Lithium ion secondary battery

Abstract

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

Description

[Technical Field]

[0001] One aspect of the present invention relates to 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. [Prior art documents] [Patent documents]

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

[0010] [Non-Patent Document 1] Toyoki Okumura et al, “Correlation of lithium ion distribution and X-ray absorption near-edge structure in O3-and O2-lithium cobalt oxides from first-principle calculation”, Journal of Materials Chemistry, 2012, 22, p.17340-17348 [Non-patent document 2] Motohashi, T. et al, “Electronic phase diagram of the layered cobalt oxide system LixCoO2(0.0≦x≦1.0)”, Physical Review B, 80(16);165114 [Non-patent document 3] Zhaohui Chen et al, “Staging Phase Transitions in LixCoO2”, Journal of The Electrochemical Society, 2002, 149(12) A1604-A1609 [Non-patent document 4] WE Counts et al, Journal of the American Ceramic Society,(1953) 36[1] 12-17. Fig.01471 [Non-Patent Document 5] Belsky, A. et al., “New developments in the Inorganic Crystal Structure Database (ICSD): accessibility in support of materials research and design”, Acta Cryst., (2002) B58 364-369. [Non-patent document 6] Dudarev, SL et al, “Electron-energy-loss spectra and the structural stability of nickel oxide: An LSDA1U study”, Physical Review B, 1998, 57(3) 1505. [Non-Patent Document 7] Zhou, F. et al, “First-principles prediction of redox potentials in transition-metal compounds with LDA+U”, Physical Review B, 2004, 70 235121. Summary of the Invention [Problem to be solved by the invention]

[0011] One aspect of the present invention is a method for producing a lithium ion secondary battery having high capacity and excellent charge / discharge cycle characteristics. It is an object of the present invention to provide a positive electrode active material and a manufacturing method thereof. Another object of the present invention is to provide a method for manufacturing a positive electrode active material. When used in lithium-ion secondary batteries, the decrease in capacity during charge / discharge cycles is suppressed. Another object of one embodiment of the present invention is to provide a positive electrode active material having a high capacity. Another object of the present invention is to provide a secondary battery having excellent charge-discharge characteristics. Another object of the present invention is to provide a secondary battery that can maintain a charged state at a high voltage for a long time. The objective of the present invention is to provide a positive electrode active material in which the elution of transition metals such as cobalt is suppressed even when the positive electrode is maintained. Another aspect of the present invention is to provide a secondary battery with high safety or reliability. This is one of the challenges.

[0012] 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

[0013] 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]

[0014] One aspect of the present invention is a positive electrode active material containing lithium, cobalt, oxygen, and magnesium. and has a compound represented by a layered rock salt structure, the compound being represented by the space group R-3m; The compound is a composite oxide containing lithium and cobalt, and the lithium and cobalt sites are The compound is a compound in which magnesium is substituted at the base position, and the compound is a particle. Magnesium is present in the region from the surface of the particle to 5 nm, and in the region more than 10 nm deep from the surface. Magnesium is present in a larger amount than the lithium region, and magnesium is substituted at the cobalt site. It is a positive electrode active material that is converted into more magnesium than magnesium.

[0015] In the above-described structure, the positive electrode active material contains, for example, fluorine.

[0016] In the above structure, for example, the compound has a cobalt coordinate in the unit cell of (0 ,0,0.5), and the oxygen coordinates are (0,0,x), 0.20≦x≦0.25, The volume of the unit cell at the charge depth is the volume of the unit cell at the charge depth of 0. The volume of the knit cell differs by 2.5% or less.

[0017] Another embodiment of the present invention is a secondary battery including any of the above positive electrode active materials.

[0018] Alternatively, in one embodiment of the present invention, the charging voltage is V, the change in V is dV, and the charging capacity is Q Let the change in Q be dQ. The relationship between dQ / dV, which is the ratio of dQ to dV, and V is In the dQ / dV vs V curve, the dQ / dV vs V curve is Measured at the following rates, measured at temperatures above 10°C and below 35°C, and the dQ / dV vs V curve is measured twice when V is between 4.54V and 4.58V, and In the range of 4.58V or less, the first peak occurs in the second measurement, and the voltage is a secondary battery whose voltage is based on the oxidation-reduction potential of lithium metal.

[0019] In the above configuration, for example, the dQ / dV vs V curve is Measured in the range of V ≤ 8V, ​​and the first voltage is measured in the range of V ≤ 4.08V and ≤ 4.18V. The second peak is present in the range of V between 4.18V and 4.25V. The voltages are based on the oxidation-reduction potential of lithium metal.

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

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

[0022] In addition, in the above configuration, for example, the positive electrode is removed from the secondary battery, and the dQ / dV vs. V curve is is measured using lithium metal as the counter electrode to the positive electrode.

[0023] Alternatively, in one embodiment of the present invention, the charging voltage is V, the change in V is dV, and the charging capacity is Q Let the change in Q be dQ. The relationship between dQ / dV, which is the ratio of dQ to dV, and V is In the dQ / dV vs V curve, the dQ / dV vs V curve is Measured at the following rates, measured at temperatures above 10°C and below 35°C, and the dQ / dV vs V curve was repeatedly measured in the range of V 4.05 V to 4.58 V, and V is 4.08V or more and 4.18V or less. V, and the second peak occurs in the range of V 4.18V to 4.25V. The voltage has a third peak at 1000 V, and the voltage is a voltage based on the redox potential of lithium metal. The first peak increases in intensity from the first to tenth measurements. The peak intensity decreased from the 30th to the 100th measurement, and the second peak , the voltage at the peak position increases from the 30th to the 100th measurements.

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

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

[0026] In addition, in the above configuration, for example, the positive electrode is removed from the secondary battery, and the dQ / dV vs. V curve is is measured using lithium metal as the counter electrode to the positive electrode.

[0027] Another embodiment of the present invention is a display device including any one of the above secondary batteries and a display unit. It is an electronic device.

[0028] Alternatively, one aspect of the present invention is a secondary battery comprising any one of the above secondary batteries, an electric motor, and It is a vehicle having the following. [Effects of the Invention]

[0029] According to one aspect of the present invention, a lithium ion secondary battery having high capacity and excellent charge-discharge cycle characteristics is provided. The present invention provides a positive electrode active material for a battery and a method for producing the same. It is possible to provide a method for producing an active material. Therefore, it is possible to provide a positive electrode active material that suppresses the decrease in capacity during charge / discharge cycles. In addition, a high-capacity secondary battery can be provided. In addition, a secondary battery with excellent charge / discharge characteristics can be provided. Furthermore, even if the charged state at high voltage is maintained for a long time, cobalt It is possible to provide a positive electrode active material in which the elution of transition metals such as zinc is suppressed. In addition, the present invention provides a highly reliable secondary battery. Apparatuses or methods for making them may be provided. [Brief explanation of the drawings]

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

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and it is understood by those skilled in the art that various modifications may be made to the modes and details thereof. The present invention will be easily understood by reading the following description of the embodiments. It is not something that is done.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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

[0044] 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.

[0045] 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.

[0046] (Embodiment 1)

[0047] In this embodiment, a positive electrode active material of one embodiment of the present invention will be described.

[0048] [Positive electrode active material structure] 1 and 2, a cathode active material 100 according to an embodiment of the present invention and a conventional cathode active material are shown. In Figures 1 and 2, the positive electrode active material is In addition, we will discuss the case where cobalt is used as the transition metal. Active materials are materials that contain elements other than lithium, cobalt, and oxygen, or that contain cobalt in the surface layer. It is a simple lithium cobalt oxide (LiCoO2) that has not been processed by coating or other methods. be.

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

[0050] As shown in Figure 2, 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. .

[0051] 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.

[0052] 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.

[0053] Repeated high voltage charging and discharging to a charge depth of about 0.88 or more. In other words, lithium cobalt oxide has a H1-3 type crystal structure and a R-3m(O3) structure in the discharged state. The crystal structure changes repeatedly between this structure and the other structure (i.e., a non-equilibrium phase change).

[0054] 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.

[0055] 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 3.5%.

[0056] 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.

[0057] 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.

[0058] <Positive Electrode Active Material of One Embodiment of the Present Invention> ≪Inside≫ In contrast, the positive electrode active material 100 of one embodiment of the present invention has a sufficiently discharged state and a high-voltage state. The change in the crystal structure and the number of transition metal atoms in the charged state at high pressure were compared. The difference in volume is small when

[0059] The crystal structure of the positive electrode active material 100 before and after charge and discharge is shown in FIG. It is a composite oxide containing aluminum, cobalt, and oxygen. It is also preferable that the compound contains a halogen such as fluorine or chlorine.

[0060] The crystal structure at charge depth 0 (discharged state) in Figure 1 is the same as that in Figure 2, R-3m(O3). On the other hand, the positive electrode active material 100 according to one embodiment of the present invention exhibits a low charge capacity when fully charged to a charge depth of about 0.88. In this case, the crystal has a structure different from that shown in FIG. 2. This crystal structure of space group R-3m is referred to herein as is called a pseudo-spinel crystal structure. The pseudo-spinel crystal shown in Figure 1 In the structural diagram, the lithium atom is used to explain the symmetry of the cobalt atom and the symmetry of the oxygen atom. Although the display of cobalt is omitted, in reality, it is about 12 atomic % of cobalt between the CoO2 layers. In both the O3 crystal structure and the pseudospinel crystal structure, However, it is preferable that magnesium exists dilutely between the CoO2 layers, that is, at the lithium sites. It is also preferable that halogens such as fluorine are present randomly and dilutely at the oxygen sites. is preferred.

[0061] 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 conventional LiCoO2. For example, as shown by the dotted line in Figure 1, ,There is almost no misalignment of the CoO2 layers in these crystal structures.

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

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

[0064] The pseudospinel crystal structure has the coordinates of cobalt and oxygen in the unit cell as Co( 0,0,0.5), O(0,0,x), and 0.20≦x≦0.25. Cut.

[0065] 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. In addition, in the process of manufacturing the positive electrode active material 100, heat treatment is preferably performed.

[0066] 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.

[0067] 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.

[0068] It should be noted that the positive electrode active material 100 has been previously described as a composite acid containing lithium, cobalt, and oxygen. Although the case where the cobalt is a nickel oxide has been described, the cobalt may contain nickel in addition to the cobalt. In this case, the number of nickel atoms in the sum of the number of cobalt and nickel atoms (Co+Ni) is The ratio of (Ni) Ni / (Co+Ni) is preferably less than 0.1, and more preferably 0.075 More preferably, it is:

[0069] If the battery is charged at a high voltage for a long period of time, transition metals will leach out of the positive electrode active material into the electrolyte. However, by having nickel in the above ratio, the positive electrode activity It may be possible to suppress the elution of transition metals from the substance 100 .

[0070] By adding nickel, the charge / discharge voltage is reduced, so for the same capacity, the voltage is reduced. This can be achieved, which may result in suppressing the elution of transition metals and the decomposition of the electrolyte. Here, the charge / discharge voltage refers to a voltage in the range from zero charge depth to a predetermined charge depth. .

[0071] ≪Surface layer≫ It is preferable that magnesium is distributed throughout the particles of the positive electrode active material 100. In addition, it is more preferable that the magnesium concentration in the surface layer of the particle is higher than the average of the entire particle. In other words, the magnesium concentration in the particle surface measured by XPS etc. is different from that measured by ICP-MS etc. It is more preferable that the magnesium concentration on the particle surface is higher than the average magnesium concentration on the whole particle. In other words, they are all crystal defects, and when charging, lithium is released from the surface, so the internal This is the part where the lithium concentration is likely to be lower than that of the other part. If the magnesium concentration in the surface layer is high, the change in the crystal structure will be more likely to occur. Furthermore, if the magnesium concentration in the surface layer is high, the electrolyte may break down. It is also expected that the corrosion resistance against hydrofluoric acid produced by dissolution will be improved.

[0072] In addition, the concentration of halogens such as fluorine in the surface layer of the positive electrode active material 100 is higher than the average of the whole particle. The presence of halogen in the surface layer, which is the region in contact with the electrolyte, Corrosion resistance to hydrofluoric acid can be effectively improved.

[0073] In this way, the surface layer of the positive electrode active material 100 has a higher concentration of magnesium and fluorine than the inside. It is preferable that the composition is different from that of the interior, and that the composition is stable at room temperature. Therefore, the surface layer may have a different crystal structure from the interior. For example, at least a part of the surface layer of the positive electrode active material 100 has a rock salt type crystal structure. In addition, when the surface layer and the inside have different crystal structures, the crystal orientation of the surface layer and the inside may be It is preferable that the directions are roughly the same.

[0074] However, if the surface layer is only MgO or only a solid solution structure of MgO and CoO(II), Therefore, the surface layer must contain at least cobalt. In the discharged state, it must also have lithium and have a path for lithium insertion and desorption. It is also preferable that the concentration of cobalt is higher than that of magnesium.

[0075] ≪Grain boundary≫ The magnesium or halogen contained in the positive electrode active material 100 is present randomly and dilutely inside. However, it is more preferable that a portion of the metal is segregated at the grain boundaries.

[0076] In other words, the magnesium concentration at and near the grain boundaries of the positive electrode active material 100 is also It is preferable that the halogen concentration at the grain boundary and its vicinity is higher than that in other regions. It is preferable that the thickness of the slit is higher than that of other areas of the slit.

[0077] Like the particle surface, the grain boundary is also a planar defect. Therefore, it is prone to instability and changes in the crystal structure. Therefore, if the magnesium concentration at and near the grain boundary is high, This makes it possible to more effectively suppress changes in the crystal structure.

[0078] In addition, when the magnesium and halogen concentrations at and near the grain boundaries are high, the positive electrode activity Even if a crack occurs along the grain boundary of a particle of material 100, the crack The magnesium and halogen concentrations are high near the surface. The corrosion resistance of the positive electrode active material against hydrofluoric acid can also be improved.

[0079] In this specification, the vicinity of the grain boundary refers to the region up to about 10 nm from the grain boundary. We will do so.

[0080] ≪Particle size≫ If the particle size of the positive electrode active material 100 is too large, it becomes difficult for lithium to diffuse. On the other hand, if the size is too small, the surface of the active material layer becomes too rough. Problems include difficulty in supporting the active material layer when coating on the body, and excessive reaction with the electrolyte. Therefore, D50 is preferably 1 μm or more and 100 μm or less, and more preferably 2 μm or more and 40 μm or less. It is more preferable that the thickness is 5 μm or less, and further more preferable that the thickness is 5 μm or more and 30 μm or less.

[0081] <Analysis method> In one embodiment of the present invention, a positive electrode active material exhibits a pseudospinel crystal structure when charged at a high voltage. Whether or not the positive electrode active material 100 is the same as the positive electrode active material 100 can be determined by subjecting the positive electrode charged at a high voltage to XRD, electron beam diffraction, etc. , neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. In particular, XRD can be used to determine the symmetry of transition metals such as cobalt contained in the positive electrode active material. High-resolution analysis, comparison of crystallinity and crystal orientation, lattice periodic distortion The positive electrode obtained by disassembling the secondary battery can be measured as it is. This is preferable in that sufficient accuracy can be obtained even when the measurement is performed in a short time.

[0082] As described above, the positive electrode active material 100 according to one embodiment of the present invention is in a state where it is charged at a high voltage. It is characterized by the fact that there is little change in the crystal structure when it is charged at a high voltage and discharged. Materials with a crystal structure that undergoes large changes in state and charge / discharge ratios of 50 wt% or more can withstand high voltage charging and discharging. Furthermore, the desired crystal structure cannot be achieved by simply adding impurity elements. It should be noted that there are cases where the coating is not suitable for the coating containing magnesium and fluorine. Although they share the common feature of being lithium phosphate, they are pseudospinel crystals when charged at high voltage. When the structure is 60 wt% or more, and when the H1-3 type crystal structure is 50 wt% or more At a certain voltage, the pseudo-spinel crystal structure is almost 100 wt %. Furthermore, if the voltage is increased, the H1-3 type crystal structure may occur. In order to determine whether or not the positive electrode active material 100 of the present embodiment is a positive electrode active material, crystallography such as XRD can be used. Structural analysis is needed.

[0083] However, when the positive electrode active material is in a high-voltage charged or discharged state, its crystalline structure changes when it comes into contact with the air. For example, the pseudo-spinel crystal structure may change to the H1-3 crystal structure. Therefore, all samples should be handled in an inert atmosphere such as argon. It is preferable to dry the mixture.

[0084] ≪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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] The separator can be made of polypropylene with a thickness of 25 μm.

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

[0090] 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.

[0091] The above is the charging voltage when lithium metal is used as the counter electrode. When charging using graphite as the negative electrode, the Charging can be performed using a value obtained by subtracting 0.1V from the charging voltage as a guideline.

[0092] In this specification, the charging voltage when lithium metal is used as the counter electrode is, for example, For the secondary battery used, the value obtained by subtracting 0.05V or more and 0.3V or less from the value is more preferable. Preferably, the voltage can be set to a value minus 0.1V.

[0093] <XRD> CuKα1 radiation calculated from the pseudospinel crystal structure and H1-3 crystal structure model The ideal powder XRD pattern of LiCo at a charge depth of 0 is shown in Figure 3. Ideal XR calculated from the crystal structure of O2 (O3) and CoO2 (O1) at charge depth 1 The patterns of LiCoO2(O3) and CoO2(O1) are also shown. CSD (Inorganic Crystal Structure Database) ) (see Non-Patent Document 5) Reflex Powder Diff, one of the modules of o(BIOVIA), The 2θ range was from 15° to 75°, and the step size was ze=0.01, wavelength λ1=1.540562×10 -10 m, λ2 are not set, Mon The H1-3 crystal structure pattern is based on the non-patent literature. The pseudospinel pattern was similarly created from the crystal structure information described in Reference 3. The crystal structure was estimated from the XRD pattern of the positive electrode active material, and the The XRD patterns were fitted using the crystal structure analysis software (Ker). Created a turn.

[0094] As shown in Figure 3, in the pseudospinel crystal structure, 2θ = 19.30 ± 0.20° (19 .10° or more and 19.50° or less), and 2θ = 45.55 ± 0.10° (45.45° More specifically, a diffraction peak appears at 2θ=19.3° or less. 0±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° or more and 45.60° or less). No peaks appear at these positions in the type 3 crystal structure and CoO2 (P-3m1, O1). Therefore, when charged at high voltage, 2θ = 19.30 ± 0.20° and 2θ = The appearance of the peak at 45.55±0.10° indicates that the positive electrode active material 100 according to one embodiment of the present invention This can be said to be a characteristic of

[0095] 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.

[0096] 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 pseudo-spinel crystal structure was preferably 50 wt% or more. It is preferable that the content is 60 wt% or more, and more preferable that the content is 66 wt% or more. It is preferable that the pseudo-spinel crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably 10 wt% or more. Furthermore, if the content is more preferably 66 wt % or more, the positive electrode active material will have sufficiently excellent cycle characteristics. This can be done.

[0097] In addition, even after more than 100 charge / discharge cycles from the start of measurement, Rietveld analysis was performed. In this case, the pseudospinel crystal structure is preferably 35 wt% or more, and more preferably 40 wt% or more. It is more preferable that the content is 43 wt % or more, and further more preferable that the content is 43 wt % or more.

[0098] In addition, the crystallite size of the pseudo-spinel structure of the positive electrode active material particles is Therefore, the same X as the positive electrode before charging and discharging is used. Even under RD measurement conditions, a clear peak of pseudospinel crystal structure was observed after high-voltage charging. On the other hand, in simple LiCoO2, some of the structure resembles a pseudospinel crystal structure. Even if it is, the crystallite size will be small and the peak will be broad and small. can be determined from the half-width of the XRD peak.

[0099] In addition, the layered rock salt structure of the particles of the positive electrode active material in the discharged state, which can be estimated from the XRD pattern, In this crystal structure, it is preferable that the lattice constant of the c-axis is small. When a foreign element substitutes for the ammonium site, or when cobalt enters the oxygen tetracoordinate site (A site), Therefore, first, the amount of Co3O4 with a different element substitution and spinel crystal structure is small. A composite oxide with a layered rock salt type crystal structure with few defects is created, and then magnesium is added. Mixing a nesium source and a fluorine source to insert magnesium into the lithium site provides good It is believed that a positive electrode active material that exhibits cycle characteristics can be produced.

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

[0101] In order to keep the c-axis lattice constant within the above range, it is preferable to have a small amount of impurities, especially cobalt. The amount of transition metals other than manganese and nickel added is preferably small. It is preferable that the content is 1000 ppm wt or less, and more preferably 1500 ppm wt or less. In addition, cation mixing between lithium and cobalt, manganese, or nickel is less likely to occur. It is preferable not to have one.

[0102] The lattice constant of the a-axis is 2.818×10 -10 m or less is preferable.

[0103] The lattice constant of the c-axis in the charged state is, for example, 14.05 × 10 -10 m or more 14. 30×10 -10 Here, the charging voltage is preferably less than 4.5V.

[0104] Alternatively, when the charging voltage is 4.5 V or higher, based on lithium metal, the c-axis The lattice constant of is, for example, 13.8×10 -10 It may be less than m.

[0105] The characteristics revealed from the XRD pattern are characteristics regarding the internal structure of the positive electrode active material. In the case of a positive electrode active material with an average particle diameter (D50) of about 1 μm to 100 μm, the inside and In comparison, the volume of the surface layer is very small, so the surface layer of the positive electrode active material 100 is different from the inside. Even if the material has a different crystal structure, it is highly likely that this will not appear in the XRD pattern.

[0106] In the positive electrode using the positive electrode active material according to one embodiment of the present invention, the XRD of the positive electrode after charging was If there is a peak at 0.70±0.20°, the half-width is V, the half-value width is 10 times or less, preferably 5 times or less, and more preferably Preferably, it is 4.3 times or less, and more preferably, it is 3.8 times or less. When D has a peak at 2θ=45.2±0.30°, the half-width is The half-width of the discharged voltage should be 4 times or less, preferably 3 times or less, of the half-width of the discharged voltage when the discharged voltage is 2.5V. The angle is preferably 0.3 times or less, and more preferably 2.8 times or less. The peak at 2θ=45.2±0.30° corresponds to the (0 0 3) plane of the O3 crystal structure. These are thought to correspond to the (1 0 4) plane of the type 3 crystal structure.

[0107] In the above, the charging voltage is 4.5V or more, based on the voltage of lithium metal. More preferably, even if the voltage is 4.45 V or more, the half-value width is in the above range.

[0108] In addition, if the XRD of the charged positive electrode shows a peak at 2θ=19.30±0.20°, In this case, the half-width is 2θ=18 before charging or when discharging to 2.5V. The half-width of the peak appearing at 0.70±0.20° should be 10 times or less, preferably 5 times or less. The charge is preferably 4.3 times or less, and more preferably 3.8 times or less. When the positive electrode and XRD have a peak at 2θ=45.55±0.10°, the half-width is Before charging or when discharging to 2.5V, 2θ=45.2±0.30° appears. The half width of the peak to be measured is 5 times or less, more preferably 4.3 times or less, and even more preferably Most are 3.8 times or less.

[0109] In the above, the charging voltage is 4.5V or more, based on the voltage of lithium metal. More preferably, it is 4.55 V or more, and even more preferably, it is 4.6 V or more, but the half width is within the above range. It is preferable that the range is as shown.

[0110] In addition, the XRD of the charged positive electrode shows, for example, 2θ=19.28±0.6°, or 2 It has a peak at θ=19.32±0.4°.

[0111] The small increase in the half-width is due to the desorption of lithium during charging. This indicates that the disorder of the crystal structure can be suppressed to a minimum. In the charge-discharge cycle characteristics of a secondary battery using the material, the decrease in discharge capacity is suppressed.

[0112] As described in Examples below, in a positive electrode using the positive electrode active material of one embodiment of the present invention, If the charge depth is deep, for example, about 4.5V on a lithium metal basis, after discharge For example, the lattice constant of the a-axis becomes smaller than the value when the material is discharged to 2.5 V. As the charge depth increases, the lattice constant of the a-axis increases. It is believed that the axial lattice constant is preferably closer to the value after discharge.

[0113] The change in the lattice constant of the a-axis is thought to correspond to, for example, Co-O bonds. The bond is considered to be highly covalent. When the charge depth is deep, the lattice constant of the a-axis is It is thought that charging is being carried out while maintaining a stable crystal structure by approaching the value after discharge. can be.

[0114] During charging, when the voltage is 4.55V or higher based on lithium metal, the lattice constant of the a-axis is For example, 2.813 x 10 -10 It is preferable that the length is m or more.

[0115] In addition, the positive electrode active material undergoes repeated charge and discharge cycles, and carrier ions, for example, For example, the desorption and insertion of lithium ions occurs repeatedly. This allows each atom to move, relaxing the structure and allowing lithium to be desorbed more stably. In such a case, the discharge capacity becomes higher, which is preferable. Sum, for example, refers to the movement of each atom to a more stable position.

[0116] ESR Here, using Figures 4 and 5, the difference between the pseudo-spinel crystal structure and other crystal structures will be explained. In the pseudo-spinel crystal structure, as shown in Fig. 1 and As shown in Figure 4A and Figure 4B, cobalt is present in the oxygen-hexacoordinated site. In cobalt with 6 oxygen coordination, the 3d orbital is e g Orbit and t 2g split into orbits, oxygen present The orbit avoiding the direction of t 2g The orbital energy is low. Some of the Baltic 2g Diamagnetic Co with all orbitals filled 3+ Cobalt is the acid The other part of the cobalt present in the hexacoordinated sites is paramagnetic Co 2+ or Co4+ Noko This paramagnetic cobalt may be Co 2+ and Co 4+ In either case, Since there is only one pair of electrons, they cannot be distinguished by ESR, but depending on the valence of the surrounding elements, Either valence may be taken.

[0117] On the other hand, conventional positive electrode active materials contain spinel that does not contain lithium in the surface layer when charged. It has been stated that the crystal structure may be of the type spinel shown in Figure 5A. It has a Co3O4 type crystal structure.

[0118] When spinel is described by the general formula A[B2]O4, element A is oxygen tetracoordinate and element B is oxygen Therefore, in this specification, the site with 4-coordinated oxygen atoms is called the A site, and the site with 6-coordinated oxygen atoms is called the B site. The site is sometimes called the B site.

[0119] In the spinel-type crystal structure of Co3O4, not only the B site with 6 oxygen atoms but also the B site with 4 oxygen atoms As shown in Figure 5B, cobalt with 4 oxygen coordination atoms is also present in the A site. Cracked e g Orbit and t 2g Of the orbitals, e g The orbital energy is low. Therefore, oxygen is tetracoordinated. Co 2+ , Co 3+ and Co 4+ Both have unpaired electrons and are paramagnetic. When particles containing sufficient spinel-type Co3O4 are analyzed by ESR, etc., it is found that Co 2 + , Co 3+ or Co 4+ A peak due to paramagnetic cobalt should be detected. .

[0120] However, in the positive electrode active material 100 according to one embodiment of the present invention, the oxygen-tetracoordinated paramagnetic cobalt Therefore, the pseudospinel referred to in this specification and the like includes Unlike normal spinel, it does not contain cobalt with four oxygen coordinates in amounts detectable by ESR. Therefore, compared to conventional examples, the positive electrode active material of one embodiment of the present invention has a signal that can be detected by ESR or the like. The peaks due to the pinel type Co3O4 may be small or too few to be recognized. Since spinel-type Co3O4 does not contribute to the charge / discharge reaction, there is little spinel-type Co3O4. Thus, the ESR analysis also shows that the positive electrode active material 100 is different from conventional examples. It can be determined that there is.

[0121] 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 It depends on the material, but it is about 1 atomic %.

[0122] When XPS analysis was performed on 100% positive electrode active material, the cobalt concentration was set to 1. The relative value of the magnesium concentration is preferably 0.4 or more and 1.5 or less, and more preferably 0.45 or more and 1.00 or less. The relative value of the concentration of halogen such as fluorine is preferably 0.05 or more and 1.5 or less. It is preferable that the ratio is 0.3 or more and 1.00 or less.

[0123] 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 684.3 eV or more and less than 685 eV. It is more preferable that the bond energy is about 6 V, which is the bond energy of lithium fluoride. 85 eV, and the binding energy of magnesium fluoride, 686 eV. In other words, when the positive electrode active material 100 contains fluorine, lithium fluoride and A bond other than magnesium fluoride is preferred.

[0124] 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 .

[0125] 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.

[0126] 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.

[0127] When EDX analysis was performed on the positive electrode active material 100, the peak of magnesium concentration in the surface layer The pores are preferably present at a depth of up to 3 nm from the surface of the positive electrode active material 100 toward the center. Preferably, the surface is present at a depth of up to 1 nm, and more preferably at a depth of up to 0.5 nm. It is more preferable that:

[0128] In addition, the distribution of fluorine contained in the positive electrode active material 100 may overlap with the distribution of magnesium. Therefore, when EDX analysis is performed, the peak of the fluorine concentration in the surface layer is It is preferable that the surface of the substrate 100 is located at a depth of 3 nm from the surface toward the center, and the depth of 1 nm It is more preferable that the ions are present at a depth of up to 0.5 nm, and even more preferable that the ions are present at a depth of up to 0.5 nm. It's nice.

[0129] When the positive electrode active material 100 was subjected to line analysis or area analysis, The ratio of the number of magnesium and cobalt atoms (Mg / Co) is between 0.020 and 0.50. It is more preferable that the ratio is 0.025 or more and 0.30 or less. It is even more preferable that the ratio is 0.030 or more and 0.040 or less. .20 or less is preferred.

[0130] ≪dQ / dVvsV curve≫ Furthermore, the positive electrode active material of one embodiment of the present invention can be charged at a high voltage and then discharged at a low voltage of, for example, 0.2 C or less. When discharging at a low rate, a characteristic voltage change may appear near the end of the discharge. The dQ / dV vs V curve obtained from the discharge curve shows that the In this case, the presence of at least one peak in the range of 3.5V to 3.9V is clearly evident. You can bite it.

[0131] In addition, the positive electrode active material of one embodiment of the present invention has a dQ / dV vs. V curve of 4.0 The first peak in the range of 5V or more and less than 4.15V, and the second peak in the range of 4.15V or more and less than 4.25V The second peak in the range of 4.5V to 4.58V, and the third peak in the range of 4.5V to 4.58V. and may have.

[0132] The positive electrode active material according to one embodiment of the present invention can be charged at a rate of 0.1 C or more and 1.0 C or less. For example, 0.5C, and the measurement temperature is, for example, 10°C or higher and 35°C or lower. When charging at 25°C, the dQ / dV vs V curve shows that the charging voltage is The first peak occurs when the voltage is between 4.08V and 4.18V, and the second peak occurs when the voltage is between 4.18V and 4.2V. The second peak in the range of 5V or less and the second peak in the range of 4.54V to 4.58V It is preferable that the chromatogram has a total of three peaks, including a first peak and a third peak in the first region.

[0133] Alternatively, in the above, a rate of 0.01 or more and less than 0.1C, more specifically, for example The rate is 0.05C, and the measurement temperature is, for example, 10°C or higher and 35°C or lower. More specifically, for example, When charging at 5°C, the charging voltage in the dQ / dV vs V curve is The first peak occurs in the range of 4.03V to 4.13V, and the second peak occurs in the range of 4.14V to 4.21V. The second peak in the range of 4.50 V or less and the second peak in the range of 4.60 V or more It is preferable that the peaks be a total of three peaks, including a first peak and a second peak.

[0134] In addition, at the charge voltage at which the first peak is observed, the positive electrode active material is in the space group P2 / It is preferable that the crystal structure represented by m is a crystal structure in which the third peak is observed. At a given voltage, the positive electrode active material preferably has a crystal structure corresponding to the space group R-3m. It's nice.

[0135] In addition, the third peak has a shape where the top of the peak is flattened compared to the Lorentz function. or the sum of two or more Lorentzian functions with the same peak height but different peak positions. The third peak preferably has a shape as described above. Examples of factors that cause the third peak to have such a shape include: It is thought that the O3 type crystal structure and the pseudospinel type crystal structure are mixed.

[0136] In addition, in a secondary battery including a positive electrode having the positive electrode active material of one embodiment of the present invention and a negative electrode, The negative electrode has graphite, and the dQ / dV vs V curve of the secondary battery is similar to that of lithium metal shown above. At least one of the first peak to the third peak in the voltage range obtained by subtracting 0.1 V from the voltage In such a case, it is preferable to repeat the charge / discharge cycle. The dQ / dV vs V curve was calculated from the curve, and the results were obtained from the first to tenth charge / discharge cycles. In this case, if the dQ / dV vs. V curve of the secondary battery has a third peak, the peak strength is It is preferable that the degree of increase is observed between the 30th and 100th charge / discharge cycles. For example, if the dQ / dV vs. V curve of the secondary battery has a third peak, When the dQ / dV vs. V curve of the secondary battery has a first peak, If the voltage at the peak position increases, the voltage at the peak position increases.

[0137] [Example of the structure of the positive electrode active material] LiCoO in which magnesium is substituted at the lithium and cobalt atom positions An example of 2 is described below.

[0138] <First principles calculation> LiC in which magnesium is substituted for the lithium atom or the cobalt atom. For oO2, the stabilization energy before and after substitution was calculated using first-principles calculations. We will explore the effects of magnesium on energy.

[0139] The crystal structure is a layered rock salt structure, the space group is R-3m, and the lattice and The atomic positions are optimized and the respective energies are calculated.

[0140] An example of the results of first-principles calculations is shown below.

[0141] The software is VASP (The Vienna Ab initio simu The functional was GGA (Generalized Generalization Package). Zed-Gradient-Approximation) + U was used. U of cobalt The potential was set to 4.91. The electronic state pseudopotential was PAW (Project The potential generated by the Coulomb wave (CW) method was used. The off-off energy was set to 520 eV. Here, the U potential is and Non-Patent Document 7.

[0142] In this specification, the energy obtained in this manner is called stabilization energy.

[0143] First, we created a 4x4x1 supercell and optimized the crystal structure of LiCoO2. The stabilization energy was calculated. At this time, the lattice constant was optimized. The k-points were The number of atoms is 48 lithium atoms, 48 ​​cobalt atoms, and 48 oxygen atoms. The number was set at 96.

[0144] Next, one lithium atom or one cobalt atom is replaced with a magnesium atom. The lattice constant was kept constant, and the optimization was performed to determine the stabilization energy.

[0145] Next, for each structure for which the stabilization energy was calculated, one lithium atom was removed. Calculate the stabilization energy of the structure, and calculate the difference in stabilization energy between before and after lithium desorption, ΔE ΔE can be expressed by the following formula. Note that the following is for LiCoO2 ( 48-x) The difference between the energy after desorption of lithium and the energy before desorption is Represents. E total (Li 48 Co 48 O 96 ) is the stabilization energy of LiCoO2, E total (Li x Co 48 O 96 ) is the (48-x) lithium atom from LiCoO2. Stabilization energy after desorption, E metal (Li) is the stabilization energy of the lithium atom The stabilization energy of the lithium atom was calculated using the body-centered cubic structure.

[0146]

number

[0147] Also, like LiCoO2, Li 48 Co 48 O 96 One lithium atom in , the structure in which (48-x) lithium atoms are removed from the magnesium-substituted structure (Li (x-1) Mg1Co 48 O 96 ) and one cobalt atom replaced by magnesium. The structure in which (48-x) lithium atoms are removed (Li x Mg1Co 47 O96 ) For each of the above, the difference in stabilization energy before and after lithium desorption is calculated as I asked.

[0148] Next, the voltage Va when lithium was removed was calculated using the following formula: Here, n is the number of moles of lithium removed, and F is the Faraday constant. be.

[0149]

number

[0150] Here, if the difference in stabilization energy ΔE is used as the Gibbs free energy ΔG, then: The following formula is obtained.

[0151]

number

[0152] The voltage Va calculated from the above formula is shown in the table below. The para indicates that the lithium at the para position has been removed. The term "meta" indicates that the lithium was removed from the meta position.

[0153] [Table 1]

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

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

[0156] Figure 7A shows the crystal structure shown in Figure 6A, where one magnesium atom is substituted for the lithium position. The crystal structure is shown in Fig. 7A as viewed from the a-axis direction, and Fig. 7B as viewed from the c-axis direction. vinegar.

[0157] FIG. 8A shows the crystal structure obtained by extracting one lithium atom from the crystal structure shown in FIG. 7A. 8B shows a view of FIG. 8A as seen from the c-axis direction.

[0158] Figure 9A shows two lithium atoms corresponding to the ortho positions in the crystal structure shown in Figure 7B. Figure 9B shows the crystal structure after extraction of two lithium atoms corresponding to the para positions. Figure 9C shows the crystal structure with three lithium atoms corresponding to the meta positions removed. Each is shown.

[0159] Figure 10A shows the crystal structure shown in Figure 6A, with one magnesium atom substituted for the cobalt position. The crystal structure is shown in Fig. 10B as viewed from the a-axis direction, and in Fig. 10C as viewed from the c-axis direction. Shows.

[0160] FIG. 11A shows the crystal structure obtained by removing one lithium atom from the crystal structure shown in FIG. 10A. 11B shows a view of FIG. 11A as seen from the c-axis direction.

[0161] FIG. 11C shows the crystal structure in which two lithium atoms are extracted from the crystal structure shown in FIG. 10B. show.

[0162] When magnesium atoms are substituted for cobalt positions, Va becomes 3.7 V or more. The value was about 0.5 V lower than when no magnesium atoms were substituted. When substituted at the lithium position, Va became even lower.

[0163] From this, it is possible to determine whether the magnesium atom is substituted at the lithium position or the cobalt position. Even in this case, a voltage drop was observed, suggesting that this could be the cause of the hump in the discharge curve. In addition, when the cobalt position is substituted, the voltage difference is relatively small compared to when there is no substitution. It is relatively small, and substitution at the lithium position may result in a more clearly observed bump. On the other hand, if the voltage is too low, the lithium is not inserted during discharge. It is also possible that ions are not inserted in the discharge.

[0164] As a positive electrode active material of one embodiment of the present invention, lithium, magnesium, cobalt, an oxide, The dQ / was calculated from the discharge curve of a secondary battery using a positive electrode active material containing silicon and fluorine. An example of a dV vs V curve is shown below. Lithium metal was used as the counter electrode. The dQ / dV vs V curves were measured for the discharge curves at the 1st, 2nd, 3rd, 5th and 10th cycles. The results are shown in Figure 43A. An enlarged view of the range from 3.4 V to 4.0 V is also shown in Figure 43B. As is clear from Figures 43A and 43B, a downward convex peak is observed. The largest peak was at about 3.9 V. As shown in the figure, the maximum peak was at 3.5 V. At least one peak was present in the range of 0.01 to 3.9V.

[0165] Thus, the positive electrode active material of one embodiment of the present invention can be charged at a high voltage, for example, at a current of 0.2 C or more. When discharging at the low rate shown below, it is clear that a characteristic voltage change appears near the end of discharge. This change is seen in the dQ / dV vs V curve, which is in the range of 3.5V to 3.9V. This can be clearly seen by the presence of at least one peak.

[0166] The results in Table 1 show that although there are some differences in the voltage values, they are in the range of 3.5V to 3.9V. The peaks are due to the substitution of magnesium at the cobalt or lithium positions. It suggests the possibility.

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

[0168] (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.

[0169] [Method for producing positive electrode active material] First, an example of a method for manufacturing a positive electrode active material 100 according to one embodiment of the present invention will be described with reference to FIG. Another example of a specific manufacturing method is shown in FIG.

[0170] <Step S11> As shown in step S11 of FIG. 12, first, a fluorine source and a salt are used as materials for the first mixture. Prepare a halogen source such as a fluorine source and a magnesium source. A lithium source may also be prepared. preferable.

[0171] 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.

[0172] In this embodiment, lithium fluoride LiF is prepared as a fluorine source and a lithium source, Magnesium fluoride (MgF2) will be prepared as a fluorine source and magnesium source. (Step S11 in FIG. 13). Lithium fluoride LiF and magnesium fluoride MgF2 are Mixing LiF:MgF2 at a molar ratio of about 65:35 has the greatest effect in lowering the melting point. On the other hand, if the amount of lithium fluoride is too large, the lithium becomes too excessive. There is a concern that the cycle characteristics may deteriorate. The molar ratio of LiF to MgF2 is preferably LiF:MgF2=x:1 (0≦x≦1.9). Preferably, LiF:MgF2=x:1 (0.1≦x≦0.5) is more preferable, and LiF:M It is more preferable that gF2=x:1 (x=nearly 0.33). is greater than 0.9 times and less than 1.1 times that value.

[0173] 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 (see step S11 in FIG. 13).

[0174] <Step S12> Next, the materials of the first mixture are mixed and crushed (steps in FIGS. 12 and 13). Mixing can be done either dry or wet, but wet mixing requires finer grinding. For mixing, a ball mill, a bead mill, etc. can be used. When using a ball mill, for example, zirconia balls can be used as the media. It is preferable to carry out this mixing and grinding step sufficiently to pulverize the first mixture. It's nice.

[0175] <Steps S13 and S14> The mixed and crushed materials are collected (step S13 in FIGS. 12 and 13), and the first A mixture is obtained (step S14 in FIGS. 12 and 13).

[0176] The first mixture has an average particle diameter (D50: also called median diameter) of 600 nm It is preferably from 1 μm to 20 μm, and more preferably from 1 μm to 10 μm. If the first mixture is finely pulverized in this way, lithium, transition metals, and When the first mixture is mixed with a composite oxide having oxygen, the first mixture is formed on the surface of the composite oxide particles. It is easy to make the first mixture adhere uniformly to the surface of the composite oxide particles. After heating, halogen and magnesium are thoroughly distributed in the surface layer of the composite oxide particles. If there is a region in the surface layer that does not contain halogen and magnesium, the charging In this case, it may be difficult for the material to have a pseudospinel crystal structure in an electrically charged state, as described below.

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

[0178] As the lithium source, for example, lithium carbonate, lithium fluoride, etc. can be used.

[0179] The transition metal may be at least one of cobalt, manganese, and nickel. The composite oxide containing lithium, transition metals, and oxygen has a layered rock-salt type crystal structure. Therefore, the mixture ratio of cobalt, manganese, and nickel is preferably such that the layered rock salt structure can be obtained. In addition, it is preferable that these transition metals are used within a range in which a layered rock salt type crystal structure can be formed. Aluminum may also be added.

[0180] As the transition metal source, oxides, hydroxides, etc. of the above transition metals can be used. As the cobalt source, for example, cobalt oxide, cobalt hydroxide, etc. can be used. As the nickel source, manganese oxide, manganese hydroxide, etc. can be used. As the aluminum source, nickel oxide, nickel hydroxide, etc. can be used. , aluminum oxide, aluminum hydroxide, etc. can be used.

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

[0182] <Step S23> Next, the mixed material is heated. This process is called "sintering" to distinguish it from the subsequent heating process. This is sometimes called the first heating or the formation of the first layer. Heating can be performed at temperatures between 800°C and 1100°C. It is preferable to carry out the treatment at a temperature of 900°C or higher and 1000°C or lower, and it is even more preferable to carry out the treatment at about 950°C. If the temperature is too low, the starting materials may not be fully decomposed and melted. On the other hand, if the temperature is too high, the transition metals may be excessively reduced, or lithium may evaporate. For example, defects may occur in which cobalt becomes divalent.

[0183] 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.

[0184] However, cooling to room temperature in step S23 is not essential. 24, Step S25 and Steps S31 to S34 If not, cooling may be to a temperature above room temperature.

[0185] <Steps S24 and S25> The sintered material is recovered (step S24 in FIG. 12), and lithium, transition metals, and A composite oxide containing oxygen is obtained (step S25 in FIG. 12). lithium, manganese oxide, lithium nickel oxide, and cobalt partially substituted with manganese This gives lithium cobalt oxide or lithium nickel-manganese-cobalt oxide.

[0186] In step S25, a compound having lithium, a transition metal, and oxygen synthesized in advance is used. In this case, steps S21 to S23 may be performed using a composite oxide (see FIG. 13). S24 can be omitted.

[0187] When using a pre-synthesized composite oxide containing lithium, transition metal, and oxygen In this specification, lithium, transition metals, and and a composite oxide containing lithium and oxygen, and a cathode active material containing lithium, cobalt, and Nickel, manganese, aluminum and oxygen are used, and elements other than the above main components are considered impurities. For example, when analyzed by glow discharge mass spectrometry, the total impurity concentration is 10,000p It is preferably 5000 ppm wt or less, and more preferably 5000 ppm wt or less. The total impurity concentration of transition metals such as titanium and arsenic is 3000 ppm wt or less. It is preferable that the content of the hydroxybenzoate is 1500 ppm by weight or less, and more preferable that the content of the hydroxybenzoate is 1500 ppm by weight or less.

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

[0189] 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.

[0190] In this embodiment, cobalt is used as the transition metal, and a pre-synthesized cobalt oxide is used. Lithium particles (Cellseed C-10N manufactured by Nippon Chemical Industry Co., Ltd.) will be used (Figure 13).

[0191] The composite oxide containing lithium, a transition metal, and oxygen in step S25 is formed by removing defects and strain. It is preferable that the crystal structure of the layered rock salt type has few impurities. It is preferable that the composite oxide contains lithium, a transition metal, and oxygen. If a large amount of impurities is included, there is a high possibility that the crystal structure will have many defects or strains.

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

[0193] 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.

[0194] <Steps S32 and S33> The mixed material is collected (step S32 in FIGS. 12 and 13), and a second mixture is obtained. (Step S33 in FIGS. 12 and 13).

[0195] 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 second mixture 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 S25. Since there is no need to separate the processes, it is simple and highly productive.

[0196] 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.

[0197] 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.

[0198] <Step S34> Next, the second mixture is heated. This step is called annealing to distinguish it from the previous heating step. Or it may be called second heating.

[0199] The annealing is preferably carried out at a suitable temperature and time. The particle size and the size of the composite oxide having lithium, transition metal and oxygen in step S25 The temperature and composition of the particles vary depending on the conditions. Small particles require lower temperatures or Shorter times may be more preferable.

[0200] For example, if the average particle diameter (D50) of the particles in step S25 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.

[0201] On the other hand, when the average particle diameter (D50) of the particles in step S25 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.

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

[0203] When the second mixture is annealed, the material with a lower melting point (e.g., fluorine) in the first mixture 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.

[0204] The elements contained in the first mixture 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

[0205] The diffusion of the elements contained in this first mixture occurs more in the surface and the interior of the composite oxide particles than in the interior of the composite oxide particles. 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.

[0206] <Step S35> The annealed material is recovered to obtain the positive electrode active material 100 according to one embodiment of the present invention.

[0207] When fabricated using the methods shown in Figures 12 and 13, the resulting film has fewer defects when charged at a high voltage. It is possible to produce a positive electrode active material with a pseudo-spinel crystal structure. Positive electrode active materials with a flannel-type crystal structure of 50% or more have excellent cycle and rate characteristics. It is a positive electrode active material.

[0208] To prepare a positive electrode active material having a pseudo-spinel crystal structure after high-voltage charging, contains magnesium and fluorine, and is annealed at an appropriate temperature and time. The magnesium source and the fluorine source are used as starting materials for the composite oxide. However, when added to the starting material of the composite oxide, the magnesium source and If the melting point of the fluorine source is higher than the firing temperature, the magnesium source and the fluorine source will not melt and will diffuse. This can lead to many defects or distortions in the layered rock salt crystal structure. Therefore, the pseudo-spinel crystal structure after high-voltage charging also has defects or may cause distortion.

[0209] Therefore, we first aimed to develop a layered rock salt type crystal structure with few impurities and few defects or distortions. It is preferable to obtain a composite oxide containing magnesium in the subsequent step. The magnesium and fluorine sources are mixed and annealed to form a composite oxide having a surface layer containing magnesium and fluorine. By producing it in this way, defects and Alternatively, a positive electrode active material having a pseudo-spinel structure with little distortion can be produced.

[0210] The positive electrode active material 100 produced in the above process may be further coated with another material. Further heating may be carried out.

[0211] For example, the positive electrode active material 100 can be mixed with a compound containing phosphoric acid. In addition, it can be heated after mixing. By mixing a compound containing phosphoric acid, A positive electrode that suppresses the elution of transition metals such as cobalt even when the battery is kept in a charged state for a long time. By heating after mixing, the phosphoric acid can be more uniformly mixed. It can be coated.

[0212] Examples of compounds containing phosphoric acid include lithium phosphate and ammonium dihydrogen phosphate. The mixing can be carried out by, for example, a solid phase method. The heating can be carried out at, for example, 800 It can be carried out at 50°C or higher for 2 hours.

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

[0214] (Embodiment 3) In this embodiment, a secondary battery having the positive electrode active material 100 described in the previous embodiment is used. In this embodiment, examples of materials that can be used for the positive electrode, the negative electrode, and the electrolyte will be described. A secondary battery in which the electrolyte is enclosed in an exterior body will be described as an example.

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

[0216] <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.

[0217] As the positive electrode active material, the positive electrode active material 100 described in the previous embodiment can be used. By using the positive electrode active material 100 described in the previous embodiment, it is possible to achieve high capacity and cycle characteristics. Therefore, a secondary battery having excellent properties can be obtained.

[0218] 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.

[0219] 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.

[0220] 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.

[0221] A graphene compound may also be used as the conductive additive.

[0222] 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).

[0223] 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.

[0224] 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.

[0225] 14A 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.

[0226] In the vertical cross section of the active material layer 200, as shown in FIG. 14B, In FIG. 14B, 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.

[0227] 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] 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.

[0232] 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

[0233] 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.

[0234] The binder may be used in combination with two or more of the above.

[0235] 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.

[0236] 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.

[0237] 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.

[0238] 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.

[0239] 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 / cm 3 More than 4.5g / cm 3 The following is the result.

[0240] <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.

[0241] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. and a binder.

[0242] <Negative electrode active material> As the negative electrode active material, for example, an alloy-based material or a carbon-based material can be used.

[0243] 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.

[0244] 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.

[0245] Carbon materials include graphite, easily graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). carbon nanotubes, graphene, carbon black, etc. stomach.

[0246] 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.

[0247] 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.

[0248] 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.

[0249] 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.

[0250] 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.

[0251] 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.

[0252] 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.

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

[0254] [Electrolyte] 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:

[0255] 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.

[0256] 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.

[0257] 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.

[0258] 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%.

[0259] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0260] The use of polymer gel electrolyte increases safety against leakage etc. The pond can be made thinner and lighter.

[0261] 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.

[0262] 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.

[0263] 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.

[0264] [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.

[0265] 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.

[0266] 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.

[0267] 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. .

[0268] 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,

[0269] [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.

[0270] [Charge / discharge method] The secondary battery can be charged and discharged, for example, as follows.

[0271] ≪CC charging≫ First, we will explain CC charging as one of the charging methods. CC charging is a method in which the battery is charged at all times during the charging period. This is a charging method in which a constant current is passed through the secondary battery and charging stops when a specified voltage is reached. Assuming that the secondary battery is an equivalent circuit with internal resistance R and secondary battery capacity C as shown in Figure 15A In this case, the secondary battery voltage V B is the voltage V across the internal resistance R R and the secondary battery capacity C Applied voltage V C It is the sum of.

[0272] During CC charging, the switch is turned on and a constant voltage is applied, as shown in Figure 15A. Current I flows through the secondary battery. During this time, current I is constant, so V R = R × I Ohm's Law According to the law, the voltage V across the internal resistance R R On the other hand, the voltage applied to the secondary battery capacity C is also constant. Pressure V C increases over time. Therefore, the secondary battery voltage V B As time passes, Both rise.

[0273] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, charging stops. When CC charging is stopped, the switch is turned off and the current I=0, as shown in Figure 15B. Therefore, the voltage V applied to the internal resistance R R Therefore, the secondary battery voltage V B is decreasing.

[0274] The secondary battery voltage V during CC charging and after CC charging is stopped B and charging current An example of this is shown in Figure 15C. The secondary battery voltage V B But C C It shows a slight decrease after charging is stopped.

[0275] ≪CCCV charging≫ Next, we will explain CCCV charging, which is a charging method different from the above. First, charge to a specified voltage using CC charging, then use CV (constant voltage) charging to charge the current This is a charging method in which charging is performed until the current becomes low, specifically until it reaches the end current value.

[0276] During CC charging, the constant current power supply is switched on and the constant current is The voltage power supply is switched off and a constant current I flows through the secondary battery. During this time, the current I Since it is constant, V R According to Ohm's law, the voltage V applied to the internal resistance R is R Also On the other hand, the voltage V applied to the secondary battery capacity C is C increases over time. Therefore, the secondary battery voltage V B increases over time.

[0277] and the secondary battery voltage V B When the voltage reaches a certain value, for example 4.3V, the CC charge is stopped. Switch to CV charging. During CV charging, the constant voltage power supply is used as shown in Figure 16B. The switch is turned on, the constant current power supply switch is turned off, and the secondary battery voltage V B becomes constant On the other hand, the voltage V applied to the secondary battery capacity C C V increases over time. B =V R +V C Therefore, the voltage V across the internal resistance R R becomes smaller over time. Voltage V across the internal resistance R R As becomes smaller, V R By Ohm's law, = R × I, The current I flowing through the battery also becomes smaller.

[0278] When the current I flowing through the secondary battery reaches a predetermined value, for example, a current equivalent to 0.01C, When CCCV charging is stopped, all switches are turned off as shown in Figure 16C. The switch is turned off and the current I becomes 0. Therefore, the voltage V applied to the internal resistance R R becomes 0V However, the voltage V applied to the internal resistance R due to CV charging R is small enough that Even if the voltage drop across the internal resistance R disappears, the secondary battery voltage V B hardly descends.

[0279] The secondary battery voltage V during CCCV charging and after CCCV charging is stopped B and An example of the charging current is shown in Figure 16D. Even if CCCV charging is stopped, the secondary battery voltage V B Gahoton It shows that the aircraft does not descend at all.

[0280] ≪CC discharge≫ Next, we will explain CC discharge, which is one of the discharge methods. CC discharge is A constant current flows from the secondary battery, and the secondary battery voltage V B is set to a predetermined voltage, for example 2.5V. This is a discharge method in which the discharge is stopped when

[0281] The secondary battery voltage V during CC discharge B An example of the discharge current is shown in Figure 17. Accordingly, the secondary battery voltage V B is shown to be descending.

[0282] Next, the discharge rate and charge rate will be explained. It is the relative ratio of the discharge current to the battery, expressed in units of C. In this case, the current equivalent to 1C is X (A). When discharging with a current of 2X (A), It is said that it was discharged at C, and when it was discharged at a current of X / 5(A), it was discharged at 0.2C. The charging rate is also the same, if you charge it with a current of 2X (A), it will be 2C. If it is charged at a current of X / 5(A), it is said to be charged at 0.2C. cormorant.

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

[0284] In this specification, the charging voltage when lithium metal is used as the counter electrode is, for example, For the secondary battery used, the value obtained by subtracting 0.05V or more and 0.3V or less from the value is more preferable. Preferably, the voltage can be set to a value minus 0.1V.

[0285] <Charge / discharge cycle characteristics> The secondary battery according to one embodiment of the present invention can suppress a decrease in discharge capacity due to charge / discharge cycles. In particular, the secondary battery according to one embodiment of the present invention can be subjected to charge / discharge cycles at a high charging voltage. Even if the battery is used in a short time, the decrease in discharge capacity can be suppressed.

[0286] The positive electrode of one embodiment of the present invention is subjected to repeated CCCV charging and CC discharging with lithium metal as the counter electrode. In the charge-discharge cycle, the upper limit voltage of the charge is preferably 4.4 V or more, more preferably 5.0 V or more. Preferably, the upper limit voltage is 4.5 V or more and 5 V or less, more preferably 4.6 V or more and 5 V or less. is the voltage when the lithium metal is used as the counter electrode, and the rate of CC charging is, for example, 0.05C or less. The maximum current is 3C or less, and more preferably 0.1C or more and 2C or less. The final current in CV charging is For example, the discharge rate is 0.001C or more and 0.05C or less, and the discharge rate in CC discharge is 0.0 Between 1C and 3C, the measurement temperature is between 10℃ and 50℃, and between 30 and 150 times When the following charge / discharge cycles are performed, the discharge capacity will be 75% or more compared to the first charge / discharge cycle. More preferably, 80% or more, even more preferably 85% or more, and even more preferably 90% or more Above.

[0287] Alternatively, a secondary battery of one embodiment of the present invention includes the positive electrode of one embodiment of the present invention and a negative electrode, The negative electrode contains graphite, and the charge and discharge cycle involves repeated CCCV charging and CC discharging. The upper limit voltage of the power supply is preferably 4.3 V or more, more preferably 4.4 V or more and 4.9 V or less, and More preferably, the upper limit voltage is 4.5 V or more and 4.9 V or less, and the upper limit voltage is 4.5 V or more and 4.9 V or less when lithium metal is used as the counter electrode. The rate of CC charging is, for example, 0.05C or more and 3C or less, more preferably is 0.1C or more and 2C or less, and the end current in CV charging is, for example, 0.001C or more and 0 0.05C or less, and the rate in CC discharge is, for example, 0.01C or more and 3C or less, The measurement temperature is between 10°C and 50°C, and the charge / discharge cycle is between 30 and 150 times. If the discharge capacity is 75% or more, more preferably 80% or more, of the first charge / discharge cycle, The ratio is preferably 85% or more, more preferably 90% or more.

[0288] In addition, after 30 to 150 charge / discharge cycles, the discharge capacity is at least 1.3 times that of a comparative secondary battery having a conventional material as a positive electrode active material, and more preferably It is 1.45 times or more, and more preferably 1.6 times or more.

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

[0290] (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.

[0291] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. Figure 18A shows a coin-type (single-layer flat type) 18A is an external view of the secondary battery, and FIG. 18B is a cross-sectional view thereof.

[0292] 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.

[0293] 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.

[0294] 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.

[0295] 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. 18B. 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.

[0296] 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.

[0297] 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).

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

[0299] [Cylindrical secondary battery] Next, an example of a cylindrical secondary battery will be described with reference to FIGS. 19A, 19B, 19C, and 19D. The following description will be given with reference to FIG. 19A. An external view of a cylindrical secondary battery 600 is shown in FIG. 19B. 19B is a schematic cross-sectional view of a cylindrical secondary battery 600. The secondary battery 600 has a positive electrode cap (battery lid) 601 on the top surface, and a battery cover on the side and bottom surfaces. The positive electrode cap and the battery can (external can) 602 are , and are insulated by a gasket (insulating packing) 610.

[0300] 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.

[0301] 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.

[0302] 19C, 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.

[0303] 19D is a top view of module 615. Conductive plate 613 is dotted for clarity. As shown in FIG. 19D, 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.

[0304] 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.

[0305] [Example of secondary battery structure] Another structural example of the secondary battery will be described with reference to FIGS.

[0306] 20A and 20B are diagrams showing the appearance of a battery pack. The secondary battery 913 has a label 910 attached thereto. Furthermore, as shown in FIG. 20B, the secondary battery 913 has a terminal 951 and a terminal 9 It has 52.

[0307] The circuit board 900 has a circuit 912. The terminal 911 is connected to the terminal terminal 951, terminal 952, antenna 914, antenna 915, and circuit 912 are connected. In addition, a plurality of terminals 911 are provided, and each of the plurality of terminals 911 is used as a control signal input terminal, It may also be a power supply terminal.

[0308] 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 Antennas such as body antennas may also be used.

[0309] Alternatively, the antenna 914 may be a flat conductor. This flat conductor may be a conductor for electric field coupling. In other words, the capacitor has two conductors. The antenna 914 may function as a single conductor. This allows only the electromagnetic and magnetic fields to be transmitted. Instead, power can be exchanged using an electric field. .

[0310] The battery pack has a layer 916 between the antenna 914 and the secondary battery 913. Layer 916 has a function of shielding an electromagnetic field generated by, for example, a secondary battery 913. For example, a magnetic material can be used as 6.

[0311] The structure of the secondary battery is not limited to that shown in FIG. 20A or 20B.

[0312] For example, as shown in FIGS. 21A and 21B, the battery pack shown in FIGS. 20A and 20B In the above, an antenna may be provided on each of a pair of opposing surfaces. FIG. 21B is an external view showing one of the pair of surfaces, and FIG. 21B is an external view showing the other of the pair of surfaces. 20A and 20B. The description of the battery pack shown in FIG. 20B can be used as appropriate.

[0313] As shown in FIG. 21A, a layer 916 is sandwiched between one of the two surfaces of a secondary battery 913, and an antenna 21B, 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.

[0314] 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.

[0315] Alternatively, as shown in FIG. 21C, the battery pack shown in FIGS. 20A and 20B may be provided with a display device 92. 0 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 device 920 is provided. 20A and 20B. The explanations can be used as appropriate.

[0316] 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.

[0317] Alternatively, as shown in FIG. 21D, the battery pack shown in FIGS. 20A and 20B may be provided with a sensor 921. The sensor 921 is electrically connected to the terminal 911 via the terminal 922. 20A and 20B. The description of the battery pack shown in 0B can be used as appropriate.

[0318] 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.

[0319] Furthermore, an example of the structure of the secondary battery 913 will be described with reference to FIGS.

[0320] The secondary battery 913 shown in FIG. 22A 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. 22A, 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.

[0321] As shown in FIG. 22B, the housing 930 shown in FIG. 22A is formed from a plurality of materials. For example, the secondary battery 913 shown in FIG. 22B 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.

[0322] 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.

[0323] Furthermore, the structure of the wound body 950 is shown in Fig. 23. The wound body 950 includes a negative electrode 931, 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.

[0324] The negative electrode 931 is connected to the terminal 911 shown in FIG. 20 via one of the terminals 951 and 952. The positive electrode 932 is connected to the terminal 951 shown in FIG. Connected to 11.

[0325] 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.

[0326] [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.

[0327] A laminated secondary battery 980 will be described with reference to FIG. The secondary battery 980 has a wound body 993 shown in FIG. 24A. The wound body 993 has a negative electrode 994 and 23. 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.

[0328] 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. .

[0329] As shown in FIG. 24B, 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.

[0330] 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.

[0331] In addition, although an example using two films is shown in Figures 24B and 24C, 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.

[0332] 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.

[0333] 24B and 24C, the wound body is inserted into the space formed by the film that serves as the outer casing. 25A and 25B. In the space formed by the film that becomes the exterior body, a plurality of rectangular positive electrodes, separators, and The secondary battery may also have a positive electrode and a negative electrode.

[0334] The laminated secondary battery 500 shown in FIG. 25A 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.

[0335] In the laminated secondary battery 500 shown in FIG. 25A, 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 .

[0336] 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.

[0337] 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. 25B. It is composed of multiple electrode layers.

[0338] In FIG. 25B, as an example, the number of electrode layers is set to 16. In FIG. 25B, 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.

[0339] An example of an external view of a laminated secondary battery 500 is shown in FIGS. 26 and 27. 26 and 27 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.

[0340] 28A 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.

[0341] [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. 26, will be described with reference to FIG. 8B and 28C.

[0342] 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.

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

[0344] Next, as shown in Figure 28C, exterior body 509 is folded at the portion indicated by the dashed 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.

[0345] 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.

[0346] 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.

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

[0348] 29A shows a schematic top view of a bendable secondary battery 250. 29C and 29D show the cut lines C1-C2, C3-C4, and C5 in FIG. 29A, respectively. A secondary battery 250 is a schematic cross-sectional view taken along line A1-A2. The positive electrode 211a and the negative electrode 211b are housed inside the battery 51. a lead 212a electrically connected to the negative electrode 211b; b extends to the outside of the package 251. In addition, in the area surrounded by the package 251, In addition to 211a and negative electrode 211b, an electrolyte (not shown) is enclosed.

[0349] The positive electrode 211a and the negative electrode 211b of the secondary battery 250 will be explained with reference to FIG. FIG. 30A illustrates the stacking order of the positive electrode 211a, the negative electrode 211b, and the separator 214. FIG. 30B 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.

[0350] As shown in FIG. 30A, 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.

[0351] 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.

[0352] 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.

[0353] As shown in FIG. 30B, 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.

[0354] Next, the exterior body 251 will be described with reference to FIGS. 29B, 29C, (D), and (E).

[0355] 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.

[0356] 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.

[0357] FIG. 29B is a cross section cut at the portion overlapping with the ridge line 271, and FIG. 29C is a cross section cut at the portion overlapping with the valley line 272. 29B and 29C 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.

[0358] 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. .

[0359] 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.

[0360] 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.

[0361] 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.

[0362] 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.

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

[0364]

number

[0365] Here, a is 0.8 or more and 3.0 or less, preferably 0.9 or more and 2.5 or less, and more preferably The value must be between 1.0 and 2.0.

[0366] FIG. 29D is a cross section including the lead 212a, and shows the secondary battery 250, the positive electrode 211a, and 29D, the bent portion 26 corresponds to the cross section of the negative electrode 211b in the longitudinal direction. 1, between the ends of the positive electrode 211a and the negative electrode 211b in the length direction and the exterior body 251 It is preferable to have a space 273 therebetween.

[0367] FIG. 29E shows a schematic cross-sectional view of the secondary battery 250 when bent. 29A.

[0368] When the secondary battery 250 is bent, a part of the exterior body 251 located on the outside of the bend stretches, and More specifically, the other part located on the outside of the exterior body 251 is deformed so as to shrink. The part where the wave is generated is deformed so that the amplitude of the wave is small and the period of the wave is large. The part located inside 251 changes so that the wave amplitude is large and the wave period is small. In this way, the exterior body 251 is deformed, and as it is bent, Since this stress is alleviated, the material that constitutes exterior body 251 itself does not need to expand or contract. As a result, the exterior body 251 is not damaged and the secondary battery 250 can be bent with a small force. can.

[0369] Furthermore, as shown in FIG. 29E, when the secondary battery 250 is bent, the positive electrode 211a and the negative electrode 211b are bent. 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.

[0370] 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.

[0371] The secondary battery 250 illustrated in FIGS. 29 and 30 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.

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

[0373] (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.

[0374] 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 31A to 31G. 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.

[0375] 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.

[0376] FIG. 31A 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.

[0377] FIG. 31B 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 31C shows the state of the bent secondary battery 7407. 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.

[0378] FIG. 31D 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. 31E 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.

[0379] FIG. 31F 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.

[0380] 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.

[0381] 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.

[0382] 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.

[0383] 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.

[0384] 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.

[0385] 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. 31E is curved and inserted into the housing 7201. , or may be incorporated into the band 7203 in a bendable state.

[0386] 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.

[0387] FIG. 31G 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.

[0388] 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.

[0389] 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.

[0390] 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.

[0391] 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 31H, 32 and 33.

[0392] By using the secondary battery of one embodiment of the present invention as a secondary battery in everyday electronic devices, it is possible to achieve lighter weight and a longer life. 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.

[0393] FIG. 31H is a perspective view of a device also known as a tobacco-containing smoking device (electronic cigarette). In 1H, 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.

[0394] Next, an example of a foldable tablet terminal is shown in Figures 32A and 32B. The tablet terminal 9600 shown in FIGS. 32A and 32B 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. 32A shows the tablet terminal 9600 in an open state, and FIG. 32B shows the tablet terminal The figure shows the 9600 closed.

[0395] 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.

[0396] 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.

[0397] 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

[0398] 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.

[0399] In addition, 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 For example, at least one of the switches 9625 to 9627 may be an interface. The other functions as a power on / off switch for the tablet device 9600. Also, for example, at least one of the switches 9625 to 9627 may The ability to switch between portrait and landscape display, or between black and white and color display For example, at least one of the switches 9625 to 9627 may have a function of switching the At least one of the display units 9631 may have a function to adjust the brightness of the display unit 9631. The brightness of 31 is the brightness detected by the light sensor built into the tablet terminal 9600 during use. It can be optimized according to the amount of external light. In addition, other detection devices such as gyro, acceleration sensor, etc. that detect tilt are also included. It may be stored.

[0400] In addition, in FIG. 32A, 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.

[0401] FIG. 32B shows the tablet terminal 9600 in a folded state. The terminal 9600 includes a housing 9630, a solar cell 9633, and a DC-DC converter 9636. A charge / discharge control circuit 9634 is also provided. Use a storage battery.

[0402] 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.

[0403] In addition, the tablet terminal 9600 shown in FIGS. 32A and 32B 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.

[0404] 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.

[0405] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 32B are shown in FIG. 32C. A block diagram is shown and explained. FIG. 32C shows 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. 32B This is the location.

[0406] 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.

[0407] 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.

[0408] Another example of electronic equipment is shown in Fig. 33. In Fig. 33, 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.

[0409] 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.

[0410] 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:

[0411] In FIG. 33, 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, The device includes a light source 8102, a secondary battery 8103, etc. In FIG. 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.

[0412] In addition, FIG. 33 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.

[0413] 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.

[0414] In FIG. 33, 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.

[0415] In addition, Figure 33 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.

[0416] In FIG. 33, 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.

[0417] 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

[0418] 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.

[0419] 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.

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

[0421] (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.

[0422] 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.

[0423] FIG. 34A 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. 19C and 19D are arranged on the floor of the vehicle. In addition, a battery pack made up of multiple secondary batteries as shown in Figure 22 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.

[0424] 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.

[0425] The automobile 8500 shown in FIG. 34B 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. 34B 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.

[0426] 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.

[0427] 34C 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. .

[0428] In addition, the scooter 8600 shown in FIG. 34C 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.

[0429] According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery is increased. 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.

[0430] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0431] In this example, a positive electrode active material according to one embodiment of the present invention and a positive electrode active material according to a comparative example were prepared. The cycle characteristics under voltage charging were evaluated, and the characteristics were analyzed using XRD.

[0432] [Preparation of positive electrode active material] <<Sample 1>> In Sample 1, copper was used as a transition metal in the manufacturing method shown in FIG. 13 of the first embodiment. A positive electrode active material having a ballast was prepared. First, the molar ratio of LiF and MgF2 was set to LiF:Mg Weigh out the material so that F2 = 1:3, add acetone as a solvent, and wet mix and grind. Mixing and grinding were carried out in a ball mill using zirconia balls at 150 rpm for 1 hour. The processed material was collected and used as the first mixture (steps S11 to S13 in FIG. 13). Step S14).

[0433] In sample 1, pre-synthesized lithium cobalt oxide was obtained from Nippon Chemical Industry Co., Ltd. Cellseed C-10N manufactured by Cellseed Co., Ltd. was used (step S25 in FIG. 13). As explained in the first embodiment, ON is a cobalt alloy with a D50 of about 12 μm and few impurities. It is lithium nitrate.

[0434] Next, the molecular weight of the lithium cobalt oxide is calculated based on the molecular weight of the magnesium atoms contained in the first mixture. The mixture was weighed so that the molecular weight was 0.5 atomic % and mixed in a dry state. The mixture was mixed in a ball mill at 150 rpm for 1 hour. The treated material was collected and mixed in a second mixing chamber. The object was determined as follows (steps S31 to S33 in FIG. 13).

[0435] Next, the second mixture was placed in an alumina crucible and heated at 850°C for 6 hours in a muffle furnace in an oxygen atmosphere. The alumina crucible was covered during the annealing. The oxygen flow rate was 10 The temperature was increased at 200°C / hr and decreased over 10 hours. The treated material was used as the positive electrode active material of Sample 1 (step S34 in FIG. 13). Top S35).

[0436] [Secondary battery production] Next, using Sample 1 prepared above, we tested a CR2032 type (diameter 20 mm) A coin-type secondary battery (height 3.2 mm) was fabricated.

[0437] The positive electrode was made of the positive electrode active material prepared above, acetylene black (AB), and polyfluoride. The positive electrode active material was mixed with PVDF in a ratio of AB:PVDF=95:3:2 (by weight). The mixed slurry was applied to a current collector. cm 2 It was.

[0438] The counter electrode was made of lithium metal.

[0439] 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 following was used.

[0440] The separator was made of polypropylene with a thickness of 25 μm.

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

[0442] The positive electrode of the secondary battery was pressed. Specifically, after applying pressure of 210 kN / m, it was pressed at 1467 kN / m. The pressure was applied at 20 N / m.

[0443] [Cycle characteristics and dQ / dV vs V curves] The secondary battery using Sample 1 was charged by CCCV (0.05C, 4.5V or 4.6V, final current 0.005C), discharge CC (0.05C, 2.5V) at 25℃ The measurement was carried out for two cycles.

[0444] After that, we started measuring the cycle characteristics. The battery was charged at 25°C using CCCV (0.2C, 4.5V or 4.6V, final voltage The charge and discharge cycle was repeated at CC (0.2C, 2.5V). The properties were evaluated.

[0445] The dQ / dV vs. V curves obtained from the charge curves for each cycle are shown in Figure 35. 5A: dQ / dV vs V curves at 1, 3, 4, 5 and 10 cycles Figure 35B shows the results at 10, 30, 50, 70 and 100 cycles. The dQ / dV vs V curves are shown.

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

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

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

[0449] As shown in Figure 35B, after 30 cycles, the first peak The peaks tended to shift to the right and the voltage values ​​corresponding to the peaks tended to increase. The peak intensity decreased with increasing cycle number, and at 100 cycles, the peak was almost nonexistent. It's almost impossible to see anymore. [Example]

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

[0451] [XRD(1)] Powder XRD analysis of the positive electrode of Sample 1 before charging using CuKα1 radiation The XRD measurements were performed in air, and the electrodes were attached to a glass plate to maintain flatness. The XRD instrument was set up for powder samples, but the sample height was adjusted according to the instrument's requirements. aligned with the measurement surface.

[0452] The obtained XRD patterns were analyzed using DIFFRAC.EVA (Bruker XRD data analysis software). The background and Kα2 were removed using the analysis software. Signals from auxiliary agents and binders, as well as from sealed containers, etc., are also removed.

[0453] Then, the lattice constants were calculated using TOPAS. At this time, no optimization of the atomic positions was performed. Only the lattice constants were fitted. GOF (good of fitness) The crystallite size and the lattice constants of the a-axis and c-axis were determined.

[0454] Next, multiple secondary batteries were fabricated using Sample 1 and subjected to CCCV charging. A positive electrode was fabricated using Sample 1 as the positive electrode active material. The amount of the positive electrode used was approximately 7 mg. / cm 2 The charging voltage was 4.5V, 4.525V, 4.55V, 4.575V and The five conditions were 4.6V and 4.6V. Secondary batteries were fabricated for each condition and evaluated. Typical charging conditions are constant current charging at 0.5C up to each charging voltage, then the current value becomes 0.01C. The battery was charged at a constant voltage until the battery reached the specified value. Each secondary battery was disassembled in an argon atmosphere glove box to remove the positive electrode. The electrolyte was removed by washing with MC (dimethyl carbonate). The samples were sealed in a sealed container and subjected to XRD analysis. The XRD patterns of the positive electrode under the conditions shown in Figures 38 and 39 are different in the range of 2θ. For comparison, the pseudospinel crystal structure, the H1-3 crystal structure, and Li 0.35 CoO The crystal structure pattern of 2 (space group R-3m, O3) is also shown. 0.35 CoO2 corresponds to the crystalline structure at a charge depth of 0.65.

[0455] Furthermore, a secondary battery different from the one used for charging conditions was used to charge and discharge the battery for 10 times. After the cycle, the cathode was removed by disassembly in a glove box and washed with DMC. The liquid was removed, the battery was sealed in an argon atmosphere, and XRD analysis was performed. After charging at a constant current of 0.5C up to 4.6V, charge at a constant voltage until the current value reaches 0.01C. The discharge conditions were CC discharge at 0.2 C and 2.5 V.

[0456] Tables 2 to 5 show the values ​​analyzed using XRD. "Before charging" is written, and charging is performed at 4.5V, 4.525V, 4.55V, 4.575V and For XRD after going up to 4.6V, the results were "4.5V", "4.525V", and "4.55V", "4.575V" and "4.6V" are written, then discharged, and Furthermore, the XRD after nine charge / discharge cycles, i.e., 10 cycles, is written as "after 10cy discharge."

[0457] Table 2 shows the crystallite size and volume ratio when fitting is performed assuming an O3 type crystal structure. and lattice constants are shown in Table 3 when fitting is performed assuming a pseudo-spinel crystal structure. Table 4 shows the crystallite size, volume ratio and lattice constant of the H1-3 type crystal structure. The crystallite size, volume ratio, and lattice constant of the sample after coating are shown in Table 1. Each table also shows the GOF (good of fitness).

[0458] [Table 2]

[0459] [Table 3]

[0460] [Table 4]

[0461] Table 5 also shows two peaks (peak 1 and The peak value and half width of peak 2) are shown in Table 6. The peak values ​​and full width at half maximum (FWHM) of the two peaks (Peak 3 and Peak 4) are Full Width at Half Maximum) and Peak Value and FWHM were calculated using TOPAS. In addition, L in the table is the value for the Lorentz function. It is a value that indicates the degree of compatibility.

[0462] [Table 5]

[0463] [Table 6]

[0464] It was suggested that at 4.55V, the O3 type crystal structure and the pseudospinel type crystal structure coexist. Above 4.575, the pseudospinel crystal structure became dominant.

[0465] The lattice constant of the a-axis is smaller at charging voltages of 4.5 V and 4.5 V compared with the values ​​before charging or after discharging. At 0.525V, the lattice constant decreases to 2.81 x 10 -10 m or more 2.83×10 -10 m As the charging voltage increased, that is, the depth of charge increased, the lattice The constants increased and tended to approach the values ​​before charging or after discharging.

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

[0467] [XRD(2)] Charge-discharge cycles were carried out under the conditions described in the previous examples for 1, 3, 10, 20, 30, and XRD was evaluated at 10 and 50 cycles. In charging, CCCV charging is performed, the charging voltage is 4.6V, and no discharging is performed after charging. The cathode was removed by disassembly in a glove box, washed with DMC to remove the electrolyte, and The sample was placed in a sealed container under a argon atmosphere and subjected to XRD analysis. 1 shows the XRD spectrum. Figures 40A, 40B and 41 show the The 2θ angle range is different. Table 7 also shows the three peaks (Peak 3, Peak 4 and Peak The peak value, FWHM, and L values ​​of the graph (graph 5) are shown.

[0468] [Table 7]

[0469] The peak observed at 2θ=19.30±0.20° increases with increasing cycle number. The larger the peak value, the greater the amount of lithium ions released. This suggests that discharge capacity may be increased. [Example]

[0470] In this example, a secondary battery was manufactured using a positive electrode active material of one embodiment of the present invention, and dQ / dVv The sV curve was obtained.

[0471] The secondary battery using Sample 1 was charged by CCCV (0.05C, 4.5V, termination Current 0.005C), discharge CC (0.05C, 2.5V) at 25°C for 2 cycles The circle was measured.

[0472] After that, at 25°C, charging was performed under CCCV (0.05C, 4.9V, final current 0.00 The charging curve was measured at 5C, 1C = 200mA / g. The dQ / dV vs V curve was obtained from the graph, and the results are shown in Figure 42.

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

[0474] Comparing Figure 35A and Figure 42, the charging rate is small (charging speed is slow). As a result, the peak tended to shift to a smaller value by about 0.2 V. [Explanation of symbols]

[0475] 100: Positive electrode active material

Claims

1. A lithium ion secondary battery having a positive electrode, the positive electrode has a positive electrode active material including lithium cobalt oxide, The positive electrode active material of the lithium ion secondary battery contains magnesium. However, the positive electrode is A plurality of batteries each having the positive electrode, a counter electrode using lithium metal, an electrolytic solution, and a separator using polypropylene were fabricated (here, lithium hexafluorophosphate was used as the electrolyte in the electrolytic solution so as to have a concentration of 1 mol / L, and the electrolytic solution was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of EC:DEC=3:7, with vinylene carbonate (VC) at 2 wt %)). Among the plurality of batteries, one battery was determined as a first battery by being subjected to constant current charging at a current value of 0.5 C up to 4.55 V in an environment of 25° C., and then to constant voltage charging at 4.55 V up to a current value of 0.01 C in an environment of 25° C. Among the plurality of batteries, one battery was charged at a constant current of 0.5 C up to 4.575 V in a 25°C environment, and then charged at a constant voltage of 4.575 V down to a current of 0.01 C in a 25°C environment, and designated as a second battery; Among the plurality of batteries, a third battery was selected from those that were subjected to constant current charging at a current value of 0.5 C up to 4.6 V in an environment of 25° C., and then to constant voltage charging at 4.6 V up to a current value of 0.01 C in an environment of 25° C. In a glove box under an argon atmosphere, the positive electrodes of the first to third batteries are removed from the first to third batteries and sealed in first to third sealed containers, respectively; Then, the positive electrodes of the first to third batteries sealed in the first to third sealed containers are analyzed by powder XRD using CuKα1 radiation, When the XRD pattern obtained by powder XRD analysis of the positive electrode of the first battery was fitted using models of an O3 type crystal structure, a pseudospinel type crystal structure, and an H1-3 type crystal structure, the positive electrode of the first battery was found to have an O3 type crystal structure and a pseudospinel type crystal structure, When the XRD pattern obtained by powder XRD analysis of the positive electrode of the third battery was fitted using models of an O3 crystal structure, a pseudospinel crystal structure, and an H1-3 crystal structure, the positive electrode of the third battery had a pseudospinel crystal structure and an H1-3 crystal structure, and the pseudospinel crystal structure was found to be more prevalent than the H1-3 crystal structure. When the XRD pattern obtained by powder XRD analysis of the positive electrode of the second battery is fitted using models of an O3 crystal structure, a pseudospinel crystal structure, and an H1-3 crystal structure, the pseudospinel crystal structure observed in the positive electrode of the second battery is more numerous than the pseudospinel crystal structure observed in the positive electrode of the second battery. Lithium-ion secondary battery.

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

3. In claim 1 or claim 2, The lithium ion secondary battery, wherein the magnesium concentration peak is present at a depth of 3 nm from the surface of the positive electrode active material when subjected to EDX ray analysis.

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