. It is preferable because it has advantages such as higher safety compared to lithium metal.

[0285] In addition, titanium dioxide (TiO2) and lithium titanium oxide (Li4 Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5 ), tungsten oxide (WO2), molybdenum oxide (MoO2), etc. can be done.

[0286] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, which has a Li3N structure. つLi 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2. 6Co 0.4 N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm 3 )of This is preferable.

[0287] When a composite nitride of lithium and transition metals is used, lithium ions are included in the negative electrode active material, As a positive electrode active material, materials that do not contain lithium ions, such as V2O5 and Cr3O8, are used. In addition, when a material containing lithium ions is used as the positive electrode active material, However, by first removing the lithium ions contained in the positive electrode active material, As the lithium-transition metal nitride, a complex nitride of lithium and a transition metal can be used.

[0288] In addition, a material that undergoes a conversion reaction can also be used as the negative electrode active material. For example, lithium oxides such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO) A transition metal oxide that does not form an alloy with aluminum may be used as the negative electrode active material. Further materials that produce this include Fe2O3, CuO, Cu2O, RuO2, and Cr2O3 oxides such as CoS 0.89 , NiS, CuS and other sulfides, Zn3N2, Cu3N, Ge Nitrides such as 3N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. This also occurs with fluoride.

[0289] The conductive additive and binder that the negative electrode active material layer can have are: The same materials as the conductive additive and binder that can be used can be used.

[0290] <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.

[0291] [Electrolyte] The electrolytic solution contains a solvent and an electrolyte. The solvent for the electrolytic solution is preferably an aprotic organic solvent. Preferably, for example, ethylene carbonate (EC), propylene carbonate (PC), Ethylene carbonate, chloroethylene carbonate, vinylene carbonate, gamma-butyro Lactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfone oxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran One of tetrahydrofuran, sulfolane, sultone, etc., or two or more of these can be used in combinations and ratios of:

[0292] In addition, a flame-retardant and non-volatile ionic liquid (room-temperature molten salt) is used as the solvent for the electrolyte. By using one or more, the internal temperature of the secondary battery can be prevented from rising due to an internal short circuit or overcharging. Even if the battery is heated, it can prevent explosion and fire of the secondary battery. The electrolyte solution is made of tetravalent cations and anions. ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations Aliphatic onium cations such as imidazolium cations and pyridinium cations The following aromatic cations are also used as anions in electrolytes: monovalent amide-based Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkanes perfluoroalkyl borate anion, tetrafluoroborate anion, perfluoroalkyl bo ... phosphate anion, hexafluorophosphate anion, or perfluoroalkyl phosphate hydrate anions, etc.

[0293] The electrolyte to be dissolved in the solvent is, for example, LiPF6, LiClO4, 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 )2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. One or more of these titanium salts may be used in any combination and ratio. This can be done.

[0294] The electrolyte used in secondary batteries is free from granular dust and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as " It is preferable to use a highly purified electrolyte solution with a low content of impurities. Specifically, the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less, more preferably 1% or less. It is preferably 0.01% or less.

[0295] In addition, the electrolyte contains vinylene carbonate, propane sultone (PS), and tert-butyl Benzene (TBB), Fluoroethylene carbonate (FEC), Lithium bis(oxa) Lithium borate (LiBOB), as well as dinitriles such as succinonitrile and adiponitrile The concentration of the additives may be, for example, The content should be between 0.1 wt% and 5 wt%.

[0296] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0297] The use of polymer gel electrolyte increases safety against leakage etc. The pond can be made thinner and lighter.

[0298] Gelled polymers include silicone gel, acrylic gel, and acrylonitrile gel. , polyethylene oxide gel, polypropylene oxide gel, fluorine-based polymer A gel or the like can be used.

[0299] Examples of polymers include polyalkylene oxides such as polyethylene oxide (PEO). Polymers with side structures, PVDF, polyacrylonitrile, etc., and their For example, a copolymer containing PVDF and hexafluoropropylene ( PVDF-HFP, a copolymer of PVDF and HFP, can be used. The polymer may have a porous shape.

[0300] In addition, instead of the electrolytic solution, a solid electrolyte containing an inorganic material such as a sulfide or oxide, It is possible to use a solid electrolyte containing a polymer material such as PEO (polyethylene oxide). When a solid electrolyte is used, there is no need to install a separator or spacer. Since the entire battery can be solidified, there is no risk of leakage, dramatically improving safety.

[0301] [Separator] The secondary battery preferably has a separator. Examples of the separator include: Paper, nonwoven fabric, glass fiber, ceramics, or nylon (polyamide), vinylon (polyamide) vinyl alcohol fiber), polyester, acrylic, polyolefin, polyurethane The separator can be made of synthetic fibers or the like. It is preferable to process the electrode into a shape and place it so as to wrap either the positive electrode or the negative electrode.

[0302] The separator may have a multi-layer structure. For example, the separator may be made of an organic material such as polypropylene or polyethylene. The material film is made of ceramic material, fluorine material, polyamide material, or a combination of these. The ceramic material can be, for example, aluminum oxide. Examples of the fluorine-based material include aluminum particles, silicon oxide particles, etc. For example, PVDF, polytetrafluoroethylene, etc. can be used. For example, nylon, aramid (meta-aramid, para-aramid), etc. can be done.

[0303] Coating with ceramic materials improves oxidation resistance, making it possible to use separators during high-voltage charging and discharging. This suppresses the deterioration of the battery and improves the reliability of the secondary battery. Coating the separator and electrodes makes them adhere more easily, improving output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, making it suitable for secondary batteries. Safety can be improved.

[0304] For example, a mixture of aluminum oxide and aramid is coated on both sides of a polypropylene film. Alternatively, aluminum oxide may be applied to the surface of the polypropylene film that comes into contact with the positive electrode. The surface that comes into contact with the negative electrode may be coated with a mixed material of rubber and aramid, and a fluorine-based material may be coated on the surface that comes into contact with the negative electrode. .

[0305] By using a multilayer separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin. Since the capacity per unit volume of the secondary battery can be increased,

[0306] [Exterior body] The exterior of the secondary battery is made of a metal material such as aluminum or a resin material. Also, a film-like outer casing can be used. , such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide On the film made of such material, a highly flexible material such as aluminum, stainless steel, copper, or nickel is applied. A metal thin film is provided, and a polyamide resin or polyester is further provided on the metal thin film as the outer surface of the exterior body. A film having a three-layer structure provided with an insulating synthetic resin film such as a terephthalate resin can be used.

[0307] <Configuration example 2 of secondary battery> As an example of the configuration of a secondary battery, the configuration of a secondary battery using a solid electrolyte layer is described below. explain.

[0308] As shown in FIG. 12A, a secondary battery 400 according to one embodiment of the present invention includes a positive electrode 410, a solid electrolyte layer 420 and a negative electrode 430 .

[0309] The positive electrode 410 includes a positive electrode current collector 413 and a positive electrode active material layer 414. The positive electrode active material layer 414 has a positive electrode active material 411 and a solid electrolyte 421. It may contain an electrical activator and a binder.

[0310] The solid electrolyte layer 420 includes a solid electrolyte 421. The solid electrolyte layer 420 includes a positive electrode 410. and the negative electrode 430, and does not have either the positive electrode active material 411 or the negative electrode active material 431. This is a challenging area.

[0311] The negative electrode 430 includes a negative electrode current collector 433 and a negative electrode active material layer 434. The negative electrode active material layer 434 has a negative electrode active material 431 and a solid electrolyte 421. In addition, when metallic lithium is used for the negative electrode 430, In this case, the negative electrode 430 may not have a solid electrolyte 421, as shown in FIG. 12B. When metallic lithium is used for the negative electrode 430, the energy density of the secondary battery 400 can be improved. This is preferable.

[0312] As shown in FIG. 13A, a combination of a positive electrode 410, a solid electrolyte layer 420, and a negative electrode 430 A secondary battery may be formed by stacking a plurality of positive electrodes 410, solid electrolyte layers 420, and By stacking the negative electrode 430 and the negative electrode 430, the voltage of the secondary battery can be increased. The schematic diagram shows a four-layer stack of a positive electrode 410, a solid electrolyte layer 420, and a negative electrode 430. This is a schematic diagram.

[0313] The secondary battery according to one embodiment of the present invention may be a thin-film all-solid-state battery. The pond is a gas phase method (vacuum deposition, pulsed laser deposition, aerosol deposition, sputtering) The cathode, solid electrolyte, anode, wiring electrodes, etc. can be formed by using the above method. For example, FIG. 13B shows an example of a thin-film all-solid-state battery 450. As shown in FIG. 13B, a substrate 44 After forming the wiring electrode 441 and the wiring electrode 442 on the substrate 40, the positive electrode 41 is 0, and then a solid electrolyte layer 420 is formed on the positive electrode 410. A thin-film all-solid-state battery 450 can be fabricated by forming a negative electrode 430 on the wire electrode 442. The substrate 440 may be a ceramic substrate, a glass substrate, a plastic substrate, a metal substrate, or the like. etc. can be used.

[0314] The solid electrolyte 421 of the solid electrolyte layer 420 may be, for example, a sulfide-based solid electrolyte, An oxide-based solid electrolyte, a halide-based solid electrolyte, or the like can be used.

[0315] Sulfide-based solid electrolytes include thiosilicon-based (Li 10 GeP2S 12 , Li 3.25 G e 0.25 P 0.75 S4, etc.), sulfide glass (70Li2S・30P2S5, 30Li 2S·26B2S3·44LiI, 63Li2S·38SiS2·1Li3PO4, 57 Li2S・38SiS2・5Li4SiO4, 50Li2S・50GeS2, etc.), sulfides Glass-ceramic (Li7P3S 11 , Li 3.25 P 0.95 S4, etc.) are included. Solid electrolytes based on ZnO have high conductivity, can be synthesized at low temperatures, and are relatively soft. Because it is soft, it has the advantage of easily maintaining conductive paths even after charging and discharging.

[0316] Oxide-based solid electrolytes include materials with a perovskite crystal structure (La 2 / 3-x L i 3x TiO3, etc.), materials with NASICON-type crystal structure (Li 1-X Al X Ti2 -X (PO4)3, etc.), materials having a garnet-type crystal structure (Li7La3Zr2O 12 , etc.), materials having a LISICON-type crystal structure (Li 14 ZnGe4O 16 , etc.), LLZ O (Li7La3Zr2O 12 ), oxide glasses (Li3PO4-Li4SiO4, 50 Li4SiO4·50Li3BO3, etc.), oxide crystallized glasses (Li 1.07 Al 0.6 9Ti 1.46 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, etc.) are included. Oxide-based solid electrolytes have the advantage of being stable in air.

[0317] Halide-based solid electrolytes include LiAlCl4, Li3InBr6, LiF, LiC l, LiBr, LiI, etc. Also, composite materials obtained by filling pores of porous alumina or porous silica with these halide-based solid electrolytes can also be used as solid electrolytes.

[0318] Also, different solid electrolytes may be mixed and used.

[0319] |>Among them, Li 1+x Al x Ti 2-x (PO4)3 (0 < x < 1) (hereinafter, LATP) contains aluminum and titanium, which are elements that the positive electrode active material 100 of one aspect of the present invention may have. Therefore, a synergistic effect can be expected for improving cycle characteristics, which is preferable. Also, an improvement in productivity due to reduction of processes can be expected. In this specification , etc., the NASICON-type crystal structure means M2(XO4)3 (M: transition metal, X: S , etc.), and , P, As, Mo, W, etc.), and the vertices are MO6 octahedrons and XO4 tetrahedra. It refers to a structure in which the molecules are arranged three-dimensionally and share the same structure.

[0320] [Shape of exterior body and secondary battery] The exterior body of the secondary battery 400 according to one embodiment of the present invention can be made of various materials and in various shapes. However, it is preferable that the positive electrode, the solid electrolyte layer, and the negative electrode have a function of applying pressure thereto. .

[0321] For example, Figure 14 shows an example of a cell for evaluating materials for all-solid-state batteries.

[0322] FIG. 14A is a schematic cross-sectional view of the evaluation cell. The evaluation cell is made up of a lower member 761 and an upper member 7 62 and a fixing screw and a wing nut 764 for fixing them. By rotating the electrode plate 753, the evaluation material is fixed. An insulator 766 is provided between the configured lower member 761 and the upper member 762. In addition, an O-ring 765 is provided between the upper member 762 and the holding screw 763 for sealing. is provided.

[0323] The material to be evaluated is placed on an electrode plate 751, surrounded by an insulating tube 752, and an electric It is pressed by the electrode plate 753. is shown in Figure 14B.

[0324] As an example of the evaluation material, a stack of a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c was used. 14A, 14B, and 14C show the same. The same symbols are used for the same parts.

[0325] The electrode plate 751 and the lower member 761 electrically connected to the positive electrode 750a are The electrode plate 750c electrically connected to the negative electrode 750c corresponds to a terminal. The electrode plate 753 and the upper member 762 can be said to correspond to the negative terminal. 51 and the electrode plate 753 while applying pressure to the evaluation material and measuring the electrical resistance, etc. It is possible.

[0326] In addition, a package with excellent airtightness is used for the exterior body of the secondary battery according to one embodiment of the present invention. For example, a ceramic package or a resin package can be used. When sealing the exterior body, the outside air should be shut out and the device should be sealed in a sealed atmosphere, such as a glove box. It is preferable to carry out the process in a furnace.

[0327] FIG. 15A shows a perspective view of a secondary battery according to one embodiment of the present invention, which has an exterior body and a shape different from those shown in FIG. 14. The secondary battery in FIG. 15A has external electrodes 771 and 772 and is made up of multiple packages. The device is sealed in an exterior body having components.

[0328] An example of a cross section taken along the dashed line in FIG. 15A is shown in FIG. 15B. The laminate having the electrolyte layer 750b and the negative electrode 750c is formed by providing an electrode layer 773a on a flat plate. A package member 770a, a frame-shaped package member 770b, and a flat electrode layer 773b The package member 770c is provided with a sealing member 770b, and the package member 770c is enclosed by the sealing member 770b. The cage members 770a, 770b, and 770c are made of an insulating material, such as a resin material or ceramic. can be used.

[0329] The external electrode 771 is electrically connected to the positive electrode 750a via the electrode layer 773a. The external electrode 772 also functions as an electrode. It is electrically connected to the negative terminal.

[0330] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0331] (Fourth embodiment) In this embodiment, the secondary battery having the positive electrode active material 100 described in the previous embodiment is The materials used in the secondary battery described in this embodiment are the same as those in the previous embodiment. The description of the form can be taken into consideration.

[0332] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. Figure 16A shows a coin-type (single-layer flat type) 16B is a cross-sectional view of the secondary battery.

[0333] The coin-type secondary battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal. The can 302 is insulated and sealed with a gasket 303 made of polypropylene or the like. The positive electrode 304 is composed of a positive electrode current collector 305 and a positive electrode active material layer 30 provided in contact with the positive electrode current collector 305. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode current collector 308 which is set in contact with the negative electrode current collector 308. The negative electrode active material layer 309 is formed by the bonding.

[0334] The positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 are active The material layer only needs to be formed on one side.

[0335] The positive electrode can 301 and the negative electrode can 302 are made of nickel and aluminum, which are corrosion-resistant to the electrolyte. Metals such as aluminum and titanium, or alloys of these and other metals (e.g., stainless steel) In addition, nickel or aluminum can be used to prevent corrosion by the electrolyte. The positive electrode can 301 is preferably coated with a positive electrode 304, and the negative electrode can 302 is preferably coated with a negative electrode 305. 07 and electrically connect to each other.

[0336] The negative electrode 307, the positive electrode 304, and the separator 310 are impregnated with an electrolyte, and the resulting structure is shown in FIG. 16B. As shown in FIG. 1, the positive electrode can 301 is placed downward, and the positive electrode 304, separator 310, negative electrode 307, and negative electrode 308 are connected to the positive electrode can 301. The positive electrode can 301 and the negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are connected with a gasket 303 interposed therebetween. Then, the laminate is pressed to form a coin-type secondary battery 300.

[0337] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, high capacity and cycle The coin-type secondary battery 300 can have excellent battery characteristics.

[0338] Here, the flow of current during charging of a secondary battery will be explained using FIG. When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In secondary batteries that use lithium, the anode (positive electrode) and cathode (cathode) is switched, and the oxidation reaction and reduction reaction are switched, so the reaction potential The electrode with a higher reaction potential is called the positive electrode, and the electrode with a lower reaction potential is called the negative electrode. Whether charging, discharging, or applying a reverse pulse current, Even when an electric current flows through it, the positive electrode is called the "positive electrode" or "+ electrode (plus electrode)" and the negative electrode is called the "positive electrode" or "+ electrode (plus electrode)". This is called the "negative electrode" or "-electrode (minus electrode)." When using the terms anode (positive electrode) and cathode (negative electrode), the following occurs during charging and discharging: This can be confusing as the anode and cathode are opposites. The term "cathode" will not be used in this specification. When using the terms cathode and positive electrode, specify whether they are charging or discharging. It will also be noted whether it corresponds to the negative pole (negative pole) or the positive pole (positive pole).

[0339] A charger is connected to the two terminals shown in Figure 16C, and the secondary battery 300 is charged. As the battery 300 is charged, the potential difference between the electrodes increases.

[0340] [Cylindrical secondary battery] Next, an example of a cylindrical secondary battery will be described with reference to FIG. 17. Cylindrical secondary battery 60 FIG. 17A shows an external view of the cylindrical secondary battery 600. FIG. 17B shows a schematic cross section of the cylindrical secondary battery 600. As shown in FIG. 17B, the cylindrical secondary battery 600 has a positive electrode cap on the top surface. The battery has a battery cover 601 and a battery can (external can) 602 on the sides and bottom. The positive electrode cap and the battery can (external can) 602 are secured by a gasket (insulating packing) 610. It is insulated.

[0341] Inside the hollow cylindrical battery can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are placed with a separator. The battery element is wound with the battery 605 sandwiched between them. The battery can 602 is closed at one end and open at the other. The battery can 602 is made of nickel, aluminum, or titanium, which is resistant to corrosion by the electrolyte. or alloys of these with other metals (e.g., stainless steel, etc.) In addition, nickel, aluminum, etc. can be used to prevent corrosion by the electrolyte. It is preferable to coat the battery can 602. Inside the battery can 602, the positive electrode, the negative electrode, and The battery element, in which the separator and the battery cell are wound, is sandwiched between a pair of opposing insulating plates 608 and 609. The inside of the battery can 602 in which the battery element is provided is filled with a non-aqueous electrolyte (not shown). The non-aqueous electrolyte can be the same as that used in coin-type secondary batteries. do.

[0342] The positive and negative electrodes used in cylindrical storage batteries are wound, so active material is formed on both sides of the current collector. A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative A negative electrode terminal (negative electrode current collecting lead) 607 is connected to the positive electrode 603. The positive electrode terminal 607 can be made of a metal material such as aluminum. 603 is resistance-welded to the safety valve mechanism 612, and the negative terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 is a PTC (Positive Temperature Coefficient) element. The positive electrode cap 601 is electrically connected to the positive electrode cap 601 via a positive electrode coefficient 611. The safety valve mechanism 612 releases the positive electrode cap 601 when the internal pressure of the battery exceeds a predetermined threshold. The PTC element 611 cuts off the electrical connection between the positive electrode 604 and the positive electrode 604. It is a thermal resistor whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current. It prevents abnormal heat generation. The PTC element is made of barium titanate (BaTiO3) Semiconductor ceramics and the like can be used.

[0343] 17C, a plurality of secondary batteries 600 are mounted on the conductive plate 613 and the conductive plate 614. A module 615 may be formed by sandwiching the secondary batteries 600 between them. They may be connected in series, or may be connected in parallel and then in series. By configuring a module 615 having a plurality of secondary batteries 600, It is possible to extract a large amount of power.

[0344] 17D is a top view of module 615. Conductive plate 613 is dotted for clarity. As shown in FIG. 17D, the module 615 electrically connects a plurality of secondary batteries 600. A conductive plate may be provided over the conductive wire 616. Furthermore, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 is overheated, it is cooled by the temperature control device 617. If it is too cold, it can be heated by the temperature control device 617. The performance of the temperature controller 617 is less affected by the outside temperature. It is preferable that the material is insulating and non-flammable.

[0345] By using the positive electrode active material described in the above embodiment for the positive electrode 604, high capacity and cycle The cylindrical secondary battery 600 can be made to have excellent battery characteristics.

[0346] [Example of secondary battery structure] Another structural example of the secondary battery will be described with reference to FIGS.

[0347] 18A and 18B are diagrams showing the external appearance of a secondary battery. The substrate 900 is connected to the antenna 914 and the antenna 915. A label 910 is attached to the secondary battery 913. Furthermore, as shown in FIG. The battery 913 is connected to a terminal 951 and a terminal 952 .

[0348] The circuit board 900 has a terminal 911 and a circuit 912. The terminal 911 is connected to the terminal 95. 1, terminal 952, antenna 914, antenna 915, and circuit 912. A plurality of terminals 911 are provided, and each of the plurality of terminals 911 is used as a control signal input terminal, a power supply terminal, It can also be a child.

[0349] The circuit 912 may be provided on the back surface of the circuit board 900. The antenna 915 is not limited to a coil shape, but may be, for example, a wire shape or a plate shape. , Planar antenna, Aperture antenna, Traveling wave antenna, EH antenna, Magnetic field antenna, Dielectric Alternatively, an antenna such as a body antenna may be used. The flat conductor may be a flat conductor. This flat conductor functions as one of the conductors for electric field coupling. In other words, the capacitor has two conductors, one of which is an anode. The antenna 914 or the antenna 915 may be activated. Furthermore, electric power can be exchanged using an electric field.

[0350] The line width of antenna 914 is preferably larger than the line width of antenna 915. This allows the amount of power received by the antenna 914 to be increased.

[0351] The secondary battery is provided with a layer 916 between the antenna 914 and the antenna 915 and the secondary battery 913. The layer 916 has a function of shielding an electromagnetic field generated by the secondary battery 913, for example. The layer 916 may be made of, for example, a magnetic material.

[0352] The structure of the secondary battery is not limited to that shown in FIG.

[0353] For example, as shown in FIGS. 19A and 19B, the secondary battery 9 shown in FIGS. 18A and 18B 13, an antenna may be provided on each of a pair of opposing surfaces. FIG. 19B is an external view showing one of the pair of surfaces, and FIG. 19B is an external view showing the other of the pair of surfaces. 18A and 18B. The description of the secondary battery shown in FIG. 18B can be used as appropriate.

[0354] As shown in FIG. 19A, a layer 916 is sandwiched between one of the two surfaces of a secondary battery 913, and an antenna 19B, a layer 914 is provided on the other of the pair of surfaces of the secondary battery 913. The layer 917 is provided with an antenna 918 sandwiched between them. The layer 917 has a function of shielding the magnetic field. can.

[0355] By adopting the above structure, the size of both the antenna 914 and the antenna 918 can be increased. The antenna 918 can perform data communication with an external device, for example. The antenna 918 has a function of being able to receive the signal. A method for communication between a secondary battery and other devices via an antenna 918 can be applied. The method is to use NFC (near field communication) between secondary batteries and other devices. It is possible to apply a response method that can be used.

[0356] Alternatively, as shown in FIG. 19C, the display device may be connected to the secondary battery 913 shown in FIGS. 18A and 18B. A display device 920 may be provided. The display device 920 is electrically connected to the terminal 911. The label 910 may not be provided in the portion where the display device 920 is provided. The same parts as those of the secondary battery shown in FIG. 18B are the same as those of the secondary battery shown in FIGS. 18A and 18B. The explanations can be used as appropriate.

[0357] The display device 920 displays, for example, an image indicating whether charging is in progress or not, an image indicating the amount of stored power, etc. The display device 920 may be, for example, an electronic paper, a liquid crystal display, an electronic For example, an electroluminescence (EL) display device can be used. By using the polarizer, the power consumption of the display device 920 can be reduced.

[0358] Alternatively, as shown in FIG. 19D, the sensor 9 is connected to the secondary battery 913 shown in FIGS. 18A and 18B. The sensor 921 is electrically connected to the terminal 911 via the terminal 922. 18A and 18B. The description of the secondary battery shown in FIG. 18B can be used as appropriate.

[0359] The sensor 921 may be, for example, a sensor for measuring displacement, position, velocity, acceleration, angular velocity, number of rotations, distance, Light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, It is sufficient if it has the function of measuring flow rate, humidity, gradient, vibration, odor, or infrared. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed can be obtained. It is also possible to detect data (such as temperature) and store it in memory within the circuit 912.

[0360] Furthermore, an example of the structure of the secondary battery 913 will be described with reference to FIG.

[0361] The secondary battery 913 shown in FIG. 20A has a terminal 951 and a terminal 952 provided inside a housing 930. The winding 950 is impregnated with an electrolyte inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is in contact with the housing by using an insulating material or the like. 20A, the housing 930 is not in contact with the housing 930. For convenience, the housing 930 is shown separately. However, in reality, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 are not covered by the housing. The housing 930 is made of a metal material (e.g., aluminum, etc.). ) or a resin material can be used.

[0362] As shown in FIG. 20B, the housing 930 shown in FIG. 20A is made of a plurality of materials. For example, the secondary battery 913 shown in FIG. 20B may have a housing 930a and a housing 930b attached thereto. The housings 930a and 930b are joined together, and a wound body 950 is provided in the area surrounded by the housings 930a and 930b. It is being done.

[0363] The housing 930a can be made of an insulating material such as organic resin. By using a material such as organic resin on the surface on which the capacitor is formed, the electric field generated by the secondary battery 913 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 provided inside the housing 930b. For example, a metal material can be used as the material.

[0364] Furthermore, the structure of the wound body 950 is shown in FIG. 21. The wound body 950 includes a negative electrode 931 and The wound body 950 has a positive electrode 932 and a separator 933. The wound body 950 has the separator 933 sandwiched therebetween. Then, the negative electrode 931 and the positive electrode 932 are stacked one on top of the other, and the laminated sheet is wound. The negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated. Multiple layers may be stacked.

[0365] The negative electrode 931 is connected to the terminal 911 shown in FIG. 18 via one of the terminals 951 and 952. The positive electrode 932 is connected to the terminal 951 shown in FIG. Connected to 11.

[0366] By using the positive electrode active material described in the above embodiment for the positive electrode 932, a high capacity and cycle life can be achieved. This makes it possible to obtain a secondary battery 913 with excellent battery characteristics.

[0367] [Laminated secondary battery] Next, an example of a laminated secondary battery will be described with reference to FIGS. If the laminated secondary battery is made flexible, it can be made with fewer flexible parts. If the secondary battery is mounted in an electronic device that has some of the same characteristics, the secondary battery can be bent in accordance with the deformation of the electronic device. It is also possible.

[0368] A laminated secondary battery 980 will be described with reference to FIG. The secondary battery 980 has a wound body 993 shown in FIG. 22A. The wound body 993 has a negative electrode 994 and 21. The wound body 993 has a positive electrode 995 and a separator 996. As with the case 950, a negative electrode 994 and a positive electrode 995 are stacked with a separator 996 sandwiched therebetween. The laminated sheet is then wound up.

[0369] The number of layers of the negative electrode 994, the positive electrode 995, and the separator 996 may be as many as necessary. The negative electrode 994 is connected to the lead electrode 997 and the lead electrode 998. The positive electrode 995 is connected to a negative electrode current collector (not shown) via one of the lead electrodes 998. The positive electrode 997 is connected to a positive electrode current collector (not shown) via the other of the electrode 997 and the lead electrode 998. .

[0370] As shown in FIG. 22B, a film 981 serving as an exterior body and a film 982 having a recess are provided. The above-mentioned wound body 993 is housed in a space formed by bonding the above-mentioned wound body 993 together by thermocompression bonding or the like. Thus, a secondary battery 980 can be fabricated as shown in FIG. The lead electrode 997 and the lead electrode 998 are provided. The film 981 and the film 982 are provided with a recess. The interior of the glass 982 is impregnated with an electrolyte.

[0371] The film 981 and the film 982 having the recesses are made of a metal material such as aluminum. The film 981 and the film 982 having the recesses can be made of a metal or resin material. If a resin material is used as the material for the recess, when an external force is applied, the film 981 and the recess The film 982 having the above structure can be deformed to produce a flexible storage battery. can be done.

[0372] In addition, although an example using two films is shown in Figures 22B and 22C, a single film may be used. A space is formed by folding the film, and the above-mentioned wound body 993 is accommodated in the space. You may also pay.

[0373] By using the positive electrode active material described in the previous embodiment for the positive electrode 995, it is possible to achieve high capacity and cycle. The secondary battery 980 can have excellent battery characteristics.

[0374] In addition, in FIG. 22, a secondary battery having a wound body in a space formed by a film that serves as an exterior body is shown. We have explained the example of 980, but as shown in Figure 23, the shape is determined by the film that forms the exterior. It can also be used as a secondary battery having a plurality of rectangular positive electrodes, separators, and negative electrodes in the space formed. good.

[0375] The laminated secondary battery 500 shown in FIG. 23A includes 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 negative electrode current collector 504 and a negative electrode active material layer 505. The battery includes an electrode 506, a separator 507, an electrolyte 508, and an exterior body 509. A separator 507 is provided between a positive electrode 503 and a negative electrode 506 provided in a battery 509. The exterior body 509 is filled with an electrolyte 508. The electrolyte solution shown in Form 2 can be used.

[0376] In the laminated secondary battery 500 shown in FIG. 23A, a positive electrode current collector 501 and a negative electrode The current collector 504 also serves as a terminal for electrical contact with the outside. The current collector 501 and the negative electrode current collector 504 are arranged so as to be partially exposed to the outside from the exterior body 509. In addition, the positive electrode current collector 501 and the negative electrode current collector 504 may be disposed outside the outer casing 509. The lead electrode is not exposed to the positive electrode current collector 501 or the negative electrode current collector 502. The lead electrode may be exposed to the outside by ultrasonic bonding to the electric body 504 .

[0377] In the laminated secondary battery 500, the exterior body 509 is made of, for example, polyethylene, polypropylene, or the like. On a membrane made of a material such as polypropylene, polycarbonate, ionomer, or polyamide, A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied. On the metal thin film, an insulating composite such as polyamide resin or polyester resin is used as the outer surface of the exterior body. A laminate film having a three-layer structure provided with a resin film can be used.

[0378] An example of the cross-sectional structure of a laminated secondary battery 500 is shown in FIG. For simplicity, an example consisting of two current collectors is shown in Fig. 23B. It is composed of multiple electrode layers.

[0379] In FIG. 23B, as an example, the number of electrode layers is set to 16. In FIG. 23B, the negative electrode current collector 504 has eight layers and the positive electrode current collector The structure shown is 16 layers in total, with 8 layers of the conductive material 501. The cross section shows eight layers of negative electrode current collectors 504 that are ultrasonically bonded together. The number is not limited to 16, and may be more or less. In addition, when the number of electrode layers is small, the secondary battery can be thin. This allows the secondary battery to be molded and has excellent flexibility.

[0380] An example of an external view of a laminated secondary battery 500 is shown in FIGS. 24 and 25. 24 and 25 show a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead The positive electrode 510 and the negative electrode 511 are provided.

[0381] 26A shows an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is a positive electrode current collector 501. The positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. The negative electrode 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). 06 has a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. The negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, i.e., a tab region. The area and shape of the tab regions of the positive electrode and negative electrode are not limited to the example shown in FIG. stomach.

[0382] [Method for manufacturing laminated secondary batteries] Here, an example of a method for manufacturing a laminated secondary battery, the external view of which is shown in FIG. 24, will be described with reference to FIG. 6B and 26C.

[0383] First, the negative electrode 506, the separator 507, and the positive electrode 503 are stacked. The negative electrode 506, separator 507, and positive electrode 503 are shown. Here, five pairs of negative electrodes and four pairs of positive electrodes are shown. Next, the bonding of the tab regions of the positive electrode 503 and the bonding of the tab region of the positive electrode on the outermost surface are shown. The positive electrode lead electrode 510 is joined to the electrode region 510. For example, ultrasonic welding or the like may be used for joining. Similarly, the tab regions of the negative electrodes 506 are joined together, and the negative electrode leads to the tab regions of the negative electrodes on the outermost surface are Then, the electrode 511 is bonded.

[0384] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are placed on the exterior body 509 .

[0385] Next, as shown in Figure 26C, exterior body 509 is folded at the portion indicated by the broken line. The outer periphery of the exterior body 509 is bonded. For example, thermocompression bonding may be used for bonding. The electrode is connected to a part (or one side) of the exterior body 509 so that the electrolyte 508 can be poured in later. An area where the two components are not mixed (hereinafter referred to as an inlet) is provided.

[0386] Next, electrolyte 508 (not shown) is introduced into the exterior body 509 through an inlet provided in the exterior body. The electrolyte solution 508 is introduced into the inside of the electrode 509 under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is bonded. A secondary battery 500 of this type can be fabricated.

[0387] By using the positive electrode active material described in the previous embodiment for the positive electrode 503, it is possible to achieve high capacity and cycle. The secondary battery 500 can have excellent battery characteristics.

[0388] [Bendable secondary battery] Next, an example of a bendable secondary battery will be described with reference to FIGS. 27 and 28. do.

[0389] 27A shows a schematic top view of a bendable secondary battery 250. 27C and 27D are cut along the lines C1-C2, C3-C4, and C5 in FIG. 27A, respectively. A secondary battery 250 is a schematic cross-sectional view taken along the line A1-A2. The positive electrode 211a and the negative electrode 211b are electrically connected to each other. and a lead 212b electrically connected to the negative electrode 211b. The positive electrode 2 extends outside the exterior body 251. In addition, the area surrounded by the exterior body 251 includes the positive electrode 2. In addition to the negative electrode 11a and the negative electrode 211b, an electrolyte (not shown) is enclosed.

[0390] The positive electrode 211a and the negative electrode 211b of the secondary battery 250 will be described with reference to FIG. FIG. 28A illustrates the stacking order of the positive electrode 211a, the negative electrode 211b, and the separator 214. FIG. 28B is a perspective view illustrating the structure of the lead 211 in addition to the positive electrode 211a and the negative electrode 211b. 2a and lead 212b.

[0391] As shown in FIG. 28A, the secondary battery 250 includes a plurality of rectangular positive electrodes 211a, a plurality of rectangular positive electrodes 211b, a plurality of rectangular positive electrodes 211c, a plurality of rectangular positive electrodes 211d, a plurality of rectangular positive electrodes 211e, a plurality of rectangular positive electrodes 211f, a plurality of rectangular positive electrodes 211g, a plurality of rectangular positive electrodes 211h ... The positive electrode 211a and the negative electrode 211b have a rectangular shape and a plurality of separators 214. 1b each have a protruding tab portion and a portion other than the tab. A positive electrode active material layer is formed on the portion other than the tab of the negative electrode 211b. A negative electrode active material layer is formed on the negative electrode.

[0392] The surfaces of the positive electrodes 211a on which the positive electrode active material layer is not formed and the surfaces of the negative electrodes 211b on which the negative electrode active material layer is not formed are The positive electrode 211a and the negative electrode 211b are stacked so that the surfaces on which no material is formed are in contact with each other. will be done.

[0393] In addition, 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 are A separator 214 is provided between the surfaces. The data 214 is shown by a dotted line.

[0394] As shown in FIG. 28B, the positive electrodes 211a and the leads 212a are connected to each other at the joints 215a. The negative electrodes 211b and the leads 212b are electrically connected at the joints 21 5b are electrically connected.

[0395] Next, exterior body 251 will be described with reference to FIGS. 27B, 27C, 27D, and 27E. do.

[0396] The exterior body 251 has a film-like shape and is configured to sandwich the positive electrode 211a and the negative electrode 211b. The exterior body 251 is folded in two as shown in FIG. The pair of sealing portions 262 are connected to the positive electrode 211a and the sealing portion 263. The seal portion 2 is provided on either side of the negative electrode 211b and can also be called a side seal. 63 has a portion overlapping with the lead 212a and the lead 212b, and is also called a top seal. It is possible.

[0397] The exterior body 251 has ridge lines 271 and valley lines at the portions overlapping the positive electrode 211a and the negative electrode 211b. It is preferable that the sealing portion 272 of the exterior body 251 has a wave shape in which the sealing portions 272 are arranged alternately. 62 and the seal portion 263 are preferably flat.

[0398] FIG. 27B is a cross section cut at the portion overlapping with the ridge line 271, and FIG. 27C is a cross section cut at the portion overlapping with the valley line 272. 27B and 27C are cross sections cut at the overlapping portion of the secondary battery 250 and the positive electrode 252. 1 corresponds to a cross section in the width direction of the anode 211a and the cathode 211b.

[0399] Here, the widthwise ends of the positive electrode 211a and the negative electrode 211b, i.e., the positive electrode 211a and the negative electrode 211b, The distance between the end of the negative electrode 211b and the seal portion 262 is defined as La. When deformation such as bending is applied to the positive electrode 211a and the negative electrode 211b, as will be described later, If the distance La is too short, the outer casing 251 The positive electrode 211a and the negative electrode 211b may rub strongly against each other, and the exterior body 251 may be damaged. In particular, if the metal film of the exterior body 251 is exposed, the metal film may be easily damaged by the electrolyte. Therefore, it is preferable to set the distance La as long as possible. On the other hand, if the distance La is made too large, the volume of the secondary battery 250 increases. .

[0400] In addition, the greater the total thickness of the stacked positive electrode 211a and negative electrode 211b, the greater the It is preferable to increase the distance La between the negative electrode 211a and the seal portion 262. stomach.

[0401] More specifically, the stacked positive electrode 211a, negative electrode 211b, and separator (not shown) When the total thickness of the actuator 214 is t, the distance La is 0.8 to 3.0 times the thickness t. Preferably, the ratio is 0.9 to 2.5 times, more preferably 1.0 to 2.0 times. By setting the distance La in this range, it is possible to make the device compact and resistant to bending. This makes it possible to realize a highly reliable battery.

[0402] Furthermore, when the distance between the pair of seal portions 262 is a distance Lb, the distance Lb is a and the width of the negative electrode 211b (here, the width Wb of the negative electrode 211b). This is preferable because it prevents the secondary battery 250 from being deformed by repeated bending or other deformation. Even if the positive electrode 211a and the negative electrode 211b come into contact with the exterior body 251, Since a part of the negative electrode 211b can be shifted in the width direction, the positive electrode 211a and the negative electrode 211 This effectively prevents the outer casing 251 from rubbing against the outer casing 251.

[0403] For example, the difference between the distance Lb between the pair of seal portions 262 and the width Wb of the negative electrode 211b is The thickness is 1.6 times or more and 6.0 times or less, preferably 1.8 times or more, the thickness t of the positive electrode 211a and the negative electrode 211b. It is preferable that the ratio is 2.0 times or more and 5.0 times or less, and more preferably 2.0 times or more and 4.0 times or less. stomach.

[0404] In other words, it is preferable that the distance Lb, the width Wb, and the thickness t satisfy the relationship of the following formula 2: Desirable.

[0405]

Number

[0406] Here, a satisfies 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, more preferably 1.0 or more and 2.0 or less.

[0407] Further, FIG. 27D is a cross section including the lead 212a and corresponds to the longitudinal cross section of the secondary battery 250, the positive electrode 211a, and the negative electrode 211b. As shown in FIG. 27D, at the bent portion 26 1, it is preferable to have a space 273 between the longitudinal ends of the positive electrode 211a and the negative electrode 211b and the exterior body 251.

[0408] FIG. 27E shows a schematic cross-sectional view when the secondary battery 250 is bent. FIG. 27E corresponds to the cross section at the cutting line B1-B2 in FIG. 27A.

[0409] When the secondary battery 250 is bent, a part of the exterior body 251 located on the outer side of the bend extends, and another part located on the inner side is deformed to shrink. More specifically, the part located on the outer side of the exterior body 251 is deformed such that the amplitude of the wave is small and the period of the wave is large. On the other hand, the part located on the inner side of the exterior body 251 is deformed such that the amplitude of the wave is large and the period of the wave is small. Thus, due to the deformation of the exterior body 251, the stress applied to the exterior body 251 with bending is relaxed, so that the material itself constituting the exterior body 251 does not need to stretch and contract. As a result, the exterior body 251 can be bent with a small force without being damaged.

[0410] Further, as shown in FIG. 27E, when the secondary battery 250 is bent, the positive electrode 211a and the negative electrode 2 ​​​At this time, the plurality of stacked positive electrodes 211a and negative electrodes 11b are displaced relative to each other. The pole 211b is fixed at one end on the seal portion 263 side by the fixing member 217, so that the pole 211b is not bent. The amount of deviation increases as the distance approaches the edge 261. The stress applied to the positive electrode 211a and the negative electrode 211b is relieved, and the positive electrode 211a and the negative electrode 211b themselves As a result, the positive electrode 211a and the negative electrode 211b are not damaged. The secondary battery 250 can be easily bent.

[0411] In addition, a space 273 is provided between the positive electrode 211a and the negative electrode 211b and the exterior body 251. By this, the positive electrode 211a and the negative electrode 211b located on the inner side when bent are attached to the exterior body 25. It can move relative to 1 without touching it.

[0412] The secondary battery 250 illustrated in FIGS. 27 and 28 has a good external appearance even when repeatedly bent and stretched. Damage to the housing, the positive electrode 211a and the negative electrode 211b, etc., is unlikely to occur, and the battery characteristics are also unlikely to deteriorate. The secondary battery 250 has a positive electrode 211a that is not easily broken down. By using such a positive electrode active material, a battery with even better cycle characteristics can be obtained.

[0413] FIG. 29A shows three laminated secondary batteries 500 attached to a first plate 521 and a second plate 522. 29B is a perspective view showing how the plate 524 is sandwiched and fixed. The first plate 521 and the second plate 522 are fixed together using the fixture 525a and the fixing fixture 525b. By fixing the distance between the battery 24, the three secondary batteries 500 can be pressurized.

[0414] 29A and 29B show an example in which three laminated secondary batteries 500 are used. However, there is no particular limitation, and four or more secondary batteries 500 can be used, and ten or more batteries can be used. If more than 100 units are used, it can be used as a power source for a small vehicle, and if more than 100 units are used, it can be used as a large power source for a vehicle. It can also be used as a power source. It also has a protection circuit to prevent overcharging and a temperature monitor. A temperature sensor for detecting the temperature may be provided in the laminated secondary battery 500 .

[0415] In all-solid-state batteries, by applying a certain pressure in the stacking direction of the stacked positive and negative electrodes, The contact state of the internal interfaces can be maintained in a good condition. Applying pressure suppresses expansion in the stacking direction caused by charging and discharging of the all-solid-state battery. This makes it possible to improve the reliability of the all-solid-state battery.

[0416] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0417] (Embodiment 5) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted in an electronic device will be described. Reveal.

[0418] First, as explained in part of the third embodiment, a bendable secondary battery is mounted on an electronic device. Examples of such a device are shown in Figures 30A to 30G. For example, television equipment (also called television or television receiver), computers, Computer monitors, digital cameras, digital video cameras, digital photo frames systems, mobile phones (also called mobile phones or mobile phone devices), portable game machines, personal digital assistants, Examples include audio playback devices and large game machines such as pachinko machines.

[0419] In addition, the flexible secondary battery can be attached to the inner or outer wall of a house or building, or to an automobile. It can also be incorporated into curved surfaces of the interior or exterior of a vehicle.

[0420] FIG. 30A shows an example of a mobile phone. A mobile phone 7400 is provided in a housing 7401. In addition to the built-in display unit 7402, operation buttons 7403, external connection port 7404, The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, etc. The secondary battery 7407 is a secondary battery according to one embodiment of the present invention. This makes it possible to provide a lightweight mobile phone with a long lifespan.

[0421] FIG. 30B shows the mobile phone 7400 in a bent state. When the battery is deformed by an external force and curved, the secondary battery 7 disposed inside the battery The state of the bent secondary battery 7407 is shown in FIG. The secondary battery 7407 is a thin storage battery. The secondary battery 7407 is fixed in a bent state. The secondary battery 7407 has a lead electrode electrically connected to the current collector. For example, the current collector is made of copper foil, and some of it is alloyed with gallium to form an active material in contact with the current collector. This improves adhesion with the polymer layer, resulting in a highly reliable configuration even when the secondary battery 7407 is bent. It is.

[0422] FIG. 30D shows an example of a bangle-type display device. The portable display device 7100 is The device includes a body 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. FIG. 30E shows the bent state of the secondary battery 7104. When the device is worn on the user's arm with the case closed, the case may deform and cause a part or all of the secondary battery 7104 to break. The curvature changes. The degree of curvature at any point on the curve is expressed by the value of the radius of the corresponding circle. The radius of curvature is called the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Part or all of the main surface of the casing or secondary battery 7104 within the range of 150 mm or more The radius of curvature of the main surface of the secondary battery 7104 is 40 mm or more and 150 mm or less. High reliability can be maintained within the range below. By using such a secondary battery, a lightweight, long-life portable display device can be provided.

[0423] FIG. 30F shows an example of a wristwatch-type mobile information terminal. The mobile information terminal 7200 includes: Housing 7201, display unit 7202, band 7203, buckle 7204, operation button 720 5, and has an input / output terminal 7206, etc.

[0424] The portable information terminal 7200 is capable of performing functions such as mobile phone calls, e-mails, document browsing and creation, music playback, internet connection, and so on. It can run various applications such as internet communication and computer games. Cut.

[0425] The display surface of the display unit 7202 is curved, and the display is performed along the curved display surface. The display portion 7202 is provided with a touch sensor, and the screen can be touched with a finger or a stylus. For example, the icon 7 displayed on the display unit 7202 can be operated by touching the You can launch the application by touching 207.

[0426] The operation button 7205 is used to set the time, turn the power on and off, and turn wireless communication on and off. It has various functions such as auto-start, silent mode activation and deactivation, power saving mode activation and deactivation, etc. For example, an operating system built into the mobile information terminal 7200 can be The system also allows the functions of the operation buttons 7205 to be freely set.

[0427] In addition, the mobile information terminal 7200 is capable of performing standardized short-range wireless communication. For example, by communicating with a wireless headset, hands-free You can also make calls.

[0428] The portable information terminal 7200 also has an input / output terminal 7206, and can be connected to other information terminals via a connector. Data can be exchanged directly through the input / output terminal 7206. The charging operation can be performed by wireless power supply without going through the input / output terminal 7206. You may go.

[0429] The display portion 7202 of the portable information terminal 7200 includes the secondary battery of one embodiment of the present invention. By using the secondary battery of one embodiment of the present invention, a lightweight and long-life portable information terminal can be provided. For example, the secondary battery 7104 shown in FIG. 30E is curved and placed inside the housing 7201. , or may be incorporated into the band 7203 in a bendable state.

[0430] The mobile information terminal 7200 preferably has a sensor. For example, a fingerprint sensor may be used as the sensor. Human body sensors such as sensors, pulse sensors, and body temperature sensors, as well as touch sensors, pressure sensors, and acceleration sensors It is preferable that a sensor, etc. be installed.

[0431] FIG. 30G shows an example of a wristband-type display device. The display device 7300 includes a display unit 73 04 and includes the secondary battery of one embodiment of the present invention. The unit 7304 may be provided with a touch sensor, and may function as a mobile information terminal. It can also be done as follows.

[0432] The display surface of the display unit 7304 is curved, and images are displayed along the curved display surface. The display device 7300 can also communicate with the display device 7300 by short-distance wireless communication according to a communication standard. You can change the situation.

[0433] The display device 7300 is also equipped with an input / output terminal, and can be directly connected to other information terminals via a connector. It is possible to exchange data and also charge via the input / output terminal. The charging operation may be performed by wireless power supply without using the input / output terminals.

[0434] When the secondary battery of one embodiment of the present invention is used as the secondary battery included in the display device 7300, A lightweight, long-life display device can be provided.

[0435] In addition, an example in which the secondary battery with good cycle characteristics shown in the above embodiment is mounted on an electronic device will be described. This will be explained using Figures 30H, 31 and 32.

[0436] By using the secondary battery of one embodiment of the present invention as a secondary battery for everyday electronic devices, it is possible to achieve a lightweight and long-lasting battery. For example, we can provide daily electronic products such as electric toothbrushes, electric shavers, Examples include electric beauty devices, and the secondary batteries for these products are designed to be easy for users to hold. Therefore, there is a demand for a secondary battery that is stick-shaped, small, lightweight, and has a large capacity.

[0437] FIG. 30H is a perspective view of a device also known as a tobacco-containing smoking device (electronic cigarette). At 0H, the electronic cigarette 7500 includes an atomizer 7501 including a heating element; a secondary battery 7504 for supplying power to the cartridge including a liquid supply bottle, a sensor, etc. To enhance safety, the secondary battery 7504 is designed to prevent overcharging and over-discharging. A protection circuit for preventing the secondary battery 7504 from being damaged may be electrically connected to the secondary battery 7504. The secondary battery 7504 has an external terminal so that it can be connected to a charging device. Since this becomes the tip when the device is used, it is desirable that the total length is short and the weight is light. The secondary battery according to one embodiment of the present invention has a high capacity and good cycle characteristics, and therefore can be used for a long period of time. This allows us to provide a small and lightweight electronic cigarette 7500 that can be used for long periods of time.

[0438] Next, an example of a foldable tablet terminal is shown in Figures 31A and 31B. The tablet terminal 9600 shown in FIGS. 31A and 31B includes a housing 9630a, a housing 963 0b, a movable part 9640 connecting the housing 9630a and the housing 9630b, a display part 9631a, and A display unit 9631 having a display unit 9631b, switches 9625 to 9627, The display unit 9631 has a flexible fastener 9629 and an operation switch 9628. By using a panel, it is possible to create a tablet terminal with a larger display area. 31A shows the tablet terminal 9600 in an open state, and FIG. 31B shows the tablet terminal The figure shows the 9600 closed.

[0439] The tablet terminal 9600 also includes a housing 9630a and a housing 9630b. The power storage unit 9635 is connected to the housing 9630a through a movable part 9640. It is provided across the body 9630b.

[0440] The entire or a part of the display portion 9631 can be used as a touch panel. By touching images, text, input forms, etc. containing icons displayed in the area, data can be For example, the entire surface of the display portion 9631a on the housing 9630a side is covered with keys. The board buttons are displayed, and information such as characters and images is displayed on the display unit 9631b on the housing 9630b side. The information may be displayed.

[0441] In addition, a keyboard is displayed on the display unit 9631b on the housing 9630b side. The display unit 9631a on the a side may be used to display information such as characters and images. The keyboard display switch button of the touch panel is displayed in the section 9631. Touching the buttons with your finger or a stylus will display a keyboard on the display 9631. It can also be set to

[0442] In addition, the touch panel area of ​​the display unit 9631a on the housing 9630a side and the touch panel area of ​​the display unit 9631b on the housing 9630b side are It is also possible to simultaneously perform touch inputs to the touch panel area of ​​the display portion 9631b.

[0443] Switches 9625 to 9627 are used to operate the tablet terminal 9600. It is not only an interface for switching between various functions, but also an interface for switching between various functions. For example, at least one of the switches 9625 to 9627 may be One acts as a power on / off switch for the tablet device 9600. Also, for example, at least one of the switches 9625 to 9627 may be The ability to switch between horizontal and vertical display, or between black and white and color display In addition, for example, at least one of the switches 9625 to 9627 may have a function to At least one of the display portions 9631 may have a function of adjusting the brightness of the display portion 9631. The brightness of 1 is the external brightness detected by the light sensor built into the tablet terminal 9600 during use. It can be optimized according to the amount of light. Note that the tablet device has a light sensor. In addition, it also incorporates other detection devices such as gyro, acceleration sensor, etc. to detect tilt. It is also acceptable to do so.

[0444] In addition, in FIG. 31A, the display unit 9631a on the housing 9630a side and the display unit 9631b on the housing 9630b side are 9631b has almost the same display area, The display area of ​​each of the display areas 31b is not particularly limited, and the size of one is different from the size of the other. For example, one may have a higher resolution display than the other. It may also be a display panel that can perform this function.

[0445] FIG. 31B 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. A charge / discharge control circuit 9634 is also provided. Use a storage battery.

[0446] As mentioned above, the tablet terminal 9600 can be folded in half, so when not in use, The housing 9630a and the housing 9630b can be folded together. By folding the tablet terminal 9600, the display portion 9631 can be protected. Furthermore, the power storage unit 9635 using the secondary battery of one embodiment of the present invention can With its high capacity and good cycle characteristics, this tablet can be used for a long period of time. A mobile terminal 9600 can be provided.

[0447] In addition, the tablet terminal 9600 shown in FIGS. 31A and 31B can be used in various Functions that display important information (still images, videos, text images, etc.), calendars, dates, or times The function to display the information on the display unit, and the function to touch input or edit the information displayed on the display unit. It has functions such as inputting characters, controlling processes using various software (programs), etc. It is possible.

[0448] The tablet terminal 9600 is equipped with a solar cell 9633 on its surface, which generates power. The solar cell 96 can supply the power to the panel, the display unit, the video signal processing unit, etc. 33 can be provided on one or both sides of the housing 9630, and can efficiently charge the power storage unit 9635. The power storage unit 9635 can be configured to use a lithium ion battery. The use of such a device has the advantage of enabling miniaturization.

[0449] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 31B are shown in FIG. 31C. A block diagram is shown and explained. In FIG. 31C, a solar cell 9633, a power storage body 9635, a DCD C converter 9636, converter 9637, switches SW1 to SW3, display unit 963 1, the storage battery 9635, the DC-DC converter 9636, the converter 96 37, switches SW1 to SW3 correspond to the charge / discharge control circuit 9634 shown in FIG. 31B This is the location.

[0450] First, an example of operation when power is generated by the solar cell 9633 using external light will be described. The power generated by the solar cell is converted into a voltage to charge the storage battery 9635. The converter 9636 increases or decreases the voltage. When power is used from the battery 9633, the switch SW1 is turned on, and the converter 963 7, the voltage is increased or decreased to the voltage required for the display unit 9631. When not displaying in 1, turn SW1 off and SW2 on to turn on the power storage unit 9635. It is sufficient to configure the device so that charging is performed.

[0451] The solar cell 9633 is shown as an example of a power generating means, but is not particularly limited thereto. Storage by other power generation means such as piezoelectric elements and thermoelectric conversion elements (Peltier elements) For example, the power supply 9635 may be configured to transmit and receive power wirelessly (contactlessly). It is also possible to combine it with a contactless power transmission module that charges the battery, or other charging means. You may do so.

[0452] Another example of electronic equipment is shown in Fig. 32. In Fig. 32, a display device 8000 is a display device according to the present invention. 8 is an example of an electronic device using a secondary battery 8004 according to one embodiment. 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, a speaker, and The secondary battery 8004 according to one embodiment of the present invention includes: The display device 8000 is provided inside a housing 8001. The display device 8000 is supplied with power from a commercial power source. It is also possible to use the power stored in the secondary battery 8004. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the present invention can be used. The display device 8000 can be used by using the secondary battery 8004 as an uninterruptible power supply. become.

[0453] The display unit 8002 is a display device having a light emitting element such as a liquid crystal display device or an organic EL element in each pixel. Optical devices, electrophoretic displays, DMD (Digital Micromirror Devices) ice), PDP (Plasma Display Panel), FED (Field A semiconductor display device such as a reflective LED (emission display) can be used.

[0454] In addition to TV broadcast reception, display devices are also used for personal computers and advertising displays. This includes all display devices for displaying information, such as:

[0455] In FIG. 32, a stationary lighting device 8100 includes a secondary battery 8 according to one embodiment of the present invention. 8103. Specifically, the lighting device 8100 includes a housing 8101, 32, the secondary battery 8103 is disposed in the housing 8. 101 and a light source 8102 are installed inside a ceiling 8104. 8, the secondary battery 8103 may be provided inside the housing 8101. The device 8100 can be supplied with power from a commercial power source or can be powered by a secondary battery 8103. The stored power can also be used. Therefore, in the event of a power outage, the power supply from the commercial power source can be reduced. Even when power is not available, the secondary battery 8103 according to one embodiment of the present invention can be used as an uninterruptible power supply. This allows the lighting device 8100 to be used.

[0456] In addition, FIG. 32 illustrates a lighting device 8100 of a fixed type provided on a ceiling 8104. However, in the secondary battery according to one embodiment of the present invention, the side wall 8105, the floor 8106, and the like are not included in the ceiling 8104. It can be used for a fixed lighting device provided in a window 8107 or a desk. It can also be used in upper lighting devices.

[0457] The light source 8102 can be an artificial light source that artificially obtains light using electricity. Specifically, this applies to incandescent lamps, discharge lamps such as fluorescent lamps, and light-emitting devices such as LEDs and organic EL elements. An example of the artificial light source is a light element.

[0458] In FIG. 32, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is 8 is an example of an electronic device using a secondary battery 8203 of one embodiment of the present invention. The indoor unit 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, and the like. In the example shown, the secondary battery 8203 is provided in the indoor unit 8200. The secondary battery 8203 may be provided in the outdoor unit 8204. Both the outdoor units 8204 may be provided with a secondary battery 8203. The battery can be supplied with power from a commercial power source or stored in a secondary battery 8203. In particular, both the indoor unit 8200 and the outdoor unit 8204 are equipped with 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 of one embodiment of the present invention as an uninterruptible power supply, Conditioner can be used.

[0459] In addition, Figure 32 shows a separate type air conditioner consisting of an indoor unit and an outdoor unit. However, it is an integrated air conditioner that has the functions of both an indoor unit and an outdoor unit in a single housing. The secondary battery according to one embodiment of the present invention can also be used for the conditioner.

[0460] In FIG. 32, an electric refrigerator-freezer 8300 includes a secondary battery 8304 according to one embodiment of the present invention. Specifically, an electric refrigerator-freezer 8300 includes a housing 8301, It has a refrigerator door 8302, a freezer door 8303, a secondary battery 8304, etc. A secondary battery 8304 is provided inside the housing 8301. The power can be supplied from a commercial power source or can be stored in a secondary battery 8304. Therefore, when power cannot be supplied from the commercial power source due to a power outage, etc. Even in this case, by using the secondary battery 8304 of one embodiment of the present invention as an uninterruptible power supply, 8300 refrigerators and freezers will be available for use.

[0461] Among the above-mentioned electronic devices, high-frequency heating devices such as microwave ovens and electric rice cookers The sub-devices require high power for a short period of time, so the power that cannot be supplied by the commercial power supply is supplemented. By using a secondary battery according to one embodiment of the present invention as an auxiliary power source for supporting This can prevent the commercial power breaker from tripping when using the

[0462] In addition, during times when electronic devices are not in use, the total amount of power that can be supplied by commercial power suppliers is also During the time period when the ratio of the amount of electricity actually used (called the electricity usage rate) is low, By storing power in the secondary battery, it is possible to prevent power usage rates from increasing outside the above time periods. For example, in the case of the electric refrigerator-freezer 8300, when the temperature is low, the refrigerator compartment door 83 02, during the night when the freezer door 8303 is not opened or closed, power is supplied to the secondary battery 8304. Then, as the temperature rises, the refrigerator door 8302 and the freezer door 8303 open and close. During the daytime, when the vehicle is in operation, the secondary battery 8304 is used as an auxiliary power source, thereby reducing the power consumption during the daytime. The rate can be kept low.

[0463] According to one embodiment of the present invention, the cycle characteristics of a secondary battery can be improved, and the reliability can be improved. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be obtained. This improves the characteristics of the secondary battery, thereby making the secondary battery itself smaller and lighter. Therefore, the secondary battery according to one embodiment of the present invention can be used in the electronic devices described in this embodiment. By incorporating the technology into the electronic device, it is possible to create an electronic device with a longer lifespan and lighter weight.

[0464] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0465] (Embodiment 6) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle will be described.

[0466] When a secondary battery is installed in a vehicle, it becomes a hybrid vehicle (HEV), an electric vehicle (EV), or It will be possible to realize next-generation clean energy vehicles such as plug-in hybrid vehicles (PHEVs). do.

[0467] FIG. 33A illustrates a vehicle using a secondary battery according to one embodiment of the present invention. The automobile 8400 shown is an electric automobile that uses an electric motor as a power source for driving. Alternatively, an electric motor and an engine can be selected and used as the power source for driving. By using one embodiment of the present invention, it is possible to realize a hybrid vehicle with a long driving range. The vehicle 8400 can be realized. The automobile 8400 also has a secondary battery. The secondary battery is The secondary battery modules shown in Figs. 17C and 17D are arranged on the floor of the vehicle. In addition, a battery pack consisting of multiple secondary batteries as shown in Figure 20 can be installed on the floor of the vehicle. The secondary battery may be installed not only to drive the electric motor 8406 but also to Supplying power to light emitting devices such as headlights 8401 and room lights (not shown) can be done.

[0468] In addition, the secondary battery is used for the displays of the car 8400, such as the speedometer and tachometer. The secondary battery can supply power to the navigation system of the automobile 8400. The power supply can be used to power semiconductor devices such as gating systems.

[0469] The automobile 8500 shown in FIG. 33B is a plug-in type secondary battery. It can be charged by receiving power from an external charging facility using a wireless power supply system. FIG. 33B shows a diagram of a secondary battery mounted on a vehicle 8500 being charged from a ground-mounted charging device 8021. 8024 shows the state in which charging is being performed via cable 8022. Charging methods and connector standards are specified by CHAdeMO (registered trademark) and Combo. The charging device 8021 may be a charging station installed in a commercial facility. It may also be a household power source. For example, plug-in technology allows the power source to be connected to an external power supply. The secondary battery 8024 mounted on the automobile 8500 can be charged by the power supply. This can be done by converting AC power to DC power via a conversion device such as an AC / DC converter. can.

[0470] Although not shown, a power receiving device is mounted on the vehicle, and power is supplied contactlessly from a power transmitting device on the ground. In this case, the power transmission device is installed on the road or on the exterior wall. By incorporating this, charging can be done not only when the vehicle is stopped but also while the vehicle is moving. The vehicle may transmit and receive power between them using the same method. A solar cell may be provided in the vehicle so that the secondary battery can be charged when the vehicle is stopped or running. To supply power in the above, an electromagnetic induction method or a magnetic field resonance method can be used.

[0471] 33C shows an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. The scooter 8600 shown in FIG. 1 includes a secondary battery 8602, a side mirror 8601, a turn signal light 86 03. The secondary battery 8602 can supply electricity to the turn signal light 8603. .

[0472] In addition, the scooter 8600 shown in FIG. 33C has a secondary battery 8602 in the storage space under the seat 8604. The secondary battery 8602 can be stored even if the under-seat storage 8604 is small. It can be stored in the under-seat storage 8604. The secondary battery 8602 is removable. When charging, the secondary battery 8602 is brought indoors, charged, and stored before driving. That's fine.

[0473] According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery is increased. Therefore, the secondary battery itself can be made smaller and lighter. If the battery itself can be made smaller and lighter, it will contribute to reducing the vehicle's weight, which will improve the cruising range. In addition, the secondary battery installed in the vehicle can be used as a power supply source for other purposes. In this case, for example, it is possible to avoid using commercial power sources during peak power demand periods. If we can avoid using commercial power sources during peak power demand periods, we can save energy and This can contribute to reducing carbon dioxide emissions. Since the secondary battery can be used for a long period of time, the amount of rare metals used, including cobalt, can be reduced. It is possible.

[0474] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0475] <Preparation of positive electrode active material> Referring to the flow chart in Figure 10, when the number of atoms of cobalt is 100, The positive electrode active material was prepared so that the number of atoms of potassium and aluminum was as shown in Table 1.

[0476] [Table 1]

[0477] First, steps S11 to S13 are carried out to mix a mixture containing magnesium and fluorine. The molar ratio of LiF to MgF2 was LiF:MgF2 = 1:3. The mixture was weighed, mixed, and crushed in a dry manner. The mixture was milled at 150 rpm for 1 hour. The material after the treatment was collected and called Mixture 902. did.

[0478] Next, Cellseed C-10N manufactured by Nippon Chemical Industry Co., Ltd. was prepared as a composite oxide ( Step S24).

[0479] Next, the mixture 902 and the composite oxide were mixed (step S31). When the number of cobalt atoms in the mixture 902 is 100, the number of magnesium atoms in the mixture 902 is The mixture was weighed so that the number of particles was the value shown in Table 1. The mixture was dry mixed. The mixture was mixed in a ball mill using a roller at 150 rpm for 1 hour.

[0480] Next, the treated material was collected to obtain a mixture 903 (step S32).

[0481] Next, the mixture 903 was placed in an alumina crucible and heated at 850°C for 6 minutes in a muffle furnace in an oxygen atmosphere. The alumina crucible was covered with a lid during the annealing. The oxygen flow rate was 10 L / min. The temperature rise rate was 200°C / hr, and the temperature drop rate was 10 hours or more. The material after the heat treatment was collected and sieved to obtain the second composite oxide (S Step S34).

[0482] Next, nickel is added in step S41, and steps S41 to S44 are repeated. Aluminum was added by repeating the steps S41 to S44. Samples under these conditions were also prepared.

[0483] First, nickel hydroxide, which is a metal source, and the second composite oxide were mixed in a ball mill. If the number of atoms of barium is 100, the number of atoms of nickel is as shown in Table 1. The mixture was mixed in a ball mill using zirconia balls at 150 rpm. After mixing, the mixture was passed through a 300 μm φ sieve. The mixture was placed in a mina crucible, covered with a lid, and annealed in an oxygen atmosphere at 850°C for 2 hours.

[0484] Next, a coating layer containing aluminum was formed by the sol-gel method. Isopropoxide was used and 2-propanol was used as the solvent. The number of aluminum atoms is mixed so that the values ​​shown in Table 1 are obtained when the number of aluminum atoms is set to 100. The resulting mixture was then placed in an alumina crucible, covered, and heated in an oxygen atmosphere for 8 hours. The mixture was annealed at 50°C for 2 hours. After that, the powder was collected through a 53 μm diameter sieve and the results are shown in Table 1. The positive electrode active materials were obtained under the conditions shown in Table 1. The atomic numbers of aluminum, nickel, and aluminum are 1, 0.5, and 0.5, respectively. The particle size distribution was measured and the results are shown in FIG.

[0485] <Preparation of secondary battery> Each positive electrode was fabricated using the positive electrode active material obtained above. A slurry of B and PVDF mixed in a ratio of active material:AB:PVDF=95:3:2 (weight ratio) The current collector was coated with the slurry, and NMP was used as the solvent for the slurry.

[0486] After the slurry was applied to the current collector, the solvent was evaporated and then a pressure of 210 kN / m was applied. After this, a pressure of 1467 kN / m was applied. Through these steps, a positive electrode was obtained. The electrode loading is approximately 7 mg / cm 2 It was decided.

[0487] Using the prepared positive electrode, a CR2032 type coin (diameter 20 mm, height 3.2 mm) was A secondary battery of this type was fabricated.

[0488] The counter electrode was made of lithium metal.

[0489] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). The mixture was EC:DEC = 3:7 (volume ratio). The secondary batteries tested contained 2 wt% vinylene carbonate (VC) in the electrolyte. did.

[0490] The separator was made of polypropylene with a thickness of 25 μm.

[0491] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0492] <Cycle characteristics> Next, the cycle characteristics of the fabricated secondary battery were evaluated. Set the voltage to CCCV (0.5C, 4.6V, final current 0.05C), and discharge to CC (0.5C, 2. The battery was repeatedly charged and discharged at a voltage of 100V (5V) to evaluate its cycle characteristics.

[0493] The results of the cycle characteristics after 50 cycles are shown in Figures 34 to 36. The horizontal axis indicates the discharge capacity maintenance. The vertical axis is the discharge rate, and the vertical axis is the discharge energy. The amount of cobalt is 100, and the values ​​of 0.5, 1.0 and 2.0 are summarized. Table 2 also shows the discharge capacity retention rate after 50 cycles when the amount of magnesium is 2.0. Table 3 shows the discharge energy.

[0494] [Table 2]

[0495] [Table 3]

[0496] Figure 37 shows two conditions where nickel and aluminum are both 0.25 and 0.5. and adding nickel and aluminum without performing steps S41 to S44. Discharge capacity maintenance under conditions where no Ni was added (as indicated in the figure legend as "Ni: -, Al: -") The discharge rate and discharge energy are shown below.

[0497] Each condition specifies that the nickel content is greater than 0.1 and less than 1, and the aluminum content is greater than 0.1 and less than 1. In addition, when the magnesium content was 1, particularly excellent properties were obtained. Sex was obtained.

[0498] <Continuous charging durability> Next, if the number of cobalt atoms is 100, the number of magnesium atoms is 1.0 or 1. 0.5, and the number of nickel and aluminum atoms is either no addition or 0.25. The electrode active material was prepared, and a secondary battery was prepared according to the above method, and the continuous charge durability was evaluated. Ta.

[0499] The secondary batteries using the respective positive electrode active materials thus prepared were charged and discharged once at 25°C. Charging was performed at CCCV (0.2C, 4.5V, final current 0.02C), with a 2-minute pause after charging. The discharge was CC (0.2C, 3.0V), and a 2-minute rest period was set after discharge. Ta.

[0500] After that, continuous charging was performed at 60°C with CCCV (0.5C). was set to 4.6 V. 1C was set to 191.7 mA / g.

[0501] When the number of magnesium atoms is 1.0 compared to the number of cobalt atoms being 100, The results when the value was set to 1.5 are shown in FIG. 38A and FIG. 38B, respectively.

[0502] Excellent continuous durability was obtained under the condition where nickel and aluminum were added.

[0503] <xps> When the number of atoms of cobalt is 100, the number of atoms of magnesium, nickel, and aluminum The amount of each of the above was adjusted to obtain the four conditions (XPS-1 to XPS-4) shown in Table 4. A positive electrode active material was prepared in accordance with the method and subjected to XPS analysis.

[0504] [Table 4]

[0505] The concentrations of each element obtained by XPS are shown in Table 5.

[0506] [Table 5]

[0507] Even when nickel was added, the results were below the detection limit in XPS analysis. Aluminum was detected under the condition where aluminum was added. The amount of magnesium was less than a quarter of that of magnesium. Aluminum may be more likely to diffuse into particles than magnesium, and Nickel may be more likely to diffuse into the particles than zinc.

[0508] <XRD of positive electrode> In the obtained positive electrode active material, the number of atoms of magnesium, nickel, and aluminum is Positive electrodes were fabricated using positive electrode active materials under the conditions of 1, 0.5 and 0.5, respectively.

[0509] This positive electrode was charged and discharged once to check the capacity, and then charged to 4.5V, 4.55V or 4 The battery was charged at 0.6V and XRD analysis was performed.

[0510] The charge for capacity confirmation was CCCV (0.2C, 4.5V, final current 0.05C), and after 2 A 20-minute rest period was set. The discharge was CC (0.2C, 3V) and a 20-minute rest period was set after discharge. The temperature was 25°C and 1C = 191mA / g.

[0511] Subsequent charging at 4.5V, 4.55V or 4.6V is CCCV (0.2C, for each voltage, After charging, the secondary battery was placed in a glove box under an argon atmosphere. The battery was disassembled, the positive electrode was removed, and it was washed with DMC. The sample was sealed in a container and subjected to XRD analysis. The results of XRD are shown in Figures 39 and 40. and 40 have different ranges of 2θ on the horizontal axis.

[0512] The lattice constant was calculated from the XRD results, and it was found that the charging voltage was 4.5V and 4.55V. and 4.6V, the a-axis is 2.812, 2.814, and 2.818[× 10 -10 m], and the c-axis is 14.28, 14.04, and 13.79 [× 10 -10 m]. [Example]

[0513] Next, a secondary battery was fabricated using a composite oxide material different from that in Example 1.

[0514] <Secondary battery production 2> As the composite oxide used in step S24, EQ-Lib-LCO manufactured by MTI was used. An electrode active material was prepared.

[0515] The manufacturing conditions are the following five conditions. The first is steps S11 to S13 and S14. Magnesium, nickel and aluminum are not added without performing steps S21 to S24. This is the condition where no Mg was added (shown as "Mg:-, Ni:-, Al:-" in Figure 42). The number of atoms of cobalt is 100, and the number of atoms of magnesium is 1.0. The conditions were as follows: no Mg or aluminum was added (Mg: 1, Ni: -, Al: -). The number of cobalt atoms is 100, the number of magnesium atoms is 1.0, and the number of nickel atoms is 1.0. The number of atoms of Mg and aluminum was set to 0.25 (Mg: 1, Ni: 0.25, The fourth is that when the number of cobalt atoms is 100, the number of magnesium atoms is The condition where the number of atoms is 1.0 and the number of atoms of nickel and aluminum is both 0.5 (M The fifth is the number of cobalt atoms, with 100 being the number of cobalt atoms. When the number of atoms of magnesium, nickel, and aluminum is set to 1.0, the The positive electrode active material prepared under the above conditions was A secondary battery was fabricated in accordance with the method of Example 1, and the cycle characteristics were evaluated. g / cm 2 The positive electrode was approximately 20 mg / cm 2 Two types of positive electrodes were prepared. The test temperature was 45°C and the upper limit voltage for charging was 4.6V.

[0516] <Cycle characteristics> The particle size distribution of the composite oxide manufactured by MTI used is shown in Figure 41. mg / cm 2 The results of the cycle characteristics of the positive electrode with a loading of approximately 20 mg / cm are shown in Figure 42. 2 and The cycle characteristics of the positive electrode are shown in Figure 43. The addition of magnesium improved the cycle characteristics. Further improvement was observed with the addition of nickel and aluminum.

[0517] <Secondary battery production 3> Lithium cobalt oxide manufactured by Aldrich was used as the composite oxide in step S24. The positive electrode active material was prepared under the following two conditions. The first is step S11. Steps S13 and S21 to S24 are not performed, and magnesium and nickel are not used. The second condition is that nickel and aluminum were not added. When the number of magnesium atoms is set to 0, the number of atoms is set to 0.5, and nickel and aluminum are added. The positive electrode active material prepared under these conditions was prepared by the method of Example 1. The cycle test temperature was 45°C, and the charging time was 100 min. The upper voltage limit was set to 4.55V.

[0518] <Cycle characteristics> The particle size distribution of the Aldrich composite oxide used is shown in Figure 44. The results of the cycle characteristics are shown in Figure 45. The addition of magnesium improved the cycle characteristics. Ta. [Example]

[0519] In this example, characteristics of a secondary battery including a positive electrode active material of one embodiment of the present invention were evaluated.

[0520] <Preparation of positive electrode active material> A positive electrode active material was produced with reference to the flow chart in FIG.

[0521] First, steps S11 to S13 are carried out to mix a mixture containing magnesium and fluorine. The molar ratio of LiF to MgF2 was LiF:MgF2 = 1:3. The weighed LiF and MgF2 were dry-ground and mixed. The treatment was carried out in a ball mill using zirconia balls at 150 rpm for 1 hour. The material was collected and designated mixture 902.

[0522] Next, CellSeed 5H manufactured by Nippon Chemical Industry Co., Ltd. was prepared as a composite oxide (Step The particle size distribution of 5H is shown in Figure 47.

[0523] Next, the mixture 902 and the composite oxide were mixed (step S31). When the number of cobalt atoms in the mixture 902 is 100, the number of magnesium atoms in the mixture 902 is The mixture was weighed so that the number of particles was 0.5 or 2. The mixture was dry mixed. The mixture was mixed with zirconia. The process was carried out in a ball mill using balls at 150 rpm for 1 hour. A condition in which no magnesium was added was also prepared.

[0524] Next, the treated material was collected to obtain a mixture 903 (step S32).

[0525] Next, the mixture 903 was placed in an alumina crucible and heated at 850°C for 6 minutes in a muffle furnace in an oxygen atmosphere. The alumina crucible was covered with a lid during the annealing. The oxygen flow rate was 10 L / min. The temperature rise rate was 200°C / hr, and the temperature drop rate was 10 hours or more. The material after the heat treatment was collected and sieved to obtain the second composite oxide (S Step S34).

[0526] Next, nickel hydroxide, which was a metal source, and the second composite oxide were mixed in a ball mill. When the number of cobalt atoms is 100, the number of nickel atoms is 0.5, so The mixture was mixed in a ball mill using zirconia balls at 150 rpm for 1 hour. After mixing, the mixture was sieved through a 300 μm φ sieve. The container was placed in a container, covered with a lid, and annealed in an oxygen atmosphere at 850°C for 2 hours.

[0527] Next, a coating layer containing aluminum was formed by the sol-gel method. The cobalt atom number was 1.0. The aluminum atoms were mixed so that the number of atoms was 0.5 when the total was 100. The resulting mixture was placed in an alumina crucible, covered, and heated at 850°C for 2 hours in an oxygen atmosphere. Thereafter, the powder was collected by sieving through a 53 μm diameter sieve to obtain a positive electrode active material.

[0528] <Preparation of secondary battery> Using the positive electrode active material obtained above, various positive electrodes were fabricated. The positive electrode (in FIG. 48, Mg:-, Ni:-, Al: The positive electrode active material, AB and PVDF, was used as the active material: AB:PVDF=9 The slurry was mixed in a weight ratio of 5:3:2 and coated on the current collector. NMP was used as the solvent.

[0529] After the slurry was applied to the current collector, the solvent was evaporated and then a pressure of 210 kN / m was applied. After this, a pressure of 1467 kN / m was applied. Through these steps, a positive electrode was obtained. The electrode loading is approximately 7 mg / cm 2 It was decided.

[0530] Using the prepared positive electrode, a CR2032 type coin (diameter 20 mm, height 3.2 mm) was A secondary battery of this type was fabricated.

[0531] Lithium metal was used as the counter electrode.

[0532] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). The mixture was EC:DEC = 3:7 (volume ratio). The secondary batteries tested contained 2 wt% vinylene carbonate (VC) in the electrolyte. did.

[0533] The separator was made of polypropylene with a thickness of 25 μm.

[0534] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0535] <Cycle characteristics> Next, the cycle characteristics of the secondary battery fabricated at 45°C were evaluated. The battery was charged and discharged three times to confirm the capacity, and then charged and discharged 50 times for a cycle test.

[0536] The charge for capacity confirmation is CCCV (0.2C, 4.5V, final current 0.02C), and after charging A 20-minute rest period was provided. Discharge was performed at CV (0.2C, 3V), and a 20-minute rest period was provided after discharge. It was established.

[0537] The charging cycle test was CCCV (0.76C, 4.6V, final current 0.02C). After charging, a 20-minute rest period was set. Discharging was performed at CV (0.76C, 3V) with a 20-minute rest period. The time was set as 1C=177.5mA / g.

[0538] The results of the cycle characteristics are shown in Figure 48. By adding nickel and aluminum, A significant improvement in cycle characteristics was observed. In addition, the amount of magnesium added affected the discharge capacity. A difference was observed, with a better discharge capacity being obtained under the condition of magnesium 0.5. [Explanation of symbols]

[0539] 100: positive electrode active material, 101: particles, 102: particles, 103: coating, 108: current collector, 1 09: Positive electrode active material layer, 111: Region, 112: Region< / xps> < / xrd> < / edx> < / xps>

Claims

1. A lithium-ion secondary battery having a positive electrode and a negative electrode, The aforementioned negative electrode has a negative electrode active material containing carbon, The positive electrode has a positive electrode active material, The positive electrode active material has particles containing cobalt, oxygen, and aluminum. The positive electrode active material has a crystalline structure having a space group of R-3m, The aforementioned crystal structure was estimated by Rietveld analysis of the pattern obtained by powder X-ray diffraction. When EDX analysis is performed on the cross-section of the aforementioned particles, The particle has a first region at a distance of 20 nm or more and 200 nm or less from the surface, and in the first region, the number of aluminum atoms in the EDX analysis is 0.04 times or more and less than 1.6 times the number of cobalt atoms. A lithium-ion secondary battery having a second region at a distance of 1 μm or more and 3 μm or less from the surface of the particles, wherein in the second region, the number of aluminum atoms in the EDX analysis is less than 0.03 times the number of cobalt atoms.

2. A lithium-ion secondary battery having a positive electrode and a negative electrode, The negative electrode has a negative electrode active material containing silicon, The positive electrode has a positive electrode active material, The positive electrode active material has particles containing cobalt, oxygen, and aluminum. The positive electrode active material has a crystalline structure having a space group of R-3m, The aforementioned crystal structure was estimated by Rietveld analysis of the pattern obtained by powder X-ray diffraction. When EDX analysis is performed on the cross-section of the aforementioned particles, The particle has a first region at a distance of 20 nm or more and 200 nm or less from the surface, and in the first region, the number of aluminum atoms in the EDX analysis is 0.04 times or more and less than 1.6 times the number of cobalt atoms. A lithium-ion secondary battery having a second region at a distance of 1 μm or more and 3 μm or less from the surface of the particles, wherein in the second region, the number of aluminum atoms in the EDX analysis is less than 0.03 times the number of cobalt atoms.

3. In claim 1 or claim 2, The cross-section of the aforementioned particle is exposed by processing using a focused ion beam processing and observation device, in a lithium-ion secondary battery.

4. A lithium-ion secondary battery having a positive electrode and a negative electrode, The aforementioned negative electrode has a negative electrode active material containing carbon, The positive electrode has a positive electrode active material, The positive electrode active material has particles containing cobalt, oxygen, nickel, and aluminum. When the pattern obtained by powder X-ray diffraction of the positive electrode active material is subjected to Rietveld analysis, it is found to have a crystalline structure with a space group of R-3m. When EDX analysis is performed on the cross-section of the aforementioned particles, The particle has a first region at a distance of 20 nm or more and 200 nm or less from the surface, and in the first region, the number of aluminum atoms in the EDX analysis is 0.04 times or more and less than 1.6 times the number of cobalt atoms. A lithium-ion secondary battery having a second region at a distance of 1 μm or more and 3 μm or less from the surface of the particles, wherein in the second region, the number of aluminum atoms in the EDX analysis is less than 0.03 times the number of cobalt atoms.

5. A lithium-ion secondary battery having a positive electrode and a negative electrode, The negative electrode has a negative electrode active material containing silicon, The positive electrode has a positive electrode active material, The positive electrode active material has particles containing cobalt, oxygen, nickel, and aluminum. When the pattern obtained by powder X-ray diffraction of the positive electrode active material is subjected to Rietveld analysis, it is found to have a crystalline structure with a space group of R-3m. When EDX analysis is performed on the cross-section of the aforementioned particles, The particle has a first region at a distance of 20 nm or more and 200 nm or less from the surface, and in the first region, the number of aluminum atoms in the EDX analysis is 0.04 times or more and less than 1.6 times the number of cobalt atoms. A lithium-ion secondary battery having a second region at a distance of 1 μm or more and 3 μm or less from the surface of the particles, wherein in the second region, the number of aluminum atoms in the EDX analysis is less than 0.03 times the number of cobalt atoms.

6. In claim 4 or claim 5, A lithium-ion secondary battery in which, in the first region, the number of nickel atoms in the EDX analysis is less than 0.5 times the number of aluminum atoms.

7. In any one of claims 4 to 6, The cross-section of the aforementioned particle is exposed by processing using a focused ion beam processing and observation device, in a lithium-ion secondary battery.

8. In any one of claims 1 to 7, The positive electrode active material is a lithium-ion secondary battery in which the number of sulfur atoms, as measured by glow discharge mass spectrometry, is 150 ppm wt or more and 2000 ppm wt or less.

9. In any one of claims 1 to 8, The positive electrode active material is a lithium-ion secondary battery in which the number of titanium atoms, as measured by glow discharge mass spectrometry, is 300 ppm wt or less.

Images