Lithium ion secondary battery

Abstract

To provide a secondary battery having good cycle characteristic and a secondary battery having high energy density.SOLUTION: A positive electrode is manufactured using a cathode active material having an approximately spherical shape whose surface is smooth. The cathode active material having an approximately spherical shape whose surface is smooth is less likely to cause concentration of stress even when a volume thereof changes due to charging and discharging. Therefore, cracks and fractures are less likely to occur. A secondary battery having good cycle characteristic can be provided by using the cathode active material. A loading capacity can be increased by using a mixture of particles different in particle diameter as the positive electrode, and it is possible to provide a secondary battery having high energy density.SELECTED DRAWING: Figure 1

Description

Technical Field

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

[0002] Note that in this specification, the power storage device refers to all elements and devices having a power storage function. For example, it includes storage batteries (also referred to as secondary batteries) such as lithium-ion secondary batteries, lithium-ion capacitors, and electric double layer capacitors.

[0003] Also, in this specification, the electronic device refers to all devices having a power storage device. Devices having a power storage device, such as electro-optical devices having a power storage device and information terminal devices having a power storage device, are all electronic devices.

Background Art

[0004] In recent years, various power storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have been actively developed. In particular, lithium-ion secondary batteries with high output and high energy density are rapidly increasing in demand along with the development of the semiconductor industry for portable information terminals such as mobile phones, smartphones, tablets, or notebook computers, portable music players, digital cameras, medical devices, or next-generation clean energy vehicles such as hybrid vehicles (HEV), electric vehicles (EV), or plug-in hybrid vehicles (PHEV). , as a source of rechargeable energy, has become essential in modern information society.

[0005] The characteristics required for lithium-ion secondary batteries include further increasing the energy density, improving the cycle characteristics, and improving the safety and long-term reliability in various operating environments.

[0006] To increase the energy density, it is effective to increase the loading amount of the positive electrode active material in the positive electrode. For example, attempts such as the following Patent Documents 1 to 4 have been made.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] One aspect of the present invention aims to provide a positive electrode for a lithium-ion secondary battery having excellent charge-discharge cycle characteristics. Or, one of the purposes is to provide a secondary battery with a high energy density. Or, one of the purposes is to provide a secondary battery having excellent charge-discharge characteristics. Further, one aspect of the present invention aims to provide a secondary battery with high safety or reliability.

Means for Solving the Problems

[0009] ​To achieve the above object, in one aspect of the present invention, a positive electrode is produced using a substantially spherical positive electrode active material having a smooth surface. Since the substantially spherical positive electrode active material having a smooth surface changes in volume during charge and discharge, stress concentration is less likely to occur. Therefore, cracks and fractures are less likely to occur. By using the positive electrode active material, a secondary battery with good cycle characteristics can be provided. Further, when particles having different particle sizes are mixed and used for the positive electrode, the loading amount can be increased, and a secondary battery with a high energy density can be provided.

[0010] One aspect of the present invention has a positive electrode active material and a current collector. The positive electrode active material is substantially spherical, has a smooth surface, is less likely to crack even when pressed during the manufacturing process, or is less likely to crack even when charge and discharge is repeated, and the positive electrode active material can be arranged at a high density on the current collector. The positive electrode active material has lithium fluoride in the surface layer portion and is less likely to sinter between adjacent particles even when heated during the manufacturing process, or is easily crushed even when sintered.

[0011] In the above, the positive electrode active material is preferably a positive electrode active material with a standard deviation of the arithmetic mean particle size of 0.2 or less.

[0012] Also, in the above, the positive electrode active material has an ideal specific surface area A i obtained from the median diameter D50, and the ratio A R of the actual specific surface area A R / A i is preferably a positive electrode active material with a smooth surface of 2 or less.

[0013] Also, in the above, the positive electrode active material has a surface fluorine binding energy measured by X-ray photoelectron spectroscopy. It is preferable that the peak position of the energy exceeds 684.4 eV and is less than 686.0 eV. Yes.

[0014] In addition, in the above, the positive electrode active material has a first particle and a second particle, and the median diameter of the second particle is preferably 0.66 times or less of the median diameter of the first particle.

[0015] Another aspect of the present invention is a method for producing a positive electrode active material, the production method having at least a first step, a second step, and a third step. The first step is a step of processing an oxide of a transition metal or a hydroxide of a transition metal into a substantially spherical shape to produce a first material. The second step is a step of mixing the first material and a lithium source to produce a first mixture. The third step is a step of heating the first mixture, which is a method for producing a positive electrode active material.

[0016] In the above, the heating temperature in the second step is preferably 700°C or higher and 900°C or lower. Yes.

[0017] Another aspect of the present invention is a positive electrode active material having a standard deviation of the arithmetic mean particle diameter of 0.2 or less and a ratio A i of an ideal specific surface area A R obtained from the median diameter D50 to the actual specific surface area A of 2 or less, and a peak position of the binding energy of fluorine on the surface measured by X-ray photoelectron spectroscopy R exceeding 684.4 eV and less than 686.0 eV, which is a positive electrode active material. i Yes. Yes. Yes.

[0018] Another aspect of the present invention is a secondary battery having the above positive electrode and a negative electrode.

Advantages of the Invention

[0019] According to one aspect of the present invention, a positive electrode for a lithium-ion secondary battery having excellent charge-discharge cycle characteristics can be provided. Or, a secondary battery having a high energy density can be provided. Or, a secondary battery having excellent charge-discharge characteristics can be provided. Or, a secondary battery having high safety or reliability can be provided. Or, a secondary battery having excellent charge-discharge characteristics can be provided. Or, a secondary battery having high safety or reliability can be provided. Or, a secondary battery having high safety or reliability can be provided.

Brief Description of the Drawings

[0020]

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Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art can make various changes to its form and details. not limited to the following description, and those skilled in the art can make various changes to its form and details. will be easily understood. The present invention is not construed as being limited to the description of the embodiments shown below.

[0022] In this specification and the like, the surface layer portion of particles such as active materials refers to the region from the surface to about 10 nm. The surface formed by cracks may also be referred to as the surface. The region deeper than the surface layer portion is referred to as the interior.

[0023] In the configuration of the invention described below, the same reference numerals are commonly used among different drawings for the same part or parts having the same or similar functions, and the repeated description thereof is omitted. In addition, when referring to similar functions, the hatch patterns may be the same and may not be particularly labeled.

[0024] In each drawing described in this specification, the size of each component, the thickness of the layer, or the region may be exaggerated for clarity. Therefore, it is not necessarily limited to that scale.

[0025] In this specification and the like, ordinal numbers such as "first" and "second" are attached to avoid confusion of components and are not numerically limiting.

[0026] A transistor is a type of semiconductor device and can realize operations such as amplification of current or voltage and switching operations for controlling conduction or non - conduction. The transistors in this specification include IGFET (Insulated Gate Field Effect Transistor) and thin - film transistors (TFT: Thin Film Transistor).

[0027] ​​​​​​​​​​In this specification and the like, a metal oxide refers to an oxide of a metal in a broad sense. Metal oxides include oxide insulators, oxide conductors (including transparent oxide conductors), and oxide semiconductors (also referred to as Oxide Semiconductor or simply OS). For example, when a metal oxide is used for the semiconductor layer of a transistor, the metal oxide may be referred to as an oxide semiconductor. That is, when a metal oxide has at least one of an amplification effect, a rectification effect, and a switching effect, the metal oxide can be referred to as a metal oxide semiconductor, abbreviated as OS. In addition, when described as an OS FET, it can be paraphrased as a transistor having a metal oxide or an oxide semiconductor.

[0028] (Embodiment 1) [Positive Electrode and Positive Electrode Active Material] An example of a positive electrode active material 100 and a positive electrode 120 having the positive electrode active material 100, which is one aspect of the present invention, will be described with reference to FIGS. 1 to 3.

[0029] FIG. 1(A) is a cross-sectional view of the positive electrode 120. FIG. 1(B) is an enlarged view of the dashed-line portion in FIG. 1(A). The positive electrode 120 includes a positive electrode active material 100 and a current collector 110. Further, the positive electrode 120 preferably includes a binder (not shown) that binds the positive electrode active materials 100 together and a conductive additive 111.

[0030] For example, as shown in FIG. 1(C), the positive electrode 120 can be manufactured by providing a frame 121 on the current collector 110 and pouring a slurry containing the positive electrode active material 100, the binder, and the conductive additive 111 into the frame 121.

[0031] The positive electrode active material 100 preferably has a median diameter D50 of the primary particles in the range of 500 nm or more and 50 μm or less, and is substantially spherical, more preferably in the range of 1 μm or more and 30 μm or less. Here, the so-called substantially spherical shape does not necessarily have to be an ideal sphere, and includes an elliptical sphere, a sphere with a part missing, a distorted sphere, and a sphere having irregularities on the surface.

[0032] In addition, the standard deviation of the arithmetic mean diameter of the positive electrode active material 100 is preferably 0.2 or less, more preferably 0.19 or less. When the particles are substantially spherical with uniform particle sizes like this, stress concentration is less likely to occur even when charging and discharging are repeated. Also, even when pressure is applied to the positive electrode 120 during the manufacturing process, the pressure is less likely to concentrate. Therefore, the positive electrode active material 100 is less likely to crack. When the positive electrode active material 100 cracks, the surface area increases excessively, leading to progress of the decomposition of the electrolyte, and also

[0033] causes deterioration such as loss of oxygen or transition metals in the positive electrode active material. Therefore, by using the positive electrode active material 100 that is less likely to crack, a secondary battery with excellent cycle characteristics can be obtained. Also, since the substantially spherical shape has less friction, it is rich in fluidity and is preferable because it is easy to increase the loading amount without applying a high pressure during the manufacturing process.

[0034] In addition, the positive electrode active material 100 preferably has a smooth surface. The positive electrode active material 100 with a smooth surface has few cracks, so it is less likely to crack even when the volume changes during charge and discharge. As an index of smoothness, for example, the ratio of the actual specific surface area A measured by the gas adsorption method by the constant volume method to the ideal specific surface area A can be used. The ideal specific surface area A R i i i i i Assume that the diameter of all particles is the same as D50, the weight is the same, and the shape is an ideal sphere, and calculate and obtain it. A R / A i is preferably 2 or less.

[0035] The median diameter D50 can be measured by a particle size distribution meter using the laser diffraction / scattering method or the like. The specific surface area can be measured by, for example, a specific surface area measuring device using the gas adsorption method by the constant volume method. It can be measured by.

[0036] Also, the particles of the positive electrode active material 100 preferably contact the particles of other positive electrode active materials 100 at multiple points. When the positive electrode active material 100 is substantially spherical with uniform shape and particle size, it becomes easier to contact other particles at multiple points. When the particles of the positive electrode active material 100 are in contact with the particles of other positive electrode active materials 100, even if the amount of the conductive assistant 111 is reduced as shown in Fig. 2(A), the conductivity between the particles of the positive electrode active material 100 can be maintained. Therefore, the loading amount of the positive electrode active material 100 in the positive electrode 120 can be increased.

[0037] Whether the particles of the positive electrode active material 100 are in contact with other particles can be determined by observation using a cross-sectional SEM (scanning electron microscope), a surface SEM, or a cross-sectional TEM (transmission electron microscope). It can be judged by.

[0038] Also, as shown in Fig. 2(B), graphene 112 may be used together with the conductive assistant 111 or instead of the conductive assistant 111. Compared with the acetylene black often used as the conductive assistant 111, since graphene 112 has high conductivity and a two-dimensional spread, the conductivity can be ensured with a small amount. Therefore, the loading amount of the positive electrode active material 100 in the positive electrode 120 can be increased. ​​​

[0039] Furthermore, the positive electrode active material 100 may have particles of different sizes, such as the first particles 100a and the second particles 10 0b shown in Fig. 2(C). At this time, if the median diameter (D50) of the second particles 100b is 0.66 times or less of the median diameter (D50) of the first particles, it is preferable because the loading amount of the positive electrode active material 100 in the positive electrode 120 can be increased.

[0040] In addition, although Fig. 2(C) shows an example having two kinds of particles with different sizes, it may have three or more kinds of particles with different sizes.

[0041] Furthermore, it is preferable that the positive electrode active material 100 contains a large amount of a material with a low melting point or a low Young's modulus in the surface layer portion. If the surface layer portion contains a large amount of a material with a low melting point or a soft material with a low Young's modulus, even when a plurality of particles aggregate or adjacent particles sinter, it is easy to break up. Note that if all of the surface layer portion of the positive electrode active material 100 is a material with a low melting point or a material with a low Young's modulus, there is a risk that the resistance during charge and discharge increases. Therefore, it is preferable that the surface layer portion of the positive electrode active material 100 is a mixture of a material with a low melting point or a low Young's modulus and the same material as the inside. Here, the material with a low melting point means a material with a lower melting point than the material inside the positive electrode active material 100. For example, when the material inside the positive electrode active material 100 is lithium cobaltate (melting point of about 1140°C ), examples of materials with a lower melting point than this include lithium fluoride (melting point 848°C), lithium carbonate (melting point 723°C), sodium fluoride (melting point 993°C), lithium chloride (melting point 6

[0042] 13°C), sodium chloride (melting point 800°C), and the like. ) ​​​​​​

[0043] Also, the material with a low Young's modulus mentioned here is a material with a lower Young's modulus than the material inside the positive electrode active material 100. For example, when the material inside the positive electrode active material 100 is lithium cobaltate (Young's modulus of about 100 GPa), materials with a lower Young's modulus than this include lithium fluoride ( Young's modulus of 65 GPa), sodium fluoride (Young's modulus of 79 GPa), sodium chloride ( Young's modulus of 40 GPa), and the like.

[0044] Whether a material with a low melting point or a low Young's modulus exists in the surface layer portion of the positive electrode active material 100 can be determined, for example, by analysis using X-ray photoelectron spectroscopy (XPS). For example, if the peak position of the binding energy of fluorine on the surface of the positive electrode active material 100 exceeds 684.4 eV and is less than 686 .0 eV, it can be known that lithium fluoride is present in the surface layer portion. Therefore, it can be determined that lithium fluoride is used as the material with a low melting point or a low Young's modulus.

[0045] <Material of the positive electrode active material> Various composite oxides can be used as the material inside the positive electrode active material 100. For example, composite oxides having a layered rock salt-type crystal structure, or a spinel-type crystal structure, etc. can be used. Also, polyanion-based positive electrode materials can be used. Examples of polyanion-based positive electrode materials include materials having an olivine-type crystal structure, NASICON-type materials, and the like. Also, not limited to composite oxides, materials without oxygen, for example, positive electrode materials having sulfur can be used.

[0046] As a material having a layered rock salt-type crystal structure, for example, a composite oxide represented by LiMO2 is used. ​It can be. Element M is preferably one or more selected from Co, Ni, and Mn. LiCoO2 is preferable because it has advantages such as a large capacity, stability in the air, and relatively high thermal stability. Furthermore, as element M, in addition to one or more selected from Co, Ni, and Mn, it may contain Al.

[0047] For example, LiNi x Mn y Co z O w (where x, y, z, and w are, for example, x = y = z = 1 / 3 or in the vicinity thereof, and w = 2 or in the vicinity thereof) can be used. Also, for example, , LiNi x Mn y Co z O w (where x, y, z, and w are, for example, x = 0.8 or in the vicinity thereof, y = 0.1 or in the vicinity thereof, z = 0.1 or in the vicinity thereof, and w = 2 or in the vicinity thereof) can be used. Also, for example, LiNi x Mn y Co z O w (where x, y, z, and w are, for example, x = 0.5 or in the vicinity thereof, y = 0.3 or in the vicinity thereof, z = 0 .2 or in the vicinity thereof, and w = 2 or in the vicinity thereof) can be used. Also, for example, L iNi x Mn y Co z O w (where x, y, z, and w are, for example, x = 0.6 or in the vicinity thereof, y = 0.2 or in the vicinity thereof, z = 0.2 or in the vicinity thereof, and w = 2 or in the vicinity thereof) can be used. Also, for example, LiNi x Mn y Co z O w (where x, y, z, and w can be, for example, x = 0.4 or in the vicinity thereof, y = 0.4 or in the vicinity thereof, z = 0.2 or in the vicinity thereof, w = 2 or in the vicinity thereof).

[0048] The vicinity means, for example, a value greater than 0.9 times and less than 1.1 times that value.

[0049] Also, at least a part of the transition metal or lithium contained in the positive electrode active material is replaced with one or more elements selected from Li, Fe, Co, Ni , Cr, Al, Mg, etc., or a material in which the positive electrode active material is doped with one or more elements selected from Fe , Co, Ni, Cr, Al, Mg, etc. may be used as the positive electrode active material. For example, LiFeO2, Li2MnO3, etc. can also be used.

[0050] In addition, among the composite oxides having a layered rock salt-type crystal structure, it is particularly preferable to use a material having a pseudo-spinel-type crystal structure when charged at a high voltage. Such a positive electrode active material is a positive electrode active material with good cycle characteristics because the change in crystal structure and volume in the charged state and the discharged state are suppressed, and the crystal structure is not easily broken even when charged and discharged repeatedly at a high voltage.

[0051] The pseudo-spinel-type crystal structure is a crystal structure that has a space group of R-3m and is not a spinel-type crystal structure, in which transition metals such as cobalt occupy the oxygen 6-coordination positions and the cation arrangement has a symmetry similar to that of the spinel type. The coordinates of cobalt and oxygen in the unit cell can be shown within the range of Co(0,0,0.5), O(0,0,x), 0.20 ≤ x ≤ 0.2 5. Also, a positive electrode active material having a pseudo-spinel-type crystal structure is used as C ​​​​​​When analyzed using powder XRD with uKα1 rays, 2θ = 19.30 ± 0.20° (19 .10° or more and 19.50° or less), and diffraction peaks appear at 2θ = 45.55 ± 0.10° (45.45° or more and 45.65° or less). More specifically, sharp diffraction peaks appear at 2θ = 19.3 0 ± 0.10° (19.20° or more and 19.40° or less), and 2θ = 45.55 ± 0. 05° (45.50° or more and 45.60° or less).

[0052] The charging at high voltage mentioned here means, for example, constant current charging until the battery voltage reaches 4.6 V (in the case of a lithium counter electrode), and then constant voltage charging until the current value becomes 0.01C .

[0053] The composite oxide having a pseudo - spinel crystal structure when charged at high voltage can be prepared, for example, after synthesizing a composite oxide having a layered rock - salt crystal structure with few impurities, mixing a fluorine source such as lithium fluoride and magnesium fluoride and a magnesium source, and heating at an appropriate temperature and time . The appropriate temperature is, for example, 600°C or more and 950 °C or less, more preferably 700°C or more and 900°C or less. The appropriate time is 1 hour or more and 100 hours or less, more preferably 2 hours or more and 60 hours or less.

[0054] Furthermore, a solid solution combining a plurality of composite oxides can be used as a positive electrode material. For example , a solid solution of LiNi x Mn y Co z O2 (x, y, z > 0, x + y + z = 1) and Li2MnO3 can be used as a positive electrode active material.

[0055] ​​As a material having a spinel crystal structure, for example, a composite oxide represented by LiM2O4 can be used. It is preferable to have Mn as the element M. For example, LiMn2O 4 can be used. Also, by having Ni in addition to Mn as the element M, the discharge voltage of the secondary battery may be improved and the energy density may be improved, which is preferable. Further, to a lithium-containing material having a spinel crystal structure containing manganese such as L iMn2O4, 5 0 mol% or less of lithium nickelate (LiNiO2, LiNi 1-x M x O2 (M = Co , Al, etc.)) is mixed, the characteristics of the secondary battery can be improved, which is preferable.

[0056] As a polyanion-based cathode material, for example, a composite oxide having oxygen, element X, metal A, and metal M can be used. Metal M is one or more of Fe, Mn, Co, Ni, Ti, V, N b, metal A is one or more of Li, Na, Mg, and element X is one or more of S, P, Mo, W, As, Si.

[0057] As a material having an olivine crystal structure, for example, a composite material (general formula LiMPO4 (M is , Fe(II), Mn(II), Co(II), Ni(II) one or more)) can be used. As representative examples of the general formula LiMPO4, LiFePO4, LiNiPO4, L iCoPO4, LiMnPO4, LiFe a Ni b PO4, LiFe a Co b PO4, L iFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4 (a + b is 1 Hereinafter, 0 < a < 1, 0 < b < 1), LiFe c Ni d Co e PO4, LiFe c Ni d M n e PO4, LiNi c Co d Mn e PO4 (c + d + e is 1 or less, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO4 (f + g + h + i is 1 or less, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), etc., lithium compounds can be used for this.

[0058] In particular, LiFePO4 satisfies well the requirements for a cathode active material, such as safety, stability, high capacity density, and the presence of lithium ions that can be extracted during initial oxidation (charging). Therefore , it is preferable.

[0059] Also, composite materials such as the general formula Li (2-j) MSiO4 (M is one or more of Fe(II), Mn(II), Co(I I), Ni(II), 0 ≤ j ≤ 2), etc., can be used. General formula Li (2-j) MSiO4 representative examples include Li (2-j) FeSiO4, Li (2- j) NiSiO4, Li (2-j) CoSiO4, Li (2-j) MnSiO4, Li ( 2-j) Fe k Ni l SiO4, Li (2-j) Fe k Co l SiO4, Li (2-j) Fe k Mnl SiO4, Li (2-j) Ni k Co l SiO4, Li (2-j) Ni k M n l SiO4 (k + l is 1 or less, 0 < k < 1, 0 < l < 1), Li (2-j) Fe m Ni n Co q SiO4, Li (2-j) Fe m Ni n Mn q SiO4, Li (2-j) Ni m Co n Mn q SiO4 (m + n + q is 1 or less, 0 < m < 1, 0 < n < 1, 0 < q < 1), Li (2-j) Fe r Ni s Co t Mn u SiO4 (r + s + t + u is 1 or less, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1), etc. can be used as the material of the lithium compound. It is possible.

[0060] Also, A x M2(XO4)3 (A = Li, Na, Mg, M = Fe, Mn, Ti, V, Nb , X = S, P, Mo, W, As, Si) can be used using the NASICON-type compound represented by the general formula. Examples of the NASICON-type compound include Fe2(MnO4)3, Fe2(SO4)3, Li3Fe2(PO4)3, etc. Also, as the material of the positive electrode active material, Li2MPO4F , Li2MP2O7, Li5MO4 (M = Fe, Mn) can be used using the compound represented by the general formula. It is possible.

[0061] Also, as the material of the positive electrode active material, the composition formula Li a Mn b Mc O d can be represented by lithium manganese composite oxide can be used. Here, element M is preferably a metal element selected from outside lithium and manganese, or silicon or phosphorus, and more preferably nickel. When measuring the entire particles of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≤ (b + c) / d < 0. 5 during discharge. In addition, in order to exhibit high capacity, it is preferable to use a lithium manganese composite oxide having regions with different crystal structures, crystal orientations, or oxygen contents in the surface layer portion and the central portion. To obtain such a lithium manganese composite oxide, for example, it is preferable to set 1. 6 ≤ a ≤ 1.848, 0.19 ≤ c / b ≤ 0.935, and 2.5 ≤ d ≤ 3. Further, it is particularly preferable to use a lithium manganese composite oxide represented by the composition formula of Li Mn Ni O3. In this specification, etc., the lithium manganese composite oxide represented by the composition formula of Li 1.68 Mn 0.8062 Ni 0.318 O3 refers to a lithium manganese composite oxide formed by setting the ratio (molar ratio) of the amounts of the raw material materials to Li2CO3:MnCO3:NiO = 0.84:0.8062:0.318. Therefore, the lithium manganese composite oxide is represented by the composition formula Li 1.68 Mn 0.8062 Ni 0.318 O3, but may deviate from this composition. = 0.84:0.8062:0.318. Therefore, the lithium manganese composite oxide is represented by the composition formula Li Mn 1.68 Mn 0. 8062 Ni 0.318 O3, but may deviate from this composition.

[0062] In addition, as the positive electrode material, perovskite-type fluorides such as NaFeF3 and FeF3, TiS 2. Metal chalcogenides (sulfides, selenides, tellurides) such as MoS2, LiMVO 4, oxides having an inverse spinel crystal structure, vanadium oxide-based (V2O5, V6O 13 , LiV3O8, etc.), manganese oxides, organic sulfur compounds, etc. can be used .

[0063] In addition, lithium-containing metal sulfides can be used as the positive electrode material. For example, Li2 TiS3, Li3NbS4, etc. can be mentioned.

[0064] In addition, as the positive electrode material, a borate-based positive electrode material represented by the general formula LiMBO3 (M is Fe(II), Mn(II), Co (II)) can be used.

[0065] A conductive material such as a carbon layer may be provided on the surface of the positive electrode active material. By providing a conductive material such as a carbon layer , the conductivity of the electrode can be improved. For example, the coating of the carbon layer on the positive electrode active material can be formed by mixing a carbohydrate such as glucose during the firing of the positive electrode active material. In addition, as the conductive material, graphene, multi-graphene, graphene oxide ( GO: Graphene Oxide) or RGO (Reduced Graphene Oxide) can be used. Here, RGO refers to a compound obtained by reducing, for example, graphene oxide (GO ).

[0066] Note that the composition of metals, silicon, phosphorus, etc. in the entire particles of the lithium manganese composite oxide can be measured, for example using ICP-MS (Inductively Coupled Plasma Mass Spectrometer). Also, the oxygen composition in the entire particles of the lithium manganese composite oxide can be measured, for example, by EDX (Energy Dispersive It can be measured using X-ray analysis. Also, by using valence evaluation of melting gas analysis and XAFS (X-ray absorption fine structure) analysis in combination with ICP-MS analysis, it can be determined. Note that the lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, niobium, zinc, indium, gallium, copper, titanium, niobium, silicon, and phosphorus.

[0067] Note that when the carrier ion is an alkali metal ion other than lithium ion or an alkaline earth metal ion, as the positive electrode active material, instead of lithium, an alkali metal (e.g., sodium, potassium, etc.), an alkaline earth metal (e.g., calcium, strontium, barium, beryllium, magnesium, etc.) may be used. For example, a sodium-containing layered oxide can be used.

[0068] Examples of materials having sodium include, for example, NaFeO2 and Na 2 / 3 [Fe 1 / 2 Mn1 / 2 O2, Na 2 / 3 [Ni 1 / 3 Mn 2 / 3 O2, Na2Fe2(SO4)3, N a3V2(PO4)3, Na2FePO4F, NaVPO4F, NaMPO4 (M is Fe(II), Mn(II), Co(II), Ni(II)), Na2FePO4F, Na 4Co3(PO4)2P2O7, etc. can be used as the material for the positive electrode active material.

[0069] ​​​These materials for the positive electrode active material 100 can be synthesized by the method described above or a known method. It is possible.

[0070] [Method for producing positive electrode active material] Next, an example of a method for processing the material of the positive electrode active material 100 into spherical shapes with a smooth surface, uniform shape, and particle size will be described. The spheroidization mentioned here means processing into a substantially spherical shape, and it is not necessary to process it into an ideal sphere.

[0071] [Physical polishing method] First, with reference to FIG. 3, a method for processing the material of the positive electrode active material into a spherical shape by physically polishing it will be described. In this method, the material of the positive electrode active material 100 described above is polished using a polishing device, and then classified using a classification device 210 capable of separating particles by size to obtain a substantially spherical positive electrode active material 100.

[0072] When using a plurality of polishing devices, it is preferable because the surface can be made smoother. For example, as shown in FIG. 3, it is preferable to use in order a polishing device 201a for rough grinding, a polishing device 201b for intermediate grinding, and a polishing device 201c for finish polishing. Each polishing device has a motor 202, a first disk 203a, and a second disk 203b. The material of the positive electrode active material is put between the first disk 203a and the second disk 203b, and the material of the positive electrode active material is physically polished by rotating one or both of the first disk 203a and the second disk 203b.

[0073] Classification can be performed by sieving, dry classification, wet classification, etc. It is preferable to use a classification device based on a centrifugal force field such as a wet cyclone because high classification accuracy can be obtained. Using a wet cyclone If so, it is preferable to recover the particles 221 that are too small using the dust collector 220.

[0074] This physical polishing method has high productivity because it enables large - scale processing with small equipment. Also, it is preferable in that the temperature rise is less than that of other methods described later. than other methods described later.

[0075] <High - frequency induction thermal plasma method> Further, the above - mentioned material of the positive electrode active material may be heated by thermal plasma to be spheroidized. For example, the plasma gas is made into thermal plasma of about 10,000 degrees by high - frequency induction, and the material of the positive electrode active material is introduced into the plasma. The spheroidized particles after the thermal plasma treatment may be classified using a wet cyclone or the like. classified using a wet cyclone or the like.

[0076] When some elements such as lithium are lost due to the high heat of the thermal plasma, it is preferable to mix with a material having the elements lost after the thermal plasma treatment. For example, it is preferable to mix with a lithium source such as lithium fluoride, lithium carbonate, or lithium chloride after the high - frequency induction thermal plasma treatment. If a material with a low melting point or a low Young's modulus is used as this lithium source, more of the material with a low melting point or a low Young's modulus can be included in the surface layer portion of the positive electrode active material 100, which is more preferable. more of the material with a low melting point or a low Young's modulus can be included in the surface layer portion of the positive electrode active material 100, which is more preferable. which is more preferable.

[0077] This high - frequency induction thermal plasma method is preferable in that it can produce the positive electrode active material 100 close to a perfect sphere. Also, since the particles can be oxidized, reduced, nitrided, or carbonized by the plasma gas, it can also serve as a process for surface modification of the positive electrode active material 100. it can also serve as a process for surface modification of the positive electrode active material 100.

[0078] Note that a part of the raw material of the positive electrode active material, for example, an oxide or hydroxide of a transition metal, is subjected to high - frequency induction It may be processed into a spherical shape by the thermal conductive plasma method. For example, the particle size of lithium cobaltate is known to be affected by the particle size of the raw material cobalt oxide or cobalt hydroxide. Therefore, it may also be possible to produce the substantially spherical positive electrode active material 100 by mixing a lithium source and an oxide or hydroxide of a transition metal processed into a spherical shape by the high-frequency induction thermal plasma method and then firing them. For example, when cobalt oxide is used as the raw material of the positive electrode active material and lithium fluoride is used as the lithium source, first, cobalt oxide is processed into a spherical shape by the high-frequency induction thermal plasma method. Next, the spherically processed cobalt oxide and lithium fluoride are mixed. The mixture is fired at, for example, 900 °C or higher and 1100 °C or lower for 10 hours. Even in such a process, it may be possible to produce the substantially spherical positive electrode active material 100.

[0079]

[0080] <Gas burner method> Alternatively, the material of the positive electrode active material 100 described above may be put into a high-temperature oxygen burner flame and melted to be spheroidized. The spheroidized particles after the treatment may be classified by a wet cyclone or the like.

[0081] This gas burner method is also preferable in that it can produce the positive electrode active material 100 close to a perfect sphere.

[0082] When some elements such as lithium are lost due to the high heat of the oxygen burner flame, it is preferable to mix with a material having the lost elements, similar to the high-frequency induction thermal plasma method.

[0083] Furthermore, similar to the high-frequency induction thermal plasma method, a part of the raw material of the positive electrode active material, for example, an oxide or hydroxide of a transition metal, may be processed into a spherical shape by the gas burner method. ​​​​​​​​​​​

[0084] The configuration described in this embodiment can be implemented in appropriate combination with other configurations described in this embodiment or configurations described in other embodiments.

[0085] (Embodiment 2) In this embodiment, examples of materials that can be used in the secondary battery having the positive electrode active material 100 described in the previous embodiment will be described. In this embodiment, a secondary battery in which a positive electrode, a negative electrode, and an electrolytic solution are wrapped in an exterior body will be described as an example.

[0086] [Positive Electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector.

[0087] [Positive Electrode Active Material Layer]< The positive electrode active material layer has at least a positive electrode active material. Further, the positive electrode active material layer may contain other substances such as a film on the surface of the active material, a conductive assistant, or a binder in addition to the positive electrode active material.

[0088] As the positive electrode active material, the positive electrode active material 100 described in the previous embodiment can be used. By using the positive electrode active material 100 described in the previous embodiment, a secondary battery with high capacity and excellent cycle characteristics can be obtained.

[0089] As the conductive assistant, a carbon material, a metal material, a conductive ceramic material, or the like can be used. Further, a fibrous material may be used as the conductive assistant. The content of the conductive assistant with respect to the total amount of the active material layer is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less.

[0090] The conductive assistant can form an electric conduction network in the active material layer. ​​​​​​​​​The agent can maintain the electrical conduction path between the positive electrode active materials. Conductivity By adding an electroconductive aid, an active material layer having high electrical conductivity can be realized. .

[0091] As the electroconductive aid, for example, natural graphite, artificial graphite such as mesocarbon microbeads, carbon fiber etc. can be used. As the carbon fiber, for example, carbon fibers such as mesophase pitch-based carbon fibers , isotropic pitch-based carbon fibers, etc. can be used. Also, as the carbon fiber, carbon nanofibers, carbon nanotubes, etc. can be used. Carbon nanotubes can be produced by, for example, a vapor phase growth method. Further, as the electroconductive aid, for example carbon black (such as acetylene black (AB)), graphite (black lead) particles , carbon materials such as graphene, fullerenes, etc. can be used. Also, for example, metals such as copper, nickel , aluminum, silver, gold, etc., metal powders, metal fibers, conductive ceramic materials, etc. can be used.

[0092] Further, a graphene compound may be used as the electroconductive aid.

[0093] The graphene compound may have excellent electrical properties such as high electrical conductivity, and excellent physical properties such as high flexibility and high mechanical strength. Also, the graphene compound has a planar shape. The graphene compound enables surface contact with low contact resistance . Also, it may have very high electrical conductivity even when thin, and can efficiently form an electrical conduction path in the active material layer with a small amount. Therefore, using the graphene compound as the electroconductive aid can increase the contact area between the active material and the electroconductive aid, which is preferable. Spr ​By using a spray drying device, it is preferable to form a graphene compound, which is a conductive aid, as a film covering the entire surface of the active material. Also, it may be preferable because it can reduce electrical resistance. Here, as the graphene compound, for example, graphene, multi-graphene, or RGO is particularly preferably used. Here, RGO refers to a compound obtained by reducing graphene oxide (GO). When using an active material with a small particle size, for example, an active material of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive aid tends to increase, and the amount of the active material supported relatively decreases. When the amount of the active material supported decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as the conductive aid, since the graphene compound can efficiently form a conductive path even in a small amount, it is not necessary to reduce the amount of the active material supported, which is particularly preferable. Here, as the graphene compound, for example, graphene, multi-graphene, or RGO is particularly preferably used. Here, RGO refers to a compound obtained by reducing graphene oxide (GO). When using an active material with a small particle size, for example, an active material of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive aid tends to increase, and the amount of the active material supported relatively decreases. When the amount of the active material supported decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as the conductive aid, since the graphene compound can efficiently form a conductive path even in a small amount, it is not necessary to reduce the amount of the active material supported, which is particularly preferable. Here, as the graphene compound, for example, graphene, multi-graphene, or RGO is particularly preferably used. Here, RGO refers to a compound obtained by reducing graphene oxide (GO).

[0094] When using an active material with a small particle size, for example, an active material of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive aid tends to increase, and the amount of the active material supported relatively decreases. When the amount of the active material supported decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as the conductive aid, since the graphene compound can efficiently form a conductive path even in a small amount, it is not necessary to reduce the amount of the active material supported, which is particularly preferable. When using an active material with a small particle size, for example, an active material of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive aid tends to increase, and the amount of the active material supported relatively decreases. When the amount of the active material supported decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as the conductive aid, since the graphene compound can efficiently form a conductive path even in a small amount, it is not necessary to reduce the amount of the active material supported, which is particularly preferable. When using an active material with a small particle size, for example, an active material of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive aid tends to increase, and the amount of the active material supported relatively decreases. When the amount of the active material supported decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as the conductive aid, since the graphene compound can efficiently form a conductive path even in a small amount, it is not necessary to reduce the amount of the active material supported, which is particularly preferable. When using an active material with a small particle size, for example, an active material of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive aid tends to increase, and the amount of the active material supported relatively decreases. When the amount of the active material supported decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as the conductive aid, since the graphene compound can efficiently form a conductive path even in a small amount, it is not necessary to reduce the amount of the active material supported, which is particularly preferable. When using an active material with a small particle size, for example, an active material of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive aid tends to increase, and the amount of the active material supported relatively decreases. When the amount of the active material supported decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as the conductive aid, since the graphene compound can efficiently form a conductive path even in a small amount, it is not necessary to reduce the amount of the active material supported, which is particularly preferable. When using an active material with a small particle size, for example, an active material of 1 μm or less, the specific surface area of the active material is large, and more conductive paths connecting the active materials are required. Therefore, the amount of the conductive aid tends to increase, and the amount of the active material supported relatively decreases. When the amount of the active material supported decreases, the capacity of the secondary battery decreases. In such a case, when using a graphene compound as the conductive aid, since the graphene compound can efficiently form a conductive path even in a small amount, it is not necessary to reduce the amount of the active material supported, which is particularly preferable.

[0095] Also, by using a spray drying device in advance, a graphene compound, which is a conductive aid, can be formed as a film covering the entire surface of the active material, and further, a conductive path can be formed between the active materials with the graphene compound. Also, by using a spray drying device in advance, a graphene compound, which is a conductive aid, can be formed as a film covering the entire surface of the active material, and further, a conductive path can be formed between the active materials with the graphene compound. Also, by using a spray drying device in advance, a graphene compound, which is a conductive aid, can be formed as a film covering the entire surface of the active material, and further, a conductive path can be formed between the active materials with the graphene compound.

[0096] As the binder, for example, 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. Also, fluororubber can be used as the binder. As the binder, for example, 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. Also, fluororubber can be used as the binder. As the binder, for example, 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. Also, fluororubber can be used as the binder. As the binder, for example, 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. Also, fluororubber can be used as the binder.

[0097] Also, as the binder, it is preferable to use, for example, a water-soluble polymer. As the water-soluble polymer, for example, polysaccharides can be used. As the polysaccharides, carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, cellulose derivatives such as diacetyl cellulose, regenerated cellulose, and starch can be used. Further, it is more preferable to use these water-soluble polymers in combination with the above-described rubber material.

[0098] Alternatively, as the binder, polystyrene, polymethyl acrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), poly ethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, isobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyvinyl chloride, ethylene propylene diene polymer, polyvinyl acetate vinyl, polymethyl methacrylate, nitrocellulose and other materials are preferably used.

[0099] The binder may be used in combination of a plurality of the above.

[0100] For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with other materials. For example, although rubber materials and the like are excellent in adhesive force and elastic force, it may be difficult to adjust the viscosity when mixed with a solvent. In such a case, for example, it is preferable to mix with a material having a particularly excellent viscosity adjusting effect. As the material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer may be used. ​ Yes. Further, as the water-soluble polymer particularly excellent in the viscosity adjustment effect, the above-mentioned polysaccharides such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxy propyl cellulose and diacetyl cellulose, cellulose derivatives such as regenerated cellulose, and starches can be used.

[0101] Note that cellulose derivatives such as carboxymethyl cellulose can be made into salts such as sodium salts and ammonium salts of carboxymethyl cellulose, etc., so that the solubility increases, and it becomes easier to exhibit the effect as a viscosity modifier. By increasing the solubility, the dispersibility with the active material and other components can also be enhanced when preparing the electrode slurry. In this specification, cellulose and cellulose derivatives used as the electrode binder shall include those salts thereof. When the water-soluble polymer dissolves in water, it has a viscosity suitable for mixing and dispersion, and the active material and other materials combined as a binder, such as styrene-butadiene rubber, etc., can be uniformly dispersed in an aqueous solution. Also, since it has a functional group, it is expected to be easily adsorbed on the surface of the active material. Further, cellulose derivatives such as carboxymethyl cellulose, for example, have many functional groups such as hydroxyl groups and carboxyl groups, and because they have functional groups, it is expected that the polymers interact with each other and exist widely covering the surface of the active material.

[0102] When the binder covering the surface of the active material or in contact with the surface forms a film, it is also expected to function as a passive film and suppress the decomposition of the electrolyte. Here, the passive film means an electrode

[0103] When the binder covering or in contact with the surface of the active material forms a film, it is also expected to function as a passive film and suppress the decomposition of the electrolyte. Here, the passive film means an electrode It is a non-conductive film or a film with extremely low electrical conductivity. For example, when a passive film is formed on the surface of the active material, it can suppress the decomposition of the electrolyte at the battery reaction potential. When a passive film is formed, it can suppress the decomposition of the electrolyte at the battery reaction potential. In addition, the passive film suppresses electrical conductivity while allowing lithium ions to conduct. This is more desirable.

[0104] <Positive current collector> As the positive current collector, highly conductive materials such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it can be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punching metal, expanded metal, etc. The current collector is preferably one with a thickness of 5 μm or more and 30 μm or less. For the positive current collector, materials with high conductivity such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it can be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punching metal, expanded metal, etc. The current collector is preferably one with a thickness of 5 μm or more and 30 μm or less. For the positive current collector, materials with high conductivity such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it can be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punching metal, expanded metal, etc. The current collector is preferably one with a thickness of 5 μm or more and 30 μm or less. For the positive current collector, materials with high conductivity such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it can be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punching metal, expanded metal, etc. The current collector is preferably one with a thickness of 5 μm or more and 30 μm or less. For the positive current collector, materials with high conductivity such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it can be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punching metal, expanded metal, etc. The current collector is preferably one with a thickness of 5 μm or more and 30 μm or less. For the positive current collector, materials with high conductivity such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it can be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punching metal, expanded metal, etc. The current collector is preferably one with a thickness of 5 μm or more and 30 μm or less. For the positive current collector, materials with high conductivity such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it can be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punching metal, expanded metal, etc. The current collector is preferably one with a thickness of 5 μm or more and 30 μm or less. For the positive current collector, materials with high conductivity such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it can be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punching metal, expanded metal, etc. The current collector is preferably one with a thickness of 5 μm or more and 30 μm or less. For the positive current collector, materials with high conductivity such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it can be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punching metal, expanded metal, etc. The current collector is preferably one with a thickness of 5 μm or more and 30 μm or less. For the positive current collector, materials with high conductivity such as metals like stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Also, the material used for the positive current collector preferably does not dissolve at the potential of the positive electrode. Additionally, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it can be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as foil, plate (sheet), net, punching metal, expanded metal, etc. The current collector is preferably one with a thickness of 5 μm or more and 30 μm or less.

[0105] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative current collector. Also, the negative electrode active material layer may have a conductive assistant and a binder. The negative electrode has a negative electrode active material layer and a negative current collector. Also, the negative electrode active material layer may have a conductive assistant and a binder.

[0106] <Negative electrode active material> As the negative electrode active material, for example, alloy-based materials, carbon-based materials, etc. can be used.

[0107] As the negative electrode active material, an element capable of performing charge and discharge reactions through alloying and dealloying reactions with lithium can be used. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used. Such elements have a larger capacity compared to carbon, and in particular, silicon has a high theoretical capacity of 4200 mAh / g. Therefore, it is preferable to use silicon as the negative electrode active material. Also, compounds containing these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V 2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3 Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, I nSb, SbSn, etc. exist. Here, elements capable of performing charge and discharge reactions through alloying and dealloying reactions with lithium, and compounds containing such elements, etc. may be referred to as alloy-based materials in some cases.

[0108] In this specification, etc., SiO refers to, for example, silicon monoxide. Alternatively, SiO can also be represented as SiO x Here, x preferably has a value near 1. For example, x is preferably 0 .2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0109] As the carbon-based material, graphite, graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, carbon black, etc. may be used.

[0110] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon​​​​ Examples include carbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spherical graphite having a spherical shape can be used as the artificial graphite. For example, MCMB may have a spherical shape, which is preferable. Also, it is relatively easy to reduce the surface area of MCMB, which may be preferable. Examples of natural graphite include flaky graphite, spheroidized natural graphite, and the like.

[0111] Graphite exhibits a potential as low as that of lithium metal when lithium ions are inserted into graphite (when forming a lithium-graphite intercalation compound) (0.05 V or more and 0.3 V or less vs. Li / L i i + ). As a result, a lithium-ion secondary battery can exhibit a high operating voltage. Furthermore, graphite has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and high safety compared to lithium metal, and thus is preferable.

[0112] In addition, oxides such as titanium dioxide (TiO2), lithium titanate (Li4T i5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5) , tungsten oxide (WO2), and molybdenum oxide (MoO2) can be used as the negative electrode active material.

[0113] In addition, Li M 3-x N (M = Co, Ni, Cu) having an Li3N-type structure, which is a complex nitride of lithium and a transition metal, can be used as the negative electrode active material. For example, Li x Co 2.6 N3 has a large charge-discharge capacity (900 mAh / g, 1890 mAh / cm 0.4 3) 3) is shown and is preferable.

[0114] When using a complex nitride of lithium and a transition metal, since the negative electrode active material contains lithium ions, it can be combined with materials such as V2O5 and Cr3O8 that do not contain lithium ions as the positive electrode active material and is preferable. Even when using a material containing lithium ions for the positive electrode active material, by previously desorbing the lithium ions contained in the positive electrode active material, it is possible to use a complex nitride of lithium and a transition metal as the negative electrode active material.

[0115] Also, a material in which a conversion reaction occurs can be used as the negative electrode active material. For example, transition metal oxides such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO) that do not form an alloy with lithium may be used as the negative electrode active material. As materials in which a conversion reaction occurs, further, oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3 CoS 0.89 sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N, and Ge3 N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3 also occur.

[0116] As the conductive assistant and binder that the negative electrode active material layer can have, the same materials as those that the positive electrode active material layer can have can be used.

[0117] [Negative electrode current collector] For the negative electrode current collector, the same materials as those for the positive electrode current collector can be used. Note that it is preferable to use a material that does not alloy with carrier ions such as lithium for the negative electrode current collector.

[0118] [Electrolyte] The electrolyte has a solvent and an electrolyte. As the solvent of the electrolyte, an aprotic organic solvent is preferred. For example, 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), 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., one kind, or two or more of these can be used in any combination and ratio. , 3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., one kind, or two or more of these can be used in any combination and ratio. combination and ratio.

[0119] In addition, as the solvent of the electrolyte, by using one or more ionic liquids (room temperature molten salts) that are flame retardant and hardly volatile, even if the internal temperature rises due to internal short circuit, overcharge, etc. in the secondary battery, rupture, ignition, etc. of the secondary battery can be prevented. An ionic liquid consists of a cation and an anion and contains an organic cation and an anion. As the organic cation used in the electrolyte, quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, etc. aliphatic onium cations such as, and aromatic cations such as imidazolium cations and pyridinium cations. Also, as the anion used in the electrolyte, monovalent amide-based anions, monovalent methide-based anions, fluorosulfonic acid anions, perfluoroalkyl aromatic cations such as imidazolium cations and pyridinium cations. Also, as the anion used in the electrolyte, monovalent amide-based anions, monovalent methide-based anions, fluorosulfonic acid anions, perfluoroalkyl Sulfonic acid anion, tetrafluoroborate anion, perfluoroalkyl borate Anions, hexafluorophosphate anions, or perfluoroalkyl phosphates -to anions, etc. may be mentioned.

[0120] In addition, examples of the electrolyte dissolved in the above solvent include LiPF6, LiClO4, Li AsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4 、Li2B 10 Cl 10 、Li2B 12 Cl 12 、LiCF3SO3、LiC4F9SO 3、LiC(CF3SO2)3、LiC(C2F5SO2)3、LiN(CF3SO2) 2、LiN(C4F9SO2)(CF3SO2)、LiN(C2F5SO2)2, etc. of lithium Salts can be used alone or in any combination and ratio of two or more of these. It is possible.

[0121] The electrolyte used in the secondary battery is preferably a highly purified electrolyte with a low content of particulate dust and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). Specifically, the weight ratio of impurities to the electrolyte is preferably 1% or less, more preferably 0.1% or less, and even more preferably 0.01% or less. Pure substances" is also referred to.) Specifically, the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less, more preferably Preferably, it is 0.01% or less.

[0122] In addition, additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), LiBOB, or dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the additive material may be, for example, 0.1 wt% or more and 5 wt% or less based on the total amount of the solvent. N, TBB), fluoroethylene carbonate (FEC), LiBOB, or succinonitrile, adiponitrile, etc. of dinitrile compounds and other additives may be added. The concentration of the additive material added Nitrile, adiponitrile and other dinitrile compounds and other additives may be added. The concentration of the additive material added For example, it may be 0.1 wt% or more and 5 wt% or less with respect to the entire solvent. .

[0123] Alternatively, a polymer gel electrolyte obtained by swelling a polymer with an electrolytic solution may be used.

[0124] By using a polymer gel electrolyte, the safety against liquid leakage and the like is enhanced. Also, the secondary battery can be made thinner and lighter.

[0125] As the polymer to be gelled, silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide-based gel, polypropylene oxide-based gel, gels of fluorine-based polymers, etc. can be used.

[0126] As the polymer, for example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, etc., and copolymers containing them can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (H FP), can be used. Also, the formed poly mer may have a porous shape.

[0127] Alternatively, instead of the electrolytic solution, a solid electrolyte having an inorganic material such as a sulfide-based or oxide-based material, or a solid electrolyte having a polymer material such as a P EO (polyethylene oxide)-based material can be used. When a solid electrolyte is used, it is not necessary to provide a separator or a spacer. Also, since the entire battery can be solidified, the risk of liquid leakage is eliminated and the safety is dramatically improved.

[0128] [Separator] Also, the secondary battery preferably has a separator. Examples of the separator include paper nonwoven fabric, glass fiber, ceramics, or nylon (polyamide), vinylon (poly​​ Vinyl alcohol-based fibers), polyester, acrylic, polyolefin, polyurethane, etc. Synthetic fibers or the like formed using the above can be used. The separator is preferably processed into an envelope shape and arranged to wrap either the positive electrode or the negative electrode.

[0129] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic-based material, a fluorine-based material, a polyamide-based material, or a mixture thereof. As the ceramic-based material, for example, aluminum oxide particles, silicon oxide particles, etc. can be used. As the fluorine-based material, for example, PVDF, polytetrafluoroethylene, etc. can be used. As the polyamide-based material, for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used. Coating with a ceramic-based material improves oxidation resistance, so it is possible to suppress deterioration of the separator during high-voltage charge and discharge and improve the reliability of the secondary battery. Also, coating with a fluorine-based material makes it easier for the separator and the electrode to adhere, and can improve the output characteristics. Coating with a polyamide-based material, especially aramid, improves heat resistance, so it is possible to improve the safety of the secondary battery. For example, a mixed material of aluminum oxide and aramid can be coated on both sides of a polypropylene film. Also, a mixed material of aluminum oxide and aramid can be coated on the surface of the polypropylene film that contacts the positive electrode, and a fluorine-based material can be coated on the surface that contacts the negative electrode.

[0130]

[0131]

[0132] When a separator with a multilayer structure is used, even if the overall thickness of the separator is thin, the safety of the secondary battery can be maintained, so that the capacity per unit volume of the secondary battery can be increased.

[0133] [Outer casing] As the outer casing of the secondary battery, for example, a metal material such as aluminum or a resin material can be used It is also possible to use a film-shaped outer casing. As the film, for example, a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. is provided with a metal thin film excellent in flexibility such as aluminum, stainless steel, copper, nickel, etc. on the film, and further, a polyamide-based resin, polyester A three-layer film provided with an insulating synthetic resin film such as a resin film on the metal thin film as the outer surface of the outer casing can be used.

[0134] [Charging and discharging method] The charging and discharging of the secondary battery can be performed, for example, as follows.

[0135] ≪CC charging≫ First, CC charging will be described as one of the charging methods. CC charging is a charging method in which a constant current is passed through the secondary battery throughout the charging period, and the charging is stopped when a predetermined voltage is reached. Assume that the secondary battery 350 has an equivalent circuit of internal resistance R and secondary battery capacity C as shown in Fig. 4(A). In this case, the secondary battery voltage V is the sum of the voltage V applied to the internal resistance R and the voltage V B applied to the secondary battery capacity C. R During CC charging, as shown in Fig. 4(A), the switch is turned on and a constant current is applied. C

[0136] During CC charging, as shown in Fig. 4(A), the switch is on, and a constant current is applied. ​​​Current I flows into the secondary battery 350. During this time, since the current I is constant, V R = R×I according to Ohm's law, the voltage V across the internal resistance R is also constant. On the other hand, the voltage V across the secondary battery capacitance C R rises with the passage of time. Therefore, the secondary battery voltage V across it C rises with the passage of time. B As time passes it rises.

[0137] And when the secondary battery voltage V B reaches a predetermined voltage, for example, 4.3V, the charging is stopped. When the CC charging is stopped, as shown in Fig. 4(B), the switch turns off and the current I = 0 . Therefore, the voltage V across the internal resistance R becomes 0V. As a result, due to the elimination of the voltage drop across the internal resistance R R , the secondary battery voltage V drops. B

[0138] Examples of the secondary battery voltage V B and the charging current during CC charging and after the CC charging is stopped are shown in Fig. 4(C). During CC charging, the secondary battery voltage V which was rising is shown to drop slightly after the CC charging is stopped. B while it was rising during CC charging, drops slightly after the CC charging is stopped.

[0139] ≪CCCV Charging≫ Next, CCCV charging, which is a charging method different from the above, will be described. CCCV charging first performs charging up to a predetermined voltage by CC charging, and then performs charging by CV (constant voltage) charging until the current flowing becomes less, specifically until it reaches the termination current value.

[0140] During CC charging, as shown in Fig. 5(A), the switch of the constant current power supply 351 is on When the switch of the constant voltage power supply 352 is turned off, a constant current I flows into the secondary battery. During this period, since the current I is constant, according to Ohm's law of V R =R×I, the voltage V across the internal resistance R is also constant. On the other hand, the voltage V R across the secondary battery capacity C increases C with the passage of time. Therefore, the secondary battery voltage V increases with the passage of time. B

[0141] And when the secondary battery voltage V B reaches a predetermined voltage, for example, 4.3V, the charging is switched from CC charging to C V charging. During the CV charging, as shown in Fig. 5(B), the switch of the constant voltage power supply is turned on, the switch of the constant current power supply is turned off, and the secondary battery voltage V B becomes constant. On the other hand, the voltage V C across the secondary battery capacity C increases with the passage of time. Since V B =V R +V C , the voltage V R across the internal resistance R decreases with the passage of time. As the voltage V across the internal resistance R decreases, according to Ohm's law of V R =R×I, the current I flowing into the secondary battery also decreases. R

[0142] And when the current I flowing into the secondary battery reaches a predetermined current, for example, a current equivalent to 0.01C, all switches are turned off to stop the charging. When the CCCV charging is stopped, as shown in Fig. 5(C) , the current I = 0. Therefore, the voltage V R across the internal resistance R becomes 0V. . However, since the voltage V R across the internal resistance R has become sufficiently small due to the CV charging, Even when the voltage drop due to the internal resistance R disappears, the secondary battery voltage V B hardly drops.

[0143] During CCCV charging and after stopping CCCV charging, the secondary battery voltage V B and the charging current example are shown in FIG. 5(D). Even when CCCV charging is stopped, the secondary battery voltage V B is shown hardly dropping.

[0144] ≪CC Discharge≫ Next, CC discharge, which is one of the discharge methods, will be described. CC discharge flows a constant current from the secondary battery throughout the discharge period, and the secondary battery voltage V is discharged when it reaches a predetermined voltage, for example, 2.5V. B This is a discharge method that stops discharging when it reaches a certain voltage.

[0145] Examples of the secondary battery voltage V B and the discharge current during CC discharge are shown in FIG. 6. As the discharge progresses, the secondary battery voltage V B is shown to be decreasing.

[0146] Next, the discharge rate and the charge rate will be described. The discharge rate is the relative ratio of the current during discharge to the battery capacity, and is expressed in units of C. In a battery with a rated capacity of X (Ah), a current equivalent to 1C is X (A). When discharging with a current of 2X (A), it is said to be discharging at 2C, and when discharging with a current of X / 5 (A), it is said to be discharging at 0.2C. Similarly, for the charge rate, when charging with a current of 2X (A), it is said to be charging at 2C, and when charging with a current of X / 5 (A), it is said to be charging at 0.2C. That is. .

[0147] (Embodiment 3) In this embodiment, the shape of the secondary battery having the positive electrode active material 100 described in the previous embodiment will be described. An example thereof will be described. The materials used in the secondary battery described in this embodiment can refer to the description of the previous embodiment.

[0148] [Coin-type secondary battery] First, an example of a coin-type secondary battery will be described. FIG. 7(A) is an external view of a coin-type (single-layer flat-type) secondary battery, and FIG. 7(B) is a cross-sectional view thereof.

[0149] The coin-type secondary battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal, which are insulated and sealed with a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact therewith. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact therewith.

[0150] Note that for the positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300, the active material layers may be formed only on one side.

[0151] The positive electrode can 301 and the negative electrode can 302 can be made of metals such as nickel, aluminum, titanium, etc. that are corrosion-resistant to the electrolyte, or alloys thereof or alloys of these with other metals (e.g., stainless steel etc.). Also, in order to prevent corrosion by the electrolyte, it is preferable to coat with nickel or aluminum etc. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 30 7 respectively.

[0152] These negative electrode 307, positive electrode 304, and separator 310 are impregnated with the electrolyte, as shown in FIG. 7(B) As shown in [Fig.], with the positive electrode can 301 facing downwards, the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are crimped via a gasket 303 to manufacture a coin-shaped secondary battery 300.

[0153] By using the positive electrode active material described in the previous embodiment for the positive electrode 304, a coin-type secondary battery 300 with high capacity and excellent cycle characteristics can be obtained.

[0154] Here, the flow of current during charging of the secondary battery will be described with reference to Fig. 7(C). When a secondary battery using lithium is regarded as a single closed circuit, the movement of lithium ions and the flow of current are in the same direction. In a secondary battery using lithium, the anode (positive electrode) and cathode (negative electrode) are reversed during charging and discharging, and the oxidation reaction and reduction reaction are also reversed. Therefore, the electrode with a high reaction potential is called the positive electrode, and the electrode with a low reaction potential is called the negative electrode. Therefore, in this specification, regardless of whether it is during charging or discharging, the positive electrode is called the "positive electrode" or the "+ electrode (plus electrode) ", and the negative electrode is called the "negative electrode" or the "- electrode (minus electrode)". When using terms such as anode (positive electrode) and cathode (negative electrode) related to oxidation and reduction reactions, it will be reversed during charging and discharging, which may cause confusion. Therefore, the terms anode ( positive electrode) and cathode (negative electrode) are not used in this specification. ", and the negative electrode is called the "negative electrode" or the "- electrode (minus electrode)". When using terms such as anode (positive electrode) and cathode (negative electrode) related to oxidation and reduction reactions, it will be reversed during charging and discharging, which may cause confusion. Therefore, the terms anode ( positive electrode) and cathode (negative electrode) are not used in this specification. positive electrode) and cathode (negative electrode) are not used in this specification.

[0155] A charger is connected to the two terminals shown in Fig. 7(C), and the secondary battery 300 is charged. As the charging of the secondary battery 300 progresses, the potential difference between the electrodes increases.

[0156] [Cylindrical Secondary Battery] Next, an example of a cylindrical secondary battery will be described with reference to FIG. 8. The cylindrical secondary battery 400 has , as shown in FIG. 8(A), a positive electrode cap (battery lid) 401 on the upper surface, and a battery can (outer can) 402 on the side surface and the bottom surface. The positive electrode cap 401 and the battery can (outer can ) 402 are insulated by a gasket (insulating packing) 410.

[0157] FIG. 8(B) is a diagram schematically showing a cross section of the cylindrical secondary battery 400. Only the bottom surface of the battery can 402 is shown in order to explain the internal structure. Inside the hollow cylindrical battery can 402, , a battery element in which a strip-shaped positive electrode 404 and a negative electrode 406 are wound with a separator 405 interposed therebetween is provided. For the battery can 402, metals such as nickel, aluminum nickel, titanium, etc. that are corrosion-resistant to the electrolytic solution, or alloys of these or alloys of these and other metals (for example, stainless steel, etc.) can be used. Further, in order to prevent corrosion by the electrolytic solution, it is preferable to coat with nickel or aluminum etc. Also, the inside of the battery can 402 in which the battery element is provided is filled with a non-aqueous electrolytic solution (not shown). The non-aqueous electrolytic solution can be the same as that used for the coin-type secondary battery.

[0158] Since the positive electrode and the negative electrode used in the cylindrical secondary battery are wound, it is preferable to form the active material on both sides of the current collector. A positive electrode terminal (positive electrode current collecting lead) 403 is connected to the positive electrode 404, and a negative electrode terminal (negative electrode current collecting lead) 407 is connected to the negative electrode 406. Both the positive electrode terminal 403 and the negative electrode terminal 407 can be made of a metal material such as aluminum. The negative electrode terminal 4 07 is welded to the bottom of the battery can 402. The positive electrode terminal 403 is welded to the conductive plate 419, and the explosion-proof ​The plate 412 and the PTC element (Positive Temperature Coeffi cient) 411 are electrically connected to the positive electrode cap 401 via the PTC element 411 is a thermal resistance element whose resistance increases when the temperature rises, and by increasing the resistance, it restricts the electric flow rate to prevent abnormal heat generation. For the PTC element, barium titanate (B aTiO3)-based semiconductor ceramics or the like can be used.

[0159] Also, as shown in FIG. 8(C), a module 415 may be configured by sandwiching a plurality of secondary batteries 400 between the conductive plates 413 and 414. The plurality of secondary batteries 400 are electrically connected to the conductive plates 413 and 414 by wires 416. The plurality of secondary batteries 400 may be connected in parallel, in series, or may be connected in series after being connected in parallel. By configuring a module 415 having a plurality of secondary batteries 400 it is possible to extract a large amount of power.

[0160] FIG. 8(D) is a top view of the module 415. For clarity, the conductive plate 413 is shown by a dotted line. As shown in FIG. 8(D), a temperature control device 417 may be provided between the plurality of secondary batteries 400. When the secondary battery 400 overheats, it can be cooled by the temperature control device 417, and when the secondary battery 400 is too cold, it can be heated by the temperature control device 417. Therefore, the performance of the module 415 is less affected by the outside air temperature. Also, a buffer material 418 can be provided between the plurality of secondary batteries 400 and between the temperature control device 417 and the secondary battery 400. By providing the buffer material 418, the secondary batteries 400 are prevented from contacting each other and the temperature control device 417, and between the temperature control device 417 and the secondary battery 400, a buffer material 418 can be provided. By providing the buffer material 418, the secondary batteries 400 are prevented from contacting each other and the temperature control device 417, and between the temperature control device 417 and the secondary battery 400, a buffer material 418 can be provided. By providing the buffer material 418, the secondary batteries 400 are prevented from contacting each other and the temperature control device 417, and between the temperature control device 417 and the secondary battery 400, a buffer material 418 can be provided. By providing the buffer material 418, the secondary batteries 400 are prevented from contacting each other and the temperature control device 417, and between the temperature control device 417 and the secondary battery 400, a buffer material 418 can be provided. By providing the buffer material 418, the secondary batteries 400 are prevented from contacting each other and the temperature control device 417, and between the temperature control device 417 and the secondary battery 400, a buffer material 418 can be provided. By providing the buffer material 418, the secondary batteries 400 are prevented from contacting each other Or, by having the temperature control device 417 come into contact with the secondary battery 400, it is possible to prevent damage to the battery can 402 and the temperature control device 417 and the like. It can be prevented from being damaged.

[0161] By using the positive electrode active material described in the previous embodiment for the positive electrode 404, a cylindrical secondary battery 400 with high capacity and excellent cycle characteristics can be obtained. It can be made into a cylindrical secondary battery 400 with excellent characteristics.

[0162] In FIGS. 8(C) and 8(D), an example of a module 415 having 24 secondary batteries 400 was described. However, as shown in FIG. 9(A), a module 420 having more secondary batteries 400 may also be used. The plurality of secondary batteries 400, conductive plates 413 and conductive plates 414 included in the module 420 are preferably arranged inside the housing 423. Further, the module 420 preferably has a positive electrode terminal 421 and a negative electrode terminal 422 that are electrically connected to the conductive plate 413 or the conductive plate 414. Further, it preferably has a temperature control device 417 and a cushioning material 418. For example, as shown in FIG. 9(A), a module 420 having more secondary batteries 400 may be used. The plurality of secondary batteries 400, conductive plates 413 and conductive plates 414 included in the module 420 are preferably arranged inside the housing 423. Further, the module 420 preferably has a positive electrode terminal 421 and a negative electrode terminal 422 that are electrically connected to the conductive plate 413 or the conductive plate 414. Further, it preferably has a temperature control device 417 and a cushioning material 418.

[0163] In FIG. 9(A), a module 420 having a cylindrical secondary battery 400 was described. However, the present invention is not limited to this. For example, a module having a secondary battery in which a plurality of strip-shaped positive electrodes and negative electrodes are stacked may be used. However, it is not limited to this. For example, a module having a secondary battery in which a plurality of strip-shaped positive electrodes and negative electrodes are stacked may be used.

[0164] Furthermore, as shown in FIG. 9(B), a larger module 430 having a plurality of modules 420 may be used. By mounting the module 430 on a vehicle 440 as shown in FIG. 9(C), for example, next-generation clean energy vehicles such as hybrid electric vehicles (HEV), electric vehicles (EV), or plug-in hybrid electric vehicles (PHEV) can be realized. By mounting the module 430 on a vehicle 440 as shown in FIG. 9(C), for example, next-generation clean energy vehicles such as hybrid electric vehicles (HEV), electric vehicles (EV), or plug-in hybrid electric vehicles (PHEV) can be realized.

[0165] ​​​​The vehicle 440 shown in Fig. 9(C) 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. By using one aspect of the present invention, a vehicle with a long cruising range can be realized.

[0166] The secondary battery can not only drive an electric motor (not shown), but also supply power to a light-emitting device such as a headlight or a room light. In addition, the secondary battery can supply power to a display device such as a speedometer, a tachometer, and a navigation system, and a semiconductor device that the vehicle 440 has.

[0167] The vehicle 440 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 secondary battery that the module 430 has. Fig. 9(C) shows a state in which charging is being performed from a ground-installed charging device 451 via a cable 452. At the time of charging, the charging method, the standard of the connector, etc. may be appropriately performed by a predetermined method such as CHAdeMO (registered trademark) or Combo. The charging device 451 may be a charging station provided in a commercial facility, or may be a household power source. For example, by the plug-in technology, the module 430 mounted on the vehicle 440 can be charged by power supply from the outside. Charging can be performed by converting AC power into DC power via a conversion device such as an AC-DC converter.

[0168] Also, although not shown, a power receiving device can be mounted on the vehicle, and power can be supplied non-contact from a ground power transmission device for charging. In the case of this non-contact power supply method, a power transmission device is installed on a road or an outer wall. By incorporating it, charging can be performed not only while the vehicle is stationary but also while it is in motion. Also, with this non-contact power supply method, power can be transmitted and received between vehicles. Furthermore, a solar cell may be provided on the exterior of the vehicle to charge the secondary battery when the vehicle is stationary or in motion. For such non-contact power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0169] Also, FIG. 9(D) is an example of a two-wheeled vehicle using the secondary battery of one aspect of the present invention. The scooter 460 shown in FIG. 9(D ) includes a secondary battery 462, a side mirror 461, and a direction indicator 464. The secondary battery 462 can supply electricity to a motor (not shown), a headlight (not shown), the direction indicator 46 4, etc.

[0170] The scooter 460 can store the secondary battery 462 in the under-seat storage. Since the secondary battery 46 2 has a high energy density, it can be stored even in a small under-seat storage space. The secondary battery 462 is removable, and during charging, the secondary battery 462 can be carried indoors, charged, and then stored before driving.

[0171] According to one aspect of the present invention, the cycle characteristics of the secondary battery are improved, and the capacity of the secondary battery can be increased. Therefore, the secondary battery itself can be made smaller and lighter. If the secondary battery itself can be made smaller and lighter, it contributes to the weight reduction of the vehicle, so the cruising range can be improved. Also, the secondary battery mounted on the vehicle can be used as a power supply other than the vehicle. In this case, for example, it is possible to avoid using a commercial power supply during the peak of power demand. If it is possible to avoid using a commercial power supply during the peak of power demand, energy conservation and two It can contribute to the reduction of carbon dioxide emissions. Also, if the cycle characteristics are good, the secondary battery can be used over a long period, reducing the usage amount of rare metals such as cobalt

[0172] [Secondary battery pack] Next, an example of a battery pack having a secondary battery and a function of protecting or controlling the secondary battery will be described with reference to FIGS. 10 and 11.

[0173] FIG. 10(A) is a diagram showing the appearance of a secondary battery pack 530. FIG. 10(B) is a diagram for explaining the configuration of the secondary battery pack 530. The secondary battery pack 530 includes a circuit board 500 and a secondary battery 513. A label 510 is attached to the secondary battery 513. The circuit board 500 is fixed by a seal 515. The secondary battery pack 530 also has an antenna 514.

[0174] The circuit board 500 has a circuit 512 having a function of protecting or controlling the secondary battery 513 . The circuit board 500 is electrically connected to a terminal 511. The circuit board 500 is also electrically connected to the antenna 514, one of the positive and negative leads 551 of the secondary battery 513, and the other of the positive and negative leads 552.

[0175] Note that the antenna 514 is not limited to a coil shape and may be, for example, linear or plate-shaped. Also, a planar antenna, aperture antenna, traveling wave antenna, EH antenna, magnetic field antenna, dielectric body antenna, or the like may be used. Alternatively, the antenna 914 may be a flat conductor . This flat conductor can function as one of the conductors for electric field coupling. That is, ​As one of the two conductors of the capacitor, the antenna 914 may function. Thus, not only electromagnetic fields and magnetic fields but also electric fields can be used to exchange power.

[0176] The secondary battery pack 530 has a layer 516 between the antenna 514 and the secondary battery 513. The layer 516 has a function that can prevent, for example, the influence of the secondary battery 513 on the electromagnetic field. As the layer 516, for example, a magnetic material can be used.

[0177] The secondary battery 513 has a wound battery element 593 as shown in Fig. 10(C). The battery element 593 has a negative electrode 594, a positive electrode 595, and a separator 596. The battery element 593 is formed by laminating the negative electrode 594 and the positive electrode 595 with the separator 596 interposed therebetween, and winding the laminated sheet.

[0178] Note that the structure of the secondary battery is not limited to that shown in Fig. 10.

[0179] For example, as shown in Figs. 11(A-1) and 11(A-2), antennas may be provided on each of a pair of opposing surfaces of the secondary battery pack 530. Fig. 11(A-1) is an external view seen from one side direction of the pair of surfaces, and Fig. 11(A-2) is an external view seen from the other side direction of the pair of surfaces. As shown in Fig. 11(A-1), the antenna 514 is provided with the layer 516 interposed therebetween on one of the pair of surfaces of the secondary battery pack 530, and as shown in Fig. 11(A-2), the antenna 518 is provided with the layer 5 17 interposed therebetween on the other of the pair of surfaces. The layer 517 has a function that can prevent, for example, the influence of the secondary battery 513 on the electric

[0180] As shown in Fig. 11(A-1), the antenna 514 is provided with the layer 516 interposed therebetween on one of the pair of surfaces of the secondary battery pack 530, and as shown in Fig. 11(A-2), the antenna 518 is provided with the layer 5 17 interposed therebetween on the other of the pair of surfaces. The layer 517 has a function that can prevent, for example, the influence of the secondary battery 513 on the electric ​​​It has a function capable of preventing the influence on the magnetic field. As the layer 517, for example, a magnetic material can be used.

[0181] By adopting the above structure, the sizes of both the antenna 514 and the antenna 518 can be increased The antenna 518 has a function capable of, for example, performing data communication with an external device. For the antenna 518, for example, an antenna having a shape applicable to the antenna 514 can be applied. As a communication method between the secondary battery and other devices via the antenna 518, for example, a response method such as NFC that can be used between the secondary battery and other devices can be applied.

[0182] Alternatively, as shown in FIG. 11(B-1), a display device 520 may be provided on the secondary battery pack 530. The display device 520 is electrically connected to the terminal 511. Note that a label 510 may not be provided at the portion where the display device 520 is provided.

[0183] The display device 520 may display, for example, an image indicating whether charging is in progress, an image indicating the remaining power, etc. As the display device 520, for example, an electronic paper, a liquid crystal display device, an electroluminescence (also referred to as EL) display device, etc. can be used. For example, by using an electronic paper, the power consumption of the display device 520 can be reduced.

[0184] Alternatively, as shown in FIG. 11(B-2), a sensor 521 may be provided on the secondary battery pack 530. The sensor 521 is electrically connected to the terminal 911 via the terminal 522.

[0185] As the sensor 521, for example, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light ​​, it suffices to have a function capable of measuring liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays. By providing the sensor 521, for example, data indicating the environment where the secondary battery is placed (such as temperature) can be detected and stored in the memory within the circuit 512. (Temperature, etc.) can also be detected and stored in the memory within the circuit 512.

[0186] [Electronic device] Next, an example of mounting a secondary battery, which is one aspect of the present invention, on an electronic device will be described with reference to FIGS. 12 and 13.

[0187] FIG. 12(A) shows an example of a mobile phone. The mobile phone 600 includes a display unit 602 incorporated in a housing 601, as well as operation buttons 603, an external connection port 604, a speaker 60 5, a microphone 606, and the like. The mobile phone 600 has a secondary battery 607. By using the secondary battery of one aspect of the present invention for the secondary battery 607, a lightweight and long-life mobile phone can be provided. By using the secondary battery of one aspect of the present invention for the secondary battery 607, a lightweight and long-life mobile phone can be provided.

[0188] The mobile phone 600 can execute various applications such as mobile phone calls, e-mails, text viewing and creation, music playback, Internet communication, and computer games.

[0189] The operation buttons 603 can have various functions such as time setting, power on / off operation, wireless communication on / off operation, execution and cancellation of the silent mode, execution and cancellation of the power-saving mode, etc. For example, the functions of the operation buttons 603 can be freely set by the operating system incorporated in the mobile phone 600. For example, the functions of the operation buttons 603 can be freely set by the operating system incorporated in the mobile phone 600.

[0190] ​In addition, the mobile phone 600 is capable of performing short-range wireless communication that complies with a communication standard. For example, by communicating with a wireless-enabled headset, it is possible to make hands-free calls.

[0191] The mobile phone 600 also has an external connection port 604 and can directly exchange data with other information terminals via a connector. Also, charging can be performed via the external connection port 604. Note that the charging operation may also be performed by wireless power supply without using the external connection port 604.

[0192] The mobile phone 600 preferably has sensors. Examples of the sensors include human body sensors such as fingerprint sensors, pulse sensors, and body temperature sensors, as well as touch sensors, pressure sensors, acceleration sensors, etc. It is preferable that these sensors are mounted.

[0193] Figures 12(B1) and 12(B2) show an example of an electronic device having a foldable display unit. The electronic device 610 has, in addition to a foldable display unit 611 incorporated in a housing 612, an external connection port 613, an external connection port 614, and a secondary battery 615. By using the secondary battery of one aspect of the present invention for the above secondary battery 615, a lightweight and long-life electronic device can be provided. By having a foldable display unit 611, it is possible to achieve both improved visibility with a large display unit and improved portability. As the display unit 611, for example, an EL display device can be used. At least a part of the display unit 611 has the function of a touch panel.

[0194]

[0195] ​​​​​​​​​​​​Also, as shown in FIG. 12(B2), the electronic device 610 may also have a display unit 616 on the back surface of the display unit 611. It may have 616.

[0196] FIG. 12(C) shows an example of an e - book terminal. The e - book terminal 620 has a display unit 621, a circuit board 622, a secondary battery 623, a power button 624, and an operation button 625. By pressing the operation button 625, operations such as page turning can be performed. By using the secondary battery of one aspect of the present invention for the secondary battery 623 described above, a lightweight and long - life e - book terminal can be provided. By pressing the operation button 625, operations such as page turning can be performed. By using the secondary battery of one aspect of the present invention for the above - mentioned secondary battery 623, a lightweight and long - life e - book terminal can be provided. By using the secondary battery of one aspect of the present invention for the secondary battery 623, a lightweight and long - life e - book terminal can be provided. provided.

[0197] The circuit board 622 has a control circuit and a memory. Transistors using metal oxide in the channel - forming region can be applied to the control circuit and the memory. Since the transistor using metal oxide in the channel - forming region has an extremely low off - current, an e - book terminal 620 with low power consumption can be obtained. Transistors using metal oxide in the channel - forming region can be applied to the control circuit and the memory. Since the transistor using metal oxide in the channel - forming region has an extremely low off - current, an e - book terminal 620 with low power consumption can be obtained. Since the transistor using metal oxide in the channel - forming region has an extremely low off - current, an e - book terminal 620 with low power consumption can be obtained. obtained.

[0198] By shifting and arranging main components such as the circuit board 622 and the secondary battery 623 from the center of the e - book terminal 620, the center of gravity can be shifted to one side, and an e - book terminal 620 that is easy to hold with one hand can be obtained. By shifting and arranging main components such as the circuit board 622 and the secondary battery 623 from the center of the e - book terminal 620, the center of gravity can be shifted to one side, and an e - book terminal 620 that is easy to hold with one hand can be obtained. obtained.

[0199] FIG. 13(A1) and FIG. 13(A2) are diagrams showing an example of an earphone - type computer. The earphone - type computer preferably has two devices, for example, a first device 650a and a second device 650b, for wearing on the left and right ears. The first device 650a and the second device 650b both have a speaker 651, a control circuit 652, a secondary battery 653, and a microphone 654. Also, the first device 650a and the second device 650b both have a speaker 651, a control circuit 652, a secondary battery 653, and a microphone 654. Also, the first device 650a and the second Each of the devices 650b preferably has an acceleration sensor and a communication antenna. It is also preferable for the device to be equipped with a GPS.

[0200] The first device 650a and the second device 650b may, for example, use a microphone 654 to capture sound. The signal is converted into an electrical signal, which is then analyzed by the control circuit 7602. If the signal is a voice, it is recognized as a voice. If the language of the voice is not the language specified by the user, it is translated into the language specified by the user. The translation result can be output from the speaker 651.

[0201] The control circuit 652 is configured by applying a transistor using a metal oxide for a channel formation region. A transistor using a metal oxide for the channel formation region has an extremely low off-state current. Therefore, the first device 650a and the second device 650b have low power consumption. This can be done.

[0202] The voice recognition function and translation function of the control circuit 652 are implemented using, for example, an RNN (Recurrent Neural Network). The system was trained using neural network techniques, including neural networks. The results can be used.

[0203] In addition, the first device 650a and the second device 650b are equipped with GPS and communication antennas. With this, you can obtain location information and use it for sports such as running. can.

[0204] In addition, the first device 650a and the second device 650b and other electronic devices can be wirelessly For example, it may be used in conjunction with the hands-free function of a mobile phone. The call sound is output from the speaker 651 of the first device 650a or the second device 650b. It is possible to output sound.

[0205] A case 655 capable of accommodating a first device 650a and a second device 650b preferably has a secondary battery 656 and a display unit 657. By having the secondary battery 7611, the secondary battery 653 included in the first device 650a and the second device 650b can be charged. Further, the display unit 657 can display the charging states of the first device 650a, the second device 650b, and the case 655. Also, a more detailed charging state may be confirmed with other associated electronic devices. By using the secondary battery according to one aspect of the present invention as a secondary battery in a consumer electronic device, a lightweight and long - life product can be provided. For example, as consumer electronic devices, an electric toothbrush, an electric shaver, an electric beauty device, etc. may be mentioned. As the secondary battery for these products, considering the ease of use by the user, a secondary battery having a stick - like shape, being small, lightweight, and having a large capacity is desired.

[0206]

[0207] Figure 13(B) is a perspective view of a device also called a tobacco - containing smoking device (electronic cigarette). In Figure 13(H), the electronic cigarette 640 is composed of an atomizer 641 including a heating element, a secondary battery 644 that supplies power to the atomizer, and a cartridge 642 including a liquid supply bottle, a sensor, etc. For enhancing safety, a protection circuit for preventing over - charging and over - discharging of the secondary battery 644 may be electrically connected to the secondary battery 644. The secondary battery 644 shown in Figure 13(B) has an external terminal so as to be connectable to a charging device. Since the secondary battery 644 becomes the tip portion in the hand - held situation, it is desirable that the total length is short and the weight is light. ​​​​​​​​​​​​​​Since the secondary battery according to one aspect of the invention has a high capacity and good cycle characteristics, it can be made small and lightweight, and can provide an electronic cigarette 640 that can be used for a long time over a long period. and can provide a small and lightweight electronic cigarette 640 that can be used for a long time over a long period.

[0208] FIG. 13(C) is a diagram for explaining a power storage system 700. The power storage system 700 includes a power generation device 702 and a power storage device 701. As the power generation device, a power generation device using solar power generation, wind power generation, wave power generation, ocean current power generation, tidal power generation, etc. can be used. By using the secondary battery according to one aspect of the present invention for the power storage device 701, a power storage device 701 with a high capacity and a long life can be obtained. and a power storage device 701. As the power generation device, a power generation device using solar power generation, wind power generation, wave power generation, ocean current power generation, tidal power generation, etc. can be used. wave power generation, ocean current power generation, tidal power generation, etc. can be used. By using the secondary battery according to one aspect of the present invention for the power storage device 701, a power storage device 701 with a high capacity and a long life can be obtained.

[0209] The configuration described in this embodiment can be implemented in appropriate combination with other configurations described in this embodiment or configurations described in other embodiments.

Description of Reference Numerals

[0210] 100 Positive electrode active material 100a Particles 100b Particles 110 Current collector 111 Conductive assistant 112 Graphene 120 Positive electrode 121 Frame 201a Polishing device 201b Polishing device 201c Polishing device 210 Classification device 220 Dust collector 221 Particles 300 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 350 Secondary battery 351 Constant current power supply 352 Constant voltage power supply 310 Separator 400 Secondary battery 401 Positive electrode cap 402 Battery can 403 Positive electrode terminal 404 Positive electrode 405 Separator 406 Negative electrode 407 Negative electrode terminal 411 PTC element 412 Explosion-proof plate 413 Conductive plate 414 Conductive plate 415 Module 416 Wire 417 Temperature control device 418 Buffer material 419 Conductive plate 420 Module 421 Positive electrode terminal 422 Negative electrode terminal 423 Housing 430 Module 440 Vehicle 451 Charging device 452 Cable 460 Scooter 461 Side mirror 462 Secondary battery 464 Direction indicator 500 Circuit board 510 Label 511 Terminal 512 Circuit 513 Secondary battery 514 Antenna 515 Seal 516 Layer 517 Layer 518 Antenna 520 Display device 521 Sensor 522 Terminal 530 Secondary battery pack 551 One side 552 The other side 593 Battery element 594 Negative electrode 595 Positive electrode 596 Separator 600 Mobile phone 601 Housing 602 Display unit 603 Operation button 604 External connection port 605 Speaker 606 Microphone 607 Secondary battery 610 Electronic device 611 Display unit 612 Housing 613 External connection port 614 External connection port 615 Secondary battery 616 Display unit 620 E-book terminal 621 Display unit 622 Circuit board 623 Secondary battery 624 Power button 625 Operation button 640 Electronic cigarette 641 Atomizer 642 Cartridge 644 Secondary battery 650a Device 650b Device 651 Speaker 652 Control circuit 653 Secondary battery 654 Microphone 655 Case 656 Secondary battery 657 Display unit 700 Power storage system 701 Power storage device 702 Power generation device 911 Terminal 914 Antenna 7602 Control circuit 7611 Secondary battery

Claims

1. A lithium ion secondary battery having a positive electrode, The positive electrode has a positive electrode active material layer, the positive electrode active material layer includes a binder, a first positive electrode active material, and a second positive electrode active material; the first positive electrode active material and the second positive electrode active material are each substantially spherical and have a smooth surface; The median diameter (D50) of the second positive electrode active material is 0.66 times or less the median diameter (D50) of the first positive electrode active material, the first positive electrode active material and the second positive electrode active material each include magnesium and lithium cobalt oxide; a surface portion of the first positive electrode active material has a lower Young's modulus than an inside of the first positive electrode active material; a surface layer portion of the second positive electrode active material has a lower Young's modulus than an inner portion of the second positive electrode active material; When the first positive electrode active material and the second positive electrode active material are analyzed by X-ray photoelectron spectroscopy, the peak positions of the fluorine binding energy are greater than 684.4 eV and less than 686.0 eV, The binder has a function of binding the first positive electrode active material and the second positive electrode active material. Lithium-ion secondary battery.

2. A lithium ion secondary battery having a positive electrode, The positive electrode has a positive electrode active material layer, the positive electrode active material layer includes a binder, a first positive electrode active material, and a second positive electrode active material; the first positive electrode active material and the second positive electrode active material are each substantially spherical and have a smooth surface; The median diameter (D50) of the second positive electrode active material is 0.66 times or less the median diameter (D50) of the first positive electrode active material, the first positive electrode active material and the second positive electrode active material each include magnesium and lithium cobalt oxide; a surface layer portion of the first positive electrode active material has a region having a lower Young's modulus than an inner portion of the first positive electrode active material; a surface layer portion of the second positive electrode active material has a region having a lower Young's modulus than an inner portion of the second positive electrode active material, When the first positive electrode active material and the second positive electrode active material are analyzed by X-ray photoelectron spectroscopy, the peak positions of the fluorine binding energy are greater than 684.4 eV and less than 686.0 eV, The binder has a function of binding the first positive electrode active material and the second positive electrode active material. Lithium-ion secondary battery.

3. A lithium ion secondary battery having a positive electrode, The positive electrode has a positive electrode active material layer, the positive electrode active material layer includes a binder, a first positive electrode active material, and a second positive electrode active material; the first positive electrode active material and the second positive electrode active material are each substantially spherical and have a smooth surface; The median diameter (D50) of the second positive electrode active material is 0.66 times or less the median diameter (D50) of the first positive electrode active material, the first positive electrode active material and the second positive electrode active material each include magnesium and lithium cobalt oxide; a surface layer portion of the first positive electrode active material has a material having a lower Young's modulus than an inner portion of the first positive electrode active material; a surface layer portion of the second positive electrode active material includes a material having a lower Young's modulus than an inner portion of the second positive electrode active material; When the first positive electrode active material and the second positive electrode active material are analyzed by X-ray photoelectron spectroscopy, the peak positions of the fluorine binding energy are greater than 684.4 eV and less than 686.0 eV, The binder has a function of binding the first positive electrode active material and the second positive electrode active material. Lithium-ion secondary battery.

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