Secondary battery

Abstract

To provide a lithium-ion secondary battery having high capacity and an excellent charge and discharge cycle performance. To provide a secondary battery having high capacity. To provide a secondary battery having excellent charge and discharge performance. To provide a secondary battery in which a decrease in capacity is suppressed even if a charging state at high voltage is kept for a long time.SOLUTION: A secondary battery includes: a positive electrode; a negative electrode; an electrolyte; and an external housing. The positive electrode includes a positive electrode active material. The positive electrode active material includes: lithium; cobalt; oxygen; magnesium; and fluorine. The number of atoms of magnesium provided in the positive electrode active material is 0.001 times or more and 0.1 times or less of the number of atoms of cobalt provided in the positive electrode active material. The positive electrode active material includes a region having a layered rock-salt crystal structure. The electrolyte includes an ionic liquid. The external housing includes: a metal layer; and a polymer layer laminated on the metal layer. The polymer layer includes a region in contact with the electrolyte solution.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Another embodiment of the present invention relates to a power storage system including a secondary battery and a battery control circuit, or to an electronic device and a vehicle including the power storage system.

[0003] In this specification, the term "power storage device" refers to elements and devices in general that have a power storage function, including, for example, storage batteries (also called secondary batteries) such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors.

[0004] In addition, in this specification, electronic devices refer to devices in general that have a power storage device, and electro-optical devices that have a power storage device, information terminal devices that have a power storage device, and the like are all electronic devices. [Background technology]

[0005] In recent years, various types of power storage devices, such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries, have been actively developed. In particular, the demand for high-output, high-energy-density lithium-ion secondary batteries has rapidly expanded in conjunction with the development of the semiconductor industry, and they are now indispensable in the modern information society as a rechargeable energy source, as they are used in portable information terminals such as mobile phones, smartphones, tablets, and notebook computers, portable music players, digital cameras, medical equipment, and next-generation clean energy vehicles (hybrid vehicles (HVs), electric vehicles (EVs), plug-in hybrid vehicles (PHVs), etc.).

[0006] The characteristics required for lithium ion secondary batteries include higher energy density, improved cycle characteristics, safety in various operating environments, and improved long-term reliability.

[0007] Therefore, improvements in the positive electrode active material have been studied with the aim of improving the cycle characteristics and increasing the capacity of lithium ion secondary batteries (Patent Documents 1 and 2). Research on the crystal structure of the positive electrode active material has also been conducted (Non-Patent Documents 1 to 3).

[0008] Non-Patent Document 4 describes the physical properties of metal fluorides.

[0009] X-ray diffraction (XRD) is one of the techniques used to analyze the crystal structure of positive electrode active materials. XRD data can be analyzed by using the Inorganic Crystal Structure Database (ICSD) introduced in Non-Patent Document 5. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2002-216760 A [Patent Document 2] JP 2006-261132 A [Non-patent literature]

[0011] [Non-Patent Document 1] Toyoki Okumura et al, “Correlation of lithium ion distribution and X-ray absorption near-edge structure in O3-and O2-lithium cobalt oxides from first-principle calculation”, Journal of Materials Chemistry, 2012, 22, p.17340-17348 [Non-Patent Document 2] Motohashi, T. et al, “Electronic phase diagram of the layered cobalt oxide system LixCoO2(0.0≦x≦1.0)”, Physical Review B, 80(16);165114 [Non-Patent Document 3] Zhaohui Chen et al, “Staging Phase Transitions in LixCoO2”, Journal of The Electrochemical Society, 2002, 149(12) A1604-A1609 [Non-Patent Document 4] WE Counts et al, “Flouride Model Systems: II, The Binary Systems CaF2-BeF2, MgF2-BeF2, and LiF-MgF2”, Journal of the American Ceramic Society,(1953) 36[1] 12-17. Fig.01471 [Non-Patent Document 5] Belsky, A. et al., “New developments in the Inorganic Crystal Structure Database (ICSD): accessibility in support of materials research and design”, Acta Cryst., (2002) B58 364-369 Summary of the Invention [Problem to be solved by the invention]

[0012] An object of one embodiment of the present invention is to provide a lithium ion secondary battery having a high capacity and excellent charge / discharge cycle characteristics, and a manufacturing method thereof. Another object of one embodiment of the present invention is to provide a secondary battery capable of rapid charging, and a manufacturing method thereof. Another object of one embodiment of the present invention is to provide a secondary battery having a high capacity, and a manufacturing method thereof. Another object of one embodiment of the present invention is to provide a secondary battery having excellent charge / discharge characteristics, and a manufacturing method thereof. Another object of one embodiment of the present invention is to provide a secondary battery in which a decrease in capacity is suppressed even when the battery is charged at a high voltage for a long period of time, and a manufacturing method thereof. Another object of one embodiment of the present invention is to provide a secondary battery having high safety or reliability, and a manufacturing method thereof. Another object of one embodiment of the present invention is to provide a secondary battery in which a decrease in capacity is suppressed even at high temperatures, and a manufacturing method thereof. Another object of one embodiment of the present invention is to provide a secondary battery having a long life, and a manufacturing method thereof.

[0013] An object of one embodiment of the present invention is to provide an extremely excellent secondary battery that can be rapidly charged, can be used at high temperatures, can have a high energy density by increasing the charging voltage, and is safe and has a long life.

[0014] An object of one embodiment of the present invention is to provide a positive electrode active material for a lithium ion secondary battery having high capacity and excellent charge / discharge cycle characteristics, and a manufacturing method thereof. Another object of one embodiment of the present invention is to provide a manufacturing method of the positive electrode active material with good productivity. Another object of one embodiment of the present invention is to provide a positive electrode active material that is used in a lithium ion secondary battery to suppress a decrease in capacity during charge / discharge cycles. Another object of one embodiment of the present invention is to provide a positive electrode active material in which elution of a transition metal such as cobalt is suppressed even when the battery is held in a charged state at a high voltage for a long period of time.

[0015] Another object of one embodiment of the present invention is to provide a novel substance, active material particles, a power storage device, or a manufacturing method thereof.

[0016] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that it is possible to extract problems other than these from the description of the specification, drawings, and claims. [Means for solving the problem]

[0017] One embodiment of the present invention is a secondary battery having a positive electrode, a negative electrode, an electrolyte, and an exterior body, the positive electrode having a positive electrode active material, the positive electrode active material having lithium, cobalt, oxygen, magnesium, and fluorine, the number of magnesium atoms in the positive electrode active material being 0.001 to 0.1 times the number of cobalt atoms in the positive electrode active material, the positive electrode active material having a region having a layered rock salt crystal structure, the electrolyte having an ionic liquid, the exterior body having a metal layer and a polymer layer laminated on the metal layer, and the polymer layer having a region in contact with the electrolyte.

[0018] In the above-mentioned structure, the ionic liquid has an imidazolium cation represented by general formula (G1), R 1 represents an alkyl group having 1 to 4 carbon atoms, and R 2 ~R 4 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R 5 preferably represents an alkyl group or a main chain composed of two or more atoms selected from C, O, Si, N, S and P atoms.

[0019] [ka]

[0020] In the above structure, the ionic liquid has a pyridinium cation represented by general formula (G2), R 6represents an alkyl group or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P, and R 7 ~R 11 It is preferable that each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0021] [ka]

[0022] In the above structure, the ionic liquid preferably has a quaternary ammonium cation.

[0023] In the above structure, the quaternary ammonium cation is one or more selected from the general formula (G4), the general formula (G5), and the general formula (G6), and R 12 ~R 17 and R 18 ~R 24 each independently represents any one of an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom; n and m are 1 to 3, α is 0 to 6, β is 0 to 6; and X or Y preferably represents, as a substituent, a linear or side chain alkyl group having 1 to 4 carbon atoms, a linear or side chain alkoxy group having 1 to 4 carbon atoms, or a linear or side chain alkoxyalkyl group having 1 to 4 carbon atoms.

[0024] [ka]

[0025] [ka]

[0026] [ka]

[0027] In the above structure, the ionic liquid has a tertiary sulfonium cation represented by general formula (G7), R 25 ~R 27 preferably each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P atoms.

[0028] [ka]

[0029] In the above structure, the ionic liquid has a quaternary phosphonium cation represented by general formula (G8), R 32 ~R 35 preferably each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P atoms.

[0030] [ka]

[0031] In the above configuration, the anion of the ionic liquid is (FSO2)2N - or (CF3SO2)2N - It is preferred that the compound has the formula:

[0032] In the above configuration, the anion of the ionic liquid is (FSO2)2N - or (CF3SO2)2N - and the negative electrode preferably comprises graphite.

[0033] Alternatively, one embodiment of the present invention is a secondary battery having a positive electrode, a negative electrode, an electrolyte, and an exterior body, the positive electrode having a positive electrode active material, the positive electrode active material having lithium, cobalt, oxygen, magnesium, and fluorine, the positive electrode active material having a region having a layered rock salt type crystal structure, the electrolyte having an ionic liquid, the ionic liquid having a cation selected from one or more of an aromatic cation, a quaternary ammonium cation, a tertiary sulfonium cation, and a quaternary phosphonium cation, the exterior body having a metal layer and a polymer layer laminated on the metal layer, the polymer layer having a region in contact with the electrolyte, the negative electrode having graphite, and when the positive electrode is charged at a constant current until the battery voltage reaches 4.5 V in an environment of 25° C. and then charged at a constant voltage until the current value reaches 0.01 C, the positive electrode has diffraction peaks at 2θ of 19.10° to 19.50° and at 2θ of 45.45° to 45.65°, respectively, when analyzed by powder X-ray diffraction using CuKα1 radiation.

[0034] In the above configuration, the anion of the ionic liquid is (FSO2)2N - or (CF3SO2)2N - It is preferred that the compound has the formula:

[0035] Alternatively, one embodiment of the present invention is a secondary battery having a positive electrode, a negative electrode, and an electrolyte solution, the positive electrode having a positive electrode active material, the positive electrode active material having lithium, cobalt, and oxygen, a first upper limit voltage for charging when the temperature during charging is in a range equal to or higher than a first temperature and lower than a second temperature, and a second upper limit voltage for charging when the temperature during charging is equal to or higher than the second temperature, the first temperature being equal to or higher than 5° C. and lower than 15° C., the second temperature being equal to or higher than 25° C. and lower than 55° C., the first value being higher than the second value by 0.02 V or more, and the first value being equal to or higher than 4.45 V and lower than 4.6 V.

[0036] In the above structure, the positive electrode active material preferably contains magnesium and fluorine.

[0037] In the above structure, the negative electrode preferably contains graphite.

[0038] Another embodiment of the present invention is an electronic device including any one of the above secondary batteries and a temperature sensor.

[0039] Another embodiment of the present invention is a vehicle including any one of the above secondary batteries and a temperature sensor. Effect of the Invention

[0040] According to one embodiment of the present invention, a lithium ion secondary battery having a high capacity and excellent charge / discharge cycle characteristics and a manufacturing method thereof can be provided. According to another embodiment of the present invention, a secondary battery capable of rapid charging and a manufacturing method thereof can be provided. According to another embodiment of the present invention, a secondary battery in which a decrease in capacity is suppressed even when the battery is charged at a high voltage for a long period of time and a manufacturing method thereof can be provided. According to another embodiment of the present invention, a secondary battery having high safety or reliability and a manufacturing method thereof can be provided. According to another embodiment of the present invention, a secondary battery in which a decrease in capacity is suppressed even at high temperatures and a manufacturing method thereof can be provided. According to another embodiment of the present invention, a secondary battery having a long life and a manufacturing method thereof can be provided.

[0041] According to one embodiment of the present invention, it is possible to provide an extremely excellent secondary battery that can be rapidly charged, can be used at high temperatures, can have a high energy density by increasing the charging voltage, is safe, and has a long life.

[0042] According to one embodiment of the present invention, it is possible to provide a positive electrode active material for a lithium ion secondary battery having a high capacity and excellent charge / discharge cycle characteristics, and a method for manufacturing the same. In addition, it is possible to provide a method for manufacturing the positive electrode active material with good productivity. According to one embodiment of the present invention, it is possible to provide a positive electrode active material that, when used in a lithium ion secondary battery, suppresses a decrease in capacity during charge / discharge cycles. According to one embodiment of the present invention, it is possible to provide a positive electrode active material in which elution of a transition metal such as cobalt is suppressed even when the battery is maintained in a charged state at a high voltage for a long period of time.

[0043] Another embodiment of the present invention can provide a novel substance, active material particles, a power storage device, or a manufacturing method thereof.

[0044] 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 have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract effects other than these from the description in the specification, drawings, claims, etc. [Brief description of the drawings]

[0045] [Figure 1] FIG. 1 is a diagram illustrating an example of a secondary battery. [Diagram 2] Fig. 2A is a diagram showing an example of a cross section of a secondary battery, and Fig. 2B is a diagram showing an example of a cross section of a secondary battery. [Diagram 3] FIG. 3 is a diagram illustrating an example of a secondary battery. [Figure 4] Fig. 4A is a diagram showing an example of an electrode, Fig. 4B is a diagram showing an example of a method for producing a secondary battery, and Fig. 4C is a diagram showing an example of a method for producing a secondary battery. [Diagram 5] 5A and 5B are diagrams illustrating an example of a method for producing a secondary battery. [Figure 6] Fig. 6A is a diagram showing an example of an electrode, Fig. 6B is a diagram showing an example of a method for producing a secondary battery, Fig. 6C is a diagram showing an example of a method for producing a secondary battery, and Fig. 6D is a diagram showing an example of a method for producing a secondary battery. [Figure 7] Fig. 7A is a diagram showing a configuration example of a secondary battery, Fig. 7B is a diagram showing a configuration example of a secondary battery, and Fig. 7C is a diagram showing a configuration example of a secondary battery. [Figure 8] FIG. 8 is a diagram illustrating a configuration example of a secondary battery. [Figure 9] Fig. 9A is a diagram showing a configuration example of a battery pack; Fig. 9B is a diagram showing a configuration example of a battery pack; [Figure 10]Fig. 10A is a diagram showing an example of the configuration of a battery pack; Fig. 10B is a diagram showing an example of the configuration of a battery pack; Fig. 10C is a diagram showing an example of the configuration of a battery pack; and Fig. 10D is a diagram showing an example of the configuration of a battery pack. [Figure 11] Fig. 11A is a diagram explaining a bendable secondary battery. Fig. 11B is a diagram explaining a bendable secondary battery. Fig. 11C is a diagram explaining a bendable secondary battery. Fig. 11D is a diagram explaining a bendable secondary battery. Fig. 11E is a diagram explaining a bendable secondary battery. [Figure 12] Fig. 12A is a diagram for explaining the radius of curvature, Fig. 12B is a diagram for explaining the radius of curvature, and Fig. 12C is a diagram for explaining the radius of curvature. [Figure 13] Fig. 13A is a diagram for explaining the radius of curvature, Fig. 13B is a diagram for explaining the radius of curvature, Fig. 13C is a diagram for explaining the radius of curvature, and Fig. 13D is a diagram for explaining the radius of curvature. [Figure 14] Fig. 14A shows an example of a cylindrical secondary battery. Fig. 14B shows an example of a cylindrical secondary battery. Fig. 14C shows an example of a plurality of cylindrical secondary batteries. Fig. 14D shows an example of a power storage system having a plurality of cylindrical secondary batteries. [Figure 15] Fig. 15A shows an example of the configuration of a battery pack, Fig. 15B shows an example of the configuration of a battery pack, and Fig. 15C shows an example of the configuration of a battery pack. [Figure 16] Fig. 16A shows a configuration example of a power storage system. Fig. 16B shows an example of a method for manufacturing the power storage system. Fig. 16C shows an example of a method for manufacturing the power storage system. Fig. 16D shows an example of a method for manufacturing the power storage system. [Figure 17] Fig. 17A is a diagram illustrating an example of a vehicle, Fig. 17B is a diagram illustrating an example of a vehicle, and Fig. 17C is a diagram illustrating an example of a vehicle. [Figure 18] Fig. 18A is a diagram illustrating an example of a vehicle, and Fig. 18B is a diagram illustrating an example of a power storage system. [Figure 19]Fig. 19A is a diagram illustrating an example of an electronic device, Fig. 19B is a diagram illustrating an example of an electronic device, and Fig. 19C is a diagram illustrating an example of an electronic device. [Figure 20] FIG. 20 is a diagram illustrating an example of an electronic device. [Figure 21] FIG. 21A is a diagram for explaining an example of an electronic device. FIG. 21B is a diagram for explaining an example of an electronic device. FIG. 21C is a diagram for explaining an example of a secondary battery. FIG. 21D is a diagram for explaining an example of an electronic device. FIG. 21E is a diagram for explaining an example of a secondary battery. FIG. 21F is a diagram for explaining an example of an electronic device. FIG. 21G is a diagram for explaining an example of an electronic device. [Figure 22] FIG. 22 is a diagram illustrating an example of an electronic device. [Diagram 23] Fig. 23A is a diagram illustrating an example of an electronic device, Fig. 23B is a diagram illustrating an example of an electronic device, and Fig. 23C is a diagram illustrating an example of an electronic device. [Figure 24] 24A and 24B are graphs showing cycle characteristics of a secondary battery; [Diagram 25] FIG. 25 is a diagram showing cycle characteristics of a secondary battery. [Figure 26] Fig. 26A is a diagram showing a charge / discharge curve of a secondary battery, and Fig. 26B is a diagram showing a charge / discharge curve of a secondary battery. [Figure 27] Fig. 27A is a diagram showing a charge / discharge curve of a secondary battery, and Fig. 27B is a diagram showing a charge / discharge curve of a secondary battery. [Figure 28] Fig. 28A is a diagram showing a charge / discharge curve of a secondary battery, and Fig. 28B is a diagram showing a charge / discharge curve of a secondary battery. [Figure 29] Fig. 29A is a diagram showing a charge / discharge curve of a secondary battery, and Fig. 29B is a diagram showing a charge / discharge curve of a secondary battery. [Diagram 30] Fig. 30A is a diagram showing a charge / discharge curve of a secondary battery, and Fig. 30B is a diagram showing a charge / discharge curve of a secondary battery. [Diagram 31] FIG. 31 is a diagram showing a charge / discharge curve of a secondary battery. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be easily understood by those skilled in the art that the form and details of the present invention can be modified in various ways. Furthermore, the present invention is not to be interpreted as being limited to the description of the embodiments shown below.

[0047] In addition, in this specification and the like, crystal planes and directions are indicated using Miller indices. In crystallography, crystal planes and directions are indicated by placing a superscript bar on the numbers, but in this specification and the like, due to restrictions on notation in applications, numbers may be indicated by placing a - (minus sign) before them instead of placing a bar above them. Also, individual directions indicating directions within a crystal are expressed with [ ], collective directions indicating all equivalent directions with < >, individual faces indicating crystal faces with ( ), and collective faces with equivalent symmetry with {}.

[0048] In this specification and the like, segregation refers to a phenomenon in which a certain element (eg, B) is spatially non-uniformly distributed in a solid composed of a plurality of elements (eg, A, B, C).

[0049] In this specification, the surface layer of a particle of an active material or the like refers to a region from the surface to a depth of about 10 nm. Surfaces caused by cracks or chips may also be called the surface. The region deeper than the surface layer is called the interior.

[0050] In this specification, the layered rock-salt type crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure having a rock-salt type ion arrangement in which cations and anions are alternately arranged, and in which the transition metal and lithium are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. Defects such as deficiencies of cations or anions may be present. Strictly speaking, the layered rock-salt type crystal structure may have a structure in which the lattice of the rock-salt type crystal is distorted.

[0051] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately, and it is acceptable for there to be a deficiency of cations or anions.

[0052] In the present specification and the like, the pseudo-spinel crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure that is in the space group R-3m and is not a spinel crystal structure, but has ions of cobalt, magnesium, etc. occupying 6-coordination oxygen positions and has a symmetry similar to that of the spinel type in the arrangement of cations. In the pseudo-spinel crystal structure, a light element such as lithium may occupy 4-coordination oxygen positions, and in this case, the arrangement of ions also has a symmetry similar to that of the spinel type.

[0053] It can also be said that the pseudo-spinel type crystal structure is a crystal structure similar to the CdCl2 type crystal structure, although it has random Li between the layers. This CdCl2 type-like crystal structure was observed when lithium nickel oxide was charged to a charge depth of 0.94 (Li 0.06 The crystal structure is close to that of lithium cobalt oxide (NiO2), but it is known that pure lithium cobalt oxide or layered rock salt type positive electrode active materials that contain a large amount of cobalt do not usually have this crystal structure.

[0054] The layered rock salt crystal and the anions of the rock salt crystal have a cubic close-packed structure (face-centered cubic lattice structure). It is presumed that the anions of the pseudo-spinel crystal also have a cubic close-packed structure. When they contact, there is a crystal plane where the orientation of the cubic close-packed structure formed by the anions is aligned. However, the space group of the layered rock salt crystal and the pseudo-spinel crystal is R-3m, which is different from the space group Fm-3m (the space group of a general rock salt crystal) and Fd-3m (the space group of a rock salt crystal with the simplest symmetry) of the rock salt crystal, so the Miller indices of the crystal planes that satisfy the above conditions are different between the layered rock salt crystal and the pseudo-spinel crystal and the rock salt crystal. In this specification, when the orientation of the cubic close-packed structure formed by the anions is aligned in the layered rock salt crystal, the pseudo-spinel crystal, and the rock salt crystal, it may be said that the crystal orientation is approximately the same.

[0055] A secondary battery has, for example, a positive electrode and a negative electrode. A material constituting the positive electrode is a positive electrode active material. The positive electrode active material is, for example, a material that undergoes a reaction that contributes to the charge / discharge capacity. Note that the positive electrode active material may contain a material that does not contribute to the charge / discharge capacity.

[0056] In this specification, etc., the positive electrode active material of one embodiment of the present invention may be expressed as a positive electrode material, a positive electrode material for a secondary battery, or the like. In this specification, etc., the positive electrode active material of one embodiment of the present invention preferably includes a compound. In this specification, etc., the positive electrode active material of one embodiment of the present invention preferably includes a composition. In this specification, etc., the positive electrode active material of one embodiment of the present invention preferably includes a composite.

[0057] (Embodiment 1) In this embodiment, an example of a secondary battery of one embodiment of the present invention will be described.

[0058] In secondary batteries, increasing the charging voltage can increase the discharge capacity and also the energy density.

[0059] On the other hand, when the charging voltage of a secondary battery is increased, the capacity may significantly decrease with the charge / discharge cycle. For example, a high charging voltage may cause the crystal structure of the positive electrode active material to become unstable.

[0060] For example, consider the case where a material containing a metal (hereinafter, metal A) that acts as a carrier ion is used as the positive electrode active material. Metal A is released from the positive electrode active material during the charging reaction. As the charging voltage is increased, a large amount of metal A is released from the positive electrode active material, which may cause a significant change in the crystal structure of the positive electrode active material. If the change in crystal structure accompanying the insertion and release of metal A is irreversible, the crystal structure may gradually collapse, resulting in a significant decrease in capacity with charge and discharge cycles.

[0061] A secondary battery using the positive electrode active material of one embodiment of the present invention can suppress collapse of a crystal structure and suppress a decrease in capacity due to charge-discharge cycles even when repeatedly charged at a high charging voltage.

[0062] Furthermore, as shown in the examples described later, it has been found that in a secondary battery using a positive electrode active material of one embodiment of the present invention, by using a positive electrode having the positive electrode active material of one embodiment of the present invention as the positive electrode and further using an ionic liquid as the main solvent of the electrolyte, the decrease in capacity due to charge / discharge cycles can be further suppressed and significantly excellent secondary battery characteristics can be achieved.

[0063] Ionic liquids are salts consisting of a combination of cations and anions. Ionic liquids are sometimes called room temperature molten salts.

[0064] Ionic liquids are low in volatility and flammability, and are stable over a wide temperature range. Because they are not easily volatilized even at high temperatures, expansion of the secondary battery due to gas generation from the electrolyte can be suppressed. Therefore, the operation of the secondary battery is stable even at high temperatures. In addition, they are low in flammability and flame-retardant.

[0065] By using an ionic liquid, a secondary battery that can be used at high temperatures and is highly safe can be realized.

[0066] For example, organic solvents such as diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) have a boiling point below 150°C and are highly volatile, so that when used at high temperatures, gas may be generated and the exterior body of the secondary battery may expand. In addition, organic solvents may have a flash point of 50°C or lower.

[0067] On the other hand, ionic liquids have low volatility and are extremely stable up to temperatures lower than the temperatures at which reactions such as decomposition occur, for example, up to about 300°C.

[0068] Thus, it is clear that the ionic liquid is stable even at high temperatures. On the other hand, if other components constituting the secondary battery, such as the positive electrode active material, the negative electrode active material, the exterior body, etc., change at high temperatures, especially if they change irreversibly, this may lead to a significant decrease in the capacity of the secondary battery.

[0069] For example, when irreversible changes occur in the crystal structure of the material constituting the positive electrode active material due to charging at high temperatures, deterioration occurs significantly in the secondary battery. For example, the capacity may decrease significantly with the charge / discharge cycle. When the temperature is high and the charging voltage is high, the crystal structure of the positive electrode may become even more unstable.

[0070] In the secondary battery of one embodiment of the present invention, by using a positive electrode active material whose crystal structure is extremely stable at high charging voltage and high temperature, excellent characteristics can be realized even when the temperature is high and the charging voltage is also high, and the effect of the ionic liquid can be fully exhibited. That is, the remarkable improvement in characteristics obtained by using the configuration of the secondary battery of one embodiment of the present invention is found by combining it with the positive electrode active material of one embodiment of the present invention.

[0071] In addition, as described below, the positive electrode active material of one embodiment of the present invention preferably contains an element X, and preferably contains a halogen in addition to the element X. When the positive electrode active material of one embodiment of the present invention contains the element X or a halogen in addition to the element X, it is suggested that the reaction with the ionic liquid on the surface of the positive electrode active material is suppressed. As described above, the ionic liquid is extremely stable even at high temperatures. On the other hand, the secondary battery of one embodiment of the present invention has an extremely wide range of reaction potential. In such a wide reaction potential, there is a concern that the reaction with the ionic liquid may occur on the surface of the active material, and it is suggested that the use of the positive electrode active material of one embodiment of the present invention suppresses the reaction with the ionic liquid, thereby realizing a more stable secondary battery.

[0072] By using the configuration of the secondary battery of one embodiment of the present invention, for example, a secondary battery that can be repeatedly charged even if the upper limit voltage of charging is increased can be realized. For example, a secondary battery that can be repeatedly charged can be realized with an upper limit voltage of charging of preferably 4.45 V or more, more preferably 4.47 V or more, further preferably 4.49 V or more, for example, about 4.5 V. Furthermore, by using the configuration of the secondary battery of one embodiment of the present invention, a decrease in discharge capacity can be significantly suppressed even if the upper limit voltage of charging is increased.

[0073] In the configuration of the secondary battery according to one embodiment of the present invention, when the temperature during charging is in the range of t(1) [°C] or more and less than t(2) [°C], it is preferable to set the upper limit voltage during charging to v(1) [V], and when the temperature during charging is t(2) [°C] or more, it is preferable to set the upper limit voltage during charging to v(2) [V]. Here, t(1) is preferably a value of 5 or more and 15 or less, and t(2) is preferably a value of 25 or more and less than 55. Furthermore, v(1) is preferably a value of 0.02 or more greater than v(2), and v(1) is preferably a value of 4.45 or more and 4.6 or less.

[0074] By using the configuration of the secondary battery of one embodiment of the present invention, it is possible to realize a secondary battery that can be repeatedly charged at a high charging voltage even at a high temperature of, for example, 42° C. or higher. For example, it is possible to realize a secondary battery that can be repeatedly charged at an environmental temperature of 42° C. or higher and an upper limit charging voltage of preferably 4.37 V or higher, more preferably 4.40 V or higher, further preferably 4.42 V or higher, further preferably 4.44 V or higher, for example, about 4.45 V.

[0075] Furthermore, it is possible to realize an excellent secondary battery even at higher temperatures. For example, it may be possible to realize a secondary battery that operates stably at temperatures between 42°C and 200°C, between 42°C and 180°C, between 42°C and 150°C, between 42°C and 120°C, between 42°C and 100°C, or between 42°C and 90°C.

[0076] For example, the secondary battery according to one embodiment of the present invention has a discharge capacity of 160 mAh / g or more after discharging an accumulated charge of 57,000 mAh / g. Here, for example, the discharge capacity is preferably measured at 0.2 C. The accumulated charge and discharge capacity are preferably calculated per weight of the positive electrode active material.

[0077] In addition, the secondary battery of one embodiment of the present invention has a discharge capacity of 160 mAh / g or more after 300 charging cycles at a charging voltage of 4.5 V at 25° C. Here, for example, the discharge capacity is preferably measured at 0.2 C. In addition, the cumulative charge amount and the discharge capacity are preferably calculated per weight of the positive electrode active material.

[0078] The secondary battery of one embodiment of the present invention is preferably used in combination with a battery control circuit. The battery control circuit preferably has a function of controlling charging, for example. Controlling charging refers to monitoring parameters of the secondary battery and changing charging conditions in accordance with the state. Examples of the parameters of the secondary battery to be monitored include the voltage, current, temperature, charge amount, impedance, and the like of the secondary battery.

[0079] The secondary battery according to one embodiment of the present invention is preferably used in combination with a sensor, which preferably has a function of measuring one or more of displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, and infrared light.

[0080] In addition, in the secondary battery of one embodiment of the present invention, charging is preferably controlled in accordance with a value measured by a sensor. An example of control of the secondary battery using a temperature sensor will be described later.

[0081] [Cathode active material] A positive electrode active material that is preferably used in the secondary battery of one embodiment of the present invention will be described below.

[0082] <Structure of positive electrode active material> The positive electrode active material preferably contains a metal (hereinafter, referred to as element A) that serves as a carrier ion. As element A, for example, alkali metals such as lithium, sodium, potassium, etc., and Group 2 elements such as calcium, beryllium, magnesium, etc. can be used.

[0083] In the positive electrode active material, carrier ions are released from the positive electrode active material as the battery is charged. If the amount of element A released is large, the amount of ions contributing to the capacity of the secondary battery is large, and the capacity is increased. On the other hand, if the amount of element A released is large, the crystal structure of the compound contained in the positive electrode active material is easily broken. The break in the crystal structure of the positive electrode active material may lead to a decrease in the discharge capacity associated with charge-discharge cycles. When the positive electrode active material of one embodiment of the present invention contains element X, the break in the crystal structure when carrier ions are released during charging of the secondary battery may be suppressed. For example, a part of element X is substituted at the position of element A. Elements such as magnesium, calcium, zirconium, lanthanum, and barium can be used as element X. For example, elements such as copper, potassium, sodium, and zinc can be used as element X. Two or more of the above elements may be used in combination as element X.

[0084] The positive electrode active material of one embodiment of the present invention preferably contains a halogen in addition to the element X. The positive electrode active material of one embodiment of the present invention preferably contains a halogen such as fluorine or chlorine. When the positive electrode active material of one embodiment of the present invention contains the halogen, the substitution of the element X at the position of the element A may be promoted.

[0085] When the positive electrode active material of one embodiment of the present invention contains the element X or contains a halogen in addition to the element X, the electrical conductivity on the surface of the positive electrode active material may be suppressed in some cases.

[0086] The positive electrode active material of one embodiment of the present invention has a metal (hereinafter, element M) whose valence changes with charging and discharging of the secondary battery. The element M is, for example, a transition metal. The positive electrode active material of one embodiment of the present invention has, for example, one or more of cobalt, nickel, and manganese as the element M, and particularly has cobalt. In addition, the position of the element M may have an element such as aluminum that does not change its valence and can have the same valence as the element M, more specifically, for example, a trivalent typical element. The aforementioned element X may be substituted, for example, at the position of the element M. In addition, when the positive electrode active material of one embodiment of the present invention is an oxide, the element X may be substituted at the position of oxygen.

[0087] As the positive electrode active material of one embodiment of the present invention, for example, a lithium composite oxide having a layered rock salt crystal structure is preferably used. More specifically, for example, as the lithium composite oxide having a layered rock salt crystal structure, lithium cobalt oxide, lithium nickel oxide, lithium composite oxide having nickel, manganese, and cobalt, lithium composite oxide having nickel, cobalt, and aluminum, etc. can be used. In addition, these positive electrode active materials are preferably represented by the space group R-3m.

[0088] In a positive electrode active material having a layered rock salt crystal structure, the crystal structure may collapse when the charge depth is increased. Here, the collapse of the crystal structure may be, for example, a displacement of layers. If the collapse of the crystal structure is irreversible, the capacity of the secondary battery may decrease with repeated charging and discharging.

[0089] The positive electrode active material of one embodiment of the present invention contains the element X, so that, for example, even if the charge depth is deep, the above-mentioned layer misalignment is suppressed. By suppressing the misalignment, the volume change during charging and discharging can be reduced. Therefore, the positive electrode active material of one embodiment of the present invention can achieve excellent cycle characteristics. In addition, the positive electrode active material of one embodiment of the present invention can have a stable crystal structure in a high-voltage charged state. Therefore, the positive electrode active material of one embodiment of the present invention may be less likely to cause a short circuit when a high-voltage charged state is maintained. In such a case, safety is further improved, which is preferable.

[0090] In the positive electrode active material of one embodiment of the present invention, the change in crystal structure and the difference in volume per the same number of transition metal atoms between a fully discharged state and a high-voltage charged state are small.

[0091] The positive electrode active material according to one embodiment of the present invention has the chemical formula AM y O Z (y>0, z>0). For example, lithium cobalt oxide may be represented as LiCoO2. For example, lithium nickel oxide may be represented as LiNiO2.

[0092] In the positive electrode active material of one embodiment of the present invention having element X, when the charge depth is 0.8 or more, it is represented by space group R-3m, and although it is not a spinel type crystal structure, ions of element M (e.g., cobalt), element X (e.g., magnesium), etc. occupy oxygen 6-coordination positions, and the arrangement of cations may have a symmetry similar to that of the spinel type. This structure is referred to as a pseudo-spinel type crystal structure in the present specification. In addition, in the pseudo-spinel type crystal structure, a light element such as lithium may occupy oxygen 4-coordination positions, and in this case, the arrangement of ions also has a symmetry similar to that of the spinel type.

[0093] The structure of the positive electrode active material becomes unstable due to the desorption of carrier ions during charging. The pseudo-spinel crystal structure can be said to be a structure that can maintain high stability even when carrier ions are desorbed.

[0094] In the case where the charge depth of the present invention is high, by using the positive electrode active material having a pseudo-spinel structure in a secondary battery, the structure of the positive electrode active material is stable and the capacity decrease due to charging and discharging can be suppressed at a voltage of, for example, 4.57V or more and less than 4.65V, or 4.59V or more and less than 4.63V, for example, about 4.6V, based on the potential of lithium metal. In addition, when graphite is used as the negative electrode active material in the secondary battery, for example, the structure of the positive electrode active material is stable and the capacity decrease due to charging and discharging can be suppressed at a voltage of, for example, preferably 4.45V or more and less than 4.6V, more preferably 4.47V or more and less than 4.55V, even more preferably 4.49V or more and less than 4.53V, for example, about 4.5V.

[0095] It can also be said that the pseudo-spinel type crystal structure is a crystal structure similar to the CdCl2 type crystal structure, although it has random Li between the layers. This CdCl2 type-like crystal structure was observed when lithium nickel oxide was charged to a charge depth of 0.94 (Li 0.06 The crystal structure is close to that of lithium cobalt oxide (NiO2), but it is known that pure lithium cobalt oxide or layered rock salt type positive electrode active materials that contain a large amount of cobalt do not usually have this crystal structure.

[0096] The layered rock salt crystal and the anions of the rock salt crystal have a cubic close-packed structure (face-centered cubic lattice structure). It is presumed that the anions of the pseudo-spinel crystal also have a cubic close-packed structure. When they contact, there is a crystal plane where the orientation of the cubic close-packed structure formed by the anions is aligned. However, the space group of the layered rock salt crystal and the pseudo-spinel crystal is R-3m, which is different from the space group Fm-3m (the space group of a general rock salt crystal) and Fd-3m (the space group of a rock salt crystal with the simplest symmetry) of the rock salt crystal, so the Miller indices of the crystal planes that satisfy the above conditions are different between the layered rock salt crystal and the pseudo-spinel crystal and the rock salt crystal. In this specification, when the orientation of the cubic close-packed structure formed by the anions is aligned in the layered rock salt crystal, the pseudo-spinel crystal, and the rock salt crystal, it may be said that the crystal orientation is approximately the same.

[0097] The pseudospinel crystal structure can show the coordinates of cobalt and oxygen in the unit cell as Co(0,0,0.5), O(0,0,x), with 0.20≦x≦0.25.

[0098] In the positive electrode active material of one embodiment of the present invention, the difference between the volume of a unit cell at a charge depth of 0 and the volume per unit cell of the pseudospinel crystal structure at a charge depth of 0.82 is preferably 2.5% or less, more preferably 2.2% or less.

[0099] In the pseudospinel crystal structure, diffraction peaks appear at 2θ=19.30±0.20° (19.10° to 19.50°) and 2θ=45.55±0.10° (45.45° to 45.65°). More specifically, sharp diffraction peaks appear at 2θ=19.30±0.10° (19.20° to 19.40°) and 2θ=45.55±0.05° (45.50° to 45.60°).

[0100] Note that the positive electrode active material of one embodiment of the present invention has a pseudo-spinel crystal structure when charged at a high voltage, but not all of the particles may have a pseudo-spinel crystal structure. Other crystal structures may be included, or a part may be amorphous. However, when Rietveld analysis is performed on the XRD pattern, the pseudo-spinel crystal structure is preferably 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more. When the pseudo-spinel crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more, the positive electrode active material can have sufficiently excellent cycle characteristics.

[0101] The number of atoms of element X is preferably 0.001 to 0.1 times the number of atoms of element M, more preferably greater than 0.01 and less than 0.04, and even more preferably about 0.02. The concentration of element X shown here may be a value obtained by performing elemental analysis of the entire particles of the positive electrode active material using, for example, ICP-MS or the like, or may be based on the value of the composition of raw materials in the process of producing the positive electrode active material.

[0102] When the element M contains cobalt and nickel, the ratio Ni / (Co+Ni) of the number of nickel atoms (Ni) to the sum of the numbers of cobalt and nickel atoms (Co+Ni) is preferably less than 0.1, and more preferably 0.075 or less.

[0103] The positive electrode active material of one embodiment of the present invention is not limited to the above-mentioned materials.

[0104] For example, a composite oxide having a spinel crystal structure can be used as the positive electrode active material. For example, a polyanion-based material can be used as the positive electrode active material. For example, a material having an olivine crystal structure, a Nasicon-based material, etc. can be used as the polyanion-based material. For example, a material having sulfur can be used as the positive electrode active material.

[0105] As a material having a spinel type crystal structure, for example, a composite oxide represented by LiM2O4 can be used. It is preferable to have Mn as the element M. For example, LiMn2O4 can be used. Furthermore, by having Ni in addition to Mn as the element M, the discharge voltage of the secondary battery can be improved and the energy density can be improved, which is preferable. Furthermore, a small amount of lithium nickel oxide (LiNiO2 or LiNi 1-x M x Mixing O2 (M=Co, Al, etc.) is preferable because it can improve the characteristics of the secondary battery.

[0106] An example of a polyanion-based material that can be used is a composite oxide having oxygen, metal A, metal M, and element Z. Metal A is one or more of Li, Na, and Mg, metal M is one or more of Fe, Mn, Co, Ni, Ti, V, and Nb, and element Z is one or more of S, P, Mo, W, As, and Si.

[0107] As a material having an olivine-type crystal structure, for example, a composite material (general formula LiMPO4 (M is one or more of Fe(II), Mn(II), Co(II), Ni(II))) can be used. Representative examples of the general formula LiMPO4 include LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, LiFe a Ni b PO4, LiFe a Co b PO4, LiFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4 (a + b is 1 or less, 0 < a < 1, 0 < b < 1), LiFe c Ni d Co e PO4, LiFe c Ni d Mn e PO4, LiNi c Co d Mn e PO4 (c + d + e is 1 or less, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO4 (f + g + h + i is 1 or less, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), etc., lithium compounds can be used.

[0108] In addition, composite materials such as the general formula Li (2-j) MSiO4 (M is one or more of Fe(II), Mn(II), Co(II), Ni(II), 0 ≦ j ≦ 2) can be used. Representative examples of the general formula Li (2-j) MSiO4 include Li (2-j) FeSiO4, Li (2-j) NiSiO4, Li (2-j) CoSiO4, Li (2-j) MnSiO4, Li (2-j) Fe k Ni l SiO4, Li (2-j) Fe k Co l SiO4, Li (2-j) Fek Mn l SiO4, Li (2-j) Ni k Co l SiO4, Li (2-j) Ni k Mn l SiO4 (k + l is 1 or less, 0 < k < 1, 0 < l < 1), Li (2-j) Fe m Ni n Co q SiO4, Li (2-j) Fe m Ni n Mn q SiO4, Li (2-j) Ni m Co n Mn q SiO4 (m + n + q is 1 or less, 0 < m < 1, 0 < n < 1, 0 < q < 1), Li (2-j) Fe r Ni s Co t Mn u Lithium compounds such as SiO4 (r + s + t + u is 1 or less, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1), etc. can be used as materials.

[0109] Also, A x NASICON-type compounds represented by the general formula M2(XO4)3 (A = Li, Na, Mg, M = Fe, Mn, Ti, V, Nb, X = S, P, Mo, W, As, Si) can be used. Examples of NASICON-type compounds include Fe2(MnO4)3, Fe2(SO4)3, Li3Fe2(PO4)3, etc. Also, as the positive electrode active material, compounds represented by the general formula Li2MPO4F, Li2MP2O7, Li5MO4 (M = Fe, Mn) can be used.

[0110] Also, as the positive electrode active material, perovskite-type fluorides such as NaFeF3, FeF3, metal chalcogenides (sulfides, selenides, tellurides) such as TiS2, MoS2, oxides having an inverse spinel-type crystal structure such as LiMVO4, vanadium oxides (V2O5, V6O 13 , LiV3O8, etc.), manganese oxides, organic sulfur compounds, etc. may be used.

[0111] In addition, as the positive electrode active material, a borate-based material represented by the general formula LiMBO3 (M is Fe(II), Mn(II), or Co(II)) may be used.

[0112] Examples of materials containing sodium include NaFeO2 and Na 2 / 3 [Fe 1 / 2 Mn 1 / 2 ]O2, Na 2 / 3 [Ni 1 / 3 Mn 2 / 3 ]O2, Na2Fe2(SO4)3, Na3V2(PO4)3, Na2FePO4F, NaVPO4F, NaMPO4 (wherein M is Fe(II), Mn(II), Co(II), or Ni(II)), Na2FePO4F, or Na4Co3(PO4)2P2O7, or other sodium-containing oxides, may be used as the positive electrode active material.

[0113] In addition, lithium-containing metal sulfides such as Li2TiS3 and Li3NbS4 may be used as the positive electrode active material.

[0114] As the positive electrode active material of one embodiment of the present invention, two or more of the materials listed above may be mixed and used.

[0115] In a typical secondary battery, as the charging voltage increases, the structure of the positive electrode active material becomes unstable, and element M contained in the positive electrode active material may dissolve into the electrolyte. For example, the capacity of the positive electrode may decrease due to the dissolution of element M into the electrolyte. The decrease in the capacity of the positive electrode leads to a decrease in the capacity of the secondary battery. Furthermore, element M dissolved into the electrolyte may precipitate on the surface of the negative electrode of the secondary battery. The precipitated element M inhibits the reaction of the negative electrode, leading to a decrease in the capacity of the secondary battery.

[0116] In a secondary battery using the positive electrode active material of one embodiment of the present invention, the structure of the positive electrode active material is stable even at a high charging voltage, so that elution of element M contained in the positive electrode active material into an electrolyte solution can be suppressed.

[0117] [Electrolyte] The secondary battery of one embodiment of the present invention preferably includes an electrolyte solution, which preferably includes an ionic liquid and a salt containing a metal that serves as a carrier ion.

[0118] When the metal that becomes the carrier ion is lithium, examples of salts containing the metal that becomes the carrier ion include LiN(FSO2)2, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiCF3SO3, LiC4F9SO3, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 10 Cl 10 , Li2B 12 Cl 12 Lithium salts such as LiPF6, LiClO4, etc., can be used alone or in any combination and ratio of two or more of these.

[0119] In particular, metal salts with fluorosulfonic acid anions and fluoroalkylsulfonic acid anions may be preferred. Among these, (C n F 2n+1 SO2)2N - Metal salts with amide anions represented by (n=0 or more and 3 or less) are highly stable at high temperatures and have high resistance to oxidation and reduction, and may be preferable in some cases.

[0120] Ionic liquids are composed of cations and anions, and contain organic cations and anions. Examples of organic cations used in the electrolytic solution include aromatic cations such as imidazolium cations and pyridinium cations, and aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations. Examples of anions used in the electrolytic solution include monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkylsulfonic acid anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, and perfluoroalkylphosphate anions.

[0121] In addition to the ionic liquid, the electrolyte may contain an aprotic solvent such as one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), DEC, EMC, methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, and sultone, or a mixture of two or more of these in any combination and ratio.

[0122] In addition, additives such as dinitrile compounds such as vinylene carbonate (VC), propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), succinonitrile, adiponitrile, fluorobenzene, cyclohexylbenzene, biphenyl, etc. may be added to the electrolyte. The concentration of the additive material may be, for example, 0.1 wt% to 5 wt% based on the total solvent.

[0123] As an ionic liquid having an imidazolium cation, for example, an ionic liquid represented by the following general formula (G1) can be used. In general formula (G1), R 1 represents an alkyl group having 1 to 4 carbon atoms, and R 2 ~R 4 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R 5 represents an alkyl group or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P. 5 A substituent may be introduced into the main chain of the copolymer. Examples of the substituent to be introduced include an alkyl group and an alkoxy group.

[0124] [ka]

[0125] As an ionic liquid having a pyridinium cation, for example, an ionic liquid represented by the following general formula (G2) may be used. In general formula (G2), R 6 represents an alkyl group or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P, and R 7 ~R 11 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 6 A substituent may be introduced into the main chain of the copolymer. Examples of the substituent to be introduced include an alkyl group and an alkoxy group.

[0126] [ka]

[0127] As the ionic liquid having a quaternary ammonium cation, for example, the ionic liquids represented by the following general formulas (G3), (G4), (G5) and (G6) can be used.

[0128] [ka]

[0129] In general formula (G3), R 28 ~R 31 each independently represents an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom.

[0130] [ka]

[0131] In general formula (G4), R 12 ~R 17 each independently represents an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom.

[0132] [ka]

[0133] In general formula (G5), R 18 ~R 24 each independently represents an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom.

[0134] [ka]

[0135] In the general formula (G6), n and m are 1 to 3. α is 0 to 6, and when n is 1, α is 0 to 4, when n is 2, α is 0 to 5, and when n is 3, α is 0 to 6. β is 0 to 6, and when m is 1, β is 0 to 4, when m is 2, β is 0 to 5, and when m is 3, β is 0 to 6. When α or β is 0, it means that it is unsubstituted. In addition, the case where both α and β are 0 is excluded. X or Y represents, as a substituent, a linear or side chain alkyl group having 1 to 4 carbon atoms, a linear or side chain alkoxy group having 1 to 4 carbon atoms, or a linear or side chain alkoxyalkyl group having 1 to 4 carbon atoms.

[0136] As an ionic liquid having a tertiary sulfonium cation, for example, an ionic liquid represented by the following general formula (G7) can be used. In general formula (G7), R 25 ~R 27 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group; or R 25 ~R 27 As the main chain, a main chain composed of two or more atoms selected from C, O, Si, N, S and P atoms may be used.

[0137] [ka]

[0138] As an ionic liquid having a quaternary phosphonium cation, for example, an ionic liquid represented by the following general formula (G8) can be used. In the general formula (G8), R 32 ~R 35 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group; or R 32 ~R 35 As the main chain, a main chain composed of two or more atoms selected from C, O, Si, N, S and P atoms may be used.

[0139] [ka]

[0140] A represented by general formulas (G1) to (G8) - As the anion, one or more of a monovalent amide anion, a monovalent methide anion, a fluorosulfonate anion, a perfluoroalkylsulfonate anion, a tetrafluoroborate anion, a perfluoroalkylborate anion, a hexafluorophosphate anion, and a perfluoroalkylphosphate anion can be used.

[0141] As monovalent amide anions, (C n F 2n+1 SO2)2N - (n = 0 to 3), and the monovalent cyclic amide anion is (CF2SO2)2N - The monovalent methide anion can be (C n F 2n+1 SO2)3C - (n = 0 to 3), the monovalent cyclic methide anion is (CF2SO2)2C - (CF3SO2) and the like can be used. As the fluoroalkylsulfonate anion, (C m F 2m+1 SO3) - (m=0 to 4). Fluoroalkylborate anions include {BF n (C m H k F 2m+1-k ) 4-n} - (n = 0 to 3, m = 1 to 4, k = 0 to 2m) and the like. The fluoroalkyl phosphate anion is, for example, {PF n (C m H k F 2m+1-k ) 6-n} - (n = 0 to 5, m = 1 to 4, k = 0 to 2m).

[0142] Furthermore, as the monovalent amide anion, for example, one or more of a bis(fluorosulfonyl)amide anion and a bis(trifluoromethanesulfonyl)amide anion can be used.

[0143] The ionic liquid may also have one or more of a hexafluorophosphate anion and a tetrafluoroborate anion.

[0144] From now on, (FSO2)2N - The anion represented by the formula FSA anion, (CF3SO2)2N - The anion represented by the formula (I) is sometimes referred to as the TFSA anion.

[0145] Specific examples of the cation of the above general formula (G1) include, for example, structural formulae (111) to (174).

[0146] [ka]

[0147] [ka]

[0148] [ka]

[0149] [ka]

[0150] [ka]

[0151] [ka]

[0152] Specific examples of the cation of the above general formula (G2) include structural formulae (701) to (719).

[0153] [ka]

[0154] [ka]

[0155] Specific examples of the cation of the above general formula (G4) include structural formulae (501) to (520).

[0156] [ka]

[0157] Specific examples of the cation of the above general formula (G5) include structural formulae (601) to (630).

[0158] [ka]

[0159] [ka]

[0160] Specific examples of the cation of the above general formula (G6) include, for example, structural formulae (301) to (309) and structural formulae (401) to (419).

[0161] [ka]

[0162] [ka]

[0163] In addition, structural formulae (301) to (309) and structural formulae (401) to (419) show examples in which m is 1 in general formula (G6), but in structural formulae (301) to (309) and structural formulae (401) to (419), m may be changed to 2 or 3.

[0164] Specific examples of the cation of the above general formula (G7) include, for example, structural formulae (201) to (215).

[0165] [ka]

[0166] In the secondary battery of one embodiment of the present invention, the positive electrode active material of one embodiment of the present invention is used and the electrolyte solution contains the above-described ionic liquid. Thus, even when the secondary battery is repeatedly used at a high charging voltage, a decrease in capacity can be suppressed and remarkably excellent characteristics can be achieved.

[0167] [Negative electrode active material] As the negative electrode active material for the secondary battery, a material capable of undergoing charge / discharge reactions by insertion / desorption of carrier ions, and a material capable of undergoing charge / discharge reactions by alloying / dealloying reactions with metal A, which serves as a carrier ion, can be used.

[0168] As the negative electrode material, carbon-based materials such as graphite, easily graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, and carbon black can be used.

[0169] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, as the artificial graphite, spherical graphite having a spherical shape can be used. For example, MCMB may have a spherical shape, which is preferable. In addition, it is relatively easy to reduce the surface area of ​​MCMB, which may be preferable. Examples of natural graphite include flake graphite and spheroidized natural graphite.

[0170] When lithium ions are inserted into graphite (when lithium-graphite intercalation compounds are formed), graphite exhibits a low potential similar to that of lithium metal (0.05 V to 0.3 V vs. Li / Li + ) This allows the lithium ion secondary battery to exhibit a high operating voltage. That is, for example, the charging voltage of the lithium ion secondary battery can be increased. Thus, the energy density of the lithium ion secondary battery can be increased. Furthermore, graphite is preferable because it has the advantages of a relatively high capacity per unit volume, a relatively small volume expansion, being inexpensive, and being safer than lithium metal.

[0171] In addition, as the negative electrode active material, for example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used. Such elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4200mAh / g. For this reason, it is preferable to use silicon as the negative electrode active material. Compounds containing these elements may also be used. For example, there are SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, SbSn, etc. Here, elements capable of carrying out charge / discharge reactions through alloying / dealloying reactions with lithium, and compounds containing such elements, are sometimes referred to as alloying materials.

[0172] In this specification, SiO refers to, for example, silicon monoxide. Alternatively, SiO x Here, x preferably has a value close to 1. Alternatively, x is, for example, preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0173] In addition, titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), and other oxides can be used.

[0174] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, Li3N type structure Li 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm 3 ) and is preferred.

[0175] When a composite nitride of lithium and a transition metal is used, lithium ions are contained in the negative electrode active material, and therefore it is preferable to combine it with a material that does not contain lithium ions, such as V2O5 or Cr3O8, as the positive electrode active material. Even when a material that contains lithium ions is used as the positive electrode active material, the composite nitride of lithium and a transition metal can be used as the negative electrode active material by first removing the lithium ions contained in the positive electrode active material.

[0176] In addition, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example, transition metal oxides that do not form an alloy with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), can be used as the negative electrode active material. Further examples of materials that undergo a conversion reaction include oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, and CoS 0.89It also occurs in sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N and Ge3N4, phosphides such as NiP2, FeP2 and CoP3, and fluorides such as FeF3 and BiF3.

[0177] In a typical secondary battery, element M contained in the positive electrode active material may dissolve into the electrolyte and precipitate on the surface of the negative electrode. The precipitated element M inhibits the reaction of the negative electrode, resulting in a decrease in the capacity of the secondary battery.

[0178] For example, consider the case where graphite is used as the negative electrode active material. In the battery reaction, carrier ions are inserted between the layers of graphite and desorbed. For example, the insertion and desorption of carrier ions occurs in the area of ​​the surface of a graphite particle where the cross section of the layer is exposed. Since the battery reaction occurs efficiently only in a specific area of ​​the particle surface, it is suggested that the particle surface is more susceptible to the effects of, for example, the precipitation of element M on the particle surface.

[0179] As described above, in a secondary battery using the positive electrode active material of one embodiment of the present invention, the elution of element M contained in the positive electrode active material into an electrolyte can be suppressed. Therefore, even when graphite is used as a negative electrode active material, for example, a high battery capacity can be maintained even if the secondary battery is used repeatedly at a high charging voltage.

[0180] In addition, the use of an ionic liquid may suppress the deterioration of graphite that occurs during charging and discharging.

[0181] In addition, in the secondary battery of one embodiment of the present invention, by increasing the concentration of carrier ions in the electrolyte solution, insertion of cations into graphite can be suppressed, and the life of the secondary battery can be extended in some cases.

[0182] In an electrolyte solution containing an ionic liquid, when lithium ions are used as carrier ions in the electrolyte solution, the concentration of the lithium salt is preferably 0.8 mol / L or more, more preferably 1 mol / L or more and 2.5 mol / L or less, and even more preferably 1.2 mol / L or more and less than 2 mol / L.

[0183] [Example of secondary battery] A secondary battery using a film-shaped exterior body is shown as an example of a power storage device in Figure 1. If the secondary battery using the film-shaped exterior body is configured to have flexibility, and is mounted in an electronic device having at least a flexible portion, the secondary battery can also be bent in accordance with the deformation of the electronic device.

[0184] FIG. 1 shows an external view of a secondary battery 500 as a secondary battery using a film-shaped exterior body. Also, FIG. 2A and FIG. 2B show the A1-A2 cross section and the B1-B2 cross section shown by the dashed line in FIG. 1. The secondary battery 500 has a positive electrode 503 having a positive electrode current collector 501 and a positive electrode active material layer 502, a negative electrode 506 having a negative electrode current collector 504 and a negative electrode active material layer 505, a separator 507, an electrolyte 508, and an exterior body 509. The separator 507 is disposed between the positive electrode 503 and the negative electrode 506 provided in the exterior body 509. Also, the interior of the exterior body 509 is filled with the electrolyte 508.

[0185] In the secondary battery 500 shown in Fig. 1 and Fig. 2, the positive electrode lead electrode 510 is ultrasonically bonded to the positive electrode current collector 501 of the positive electrode 503, and the negative electrode lead electrode 511 is ultrasonically bonded to the negative electrode current collector 504 of the negative electrode 506. The positive electrode current collector 501 and the negative electrode current collector 504 can also serve as terminals for obtaining electrical contact with the outside. In that case, the positive electrode current collector 501 and the negative electrode current collector 504 may be arranged so that a part of them is exposed to the outside from the exterior body 509 without using a lead electrode.

[0186] In addition, while the positive electrode lead electrode 510 and the negative electrode lead electrode 511 are arranged on the same side in FIG. 1, the positive electrode lead electrode 510 and the negative electrode lead electrode 511 may be arranged on different sides as shown in FIG. 3. In this manner, the secondary battery of one embodiment of the present invention has a high degree of design freedom since the lead electrodes can be freely arranged. Therefore, the degree of design freedom of a product using the secondary battery of one embodiment of the present invention can be increased. In addition, the productivity of a product using the secondary battery of one embodiment of the present invention can be increased.

[0187] <Exterior body> In the secondary battery 500, the exterior body 509 can be, for example, a film in which a polymer layer or the like is coated on both sides of a metal thin film. More specifically, for example, a metal thin film having excellent flexibility, such as aluminum, stainless steel, copper, or nickel, can be used as the metal thin film, a first polymer layer can be provided on the surface that will become the inner surface of the exterior body, a second polymer layer can be provided on the surface that will become the outer surface of the exterior body, and a film having a three-layer structure of the first polymer layer, the metal thin film on the first polymer layer, and the second polymer layer on the metal thin film can be used. The first polymer layer and the second polymer layer are preferably insulating synthetic resin films. Also, a thermoplastic resin can be used as the first polymer layer and the second polymer layer, and it is particularly preferable to use a thermoplastic resin for the first polymer layer.

[0188] The first polymer layer and the second polymer layer can be made of a material that inhibits reaction with the ionic liquid, such as a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, polyester, etc. As the polyamide, for example, nylon can be used.

[0189] In addition, in FIG. 2, as an example, the number of pairs of the facing positive electrode active material layers and the negative electrode active material layers is five, but of course the number of pairs of electrodes is not limited to five and may be more or less. When the number of electrode layers is large, a secondary battery having a larger capacity can be obtained. Also, when the number of electrode layers is small, a secondary battery that can be made thin and has excellent flexibility can be obtained.

[0190] In the above configuration, the exterior body 509 of the secondary battery can be deformed so that the minimum radius of curvature is, for example, 3 mm or more and 30 mm or less, more preferably 3 mm or more and 10 mm or less. The film that is the exterior body of the secondary battery is composed of one or two sheets, and in the case of a secondary battery with a laminated structure, the cross-sectional structure of the curved battery is a structure sandwiched between two curves of the film that is the exterior body.

[0191] [Example of how to make a secondary battery] Next, an example of a method for producing a secondary battery will be described.

[0192] First, the negative electrode 506, the separator 507, and the positive electrode 503 are laminated. FIG. 4A shows an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a positive electrode current collector 501, and a positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. The positive electrode 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter, referred to as a tab region). The negative electrode 506 has a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. The negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, a tab region. The area and shape of the tab regions of the positive electrode and the negative electrode are not limited to the example shown in FIG. 4A.

[0193] FIG. 4B shows a stack of negative electrodes 506, separators 507, and positive electrodes 503. Here, an example is shown in which five pairs of negative electrodes and four pairs of positive electrodes are used. Next, the tab regions of the positive electrodes 503 are joined together, and a positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For example, ultrasonic welding or the like may be used for the joining. Similarly, the tab regions of the negative electrodes 506 are joined together, and a negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0194] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are placed on the exterior body 509 .

[0195] Next, as shown in Fig. 4C, exterior body 509 is folded at the portion indicated by the dashed line. After that, the outer periphery of exterior body 509 is joined. For the joining, for example, thermocompression bonding or the like may be used. At this time, a region (hereinafter referred to as an inlet) that is not joined is provided in a part (or one side) of exterior body 509 so that electrolyte 508 can be poured in later.

[0196] Next, the electrolyte 508 (not shown) is introduced into the inside of the exterior body 509 through an inlet provided in the exterior body 509. For example, as shown in FIG. 5A, in the exterior body 509, a sealing portion 521 along the first side and a sealing portion 522 along the second side are sealed, and the third side is not sealed. Here, in the sealing portion 522, a bonding layer may be sandwiched between the positive electrode lead electrode 510 and the exterior body 509 and between the negative electrode lead electrode 511 and the exterior body 509, respectively, to seal the exterior body 509. Next, the electrolyte 508 is introduced through an opening located on the third side. Thereafter, as shown in FIG. 5B, the sealing portion 523 along the third side is sealed. The electrolyte 508 is preferably introduced under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is joined. In this manner, a laminated secondary battery 500 can be produced.

[0197] Next, aging after the secondary battery is produced will be described. It is preferable to perform aging after the secondary battery is produced. An example of aging conditions will be described below. First, charging is performed at a rate of 0.001C or more and 0.2C or less. The temperature may be, for example, room temperature or more and 50°C or less. Here, if the reaction potential of the positive electrode or negative electrode exceeds the range of the potential window of the electrolyte 508, the electrolyte may be decomposed by charging and discharging the secondary battery. If gas is generated by the decomposition of the electrolyte, if the gas accumulates in the cell, an area where the electrolyte cannot contact the electrode surface will be generated. In other words, the effective reaction area of ​​the electrode is reduced, which corresponds to an increase in effective resistance.

[0198] In addition, if the resistance becomes excessively high, the negative electrode potential will drop, causing lithium insertion into the graphite and lithium deposition on the graphite surface. This lithium deposition may lead to a decrease in capacity. For example, if a film or the like grows on the surface after lithium deposition, the lithium deposited on the surface cannot be re-eluted, and the amount of lithium that does not contribute to the capacity will increase. In addition, if the deposited lithium physically collapses and loses electrical continuity with the electrode, lithium that does not contribute to the capacity will also be generated. Therefore, it is preferable to remove the gas before the potential of the negative electrode reaches the lithium potential due to the rise in charging voltage.

[0199] After degassing, the battery may be held in a charged state at a temperature higher than room temperature, preferably 30° C. to 60° C., more preferably 35° C. to 50° C., for example, for 1 hour to 100 hours. During the initial charging, the electrolyte decomposed on the surface forms a coating on the graphite surface. Therefore, for example, by holding the battery at a temperature higher than room temperature after degassing, the formed coating may be densified.

[0200] [Example of stacking positive and negative electrodes and separators] Next, various examples of lamination of the positive electrode, the negative electrode and the separator are shown.

[0201] In the configuration shown in FIG. 6A, one separator 123 is folded back multiple times so as to be sandwiched between the positive electrode active material layer 122 and the negative electrode active material layer 126. In the configuration shown in FIG. 6A, the positive electrode active material layer 122 is provided on both sides or one side of the positive electrode current collector 121 in the positive electrode 111, and the negative electrode active material layer 126 is provided on both sides or one side of the negative electrode current collector 125 in the negative electrode 115. In the configuration shown in FIG. 6A, six pairs of the positive electrode active material layer 122 and the negative electrode active material layer 126 face each other with the separator 123 in between, and it is preferable that the separator 123 is folded back at least five times. In addition, the separator 123 may not only be provided so as to be sandwiched between the positive electrode active material layer 122 and the negative electrode active material layer 126, but may also be extended to bundle a plurality of positive electrodes 111 and negative electrodes 115 together.

[0202] Fig. 6D shows an example in which a plurality of electrode assemblies are covered with a wound separator. Fig. 6B is a cross-sectional view of a first electrode assembly 130, and Fig. 6C is a cross-sectional view of a second electrode assembly 131. Fig. 6D is a cross-sectional view taken along dashed dotted line A1-A2 in Fig. 1. Note that Fig. 6D shows only the first electrode assembly 130, the second electrode assembly 131, and the separator 123 for clarity.

[0203] As shown in Fig. 6B, in the first electrode assembly 130, a positive electrode 111a having a positive electrode active material layer 122 on both sides of a positive electrode collector 121, a separator 123, a negative electrode 115a having a negative electrode active material layer 126 on both sides of a negative electrode collector 125, a separator 123, and a positive electrode 111a having a positive electrode active material layer 122 on both sides of a positive electrode collector 121 are laminated in this order. Also, as shown in Fig. 6C, in the second electrode assembly 131, a negative electrode 115a having a negative electrode active material layer 126 on both sides of a negative electrode collector 125, a separator 123, a positive electrode 111a having a positive electrode active material layer 122 on both sides of a positive electrode collector 121, a separator 123, and a negative electrode 115a having a negative electrode active material layer 126 on both sides of a negative electrode collector 125 are laminated in this order.

[0204] As shown in Fig. 6D, the secondary battery 500 has a plurality of first electrode assemblies 130 and a plurality of second electrode assemblies 131. As further shown in Fig. 6D, the plurality of first electrode assemblies 130 and the plurality of second electrode assemblies 131 are covered by a wound separator 123.

[0205] [Secondary battery example 2] 7A includes a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked with the separator 933 sandwiched therebetween, and the laminated sheet is wound. Note that the negative electrode 931, the positive electrode 932, and the separator 933 may be stacked a plurality of times. The number of layers of the stack of the negative electrode 931, the positive electrode 932, and the separator 933 may be appropriately designed according to the required capacity and element volume.

[0206] As shown in Fig. 7B, a film 981 serving as an exterior body and a film 982 having a recess are bonded together by thermocompression or the like to form a space, and the above-mentioned wound body 950 is stored in the space, thereby producing a secondary battery 913 shown in Fig. 7C. The wound body 950 has terminals 951 and 952, and is impregnated with an electrolyte solution inside the film 981 and the film 982 having a recess. The terminals 951 and 952 are, for example, lead electrodes.

[0207] The film 981 and the film 982 having the recessed portion can be made of the same materials and have the same shapes as those of the exterior body 509 .

[0208] Although an example in which two films are used is shown in FIG. 7B and FIG. 7C, a space may be formed by folding one film, and the above-mentioned wound body 950 may be housed in the space.

[0209] 8 shows an example in which a prismatic case is used as the housing 930. For example, a prismatic can can be used as the housing 930. The housing 930 may also have a shape such as a cylinder. For example, the description of a battery can described later can be referred to for the can.

[0210] The wound body 950 is impregnated with the electrolyte inside the housing 930. The terminal 952 contacts the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like. Note that in FIG. 8, the housing 930 is shown separated for convenience, but in reality, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of a metal material (e.g., aluminum) or a resin material.

[0211] [Battery pack example 1] 9A and 9B are diagrams showing the external appearance of a battery pack. The battery pack has a circuit board 900 and a secondary battery 913. A label 910 is attached to the secondary battery 913. Furthermore, as shown in FIG. 9B, the secondary battery 913 has a terminal 951 and a terminal 952. The circuit board 900 is fixed with a sticker 915.

[0212] The circuit board 900 has a terminal 911 and a battery control circuit 912. The terminal 911 is connected to a terminal 951, a terminal 952, an antenna 914, and a battery control circuit 912 via the circuit board 900. Note that a plurality of terminals 911 may be provided, and each of the plurality of terminals 911 may serve as a control signal input terminal, a power supply terminal, or the like.

[0213] The battery control circuit 912 may be provided on the back surface of the circuit board 900. The antenna 914 is not limited to a coil shape, and may be, for example, a wire shape or a plate shape. In addition, an antenna such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, or a dielectric antenna may be used. Alternatively, the antenna 914 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. In other words, the antenna 914 may function as one of the two conductors of the capacitor. This allows power to be exchanged not only by electromagnetic fields and magnetic fields, but also by electric fields.

[0214] The battery pack has a layer 916 between the antenna 914 and the secondary battery 913. The layer 916 has a function of, for example, shielding an electromagnetic field caused by the secondary battery 913. The layer 916 can be made of, for example, a magnetic material.

[0215] The battery pack also preferably has a temperature sensor.

[0216] <Battery control circuit> The battery control circuit 912 can be used as a battery control circuit. The battery control circuit 912 preferably has a charge control circuit. The battery control circuit 912 also has a switch. The switch can be configured using, for example, a transistor.

[0217] A first transmission path that is connected to a terminal 951 of the secondary battery 913 and transmits power output from the secondary battery 913 is electrically connected to a terminal of a charge control circuit in the battery control circuit 912. A second transmission path that is connected to a terminal 952 of the secondary battery 913 is electrically connected to a switch provided in the battery control circuit 912. The switch has a function of cutting off the second transmission path. The switch controls the conductive and cut-off operations, and can also be called a switching means that switches between supply and cut-off.

[0218] When the battery control circuit 912 detects an abnormality such as a micro-short circuit, the second transmission path can be cut off by inputting a signal to the gate of a switch that cuts off the second transmission path. By cutting off the second transmission path, it is possible to stop the supply of current from the charger or to the mobile device in which the secondary battery 913 is mounted. In addition, by holding the signal voltage applied to the gate of the switch that cuts off the second transmission path in a memory circuit (including a transistor using an oxide semiconductor), it is possible to maintain the cutoff for a long period of time. Therefore, a highly safe charging control system can be provided.

[0219] When the secondary battery 913 is charged by supplying power from a charger, the secondary battery 913 enters a charging state, and the battery control circuit 912 monitors the behavior of the voltage, current, etc. at the electrodes 971 and 972, and if an abnormality is detected, the second transmission path is cut off and charging is stopped.

[0220] A charger can be, for example, a device that has an adapter to connect to an external power source, or a device that transmits power using a wireless signal. Note that a charger may also be built into an electronic device such as a mobile device.

[0221] <Example of temperature control> Next, an example of controlling the secondary battery of one embodiment of the present invention in accordance with the environmental temperature will be described. The temperature can be measured using a temperature sensor.

[0222] The secondary battery of one embodiment of the present invention can be repeatedly charged and discharged at an extremely high charging voltage. As will be described in the Examples below, the secondary battery of one embodiment of the present invention can be repeatedly operated stably at a higher charging voltage when the temperature is lower.

[0223] An example of controlling charging conditions in accordance with temperature in a secondary battery of one embodiment of the present invention will be described below.

[0224] When the temperature during charging is in a range of equal to or higher than a first temperature and lower than a second temperature, the upper limit voltage during charging is set to a first value, and when the temperature during charging is equal to or higher than a second temperature, the upper limit voltage during charging is set to a second value.

[0225] The first temperature is, for example, 5° C. or more and less than 15° C., and the second temperature is, for example, 25° C. or more and less than 55° C. Alternatively, the first temperature is, for example, 8° C. or more and less than 15° C., and the second temperature is, for example, 30° C. or more and less than 55° C.

[0226] The first value may be at least 0.02V higher than the second value, alternatively at least 0.04V higher, alternatively at least 0.06V higher, alternatively at least 0.08V higher, for example 0.05V.

[0227] The first value is 4.45V or more and 4.6V or less, more preferably 4.47V or more and less than 4.6V, even more preferably 4.47V or more and less than 4.55V, or 4.49V or more and less than 4.53V, for example, about 4.5V.

[0228] As described above, by controlling the charging conditions of the secondary battery, it is possible to suppress deterioration of the secondary battery and extend its life.

[0229] [Battery pack example 2] The structure of the battery pack is not limited to that shown in FIG.

[0230] For example, as shown in Figures 10A and 10B, an antenna may be provided on each of a pair of opposing surfaces of a secondary battery 913 shown in Figures 9A and 9B. Figure 10A is an external view showing one of the pair of surfaces, and Figure 10B is an external view showing the other of the pair of surfaces. Note that the description of the secondary battery shown in Figures 9A and 9B can be used as appropriate for the same parts as those of the secondary battery shown in Figures 8A and 8B.

[0231] 10A, an antenna 914 is provided on one of a pair of surfaces of a secondary battery 913 with a layer 916 sandwiched therebetween, and as shown in Fig. 10B, an antenna 918 is provided on the other of the pair of surfaces of the secondary battery 913 with a layer 917 sandwiched therebetween. The layer 917 has a function of, for example, being able to shield an electromagnetic field caused by the secondary battery 913. The layer 917 can be made of, for example, a magnetic material.

[0232] The above structure allows the sizes of both the antenna 914 and the antenna 918 to be increased. The antenna 918 has a function of performing data communication with, for example, an external device. For example, an antenna having a shape applicable to the antenna 914 can be applied to the antenna 918. As a communication method between the secondary battery and other devices via the antenna 918, a response method that can be used between the secondary battery and other devices, such as NFC (near field wireless communication), can be applied.

[0233] Alternatively, as shown in Fig. 10C, a display device 920 may be provided on the secondary battery 913 shown in Figs. 9A and 9B. The display device 920 is electrically connected to a terminal 911. Note that the label 910 does not need to be provided on the portion where the display device 920 is provided. Note that the description of the secondary battery shown in Figs. 9A and 9B can be appropriately applied to the same portions as those of the secondary battery shown in Figs. 9A and 9B.

[0234] For example, an image indicating whether charging is in progress, an image indicating the amount of stored power, etc. may be displayed on the display device 920. For example, electronic paper, a liquid crystal display device, an electroluminescence (EL) display device, etc. can be used as the display device 920. For example, the use of electronic paper can reduce the power consumption of the display device 920.

[0235] Alternatively, as shown in Fig. 10D, a sensor 921 may be provided in the secondary battery 913 shown in Fig. 9A and Fig. 9B. The sensor 921 is electrically connected to the terminal 911 via a terminal 922. Note that the description of the secondary battery shown in Fig. 9A and Fig. 9B can be appropriately applied to the same parts as those of the secondary battery shown in Fig. 9A and Fig. 9B.

[0236] The sensor 921 may have a function of measuring, for example, displacement, position, speed, acceleration, angular velocity, number of rotations, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared ray. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed (such as temperature) can be detected and stored in the memory in the battery control circuit 912.

[0237] Further, a structural example of the secondary battery 913 will be described with reference to FIGS. 11A to 11E.

[0238] [Various configuration examples] FIG. 11A shows a schematic top view of a bendable secondary battery 250. FIG. 11B, FIG. 11C, FIG. 11D, and FIG. 11E are schematic cross-sectional views taken along the lines C1-C2, C3-C4, A1-A2, and B1-B2 in FIG. 11A, respectively. The secondary battery 250 includes an exterior body 251 and an electrode laminate 210 housed inside the exterior body 251. The electrode laminate 210 has a structure in which at least a positive electrode 211a and a negative electrode 211b are laminated. A lead 212a electrically connected to the positive electrode 211a and a lead 212b electrically connected to the negative electrode 211b extend outside the exterior body 251. In addition to the positive electrode 211a and the negative electrode 211b, an electrolyte (not shown) is enclosed in the area surrounded by the exterior body 251. Although not shown in FIG. 11B etc., for example, a separator is disposed between the positive electrode 211a and the negative electrode 211b.

[0239] Next, exterior body 251 will be described with reference to FIGS. 11B, 11C, 11D, and 11E.

[0240] The exterior body 251 has a film-like shape and is folded in two to sandwich the positive electrode 211a and the negative electrode 211b. The exterior body 251 has a folded portion 261, a pair of sealing portions 262, and a sealing portion 263. The pair of sealing portions 262 are provided to sandwich the positive electrode 211a and the negative electrode 211b, and can also be called side seals. The sealing portion 263 has a portion overlapping the lead 212a and the lead 212b, and can also be called a top seal.

[0241] It is preferable that exterior body 251 has a corrugated shape in which ridge lines 271 and valley lines 272 are alternately arranged in the portions overlapping with positive electrode 211a and negative electrode 211b. In addition, it is preferable that seal portion 262 and seal portion 263 of exterior body 251 are flat.

[0242] Fig. 11B is a cross section taken at a portion overlapping with ridge line 271, and Fig. 11C is a cross section taken at a portion overlapping with valley line 272. Fig. 11B and Fig. 11C both correspond to cross sections in the width direction of secondary battery 250 and positive electrode 211a and negative electrode 211b.

[0243] Here, the distance between the end of the negative electrode 211b in the width direction, i.e., the end of the negative electrode 211b, and the seal portion 262 is defined as the distance La. When the secondary battery 250 is deformed, such as by bending, the positive electrode 211a and the negative electrode 211b are deformed so as to be displaced from each other in the length direction, as described below. At that time, if the distance La is too short, the exterior body 251 may be strongly rubbed against the positive electrode 211a and the negative electrode 211b, and the exterior body 251 may be damaged. In particular, if the metal film of the exterior body 251 is exposed, the metal film may be corroded by the electrolyte. Therefore, it is preferable to set the distance La as long as possible. On the other hand, if the distance La is made too large, the volume of the secondary battery 250 increases.

[0244] Moreover, it is preferable that the distance La between the positive electrode 211a and the negative electrode 211b and the seal portion 262 is increased as the total thickness of the stacked positive electrode 211a and negative electrode 211b is increased.

[0245] More specifically, when the total thickness of the laminated positive electrode 211a, negative electrode 211b, and separator 214 (not shown) is t, the distance La is preferably 0.8 to 3.0 times, more preferably 0.9 to 2.5 times, and even more preferably 1.0 to 2.0 times, of the thickness t. By setting the distance La in this range, a compact battery with high reliability against bending can be realized.

[0246] Furthermore, when the distance between the pair of seal portions 262 is distance Lb, it is preferable to set distance Lb sufficiently larger than the width of positive electrode 211a and negative electrode 211b (here, width Wb of negative electrode 211b). As a result, even if positive electrode 211a and negative electrode 211b come into contact with exterior body 251 when secondary battery 250 is repeatedly deformed, such as by bending, parts of positive electrode 211a and negative electrode 211b can be displaced in the width direction, so that rubbing between positive electrode 211a and negative electrode 211b and exterior body 251 can be effectively prevented.

[0247] For example, it is preferable that the difference between the distance Lb between the pair of seal portions 262 and the width Wb of the negative electrode 211b is 1.6 to 6.0 times, preferably 1.8 to 5.0 times, and more preferably 2.0 to 4.0 times the thickness t of the positive electrode 211a and the negative electrode 211b.

[0248] 11D is a cross section including lead 212a, and corresponds to a cross section in the longitudinal direction of secondary battery 250, positive electrode 211a, and negative electrode 211b. As shown in FIG. 11D, at bent portion 261, it is preferable to have space 273 between the longitudinal ends of positive electrode 211a and negative electrode 211b and exterior body 251. Lead 212a is joined to positive electrode 211a in region 215a.

[0249] Fig. 11E shows a schematic cross-sectional view of the bent secondary battery 250. Fig. 11E corresponds to the cross section taken along the cutting line B1-B2 in Fig. 11A.

[0250] When the secondary battery 250 is bent, a part of the exterior body 251 located on the outside of the bend is stretched, and another part located on the inside is deformed so as to contract. More specifically, the part located on the outside of the exterior body 251 is deformed so that the wave amplitude becomes smaller and the wave period becomes larger. On the other hand, the part located on the inside of the exterior body 251 is deformed so that the wave amplitude becomes larger and the wave period becomes smaller. In this way, the deformation of the exterior body 251 relieves the stress applied to the exterior body 251 due to bending, so that the material constituting the exterior body 251 itself does not need to expand or contract. As a result, the exterior body 251 is not damaged, and the secondary battery 250 can be bent with a small force.

[0251] 11E, when the secondary battery 250 is bent, the positive electrode 211a and the negative electrode 211b are displaced relative to each other. At this time, since one end of the multiple stacked positive electrodes 211a and negative electrodes 211b on the seal portion 263 side is fixed by the fixing member 217, the positive electrodes 211a and negative electrodes 211b are displaced such that the amount of displacement increases toward the bent portion 261. This relieves the stress applied to the positive electrodes 211a and negative electrodes 211b, and the positive electrodes 211a and negative electrodes 211b themselves do not need to expand or contract. As a result, the secondary battery 250 can be bent without damaging the positive electrodes 211a and negative electrodes 211b.

[0252] Furthermore, by providing space 273 between positive electrode 211a and negative electrode 211b and exterior body 251, positive electrode 211a and negative electrode 211b located on the inside when bent can be relatively displaced without coming into contact with exterior body 251.

[0253] The radius of curvature of a surface will be described with reference to Figures 12A, 12B, and 12C. In Figure 12A, in a plane 1701 obtained by cutting a curved surface 1700, a part of a curve 1702 included in the curved surface 1700 is approximated to an arc of a circle, the radius of the circle is set as a radius of curvature 1703, and the center of the circle is set as a center of curvature 1704. Figure 12B shows a top view of the curved surface 1700. Figure 12C shows a cross-sectional view of the curved surface 1700 cut by the plane 1701. When a curved surface is cut by a plane, the radius of curvature of the curve that appears in the cross-section will differ depending on the angle of the plane with respect to the curved surface and the cutting position, but in this specification and the like, the smallest radius of curvature is set as the radius of curvature of the surface.

[0254] When a secondary battery, which has two films as an exterior body and sandwiches electrodes, electrolyte, etc. 1805, is curved, the radius of curvature 1802 of the film 1801 on the side closer to the center of curvature 1800 of the secondary battery is smaller than the radius of curvature 1804 of the film 1803 on the side farther from the center of curvature 1800 (FIG. 13A). When the secondary battery is curved to have an arc-shaped cross section, a compressive stress is applied to the surface of the film closer to the center of curvature 1800, and a tensile stress is applied to the surface of the film farther from the center of curvature 1800 (FIG. 13B). If a pattern formed of recesses or protrusions is formed on the surface of the exterior body, the influence of distortion can be suppressed within an allowable range even if compressive stress or tensile stress is applied in this way. Therefore, the secondary battery can be deformed so that the minimum radius of curvature of the exterior body on the side closer to the center of curvature is, for example, 3 mm to 30 mm, more preferably 3 mm to 10 mm.

[0255] The cross-sectional shape of the secondary battery is not limited to a simple arc shape, and can be a shape that has a part of an arc, such as the shape shown in Fig. 13C, a wavy shape (Fig. 13D), an S-shape, etc. When the curved surface of the secondary battery has a shape with multiple centers of curvature, the curved surface with the smallest radius of curvature among the radii of curvature at each of the multiple centers of curvature can be deformed so that the minimum radius of curvature of the exterior body closer to the center of curvature of the two exterior bodies is, for example, 3 mm or more and 30 mm or less, more preferably 3 mm or more and 10 mm or less.

[0256] [Cylindrical secondary battery] An example of a cylindrical secondary battery will be described with reference to Fig. 14A. As shown in Fig. 14A, a cylindrical secondary battery 400 has a positive electrode cap (battery lid) 401 on the top surface, and a battery can (external can) 402 on the side and bottom surfaces. The positive electrode cap 401 and the battery can (external can) 402 are insulated by a gasket (insulating packing) 410.

[0257] Fig. 14B is a schematic diagram showing a cross section of a cylindrical secondary battery. The cylindrical secondary battery shown in Fig. 14B has a positive electrode cap (battery lid) 601 on the top surface, and a battery can (external can) 602 on the side and bottom surfaces. The positive electrode cap and battery can (external can) 602 are insulated by a gasket (insulating packing) 610.

[0258] Inside a hollow cylindrical battery can 602, a battery element is provided in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 sandwiched therebetween. Although not shown, the battery element is wound around a center pin. One end of the battery can 602 is closed and the other end is open. For the battery can 602, metals such as nickel, aluminum, and titanium that are resistant to corrosion by the electrolyte, or alloys of these metals and other metals (e.g., stainless steel, etc.) can be used. In addition, in order to prevent corrosion by the electrolyte, it is preferable to coat the battery can 602 with nickel, aluminum, or the like. Inside the battery can 602, the battery element in which the positive electrode, the negative electrode, and the separator are wound is sandwiched between a pair of opposing insulating plates 608 and 609. In addition, a nonaqueous electrolyte (not shown) is injected inside the battery can 602 in which the battery element is provided. The nonaqueous electrolyte can be the same as that of a coin-type secondary battery.

[0259] Since the positive and negative electrodes used in a cylindrical storage battery are wound, it is preferable to form an active material on both sides of the current collector. A positive electrode terminal (positive electrode current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collector lead) 607 is connected to the negative electrode 606. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of a metal material such as aluminum. The positive electrode terminal 603 is resistance-welded to a safety valve mechanism 613, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 613 is electrically connected to the positive electrode cap 601 via a PTC (Positive Temperature Coefficient) element 611. The safety valve mechanism 613 cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the rise in the internal pressure of the battery exceeds a predetermined threshold value. The PTC element 611 is a thermosensitive resistor whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current to prevent abnormal heat generation. Barium titanate (BaTiO3)-based semiconductor ceramics can be used for the PTC element.

[0260] 14C shows an example of a power storage system 415. The power storage system 415 has a plurality of secondary batteries 400. The positive electrode of each secondary battery is in contact with and electrically connected to a conductor 424 separated by an insulator 425. The conductor 424 is electrically connected to a control circuit 420 via a wiring 423. In addition, the negative electrode of each secondary battery is electrically connected to the control circuit 420 via a wiring 426. The above-mentioned battery control circuit 912 can be applied as the control circuit 420.

[0261] 14D shows an example of a power storage system 415. The power storage system 415 has a plurality of secondary batteries 400, and the plurality of secondary batteries 400 are sandwiched between a conductive plate 413 and a conductive plate 414. The plurality of secondary batteries 400 are electrically connected to the conductive plate 413 and the conductive plate 414 by wiring 416. The plurality of secondary batteries 400 may be connected in parallel, may be connected in series, or may be connected in parallel and then further connected in series. By configuring the power storage system 415 having a plurality of secondary batteries 400, it is possible to extract a large amount of power.

[0262] A plurality of secondary batteries 400 may be connected in parallel and then further connected in series.

[0263] A temperature control device may be provided between the multiple secondary batteries 400. When the secondary batteries 400 are overheated, they can be cooled by the temperature control device, and when the secondary batteries 400 are too cold, they can be heated by the temperature control device. Therefore, the performance of the power storage system 415 is less susceptible to the effect of the outside air temperature.

[0264] 14D, power storage system 415 is electrically connected to control circuit 420 via wiring 421 and wiring 422. Wiring 421 is electrically connected to the positive electrodes of multiple secondary batteries 400 via conductive plate 413, and wiring 422 is electrically connected to the negative electrodes of multiple secondary batteries 400 via conductive plate 414.

[0265] [Battery pack example 3] Next, an example of a power storage system of one embodiment of the present invention will be described with reference to FIG.

[0266] Fig. 15A is a diagram showing the appearance of secondary battery pack 531. Fig. 15B is a diagram explaining the configuration of secondary battery pack 531. Secondary battery pack 531 has circuit board 540 and secondary battery 513. Label 529 is attached to secondary battery 513. Circuit board 540 is fixed by sticker 515. Secondary battery pack 531 also has antenna 517.

[0267] 15B, for example, a secondary battery pack 531 has a control circuit 590 on a circuit board 540. The circuit board 540 is electrically connected to a terminal 514. The circuit board 540 is also electrically connected to an antenna 517, one 551 of a positive electrode lead and a negative electrode lead of a secondary battery 513, and the other 552 of a positive electrode lead and a negative electrode lead. The above-mentioned battery control circuit 912 can be applied to the control circuit 590.

[0268] 15C , a circuit system 590a may be provided on a circuit board 540, and a circuit system 590b may be electrically connected to the circuit board 540 via a terminal 514. For example, a part of a control circuit according to one embodiment of the present invention is provided in the circuit system 590a, and another part is provided in the circuit system 590b.

[0269] The antenna 517 is not limited to a coil shape, and may be, for example, a wire shape or a plate shape. In addition, antennas such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, and a dielectric antenna may be used. Alternatively, the antenna 517 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. In other words, the antenna 517 may function as one of the two conductors of a capacitor. This allows power to be exchanged not only by electromagnetic fields and magnetic fields, but also by electric fields.

[0270] The secondary battery pack 531 has a layer 519 between the antenna 517 and the secondary battery 513. The layer 519 has a function of, for example, shielding an electromagnetic field caused by the secondary battery 513. The layer 519 can be made of, for example, a magnetic material.

[0271] As the secondary battery 513, the various secondary batteries described above can be used.

[0272] This embodiment mode can be appropriately combined with the descriptions of other embodiment modes.

[0273] (Embodiment 2) In this embodiment, an example of a power storage system including a secondary battery of one embodiment of the present invention and a battery control circuit will be described.

[0274] Fig. 16A is a conceptual diagram of a power storage system in which a battery control circuit 912 formed on a flexible substrate, which is a flexible film, is mounted on a secondary battery 913. A circuit substrate 900 is formed using a flexible substrate. Figs. 16B, 16C, and 16D are diagrams for explaining a method for manufacturing the power storage system shown in Fig. 16A.

[0275] Fig. 16B shows a secondary battery 913. The secondary battery 913 has a terminal 951 and a terminal 952. Fig. 16C shows the circuit board 900 in an unfolded state.

[0276] As shown in FIG. 16D, the circuit board 900 is bent and wrapped around the secondary battery 913, thereby forming the power storage system shown in FIG. 16A.

[0277] The power storage system of one embodiment of the present invention includes a secondary battery 913 and a battery control circuit 912. The battery control circuit 912 includes a switch. The switch can be formed using a transistor, for example.

[0278] The power storage system of one embodiment of the present invention preferably includes a layer 916 and an antenna 914 formed over the circuit board 900. The layer 916 is, for example, an insulating sheet. The antenna 914 is electrically connected to, for example, a battery control circuit 912. The battery control circuit 912 includes, for example, a circuit for transmitting and receiving a signal from the antenna 914, such as a modulation circuit, a demodulation circuit, and the like.

[0279] A first transmission path that is connected to terminal 951 of secondary battery 913 and transmits power output from secondary battery 913 is electrically connected to a terminal of the charge control circuit via electrode 971. A second transmission path that is connected to terminal 952 of secondary battery 913 is connected to a switch that cuts off the second transmission path via electrode 972. The switch controls the conduction and cutoff operations and can also be called a switching means that switches between supply and cutoff.

[0280] The method of forming the battery control circuit 912 on the circuit board 900 involves forming the battery control circuit 912 on a semiconductor substrate, peeling it off using a peeling method, and then fixing it on the circuit board 900. A known technique can be used for the peeling method. Alternatively, the battery control circuit 912 may be formed on a semiconductor substrate, the back surface of the substrate may be polished, and then fixed on the circuit board 900. Alternatively, the battery control circuit 912 may be partially cut off using a laser beam, that is, laser cut, and then fixed on the circuit board 900. Alternatively, the battery control circuit 912 may be directly formed on the circuit board 900. Alternatively, the battery control circuit 912 formed on a glass substrate may be peeled off, and then fixed on the circuit board 900.

[0281] When the battery control circuit 912 detects an abnormality such as a micro-short circuit, the second transmission path can be cut off by inputting a signal to the gate of a switch that cuts off the second transmission path. By cutting off the second transmission path, it is possible to stop the supply of current from the charger or to an electronic device or the like connected to the battery control circuit 912. Furthermore, by holding the signal voltage applied to the gate of the switch that cuts off the second transmission path in a memory circuit (including a transistor using an oxide semiconductor), the cutoff can be maintained for a long period of time. Therefore, a highly safe power storage system can be provided.

[0282] When the secondary battery 913 is charged by supplying power from a charger, the secondary battery 913 enters a charging state, and the battery control circuit 912 monitors the behavior of the voltage, current, etc. at the electrodes 971 and 972, and if an abnormality is detected, the second transmission path is cut off and charging is stopped.

[0283] A charger can be, for example, a device that has an adapter to connect to an external power source, or a device that transmits power using a wireless signal. Note that a charger may also be built into an electronic device such as a mobile device.

[0284] This embodiment mode can be appropriately combined with the descriptions of other embodiment modes.

[0285] (Embodiment 3) In this embodiment, an example in which a secondary battery of one embodiment of the present invention is mounted on a vehicle will be described. Examples of the vehicle include an automobile, a motorcycle, a bicycle, and the like.

[0286] The secondary battery of one embodiment of the present invention has a high energy density. It also has a long life and excellent reliability. In addition, by using the secondary battery of one embodiment of the present invention in combination with a battery control circuit, the life of the secondary battery can be further extended in some cases, which is preferable. In addition, by using the secondary battery of one embodiment of the present invention in combination with a battery control circuit, the safety of electronic devices, vehicles, and the like in which the secondary battery is mounted can be improved.

[0287] An example of a power storage system in which a secondary battery of one embodiment of the present invention and a battery control circuit are combined and installed in a vehicle will be described below, but in the configuration described below, the power storage system installed in the vehicle may have a configuration that does not include the above-described battery control circuit. For example, only the secondary battery of one embodiment of the present invention may be applied to the vehicle described below.

[0288] By installing an energy storage system in a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs) can be realized.

[0289] 17A, 17B, and 17C illustrate an example of a vehicle using a power storage system according to one embodiment of the present invention. An automobile 8400 illustrated in FIG. 17A is an electric automobile using an electric motor as a power source for running. Alternatively, the automobile 8400 is a hybrid automobile in which an electric motor and an engine can be appropriately selected and used as a power source for running. By using one embodiment of the present invention, a vehicle with a long cruising distance can be realized. The automobile 8400 includes a power storage system. The power storage system not only drives an electric motor 8406 but also supplies power to a light-emitting device such as a headlight 8401 or a room light (not shown).

[0290] The power storage system can also supply power to display devices such as a speedometer and a tachometer included in the automobile 8400. The power storage system can also supply power to a navigation system included in the automobile 8400.

[0291] The automobile 8500 shown in FIG. 17B can be charged by receiving power supply from an external charging facility to the power storage system 8024 of the automobile 8500 by a plug-in method, a non-contact power supply method, or the like. FIG. 17B shows a state in which charging is being performed from a ground-mounted charging device 8021 to the power storage system 8024 mounted on the automobile 8500 via a cable 8022. When charging, the charging method and connector standards may be appropriately performed by a predetermined method such as CHAdeMO (registered trademark) or Combo. The charging device 8021 may be a charging station installed in a commercial facility, or may be a home power source. For example, the power storage system 8024 mounted on the automobile 8500 can be charged by an external power supply using plug-in technology. Charging can be performed by converting AC power to DC power via a conversion device such as an AC-DC converter.

[0292] Although not shown, a power receiving device may be mounted on a vehicle, and charging may be performed by supplying power contactlessly from a ground power transmitting device. In the case of this contactless power supply method, by incorporating a power transmitting device in a road or an exterior wall, charging may be performed not only while the vehicle is stopped but also while the vehicle is moving. This contactless power supply method may also be used to transmit and receive power between vehicles. Furthermore, a solar cell may be provided on the exterior of the vehicle, and the power storage system may be charged while the vehicle is stopped or moving. An electromagnetic induction method or a magnetic resonance method may be used for such contactless power supply.

[0293] 17C is an example of a two-wheeled vehicle using the power storage system of one embodiment of the present invention. A scooter 8600 shown in FIG 17C includes a power storage system 8602, a side mirror 8601, and a turn signal light 8603. The power storage system 8602 can supply electricity to the turn signal light 8603.

[0294] 17C, the power storage system 8602 can be stored in the under-seat storage 8604. The power storage system 8602 can be stored in the under-seat storage 8604 even if the under-seat storage 8604 is small.

[0295] 18A is an example of an electric bicycle using the power storage system of one embodiment of the present invention. The power storage system of one embodiment of the present invention can be applied to an electric bicycle 8700 shown in FIG.

[0296] The electric bicycle 8700 includes a power storage system 8702. The power storage system 8702 can supply electricity to a motor that assists a rider. The power storage system 8702 is portable, and is shown in a state removed from the bicycle in FIG. 18B. The power storage system 8702 includes a plurality of built-in storage batteries 8701 of the power storage system of one embodiment of the present invention, and the remaining battery charge and the like can be displayed on a display unit 8703. The power storage system 8702 also includes a control circuit 8704 of one embodiment of the present invention. The control circuit 8704 is electrically connected to the positive and negative electrodes of the storage batteries 8701. The battery control circuit described in the above embodiment can be used as the control circuit 8704.

[0297] This embodiment mode can be appropriately combined with the descriptions of other embodiment modes.

[0298] (Embodiment 4) In this embodiment, an example in which a secondary battery of one embodiment of the present invention is mounted on an electronic device will be described.

[0299] The secondary battery of one embodiment of the present invention has a high energy density. It also has a long life and excellent reliability. In addition, by using the secondary battery of one embodiment of the present invention in combination with a battery control circuit, the life of the secondary battery can be further extended in some cases, which is preferable. In addition, by using the secondary battery of one embodiment of the present invention in combination with a battery control circuit, the safety of electronic devices, vehicles, and the like in which the secondary battery is mounted can be improved.

[0300] An example of a power storage system in which a secondary battery of one embodiment of the present invention and a battery control circuit are combined and installed in an electronic device will be described below, but in the configuration described below, the power storage system implemented in the electronic device may have a configuration that does not include the above-described battery control circuit. For example, only the secondary battery of one embodiment of the present invention may be applied to the electronic device described below.

[0301] 19A and 19B show an example of a tablet terminal (including a clamshell terminal) that can be folded in two. The tablet terminal 9600 shown in FIG. 19A and FIG. 19B has a housing 9630a, a housing 9630b, a movable part 9640 that connects the housings 9630a and 9630b, a display part 9631, a display mode changeover switch 9626, a power switch 9627, a power saving mode changeover switch 9625, a fastener 9629, and an operation switch 9628. By using a flexible panel for the display part 9631, a tablet terminal having a wider display part can be obtained. FIG. 19A shows the tablet terminal 9600 in an open state, and FIG. 19B shows the tablet terminal 9600 in a closed state.

[0302] The tablet terminal 9600 further includes a power storage unit 9635 inside the housing 9630a and the housing 9630b. The power storage unit 9635 passes through the movable portion 9640 and is provided across the housings 9630a and 9630b.

[0303] A part of the display portion 9631 can be a touch panel area, and data can be input by touching the displayed operation keys. Also, keyboard buttons can be displayed on the display portion 9631 by touching a position on the touch panel where a keyboard display switching button is displayed with a finger or a stylus.

[0304] Furthermore, the display mode changeover switch 9626 can change the display orientation, such as portrait or landscape, and can select black and white or color display. The power saving mode changeover switch 9625 can optimize the display brightness according to the amount of external light during use detected by an optical sensor built into the tablet terminal 9600. The tablet terminal may be equipped with not only an optical sensor, but also other detection devices such as a gyro, an acceleration sensor, or other sensors that detect tilt.

[0305] 19B shows a tablet terminal in a closed state, which includes a housing 9630, a solar cell 9633, and the power storage system of one embodiment of the present invention. The power storage system includes a control circuit 9634 and a power storage unit 9635. The battery control circuit described in the above embodiment can be used for the control circuit 9634.

[0306] Note that the tablet terminal 9600 can be folded in half, so that the housing 9630a and the housing 9630b can be folded together when not in use. By folding, the display portion 9631 can be protected, thereby improving durability of the tablet terminal 9600.

[0307] In addition, the tablet terminal shown in Figures 19A and 19B can have a function to display various information (still images, videos, text images, etc.), a function to display a calendar, date or time on the display unit, a touch input function to perform touch input operations or edit information displayed on the display unit, and a function to control processing using various software (programs), etc.

[0308] A solar cell 9633 attached to the surface of the tablet terminal can supply power to a touch panel, a display unit, a video signal processor, or the like. Note that the solar cell 9633 can be provided on one or both sides of the housing 9630, and a configuration can be adopted in which the power storage unit 9635 can be efficiently charged.

[0309] 19A and 19B, a configuration in which the control circuit using the battery control circuit described in the above embodiment is applied to a foldable tablet terminal is described; however, other configurations may be used. For example, as illustrated in FIG. 19C, the present invention may be applied to a notebook personal computer that is a clamshell terminal. FIG. 19C illustrates a notebook personal computer 9601 that includes a display unit 9631 in a housing 9630a and a keyboard unit 9650 in a housing 9630b. The notebook personal computer 9601 includes a control circuit 9634 described in FIG. 19A and FIG. 19B and a power storage unit 9635. The control circuit 9634 may be the battery control circuit described in the above embodiment.

[0310] FIG. 20 illustrates an example of another electronic device. In FIG. 20, a display device 8000 is an example of an electronic device in which the power storage system of one embodiment of the present invention is implemented. Specifically, the display device 8000 corresponds to a display device for receiving TV broadcasts and includes a housing 8001, a display unit 8002, a speaker unit 8003, a secondary battery 8004, and the like. A detection system according to one embodiment of the present invention is provided inside the housing 8001. The display device 8000 can receive power from a commercial power source or can use power stored in the secondary battery 8004.

[0311] The display unit 8002 can be a liquid crystal display device, a light-emitting device having a light-emitting element such as an organic EL element in each pixel, an electrophoretic display device, a semiconductor display device such as a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), or an FED (Field Emission Display).

[0312] The voice input device 8005 also uses a secondary battery. The voice input device 8005 has the power storage system described in the above embodiment. The voice input device 8005 has a plurality of sensors including a microphone (optical sensor, temperature sensor, humidity sensor, air pressure sensor, illuminance sensor, motion sensor, and the like) in addition to wireless communication elements, and can perform power control of other devices, such as the display device 8000, or light adjustment of the lighting device 8100, in response to verbal commands from the user. The voice input device 8005 can operate peripheral devices by voice, and can serve as a substitute for a manual remote control.

[0313] In addition, the voice input device 8005 has wheels or mechanical movement means, and moves in the direction in which the user's voice can be heard, accurately picking up commands using a built-in microphone and displaying the contents on the display unit 8008, or allowing touch input operations to be performed on the display unit 8008.

[0314] The voice input device 8005 can also function as a charging dock for a mobile information terminal 8009 such as a smartphone. The mobile information terminal 8009 and the voice input device 8005 can exchange power by wire or wirelessly. The mobile information terminal 8009 does not need to be carried around indoors, and it is desirable to ensure the required capacity while avoiding deterioration due to a load on the secondary battery, so that the voice input device 8005 can perform management and maintenance of the secondary battery. In addition, since the voice input device 8005 has a speaker 8007 and a microphone, it is possible to have a hands-free conversation even when the mobile information terminal 8009 is charging. In addition, if the capacity of the secondary battery of the voice input device 8005 decreases, it is sufficient to move in the direction of the arrow and charge it wirelessly from a charging module 8010 connected to an external power source.

[0315] The voice input device 8005 may be placed on a stand. The voice input device 8005 may be provided with wheels or a mechanical moving means so that it can be moved to a desired position, or the voice input device 8005 may be fixed to a desired position, for example, on a floor, without being provided with a stand or wheels.

[0316] The display device includes all display devices for displaying information, such as display devices for receiving TV broadcasts, display devices for personal computers, display devices for advertisements, and the like.

[0317] 20, a stationary lighting device 8100 is an example of an electronic device using a secondary battery 8103 controlled by a microprocessor (including APS) that controls charging. Specifically, the lighting device 8100 has a housing 8101, a light source 8102, a secondary battery 8103, and the like. FIG. 20 illustrates a case in which the secondary battery 8103 is provided inside a ceiling 8104 on which the housing 8101 and the light source 8102 are installed, but the secondary battery 8103 may be provided inside the housing 8101. The lighting device 8100 can receive power from a commercial power source, and can also use power stored in the secondary battery 8103.

[0318] Although Figure 20 shows an example of a stationary lighting device 8100 installed on a ceiling 8104, the secondary battery 8103 can also be used in a stationary lighting device installed on something other than the ceiling 8104, such as a side wall 8105, a floor 8106, or a window 8107, or can also be used in a table-top lighting device, etc.

[0319] An artificial light source that artificially obtains light using electric power can be used as the light source 8102. Specifically, examples of the artificial light source include discharge lamps such as incandescent lamps and fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements.

[0320] In FIG. 20, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is an example of an electronic device using a secondary battery 8203. Specifically, the indoor unit 8200 has a housing 8201, an air outlet 8202, a secondary battery 8203, and the like. FIG. 20 illustrates an example in which the secondary battery 8203 is provided in the indoor unit 8200, but the secondary battery 8203 may be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power from a commercial power source, or can use power stored in the secondary battery 8203.

[0321] 20, an electric refrigerator-freezer 8300 is an example of an electronic device using a secondary battery 8304. Specifically, the electric refrigerator-freezer 8300 has a housing 8301, a refrigerator door 8302, a freezer door 8303, a secondary battery 8304, and the like. In FIG. 20, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator-freezer 8300 can receive power from a commercial power source, and can also use power stored in the secondary battery 8304.

[0322] Also, by storing power in the secondary battery during time periods when electronic devices are not used, particularly during time periods when the ratio of the amount of power actually used to the total amount of power that can be supplied by the commercial power source (called the power usage rate) is low, it is possible to prevent the power usage rate from increasing outside of the above time periods. For example, in the case of an electric refrigerator-freezer 8300, power is stored in the secondary battery 8304 during the night when the temperature is low and the refrigerator door 8302 and the freezer door 8303 are not opened or closed. Then, during the daytime when the temperature is high and the refrigerator door 8302 and the freezer door 8303 are opened and closed, the secondary battery 8304 is used as an auxiliary power source, thereby making it possible to keep the daytime power usage rate low.

[0323] In addition to the electronic devices described above, the secondary battery can be mounted on any electronic device. According to one embodiment of the present invention, the cycle characteristics of the secondary battery are improved. Therefore, by mounting a microprocessor (including an APS) that controls charging, which is one embodiment of the present invention, on the electronic device described in this embodiment, the electronic device can have a longer life. This embodiment can be implemented in appropriate combination with other embodiments.

[0324] 21A to 21G show examples of electronic devices to which the power storage system of one embodiment of the present invention is applied. Examples of electronic devices to which the power storage system of one embodiment of the present invention is applied include television devices (also referred to as televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also referred to as mobile phones or mobile phone devices), portable game machines, personal digital assistants, audio players, and large game machines such as pachinko machines.

[0325] 21A illustrates an example of a mobile phone. The mobile phone 7400 includes a display portion 7402 built into a housing 7401, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like. Note that the mobile phone 7400 includes the power storage system of one embodiment of the present invention. The power storage system of one embodiment of the present invention includes, for example, a storage battery 7407 and the battery control circuit described in the above embodiment.

[0326] FIG. 21B shows a state in which the mobile phone 7400 is bent. When the mobile phone 7400 is deformed by an external force and bent as a whole, the storage battery 7407 provided therein may also be bent. In such a case, it is preferable to use a flexible storage battery as the storage battery 7407. FIG. 21C shows a bent state of the flexible storage battery. A control circuit 7408 is electrically connected to the storage battery. The battery control circuit described in the above embodiment can be used as the control circuit 7408.

[0327] In addition, a storage battery having a flexible shape can be installed along the curved surfaces of the inner or outer walls of a house or building, or the interior or exterior of an automobile.

[0328] 21D illustrates an example of a bangle-type display device. A portable display device 7100 includes a housing 7101, a display portion 7102, operation buttons 7103, and a power storage system of one embodiment of the present invention. The power storage system of one embodiment of the present invention includes, for example, a storage battery 7104 and the battery control circuit described in the above embodiment.

[0329] 21E shows an example of a wristwatch-type portable information terminal 7200. A portable information terminal 7200 includes a housing 7201, a display portion 7202, a band 7203, a buckle 7204, operation buttons 7205, an input / output terminal 7206, and the like.

[0330] The portable information terminal 7200 can execute various applications such as mobile telephone, e-mail, document browsing and creation, music playback, Internet communication, and computer games.

[0331] The display surface of the display portion 7202 is curved, and display can be performed along the curved display surface. The display portion 7202 is also provided with a touch sensor, and can be operated by touching the screen with a finger, a stylus, or the like. For example, an application can be started by touching an icon 7207 displayed on the display portion 7202.

[0332] The operation button 7205 can have various functions, such as time setting, power on / off operation, wireless communication on / off operation, silent mode activation / cancellation, power saving mode activation / cancellation, etc. For example, the function of the operation button 7205 can be freely set by an operating system built into the mobile information terminal 7200.

[0333] The mobile information terminal 7200 can also perform short-distance wireless communication according to a communication standard. For example, the mobile information terminal 7200 can communicate with a wireless headset to enable hands-free calling.

[0334] The portable information terminal 7200 also includes an input / output terminal 7206, and can directly exchange data with other information terminals via a connector. Charging can also be performed via the input / output terminal 7206. Note that charging may be performed by wireless power supply without using the input / output terminal 7206.

[0335] The portable information terminal 7200 includes the power storage system of one embodiment of the present invention. The power storage system includes a storage battery and the battery control circuit described in the above embodiment.

[0336] The portable information terminal 7200 preferably has a sensor. For example, it is preferable to mount a human body sensor such as a fingerprint sensor, a pulse sensor, or a body temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, or the like, as the sensor.

[0337] 21F illustrates an example of an armband-type display device. The display device 7300 includes a display portion 7304 and a secondary battery of one embodiment of the present invention. The display device 7300 can also include a touch sensor in the display portion 7304 and can function as a portable information terminal.

[0338] The display surface of the display portion 7304 is curved, and display can be performed along the curved display surface. In addition, the display device 7300 can change the display state by short-range wireless communication according to a communication standard.

[0339] The display device 7300 also includes an input / output terminal, and can directly exchange data with other information terminals via a connector. Charging can also be performed via the input / output terminal. Note that charging may be performed by wireless power supply without using the input / output terminal.

[0340] By using the secondary battery of one embodiment of the present invention as a secondary battery in daily electronic devices, products that are lightweight and have a long life can be provided. For example, daily electronic devices include electric toothbrushes, electric shavers, and electric beauty devices. For the secondary battery of these products, a stick-shaped secondary battery that is small, lightweight, and has a large capacity is desired in consideration of ease of holding by users.

[0341] FIG. 21G is a perspective view of a device also called a tobacco-receiving smoking device (electronic cigarette). In FIG. 21G, the electronic cigarette 7500 is composed of an atomizer 7501 including a heating element, a secondary battery 7504 that supplies power to the atomizer, and a cartridge 7502 including a liquid supply bottle, a sensor, and the like. To enhance safety, a protection circuit that prevents overcharging and overdischarging of the secondary battery 7504 may be electrically connected to the secondary battery 7504. The secondary battery 7504 shown in FIG. 21G has an external terminal so that it can be connected to a charging device. Since the secondary battery 7504 is the tip part when held, it is desirable that the total length is short and the weight is light. Since the secondary battery of one embodiment of the present invention has a high capacity and good cycle characteristics, a small and lightweight electronic cigarette 7500 that can be used for a long period of time can be provided.

[0342] Next, an example of an electronic device including a battery control circuit of one embodiment of the present invention will be described with reference to FIG.

[0343] The robot 7000 includes a secondary battery, an illuminance sensor, a microphone, a camera, a speaker, a display, various sensors (infrared sensors, ultrasonic sensors, acceleration sensors, piezoelectric sensors, optical sensors, gyro sensors, etc.), a moving mechanism, etc. The power storage system including the battery control circuit of one embodiment of the present invention can be applied to the secondary battery of the robot 7000 to control and protect the secondary battery, etc.

[0344] The microphone has a function of detecting acoustic signals such as the user's voice and environmental sounds. The speaker has a function of emitting audio signals such as voice and warning sounds. The robot 7000 can analyze the audio signal input via the microphone and emit the necessary audio signal from the speaker. The robot 7000 can communicate with the user using the microphone and the speaker.

[0345] The camera has a function of capturing an image of the surroundings of the robot 7000. The robot 7000 also has a function of moving using a moving mechanism. The robot 7000 can capture an image of the surroundings using the camera and detect the presence or absence of an obstacle when moving by analyzing the image.

[0346] The flying object 7120 has propellers, a camera, a secondary battery, etc., and has the ability to fly autonomously.

[0347] Furthermore, by applying a power storage system in which a battery control circuit of one embodiment of the present invention is mounted to a secondary battery of the flying object 7120, the secondary battery can be controlled and protected in addition to being lightweight.

[0348] The cleaning robot 7140 has a secondary battery, a display disposed on its upper surface, a plurality of cameras disposed on its side surface, a brush, operation buttons, various sensors, and the like. Although not illustrated, the cleaning robot 7140 is also provided with tires, a suction port, and the like. The cleaning robot 7140 can move on its own, detect dust, and suck up the dust from a suction port disposed on its lower surface. By using a power storage system equipped with a battery control circuit of one embodiment of the present invention that is electrically connected to the secondary battery of the cleaning robot 7140, the number of components used can be reduced and an abnormality such as a micro-short circuit in the secondary battery can be detected.

[0349] An electric vehicle 7160 is shown as an example of a moving object. The electric vehicle 7160 includes a secondary battery, tires, brakes, a steering device, a camera, and the like. By using a power storage system equipped with a battery control circuit of one embodiment of the present invention connected to a secondary battery of the electric vehicle 7160, the number of components used can be reduced and abnormalities such as a micro-short circuit in the secondary battery can be detected.

[0350] In the above description, an electric vehicle is described as an example of a moving object, but the moving object is not limited to an electric vehicle. For example, moving objects include trains, monorails, ships, and flying objects (helicopters, unmanned aerial vehicles (drones), airplanes, and rockets). By applying a power storage system equipped with a battery control circuit according to one embodiment of the present invention that is electrically connected to a secondary battery of these moving objects, the number of components used can be reduced and abnormalities such as a micro-short circuit in the secondary battery can be detected.

[0351] A secondary battery including a battery control circuit according to one embodiment of the present invention can be incorporated in a smartphone 7210, a PC (personal computer) 7220, a game console 7240, or the like.

[0352] The smartphone 7210 is an example of a portable information terminal. The smartphone 7210 has a microphone, a camera, a speaker, various sensors, and a display unit. These peripheral devices are controlled by a charging control circuit. By using a power storage system including a battery control circuit of one embodiment of the present invention that is electrically connected to a secondary battery of the smartphone 7210, the number of components used can be reduced and the secondary battery can be controlled and protected, thereby improving safety.

[0353] The PC7220 is an example of a notebook PC. By applying a power storage system including a battery control circuit of one embodiment of the present invention that is electrically connected to a secondary battery of the notebook PC, the number of components used can be reduced, and the secondary battery can be controlled and protected, thereby improving safety.

[0354] The game console 7240 is an example of a portable game console. The game console 7260 is an example of a home-use stationary game console. A controller 7262 is connected to the game console 7260 wirelessly or via a wire. By applying a power storage system including a battery control circuit of one embodiment of the present invention to the controller 7262, the number of components used can be reduced and the secondary battery can be controlled and protected, thereby improving safety.

[0355] Fig. 23A shows an example of a wearable device. The wearable device uses a secondary battery as a power source. In order to increase water resistance in daily use or outdoor use, a wearable device that can be charged wirelessly as well as by wire with an exposed connector is desired.

[0356] For example, it can be mounted on a glasses-type device 490 as shown in Fig. 23A. Glasses-type device 490 has a frame 490a and a display unit 490b. By mounting a secondary battery on the temples of curved frame 490a, glasses-type device 490 can be made lightweight, well-balanced in weight, and capable of long continuous use.

[0357] Also, it can be mounted on a headset type device 491. Headset type device 491 has at least a microphone unit 491a, a flexible pipe 491b, and an earphone unit 491c. A secondary battery can be provided in flexible pipe 491b or in earphone unit 491c.

[0358] Also, it can be mounted on a device 402 that can be directly attached to the body. A secondary battery 402b can be provided inside a thin housing 402a of the device 402.

[0359] Moreover, it can be mounted on a device 403 that can be attached to clothing. A secondary battery 403b can be provided inside a thin housing 403a of the device 403.

[0360] Also, it can be mounted on a belt type device 406. The belt type device 406 has a belt part 406a and a wireless power supply receiving part 406b, and a secondary battery can be mounted inside the belt part 406a.

[0361] Moreover, it can be mounted on a wristwatch type device 405. The wristwatch type device 405 has a display unit 405a and a belt unit 405b, and a secondary battery can be provided in the display unit 405a or the belt unit 405b.

[0362] Display unit 405a can display not only the time, but also various other information such as incoming e-mails and phone calls.

[0363] In addition, since the wristwatch type device 405 is a wearable device that is directly wrapped around the arm, it may be equipped with sensors that measure the user's pulse, blood pressure, etc. Data on the user's amount of exercise and health can be accumulated and used to maintain health.

[0364] The wristwatch type device 405 shown in FIG. 23A will be described in detail below.

[0365] FIG. 23B shows a perspective view of wristwatch type device 405 removed from the wrist.

[0366] A side view is shown in Fig. 23C. Fig. 23C shows that secondary battery 913 is built in. Secondary battery 913 is provided at a position overlapping with display unit 405a, and is small and lightweight.

[0367] Moreover, it is preferable that the wristwatch type device 405 has a battery control circuit therein that is electrically connected to the secondary battery 913 .

[0368] This embodiment mode can be appropriately combined with the descriptions of other embodiment modes.

[0369] (Additional Notes Regarding the Description of the Present Specification, etc.) The above embodiment and each configuration in the embodiment will be described below with additional notes.

[0370] The configurations shown in each embodiment can be combined with the configurations shown in other embodiments as appropriate to form one aspect of the present invention. In addition, when multiple configuration examples are shown in one embodiment, the configuration examples can be combined as appropriate.

[0371] In addition, the content (or a part of the content) described in one embodiment can be applied to, combined with, or replaced by another content (or a part of the content) described in that embodiment, and / or the content (or a part of the content) described in one or more other embodiments.

[0372] The contents described in the embodiments refer to contents described in each embodiment using various figures or contents described using text in the specification.

[0373] In addition, a figure (or a part thereof) described in one embodiment can be combined with another part of that figure, with another figure (or a part thereof) described in that embodiment, and / or with a figure (or a part thereof) described in one or more other embodiments to form even more figures.

[0374] In addition, in the present specification and the like, in the block diagrams, the components are classified by function and shown as mutually independent blocks. However, in actual circuits and the like, it is difficult to separate the components by function, and there may be cases where one circuit is involved in multiple functions, or where one function is involved across multiple circuits. Therefore, the blocks in the block diagrams are not limited to the components described in the specification, and may be rephrased appropriately according to the situation.

[0375] In addition, in the drawings, the size, layer thickness, or region are shown at an arbitrary size for convenience of explanation. Therefore, they are not necessarily limited to the scale. Note that the drawings are shown diagrammatically for clarity, and are not limited to the shapes or values ​​shown in the drawings. For example, it is possible to include variations in signals, voltages, or currents due to noise, or variations in signals, voltages, or currents due to timing deviations.

[0376] In this specification and the like, when describing the connection relationship of a transistor, the term "one of the source or drain" (or first electrode or first terminal) is used, and the other of the source and drain is used as "the other of the source or drain" (or second electrode or second terminal). This is because the source and drain of a transistor vary depending on the structure or operating conditions of the transistor. Note that the source and drain of a transistor can be appropriately referred to as source (drain) terminal, source (drain) electrode, etc. depending on the situation.

[0377] In addition, the terms "electrode" and "wiring" used in this specification and the like do not limit the functionality of these components. For example, an "electrode" may be used as part of a "wiring", and vice versa. Furthermore, the terms "electrode" and "wiring" include cases where multiple "electrodes" or "wirings" are formed integrally.

[0378] In addition, in this specification and the like, the terms voltage and potential can be interchanged as appropriate. Voltage is a potential difference from a reference potential, and if the reference potential is a ground voltage, for example, voltage can be interchanged as potential. Ground potential does not necessarily mean 0V. Note that potential is relative, and the potential applied to wiring, etc. may be changed depending on the reference potential.

[0379] In this specification and the like, the terms "film" and "layer" can be interchanged depending on the circumstances. For example, the term "conductive layer" can be changed to the term "conductive film". Or, for example, the term "insulating film" can be changed to the term "insulating layer".

[0380] In this specification, a switch refers to a device that has a function of controlling whether a current flows or not by being in a conductive state (on state) or a non-conductive state (off state), or a device that has a function of selecting and switching a path for a current to flow.

[0381] In this specification, the channel length refers to, for example, in a top view of a transistor, a region where a semiconductor (or a portion in the semiconductor through which current flows when the transistor is on) and a gate overlap, or a distance between the source and drain in a region where a channel is formed.

[0382] In this specification, the channel width refers to, for example, the length of the region where a semiconductor (or the portion in the semiconductor through which current flows when the transistor is on) and a gate electrode overlap, or the length of the portion where a source and a drain face each other in a region in which a channel is formed.

[0383] In this specification, "A and B are connected" includes not only a direct connection between A and B, but also an electrical connection between A and B. Here, "A and B are electrically connected" means that an object having some electrical effect exists between A and B, allowing transmission and reception of electrical signals between A and B. EXAMPLES

[0384] In this example, a manufacturing method of a secondary battery of one embodiment of the present invention and characteristics of the manufactured secondary battery will be described.

[0385] [Preparation of positive electrode active material] A positive electrode active material was prepared.

[0386] First, a first mixture containing magnesium and fluorine was prepared. LiF and MgF2 were weighed out so that the molar ratio of LiF:MgF2 was 1:3, and acetone was added as a solvent to wet mix and grind. Mixing and grinding were performed in a ball mill using zirconia balls at 400 rpm for 12 hours. The material after the treatment was collected and used as the first mixture.

[0387] Next, lithium cobalt oxide was prepared as a composite oxide containing lithium and cobalt. More specifically, Cellseed C-10N manufactured by Nippon Chemical Industry Co., Ltd. was prepared.

[0388] Next, the magnesium atom weight of the first mixture was weighed out to be 0.5 atomic % relative to the molecular weight of lithium cobalt oxide, and then mixed in a dry state. The mixing was performed in a ball mill using zirconia balls at 150 rpm for 1 hour. The material after the processing was collected and used as the second mixture.

[0389] Next, the second mixture was placed in an alumina crucible and annealed in a muffle furnace in an oxygen atmosphere at 850°C for 60 hours. The alumina crucible was covered during annealing. The oxygen flow rate was 10 L / min. The temperature was increased at 200°C / hr, and decreased over 10 hours or more. The material after the heat treatment was used as the positive electrode active material.

[0390] [Preparation of positive electrode] Next, a positive electrode was prepared using the positive electrode active material prepared above. The positive electrode active material prepared above, acetylene black (AB), and polyvinylidene fluoride (PVDF) were mixed in a ratio of positive electrode active material:AB:PVDF=95:3:2 (weight ratio), and a slurry was prepared using NMP as a solvent. The prepared slurry was applied to a current collector, and the solvent was volatilized. Thereafter, a press of 179 kN / m was performed at 120°C, and then a press of 1249 kN / m was performed to form a positive electrode active material layer on the current collector, and a positive electrode P1 was prepared. The amount of the positive electrode active material carried by the positive electrode P1 was changed depending on the battery cell used. An aluminum foil with a thickness of 20 μm was used as the current collector. The positive electrode active material layer was provided on one side of the current collector.

[0391] [Preparation of negative electrode] A negative electrode was prepared using graphite as the negative electrode active material.

[0392] Two types of graphite were used to fabricate negative electrodes. The first type had a specific surface area of ​​6.3 m 2 Spheroidized natural graphite with a specific surface area of ​​1.5 m2 / g and an average particle size of 15 μm was used, and mixed with CMC-Na and SBR in a ratio of graphite:CMC-Na:SBR=97:1.5:1.5 (weight ratio). A slurry was prepared using water as a solvent. 2 / g MCMB graphite was mixed with a conductive additive, CMC-Na, and SBR in a weight ratio of graphite:conductive additive:CMC-Na:SBR=96:1:1:2, and a slurry was prepared using water as a solvent.

[0393] The polymerization degree of the CMC-Na used was 600 to 800, and the viscosity of the aqueous solution when used as a 1 weight% aqueous solution was in the range of 300 mPa·s to 500 mPa·s. In addition, vapor-grown carbon fiber VGCF (registered trademark)-H (manufactured by Showa Denko K.K., fiber diameter 150 nm, specific surface area 13 m) was used as a conductive additive. 2 / g) was used.

[0394] Each of the slurries was applied to a current collector and dried to form a negative electrode active material layer on the current collector. A copper foil with a thickness of 18 μm was used as the current collector. The negative electrode active material layer was provided on both sides of the current collector.

[0395] The negative electrode using the first type of graphite is called negative electrode N1, and the negative electrode using the second type of graphite is called negative electrode N2. The amounts of negative electrode active material carried by negative electrode N1 and negative electrode N2 were changed depending on the battery cell used.

[0396] [Preparation of secondary battery] Using the positive electrode and negative electrode prepared above, a secondary battery was prepared using a film as an exterior body.

[0397] The separator used was cellulose with a thickness of 50 μm.

[0398] The positive electrode, separator, negative electrode, separator, and positive electrode were stacked in this order. The two positive electrodes were arranged so that the positive electrode active material on one side of the current collector faced the negative electrode active material with the separator in between.

[0399] Leads were attached to the positive and negative electrodes, respectively.

[0400] The laminate obtained by laminating the positive electrode, the negative electrode, and the separator was sandwiched between an exterior body folded in half, and the laminate was arranged so that one end of the lead was exposed to the outside of the exterior body. Next, one side of the exterior body was left as an open portion, and the other sides were sealed.

[0401] A film in which a polypropylene layer, an acid-modified polypropylene layer, an aluminum layer, and a nylon layer were laminated in this order was used as the film to be used as the exterior body. The thickness of the film was about 110 μm. The film to be used as the exterior body was folded so that the nylon layer was disposed on the surface to be disposed on the outside of the exterior body, and the polypropylene layer was disposed on the surface to be disposed on the inside of the exterior body. The thickness of the aluminum layer was about 40 μm, the thickness of the nylon layer was about 25 μm, and the total thickness of the polypropylene layer and the acid-modified polypropylene layer was about 45 μm.

[0402] Next, in an argon gas atmosphere, an electrolyte was injected from the side that was left as an open portion.

[0403] A total of five types of electrolyte solutions (electrolytes Sol_1, Sol_2, Sol_3, Sol_4 and Sol_5) were prepared, and one of the electrolyte solutions was used in each secondary battery.

[0404] The electrolytes Sol_1 and Sol_2 are explained below. EMI-FSA shown in structural formula (G11) was used as the solvent. In electrolyte Sol_1, LiFSA (lithium bis(fluorosulfonyl)amide) was used as the electrolyte, and the concentration of the electrolyte in the electrolyte was 2.15 mol / L. In electrolyte Sol_2, LiTFSA (lithium bis(trifluoromethanesulfonyl)amide) was used as the electrolyte, and the concentration of the electrolyte in the electrolyte was 1.50 mol / L.

[0405] [ka]

[0406] The electrolyte solution Sol_3 will be described. BMI-FSA shown in structural formula (G12) was used as the solvent. LiFSA (lithium bis(fluorosulfonyl)amide) was used as the electrolyte. The concentration of the electrolyte in the electrolyte solution was 1.93 mol / L.

[0407] [ka]

[0408] The electrolyte solution Sol_4 will be described. P13-FSA shown in structural formula (G13) was used as the solvent. LiFSA (lithium bis(fluorosulfonyl)amide) was used as the electrolyte. The concentration of the electrolyte in the electrolyte solution was 1.80 mol / L.

[0409] [ka]

[0410] The electrolyte solution Sol_5 is explained. The solvent used was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) with a volume ratio of EC:DEC = 3:7. The electrolyte used was lithium hexafluorophosphate (LiPF6). The concentration of the electrolyte in the electrolyte solution was 1.00 mol / L.

[0411] The solvents and electrolytes used in each electrolytic solution are shown in Table 1.

[0412] [Table 1]

[0413] Next, in a reduced pressure atmosphere, the side of the exterior body that had been left as an open portion was sealed.

[0414] Through the above steps, a secondary battery was produced.

[0415] [aging] Next, the secondary battery was subjected to aging.

[0416] First, the secondary battery was sandwiched between two plates and charged at CC (0.01C, capacity 15mAh / g). After that, the two plates were removed, and one side of the exterior body was cut in an argon atmosphere to open it, degas it, and reseal it. Here, CC stands for constant current. Here, the capacity of the secondary battery was calculated per weight of the positive electrode active material. The C rate was calculated based on the charge / discharge cycle conditions at 1C. The charge voltage in the cycle characteristic evaluation was calculated as 190mA / g at 4.4V, 210mAh / g at 4.45V, and 220mAh / g at 4.5V.

[0417] Next, the secondary battery was sandwiched between two plates and charged at CC (0.1 C, capacity 120 mAh / g). After that, the two plates were removed and the battery was kept at 0°C for 24 hours, after which one side of the exterior body was cut to open it in an argon atmosphere, the gas was released, and the battery was resealed.

[0418] [Evaluation of charge / discharge characteristics] Next, the secondary battery was sandwiched between two plates, charged with CCCV (0.1C, end current 0.01C), and discharged with CC (0.2C, 2.5V). The charging voltage was set to the charging voltage used in the evaluation of cycle characteristics. Here, CV stands for constant voltage.

[0419] Thereafter, charging was performed with CCCV (0.2 C, end current 0.01 C) and discharging with CC (0.2 C, 2.5 V) and charging and discharging were repeated three times. The charging voltage was set to the charging voltage in the evaluation of cycle characteristics.

[0420] [Evaluation of cycle characteristics 1] Next, the cycle characteristics of the secondary battery were evaluated at 25°C.

[0421] As the battery cells, cells Cel_1 to Cel_7 shown in Table 2 were produced. Table 2 shows the combinations of the positive electrode, negative electrode, and electrolyte solution used, as well as the charge voltage.

[0422] [Table 2]

[0423] In terms of the C rate and the capacity ratio described below, the positive electrode capacity was set to 190 mAh / g when the charging voltage was 4.4 V. The positive electrode capacity was set to 210 mAh / g when the charging voltage was 4.45 V. The positive electrode capacity was set to 220 mAh / g when the charging voltage was 4.5 V.

[0424] The amount of the positive electrode active material carried in the positive electrode P1 was approximately 6.5 mg / cm for the cells Cel_1 to Cel_4. 2 , Cells Cel_5 to Cel_7 are approximately 11 mg / cm 2 It was decided.

[0425] The area of ​​the positive electrode active material layer in the positive electrode P1 is 8.194 cm 2 It was decided.

[0426] The amount of the negative electrode active material carried by the negative electrode N1 and the negative electrode N2 in each battery cell was adjusted so that the capacity ratio was approximately 77% or more and 83% or less. Here, the capacity ratio is a value expressed as a percentage of the positive electrode capacity to the negative electrode capacity. In calculating the capacity ratio, the negative electrode capacity was set to 330 mAh / g based on the weight of the negative electrode active material. The amount of the negative electrode active material carried was calculated by dividing the total amount carried in the negative electrode active material layers provided on both sides of the current collector by half.

[0427] Charging was performed by CCCV (0.2 C, end current 0.02 C), and discharging was performed by CC (0.2 C, 2.5 V). The capacity of the secondary battery was calculated based on the weight of the positive electrode active material.

[0428] The evaluation results of the cycle characteristics at 25° C. are shown in FIGS. 24A, 24B and 25.

[0429] Fig. 24A shows the cycle characteristics of cells Cel_1 to Cel_4, with the horizontal axis indicating the number of cycles and the vertical axis indicating the discharge capacity. Fig. 24B shows an enlarged view of the vertical axis of Fig. 24A.

[0430] FIG. 25 shows the results of the cycle characteristics of cells Cel_5 to Cel_7.

[0431] 26A, 26B, 27A, and 27B show the charge / discharge curves of cells Cel_1 to Cel_4, respectively. The solid line shows the curve for the first cycle, and the dotted line shows the curve for the 100th cycle. In each charge / discharge curve, the vertical axis shows the charge or discharge voltage, and the horizontal axis shows the capacity.

[0432] 26A, 26B, 27A, and 27B show that all of the cells Cel_1 to Cel_4 had favorable charge / discharge curves in the first cycle even when the charge voltage was set to an extremely high value of 4.5 V. This suggests that the crystal structure of the positive electrode active material of one embodiment of the present invention is highly stable even at a high charge voltage.

[0433] Furthermore, from Figures 24A and 24B, it was found that the cells Cel_1, Cel_2, and Cel_3, which had an ionic liquid as the electrolyte, maintained a capacity value of 80% or more of the initial discharge capacity after 300 cycles, demonstrating extremely excellent characteristics.

[0434] Furthermore, as shown in FIG. 25, it was found that even in cells in which the amounts of positive and negative active materials were increased and the type of graphite was changed, excellent cycle characteristics were obtained even when the charging voltage was increased to 4.5 V.

[0435] From the above, it was found that in the secondary battery of one embodiment of the present invention, remarkably excellent characteristics can be obtained by using an excellent positive electrode active material and an ionic liquid as an electrolyte solution.

[0436] [Evaluation of cycle characteristics 2] Next, the cycle characteristics of the secondary battery were evaluated at 45°C.

[0437] As the battery cells, cells Cel_11 to Cel_23 shown in Table 3 were produced. Table 3 shows the combinations of the positive electrode, negative electrode, and electrolyte solution used, as well as the charge voltage.

[0438] [Table 3]

[0439] The amount of the positive electrode active material carried in the positive electrode P1 was approximately 6.5 mg / cm for the cells Cel_11 to Cel_20. 2 , Cells Cel_21 to Cel_23 are approximately 11 mg / cm 2 It was decided.

[0440] The area of ​​the positive electrode active material layer in the positive electrode P1 is 8.194 cm 2 It was decided.

[0441] The amounts of the negative electrode active materials carried in the negative electrodes N1 and N2 in each battery cell were adjusted so that the capacity ratio was approximately 77% or more and 83% or less.

[0442] Charging was performed by CCCV (0.2 C, end current 0.02 C), and discharging was performed by CC (0.2 C, 2.5 V). The capacity of the secondary battery was calculated based on the weight of the positive electrode active material.

[0443] At 45° C., the cycle characteristics of cells Cel_11 to Cel_13 are shown in FIG. 28A, the cycle characteristics of cells Cel_14 to Cel_16 in FIG. 28B, the cycle characteristics of cells Cel_17 to Cel_20 in FIG. 29A, and the cycle characteristics of cells Cel_21 to Cel_23 in FIG. 29B.

[0444] 28A and 28B show that the cell using an ionic liquid as the electrolyte showed very little decrease in discharge capacity even at a charge voltage of 4.45 V. On the other hand, the cell using an organic electrolyte started to show a decrease in discharge capacity at a charge voltage of 4.45 V.

[0445] As shown in Fig. 29A, when the charging voltage was set to 4.5 V, a gradual decrease in discharge capacity was observed even in the cell using ionic liquid as the electrolyte. On the other hand, as shown in Figs. 24A and 24B, good characteristics were obtained even when the charging voltage was set to 4.5 V at 25°C. This suggests that by controlling the charging voltage according to the temperature range used, it is possible to suppress the decrease in discharge capacity that occurs with the use of the secondary battery and to produce a secondary battery with a long life.

[0446] Moreover, as shown in FIG. 29B, it was found that even in a cell in which the amounts of the positive electrode active material and the negative electrode active material were increased and the type of graphite was changed, excellent cycle characteristics were obtained at a charge voltage of 4.45 V.

[0447] [Evaluation of rate characteristics] Next, the rate characteristics were evaluated at 10°C.

[0448] As the battery cells, cells Cel_31 to Cel_33 shown in Table 4 were produced. Table 4 shows the combinations of the positive electrode, negative electrode, and electrolyte solution used, and the charge voltage.

[0449] [Table 4]

[0450] The amount of the positive electrode active material carried by the positive electrode P1 is approximately 6.5 mg / cm 2 The amount of the negative electrode active material carried in the negative electrode N1 was adjusted so that the capacity ratio was approximately 84% or more and 87% or less.

[0451] In the positive electrode, the area of ​​the positive electrode active material layer formed on the current collector is 8.194 cm 2 It was decided.

[0452] Charging was performed by CCCV (0.2 C, end current 0.02 C), and discharging was performed by CC (2.5 V). Discharging was performed at discharge rates of 0.1, 0.2, 0.5, and 1 [C] in that order. The capacity of the secondary battery was calculated based on the weight of the positive electrode active material.

[0453] The cycle characteristics of cells Cel_31 to Cel_33 at 10° C. are shown in FIGS. 30A, 30B, and 31, respectively.

[0454] 30A, 30B, and 31 show that even at a relatively low temperature of 10°C, a discharge capacity of 98% or more of that at 0.1C was obtained at a rate of 0.5C. At a rate of 1C, Cel_31 achieved a discharge capacity of 97% or more of that at 0.1C, demonstrating excellent rate characteristics. A decrease in discharge capacity was observed in Cel_32, remaining at approximately 60% of that at 0.1C. [Explanation of symbols]

[0455] 111: positive electrode, 111a: positive electrode, 115: negative electrode, 115a: negative electrode, 121: positive electrode current collector, 122: positive electrode active material layer, 123: separator, 125: negative electrode current collector, 126: negative electrode active material layer, 130: electrode assembly, 131: electrode assembly, 211a: positive electrode, 211b: negative electrode, 212a: lead, 212b: lead, 214: separator, 250: secondary battery, 251: exterior body, 400: secondary battery, 401: positive electrode cap, 402: device, 402a: housing, 402b: secondary battery, 403: device, 403a: housing, 403b: secondary battery, 405: wristwatch type device, 405a: display unit, 405b: belt unit, 406: belt type device, 406a: belt unit, 406b: wireless power supply receiving unit, 413: conductive plate, 414: conductive plate, 415: power storage system, 416: wiring, 420: control circuit, 421: wiring, 422: wiring, 423: wiring, 424: conductor, 425: insulator, 426: wiring, 490: glasses type device, 490a: frame, 490b: display unit, 491: headset type device, 491a: microphone unit, 491b: flexible pipe, 491c: earphone unit, 500: secondary battery, 501: positive electrode current collector, 50 2: positive electrode active material layer, 503: positive electrode, 504: negative electrode current collector, 505: negative electrode active material layer, 506: negative electrode, 507: separator, 508: electrolyte, 509: exterior body, 510: positive electrode lead electrode, 511: negative electrode lead electrode, 513: secondary battery, 514: terminal, 515: seal, 517: antenna, 519: layer, 521: sealing portion, 522: sealing portion, 523: sealing portion, 529: label, 531: secondary battery pack, 540: circuit board, 551: one side, 552: other side, 590: control circuit, 590a: circuit system, 590b: circuit system, 601: positive electrode cap, 602: battery Can, 603: positive electrode terminal, 604: positive electrode, 605: separator, 606: negative electrode, 607: negative electrode terminal, 608: insulating plate, 609: insulating plate, 611: PTC element, 613: safety valve mechanism, 730: charging control circuit, 900: circuit board, 910: label, 911: terminal, 912: battery control circuit, 913: secondary battery, 914: antenna, 915: seal, 916: layer, 917: layer, 918: antenna, 920: display device, 921: sensor, 922: terminal, 930: housing, 931: negative electrode, 932: positive electrode, 933: separator, 950: wound body, 951: terminal, 952: terminal,971: electrode, 972: electrode, 981: film, 982: film, 1700: curved surface, 1701: plane, 1702: curve, 1703: radius of curvature, 1704: center of curvature, 1800: center of curvature, 1801: film, 1802: radius of curvature, 1803: film, 1804: radius of curvature, 7000: robot, 7100: portable display device, 7101: housing, 7102: display unit, 7103: operation button, 7104: storage battery, 7120: flying object, 7140: cleaning robot, 7160: electric vehicle, 7200: portable information terminal, 7201: housing, 7202: display unit, 720 3: band, 7204: buckle, 7205: operation button, 7206: input / output terminal, 7207: icon, 7210: smartphone, 7220: PC, 7240: game machine, 7260: game machine, 7262: controller, 7300: display device, 7304: display unit, 7400: mobile phone, 7401: housing, 7402: display unit, 7403: operation button, 7404: external connection port, 7405: speaker, 7406: microphone, 7407: storage battery, 7408: control circuit, 7500: electronic cigarette, 7501: atomizer, 7504: secondary battery, 8000: display Device, 8001: housing, 8002: display unit, 8003: speaker unit, 8004: secondary battery, 8005: voice input device, 8007: speaker, 8008: display unit, 8009: mobile information terminal, 8010: charging module, 8021: charging device, 8022: cable, 8024: power storage system, 8100: lighting device, 8101: housing, 8102: light source, 8103: secondary battery, 8104: ceiling, 8105: side wall, 8106: floor, 8107: window, 8200: indoor unit, 8201: housing, 8202: air outlet, 8203: secondary battery, 8204: outdoor unit, 8300: electricity Refrigerator-freezer, 8301: Housing, 8302: Refrigerator door, 8303: Freezer door, 8304: Secondary battery, 8400: Automobile, 8401: Headlight, 8406: Electric motor, 8500: Automobile, 8600: Scooter, 8601: Side mirror, 8602: Energy storage system, 8603: Turn signal, 8604: Under-seat storage, 8700: Electric bicycle, 8701: Storage battery, 8702: Energy storage system, 8703: Display, 8704: Control circuit, 9600: Tablet terminal, 9601: Notebook personal computer, 9625: Switch, 9626: Switch,9627: power switch, 9628: operation switch, 9629: fastener, 9630: housing, 9630a: housing, 9630b: housing, 9630B: housing, 9631: display unit, 9633: solar cell, 9634: control circuit, 9635: power storage unit, 9640: movable unit, 9650: keyboard unit,

Claims

1. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, The positive electrode active material contains lithium, cobalt, oxygen, magnesium, and fluorine, The electrolyte solution comprises an ionic liquid, The ionic liquid is at least one selected from the group consisting of an aromatic cation, a quaternary ammonium cation, a tertiary sulfonium cation, and a quaternary phosphonium cation.

2. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, the positive electrode active material comprises lithium cobalt oxide, magnesium, and fluorine; The electrolyte solution comprises an ionic liquid, The ionic liquid is at least one selected from the group consisting of an aromatic cation, a quaternary ammonium cation, a tertiary sulfonium cation, and a quaternary phosphonium cation.

3. In claim 1 or 2, The aromatic cation is at least one selected from an imidazolium cation and a pyridinium cation.

4. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, The positive electrode active material contains lithium, cobalt, oxygen, magnesium, and fluorine, The electrolyte solution comprises an ionic liquid, The secondary battery, wherein the ionic liquid is one or more selected from the following general formulas (G4), (G5), and (G6): 【Chemistry 1】 (In the formula, R １２ ~R １７ and R １８ ~R ２４ each independently represents an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom; n and m are 1 to 3; α is 0 to 6; β is 0 to 6; and X or Y represents, as a substituent, a linear or side chain alkyl group having 1 to 4 carbon atoms, a linear or side chain alkoxy group having 1 to 4 carbon atoms, or a linear or side chain alkoxyalkyl group having 1 to 4 carbon atoms.

5. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, the positive electrode active material comprises lithium cobalt oxide, magnesium, and fluorine; The electrolyte solution comprises an ionic liquid, The secondary battery, wherein the ionic liquid is one or more selected from the following general formulas (G4), (G5), and (G6): 【Chemistry 2】 (In the formula, R １２ ~R １７ and R １８ ~R ２４ each independently represents an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom; n and m are 1 to 3; α is 0 to 6; β is 0 to 6; and X or Y represents, as a substituent, a linear or side chain alkyl group having 1 to 4 carbon atoms, a linear or side chain alkoxy group having 1 to 4 carbon atoms, or a linear or side chain alkoxyalkyl group having 1 to 4 carbon atoms.

6. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, The positive electrode active material contains lithium, cobalt, oxygen, magnesium, and fluorine, The electrolyte solution comprises an ionic liquid, The ionic liquid has a compound represented by the following general formula (G1): 【Chemistry 3】 (In the formula, R １ represents an alkyl group having 1 to 4 carbon atoms; R ２ ~R ４ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R ５ represents an alkyl group or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P.

7. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, the positive electrode active material comprises lithium cobalt oxide, magnesium, and fluorine; The electrolyte solution comprises an ionic liquid, The ionic liquid has a compound represented by the following general formula (G1): 【Chemistry 4】 (In the formula, R １ represents an alkyl group having 1 to 4 carbon atoms; R ２ ~R ４ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R ５ represents an alkyl group or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P.

8. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, The positive electrode active material contains lithium, cobalt, oxygen, magnesium, and fluorine, The electrolyte solution comprises an ionic liquid, The secondary battery, wherein the ionic liquid has a compound represented by the following general formula (G2): 【Chemistry 5】 (In the formula, R ６ represents an alkyl group or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P; R ７ ~R １１ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

9. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, the positive electrode active material comprises lithium cobalt oxide, magnesium, and fluorine; The electrolyte solution comprises an ionic liquid, The secondary battery, wherein the ionic liquid has a compound represented by the following general formula (G2): 【Chemistry 6】 (In the formula, R ６ represents an alkyl group or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P; R ７ ~R １１ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

10. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, The positive electrode active material contains lithium, cobalt, oxygen, magnesium, and fluorine, The electrolyte solution comprises an ionic liquid, The secondary battery, wherein the ionic liquid has a compound represented by the following general formula (G7): 【Chemistry 7】 (In the formula, R ２５ ~R ２７ each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P.

11. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, the positive electrode active material comprises lithium cobalt oxide, magnesium, and fluorine; The electrolyte solution comprises an ionic liquid, The secondary battery, wherein the ionic liquid has a compound represented by the following general formula (G7): 【Chemistry 8】 (In the formula, R ２５ ~R ２７ each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P.

12. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, The positive electrode active material contains lithium, cobalt, oxygen, magnesium, and fluorine, The electrolyte solution comprises an ionic liquid, The secondary battery, wherein the ionic liquid has a compound represented by the following general formula (G8): 【Chemistry 9】 (In the formula, R ３２ ~R ３５ each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P.

13. The battery has a positive electrode, a negative electrode, an electrolyte, and an outer casing, The positive electrode has a positive electrode active material, the positive electrode active material comprises lithium cobalt oxide, magnesium, and fluorine; The electrolyte solution comprises an ionic liquid, The secondary battery, wherein the ionic liquid has a compound represented by the following general formula (G8): 【Chemistry 10】 (In the formula, R ３２ ~R ３５ each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P.

14. In any one of claims 1 to 13, As the anion of the ionic liquid, (FSO ２ ) ２ N － Or (CF ３ SO ２ ) ２ N － A secondary battery having the above structure.

15. In any one of claims 1 to 14, The secondary battery, in which the electrolyte contains, in addition to the ionic liquid, one or more selected from ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), DEC, EMC, methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, and sultone.

16. In any one of claims 1 to 15, The negative electrode of the secondary battery comprises graphite.

17. In any one of claims 1 to 16, when a temperature of the secondary battery in a first charging step is in a range of a first temperature or more and less than a second temperature, an upper limit voltage of the first charging step is a first value; when a temperature of the secondary battery during the second charge is equal to or higher than the second temperature, an upper limit voltage of the second charge is a second value; the first temperature is equal to or greater than 5° C. and less than 15° C.; the second temperature is equal to or greater than 25° C. and less than 55° C.; the first value is greater than the second value by 0.02 V or more; The first value is 4.45V or more and 4.6V or less.

18. In any one of claims 1 to 17, When the secondary battery is charged to 4.5 V by CCCV charging at 25° C. and then CC discharged to 2.5 V 300 times, the 300th discharge capacity is 80% or more of the initial discharge capacity.

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