Positive electrode active material, method for manufacturing positive electrode active material, and secondary battery

Abstract

The present invention relates to a lithium ion secondary battery, a hybrid vehicle, an electric vehicle, and a plug-in hybrid vehicle. The lithium ion secondary battery includes a positive electrode and a negative electrode. Among them, the positive electrode includes a positive electrode active material containing cobalt. The positive electrode active material contains the cobalt, aluminum, and fluorine in a surface layer portion. In the surface layer portion, the aluminum has a concentration gradient, and in the line analysis result using energy dispersive X-ray analysis, the fluorine has a peak detected in a region closer to the surface of the positive electrode active material than the peak of the aluminum.

Description

[0001] This application is a divisional application of the patent application with the application date of November 17, 2017, application number 201711141051.6, and invention title "Positive Electrode Active Material, Method for Manufacturing Positive Electrode Active Material, and Secondary Battery". Technical Field

[0002] One aspect of the present invention relates to an article, method, or manufacturing method. Alternatively, the present invention relates to a process, machine, manufacture, or composition of matter. One aspect of the present invention relates to a method for manufacturing a semiconductor device, display device, light-emitting device, power storage device, lighting device, or electronic device. One aspect of the present invention particularly relates to an electronic device and its operating system.

[0003] Note that in this specification, the power storage device refers to all elements and devices having a power storage function. For example, storage batteries such as lithium-ion secondary batteries (also referred to as secondary batteries), lithium-ion capacitors, and electric double layer capacitors are all included in the category of power storage devices.

[0004] Note that in this specification, an electronic device refers to all devices having a power storage device, such as an electro-optical device having a power storage device and an information terminal device having a power storage device, etc. are all electronic devices. Background Art

[0005] In recent years, research and development of various power storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have been increasingly active. In particular, with the development of the semiconductor industry for portable information terminals such as mobile phones, smartphones, notebook personal computers, portable music players, digital cameras, medical devices, new generation clean energy vehicles such as hybrid electric vehicles (HEV), electric vehicles (EV), or plug-in hybrid electric vehicles (PHEV), the demand for high-output and large-capacity lithium-ion secondary batteries has increased sharply, and they have become indispensable items in modern information society as an energy supply source that can be charged.

[0006] As the characteristics required for current lithium-ion secondary batteries, there are: larger capacity, improvement of cycle characteristics, improvement of safety and long-term reliability under various working environments, etc.

[0007] Therefore, improvements to the positive electrode active material for the purpose of improving the cycle characteristics and increasing the capacity of lithium-ion secondary batteries have been investigated (Patent Document 1, Patent Document 2, and Patent Document 3).

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. Hei 8-236114

[0009] [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-124262

[0010] [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-358953 SUMMARY OF THE INVENTION

[0011] However, there is still room for improvement in various aspects such as cycle characteristics, capacity, charge-discharge characteristics, reliability, safety, or cost of lithium-ion secondary batteries and the positive electrode active materials used therefor.

[0012] One of the objects of one embodiment of the present invention is to provide a positive electrode active material that suppresses a decrease in capacity during charge-discharge cycles when used in a lithium-ion secondary battery. Another object of one embodiment of the present invention is to provide a high-capacity secondary battery. Another object of one embodiment of the present invention is to provide a secondary battery having good charge-discharge characteristics. Another object of one embodiment of the present invention is to provide a secondary battery having high safety or reliability.

[0013] Another object of one embodiment of the present invention is to provide a novel substance, active material, power storage device, or a method for manufacturing them.

[0014] Note that the description of the above objects does not preclude the existence of other objects. In addition, one embodiment of the present invention does not need to achieve all of the above objects. Further, objects other than the above can be known and extracted from the descriptions in the specification, drawings, claims, etc.

[0015] To achieve the above objects, in one embodiment of the present invention, a coating layer containing aluminum and a coating layer containing magnesium are provided in the surface layer portion of the positive electrode active material.

[0016] One embodiment of the present invention is a positive electrode active material including a first region, a second region, and a third region. The first region exists inside the positive electrode active material. The second region covers at least a part of the first region. The third region covers at least a part of the second region. The first region contains lithium, a transition metal, and oxygen. The second region contains lithium, aluminum, a transition metal, and oxygen. The third region contains magnesium and oxygen.

[0017] In the above structure, the third region may contain fluorine.

[0018] In the above structure, the third region may contain a transition metal.

[0019] In the above structure, the first region and the second region may have a layered rock salt-type crystal structure, and the third region may have a rock salt-type crystal structure.

[0020] In the above structure, the transition metal may be cobalt.

[0021] Further, one aspect of the present invention is a positive electrode active material containing lithium, aluminum, a transition metal, magnesium, oxygen, and fluorine. When the total amount of lithium, aluminum, the transition metal, magnesium, oxygen, and fluorine present in the surface layer portion of the positive electrode active material measured by X-ray photoelectron spectroscopy is 100 atomic%, the aluminum concentration is 0.1 atomic% or more and 10 atomic% or less, the magnesium concentration is 5 atomic% or more and 20 atomic% or less, and the fluorine concentration is 3.5 atomic% or more and 14 atomic% or less.

[0022] Further, one aspect of the present invention is a secondary battery including a positive electrode containing the above positive electrode active material, a negative electrode, an electrolytic solution, and an outer package body.

[0023] Further, one aspect of the present invention is a method for manufacturing a positive electrode active material, including the following steps: dissolving an aluminum alkoxide in an alcohol; mixing an aluminum alkoxide alcohol solution obtained by dissolving the aluminum alkoxide in the alcohol with particles containing lithium, a transition metal, magnesium, oxygen, and fluorine; stirring a mixture of the aluminum alkoxide alcohol solution and the particles containing lithium, a transition metal, magnesium, oxygen, and fluorine in an atmosphere containing water vapor; collecting a precipitate from the mixture; and heating the collected precipitate at 500°C or higher and 1200°C or lower in an oxygen-containing atmosphere for a holding time of 50 hours or less.

[0024] According to one aspect of the present invention, a positive electrode active material that suppresses a reduction in capacity during charge and discharge when used in a lithium ion secondary battery can be provided. Further, according to one aspect of the present invention, a high-capacity secondary battery can be provided. Further, according to one aspect of the present invention, a secondary battery having good charge and discharge characteristics can be provided. Further, according to one aspect of the present invention, a secondary battery having high safety or reliability can be provided. According to one aspect of the present invention, a novel substance, active material, power storage device, or a method for manufacturing them can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figures 1A to 1C is a diagram illustrating an example of a positive electrode active material;

[0026] Figure 2 is a diagram illustrating an example of a method for manufacturing a positive electrode active material;

[0027] Figure 3A and Figure 3B is a cross-sectional view of an active material layer when a graphene compound is used as a conductive assistant;

[0028] Figure 4A and Figure 4B is a diagram illustrating a coin-type secondary battery;

[0029] Figure 5A and Figure 5BIt is a diagram illustrating a cylindrical secondary battery;

[0030] Figure 6A and Figure 6B It is a diagram illustrating an example of a secondary battery;

[0031] Figure 7A1 、 Figure 7A2 、 Figure 7B1 and Figure 7B2 It is a diagram illustrating an example of a secondary battery;

[0032] Figure 8A and Figure 8B It is a diagram illustrating an example of a secondary battery;

[0033] Figure 9A and Figure 9B It is a diagram illustrating an example of a secondary battery;

[0034] Figure 10 It is a diagram illustrating an example of a secondary battery;

[0035] Figures 11A to 11C It is a diagram illustrating a laminated secondary battery;

[0036] Figure 12A and Figure 12B It is a diagram illustrating a laminated secondary battery;

[0037] Figure 13 It is a diagram showing the appearance of a secondary battery;

[0038] Figure 14 It is a diagram showing the appearance of a secondary battery;

[0039] Figures 15A to 15C It is a diagram illustrating the manufacturing method of a secondary battery;

[0040] Figure 16A 、 Figure 16B1 、 Figure 16B2 、 Figure 16C and Figure 16D It is a diagram illustrating a flexible secondary battery;

[0041] Figure 17A and Figure 17B It is a diagram illustrating a flexible secondary battery;

[0042] Figures 18A to 18H It is a diagram illustrating an example of an electronic device;

[0043] Figures 19A to 19C It is a diagram illustrating an example of an electronic device;

[0044] Figure 20 It is a diagram illustrating an example of an electronic device;

[0045] Figures 21A to 21C It is a figure showing an example of an electronic device;

[0046] Figure 22A and Figure 22B It is a graph showing the cycle characteristics of a secondary battery using the positive electrode active material of Example 1;

[0047] Figures 23A to 23C It is a STEM image of the positive electrode active material of Example 2;

[0048] Figure 24A1 , Figure 24A2 , Figure 24A3 , Figure 24B1 , Figure 24B2 and Figure 24B3 It is a STEM-FFT image of the positive electrode active material of Example 2;

[0049] Figure 25A1 , Figure 25A2 , Figure 25B1 , Figure 25B2 , Figure 25C It is a STEM image and EDX elemental mapping of the positive electrode active material of Example 2;

[0050] Figures 26A to 26C It is a STEM image and EDX line analysis of the positive electrode active material of Example 2. Detailed Embodiments

[0051] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following description, and those of ordinary skill in the art can easily understand that its mode and details can be transformed into various forms. In addition, the present invention should not be construed as being limited only to the content described in the following embodiments.

[0052] In this specification and the like, crystallographic planes and orientations are represented by Miller indices. In crystallography, a bar is attached to a number to represent a crystallographic plane and an orientation. However, in this specification and the like, due to symbol limitations in patent applications, a minus sign (-) is attached to the number to represent a crystallographic plane and an orientation, instead of attaching a bar to the number. In addition, “[]” represents an individual orientation showing the orientation within a crystal, “<>” represents a set orientation showing all equivalent crystal directions, “()” represents an individual plane showing a crystallographic plane, and “{}” represents a set plane having equivalent symmetry.

[0053] In this specification and the like, segregation refers to a phenomenon in which a certain element (for example, B) is unevenly distributed in a solid containing multiple elements (for example, A, B, C).

[0054] In this specification and the like, the layered rock salt-type crystal structure of the composite oxide containing lithium and transition metals refers to the following crystal structure: having a rock salt-type ionic arrangement in which cations and anions are alternately arranged, and the transition metals and lithium are regularly arranged to form a two-dimensional plane, so that lithium can diffuse two-dimensionally therein. In addition, it may also include defects such as vacancies of cations or anions. Strictly speaking, the layered rock salt-type crystal structure is sometimes a structure formed by lattice deformation of the rock salt-type crystal.

[0055] In addition, in this specification and the like, the rock salt-type crystal structure refers to a structure in which cations and anions are alternately arranged. In addition, it may also include vacancies of cations or anions.

[0056] The anions in the layered rock salt-type crystal and the rock salt-type crystal form a cubic close-packed structure (face-centered cubic lattice structure). When the layered rock salt-type crystal and the rock salt-type crystal are in contact, there is a crystal plane in which the orientation of the cubic close-packed structure formed by the anions is aligned. The space group of the layered rock salt-type crystal is R-3m, which is different from the space groups Fm-3m (the space group of a general rock salt-type crystal) and Fd-3m (the space group of a rock salt-type crystal with the simplest symmetry) of the rock salt-type crystal. Therefore, the Miller indices of the crystal planes of the layered rock salt-type crystal and the rock salt-type crystal that satisfy the above conditions are different. In this specification, in the layered rock salt-type crystal and the rock salt-type crystal, the alignment of the orientation of the cubic close-packed structure formed by the anions means that the crystal orientations are generally aligned.

[0057] It is possible to judge the alignment of the crystal orientations of two regions based on TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. In addition, X-ray diffraction, electron diffraction, neutron diffraction, etc. can be used as the basis for judgment. In TEM images and the like, the arrangement of cations and anions is observed as a repetition of bright lines and dark lines. When the orientation of the cubic close-packed structure is aligned in the layered rock salt-type crystal and the rock salt-type crystal, it can be observed that the angle formed by the repetition of the bright lines and dark lines is 5 degrees or less, more preferably 2.5 degrees or less. Note that in TEM images and the like, it is sometimes not possible to clearly observe light elements such as oxygen and fluorine. In this case, the alignment of the orientation can be judged based on the arrangement of metal elements.

[0058] Embodiment 1

[0059] [Structure of the positive electrode active material]

[0060] First, use Figures 1A to 1C to illustrate the positive electrode active material 100 of one aspect of the present invention. As Figure 1A and Figure 1BAs shown, the positive electrode active material 100 includes a first region 101, a second region 102, and a third region 103. The first region 101 exists inside the positive electrode active material 100. The second region 102 covers at least a part of the first region 101. The third region 103 covers at least a part of the second region 102.

[0061] In addition, as Figure 1B shown, the third region 103 exists inside the positive electrode active material 100. For example, when the first region 101 is polycrystalline, the third region 103 can exist near the grain boundary. In addition, the third region 103 can exist near a portion of the positive electrode active material 100 having a crystal defect. In Figures 1A to 1C , a part of the grain boundary is indicated by a dotted line. Note that in this specification and the like, a crystal defect refers to a defect that can be observed in a TEM image or the like, that is, a structure in which other elements enter the crystal, a void, or the like.

[0062] Furthermore, although not shown, the second region 102 can exist inside the positive electrode active material 100. For example, when the first region 101 is polycrystalline, the second region 102 can exist near the grain boundary. In addition, the second region 102 can exist near a portion of the positive electrode active material 100 having a crystal defect.

[0063] The second region 102 may not cover the entire first region 101. Similarly, the third region 103 may not cover the entire second region 102. The third region 103 can exist in a manner of contacting the first region 101.

[0064] In other words, the first region 101 exists inside the positive electrode active material 100, and the second region 102 and the third region 103 exist in the surface layer portion of the positive electrode active material 100. The second region 102 and the third region 103 in the surface layer portion are used as a covering layer of the positive electrode active material. And, the third region 103 and the second region 102 can exist inside the particles of the positive electrode active material 100.

[0065] When the particle size of the positive electrode active material 100 is too large, there are problems such as difficulty in lithium diffusion; when coated on a current collector, the surface of the active material layer is too rough, etc. On the other hand, when the particle size of the positive electrode active material 100 is too small, there are problems such as difficulty in coating the material on a current collector; excessive reaction with the electrolyte, etc. Therefore, the D50 (also referred to as the median particle size) is preferably 0.1 μm or more and 100 μm or less, more preferably 1 μm or more and 40 μm or less.

[0066] In addition, in order to increase the density of the positive electrode active material layer, it is also effective to mix large particles (about 20 μm or more and about 40 μm or less) and small particles (about 1 μm), and use the small particles to fill the gaps between the large particles. Therefore, there can be two or more peaks in the particle size distribution.

[0067] <First region 101>

[0068] The first region 101 contains lithium, a transition metal, and oxygen. It can be said that the first region 101 contains a composite oxide containing lithium and a transition metal.

[0069] As the transition metal contained in the first region 101, a metal that is likely to form a layered rock salt type composite oxide with lithium is preferably used. For example, one or more of manganese, cobalt, and nickel can be used. That is, as the transition metal contained in the first region 101, only cobalt can be used, cobalt and manganese can be used, or cobalt, manganese, and nickel can be used. The first region 101 can also contain a metal other than a transition metal such as aluminum in addition to the transition metal.

[0070] That is, the first region 101 can contain a composite oxide containing lithium and a transition metal such as lithium cobaltate, lithium nickelate, lithium cobaltate in which a part of cobalt is replaced by manganese, nickel-manganese-cobaltate, and nickel-cobalt-aluminate.

[0071] The first region 101 is a region that particularly contributes to the charge and discharge reaction in the positive electrode active material 100. In order to increase the capacity when the positive electrode active material 100 is used in a secondary battery, the volume of the first region 101 is preferably larger than that of the second region 102 and the third region 103.

[0072] The first region 101 can be either single crystal or polycrystalline. For example, the first region 101 can be polycrystalline with an average grain size of 280 nm or more and 630 nm or less. When the first region 101 is polycrystalline, the crystal grain boundaries can sometimes be observed by TEM or the like. In addition, the average of the crystal grain diameters is calculated from the half width of XRD.

[0073] Since polycrystals have an obvious crystal structure, a sufficient two-dimensional diffusion path for lithium ions is ensured. And compared with single crystals, polycrystals are easier to produce, so polycrystals are preferred as the first region 101.

[0074] In a layered rock salt-type crystal structure, lithium easily diffuses two-dimensionally, so this structure is preferred as the first region 101. Additionally, when the first region 101 has a layered rock salt-type crystal structure, unexpectedly, segregation of magnesium, which will be described later, easily occurs. However, it is not necessarily required that the entire first region 101 has a layered rock salt-type crystal structure. For example, a part of the first region 101 may have crystal defects, a part of the first region 101 may be amorphous, or the first region 101 may have other crystal structures.

[0075] <Second region 102>

[0076] The second region 102 contains lithium, aluminum, a transition metal, and oxygen. It can be said that aluminum replaces a part of the transition metal positions in a composite oxide containing lithium and a transition metal. The transition metal contained in the second region 102 is preferably the same element as the transition metal contained in the first region 101. In this specification and the like, "position" refers to the position that a certain element needs to occupy in the crystal.

[0077] The second region 102 may also contain fluorine.

[0078] When the second region 102 contains aluminum, the cycle characteristics of the positive electrode active material 100 can be improved. The aluminum contained in the second region 102 may have a concentration gradient. Aluminum is preferably present in a part of the transition metal positions in the composite oxide containing lithium and a transition metal, but it may also exist in other states. For example, aluminum may exist as aluminum oxide (Al2O3).

[0079] Generally, with the repetition of charge and discharge, side reactions such as the dissolution of transition metals such as cobalt or manganese into the electrolyte, oxygen detachment, and instability of the crystal structure occur, and the deterioration of the positive electrode active material progresses. However, since the positive electrode active material 100 according to one embodiment of the present invention includes the second region 102 containing aluminum in the surface layer portion, the crystal structure of the composite oxide containing lithium and a transition metal in the first region 101 can be made more stable. Therefore, the cycle characteristics of the secondary battery including the positive electrode active material 100 can be improved.

[0080] The second region 102 preferably has a layered rock salt-type crystal structure. By the second region 102 having a layered rock salt-type crystal structure, its crystal orientation is easily aligned with the crystal orientations of the first region 101 and the third region 103. When the crystal orientations of the first region 101, the second region 102, and the third region 103 are substantially aligned, the second region 102 and the third region 103 can be used as a more stable covering layer.

[0081] When the second region 102 is too thin, its function as a coating layer decreases. However, when the second region 102 is too thick, it may lead to a reduction in capacity. Therefore, the second region 102 preferably exists at a position from the surface of the positive electrode active material 100 to a depth of 30 nm, more preferably to a depth of 15 nm.

[0082] <The third region 103>

[0083] The third region 103 contains magnesium and oxygen. It can be said that the third region 103 contains magnesium oxide.

[0084] The third region 103 may also contain the same transition metals as the first region 101 and the second region 102. And, the third region 103 may contain fluorine. When the third region 103 contains fluorine, a part of the oxygen in magnesium oxide can be replaced by fluorine.

[0085] Since the magnesium oxide contained in the third region 103 is an electrochemically stable material, it is not easily deteriorated even when repeatedly charged and discharged, so it is suitable for the coating layer. That is, when the positive electrode active material 100 includes the third region 103 in addition to the second region 102 in the surface layer portion, the crystal structure of the composite oxide containing lithium and transition metals in the first region 101 can be made more stable. Therefore, the cycle characteristics of the secondary battery including the positive electrode active material 100 can be improved. At a voltage exceeding 4.3 V (vs. Li / Li + )), especially when charging and discharging at a high voltage of 4.5 V (vs. Li / Li + ) or more, the structure of one embodiment of the present invention exhibits a remarkable effect.

[0086] When the third region 103 has a rock salt-type crystal structure, it is easy to align with the crystal orientation of the second region 102 and is easily used as a stable coating layer, so it is preferred. However, the entire third region 103 does not necessarily need to have a rock salt-type crystal structure. For example, a part of the third region 103 can be amorphous, and the third region 103 can have other crystal structures.

[0087] When the third region 103 is too thin, its function as a coating layer decreases. However, when the third region 103 is too thick, it may lead to a reduction in capacity. Therefore, the third region 103 preferably exists at a position from the surface of the positive electrode active material 100 to a depth of 0.5 nm or more and 50 nm or less, more preferably to a depth of 0.5 nm or more and 5 nm or less.

[0088] Because it is important that the third region 103 contains an electrochemically stable material, the elements contained in the third region 103 do not necessarily have to be magnesium. For example, instead of magnesium or in addition to magnesium, main group elements such as calcium and beryllium can also be contained. And, instead of fluorine or in addition to fluorine, chlorine can also be contained.

[0089] <The boundaries between the respective regions>

[0090] The compositions of the first region 101, the second region 102, and the third region 103 are different from each other. However, the elements contained in each region sometimes have a concentration gradient. For example, the aluminum contained in the second region 102 sometimes has a concentration gradient. In addition, since the third region 103 is preferably a region where magnesium segregation described later occurs, it sometimes has a concentration gradient of magnesium. Therefore, the boundaries between the respective regions are sometimes unclear.

[0091] Based on TEM images, STEM images, FFT (Fast Fourier Transform) analysis, EDX (Energy Dispersive X-ray Analysis), analysis in the depth direction using ToF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry), XPS (X-ray Photoelectron Spectroscopy), Auger electron spectroscopy, TDS (Thermal Desorption Spectroscopy), etc., the compositional differences among the first region 101, the second region 102, and the third region 103 can be confirmed. In EDX measurement, a method of sometimes measuring while scanning the edge region and performing two-dimensional evaluation within the region is called EDX surface analysis. In addition, a method of sometimes extracting data of a linear region from the surface analysis of EDX and evaluating the atomic concentration distribution within the positive electrode active material particles is called line analysis.

[0092] For example, in TEM images and STEM images, the differences in constituent elements are observed as differences in image brightness, so it can be observed that the constituent elements of the first region 101, the second region 102, and the third region 103 are different from each other. In addition, in the surface analysis of EDX (for example, element mapping), it can also be observed that the first region 101, the second region 102, and the third region 103 contain different elements.

[0093] In addition, in the line analysis of EDX and the depth direction analysis using ToF-SIMS, the concentration peaks of the respective elements contained in the first region 101, the second region 102, and the third region 103 can be detected.

[0094] However, it is not always possible to observe a clear boundary between the first region 101, the second region 102, and the third region 103 in various analyses.

[0095] In this specification and the like, the range of the third region 103 existing in the surface layer portion of the positive electrode active material 100 is from the surface of the positive electrode active material 100 to the position where the magnesium concentration reaches 1 / 5 of the peak value. As an analysis method, the above-mentioned line analysis of EDX and the depth direction analysis using ToF-SIMS, etc. can be used.

[0096] The concentration peak of magnesium preferably appears in the range of a depth of 3 nm from the surface of the positive electrode active material 100 towards the center, more preferably in the range of a depth of 1 nm, and further preferably in the range of a depth of 0.5 nm.

[0097] Although it varies depending on the manufacturing method, in the case of the manufacturing method described later, the depth at which the magnesium concentration becomes 1 / 5 of the peak value is in the range of about 2 nm to 5 nm from the surface of the positive electrode active material.

[0098] The third region 103 existing inside the first region 101 is a region where the concentration of the main group element detected by depth direction analysis is 1 / 5 or more of the peak value.

[0099] The fluorine distribution of the positive electrode active material 100 preferably overlaps with the magnesium distribution. Therefore, preferably, fluorine also has a concentration gradient, and the concentration peak of fluorine appears in the range of a depth of 3 nm from the surface of the positive electrode active material 100 towards the center, more preferably in the range of a depth of 1 nm, and further preferably in the range of a depth of 0.5 nm.

[0100] In this specification and the like, the second region 102 existing in the surface layer portion of the positive electrode active material 100 is a region where the aluminum concentration detected by depth direction analysis is 1 / 2 or more of the peak value. The second region 102 existing inside the first region 101 near the grain boundary or near the crystal defect is a region where the aluminum concentration detected by depth direction analysis is 1 / 2 or more of the peak value. As the analysis method, the line analysis of the above-mentioned EDX and the depth direction analysis using ToF-SIMS etc. can be used.

[0101] Therefore, sometimes the third region 103 and the second region 102 overlap. However, preferably, the third region 103 exists in a region closer to the surface of the positive electrode active material particle than the second region 102. The concentration peak of magnesium preferably appears in a region closer to the surface of the positive electrode active material particle than the concentration peak of aluminum.

[0102] The concentration peak of aluminum preferably appears in the range of a depth of 0.5 nm or more and 20 nm or less from the surface of the positive electrode active material 100, more preferably in the range of a depth of 1 nm or more and 5 nm or less.

[0103] In addition to the above-mentioned ToF-SIMS, EDX (surface analysis and line analysis), the concentrations of aluminum, magnesium, and fluorine can also be analyzed by XPS, Auger electron spectroscopy, TDS, etc.

[0104] The measurement range of XPS is about 5 nm from the surface of the positive electrode active material 100. Therefore, the elemental concentration present at a position about 5 nm from the surface can be quantitatively analyzed. Thus, when the thickness of the third region 103 is less than 5 nm from the surface, the elemental concentration of the region where a part of the third region 103 and a part of the second region 102 are combined can be quantitatively analyzed, and when the thickness of the third region 103 is 5 nm or more from the surface, the elemental concentration of the third region 103 can be quantitatively analyzed.

[0105] In the XPS measurement from the surface of the positive electrode active material 100, when the total amount of lithium, aluminum, transition metals contained in the first region 101, magnesium, oxygen, and fluorine is 100 atomic%, the aluminum concentration is preferably 0.1 atomic% or more and 10 atomic% or less, more preferably 0.1 atomic% or more and 2 atomic% or less. The magnesium concentration is preferably 5 atomic% or more and 20 atomic% or less. The fluorine concentration is 3.5 atomic% or more and 14 atomic% or less.

[0106] As described above, since the elements contained in the first region 101, the second region 102, and the third region 103 sometimes have a concentration gradient, the first region 101 may also contain the elements contained in the second region 102 and the third region 103. Similarly, the third region 103 may also contain the elements contained in the first region 101 and the second region 102. The first region 101, the second region 102, and the third region 103 may also contain other elements such as carbon, sodium, calcium, chlorine, and zirconium.

[0107] [Coating of the second region]

[0108] The second region 102 can be formed by coating composite oxide particles containing lithium and transition metals with a material containing aluminum.

[0109] As a method of coating with a material containing aluminum, liquid phase methods such as the sol-gel method, solid phase methods, sputtering methods, evaporation coating methods, CVD (chemical vapor deposition) methods, PLD (pulsed laser deposition) methods, etc. can be used. In the present embodiment, the sol-gel method that can be expected to achieve uniform coating and can be processed at atmospheric pressure is adopted.

[0110] When the sol-gel method is adopted, first, an aluminum alkoxide is dissolved in an alcohol, and this solution is mixed with composite oxide particles containing lithium and transition metals, and stirred in an atmosphere containing water vapor. By placing it in an atmosphere containing H2O, a hydrolysis and polycondensation reaction of water and the aluminum alkoxide occurs on the surface of the composite oxide particles containing lithium and transition metals, and a gel-like layer containing aluminum is formed on the surface of the particles. Then, the particles are collected and dried. The manufacturing method will be described in detail later.

[0111] Note that, in the present embodiment, an example in which the composite oxide particles containing lithium and a transition metal are covered with a material containing aluminum before being coated on the positive electrode current collector is described, but one aspect of the present invention is not limited thereto. After forming a positive electrode active material layer including the composite oxide particles containing lithium and a transition metal on the positive electrode current collector, the positive electrode current collector and the positive electrode active material layer may be immersed in a solution containing an aluminum alkoxide.

[0112] [Segregation in the third region]

[0113] The third region 103 can also be formed by a liquid phase method such as a sputtering method, a solid phase method, or a sol-gel method. However, the inventors have found that when heating is performed after mixing a magnesium source and a fluorine source with the material of the first region 101, magnesium segregates on the outermost surface of the positive electrode active material particles, thereby forming the third region 103. In addition, the inventors have also found that when the third region 103 formed in this way is included, a positive electrode active material 100 having good cycle characteristics is achieved.

[0114] When heating is performed as described above to cause magnesium to segregate on the outermost surface of the positive electrode active material particles to form the third region 103, the heating is preferably performed after covering the composite oxide particles containing lithium, a transition metal, magnesium, and fluorine with a material containing aluminum. This is because, unexpectedly, after covering with a material containing aluminum, magnesium segregates on the outermost surface of the positive electrode active material particles. The manufacturing method will be described in detail later.

[0115] When magnesium segregates, when the composite oxide containing lithium and a transition metal included in the first region 101 is polycrystalline or has crystal defects, magnesium may segregate not only in the surface layer portion but also near the grain boundaries or crystal defects of the composite oxide containing lithium and a transition metal. Magnesium segregating near the grain boundaries or crystal defects contributes to the more stabilization of the crystal structure of the composite oxide containing lithium and a transition metal included in the first region 101.

[0116] When the ratio of magnesium and fluorine in the raw materials is in the range of Mg:F = 1:x (1.5 ≤ x ≤ 4) (atomic ratio), magnesium segregation occurs efficiently, so it is preferable. In addition, more preferably, Mg:F is about 1:2 (atomic ratio).

[0117] Since the third region 103 formed by segregation is formed by epitaxial growth, the crystal orientations of the second region 102 and the third region 103 may be partially substantially aligned. That is, the second region 102 and the third region 103 may be in topotaxy. When the crystal orientations of the second region 102 and the third region 103 are substantially aligned, they are used as a better covering layer.

[0118] Note that in this specification and the like, topological derivation means: having a three-dimensional structural similarity; or having the same orientation crystallographically. Therefore, in the case of topological derivation, when observing a part of the cross section, the crystal orientations of two regions (for example, a base region and a region formed by growth) are substantially aligned.

[0119] <Fourth Region 104>

[0120] Above, an example in which the positive electrode active material 100 includes the first region 101, the second region 102, and the third region 103 has been described, but one aspect of the present invention is not limited thereto. For example, as Figure 1C shown, the positive electrode active material 100 may also include a fourth region 104. The fourth region 104 may be provided, for example, in a manner of being in contact with at least a part of the third region 103. The fourth region 104 may be a film containing carbon such as a graphene compound, or may be a film containing a decomposition product of lithium or an electrolyte. When the fourth region 104 is a film containing carbon, the conductivity between the positive electrode active materials 100 and the conductivity between the positive electrode active material 100 and the current collector can be improved. When the fourth region 104 is a film containing a decomposition product of lithium or an electrolyte, an excessive reaction with the electrolyte can be suppressed and the cycle characteristics when used in a secondary battery can be improved.

[0121] [Manufacturing Method]

[0122] Use Figure 2 An example of a manufacturing method of the positive electrode active material 100 when including the first region 101, the second region 102, and the third region 103 will be described. In one example of this manufacturing method, the first region contains cobalt as a transition metal, and the second region is formed by a sol-gel method using an aluminum alkoxide. Then, heating is performed to segregate magnesium on the surface to form the third region 103.

[0123] First, starting materials are prepared (S11). As the starting materials, composite oxide particles containing lithium, cobalt, fluorine, and magnesium are used.

[0124] When synthesizing composite oxide particles containing lithium, cobalt, fluorine, and magnesium, first, a lithium source, a cobalt source, a magnesium source, and a fluorine source are weighed. As the lithium source, for example, lithium carbonate, lithium fluoride, lithium hydroxide, etc. can be used. As the cobalt source, for example, cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide, cobalt carbonate, cobalt oxalate, cobalt sulfate, etc. can be used. As the magnesium source, for example, magnesium oxide, magnesium fluoride, etc. can be used. As the fluorine source, for example, lithium fluoride, magnesium fluoride, etc. can be used. That is, lithium fluoride can be used both as a lithium source and as a fluorine source, and magnesium fluoride can be used both as a magnesium source and as a fluorine source.

[0125] The atomic ratio of magnesium and fluorine in the raw materials is preferably Mg:F = 1:x (1.5 ≤ x ≤ 4), more preferably about Mg:F = 1:2 (atomic ratio). In the case of the above atomic ratio, when heating is carried out in the subsequent process, magnesium segregation is likely to occur.

[0126] Next, weigh the starting materials for mixing. In the mixing, for example, a ball mill, a sand mill, etc. can be used.

[0127] Next, calcine the mixed starting materials. The calcination is preferably carried out at 800 °C or higher and 1050 °C or lower, more preferably at 900 °C or higher and 1000 °C or lower. The calcination time is preferably 2 hours or more and 20 hours or less. The calcination is preferably carried out in a dry atmosphere such as dry air. As the dry atmosphere, for example, an atmosphere with a dew point of -50 °C or lower is preferred, and an atmosphere with a dew point of -100 °C or lower is more preferred. In this embodiment, heating is carried out under the following conditions: 1000 °C; 10 hours; a heating rate of 200 °C / h; flowing dry air with a dew point of -109 °C at 10 L / min. Then, cool the heated material to room temperature.

[0128] Through the above process, composite oxide particles containing lithium, cobalt, fluorine, and magnesium can be synthesized.

[0129] In addition, as the starting material, pre-synthesized composite oxide particles of lithium and cobalt can be used. For example, lithium cobaltate particles (trade name: C-20F) manufactured by NIPPON CHEMICAL INDUSTRIAL CO., LTD. can be used as the starting material. The particles are lithium cobaltate particles having a particle size of about 20 μm and containing fluorine, magnesium, calcium, sodium, silicon, sulfur, and phosphorus in the region from the surface to the region analyzable by XPS. In this embodiment, lithium cobaltate particles (trade name: C-20F) manufactured by NIPPON CHEMICAL INDUSTRIAL CO., LTD. are used as the starting material.

[0130] Next, dissolve the aluminum alkoxide in an alcohol and mix the solution with the particles of the starting material (S12).

[0131] As the aluminum alkoxide, trimethoxy aluminum, triethoxy aluminum, tri-n-propoxy aluminum, tri-i-propoxy aluminum, tri-n-butoxy aluminum, tri-i-butoxy aluminum, tri-sec-butoxy aluminum, tri-t-butoxy aluminum, etc. can be used. As the solvent for dissolving the aluminum alkoxide, methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol, etc. can be used.

[0132] Note that the alkoxide group of the aluminum alkoxide and the alcohol used as the solvent can be of different types, but it is particularly preferred that they are of the same type.

[0133] Next, the above mixture is stirred in an atmosphere containing water vapor (S13). Due to the above treatment, H2O in the atmosphere reacts with aluminum isopropoxide to undergo hydrolysis and polycondensation reactions. As a result, a gel-like layer containing aluminum is formed on the surface of the lithium cobaltate particles containing magnesium and fluorine.

[0134] For example, a magnetic stirrer can be used for stirring. The stirring time only needs to be a time sufficient for the water in the atmosphere to react with aluminum isopropoxide to undergo hydrolysis and polycondensation reactions. For example, stirring can be carried out at 25°C for 4 hours at a humidity of 90% RH (Relative Humidity).

[0135] As described above, by reacting an aluminum alkoxide with water at room temperature, a more uniform and higher-quality aluminum-containing coating layer can be formed compared to, for example, heating at a temperature higher than the boiling point of the alcohol in the solvent (e.g., 100°C or higher).

[0136] The precipitate is collected from the treated mixture (S14). As the collection method, filtration, centrifugation, drying and solidification, etc. can be used. In this embodiment, the precipitate is collected by filtration. Filter paper is used in the filtration, and the residue is washed with the same alcohol as the solvent in which the aluminum alkoxide is dissolved.

[0137] Next, the collected residue is dried (S15). In this embodiment, vacuum drying is carried out at 70°C for 1 hour.

[0138] Next, the dried powder is heated (S16). Through this heating, the magnesium and fluorine contained in the starting material segregate on the surface to form the third region 103.

[0139] The heating is preferably carried out at a specified temperature and a holding time of 50 hours or less, more preferably 1 hour or more and 10 hours or less. Here, the specified temperature refers to the holding temperature. The specified time is preferably 500°C or higher and 1200°C or lower, more preferably 700°C or higher and 1000°C or lower, and further preferably around 800°C. The heating is preferably carried out in an atmosphere containing oxygen. In this embodiment, the heating is carried out under the following conditions: the specified temperature is 800°C; the holding time is 2 hours; the heating rate is 200°C / h; the flow rate of dry air is 10 L / min. Cooling is carried out for the same time as the heating or for a time exceeding the heating time.

[0140] Next, it is preferable to cool the heated powder and perform a grinding process (S17). The grinding process can be carried out, for example, by sieving the powder.

[0141] Through the above process, a positive electrode active material 100 of one embodiment of the present invention can be manufactured.

[0142] Embodiment 2

[0143] In the present embodiment, examples of materials for a secondary battery that can be used for the positive electrode active material 100 described in the above embodiment will be described. In the present embodiment, a secondary battery in which the positive electrode, negative electrode, and electrolyte are surrounded by an outer packaging body will be described as an example.

[0144] [Positive Electrode]

[0145] The positive electrode includes a positive electrode active material layer and a positive electrode current collector.

[0146] <Positive Electrode Active Material Layer〉

[0147] The positive electrode active material layer contains a positive electrode active material. In addition, the positive electrode active material layer may also contain a conductive additive and a binder.

[0148] As the positive electrode active material, the positive electrode active material 100 described in the above embodiment can be used. By using the positive electrode active material 100 described in the above embodiment, a secondary battery with high capacity and excellent cycle characteristics can be achieved.

[0149] As the conductive additive, a carbon material, a metal material, a conductive ceramic material, etc. can be used. In addition, as the conductive additive, a fibrous material can also be used. The ratio of the conductive additive in the total amount of the active material layer is preferably 1 wt% or more and 10 wt% or less, more preferably 1 wt% or more and 5 wt% or less.

[0150] By using the conductive additive, a conductive network can be formed in the electrode. By using the conductive additive, the conduction path between the positive electrode active materials can be maintained. By adding the conductive additive to the active material layer, an active material layer with high conductivity can be achieved.

[0151] As the conductive additive, for example, natural graphite, artificial graphite such as mesocarbon microbeads, carbon fiber, etc. can be used. As the carbon fiber, for example, mesophase pitch-based carbon fiber, isotropic pitch-based carbon fiber, etc. can be used. As the carbon fiber, carbon nanofiber or carbon nanotube, etc. can be used. For example, carbon nanotubes can be manufactured by a vapor growth method, etc. As the conductive additive, for example, carbon black (such as acetylene black (AB)), graphite (graphite) particles, graphene, fullerene, etc. can be used. In addition, for example, metal powders or metal fibers such as copper, nickel, aluminum, silver, gold, etc., conductive ceramic materials, etc. can be used.

[0152] In addition, a graphene compound can also be used as the conductive additive.

[0153] Graphene compounds sometimes have excellent electrical properties such as high electrical conductivity, as well as excellent physical properties such as high flexibility and high mechanical strength. In addition, graphene compounds have a planar shape. Graphene compounds can form a surface contact with low contact resistance. Graphene compounds sometimes have very high electrical conductivity even when thin, so conductive paths can be efficiently formed in a small amount in the active material layer. Therefore, by using a graphene compound as a conductive aid, the contact area between the active material and the conductive aid can be increased, so it is preferred. In addition, sometimes by using a graphene compound as a conductive aid, the resistance can be reduced, so it is preferred. Here, particularly preferably, graphene, multi-layer graphene, or reduced graphene oxide (hereinafter, RGO) is used as the graphene compound. Here, RGO refers to a compound obtained by reducing graphene oxide (GO), for example.

[0154] 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 is large, so more conductive paths for connecting the active materials to each other are required. Therefore, the amount of the conductive aid tends to increase, and the content of the active material tends to relatively decrease. When the content of the active material decreases, the capacity of the secondary battery also decreases. In this case, since it is not necessary to reduce the content of the active material, it is particularly preferred to use a graphene compound that can efficiently form a conductive path even in a small amount.

[0155] Hereinafter, as an example, a cross-sectional structure example of the active material layer 200 containing a graphene compound as a conductive aid will be described.

[0156] Figure 3A It is a longitudinal sectional view of the active material layer 200. The active material layer 200 includes granular positive electrode active material 100, a graphene compound 201 used as a conductive aid, and a binder (not shown). Here, as the graphene compound 201, graphene or multi-layer graphene can be used, for example. In addition, the graphene compound 201 preferably has a sheet shape. The graphene compound 201 can be formed into a single sheet shape in such a way that a plurality of multi-layer graphenes or (and) a plurality of single-layer graphenes partially overlap.

[0157] In the longitudinal section of the active material layer 200, as Figure 3A shown, the sheet-shaped graphene compound 201 is substantially uniformly dispersed inside the active material layer 200. In Figure 3AIn [the figure], although the graphene compound 201 is schematically shown as a thick line, actually the graphene compound 201 is a film with a thickness of a single layer or multiple layers of carbon molecules. Since multiple graphene compounds 201 are formed in such a way as to wrap or cover multiple granular positive electrode active materials 100 or to adhere to the surfaces of multiple granular positive electrode active materials 100, the graphene compound 201 makes surface contact with the positive electrode active material 100.

[0158] Herein, by combining multiple graphene compounds with each other, a net-like graphene compound sheet (hereinafter referred to as a graphene compound net or a graphene net) can be formed. When the graphene net covers the active material, the graphene net can be used as an adhesive for binding compounds to each other. Therefore, the amount of the adhesive can be reduced or the adhesive can be not used, whereby the proportion of the active material in the electrode volume or the electrode weight can be increased. That is to say, the capacity of the power storage device can be improved.

[0159] Herein, preferably, graphene oxide is used as the graphene compound 201, the graphene oxide and the active material are mixed to form a layer that will become the active material layer 200, and then reduction is performed. By using graphene oxide with extremely high dispersibility in a polar solvent in the formation of the graphene compound 201, the graphene compound 201 can be dispersed in the active material layer 200 substantially uniformly. The solvent is volatilized and removed from the dispersion medium containing uniformly dispersed graphene oxide, and the graphene oxide is reduced. Therefore, the graphene compounds 201 remaining in the active material layer 200 partially overlap with each other and are dispersed in a manner of making surface contact, whereby a three-dimensional conduction path can be formed. In addition, the reduction of graphene oxide can also be performed, for example, by heat treatment or using a reducing agent.

[0160] Therefore, different from granular conductive aids such as acetylene black that make point contact with the active material, the graphene compound 201 can make surface contact with a low contact resistance. Therefore, the conductivity between the granular positive electrode active material 100 and the graphene compound 201 can be improved with less graphene compound 201 than general conductive aids. Therefore, the ratio of the granular positive electrode active material 100 in the active material layer 200 can be increased. Thereby, the discharge capacity of the power storage device can be increased.

[0161] As the binder, rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. are preferably used. Fluororubber can also be used as the binder.

[0162] In addition, water-soluble polymers are preferably used as the binder. As the water-soluble polymer, polysaccharides etc. can be used, for example. As the polysaccharide, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, regenerated cellulose, etc., starch, etc. can be used. It is more preferable to use these water-soluble polymers and the above rubber materials in combination.

[0163] Alternatively, materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), ethylene-propylene-diene terpolymer, polyvinyl acetate, nitrocellulose, etc. are preferably used as the binder.

[0164] As the binder, multiple kinds of the above materials can also be used in combination.

[0165] For example, a material with a particularly high viscosity adjustment function can also be combined with other materials and used. For example, although rubber materials etc. have high adhesive force and high elasticity, it is sometimes difficult to adjust the viscosity when mixed in a solvent. In such a case, for example, it is preferable to mix with a material with a particularly high viscosity adjustment function. As the material with a particularly high viscosity adjustment function, a water-soluble polymer can be used, for example. In addition, as the water-soluble polymer with a particularly good viscosity adjustment function, the above polysaccharides can be used, and cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose and diacetyl cellulose, regenerated cellulose, etc., starch can be used.

[0166] Note that for cellulose derivatives such as carboxymethyl cellulose, the solubility is increased, for example, by converting them into salts such as sodium salt, ammonium salt of carboxymethyl cellulose, etc., and it is easy to exhibit the effect as a viscosity regulator. Due to the increased solubility, the dispersibility of the active material and other constituent elements can be improved when forming the electrode paste. In this specification, the cellulose and cellulose derivatives used as the binder for the electrode include their salts.

[0167] By dissolving a water-soluble polymer in water to stabilize its viscosity, an active substance and other materials used as a binder combination, such as styrene-butadiene rubber, can be stably dispersed in an aqueous solution. Since the water-soluble polymer has functional groups, it is expected to easily and stably adhere to the surface of the active substance. Most cellulose derivatives such as carboxymethyl cellulose have functional groups such as hydroxyl groups and carboxyl groups. Because of having functional groups, the polymers are expected to interact and widely cover the surface of the active substance.

[0168] When the binder covering or in contact with the surface of the active substance forms a film, it is also expected to be used as a passive film to exert the effect of suppressing the decomposition of the electrolyte. Here, the passive film is a film having no electron conductivity or extremely low conductivity. For example, when the passive film is formed on the surface of the active substance, it suppresses the decomposition of the electrolyte at the battery reaction potential. More preferably, the passive film can transmit lithium ions while suppressing conductivity.

[0169] <Positive current collector>

[0170] As the positive current collector, highly conductive materials such as metals and their alloys such as stainless steel, gold, platinum, aluminum, and titanium can be used. In addition, the material used for the positive current collector is preferably not dissolved by the potential of the positive electrode. In addition, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, and molybdenum to improve heat resistance can also be used. In addition, it can also be formed using a metal element that reacts with silicon to form a silicide. As the metal element that reacts with silicon to form a silicide, there are zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately have shapes such as foil, plate (sheet), mesh, punched metal mesh, and drawn metal mesh. The thickness of the current collector is preferably 5 μm or more and 30 μm or less.

[0171] [Negative electrode]

[0172] The negative electrode includes a negative electrode active material layer and a negative current collector. The negative electrode active material layer may also contain a conductive additive and a binder.

[0173] <Negative electrode active material>

[0174] As the negative electrode active material, for example, alloy materials or carbon materials can be used.

[0175] As the negative electrode active material, an element capable of performing charge and discharge reactions through alloying / dealloying reactions with lithium can be used. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium, etc. can be used. The capacity of such an element is larger than that of carbon. In particular, the theoretical capacity of silicon is large, being 4200 mAh / g. Therefore, it is preferable to use silicon for the negative electrode active material. In addition, compounds containing these elements can also be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, and SbSn, etc. can be cited. Sometimes, an element capable of performing charge and discharge reactions through alloying / dealloying reactions with lithium and a compound containing the element, etc. are referred to as alloy-like materials.

[0176] In this specification, etc., SiO refers to silicon monoxide, for example. Or SiO can also be expressed as SiO x . Here, x preferably represents a value near 1. For example, x is preferably 0.2 or more and 1.5 or less, more preferably 0.3 or more and 1.2 or less.

[0177] As the carbonaceous material, graphite, graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, carbon black, etc. can be used.

[0178] As graphite, artificial graphite or natural graphite, etc. can be cited. As artificial graphite, for example, mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. can be cited. Here, spherical graphite having a spherical shape can be used as artificial graphite. For example, MCMB sometimes has a spherical shape, so it is preferable. In addition, MCMB is relatively easy to reduce its surface area, so it is sometimes preferable. As natural graphite, for example, flake graphite, spheroidized natural graphite, etc. can be cited.

[0179] When lithium ions are intercalated in graphite (when a lithium-graphite intercalation compound is formed), graphite shows a low potential similar to that of lithium metal (0.05 V or more and 0.3 V or less vs. Li / Li + ). Thus, the lithium ion secondary battery can show a high operating voltage. Graphite also has the following advantages: a relatively large capacity per unit volume; a relatively small volume expansion; being relatively inexpensive; having higher safety compared to lithium metal, etc., so it is preferable.

[0180] In addition, as the negative electrode active material, oxides such as titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), etc. can be used.

[0181] In addition, as the negative electrode active material, Li 3-x M x N (M = Co, Ni, Cu) having a Li3N-type structure containing a nitride of lithium and a transition metal can be used. For example, Li 2.6 Co 0.4 N3 exhibits a large charge-discharge capacity (900 mAh / g, 1890 mAh / cm 3 ), so it is preferred.

[0182] When a nitride containing lithium and a transition metal is used as the negative electrode active material, lithium ions are contained in the negative electrode active material. Therefore, the negative electrode active material can be combined with materials such as V2O5 and Cr3O8 that do not contain lithium ions and are used as the positive electrode active material, so it is preferred. Note that when a material containing lithium ions is used as the positive electrode active material, by previously deintercalating the lithium ions contained in the positive electrode active material, a nitride containing lithium and a transition metal can also be used as the negative electrode active material.

[0183] In addition, materials that cause a conversion reaction can also be used for the negative electrode active material. For example, transition metal oxides such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO) that do not form an alloy with lithium are used for the negative electrode active material. As materials that cause a conversion reaction, oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, sulfides such as CoS 0.89 , NiS, and CuS, nitrides such as Zn3N2, Cu3N, and Ge3N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3 can also be cited.

[0184] As the conductive assistant and binder that can be contained in the negative electrode active material layer, the same materials as those that can be contained in the positive electrode active material layer can be used.

[0185] [Negative electrode current collector]

[0186] As the negative electrode current collector, the same materials as those of the positive electrode current collector can be used. In addition, as the negative electrode current collector, a material that does not alloy with carrier ions such as lithium is preferably used.

[0187] [Electrolyte solution]

[0188] The electrolyte contains a solvent and an electrolyte. As the solvent of the electrolyte, an aprotic organic solvent is preferably used. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, vinyl chloride carbonate, vinylene carbonate, γ-butyrolactone, 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, ethylene glycol dimethyl ether (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. can be used, or two or more of the above can be used in any combination and ratio.

[0189] In addition, when a gelled polymer material is used as the solvent of the electrolyte, the safety against leakage is improved. Moreover, the thinning and lightening of the secondary device can be achieved. Typical examples of the gelled polymer material include silicone gel, acrylic acid gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, fluoropolymer gel, etc.

[0190] In addition, by using one or more ionic liquids (room temperature molten salts) having flame retardancy and low volatility as the solvent of the electrolyte, even if the internal temperature rises due to internal short circuit, overcharge, etc. of the power storage device, the rupture or ignition of the power storage device can be prevented. The ionic liquid is composed of a cation and an anion, and contains an organic cation and an anion. As the organic cation used for the electrolyte, aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations and quaternary phosphonium cations, or aromatic cations such as imidazolium cations and pyridinium cations can be cited. In addition, as the anion used for the electrolyte, monovalent amide anions, monovalent methylide anions, fluorosulfonic acid anions, perfluoroalkylsulfonic acid anions, tetrafluoroboric acid anions, perfluoroalkylboric acid anions, hexafluorophosphoric acid anions or perfluoroalkylphosphoric acid anions, etc. can be cited.

[0191] In addition, as the electrolyte dissolved in the above solvent, for example, LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 10 Cl 10 、Li2B 12 Cl 12, one of lithium salts such as LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc., or two or more of the above can be used in any combination and ratio.

[0192] As the electrolyte for the power storage device, it is preferable to use a highly purified electrolyte with a small content of particulate dust or elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). Specifically, the ratio of impurities in the weight of the electrolyte is 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

[0193] In addition, additives such as vinylene carbonate, propanesultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), LiBOB, or dinitrile compounds such as succinonitrile and adiponitrile can also be added to the electrolyte. The concentration of the additive can be set to, for example, 0.1 wt% or more and 5 wt% or less in the entire solvent.

[0194] In addition, a polymer gel electrolyte in which a polymer is swollen with an electrolyte can also be used.

[0195] As the polymer, for example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, etc., and copolymers containing these can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. In addition, the formed polymer can also have a porous shape.

[0196] In addition, a solid electrolyte containing an inorganic material such as a sulfide-based or oxide-based material, or a solid electrolyte containing a polymer material such as a PEO (polyethylene oxide)-based material can be used instead of the electrolyte. When using a solid electrolyte, there is no need to provide a separator or spacer. In addition, since the entire battery can be solidified, there is no concern about leakage of liquid, and the safety is significantly improved.

[0197] [Separator]

[0198] In addition, the secondary battery preferably includes a separator. As the separator, for example, the following materials can be used: fibers having cellulose such as paper, non-woven fabric, glass fiber, ceramics, or synthetic fibers containing nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic resin, polyolefin, polyurethane, etc. It is preferable to process the separator into a bag shape and dispose it so as to surround either the positive electrode or the negative electrode.

[0199] The separator may have a multi-layer structure. For example, organic material films such as polypropylene and polyethylene can be coated with ceramic materials, fluorine materials, polyamide materials or mixtures thereof. As the ceramic material, for example, alumina particles, silica particles, etc. can be used. As the fluorine material, for example, PVDF, polytetrafluoroethylene, etc. can be used. As the polyamide material, for example, nylon, aromatic polyamide (meta-aramid, para-aramid), etc. can be used.

[0200] By coating the ceramic material, the antioxidant property can be improved, thereby suppressing the deterioration of the separator during high-voltage charge and discharge, and thus improving the reliability of the secondary battery. By coating the fluorine material, it is easy to make the separator in close contact with the electrode, and the output characteristics can be improved. By coating the polyamide material (especially aromatic polyamide), the heat resistance can be improved, thereby improving the safety of the secondary battery.

[0201] For example, a mixed material of alumina and aromatic polyamide can be coated on both sides of the polypropylene film. Or, a mixed material of alumina and aromatic polyamide can be coated on the surface of the polypropylene film in contact with the positive electrode, and a fluorine material can be coated on the surface in contact with the negative electrode.

[0202] By using a separator with a multi-layer structure, the safety of the secondary battery can be ensured even if the total thickness of the separator is small, so the capacity per unit volume of the secondary battery can be increased.

[0203] Embodiment 3

[0204] In this embodiment, an example of the shape of a secondary battery including the positive electrode active material 100 described in the above embodiment is described. The materials used for the secondary battery described in this embodiment can refer to the description of the above embodiment.

[0205] [Coin-type secondary battery]

[0206] First, an example of a coin-type secondary battery is described. Figure 4A is an external view of a coin-type (single-layer flat type) secondary battery, Figure 4B is a cross-sectional view thereof.

[0207] In the coin-type secondary battery 300, the positive electrode can 301 that also serves as the positive electrode terminal and the negative electrode can 302 that also serves as the negative electrode terminal are insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact therewith. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact therewith.

[0208] In the positive electrode 304 and the negative electrode 307 of the coin-type secondary battery 300, the active material layers can be formed on one surface of the positive electrode and the negative electrode, respectively.

[0209] As the positive electrode can 301 and the negative electrode can 302, metals such as nickel, aluminum, and titanium, their alloys, or alloys of them and other metals (such as stainless steel, etc.) that are corrosion-resistant to the electrolyte can be used. Additionally, in order to prevent corrosion caused by the electrolyte, the positive electrode can 301 and the negative electrode can 302 are preferably covered with nickel or aluminum, etc. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307.

[0210] By impregnating these negative electrode 307, positive electrode 304, and separator 310 in the electrolyte, as Figure 4B shown, the positive electrode can 301 is disposed below, and the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are stacked in order, and the positive electrode can 301 and the negative electrode can 302 are pressed together with a gasket 303 interposed therebetween to manufacture the coin-type secondary battery 300.

[0211] By using the positive electrode active material described in the above embodiment for the positive electrode 304, a coin-type secondary battery 300 with high capacity and excellent cycle characteristics can be achieved.

[0212] [Cylindrical secondary battery]

[0213] Next, an example of a cylindrical secondary battery will be described with reference to Figure 5A and Figure 5B As shown in Figure 5A the cylindrical secondary battery 600 has a positive electrode cap (battery cap) 601 on the top surface, and a battery can (outer can) 602 on the side surface and the bottom surface. The above positive electrode cap 601 and the battery can (outer can) 602 are insulated by a gasket (insulating gasket) 610.

[0214] Figure 5BFIG. is a cross-sectional view schematically showing a cylindrical secondary battery. A battery element is provided inside a hollow cylindrical battery can 602. In this battery element, a strip-shaped positive electrode 604 and a strip-shaped negative electrode 606 are wound with a separator 605 interposed therebetween. Although not shown, the battery element is wound around a center pin. One end of the battery can 602 is closed and the other end is open. As the battery can 602, metals such as nickel, aluminum, and titanium, alloys thereof, or alloys of them and other metals (such as stainless steel, etc.) that are corrosion-resistant to the electrolyte can be used. In addition, in order to prevent corrosion caused by the electrolyte, the battery can 602 is preferably covered with nickel or aluminum, etc. Inside the battery can 602, the battery element in which the positive electrode, negative electrode, and separator are wound is sandwiched by a pair of opposing insulating plates 608 and insulating plate 609. In addition, a non-aqueous electrolyte (not shown) is injected into the inside of the battery can 602 in which the battery element is provided. As the non-aqueous electrolyte, the same electrolyte as that used in the coin-type secondary battery can be used.

[0215] Since the positive electrode and negative electrode for the cylindrical secondary battery are wound, the active material is preferably formed on both surfaces of the current collector. The positive electrode 604 is connected to a positive electrode terminal (positive electrode current collector wire) 603, and the negative electrode 606 is connected to a negative electrode terminal (negative electrode current collector wire) 607. As the positive electrode terminal 603 and the negative electrode terminal 607, metal materials such as aluminum can be used. The positive electrode terminal 603 is resistance-welded to the safety valve mechanism 612, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 and the positive electrode cap 601 are electrically connected through a PTC (Positive Temperature Coefficient) element 611. When the internal pressure of the battery rises above a specified threshold value, the safety valve mechanism 612 cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604. In addition, the PTC element 611 is a thermosensitive resistance element whose resistance increases when the temperature rises, and limits the current flow by increasing the resistance to prevent abnormal heating. As the PTC element, barium titanate (BaTiO3)-type semiconductor ceramics, etc. can be used.

[0216] By using the positive electrode active material described in the above embodiment for the positive electrode 604, a cylindrical secondary battery 600 with high capacity and excellent cycle characteristics can be realized.

[0217] [Structural examples of the power storage device]

[0218] Refer to Figures 6A to 10 Other structural examples of the power storage device will be described.

[0219] Figure 6A and Figure 6B FIG. is an external view of the power storage device. The power storage device includes a circuit board 900 and a secondary battery 913. A label 910 is attached to the secondary battery 913. Furthermore, asFigure 6B As shown, the power storage device includes a terminal 951, a terminal 952, an antenna 914, and an antenna 915.

[0220] The circuit substrate 900 includes a terminal 911 and a circuit 912. The terminal 911 is connected to the terminal 951, the terminal 952, the antenna 914, the antenna 915, and the circuit 912. Additionally, multiple terminals 911 can be provided and used as control signal input terminals, power supply terminals, etc. respectively.

[0221] The circuit 912 can also be provided on the back surface of the circuit substrate 900. Additionally, the shapes of the antenna 914 and the antenna 915 are not limited to a coil shape, and can be, for example, a linear shape or a plate shape. Additionally, antennas such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, or a dielectric antenna can also be used. Alternatively, the antenna 914 or the antenna 915 can also be a flat plate-shaped conductor. This flat plate-shaped conductor can also be used as one of the conductors for electric field coupling. In other words, the antenna 914 or the antenna 915 can also be used as one of the two conductors of a capacitor. Thus, power can be exchanged not only using electromagnetic and magnetic fields, but also using an electric field.

[0222] The line width of the antenna 914 is preferably greater than the line width of the antenna 915. Thus, the amount of electric power received by the antenna 914 can be increased.

[0223] The power storage device includes a layer 916 between the antenna 914, the antenna 915, and the secondary battery 913. The layer 916 has, for example, a function of shielding the electromagnetic field from the secondary battery 913. As the layer 916, a magnetic body can be used, for example.

[0224] The structure of the power storage device is not limited to Figure 6A and Figure 6B the structure shown.

[0225] For example, as shown in Figure 7A1 and Figure 7A2 , antennas can also be provided on a pair of opposing surfaces of the secondary battery 913 shown in Figure 6A and Figure 6B . Figure 7A1 is an external view of one side of the above-mentioned pair of surfaces, Figure 7A2 is an external view of the other side of the above-mentioned pair of surfaces. Additionally, parts identical to those of the power storage device shown in Figure 6A and Figure 6B can be appropriately cited Figure 6A and Figure 6B for the description of the power storage device shown.

[0226] As shown in Figure 7A1As shown, an antenna 914 is provided with a layer 916 interposed therebetween on one of a pair of surfaces of the secondary battery 913, as Figure 7A2 shown, an antenna 915 is provided with a layer 917 interposed therebetween on the other of a pair of surfaces of the secondary battery 913. The layer 917 has, for example, a function of shielding an electromagnetic field from the secondary battery 913. As the layer 917, a magnetic body can be used, for example.

[0227] By adopting the above structure, the sizes of both the antenna 914 and the antenna 915 can be increased.

[0228] Alternatively, as Figure 7B1 and Figure 7B2 shown, different antennas are provided on opposite pairs of surfaces of the secondary battery 913 shown in Figure 6A and Figure 6B respectively. Figure 7B1 is an external view of one side of the above pair of surfaces, Figure 7B2 is an external view of the other side of the above pair of surfaces. In addition, the same parts as those of the power storage device shown in Figure 6A and Figure 6B can be appropriately cited for the description of the power storage device shown in Figure 6A and Figure 6B respectively.

[0229] As Figure 7B1 shown, an antenna 914 and an antenna 915 are provided with a layer 916 interposed therebetween on one of a pair of surfaces of the secondary battery 913, as Figure 7B2 shown, an antenna 918 is provided with a layer 917 interposed therebetween on the other of a pair of surfaces of the secondary battery 913. The antenna 918 has, for example, a function of performing data communication with an external device. As the antenna 918, an antenna having a shape applied to the antenna 914 and the antenna 915 can be used, for example. As a communication method between the power storage device using the antenna 918 and other devices, a response method such as NFC that can be used between the power storage device and other devices can be used.

[0230] Alternatively, as Figure 8A shown, a display device 920 can also be provided on the secondary battery 913 shown in Figure 6A and Figure 6B The display device 920 is electrically connected to the terminal 911 through the terminal 919. In addition, a label 910 may not be attached to the portion where the display device 920 is provided. Furthermore, the same parts as those of the power storage device shown in Figure 6A and Figure 6B can be appropriately cited for the description of the power storage device shown in Figure 6A and Figure 6B respectively.

[0231] On the display device 920, for example, an image showing whether charging is in progress, an image showing the remaining battery level, etc. can be displayed. As the display device 920, for example, an electronic paper, a liquid crystal display device, an electroluminescent (also referred to as EL) display device, etc. can be used. For example, by using an electronic paper, the power consumption of the display device 920 can be reduced.

[0232] Alternatively, as Figure 8B shown, a sensor 921 can also be provided in the Figure 6A and Figure 6B secondary battery 913 shown. The sensor 921 is electrically connected to the terminal 911 through the terminal 922. In addition, the same parts as those of the Figure 6A and Figure 6B energy storage device shown can be appropriately cited for the description of the Figure 6A and Figure 6B energy storage device shown.

[0233] The sensor 921 can, for example, have a function of measuring the following factors: displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, slope, vibration, odor, or infrared rays. By providing the sensor 921, for example, data (such as temperature) showing the environment where the energy storage device is provided can be detected and stored in the memory in the circuit 912.

[0234] Furthermore, referring to Figure 9A and Figure 9B and Figure 10 a structural example of the secondary battery 913 will be described.

[0235] Figure 9A The secondary battery 913 shown in Figure 9A includes a wound body 950 provided with a terminal 951 and a terminal 952 inside a casing 930. The wound body 950 is immersed in an electrolyte inside the casing 930. The terminal 952 is in contact with the casing 930, and the terminal 951 is prevented from contacting the casing 930 by an insulating material or the like. Note that, for convenience, although the casing 930 is separately shown in Figure 9A , in fact, the wound body 950 is covered by the casing 930, and the terminals 951 and 952 extend outside the casing 930. As the casing 930, a metal material (such as aluminum, etc.) or a resin material can be used.

[0236] In addition, as Figure 9B shown, the casing 930 shown in Figure 9A can also be formed using multiple materials. For example, in Figure 9BIn the secondary battery 913 shown, a frame 930a and a frame 930b are attached, and a wound body 950 is provided in the region surrounded by the frame 930a and the frame 930b.

[0237] As the frame 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin for the surface forming the antenna, shielding of the electric field of the secondary battery 913 can be suppressed. In addition, if the shielding of the electric field by the frame 930a is small, an antenna such as an antenna 914 or an antenna 915 can also be provided inside the frame 930a. As the frame 930b, for example, a metal material can be used.

[0238] Furthermore, Figure 10 The structure of the wound body 950 is shown. The wound body 950 includes a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is formed by overlapping the negative electrode 931 and the positive electrode 932 with each other with the separator 933 interposed therebetween to form a laminated sheet, and winding the laminated sheet. In addition, a plurality of laminations of the negative electrode 931, the positive electrode 932, and the separator 933 can also be laminated.

[0239] The negative electrode 931 is connected to Figure 6A and Figure 6B the terminal 911 shown through one of the terminals 951 and 952. The positive electrode 932 is connected to Figure 6A and Figure 6B the terminal 911 shown through the other of the terminals 951 and 952.

[0240] By using the positive electrode active material described in the above embodiment for the positive electrode 932, a secondary battery 913 with high capacity and excellent cycle characteristics can be realized.

[0241] [Laminated secondary battery]

[0242] Next, with reference to Figures 11A to 16A 、 Figure 16B1 、 Figure 16B2 、 Figure 16C and Figure 16D an example of a laminated secondary battery will be described. When a laminated secondary battery having flexibility is mounted on an electronic device having flexibility at least in part, the secondary battery can be bent along the deformation of the electronic device.

[0243] With reference to Figures 11A to 11C the laminated secondary battery 980 will be described. The laminated secondary battery 980 includes Figure 11A the wound body 993 shown. The wound body 993 includes a negative electrode 994, a positive electrode 995, and a separator 996. Similar to Figure 10Similarly to the winding body 950 described above, the winding body 993 is formed by overlapping the negative electrode 994 and the positive electrode 995 with the separator 996 interposed therebetween to form a laminate sheet, and winding the laminate sheet.

[0244] In addition, the number of laminations of the laminate composed of the negative electrode 994, the positive electrode 995, and the separator 996 can be appropriately designed according to the required capacity and the element volume. The negative electrode 994 is connected to a negative electrode current collector (not shown) through one of the lead electrodes 997 and 998, and the positive electrode 995 is connected to a positive electrode current collector (not shown) through the other of the lead electrodes 997 and 998.

[0245] As Figure 11B shown, the above-described winding body 993 is accommodated in a space formed by laminating a film 981 to be an outer packaging body and a film 982 having a concave portion by thermal pressing or the like, whereby the secondary battery 980 Figure 11C shown can be manufactured. The winding body 993 includes the lead electrodes 997 and 998 and is impregnated with an electrolytic solution in the space formed by the film 981 and the film 982 having a concave portion.

[0246] The film 981 and the film 982 having a concave portion are made of a metal material such as aluminum or a resin material, for example. When a resin material is used as the material for the film 981 and the film 982 having a concave portion, the film 981 and the film 982 having a concave portion can be deformed when a force is applied from the outside, and a flexible secondary battery can be manufactured.

[0247] In addition, in Figure 11B and Figure 11C an example of using two films is shown, but it is also possible to bend one film to form a space and accommodate the above-described winding body 993 in the space.

[0248] By using the positive electrode active material described in the above embodiment for the positive electrode 995, a secondary battery 980 with high capacity and excellent cycle characteristics can be realized.

[0249] Although in Figures 11A to 11C an example of the secondary battery 980 including a winding body in a space formed by a film to be an outer packaging body is shown, it is also possible to adopt a secondary battery including a plurality of rectangular positive electrodes, separators, and negative electrodes in a space formed by a film to be an outer packaging body as Figure 12A and Figure 12B shown.

[0250] Figure 12AThe laminated secondary battery 500 shown includes a positive electrode 503 including a positive electrode current collector 501 and a positive electrode active material layer 502; a negative electrode 506 including a negative electrode current collector 504 and a negative electrode active material layer 505; a separator 507; an electrolytic solution 508; and an outer package 509. A separator 507 is provided between the positive electrode 503 and the negative electrode 506 disposed within the outer package 509. Further, the outer package 509 is filled with the electrolytic solution 508. As the electrolytic solution 508, the electrolytic solution shown in Embodiment 2 can be used.

[0251] In Figure 12A In the laminated secondary battery 500 shown, the positive electrode current collector 501 and the negative electrode current collector 504 also serve as terminals for making electrical contact with the outside. Accordingly, a part of the positive electrode current collector 501 and the negative electrode current collector 504 may be exposed to the outside of the outer package 509. Further, the wire electrode is ultrasonically welded to the positive electrode current collector 501 or the negative electrode current collector 504 so that the wire electrode is exposed to the outside of the outer package 509 without exposing the positive electrode current collector 501 and the negative electrode current collector 504 to the outside of the outer package 509.

[0252] In the laminated secondary battery 500, as the outer package 509, for example, a laminated film having the following three-layer structure can be used: a highly flexible metal film such as aluminum, stainless steel, copper, or nickel is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or a polyester resin is provided as the outer surface of the outer package on the metal film.

[0253] In addition, Figure 12B An example of the cross-sectional structure of the laminated secondary battery 500 is shown. For simplicity, Figure 12A An example including two current collectors is shown, but an actual battery includes a plurality of electrode layers.

[0254] Figure 12B One example of Figure 12B shows a structure of a total of 16 layers including 8 layers of the negative electrode current collector 504 and 8 layers of the positive electrode current collector 501. In addition, Figure 12B A cross-section of the extraction portion of the negative electrode is shown, and the 8-layer negative electrode current collector 504 is ultrasonically welded. Of course, the number of electrode layers is not limited to 16, and may be more than 16 or less than 16. In the case where the number of electrode layers is large, a secondary battery having a larger capacity can be manufactured. Further, in the case where the number of electrode layers is small, a thin and highly flexible secondary battery can be manufactured.

[0255] Here, Figure 13 andFigure 14 An example of an external view of the laminated secondary battery 500 is shown. In Figure 13 and Figure 14 include: a positive electrode 503; a negative electrode 506; a separator 507; an outer packaging body 509; a positive electrode lead electrode 510; and a negative electrode lead electrode 511.

[0256] Figure 15A An external view of the positive electrode 503 and the negative electrode 506 is shown. The positive electrode 503 includes a positive electrode current collector 501, and a positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. In addition, the positive electrode 503 has a region where a part of the positive electrode current collector 501 is exposed (hereinafter, referred to as a tab region). The negative electrode 506 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. In addition, the negative electrode 506 has a region where a part of the negative electrode current collector 504 is exposed, that is, a tab region. The area or shape of the tab regions of the positive electrode and the negative electrode is not limited to Figure 15A the example shown.

[0257] [Manufacturing method of laminated secondary battery]

[0258] Here, with reference to Figure 15B and Figure 15C an example of the manufacturing method of the laminated secondary battery whose external view is shown in Figure 13 will be described.

[0259] First, stack the negative electrode 506, the separator 507, and the positive electrode 503. Figure 15B The stacked negative electrode 506, separator 507, and positive electrode 503 are shown. Here, an example of using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. Next, the tab regions of the positive electrodes 503 are joined to each other, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. As the joining, for example, ultrasonic welding or the like can be used. Similarly, the tab regions of the negative electrodes 506 are joined to each other, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0260] Next, arrange the negative electrode 506, the separator 507, and the positive electrode 503 on the outer packaging body 509.

[0261] Next, as Figure 15C shown, fold the outer packaging body 509 along the portion indicated by the dotted line. Then, join the outer peripheral portion of the outer packaging body 509. As the joining, for example, hot pressing or the like can be used. At this time, in order to inject the electrolyte 508 later, a region that is not joined to a part (or one side) of the outer packaging body 509 (hereinafter, referred to as an inlet) is provided.

[0262] Next, the electrolytic solution 508 is introduced from the inlet provided in the outer package 509 into the inside of the outer package 509. It is preferable to introduce the electrolytic solution 508 under a reduced-pressure atmosphere or an inert gas atmosphere. Finally, the inlet is joined. Thus, the laminated secondary battery 500 can be manufactured.

[0263] By using the positive electrode active material described in the above embodiment for the positive electrode 503, a secondary battery 500 with high capacity and excellent cycle characteristics can be achieved.

[0264] [Flexible secondary battery]

[0265] Next, with reference to Figure 16A , Figure 16B1 , Figure 16B2 , Figure 16C and Figure 16D as well as Figure 17A and Figure 17B an example of a flexible secondary battery will be described.

[0266] Figure 16A A plan view schematic diagram of the flexible battery 250 is shown. Figure 16B1 , Figure 16B2 , Figure 16C are respectively cross-sectional schematic diagrams along the cut lines C1 - C2, C3 - C4, and A1 - A2 in Figure 16A . The battery 250 includes an outer package 251, a positive electrode 211a and a negative electrode 211b accommodated inside the outer package 251. A wire 212a electrically connected to the positive electrode 211a and a wire 212b electrically connected to the negative electrode 211b extend outside the outer package 251. In addition, an electrolytic solution (not shown) is sealed in the area surrounded by the outer package 251 in addition to the positive electrode 211a and the negative electrode 211b.

[0267] With reference to Figure 17A and Figure 17B the positive electrode 211a and the negative electrode 211b included in the battery 250 will be described. Figure 17A is a perspective view illustrating the lamination order of the positive electrode 211a, the negative electrode 211b, and the separator 214. Figure 17B is a perspective view showing the wires 212a and 212b in addition to the positive electrode 211a and the negative electrode 211b.

[0268] As Figure 17A shown, the battery 250 includes a plurality of rectangular positive electrodes 211a, a plurality of rectangular negative electrodes 211b, and a plurality of separators 214. The positive electrode 211a and the negative electrode 211b each include 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 on one surface of the positive electrode 211a, and a negative electrode active material layer is formed on the portion other than the tab on one surface of the negative electrode 211b.

[0269] The positive electrode 211a and the negative electrode 211b are stacked such that the surfaces of the positive electrode 211a where the positive electrode active material layer is not formed are in contact with each other, and the surfaces of the negative electrode 211b where the negative electrode active material layer is not formed are in contact with each other.

[0270] In addition, a separator 214 is provided between the surface of the positive electrode 211a where the positive electrode active material layer is formed and the surface of the negative electrode 211b where the negative electrode active material layer is formed. For convenience, in Figure 17A the separator 214 is indicated by a dashed line.

[0271] As Figure 17B shown, a plurality of positive electrodes 211a are electrically connected to the wire 212a at the joint portion 215a. In addition, a plurality of negative electrodes 211b are electrically connected to the wire 212b at the joint portion 215b.

[0272] Next, with reference to Figure 16B1 , Figure 16B2 , Figure 16C , Figure 16D the outer package 251 will be described.

[0273] The outer package 251 has a film shape and is folded in half so as to sandwich the positive electrode 211a and the negative electrode 211b. The outer package 251 includes a folded portion 261, a pair of sealing portions 262, and a sealing portion 263. The pair of sealing portions 262 are provided so as to sandwich the positive electrode 211a and the negative electrode 211b and may also be referred to as side seals. In addition, the sealing portion 263 includes a portion overlapping with the wire 212a and the wire 212b and may also be referred to as a top seal.

[0274] The outer package 251 preferably has a corrugated shape in which ridge lines 271 and valley bottom lines 272 are alternately arranged in the portion overlapping with the positive electrode 211a and the negative electrode 211b. In addition, the sealing portions 262 and 263 of the outer package 251 are preferably flat.

[0275] Figure 16B1 is a cross section taken at a portion overlapping with the ridge line 271, Figure 16B2 is a cross section taken at a portion overlapping with the valley bottom line 272. Figure 16B1 , Figure 16B2 both correspond to cross sections in the width direction of the battery 250, the positive electrode 211a, and the negative electrode 211b.

[0276] Here, the distance between the end portion in the width direction of the negative electrode 211b and the sealing portion 262 is the distance La. When the battery 250 is deformed such as being bent, as will be described later, the positive electrode 211a and the negative electrode 211b are deformed so as to be offset from each other in the length direction. At this time, when the distance La is too short, there is a possibility that the outer package 251 strongly rubs against the positive electrode 211a and the negative electrode 211b, causing damage to the outer package 251. In particular, when the metal film of the outer package 251 is exposed, the metal film may be corroded by the electrolyte. Therefore, it is preferable to set the distance La as long as possible. On the other hand, when the distance La is too long, the volume of the battery 250 increases.

[0277] In addition, it is preferable that the greater the total thickness of the stacked positive electrode 211a and negative electrode 211b, the longer the distance La between the end portion of the negative electrode 211b and the sealing portion 262.

[0278] More specifically, when the total thickness of the stacked positive electrode 211a, negative electrode 211b, and separator 214 (not shown) is the thickness t, the distance La is 0.8 times or more and 3.0 times or less of the thickness t, preferably 0.9 times or more and 2.5 times or less, and more preferably 1.0 times or more and 2.0 times or less. By setting the distance La within the above range, a small and highly reliable battery against bending can be achieved.

[0279] In addition, when the distance between the pair of sealing portions 262 is the distance Lb, it is preferable that the distance Lb is sufficiently larger than the width Wb of the negative electrode 211b. Thus, when the battery 250 is repeatedly deformed such as being bent, since even when the positive electrode 211a and the negative electrode 211b come into contact with the outer package 251, a part of the positive electrode 211a and the negative electrode 211b can be offset in the width direction, it is possible to effectively prevent the positive electrode 211a and the negative electrode 211b from rubbing against the outer package 251.

[0280] For example, the difference between the distance Lb between the pair of sealing portions 262 and the width Wb of the negative electrode 211b is 1.6 times or more and 6.0 times or less of the thickness t of the positive electrode 211a and the negative electrode 211b, preferably 1.8 times or more and 5.0 times or less, and more preferably 2.0 times or more and 4.0 times or less.

[0281] In other words, the distance Lb, the width Wb, and the thickness t preferably satisfy the following formula 1.

[0282] [Formula 1]

[0283]

[0284] 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 1.0 or more and 2.0 or less.

[0285] In addition, Figure 16C is a cross-section including the wire 212a, which is a cross-section corresponding to the longitudinal direction of the battery 250, the positive electrode 211a, and the negative electrode 211b. As Figure 16C shown, it is preferable to include a space 273 between the outer packaging body 251 and the ends of the positive electrode 211a and the negative electrode 211b in the longitudinal direction in the folding portion 261.

[0286] Figure 16D The cross-sectional schematic diagram when the battery 250 is bent is shown. Figure 16D It corresponds to the cross-section along the cutting line B1 - B2 in Figure 16A .

[0287] When the battery 250 is bent, a part of the outer packaging body 251 located outside the bent portion deforms and extends, and another part of the outer packaging body 251 located inside the bent portion deforms and contracts. More specifically, the part of the outer packaging body 251 located outside the bend deforms in such a way that the amplitude of the wave is small and the period of the wave is large. On the other hand, the part of the outer packaging body 251 located inside the bend deforms in such a way that the amplitude of the wave is large and the period of the wave is small. By deforming the outer packaging body 251 in the above manner, the stress applied to the outer packaging body 251 due to bending can be alleviated, and thus the material of the outer packaging body 251 itself does not necessarily need to have stretchability. As a result, the battery 250 can be bent with a small force without damaging the outer packaging body 251.

[0288] In addition, as Figure 16D shown, when the battery 250 is bent, the positive electrode 211a and the negative electrode 211b are respectively offset relative to each other. At this time, since the ends of the plurality of stacked positive electrodes 211a and negative electrodes 211b on the side of the sealing portion 263 are fixed by the fixing member 217, they are offset in such a way that the closer they are to the folding portion 261, the greater the offset amount. Thus, the stress applied to the positive electrode 211a and the negative electrode 211b can be alleviated, and the positive electrode 211a and the negative electrode 211b themselves do not necessarily need to have stretchability. As a result, the battery 250 can be bent without damaging the positive electrode 211a and the negative electrode 211b.

[0289] In addition, since there is a space 273 between the ends of the positive electrode 211a and the negative electrode 211b and the outer packaging body 251, the ends of the positive electrode 211a and the negative electrode 211b located inside can be offset relative to each other in such a way that they do not contact the outer packaging body 251 during bending.

[0290] Figure 16A , Figure 16B1 , Figure 16B2 , Figure 16C and Figure 16D as well as Figure 17A and Figure 17BThe exemplified battery 250 is a battery that is not easily damaged in its outer packaging, nor in its positive electrode 211a and negative electrode 211b even when repeatedly bent and stretched, and whose battery characteristics are not easily deteriorated. By using the positive electrode active material described in the above embodiment for the positive electrode 211a included in the battery 250, a battery with high capacity and excellent cycle characteristics can be achieved.

[0291] Embodiment 4

[0292] In this embodiment, an example of mounting a secondary battery of one aspect of the present invention in an electronic device will be described.

[0293] First, Figures 18A to 18G An example of mounting a flexible secondary battery described in a part of Embodiment 3 in an electronic device is shown. As an electronic device to which the flexible secondary battery is applied, for example, a television device (also referred to as a television or a television receiver), a display for a computer or the like, a digital camera, a digital video camera, a digital photo frame, a mobile phone (also referred to as a mobile telephone, a mobile phone device), a portable game machine, a portable information terminal, a sound reproduction device, a large game machine such as a pachinko machine, etc. can be cited.

[0294] In addition, a secondary battery having flexibility can be assembled along the curved surfaces of the inner walls or outer walls of houses and high-rise buildings, or the interior or exterior decorations of automobiles.

[0295] Figure 18A An example of a mobile phone is shown. The mobile phone 7400 includes an operation button 7403, an external connection port 7404, a speaker 7405, a microphone 7406, etc. in addition to a display unit 7402 assembled in a housing 7401. In addition, the mobile phone 7400 has a secondary battery 7407. By using a secondary battery of one aspect of the present invention as the secondary battery 7407, a lightweight and long-life mobile phone can be provided.

[0296] Figure 18B A state in which the mobile phone 7400 is bent is shown. When the mobile phone 7400 is deformed by an external force and bent as a whole, the secondary battery 7407 provided inside it is also bent. Figure 18C A state of the bent secondary battery 7407 at this time is shown. The secondary battery 7407 is a thin battery. The secondary battery 7407 is fixed in a bent state. The secondary battery 7407 has a wire electrode electrically connected to a current collector 7409.

[0297] Figure 18D An example of a bracelet-type display device is shown. The portable display device 7100 includes a housing 7101, a display unit 7102, an operation button 7103, and a secondary battery 7104. In addition, Figure 18EShows a bent secondary battery 7104. When the bent secondary battery 7104 is worn on a user's arm, the outer shell of the secondary battery 7104 deforms, causing a change in the curvature of part or all of the secondary battery 7104. The value representing the degree of bending of any point on a curve in terms of the value of the equivalent circle radius is the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, part or all of the outer shell or the main surface of the secondary battery 7104 deforms within the range where the radius of curvature is 40 mm or more and 150 mm or less. As long as the radius of curvature in the main surface of the secondary battery 7104 is within the range of 40 mm or more and 150 mm or less, high reliability can be maintained. By using the secondary battery of one embodiment of the present invention as the above-mentioned secondary battery 7104, a lightweight and long-life portable display device can be provided.

[0298] Figure 18F Is an example of a watch-type portable information terminal. The portable information terminal 7200 includes an outer shell 7201, a display unit 7202, a band 7203, a buckle 7204, operation buttons 7205, input / output terminals 7206, etc.

[0299] The portable information terminal 7200 can execute various application programs such as mobile phones, emails, reading and writing of articles, music playback, network communication, computer games, etc.

[0300] The display surface of the display unit 7202 is bent and can display along the bent display surface. In addition, the display unit 7202 is equipped with a touch sensor, and the screen can be touched with a finger or a stylus, etc. for operation. For example, by touching the icon 7207 displayed on the display unit 7202, an application program can be launched.

[0301] In addition to time setting, the operation buttons 7205 can also have various functions such as a power switch, a switch for wireless communication, setting and canceling of a silent mode, setting and canceling of a power-saving mode, etc. For example, by using the operating system installed in the portable information terminal 7200, the functions of the operation buttons 7205 can be freely set.

[0302] In addition, the portable information terminal 7200 can execute short-range wireless communication standardized for communication. For example, by communicating with a wirelessly communicable headset, hands-free calling can be performed.

[0303] In addition, the portable information terminal 7200 is equipped with input / output terminals 7206, and data can be directly sent to other information terminals or received from other information terminals through a connector. In addition, charging can also be performed through the input / output terminals 7206. In addition, the charging operation can also be performed using wireless power supply without using the input / output terminals 7206.

[0304] The display unit 7202 of the portable information terminal 7200 includes a secondary battery according to one embodiment of the present invention. By using the secondary battery according to one embodiment of the present invention, a lightweight and long-life portable information terminal can be provided. For example, the Figure 18E shown secondary battery 7104 can be assembled inside the housing 7201, or the bendable secondary battery 7104 can be assembled inside the band 7203.

[0305] The portable information terminal 7200 preferably includes a sensor. As the sensor, for example, a fingerprint sensor, a pulse sensor, a body temperature sensor, etc., which are human body sensors, a touch sensor, a pressure sensor, an acceleration sensor, etc. are preferably installed.

[0306] Figure 18G An example of an armband type display device is shown. The display device 7300 includes a display unit 7304 and a secondary battery according to one embodiment of the present invention. The display device 7300 may also have a touch sensor in the display unit 7304 and be used as a portable information terminal.

[0307] The display surface of the display unit 7304 is bent, and display can be performed along the bent display surface. In addition, the display device 7300 can change the display situation by using short-range wireless communication standardized for communication, etc.

[0308] The display device 7300 has input / output terminals, and data can be directly sent to other information terminals or received from other information terminals through a connector. In addition, charging can also be performed through the input / output terminals. In addition, the charging operation can also be performed by wireless power supply without using the input / output terminals.

[0309] By using the secondary battery according to one embodiment of the present invention as the secondary battery included in the display device 7300, a lightweight and long-life display device can be provided.

[0310] In addition, with reference to Figure 18H , Figures 19A to 19C and Figure 20 An example of installing the secondary battery with excellent cycle characteristics shown in the above embodiment in an electronic device will be described.

[0311] By using the secondary battery according to one embodiment of the present invention as the secondary battery of a consumer electronic device, a lightweight and long-life product can be provided. For example, as consumer electronic devices, an electric toothbrush, an electric shaver, an electric beauty device, etc. can be cited. The secondary battery in these products is expected to have a rod shape, be small, lightweight, and have a large capacity for easy gripping by the user.

[0312] Figure 18H is a perspective view of a device called a liquid-containing smoking device (electronic cigarette). InFigure 18H In [description of the electronic cigarette], the electronic cigarette 7500 includes: an atomizer 7501 including a heating element; a secondary battery 7504 for powering the atomizer; and a cartridge 7502 including a liquid supply container, a sensor, etc. To improve safety, a protection circuit for preventing overcharging and over-discharging of the secondary battery 7504 can also be electrically connected to the secondary battery 7504. Figure 18H The secondary battery 7504 shown includes external terminals for connecting to a charger. When being taken, the secondary battery 7504 is located at the top end, so it is preferably shorter in total length and lighter in weight. Since the secondary battery of one embodiment of the present invention has a high capacity and excellent cycle characteristics, a small and lightweight electronic cigarette 7500 that can be used for a long time over a long period can be provided.

[0313] Next, Figure 19A and Figure 19B An example of a tablet terminal capable of being folded in half is shown. Figure 19A and Figure 19B The tablet terminal 9600 shown includes a housing 9630a, a housing 9630b, a movable part 9640 connecting the housing 9630a and the housing 9630b, a display part 9631, a display mode changeover switch 9626, a power switch 9627, a power saving mode changeover switch 9625, a fastener 9629, and an operation switch 9628. By using a flexible panel for the display part 9631, a tablet terminal with a larger display part can be realized. Figure 19A The state of opening the tablet terminal 9600 is shown. Figure 19B The state of closing the tablet terminal 9600 is shown.

[0314] The tablet terminal 9600 has a power storage body 9635 inside the housing 9630a and the housing 9630b. The power storage body 9635 is disposed through the movable part 9640 in the housing 9630a and the housing 9630b.

[0315] In the display part 9631, a part of it can be used as an area of a touch screen, and data can be input by touching the displayed operation keys. In addition, by using a finger or a stylus to touch the position of the keyboard display changeover button on the touch screen, keyboard buttons can be displayed on the display part 9631.

[0316] In addition, the display mode changeover switch 9626 can switch the display direction such as portrait display and landscape display and select the changeover such as black and white display or color display. According to the amount of external light detected by the light sensor built in the tablet terminal 9600 during use, the power saving mode changeover switch 9625 can set the brightness of the display to the most suitable brightness. In addition to the light sensor, the tablet terminal can also be built in with other detection devices such as a gyroscope and an acceleration sensor for detecting the inclination.

[0317] Figure 19B is in a closed state, and the tablet terminal includes a housing 9630, a solar cell 9633, and a charge-discharge control circuit 9634 having a DCDC converter 9636. A secondary battery according to one aspect of the present invention is used as the power storage body 9635.

[0318] In addition, the tablet terminal 9600 can be folded in half, so when not in use, the housing 9630a and the housing 9630b can be folded in an overlapping manner. By folding the housing 9630a and the housing 9630b, the display unit 9631 can be protected, and the durability of the tablet terminal 9600 can be improved. In addition, since the power storage body 9635 using the secondary battery according to one aspect of the present invention has a high capacity and excellent cycle characteristics, a tablet terminal 9600 that can be used for a long time over a long period can be provided.

[0319] In addition, Figure 19A and Figure 19B the tablet terminal shown may also have the following functions: displaying various types of information (static images, moving images, character images, etc.); displaying a calendar, date, or time, etc. on the display unit; touch input for performing a touch input operation or editing on the information displayed on the display unit; control processing by various software (programs), etc.

[0320] By using the solar cell 9633 mounted on the surface of the tablet terminal, power can be supplied to the touch screen, the display unit, the image signal processing unit, etc. Note that the solar cell 9633 can be provided on one surface or both surfaces of the housing 9630, and the power storage body 9635 can be efficiently charged.

[0321] In addition, with reference to Figure 19C the block diagram shown, the structure and operation of the charge-discharge control circuit 9634 shown in Figure 19B will be described. Figure 19C The solar cell 9633, the power storage body 9635, the DCDC converter 9636, the converter 9637, the switches SW1 to SW3, and the display unit 9631 are shown. The power storage body 9635, the DCDC converter 9636, the converter 9637, and the switches SW1 to SW3 correspond to Figure 19B the charge-discharge control circuit 9634 shown.

[0322] First, an example of the operation when generating electricity using external light in a solar cell 9633 will be described. A DCDC converter 9636 is used to step up or step down the electricity generated by the solar cell to a voltage for charging the power storage body 9635. Also, when operating the display unit 9631 using the electricity from the solar cell 9633, the switch SW1 is turned on, and the converter 9637 steps up or steps down the voltage to the voltage required by the display unit 9631. Additionally, a structure can be adopted in which when the display in the display unit 9631 is not being performed, SW1 is turned off and SW2 is turned on to charge the power storage body 9635.

[0323] Note that although the solar cell 9633 is shown as an example of a power generation unit, it is not limited thereto, and other power generation units such as a piezoelectric element or a thermoelectric conversion element (Peltier element) can also be used to charge the power storage body 9635. For example, a wireless power transmission module that can transmit and receive power in a wireless (non-contact) manner for charging or a combination of other charging methods can also be used.

[0324] Figure 20 Examples of other electronic devices are shown. In Figure 20 the display device 8000 is an example of an electronic device using a secondary battery 8004 according to one aspect of the present invention. Specifically, the display device 8000 corresponds to a display device for receiving television broadcasts and includes a housing 8001, a display unit 8002, a speaker unit 8003, and a secondary battery 8004, etc. The secondary battery 8004 according to one aspect of the present invention is provided inside the housing 8001. The display device 8000 can receive power supply from a commercial power source and can also use the power stored in the secondary battery 8004. Therefore, even when power supply from a commercial power source cannot be received due to a power outage or the like, the display device 8000 can be utilized by using the secondary battery 8004 according to one aspect of the present invention as an uninterruptible power supply.

[0325] As the display unit 8002, a semiconductor display device such as a liquid crystal display device, a light-emitting device having a light-emitting element such as an organic EL element in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), and an FED (Field Emission Display) can be used.

[0326] In addition to the display device for receiving television broadcasts, the display device also includes all display devices for displaying information, such as display devices for personal computers or display devices for advertisements, etc.

[0327] In Figure 20 , the embedded lighting device 8100 is an example of an electronic device using the secondary battery 8103 according to one aspect of the present invention. Specifically, the lighting device 8100 includes a housing 8101, a light source 8102, a secondary battery 8103, etc. Although in Figure 20 an example is shown where the secondary battery 8103 is provided inside the ceiling 8104 in which the housing 8101 and the light source 8102 are embedded, the secondary battery 8103 can also be provided inside the housing 8101. The lighting device 8100 can receive power supply from a commercial power source and can also use the power stored in the secondary battery 8103. Therefore, even when power supply from a commercial power source cannot be received due to a power outage or the like, the lighting device 8100 can be utilized by using the secondary battery 8103 according to one aspect of the present invention as an uninterruptible power supply.

[0328] In addition, although in Figure 20 an example is shown of the embedded lighting device 8100 provided in the ceiling 8104, the secondary battery according to one aspect of the present invention can be used for embedded lighting devices provided on, for example, side walls 8105, floors 8106, or windows 8107 other than the ceiling 8104, and can also be used for desk lamps, etc.

[0329] In addition, as the light source 8102, an artificial light source that artificially obtains light using electricity can be used. Specifically, as examples of the above artificial light sources, incandescent lamps, discharge lamps such as fluorescent lamps, and light-emitting elements such as LEDs or organic EL elements can be cited.

[0330] In Figure 20 the air conditioner having the indoor unit 8200 and the outdoor unit 8204 is an example of an electronic device using the secondary battery 8203 according to one aspect of the present invention. Specifically, the indoor unit 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, etc. Although in Figure 20FIG. 8203 illustrates a case where the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may also be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power supply from a commercial power source, or can also use the power stored in the secondary battery 8203. In particular, when the secondary battery 8203 is provided in both the indoor unit 8200 and the outdoor unit 8204, even when power supply from the commercial power source cannot be received due to a power outage or the like, the air conditioner can be utilized by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply.

[0331] In addition, although a split air conditioner composed of an indoor unit and an outdoor unit is illustrated in Figure 20 , the secondary battery according to one aspect of the present invention can also be used for an integrated air conditioner having the functions of an indoor unit and an outdoor unit in one housing.

[0332] In Figure 20 , the electric refrigerator-freezer 8300 is an example of an electronic device using the secondary battery 8304 according to one aspect of the present invention. Specifically, the electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator door 8302, a freezer door 8303, the secondary battery 8304, and the like. In Figure 20 , the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator-freezer 8300 can receive power supply from a commercial power source, or can also use the power stored in the secondary battery 8304. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, the electric refrigerator-freezer 8300 can be utilized by using the secondary battery 8304 according to one aspect of the present invention as an uninterruptible power supply.

[0333] In addition, during a period when the electronic device is not in use, especially during a period when the ratio of the actually used amount of electric power to the total amount of electric power that can be supplied by the commercial power source (referred to as the power utilization rate) is low, the electric power is stored in the secondary battery, thereby suppressing an increase in the power utilization rate during a period other than the above period. For example, in the case of the electric refrigerator-freezer 8300, during the night when the temperature is low and the refrigerator door 8302 or the freezer door 8303 is not opened or closed, the electric power is stored in the secondary battery 8304. And during the day when the temperature is high and the refrigerator door 8302 or the freezer door 8303 is opened or closed, the secondary battery 8304 is used as an auxiliary power source, thereby suppressing the power utilization rate during the day.

[0334] A secondary battery according to one embodiment of the present invention is not limited to being installed in the above-described electronic device, and can also be installed in all electronic devices. By adopting one embodiment of the present invention, the cycle characteristics of the secondary battery can be improved. In addition, by adopting one embodiment of the present invention, a high-capacity secondary battery can be realized, and the secondary battery itself can be miniaturized and lightened. Therefore, by installing the secondary battery according to one embodiment of the present invention in the electronic device described in this embodiment, an electronic device with a longer service life and lighter weight can be provided. This embodiment can be implemented in appropriate combination with other embodiments.

[0335] Embodiment 5

[0336] In this embodiment, an example of installing a secondary battery according to one embodiment of the present invention in a vehicle is shown.

[0337] When a secondary battery is installed in a vehicle, new-generation clean energy vehicles such as hybrid electric vehicles (HEVs), electric vehicles (EVs), or plug-in hybrid electric vehicles (PHEVs) can be realized.

[0338] In Figures 21A to 21C an example of a vehicle using a secondary battery according to one embodiment of the present invention is illustrated. Figure 21A The automobile 8400 shown is an electric vehicle that uses an electric motor as a power source for driving. Alternatively, the automobile 8400 is a hybrid electric vehicle that can appropriately use an electric motor or an engine as a power source for driving. By using one embodiment of the present invention, a vehicle with a long driving range can be realized. In addition, the automobile 8400 is equipped with a secondary battery. As the secondary battery, a plurality of Figure 5A and Figure 5B shown small cylindrical secondary batteries can be arranged in the floor portion inside the vehicle and used. In addition, a battery pack formed by combining a plurality of Figure 14 shown secondary batteries can be provided in the floor portion inside the vehicle. The secondary battery not only drives the electric motor 8406, but can also supply power to lighting devices such as the headlight 8401 or an interior light (not shown).

[0339] In addition, the secondary battery can supply power to display devices such as a speedometer and a tachometer provided in the automobile 8400. Furthermore, the secondary battery can supply power to semiconductor devices such as a navigation system provided in the automobile 8400.

[0340] In Figure 21B the automobile 8500 shown, the secondary battery provided in the automobile 8500 can be charged by receiving power from an external charging device by means of a plug-in method or a non-contact power supply method. Figure 21BFig. 0 shows a case where a secondary battery 8024 installed in an automobile 8500 is charged by a charging device 8021 of a ground-mounted type via a cable 8022. When charging is performed, as the charging method, the specifications of the connector, etc., it can be appropriately performed according to the regulations of CHAdeMO (registered trademark) or the Combined Charging System, etc. As the charging device 8021, a charging station installed in a commercial facility or a power source at home can also be used. For example, by using plug-in technology to supply power from the outside, the secondary battery 8024 installed in the automobile 8500 can be charged. The charging can be performed by converting AC power into DC power through a conversion device such as an AC / DC converter.

[0341] In addition, although not shown, a power receiving device can also be installed in the vehicle and power can be supplied non-contact from a power transmitting device on the ground for charging. When using the non-contact power supply method, by assembling the power transmitting device in a road or an outer wall, charging can be performed not only during parking but also during driving. In addition, the non-contact power supply method can also be used to transmit and receive power between vehicles. Furthermore, a solar cell can be provided outside the vehicle to charge the secondary battery when parked or driving. Such non-contact power supply can be achieved by the electromagnetic induction method or the magnetic field resonance method.

[0342] Figure 21C This is an example of a two-wheeled vehicle using a secondary battery according to one embodiment of the present invention. Figure 21C The shown scooter 8600 includes a secondary battery 8602, a rearview mirror 8601, and a direction indicator 8603. The secondary battery 8602 can supply power to the direction indicator 8603.

[0343] In addition, in Figure 21C the shown scooter 8600, the secondary battery 8602 can be housed in the under-seat storage portion 8604. Even if the under-seat storage portion 8604 is small, the secondary battery 8602 can be housed in the under-seat storage portion 8604. The secondary battery 8602 is detachable, so when charging, the secondary battery 8602 is carried indoors and charged, and the secondary battery 8602 is housed before driving.

[0344] By adopting one embodiment of the present invention, the cycle characteristics and capacity of a secondary battery can be improved. Thereby, the secondary battery itself can be made smaller and lighter. In addition, if the secondary battery itself can be made smaller and lighter, it helps to achieve the weight reduction of the vehicle, thereby extending the driving distance. In addition, the secondary battery installed in the vehicle can be used as a power supply source outside the vehicle. At this time, for example, it is possible to avoid using commercial power during peak power demand. If it is possible to avoid using commercial power during peak power demand, it helps to save energy and reduce carbon dioxide emissions. In addition, if the cycle characteristics are excellent, the secondary battery can be used for a long period, thereby reducing the usage amount of rare metals such as cobalt.

[0345] This embodiment can be implemented by appropriately combining with other embodiments.

[0346] Example 1

[0347] In this example, secondary batteries using positive electrode active materials including different coating layers are used to show the comparison results of their characteristics.

[0348] <Manufacture of positive electrode active material>

[0349] Positive electrode active materials as Sample 1 to Sample 5 are prepared. The manufacturing method of each sample is as follows.

[0350] <<Sample 1>>

[0351] In order to form Sample 1 of a positive electrode active material whose interior contains lithium cobaltate and whose surface layer portion includes a coating layer containing aluminum and magnesium, after forming a coating layer containing aluminum on lithium cobaltate particles containing magnesium and fluorine by the sol-gel method, heating is performed.

[0352] As the lithium cobaltate particles containing magnesium and fluorine, particles manufactured by Nippon Chemical Industry Co., Ltd. (trade name: C-20F) are used.

[0353] 0.0348 g of tri-i-propoxyaluminum is added and dissolved in 20 ml of 2-propanol. 5 g of lithium cobaltate particles containing magnesium and fluorine are added to the 2-propanol solution of tri-i-propoxyaluminum.

[0354] At 25 °C with a humidity of 90% RH, the mixture is stirred for 4 hours using a magnetic stirrer. Through the above treatment, H2O in the atmosphere reacts with tri-i-propoxyaluminum for hydrolysis and polycondensation reactions, thereby forming a layer containing aluminum on the surface of the lithium cobaltate particles containing magnesium and fluorine.

[0355] The treated mixture is filtered, and the residue is collected. A Kiriyama filter paper (No. 4) is used as the filter during filtration.

[0356] The collected residue is vacuum dried at 70 °C for 1 hour.

[0357] The dried powder is heated. The heating is carried out under the following conditions: the temperature is 800 °C (heating rate is 200 °C / h); the holding time is 2 hours; in a dry air atmosphere.

[0358] The heated powder is cooled and subjected to a grinding process. The grinding process can be carried out, for example, by sieving the powder, and a sieve with a pore size of 53 μm is used.

[0359] The particles obtained by the grinding process are regarded as the positive electrode active material of Sample 1.

[0360] 《Sample 2》

[0361] In order to form Sample 2 (comparative example) which is a positive electrode active material containing lithium cobaltate in its interior and a magnesium-containing covering layer in its surface layer portion, lithium cobaltate particles containing magnesium and fluorine are heated.

[0362] As the lithium cobaltate particles containing magnesium and fluorine, particles manufactured by Nippon Chemical Industry Co., Ltd. (trade name: C-20F) are used.

[0363] The lithium cobaltate particles containing magnesium and fluorine are heated. The heating is carried out under the following conditions: the temperature is 800 °C (heating rate is 200 °C / h); the holding time is 2 hours; in an oxygen atmosphere.

[0364] The particles obtained by cooling the heated powder and sieving it with a sieve having a pore size of 53 μm are regarded as the positive electrode active material of Sample 2.

[0365] 《Sample 3》

[0366] In order to form Sample 3 (comparative example) which is a positive electrode active material containing lithium cobaltate with magnesium and fluorine but without sufficient segregation of magnesium in the surface layer portion, lithium cobaltate particles containing magnesium and fluorine that are not heated are used.

[0367] As the lithium cobaltate particles containing magnesium and fluorine, particles manufactured by Nippon Chemical Industry Co., Ltd. (trade name: C-20F) are used.

[0368] 《Sample 4》

[0369] In order to form Sample 4 (comparative example) which is a positive electrode active material containing lithium cobaltate in its interior and an aluminum-containing covering layer in its surface layer portion, an aluminum-containing covering layer is formed on lithium cobaltate particles without magnesium by the sol-gel method and then heated.

[0370] As the lithium cobaltate particles without magnesium, particles manufactured by Nippon Chemical Industry Co., Ltd. (trade name: C-10N) are used. These are lithium cobaltate particles in which magnesium is not detected by XPS and about 1 atomic % of fluorine is detected.

[0371] Similar to Sample 1, after forming a coating layer containing aluminum on the lithium cobalt oxide particles by the sol-gel method, heating, drying, and sieving were carried out. The particles thus manufactured were regarded as the positive electrode active material of Sample 4.

[0372] 《Sample 5》

[0373] To form Sample 5 (comparative example) as the positive electrode active material without a coating layer, lithium cobalt oxide particles without magnesium and without heating were used.

[0374] As the lithium cobalt oxide particles without magnesium, particles manufactured by Nippon Chemical Industry Co., Ltd. (trade name: C-10N) were used.

[0375] Table 1 shows the conditions of Samples 1 to 5.

[0376] [Table 1]

[0377]

[0378] <Cycling characteristics>

[0379] CR2032 (diameter: 20 mm, height: 3.2 mm) coin-type secondary batteries were manufactured using the positive electrode active materials of Samples 1 to 5 manufactured above, and the cycling characteristics were evaluated.

[0380] As the positive electrode, a positive electrode was manufactured by coating a slurry obtained by mixing the positive electrode active material (LiCoO2), acetylene black (AB), and polyvinylidene fluoride (PVDF) of Samples 1 to 5 at a weight ratio of LiCoO2:AB:PVDF = 95:2.5:2.5 on a current collector made of aluminum foil.

[0381] Lithium metal was used as the counter electrode.

[0382] As the electrolyte contained in the electrolyte, 1 mol / L lithium hexafluorophosphate (LiPF6) was used, and as the electrolyte, an electrolyte obtained by adding 2 wt% vinylene carbonate (VC) to a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of EC:DEC = 3:7 was used.

[0383] The positive electrode can and the negative electrode can were formed of stainless steel (SUS).

[0384] Set the measured temperature in the cycle characteristic test to 25 °C. As charging, perform the following charging: perform constant current charging at 68.5 mA / g (current density per active material weight) under the condition that the upper limit voltage is 4.6 V, and then perform constant voltage charging until the current density reaches 1.4 mA / g. As discharging, perform constant current discharging at 68.5 mA / g (current density per active material weight) under the condition that the lower limit voltage is 2.5 V.

[0385] Figure 22A and Figure 22B are cycle characteristic charts of secondary batteries using the positive electrode active materials of Samples 1 to 5 as samples. Figure 22A is a chart of the energy density during charging at 4.6 V, Figure 22B is a chart of the energy density retention rate during charging at 4.6 V. Note that the energy density is the product of the discharge capacity and the average discharge voltage. The energy density retention rate is obtained with the peak value of the energy density as 100%.

[0386] As Figure 22A and Figure 22B shown, compared with Sample 5 which is lithium cobaltate without a coating layer, Sample 4 which is a positive electrode active material forming a coating layer containing aluminum shows slightly better cycle characteristics.

[0387] In the comparison between Samples 2 and 3 which are lithium cobaltate particles containing magnesium and fluorine, the cycle characteristics of Sample 2 which is heated are greatly improved compared with Sample 3 which is not heated. It can be considered that this is due to the effect of magnesium segregation on the surface layer of the lithium cobaltate particles due to heating.

[0388] In addition, Sample 1 which is a positive electrode active material forming a coating layer containing aluminum on lithium cobaltate particles containing magnesium and fluorine shows excellent cycle characteristics. These characteristics are better than those of Sample 2 with magnesium segregation on the surface layer and Sample 4 with a coating layer containing aluminum. From this, it can be known that by providing a coating layer containing aluminum and magnesium, better cycle characteristics can be obtained than in the case of only including a coating layer containing aluminum or only including a coating layer containing magnesium.

[0389] Example 2

[0390] In this example, the characteristics of lithium cobaltate particles including a coating layer containing aluminum and magnesium are clarified through various analyses.

[0391] <xps>

[0392] The samples 1, 2, and 3 of Example 1 were subjected to XPS analysis from the surface. In addition, the particles of sample 1 of Example 1 after sol-gel treatment and drying and before heating were regarded as sample 6, and XPS analysis was similarly performed on it. Table 2 shows the analysis results. Note that in the analysis results, rounding is performed to the second decimal place, so the total may sometimes not be 100%.

[0393] [Table 2]

[0394]

[0395] Table 3 shows the atomic ratio when calculated with the total amount of lithium, aluminum, cobalt, magnesium, oxygen, and fluorine as 100 atomic% using the results of Table 2.

[0396] [Table 3]

[0397]

[0398] In XPS analysis, it is possible to quantitatively analyze at a position about 5 nm from the surface of the positive electrode active material. As shown in Table 2, in samples 1 and 2 which are positive electrode active materials subjected to heating, the atomic ratio of magnesium is significantly increased compared to samples 6 and 3 which are not heated. That is, it is known that by heating, magnesium segregates in the region about 5 nm from the surface.

[0399] In addition, regarding samples 1 and 6 in which a coating layer containing aluminum is formed by the sol-gel method, the atomic ratio of aluminum in sample 1 subjected to heating is smaller than that in sample 6 not subjected to heating. Therefore, it can be speculated that by heating, aluminum diffuses from the region about 5 nm from the surface.

[0400] Therefore, it can be speculated that in the case of sample 1 which includes a coating layer containing aluminum and magnesium, more magnesium exists on the outermost surface, and aluminum exists in a region deeper than magnesium.

[0401] <stem-fft>

[0402] Next, Figures 23A to 23C and Figure 24A1 , Figure 24A2 , Figure 24A3 , Figure 24B1 , Figure 24B2 , Figure 24B3 show the results of STEM observation and FFT analysis of Sample 1.

[0403] Figures 23A to 23C is a bright-field STEM image of a cross-section near the surface of the positive electrode active material of Sample 1. According to Figure 23C it can be seen that: in the surface layer part of the positive electrode active material particles, there is an element that is observed to be brighter than other elements and is presumed to be magnesium. In addition, it is also observed that: in the range observable according to Figure 23C the crystal orientation from the inside to the surface is roughly the same.

[0404] Figure 24A1 is a HAADF-STEM image of a cross-section near the surface of the positive electrode active material of Sample 1. Figure 24A1 The FFT (Fast Fourier Transform) image of the area shown as FFT1 in Figure 24A2 is Figure 24A2 Part of the bright spots in the FFT image of Figure 24A3 is called A, B, C, and O as shown.

[0405] The measured values of the bright spots in the FFT image of the area shown as FFT1 are: the d between OA is 0.25 nm, the d between OB is 0.16 nm, and the d between OC is 0.26 nm. In addition, ∠AOB is 37°, ∠BOC is 36°, and ∠AOC is 73°.

[0406] The above values are close to the distances and angles obtained from the data of magnesium oxide (MgO) (ICDD 45-0945) and cobalt oxide (CoO) (ICDD 48-1719) based on ICDD (International Centre for Diffraction Data) data.

[0407] In the case of magnesium oxide, the d between OA (1-11) is 0.24 nm, the d between OB (0-22) is 0.15 nm, the d between OC (-1-11) is 0.24 nm, ∠AOB is 35°, ∠BOC is 35°, and ∠AOC is 71°.

[0408] In the case of cobalt oxide, the d value between OA (1-11) is 0.25 nm, the d value between OB (0-22) is 0.15 nm, the d value between OC (-1-11) is 0.25 nm, ∠AOB is 35°, ∠BOC is 35°, and ∠AOC is 71°.

[0409] It can be seen from this that the region about 2 nm from the surface of the positive electrode active material particles shown by FFT1 is a region having a rock salt-type crystal structure and is an image of

[011] incidence. In addition, it is speculated that the region shown by FFT1 contains magnesium oxide or cobalt oxide, or contains both magnesium oxide and cobalt oxide.

[0410] Figure 24B1 is the HAADF-STEM image of the cross-section near the surface of the same positive electrode active material, Figure 24A1 and the FFT image of the region shown by FFT2 in Figure 24B1 is Figure 24B2 . Part of the bright spots of the FFT image of Figure 24B2 is called A, B, C, and O as shown in Figure 24B3 .

[0411] The measured values of the bright spots of the FFT image of the region shown by FFT2 are: the d value between OA is 0.51 nm, the d value between OB is 0.21 nm, and the d value between OC is 0.25 nm. In addition, ∠AOB is 55°, ∠BOC is 24°, and ∠AOC is 79°.

[0412] The above values are close to the distances and angles obtained from the data of lithium cobaltate (LiCoO2) (ICDD50-0653) and LiAl 0.2 Co 0.8 O2 (ICDD89-0912) based on ICDD data.

[0413] In the case of lithium cobaltate (LiCoO2), the d value between OA (003) is 0.47 nm, the d value between OB (104) is 0.20 nm, the d value between OC (101) is 0.24 nm, ∠AOB is 55°, ∠BOC is 25°, and ∠AOC is 80°.

[0414] In the case of LiAl 0.2 Co 0.8 O2, the d value between OA (003) is 0.47 nm, the d value between OB (104) is 0.20 nm, the d value between OC (101) is 0.24 nm, ∠AOB is 55°, ∠BOC is 25°, and ∠AOC is 80°.

[0415] It can be seen from this that the region about 3 nm to 6 nm from the surface of the positive electrode active material particles shown by FFT2 has the same structure as that of lithium cobaltate and LiAl 0.2 Co 0.8 Regions with the same layered rock salt-type crystal structure as O2, and are images incident at [0-10].

[0416] <STEM-EDX (Element mapping, line analysis)>

[0417] Next, Figure 25A1 , Figure 25A2 , Figure 25B1 , Figure 25B2 , Figure 25C and Figures 26A to 26C Show the EDX analysis results of Sample 1.

[0418] Figure 25A1 , Figure 25A2 , Figure 25B1 , Figure 25B2 and Figure 25C Are the STEM-EDX analysis results of the cross-section near the surface of the positive electrode active material of Sample 1. Figure 25A1 Is a HAADF-STEM image, Figure 25A2 Is the element mapping of cobalt, Figure 25B1 Is the element mapping of aluminum, Figure 25B2 Is the element mapping of magnesium, Figure 25C Is the element mapping of fluorine.

[0419] As Figure 25B1 shown, it is observed that aluminum is distributed in a region about 10 nm from the surface of the positive electrode active material. As Figure 25B2 shown, it is observed that magnesium is segregated in a region about 3 nm from the surface of the positive electrode active material. As Figure 25C shown, almost no fluorine is detected near the surface, and it is considered that this is because fluorine, a light element, is not easily detected by EDX.

[0420] Figures 26A to 26C Are the STEM-EDX line analysis results of the cross-section near the surface of the positive electrode active material of Sample 1. Figure 26A Is a HAADF-STEM image. Figure 26B Is a chart showing the results of EDX line analysis in the direction of the white arrow for the region surrounded by the white line in Figure 26A . Figure 26C Is a chart magnifying a part of Figure 26B . In Figures 26A to 26C , almost no fluorine is detected either.

[0421] From Figure 26C it can be known that: magnesium and aluminum exist near the surface of the positive electrode active material of Sample 1, and magnesium is distributed closer to the surface than aluminum. In addition, it can be known that: the peak of magnesium is closer to the surface than the peak of aluminum. In addition, it is speculated that: cobalt and oxygen exist from the outermost surface of the positive electrode active material particles.

[0422] Based on the above XPS and EDX analysis results, it was confirmed that: Sample 1 is a positive electrode active material of one embodiment of the present invention, which includes lithium cobaltate in the first region, lithium, aluminum, cobalt, and oxygen in the second region, and magnesium and oxygen in the third region. In addition, it was found that: in Sample 1, a part of the second region overlaps with a part of the third region.

[0423] In Figure 26B the chart of, the oxygen detection amount is stable at a distance of more than 11 nm. Then, the average value O ave of the oxygen detection amount in this stable region was obtained, and the value showing 50% closest to the average value O ave is 0.5O ave The distance x of the measurement point of the measurement value is assumed to be the outermost surface of the positive electrode active material particles.

[0424] In this embodiment, the average O ave of the oxygen detection amount in the range of more than 11 nm and less than 40 nm is 777. The x-axis of the measurement point of the measurement value showing 388.5 which is 50% closest to 777 is at a distance of 9.5 nm. Thus, in this embodiment, the Figure 26B distance of 9.5 nm in the chart is estimated to be the outermost surface of the positive electrode active material particles.

[0425] When the outermost surface of the positive electrode active material particles is at a distance of 9.5 nm, the peak of magnesium coincides with the outermost surface, and the peak of aluminum appears 2.3 nm away from the outermost surface.

[0426] Based on the results of the above Embodiment 1 and Embodiment 2, it can be seen that: when a positive electrode active material of one embodiment of the present invention, which includes lithium cobaltate in the first region 101, lithium, aluminum, cobalt, and oxygen in the second region 102, and magnesium and oxygen in the third region 103, is used in a secondary battery, particularly good cycle characteristics can be obtained. < / xps>

Claims

1. A lithium ion secondary battery, comprising a positive electrode including positive electrode active material particles, the positive electrode active material particles comprising a first region, a second region near the surface, and a third region near the surface, the first region containing lithium, cobalt, and oxygen, the second region containing lithium, aluminum, cobalt, and oxygen, the third region containing magnesium and oxygen, a peak in the concentration of aluminum appearing in a range of 0.5 nm or more and 20 nm or less in depth from the surface of the positive electrode active material particles, the second region being a region where the concentration of aluminum detected by line analysis of STEM-EDX is 1 / 2 or more of the peak value of the concentration of aluminum, the third region being a region where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 or more of the peak value of the concentration of magnesium, the second region having a region deeper from the surface of the positive electrode active material particles than the third region, the third region having a rock salt type crystal structure.

2. A lithium ion secondary battery, comprising a positive electrode including positive electrode active material particles, the positive electrode active material particles comprising a first region, a second region near the surface, and a third region near the surface, the first region containing lithium, cobalt, and oxygen, the second region containing lithium, aluminum, cobalt, and oxygen, the third region containing magnesium and oxygen, the second region being a region where the concentration of aluminum detected by line analysis of STEM-EDX is 1 / 2 or more of the peak value of the concentration of aluminum, the third region being a region where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 or more of the peak value of the concentration of magnesium, the second region having a region deeper from the surface of the positive electrode active material particles than the third region, the second region containing aluminum having a concentration gradient, the third region containing magnesium having a concentration gradient, the third region having a rock salt type crystal structure.

3. A lithium ion secondary battery, comprising a positive electrode including positive electrode active material particles, the positive electrode active material particles comprising a first region, a second region near the surface, and a third region near the surface, the first region containing lithium, cobalt, and oxygen, The second region contains lithium, aluminum, cobalt, and oxygen, The third region contains magnesium, oxygen, and fluorine, The peak of the concentration of aluminum appears in the range of a depth of more than 0.5 nm and less than 20 nm from the surface of the positive electrode active material particles, The second region is a region where the concentration of aluminum detected by line analysis of STEM-EDX is 1 / 2 or more of the peak of the concentration of aluminum, The third region is a region where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 or more of the peak of the concentration of magnesium, The second region has a region deeper from the surface of the positive electrode active material particles than the third region, The third region has a rock-salt type crystal structure.

4. A lithium ion secondary battery, comprising a positive electrode including positive electrode active material particles, The positive electrode active material particles include a first region, a second region near the surface, and a third region near the surface, The first region contains lithium, cobalt, and oxygen, The second region contains lithium, aluminum, cobalt, and oxygen, The third region contains magnesium, oxygen, and fluorine, The peak of the concentration of aluminum appears in the range of a depth of more than 2.3 nm and less than 20 nm from the surface of the positive electrode active material particles, The second region is a region where the concentration of aluminum detected by line analysis of STEM-EDX is 1 / 2 or more of the peak of the concentration of aluminum, The third region is a region where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 or more of the peak of the concentration of magnesium, The second region has a region deeper from the surface of the positive electrode active material particles than the third region, The third region has a rock-salt type crystal structure.

5. A lithium ion secondary battery, comprising a positive electrode including positive electrode active material particles, The positive electrode active material particles include a first region, a second region near the surface, and a third region near the surface, The first region contains lithium, cobalt, and oxygen, The second region contains lithium, aluminum, cobalt, and oxygen, The third region contains magnesium, oxygen, and fluorine, The second region is a region where the concentration of aluminum detected by line analysis of STEM-EDX is 1 / 2 or more of the peak of the concentration of aluminum, The third region is a region where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 or more of the peak value of the concentration of magnesium. The second region has a region deeper from the surface of the positive electrode active material particles than the third region. The aluminum contained in the second region has a concentration gradient. The magnesium and fluorine contained in the third region have a concentration gradient. The third region has a rock salt-type crystal structure.

6. A lithium ion secondary battery comprising a positive electrode including positive electrode active material particles and a conductive assistant. The positive electrode active material particles include a first region, a second region near the surface, and a third region near the surface. The first region contains lithium, cobalt, and oxygen. The second region contains lithium, aluminum, cobalt, and oxygen. The third region contains magnesium and oxygen. The peak value of the concentration of aluminum appears in the range of 0.5 nm or more and 20 nm or less from the surface of the positive electrode active material particles. The second region is a region where the concentration of aluminum detected by line analysis of STEM-EDX is 1 / 2 or more of the peak value of the concentration of aluminum. The third region is a region where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 or more of the peak value of the concentration of magnesium. The second region has a region deeper from the surface of the positive electrode active material particles than the third region. The third region has a rock salt-type crystal structure. The conductive assistant contains carbon fiber.

7. A lithium ion secondary battery comprising a positive electrode including positive electrode active material particles and a conductive assistant. The positive electrode active material particles include a first region, a second region near the surface, and a third region near the surface. The first region contains lithium, cobalt, and oxygen. The second region contains lithium, aluminum, cobalt, and oxygen. The third region contains magnesium, oxygen, and fluorine. The second region is a region where the concentration of aluminum detected by line analysis of STEM-EDX is 1 / 2 or more of the peak value of the concentration of aluminum. The third region is a region where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 or more of the peak value of the concentration of magnesium. The second region has a region deeper from the surface of the positive electrode active material particles than the third region. The third region has a rock salt type crystal structure. The conductive additive contains carbon fiber.

8. A lithium ion secondary battery comprising a positive electrode including positive electrode active material particles and a conductive additive, The positive electrode active material particles include a first region, a second region near the surface, and a third region near the surface, The first region contains lithium, cobalt, and oxygen, The second region contains lithium, aluminum, cobalt, and oxygen, The third region contains magnesium and oxygen, The peak of the concentration of aluminum appears in the range of a depth of 2.3 nm or more and 20 nm or less from the surface of the positive electrode active material particles, The second region is a region where the concentration of aluminum detected by line analysis of STEM-EDX is 1 / 2 or more of the peak of the concentration of aluminum, The third region is a region where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 or more of the peak of the concentration of magnesium, The second region has a region deeper from the surface of the positive electrode active material particles than the third region, The aluminum contained in the second region has a concentration gradient, The magnesium contained in the third region has a concentration gradient, The third region has a rock salt type crystal structure, The conductive additive contains carbon fiber.

9. A lithium ion secondary battery comprising a positive electrode including positive electrode active material particles and a conductive additive, The positive electrode active material particles include a first region, a second region near the surface, and a third region near the surface, The first region contains lithium, cobalt, and oxygen, The second region contains lithium, aluminum, cobalt, and oxygen, The third region contains magnesium and oxygen, The second region is a region where the concentration of aluminum detected by line analysis of STEM-EDX is 1 / 2 or more of the peak of the concentration of aluminum, The third region is a region where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 or more of the peak of the concentration of magnesium, The second region has a region deeper from the surface of the positive electrode active material particles than the third region, The third region has a rock-salt type crystal structure, The conductive additive is graphene or few-layer graphene.

10. A lithium ion secondary battery, comprising a positive electrode including positive electrode active material particles and a conductive additive, wherein the positive electrode active material particles include a first region, a second region near the surface, and a third region near the surface, the first region contains lithium, cobalt, and oxygen, the second region contains lithium, aluminum, cobalt, and oxygen, the third region contains magnesium and oxygen, the second region is a region where the concentration of aluminum detected by line analysis of STEM-EDX is 1 / 2 or more of the peak value of the concentration of aluminum, the third region is a region where the concentration of magnesium detected by line analysis of STEM-EDX is 1 / 5 or more of the peak value of the concentration of magnesium, the second region has a region deeper than the third region from the surface of the positive electrode active material particles, the aluminum contained in the second region has a concentration gradient, the magnesium contained in the third region has a concentration gradient, the third region has a rock-salt type crystal structure, the conductive additive is graphene or few-layer graphene.

11. The lithium ion secondary battery according to any one of claims 6 to 8, wherein, The carbon fiber is a carbon nanofiber or a carbon nanotube.

12. The lithium ion secondary battery according to any one of claims 6 to 10, wherein, The content of the conductive additive relative to the total amount of the positive electrode active material layer is 1 wt% or more and 10 wt% or less.

13. The lithium ion secondary battery according to any one of claims 1 to 10, wherein, The third region also exists inside the first region.

14. The lithium ion secondary battery according to any one of claims 1 to 10, wherein, The second region and the third region also exist inside the first region.

15. The lithium ion secondary battery according to any one of claims 1 to 10, wherein, The first region contains nickel and manganese.

16. The lithium ion secondary battery according to any one of claims 1 to 10, further comprising a plurality of positive electrode active material particles including the positive electrode active material particles, wherein a median particle size of the plurality of positive electrode active material particles is 1 μm or more and 40 μm or less.

17. A lithium-ion secondary battery, comprising a positive electrode including positive electrode active material particles and a conductive additive, wherein the positive electrode active material particles include a composite oxide containing lithium, nickel, cobalt, and manganese, the positive electrode active material particles include a first region, a second region near the surface, and a third region near the surface, the first region contains lithium, nickel, cobalt, and manganese, the second region contains lithium, nickel, cobalt, manganese, aluminum, and oxygen, the third region contains magnesium and oxygen, the second region has a region deeper from the surface of the positive electrode active material particles than the third region, the third region has a rock-salt type crystal structure, the conductive additive contains graphene or multi-layer graphene, a region of a part of the graphene or the multi-layer graphene is a region provided so as to cover the surface of the positive electrode active material particles.

18. A lithium-ion secondary battery, comprising a positive electrode including positive electrode active material particles and a conductive additive, wherein the positive electrode active material particles include a composite oxide containing lithium, nickel, cobalt, and manganese, the positive electrode active material particles include a first region, a second region near the surface, and a third region near the surface, the first region contains lithium, nickel, cobalt, and manganese, the second region contains lithium, nickel, cobalt, manganese, aluminum, and oxygen, the third region contains magnesium and oxygen, the second region has a region deeper from the surface of the positive electrode active material particles than the third region, the positive electrode active material particles contain aluminum and fluorine near the surface, the third region has a rock-salt type crystal structure, the conductive additive contains graphene or multi-layer graphene, a region of a part of the graphene or the multi-layer graphene is a region provided so as to cover the surface of the positive electrode active material particles.

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