Method for manufacturing secondary battery and secondary battery

Abstract

This invention relates to a method for manufacturing a secondary battery and the secondary battery itself. A method for manufacturing a positive electrode active material with a large charge / discharge capacity is provided. Furthermore, a method for manufacturing a positive electrode active material with a high charge / discharge voltage is provided. Additionally, a method for manufacturing a positive electrode active material with minimal degradation is provided. The positive electrode active material is formed by the following steps: a process for forming a composite oxide comprising lithium, nickel, manganese, cobalt, and oxygen; and a process for mixing the composite oxide and a calcium compound, and then heating at a temperature of 500°C or higher and 1100°C or lower for 2 hours or higher and 20 hours or lower. Through this heating, calcium is distributed at a suitable concentration in the surface layer of the positive electrode active material.

Description

[Technical Field]

[0001] One embodiment of the present invention relates to an article, method, or manufacturing method. Additionally, the present invention relates to a process, machine, manufacture, or composition of matter. One embodiment of the present invention relates to a method of manufacturing an energy storage device including a secondary battery, a semiconductor device, a display device, a light-emitting device, an energy storage device, a lighting device, an electronic device, or the like.

[0002] Note that in this specification, energy storage device refers to all components and devices with energy storage function. For example, batteries such as lithium-ion secondary batteries (also called secondary batteries), lithium-ion capacitors, and double-layer capacitors are all included in the scope of energy storage device.

[0003] Note that in this specification, electronic device refers to all devices with energy storage devices, such as electro-optical devices with energy storage devices and information terminal devices with energy storage devices. [Previous Technology]

[0004] In recent years, research and development of various energy storage devices, such as lithium-ion secondary batteries, lithium-ion capacitors, air batteries, and all-solid-state batteries, has become increasingly active. In particular, the demand for high-output, high-capacity lithium-ion secondary batteries has increased dramatically with the development of the semiconductor industry, and they have become an indispensable item in modern information society as a rechargeable energy source.

[0005] Therefore, improvements to the positive electrode active material aimed at improving the cycle characteristics and increasing the capacity of lithium-ion secondary batteries are examined (for example, Patent Document 1).

[0006] [Patent Document 1] Japanese PCT International Application Translation No. 2014-531718 [Summary of the Invention]

[0007] It is hoped that improvements can be made to lithium-ion secondary batteries and the positive electrode active materials used therein in terms of capacity, cycle characteristics, charge and discharge characteristics, reliability, safety or cost.

[0008] In view of the above problems, one objective of an embodiment of the present invention is to provide a positive electrode active material with less degradation. Another objective of an embodiment of the present invention is to provide a secondary battery with less degradation. Furthermore, one objective of an embodiment of the present invention is to provide a secondary battery with high safety.

[0009] Furthermore, one objective of one embodiment of the present invention is to provide a positive electrode active material, an energy storage device, or a method for manufacturing the same.

[0010] Note that the description of these objectives does not preclude the existence of other objectives. Note that one embodiment of the present invention does not need to achieve all of the above objectives. In addition, objectives other than those described above can be extracted from the description in the specification, drawings, and claims.

[0011] One embodiment of the present invention is a method for manufacturing a secondary battery, comprising the following steps: a process for forming a composite oxide comprising lithium, nickel, manganese, cobalt and oxygen; and a process for mixing the composite oxide and a calcium compound, and then heating at a temperature of 500°C or higher and 1100°C or lower for 2 hours or more and 20 hours or less.

[0012] In the above-mentioned method for manufacturing secondary batteries, the calcium compound is preferably calcium carbonate or calcium fluoride.

[0013] In the above-mentioned method for manufacturing a secondary battery, when the total number of nickel, manganese and cobalt atoms contained in the composite oxide is 100, the number of nickel atoms is preferably 50 or more.

[0014] In another embodiment of the present invention, a secondary battery including a positive electrode is provided, wherein the positive electrode includes a positive electrode active material, the positive electrode active material includes lithium, nickel, manganese, cobalt, oxygen and additive elements, the additive elements being one or more selected from calcium, fluorine, sodium, iron, arsenic, sulfur and copper, the positive electrode active material includes a surface portion and an interior portion, and the concentration of one or more of the additive elements is higher in the surface portion than in the interior portion.

[0015] In the above-mentioned secondary battery, preferably, the positive electrode active material includes a plurality of primary particles and secondary particles of the plurality of primary particles bonded together, and the concentration of one or more of the added elements is higher in the surface portion of the primary particles than in the interior portion.

[0016] In the above-mentioned secondary battery, the preferred added element is calcium or fluorine.

[0017] According to one embodiment of the present invention, a positive electrode active material with less degradation can be provided. Furthermore, according to one embodiment of the present invention, a secondary battery with less degradation can be provided. In addition, according to one embodiment of the present invention, a secondary battery with high safety can be provided.

[0018] In addition, according to one embodiment of the present invention, a positive electrode active material, an energy storage device or a method for manufacturing the same may be provided.

[0019] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily require all of the above-described effects. Furthermore, effects other than those described above are clearly visible from the description in the specification, drawings, claims, etc., and effects other than those described above can be derived from the description in the specification, drawings, claims, etc.

Implementation Method

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following description, and those skilled in the art will readily understand that its methods and details can be varied in various forms. Furthermore, the present invention should not be construed as being limited only to the contents described in the following embodiments.

[0022] A secondary battery includes, for example, a positive electrode and a negative electrode. A positive electrode active material can be cited as a material constituting the positive electrode. For example, the positive electrode active material is a substance that performs a reaction that contributes to the capacity of charging and discharging. Alternatively, a portion of the positive electrode active material may include a substance that does not contribute to the capacity of charging and discharging.

[0023] In this specification, the positive electrode active material of one embodiment of the present invention is sometimes referred to as a positive electrode material, a positive electrode material for a secondary battery, or a composite oxide, etc. Furthermore, in this specification, the positive electrode active material of one embodiment of the present invention preferably comprises a compound. Furthermore, in this specification, the positive electrode active material of one embodiment of the present invention preferably comprises a composition. Furthermore, in this specification, the positive electrode active material of one embodiment of the present invention preferably comprises a composite.

[0024] In addition, in this specification, "crack" includes: cracks generated during the manufacturing process of the positive electrode active material; and cracks generated due to pressurization and charging / discharging after the manufacturing process.

[0025] In this specification, the term "surface portion" of particles such as active substances refers, for example, to a region within 50 nm, more preferably 35 nm, further preferably 20 nm, and most preferably 10 nm, extending from the surface inwards. A surface created by a crack (also called a fissure) may also be referred to as the "surface." Furthermore, a region deeper than the surface portion is referred to as the "interior."

[0026] Furthermore, in this specification and the like, when simply referred to as a defect, a defect means a crystallization defect or a lattice defect. Defects include point defects, dislocations, stacked defects as two-dimensional defects, and voids as three-dimensional defects.

[0027] In addition, in this specification, the particles are not limited to spherical (with a circular cross-sectional shape). The cross-sectional shape of each particle can also be elliptical, rectangular, trapezoidal, triangular, quadrilateral with arc corners, asymmetrical shape, etc., and each particle can also be amorphous.

[0028] In addition, in this specification, space groups are represented by short notation using international symbols (or Hermann-Mauguin notation). Crystallographic planes and orientations are represented by Miller indices. Each facet of a crystallographic plane is indicated by ( ). Orientation is indicated by [ ]. Reciprocal lattice points are also represented by the same indices, but without parentheses. In crystallography, superscript lines are added to numbers to indicate crystallographic planes, orientations, and space groups. However, in this specification, due to the limitations of the symbols used in the patent applications, sometimes a - (negative number sign) is added before the digits to indicate crystallographic planes and orientations instead of adding superscript lines to the digits.

[0029] Discharge rate refers to the ratio of the discharge current to the battery capacity, and is expressed in units of C. In a battery with a rated capacity of XAh, the current equivalent to 1C is XA. When discharging at a current of 2XA, it can be said to be discharging at 2C, and when discharging at a current of X / 5A, it can be said to be discharging at 0.2C. Similarly, the charge rate is the same; when charging at a current of 2XA, it can be said to be charging at 2C, and when charging at a current of X / 5A, it can be said to be charging at 0.2C.

[0030] Constant current charging refers to a method of charging at a certain charging rate. Constant voltage charging refers to a method of charging at a certain voltage after reaching the upper limit voltage. Constant current discharging refers to a method of discharging at a certain discharge rate.

[0031] In addition, in this specification, a value near a certain value A refers to a value that is greater than or equal to 0.9 × A and less than or equal to 1.1 × A.

[0032] Furthermore, in this specification and other documents, a secondary battery using a positive electrode and a positive electrode active material as an embodiment of the present invention is sometimes shown, although examples of using lithium metal as the counter electrode are sometimes shown. However, the secondary battery of one embodiment of the present invention is not limited to this. Other materials can also be used for the negative electrode, such as graphite, lithium titanate, etc. The properties of the positive electrode and the positive electrode active material of one embodiment of the present invention, such as the fact that the crystal structure is not easily collapsed even with repeated charging and discharging, and good cycle characteristics can be obtained, are not limited by the negative electrode material. In addition, in the secondary battery of one embodiment of the present invention, for example, an example is shown where lithium is charged and discharged at a voltage higher than the general charging voltage, that is, about 4.7V, but it is also possible to charge and discharge at a lower voltage. When charging and discharging at a lower voltage, it is expected that the cycle characteristics can be further improved compared with the situation shown in this specification and other documents.

[0033] Furthermore, unless otherwise specified in this specification, the charging voltage and discharging voltage refer to the voltage when lithium is used as the counter electrode. Note that the charging and discharging voltage of a secondary battery varies depending on the material used for the negative electrode, even when using the same positive electrode. For example, the potential of graphite is approximately 0.1V (vs Li / Li+), so when graphite is used as the negative electrode, the charging and discharging voltage decreases by about 0.1V compared to when lithium is used as the counter electrode. Additionally, in this specification, when the charging voltage of the secondary battery is, for example, 4.7V or higher, the plateau region of the discharging voltage does not need to be 4.7V or higher.

[0034] Embodiment 1 In this embodiment, an example of a method for manufacturing a positive electrode active material according to an embodiment of the present invention will be described.

[0035] In order to manufacture a positive electrode active material 100 having the distribution, composition and / or crystal structure of the added elements as shown in Embodiment 2, the method of adding the added elements is important. Furthermore, good crystallinity of the internal 101b is also important.

[0036] Therefore, in the process of manufacturing the positive electrode active material 100, it is preferable to first synthesize a composite oxide containing lithium and transition metal M (e.g., lithium nickel-cobalt-manganese oxide), and then mix and add element sources for heating treatment.

[0037] In methods for synthesizing composite oxides containing additive elements, lithium, and transition metal M by simultaneously mixing a transition metal M source, a lithium source, and an additive element source, it is sometimes difficult to increase the additive element concentration in the surface layer 101a. Furthermore, after synthesizing the composite oxide containing lithium and transition metal M, if only the additive element source is mixed without heating, the additive element does not dissolve but only adheres to the composite oxide containing lithium and transition metal M. Unless sufficiently heated, it is difficult to achieve good distribution of the additive element. Therefore, it is preferable to mix the additive element source after synthesizing the composite oxide containing lithium and transition metal M and then perform a heat treatment. This heat treatment after mixing the additive element source is sometimes referred to as annealing.

[0038] However, when the annealing temperature is too high, the possibility of cation mixing and lithium entering the transition metal M site or transition metal M entering the lithium site increases. This leads to a decrease in discharge capacity, which is not desirable. Furthermore, it may cause the following adverse effects: transition metal M is reduced to divalent; lithium is evaporated; etc.

[0039] Therefore, it is preferable to use a mixture of the added element source and the material used as a co-solvent. When its melting point is lower than that of the composite oxide containing lithium and transition metal M, it can be said that the material is used as a co-solvent. For example, fluorine compounds such as lithium fluoride are preferred. When a co-solvent is added, the melting point of the composite oxide containing the added element source, lithium, and transition metal M decreases. By lowering the melting point, the added element can be well distributed at a temperature where cation mixing is less likely to occur.

[0040] An example of the manufacturing method after the above annealing is illustrated using Figures 1 and 2.

[0041] First, as step S21 in Figure 1, a transition metal source M 801 is prepared.

[0042] As the transition metal M, one or more selected from manganese, cobalt, and nickel may be used, for example. For example, as the transition metal M, the following may be used: using only cobalt; using only nickel; using both cobalt and manganese; using both cobalt and nickel; or using cobalt, manganese, and nickel.

[0043] When one or more of manganese, cobalt and nickel are used as transition metal M, the mixing is preferably within the range that can have a layered rock salt type crystal structure.

[0044] A high proportion of nickel in the transition metal M allows for the formation of inexpensive and high-capacity positive electrode active materials, which is preferable. For example, when the total number of nickel, manganese, and cobalt atoms in the positive electrode active material 100 is 100, the number of nickel atoms is preferably 33 or more, more preferably 50 or more, and even more preferably 80 or more. However, if the proportion of nickel is too high, there are concerns about reduced chemical stability and heat resistance. Therefore, when the total number of nickel, manganese, and cobalt atoms in the positive electrode active material is 100, the number of nickel atoms is preferably 95 or less.

[0045] When the transition metal M contains manganese, the heat resistance and chemical stability are improved, which is preferable. However, when the ratio of manganese is too high, there is a tendency for the discharge voltage and discharge capacity to decrease. Therefore, for example, when the total number of nickel, manganese and cobalt atoms contained in the positive electrode active material is 100, the number of manganese atoms is preferably 2.5 or more and 33 or less.

[0046] When the transition metal M contains cobalt, the average discharge voltage is high and cobalt contributes to the stabilization of the layered rock-salt structure, thus enabling a highly reliable secondary battery, which is preferable. However, cobalt is more expensive and less stable than nickel and manganese, so there are concerns that the manufacturing cost of the secondary battery will increase significantly if the proportion of cobalt is too high. Therefore, for example, when the total number of nickel, manganese, and cobalt atoms contained in the positive electrode active material 100 is 100, the number of cobalt atoms is preferably 2.5 or more and 34 or less.

[0047] Preferably, an aqueous solution containing the transition metal M is prepared as the transition metal M source 801. As the aqueous solution containing cobalt used as the transition metal M source 801, an aqueous solution containing cobalt sulfate or an aqueous solution containing cobalt nitrate can be used, etc. As the aqueous solution containing nickel, an aqueous solution containing nickel sulfate or an aqueous solution containing nickel nitrate can be used, etc. As the aqueous solution containing manganese, an aqueous solution containing manganese sulfate or an aqueous solution containing manganese nitrate can be used, etc.

[0048] Next, as step S22, it is preferable to prepare to add element X source a802.

[0049] As the added element X, it is preferable to use one or more selected from alkaline earth metals such as calcium or magnesium, halogens such as fluorine, sodium, iron, arsenic, sulfur, and copper. In particular, it is preferable to use one or both selected from calcium and fluorine.

[0050] Element X can be added in steps S35, S43, or S62, in addition to step S22. Element X can be added in one or more of the above steps. Therefore, all elements X can be added in one step, different elements can be added in each step, or the same element can be added multiple times. The source of element X can be prepared in one or more steps of S22, S35, S43, and S62 in such a way that the added elements ultimately included in the positive electrode active material 100 are in appropriate proportions.

[0051] When calcium is used as the source of element X, a8O2, it is preferable to manufacture a positive electrode active material 100 with good charge-discharge cycle characteristics. Calcium has a larger ionic radius than lithium, nickel, manganese, and cobalt, so it is easy for calcium to be concentrated in the surface layer of the positive electrode active material 100. Furthermore, since calcium is a typical divalent element, it is suitable as an additive element for contributing to the stabilization of the crystal structure of the surface layer. By stabilizing the crystal structure of the surface layer, the dissolution of transition metal M from the positive electrode active material 100 and the removal of oxygen can be expected to be suppressed. Moreover, when the additive element is concentrated in defects such as grain boundaries, cracks, and voids, the bonding force can be improved. However, there is a concern that excessive calcium may reduce the charge-discharge capacity. Therefore, the proportion of calcium contained in the positive electrode active material 100 is preferably 0.1 atomic% or more and 2 atomic% or less. As a calcium source, calcium compounds such as calcium fluoride, calcium carbonate, calcium oxide, calcium hydroxide, calcium chloride, calcium aluminate, calcium titanate, and calcium zirconate can be used. Here, the amount of calcium contained in the positive electrode active material 100 can be, for example, a value obtained by analyzing all elements of the positive electrode active material 100 using GD-MS (glow discharge mass spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), or a value based on the proportions of raw materials used in the manufacturing process of the positive electrode active material 100.

[0052] Furthermore, when the source a802 for added element X contains fluorine, a positive electrode active material 100 with good charge-discharge cycle characteristics can be manufactured, which is preferable. Fluoride is used as a co-solvent contributing to the diffusion of other added elements X such as calcium. Therefore, by including fluoride, other added elements X can be distributed in the surface layer at an appropriate concentration. In addition, fluorine is a monovalent anion, and when part of the oxygen in the surface layer is replaced by fluorine, the lithium desorption energy decreases. This is because the redox potential of cobalt ions as lithium desorbs differs depending on the presence or absence of fluorine. That is, without fluorine, cobalt ions change from trivalent to quadrivalent as lithium desorbs, while with fluorine, cobalt ions change from divalent to trivalent as lithium desorbs. The redox potential of cobalt ions differs in the two cases mentioned above. Therefore, when part of the oxygen in the surface layer of the positive electrode active material 100 is replaced by fluorine, the desorption and insertion of lithium ions near fluorine can be said to occur smoothly. Therefore, when used in a secondary battery, charge-discharge characteristics, rate characteristics, etc., are improved, which is preferable. However, there is a concern that excessive fluorine content may reduce charge and discharge capacity. Therefore, the fluorine content in the positive electrode active material 100 is preferably 0.0003% by weight or more and 0.1% by weight or less, more preferably 0.01% by weight or more and 0.03% by weight or less. The amount of fluorine in the positive electrode active material 100 described here can be, for example, a value obtained by analyzing all elements of the positive electrode active material 100 using GD-MS, ICP-MS, etc., or a value based on the raw material formulation in the manufacturing process of the positive electrode active material 100. Examples of fluorine sources that can be used include calcium fluoride (CaF2), lithium fluoride (LiF), magnesium fluoride (MgF2), aluminum fluoride (AlF3), titanium fluoride (TiF4), cobalt fluoride (CoF2, CoF3), nickel fluoride (NiF2), zirconium fluoride (ZrF4), vanadium fluoride (VF5), manganese fluoride, iron fluoride, chromium fluoride, niobium fluoride, zinc fluoride (ZnF2), sodium fluoride (NaF), potassium fluoride (KF), barium fluoride (BaF2), cerium fluoride (CeF2), lanthanum fluoride (LaF3), and sodium aluminum hexafluoride (Na3AlF6). Furthermore, the fluorine source is not limited to solids; for example, fluorine (F2), carbon fluoride, sulfur fluoride, and oxygen fluoride (OF2, O2F2, O3F2, O4F2, O2F) can be mixed in the atmosphere during the heating process described later. Alternatively, multiple fluorine sources can be mixed and used.

[0053] Furthermore, when sodium is included in the element source X a802, the ionic radius of sodium is larger than that of lithium, so sodium may contribute to the stabilization of the layered rock salt-type crystal structure. However, there is a concern that excessive sodium may reduce the charge and discharge capacity. Therefore, the sodium content in the positive electrode active material 100 is preferably 0.003% by weight or more and 0.03% by weight or less. Sodium sources such as sodium fluoride, sodium carbonate, sodium oxide, sodium hydroxide, and sodium chloride can be used. Here, the amount of sodium included in the positive electrode active material 100 can be, for example, a value obtained by analyzing all elements of the positive electrode active material 100 using GD-MS, ICP-MS, etc., or a value based on the formulation of raw materials in the manufacturing process of the positive electrode active material 100.

[0054] Furthermore, when element X source a802 contains iron, it is likely to become a positive electrode active material with good charge-discharge characteristics, which is preferable. During the initial charging phase of a secondary battery, i.e., when lithium is extracted from the positive electrode active material, the internal resistance of the layered rock salt-type crystalline structure of the positive electrode active material tends to increase. Therefore, by using a positive electrode active material 100 containing a tetravalent metal such as iron, lithium can be easily removed, potentially suppressing the internal resistance during the initial charging phase. However, there is a concern that excessive iron content may reduce the stability of the layered rock salt-type crystalline structure. Therefore, the iron content in the positive electrode active material 100 is preferably 0.001% by weight or more and 0.01% by weight or less, more preferably 0.004% by weight or less. Here, the amount of iron in the positive electrode active material 100 can be, for example, a value obtained by analyzing all elements of the positive electrode active material 100 using GD-MS, ICP-MS, etc., or a value based on the proportion of raw materials used in the manufacturing process of the positive electrode active material 100. As an iron source, for example, single iron, iron oxide, iron hydroxide, iron alkoxide, iron fluoride, etc. can be used.

[0055] Furthermore, when the added element X source a802 contains arsenic, it is possible to obtain a positive electrode active material 100 with good charge-discharge cycle characteristics. Similar to phosphorus, arsenic contributes to the stabilization of the crystal structure, for example, as a polyanion. However, there is a concern that excessive arsenic may reduce the charge-discharge capacity. Therefore, the arsenic content in the positive electrode active material 100 is preferably 0.01% by weight or more and 0.1% by weight or less. Here, the amount of arsenic contained in the positive electrode active material 100 can be, for example, a value obtained by analyzing all elements of the positive electrode active material 100 using GD-MS, ICP-MS, etc., or a value based on the formulation of raw materials in the manufacturing process of the positive electrode active material 100. As an arsenic source, for example, single arsenic, arsenic oxide, arsenate hydrate, calcium arsenate, etc., can be used.

[0056] Furthermore, when magnesium is included in the element source X a802, it is sometimes possible to produce a positive electrode active material 100 with good charge-discharge cycle characteristics in the same way as calcium. However, although magnesium is a typical divalent element, positive electrode active materials 100 with a nickel ratio of 20 atomic% or more in the transition metal M are not easily concentrated in the surface layer, and therefore do not easily contribute to the stabilization of the surface layer. Therefore, there is a tendency for the more magnesium, the lower the charge-discharge capacity. Therefore, the magnesium ratio contained in the positive electrode active material 100 is preferably 0.5 wt% or more, and more preferably 0.01 wt% or less. Here, the amount of magnesium contained in the positive electrode active material 100 can be, for example, a value obtained by analyzing all elements of the positive electrode active material 100 using GD-MS, ICP-MS, etc., or a value based on the formulation of raw materials in the manufacturing process of the positive electrode active material 100.

[0057] Next, as step S31, the above-mentioned transition metal M source 801 and added element X source a 802 are mixed to obtain the mixture 811 of step S32.

[0058] Next, as step S33, aqueous solution A812 is prepared, as step S34, solution B813 is prepared, and as step S35, source b814 for adding element X is prepared.

[0059] As the aqueous solution A812, any one or more of an aqueous solution and ammonia water containing one or more chelating agents selected from glycine, oxamyl, 1-nitroso-2-naphthol or 2-mercaptobenzothiazole can be used.

[0060] As an aqueous solution B813, any one or more mixtures of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution and lithium oxide aqueous solution can be used.

[0061] For adding element X source b814, please refer to the record of adding element X source a802.

[0062] Next, as step S36, the mixture 811 of step S32 above, aqueous solution A812, aqueous solution B813 and added element source b814 are mixed.

[0063] As step S36, a mixing method can be used by adding the mixture 811 from step S32, the aqueous solution B813, and the added element source b814 dropwise to the aqueous solution A812 placed in the reaction vessel. To maintain the pH of the mixed solution in the reaction vessel within a specified range, it is preferable to add the aqueous solution B813 dropwise in addition to adding the mixture 811 from step S32 at a certain rate. During the mixing in step S36, the solution in the reaction vessel is preferably stirred using a stirring blade or stirrer, and the solution, mixture 811, aqueous solution A812, and aqueous solution B813 in the reaction vessel are preferably bubbled with nitrogen to remove dissolved oxygen. During the mixing in step S36, the pH of the solution in the reaction vessel is preferably 9 or higher and 11 or lower, more preferably 10.0 or higher and 10.5 or lower. During the mixing in step S36, the temperature of the solution in the reaction vessel is preferably 40°C or higher and 80°C or lower, more preferably 50°C or higher and 70°C or lower.

[0064] Additionally, as step S36, a mixing method can be used by adding aqueous solutions A812 and B813 dropwise to the mixture 811 of step S32 and the added element source b814 placed in the reaction vessel. To maintain the solute ion concentration and hydroxyl concentration of aqueous solution A812 within a specified range, it is preferable to adjust the dropping rate of aqueous solution A812 and aqueous solution B813. During the mixing in step S36, the solution in the reaction vessel is preferably stirred using a stirring blade or stirrer, and the solution in the reaction vessel, the mixture 811 of step S32, aqueous solution A812, and aqueous solution B813 are preferably bubbled with nitrogen to remove dissolved oxygen. During the mixing in step S36, the temperature of the solution in the reaction vessel is preferably 40°C or higher and 80°C or lower, more preferably 50°C or higher and 70°C or lower.

[0065] Alternatively, the aqueous solution A812 may not be used in step S36. For example, a certain amount of aqueous solution B813 may be added dropwise to the mixture 811 of step S32 and the added element source b814 placed in the reaction vessel. In the mixing of step S36, the solution in the reaction vessel is preferably stirred using a stirring blade or a stirrer, and the solution in the reaction vessel, the mixture 811 of step S32, and the aqueous solution B813 are preferably bubbled with nitrogen to remove dissolved oxygen. In the mixing of step S36, the temperature of the solution in the reaction vessel is preferably above 40°C and below 80°C, more preferably above 50°C and below 70°C.

[0066] In addition, as step S36, besides the mixture 811, aqueous solution A812, aqueous solution B813, and added element source b814 from step S32, pure water can also be used. To maintain the pH of the mixed solution in the reaction vessel within a specified range, it is preferable that, in addition to adding the mixture 811 and aqueous solution A812 from step S32 dropwise at a certain rate, aqueous solution B813 is also appropriately added dropwise to the pure water placed in the reaction vessel. During the mixing in step S36, the solution in the reaction vessel is preferably stirred using a stirring blade or stirrer, and the solution in the reaction vessel, the mixture 811, aqueous solution A812, and aqueous solution B813 from step S32 are preferably bubbled with nitrogen to remove dissolved oxygen. During the mixing in step S36, the pH of the solution in the reaction vessel is preferably 9 or higher and 11 or lower, more preferably 10.0 or higher and 10.5 or lower. In the mixing process of step S36, the temperature of the solution in the reaction vessel is preferably above 40°C and below 80°C, and more preferably above 50°C and below 70°C.

[0067] Next, as step S37, the solution containing the hydroxide containing the transition metal M formed by the mixing in step S36 is filtered and washed with water. The washed hydroxide containing the transition metal M is dried and recovered to obtain the precursor 821 of step S41. The water used for washing is preferably pure water with a resistivity of preferably 1 MΩ·cm or more, more preferably 10 MΩ·cm or more, and even more preferably 15 MΩ·cm or more with few impurities. By using pure water with few impurities for washing, impurities in the hydroxide containing the transition metal M can be removed, and a high-purity hydroxide containing the transition metal M can be obtained as the precursor 821. Note that in this specification, the precursor refers to a precursor of a composite oxide containing lithium and the transition metal M.

[0068] Next, as step S42, lithium source 822 is prepared, and as step S43, element X source c823 is prepared. Then, as step S51, the precursor 821, lithium source 822, and element X source c823 from step S41 are mixed. After mixing, the mixture 831 from step S53 is recovered in step S52. Mixing can be performed by dry or wet methods. For example, a ball mill or a sand mill can be used for mixing. When using a ball mill, zirconia balls are preferably used as the media. In addition, when using a ball mill or a sand mill, the circumferential speed is preferably set to 100 mm / s or more and 2000 mm / s or less in order to suppress contamination from the media or materials. Note that in this embodiment, the circumferential speed is set to 838 mm / s (rotation speed of 400 rpm, diameter of ball mill of 40 mm).

[0069] As the lithium source 822, lithium hydroxide, lithium carbonate, lithium nitrate, lithium fluoride, etc. can be used, for example. For the addition of element X source c823, please refer to the description of the addition of element X source a802.

[0070] Next, as step S54, the mixture 831 from step S53 is heated. To distinguish it from subsequent heating processes, this process is sometimes referred to as calcination or first heating. Heating is preferably performed at 600°C or higher and below 1100°C, more preferably at 650°C or higher and below 950°C, and even more preferably at 700°C or higher and below 850°C.

[0071] The heating time can be, for example, more than 1 hour and less than 100 hours, preferably more than 2 hours and less than 20 hours. The shorter the heating time, the higher the productivity, so it is preferred. Heating is preferably carried out in an oxygen-containing atmosphere with low moisture content, such as oxygen or dry air (e.g., a dew point of -50°C or less, preferably -80°C or less). In this embodiment, heating is carried out in an atmosphere with a dew point of -93°C. In addition, when heating is carried out in an atmosphere where the impurity concentrations of CH4, CO, CO2, and H2 are all less than 5 ppb (parts per billion), impurities that may mix into the material can be suppressed, so it is preferred.

[0072] For example, when heating at 850°C for 10 hours, the heating rate is preferably 200°C / h, and the flow rate of the dry atmosphere is preferably 10L / min. The heated material can then be cooled to room temperature. For example, the cooling time from the specified temperature to room temperature is preferably 10 hours or more and 50 hours or less. However, the cooling in step S54 does not necessarily have to be reduced to room temperature.

[0073] The furnace used in the heating step S54 is preferably a furnace made of a material that does not contain impurities. In this embodiment, an alumina furnace with a purity of 99.9% is used.

[0074] Next, it is preferable to grind the material from step S55 (after heating) using a mortar and pestle. Furthermore, it is preferable to use a mortar made of a material free of impurities. Specifically, it is preferable to use a mortar made of alumina with a purity of 90 wt% or more, and more preferably 99 wt% or more. Alternatively, the same conditions as in step S54 may be used in the heating process described later, other than step S54.

[0075] By means of the above steps, a composite oxide 832 containing lithium and transition metal M is obtained (step S61).

[0076] Next, in step S62, prepare to add element X source d833.

[0077] The description of the added element source d833 as the added element source a802 can be referred to, but it is particularly preferred here that the element is present in the surface portion of the positive electrode active material 100. For example, in step S62, it is preferred to prepare a calcium source and a fluorine source.

[0078] When using a wet mixing and grinding process, a solvent is also prepared. As a solvent, ketones such as acetone, alcohols such as ethanol and isopropanol, diethyl ether, dioxane, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc., can be used. Preferably, an aprotic solvent that does not readily react with lithium is used. In this embodiment, dehydrated acetone with a purity of 99.5% or higher is used.

[0079] Next, as step S71, the composite oxide 832 from step S61 and the added element X source d833 from step S62 are mixed. After mixing, the mixture 841 from step S73 is recovered in step S72. Mixing can be carried out by dry or wet methods. For example, a ball mill or a sand mill can be used for mixing. When using a ball mill, it is preferable to use zirconia balls as the media. In addition, when using a ball mill or a sand mill, in order to suppress contamination from the media or materials, the circumferential speed is preferably set to 100 mm / s or more and 2000 mm / s or less. Note that in this embodiment, the circumferential speed is set to 838 mm / s (rotation speed of 400 rpm, diameter of ball mill of 40 mm).

[0080] Next, as step S74, the mixture 841 from step S73 is heated. To distinguish it from subsequent heating processes, this process is sometimes referred to as degradation or second heating. The heating temperature for step S74 is preferably 500°C or higher and 1100°C or lower, more preferably 600°C or higher and 900°C or lower, and even more preferably 650°C or higher and 850°C or lower. There is a concern that if the annealing temperature is too high, the initial particles of the positive electrode active material 100 may become too large. If the initial particles are too large, the distortion during charging and discharging increases, leading to the breakage of the positive electrode active material 100.

[0081] Alternatively, heating in a roller kiln may be performed during the heating process in step S74. When heating in a roller kiln, it is preferable to process the mixture 841 using a heat-resistant container with a lid.

[0082] The heating time can be, for example, more than 1 hour and less than 100 hours, preferably more than 2 hours and less than 20 hours. Heating is preferably performed in an oxygen-containing atmosphere with low moisture content, such as oxygen or dry air (e.g., a dew point of -50°C or less, preferably -80°C or less). In this embodiment, heating is performed in an atmosphere with a dew point of -93°C. Furthermore, when heating is performed in an atmosphere where the impurity concentrations of CH4, CO, CO2, and H2 are all below 5 ppb (parts per billion), impurities that may mix into the material can be suppressed, which is therefore preferable.

[0083] For example, when heating at 800°C for 2 hours, the heating rate is preferably 200°C / h, and the oxygen flow rate is preferably 10 L / min. Then, the heated material can be cooled to room temperature. For example, the cooling time from the specified temperature to room temperature is preferably 10 hours or more and 50 hours or less. However, the cooling in step S74 does not necessarily have to be reduced to room temperature.

[0084] Next, in step S75, the calcined material is ground to obtain the positive electrode active material 100 of step S76.

[0085] Next, an example of a manufacturing method different from that in Figure 1 will be explained using Figure 2. Since many parts are the same as in Figure 1, the differences will be mainly explained. For the parts that are the same, please refer to the explanation in Figure 1.

[0086] First, as step S61 in FIG2, a pre-synthesized composite oxide 832 containing lithium and transition metal M is prepared. The composite oxide 832 preferably contains an additive element X. More preferably, the additive element X contained in the composite oxide 832 is an element that is uniformly distributed within the positive electrode active material 100. Specifically, it preferably contains one or more selected from sodium, iron, and arsenic as additive element X.

[0087] By using the pre-synthesized composite oxide 832, the processes from steps S21 to S55 in FIG1 can be omitted.

[0088] Next, as step S62, element X source d833 is prepared to be added. Here, similar to step S62 in FIG1, it is preferable to prepare an element that is present in the surface portion of the positive electrode active material 100. For example, in step S62, it is preferable to prepare a calcium source and a fluorine source.

[0089] Steps S71 to S76 can be referred to the description in Figure 1.

[0090] As described above, by introducing multiple additive elements X through a process of segmentation, the distribution of each element in the depth direction can sometimes be changed. For example, the concentration of a specific additive element in the surface layer can be higher than that in the interior of the positive electrode active material 100. In addition, compared with the interior, the ratio of the number of transition metal M atoms to the number of specific additive elements can be further increased in the surface layer.

[0091] This embodiment can be used in combination with other embodiments.

[0092] Embodiment 2 In this embodiment, the positive electrode active material 100 of one embodiment of the present invention is illustrated using Figures 3A to 4D.

[0093] Figure 3A is a cross-sectional view of the positive electrode active material 100. The positive electrode active material 100 includes a plurality of primary particles 101. At least a portion of the plurality of primary particles 101 are bonded together to form secondary particles 102. Figure 3B is an enlarged view of the secondary particles 102. The positive electrode active material 100 may also include voids 105. Note that the shapes of the primary particles 101 and secondary particles 102 shown in Figures 3A and 3B are examples and are not limited thereto.

[0094] In this specification, etc., a primary particle refers to the smallest unit of a solid with a clearly defined boundary in a microscope image such as a SEM image, TEM image, or STEM image. A secondary particle refers to a particle in which multiple primary particles are bonded together. The situation where particles are fixed by heating and agglomeration is called "bonding." There are no restrictions on the heating temperature, crystallization state, or elemental distribution when referring to the situation where particles are fixed by agglomeration as "bonding together." Furthermore, there are no restrictions on the bonding forces between the multiple primary particles at this time. The bonding force can be any one of covalent bonds, ionic bonds, hydrophobic interactions, van der Waals forces, or other intermolecular interactions, and multiple bonding forces can also occur. Additionally, when simply referred to as a "particle," both primary and secondary particles are included.

[0095] <Contains elements> The positive electrode active material 100 contains lithium, transition metal M, oxygen and added element X.

[0096] The positive electrode active material 100 can also be referred to as a material to which multiple additives are added to a composite oxide represented by LiMO2. Note that the positive electrode active material of one embodiment of the present invention may have a crystalline structure of a lithium composite oxide represented by LiMO2, and its composition is not strictly limited to Li:M:O = 1:1:2.

[0097] The transition metal M included in the positive electrode active material 100 is preferably a metal that can form a layered rock salt-type composite oxide belonging to space group R-3m together with lithium. For example, one or more of manganese, cobalt, and nickel can be used. That is, the transition metal included in the positive electrode active material 100 can be only cobalt or nickel, or it can be both cobalt and manganese, or both cobalt and nickel, or all three of cobalt, manganese, and nickel. That is, the positive electrode active material 100 can include composite oxides containing lithium and transition metal M, such as lithium cobalt oxide, lithium nickel oxide, lithium nickel oxide in which part of nickel is replaced by manganese, lithium nickel oxide in which part of nickel is replaced by cobalt, and nickel-cobalt-manganese oxide.

[0098] As an added element X, it is preferred to use one or more selected from calcium, fluorine, sodium, iron, arsenic, sulfur, and copper.

[0099] The appropriate ratio of each element included in the positive electrode active material 100 can be referred to the description in Embodiment 1.

[0100] <Distribution of elements> In the positive electrode active material 100, one or more of element X are preferably added to have a concentration gradient.

[0101] For example, preferably, the original particle 101 includes a surface portion 101a and an interior portion 101b, wherein the concentration of the added element X in the surface portion 101a is higher than that in the interior portion 101b. In Figures 3A and 3B, the concentration of the added element X in the original particle 101 is represented by a gradient. A darker color concentration, i.e., close to black, indicates a high concentration of the added element. A lighter color concentration, i.e., close to white, indicates a low concentration of the added element.

[0102] In addition, the concentration of added elements at the interface 103 between the original particles and near the interface 103 is preferably higher than that inside the original particles 101b. In this specification, the area near the interface 103 refers to the region from the interface 103 to about 10 nm.

[0103] Figure 4A shows an example of the concentration distribution of added elements between the dotted lines AB of the positive electrode active material 100 shown in Figure 3B. In Figure 4A, the horizontal axis represents the distance between the dotted lines AB in Figure 3B and the vertical axis represents the concentration of added elements.

[0104] Compared to the original particle 101, there are regions with high concentrations of added elements in and around interface 103. Note that the shape of the concentration distribution of the added elements is not limited to the shape shown in Figure 4A.

[0105] Furthermore, when multiple additive elements X are included, it is preferable that the peak positions of the concentrations differ depending on the additive.

[0106] For example, as shown in Figures 3A, 3B and 4B, calcium and fluorine can be examples of additive elements X that preferably have a concentration gradient increasing from the interior 101b to the surface.

[0107] Furthermore, as shown in FIG4C, the other added element X preferably has a concentration peak in the positive electrode active material 100 in a region closer to the interior 101b, such as in FIG4B, where the additive is distributed. The concentration peak can exist in the surface portion or in a region deeper than the surface portion. For example, it is preferable to have a concentration peak in a region 5 nm or more away from the surface and 30 nm or less.

[0108] Furthermore, as shown in FIG4D, the other added element X is preferably uniformly present within the interior 101b of the positive electrode active material 100. Examples of elements that preferably have the distribution described above include sodium, iron, arsenic, and copper.

[0109] Furthermore, preferably, in one embodiment of the positive electrode active material 100, the concentration of a portion of the metal, such as manganese, contained in the original particles 101 of the positive electrode active material 101 is higher than the average concentration of the entire positive electrode active material 100 or the concentration of the interior 101b. For example, preferably, the concentration of manganese in the surface portion 101a, as measured by XPS, is higher than the average concentration of the element in the entire positive electrode active material 100, as measured by ICP-MS, etc. Alternatively, preferably, there is a concentration gradient in which the concentration of manganese increases from the interior to the surface in line analysis such as EDX (Energy Dispersive X-ray Spectroscopy) and EPMA (Electron Probe Microscopy).

[0110] Unlike the interior of the crystal, the particle surface is in a state of bond cleavage, and because lithium is extracted from the surface during charging, the lithium concentration on the particle surface is lower than that inside the particle 101b. Therefore, the particle surface tends to be unstable, and the crystal structure is easily destroyed. When the concentration of added elements in the surface layer 101a is high, changes in the crystal structure can be suppressed more effectively. In addition, when the concentration of added elements in the surface layer 101a is high, it is expected to improve the corrosion resistance to hydrofluoric acid generated by electrolyte decomposition.

[0111] Thus, preferably, the concentration of added elements in the surface layer 101a of the positive electrode active material 100 of one embodiment of the present invention is higher than that in the interior 101b; and it has a different composition from the interior 101b. The surface layer 101a preferably has a crystalline structure stable at room temperature (25°C). Therefore, the surface layer 101a may also have a crystalline structure different from the interior 101b. For example, at least a portion of the surface layer 101a of the positive electrode active material 100 of one embodiment of the present invention may have a rock salt-type crystalline structure. Note that when the surface layer 101a has a crystalline structure different from the interior 101b, the orientation of the crystals in the surface layer 101a and the interior 101b is preferably substantially the same.

[0112] For example, the crystal structure preferably changes continuously from the interior 101b of the layered rock salt type to the surface and surface portion 101a of the rock salt type or having characteristics of both the rock salt type and the layered rock salt type. Alternatively, the surface portion 101a having characteristics of the rock salt type or having characteristics of both the rock salt type and the layered rock salt type is preferably aligned with the interior 101b of the layered rock salt type.

[0113] Furthermore, in this specification, the layered rock-salt type crystal structure belonging to space group R-3m of the composite oxide containing lithium and transition metal M refers to the following crystal structure: it has a rock-salt type ionic arrangement with alternating cations and anions, and the transition metal M and lithium are arranged regularly to form a two-dimensional plane, thus allowing lithium to diffuse in two dimensions. Additionally, it may also include defects such as vacancies of cations or anions. Strictly speaking, the layered rock-salt type crystal structure is sometimes a structure formed by lattice deformation of rock-salt type crystals.

[0114] In addition, rock salt-type crystal structures have cubic crystal structures with space group Fm-3m, in which cations and anions are arranged alternately. In addition, it may also include vacancies of cations or anions.

[0115] In addition, electron diffraction, TEM images, and cross-sectional STEM images can be used to determine whether a layered rock salt crystal structure or a rock salt crystal structure exists.

[0116] The positions of cations in the rock salt type crystal structure are not different, but in the layered rock salt type crystal structure, there are two types of cation positions: one where lithium occupies most of the position and the other where transition metal M occupies the position. Both rock salt type and layered rock salt type have a stacked structure in which two-dimensional planes of cations and two-dimensional planes of anions are arranged alternately. In the bright spots of the electron diffraction image of the crystal planes forming the above two-dimensional planes, when the origin is 000 with the central spot (through the spot), the bright spot closest to the central spot is, for example, the bright spot of the (111) plane of the ideal rock salt type crystal structure or the bright spot of the (003) plane of the ideal layered rock salt type crystal structure. For example, when comparing the electron diffraction images of rock salt type MgO and layered rock salt type LiCoO2, the distance between the bright spots of the (003) plane of LiCoO2 is observed to be about half the distance between the bright spots of the (111) plane of MgO. Therefore, in cases where the analysis region includes two phases, rock-type MgO and layered rock-type LiCoO2, the electron diffraction image shows an alternating pattern of bright and dim bright spots. Bright spots common to both rock-type and layered rock-type phases are brighter, while those occurring only in the layered rock-type phase are dimmer.

[0117] Furthermore, in cross-sectional STEM images, when observing a layered rock salt-type crystal structure from a direction perpendicular to the c-axis, layers with higher brightness and layers with lower brightness are observed alternately. The positions of the cations in the rock salt type are not distinct, so the aforementioned characteristics are not observed. When employing a crystal structure exhibiting characteristics of both the rock salt type and the layered rock salt type, when observed from a specific crystal orientation, layers with higher brightness and layers with lower brightness are observed alternately in cross-sectional STEM images, and in the lower brightness layer, i.e., a portion of the lithium layer, there exists a metal with an atomic number greater than lithium.

[0118] Layered rock salt crystals and rock salt crystals form cubic close-packed structures (face-centered cubic lattice structures) respectively. Thus, when these crystals come into contact, there are aligned crystal planes of the cubic close-packed structure formed by the anions.

[0119] Alternatively, it can be explained as follows. The anions on the {111} facets of a cubic crystal have a triangular lattice. Layered rock salt has a space group R-3m and a rhombohedral structure. For ease of understanding, it is usually represented by a composite hexagonal lattice, and the (000l) facets of the layered rock salt have a hexagonal lattice. The triangular lattice of the {111} facets of the cubic crystal has the same atomic arrangement as the hexagonal lattice of the (000l) facets of the layered rock salt. The integrability of the two lattices can be called the alignment conformity of the cubic close-packed structure.

[0120] Note that the space group for layered rock salt crystals is R-3m, which is different from the space group Fm-3m (the general space group for rock salt crystals). Therefore, the Miller indices of the crystal planes satisfying the above conditions differ between layered rock salt crystals and rock salt crystals. In this specification, sometimes the consistent orientation of the cubic close-packed structure formed by anions in layered rock salt crystals and rock salt crystals refers to a state in which the crystal orientation is approximately consistent.

[0121] The following images can be used to determine that the crystal orientation of two regions is roughly the same: TEM (Transmission Electron Microscope) images, STEM (Scanning Transmission Electron Microscope) images, HAADF-STEM (High-angle Annular Dark Field Scanning TEM) images, ABF-STEM (Annular Bright-Field Scanning Transmission Electron Microscope) images, electron diffraction, and FFT (Fast Fourier Transform) of TEM and STEM images. Additionally, XRD (X-ray Diffraction) and neutron diffraction can also be used as criteria for judgment.

[0122] Figure 5 shows an example of a TEM image in which the alignment of layered rock salt type LRS and rock salt type RS is approximately the same. Images reflecting the crystal structure can be obtained from TEM images, STEM images, HAADF-STEM images, ABF-STEM images, etc.

[0123] For example, contrast from crystal planes can be obtained from high-resolution TEM images. Due to electron beam diffraction and interference, for example, when the electron beam is incident on the c-axis of a composite hexagonal lattice perpendicular to layered rock salt, repetitions of high-contrast bands (bright bands) and dark bands (dark bands) from the (0003) plane can be obtained. Therefore, when repetitions of bright and dark lines are observed in TEM images, and the angle between bright lines (e.g., between LRS and LLRS in Figure 5) is less than 5 degrees or less, it can be judged that the crystal planes are roughly consistent, that is, the crystal orientation is roughly consistent. Similarly, when the angle between dark lines is less than 5 degrees or less or less than 2.5 degrees, it can also be judged that the crystal orientation is roughly consistent.

[0124] Furthermore, in HAADF-STEM images, contrast is obtained in proportion to atomic number; the higher the atomic number of an element, the brighter it appears. For example, when using layered rock salt type lithium nickel-cobalt-manganese oxide belonging to space group R-3m, the atomic numbers of manganese (atomic number 25), cobalt (atomic number 27), and nickel (atomic number 28), which are transition metals M, are higher than those of lithium and oxygen. Therefore, the electron beam is more strongly scattered at the positions of transition metal M atoms, and the arrangement of transition metal M atoms is observed as a bright line or a high-brightness dot arrangement. Thus, when observing layered rock salt type crystalline lithium nickel-cobalt-manganese oxide in a direction perpendicular to the c-axis, the arrangement of transition metal M is observed as a bright line or a high-brightness dot arrangement in the direction perpendicular to the c-axis, while the arrangement of lithium and oxygen atoms is observed as a dark line or a lower-brightness area. The same applies when fluorine (atomic number 9) and calcium (atomic number 20) are included as additive elements in lithium nickel-cobalt-manganese oxide.

[0125] Therefore, in HAADF-STEM images, the repetition of bright and dark lines is observed in two regions with different crystal structures. When the angle between the bright lines is less than 5 degrees or less than 2.5 degrees, it can be determined that the atomic arrangement is roughly the same, that is, the crystal orientation is roughly the same. Similarly, when the angle between the dark lines is less than 5 degrees or less than 2.5 degrees, it can also be determined that the crystal orientation is roughly the same.

[0126] In addition, in ABF-STEM, the smaller the atomic number, the brighter the element appears. However, just like HAADF-STEM, the contrast corresponding to the atomic number can be obtained. Therefore, the orientation of the crystal can be determined in the same way as the HAADF-STEM image.

[0127] Figure 6A shows an example of STEM images showing roughly aligned layered rock salt crystal LRS and rock salt crystal RS. Figure 6B shows the FFT pattern of the region of rock salt crystal RS, and Figure 6C shows the FFT pattern of the region of layered rock salt crystal LRS. The left side of Figures 6B and 6C shows the composition, JCPDS card number, and the d-values ​​and angles to be calculated later. The right side shows the measured values. Spots marked with 'O' indicate zero-order diffraction.

[0128] Spot A in Figure 6B originates from the 11-1 reflection of a cubic crystal. Spot A in Figure 6C originates from the 0003 reflection of a layered rock salt type. From Figures 6B and 6C, it can be seen that the orientation of the 11-1 reflection of the cubic crystal is approximately the same as the orientation of the 0003 reflection of the layered rock salt type. That is to say, it can be seen that the straight line AO ​​passing through Figure 6B is approximately parallel to the straight line AO ​​passing through Figure 6C. Here, "approximately the same" and "approximately parallel" refer to the case where the angle is less than 5 degrees or less than 2.5 degrees.

[0129] As described above, sometimes in FFT and electron diffraction, the alignment of layered rock salt crystals and rock salt crystals is approximately the same, and the <0003> orientation of the layered rock salt crystals is approximately the same as the <11-1> orientation of the rock salt crystals. In this case, their reciprocal lattice points are preferably speckled, that is, not continuous with other reciprocal lattice points. The speckled reciprocal lattice points and their non-continuity with other reciprocal lattice points indicate high crystallinity.

[0130] Furthermore, as mentioned above, when the orientation of the 11-1 reflection of the cubic crystal is approximately the same as the orientation of the 0003 reflection of the layered rock salt type, depending on the incident orientation of the electron beam, spots not originating from the 0003 reflection of the layered rock salt type can sometimes be observed in the reciprocal space, which is different from the orientation of the 0003 reflection of the layered rock salt type. For example, the spot marked B in FIG6C originates from the 1014 reflection of the layered rock salt type. This spot is sometimes observed at an angle of 52˚ or more and 56˚ or less from the orientation of the reciprocal lattice point (A in FIG6C) originating from the 0003 reflection of the layered rock salt type (i.e., ∠AOB is 52˚ or more and 56˚ or less) and d is 0.19 nm or more and 0.21 nm or less. Note that the above index is only an example and does not need to be consistent with this index. For example, reciprocal lattice points equivalent to 0003 and 1014 can also be used.

[0131] Similarly, sometimes spots not originating from the 11-1 reflection of a cubic crystal are observed in reciprocal lattice space, in a direction different from the direction from which the 11-1 reflection of a cubic crystal is observed. For example, the spot marked B in Figure 6B originates from the 200° reflection of a cubic crystal. Sometimes diffracted spots are observed at locations where the orientation of the reflection originating from the 11-1 of a cubic crystal (A in Figure 6B) is 54° or higher and 56° or lower (i.e., ∠AOB is 54° or higher and 56° or lower). Note that the above indices are merely examples and do not need to be consistent with them. For example, reciprocal lattice points equivalent to 11-1 and 200° can also be used.

[0132] Note that it is known that layered rock salt type positive electrode active materials such as lithium cobalt oxide tend to exhibit crystalline surfaces on the (0003) plane and its equivalent plane, as well as the (10-14) plane and its equivalent plane. Therefore, when carefully observing the shape of positive electrode active materials using SEM or similar methods, for example, by using FIB or similar methods to thin the sample in TEM with an electron beam incident at [12-10] to facilitate observation of the (0003) plane. In order to determine the consistency of crystal orientation, it is preferable to thin the sample to facilitate observation of the layered rock salt type (0003) plane.

[0133] The roughly consistent crystal orientation of the surface layer 101a and the interior layer 101b means that the surface layer 101a and the interior layer 101b have a stable bond. Therefore, when the positive electrode active material 100 is used in a secondary battery, changes in the crystal structure of the interior layer 101b caused by charging and discharging can be effectively suppressed. In addition, even if lithium is extracted from the interior layer 101b during charging, the stable bond of the surface layer 101a can suppress the detachment of transition metals such as cobalt M and oxygen from the interior layer 101b. Furthermore, the area in contact with the electrolyte can be made of a chemically stable material. Therefore, a secondary battery with high cycle characteristics can be manufactured.

[0134] Note that when the surface layer 101a is a compound containing only element X and oxygen, the lithium insertion / extraction pathway may be blocked, which is not preferable. For example, when magnesium is added, it is possible to form a nickel of transition metal M and a solid solution Ni1-xMgxO with a rock salt-type crystal structure. In this case, when the solid solution Ni1-xMgxO occupies most of the surface layer 101a, the lithium insertion / extraction pathway is blocked, which is not preferable.

[0135] On the other hand, calcium and barium are alkaline earth metals like magnesium, but they do not form solid solutions of nickel and rock salt-type oxides. Therefore, they are preferred as they easily maintain the diffusion path of lithium.

[0136] Therefore, the surface layer 101a needs to contain at least a transition metal M, and also contains lithium during discharge to provide a path for lithium insertion and extraction. In addition, the concentration of the transition metal M is preferably higher than the concentration of each added element X.

[0137] In addition, the transition metal M (especially cobalt and nickel) is preferably uniformly dissolved in the positive electrode active material 100.

[0138] When element X is added and distributed as described above, the degradation of the positive electrode active material 100 can be reduced even after charging and discharging. In other words, the degradation of the secondary battery can be suppressed. In addition, a secondary battery with high safety can be realized.

[0139] Generally, as a secondary battery is repeatedly charged and discharged, changes occur in the positive electrode active material, such as the dissolution of the transition metal M into the electrolyte, oxygen loss, and instability of the crystal structure, leading to degradation of the positive electrode active material. When the positive electrode active material deteriorates, it can sometimes cause a decrease in the capacity of the secondary battery. Note that in this specification, the phenomenon of chemical and structural changes in the positive electrode active material, such as the dissolution of the transition metal M into the electrolyte, oxygen loss, and instability of the crystal structure, is sometimes referred to as degradation of the positive electrode active material. In this specification, a decrease in the capacity of the secondary battery is sometimes also referred to as degradation of the secondary battery.

[0140] Metals dissolved from the positive electrode active material are reduced and deposited on the negative electrode, which can sometimes hinder the redox reaction in the negative electrode. When metals are deposited on the negative electrode, it can sometimes lead to degradation such as capacity reduction.

[0141] The lattice of the positive electrode active material expands and contracts due to the insertion and extraction of lithium during charging and discharging, sometimes resulting in lattice volume changes and distortions. These lattice volume changes and distortions lead to the cracking of the positive electrode active material, sometimes causing degradation such as capacity reduction. In addition, the cracking of the positive electrode active material sometimes occurs at the interface 103 between the original particles.

[0142] When the internal temperature of a secondary battery becomes high, oxygen may detach from the positive electrode active material, potentially compromising the battery's safety. Furthermore, the detachment of oxygen alters the crystal structure of the positive electrode active material, sometimes leading to degradation such as capacity reduction. Note that oxygen may detach from the positive electrode active material during lithium insertion and extraction during charging and discharging.

[0143] Therefore, a positive electrode active material 100 is manufactured that contains an additive element or compound (e.g., an oxide of the additive element) that is chemically and structurally stable compared to a lithium composite oxide represented by LiMO2 in the surface layer 101a or on the interface 103. Thus, the positive electrode active material 100 is chemically and structurally stable, and structural changes, volume changes, and distortions due to charging and discharging can be suppressed. In other words, the crystal structure of the positive electrode active material 100 becomes more stable, and changes in the crystal structure can be suppressed even with repeated charging and discharging. Furthermore, cracking of the positive electrode active material 100 can be suppressed. That is, degradation such as capacity loss can be suppressed, which is preferable. When the charging voltage is high and the amount of lithium present in the positive electrode decreases during charging, the crystal structure becomes unstable and easily deteriorates. By using the positive electrode active material 100 of one embodiment of the present invention, the crystal structure can be made more stable, thus suppressing degradation such as capacity loss, which is particularly preferable.

[0144] Since the positive electrode active material 100 of one embodiment of the present invention has a stable crystal structure, the dissolution of the transition metal M from the positive electrode active material can be suppressed. In other words, degradation such as capacity loss can be suppressed, which is preferred.

[0145] Furthermore, in one embodiment of the present invention, when the positive electrode active material 100 breaks along the interface 103 between the original particles 101, the surface of the broken original particles 101 contains compounds of added elements. In other words, changes such as oxygen desorption and unstable crystal structure can also be suppressed in the broken positive electrode active material 100, thus reducing the degradation of the positive electrode active material 100. In other words, the degradation of the secondary battery can be suppressed.

[0146] The content shown in this embodiment can be used in combination with the content shown in other embodiments.

[0147] Embodiment 3 In this embodiment, a lithium-ion secondary battery incorporating a positive electrode active material according to one embodiment of the present invention will be described. The secondary battery includes at least an outer casing, a current collector, an active material (positive electrode active material or negative electrode active material), a conductive material, and an adhesive. It also includes an electrolyte in which lithium salts or the like are dissolved. When using a secondary battery utilizing an electrolyte, a positive electrode, a negative electrode, and a separator between the positive and negative electrodes are provided.

[0148] [Positive Electrode] The positive electrode includes a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer preferably includes the positive electrode active material shown in Embodiment 2, and may also include an adhesive, conductive material, etc.

[0149] Figure 7 is a cross-sectional schematic diagram showing an example of a positive electrode.

[0150] The current collector 550 is a metal foil, and a positive electrode is formed by coating a slurry onto the metal foil and then drying it. Sometimes, it is pressed after drying. In the positive electrode, an active material layer is formed on the current collector 550.

[0151] The slurry is a liquid material used to form an active material layer on the current collector 550, comprising at least an active material, a binder, and a solvent, and preferably also containing a conductive material. The slurry is sometimes referred to as an electrode slurry or an active material slurry, and sometimes as a positive electrode slurry when forming a positive electrode active material layer, and sometimes as a negative electrode slurry when forming a negative electrode active material layer.

[0152] Conductive materials, also known as conductive agents or conductive additives, are made of carbon. By attaching a conductive material to multiple active substances, the conductivity of these active substances is improved through electrical connection. Note that "attachment" does not refer to physical contact between the active substances and the conductive material, but rather includes situations such as: covalent bonding; Van der Waals force bonding; the conductive material covering a portion of the surface of the active substance; the conductive material embedded in the surface irregularities of the active substance; and electrical connection without direct contact.

[0153] Carbon materials used as conductive materials typically include carbon black (furnace black, acetylene black, graphite, etc.).

[0154] In FIG7, acetylene black 553, graphene and graphene compound 554, and carbon nanotubes 555 are shown as conductive materials. In addition, the positive electrode active material 100 shown in Embodiment 1 corresponds to the active material 561 in FIG7.

[0155] To fix the current collector 550, such as the metal foil, and the active material, the positive electrode of the secondary battery is mixed with a binder (resin). The binder is also called a adhesive. The binder is a polymer material, and when a large amount of binder is included, the ratio of active material in the positive electrode decreases, and the discharge capacity of the secondary battery decreases. Therefore, a minimum amount of binder is mixed in.

[0156] Because of its excellent electrical, mechanical or chemical properties, graphene is expected to be used in various technological fields such as graphene-based electric field effect transistors and solar cells.

[0157] The graphene compounds used in this specification include multilayer graphene, multigraphene, graphene oxide, multilayer graphene oxide, multi-graphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, and reduced multi-graphene oxide. Graphene compounds refer to compounds containing carbon and having a two-dimensional structure formed by six-membered rings composed of carbon atoms, with shapes such as flat sheets or plates. Furthermore, a curved shape is preferred. They can also be called carbon sheets. It is preferable that they have functional groups. Furthermore, graphene compounds can also be coiled into nanofibers.

[0158] Graphene and graphene compounds sometimes possess excellent electrical properties such as high conductivity, as well as excellent physical properties such as high flexibility and high mechanical strength. Furthermore, graphene and graphene compounds have a sheet-like shape. Graphene and graphene compounds sometimes have curved surfaces, enabling surface contact with low contact resistance. Graphene and graphene compounds sometimes exhibit very high conductivity even when thin, thus allowing conductive paths to be formed efficiently in a small amount within the active material layer. Therefore, by using graphene and graphene compounds as conductive materials, the contact area between the active material and the conductive material can be increased. Preferably, graphene or graphene compounds are at least a portion of the secondary particles 102 in the positive electrode active material 100, which are clinged or sticked around it. Preferably, graphene or graphene compounds are superimposed on at least a portion of the active material. Preferably, the shape of graphene or graphene compounds is consistent with at least a portion of the shape of the secondary particles 102. The shape of the secondary particle 102 refers, for example, to the unevenness or concavity of the secondary particle 102 itself or to the unevenness or concavity formed by multiple secondary particles 102. Furthermore, graphene or a graphene compound is preferably present in at least a portion surrounding the secondary particle 102. Additionally, the graphene or graphene compound may also have pores.

[0159] Additionally, in Figure 7, the areas not filled by the active material 561, graphene and graphene compound 554, acetylene black 553, and carbon nanotubes 555 refer to voids or binders. Voids are necessary for electrolyte penetration, but too many voids reduce electrode density, while too few voids prevent electrolyte penetration, and residual voids after the secondary battery is completed reduce energy density.

[0160] Note that it is not necessary to include all three of the following as a conductive material: acetylene black 553, graphene and graphene compound 554, and carbon nanotube 555. It is sufficient to include at least one conductive material.

[0161] By using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode, a secondary battery with high energy density and good output characteristics can be obtained.

[0162] A secondary battery can be manufactured by the following steps: using the positive electrode of Figure 7, a separator is stacked on the positive electrode, and a negative electrode is stacked on the separator. The stack is placed in a container (outer packaging, metal can, etc.) and an electrolyte is filled in the container.

[0163] In addition, an example of a secondary battery using an electrolyte is shown above, but it is not limited to this.

[0164] For example, the positive electrode active material 100 shown in Embodiment 1 can also be used to manufacture a semi-solid battery or a full-solid battery.

[0165] In this specification, a semi-solid battery refers to a battery in which at least one of the electrolyte layer, positive electrode, and negative electrode contains a semi-solid material. Here, "semi-solid" does not mean that the proportion of solid material is 50%. "Semi-solid" means having solid properties such as small volume change, and having a portion of it with properties close to those of a liquid, such as flexibility. When possessing the above properties, a single material or multiple materials can be used. For example, a material in which a liquid material is impregnated with a solid material having a porous shape can also be used.

[0166] Furthermore, in this specification, a polymer electrolyte secondary battery refers to a secondary battery in which the electrolyte layer between the positive and negative electrodes comprises a polymer. Polymer electrolyte secondary batteries include dry (or intrinsic) polymer electrolyte batteries and polymer gel electrolyte batteries. Additionally, polymer electrolyte secondary batteries may also be referred to as semi-solid batteries.

[0167] When a semi-solid battery is manufactured using the positive electrode active material 100 shown in Embodiment 1, the semi-solid battery becomes a secondary battery with a large charge / discharge capacity. Furthermore, it can become a semi-solid battery with a high charge / discharge voltage. Additionally, a semi-solid battery with high safety or reliability can be achieved.

[0168] Alternatively, the positive electrode active material described in Embodiment 1 may be mixed with other positive electrode active materials for use.

[0169] Other positive electrode active materials include, for example, composite oxides with olivine-type crystal structure, layered rock salt-type crystal structure, or spinel-type crystal structure. Examples include compounds such as LiFePO4, LiFeO2, LiNiO2, LiMn2O4, V2O5, Cr2O5, and MnO2.

[0170] In addition, as other positive electrode active materials, lithium nickel oxide (LiNiO2 or LiNi1-xMxO2 (0 < x < 1) (M = Co, Al, etc.)) mixed in with lithium-containing materials containing manganese such as LiMn2O4 and having a spinel-type crystal structure is preferred. By adopting this structure, the characteristics of the secondary battery can be improved.

[0171] Additionally, as other positive electrode active materials, lithium manganese composite oxides that can be represented by the formula LiaMnbMcOd can be used. Here, element M is preferably a metal element selected from metal elements other than lithium and manganese, or silicon and phosphorus, and more preferably nickel. Furthermore, when measuring the overall particle composition of the lithium manganese composite oxide, it is preferable that 0 < a / (b+c) < 2, c > 0, and 0.26 ≤ (b+c) / d < 0.5 during discharge. Note that the metal, silicon, phosphorus, and other compositions of the overall particle composition of the lithium manganese composite oxide can be determined, for example, using ICP-MS. In addition, the oxygen composition of the overall particle composition of the lithium manganese composite oxide can be determined, for example, using EDX. Furthermore, the oxygen composition of the overall particle composition of the lithium manganese composite oxide can also be calculated by valence evaluation using fusion gas analysis and XAFS (X-ray Absorption Fine Structure) analysis together with ICP-MS analysis. In addition, lithium manganese composite oxide refers to an oxide that contains at least lithium and manganese, and may also contain at least one or more elements selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon and phosphorus.

[0172] <Adhesive> Preferred adhesives include, for example, styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene-propylene-diene copolymer. Fluororubber can also be used as an adhesive.

[0173] Furthermore, a water-soluble polymer is preferably used as the adhesive. Polysaccharides can also be used as water-soluble polymers, for example. Among the polysaccharides, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose, as well as starch, can be used. It is more preferable to use these water-soluble polymers and the aforementioned rubber material together.

[0174] Alternatively, as an adhesive, it is preferable to use materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, nitrocellulose, etc.

[0175] As an adhesive, multiple of the above materials can also be used in combination.

[0176] For example, materials with particularly good viscosity-regulating effects can also be used in combination with other materials. For example, although rubber materials and the like have high adhesion and high elasticity, viscosity regulation can sometimes be difficult when mixed in a solvent. In such cases, it is preferable to mix with a material with particularly good viscosity-regulating effects. As a material with particularly good viscosity-regulating effects, a water-soluble polymer can be used, for example. In addition, as a water-soluble polymer with particularly good viscosity-regulating function, the aforementioned polysaccharides can be used, such as cellulose derivatives or starches such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose.

[0177] Note that cellulose derivatives such as carboxymethyl cellulose, for example, by being converted into salts such as sodium or ammonium salts of carboxymethyl cellulose, have increased solubility and thus readily function as viscosity modifiers. Due to the increased solubility, the dispersibility of the active material with other components can be improved when forming the electrode slurry. In this specification, cellulose and cellulose derivatives used as binders for electrodes include their salts.

[0178] By dissolving water-soluble polymers in water to stabilize their viscosity, active substances or other materials used as binders, such as styrene-butadiene rubber, can be stably dispersed in aqueous solutions. Because water-soluble polymers possess functional groups, they are expected to readily and stably adhere to the surface of active substances. Cellulose derivatives, such as carboxymethyl cellulose, often possess functional groups such as hydroxyl or carboxyl groups. Because of these functional groups, the polymers are expected to interact and extensively cover the surface of active substances.

[0179] When an adhesive film is formed covering or in contact with the surface of the active material, it is also desirable for it to function as a passivation film to suppress electrolyte decomposition. Here, the passivation film is a film with no electronic conductivity or extremely low electrical conductivity, for example, suppressing electrolyte decomposition at the battery reaction potential when the passivation film is formed on the surface of the active material. More preferably, the passivation film can transport lithium ions while suppressing conductivity.

[0180] <Positive Electrode Current Collector> As a positive electrode current collector, highly conductive materials such as stainless steel, gold, platinum, aluminum, titanium, and their alloys can be used. Furthermore, the material used for the positive electrode current collector is preferably one that does not dissolve due to the potential of the positive electrode. Additionally, as a positive electrode current collector, aluminum alloys with added elements that improve heat resistance, such as silicon, titanium, neodymium, scandium, and molybdenum, can be used. Furthermore, metallic elements that react with silicon to form silicates can also be used. Metallic elements that react with silicon to form silicates include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The current collector can be appropriately shaped as foil, plate, sheet, mesh, perforated metal mesh, or expanded metal mesh. The thickness of the current collector is preferably 5 μm or more and 30 μm or less.

[0181] [Negative Electrode] The negative electrode includes a negative electrode active material layer and a negative electrode current collector. In addition, the negative electrode active material layer may also include a negative electrode active material and a conductive material and an adhesive.

[0182] <Negative Electrode Active Material> As a negative electrode active material, alloy materials, carbon materials, and mixtures thereof can be used, for example.

[0183] As the negative electrode active material, elements capable of undergoing charge-discharge reactions through alloying / dealloying reactions with lithium can be used. For example, materials containing one or more of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium can be used. These elements have higher capacities than carbon, especially silicon, which has a theoretical capacity of 4200 mAh / g. Therefore, silicon is preferred as the negative electrode active material. Alternatively, compounds containing these elements can also be used. Examples include SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, and SbSn. Elements that can undergo charge-discharge reactions through alloying / dealloying with lithium, and compounds containing such elements, are sometimes referred to as alloy materials.

[0184] In this specification, SiO refers to silicon monoxide, for example. Alternatively, SiO may be represented as SiOx. Here, x is preferably a value of 1 or close to 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.

[0185] As a carbon-based material, graphite, easily graphitized carbon (soft carbon), difficult-to-graphitize carbon (hard carbon), carbon nanotubes, graphene, carbon black, etc. can be used.

[0186] Examples of graphite include synthetic graphite and natural graphite. Examples of synthetic graphite include mesophase carbon microspheres (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spherical graphite with a spherical shape can be used as synthetic graphite. For example, MCMB sometimes has a spherical shape, which is preferred. Furthermore, MCMB is relatively easy to reduce its surface area, which is sometimes preferred. Examples of natural graphite include flake graphite and spheroidized natural graphite.

[0187] When lithium ions are intercalated in graphite (during the formation of lithium-graphite intercalation compounds), graphite exhibits a low potential similar to that of lithium metal (above 0.05V and below 0.3V vs. Li / Li+). Therefore, lithium-ion secondary batteries using graphite can exhibit high operating voltages. Graphite also has the following advantages: higher capacity per unit volume; smaller volume expansion; lower cost; and higher safety compared to lithium metal, making it a superior choice.

[0188] In addition, as negative electrode active materials, oxides such as titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O12), lithium-graphite intercalation compound (LixC6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), and molybdenum oxide (MoO2) can be used.

[0189] In addition, as the negative electrode active material, Li3-xMxN (M=Co, Ni, Cu) with a Li3N-type structure containing lithium and transition metal nitrides can be used. For example, Li2.6Co0.4N3 exhibits a large charge-discharge capacity (900 mAh / g, 1890 mAh / cm3), so it is preferred.

[0190] When using nitrides containing lithium and transition metals, lithium ions are present in the negative electrode active material. Therefore, it is preferable to combine them with materials that do not contain lithium ions, such as V2O5 and Cr3O8, which are used as positive electrode active materials. Note that even when using materials containing lithium ions as positive electrode active materials, lithium nitrides containing lithium and transition metals can be used as negative electrode active materials by pre-deintercalating and deintercalating the lithium ions contained in the positive electrode active material.

[0191] In addition, materials that induce the conversion reaction can also be used as negative electrode active materials. For example, transition metal oxides that do not form alloys with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), can be used as negative electrode active materials. Other materials that induce the conversion reaction include oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3; sulfides such as CoS0.89, NiS, and CuS; nitrides such as Zn3N2, Cu3N, and Ge3N4; phosphides such as NiP2, FeP2, and CoP3; and fluorides such as FeF3 and BiF3.

[0192] The conductive material and adhesive that may be included in the negative electrode active material layer may be the same material that may be included in the positive electrode active material layer.

[0193] <Negative Electrode Current Collector> As a negative electrode current collector, in addition to using the same materials as the positive electrode current collector, copper foil, copper foil, etc. can also be used. Furthermore, as a negative electrode current collector, it is preferable to use a material that does not alloy with carrier ions such as lithium.

[0194] [Isolator] An isolator is disposed between the positive and negative electrodes. As the isolator, materials such as cellulose fibers like paper, non-woven fabrics, glass fibers, ceramics, or synthetic fibers containing nylon (polyamide), vinylon (polyvinyl alcohol fibers), polyester, acrylic resin, polyolefins, polyurethane, etc., can be used. Preferably, the isolator is processed into a bag shape and disposed in a manner that surrounds either the positive or negative electrode.

[0195] The separator can have a multilayer structure. For example, ceramic materials, fluorinated materials, polyamide materials, or mixtures thereof can be coated onto organic materials such as polypropylene and polyethylene. Examples of ceramic materials include alumina particles and silicon oxide particles. Examples of fluorinated materials include PVDF and polytetrafluoroethylene. Examples of polyamide materials include nylon and aromatic polyamides (meta-aromatic polyamides, para-aromatic polyamides).

[0196] Coating with ceramic materials can improve oxidation resistance, thereby suppressing the degradation of the separator during high-voltage charging and discharging, and thus improving the reliability of the secondary battery. Coating with fluorine materials facilitates a tighter connection between the separator and the electrode, thereby improving output characteristics. Coating with polyamide materials (especially aromatic polyamides) can improve heat resistance, thereby improving the safety of the secondary battery.

[0197] For example, a mixture of alumina and aromatic polyamide can be coated on both sides of the polypropylene film. Alternatively, the side of the polypropylene film in contact with the positive electrode can be coated with a mixture of alumina and aromatic polyamide, while the side in contact with the negative electrode can be coated with a fluorinated material.

[0198] By using a multi-layered separator, the safety of the secondary battery can be ensured even if the total thickness of the separator is small, thus increasing the capacity per unit volume of the secondary battery.

[0199] [Electrolyte] The electrolyte comprises a solvent and an electrolyte. Preferably, an aprotic organic solvent is used as the solvent for the electrolyte, such as one of the following: ethylene carbonate (EC), propylene carbonate (PC), butenyl carbonate, vinyl chloride carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethyl glycol ether (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, cyclobutane, sulfolactone, etc., or two or more of the above can be used in any combination and ratio.

[0200] By using one or more flame-retardant and non-volatile ionic liquids (room temperature molten salts) as solvents for the electrolyte, even if the internal temperature of the storage device rises due to internal short circuits or overcharging, it can prevent the storage device from cracking and catching fire. Ionic liquids are composed of cations and anions, including organic cations and anions. Examples of organic cations used in the electrolyte include aliphatic onium cations such as quaternary ammonium cations, tertiary strontium cations, and quaternary phosphonium cations, or aromatic cations such as imidazolium cations and pyridinium cations. Examples of anions used in the electrolyte include monovalent amide anions, monovalent methylide anions, fluorosulfonic acid anions, perfluoroalkyl sulfonic acid anions, tetrafluoroborate anions, perfluoroalkyl borate anions, hexafluorophosphate anions, or perfluoroalkyl phosphate anions.

[0201] In addition, as the electrolyte dissolved in the above-mentioned solvent, one or more of the following lithium salts can be used in any combination and ratio: LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B10Cl10, Li2B12Cl12, LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, and lithium dioxoborate (Li(C2O4)2, abbreviated as LiBOB).

[0202] As the electrolyte for the energy storage device, it is preferable to use a highly purified electrolyte with low content of particulate dust or elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). Specifically, the weight ratio of impurities to electrolyte is 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

[0203] In addition, additives such as vinylene carbonate, propanesulfonate lactone (PS), terebutylbenzene (TBB), fluoroethylene vinyl carbonate (FEC), lithium dioxoborate (LiBOB), or dinitrile compounds such as succinate and adiponitrile can be added to the electrolyte. The concentration of the additive can be set, for example, to be more than 0.1 wt% and less than 5 wt% in the total solvent.

[0204] Alternatively, a polymer gel electrolyte in which the polymer has swollen in an electrolyte solution can also be used.

[0205] When using a polymer gel electrolyte, safety is improved against liquid leaks, etc. Furthermore, it enables the secondary battery to be made thinner and lighter.

[0206] As the gelling polymer, silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, fluoropolymer gel, etc., can be used. For example, polymers with a polyoxyalkylene structure such as polyethylene oxide (PEO), PVDF and polyacrylonitrile, and copolymers containing these can be used. For example, PVDF-HFP, a copolymer of PVDF and hexafluoropropylene (HFP), can be used. Furthermore, the formed polymer can also have a porous shape.

[0207] Furthermore, a solid electrolyte can be used instead of a liquid electrolyte, either an inorganic electrolyte containing sulfides or oxides, or a solid electrolyte containing polymeric materials such as PEO (polyethylene oxide). When using a solid electrolyte, there is no need to install separators or spacers. In addition, since the entire battery can be solidified, there is no concern about liquid leakage, thus significantly improving safety.

[0208] Therefore, the positive electrode active material 100 obtained in Embodiment 1 can be applied to an all-solid-state battery. By applying this positive electrode slurry or electrode to an all-solid-state battery, an all-solid-state battery with high safety and good performance can be obtained.

[0209] [Outer Packaging] The outer packaging of the secondary battery can be made of metal materials such as aluminum or resin materials. Alternatively, a thin film-like outer packaging can also be used. As a film, for example, a three-layer structure can be used: a flexible metal film such as aluminum, stainless steel, copper, or nickel is set on a film made of materials such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide; and an insulating synthetic resin film such as polyamide resin or polyester resin can be set on the metal film as the outer surface of the outer packaging.

[0210] The content shown in this embodiment can be combined with the content shown in other embodiments.

[0211] Embodiment 4 In this embodiment, examples of various shapes of secondary batteries including positive or negative electrodes manufactured by the manufacturing method described in the above embodiments will be described.

[0212] [Coin-type secondary battery] An example of a coin-type secondary battery is described. Figure 8A is an exploded perspective view of a coin-type (single-layer flat type) secondary battery, Figure 8B is its external view, and Figure 8C is its cross-sectional view. Coin-type secondary batteries are mainly used in small electronic devices. In this specification, coin-type batteries include button-type batteries.

[0213] To facilitate understanding of the overlapping relationships (vertical and positional relationships) of the components, Figure 8A is a schematic diagram. Therefore, Figure 8A is not completely identical to Figure 8B.

[0214] In Figure 8A, the positive electrode 304, the separator 310, the negative electrode 307, the spacer 322, and the gasket 312 are stacked. The above components are sealed with the negative electrode canister 302 and the positive electrode canister 301. Note that the gasket used for sealing is not shown in Figure 8A. The spacer 322 and the gasket 312 are used to protect the interior or fix the position inside the canisters when pressing the positive electrode canister 301 and the negative electrode canister 302 together. The spacer 322 and the gasket 312 are made of stainless steel or insulating material.

[0215] The stacked structure on which the positive electrode active material layer 306 is formed on the positive electrode current collector 305 is referred to as the positive electrode 304.

[0216] To prevent short circuits between the positive and negative electrodes, an isolator 310 and an annular insulator 313 are configured to cover the sides and top surface of the positive electrode 304. The area of ​​the isolator 310 is larger than the area of ​​the positive electrode 304.

[0217] Figure 8B is a perspective view of the manufactured coin-shaped secondary battery.

[0218] In the coin-type secondary battery 300, the positive electrode container 301, which also serves as the positive terminal, and the negative electrode container 302, which also serves as the negative terminal, are insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 disposed in contact with it. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 disposed in contact with it. Furthermore, the negative electrode 307 is not limited to a laminated structure; lithium metal foil or an alloy foil of lithium and aluminum can also be used.

[0219] In the positive electrode 304 and negative electrode 307 used in the coin-type secondary battery 300, the active material layer can be formed on one surface of the positive electrode and the negative electrode, respectively.

[0220] As the positive electrode container 301 and the negative electrode container 302, metals such as nickel, aluminum, and titanium, alloys thereof, and alloys thereof with other metals (e.g., stainless steel) that are resistant to corrosion by the electrolyte can be used. Furthermore, to prevent corrosion caused by the electrolyte, the positive electrode container 301 and the negative electrode container 302 are preferably covered with nickel or aluminum. The positive electrode container 301 is electrically connected to the positive electrode 304, and the negative electrode container 302 is electrically connected to the negative electrode 307.

[0221] A coin-shaped secondary battery 300 is manufactured by immersing the negative electrode 307, positive electrode 304 and separator 310 in an electrolyte, as shown in FIG8C, by placing the positive electrode tank 301 below and stacking the positive electrode 304, separator 310, negative electrode 307 and negative electrode tank 302 in sequence, and pressing the positive electrode tank 301 and negative electrode tank 302 together with a gasket 303.

[0222] By using the above-described structure, a coin-type secondary battery 300 with high capacity and good cycle characteristics can be manufactured.

[0223] [Cylindrical Secondary Battery] Next, an example of a cylindrical secondary battery will be described with reference to FIG9A. As shown in FIG9A, the top surface of the cylindrical secondary battery 616 includes a positive electrode cover (battery cover) 601, and its side and bottom surfaces include a battery canister (outer canister) 602. The positive electrode cover 601 and the battery canister (outer canister) 602 are insulated by a gasket (insulating gasket) 610.

[0224] Figure 9B is a schematic cross-sectional view of a cylindrical secondary battery. The cylindrical secondary battery shown in Figure 9B has a positive electrode cover (battery cover) 601 on the top surface and battery canisters (outer canisters) 602 on the sides and bottom surface. The positive electrode cover and the battery canisters (outer canisters) 602 are insulated from each other by a gasket (insulating gasket) 610.

[0225] A battery element is disposed inside a hollow cylindrical battery can 602, in which a strip-shaped positive electrode 604 and a strip-shaped negative electrode 606 are wound around an insulator 605. Although not shown, the battery element is wound around a central axis. One end of the battery can 602 is closed and the other end is open. The battery can 602 can be made of metals such as nickel, aluminum, and titanium, alloys thereof, and alloys thereof with other metals (e.g., stainless steel) that are resistant to electrolyte corrosion. In addition, to prevent corrosion caused by the electrolyte, the battery can 602 is preferably covered with nickel or aluminum. Inside the battery can 602, the battery element, in which the positive electrode, negative electrode, and insulator are wound, is held between a pair of opposing insulating plates 608 and 609. Furthermore, a non-aqueous electrolyte (not shown) is injected into the interior of the battery can 602 in which the battery element is disposed. As the non-aqueous electrolyte, the same electrolyte as that used in coin-type secondary batteries can be used.

[0226] Because the positive and negative electrodes of the cylindrical battery are wound, it is preferable that the active material is formed on both sides of the current collector. Note that Figures 9A to 9D show a secondary battery 616 in which the height of the cylinder is greater than the diameter of the cylinder, but it is not limited to this. Alternatively, a secondary battery in which the diameter of the cylinder is greater than the height of the cylinder can also be used. By adopting the above structure, for example, miniaturization of the secondary battery can be achieved.

[0227] By using the positive electrode active material 100, which can be obtained in Embodiment 1, on the positive electrode 604, a cylindrical secondary battery 616 with high capacity and good cycle characteristics can be manufactured.

[0228] The positive electrode 604 is connected to the positive terminal (positive current collector) 603, and the negative electrode 606 is connected to the negative terminal (negative current collector) 607. Both the positive terminal 603 and the negative terminal 607 can be made of metal materials such as aluminum. The positive terminal 603 is resistively soldered to the safety valve mechanism 613, and the negative terminal 607 is resistively soldered to the bottom of the battery canister 602. The safety valve mechanism 613 is electrically connected to the positive electrode cap 601 via a PTC (Positive Temperature Coefficient) element 611. When the internal pressure of the battery rises above a specified critical value, the safety valve mechanism 613 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604. Furthermore, the PTC element 611 is a heat-sensitive resistor whose resistance increases with temperature, and the increased resistance limits the current to prevent abnormal heating. As the PTC element, a semiconductor ceramic such as barium titanate (BaTiO3) can be used.

[0229] Figure 9C shows an example of an energy storage system 615. The energy storage system 615 includes a plurality of secondary batteries 616. The positive terminal of each secondary battery is in contact with a conductor 624 separated by an insulator 625, and the positive terminals are electrically connected to each other. The conductor 624 is electrically connected to a control circuit 620 via wiring 623. In addition, the negative terminal of each secondary battery is electrically connected to the control circuit 620 via wiring 626. As the control circuit 620, a protection circuit for preventing overcharging or over-discharging, etc., can be used.

[0230] Figure 9D shows an example of an energy storage system 615. The energy storage system 615 includes a plurality of secondary batteries 616 sandwiched between a conductive plate 628 and a conductive plate 614. The plurality of secondary batteries 616 are electrically connected to the conductive plates 628 and 614 via wiring 627. The plurality of secondary batteries 616 can be connected in parallel or in series. By constructing an energy storage system 615 including a plurality of secondary batteries 616, a large amount of power can be obtained.

[0231] In addition, multiple secondary batteries 616 can also be connected in parallel and then in series.

[0232] Alternatively, a temperature control device may be included among the multiple secondary batteries 616. The temperature control device can cool the secondary battery 616 when it overheats and heat it when it becomes too cold. Therefore, the performance of the energy storage system 615 is less susceptible to external temperature fluctuations.

[0233] In addition, in FIG9D, the energy storage system 615 is electrically connected to the control circuit 620 through wiring 621 and wiring 622. Wiring 621 is electrically connected to the positive terminal of the plurality of secondary batteries 616 through conductive plate 628, and wiring 622 is electrically connected to the negative terminal of the plurality of secondary batteries 616 through conductive plate 614.

[0234] [Other structural examples of secondary batteries] Structural examples of secondary batteries are illustrated using Figures 10A to 10C and Figures 11A to 11C.

[0235] The secondary battery 913 shown in FIG10A includes a wound body 950 with terminals 951 and 952 disposed inside the housing 930. The wound body 950 is immersed in electrolyte inside the housing 930. Terminals 952 are in contact with the housing 930, while insulating material prevents terminals 951 from contacting the housing 930. Note that, for convenience, although the housing 930 is shown separately in FIG10A, in reality the wound body 950 is covered by the housing 930, and terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of metal (e.g., aluminum) or resin.

[0236] In addition, as shown in FIG10B, the outer casing 930 shown in FIG10A can also be formed using multiple materials. For example, in the secondary battery 913 shown in FIG10B, outer casings 930a and 930b are attached together, and a winding body 950 is provided in the area surrounded by outer casings 930a and 930b.

[0237] As the outer casing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin to form the surface of the antenna, the shielding caused by the electric field of the secondary battery 913 can be suppressed. In addition, if the electric field shielding caused by the outer casing 930a is small, the antenna can also be installed inside the outer casing 930a. As the outer casing 930b, for example, a metal material can be used.

[0238] Furthermore, Figure 10C shows the structure of the wound body 950. The wound body 950 includes a negative electrode 931, a positive electrode 932, and an insulator 933. The wound body 950 is formed by sandwiching the insulator 933, overlapping the negative electrode 931 and the positive electrode 932 to form a laminate, and then winding the laminate. Alternatively, multiple laminates of negative electrode 931, positive electrode 932, and insulator 933 may also be stacked.

[0239] Alternatively, a secondary battery 913 including a wound body 950a, as shown in Figures 11A to 11C, can also be used. The wound body 950a shown in Figure 11A includes a negative electrode 931, a positive electrode 932, and an insulator 933. The negative electrode 931 includes a negative electrode active material layer 931a. The positive electrode 932 includes a positive electrode active material layer 932a.

[0240] By using the positive electrode active material 100, which can be obtained in Embodiment 1, in the positive electrode 932, a high-capacity secondary battery 913 with good cycle characteristics can be manufactured.

[0241] The width of the separator 933 is greater than that of the negative electrode active material layer 931a and the positive electrode active material layer 932a, and the separator 933 is wound in a manner that overlaps with the negative electrode active material layer 931a and the positive electrode active material layer 932a. Furthermore, from a safety point of view, it is preferable that the width of the negative electrode active material layer 931a is greater than that of the positive electrode active material layer 932a. Additionally, the above-described shape of the wound body 950a offers good safety and productivity, and is therefore preferred.

[0242] As shown in Figure 11B, the negative terminal 931 is electrically connected to terminal 951. Terminal 951 is electrically connected to terminal 911a. Additionally, the positive terminal 932 is electrically connected to terminal 952. Terminal 952 is electrically connected to terminal 911b.

[0243] As shown in Figure 11C, the wound body 950a and the electrolyte are covered by the casing 930 to form a secondary battery 913. The casing 930 is preferably equipped with a safety valve, overcurrent protection elements, etc. The safety valve is a valve designed to prevent the interior of the casing 930 from being opened by a specified internal pressure to prevent battery rupture.

[0244] As shown in FIG11B, the secondary battery 913 may also include multiple wound bodies 950a. By using multiple wound bodies 950a, a secondary battery 913 with a larger charge and discharge capacity can be realized. For other components of the secondary battery 913 shown in FIG11A and FIG11B, please refer to the description of the secondary battery 913 shown in FIG10A to FIG10C.

[0245] <Laminated Secondary Battery> Next, Figures 12A and 12B are external views showing an example of a laminated secondary battery. Both Figures 12A and 12B show the positive electrode 503, the negative electrode 506, the separator 507, the outer packaging 509, the positive electrode lead electrode 510, and the negative electrode lead electrode 511.

[0246] Figure 13A is an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 includes a positive current collector 501, and a positive active material layer 502 is formed on the surface of the positive current collector 501. Additionally, the positive electrode 503 has an area where the positive current collector 501 is partially exposed (hereinafter referred to as the tab region). The negative electrode 506 includes a negative current collector 504, and a negative active material layer 505 is formed on the surface of the negative current collector 504. Additionally, the negative electrode 506 has an area where the negative current collector 504 is partially exposed, i.e., the tab region. The area and shape of the tab regions of the positive and negative electrodes are not limited to the example shown in Figure 13A.

[0247] <Manufacturing Method of Laminated Secondary Battery> Here, an example of a manufacturing method of a laminated secondary battery, whose appearance is shown in FIG12A, will be described with reference to FIGS. 13B and 13C.

[0248] First, the negative electrode 506, the insulator 507, and the positive electrode 503 are stacked. Figure 13B shows the stacked negative electrode 506, insulator 507, and positive electrode 503. Here, an example using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. Alternatively, it can be described as a stack composed of a negative electrode, an insulator, and a positive electrode. Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode wire electrode 510 is joined to the tab region of the outermost positive electrode. As a joining method, for example, ultrasonic welding can be used. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode wire electrode 511 is joined to the tab region of the outermost negative electrode.

[0249] Next, a negative electrode 506, an isolator 507 and a positive electrode 503 are disposed on the outer packaging body 509.

[0250] Next, as shown in FIG13C, the outer packaging body 509 is folded along the portion indicated by the dotted line. Then, the outer periphery of the outer packaging body 509 is joined. As a joining method, for example, heat pressing can be used. At this time, in order to inject the electrolyte 508 later, an area (hereinafter referred to as the inlet) that is not joined to a part (or an edge) of the outer packaging body 509 is provided.

[0251] Next, electrolyte 508 (not shown) is introduced into the inside of the outer packaging 509 through an inlet provided in the outer packaging 509. Preferably, electrolyte 508 is introduced under a reduced pressure atmosphere or an inert gas atmosphere. Finally, the inlet is closed. In this way, a laminated secondary battery 500 can be manufactured.

[0252] By using the positive electrode active material 100 that can be obtained in Embodiment 1 to the positive electrode 503, a high-capacity secondary battery 500 with good cycle characteristics can be manufactured.

[0253] [Example of a battery pack] Using Figures 14A to 14C, an example of a secondary battery pack according to one embodiment of the present invention that can be wirelessly charged using an antenna is illustrated.

[0254] Figure 14A is a diagram showing the appearance of the secondary battery pack 531, which has a thin cuboid shape (or a relatively thick flat plate shape). Figure 14B is a diagram illustrating the structure of the secondary battery pack 531. The secondary battery pack 531 includes a circuit board 540 and a secondary battery 513. A label 529 is attached to the secondary battery 513. The circuit board 540 is secured by a sealing tape 515. In addition, the secondary battery pack 531 includes an antenna 517.

[0255] The interior of the secondary battery 513 may have a structure including a wound body or a structure including a stacked body.

[0256] As shown in FIG14B, a control circuit 590 is provided on a circuit board 540, for example, in the secondary battery pack 531. The circuit board 540 is electrically connected to terminal 514. Furthermore, the circuit board 540 is electrically connected to one of the positive and negative terminals 551 of the antenna 517 and the other of the positive and negative terminals 552 of the secondary battery 513.

[0257] In addition, as shown in FIG14C, it may also include a circuit system 590a disposed on the circuit board 540 and a circuit system 590b electrically connected to the circuit board 540 through a terminal 514.

[0258] Furthermore, the shape of antenna 517 is not limited to a coil shape; for example, it can be a wire or a plate shape. Additionally, planar antennas, aperture antennas, traveling wave antennas, EH antennas, magnetic field antennas, or dielectric antennas can also be used. Alternatively, antenna 517 can also be a planar conductor. This planar conductor can also be used as one of the conductors for electric field coupling. In other words, antenna 517 can also be used as one of the two conductors in a capacitor. Thus, not only electromagnetic and magnetic fields can be utilized, but also electric fields can be used to exchange power.

[0259] The secondary battery pack 531 includes a layer 519 between the antenna 517 and the secondary battery 513. The layer 519, for example, has the function of shielding electromagnetic fields from the secondary battery 513. As the layer 519, a magnetic material can be used, for example.

[0260] The content of this embodiment can be freely combined with the content of other embodiments.

[0261] Embodiment 5 In this embodiment, an example of manufacturing an all-solid-state battery using the positive electrode active material 100 that can be obtained in Embodiment 1 is shown.

[0262] As shown in FIG15A, a secondary battery 400 according to one embodiment of the present invention includes a positive electrode 410, a solid electrolyte layer 420 and a negative electrode 430.

[0263] The positive electrode 410 includes a positive current collector 413 and a positive active material layer 414. The positive active material layer 414 includes a positive active material 411 and a solid electrolyte 421. The positive active material 411 uses the positive active material 100 that can be obtained in Embodiment 1. The positive active material layer 414 may also include a conductive material and an adhesive.

[0264] The solid electrolyte layer 420 includes a solid electrolyte 421. The solid electrolyte layer 420 is located between the positive electrode 410 and the negative electrode 430, and does not include the positive electrode active material 411 or the negative electrode active material 431.

[0265] The negative electrode 430 includes a negative electrode current collector 433 and a negative electrode active material layer 434. The negative electrode active material layer 434 includes a negative electrode active material 431 and a solid electrolyte 421. Alternatively, the negative electrode active material layer 434 may also include a conductive material and a binder. Note that when lithium metal is used for the negative electrode active material 431, particles are not required, so as shown in FIG15B, a negative electrode 430 excluding the solid electrolyte 421 can be formed. When lithium metal is used for the negative electrode 430, the energy density of the secondary battery 400 can be increased, which is preferable.

[0266] The solid electrolyte 421 included in the solid electrolyte layer 420 may be, for example, a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, etc.

[0267] Sulfide solid electrolytes include sulfide silicates (Li10GeP2S12, Li3.25Ge0.25P0.75S4, etc.), sulfide glasses (70Li2S･30P2S5, 30Li2S･26B2S3･44LiI, 63Li2S･38SiS2･1Li3PO4, 57Li2S･36SiS2･5Li4SiO4, 50Li2S･50GeS2, etc.), and sulfide crystalline glasses (Li7P3S11, Li3.25P0.95S4, etc.). Sulfide solid electrolytes have the following advantages: they are materials with high conductivity; they can be synthesized at low temperatures; they are relatively soft, so they easily maintain the conductive path even after charge and discharge; etc.

[0268] Oxide solid electrolytes include materials with perovskite-type crystal structures (La2 / 3-xLi3xTiO3, etc.), materials with NASICON-type crystal structures (Li1-YAlYTi2-Y(PO4)3, etc.), materials with garnet-type crystal structures (Li7La3Zr2O12, etc.), materials with LISICON-type crystal structures (Li14ZnGe4O16, etc.), LLZO (Li7La3Zr2O12), oxide glasses (Li3PO4-Li4SiO4, 50Li4SiO4·50Li3BO3, etc.), and oxide crystal glasses (Li1.07Al0.69Ti1.46(PO4)3, Li1.5Al0.5Ge1.5(PO4)3, etc.). The advantage of oxide solid electrolytes is their stability in the atmosphere.

[0269] Halogenated solid electrolytes include LiAlCl4, Li3InBr6, LiF, LiCl, LiBr, LiI, etc. In addition, composite materials made by filling the fine pores of porous alumina or porous silicon dioxide with these halide-based solid electrolytes can also be used as solid electrolytes.

[0270] In addition, different solid electrolytes can be mixed for use.

[0271] Among them, Li1+xAlxTi2-x(PO4)3 (0≤x≤1) (hereinafter referred to as LATP), which has a NASICON-type crystal structure, contains aluminum and titanium, elements that can be used as the positive electrode active material of a secondary battery 400 in one embodiment of the present invention. Therefore, it is expected to have a multiplicative effect on improving cycle characteristics, and is therefore preferred. In addition, it is also expected that the manufacturing process will be reduced to improve productivity. Note that in this specification, etc., the NASICON-type crystal structure refers to a compound represented by M2(XO4)3 (M: transition metal, X: S, P, As, Mo, W, etc.), which has a structure in which MO6 octahedrons and XO4 tetrahedrons share vertices and are arranged in three dimensions.

[0272] [Shape of outer packaging and secondary battery] The outer packaging of the secondary battery 400 according to one embodiment of the present invention can be made of various materials and shapes, preferably of materials and shapes that have a pressurizing function for the positive electrode, the solid electrolyte layer and the negative electrode.

[0273] For example, Figures 16A to 16C show an example of a cell used to evaluate materials for all-solid-state batteries.

[0274] Figure 16A is a cross-sectional schematic diagram of the evaluation unit, which includes a lower member 761, an upper member 762, and a fixing screw or wing nut 764 for fixing them. The evaluation material is fixed by rotating the pressing screw 763 to press the electrode plate 753. An insulator 766 is provided between the lower member 761 and the upper member 762, which are made of stainless steel. In addition, an O-ring 765 for sealing is provided between the upper member 762 and the pressing screw 763.

[0275] The evaluation material is placed on the electrode plate 751, surrounded by the insulating tube 752, and pressed down by the electrode plate 753. Figure 16B shows a magnified perspective view of the vicinity of the evaluation material.

[0276] An example of a material for evaluation, comprising a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c, is shown, and a cross-sectional view of it is shown in FIG16C. Note that the same parts in FIG16A to FIG16C are denoted by the same symbols.

[0277] The electrode plate 751 and the lower member 761, which are electrically connected to the positive electrode 750a, can be regarded as the positive terminal. The electrode plate 753 and the upper member 762, which are electrically connected to the negative electrode 750c, can be regarded as the negative terminal. In addition, the resistance and the like can be measured by pressing the evaluation material with the electrode plate 751 and the electrode plate 753.

[0278] Furthermore, in one embodiment of the present invention, the outer packaging of the secondary battery is preferably an airtight enclosure. For example, a ceramic enclosure or a resin enclosure may be used. Additionally, when sealing the outer packaging, it is preferably done in a sealed atmosphere that prevents atmospheric entry, such as inside a glove box.

[0279] FIG17A is a perspective view showing a secondary battery of one embodiment of the present invention having an outer packaging and shape different from that of FIGS16A to 16C. The secondary battery of FIG17A includes external electrodes 771, 772 and is sealed by an outer packaging having multiple encapsulation components.

[0280] Figure 17B shows an example of a cross-section taken along the dotted line in Figure 17A. The stack comprising a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is sealed by an encapsulation member 770a with an electrode layer 773a disposed on a flat plate, a frame-shaped encapsulation member 770b, and an encapsulation member 770c with an electrode layer 773b disposed on a flat plate. The encapsulation members 770a, 770b, and 770c can be made of insulating materials, such as resin materials and ceramics.

[0281] External electrode 771 is electrically connected to positive electrode 750a through electrode layer 773a and serves as positive terminal. In addition, external electrode 772 is electrically connected to negative electrode 750c through electrode layer 773b and serves as negative terminal.

[0282] By using the positive electrode active material 100 that can be obtained in Embodiment 1, an all-solid-state secondary battery with high energy density and good output characteristics can be realized.

[0283] The content of this embodiment can be appropriately combined with the content of other embodiments.

[0284] Embodiment 6 In this embodiment, FIG18C illustrates an example of a secondary battery, different from the cylindrical secondary battery shown in FIG9D, being used in an electric vehicle (EV).

[0285] In an electric vehicle, a first battery 1301a and 1301b are provided as a secondary battery for main drive, and a second battery 1311 is provided to supply power to an inverter 1312 that starts the engine 1304. The second battery 1311 is also referred to as a cranking battery (or starting battery). The second battery 1311 only needs to have high output and does not need to have high capacity. In addition, the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

[0286] The internal structure of the first battery 1301a can be either a wound type as shown in FIG10A or FIG11C, or a stacked type as shown in FIG12A or FIG12B. Alternatively, the first battery 1301a can also use the all-solid-state battery of Embodiment 5. By using the all-solid-state battery of Embodiment 5 as the first battery 1301a, high capacity, improved safety, and miniaturization and weight reduction can be achieved.

[0287] In this embodiment, an example of connecting the first batteries 1301a and 1301b in parallel is shown, but more than three batteries can also be connected in parallel. Furthermore, if sufficient power can be stored in the first battery 1301a, the first battery 1301b may not be required. By constructing a battery pack from multiple secondary batteries, a greater amount of power can be extracted. Multiple secondary batteries can be connected in parallel, in series, or in parallel followed by series connection. Sometimes, multiple secondary batteries are referred to as a battery pack.

[0288] In order to cut off power from multiple secondary batteries, the vehicle secondary battery includes a charging plug or circuit breaker that can disconnect high voltage without the use of tools, which is provided in the first battery 1301a.

[0289] Furthermore, the power from the first batteries 1301a and 1301b is primarily used to rotate the engine 1304, and also supplies power to 42V series vehicle components (electric power steering system 1307, heater 1308, defogger 1309, etc.) via the DC-DC circuit 1306. In the case where the rear wheels include a rear-mounted engine 1317, the first battery 1301a is used to rotate the rear-mounted engine 1317.

[0290] In addition, the second battery 1311 supplies power to 14V series vehicle components (audio system 1313, power windows 1314, lights 1315, etc.) through the DC-DC circuit 1310.

[0291] Additionally, the first battery 1301a will be described using FIG18A.

[0292] Figure 18A shows an example of using nine triangular secondary batteries 1300 as a battery pack 1415. Furthermore, the nine triangular secondary batteries 1300 are connected in series, with one electrode fixed using a fixing part 1413 made of an insulator and the other electrode fixed using a fixing part 1414 made of an insulator. In this embodiment, an example using fixing parts 1413 and 1414 is shown, but they can also be stored in a battery storage box (also called a housing). Assuming the vehicle is subjected to vibration or shaking from the outside (road surface, etc.), it is preferable to use fixing parts 1413 and 1414 and a battery storage box to fix multiple secondary batteries. Additionally, one electrode is electrically connected to the control circuit section 1320 via wiring 1421. Additionally, the other electrode is electrically connected to the control circuit section 1320 via wiring 1422.

[0293] In addition, the control circuit section 1320 may also use a memory circuit that includes a transistor utilizing an oxide semiconductor. Sometimes, a charging control circuit or battery control system that includes a memory circuit utilizing an oxide semiconductor transistor is referred to as BTOS (Battery operating system or Battery oxide semiconductor).

[0294] Preferably, a metal oxide used as an oxide semiconductor is used. For example, In-M-Zn oxide (element M is selected from one or more of aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium) is preferred as the oxide. In particular, CAAC-OS (C-Axis Aligned Crystal Oxide Semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor) is preferred as the oxide. In addition, In-Ga oxide and In-Zn oxide can also be used as oxides. CAAC-OS is an oxide semiconductor comprising multiple crystalline regions, the c-axis of which is aligned in a specific direction. In addition, the specific direction refers to the thickness direction of the CAAC-OS film, the normal direction of the surface to which the CAAC-OS film is formed, or the normal direction of the surface of the CAAC-OS film. In addition, the crystalline regions are regions with a periodic atomic arrangement. Note that when atomic arrangement is considered as lattice arrangement, the crystalline region is also a region with consistent lattice arrangement. Furthermore, CAAC-OS has a region where multiple crystalline regions are connected in the ab-plane direction, and sometimes this region exhibits distortion. Distortion refers to the portion of the lattice arrangement direction that changes between regions with consistent lattice arrangement and other regions with consistent lattice arrangement in a region where multiple crystalline regions are connected. In other words, CAAC-OS refers to an oxide semiconductor with c-axis orientation and no obvious orientation in the ab-plane direction. Additionally, CAC-OS, for example, refers to a configuration in which elements contained in a metal oxide are non-uniformly distributed, and the size of the material containing the non-uniformly distributed elements is 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 3 nm or approximately. Note that below, the state in which one or more metal elements are non-uniformly distributed in a metal oxide and the regions containing those metal elements are mixed is also referred to as mosaic or patch-like, and the size of this region is 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 3 nm or approximately.

[0295] Furthermore, CAC-OS refers to a structure in which the material is separated into a first region and a second region, forming a mosaic pattern, and the first region is distributed in the film (hereinafter also referred to as cloud-like). That is to say, CAC-OS refers to a composite metal oxide having a structure in which the first region and the second region are mixed.

[0296] Here, each of the atomic ratios of In, Ga, and Zn relative to the metal elements constituting the CAC-OS of the In-Ga-Zn oxide is denoted as [In], [Ga], and [Zn]. For example, in the CAC-OS of the In-Ga-Zn oxide, a first region is a region where [In] is greater than [In] in the composition of the CAC-OS film. A second region is a region where [Ga] is greater than [Ga] in the composition of the CAC-OS film. Alternatively, for example, a first region is a region where [In] is greater than [In] in the second region and [Ga] is less than [Ga] in the second region. A second region is a region where [Ga] is greater than [Ga] in the first region and [In] is less than [In] in the first region.

[0297] Specifically, the first region described above is a region whose main component is indium oxide or indium zinc oxide. Furthermore, the second region described above is a region whose main component is gallium oxide or gallium zinc oxide. In other words, the first region can be referred to as a region whose main component is In. Furthermore, the second region described above can be referred to as a region whose main component is Ga.

[0298] Note that sometimes the clear boundary between the first region and the second region mentioned above cannot be observed.

[0299] For example, in the CAC-OS of In-Ga-Zn oxide, based on the EDX mapping image obtained by energy dispersive X-ray analysis (EDX), a structure with a non-uniformly distributed and mixed region of In as the main component (first region) and Ga as the main component (second region) can be identified.

[0300] When CAC-OS is used in a transistor, the complementary effect of conductivity arising from the first region and insulation arising from the second region enables CAC-OS to have a switching function (the function of controlling conduction / turn-off). In other words, a part of the CAC-OS material has a conductive function and another part has an insulating function, and the material as a whole has a semiconductor function. By separating the conductive and insulating functions, each function can be maximized. Therefore, by using CAC-OS in a transistor, high on-state current (Ion), high field-effect mobility (μ), and good switching operation can be achieved.

[0301] Oxide semiconductors have various structures and properties. In one embodiment of the present invention, the oxide semiconductor may also include two or more of amorphous oxide semiconductors, polycrystalline oxide semiconductors, a-like OS, CAC-OS, nc-OS, and CAAC-OS.

[0302] Furthermore, the control circuit section 1320 preferably uses a transistor containing an oxide semiconductor because this transistor can be used in high-temperature environments. To simplify the manufacturing process, the control circuit section 1320 can also be formed using a monopolar transistor. The operating ambient temperature range of a transistor containing an oxide semiconductor in the semiconductor layer is larger than that of a monocrystalline Si transistor, i.e., above -40°C and below 150°C, and the characteristic changes of the secondary battery when overheated are smaller than those of a monocrystalline Si transistor. The off-state current of the transistor containing the oxide semiconductor is also below the lower limit of measurement at 150°C, but the off-state current characteristics of the monocrystalline Si transistor are highly temperature-dependent. For example, at 150°C, the off-state current of the monocrystalline Si transistor increases, and the current switching ratio does not become sufficiently large. The control circuit section 1320 can improve safety. In addition, by combining it with a secondary battery using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode, a multiplicative effect on safety can be obtained.

[0303] The control circuit section 1320, which includes a memory circuit utilizing an oxide semiconductor transistor, can also be used as an automatic control device for secondary batteries that are susceptible to instability due to factors such as micro-short circuits. Examples of functions that address the causes of instability include overcharge prevention, overcurrent prevention, overheat control during charging, maintaining cell balance in the battery pack, over-discharge prevention, capacity measurement, automatic control of charging voltage and current based on temperature, control of charging current based on degradation level, detection of abnormal micro-short circuit behavior, and prediction of micro-short circuit anomalies. The control circuit section 1320 has at least one of these functions. Furthermore, the automatic control device for secondary batteries can be miniaturized.

[0304] In addition, a micro-short circuit refers to an extremely small short circuit inside a secondary battery. It is not a state where the battery cannot charge or discharge due to a short circuit between the positive and negative terminals, but rather a phenomenon where a short-circuit current flows slightly through a very small portion of the short circuit. Since even a short and extremely small portion can produce a large voltage change, this abnormal voltage value can affect the prediction of the subsequent charging and discharging state of the secondary battery.

[0305] One of the reasons for the occurrence of micro short circuits is believed to be due to the uneven distribution of the positive electrode active material caused by repeated charging and discharging, resulting in local current concentration in a part of the positive electrode and a part of the negative electrode, which renders part of the insulator ineffective, or by the occurrence of side reactants due to side reactions, leading to micro short circuits.

[0306] In addition, the control circuit section 1320 detects the terminal voltage of the secondary battery in addition to the micro-short circuit, and manages the charging and discharging state of the secondary battery. For example, in order to prevent overcharging, both the output transistor of the charging circuit and the shut-off switch can be turned off almost simultaneously.

[0307] Additionally, Figure 18B shows an example of a block diagram of the battery pack 1415 shown in Figure 18A.

[0308] The control circuit section 1320 includes: a switch section 1324 that includes at least a switch to prevent overcharging and a switch to prevent over-discharging; a control circuit 1322 that controls the switch section 1324; and a voltage measuring section for the first battery 1301a. In the control circuit section 1320, the upper and lower limit voltages of the secondary battery are set to control the upper limit of the current flowing from the outside and the upper limit of the output current flowing to the outside. The range above the lower limit voltage and below the upper limit voltage of the secondary battery is a recommended voltage range. When the voltage is outside this range, the switch section 1324 functions as a protection circuit. Furthermore, since the control circuit section 1320 controls the switch section 1324 to prevent over-discharging and overcharging, it can also be called a protection circuit. For example, when the control circuit 1322 detects a voltage that would lead to overcharging, it blocks the current by closing the switch of the switch section 1324. Alternatively, a PTC element can be provided in the charging / discharging path to enable a current-blocking function based on temperature rise. In addition, the control circuit section 1320 includes external terminal 1325 (+IN) and external terminal 1326 (-IN).

[0309] The switching unit 1324 can be constructed by combining n-channel transistors and p-channel transistors. Besides switches using Si transistors (monolithic silicon), the switching unit 1324 can also be constructed using power transistors such as Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), and GaOx (gallium oxide; x is a real number greater than 0). Furthermore, memory elements using OS transistors can be freely configured by stacking them on circuits using Si transistors, making integration easy. Additionally, OS transistors can be manufactured using the same manufacturing equipment as Si transistors, thus enabling low-cost manufacturing. In other words, by stacking a control circuit unit 1320 using OS transistors on the switching unit 1324, the switching unit 1324 and the control circuit unit 1320 can be integrated into a single chip. The size occupied by the control circuit section 1320 can be reduced, thus enabling miniaturization.

[0310] The first batteries 1301a and 1301b mainly supply power to 42V series (high voltage series) vehicle equipment, while the second battery 1311 supplies power to 14V series (low voltage series) vehicle equipment.

[0311] This embodiment shows an example in which both the first battery 1301a and the second battery 1311 use lithium-ion secondary batteries. The second battery 1311 may also use a lead-acid battery, an all-solid-state battery, or an electric double-layer capacitor. For example, the all-solid-state battery of Embodiment 5 may also be used. By using the all-solid-state battery of Embodiment 5 as the second battery 1311, high capacity can be achieved, thereby enabling miniaturization and weight reduction.

[0312] Furthermore, the regenerative energy generated by the rotation of the tire 1316 is transmitted to the engine 1304 via the transmission 1305, and charged to the second battery 1311 from the engine controller 1303 and battery controller 1302 via the control circuit section 1321. Additionally, the first battery 1301a is charged from the battery controller 1302 via the control circuit section 1320. Furthermore, the first battery 1301b is charged from the battery controller 1302 via the control circuit section 1320. For efficient charging of regenerative energy, it is preferable that the first batteries 1301a and 1301b can be charged at high speed.

[0313] The battery controller 1302 can set the charging voltage and charging current of the first batteries 1301a and 1301b. The battery controller 1302 sets the charging conditions according to the charging characteristics of the secondary batteries used and performs high-speed charging.

[0314] Additionally, although not shown, when the electric vehicle is connected to an external charger, the charger's socket or connecting cable is electrically connected to the battery controller 1302. Power supplied from the external charger charges the first batteries 1301a and 1301b through the battery controller 1302. While some chargers have a control circuit that does not utilize the battery controller 1302, it is preferable to charge the first batteries 1301a and 1301b through the control circuit section 1320 to prevent overcharging. Sometimes, the charger's socket or connecting cable also has a control circuit. The control circuit section 1320 is sometimes referred to as an ECU (Electronic Control Unit). The ECU connects to the CAN (Controller Area Network) installed in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. Furthermore, the ECU includes a microcomputer. Alternatively, the ECU may use a CPU or GPU.

[0315] External chargers installed in charging stations, etc., include 100V sockets, 200V sockets, and three-phase 200V 50kW sockets. Alternatively, they can be charged by receiving power from external charging devices through contactless power supply methods.

[0316] When performing high-speed charging, in order to charge in a short time, a secondary battery that can withstand charging at high voltage is expected.

[0317] Furthermore, the secondary battery of this embodiment uses the positive electrode active material 100 that can be obtained in Embodiment 1. Additionally, when graphene is used as the conductive material and the load can be increased even with a thicker electrode layer, capacity loss can be suppressed to maintain a high capacity, resulting in a synergistic effect that significantly improves the electrical characteristics of the secondary battery. In particular, it is very effective for secondary batteries used in vehicles, enabling vehicles with a longer driving range without increasing the weight ratio of the secondary battery relative to the total vehicle weight; specifically, a driving range of 500 km or more per charge.

[0318] In particular, by using the positive electrode active material 100 described in Embodiment 1, the operating voltage of the secondary battery in this embodiment can be increased, thereby increasing the usable capacity as the charging voltage increases. Furthermore, by using the positive electrode active material 100 described in Embodiment 1 as the positive electrode, a vehicle secondary battery with good cycle characteristics can be provided.

[0319] Next, a secondary battery that is installed in a vehicle as one embodiment of the present invention will be described, typically a transport vehicle.

[0320] Furthermore, the secondary batteries or energy storage devices shown in any of Figures 9C, 11C, and 18A can be installed in vehicles such as hybrid electric vehicles (HV), electric vehicles (EV), or plug-in hybrid electric vehicles (PHV). Additionally, the secondary batteries can be installed in agricultural machinery, electric bicycles (including electric-assisted bicycles), motorcycles, electric wheelchairs, electric transport vehicles, small or large ships, submarines, fixed-wing aircraft and rotary-wing aircraft, as well as aircraft, rockets, artificial satellites, space probes, planetary probes, spacecraft, and other transport vehicles. The secondary battery in one embodiment of the present invention can be a high-capacity secondary battery. Therefore, the secondary battery in one embodiment of the present invention is suitable for miniaturization and lightweighting, and can be used in transport vehicles.

[0321] Figures 19A to 19D show a transport vehicle using one embodiment of the present invention. The vehicle 2001 shown in Figure 19A is an electric vehicle that uses an electric motor as a power source for driving. Alternatively, the vehicle 2001 is a hybrid vehicle that can appropriately select an electric motor and an engine as a power source for driving. When installing a secondary battery in the vehicle, the example of the secondary battery shown in Embodiment 4 can be provided in one or more parts. The vehicle 2001 shown in Figure 19A includes a battery pack 2200, which includes a secondary battery module connected to a plurality of secondary batteries. In addition, it is preferable to also include a charging control device electrically connected to the secondary battery module.

[0322] Furthermore, in the vehicle 2001, the secondary battery can be charged by supplying power from an external charging device using methods such as plug-in or contactless power supply. When charging, the charging method and connector specifications should be appropriately conforming to the specifications of CHAdeMO (a trademark registered in Japan) or the "Combined Charging System." Charging devices can also be installed at charging stations in commercial facilities or at home. For example, by using plug-in technology to supply power from an external source, the battery storage device installed in the vehicle 2001 can be charged. AC power can be converted to DC power using a conversion device such as an AC / DC converter for charging.

[0323] Alternatively, although not shown in the diagram, the receiving device can be installed in the vehicle and charged by receiving power from a ground-based power supply device without contact. When using a contactless power supply method, by assembling the power supply device in the road or exterior wall, charging can be performed both while the vehicle is parked and while it is in motion. Furthermore, this contactless power supply method can be used to transmit and receive power between two vehicles. Moreover, solar cells can be installed on the exterior of the vehicle to charge the secondary battery when parked or in motion. Such contactless power supply can be achieved using electromagnetic induction or magnetic field resonance.

[0324] Figure 19B shows a large transport vehicle 2002, including an electrically controlled engine, as an example of a transport vehicle. The secondary battery module of the transport vehicle 2002 is, for example, a secondary battery module with a maximum voltage of 170V, consisting of 48 battery cells connected in series, each with a nominal voltage of 3.0V or higher and 5.0V or lower. Except for the number of secondary batteries constituting the secondary battery module, the battery pack 2201 has the same function as in Figure 19A, so further explanation is omitted.

[0325] Figure 19C shows, as an example, a large transport vehicle 2003 including an electrically controlled engine. The secondary battery module of the transport vehicle 2003 is, for example, a secondary battery module with a maximum voltage of 600V consisting of 100 or more secondary batteries connected in series with a nominal voltage of 3.0V or higher and 5.0V or lower. By using the positive electrode active material 100 described in Embodiment 1 as the positive electrode, a secondary battery with good frequency characteristics and charge-discharge cycle characteristics can be manufactured, thereby contributing to the high performance and long lifespan of the transport vehicle 2003. Furthermore, apart from differences such as the number of secondary batteries constituting the secondary battery module, the battery pack 2202 has the same function as in Figure 19A, so its description is omitted.

[0326] Figure 19D shows, as an example, an aircraft 2004 equipped with a fuel-burning engine. The aircraft 2004 shown in Figure 19D includes landing wheels, so it can be said that the aircraft 2004 is a type of transport vehicle. Multiple secondary batteries are connected in the aircraft 2004 to form a secondary battery module, and a battery pack 2203 with a secondary battery module and a charging control device is included.

[0327] The secondary battery module of the aircraft 2004, for example, has eight 4V secondary batteries connected in series with a maximum voltage of 32V. Except for the number of secondary batteries constituting the secondary battery module of the battery pack 2203, it has the same function as that in FIG19A, so the description is omitted.

[0328] The content of this embodiment can be appropriately combined with the content of other embodiments.

[0329] Embodiment 7 In this embodiment, an example of installing a secondary battery according to an embodiment of the present invention in a building is illustrated using Figures 20A and 20B.

[0330] The house shown in Figure 20A includes an energy storage device 2612 and a solar panel 2610 having a secondary battery module according to one embodiment of the present invention. The energy storage device 2612 is electrically connected to the solar panel 2610 via wiring 2611 or the like. Furthermore, the energy storage device 2612 can be electrically connected to a ground-mounted charging device 2604. The power obtained from the solar panel 2610 can be charged into the energy storage device 2612. Additionally, the power stored in the energy storage device 2612 can be charged into the secondary battery included in the vehicle 2603 via the charging device 2604. The energy storage device 2612 is preferably installed in an underfloor space. By installing it in an underfloor space, floor space can be effectively utilized. Alternatively, the energy storage device 2612 can also be installed on the floor.

[0331] The electricity stored in the energy storage device 2612 can also be supplied to other electronic devices in the house. Therefore, even when power supply from commercial power sources is unavailable due to power outages or other reasons, electronic devices can be utilized by using the energy storage device 2612 of one embodiment of the present invention as an uninterruptible power supply system.

[0332] FIG20B shows an example of an energy storage device 700 according to one embodiment of the present invention. As shown in FIG20B, an energy storage device 791 according to one embodiment of the present invention is provided in the space 796 under the floor of a building 799. In addition, the control circuit described in Embodiment 6 can also be provided in the energy storage device 791. By using a secondary battery in the energy storage device 791 with the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode, a long-life energy storage device 791 can be realized.

[0333] A control device 790 is provided in the energy storage device 791. The control device 790 is electrically connected to the distribution panel 703, the energy storage controller 705 (also called the control device), the display 706 and the router 709 through wiring.

[0334] Power is supplied from commercial power supply 701 to distribution panel 703 through lead-in installation part 710. In addition, power from energy storage device 791 and power from commercial power supply 701 are both supplied to distribution panel 703, which supplies the power to general load 707 and energy storage load 708 through sockets (not shown).

[0335] As a general load 707, electronic devices such as televisions and personal computers can be cited as examples, and as an energy storage load 708, electronic devices such as microwave ovens, refrigerators, and air conditioners can be cited as examples.

[0336] The energy storage controller 705 includes a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 has the function of measuring the power consumption of the general load 707 and the energy storage load 708 during a day (e.g., from 0:00 to 24:00). In addition, the measurement unit 711 may also have the function of measuring the power of the energy storage device 791 and the power supplied from the commercial power supply 701. In addition, the prediction unit 712 has the function of predicting the power required by the general load 707 and the energy storage load 708 for the next day based on the power consumption of the general load 707 and the energy storage load 708 during the day. In addition, the planning unit 713 has the function of determining the charging and discharging plan of the energy storage device 791 based on the power required predicted by the prediction unit 712.

[0337] The electrical power consumed by the general load 707 and the energy storage load 708, as measured by the measuring unit 711, can be confirmed using the display 706. Alternatively, it can be confirmed using electronic devices such as televisions and personal computers via the router 709. Furthermore, it can be confirmed using portable electronic terminals such as smartphones and tablets via the router 709. Additionally, the power demand predicted by the prediction unit 712 for each time period (or each hour) can be confirmed using the display 706, electronic devices, or portable electronic terminals.

[0338] The content of this embodiment can be appropriately combined with the content of other embodiments.

[0339] Embodiment 8 In this embodiment, an example is shown of installing an energy storage device according to one embodiment of the present invention on a two-wheeled vehicle or bicycle.

[0340] FIG21A shows an example of an electric bicycle using an energy storage device according to an embodiment of the present invention. The electric bicycle 8700 shown in FIG21A can use an energy storage device according to an embodiment of the present invention. For example, an energy storage device according to an embodiment of the present invention includes a plurality of batteries and a protection circuit.

[0341] The electric bicycle 8700 includes a power storage device 8702. The power storage device 8702 supplies power to the motor that assists the rider. Furthermore, the power storage device 8702 is portable; Figure 21B shows the power storage device 8702 removed from the bicycle. The power storage device 8702 has a built-in battery 8701 included in a power storage device according to one embodiment of the present invention, and the remaining power can be displayed by a display unit 8703. Additionally, the power storage device 8702 includes a control circuit 8704, as shown in Embodiment 6, capable of controlling the charging of the secondary battery or detecting abnormalities. The control circuit 8704 is electrically connected to the positive and negative terminals of the battery 8701. Alternatively, a small solid-state secondary battery, as shown in Figures 17A and 17B, can be provided in the control circuit 8704. By providing the small solid-state secondary battery shown in Figures 17A and 17B in the control circuit 8704, power can be supplied to maintain data in the memory circuit including the control circuit 8704 for a long period. Furthermore, by combining it with a secondary battery that uses the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode, a synergistic effect on safety can be achieved. The secondary battery and control circuit 8704 that use the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode greatly contribute to reducing accidents such as fires caused by secondary batteries.

[0342] FIG21C shows an example of a two-wheeled vehicle using an energy storage device according to one embodiment of the present invention. The small motorcycle 8600 shown in FIG21C includes an energy storage device 8602, a side mirror 8601, and turn signals 8603. The energy storage device 8602 can supply power to the turn signals 8603. In addition, the energy storage device 8602, which is equipped with multiple secondary batteries using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode, can have a high capacity and can contribute to miniaturization.

[0343] Furthermore, in the small motorcycle 8600 shown in FIG21C, the battery storage device 8602 can be housed in the under-seat storage section 8604. Even if the under-seat storage section 8604 is small, the battery storage device 8602 can still be housed in the under-seat storage section 8604.

[0344] The content of this embodiment can be appropriately combined with the content of other embodiments.

[0345] Embodiment 9 In this embodiment, an example of installing a secondary battery according to one embodiment of the present invention in an electronic device will be described. Examples of electronic devices equipped with a secondary battery include television sets (also called televisions or television receivers), displays for computers, digital cameras, digital camcorders, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game consoles, portable information terminals, audio playback devices, pinball machines, and other large-scale game machines. Examples of portable information terminals include laptop computers, tablet computers, e-book terminals, and mobile phones.

[0346] Figure 22A shows an example of a mobile phone. In addition to the display unit 2102 mounted on the housing 2101, the mobile phone 2100 also includes operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, etc. Furthermore, the mobile phone 2100 includes a secondary battery 2107. By including a secondary battery 2107 with the positive electrode active material 100 described in Embodiment 1 as the positive electrode, high capacity can be achieved, and a space-saving structure that can meet the requirements of housing miniaturization can be realized.

[0347] The 2100 mobile phone can perform various applications such as mobile phone calls, emails, article reading and writing, music playback, internet communication, and computer games.

[0348] In addition to time setting, operation button 2103 can also have various functions such as power switch, wireless communication switch, setting and canceling silent mode, setting and canceling power saving mode, etc. For example, by using the operating system assembled in mobile phone 2100, the function of operation button 2103 can be freely set.

[0349] In addition, the mobile phone 2100 can perform short-range wireless communication according to communication standards. For example, hands-free calling can be made by communicating with a wireless headset.

[0350] In addition, the mobile phone 2100 has an external connection port 2104, which can send data to or receive data from other information terminals directly via a connector. It can also be charged via the external connection port 2104. Furthermore, charging can also be performed wirelessly without using the external connection port 2104.

[0351] The mobile phone 2100 preferably includes a sensor. The sensor is preferably a human body sensor such as a fingerprint sensor, pulse sensor, body temperature sensor, touch sensor, pressure sensor, acceleration sensor, etc.

[0352] Figure 22B shows an unmanned aerial vehicle 2300 including multiple rotors 2302. The unmanned aerial vehicle 2300 is also referred to as a drone. The unmanned aerial vehicle 2300 includes a secondary battery 2301, a camera 2303, and an antenna (not shown) according to one embodiment of the present invention. The unmanned aerial vehicle 2300 can be operated remotely via the antenna. The secondary battery using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode has high energy density and high safety, so it can be used safely for a long period of time, and is therefore suitable as a secondary battery installed in the unmanned aerial vehicle 2300.

[0353] Figure 22C shows an example of a robot. The robot 6400 shown in Figure 22C includes a secondary battery 6409, an illumination sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6407, a movement mechanism 6408, a computing device, etc.

[0354] The microphone 6402 has the function of detecting the user's voice and surrounding sounds. In addition, the speaker 6404 has the function of emitting sound. The robot 6400 can communicate with the user through the microphone 6402 and the speaker 6404.

[0355] The display unit 6405 has the function of displaying various information. The robot 6400 can display the information required by the user on the display unit 6405. The display unit 6405 may also be equipped with a touch panel. In addition, the display unit 6405 can be a detachable information terminal, which can be charged and transmit and receive data by setting it in a fixed position on the robot 6400.

[0356] The upper camera 6403 and the lower camera 6406 are capable of capturing images of the surrounding environment of the robot 6400. Additionally, the obstacle sensor 6407 can detect whether there are obstacles in the direction the robot 6400 is moving using the movement mechanism 6408. The robot 6400 can safely move by using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407 to assess its surrounding environment.

[0357] The robot 6400 is internally equipped with a secondary battery 6409 and a semiconductor device or electronic component according to an embodiment of the present invention. The secondary battery that uses the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode has high energy density and high safety, so it can be used safely for a long time. Therefore, it is very suitable as a secondary battery 6409 installed in the robot 6400.

[0358] Figure 22D shows an example of a robotic vacuum cleaner. The robotic vacuum cleaner 6300 includes a display 6302 disposed on the surface of the housing 6301, multiple cameras 6303 disposed on the side, a brush 6304, operation buttons 6305, a secondary battery 6306, various sensors, etc. Although not shown, the robotic vacuum cleaner 6300 also includes wheels, a suction port, etc. The robotic vacuum cleaner 6300 can move autonomously and can detect debris 6310 and suck it into the suction port located below.

[0359] For example, the robotic vacuum cleaner 6300 can determine whether there are obstacles such as walls, furniture, or steps by analyzing images captured by the camera 6303. Furthermore, when image analysis detects objects such as wires that may become entangled with the brush 6304, the rotation of the brush 6304 can be stopped. The internal area of ​​the robotic vacuum cleaner 6300 is equipped with a secondary battery 6306 and a semiconductor device or electronic component according to an embodiment of the present invention. The secondary battery, which uses the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode, has high energy density and high safety, and can be used safely for a long period of time, making it suitable as the secondary battery 6306 installed in the robotic vacuum cleaner 6300.

[0360] Figure 23A shows an example of a wearable device. The wearable device is powered by a rechargeable battery. In addition, in order to improve the splash, water, or dust resistance of the wearable device when used in daily life or outdoors, users not only want the wearable device to be able to perform wired charging with the connector portion exposed for connection, but also wireless charging.

[0361] For example, a secondary battery according to one embodiment of the present invention can be mounted on the eyeglasses-type device 4000 shown in FIG. 23A. The eyeglasses-type device 4000 includes a frame 4000a and a display unit 4000b. By mounting the secondary battery in the temple of the frame 4000a, which has a curved shape, a lightweight eyeglasses-type device 4000 with good weight balance and long continuous use time can be realized. The secondary battery using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode has a high energy density and can realize a space-saving structure that can meet the miniaturization requirements of the casing.

[0362] Alternatively, the secondary battery according to one embodiment of the present invention can be mounted on a headset-type device 4001. The headset-type device 4001 includes at least a microphone portion 4001a, a flexible tube 4001b, and an earphone portion 4001c. Furthermore, the secondary battery can be disposed within the flexible tube 4001b or the earphone portion 4001c. The secondary battery using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode has a high energy density and can achieve a space-saving structure that meets the requirements for miniaturization of the casing.

[0363] Furthermore, the secondary battery of one embodiment of the present invention can be installed on a device 4002 that can be directly attached to the body. Additionally, the secondary battery 4002b can be housed within the thin casing 4002a of the device 4002. The secondary battery using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode has a high energy density and can achieve a space-saving structure that meets the requirements for miniaturization of the casing.

[0364] Furthermore, the secondary battery of one embodiment of the present invention can be installed in a device 4003 that can be attached to clothing. Additionally, the secondary battery 4003b can be housed within the thin casing 4003a of the device 4003. The secondary battery using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode has a high energy density and can achieve a space-saving structure that meets the requirements for miniaturization of the casing.

[0365] Alternatively, the secondary battery of one embodiment of the present invention can be mounted on a belt-type device 4006. The belt-type device 4006 includes a belt portion 4006a and a wireless power receiving portion 4006b, and the secondary battery can be mounted in the internal region of the belt portion 4006a. The secondary battery using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode has a high energy density and can achieve a space-saving structure that can meet the requirements of miniaturization of the casing.

[0366] Alternatively, the secondary battery according to one embodiment of the present invention can be mounted on a watch-type device 4005. The watch-type device 4005 includes a display section 4005a and a watchband section 4005b, and the secondary battery can be disposed on the display section 4005a or the watchband section 4005b. The secondary battery using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode has a high energy density and can achieve a space-saving structure that can meet the requirements for miniaturization of the casing.

[0367] The display unit 4005a can display not only the time, but also various information such as emails and incoming phone calls.

[0368] Furthermore, since the watch-type device 4005 is a wearable device that is directly wrapped around the wrist, it can also be equipped with sensors that measure the user's pulse, blood pressure, etc. As a result, the user's exercise data and health-related information can be stored for health management.

[0369] Figure 23B is a perspective view showing a watch-type device 4005 removed from the wrist.

[0370] Additionally, Figure 23C is a side view. Figure 23C shows the case where the secondary battery 913 is built into the internal area. The secondary battery 913 is the secondary battery shown in Embodiment 4. The secondary battery 913 is positioned overlapping with the display unit 4005a, which allows for high density and high capacity, as well as small size and light weight.

[0371] The watch-type device 4005 needs to be small and lightweight, so by using the positive electrode active material 100 that can be obtained in Embodiment 1 as the positive electrode of the secondary battery 913, a secondary battery 913 with high energy density and small size can be realized.

[0372] Figure 23D shows an example of a wireless earphone. Here, a wireless earphone including a pair of main bodies 4100a and 4100b is shown, but the main bodies do not need to be a pair.

[0373] The main bodies 4100a and 4100b include a driver unit 4101, an antenna 4102, and a secondary battery 4103. A display unit 4104 may also be included. Preferably, they include a substrate housing circuitry such as a wireless IC and charging terminals. A microphone may also be included.

[0374] The storage box 4110 includes a secondary battery 4111. Preferably, it includes a substrate containing circuitry such as a wireless IC and a charging control IC, and charging terminals. It may also include a display unit, buttons, etc.

[0375] The main bodies 4100a and 4100b can communicate wirelessly with other electronic devices such as smartphones. Therefore, sound data received from other electronic devices can be reproduced in the main bodies 4100a and 4100b. Furthermore, when the main bodies 4100a and 4100b include microphones, sound obtained through the microphones can be transmitted to other electronic devices for processing, and then the sound data can be transmitted back to the main bodies 4100a and 4100b for reproduction. Thus, it can be used, for example, as a translator.

[0376] Additionally, the secondary battery 4111 included in the storage box 4100 can be charged to the secondary battery 4103 included in the main body 4100a. The secondary batteries 4111 and 4103 can be coin-shaped or cylindrical batteries as described in the above embodiment. The secondary battery using the positive electrode active material 100 obtained in Embodiment 1 as the positive electrode has a high energy density. By using the positive electrode active material 100 in the secondary batteries 4103 and 4111, a space-saving structure capable of meeting the miniaturization requirements of wireless earphones can be achieved.

[0377] This embodiment can be implemented in appropriate combination with other embodiments. Example

[0378] In this embodiment, a positive electrode active material is manufactured by a manufacturing method according to an embodiment of the present invention, and the charge-discharge cycle characteristics of the positive electrode active material and the charge-discharge cycle characteristics of a positive electrode active material as a comparative example are compared.

[0379] <Manufacturing of positive electrode active material> The sample manufactured in this embodiment is described with reference to the manufacturing method shown in FIG2.

[0380] <Sample 1> First, as a composite oxide 832 comprising the additive element X in step S61, lithium nickel-cobalt-manganese oxide (EQ-Lib-LNCM811 manufactured by MTI Corporation) is prepared. This material contains nickel, cobalt, and manganese as the transition metal M, wherein the contents of nickel, manganese, and cobalt are 47.50±1.50 wt%, 5.50±0.60 wt%, and 6.60±0.60 wt%, respectively. In addition, as the additive element X, it contains iron at 0.004 wt% or less, typically around 0.0016 wt%.

[0381] Furthermore, calcium carbonate is prepared as the added element X source d in step S62.

[0382] Next, calcium carbonate was weighed at 0.5 mol% relative to lithium nickel-cobalt-manganese oxide and mixed using a dry method. The mixing was carried out under the following conditions: using a ball mill with 1 mm diameter zirconia balls as the medium, at 150 rpm for 1 hour. The mixture was then sieved through a 300 μm sieve to obtain mixture 841.

[0383] Next, as step S74, a mixture 841 of lithium nickel-cobalt-manganese oxide and calcium carbonate is heated. The mixture 841 is placed in an alumina furnace, covered, and heated in a muffle furnace at 800°C for 2 hours. The oxygen flow rate is 5L / min, and the temperature rise is 200°C / hour. Then, the heated material is allowed to cool to room temperature. The cooling time from 800°C to room temperature is 10 hours or more.

[0384] Next, the heated material was sieved through a sieve with a mesh size of 53 μm to obtain the positive electrode active material. This positive electrode active material is designated as Sample 1.

[0385] <Sample 2> The positive electrode active material manufactured in the same manner as Sample 1, except that calcium fluoride is used as the source of added element X d, is denoted as Sample 2.

[0386] <Sample 3> The positive electrode active material manufactured in the same manner as Sample 1, except that calcium chloride is used as the source of added element X, is denoted as Sample 3.

[0387] <Sample 4> The positive electrode active material manufactured in the same manner as Sample 1, except that lithium fluoride is used as the source of added element X d and the lithium fluoride is mixed in a manner relative to 1 mol% of nickel-cobalt-manganese lithium oxide, is designated as Sample 4.

[0388] <Sample 5> The positive electrode active material manufactured in the same manner as Sample 1, except that lithium fluoride and lithium carbonate are used as the source of added element X d and are mixed in a manner that is 0.5 mol% and 0.5 mol% respectively relative to lithium nickel-cobalt-manganese oxide, is designated as Sample 5.

[0389] <Sample 6> The positive electrode active material manufactured in the same manner as Sample 5 except that the heating temperature is 700℃ is designated as Sample 6.

[0390] <Sample 7> The positive electrode active material manufactured in the same manner as Sample 5 except that the heating temperature is 900℃ is designated as Sample 7.

[0391] <Sample 8> The positive electrode active material manufactured in the same manner as Sample 1, except that lithium fluoride and sodium fluoride are used as the source of added element X d and are mixed in a manner that is 0.5 mol% and 0.5 mol% respectively relative to lithium nickel-cobalt-manganese oxide, is designated as Sample 8.

[0392] <Sample 9> The positive electrode active material manufactured in the same manner as Sample 1, except that lithium fluoride and calcium fluoride are used as the source of added element X d and are mixed in a manner that is 0.5 mol% and 0.5 mol% respectively relative to lithium nickel-cobalt-manganese oxide, is designated as Sample 9.

[0393] <Sample 10> The positive electrode active material manufactured in the same manner as Sample 9 except that the heating time is 20 hours is denoted as Sample 10.

[0394] <Sample 11> The positive electrode active material manufactured in the same manner as Sample 9 except that the heating time is 60 hours is denoted as Sample 11.

[0395] <Sample 12> The positive electrode active material manufactured in the same manner as Sample 9 except that the heating temperature is 700°C is designated as Sample 12.

[0396] <Sample 13> The positive electrode active material manufactured in the same manner as Sample 9 except that the heating temperature is 900℃ is designated as Sample 13.

[0397] <Sample 14> The positive electrode active material manufactured in the same manner as Sample 1, except that lithium fluoride and aluminum fluoride are used as the source of added element X d and are mixed in a manner that is 0.89 mol% and 0.5 mol% respectively relative to lithium nickel-cobalt-manganese oxide.

[0398] <Sample 15> The positive electrode active material manufactured in the same manner as Sample 14 except that the heating time is 20 hours is denoted as Sample 15.

[0399] <Sample 16> The positive electrode active material manufactured in the same manner as Sample 1, except that lithium fluoride and lithium titanate are used as the source of added element X d, and lithium fluoride and lithium titanate are mixed in a manner relative to lithium nickel-cobalt-manganese oxide at 0.89 mol% and 0.13 mol% respectively, and the heating time is 20 hours, is designated as Sample 16.

[0400] <Sample 17> The positive electrode active material manufactured in the same manner as Sample 1, except that lithium fluoride and magnesium fluoride are used as the source of added element X d, and lithium fluoride and magnesium fluoride are mixed in a manner relative to lithium nickel-cobalt-manganese oxide at 0.5 mol% and 0.5 mol% respectively, and the heating time is 20 hours, is designated as Sample 17.

[0401] <Sample 20> Lithium nickel-cobalt-manganese oxide without the addition of element X source d and without heating is designated as Sample 20 (comparative example). Sometimes this Sample 20 is referred to as the untreated sample.

[0402] <Sample 21> The positive electrode active material that does not contain added element X source d and is heated at 800℃ for 2 hours is designated as Sample 21.

[0403] Table 1 shows the manufacturing conditions of samples 1 to 21.

[0404]

[0405] <Cycling Characteristics> Next, secondary batteries were manufactured using samples 1 to 21 and their cycling characteristics were evaluated.

[0406] First, a slurry is prepared by mixing the positive electrode active material, acetylene black (AB), and PVDF in a ratio of positive electrode active material:AB:PVDF = 95:3:2 (by weight). This slurry is then coated onto an aluminum current collector. NMP is used as the solvent for the slurry.

[0407] After coating the slurry onto the current collector, the solvent is allowed to evaporate. The positive electrode is obtained through the above process. The active material loading of the positive electrode is approximately 7 mg / cm², and the density is above 3.4 g / cc.

[0408] A coin-shaped battery cell of type CR2032 (diameter 20mm, height 3.2mm) is manufactured using the formed positive electrode.

[0409] Lithium metal is used as the counter electrode.

[0410] Lithium hexafluorophosphate (LiPF6) at 1 mol / L is used as the electrolyte in the electrolyte solution. As the electrolyte solution, 2 wt% of ethylene carbonate (VC) is added as an additive to a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3:7.

[0411] A 25μm thick polypropylene is used as the separator.

[0412] The positive electrode container and the negative electrode container are made of stainless steel (SUS).

[0413] Cyclic tests were performed under the following conditions: charging voltage of 4.4V; ambient temperature of 45°C, 25°C, or -20°C; charging at CC / CV (0.5C, 0.05C cut); discharging at CC (0.5C, 2.5V cut); and a 10-minute rest period was set before the next charge. In this embodiment, 1C is 200mA / g.

[0414] Figure 24A shows the results of charge-discharge cycle tests at 45°C for samples 1 to 3, 20 and 21. Figure 24B shows the results at 25°C. Figure 24C shows the results at -20°C.

[0415] At 45°C and 25°C, the discharge capacity of sample 3, which contained calcium fluoride, was further reduced compared to other samples. Samples 1, 2, 20, and 21 exhibited good charge-discharge cycle characteristics, with heated samples 1, 2, and 21 showing even better charge-discharge cycle characteristics. In particular, sample 1, which contained calcium carbonate, and sample 2, which contained calcium fluoride, showed very good charge-discharge cycle characteristics.

[0416] On the other hand, the change in discharge capacity at -20°C is unstable. Compared with the untreated sample 20, the other samples show good charge-discharge cycle characteristics, among which sample 1 with added calcium carbonate has the best charge-discharge cycle characteristics.

[0417] Figure 25A shows the results of charge-discharge cycle tests at 45°C for samples 4 to 7 and sample 20. Figure 25B shows the results at 25°C. Figure 25C shows the results at -20°C.

[0418] At 45°C, the untreated sample 20 exhibited the best charge-discharge cycle characteristics. However, at 25°C, the sample 5, which contained lithium fluoride and lithium carbonate, showed the best charge-discharge cycle characteristics. On the other hand, at -20°C, samples 4 to 7 showed better charge-discharge cycle characteristics compared to the untreated sample 20.

[0419] Figure 26A shows the results of charge-discharge cycle tests at 45°C for samples 8 to 13 and sample 20. Figure 26B shows the results at 25°C. Figure 26C shows the results at -20°C.

[0420] At 45°C, samples 9, 10, and the untreated sample 20 exhibited similar charge-discharge cycle characteristics. Sample 8, with added sodium fluoride, showed a high initial capacity, but the capacity decreased significantly with charge-discharge cycles. At 25°C, samples 9 and 10, with added lithium fluoride and calcium fluoride, exhibited significantly better charge-discharge cycle characteristics than sample 20.

[0421] On the other hand, at -20°C, samples 8 to 13 showed better charge-discharge cycle characteristics compared to untreated sample 20.

[0422] Figure 27A shows the results of charge-discharge cycle tests at 45°C for samples 14 to 17 and sample 20. Figure 27B shows the results at 25°C. Figure 27C shows the results at -20°C.

[0423] At 45°C and 25°C, the untreated sample 20 exhibited the best charge-discharge cycle characteristics. On the other hand, at -20°C, samples 14 to 17 showed better charge-discharge cycle characteristics compared to the untreated sample 20.

[0424] Figures 28A to 29 are graphs showing the discharge capacity retention and maximum discharge capacity at 50 cycles for samples 1 to 4, 8, 9, 14 and 21, which were heated at 800°C for 2 hours. The positive electrode active material located in the upper right of the graph can be considered a good positive electrode active material with high charge-discharge cycle characteristics and discharge capacity.

[0425] Figure 28A is a graph at 45℃. It can be seen that Sample 1 with added calcium carbonate, Sample 2 with added calcium fluoride, and Sample 21 without added element X source d but heated have good charge-discharge cycle characteristics.

[0426] Figure 28B is a graph at 25°C. It can be seen that sample 9, which contains lithium fluoride and calcium fluoride, has good cycling characteristics.

[0427] Figure 29 is a graph at -20℃. Sample 1 with added calcium carbonate, Sample 5 with added lithium fluoride and lithium carbonate, Sample 8 with added lithium fluoride and sodium fluoride, and Sample 4 with added lithium fluoride all have good charge-discharge cycle characteristics.

[0428] Next, charge-discharge cycle tests were performed on samples 1 to 3 and sample 20 at a charging voltage of 4.5V. The ambient temperature was 45°C or 25°C. Charging was performed at CC / CV (0.5C, 0.05C cut), and discharging was performed at CC (0.5C, 2.5V cut), with a 10-minute rest period set before the next charge.

[0429] Figure 30A is a graph of discharge capacity at 45°C, and Figure 30B is a graph of discharge capacity retention at 45°C. Figure 31A is a graph of discharge capacity at 25°C, and Figure 31B is a graph of discharge capacity retention at 25°C.

[0430] Similar to the case with a charging voltage of 4.4V, the discharge capacity of sample 3 with added calcium fluoride was further reduced compared to other samples.

[0431] Sample 1 with added calcium carbonate and Sample 2 with added calcium fluoride exhibited better charge-discharge cycle characteristics than the untreated Sample 20. Sample 2 had a slightly better discharge capacity retention than the other samples, but Sample 1 showed better discharge capacity and better characteristics than the other samples. [Simplified Explanation of the Diagram]

[0020] [Fig. 1] is a diagram illustrating an example of a method for manufacturing a positive electrode active material; [Fig. 2] is a diagram illustrating an example of a method for manufacturing a positive electrode active material; [Fig. 3A] and [Fig. 3B] are diagrams illustrating an example of a positive electrode active material; [Fig. 4A] to [Fig. 4D] are diagrams illustrating an example of a positive electrode active material; [Fig. 5] is an example of a TEM image illustrating generally consistent crystal orientation; [Fig. 6A] is an example of a STEM image illustrating generally consistent crystal orientation; [Fig. 6B] is an FFT pattern of a region of rock salt-type crystal RS; [Fig. 6C] is an FFT pattern of a region of layered rock salt-type crystal LRS; [Fig. 7] is a cross-sectional view illustrating an example of a positive electrode of a secondary battery; [Fig. 8A] is an exploded perspective view of a coin-type secondary battery; [Fig. 8B] is a perspective view of a coin-type secondary battery; [Fig. 8C] is a cross-sectional perspective view of a coin-type secondary battery. [Figure 9A] is an example of a cylindrical secondary battery; [Figure 9B] is an example of a cylindrical secondary battery; [Figure 9C] is an example of multiple cylindrical secondary batteries; [Figure 9D] is an example of an energy storage system including multiple cylindrical secondary batteries; [Figure 10A] and [Figure 10B] are diagrams illustrating examples of secondary batteries; [Figure 10C] is a diagram showing the interior of a secondary battery; [Figures 11A] to [Figure 11C] are diagrams illustrating examples of secondary batteries; [Figures 12A] and [Figure 12B] are diagrams showing the exterior of a secondary battery; [Figures 13A] to [Figure 13C] are diagrams illustrating a method for manufacturing a secondary battery; [Figures 14A] to [Figure 14C] are diagrams showing an example of the structure of an energy storage device; [Figures 15A] and [Figure 15B] are diagrams illustrating examples of secondary batteries; [Figures 16A] to [Figure 16C] are diagrams illustrating examples of secondary batteries; [Figures 17A and [Figure 17B] are diagrams illustrating examples of secondary batteries. [Fig. 18A] is a perspective view of the energy storage device; [Fig. 18B] is a block diagram of the energy storage device; [Fig. 18C] is a block diagram of a vehicle including an engine; [Figs. 19A] to [Figs. 19D] are diagrams illustrating an example of a transport vehicle; [Figs. 20A] and [Figs. 20B] are diagrams illustrating the energy storage device; [Fig. 21A] is a diagram illustrating an electric bicycle; [Fig. 21B] is a diagram showing the secondary battery of an electric bicycle; [Fig. 21C] is a diagram illustrating an electric motorcycle; [Figs. 22A] to [Figs. 22D] are diagrams illustrating an example of an electronic device; [Fig. 23A] shows an example of a wearable device; [Fig. 23B] is a perspective view of a watch-type device; [Fig. 23C] is a side view of the watch-type device; [Fig. 23D] is a diagram illustrating an example of a wireless headset; [Figs. 24A] to [Figs. 24C] are graphs showing the charge-discharge cycle characteristics of the positive electrode active material of Example 1; Figures 25A to 25C are graphs showing the charge-discharge cycle characteristics of the positive electrode active material of Example 1; Figures 26A to 26C are graphs showing the charge-discharge cycle characteristics of the positive electrode active material of Example 1;Figures 27A to 27C are graphs showing the charge-discharge cycle characteristics of the positive electrode active material of Example 1; Figures 28A and 28B are graphs showing the discharge capacity retention and maximum discharge capacity of the positive electrode active material of Example 1; Figure 29 is a graph showing the discharge capacity retention and maximum discharge capacity of the positive electrode active material of Example 1; Figures 30A and 30B are graphs showing the charge-discharge cycle characteristics of the positive electrode active material of Example 1; and Figures 31A and 31B are graphs showing the charge-discharge cycle characteristics of the positive electrode active material of Example 1.

Claims

1. A secondary battery comprising a positive electrode, wherein: The positive electrode contains a positive electrode active material, which contains secondary particles, which include primary particles within the secondary particles. The primary particles contain nickel, manganese, cobalt, oxygen, calcium, and fluorine. The primary particles contain a surface portion and an interior portion, the interior portion containing a layered rock salt-type crystalline structure. The concentration of each of calcium and fluorine is higher in the surface portion than in the interior portion.

2. As in request item 1, the secondary battery, wherein: The surface portion of the original particle contains a rock salt-type crystalline structure, and the crystal orientation of the surface portion and the interior is generally consistent with each other.

3. A secondary battery comprising a positive electrode, wherein: The positive electrode contains a positive electrode active material, which contains secondary particles, and the secondary particles contain primary particles within the secondary particles. The primary particles contain nickel, manganese, cobalt, oxygen, and calcium. The primary particles contain a first region and a second region covering at least a portion of the first region. The first region contains a layered rock salt-type crystal structure. When the total number of nickel, manganese, and cobalt atoms included in the positive electrode active material is 100, the number of nickel atoms is 80 or more. In the primary particles, the concentration of calcium in the second region is higher than that in the first region.

4. As in request item 3, the secondary battery, wherein: The positive electrode active material also contains fluorine, and the concentration of fluorine in the original particle is higher in the second region than in the first region.

5. As in request item 3, the secondary battery, wherein: The positive electrode active material also contains iron, and the concentration of iron in the original particle is higher in the second region than in the first region.

6. As in request item 3, the secondary battery, wherein: In the original particle, the second region contains a rock salt-type crystalline structure, and the crystal orientations in the second region and the first region are generally consistent with each other.

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