Positive electrode active material particles

Abstract

Provided are: lithium-excess positive electrode active material particles having a stabilized crystal structure; and a secondary battery including the particles. These positive electrode active material particles comprise lithium, a transition metal M (M is one or more selected from Mn, Cr, Mo, Nb, V, Fe, Ni, Ti, and Ru), oxygen, magnesium, and fluorine, wherein: Li / M (atomic ratio) in the positive electrode active material particles is more than 1; the positive electrode active material particles each have a core, a barrier film outside the core, and a shell outside the barrier film; more magnesium and fluorine are detected in the shell than in the core; crystalline orientations of the core and the shell substantially coincide with each other; and the shell has a fluoride.

Description

positive electrode active material particles

[0001] One aspect of the present invention relates to a product, a method, or a method of manufacture; or to a process, a machine, a manufacture, or a composition of matter. Another aspect of the present invention relates to an energy storage device including a secondary battery, a semiconductor device, a display device, a light-emitting device, a lighting device, an electronic device, or a method of manufacturing the same.

[0002] In this specification, "electronic equipment" refers to all devices that have an energy storage device, and all electro-optical devices with an energy storage device, information terminal devices with an energy storage device, etc., are considered electronic equipment.

[0003] In recent years, there has been a great deal of activity in the development of lithium-ion secondary batteries, lithium-ion capacitors, air batteries, and various energy storage devices. In particular, lithium-ion secondary batteries, which offer high output and high energy density, are seeing a rapid increase in demand in portable information terminals such as mobile phones, smartphones, and notebook computers, as well as portable music players, digital cameras, medical devices, and next-generation clean energy vehicles such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs). This rapid expansion, coupled with the development of the semiconductor industry, has made them an indispensable source of rechargeable energy for modern society.

[0004] In lithium-ion secondary batteries, lithium cobalt oxide (LiCoO), which has a layered rock salt-type crystalline structure, is used as a high-capacity positive electrode active material. ２ ), lithium nickel-cobalt-manganate (LiNi ａ Co ｂ Mn ｃ O ２ Examples such as a + b + c = 1 have been put into practical use.

[0005] However, research and development are underway to achieve even higher capacity. Among these, cathode active materials known as lithium-rich or lithium-excessive systems are attracting attention because they can store far more lithium ions than current lithium cobalt oxide, lithium nickel cobalt manganese oxide, etc. (Non-Patent Documents 1 to 5).

[0006] Reversible Oxygen Participation to the Redox Processes Revealed for Li▲1.20▼Mn▲0.54▼Co▲0.13▼Ni▲0.13▼O▲2▼.Hideyuki Koga et al.,Journal of The Electrochemical Society,160(6)A786−A792(2013)Functioning Mechanism of AlF▲3▼ Coating on the Li− and Mn−Rich Cathode Materials.Jianming Zheng et al.,Chemistry of Materials,26,6320−6327(2014)Lithium− and Manganese−Rich Oxide Cathode Materials for High−Energy Lithium Ion Batteries.Jun Wang et al.,Advanced Energy Materials,6,1600906(2016)Challenges and Recent Advances in High Capacity Li−Rich Cathode Materials for High Energy Density Lithium−Ion Batteries.Wei He et al.,Advanced materials,33,2005937(2021)In situ formed partially disordered phases as earth−abundant Mn−rich cathode materials.Zijian Cai et al.,Nature Energy(2023).https: / / doi.org / 10.1038 / s41560−023−01375−9

[0007] Lithium-rich cathode active materials offer numerous advantages. For example, it is possible to increase the discharge capacity per unit weight of the cathode active material to 250 mAh / g or more, and even to 300 mAh / g or more. Simultaneously, it is possible to increase the energy density per unit weight to, for example, 1000 Wh / kg or more. Furthermore, instead of cobalt, which has cost and other issues, manganese, which is cheaper and more abundant, can be used as the main transition metal.

[0008] On the other hand, there are challenges such as a large decrease in the initial discharge capacity relative to the initial charge capacity, poor rate characteristics, and a large decrease in voltage and / or discharge capacity during charge-discharge cycle tests. This is thought to be because, in lithium-ion secondary batteries using lithium-rich cathode active material particles, a change in crystal structure and / or oxygen desorption occur when lithium is desorbed.

[0009] Therefore, one aspect of the present invention aims to provide lithium-rich positive electrode active material particles or composite oxides in which the decrease in the initial discharge capacity relative to the initial charge capacity is suppressed. Alternatively, one aspect aims to provide lithium-rich positive electrode active material particles or composite oxides with good rate characteristics. Alternatively, one aspect aims to provide lithium-rich positive electrode active material particles or composite oxides in which the decrease in voltage or discharge capacity during the charge-discharge cycle is suppressed. Alternatively, one aspect aims to provide lithium-rich positive electrode active material particles or composite oxides in which changes in crystal structure during charging are suppressed. Alternatively, one aspect aims to provide lithium-rich positive electrode active material particles or composite oxides in which oxygen desorption is suppressed. Alternatively, one aspect aims to provide positive electrode active material particles or composite oxides with a large discharge capacity. Alternatively, one aspect aims to provide a secondary battery with high safety or reliability.

[0010] Furthermore, one aspect of the present invention aims to provide novel positive electrode active material particles, composite oxides, energy storage devices, or methods for producing them.

[0011] Furthermore, the description of these problems does not preclude the existence of other problems. Moreover, one aspect of the present invention does not need to solve all of these problems. It is possible to extract other problems from the description, drawings, and claims.

[0012] To solve the above problems, in one aspect of the present invention, positive electrode active material particles are provided with a structure in which the core is covered with a barrier film, and the barrier film is configured to contain a large amount of additive elements, including magnesium. Furthermore, a fluoride salt that functions as a flux is used to effectively dope the barrier film with the additive elements. In addition, a shell is provided on the outside to protect the barrier film.

[0013] One aspect of the present invention is a positive electrode active material particle comprising lithium, a transition metal M (where M is one or more selected from Mn, Cr, Mo, Nb, V, Fe, Ni, Ti, and Ru), oxygen, magnesium, and fluorine, wherein the positive electrode active material particle has a Li / M (atomic ratio) greater than 1, and comprises a core, a barrier film outside the core, and a shell outside the barrier film, wherein the shell contains more magnesium and fluorine than the core, the crystal orientation of the core and shell is substantially the same, and the barrier film contains fluoride.

[0014] In the above, it is preferable that the barrier film has more of one or more elements selected from titanium, aluminum, nickel, zirconium, vanadium, iron, manganese, chromium, niobium, arsenic, zinc, silicon, sulfur, phosphorus, boron, bromine, and beryllium than the core, and that the fluoride in the shell has one or more elements selected from lithium fluoride, aluminum fluoride, iron fluoride, calcium fluoride, cobalt fluoride, and lithium tetrafluoroaluminate.

[0015] Furthermore, in the above, it is preferable that the core has a layered rock salt type or irregular rock salt type crystalline structure.

[0016] Furthermore, in the above, it is preferable that the barrier film has a rock salt type or spinel type crystal structure.

[0017] According to one aspect of the present invention, it is possible to provide lithium-rich positive electrode active material particles or composite oxides in which the decrease in the initial discharge capacity relative to the initial charge capacity is suppressed. Alternatively, it is possible to provide lithium-rich positive electrode active material particles or composite oxides with good rate characteristics. Alternatively, it is possible to provide lithium-rich positive electrode active material particles or composite oxides in which the decrease in voltage or discharge capacity during the charge-discharge cycle is suppressed. Alternatively, it is possible to provide lithium-rich positive electrode active material particles or composite oxides in which changes in crystal structure during charging are suppressed. Alternatively, it is possible to provide lithium-rich positive electrode active material particles or composite oxides in which oxygen desorption is suppressed. Alternatively, it is possible to provide positive electrode active material particles or composite oxides with a large discharge capacity. Alternatively, it is possible to provide a secondary battery with high safety or reliability.

[0018] Furthermore, according to one aspect of the present invention, novel positive electrode active material particles, composite oxides, energy storage devices, or methods for producing them can be provided.

[0019] Furthermore, the description of these effects does not preclude the existence of other effects. Moreover, one aspect of the present invention does not necessarily have to possess all of these effects. Other effects will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other effects from the description in the specification, drawings, and claims.

[0020] Figures 1A and 1B are schematic cross-sectional views of positive electrode active material particles according to one embodiment of the present invention. Figures 2A, 2B, and 2C illustrate the crystal structure of the positive electrode active material particles according to one embodiment of the present invention. Figures 3A, 3B, 3C, and 3D illustrate the positive electrode according to one embodiment of the present invention. Figures 4A and 4B illustrate a lithium-ion secondary battery according to one embodiment of the present invention. Figures 5A, 5B, and 5C illustrate a lithium-ion secondary battery according to one embodiment of the present invention. Figures 6A, 6B, 6C, and 6D illustrate a lithium-ion secondary battery and energy storage system according to one embodiment of the present invention. Figures 7A, 7B, and 7C illustrate a lithium-ion secondary battery according to one embodiment of the present invention. Figures 8A, 8B, and 8C illustrate a lithium-ion secondary battery according to one embodiment of the present invention. Figures 9A, 9B, and 9C illustrate an electric vehicle according to one embodiment of the present invention. Figures 10A, 10B, 10C, and 10D illustrate a transport vehicle according to one embodiment of the present invention. Figures 11A, 11B, and 11C illustrate a motorcycle, etc., according to one embodiment of the present invention. Figures 12A, 12B, 12C, and 12D illustrate an electronic device, etc., according to one embodiment of the present invention. Figures 13A, 13B, 13C, and 13D show an example of space equipment.

[0021] The following describes embodiments for carrying out the present invention with reference to drawings and other illustrations. However, the present invention is not limited to the following embodiments. It is possible to modify the embodiments for carrying out the invention without departing from the spirit of the present invention.

[0022] Furthermore, ordinal numbers such as "first," "second," etc., in this specification are added to avoid confusion of constituent elements and do not indicate any order or rank, such as sequence or stacking order. Even if an ordinal number is not used for a term in this specification, it may be used in the claims to avoid confusion of constituent elements. Even if an ordinal number is used for a term in this specification, a different ordinal number may be used in the claims. Even if an ordinal number is used for a term in this specification, it may be omitted in the claims.

[0023] In this specification, space groups are expressed using international notation (or Hermann-Mauguin notation) in short notation. Crystal planes and crystal directions are expressed using Miller indices. In crystallography, space groups, crystal planes, and crystal directions are expressed by superscripting numbers, but in this specification, due to formatting constraints, a minus sign (-) may be placed before the number instead of a superscript. Individual orientations indicating directions within a crystal are represented by [ ], collective orientations indicating all equivalent directions are represented by < >, individual crystal planes are represented by ( ), and collective planes with equivalent symmetry are represented by {}. Furthermore, a trigonal crystal represented by the space group R-3m is sometimes represented by a hexagonal composite hexagonal lattice for ease of understanding the structure. In addition to (hkl), (hkil) may also be used as Miller indices, where i is -(h+k). In this specification, unless otherwise specified, the crystal planes and other features of the space group R-3m are represented by a composite hexagonal lattice.

[0024] In this specification, when simply referring to a positive electrode active material or positive electrode active material particles, depending on the analytical method, it may refer to multiple positive electrode active material particles or to a single positive electrode active material particle. For example, in descriptions of scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDX) line analysis, STEM-electron energy loss spectroscopy (STEM-EELS), and electron diffraction, unless otherwise specified, it refers to a single positive electrode active material particle. On the other hand, in the cases of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and various mass spectrometry methods, unless otherwise specified, it refers to multiple positive electrode active material particles.

[0025] In this specification, the term "particle" is not limited to spherical shapes (circular cross-sections), but includes individual particles with elliptical, rectangular, trapezoidal, triangular, rounded quadrilateral, asymmetrical shapes, and other cross-sectional shapes. Furthermore, individual particles may have irregular shapes. In addition, the term "particle" includes both primary and secondary particles.

[0026] Furthermore, when describing the characteristics of positive electrode active material particles, it is not necessary for all particles to possess those characteristics. For example, if 50% or more, preferably 70% or more, and more preferably 90% or more of three or more randomly selected positive electrode active material particles possess the desirable characteristics described later, it can be said that this sufficiently improves the characteristics of a secondary battery having such positive electrode active material particles.

[0027] Furthermore, the distribution of an element refers to the region in which that element is continuously detected within a non-noise range using a certain continuous analytical method. A region in which an element is continuously detected within a non-noise range can also be defined as a region in which the element is always detected when the analysis is performed multiple times.

[0028] Furthermore, the space group of a crystal structure is identified by XRD, electron diffraction, neutron diffraction, etc. Therefore, in this specification, "belonging to a certain space group," "being part of a certain space group," or "being a certain space group" can be rephrased as "being identified to a certain space group."

[0029] In this specification, a rock salt-type crystal structure refers to a cubic crystal structure in which cations and anions are arranged alternately. It can also be described as a crystal structure in which anions are arranged in cubic close-packing and cations occupy all octahedral positions. There may be one type of cation and one type of anion, or multiple types. There may also be vacancies in the cations or anions.

[0030] Furthermore, in this specification, a layered rock salt crystal structure is defined as a crystal structure that shares with the rock salt type in that anions are arranged in cubic close-packing and cations and anions are arranged alternately in octahedral positions, and in addition, it is clear that multiple types of cations exist, and at least one of these cations forms a two-dimensional plane. If lithium ions form a two-dimensional plane, two-dimensional diffusion of lithium is possible. Defects such as vacancies in cations or anions are acceptable.

[0031] Furthermore, in this specification, the term "disordered rock salt" type crystal structure refers to a crystal structure that has a cubic crystal system, in which anions are arranged in cubic close-packed arrangement, and cations and anions are arranged alternately at octahedral positions, sharing commonalities with the rock salt type, but in addition, it is clear that multiple types of cations are present, and the arrangement of these cations is irregular. In lithium-rich cathode active material particles, an irregular arrangement of cations means that the ratio of the occurrence frequency of each cation species is almost fixed at each cation site, and no significant difference is observed between cation sites. For example, in HAADF-STEM (High-angle annular dark-field scanning transmission electron microscope) images, there is no significant difference in the contrast of the cation sites. Defects such as vacancies of cations or anions may be present.

[0032] Furthermore, in this specification, the term "spinel type" refers to a type having a cubic crystal structure and general formula AB ２ O ４ This refers to a crystal structure in which anions are arranged in cubic close-packed arrangement and cations exist in octahedral and tetrahedral positions. The atomic ratio of cations in octahedral and tetrahedral positions is 2:1, but this atomic ratio does not need to be strict; for example, it can be a:1 (where a is between 1.9 and 2.1). It is preferable to determine that it is a spinel-type crystal structure from, for example, a STEM image, a TEM image, an electron diffraction pattern, an FFT pattern of a TEM image or an FFT pattern of a STEM image, or STEM-EELS.

[0033] In all types of rock salt crystals—layered rock salt, disordered rock salt, and spinel—the anions are arranged in a cubic close-packed structure. Furthermore, if the anion arrangement is roughly close to cubic close-packed, it can be considered cubic close-packed. A cubic close-packed anion arrangement refers to a state where the anions of the second layer are placed on top of the voids of the anions in the first layer, and the anions of the third layer are placed directly above the voids of the anions in the second layer, but not directly above the anions of the first layer. Therefore, the anions do not necessarily have to be strictly cubic. Also, since real crystals always have defects, the analysis results do not necessarily match the theory. For example, in FFT (Fast Fourier Transform) patterns such as electron diffraction patterns or TEM images, spots may appear at positions slightly different from the theoretical positions. For example, if the orientation from the theoretical position is 5 degrees or less, or 2.5 degrees or less, it can be said that it adopts a cubic close-packed structure.

[0034] Furthermore, positive electrode active material particles to which additive elements that improve conductivity and / or additive elements that stabilize the crystal structure are added may be expressed as composite oxides, positive electrode materials, positive electrode materials, positive electrode materials for secondary batteries, etc. In this specification, it is preferable that the positive electrode active material particles of one aspect of the present invention have a compound. In this specification, it is preferable that the positive electrode active material particles of one aspect of the present invention have a composition. In this specification, it is preferable that the positive electrode active material particles of one aspect of the present invention have a composite. In this specification, a composite oxide refers to an oxide having multiple types of cations. A composite oxide has oxygen as an anion, but is not limited to oxygen alone; it may also have anions such as fluorine and chlorine in addition to oxygen.

[0035] As the charging voltage of a secondary battery increases, the voltage at the positive electrode generally rises. The positive electrode active material particles in one embodiment of the present invention have a stable crystal structure even at high voltages. Because the crystal structure of the positive electrode active material particles is stable in the charged state, the decrease in charge / discharge capacity due to repeated charging and discharging can be suppressed.

[0036] Unless otherwise specified, the materials (cathode active material, anode active material, electrolyte, separator, etc.) of the secondary battery shall be described in the state before deterioration. It is assumed that a decrease in discharge capacity due to the aging process and / or burn-in process in the secondary battery manufacturing stage is not called deterioration. For example, when a lithium-ion secondary single cell and a lithium-ion secondary battery pack (hereinafter referred to as a lithium-ion secondary battery) have a discharge capacity of 97% or more of the rated capacity, it can be said to be in the state before deterioration. The rated capacity conforms to JIS C 8711:2019 in the case of a lithium-ion secondary battery for portable devices. In the case of other lithium-ion secondary batteries, it conforms to each JIS, IEC standard, etc. for electric vehicle propulsion, industrial use, etc., not limited to the above JIS standard.

[0037] (Embodiment 1) In this embodiment, the characteristics of the cathode active material particles of one aspect of the present invention will be described using FIGS. 1 and 2.

[0038] The cathode active material particles 100 of one aspect of the present invention contain lithium, a transition metal M, oxygen, and an additive element. The cathode active material particles 100 are preferably a compound obtained by adding an additive element to lithium-excess cathode active material particles.

[0039] [Lithium-excess cathode active material particles] Lithium-excess cathode active material particles refer to a composite oxide having a composition of Li ｘ M ２−ｘ O ２ (where M is one or more selected from Mn, Ni, Co, Cr, Mo, Nb, V, Fe, Ti, and Ru, 1 < x < 2). Note that part of O may be substituted with other anions such as F and / or Cl.

[0040] As is clear from being represented by Li ｘ M ２−ｘ O ２ (1 < x < 2), the Li / M (atomic ratio) of the lithium-excess cathode active material particles is greater than 1. It is also preferable that the cathode active material particles 100 of one aspect of the present invention obtained by adding an additive element to the lithium-excess cathode active material particles have a Li / M greater than 1.

[0041] Examples of lithium-rich cathode active material particles include layered rock salt type composite oxides and irregular rock salt type composite oxides.

[0042] <Layered rock salt type> Layered rock salt type lithium-rich cathode active material particles (also called lithium-rich layered oxide) include Li ２ MnO ３ And LiMO ２ The material includes a compound formed by mixing (M is one or more selected from Mn, Ni, Co, Cr, Mo, Nb, V, Fe, Ti, and Ru) in a certain proportion. LiMO ２ For example, LiCoO ２ LiNiO ２ LiNi ａ Co ｂ Mn ｃ O ２ Examples include (a + b + c = 1).

[0043] Li ２ MnO ３ It has a crystal structure with space group C2 / m symmetry, and LiMO ２ It has a crystal structure with space group R-3m symmetry. Li ２ MnO ３ and LiMO ２ A material synthesized by mixing these elements in a certain proportion becomes a solid solution having a P2 / m crystal structure, a C2 / m crystal structure, or an R-3m crystal structure. Alternatively, it becomes a composite structure having regions of a C2 / m crystal structure and regions of an R-3m crystal structure. Furthermore, this composite structure may have a region of a P2 / m crystal structure in place of, or in addition to, either a region of a C2 / m crystal structure or a region of an R-3m crystal structure.

[0044] Li of the space group C² / m ２ MnO ３ and LiMO of space group R-3m ２In all of these structures, the cation and anion are adjacent to each other, each occupying an octahedral position. Even when these solid solutions adopt a crystal structure of space group P2 / m, the cation and anion can each occupy an octahedral position. These structures are octahedrons with anions at the vertices and cations at the center that share edges, and can be described as distorted rock salt structures. Furthermore, when the cations are regularly arranged, these composite oxides having crystal structures of space group P2 / m, C2 / m, and / or R-3m can all have a layered rock salt type crystal structure.

[0045] For example, layered rock salt type lithium-rich cathode active material particles include 0.3Li ２ MnO ３ -0.7Li(Ni １／３ Co １／３ Mn １／３ ) O ２ Li is also written as Li １．１４ Mn ０．４６ Ni ０．２ Co ０．２ O ２ , 0.5Li ２ MnO ３ -0.5Li(Ni １／３ Mn １／３ Co １／３ O ２ Li １．２ Mn ０．５４ Co ０．１３ Ni ０．１３ O ２ , 0.5Li ２ MnO ３ -0.5Li(Ni １／２ Mn １／２ O ２ Li １．２ Mn ０．６ Ni ０．２ O ２ LiCoO ２ -Li ２ MnO ３ It is also written as Li (Li ｘ／３ Mn ２ｘ／３ Co １−ｘ ) O ２ (0 ≤ x ≤ 1), etc., can be used.

[0046] <Irregular Rock Salt Type> Irregular rock salt type lithium-rich cathode active material particles have a composition of Li ｘ M ２−ｘ O ２ (M is represented as one or more selected from Mn, Ni, Co, Cr, Mo, Nb, V, Fe, Ti, and Ru, 1 < x < 2), and refers to a composite oxide having a rock salt-type crystal structure and an irregular arrangement of cations. Some of the O may be substituted with other anions such as F and / or Cl.

[0047] Examples of elemental combinations that can be used in irregular rock salt-type lithium-rich cathode active material particles include Li-Cr-Mo-O, Li-Ti-Mn-O, Li-Ni-Mn-O, Li-Nb-Mn-O, Li-Nb-Fe-O, Li-Ti-Fe-O, Li-Ti-Ni-O, Li-V-O, Li-Nb-V-O, Li-V-O-F, Li-Mn-O-F, Li-Mn-O-F, Li-Mn-O-F, Li-Mo-O-F, etc.

[0048] [Additive Elements] The positive electrode active material particles 100 preferably contain one or more additive elements selected from magnesium, fluorine, titanium, aluminum, nickel, cobalt, manganese, zirconium, vanadium, iron, manganese, chromium, niobium, arsenic, zinc, silicon, sulfur, phosphorus, boron, bromine, and beryllium.

[0049] [Barrier film] The positive electrode active material particles 100 also have a core 100b and a barrier film 100a on the outside of the core, as shown in Figure 1A.

[0050] Core 100b has the characteristics of lithium-rich cathode active material particles. For example, it has the same crystal structure and / or composition as lithium-rich cathode active material particles. Therefore, it is preferable that core 100b has a layered rock salt type or irregular rock salt type crystal structure. It is also preferable that it has the composition described above.

[0051] The barrier film 100a contains more of the additive elements than the core 100b. In other words, the barrier film 100a has a higher concentration and / or detectable amount of the additive elements than the core 100b.

[0052] If an element not present in core 100b is used as an additive element, it is preferable that the element be detected in the barrier film 100a. If an element present in core 100b is used as an additive element, it is preferable that the element be detected in core 100b as well, and that the concentration and / or amount detected in the barrier film 100a is higher than that in core 100b.

[0053] Since the barrier film 100a contains more additive elements than the core 100b, its composition differs from that of the core 100b. Therefore, it is preferable that the crystal structure of the barrier film 100a also differs from that of the core 100b. For example, it is preferable that the barrier film 100a has a rock salt type, irregular rock salt type, or spinel type crystal structure.

[0054] However, the core 100b and the barrier film 100a may have the same crystal structure. For example, the core 100b and the barrier film 100a may both have an irregular rock salt type crystal structure, although they may have different constituent elements and / or ratios of constituent elements.

[0055] The barrier film 100a, which includes the surface of the positive electrode active material particles 100 or is a region close to the surface, has a rock salt type or spinel type crystal structure, which is expected to suppress side reactions with the electrolyte and / or electrolyte.

[0056] <Approximately Matching Orientation> When the crystal structures of the barrier film 100a and the core 100b are different, it is preferable that the orientations of the crystal structures of both are approximately matching.

[0057] In this specification, it is sometimes said that the crystal orientations are approximately identical when the orientations of the cubic close-packed structure composed of anions are aligned in rock salt type, layered rock salt type, disordered rock salt type, and spinel type. Furthermore, having a three-dimensional structural similarity such that the crystal orientations are approximately identical, or having the same crystallographic orientation, is called topotaxy.

[0058] The approximate agreement of crystal orientation in two regions can be determined from TEM (Transmission Electron Microscope) images, STEM (Scanning Transmission Electron Microscope) images, HAADF-STEM images, ABF-STEM (Annular Bright-Field Scanning Transmission Electron Microscope) images, electron diffraction patterns, etc. It can also be determined from the FFT patterns of TEM images and STEM images, etc. Furthermore, XRD (X-ray Diffraction) and neutron diffraction can also be used as criteria for determination.

[0059] TEM and STEM images provide images that reflect the crystal structure. Electron diffraction patterns, on the other hand, can provide information about the crystal orientation at specific locations. In particular, nanobeam electron diffraction is useful for obtaining information about the crystal orientation in narrow regions.

[0060] When the crystal planes of the layered rock salt and the rock salt structure coincide, this coincidence can be observed using high-resolution STEM images, electron diffraction patterns, etc. It is preferable to use different electron diffraction techniques, such as limited-field diffraction and nanobeam diffraction, depending on the particle size and / or the range of the rock salt structure of the barrier film 100a.

[0061] For example, in HAADF-STEM images, contrast proportional to atomic number is obtained, and elements with larger atomic numbers are observed brighter. For example, Li ｘ M ２−ｘ O ２ In the case where (M is one or more selected from Mn, Ni, Co, Cr, Mo, Nb, V, Fe, Ti, and Ru, 1 < x < 2), since the transition metal M has the largest atomic number, the electron beam is strongly scattered at the position of the transition metal M, and if there is an array of transition metal M, it will be observed as an array of points with high brightness.

[0062] Therefore, in HAADF-STEM images, when an electron beam is incident perpendicular to the c-axis of a layered rock salt composite hexagonal lattice, an array of brightly luminous points originating from the transition metal M on the (003) plane is obtained as a bright band (bright strip). Similarly, when an electron beam is incident perpendicular to the (111) plane of the rock salt, an array of points originating from the metallic element on the (111) plane is obtained as a bright band. In this way, if repetitions of bright bands are observed in both regions of the STEM image, and the angle between bright lines is 5 degrees or less or 2.5 degrees or less, or if the difference in the spacing of the bright bands is within 15%, it can be determined that the crystal planes are roughly coincidental, that is, the crystal orientation is roughly coincidental.

[0063] Therefore, in HAADF-STEM images, if an array of highly luminous points is observed in two regions with different crystal structures, and the angle between these arrays is 5 degrees or less or 2.5 degrees or less, or if the difference in the spacing between these arrays is within 15%, it can be determined that the crystal orientations are roughly consistent.

[0064] In ABF-STEM, elements with smaller atomic numbers appear brighter, but since contrast corresponding to atomic number is obtained, similar to HAADF-STEM, the orientation of the crystal can be determined in the same way as with HAADF-STEM images.

[0065] Furthermore, information about the crystal orientation for each region can be obtained from the FFT pattern of a TEM image, the FFT pattern of a STEM image, or the electron diffraction pattern. For example, it is possible to obtain information on whether the

[001] direction in a region of layered rock salt structure having a crystal structure of space group R-3m and the <111> direction in a region of rock salt structure having a crystal structure of space group Fm-3m are roughly coincide. If the crystal orientations coincide by 5 degrees or less or 2.5 degrees or less, it can be determined that the crystal planes roughly coincide, that is, the crystal orientations roughly coincide.

[0066] In this case, it is preferable that these reciprocal lattice points are spot-like, that is, they do not form a concentric ring continuous with other reciprocal lattice points. The fact that the reciprocal lattice points are spot-like and not continuous with other reciprocal lattice points indicates high crystallinity.

[0067] Similarly, if the orientations of irregular salt deposits and salt deposits are roughly the same, the <111> directions of both may roughly coincide. Also, if the orientations of irregular salt deposits and spinel deposits are roughly the same, the <111> directions of both may roughly coincide. Furthermore, if the orientations of layered salt deposits and spinel deposits are roughly the same, the <111> directions of both may roughly coincide.

[0068] It is known that layered rock salt type positive electrode active material particles of space group R-3m tend to exhibit (001) planes and equivalent planes, as well as (104) planes and equivalent planes, as crystal planes. Therefore, when observing the (001) plane with a TEM, for example, it is preferable to first select positive electrode active material particles in which the crystal plane expected to be the (001) plane is observed using a SEM, and then thin the positive electrode active material particles using a FIB (Focused Ion Beam), for example, so that the (001) plane can be observed with the electron beam incident at

[120] in a TEM. When it is desired to determine the consistency of the crystal orientation, it is preferable to thin the layered rock salt type so that the (001) plane is easily observable. Similarly, in the case of positive electrode active material particles with other crystal structures, it is preferable to thin the layer so that the arrangement of the transition metal M is easily observable.

[0069] The barrier film 100a and the core 100b have roughly identical crystal structures, allowing the barrier film 100a, which contains a large amount of additive elements, to function as a pillar supporting the crystal structure of the positive electrode active material particles 100. Among the additive elements, magnesium is particularly preferred because its strong bonding with oxygen is expected to provide high functionality as a pillar for the positive electrode active material particles 100. In other words, the presence of additive elements stabilizes the crystal structure of the surface and bulk of the positive electrode active material particles 100. Therefore, changes in the crystal structure of the positive electrode active material particles 100 during charging and / or the release of oxygen can be suppressed.

[0070] Therefore, the positive electrode active material particles 100 can be made in which the decrease in the initial discharge capacity relative to the initial charge capacity is suppressed, or positive electrode active material particles 100 with good rate characteristics, or positive electrode active material particles 100 in which the decrease in voltage or discharge capacity during the charge-discharge cycle is suppressed.

[0071] <Example of roughly matching orientation> For the crystal structures of the barrier film 100a and the core 100b to be different and their orientations to be roughly matching, it is necessary that the anion packing structure is common and that there is no large mismatch in the lattice constants of the two. More precisely, considering the case where the space groups are different, it is necessary that there is no large mismatch in the metal-metal distance and the interlayer distance. Here, the metal-metal distance is the average of the distances between the nearest metal atoms in the same layer. The interlayer distance is the average distance between two metal layers. A metal layer refers to a plane on which metal atoms are arranged, and in the case of rock salt structure and irregular rock salt structure (Fm-3m), it refers to the (111) plane. In the case of layered rock salt structure, if R-3m it refers to the (001) plane, if C / 2m it refers to the (001) plane, and if P2 / m it refers to the (001) plane. In the case of spinel structure (Fd-3m), it refers to the (111) plane. When there are multiple types of metals and they are arranged in a regular pattern, the term can sometimes refer to the plane in which the largest number of metals of the same type are arranged.

[0072] Regarding the metal-to-metal distance and interlayer distance, if the core 100b / barrier film 100a ratio is between 0.94 and 1.06, the crystal structures can be roughly matched.

[0073] The following are examples of cases where the crystal structures of the barrier film 100a and the core 100b are different, but the crystal orientations can be roughly the same.

[0074] First, we will describe an example in which the core 100b has the crystalline structure and composition of layered rock salt-type lithium-rich cathode active material particles, and the barrier film 100a has a rock salt-type crystalline structure.

[0075] Layered rock salt type lithium-rich cathode active material particles are Li ２ MnO ３ And LiMO ２ Since the material is synthesized by mixing (M is one or more selected from Mn, Ni, Co, Cr, Mo, Nb, V, Fe, Ti, and Ru) in a certain proportion, the metal-to-metal distance and interlayer distance of core 100b are Li ２ MnO ３ And LiMO ２ It is thought to be one of the values ​​in the range. Table 1 shows the known Li ２ MnO ３shows the experimental values of the metal-metal distance and the interlayer distance. Similarly, for LiMO ２ as an example, the known LiCoO ２ , LiNiO ２ , LiNi １／２ Mn １／２ O ２ , and LiNi １／３ Mn １／３ Co １／３ O ２ show the experimental values. In all cases, the metal-metal distance is 2.816 Å or more and 2.887 Å or less with four significant figures, and the interlayer distance is 2.342 Å or more and 2.382 Å or less.

[0076] The upper part of FIG. 2A shows a schematic diagram of the (001) plane of the crystal structure of Li ２ MnO ３ with the space group C2 / m, and the lower part shows a schematic diagram of a plane perpendicular to the (001) plane. The (001) plane of the crystal structure of Li ２ MnO ３ is a plane on which the metals are arranged in layers. For clarity, the upper (001) plane in FIG. 2A shows an extraction of one metal layer and the oxygen layers above and below it. In the plane perpendicular to these in the lower part, only the bonds between one metal layer and the oxygen layers above and below it are shown.

[0077] Note that for Li ２ MnO ３ with the ICSD Collection Code: 73370, the crystal structure has a layer in which Li and Mn are mixed as the metal layer and a layer of only Li. Both are parallel or approximately parallel to the a-axis and the b-axis. Also, the metal sites in the layer where Li and Mn are mixed are partially occupied by Li and Mn. However, for simplicity of the figure, in FIG. 2A, for the layer where Li and Mn are mixed, the element with the larger occupancy is shown as a representative. Since the metal sites of Li ２ MnO ３ are deviated from the regular triangular arrangement, the metal-metal distance in Li ２ MnO ３ can be obtained by the following two methods.

[0078] One method involves determining the intermetallic distance from the average of the metal-atom distances in a mixed layer of Li and Mn. The layer containing only Li was not used in the calculation because the atomic positions are slightly offset from the same plane. The metal-to-metal intermetallic distance obtained using this method was 2.842 Å to four significant figures.

[0079] Another approach is to assume that when the distance between metals is x, the length of the a-axis is 4.921 Å, which is (√3)x, and the length of the b-axis is 8.526 Å, which is 3x. Then, the product of the lengths of the a-axis and b-axis is 41.95645 Å. ２ is 3(√3)x ２ This is a method for calculating x when the result is as follows. The metal-to-metal distance obtained using this method was 2.842 Å to four significant figures. Thus, the metal-to-metal distances obtained using the two methods were the same to four significant figures.

[0080] LiMO is shown in the upper part of Figure 2B. ２ As an example, the space group R-3m is LiCoO ２ The (001) plane of the crystal structure is shown, and a schematic diagram of the plane perpendicular to the (001) plane is shown in the lower section. LiCoO ２ The (001) plane of the crystal structure is the plane where the metal is arranged in layers. To clarify the figure, the (001) plane in the upper part of Figure 2B shows an excerpt of one metal layer and the oxygen layers above and below it. In the plane perpendicular to these in the lower part, only the one metal layer and the oxygen layers above and below it show bonding.

[0081] Since the barrier film 100a has a higher concentration and / or detection amount of the added element than the core 100b, the metal-to-metal distance and interlayer distance of the barrier film 100a are thought to be between the values ​​of the rock salt-type oxide of the added element and the crystal structure of the core 100b. Here, magnesium, cobalt, nickel, and manganese are taken as examples of added elements, and Table 1 shows experimental values ​​of the metal-to-metal distance and interlayer distance for known MgO, CoO, NiO, and MnO. In all cases, the metal-to-metal distance is between 2.954 Å and 3.144 Å (to four significant figures), and the interlayer distance is between 2.412 Å and 2.567 Å.

[0082] Figure 2C shows, in the upper panel, the (111) plane of the crystal structure of MgO, with space group Fm-3m, as an example of a rock salt-type oxide of an added element, and in the lower panel, a schematic diagram of a plane perpendicular to the (111) plane. The (111) plane of the MgO crystal structure is the plane in which the metal is arranged in layers. To make the diagram clearer, the (111) plane in Figure 2C is shown as an excerpt of one metal layer and the oxygen layers above and below it. In the plane perpendicular to this, bonding is shown only in the one metal layer and the oxygen layers above and below it.

[0083] As shown in Figures 2A to 2C, these oxides, although belonging to different space groups, share the common features of cubic close-packed oxygen and alternating arrangement of cations and anions. Furthermore, as indicated by the dotted lines in Figures 2A to 2C, the cations are all located in octahedral positions.

[0084] Table 1 shows the relative values ​​of each distance when the metal-to-metal distance and interlayer distance of MgO are set to 1. ２ MnO ３ and LiCoO ２ Therefore, since the interlayer distance varies depending on the location of the layer, the average value is shown.

[0085] When the metal-to-metal distance and interlayer distance of MgO are set to 1, the relative values ​​of the metal-to-metal distance and interlayer distance are both between 0.94 and 1.06, clearly indicating that there is no significant mismatch between these crystal structures. Therefore, if the core 100b has the composition and crystal structure of the layered rock salt type lithium-rich cathode active material particles exemplified above, and the barrier film 100a has magnesium, cobalt, nickel and / or manganese as additive elements and has a rock salt type crystal structure, the crystal structures of the barrier film 100a and the core 100b can be approximately identical.

[0086]

[0087] Next, we will describe an example in which the core 100b has the crystal structure and composition of irregular rock salt-type lithium-rich cathode active material particles, and the barrier film 100a has a rock salt-type crystal structure. Since the irregular rock salt-type crystal structure of the core 100b is the same as the rock salt-type crystal structure of the barrier film, the two can be compared using lattice constants.

[0088] Non-patent document 5 describes a lithium-rich cathode active material having an irregular rock salt-type crystal structure. １．０５ Mn ０．８５ Ti ０．１ O ２ Li １．１０ Mn ０．７０ Ti ０．２ O ２ and Li １．１５ Mn ０．５５ Ti ０．３ O ２ It has been shown that the lattice constant a is between 4.16 Å and 4.17 Å.

[0089] Here, we will take magnesium as an example of an additive element. The lattice constant a of MgO is 4.217 Å.

[0090] From these findings, it is clear that the lattice constant a of the irregular rock salt type lithium-rich cathode active material particles is between 0.986 and 0.988, and that there is no significant mismatch between these crystal structures.

[0091] Therefore, if the core 100b has the composition and crystal structure of the irregular rock salt type lithium-rich cathode active material particles exemplified above, and the barrier film 100a has magnesium as an additive element and has a rock salt type crystal structure, the crystal orientations of the barrier film 100a and the core 100b can be approximately the same.

[0092] Next, an example in which the core 100b or barrier film 100a has a spinel-type crystal structure will be described. When evaluating the approximate agreement of crystal orientation between the spinel type and other crystal structures, it is preferable to compare the stacking of oxygen and the relative value of the interlayer distance of the oxygen layer.

[0093] Examples of spinel types (space group: Fd-3m) containing Li and Mn include LiMn from ICSD Collection Code: 73370. ２ O ４ It has the following crystal structure. The stacking of the spinel-type oxygen layer is cubic close-packed, and is ABCABC... stacking with respect to the <111> direction.

[0094] The oxygen layer of the rock salt type is also cubically close-packed, with ABCABC… stacking in the <111> direction. The oxygen layer of the layered rock salt type R-3m is also cubically close-packed, with ABCABC… stacking in the

[001] direction. The oxygen layer of the layered rock salt type C / 2m is also cubically close-packed, with ABCABC… stacking in the direction generally perpendicular to the c-plane.

[0095] Therefore, spinel-type LiMn ２ O ４ If the interlayer distance and oxygen-oxygen distance of the stacking oxygen layers are consistent, the crystal orientation will roughly match that of the rock salt structure (Fm-3m) and the layered rock salt structure (R-3m, C / 2m).

[0096] In the rock salt crystal structure of space group Fm-3m, the metal-to-metal distance is the same as the oxygen-to-oxygen distance. Similarly, the interlayer distance of the metal layer is the same as the interlayer distance of the oxygen layer. LiCoO ２ In layered rock salt structures of space group R-3m, such as LiCoO, the metal-to-metal distance is the same as the oxygen-to-oxygen distance. ２ In layered salt deposits such as those described above, oxygen and metal are arranged alternately, and the average interlayer distance of the metal layers is the same as the average interlayer distance of the oxygen layers. ２ MnO ３ In the (001) plane, oxygen and metal are arranged alternately in a direction perpendicular to the plane, and the average interlayer distance of the metal layers is the same as the average interlayer distance of the oxygen layers. In a layered rock salt type with space group C / 2m, the latter method described above for determining the metal-to-metal distance can also be applied to determining the oxygen-to-oxygen distance. That is, the oxygen-to-oxygen distance within the same plane is the same as the metal-to-metal distance determined earlier. Therefore, the metal-to-metal distances shown in Table 1 can be said to be the same as the oxygen-to-oxygen distances. Similarly, the interlayer distance of the metal layers can be said to be the same as the interlayer distance of the oxygen layers.

[0097] LiMn ２ O ４The position of oxygen in the (111) plane is offset from its position in the triangular lattice. Therefore, assuming that oxygen is arranged so that it lies in the same plane as the triangular lattice, we assume the distance between the triangular lattices is the oxygen-oxygen distance. Under this assumption, the calculated oxygen-oxygen distance is 2.908 Å, and the relative value of MgO to the oxygen-oxygen distance is 0.98.

[0098] LiMn ２ O ４ Since the oxygen positions are offset from the (111) plane, we similarly take the average of each oxygen position on the (111) plane as the oxygen position on the (111) plane, and assume that the distance of the oxygen layer in the

[111] direction obtained using the oxygen positions on the (111) plane is the interlayer distance of the oxygen layer. Under this assumption, the calculated interlayer distance of the oxygen layer is 2.375 Å, and the relative value to the interlayer distance of the oxygen layer of MgO is 0.98. Thus LiMn ２ O ４ The relative values ​​for both the oxygen-oxygen distance and the interlayer distance of the oxygen layer, relative to MgO, are in the range of 0.94 to 1.06.

[0099] Therefore, core 100b is LiMn ２ O ４ If it has a spinel-type structure like this, the crystal orientation can roughly coincide with that of a rock salt-type barrier film 100a containing Mg. ２ O ４ When it has a spinel-type structure like this, the crystal orientation may roughly coincide with that of the core 100b which has a layered rock salt type and / or irregular rock salt type crystal structure.

[0100] The particle size of the positive electrode active material particles 100 is preferably 500 nm or less in diameter, more preferably 250 nm or less, and even more preferably around 100 nm, in order to suppress the diffusion resistance of lithium within the particles. On the other hand, if the particle size is too small, disadvantages such as aggregation may occur. Therefore, the diameter is preferably 25 nm or more, and more preferably 50 nm or more.

[0101] Furthermore, unless otherwise specified, the characteristics of the primary particles of the positive electrode active material particles 100 will be described, but the positive electrode active material particles may also have secondary particles formed by aggregation, adhesion, and / or sintering of multiple primary particles. Having secondary particles is preferable because it increases the particle size and facilitates coating onto the current collector, etc.

[0102] When the positive electrode active material particles 100 have secondary particles, a barrier film 100a may be formed on each of the primary particles contained within the secondary particles. Alternatively, the barrier film 100a may be formed on the secondary particles as a single particle. In other words, there may be primary particles inside the secondary particles that do not have a barrier film 100a. Furthermore, additive elements may be used as sintering aids when granulating primary particles into secondary particles.

[0103] If the barrier film 100a is too thin, it may not be able to sufficiently stabilize the surface and bulk of the positive electrode active material particles 100. Therefore, the thickness of the barrier film 100a is preferably 1 nm or more, and more preferably 2 nm or more. It can also be 3 nm or more, or 5 nm or more. On the other hand, a thinner barrier film 100a makes it easier to increase the charge / discharge capacity. For this reason, the thickness of the barrier film 100a is preferably 10 nm or less.

[0104] While it is preferable that the barrier film 100a has a rock salt type or spinel type crystal structure, the rock salt type or spinel type crystal structure does not have to be present only in the barrier film 100a. For example, a part of the core 100b may have a rock salt type or spinel type crystal structure.

[0105] Furthermore, the barrier film 100a does not necessarily need to cover the entire surface of the positive electrode active material particles 100. However, in order to function as a pillar, it is preferable that the barrier film 100a covers 50% or more, preferably 70% or more, and more preferably 90% or more, of the surface of the positive electrode active material particles 100.

[0106] Furthermore, the barrier film 100a does not have to be entirely of the rock salt type or spinel type crystalline structure. For example, it may be partially amorphous or have other crystalline structures. Similarly, the core 100b does not have to be entirely of the layered rock salt type or disordered rock salt type crystalline structure. For example, it may be partially amorphous or have other crystalline structures.

[0107] [Shell] In addition, in one embodiment of the present invention, the positive electrode active material preferably has a shell 101 on the outside of the barrier film 100a, as shown in Figure 1B, for positive electrode active material particles 102. The presence of the shell 101 can suppress the release of oxygen from the barrier film 100a, the elution of cations, etc. As the shell 101, lithium fluoride, aluminum fluoride, iron fluoride, calcium fluoride, cobalt fluoride, lithium tetrafluoroaluminate (LiAlF) ４ It is preferable to use fluorides such as fluorine. Fluorine readily forms compounds with high chemical stability. Therefore, by providing fluorine at the interface between the positive electrode active material particles 100 and the electrolyte, it is expected that the release of oxygen from the positive electrode active material particles 100 can be suppressed. This reduces lattice oxygen (O ２− ) becomes easier to retain. Furthermore, LiAlF ４ Using a lithium-containing fluoride, as shown above, is more preferable because it is expected to increase ionic conductivity.

[0108] Furthermore, it is preferable that the crystal orientations of the shell 101 and the barrier film 100a are approximately identical. Moreover, it is preferable that the crystal orientations of the shell 101, the barrier film 100a, and the core 100b are approximately identical. By having approximately identical orientations, a more stable shell 101 can be made, and thus the detachment of oxygen from the barrier film 100a, the elution of cations, etc. can be more effectively suppressed.

[0109] <Crystal structure in the charged state> In one embodiment of the present invention, the positive electrode active material is expected to have its phase change in the crystal structure suppressed in the charged state due to the effects of the barrier film 100a and / or shell 101 described above.

[0110] Phase changes in the crystal structure during charging can be evaluated using diffraction methods, including X-ray diffraction (XRD).

[0111] [Analysis] <Composition> The composition of the positive electrode active material particles 100 in one embodiment of the present invention is preferably evaluated by combining multiple analyses. For example, among the elements contained in the positive electrode active material particles 100, it is preferable to determine the proportions of the main components, lithium, transition metal M, and oxygen, using ICP-MS (inductively coupled plasma mass spectrometry) or the like. For the additive elements, it is preferable to determine the proportions using an analysis sensitive to trace elements, such as GD-MS (glow discharge mass spectrometry).

[0112] <Distribution of Additive Elements> The distribution of additive elements in the positive electrode active material particles 100 according to one embodiment of the present invention is preferably evaluated by cross-sectional analysis of the positive electrode active material particles 100. For example, cross-sectional STEM-EDX is preferred because it has high spatial resolution. In order to further increase the spatial resolution in STEM-EDX ray analysis, it is preferable that the beam diameter of the electron beam (also called beam diameter, probe diameter, or probe diameter) is small. The beam diameter in STEM-EDX ray analysis is preferably 0.3 nm or less, more preferably 0.2 nm or less, and even more preferably 0.1 nm or less.

[0113] Furthermore, cross-sectional EPMA (electron probe microanalyzer) is preferable because it has a low detection limit for elements.

[0114] Multiple analyses can be combined and evaluated as needed.

[0115] The interface between the barrier film 100a and the core 100b is defined as a series of points that show a detection amount closest to half the sum of the detection amount of the element in the center of the positive electrode active material particles 100 and the detection amount of the part near the surface of the positive electrode active material particles 100 that is detected most abundantly. If there are multiple additive elements, the element that is easiest to detect and / or quantify is selected based on the composition of the positive electrode active material particles 100. For example, if there is an additive element that is not contained in the core 100b, it is preferable to use it. It is also preferable to use an element whose characteristic X-ray spectrum overlaps less with the elements contained in the core 100b. It is also preferable to use an element that is detected more abundantly near the surface.

[0116] <Surface> In one embodiment of the present invention, the positive electrode active material particles are compounds having a transition metal M and oxygen that can be inserted into and removed from lithium. Therefore, in this specification, the interface between the region where the transition metal M and oxygen that undergo oxidation-reduction with lithium insertion and removal are present and the region where they are absent is considered the surface of the positive electrode active material particles. Surfaces formed by slip, cracks, and / or fissures may also be considered the surface of the positive electrode active material particles. When the positive electrode active material particles are subjected to analysis, a protective film may be applied to the surface, but the protective film is not included in the positive electrode active material particles. As the protective film, a single-layer or multi-layer film of carbon, metal, oxide, resin, etc. may be used.

[0117] For similar reasons, the positive electrode active material particles in one aspect of the present invention are aluminum oxide (Al ２ O ３ This excludes metal oxides that do not have lithium sites that can contribute to charging and discharging, such as those mentioned above, as well as carbonates, hydroxyl groups, etc., that are chemically adsorbed after the production of the positive electrode active material particles. Adhered metal oxides refer to, for example, metal oxides whose crystal structure does not roughly match that of lithium-rich positive electrode active material particles.

[0118] Furthermore, electrolytes, organic solvents, binders, conductive materials, or compounds derived from these that adhere to the positive electrode active material particles are not included in the positive electrode active material particles.

[0119] In STEM-EDX ray analysis, due to the principle or measurement errors, the graph of the detected characteristic X-rays of an element does not change sharply, making it difficult to precisely determine the surface. Therefore, when referring to the depth direction in STEM-EDX ray analysis, the detected amount of characteristic X-rays of the transition metal M is considered to be the average value M of the detected characteristic X-rays of the transition metal M inside the surface. ＡＶＥ And the average value M of the detected characteristic X-rays of the above transition metal M in the background. ＢＧ The point where the sum of the two is 50%, or where the amount of oxygen characteristic X-rays detected is equal to the average value of the amount of oxygen characteristic X-rays detected inside. ＡＶＥ And the average value of the detected characteristic X-rays of background oxygen O ＢＧ The reference point is the point at which the sum of the two values ​​becomes 50%. Note that if the point at which the detected amount of characteristic X-rays of the transition metal M becomes 50% of the sum of the average detected amount of characteristic X-rays of the internal transition metal M and the average detected amount of characteristic X-rays of the background transition metal M is different from the point at which the detected amount of characteristic X-rays of oxygen becomes 50% of the sum of the average detected amount of characteristic X-rays of internal oxygen and the average detected amount of characteristic X-rays of background oxygen, it is thought to be due to the influence of oxygen-containing metal oxides, carbonates, etc. adhering to the surface, and therefore the point at which the detected amount of characteristic X-rays of the transition metal M becomes 50% of the average detected amount of characteristic X-rays of internal transition metal M ＡＶＥ And the average value M of the detected characteristic X-rays of the above transition metal M in the background. ＢＧ The point at 50% of the sum of these can be adopted as the reference point. In the case of positive electrode active material particles 100 having multiple transition metals M, the transition metal element M that has the highest amount of characteristic X-rays detected inside is selected. ＡＶＥ and M ＢＧ The above reference points can be determined using this method.

[0120] The average value M of the detected characteristic X-rays of the above transition metal M in the background. ＢＧ For example, the average value M of the detected characteristic X-rays of the transition metal M can be determined by averaging the range of 2 nm or more, preferably 3 nm or more, outside the positive electrode active material particles 100, while avoiding the vicinity where the detection amount of characteristic X-rays of the transition metal M begins to increase. ＡＶＥThe average value of the background characteristic X-ray O is obtained by averaging a range of 2 nm or more, preferably 3 nm or more, from a depth of 30 nm or more, preferably more than 50 nm, in the region where the detection amount of characteristic X-rays of transition metal M and oxygen saturates and stabilizes, for example, from the region where the detection amount of characteristic X-rays of transition metal M begins to increase. ＢＧ and the average value of the detected amount of characteristic X-rays of the internal oxygen O ＡＶＥ This can be calculated in a similar manner.

[0121] Furthermore, the surface of the positive electrode active material particles in cross-sectional STEM (scanning transmission electron microscope) images, etc., is defined as the boundary between the region where an image originating from the crystal structure of the positive electrode active material particles is observed and the region where it is not observed, and is the outermost region where atomic columns originating from the nuclei of metal elements with atomic numbers greater than lithium among the metal elements constituting the positive electrode active material particles are confirmed. Alternatively, it is defined as the intersection of the tangent line drawn to the brightness profile from the surface toward the bulk in the STEM image and the depth axis. The surface in STEM images, etc., may also be determined in conjunction with analyses that have higher spatial resolution.

[0122] Furthermore, the spatial resolution of STEM-EDX is approximately 1 nm. Therefore, the maximum value of the additive element profile may be off by approximately 1 nm. For example, even if the maximum value of the additive element profile, such as magnesium, lies outside the surface determined above, if the difference between the maximum value and the surface is less than 1 nm, it can be considered an error.

[0123] Furthermore, in STEM-EDX analysis, the peak refers to the detection intensity in each element profile, or the maximum value of the characteristic X-ray for each element. Noise in STEM-EDX analysis can include measurements with a width at half maximum (FWHM) below the spatial resolution (R), for example, R / 2 or less.

[0124] Scanning the same location multiple times under the same conditions can reduce the effects of noise. For example, the cumulative values ​​from six scans can be used as the profile for each element. The number of scans is not limited to six; more scans can be performed, and the cumulative values ​​from those scans can be used as the profile for each element.

[0125] STEM-EDX radiation analysis can be performed, for example, as follows: First, a protective film is deposited on the surface of the positive electrode active material particles. For example, carbon can be deposited using an ion sputtering apparatus (Hitachi High-Tech MC1000).

[0126] Next, the positive electrode active material particles are thinned to prepare a STEM cross-sectional sample. For example, thinning can be performed using a FIB-SEM device (Hitachi High-Tech XVision 200TBS). In this case, pickup is performed using an MPS (microprobing system), and the finishing conditions can be set to, for example, an acceleration voltage of 10kV.

[0127] STEM-EDX ray analysis can be performed using, for example, a STEM instrument (Hitachi High-Tech HD-2700), and an EDAX Octane T Ultra W (two-pronged) EDX detector. During EDX ray analysis, the emission current of the STEM instrument should be set to 6 μA to 10 μA, and the area of ​​the thinned sample with little depth and unevenness should be measured. The magnification should be, for example, around 150,000x. The conditions for EDX ray analysis can be drift correction enabled, line width 42 nm, pitch 0.2 nm, and 6 or more frames.

[0128] <Particle size distribution analysis using cross-sectional SEM images of the positive electrode> For example, the particle size distribution of the positive electrode active material particles 100 can be calculated from the cross-sectional SEM images of the positive electrode active material particles 100 using the following method.

[0129] First, from the acquired cross-sectional SEM image, an analysis region is extracted so that sufficient cross-sections of the positive electrode active material particles 100 can be obtained for image analysis. For example, it is preferable to extract a region in which 100 or more cross-sections of the positive electrode active material particles 100 can be obtained.

[0130] Furthermore, image processing software functions may be used to extract cross-sectional SEM images. For example, ImageJ may be used as the image processing software, and its `crop` function may be used to extract the images.

[0131] Next, the first image extracted using image processing software is binarized, and particle analysis is performed.

[0132] Image processing software such as ImageJ can be used. The binarization process is described below. The first image, which is shown in 256-value grayscale, is used as a frequency graph excluding black (value 0) and white (value 255), and the low-value side (HWHM_L) and high-value side (HWHM_H) are determined as the half-width at half maximum (HWHM) of the maximum peak in the frequency graph. Next, from the value that is the peak top (maximum frequency) of the maximum peak, the lowest value a of the range that is twice the width of HWHM_L on the low-value side and the highest value b of the range that is twice the width of HWHM_H on the high-value side are determined.

[0133] Next, a binarization process is performed so that values ​​less than a are white, values ​​between a and b are black, and values ​​greater than b are white. Specifically, the ImageJ Threhold function is used to perform binarization as Threhold(a,b). Then, using the conditions Gray Morphology (radius=3, operator=open, type=circle) and Gray Morphology (radius=1, operator=close, type=circle), random bright spots thought to be caused by conductive materials are removed, and a second image can be obtained.

[0134] Next, using the second image, the ImageJ Analyze Particles function was used to determine the particle size (projected area) of 0.5 μm. ２ 700 μm or more ２ The following particles are detected, and the area S of each particle is obtained. Next, the diameter r of each particle is calculated based on the area S of each particle (Equation 1).

[0135]

[0136] In this way, the particle size distribution can be calculated from the cross-sectional SEM image. Performing the above analysis is called performing particle size distribution analysis using the cross-sectional SEM image of the positive electrode.

[0137] <XRD> The equipment and conditions for XRD measurement are not particularly limited. For example, measurements can be taken with the following equipment and conditions: XRD equipment: Bruker D8 ADVANCE, X-ray: CuKα１ Output: 40kV, 40mA, Slit width: Div. Slit, 0.5°, Detector: LynxEye, Scanning method: 2θ / θ continuous scan, Measurement range (2θ): 15° to 90°, Step width (2θ): 0.01°, Setting counting time: 1 second / step, Sample stage rotation: 15rpm.

[0138] If the sample to be measured is a powder, it can be set up by placing it in a glass sample holder or by sprinkling the sample onto a grease-coated silicon anti-reflective plate. If the sample to be measured is a positive electrode, the positive electrode can be attached to a substrate of appropriate thickness with double-sided tape, and the positive electrode active material layer can be set up to match the measurement surface required by the instrument. If the positive electrode active material layer is higher than the measurement surface required by the instrument, the diffraction pattern will shift overall to the higher angle side, and if it is lower, it will shift overall to the lower angle side. In this case, it is preferable to correct the shift in the diffraction pattern using crystal structure analysis software or the like.

[0139] This embodiment can be appropriately combined with the contents of other embodiments.

[0140] (Embodiment 2) This embodiment describes an example of a method for producing positive electrode active material particles according to one aspect of the present invention.

[0141] [Preparation Method 1] First, Li ｘ M ２−ｘ O ２ A composite oxide is prepared, represented by (where M is one or more selected from Mn, Ni, Co, Cr, Mo, Nb, V, Fe, Ti, and Ru, with 1 < x < 2).

[0142] Li ｘ M ２−ｘ O ２ The method of preparation is not particularly limited, but can be carried out by a solid-phase method, for example. When using a solid-phase method, lithium carbonate (Li) can be used as the lithium source. ２ CO ３ ), lithium hydroxide (LiOH) and / or lithium oxide (Li ２ O), etc. can be used. As the M source, oxides of transition metals M can be used, for example, manganese oxide (Mn ２ O３ MnO ２ and / or MnO), manganese carbonate (MnCO) ３ ), nickel hydroxide (Ni(OH) ２ ), nickel oxide (NiO ２ ), cobalt hydroxide (Co(OH) ２ ), cobalt oxide (Co ２ O ３ ), ruthenium oxide (RuO ２ ), iron oxide (Fe ２ O ３ ), titanium oxide (TiO ２ ), vanadium oxide (V ２ O ３ ), molybdenum dioxide (MoO ２ ) etc. can be used.

[0143] Next, the lithium source and the M source are mixed. Performing a grinding step during mixing is useful for reducing the particle size. It is preferable to use a bead mill and / or a ball mill for the grinding step. A planetary ball mill can be used as the ball mill. Either a dry or wet ball mill may be used.

[0144] Next, the first mixture prepared above is heated. The heating temperature can be, for example, 900°C to 1200°C. The heating time can be, for example, 15 minutes to 10 hours. Layered rock salt type Li ｘ M ２−ｘ O ２ When preparing it, it is preferable to heat it in an oxygen-containing atmosphere. Irregular rock salt type Li ｘ M ２−ｘ O ２ When preparing it, it is preferable to heat it in an inert atmosphere such as argon or nitrogen.

[0145] It is preferable to perform a crushing step after the heating step to further reduce the particle size. It is preferable to use a bead mill, ball mill, and / or mixer for the crushing step.

[0146] Next, prepare the source of additive elements. In this specification, the term "additive elements" is synonymous with "mixture" or "part of the raw materials." The additive element source can be individual additive elements or compounds of additive elements.

[0147] When magnesium is used as an additive element, magnesium oxide (MgO) and / or magnesium fluoride (MgF) should be used as the magnesium source. ２ ) etc. can be used. When fluorine is used as an additive element, the fluorine source is preferably a fluoride of a typical metal element, such as lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF) and / or magnesium fluoride (MgF). ２ ) etc. can be used. Given that it will be used in lithium-ion secondary batteries, lithium fluoride is particularly preferred as the fluorine source.

[0148] These fluorides of typical metal elements can function as fluxes in the subsequent heating process, promoting the diffusion and doping of additive elements in the barrier film 100a. Mixtures containing fluorides are preferred because their melting point is lower than the decomposition temperature of lithium-rich cathode active material particles and they are also safer.

[0149] Furthermore, since fluorine may be lost due to volatilization or other factors after functioning as a flux, even if fluorine is added as an additive element, it is possible that fluorine may not be detected in the positive electrode active material particles 100 after fabrication.

[0150] Next, lithium-rich cathode active material particles and an additive element source are mixed to prepare a second mixture.

[0151] Next, the second mixture is heated. If the heating temperature is too low, doping with the additive elements may become uneven and / or insufficient. Therefore, a heating temperature of 500°C or higher is preferable, and 700°C or higher is more preferable. On the other hand, if the temperature is too high, the lithium-rich cathode active material particles may decompose due to thermal decomposition, so a heating temperature of 1050°C or lower is preferable. Furthermore, to suppress the volatilization of fluorides, including LiF, a temperature of 900°C or lower is more preferable.

[0152] Shorter heating times generally lead to higher productivity, but if they are too short, the diffusion and doping of the added elements may be insufficient. A heating time of, for example, between 2 and 10 hours is preferable.

[0153] In the heating process, the lithium-rich positive electrode active material particles and the additive element source partially melt, and the additive elements, including magnesium, are effectively diffused and doped. Because of the partial melting, the crystal structure of the barrier film 100a is influenced by the crystal structure of the core 100b, and the crystal structures of the barrier film 100a and the core 100b are approximately identical. The barrier film 100a formed in this way stabilizes the crystal structure of the surface and bulk of the positive electrode active material particles 100. Therefore, changes in the crystal structure of the positive electrode active material particles 100 during charging and / or the release of oxygen can be suppressed.

[0154] Note that the optimal heating temperature and heating time may vary depending on the particle size of the lithium-rich positive electrode active material particles.

[0155] Through the above process, positive electrode active material particles 100 can be produced.

[0156] [Manufacturing Method 2] In Manufacturing Method 1, lithium-rich cathode active material particles were synthesized and then additive elements were added and heated. However, the manufacturing method of cathode active material particles according to one embodiment of the present invention is not limited to this. Additive elements may be added at other times, or added multiple times. The timing may be changed depending on the element. Manufacturing Method 2 describes an example in which additive elements are added at different timings than in Manufacturing Method 1.

[0157] In manufacturing method 2, lithium-rich cathode active material particles, i.e., Li ｘ M ２−ｘ O ２Additive elements are added in the process of producing a composite oxide represented by (M being one or more selected from Mn, Ni, Co, Cr, Mo, Nb, V, Fe, Ti, and Ru, 1 < x < 2). In other words, the lithium source, M source, and additive element source are mixed and heated to synthesize the oxide. Even in such a production process, it is possible to make the barrier film 100a contain a large amount of the additive element by using the additive element and heating conditions. For example, by using an additive element with a low solid solubility limit in lithium-rich cathode active material particles, a barrier film 100a containing a large amount of the additive element can be formed.

[0158] Except for the timing of adding the additive elements, you can refer to Method 1 of the preparation process.

[0159] This embodiment can be appropriately combined with the contents of other embodiments.

[0160] (Embodiment 3) In this embodiment, the configuration of the lithium-ion secondary battery will be described.

[0161] [Positive Electrode] The positive electrode comprises a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer has positive electrode active material particles and may further have at least one of a conductive additive and a binder. The positive electrode active material particles can be those described in the previous embodiment.

[0162] Alternatively, the positive electrode active material particles described in the previous embodiment may be mixed with other positive electrode active material particles and used together.

[0163] Other positive electrode active material particles include composite oxides having olivine-type crystal structures, layered rock salt-type crystal structures, or spinel-type crystal structures. For example, LiFePO ４ LiFeO ２ LiNiO ２ LiMn ２ O ４ , V ２ O ５ , Cr ２ O ５ MnO ２ Examples of such compounds include the following.

[0164] In addition, LiMn is used as another positive electrode active material particle. ２ O ４Lithium-containing materials having a spinel-type crystal structure containing manganese, etc., are treated with lithium nickelate (LiNiO2). ２ Or LiNi １−ｘ M ｘ O ２ It is preferable to mix (0 < x < 1) (M = Co, Al, etc.). By using this configuration, the characteristics of the secondary battery can be improved.

[0165] In addition, as other positive electrode active material particles, the composition formula Li ａ Mn ｂ M ｃ O ｄ A lithium manganese composite oxide can be used, which can be represented as follows: Here, element M is preferably a metallic element selected from lithium and manganese, or silicon or phosphorus, and more preferably nickel. Furthermore, when measuring the entire particle of the lithium manganese composite oxide, it is preferable that 0 < a / (b+c) < 2, c > 0, and 0.26 ≤ (b+c) / d < 0.5 are satisfied during discharge. The composition of metals, silicon, phosphorus, etc., of the entire particle of the lithium manganese composite oxide can be measured, for example, using ICP-MS (inductively coupled plasma mass spectrometer). The oxygen composition of the entire particle of the lithium manganese composite oxide can be measured, for example, using EDX (energy dispersive X-ray spectrometry). It can also be determined by using molten gas analysis and valence evaluation of XAFS (X-ray absorption fine structure) analysis in combination with ICPMS analysis. Lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may also contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, and phosphorus.

[0166] Figure 3A shows an example of a schematic diagram of the cross-section of the positive electrode.

[0167] The current collector 550 can be made of, for example, metal foil. The positive electrode can be formed by applying a slurry to the metal foil and drying it. Pressing may also be applied after drying. The positive electrode is formed by forming an active material layer on the current collector 550.

[0168] A slurry is a liquid material used to form an active material layer on the current collector 550, and it contains an active material, a binder, and a solvent, preferably further mixed with a conductive additive. The slurry is also sometimes called an electrode slurry or an active material slurry, and when forming a positive electrode active material layer, it is called a positive electrode slurry, and when forming a negative electrode active material layer, it is sometimes called a negative electrode slurry.

[0169] The positive electrode active material particles 561 have the function of taking in and / or releasing lithium ions during charging and discharging. In one embodiment of the present invention, the positive electrode active material particles 561 can be made of a material that does not degrade much during charging and discharging, even at high charging voltages.

[0170] The positive electrode active material particles 561 used in one embodiment of the present invention can be any material that exhibits little degradation during charging and discharging, even at high charging voltages, and those described in Embodiment 1 can be used. Furthermore, the positive electrode active material particles 561 can be made from two or more materials with different particle sizes, as long as they exhibit little degradation during charging and discharging, even at high charging voltages.

[0171] Conductive additives, also called conductivity imparters or conductive materials, can be made of carbon. By attaching a conductive additive between multiple active materials, the multiple active materials are electrically connected to each other, increasing conductivity. In this specification, "attachment" does not only refer to physical contact between the active materials and the conductive additive, but also includes cases where covalent bonding occurs, bonding occurs due to van der Waals forces, the conductive additive covers a portion of the surface of the active materials, the conductive additive fits into surface irregularities of the active materials, or where they are electrically connected even without physical contact.

[0172] Specific examples of carbon materials that can be used as conductive additives include carbon black (furnace black, acetylene black, graphite, etc.).

[0173] Figure 3A shows carbon black 553 as a conductive additive.

[0174] As the positive electrode of a lithium-ion secondary battery, a binder (resin) may be mixed to fix the current collector 550, such as metal foil, and the active material. The binder is also called a binding agent. The binder is a polymer material, and if a large amount of binder is included, the proportion of active material in the positive electrode decreases, reducing the discharge capacity of the lithium-ion secondary battery. Therefore, it is preferable to mix in the minimum amount of binder. In Figure 3A, the areas not filled with positive electrode active material particles 561, the second active material 562, and carbon black 553 refer to voids or binder.

[0175] Although Figure 3A shows an example in which the positive electrode active material particles 561 are spherical, the figure is not particularly limited. For example, the cross-sectional shape of the positive electrode active material particles 561 may be elliptical, rectangular, trapezoidal, conical, a polygon with rounded corners, or asymmetrical. For example, Figure 3B shows an example in which the positive electrode active material particles 561 have a polygonal shape with rounded corners.

[0176] Furthermore, in the positive electrode of Figure 3B, graphene 554 is used as the carbon material used as a conductive additive. Figure 3B shows a positive electrode active material layer having positive electrode active material particles 561, graphene 554, and carbon black 553 formed on the current collector 550.

[0177] In the step of mixing graphene 554 and carbon black 553 to obtain an electrode slurry, it is preferable that the weight of the carbon black to be mixed be 1.5 times or more and 20 times or less the weight of the graphene, preferably 2 times or more and 9.5 times or less.

[0178] Furthermore, when the mixture of graphene 554 and carbon black 553 is within the above range, the dispersion stability of carbon black 553 is excellent during slurry preparation, and aggregation is less likely to occur. Also, when the mixture of graphene 554 and carbon black 553 is within the above range, a higher electrode density can be achieved compared to a positive electrode using only carbon black 553 as a conductive additive. By increasing the electrode density, the volume per unit weight can be increased. Specifically, the density of the positive electrode active material layer measured by gravimetric measurement can be 3.5 g / cc or higher.

[0179] Furthermore, although the electrode density is lower compared to positive electrodes using only graphene as a conductive additive, rapid charging can be achieved by using the above-mentioned range for the mixture of the first carbon material (graphene) and the second carbon material (acetylene black). For this reason, it is particularly effective when used as a lithium-ion secondary battery for automobiles.

[0180] Figure 3C illustrates an example of a cathode using carbon fiber 555 instead of graphene. Figure 3C shows a different example from Figure 3B. Using carbon fiber 555 prevents aggregation of carbon black 553 and improves dispersibility.

[0181] In Figure 3C, the areas not filled with positive electrode active material particles 561, carbon fibers 555, and carbon black 553 represent voids or binders.

[0182] Furthermore, Figure 3D illustrates another example of a positive electrode. Figure 3C shows an example in which carbon fiber 555 is used in addition to graphene 554. Using both graphene 554 and carbon fiber 555 can prevent aggregation of carbon black such as carbon black 553 and further improve dispersibility.

[0183] In Figure 3D, the areas not filled with positive electrode active material particles 561, carbon fibers 555, graphene 554, and carbon black 553 represent voids or binders.

[0184] A lithium-ion secondary battery can be manufactured by using one of the positive electrodes shown in Figures 3A to 3D, placing a separator on top of the positive electrode, and placing the resulting laminate on top of the separator, then placing it in a container (such as an outer casing or metal can), and filling the container with a liquid electrolyte.

[0185] <Binder> As a binder, it is preferable to use rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene-propylene-diene copolymer. Fluororubber can also be used as a binder. The above rubber materials can be dispersed in a dispersion medium and used. As a dispersion medium, one or more of the following can be used: water, N-methylpyrrolidone (NMP), methanol, ethanol, acetone, tetrahydrofuran (THF), dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0186] Furthermore, a water-soluble polymer can be used as a binder. Examples of water-soluble polymers include polysaccharides. Examples of polysaccharides include cellulose derivatives such as carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, diacetylcellulose, and regenerated cellulose, or starch. It is also preferable to use these water-soluble polymers in combination with the aforementioned rubber material.

[0187] Alternatively, materials such as polystyrene, methyl polyacrylate, 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 polymer, polyvinyl acetate, and nitrocellulose may be used as binders.

[0188] You may use a combination of several of the binders mentioned above.

[0189] When a binder covers or is in contact with the surface of the active material, it is expected to act as a passivation film, suppressing the decomposition of the electrolyte. Here, a "passivation film" is a film that does not conduct electricity, or has extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, the decomposition of the electrolyte can be suppressed at the battery reaction potential. Furthermore, it is even more desirable for the passivation film to suppress electrical conductivity while still allowing lithium ions to conduct.

[0190] <Positive Electrode Current Collector> As the current collector, highly conductive materials such as stainless steel, gold, platinum, aluminum, titanium, and alloys thereof can be used. Furthermore, it is preferable that the material used for the positive electrode current collector does not dissolve at the potential of the positive electrode. In addition, aluminum alloys to which elements that improve heat resistance, such as silicon, titanium, neodymium, scandium, and molybdenum, have been added can be used. Alternatively, it may be formed from a metallic element that reacts with silicon to form a silicide. Metallic elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The current collector can be in various shapes such as foil, plate, sheet, mesh, perforated metal, or expanded metal as appropriate. The current collector should preferably have a thickness of 5 μm or more and 30 μm or less.

[0191] [Negative electrode] The negative electrode comprises a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also contain a negative electrode active material, a conductive additive, and a binder.

[0192] <Negative electrode active material> As the negative electrode active material, for example, alloy materials and / or carbon materials can be used.

[0193] The carbon material used for the negative electrode active material may be one or more selected from graphite, easily graphitizable carbon (soft carbon), difficult-to-graphitize carbon (hard carbon), carbon fibers (carbon nanotubes), graphene, carbon black, etc.

[0194] Graphite can be artificial graphite or natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spheroidal graphite having a spherical shape can be used as the artificial graphite. For example, MCMB may have a spherical shape and is therefore preferable. Furthermore, MCMB is relatively easy to reduce its surface area and is therefore preferable in some cases. Examples of natural graphite include flake graphite and spheroidized natural graphite.

[0195] Graphite exhibits a potential as low as lithium metal (0.05V to 0.3V vs. Li / Li) when lithium ions are inserted into it (during the formation of lithium-graphite intercalation compounds). ＋ This allows lithium-ion secondary batteries using graphite to exhibit a high operating voltage. Furthermore, graphite is preferable because it has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and higher safety compared to lithium metal.

[0196] Furthermore, the negative electrode active material can be an element capable of undergoing charge-discharge reactions through alloying and dealloying reactions with lithium. For example, one or more materials selected from silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc., can be used. Such elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4200 mAh / g. Compounds containing these elements may also be used. For example, SiO, Mg ２ Si, Mg ２ Ge, SnO, SnO ２ Mg ２ Sn, SnS ２ , V ２ Sn ３ FeSn ２ CoSn ２ Ni ３ Sn ２ ,Cd ６ Sn ５ Ag ３ Sn, Ag ３ Sb, Ni ２ MnSb, CeSb３ LaSn ３ La ３ Co ２ Sn ７ CoSb ３ Examples include InSb and SbSn. Here, elements capable of undergoing charge-discharge reactions through alloying and de-alloying reactions with lithium, and compounds containing such elements, are sometimes referred to as alloying materials.

[0197] In this specification, "SiO" refers to silicon monoxide, for example. Alternatively, SiO refers to SiO ｘ It can also be expressed as follows. Here, x preferably has a value of 1 or a value in the vicinity of 1. For example, x is preferably between 0.2 and 1.5, and preferably between 0.3 and 1.2.

[0198] Furthermore, titanium dioxide (TiO) is used as the negative electrode active material. ２ ), lithium titanium oxide (Li ４ Ti ５ O １２ ), lithium-graphite intercalation compound (Li ｘ C ６ ), niobium pentoxide (Nb ２ O ５ ), tungsten dioxide (WO ２ ), molybdenum dioxide (MoO ２ One or more oxides selected from the following can be used.

[0199] Furthermore, as the negative electrode active material, lithium and a nitride of a transition metal, Li ３ Li with an N-type structure ３−ｘ M ｘ N (M = Co, Ni, Cu) can be used. For example, Li ２．６ Co ０．４ N has a large discharge capacity (900 mAh / g, 1890 mAh / cm²). ３ ) indicates a preference.

[0200] When lithium and transition metal nitrides are used, lithium ions are contained in the negative electrode active material, so the positive electrode active material particles do not contain lithium ions. ２ O ５ , Cr ３ O ８It is preferable that it be combined with materials such as the above. Furthermore, even when a material containing lithium ions is used for the positive electrode active material particles, lithium and a nitride of a transition metal can be used as the negative electrode active material by desorbing the lithium ions contained in the positive electrode active material particles in advance.

[0201] Furthermore, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example, transition metal oxides that do not form alloys with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), may be used as the negative electrode active material. As for materials that undergo a conversion reaction, Fe ２ O ３ ,CuO,Cu ２ O, RuO ２ , Cr ２ O ３ Oxides such as CoS ０．８９ , sulfides such as NiS and CuS, Zn ３ N ２ ,Cd ３ N, Ge ３ N ４ Nitrides such as NiP ２ FeP ２ CoP ３ Phosphates such as FeF ３ BiF ３ This can also occur with fluorides such as these.

[0202] Furthermore, multiple negative electrode active materials may be used in combination; for example, a negative electrode active material mixed with graphite and silicon particles may be used. Silicon particles refer to silicon powder used as a material for the negative electrode active material of a lithium-ion secondary battery, and the average particle size of the particle size distribution, i.e., the average particle diameter, is around 100 nm, and are sometimes called nanosilicon particles. It is preferable to grind the silicon raw material and adjust the particle size to a uniform particle size. The silicon particles may contain at least one of silicon, silicon oxide, or silicon alloy. While laser diffraction particle size distribution measurement is typically used to measure particle size, the method is not limited to laser diffraction particle size distribution measurement, and the major axis of the particle cross-section may be measured by analysis such as SEM (scanning electron microscope) or TEM (transmission electron microscope).

[0203] Furthermore, the same materials as those used for the conductive additive and binder in the positive electrode active material layer can be used for the conductive additive and binder in the negative electrode active material layer.

[0204] <Negative Electrode Current Collector> In addition to the same materials as the positive electrode current collector, copper and other materials can also be used for the negative electrode current collector. It is preferable to use a material for the negative electrode current collector that does not alloy with carrier ions such as lithium.

[0205] [Electrolyte] The electrolyte contains an organic solvent, but the organic solvent of the electrolyte in one aspect of the present invention is not limited to being a liquid at 25°C, but may be a solid at 25°C or a semi-solid at room temperature. Furthermore, while it is preferable that the organic solvent of the electrolyte in one aspect of the present invention be a liquid over a wide temperature range including below freezing point and high temperatures, it is not limited to this. The organic solvent may be a liquid, a solid, or a semi-solid over a wide temperature range including below freezing point and high temperatures.

[0206] As the organic solvent, aprotic organic solvents are preferred, and for example, one of the following can be used: ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 1,3-propanesultone (PS), fluoroethylene carbonate (FEC), methyl 3,3,3-trifluoropropionate (MTFP), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., or two or more of these can be used in any combination and ratio.

[0207] Because PS has HOMO and LUMO levels equivalent to EC and DEC, it is not easily oxidized or reduced even at high cutoff voltages, and when it decomposes on the surface of the positive electrode active material particles, it tends to become a polymer. Therefore, it has the advantage of having a small molecular weight decomposition product that is less likely to gasify. For this reason, the electrolyte preferably contains 0.1 wt% to 10 wt% PS, and more preferably 0.25 wt% to 7.5 wt% PS.

[0208] FEC is a cyclic carbonate with a high dielectric constant, and when used in organic solvents, it promotes the dissociation of lithium salts. On the other hand, because FEC has electron-withdrawing substituents, desolvation with lithium ions proceeds more easily than with EC. Specifically, the solvation energy of lithium ions in FEC is lower than that of EC, which does not have electron-withdrawing substituents. Therefore, lithium ions are more easily released from the surface of the positive electrode active material particles and the negative electrode active material, which can lower the internal resistance of the secondary battery. Furthermore, because FEC has a deep Highest Occupied Molecular Orbital (HOMO) level, it is less susceptible to oxidation, improving oxidation resistance. However, the high viscosity of FEC is a concern. Therefore, it is preferable to use a mixed organic solvent containing not only FEC but also MTFP as the electrolyte. MTFP is a type of linear carbonate that can lower the viscosity of the electrolyte or maintain the viscosity at room temperature (typically 25°C) even at low temperatures (typically 0°C). Furthermore, although MTFP has a lower solvation energy than methyl propionate (abbreviated as "MP") which does not have electron-withdrawing substituents, it may still generate solvation with lithium ions when used in an electrolyte. When using a mixed organic solvent containing both FEC and MTFP, the volume ratio is preferably y is 2 to 20, and more preferably 4 to 9, where FEC:MTFP = 1:y.

[0209] The organic solvents mentioned above contain particulate debris or molecules other than the constituent molecules of the organic solvent (hereinafter also simply referred to as "impurities"), and oxygen (O ２ ), water (H ２ It is preferable that the content of (O) or water is low and that the purity is high. It is also preferable that reaction by-products during synthesis are suppressed through appropriate purification. Specifically, the electrolyte impurities should be 100 ppm or less, preferably 50 ppm or less, and more preferably less than 10 ppm. The concentration of water among the impurities can be detected by Karl Fischer titration.

[0210] Furthermore, it is preferable that the above-mentioned organic solvent shows virtually no peaks attributable to impurities when measured by NMR or other methods. "Very virtually undetectable" means that the ratio of the integrated area of ​​the peaks attributable to impurities to the integrated area of ​​the peaks attributable to the main component (simply called the integral ratio) is 0.005 or less, preferably 0.002 or less. The apparatus used for NMR measurement is not particularly limited, but for example, Bruker's "AVANCE III 400" can be used. Also, in 1H-NMR measurement, the central peak among the five peaks of acetonitrile derived from acetonitrile-d3 used as the solvent can be set to 1.94 ppm.

[0211] For example, in the case of MTF, when 1H-NMR is measured using acetonitrile-d3 solvent, it is known that four peaks occur with δ between 3.29 ppm and 3.43 ppm. However, if other peaks occur in the vicinity of this, for example, if a peak occurs with δ between 3.24 ppm and 3.29 ppm, that peak is considered to be due to impurities. Therefore, if the ratio (integral ratio) of the peak area between 3.24 ppm and 3.29 ppm to the peak area between 3.29 ppm and 3.43 ppm is 0.005 or less, preferably 0.002 or less, it can be said that peaks due to impurities are almost not detectable.

[0212] Furthermore, by using one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the solvent for the electrolyte, it is possible to prevent the energy storage device from rupturing or catching fire even if the internal temperature rises due to an internal short circuit or overcharging. Ionic liquids consist of cations and anions, and include organic cations and anions. Examples of organic cations used in the electrolyte include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, as well as aromatic cations such as imidazolium cations and pyridinium cations. Examples of anions used in the electrolyte include monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkyl sulfonate anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, or perfluoroalkyl phosphate anions.

[0213] Furthermore, the electrolyte to be dissolved in the above solvent is, for example, LiPF ６ LiClO ４ LiAsF ６ LiBF ４ LiAlCl ４ , LiSCN, LiBr, LiI, Li ２ SO ４ Li ２ B １０ Cl １０ Li ２ B １２ Cl １２ LiCF ３ SO ３ LiC ４ F ９ SO ３ LiC (CF ３ SO ２ ) ３ LiC(C ２ F ５ SO ２ ) ３ ,LiN(CF ３ SO ２ ) ２ ,LiN(C ４ F ９ SO ２ ) (CF ３SO ２ ), LiN(C ２ F ５ SO ２ ) ２ Lithium bis(oxalate) borate (Li(C) ２ O ４ ) ２ Lithium salts such as LiBOB can be used individually, or two or more of these can be used in any combination and ratio.

[0214] It is preferable to use a highly purified electrolyte in which particulate matter or elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities") are present in small amounts. Specifically, it is preferable that the weight ratio of impurities to the electrolyte be 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

[0215] Alternatively, a polymer gel electrolyte, obtained by swelling a polymer with an electrolyte solution, may be used.

[0216] Using polymer gel electrolytes enhances safety against leakage and other issues. Furthermore, it enables the secondary battery to be made thinner and lighter.

[0217] As the polymer to be gelled, silicone gels, acrylic gels, acrylonitrile gels, polyethylene oxide gels, polypropylene oxide gels, fluorine-based polymer gels, etc., can be used. For example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and copolymers containing them can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. Furthermore, the formed polymer may have a porous structure.

[0218] Furthermore, as the electrolyte, a solid electrolyte containing inorganic materials such as sulfide-based or oxide-based materials, or a solid electrolyte containing polymeric materials such as PEO (polyethylene oxide)-based materials can be used. When a solid electrolyte is used, the installation of separators or spacers becomes unnecessary. In addition, since the entire battery can be solidified, the risk of leakage is eliminated, and safety is dramatically improved.

[0219] [Separator] When the electrolyte contains a liquid electrolyte (also called an electrolyte solution), a separator is placed between the positive electrode and the negative electrode. As a separator, for example, materials such as paper and other cellulose fibers, nonwoven fabrics, glass fibers, ceramics, or synthetic fibers made of nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polypropylene (indicated as PP), polyimide (indicated as PI), polyester, acrylic, polyolefin, polyurethane can be used. Polyimide is particularly preferable as a separator because it has excellent heat resistance and chemical resistance, and its use can improve the safety of secondary batteries. The porosity of the separator film thickness can be 35% to 90%, preferably 60% to 85%. A separator made of polypropylene can have a porosity of 35% to 45%. A separator made of polyimide can have a porosity of 75% to 85%. The film thickness of the separator is preferably 10 μm to 80 μm, and more preferably 20 μm to 60 μm. Separators using polyimide can have a high porosity and can be made into thick films (typically with a film thickness of 50 μm to 60 μm), which is preferable.

[0220] It is preferable that the separator be processed into a bag shape and positioned to enclose either the positive or negative electrode.

[0221] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic material, a fluorine material, a polyamide material, or a mixture thereof. Examples of ceramic materials include aluminum oxide particles and silicon oxide particles. Examples of fluorine materials include PVDF and polytetrafluoroethylene. Examples of polyamide materials include nylon and aramid (meta-aramid, para-aramid).

[0222] By using a multilayer separator, the safety of the lithium-ion secondary battery can be maintained even if the overall thickness of the separator is thin, thus increasing the capacity per unit volume of the lithium-ion secondary battery.

[0223] [Outer Covering] For the outer covering of a lithium-ion secondary battery, metal materials such as aluminum or resin materials can be used. Alternatively, a film-like outer covering can be used. As a film, for example, a three-layer film can be used, in which a highly flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided on a film made of materials such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or polyester resin is provided on the metal thin film as the outer surface of the outer covering.

[0224] This embodiment can be used in combination with other embodiments.

[0225] (Embodiment 4) This embodiment describes an example of the form of a lithium-ion secondary battery.

[0226] [Laminated Lithium-Ion Secondary Battery] An example of the form of a laminated lithium-ion secondary battery 500 is shown in Figures 4A and 4B. Figures 4A and 4B are external views, and the lithium-ion secondary battery 500 has the electrolyte and separator (these are not shown in Figure 4) described in the above embodiment, a negative electrode 506, and a positive electrode 507. In the lithium-ion secondary battery 500, it is preferable that the negative electrode 506 has a larger area than the positive electrode 507. Furthermore, the lithium-ion secondary battery 500 has a negative electrode lead electrode 510 electrically connected to the negative electrode 506, and a positive electrode lead electrode 511 electrically connected to the positive electrode 507. The electrolyte layer, the negative electrode 506, and the positive electrode 507 are housed in an outer casing 509, and a part of the negative electrode lead electrode 510 and a part of the positive electrode lead electrode 511 protrude from the outer casing 509. A part of the outer circumference of the outer casing 509 has an adhesive region 508. Figure 4A shows an example configuration in which the negative lead electrode 510 and the positive lead electrode 511 protrude from the same side of the outer casing 509, and the adhesive region 508 is located at least on the side from which each lead electrode protrudes and on two sides adjacent to that side. Figure 4B shows an example configuration in which the side from which the negative lead electrode 510 protrudes from the outer casing 509 and the side from which the positive lead electrode 511 protrudes from the outer casing 509 are opposite each other, and the adhesive region 508 is located at least on the two sides from which each lead electrode protrudes and on the side sandwiched between those two sides. In Figures 4A and 4B, the sides where the adhesive region 508 is not located preferably correspond to the sides where the outer casing 509 is folded.

[0227] By using the positive electrode active material particles of the present invention in a laminate-type lithium-ion secondary battery 500, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0228] [Coin-type lithium-ion secondary battery] An example of a coin-type lithium-ion secondary battery is described below. Figure 5A is an exploded perspective view of a coin-type (single-layer flat type) lithium-ion secondary battery, Figure 5B is an external view, and Figure 5C is a cross-sectional view thereof. Coin-type lithium-ion secondary batteries are mainly used in small electronic devices. In this specification, the term "coin-type lithium-ion secondary battery" includes "button-type lithium-ion secondary battery."

[0229] Figure 5A is a schematic diagram to show the overlapping (upper and lower relationships and positional relationships) of the components for clarity. Therefore, Figures 5A and 5B are not perfectly identical corresponding diagrams.

[0230] Figure 5A shows how the positive electrode 304, negative electrode 307, spacer 342, and washer 332 are stacked and sealed by the negative electrode can 302 and positive electrode can 301. Note that the electrolyte and separator described in the above embodiment are not shown in Figure 5A. The spacer 342 and washer 332 are used to protect the inside or fix the position inside the can when the positive electrode can 301 and negative electrode can 302 are pressed together. The spacer 342 or washer 332 is made of stainless steel or an insulating material.

[0231] The positive electrode 304 is a laminated structure in which a positive electrode active material layer 306 is formed on a positive electrode current collector 305.

[0232] Figure 5B is a perspective view of the completed coin-type lithium-ion secondary battery 300.

[0233] The coin-type lithium-ion secondary battery 300 may have a positive electrode casing 301, which also serves as the positive electrode terminal, and a negative electrode casing 302, which also serves as the negative electrode terminal, 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 with it. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with it. The positive electrode casing 301 is electrically connected to the positive electrode 304, and the negative electrode casing 302 is electrically connected to the negative electrode 307.

[0234] Furthermore, it is preferable that the positive electrode 304 and negative electrode 307 used in the coin-type lithium-ion secondary battery 300 each have the active material layer formed on only one side.

[0235] As shown in Figure 5C, the positive electrode can 301 is placed at the bottom, and the positive electrode 304, negative electrode 307, and negative electrode can 302 are stacked in this order. The positive electrode can 301 and the negative electrode can 302 are then crimped together via a gasket 303 to manufacture a coin-shaped lithium-ion secondary battery 300.

[0236] By using the positive electrode active material particles of the present invention in a coin-type lithium-ion secondary battery 300, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0237] [Cylindrical Lithium-ion Secondary Battery] An example of a cylindrical lithium-ion secondary battery will be described with reference to Figure 6A. As shown in Figure 6A, the cylindrical lithium-ion secondary battery 616 has a positive electrode cap (battery cover) 601 on the top surface and a battery casing (outer casing) 602 on the sides and bottom. The positive electrode cap 601 and the battery casing (outer casing) 602 are insulated by a gasket (insulating packing) 610.

[0238] Figure 6B is a schematic diagram showing a cross-section of a cylindrical lithium-ion secondary battery. The cylindrical lithium-ion secondary battery shown in Figure 6B has a positive electrode cap (battery cover) 601 on the top surface and a battery casing (outer casing) 602 on the sides and bottom. The positive electrode cap and the battery casing (outer casing) 602 are insulated from each other by a gasket (insulating packing) 610.

[0239] Inside the hollow cylindrical battery can 602, a battery element is provided, in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with an electrolyte layer 605 in between. Although not shown, the battery element is wound around a central axis. The battery can 602 is closed at one end and open at the other end. Inside the battery can 602, the battery element, in which the positive electrode, negative electrode, and separator are wound, is sandwiched between a pair of opposing insulating plates 608 and 609. Furthermore, the inside of the battery can 602 in which the battery element is provided is filled with an electrolyte (not shown) according to one embodiment of the present invention.

[0240] Since the positive and negative electrodes used in cylindrical storage batteries are wound, it is preferable to form the active material on both sides of the current collector. Although Figures 6A to 6D illustrate a lithium-ion secondary battery 616 in which the height of the cylinder is greater than the diameter of the cylinder, the battery is not limited to this. A lithium-ion secondary battery in which the diameter of the cylinder is greater than the height of the cylinder is also possible. With such a configuration, for example, it is possible to miniaturize the lithium-ion secondary battery.

[0241] A positive electrode terminal (positive electrode current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collector lead) 607 is connected to the negative electrode 606. Aluminum can be used for the positive electrode terminal 603, and copper or other metal materials can be used for the negative electrode terminal 607. The positive electrode terminal 603 is resistance-welded to the safety valve mechanism 613, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 613 is electrically connected to the positive electrode cap 601 via a PTC element (Positive Temperature Coefficient) 611. The safety valve mechanism 613 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the internal pressure of the battery exceeds a predetermined threshold. The PTC element 611 is a thermosensitive resistance element whose resistance increases when the temperature rises, limiting the current and preventing abnormal heat generation. PTC elements include barium titanate (BaTiO ３ ) ceramic materials and the like can be used.

[0242] Figure 6C shows an example of an energy storage system 615. The energy storage system 615 has multiple lithium-ion secondary batteries 616 and is sometimes called a battery pack. The positive electrode of each lithium-ion secondary battery is in contact with a conductor 624 separated by an insulator 625 and is electrically connected. The conductor 624 is electrically connected to a control circuit 620 via wiring 623. The negative electrode of each lithium-ion secondary battery is also electrically connected to the control circuit 620 via wiring 626. The control circuit 620 can be a protective circuit to prevent overcharging or over-discharging, etc.

[0243] Figure 6D shows an example of an energy storage system 615. The energy storage system 615 has multiple lithium-ion secondary batteries 616, which are sandwiched between conductive plates 628 and 614. The multiple lithium-ion secondary batteries 616 are electrically connected to the conductive plates 628 and 614 by wiring 627. The multiple lithium-ion secondary batteries 616 may be connected in parallel, in series, or connected in parallel and then in series. By configuring an energy storage system 615 with multiple lithium-ion secondary batteries 616, a large amount of power can be extracted.

[0244] Multiple lithium-ion secondary batteries 616 may be connected in parallel and then further connected in series.

[0245] A temperature control device may be provided between the multiple lithium-ion secondary batteries 616. When a lithium-ion secondary battery 616 overheats, it can be cooled by the temperature control device, and when a lithium-ion secondary battery 616 becomes too cold, it can be heated by the temperature control device. This makes the performance of the energy storage system 615 less susceptible to the influence of ambient temperature.

[0246] Furthermore, in Figure 6D, the energy storage system 615 is electrically connected to the control circuit 620 via wiring 621 and wiring 622. Wiring 621 is electrically connected to the positive electrodes of the multiple lithium-ion secondary batteries 616 via conductive plate 628, and wiring 622 is electrically connected to the negative electrodes of the multiple lithium-ion secondary batteries 616 via conductive plate 614.

[0247] By using the positive electrode active material particles of the present invention in a cylindrical lithium-ion secondary battery 616, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0248] [Other structural examples of lithium-ion secondary batteries] Structural examples of lithium-ion secondary batteries will be explained using Figures 7 and 8.

[0249] The lithium-ion secondary battery 913 shown in Figure 7A has a wound body 950 with terminals 951 and 952 provided inside a housing 930. The wound body 950 is impregnated with an electrolyte according to one embodiment of the present invention inside the housing 930. Terminal 952 is in contact with the housing 930, while terminal 951 is not in contact with the housing 930 by using an insulating material or the like. In Figure 7A, the housing 930 is shown separated for convenience, but in reality, the wound body 950 is covered by the housing 930, and terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of a metal material (e.g., aluminum), a composite material of metal and resin, etc.

[0250] Furthermore, as shown in Figure 7B, the housing 930 shown in Figure 7A may be formed from multiple materials. For example, in the lithium-ion secondary battery 913 shown in Figure 7B, housing 930a and housing 930b are bonded together, and a winding body 950 is provided in the area surrounded by housing 930a and housing 930b.

[0251] An insulating material can be used for the housing 930a. In particular, by using a material such as organic resin on the surface where the antenna is formed, shielding of the electric field by the lithium-ion secondary battery 913 can be suppressed. If the shielding of the electric field by the housing 930a is small, the antenna may be provided inside the housing 930a. For the housing 930b, for example, a metal material can be used.

[0252] Furthermore, the structure of the wound body 950 is shown in Figure 7C. The wound body 950 has a negative electrode 931, a positive electrode 932, and an electrolyte layer 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked on top of each other with the electrolyte layer 933 in between, and the stacked sheet is wound up. Note that multiple stacks of the negative electrode 931, positive electrode 932, and electrolyte layer 933 may be stacked.

[0253] Alternatively, the lithium-ion secondary battery 913 may have a wound body 950a as shown in Figures 8A to 8C. The wound body 950a shown in Figure 8A has a negative electrode 931, a positive electrode 932, and an electrolyte layer 933. The negative electrode 931 has a negative electrode active material layer 931a. The positive electrode 932 has a positive electrode active material layer 932a.

[0254] The electrolyte layer 933 has a wider width than the negative electrode active material layer 931a and the positive electrode active material layer 932a, and is wound so as to overlap with the negative electrode active material layer 931a and the positive electrode active material layer 932a. Furthermore, it is preferable from a safety standpoint that the negative electrode active material layer 931a is wider than the positive electrode active material layer 932a. A wound body 950a of this shape is also preferable due to its good safety and productivity.

[0255] As shown in Figure 8B, the negative electrode 931 is electrically connected to terminal 951. Terminal 951 is electrically connected to terminal 911a. The positive electrode 932 is electrically connected to terminal 952. Terminal 952 is electrically connected to terminal 911b.

[0256] As shown in Figure 8C, the coiled body 950a is covered by the housing 930, forming a lithium-ion secondary battery 913. It is preferable to provide a safety valve, an overcurrent protection element, etc., in the housing 930. The safety valve is a valve that opens the inside of the housing 930 at a predetermined internal pressure in order to prevent the battery from rupturing.

[0257] As shown in Figure 8B, the lithium-ion secondary battery 913 may have multiple windings 950a. By using multiple windings 950a, a lithium-ion secondary battery 913 with a larger charge / discharge capacity can be made. Other elements of the lithium-ion secondary battery 913 shown in Figures 8A and 8B can be referenced from the description of the lithium-ion secondary battery 913 shown in Figures 7A to 7C.

[0258] By using the positive electrode active material particles of the present invention in a lithium-ion secondary battery 913 having a wound body, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0259] The contents of this embodiment can be appropriately combined with the contents of other embodiments.

[0260] (Embodiment 5) In this embodiment, an example of application to an electric vehicle (EV) is shown using Figure 9.

[0261] As shown in Figure 9A, the electric vehicle is equipped with a first battery 1301a, 1301b as the main lithium-ion secondary battery for propulsion, and a second battery 1311 that supplies power to the inverter 1312 for starting the motor 1304. By using the positive electrode active material particles of the present invention in the first batteries 1301a, 1301b, it is possible to create a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics.

[0262] The second battery 1311 is also called the cranking battery (or starter battery). The second battery 1311 only needs to be able to output high power, and does not require a large capacity, so the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

[0263] The internal structure of the first battery 1301a may be wound or stacked. Furthermore, the first battery 1301a may use the all-solid-state battery of Embodiment 6. Using the all-solid-state battery of Embodiment 6 for the first battery 1301a allows for higher capacity, improved safety, and miniaturization and weight reduction.

[0264] In this embodiment, an example is shown in which two first batteries 1301a and 1301b are connected in parallel, but three or more may be connected in parallel. Also, if the first battery 1301a can store sufficient power, the first battery 1301b may not be necessary. By configuring a battery pack having multiple lithium-ion secondary batteries, a large amount of power can be extracted. Multiple lithium-ion secondary batteries may be connected in parallel, in series, or connected in parallel and then in series. Multiple lithium-ion secondary batteries are also called a battery pack.

[0265] Furthermore, the lithium-ion secondary battery for use in vehicles has a service plug or circuit breaker that can cut off high voltage without using tools in order to cut off power from multiple lithium-ion secondary batteries, and is provided on the first battery 1301a.

[0266] Furthermore, the power from the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but also supplies power to 42V onboard components (electric power steering 1307, heater 1308, defogger 1309, etc.) via the DC / DC circuit 1306. Even when there is a rear motor 1317 on the rear wheels, the first battery 1301a is used to rotate the rear motor 1317.

[0267] Furthermore, the second battery 1311 supplies power to 14V automotive components (audio system 1313, power windows 1314, lights 1315, etc.) via the DC / DC circuit 1310.

[0268] Furthermore, the first battery 1301a will be explained using Figure 9B.

[0269] Figure 9B shows an example where nine rectangular lithium-ion secondary batteries 1300 are arranged in a single battery pack 1415. In this example, nine rectangular lithium-ion secondary batteries 1300 are connected in series, with one electrode fixed by an insulating fixing part 1413 and the other electrode fixed by an insulating fixing part 1414. While this embodiment shows an example of fixing with fixing parts 1413 and 1414, the batteries may also be housed in a battery housing box (also called a casing). Since vehicles are expected to be subjected to vibrations or shaking from external sources (such as the road surface), it is preferable to fix multiple lithium-ion secondary batteries using fixing parts 1413, 1414 and a battery housing box. Furthermore, one electrode is electrically connected to the control circuit unit 1320 by wiring 1421, and the other electrode is electrically connected to the control circuit unit 1320 by wiring 1422.

[0270] Furthermore, the control circuit unit 1320 may also use a memory circuit that includes a transistor made of an oxide semiconductor. A charging control circuit or battery control system having a memory circuit that includes a transistor made of an oxide semiconductor may be referred to as BTOS (Battery operating system or Battery oxide semiconductor).

[0271] It is preferable to use a metal oxide that functions as an oxide semiconductor. For example, as the oxide, a metal oxide such as In-M-Zn oxide (where element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or magnesium) is preferable. In particular, the In-M-Zn oxide that can be used as the oxide is preferably CAAC-OS (C-Axis Aligned Crystal Oxide Semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor). Alternatively, In-Ga oxide or In-Zn oxide may be used as the oxide. CAAC-OS is an oxide semiconductor having multiple crystalline regions, the c-axis of which is oriented in a specific direction. This specific direction is the thickness direction of the CAAC-OS film, the normal direction to the surface on which the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film. A crystalline region is a region with periodic atomic arrangement. If the atomic arrangement is considered a lattice arrangement, then a crystalline region is also a region with a aligned lattice arrangement. Furthermore, CAAC-OS has regions where multiple crystalline regions are connected in the a-b plane direction, and these regions may exhibit distortion. Distortion refers to a point in the region where multiple crystalline regions are connected where the orientation of the lattice arrangement changes between a region with a aligned lattice arrangement and another region with a aligned lattice arrangement. In short, CAAC-OS is an oxide semiconductor that is c-axis oriented and does not exhibit clear orientation in the a-b plane direction.

[0272] Furthermore, since it can be used in low-temperature environments, it is preferable that the control circuit section 1320 uses a transistor made of an oxide semiconductor. To simplify the process, the control circuit section 1320 may also be formed using a unipolar transistor. Transistors using an oxide semiconductor in the semiconductor layer have an operating ambient temperature range of -40°C to 150°C, which is wider than that of single-crystal Si, and the change in characteristics is smaller than that of single crystal even when the lithium-ion secondary battery is heated. The off-current of a transistor using an oxide semiconductor is below the lower limit of measurement regardless of temperature, even at 150°C, but the off-current characteristics of a single-crystal Si transistor are highly temperature-dependent. For example, at 150°C, the off-current of a single-crystal Si transistor increases, and the current on / off ratio does not become sufficiently large. The control circuit section 1320 can improve safety.

[0273] The control circuit unit 1320, which uses a memory circuit including an oxide semiconductor transistor, can also function as an automatic control device for lithium-ion secondary batteries to address 10 causes of instability, such as micro-short circuits. Functions to eliminate the 10 causes of instability include overcharge prevention, overcurrent prevention, overheat control during charging, cell balancing in the battery pack, over-discharge prevention, remaining charge indicator, automatic control of charging voltage and current according to temperature, charging current control according to the degree of degradation, detection of abnormal behavior related to micro-short circuits, and prediction of abnormalities related to micro-short circuits. The control circuit unit 1320 has at least one of these functions. Furthermore, it is possible to miniaturize the automatic control device for lithium-ion secondary batteries.

[0274] Furthermore, a microshort refers to a tiny short circuit inside a lithium-ion secondary battery. One of the causes of microshorts is said to be that, due to multiple charge-discharge cycles, the uneven distribution of positive electrode active material particles causes localized current concentration in parts of the positive electrode and parts of the negative electrode, or that micro-short circuits occur due to the generation of by-reactants from side reactions.

[0275] Furthermore, in addition to detecting micro-shorts, the control circuit unit 1320 also detects the terminal voltage of the lithium-ion secondary battery and manages the charging and discharging state of the lithium-ion secondary battery. For example, to prevent overcharging, both the output transistor and the cutoff switch of the charging circuit can be turned off almost simultaneously.

[0276] Furthermore, an example of a block diagram of the battery pack 1415 shown in Figure 9B is shown in Figure 9C.

[0277] The control circuit unit 1320 includes at least a switch to prevent overcharging, a switch unit 1324 including a switch to prevent over-discharging, a control circuit 1322 that controls the switch unit 1324, and a voltage measurement unit for the first battery 1301a. The control circuit unit 1320 has upper and lower voltage limits set for the lithium-ion secondary battery used, and limits the upper limit of external current and the upper limit of output current to the outside. Within the range between the lower voltage and upper voltage of the lithium-ion secondary battery, it is within the voltage range for which use is recommended, and if it goes outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit unit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent over-discharge and overcharge. For example, if the control circuit 1322 detects a voltage that is likely to cause overcharging, it cuts off the current by turning off the switch of the switch unit 1324. Furthermore, a PTC element may be provided in the charge / discharge path to provide a function to cut off the current in response to the rise in temperature. Furthermore, the control circuit unit 1320 has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0278] The switch unit 1324 can be constructed by combining an n-channel transistor and a p-channel transistor. The switch unit 1324 is not limited to a switch having a Si transistor using single-crystal silicon, but for example, Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaO ｘThe switch section 1324 may be formed using a power transistor having (gallium oxide; x is a real number greater than 0), etc. Furthermore, since memory elements using OS transistors can be freely arranged by stacking them on circuits using Si transistors, integration can be easily achieved. By stacking a control circuit section 1320 using OS transistors on the switch section 1324 and integrating them, it is possible to create a single chip, enabling miniaturization.

[0279] The first batteries 1301a and 1301b primarily supply power to 42V (high-voltage) onboard equipment, while the second battery 1311 supplies power to 14V (low-voltage) onboard equipment. Lead-acid batteries are often used for the second battery 1311 due to cost advantages. While using a lithium-ion secondary battery for the second battery 1311 offers the advantage of being maintenance-free, prolonged use, such as more than three years, may lead to malfunctions that could not be detected during manufacturing. In particular, if the second battery 1311, which starts the inverter, becomes inoperable, the motor may not be able to start even if the first batteries 1301a and 1301b have remaining capacity. To prevent this, if the second battery 1311 is a lead-acid battery, power is supplied from the first battery to the second battery to keep it constantly fully charged.

[0280] In this embodiment, an example is shown in which lithium-ion secondary batteries are used for both the first battery 1301a and the second battery 1311. However, the second battery 1311 may be a lead-acid battery, an all-solid-state battery, or an electric double-layer capacitor. By using the positive electrode active material particles of the present invention in the lithium-ion secondary battery described above, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0281] Furthermore, the regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305 and charged to the second battery 1311 via the control circuit unit 1321 from the motor controller 1303 and battery controller 1302. Alternatively, it is charged to the first battery 1301a via the control circuit unit 1320 from the battery controller 1302. Alternatively, it is charged to the first battery 1301b via the control circuit unit 1320 from the battery controller 1302. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b are capable of rapid charging.

[0282] The battery controller 1302 can set the charging voltage and charging current of the first batteries 1301a and 1301b. The battery controller 1302 can set the charging conditions according to the charging characteristics of the lithium-ion secondary battery used and enable rapid charging.

[0283] Although not shown in the diagram, when connected to an external charger, the charger's outlet or connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger is charged to the first batteries 1301a and 1301b via the battery controller 1302. In some cases, the charger may have a control circuit and may not use the functions of the battery controller 1302, but it is preferable to charge the first batteries 1301a and 1301b via the control circuit unit 1320 to prevent overcharging. In some cases, the connection cable or the charger's connection cable may also have a control circuit. The control circuit unit 1320 is sometimes called an ECU (Electronic Control Unit). The ECU is connected to a CAN (Controller Area Network) installed in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. The ECU also includes a microcomputer. The ECU uses a CPU or GPU.

[0284] External chargers installed in charging stands, etc. include 100V outlets, 200V outlets, three-phase 200V and 50kW, etc. It is also possible to receive power supply from external charging equipment by means of non-contact power supply or the like and charge the battery.

[0285] Next, an example of mounting a lithium-ion secondary battery, which is one aspect of the present invention, on a vehicle, typically a transportation vehicle, will be described.

[0286] In addition, when a lithium-ion secondary battery is mounted on a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV) can be realized. It is also possible to mount a lithium-ion secondary battery on transportation vehicles such as agricultural machinery, motorized bicycles including electric assist bicycles, motorcycles, electric wheelchairs, electric carts, small or large ships, submarines, aircraft such as fixed-wing aircraft and rotary-wing aircraft, rockets, artificial satellites, space exploration vehicles, planetary exploration vehicles, and spacecraft.

[0287] In FIGS. 10A to 10D, a transportation vehicle using one aspect of the present invention is illustrated. The automobile 2001 shown in FIG. 10A is an electric vehicle that uses an electric motor as a power source for running. Alternatively, it is a hybrid vehicle that can appropriately select and use an electric motor and an engine as power sources for running. When a lithium-ion secondary battery is mounted on a vehicle, an example of the lithium-ion secondary battery shown in the above embodiment is installed at one or more locations. By using the positive electrode active material particles of the present invention for the lithium-ion secondary battery mounted on the vehicle, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0288] The automobile 2001 shown in FIG. 10A has a battery pack 2200, and the battery pack has a battery module to which a plurality of lithium-ion secondary batteries are connected. Further, it is preferable that the battery pack 2200 has a charge control device electrically connected to the battery module.

[0289] In addition, the motor vehicle 2001 can be charged by receiving power supply from an external charging facility by a plug-in method, a non-contact power supply method, or the like to the lithium-ion secondary battery included in the motor vehicle 2001. When charging, the charging method, the standard of the connector, etc. may be appropriately performed in a predetermined method such as CHAdeMO (registered trademark) or Combo. As the external charging facility, a charging station provided in a commercial facility, a household power supply, or the like can be used. For example, by the plug-in technology, the power storage device mounted on the motor vehicle 2001 can be charged by external power supply. Charging can be performed by converting AC power into DC power via a conversion device such as an AC / DC converter.

[0290] Although not shown, a power receiving device can also be mounted on the vehicle to supply power non-contact from a power transmission device on the ground for charging. In the case of this non-contact power supply method, by incorporating the power transmission device into a road or an outer wall, charging can be performed not only while the vehicle is stopped but also while it is running. Also, power transmission and reception can be performed between two vehicles using this non-contact power supply method. Furthermore, a solar cell can be provided on the exterior of the vehicle to charge the lithium-ion secondary battery when the vehicle is stopped and when it is running. For such non-contact power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0291] FIG. 10B shows a large transport vehicle 2002 having an electrically controlled motor as an example of a transport vehicle. The battery module of the transport vehicle 2002 has, for example, four lithium-ion secondary batteries with a nominal voltage of 3.0 V or more and 5.0 V or less as cell units, and a maximum voltage of 170 V with 48 cells connected in series. Since it has the same function as the battery pack shown in FIG. 9B except that the number of lithium-ion secondary batteries in the battery pack 2201 is different, the description thereof is omitted. By using the positive electrode active material particles of the present invention for the lithium-ion secondary battery of the battery pack 2201, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0292] Figure 10C shows, as an example, a large transport vehicle 2003 equipped with an electrically controlled motor. The battery module of the transport vehicle 2003 can have a maximum voltage of 600V by connecting, for example, 100 or more lithium-ion secondary batteries with a nominal voltage of 3.0V to 5.0V in series. The battery module 2202 of the transport vehicle 2003 has the same functions as the battery pack shown in Figure 9B, except for differences in the number of cells connected in series or the number of lithium-ion secondary batteries constituting the battery module, so its explanation is omitted. By using the positive electrode active material particles of the present invention in the lithium-ion secondary batteries of the module, it is possible to create a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics.

[0293] Figure 10D shows an example of an aircraft 2004 having a fuel-burning engine. The aircraft 2004 shown in Figure 10D has wheels for takeoff and landing, and can therefore be considered part of a transport vehicle. It has a battery pack 2203 which includes a battery module formed by connecting multiple lithium-ion secondary batteries and a charge control device.

[0294] The battery module of aircraft 2004 has a maximum voltage of 32V, for example, by connecting eight 4V lithium-ion secondary batteries in series. Except for the number of lithium-ion secondary batteries that make up the battery module of battery pack 2203, it has the same functions as the battery pack shown in Figure 9B, so the explanation will be omitted.

[0295] The contents of this embodiment can be appropriately combined with the contents of other embodiments.

[0296] (Embodiment 6) This embodiment shows an example in which a lithium-ion secondary battery according to one aspect of the present invention is mounted on a vehicle such as a motorcycle or bicycle.

[0297] Figure 11A shows an example of an electric bicycle using a lithium-ion secondary battery according to one embodiment of the present invention. The lithium-ion secondary battery according to one embodiment of the present invention can be applied to the electric bicycle 8700 shown in Figure 11A. The lithium-ion secondary battery according to one embodiment of the present invention may have a protection circuit.

[0298] The electric bicycle 8700 is equipped with a power storage device 8702. The power storage device 8702 can supply electricity to a motor that assists the rider. The power storage device 8702 is also portable, and Figure 11B shows it detached from the bicycle. The power storage device 8702 also contains multiple lithium-ion secondary batteries 8701 according to one embodiment of the present invention, and the remaining battery level and other information can be displayed on a display unit 8703. By using the positive electrode active material particles of the present invention in the lithium-ion secondary battery 8701, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0299] Furthermore, the energy storage device 8702 has a control circuit 8704 capable of controlling the charging of the lithium-ion secondary battery or detecting abnormalities, as exemplified in Embodiment 8. The control circuit 8704 is electrically connected to the positive and negative electrodes of the lithium-ion secondary battery 8701. This can greatly contribute to eliminating accidents such as fires caused by lithium-ion secondary batteries.

[0300] Figure 11C shows an example of a motorcycle using a lithium-ion secondary battery according to one embodiment of the present invention. The scooter 8600 shown in Figure 11C is equipped with a power storage device 8602, side mirrors 8601, and turn signals 8603. The power storage device 8602 can supply electricity to the turn signals 8603. By using the positive electrode active material particles of the present invention in a lithium-ion secondary battery, it is possible to create a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics.

[0301] The scooter 8600 shown in Figure 11C can accommodate a power storage device 8602 in the under-seat storage compartment 8604. The power storage device 8602 can be stored in the under-seat storage compartment 8604 even if the under-seat storage compartment 8604 is small.

[0302] The contents of this embodiment can be appropriately combined with the contents of other embodiments.

[0303] (Embodiment 7) This embodiment describes an example of mounting a lithium-ion secondary battery, which is one aspect of the present invention, in an electronic device. Examples of electronic devices on which a lithium-ion secondary battery is mounted include television equipment (also called televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game consoles, personal information terminals, sound playback devices, and large game machines such as pachinko machines. Personal information terminals include notebook personal computers, tablet terminals, e-book readers, and mobile phones.

[0304] Figure 12A shows an example of a mobile phone. The mobile phone 2100 includes a display unit 2102 built into the housing 2101, as well as operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. The mobile phone 2100 also has a lithium-ion secondary battery 2107. By using the positive electrode active material particles of the present invention in the lithium-ion secondary battery, it is possible to create a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics.

[0305] The mobile phone 2100 can run various applications such as making mobile phone calls, sending emails, reading and creating documents, playing music, communicating on the internet, and playing computer games.

[0306] The operation button 2103 can be assigned various functions, including time setting, power on / off operation, wireless communication on / off operation, silent mode activation / deactivation, and power saving mode activation / deactivation. For example, the function of the operation button 2103 can be freely configured by the operating system built into the mobile phone 2100.

[0307] Furthermore, the mobile phone 2100 is capable of performing standardized short-range wireless communication. For example, it can communicate with a wireless communication-enabled headset to enable hands-free calling.

[0308] Furthermore, the mobile phone 2100 is equipped with an external connection port 2104, which allows for direct data exchange with other information terminals via a connector. It can also be charged via the external connection port 2104. Note that charging may also be performed wirelessly without using the external connection port 2104.

[0309] The mobile phone 2100 preferably has sensors. For example, it is preferable that the sensor includes a fingerprint sensor, a pulse sensor, a body temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, and the like.

[0310] Figure 12B shows an unmanned aerial vehicle 2300 having multiple rotors 2302. The unmanned aerial vehicle 2300 is sometimes called a drone. The unmanned aerial vehicle 2300 has a lithium-ion secondary battery 2301, a camera 2303, and an antenna (not shown), which are embodiments of the present invention. The unmanned aerial vehicle 2300 can be remotely controlled via the antenna. By using the positive electrode active material particles of the present invention in the lithium-ion secondary battery, it is possible to make a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics.

[0311] Figure 12C shows an example of a robot. The robot 6400 shown in Figure 12C is equipped with a lithium-ion secondary battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6407, a movement mechanism 6408, a computing device, and the like.

[0312] Microphone 6402 has the function of detecting the user's voice and ambient sounds. Speaker 6404 has the function of emitting sound. Robot 6400 can communicate with the user using microphone 6402 and speaker 6404.

[0313] The display unit 6405 has the function of displaying various types of information. The robot 6400 can display the information desired by the user on the display unit 6405. The display unit 6405 may be equipped with a touch panel. The display unit 6405 may also be a detachable information terminal, and by installing it in a fixed position on the robot 6400, charging and data transfer can be made possible.

[0314] The upper camera 6403 and the lower camera 6406 have the function of imaging the area around the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize its surrounding environment and move safely using the upper camera 6403, the lower camera 6406 and the obstacle sensor 6407.

[0315] The robot 6400 is equipped with a lithium-ion secondary battery 6409 according to one aspect of the present invention and a semiconductor device or electronic components in its internal region. By using the positive electrode active material particles of the present invention in the lithium-ion secondary battery, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0316] Figure 12D shows an example of a cleaning robot. The cleaning robot 6300 has a display unit 6302 located on the top surface of the housing 6301, multiple cameras 6303 located on the sides, a brush 6304, operation buttons 6305, a lithium-ion secondary battery 6306, and various sensors. Although not shown, the cleaning robot 6300 is equipped with wheels, a suction port, etc. The cleaning robot 6300 is self-propelled, can detect dirt 6310, and can suck up the dirt from a suction port located on the bottom surface.

[0317] For example, the cleaning robot 6300 can analyze images captured by the camera 6303 to determine the presence or absence of obstacles such as walls, furniture, or steps. Furthermore, if the image analysis detects an object that might become entangled in the brush 6304, such as wiring, the rotation of the brush 6304 can be stopped. The cleaning robot 6300 is equipped with a lithium-ion secondary battery 6306 according to one embodiment of the present invention and a semiconductor device or electronic components within its internal region. By using the positive electrode active material particles of the present invention in the lithium-ion secondary battery, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained.

[0318] This embodiment can be implemented in appropriate combination with other embodiments.

[0319] (Embodiment 8) This embodiment describes an example in which a lithium-ion secondary battery, which is one aspect of the present invention, is implemented in space equipment.

[0320] Figure 13A shows satellite 6800 as an example of space equipment. Satellite 6800 consists of a body 6801, a solar panel 6802, an antenna 6803, and a lithium-ion secondary battery 6805. The solar panel is sometimes called a solar cell module.

[0321] When sunlight shines on the solar panel 6802, the power necessary for the satellite 6800 to operate is generated. However, in situations where, for example, sunlight does not shine on the solar panel, or when the amount of sunlight shining on the solar panel is low, the amount of power generated will decrease. Therefore, there is a possibility that the power necessary for the satellite 6800 to operate will not be generated. To operate the satellite 6800 even under conditions where the amount of power generated is low, it is advisable to provide the satellite 6800 with a lithium-ion secondary battery 6805. By using the positive electrode active material particles of the present invention in the lithium-ion secondary battery, it is possible to create a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics.

[0322] The artificial satellite 6800 can generate signals. These signals can be transmitted via the antenna 6803 and received, for example, by a receiver installed on the ground or by other artificial satellites. By receiving the signals transmitted by the artificial satellite 6800, for example, the position of the receiver that received the signals can be measured. From the above, the artificial satellite 6800 can constitute, for example, a satellite positioning system.

[0323] Alternatively, the artificial satellite 6800 can be configured to have sensors. For example, by being configured to have a visible light sensor, the artificial satellite 6800 can have the function of detecting sunlight reflected by an object provided on the ground. Or, by being configured to have a thermal infrared sensor, the artificial satellite 6800 can have the function of detecting thermal infrared rays emitted from the earth's surface. From the above, the artificial satellite 6800 can have the function as, for example, an earth observation satellite.

[0324] FIG. 13B shows an example of space equipment, an explorer 6900 having a solar sail (also called a solar sail). The explorer 6900 has a fuselage 6901, a solar sail 6902, and a lithium-ion secondary battery 6905. By using the positive electrode active material particles of the present invention in the lithium-ion secondary battery, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained. When photons emitted from the sun hit the surface of the solar sail 6902, momentum is transferred to the solar sail 6902. Therefore, the surface of the solar sail 6902 preferably has a thin film with a high reflectivity, and further preferably faces the direction of the sun.

[0325] Also, the solar sail 6902 can be designed to be in a small folded state until it exits the atmosphere and to be deployed in a large sheet shape as shown in FIG. 13B in the outer space of the earth (space).

[0326] Figure 13C shows a spacecraft 6910 as an example of space equipment. The spacecraft 6910 comprises a body 6911, a solar panel 6912, and a lithium-ion secondary battery 6913. By using the positive electrode active material particles of the present invention in the lithium-ion secondary battery, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained. The body 6911 may have, for example, a pressurized chamber and an unpressurized chamber. The pressurized chamber may be designed to accommodate a crew. The electricity generated when sunlight is irradiated onto the solar panel 6912 can be used to charge the lithium-ion secondary battery 6913.

[0327] Figure 13D shows a rover 6920 as an example of space equipment. The rover 6920 comprises a body 6921 and a lithium-ion secondary battery 6923. By using the positive electrode active material particles of the present invention in the lithium-ion secondary battery, a secondary battery with high capacity, high discharge capacity, and excellent cycle characteristics can be obtained. The rover 6920 may also have a solar panel 6922.

[0328] The rover 6920 may be designed to accommodate a crew. The lithium-ion secondary battery 6923 may be charged with electricity generated by sunlight irradiating the solar panel 6912, or it may be charged with electricity generated by other power sources, such as a fuel cell or a radioisotope thermoelectric converter.

[0329] The contents of this embodiment can be appropriately combined with the contents of other embodiments.

[0330] 100: Positive electrode active material particles, 100a: Barrier film, 100b: Core, 101: Shell, 102: Positive electrode active material particles, 300: Lithium-ion secondary battery, 301: Positive electrode can, 302: Negative electrode can, 303: Gasket, 304: Positive electrode, 305: Positive electrode current collector, 306: Positive electrode active material layer, 307: Negative electrode, 308: Negative electrode current collector, 309: Negative electrode active material layer, 332: Washer, 342: Spacer, 500: Lithium-ion secondary battery, 506: Negative electrode, 507: Positive electrode, 508: Adhesion region, 509: Outer casing, 510: Negative electrode lead electrode, 511: Positive electrode lead electrode, 550: Current collector, 5 53: Carbon black, 554: Graphene, 555: Carbon fiber, 561: Positive electrode active material particles, 562: Second active material, 601: Positive electrode cap, 602: Battery can, 603: Positive electrode terminal, 604: Positive electrode, 605: Electrolyte layer, 606: Negative electrode, 607: Negative electrode terminal, 608: Insulating plate, 609: Insulating plate, 611: PTC element, 613: Safety valve mechanism, 614: Conductive plate, 615: Energy storage system, 616: Lithium-ion secondary battery, 620: Control circuit, 621: Wiring, 622: Wiring, 623: Wiring, 624: Conductor, 625: Insulator, 626: Wiring, 627: Wiring, 628 : Conductive plate, 911a: Terminal, 911b: Terminal, 913: Lithium-ion secondary battery, 930: Housing, 930a: Housing, 930b: Housing, 931: Negative electrode, 931a: Negative electrode active material layer, 932: Positive electrode, 932a: Positive electrode active material layer, 933: Electrolyte layer, 950: Winding body, 950a: Winding body, 951: Terminal, 952: Terminal, 1300: Rectangular lithium-ion secondary battery, 1301a: First battery, 1301b: First battery, 1302: Battery controller, 1303: Motor controller, 1304: Motor, 1305: Gear, 1306: DC / DC circuit, 1 307: Electric power steering, 1308: Heater, 1309: Defogger, 1310: DC / DC circuit, 1311: Second battery, 1312: Inverter, 1313: Audio, 1314: Power windows, 1315: Lights, 1316: Tires, 1317: Rear motor, 1320: Control circuit section, 1321: Control circuit section, 1322: Control circuit, 1324: Switch section, 1413: Fixing section, 1414: Fixing section, 1415: Battery pack, 1421: Wiring, 1422: Wiring, 2001: Automobile, 2002: Transport vehicle, 2003: Transport vehicle, 2004: Aircraft,2100: Mobile phone, 2101: Housing, 2102: Display unit, 2103: Operation buttons, 2104: External connection port, 2105: Speaker, 2106: Microphone, 2107: Lithium-ion secondary battery, 2200: Battery pack, 2201: Battery pack, 2202: Battery module, 2203: Battery pack, 2300: Unmanned aerial vehicle, 2301: Lithium-ion secondary battery, 2302: Rotor, 2303: Camera, 6300: Cleaning robot, 6301: Housing, 6302: Display unit, 6303: Camera, 6304: Brush, 6305: Operation button, 6306: Lithium-ion secondary battery, 6310: Dust, 6400: Robot, 6401: Illuminance sensor, 6402: Microphone, 6403: Upper camera, 6404: Speaker, 6405: Display unit, 6406: Lower camera, 6407: Obstacle sensor, 6408: Moving mechanism, 6409: Lithium-ion secondary battery, 6800: Artificial satellite, 6801: Body, 6802: Solar panel, 6803: Antenna, 6805: Lithium-ion secondary battery, 6900: Probe, 6901: Body, 6902: Solar sail, 6905: Lithium-ion secondary battery, 6910: Spacecraft, 6911: Body, 6912: Solar panel, 691 3: Lithium-ion secondary battery, 6920: Rover, 6921: Aircraft body, 6922: Solar panel, 6923: Lithium-ion secondary battery, 8600: Scooter, 8601: Side mirror, 8602: Energy storage device, 8603: Turn signal light, 8604: Under-seat storage, 8700: Electric bicycle, 8701: Lithium-ion secondary battery, 8702: Energy storage device, 8703: Display unit, 8704: Control circuit,

Claims

A positive electrode active material particle having lithium, a transition metal M (where M is one or more selected from Mn, Cr, Mo, Nb, V, Fe, Ni, Ti, and Ru), oxygen, magnesium, and fluorine, The positive electrode active material particles have a Li / M (atomic ratio) greater than 1. The positive electrode active material particles are, The core and The barrier film outside the core, It has a shell outside the barrier film, The barrier film has more magnesium and fluorine than the core, and the crystal orientation of the core and the barrier film is roughly the same. The aforementioned shell is a positive electrode active material particle having fluoride. 　 In claim 1, The barrier film has more of one or more elements selected from titanium, aluminum, nickel, zirconium, vanadium, iron, manganese, chromium, niobium, arsenic, zinc, silicon, sulfur, phosphorus, boron, bromine, and beryllium than the core. The fluoride contained in the shell is a positive electrode active material particle having one or more selected from lithium fluoride, aluminum fluoride, iron fluoride, calcium fluoride, cobalt fluoride, and lithium tetrafluoroaluminate. 　 The positive electrode active material particles in claim 1, wherein the core has a layered rock salt type or irregular rock salt type crystalline structure. 　 The barrier film comprises positive electrode active material particles having a rock salt type or spinel type crystal structure.

Images