Battery, electronic device, and vehicle

Abstract

Provided is a non-aqueous solvent having a wide useable temperature range, a low viscosity, a high lithium-ion conductivity at a low temperature, and a high heat resistance. The non-aqueous solvent has an ionic liquid and a low temperature organic electrolyte, and has a low viscosity at low temperatures as well, and a high carrier ion conductivity. An electrolyte containing 30-65% by volume of ethyl methyl carbonate can be used as the low temperature organic electrolyte. It is preferable that a battery, using said non-aqueous solvent as the electrolyte, has a wide usable temperature range.

Description

Batteries, electronic devices and vehicles

[0001] The present invention relates to a battery, particularly a secondary battery, and an electronic device or vehicle equipped with the battery.

[0002] Among batteries, secondary batteries can be used repeatedly by charging and discharging, and are also called storage batteries. Secondary batteries that use lithium ions as carrier ions are called lithium-ion secondary batteries, and they can be made larger in capacity and smaller in size, so research and development into them is actively underway.

[0003] One of the problems with secondary batteries is their susceptibility to environmental temperature. For example, a drop in environmental temperature leads to a decrease in the viscosity of the secondary battery's electrolyte, which reduces the conductivity of carrier ions. This decrease in electrolyte performance leads to a decrease in the secondary battery's performance, such as an increase in its internal resistance.

[0004] Electric vehicles are vehicles that use secondary batteries to drive their motors, but because the electrolyte is affected by environmental temperatures such as cold and heat, it has been difficult for electric vehicles to become widespread in cold or tropical regions.

[0005] In addition to electric vehicles, vehicles equipped with secondary batteries include hybrid vehicles, which are powered by both an engine and a motor. Among hybrid vehicles, there are also plug-in hybrid vehicles that can be charged from an electrical outlet. Electronic devices equipped with secondary batteries include mobile phones, smartphones, portable information terminals such as laptop computers, portable music players, digital cameras, and medical equipment.

[0006] It is desirable for secondary batteries installed in these electric vehicles, hybrid vehicles, plug-in hybrid vehicles, and electronic devices to be able to exhibit stable performance regardless of the environmental temperature during use. Furthermore, high safety is also required.

[0007] Ionic liquids, which are flame-retardant, are known as highly safe electrolytes. Patent Document 1 discloses that, in consideration of safety issues in lithium-ion secondary batteries, electrolytes containing ionic liquids have a viscosity within a certain range.

[0008] JP 2018-116840 A

[0009] However, Patent Document 1 does not recognize the problem regarding the temperature range in which the secondary battery can be used.

[0010] Therefore, an object of the present invention is to provide a non-aqueous solvent usable over a wide temperature range and a method for manufacturing the same, a secondary battery having the non-aqueous solvent and a method for manufacturing the same, and a vehicle equipped with the secondary battery and a method for manufacturing the same.

[0011] Another object of the present invention is to provide a nonaqueous solvent containing an ionic liquid that has low viscosity at least even at low temperatures, and a method for manufacturing the same. Another object of the present invention is to provide a secondary battery containing the nonaqueous solvent, and a method for manufacturing the same. Another object of the present invention is to provide a vehicle equipped with the secondary battery, and a method for manufacturing the same.

[0012] Another object of the present invention is to provide a non-aqueous solvent having high lithium ion conductivity at least at low temperatures and a method for manufacturing the same, a secondary battery having the non-aqueous solvent and a method for manufacturing the same, and a vehicle equipped with the secondary battery and a method for manufacturing the same.

[0013] Another object of the present invention is to provide a non-aqueous solvent having high heat resistance and a method for manufacturing the same. Another object of the present invention is to provide a secondary battery having the non-aqueous solvent and a method for manufacturing the same. Another object of the present invention is to provide a vehicle equipped with the secondary battery and a method for manufacturing the same.

[0014] It is not necessary to solve all of these problems by one embodiment of the present invention. Problems other than these can be extracted from the description of the specification, drawings, and claims of this application. Furthermore, the description of these problems does not preclude the existence of other problems related to safety, etc.

[0015] To solve the above problems, the present inventors conducted extensive research and found that adding a low-viscosity organic solvent to an ionic liquid can reduce the viscosity of the non-aqueous solvent even at low temperatures. They also found that mixing a conventional organic solvent with a low-viscosity organic solvent can reduce the viscosity of the non-aqueous solvent even at low temperatures. Low viscosity increases the conductivity of the non-aqueous solvent, thereby improving carrier ion conductivity, such as lithium ion conductivity. Using this non-aqueous solvent as an electrolyte for a secondary battery can provide a secondary battery with high carrier ion conductivity, such as lithium ion conductivity, at least at low temperatures.

[0016] Furthermore, when the ionic liquid is present in the non-aqueous solvent in an amount of 20% by volume to 80% by volume, more preferably 50% by volume, the viscosity of the non-aqueous solvent at low temperatures falls within a preferred range. In this specification, the volume of the electrolyte refers to the volume measured at 25°C. The volume ratio may be the mixing ratio in the preparation process or may be a ratio determined from various analytical results.

[0017] Furthermore, while low-viscosity organic solvents alone have difficulty in providing high-temperature resistance and high-voltage resistance, by mixing a conventional organic solvent, high-temperature resistance and high-voltage resistance can be provided. Taking into account the carrier ion conductivity at low temperatures, high heat resistance, and high-voltage resistance, a nonaqueous solvent usable over a wide temperature range can be provided. Furthermore, a secondary battery containing the nonaqueous solvent and a vehicle equipped with the secondary battery can be provided.

[0018] One aspect of the present invention is a battery having an electrolyte, the electrolyte comprising an ionic liquid and an organic electrolyte, the organic electrolyte comprising a cyclic carbonate, methyl ethyl carbonate, and dimethyl carbonate, the methyl ethyl carbonate accounting for 30% by volume or more and 65% by volume or less of the organic electrolyte.

[0019] In the above, the ionic liquid preferably accounts for 20% by volume or more and 80% by volume or less of the electrolyte.

[0020] In the above, the ionic liquid preferably has the following structural formula (111) and the following structural formula (H11).

[0021]

[0022] In the above, the cyclic carbonate preferably contains ethylene carbonate, and the ethylene carbonate preferably accounts for 25% by volume or more and 35% by volume or less of the organic electrolyte.

[0023] Another embodiment of the present invention is a battery having an organic electrolyte, the organic electrolyte comprising a cyclic carbonate and three or more types of chain carbonates, wherein when a first organic electrolyte contained in the battery before a cycle test and a second organic electrolyte contained in the battery after a cycle test are subjected to nuclear magnetic resonance analysis, the difference between the proportion of the chain carbonate in the first organic electrolyte and the proportion of the chain carbonate in the second organic electrolyte is 20 points or less, and the cycle test is performed in a 45°C environment, by charging the battery at a constant current of 100 mA / g up to a voltage of 4.6 V, followed by constant voltage charging until the current value reaches 10 mA / g, and then discharging the battery at a constant current of 100 mA / g down to a voltage of 2.5 V, 50 times each.

[0024] In the above, the electrolyte preferably contains lithium hexafluorophosphate.

[0025] The battery is preferably a flexible battery.

[0026] The nonaqueous solvent of one embodiment of the present invention has low viscosity even at low temperatures. Furthermore, the nonaqueous solvent of one embodiment of the present invention has high heat resistance. Because of the low viscosity at low temperatures and high heat resistance, the nonaqueous solvent of one embodiment of the present invention can be used over a wide temperature range.

[0027] The nonaqueous solvent can be used as an electrolyte for the secondary battery, and the secondary battery of one embodiment of the present invention can be used over a wide temperature range.Furthermore, the secondary battery can be mounted on a vehicle, and the vehicle of one embodiment of the present invention can be used over a wide temperature range.

[0028] A nonaqueous solvent with high heat resistance is highly safe. The nonaqueous solvent can be used as an electrolyte of a secondary battery, and the secondary battery of one embodiment of the present invention has high safety. Furthermore, the secondary battery can be mounted on a vehicle, and the vehicle of one embodiment of the present invention has high safety.

[0029] Configurations and effects other than those described above will become apparent from the following description of the embodiments.

[0030] FIGS. 1A and 1B are cross-sectional views illustrating an example of the configuration of a secondary battery. FIG. 2 is a view illustrating the crystalline structure of a positive electrode active material. FIG. 3 is a view illustrating the crystalline structure of a conventional positive electrode active material. FIG. 4 is a view illustrating an XRD pattern calculated from the crystalline structure. FIG. 5 is a view illustrating an XRD pattern calculated from the crystalline structure. FIGS. 6A and 6B are views illustrating XRD patterns calculated from the crystalline structure. FIGS. 7A to 7C are perspective and cross-sectional views illustrating an example of the configuration of a coin-type secondary battery. FIGS. 8A to 8C are views illustrating an example of the configuration of a secondary battery. FIGS. 9A and 9B are views illustrating an example of the configuration of a secondary battery. FIG. 9C is a view illustrating an example of a battery pack having multiple secondary batteries. FIGS. 10A to 10C are views illustrating an example of a battery pack having multiple secondary batteries. FIGS. 11A to 11C are views illustrating an example of a battery pack having multiple secondary batteries. FIG. 12A is a perspective view illustrating an example of the configuration of a secondary battery, and FIG. 12B is a top view illustrating an example of the configuration of a secondary battery. FIGS. 13A and 13B are cross-sectional views illustrating an example of the configuration of a secondary battery. FIGS. 14A to 14E are views illustrating an example of the configuration of a secondary battery. FIGS. 15A to 15C are views illustrating an example of the configuration of a secondary battery. FIGS. 16A to 16C are views illustrating an example of the configuration of a secondary battery. FIGS. 17A to 17C are views illustrating electronic devices of one embodiment of the present invention. FIGS. 18A and 18B are views illustrating electronic devices of one embodiment of the present invention. FIGS. 19A to 19D are views illustrating electronic devices of one embodiment of the present invention. FIGS. 20A to 20D are views illustrating electronic devices of one embodiment of the present invention. FIGS. 21A to 21C are views illustrating electronic devices of one embodiment of the present invention. FIGS. 22A to 22C are views illustrating electronic devices of one embodiment of the present invention. FIG. 23A is a view illustrating an electric bicycle, and FIG. 23B is a view illustrating a secondary battery of the electric bicycle. FIG. 23C is a view illustrating an example of a battery pack. FIG. 23D is a view illustrating an electric motorcycle. Fig. 24A is a perspective view of a power storage device, Fig. 24B is a block diagram of the power storage device, and Fig. 24C is a block diagram of a vehicle having a motor. Figs. 25A to 25E are diagrams explaining an example of a transportation vehicle. Figs. 26A to 26D are diagrams showing an example of space equipment. Fig. 27 is a graph showing the viscosity of an electrolyte.28A to 28C are photographs showing the wettability of the electrolyte. 29A to 29C are photographs showing the wettability of the electrolyte. 30A and 30B are graphs showing the charge-discharge cycle characteristics of a secondary battery. 31A and 31B are graphs showing the charge-discharge cycle characteristics of a secondary battery. 32A and 32B are graphs showing the charge-discharge cycle characteristics of a secondary battery. 33A and 33B are graphs showing the charge-discharge cycle characteristics of an electrolyte. １ 34A and 34B show the 1 H NMR spectra of the electrolyte. １ 35 is a graph showing the composition of the electrolyte. 36A and 36B are graphs showing the composition of the electrolyte.

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various modifications can be made to the embodiments and details. Furthermore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0032] (Embodiment 1) In this embodiment, a nonaqueous solvent of the present invention will be described.

[0033] A nonaqueous solvent according to one embodiment of the present invention is a mixture of at least an ionic liquid and a low-viscosity organic electrolyte. The proportion of the ionic liquid is 20% by volume or more and 80% by volume or less, more preferably 50% by volume, based on the total volume of the nonaqueous solvent. A nonaqueous solvent containing the ionic liquid in this proportion can have low viscosity even at low temperatures. Therefore, a nonaqueous solvent having high carrier ion conductivity even at low temperatures and usable over a wide temperature range can be provided. Using the nonaqueous solvent as an electrolyte for a secondary battery can provide a secondary battery usable over a wide temperature range. Installing the secondary battery in a vehicle can provide a vehicle usable over a wide temperature range.

[0034] Furthermore, a nonaqueous solvent according to one embodiment of the present invention is a mixture of a conventional organic solvent and a low-viscosity organic solvent. In particular, by using a mixture of a chain carbonate contained in a conventional organic solvent and multiple low-viscosity chain carbonates, the viscosity of the nonaqueous solvent can be reduced even at low temperatures. While a low-viscosity organic solvent alone has problems with high-temperature resistance and high-voltage resistance, mixing a conventional organic solvent with the nonaqueous solvent provides high-temperature resistance and high-voltage resistance. Given the carrier ion conductivity, high heat resistance, and high-voltage resistance at low temperatures, a nonaqueous solvent usable over a wide temperature range can be provided. Furthermore, a secondary battery containing the nonaqueous solvent and a vehicle equipped with the secondary battery can be provided.

[0035] <Ionic Liquid> Ionic liquids that can be used in one embodiment of the present invention will be described. Ionic liquids, sometimes referred to as room-temperature molten salts, have cations and anions. The basic skeleton of the cation is imidazolium-based, ammonium-based, pyrrolidinium-based, piperidinium-based, pyridinium-based, or phosphonium-based. Ionic liquids whose basic skeleton of the cation is imidazolium-based have lower viscosity than ammonium-based ionic liquids. Low viscosity tends to increase the conductivity of carrier ions. Furthermore, physical properties such as viscosity can be controlled by the alkyl group or the like on the side chain of the cation.

[0036] The anion may be a halide ion, tetrafluoroborate, hexafluorophosphate, bis(trifluoromethylsulfonyl)amide, or bis(fluorosulfonyl)imide.

[0037] The anion of the ionic liquid that can be used in one embodiment of the present invention will be described below. The anion can be 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, a perfluoroalkylphosphate anion, a tetrafluoroborate anion, and the like.

[0038] The monovalent amide anion is represented by the general formula (Cｎ F ２ｎ＋１ SO ２ ) ２ N − (n=0 or more and 3 or less).

[0039] In the above general formula, when n=0, it is a bis(fluorosulfonyl)imide anion, which is represented by structural formula (H11). The abbreviation for bis(fluorosulfonyl)imide anion is FSI or FSA.

[0040]

[0041] In the above general formula, when n=1, it is a bis(trifluoromethanesulfonyl)imide anion, which is represented by structural formula (H12). The abbreviation for bis(trifluoromethanesulfonyl)imide anion is TFSI or TFSA.

[0042]

[0043] One of the monovalent cyclic amide anions is 4,4,5,5-tetrafluoro-1,3,2-dithiazolidinetetraoxide anion, which is represented by structural formula (H13).

[0044]

[0045] The monovalent methide anion is represented by the general formula (C ｎ F ２ｎ＋１ SO ２ ) ３ C − (n=0 or more and 3 or less).

[0046] One of the monovalent cyclic methide anions is 4,4,5,5-tetrafluoro-2-[(trifluoromethyl)sulfonyl]-1,3-dithiolane tetraoxide anion, which is represented by structural formula (H14).

[0047]

[0048] The fluoroalkylsulfonate anion is represented by the general formula (C ｍ F ２ｍ＋１ SO ３ ) − (m=0 or more and 4 or less).

[0049] In the above general formula, when m=0, it is a fluorosulfonate anion, and when m=1, 2, 3, or 4, it is a perfluoroalkylsulfonate anion.

[0050] Fluoroalkylborate anions have the general formula {BF ｎ (C ｍ H ｋ F ２ｍ＋１−ｋ ) ４−ｎ} − (n=0 to 3, m=1 to 4, k=0 to 2m).

[0051] The fluoroalkyl phosphate anion has the general formula {PF ｎ (C ｍ H ｋ F ２ｍ＋１−ｋ ) ６−ｎ} − (n=0 to 5, m=1 to 4, k=0 to 2m).

[0052] One or more of these anions can be used.

[0053] The cation of the ionic liquid of the present invention will now be described.

[0054] The cation of the ionic liquid of the present invention has an imidazolium-based cation represented by general formula (G1). − indicates an anion.

[0055]

[0056] In the above 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 having 1 to 6 carbon atoms, or an ether group, a thioether group, or a siloxane having a main chain composed of two or more atoms selected from C, O, Si, N, S, and P atoms. − Preferably, has an FSI or TFSI anion.

[0057] The ionic liquid of the present invention has a pyridinium-based cation represented by general formula (G2). − indicates an anion.

[0058]

[0059] In the above general formula (G2), R ６ has a main chain composed of two or more atoms selected from an alkyl group having 1 to 6 carbon atoms or C, O, Si, N, S, and P atoms. ７ ~R １１ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ８ or R ９ In the general formula (G2), A may represent a hydroxyl group. − Preferably, has an FSI or TFSI anion.

[0060] The ionic liquid of the present invention may have a quaternary ammonium cation. For example, it has a quaternary ammonium cation represented by general formula (G3). In general formula (G3), A − indicates an anion.

[0061]

[0062] In the above 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. − represents an anion, and preferably has an FSI anion or a TFSI anion.

[0063] The ionic liquid of the present invention has a cation represented by general formula (G4). − indicates an anion.

[0064]

[0065] In the above general formula (G4), R １２ and R １７R each independently represents an alkyl group having 1 to 3 carbon atoms. １３ ~R １６ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. − Preferably, has an FSI or TFSI anion.

[0066] The ionic liquid of the present invention has a cation represented by general formula (G5). − indicates an anion.

[0067]

[0068] In the above general formula (G5), R １８ and R ２４ R each independently represents an alkyl group having 1 to 3 carbon atoms. １９ ~R ２３ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. − Preferably, has an FSI or TFSI anion.

[0069] The ionic liquid of the present invention has a cation represented by general formula (G6). − indicates an anion.

[0070]

[0071] In the general formula (G6), n and m are 1 or more and 3 or less, α is 0 or more and 6 or less, β is 0 or more and 6 or less, 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. − Preferably, has an FSI or TFSI anion.

[0072] The ionic liquid of the present invention has a tertiary sulfonium cation represented by general formula (G7). −indicates an anion.

[0073]

[0074] In the above 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. ２５ ~R ２７ each independently has a main chain composed of two or more atoms selected from C, O, Si, N, S, and P atoms. − Preferably, has an FSI or TFSI anion.

[0075] The ionic liquid of the present invention has a quaternary phosphonium cation represented by the following general formula (G8): − indicates an anion.

[0076]

[0077] In the above 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. ３２ ~R ３５ each independently has a main chain composed of two or more atoms selected from C, O, Si, N, S, and P atoms. − Preferably, has an FSI or TFSI anion.

[0078] Specific examples of the cation of the general formula (G1) include structural formulas (111) to (174). Structural formula (111) is a 1-ethyl-3-methylimidazolium cation, abbreviated as EMI. Structural formula (113) is a 1-butyl-3-methylimidazolium cation, abbreviated as BMI.

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085] Specific examples of the cation of the above general formula (G2) include structural formulae (701) to (719).

[0086]

[0087]

[0088] Specific examples of the cation of the general formula (G4) include structural formulae (501) to (520).

[0089]

[0090] Specific examples of the cation of the general formula (G5) include structural formulae (601) to (630).

[0091]

[0092]

[0093] Specific examples of the cation of the general formula (G6) include structural formulae (301) to (309) and structural formulae (401) to (419).

[0094]

[0095]

[0096] In addition, structural formulas (301) to (309) and structural formulas (401) to (419) show examples in which m is 1 in general formula (G6), but m may be changed to 2 or 3 in structural formulas (301) to (309) and structural formulas (401) to (419).

[0097] Specific examples of the cation of the general formula (G7) include structural formulae (201) to (215).

[0098]

[0099] Since such ionic liquids are liquids composed only of ions, they have strong electrostatic interactions, are nonvolatile, thermally stable, and highly heat-resistant. Secondary batteries using such ionic liquids as electrolytes are non-flammable within the operating temperature range and are therefore highly safe.

[0100] <Organic Electrolyte> An organic electrolyte that can be used in one embodiment of the present invention will be described. The organic electrolyte contains a cyclic carbonate and a chain carbonate. The cyclic carbonate has a high dielectric constant and therefore functions to promote dissociation of the lithium salt. The chain carbonate also functions to reduce the viscosity of the electrolyte.

[0101] The cyclic carbonate preferably accounts for 25 to 35% by volume of the organic electrolyte, and more preferably about 30% by volume. If the cyclic carbonate content is too low, the lithium salt may not dissociate sufficiently. On the other hand, if the cyclic carbonate content is too high, the viscosity may become too high, especially at low temperatures.

[0102] It is preferable that the organic electrolyte be a chain carbonate other than the cyclic carbonate. That is, the chain carbonate preferably accounts for 65% to 75% by volume of the organic electrolyte, and more preferably about 70% by volume. If the amount of the chain carbonate is too small, the viscosity may become too high, especially at low temperatures. On the other hand, if the amount of the chain carbonate is too large, the lithium salt may not dissociate sufficiently.

[0103] Examples of the chain carbonate that can be used include methyl ethyl carbonate (ethyl methyl carbonate, EMC), dimethyl carbonate (dimethyl carbonate, DMC), diethyl carbonate (diethyl carbonate, DEC), 1,2-dimethoxyethane (DME), and mixtures thereof.

[0104] Among them, EMC and DMC are chain carbonates with low viscosity, while DEC is a chain carbonate that has been widely used and has high resistance to high temperatures and high voltages.

[0105] Examples of cyclic carbonates that can be used include ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), and mixtures thereof.

[0106] Furthermore, a fluorinated cyclic carbonate may be used as the cyclic carbonate. Fluorinated cyclic carbonates have a high flash point and can enhance safety. A secondary battery using such a fluorinated cyclic carbonate as an electrolyte is not flammable within the temperature range in which it is used, and is therefore highly safe.

[0107] The fluorinated cyclic carbonate may be fluorinated ethylene carbonate, such as monofluoroethylene carbonate (fluoroethylene carbonate, FEC, F1EC), difluoroethylene carbonate (DFEC, F2EC), trifluoroethylene carbonate (F3EC), or tetrafluoroethylene carbonate (F4EC). DFEC includes isomers such as cis-4,5 and trans-4,5 isomers.

[0108] Furthermore, a cyclic carbonate having a cyano group can also be used as the cyclic carbonate. The cyano group and the fluoro group of a fluorinated cyclic carbonate are also called electron-withdrawing groups.

[0109] Furthermore, when the organic electrolyte uses EC as the cyclic carbonate and EMC and DMC as the chain carbonates, the volume ratio of EC:EMC:DMC=30:x:(70-x) preferably satisfies 30≦x≦65. That is, it is preferable that EMC occupies 30% by volume or more and 65% by volume or less of the organic electrolyte. Because EMC has a low melting point of -54°C, having EMC in this range can lower the melting point of the organic electrolyte and further increase carrier ion conductivity at low temperatures.

[0110] In the present invention, the ionic liquid and the organic electrolyte such as a cyclic carbonate or a chain carbonate account for 5% by volume or more of the total electrolyte, and are not present in small amounts such as additives.

[0111] The nonaqueous solvent of the present invention is a mixture of at least the ionic liquid and an organic electrolyte. The proportion of the ionic liquid is preferably 20% by volume or more and 50% by volume or less relative to the total nonaqueous solvent. A nonaqueous solvent containing the ionic liquid in this proportion can have high heat resistance. Because of its high heat resistance and high carrier ion conductivity at the low temperatures, a nonaqueous solvent usable over a wide temperature range can be provided.

[0112] <Lithium Salt> The lithium salt dissolved in the ionic liquid of the present invention is preferably a lithium salt having a halogen. More preferably, it is a fluorine-containing imide lithium salt. The fluorine-containing imide lithium salt is Li(CF ３ SO ２ ) ２ N (hereinafter, also referred to as "LiTFSI" or "LiTFSA"), Li(C ２ F ５ SO ２ ) ２ N (hereinafter, also referred to as "LiBETI"), or Li(SO ２ F) ２ N (hereinafter, also referred to as "LiFSI" or "LiFSA") can be used.

[0113] Another example of a halogen-containing lithium salt is lithium hexafluorophosphate (LiPF ６ ), LiBF ４ , LiClO ４ etc. can be used.

[0114] Furthermore, LiBOB (lithium bis(oxalato)borate) may be used as another halogen-free lithium salt.

[0115] These lithium salts may be used alone or in combination.

[0116] <Additives> The electrolyte may contain additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), or dinitrile compounds such as succinonitrile and adiponitrile. The concentration of the additive may be, for example, 0.1 wt % to 5 wt % of the total electrolyte.

[0117] When a conventional organic electrolyte is mixed with a low-viscosity organic electrolyte, for example, a mixture of DEC, EMC, and DMC can be used as the chain carbonate. For example, a volume ratio of EC:EMC:DMC:DEC=12:7:7:14 can be used. By using an electrolyte with this composition, it is possible to obtain an electrolyte that has low viscosity at low temperatures and is resistant to high temperatures and high voltages. Here, low temperatures refer to, for example, temperatures below 0°C. High temperatures refer to, for example, temperatures above 45°C.

[0118] A secondary battery having an electrolyte resistant to high temperatures and high voltages exhibits little decomposition of the electrolyte before and after a cycle test under high temperature and high voltage conditions. Therefore, the change in the ratio of cyclic carbonate to chain carbonate in the electrolyte is small. For example, if the change in the ratio of chain carbonate in the electrolyte before and after a cycle test is 30 points or less, preferably 20 points or less, and more preferably 15 points or less, it can be said that the decomposition of the electrolyte is sufficiently small.

[0119] The proportion of compounds contained in the organic electrolyte can be analyzed by, for example, nuclear magnetic resonance (NMR), gas chromatography (GC / MS), high performance liquid chromatography (HPLC), or the like.

[0120] For example, the high-temperature and high-voltage cycle test can be performed under the following conditions: charging the secondary battery at a constant current of 100 mA / g up to a voltage of 4.6 V in a 45°C environment, followed by constant-voltage charging at a current of 10 mA / g down to a voltage of 10 mA / g, and then discharging at a constant current of 100 mA / g down to a voltage of 2.5 V, with each cycle repeated 50 times.

[0121] This embodiment can be used in combination with other embodiments.

[0122] Embodiment Mode 2 In this embodiment mode, an example of a secondary battery of the present invention will be described with reference to FIG.

[0123] 1A and 1B are schematic cross-sectional views illustrating a positive electrode 20, a negative electrode 30, and a separator 40 included in a secondary battery 10 of one embodiment of the present invention shown in FIG.

[0124] 1A , the positive electrode 20 has a positive electrode current collector 22 and a positive electrode active material layer 23. The negative electrode 30 has a negative electrode current collector 32 and a negative electrode active material layer 33. The positive electrode 20 and the negative electrode 30 are stacked with the separator 40 interposed between them such that the positive electrode active material layer 23 and the negative electrode active material layer 33 face each other.

[0125] 1B , a cross-sectional view of a portion of the negative electrode 30 is enlarged, and a negative electrode active material layer 33 provided on a negative electrode current collector 32 includes a negative electrode active material 34 and a binder 35. The negative electrode active material layer 33 may include a conductive material 36 in addition to the negative electrode active material 34 and the binder 35. However, if the conductivity of the negative electrode active material 34 is sufficiently high, the conductive material 36 may not be included.

[0126] Similarly, the positive electrode active material layer 23 provided on the positive electrode current collector 22 includes a positive electrode active material and a binder. The positive electrode active material layer 23 may include a conductive material in addition to the positive electrode active material and the binder, but may not include a conductive material if the conductivity of the positive electrode active material is sufficiently high.

[0127] Although not shown, the separator 40, the positive electrode active material layer 23, and the negative electrode active material layer 33 are impregnated with the electrolyte of the previous embodiment.

[0128] [Separator] It is preferable to use a material that is stable against the electrolyte and has excellent liquid retention properties for the separator 40. Examples of separators that can be used include those made of cellulose-containing fibers such as paper, nonwoven fabrics, glass fibers, ceramics, or synthetic fibers made of nylon (polyamide), vinylon (polyvinyl alcohol-based fibers), polyester, polyimide, acrylic, polyolefin, or polyurethane.

[0129] It is preferable to use a material for the separator that has high wettability with respect to the electrolyte. The higher the wettability, the higher the carrier ion conductivity. For example, the wettability can be evaluated by the sessile drop method, in which an electrolyte is dropped onto the separator and the contact angle is measured. In this case, a contact angle of 25° or less, more preferably less than 10°, can be said to be sufficiently high wettability.

[0130] It is also preferable to use a separator with low air resistance, i.e., one that is easily permeable to gas. By using a separator with low air resistance, it is possible to increase carrier ion conductivity at extremely low temperatures, such as −40° C.

[0131] The air resistance measured by the Gurley test is preferably 600 seconds or less, more preferably 200 seconds or less. A lower air resistance can increase carrier ion conductivity. On the other hand, if the air resistance is too low, a short circuit may occur, resulting in safety problems. Therefore, the air resistance measured by the Gurley test is preferably 61 seconds or more, more preferably 70 seconds or more.

[0132] The separator preferably has a porosity of 30% to 85%, preferably 45% to 65%. A high porosity is preferable because it facilitates electrolyte impregnation. The porosity of the separator may be different between the positive electrode side and the negative electrode side, and it is preferable that the porosity on the positive electrode side is higher than the porosity on the negative electrode side. To achieve different porosities, the same material may be used but with different porosities, or different materials with different porosities may be used. When different materials are used, the porosities of the separator can be made different by stacking them.

[0133] The thickness of the separator is preferably 5 μm or more and 200 μm or less, and more preferably 5 μm or more and 100 μm or less.

[0134] The separator preferably has an average pore diameter of 40 nm to 3 μm, preferably 70 nm to 1 μm. A larger average pore diameter is preferable because carrier ions can easily pass through. The average pore diameter of the separator may be different between the positive electrode side and the negative electrode side, and it is preferable that the average pore diameter on the positive electrode side is larger than the average pore diameter on the negative electrode side. To make the average pore diameters different, there are configurations in which the average pore diameters are made different for the same material, or configurations in which different materials with different average pore diameters are used. When different materials are used, the average pore diameters of the separator can be made different by stacking them.

[0135] The separator preferably has a heat resistance of 200° C. or higher.

[0136] It is preferable to use a separator made of polyimide, having a thickness of 10 μm or more and 50 μm or less and a porosity of 75% or more and 85% or less, since this improves the output characteristics of the secondary battery.

[0137] The separator may be processed into a bag shape, and the bag-shaped separator may be disposed so as to wrap or sandwich either the positive electrode or the negative electrode.

[0138] The overall thickness of the separator is preferably 1 μm to 100 μm, and as long as it is within this thickness range, the separator may have either a single-layer structure or a multilayer structure. In the case of a multilayer structure, an organic material film such as polypropylene or polyethylene may be coated with a ceramic material, a fluorine-based material, a polyamide material, or a mixture thereof. Examples of ceramic materials include aluminum oxide particles or silicon oxide particles. Examples of fluorine-based materials include PVDF or polytetrafluoroethylene. Examples of polyamide materials include nylon or aramid (meta-aramid, para-aramid).

[0139] Coating the separator surface with a ceramic material improves oxidation resistance, suppressing separator degradation during high-voltage charging and discharging and improving the reliability of the secondary battery. Coating the separator surface with a fluorine-based material also improves adhesion between the separator and electrodes, improving output characteristics. Coating the separator surface with a polyamide-based material, especially aramid, improves heat resistance, improving the safety of the secondary battery.

[0140] For example, both sides of a polypropylene film may be coated with a mixed material of aluminum oxide and aramid, or the surface of the polypropylene film that contacts the positive electrode may be coated with a mixed material of aluminum oxide and aramid, and the surface that contacts the negative electrode may be coated with a fluorine-based material.

[0141] The use of such a multilayer separator allows the functions of each material to be imparted to the separator, so that even if the separator as a whole is thin, insulation between the positive and negative electrodes can be ensured and the safety of the secondary battery can be maintained, which is preferable because it allows the capacity per volume of the secondary battery to be increased.

[0142] [Positive Electrode Active Material] The positive electrode active material is sometimes called positive electrode active material particles due to its shape, but it can take various shapes other than particulates. The positive electrode active material may be primary particles having multiple crystallites or secondary particles formed by aggregation of primary particles.

[0143] The positive electrode active material can be a material capable of inserting and extracting carrier ions, such as lithium ions, sodium ions, potassium ions, calcium ions, strontium ions, barium ions, beryllium ions, or magnesium ions.

[0144] Materials into which lithium ions can be inserted and extracted include lithium composite oxides having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure. For example, a lithium composite oxide having an olivine-type crystal structure is LiMPO ４(where M = Fe, Mn, Ni, or Co). Fe and Mn are expected to be the next generation positive electrode materials because of their excellent thermal stability. For example, a lithium composite oxide with a layered rock salt crystal structure is LiMO ２ (where M=Fe, Mn, Ni, or Co). When Co is present, it is represented as LiCoO ２ This is sometimes referred to as LCO or lithium cobalt oxide. Lithium composite oxides having a layered rock salt crystal structure may contain multiple elements of Fe, Mn, Ni, and Co. Those containing Ni, Mn, and Co are called LiNiCoMnO. ２ The ratio of Ni:Co:Mn may be Ni:Co:Mn=1:1:1 or its vicinity, 8:1:1 or its vicinity, or 5:2:3 or its vicinity. ２ O ５ , Nb ２ O ５ For example, lithium composite oxides with a spinel-type crystal structure are known as lithium manganese spinel (LiMn ２ O ４ ) etc.

[0145] The lithium composite oxide may contain at least one element selected from the group consisting of nickel, chromium, aluminum, iron, magnesium, molybdenum, zinc, zirconium, indium, gallium, copper, titanium, niobium, silicon, fluorine, phosphorus, etc. A lithium composite oxide containing Ni, Mn, and Co and containing aluminum may be referred to as NCMA. A lithium composite oxide containing Ni and Co and containing aluminum may be referred to as NCA.

[0146] The positive electrode active material has an average particle size of 1 μm to 50 μm, preferably 5 μm to 20 μm. In the case of a ternary composite oxide such as NCM, the positive electrode active material can be considered as secondary particles, and the average particle size of the secondary particles is 1 μm to 50 μm, preferably 5 μm to 20 μm.

[0147] To increase the packing density of the active material, a positive electrode active material with a different particle size may be added. Different particle sizes refer to different maximum values ​​of the average particle size.

[0148] The positive electrode active material may have grain boundaries located between crystallites.

[0149] The positive electrode active material may have an additive element near the surface. The surface vicinity includes a surface layer portion of the positive electrode active material. The surface layer portion is present within 50 nm, more preferably within 35 nm, even more preferably within 20 nm, and most preferably within 10 nm from the surface of the positive electrode active material toward the inside in a cross-sectional view.

[0150] The additive element may be unevenly distributed near the surface. "Uneven distribution" refers to the state in which the additive element is unevenly or unevenly distributed, and the concentration of the additive element is higher in one region than in another. Uneven distribution may also be expressed as segregation or precipitation.

[0151] Depending on the type, some additive elements may not contribute to the capacity of the positive electrode active material. The uneven distribution of the additive elements can be confirmed by the presence of a higher concentration of the additive elements near the surface than inside the positive electrode active material. The presence of the additive elements at least near the surface can prevent structural deterioration during charge and discharge, resulting in a positive electrode active material that is less susceptible to deterioration.

[0152] A structure in which a surface layer is provided on the inside of an active material is sometimes referred to as a core-shell structure.

[0153] The electrolyte solution of one embodiment of the present invention has high voltage resistance, and therefore, when combined with a positive electrode active material having high voltage resistance, a secondary battery that can be charged and discharged even at high voltage can be preferably formed. Examples of the positive electrode active material having high voltage resistance include a positive electrode active material having an O3′-type crystal structure or a monoclinic O1(15)-type crystal structure during charging, which are described with reference to FIGS.

[0154] The positive electrode active material having high voltage resistance contains lithium, cobalt, oxygen, and an additive element. Alternatively, the positive electrode active material may be lithium cobalt oxide (LiCoO ２Of the transition metals contained in the positive electrode active material, cobalt preferably accounts for 75 atomic % or more, more preferably 90 atomic % or more, and even more preferably 95 atomic % or more.

[0155] The positive electrode active material having high voltage resistance is in a discharged state, that is, Li ｘ CoO ２ In the case where x = 1 in the formula, it is preferable that the composite oxide has a layered rock-salt type crystal structure belonging to the space group R-3m. Layered rock-salt type composite oxides have high discharge capacity, have two-dimensional lithium ion diffusion paths, are suitable for lithium ion insertion / extraction reactions, and are excellent as positive electrode active materials for secondary batteries. Therefore, it is particularly preferable that the interior, which occupies most of the volume of the positive electrode active material, has a layered rock-salt type crystal structure. Figure 2 shows the layered rock-salt type crystal structure, labeled R-3mO3.

[0156] The surface layer of the high-voltage resistant positive electrode active material preferably has a function of reinforcing the internal layer structure of cobalt and oxygen octahedra to prevent destruction even when lithium is removed from the positive electrode active material upon charging. The term "reinforcement" used here refers to suppressing structural changes in the surface layer and internal part of the positive electrode active material, such as oxygen desorption and / or shifting of the layer structure of cobalt and oxygen octahedra, and / or suppressing oxidative decomposition of the electrolyte on the surface of the positive electrode active material.

[0157] Therefore, the surface layer portion of the positive electrode active material preferably has a different crystal structure from the interior. Furthermore, the surface layer portion preferably has a composition and crystal structure that are more stable at room temperature (25° C.) than the interior. For example, at least a portion of the surface layer portion of the positive electrode active material according to one embodiment of the present invention preferably has a rock salt crystal structure. Alternatively, the surface layer portion preferably has both a layered rock salt crystal structure and a rock salt crystal structure. Alternatively, the surface layer portion preferably has characteristics of both a layered rock salt crystal structure and a rock salt crystal structure.

[0158] The surface layer is the region where lithium ions are first released during charging, and is the region where the lithium concentration is likely to be lower than the interior. In addition, it can be said that the atoms on the surface of the particles of the positive electrode active material in the surface layer are in a state where some of the bonds are broken. Therefore, the surface layer is prone to become unstable, and is the region where the deterioration of the crystal structure is likely to begin. For example, if the crystal structure of the layered structure consisting of octahedra of cobalt and oxygen in the surface layer is displaced, the effect will be transmitted to the interior, causing the crystal structure of the layered structure to be displaced internally as well, which is thought to lead to the deterioration of the crystal structure of the entire positive electrode active material. On the other hand, if the surface layer can be sufficiently stabilized, Li ｘ CoO ２ Even when the value of x is small, for example, 0.24 or less, the layered structure of the internal cobalt and oxygen octahedra can be made less susceptible to breakage.Furthermore, the displacement of the internal cobalt and oxygen octahedra can be suppressed.

[0159] In order to give the surface layer a stable composition and crystalline structure, it is preferable that the surface layer contain an additive element, and more preferably, a plurality of additive elements. Furthermore, it is preferable that the surface layer has a higher concentration of one or more selected from the additive elements than the interior. Furthermore, it is preferable that one or more selected from the additive elements contained in the positive electrode active material have a concentration gradient. Furthermore, it is more preferable that the distribution of the additive element in the positive electrode active material differs depending on the additive element. For example, it is more preferable that the depth of the peak of the detection amount in the surface layer from the surface or the reference point in the EDX-ray analysis described below differs depending on the additive element. Here, the detection amount peak refers to the maximum value of the detection amount in the surface layer or within 50 nm from the surface. The detection amount refers to, for example, the count in the EDX-ray analysis.

[0160] The additive element is preferably one or more selected from magnesium, fluorine, nickel, aluminum, titanium, zirconium, vanadium, iron, manganese, chromium, niobium, arsenic, zinc, silicon, sulfur, phosphorus, boron, bromine, and beryllium.

[0161] The positive electrode active material has the above-described additive element and / or crystalline structure in a discharged state, and therefore, Li ｘ CoO２ The crystal structure when x is small is different from that of conventional positive electrode active materials. Here, "small x" means 0.1<x≦0.24.

[0162] The change in the crystal structure of a conventional positive electrode active material is shown in FIG. 3. The conventional positive electrode active material shown in FIG. 3 is lithium cobalt oxide (LiCoO ２ )

[0163] As shown in Figure 3, when x = 0.12, conventional lithium cobalt oxide has a crystal structure of the space group R-3m. This structure is similar to CoO, such as trigonal O1 type. ２ and LiCoO such as R-3m O ２ It can also be said that the structure of and the structure of are stacked alternately. Therefore, this crystal structure is sometimes called an H1-3 crystal structure. Note that actual lithium insertion / extraction does not necessarily occur uniformly within the positive electrode active material, and the lithium concentration may be uneven, so experimentally, an H1-3 crystal structure is observed from about x = 0.25. In fact, the number of cobalt atoms per unit cell in the H1-3 crystal structure is twice that of other structures. However, in Figure 3 and other parts of this specification, to facilitate comparison with other crystal structures, the c-axis of the H1-3 crystal structure is shown as half the unit cell.

[0164] Li ｘ CoO ２ When charging and discharging are repeated so that x in the formula is 0.24 or less, conventional lithium cobalt oxide undergoes repeated changes in crystal structure (i.e., non-equilibrium phase changes) between the H1-3 type crystal structure and the R-3m O3 structure in the discharged state.

[0165] However, these two crystal structures are different from CoO ２ As shown by the dotted lines and arrows in FIG. 3, in the H1-3 type crystal structure, CoO ２ The layer is significantly different from the R-3m O3 in the discharged state. Such dynamic structural changes can adversely affect the stability of the crystal structure.

[0166] In addition, the H1-3 type crystal structure has CoO like the trigonal O1 type. ２A structure with continuous layers is likely to be unstable.

[0167] Therefore, when charging and discharging is repeated so that x becomes 0.24 or less, the crystal structure of conventional lithium cobalt oxide collapses. This collapse of the crystal structure causes a deterioration in cycle characteristics. This is because the collapse of the crystal structure reduces the number of sites where lithium can exist stably and makes it difficult for lithium to be inserted and extracted.

[0168] On the other hand, in the positive electrode active material having high voltage resistance shown in FIG. ｘ CoO ２ The change in the crystal structure between the discharge state where x is 1 and the state where x is 0.24 or less is smaller than that of conventional positive electrode active materials. More specifically, the change in the crystal structure between the discharge state where x is 1 and the state where x is 0.24 or less is smaller than that of conventional positive electrode active materials. ２ The layer misalignment can be reduced. Also, the volume change per cobalt atom can be reduced. Therefore, the positive electrode active material does not easily lose its crystal structure even when repeatedly charged and discharged so that x is 0.24 or less, and excellent cycle characteristics can be achieved. In addition, the positive electrode active material has a low Li ｘ CoO ２ In the state where x is 0.24 or less, the positive electrode active material can have a more stable crystal structure than conventional positive electrode active materials. ｘ CoO ２ When the value of x in the formula (1) is kept at 0.24 or less, short circuits are unlikely to occur. In such a case, the safety of the secondary battery is further improved, which is preferable.

[0169] When x is about 0.2, the positive electrode active material has a crystal structure belonging to the trigonal space group R-3m. ２ The layer symmetry is the same as that of O3. Therefore, this crystal structure is called an O3'-type crystal structure. This crystal structure is shown in Figure 2 with the notation R-3m O3'.

[0170] In the O3'-type crystal structure, the coordinates of cobalt and oxygen in the unit cell can be expressed in the range of Co(0,0,0.5), O(0,0,x), 0.20≦x≦0.25. Furthermore, the lattice constant of the unit cell is preferably 2.797≦a≦2.837 (Å), more preferably 2.807≦a≦2.827 (Å), typically a=2.817 (Å). The c-axis is preferably 13.681≦c≦13.881 (Å), more preferably 13.751≦c≦13.811 (Å), typically c=13.781 (Å).

[0171] When x is about 0.15, the positive electrode active material has a crystal structure belonging to the monoclinic space group P2 / m. ２ There is one layer. In addition, the amount of lithium present in the positive electrode active material is about 15 atomic % in the discharged state. Therefore, this crystal structure is called a monoclinic O1(15) type crystal structure. This crystal structure is shown in Figure 2, labeled P2 / m monoclinic O1(15).

[0172] The monoclinic O1(15) type crystal structure has the coordinates of cobalt and oxygen in the unit cell as Co1(0.5,0,0.5), Co2(0,0.5,0.5), O1(X Ｏ１ , 0, Z Ｏ１ ), 0.23≦X Ｏ１ ≦0.24, 0.61≦Z Ｏ１ ≦0.65, O2(X Ｏ２ , 0.5, Z Ｏ２ ), 0.75≦X Ｏ２ ≦0.78, 0.68≦Z Ｏ２ The lattice constants of the unit cell are a = 4.880 ± 0.05 Å, b = 2.817 ± 0.05 Å, c = 4.839 ± 0.05 Å, α = 90°, β = 109.6 ± 0.1°, and γ = 90°.

[0173] This crystal structure can also show lattice constants in the space group R-3m if some error is allowed. In this case, the coordinates of cobalt and oxygen in the unit cell are Co(0,0,0.5), O(0,0,Z Ｏ ), 0.21≦Z ＯThe lattice constants of the unit cell are a = 2.817 ± 0.02 Å and c = 13.68 ± 0.1 Å.

[0174] As shown by the dotted line in FIG. 2, the CoO ２ There is almost no layer misalignment.

[0175] The difference in volume per the same number of cobalt atoms between R-3m O3 in a discharged state and the O3' type crystal structure is 2.5% or less, more specifically 2.2% or less, typically 1.8%.

[0176] The difference in volume per the same number of cobalt atoms between R-3m O3 in a discharged state and the monoclinic O1(15) type crystal structure is 3.3% or less, more specifically 3.0% or less, typically 2.5%.

[0177] CuKα calculated from the O3' type crystal structure, the monoclinic O1(15) type crystal structure, and the H1-3 type crystal structure model １ The ideal powder XRD patterns are shown in Figures 4, 5, 6A and 6B. ｘ CoO ２ LiCoO where x=1 ２ Also shown are idealized XRD patterns calculated from the crystal structure of O3 and trigonal O1 with x = 0. Figures 6A and 6B show the XRD patterns of the O3'-type crystal structure, the monoclinic O1(15)-type crystal structure, and the H1-3-type crystal structure, with Figure 6A showing an enlarged view of the region in the 2θ range of 18° to 21°, and Figure 6B showing an enlarged view of the region in the 2θ range of 42° to 46°.

[0178] As shown in Figures 4, 6A and 6B, in the O3' type crystal structure, diffraction peaks appear at 2θ = 19.25 ± 0.12° (19.13° or more and less than 19.37°) and 2θ = 45.47 ± 0.10° (45.37° or more and less than 45.57°).

[0179] In addition, in the monoclinic O1(15) type crystal structure, diffraction peaks appear at 2θ=19.47±0.10° (19.37° or more and 19.57° or less) and 2θ=45.62±0.05° (45.57° or more and 45.67° or less).

[0180] However, as shown in Figures 5, 6A and 6B, no peaks appear at these positions in the H1-3 type crystal structure and trigonal O1. ｘ CoO ２ It can be said that the appearance of peaks at 19.13° or more and less than 19.37° and / or 19.37° or more and 19.57° or less, and at 45.37° or more and less than 45.57° and / or 45.57° or more and 45.67° or less when x is small in the graph is a characteristic of the positive electrode active material.

[0181] This can be said to be because, in the positive electrode active material, the positions at which XRD diffraction peaks appear are close between the crystal structures where x = 1 and where x ≦ 0.24. More specifically, for the main diffraction peaks of the crystal structures where x = 1 and where x ≦ 0.24, the difference in 2θ between the peaks that appear at 2θ of 42° or more and 46° or less is 0.7° or less, more preferably 0.5° or less.

[0182] The positive electrode active material is Li ｘ CoO ２ When x in the formula is small, the particles have an O3'-type and / or monoclinic O1(15)-type crystal structure, but not all of the particles have an O3'-type and / or monoclinic O1(15)-type crystal structure. Other crystal structures may be included, or some may be amorphous. However, when Rietveld analysis is performed on the XRD pattern, the O3'-type and / or monoclinic O1(15)-type crystal structure is preferably 50% or more, more preferably 60% or more, and even more preferably 66% or more. If the O3'-type and / or monoclinic O1(15)-type crystal structure is 50% or more, more preferably 60% or more, and even more preferably 66% or more, the positive electrode active material can have sufficiently excellent cycle characteristics.

[0183] [Binder] The binder is provided in the positive electrode and / or negative electrode to prevent the active material or conductive material from slipping off the current collector. The binder also plays a role in binding the active material and the conductive material. For this reason, the binder may be positioned so as to be in contact with the current collector, be positioned between the active material and the conductive material, or be positioned so as to be entangled with the conductive material.

[0184] The binder contains a polymeric resin. Adding a large amount of binder can reduce the proportion of the positive electrode active material in the active material layer. A reduced proportion of the active material reduces the discharge capacity of the secondary battery, so the amount of binder mixed is kept to a minimum.

[0185] [Conductive Material] To enhance the conductivity of the positive electrode and / or negative electrode, the positive electrode and / or negative electrode preferably contain a conductive material. For example, the positive electrode active material may be a complex oxide and therefore have high resistance. This makes it difficult to collect current from the positive electrode active material to the positive electrode current collector. Therefore, the conductive material functions to assist the current path between the active material and the current collector, the current path between multiple active materials, and the current path between multiple active materials and the current collector. To fulfill this function, the conductive material is made of a material with lower resistance than the active material. The conductive material may be positioned so as to contact the current collector or may be positioned in the gaps between the active material.

[0186] Conductive materials are also called conductivity imparting agents or conductivity assistants based on their role, and carbon materials or metal materials are used. Carbon materials used as conductive materials include carbon black (furnace black, acetylene black, graphite, etc.). Carbon black has a smaller particle size than the positive electrode active material. Fibrous carbon materials used as conductive materials include carbon nanotubes (CNT) and VGCF (registered trademark). Sheet-shaped carbon materials used as conductive materials include multilayer graphene.

[0187] Particulate conductive materials can penetrate into the gaps between the positive electrode active materials and are prone to aggregation. Therefore, particulate conductive materials can support the conductive paths between closely spaced positive electrode active materials (between adjacent positive electrode active materials). Fibrous or sheet-like conductive materials also have folded regions, but are larger than the positive electrode active materials. Therefore, fibrous or sheet-like conductive materials can support the conductive paths between adjacent positive electrode active materials as well as between spaced positive electrode active materials. It is recommended to mix particulate, fibrous, and sheet-like conductive materials.

[0188] When graphene is used as the sheet-like conductive material and is mixed with carbon black as the particulate conductive material, the weight of the carbon black in the slurry is preferably 1.5 to 20 times, and more preferably 2 to 9.5 times, the weight of the graphene.

[0189] Furthermore, when the mixture ratio of graphene and carbon black is within the above range, the carbon black is easily dispersed without aggregation. Furthermore, when the mixture ratio of graphene and carbon black is within the above range, the electrode density can be increased compared to when only carbon black is used as the conductive material. Increasing the electrode density can increase the capacity per unit weight. Specifically, the density of the positive electrode active material layer measured gravimetrically can be increased to more than 3.5 g / cc.

[0190] In addition, when comparing a positive electrode using only graphene as the conductive material with a positive electrode using a mixture of graphene and carbon black, by setting the mixture ratio of graphene and carbon black within the above range, it is possible to support rapid charging. For example, rapid charging of portable information terminals is also possible, improving convenience. Furthermore, if a vehicle is equipped with a secondary battery capable of rapid charging, the effect of so-called regenerative charging, in which temporary power is generated when the vehicle brakes, is enhanced and the amount of power is charged, is preferably enhanced.

[0191] [Current Collector] For the positive electrode current collector and the negative electrode current collector, a metal foil containing aluminum, titanium, copper, nickel, or the like can be used.

[0192] [Negative Electrode Active Material] Examples of the negative electrode active material include alloy-based materials and carbon-based materials. The negative electrode active material used in the secondary battery of one embodiment of the present invention preferably contains fluorine as a halogen. Fluorine has a high electronegativity, and the presence of fluorine in the surface layer of the negative electrode active material may have the effect of facilitating the desorption of the solvated solvent from the surface of the negative electrode active material.

[0193] As the negative electrode active material, an element capable of undergoing a charge / discharge reaction by alloying / dealloying with lithium can be used. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used. These elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4200 mAh / g. For this reason, it is preferable to use silicon as the negative electrode active material. Alternatively, a compound containing these elements may be used. For example, SiO (silicon monoxide, SiO Ｘ where x is preferably 0.2 or more and 1.5 or less), Mg ２ Si, Mg ２ Ge, SnO, SnO ２ , Mg ２ Sn, SnS ２ , V ２ Sn ３ , FeSn ２ , CoSn ２ , Ni ３ Sn ２ , Cu ６ Sn ５ , Ag ３ Sn, Ag ３ Sb, Ni ２ MnSb, CeSb ３ , LaSn ３ , La ３ Co ２ Sn ７ , CoSb ３ , InSb, SbSn, etc. Here, elements that can undergo charge-discharge reactions by alloying / dealloying reactions with lithium, and compounds containing such elements, are sometimes referred to as alloy-based materials.

[0194] Silicon nanoparticles can be used as the silicon-containing negative electrode active material. The median diameter (D50) of the silicon nanoparticles is 5 nm or more and less than 1 μm, preferably 10 nm or more and 300 nm or less, and more preferably 10 nm or more and 100 nm or less. The silicon nanoparticles may be crystalline. Furthermore, the silicon nanoparticles may have a crystalline region and an amorphous region.

[0195] The silicon-containing negative electrode active material may be in the form of silicon monoxide particles containing one or more silicon crystal grains. The silicon monoxide may be amorphous. The silicon monoxide particles may be carbon-coated. The carbon-coated particles may be mixed with graphite to form the negative electrode active material.

[0196] Examples of carbon-based materials that can be used include graphite, graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, and carbon black. It is preferable to incorporate fluorine into these carbon-based materials. A carbon-based material containing fluorine can also be called a particulate or fibrous fluorinated carbon material. When measuring a carbon-based material by X-ray photoelectron spectroscopy, the fluorine concentration is preferably 1 atomic % or more relative to the total concentration of fluorine, oxygen, lithium, and carbon.

[0197] Furthermore, although negative electrode active materials may undergo volume changes during charge and discharge, disposing an organic compound containing fluorine, such as a fluorinated carbonate, between the negative electrode active materials makes them slippery even when volume changes occur during charge and discharge, suppressing cracks and improving cycle characteristics. It is important that an organic compound containing fluorine is present between multiple negative electrode active materials.

[0198] 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, spherical graphite having a spherical shape can be used as the artificial graphite. For example, MCMB may have a spherical shape and is preferred. Furthermore, it is relatively easy to reduce the surface area of ​​MCMB and this may be preferred. Examples of natural graphite include flake graphite and spherical natural graphite.

[0199] When lithium ions are inserted into graphite (when a lithium-graphite intercalation compound is formed), the graphite exhibits a potential as low as that of metallic lithium (0.05 V to 0.3 V vs. Li / Li ＋ This allows lithium-ion secondary batteries to exhibit high operating voltages. Graphite is also preferred because it has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and higher safety compared to lithium metal.

[0200] Titanium dioxide (TiO ２ ), lithium titanium oxide (Li ４ Ti ５ O １２ ), lithium-graphite intercalation compound (Li ｘ C ６ ), niobium pentoxide (Nb ２ O ５ ), tungsten oxide (WO ２ ), molybdenum oxide (MoO ２ ) and other oxides can be used.

[0201] In addition, as the negative electrode active material, a composite nitride of lithium and a transition metal, Li ３ Li with N-type structure ３−ｘ M ｘ N (M=Co, Ni, Cu) can be used. For example, Li ２．６ Co ０．４ N ３ has a large charge / discharge capacity (900 mAh / g, 1890 mAh / cm ３ ) and is preferred.

[0202] When a composite nitride of lithium and a transition metal is used, lithium ions are contained in the negative electrode active material, so V, which does not contain lithium ions, can be used as the positive electrode active material. ２ O ５ , Cr ３ O ８ It is preferable that the composite nitride of lithium and a transition metal can be used as the negative electrode active material, even when a material containing lithium ions is used as the positive electrode active material, by first removing the lithium ions contained in the positive electrode active material.

[0203] Furthermore, a material that undergoes a conversion reaction can also be used as the negative electrode active material. For example, a transition metal oxide that does not form an alloy with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), or iron oxide (FeO), may be used as the negative electrode active material. The conversion reaction can also occur when Fe ２ O ３ ,CuO,Cu ２ O, RuO ２ , Cr ２ O ３ oxides such as CoS ０．８９ , sulfides such as NiS and CuS, Zn ３ N ２ , Cu ３ N, Ge ３ N ４ Nitrides such as NiP ２ , FeP ２ , CoP ３ Phosphides such as FeF ３ , BiF ３ This also occurs with fluorides such as

[0204] [Fluorine-Modified Conductive Material] The conductive material of the negative electrode is preferably modified with fluorine. For example, the conductive material may be any of the above-mentioned conductive materials modified with fluorine.

[0205] The fluorine modification of the conductive material can be performed by, for example, a treatment with a fluorine-containing gas, a heat treatment, a plasma treatment in a fluorine-containing gas atmosphere, etc. Examples of the fluorine-containing gas include fluorine gas and fluoromethane (CF ４ ), and other lower fluorine-containing hydrocarbon gases can be used.

[0206] Alternatively, the conductive material may be immersed in a solution containing hydrofluoric acid, tetrafluoroboric acid, hexafluorophosphoric acid, or the like, or a solution containing a fluorine-containing ether compound, for example, to modify the conductive material with fluorine.

[0207] Fluorine modification of the conductive material is expected to stabilize the structure of the conductive material and suppress side reactions during the charge and discharge process of the secondary battery. Suppression of side reactions can improve charge and discharge efficiency. Furthermore, it can suppress a decrease in capacity due to repeated charge and discharge. Therefore, by using a fluorine-modified conductive material in the negative electrode of one embodiment of the present invention, an excellent secondary battery can be realized.

[0208] By stabilizing the structure of the conductive material, the conductive properties are stabilized, and high output characteristics may be achieved.

[0209] This embodiment can be used in combination with other embodiments.

[0210] Embodiment Mode 3 In this embodiment mode, examples of a plurality of types of shapes of secondary batteries including the materials and the like described in the previous embodiment mode will be described.

[0211] [Coin-type secondary battery] An example of a coin-type secondary battery will be described below. Fig. 7B is an external view of a coin-type (single-layer flat) secondary battery, Fig. 7A is a diagram illustrating the configuration thereof, and Fig. 7C is a cross-sectional view thereof.

[0212] In the coin-type secondary battery 300, a positive electrode can 301, which also serves as a positive electrode terminal, and a negative electrode can 302, which also serves as a negative electrode terminal, are insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with the negative electrode current collector.

[0213] It is to be noted that the positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 each only need to have an active material layer formed on one side.

[0214] The positive electrode can 301 and the negative electrode can 302 can be made of a metal such as nickel, aluminum, or titanium that is corrosion-resistant to the electrolyte, or an alloy of these metals or an alloy of these metals with other metals (e.g., stainless steel). Furthermore, to prevent corrosion by the electrolyte, it is preferable to coat them with nickel, aluminum, or the like. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307.

[0215] These negative electrode 307, positive electrode 304, and separator 310 are immersed in an electrolyte, and as shown in FIG. 7A , the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are stacked in this order with the positive electrode can 301 facing downwards, and the positive electrode can 301 and the negative electrode can 302 are crimped together via a gasket 303, thereby producing a coin-type secondary battery 300.

[0216] By using the electrolyte described in the previous embodiment as the electrolyte of the secondary battery, it is possible to provide a secondary battery that can be used in a wide temperature range.

[0217] [Secondary Battery Having a Wound Body] A secondary battery having a wound body will be described with reference to Fig. 8. A wound body 950a shown in Fig. 8A has a negative electrode 931, a positive electrode 932, and a separator 933. The negative electrode 931 has a negative electrode active material layer 931a. The positive electrode 932 has a positive electrode active material layer 932a.

[0218] The separator 933 has a width wider than the negative electrode active material layer 931 a and the positive electrode active material layer 932 a, and is wound so as to overlap the negative electrode active material layer 931 a and the positive electrode active material layer 932 a. From the standpoint of safety, it is preferable that the negative electrode active material layer 931 a be wider than the positive electrode active material layer 932 a. A wound body 950 a having such a shape is preferable due to its high safety and productivity.

[0219] 8A and 8B , the negative electrode 931 is electrically connected to a terminal 951. The terminal 951 is electrically connected to a terminal 911a. The positive electrode 932 is electrically connected to a terminal 952. The terminal 952 is electrically connected to a terminal 911b. The wound body 950a is immersed in an electrolyte inside the housing 930.

[0220] As shown in Fig. 8C, the wound body 950a and the electrolyte are covered with a housing 930 to form a secondary battery 913. The housing 930 is preferably provided with a safety valve, an overcurrent protection element, and the like. The safety valve is a valve that opens when a predetermined pressure is reached inside the housing 930 to prevent the battery from exploding. The housing 930 can be made of a metal material (e.g., aluminum) or a resin material.

[0221] 8B, the secondary battery 913 may have a plurality of wound bodies 950a. By using a plurality of wound bodies 950a, the secondary battery 913 can have a larger charge / discharge capacity.

[0222] By using the electrolyte described in the previous embodiment as the electrolyte of the secondary battery, it is possible to provide a secondary battery that can be used in a wide temperature range.

[0223] [Cylindrical Secondary Battery] An example of a cylindrical secondary battery will be described with reference to Figures 9A and 9B. As shown in Figure 9A, a cylindrical secondary battery 616 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 battery can (external can) 602 is formed from a metal material and has excellent water barrier properties and gas barrier properties. The positive electrode cap 601 and the battery can (external can) 602 are insulated by a gasket (insulating packing) 610.

[0224] As shown in FIG. 9B , a battery element is provided inside a hollow cylindrical battery can 602. The battery element is wound around a center pin (not shown). One end of the battery can 602 is closed and the other end is open. The battery can 602 can be made of a metal, such as nickel, aluminum, or titanium, or an alloy of these metals or an alloy of these metals with other metals (e.g., stainless steel), which is corrosion-resistant to electrolytes. To prevent corrosion by the electrolyte, the battery can 602 is preferably coated with nickel, aluminum, or the like. Inside the battery can 602, the wound battery element, consisting of the positive electrode, negative electrode, and separator, is sandwiched between a pair of opposing insulating plates 608 and 609. An electrolyte (not shown) is injected into the battery can 602, where the battery element is provided. The electrolyte can be the same as that used in coin-type secondary batteries.

[0225] Since the positive and negative electrodes used in cylindrical secondary batteries are wound up, it is preferable to form active materials on both sides of the current collector.

[0226] By using the electrolyte described in the previous embodiment as the electrolyte of the secondary battery, it is possible to provide a secondary battery that can be used in a wide temperature range.

[0227] 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 increase in internal pressure of the battery exceeds a predetermined threshold. The PTC element 611 is a thermosensitive resistor whose resistance increases as the temperature increases, and the increased resistance limits the amount of current to prevent abnormal heat generation. The PTC element is made of barium titanate (BaTiO ３)-based semiconductor ceramics, etc. can be used.

[0228] 9C shows an example of a battery pack 615. The battery pack 615 has a plurality of secondary batteries 616. Each secondary battery is electrically connected to a conductive plate 628 and a conductive plate 614. To clarify the configuration, only a portion of the conductive plate 628 is shown.

[0229] The plurality of secondary batteries 616 may be connected in parallel by conductive plates and wiring, or in series, or may be connected in parallel and then in series. By configuring a battery pack 615 having a plurality of secondary batteries 616, a large amount of power can be extracted.

[0230] The conductive plate 628 and the conductive plate 614 are electrically connected to a control circuit 620 via wiring 621 and wiring 622, respectively. As the control circuit 620, a charge / discharge control circuit that performs charging / discharging and the like and a protection circuit that prevents overcharging or overdischarging can be applied.

[0231] Furthermore, a temperature control device may be provided between the multiple secondary batteries 616. When a secondary battery 616 is overheated, it can be cooled by the temperature control device, and when a secondary battery 616 is too cold, it can be heated by the temperature control device. This makes it difficult for the performance of the battery pack 615 to be affected by the outside temperature.

[0232] [Battery Pack Having Multiple Types of Secondary Batteries] A battery pack in which secondary batteries having different electrolytes are arranged will be described with reference to FIGS. 10 and 11. FIG.

[0233] The battery pack 100 shown in FIG. 10A includes a secondary battery 101 and a secondary battery 102 adjacent to each other. The secondary battery 101 has an electrolyte with excellent carrier ion conductivity even at low temperatures, as described in the previous embodiment. The secondary battery 102 is a secondary battery that can achieve high charge / discharge characteristics and cycle characteristics in a medium temperature range. The medium temperature range refers to, for example, a temperature range of 0° C. or higher and 45° C. or lower. In order to achieve high charge / discharge characteristics in the medium temperature range, the secondary battery 102 preferably has an organic solvent as the electrolyte. Furthermore, using an organic solvent as the electrolyte allows for more inexpensive production.

[0234] With this configuration, in a low-temperature environment, the heat generated by the charging and discharging of the secondary battery 101 can be used as an internal heat source to heat the secondary battery 102. By heating the secondary battery 102 to a medium temperature range or approaching the medium temperature range, the high charge and discharge characteristics of the secondary battery 102 can be utilized.

[0235] In this specification, A and B being adjacent does not necessarily mean that A and B are in contact, but that they are close enough to allow thermal conduction. For example, if A and B are in the same container, box, bundle, etc., they can be said to be adjacent.

[0236] 10A shows an example in which the secondary batteries 101 and 102 of the battery pack 100 are both rectangular parallelepipeds and are arranged with their largest surfaces facing each other. This arrangement can improve the efficiency of heat conduction.

[0237] A rectangular parallelepiped is a hexahedron with all faces formed by rectangles. In this specification, these rectangles do not have to be strictly rectangular, and they do not have to be strictly flat. For example, a positive electrode terminal and / or a negative electrode terminal may be provided on one side, or the surface may have irregularities to increase strength. Such a shape may also be referred to as a substantially rectangular parallelepiped.

[0238] In the battery pack 100, it is preferable to arrange the secondary battery 102 so as to surround or sandwich the secondary battery 101 that operates in a low-temperature environment. It can even be said that it is preferable to arrange the secondary battery 101 on the inside.

[0239] Fig. 10B shows an example of a battery pack 100 having six secondary batteries 102 sandwiching one secondary battery 101. Fig. 10C shows an example of a battery pack 100 having three secondary batteries 101 and four secondary batteries 102 alternately.

[0240] With this configuration, heat generated from the secondary batteries 101 can be efficiently transferred to the secondary batteries 102. Furthermore, even if the number of secondary batteries 101, which tends to be costly, is small, a storage battery with a wide operating temperature range can be obtained.

[0241] FIG. 11A shows an example in which both the secondary battery 101 and the secondary battery 102 of the battery pack 100 are cylindrical.

[0242] In this specification, a cylindrical shape refers to a solid body having circular bottom and top surfaces. These circles do not have to be strictly circular, and they do not have to be strictly flat. For example, a positive electrode terminal and / or a negative electrode terminal may be provided, and the body may have irregularities to increase strength. Such a shape may also be referred to as a substantially cylindrical shape.

[0243] As in the case of a rectangular parallelepiped, Fig. 11B shows an example of a battery pack 100 having eight secondary batteries 102 surrounding one secondary battery 101. Fig. 11C shows an example of a battery pack 100 having fourteen secondary batteries 102 surrounding four secondary batteries 101.

[0244] Preferably, the battery pack 100 further includes a temperature sensor and a control circuit. The temperature sensor has a function of detecting at least the temperature of the secondary battery 102. The control circuit preferably has a function of causing the secondary battery 101 to self-heat when the temperature of the secondary battery 102 is lower than the operating temperature range, thereby heating the secondary battery 102 to the operating temperature range.

[0245] For example, in the case of a battery pack 100 having a secondary battery 101 with an operating temperature range of -20°C or higher and 0°C or lower, a secondary battery 102 with an operating temperature range of 0°C or higher and 45°C or lower, a temperature sensor, and a control circuit, it is preferable that the control circuit has a function of causing the secondary battery 101 to self-heat and heat up when the temperature sensor detects that the temperature of the secondary battery 102 is below 0°C, thereby keeping the temperature of the secondary battery 102 within the range of 0°C or higher and 45°C or lower.

[0246] Note that within the operating temperature range of the secondary battery 102, the secondary battery 101 may or may not be driven, i.e., charged or discharged. For example, the control circuit may have a function to drive the secondary battery 101 when the temperature is below 25°C and not drive the secondary battery 101 when the temperature is 25°C or higher.

[0247] There is no particular limitation on the method for causing self-heating of the secondary battery 101. Self-heating of the secondary battery 101 occurs even when normal charging and discharging is performed.

[0248] Furthermore, it is more preferable that the control circuit not only controls the temperature but also has a function of detecting at least one of overcharging, overdischarging, and overcurrent, and protecting the secondary batteries 101 and 102 .

[0249] [Flexible Battery] The flexible battery will be described with reference to FIGS. 12 to 16. FIG.

[0250] Fig. 12B is a top view of the secondary battery 10 shown in Fig. 12A. The secondary battery 10 shown in Fig. 12A and Fig. 12B has an exterior body 50, and a positive electrode lead 21 and a negative electrode lead 31 extending from the inside of a space enclosed by the exterior body 50 to the outside.

[0251] 13A and 13B are schematic cross-sectional views of the cut surface taken along dashed line X1'-X2' shown in Fig. 12B, with Fig. 13A showing the secondary battery 10 in an unbent state (stretched state) and Fig. 13B showing the secondary battery 10 in a curved state (bent state). Note that separators are omitted from Figs. 13A and 13B to avoid cluttering the drawings.

[0252] 12A , 12B , etc., the secondary battery 10 can be repeatedly deformed into at least two shapes, such as an uncurved shape and a curved shape. Furthermore, the shapes that the secondary battery 10 of one embodiment of the present invention can assume are not limited to those shown in FIGS. 12A , 12B , etc. The secondary battery 10 may be deformed into two shapes, a shape curved with a first radius of curvature and a shape curved with a second radius of curvature different from the first radius of curvature, or a shape curved with a third radius of curvature different from both the first radius of curvature and the second radius of curvature.

[0253] 12A, 12B, etc. show a shape in which the entire secondary battery 10 is uniformly curved, but the secondary battery 10 may have a first region curved with a first radius of curvature and a second region curved with a second radius of curvature different from the first radius of curvature. Also, the secondary battery 10 may have regions curved with two or more different radii of curvature.

[0254] [Example of Electrode Stack] Hereinafter, a configuration example of a stack having a plurality of stacked electrodes that can be used in a flexible battery will be described.

[0255] 14A shows a top view of a positive electrode current collector 72, FIG. 14B shows a separator 73, FIG. 14C shows a negative electrode current collector 74, FIG. 14D shows a sealing layer 75 and a lead electrode 76, and FIG. 14E shows a top view of a film-like exterior body 11.

[0256] 14A and 14B, the dimensions of the area 71 surrounded by the dashed line in Fig. 14E are approximately the same as those of the separator 73 in Fig. 14B. The broken line in Fig. 14E and the area between the broken line and the end are joints 83 and 84, respectively.

[0257] 15A shows an example in which positive electrode active material layers 78 are provided on both sides of a positive electrode current collector 72. More specifically, the layers are arranged in the following order: a negative electrode current collector 74, a negative electrode active material layer 79, a separator 73, a positive electrode active material layer 78, a positive electrode current collector 72, a positive electrode active material layer 78, a separator 73, a negative electrode active material layer 79, and a negative electrode current collector 74. A cross-sectional view of this laminated structure cut along plane 80 is shown in FIG.

[0258] 15A shows an example in which two separators are used, it is also possible to use a structure in which one separator is folded and sealed at both ends to form a bag shape, and the positive electrode current collector 72 is housed therein. Positive electrode active material layers 78 are formed on both sides of the positive electrode current collector 72 housed in the bag-shaped separator.

[0259] It is also possible to provide anode active material layers 79 on both sides of the anode current collector 74. Fig. 15C shows an example of a secondary battery in which three anode current collectors 74 having anode active material layers 79 on both sides, four cathode current collectors 72 having cathode active material layers 78 on both sides, and eight separators 73 are sandwiched between two anode current collectors 74 having anode active material layers 79 on only one side. In this case, four pouch-shaped separators may be used instead of eight separators.

[0260] Increasing the number of layers can increase the capacity of the secondary battery. Also, by providing positive electrode active material layers 78 on both sides of the positive electrode current collector 72 and negative electrode active material layers 79 on both sides of the negative electrode current collector 74, the thickness of the secondary battery can be reduced.

[0261] When stacking in this manner and fixing and electrically connecting all of the positive electrode current collectors 72, ultrasonic welding is used, which allows for joining at one time. Furthermore, if ultrasonic welding is performed while overlapping the lead electrode in addition to the positive electrode current collector 72, electrical connection can be made efficiently.

[0262] Ultrasonic welding can be performed by overlapping the tab portion with the tab portion of another positive electrode current collector and applying ultrasonic waves while applying pressure.

[0263] Furthermore, the separator 73 preferably has a shape that makes it difficult for the positive electrode current collector 72 and the negative electrode current collector 74 to electrically short-circuit. For example, as shown in FIG. 16A , it is preferable to make the width of each separator 73 larger than the positive electrode current collector 72 and the negative electrode current collector 74, because this prevents the positive electrode current collector 72 and the negative electrode current collector 74 from contacting each other even when their relative positions are displaced due to deformation such as bending. Furthermore, it is preferable to have one separator 73 folded like an accordion as shown in FIG. 16B or one separator 73 wound alternately around the positive electrode current collector 72 and the negative electrode current collector 74 as shown in FIG. 16C , because this prevents the positive electrode current collector 72 and the negative electrode current collector 74 from contacting each other even when their relative positions are displaced. Furthermore, FIGS. 16B and 16C show examples in which a portion of the separator 73 is provided so as to cover the side surface of the stacked structure of the positive electrode current collector 72 and the negative electrode current collector 74.

[0264] 16 does not show the positive electrode active material layer 78 and the negative electrode active material layer 79, the method for forming them may be the same as that described above. Also, while an example in which the positive electrode current collectors 72 and the negative electrode current collectors 74 are alternately arranged has been shown here, a configuration in which two positive electrode current collectors 72 or two negative electrode current collectors 74 are continuous with each other as described above may also be used.

[0265] In this embodiment, an example of a structure in which a rectangular film is folded in the center and the two edges are overlapped to seal the film is shown, but the shape of the film is not limited to a rectangle. The shape of the film is also not limited to a rectangle and may be any other symmetrical shape such as a triangle, square, pentagon, or other polygon, a circle, or a star.

[0266] This embodiment can be used in combination with other embodiments.

[0267] 17 to 26 , examples of electronic devices incorporating a secondary battery according to one embodiment of the present invention are described. Examples of electronic devices incorporating a secondary battery include electric vehicles (EVs), electric bicycles, electric motorcycles, television sets (also referred to as televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (also referred to as mobile phones or mobile phone sets), portable game consoles, personal digital assistants (PDAs), sound players, and large game consoles such as pachinko machines. Examples of PDAs include notebook personal computers, tablet devices, e-book readers, and mobile phones.

[0268] The electronic device 6500 shown in FIG. 17A is a portable information terminal that can be used as a smartphone.

[0269] The electronic device 6500 includes at least a first housing 6501a, a second housing 6501b, a hinge portion 6519, a display portion 6502a, a power button 6503, a button 6504, a speaker 6505, and a microphone 6506. The display portion 6502a has a touch panel function. The first housing 6501a and the second housing 6501b are connected to each other via the hinge portion 6519.

[0270] In addition, the electronic device 6500 can be folded at the hinge portion 6519.

[0271] FIG. 17B is a schematic cross-sectional view including the end portion of the housing 6501 (6501a, 6501b) on the microphone 6506 side.

[0272] A light-transmitting protective member 6510 is provided on the display surface side of the housing 6501 (6501a, 6501b), and a display panel 6511, an optical member 6512, a touch sensor panel 6513, a printed circuit board 6517, and a first battery 6518a are arranged in the space surrounded by the housing 6501 (6501a, 6501b) and the protective member 6510.

[0273] A display panel 6511, an optical member 6512, and a touch sensor panel 6513 are fixed to the protective member 6510 by adhesive layers (not shown).

[0274] In a region outside the display portion 6502a, a part of the display panel 6511 is folded back, and the folded back part is connected to an FPC 6515. An IC 6516 is mounted on the FPC 6515. The FPC 6515 is connected to a terminal provided on a printed circuit board 6517.

[0275] A flexible display can be applied to the display panel 6511. The flexible display is configured using a plurality of flexible films and uses a plurality of light-emitting elements arranged in a matrix. It is preferable to use an EL element (also referred to as an EL device) such as an OLED or a QLED as the light-emitting element. Examples of light-emitting materials included in the EL element include a fluorescent material (fluorescent material), a phosphorescent material (phosphorescent material), an inorganic compound (such as a quantum dot material), and a material that exhibits thermally activated delayed fluorescence (thermally activated delayed fluorescence (TADF) material). Furthermore, an LED such as a micro LED can also be used as the light-emitting element.

[0276] By using a flexible display, the display panel 6511 can be provided at a position overlapping with the first housing 6501 a, the second housing 6501 b, and the hinge portion 6519, and the display panel 6511 can be bent at the hinge portion 6519.

[0277] By using a flexible display, the internal space of the housing 6501 (6501a, 6501b) can be effectively utilized, and an extremely lightweight electronic device can be realized. In addition, since the display panel 6511 is extremely thin, the thickness of the electronic device can be reduced, and a large-capacity first battery 6518a can also be mounted thereon.

[0278] Furthermore, in order to use a large-capacity battery, the electronic device 6500 is configured to include a second battery 6518b inside the cover portion 6520. Although a connection portion is not shown, the first battery 6518a and the second battery 6518b are electrically connected to each other. The flexible battery of one embodiment of the present invention can be used as the first battery 6518a and the second battery 6518b.

[0279] By using a flexible battery, the battery can be provided at a position overlapping with the first housing 6501 a, the second housing 6501 b, and the hinge portion 6519 , and the battery can be bent at the hinge portion 6519 .

[0280] FIG. 17C is a cross-sectional schematic view including hinge portion 6519.

[0281] The first battery 6518a and the second battery 6518b preferably have battery connectors 6521 (6521a, 6521b) having positive and negative leads in an area overlapping with the hinge portion 6519 or in the vicinity of the area overlapping with the hinge portion 6519. The battery connectors 6521 can be electrically connected to a printed circuit board 6523 via FPCs 6522 (6522a, 6522b). The battery connectors 6521 can have protection circuits such as an overcharge protection circuit, an overdischarge protection circuit, an overcurrent protection circuit, and an overheating protection circuit.

[0282] In this manner, by providing the battery connection portion 6521 of the battery 6518 extending from one side of the hinge portion 6519 to the other side in an area overlapping with the hinge portion 6519 or in the vicinity of the area overlapping with the hinge portion 6519, it is possible to reduce stress applied to the positive electrode lead connection portion or the negative electrode lead connection portion of the battery 6518 when the battery 6518 is bent, as described in Embodiment 1. In other words, it is possible to suppress deterioration of the battery 6518 due to bending.

[0283] Furthermore, the first battery 6518a and the second battery 6518b preferably have a fixed portion with the housing 6501 (6501a, 6501b) and a fixed portion with the cover portion 6520 in an area overlapping with the hinge portion 6519 or in the vicinity of the area overlapping with the hinge portion 6519. By making the first battery 6518a and the second battery 6518b slidable within the housing 6501 (6501a, 6501b) and the cover portion 6520, respectively, other than the fixed portions, the battery 6518 can be easily bent inside the electronic device 6500.

[0284] In addition, by folding back a part of the display panel 6511 and arranging a connection portion with the FPC 6515 on the back side of the pixel portion, an electronic device with a narrow frame can be realized.

[0285] By using the flexible battery of one embodiment of the present invention as one or both of the first battery 6518a and the second battery 6518b, a part of the electronic device 6500 can be bent, and the electronic device 6500 can be miniaturized and highly portable.

[0286] 18A is a perspective view showing a state in which the portion indicated by the dotted line in FIG. 17A is folded. The electronic device 6500 can be folded in two, and the display portion 6502a and the second battery 6518b can be folded repeatedly.

[0287] 18A shows a configuration in which the second display unit 6502b is provided in the area where the cover unit 6520 slides when folded. Even when folded in two, the user can visually check the second display unit 6502b to see a simple time display or a notification display of incoming email.

[0288] 18B is a schematic diagram showing a cross section of the cover when the electronic device 6500 is folded. For simplicity, the inside of the housing 6501 (6501a, 6501b) is not shown in FIG.

[0289] 18B, the hinge portion 6519 can also be called a connecting portion, and is not limited to the example of a structure in which a plurality of pillars are connected, and can have various forms. In particular, it is preferable to have a mechanism that allows the display portion 6502a and the second battery 6518b to be bent without expanding or contracting.

[0290] Although second battery 6518b is shown inside cover 6520, multiple second batteries may be included. Cover 6520 may also include a charging control circuit or a wireless charging circuit for second battery 6518b inside.

[0291] The cover portion 6520 is partially fixed to the housing 6501 (6501a and 6501b), and a portion overlapping with the hinge portion 6519 and a portion overlapping with the second display portion 6502b after being bent and slid are not fixed.

[0292] Furthermore, the cover unit 6520 does not need to be fixed to the housing 6501 (6501a, 6501b) and may be detachable. When a large capacity is not required, the electronic device 6500 can be used by detaching the cover unit 6520 and using only the first battery 6518a. Furthermore, if the detached second battery 6518b is charged, the first battery 6518a can be replenished when the second battery 6518b is reconnected to the first battery 6518a. Therefore, the cover unit 6520 can also be used as a mobile battery.

[0293] 18A and 18B show an example in which the display unit 6502a is folded in half so that the display surface thereof faces inward, but this is not particularly limited thereto, and depending on the configuration of the hinge portion 6519, it may also be possible to fold the display unit 6502a in half so that the display surface faces outward.

[0294] The flexible battery of one embodiment of the present invention has high reliability against repeated deformation and can therefore be suitably used in such foldable devices.

[0295] 19A shows an example of a mobile phone. The mobile phone 2100 includes a display portion 2102 built into a housing 2101, an operation button 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. The mobile phone 2100 includes a secondary battery 2107. By using the secondary battery 2107 containing the electrolyte described in Embodiment 1, the mobile phone 2100 can be used in a wide temperature range.

[0296] The mobile phone 2100 can execute various applications such as mobile phone calls, e-mail, document browsing and creation, music playback, internet communication, and computer games.

[0297] The operation button 2103 can be provided with various functions such as time setting, power on / off operation, wireless communication on / off operation, silent mode activation / deactivation, power saving mode activation / deactivation, etc. For example, the functions of the operation button 2103 can be freely set by an operating system incorporated in the mobile phone 2100.

[0298] The mobile phone 2100 is also capable of performing standardized short-range wireless communication, and can also make hands-free calls by communicating with a wirelessly enabled headset, for example.

[0299] The mobile phone 2100 also includes an external connection port 2104, which allows direct data exchange with other information terminals via a connector. Charging can also be performed via the external connection port 2104. Note that charging may be performed by wireless power supply without using the external connection port 2104.

[0300] The mobile phone 2100 preferably has a sensor, such as a fingerprint sensor, a pulse sensor, a body temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, or the like.

[0301] 19B illustrates an unmanned aerial vehicle 2300 having a plurality of rotors 2302. The unmanned aerial vehicle 2300 is sometimes called a drone. The unmanned aerial vehicle 2300 includes a secondary battery 2301 according to one embodiment of the present invention, a camera 2303, and an antenna (not shown). The unmanned aerial vehicle 2300 can be remotely controlled via the antenna. The secondary battery having the electrolyte described in Embodiment 1 has a wide usable temperature range and is therefore suitable as a secondary battery to be mounted on the unmanned aerial vehicle 2300.

[0302] Fig. 19C shows an example of a robot. A robot 6400 shown in Fig. 19C includes a secondary battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6407, a movement mechanism 6408, a computing device, etc.

[0303] The microphone 6402 has a function of detecting the user's speaking voice, environmental sounds, etc. The speaker 6404 has a function of emitting sound. The robot 6400 can communicate with the user using the microphone 6402 and the speaker 6404.

[0304] The display unit 6405 has a function of displaying various information. The robot 6400 can display information desired by the user on the display unit 6405. The display unit 6405 may be equipped with a touch panel. The display unit 6405 may also be a detachable information terminal, which can be installed in a fixed position on the robot 6400 to enable charging and data transfer.

[0305] The upper camera 6403 and the lower camera 6406 have the function of capturing images of the surroundings of the robot 6400. Furthermore, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize the surrounding environment and move safely using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407.

[0306] The robot 6400 includes a secondary battery 6409 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal region. The secondary battery having the electrolyte described in Embodiment 1 has a wide usable temperature range and is therefore suitable as the secondary battery 6409 to be mounted on the robot 6400.

[0307] 19D shows an example of a cleaning robot. The cleaning robot 6300 includes a display unit 6302 arranged on the top surface of a housing 6301, a plurality of cameras 6303 arranged on the side surfaces, a brush 6304, an operation button 6305, a secondary battery 6306, various sensors, and the like. Although not shown, the cleaning robot 6300 is provided with tires, a suction port, and the like. The cleaning robot 6300 can move by itself, detect dust 6310, and suck up the dust from a suction port arranged on the bottom surface.

[0308] For example, the cleaning robot 6300 can analyze an image captured by the camera 6303 and determine whether or not there is an obstacle such as a wall, furniture, or a step. Furthermore, when an object that may become entangled in the brush 6304, such as a wire, is detected through image analysis, the cleaning robot 6300 can stop rotation of the brush 6304. The cleaning robot 6300 includes a secondary battery 6306 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal region. The secondary battery having the electrolyte described in Embodiment 1 has a wide usable temperature range and is therefore suitable as the secondary battery 6306 to be mounted on the cleaning robot 6300.

[0309] 20A shows an example of a wearable device. The wearable device uses a secondary battery as a power source. Furthermore, in order to improve splash-proof, water-resistant, or dust-proof performance when used at home or outdoors, there is a demand for a wearable device that can be charged wirelessly as well as via a wired connection with an exposed connector.

[0310] For example, a secondary battery according to one embodiment of the present invention can be mounted on an eyeglasses-type device 4000 as shown in FIG. 20A . The eyeglasses-type device 4000 includes a frame 4000 a and a display portion 4000 b. Mounting a secondary battery on temple portions of the curved frame 4000 a makes it possible to provide the eyeglasses-type device 4000 with a lightweight design, a well-balanced weight, and a long continuous use time. The secondary battery having the electrolyte described in Embodiment 1 has a wide usable temperature range and is therefore suitable as a secondary battery to be mounted on the eyeglasses-type device 4000.

[0311] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on the headset device 4001. The headset device 4001 includes at least a microphone unit 4001a, a flexible pipe 4001b, and an earphone unit 4001c. The secondary battery can be provided in the flexible pipe 4001b or the earphone unit 4001c. The secondary battery having the electrolyte described in Embodiment 1 can be used in a wide temperature range and is therefore suitable as a secondary battery to be mounted on the headset device 4001.

[0312] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a device 4002 that can be directly attached to the body. A secondary battery 4002b can be provided in a thin housing 4002a of the device 4002. The secondary battery having the electrolyte described in Embodiment 1 can be used in a wide temperature range and is therefore suitable as a secondary battery to be mounted on the device 4002.

[0313] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a device 4003 that can be attached to clothing. A secondary battery 4003b can be provided in a thin housing 4003a of the device 4003. The secondary battery having the electrolyte described in Embodiment 1 can be used in a wide temperature range and is therefore suitable as a secondary battery to be mounted on the device 4003.

[0314] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on the belt-type device 4006. The belt-type device 4006 includes a belt portion 4006a and a wireless power receiving portion 4006b, and the secondary battery can be mounted in an internal region of the belt portion 4006a. The secondary battery having the electrolyte described in Embodiment 1 can be used in a wide temperature range and is therefore suitable as a secondary battery to be mounted on the belt-type device 4006.

[0315] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on the wristwatch device 4005. The wristwatch device 4005 has a display portion 4005a and a belt portion 4005b, and the secondary battery can be provided on the display portion 4005a or the belt portion 4005b. The secondary battery having the electrolyte described in Embodiment 1 can be used in a wide temperature range and is therefore suitable as a secondary battery to be mounted on the wristwatch device 4005.

[0316] The display unit 4005a can display not only the time but also various other information such as incoming emails and phone calls.

[0317] Furthermore, since the wristwatch device 4005 is a wearable device that is worn directly on the arm, it may be equipped with sensors that measure the user's pulse, blood pressure, etc. Data on the user's exercise volume and health can be accumulated to manage the user's health.

[0318] FIG. 20B shows a perspective view of the wristwatch-type device 4005 removed from the wrist.

[0319] 20C shows a side view of the display device 4005. Fig. 20C illustrates a state in which a secondary battery 913 is built in the internal region. The secondary battery 913 is the secondary battery described in the above embodiment. The secondary battery 913 is provided at a position overlapping with the display portion 4005a, and can have high density and high capacity, and is small and lightweight.

[0320] 20D shows an example of a wireless earphone. Here, the wireless earphone is shown having a pair of main bodies 4100a and 4100b, but this does not necessarily have to be a pair.

[0321] The main bodies 4100a and 4100b each have a driver unit 4101, an antenna 4102, and a secondary battery 4103. They may also have a display unit 4104. They also preferably have a substrate on which a circuit such as a wireless IC is mounted, a charging terminal, and the like. They may also have a microphone.

[0322] The case 4110 has a secondary battery 4111. It is preferable that the case 4110 also has a board on which circuits such as a wireless IC and a charge control IC are mounted, and a charging terminal. It may also have a display unit, buttons, and the like.

[0323] The main units 4100a and 4100b can wirelessly communicate with other electronic devices such as smartphones. This allows sound data and the like sent from other electronic devices to be played back on the main units 4100a and 4100b. If the main units 4100a and 4100b have microphones, the sound picked up by the microphones can be sent to the other electronic device, and the sound data after processing by the electronic device can be sent back to the main units 4100a and 4100b for playback. This allows the devices to be used as, for example, translation devices.

[0324] The secondary battery 4103 included in the main body 4100a can be charged from the secondary battery 4111 included in the case 4110. The coin-type secondary battery, the cylindrical secondary battery, or the like described in the above embodiments can be used as the secondary battery 4111 and the secondary battery 4103. The secondary battery including the electrolyte described in Embodiment 1 has a wide usable temperature range and is therefore suitable as a secondary battery to be mounted in a wireless earphone.

[0325] 21A to 21C show examples of eyeglass-type devices different from those described above. Fig. 21A is a perspective view of an eyeglass-type device 5000.

[0326] The glasses-type device 5000 has a function as a so-called portable information terminal, and can execute various programs and play various contents by connecting to the Internet. For example, the glasses-type device 5000 has a function to display augmented reality content in AR (Augmented Reality) mode. The glasses-type device 5000 may also have a function to display virtual reality content in VR (Virtual Reality) mode. Note that the glasses-type device 5000 may also have a function to display substitutional reality (SR) or mixed reality (MR) content in addition to AR and VR.

[0327] The eyeglass-type device 5000 includes a housing 5001, an optical member 5004, a wearing device 5005, a light-shielding portion 5007, earphones 5008, and the like. The housing 5001 preferably has a cylindrical shape. The eyeglass-type device 5000 is preferably configured to be wearable on the user's head. It is more preferable that the housing 5001 of the eyeglass-type device 5000 is worn on the user's head above the outer circumferential line of the head that passes through the eyebrows and ears. By forming the housing 5001 in a cylindrical shape that curves along the user's head, the wearability of the eyeglass-type device 5000 can be improved. The housing 5001 is fixed to the optical member 5004. The optical member 5004 is fixed to the wearing device 5005 via the light-shielding portion 5007 or via the housing 5001. The eyeglass-type device 5000 also includes two types of imaging devices (cameras 5031 and 5032) for capturing images of the outside. The camera 5031 has a function of capturing an image in front of the housing 5001 and includes a wide-angle lens for capturing an image within a range of, for example, approximately 1 m from the eyeglass-type device 5000. The camera 5031 is an imaging device primarily for capturing images for performing gesture operations using the user's hand movements. The camera 5032 is an imaging device primarily for capturing landscape images and includes a telephoto lens than the camera 5031. That is, the camera 5032 has a longer focal length and a narrower angle of view than the camera 5031. The cameras 5031 and 5032 may each have a zoom mechanism for changing the focal length. In this case, the camera 5032 may be selected so that the maximum focal length of the camera 5032 is greater than the maximum focal length of the camera 5031. The eyeglass-type device 5000 also includes a pair of imaging devices (cameras 5033) for capturing images of the inside. Each of the pair of cameras 5033 is a camera for capturing an image of the right eye or the left eye. The camera 5033 is preferably sensitive to infrared light. The camera 5033 can capture images of the user's right and left eyes, respectively, so that the images can be used for iris authentication, healthcare, eye tracking, etc. Although not shown here, it is preferable to have a light source that emits infrared light for illumination. The eyeglass-type device 5000 may also be configured to have one camera 5033 that captures images of both eyes.Alternatively, the glasses-type device 5000 may be configured to have one camera 5033 that captures an image of one eye.

[0328] The eyeglasses-type device 5000 has a display device 5021, a reflector 5022, a flexible battery 5024, and a system unit. The display device 5021, the reflector 5022, the flexible battery 5024, and the system unit are preferably provided inside a housing 5001. The system unit may be provided with a control unit, a storage unit, a communication unit, a sensor, and the like that are included in the eyeglasses-type device 5000. The system unit is also preferably provided with a charging circuit, a power supply circuit, and the like. The flexible battery 5024 is bendable and can be mounted on a curved portion.

[0329] Each part of the eyeglass-type device 5000 in Fig. 21A is shown in Fig. 21B. Fig. 21B is a schematic diagram for explaining the details of each part of the eyeglass-type device 5000 shown in Fig. 21A. Fig. 21C is a schematic side view for explaining the eyeglass-type device 5000.

[0330] 21B , a flexible battery 5024, a system unit 5026, and a system unit 5027 are provided along the cylinder of a cylindrical housing 5001. In addition, a system unit 5025 is provided along the flexible battery 5024 etc.

[0331] The housing 5001 preferably has a curved cylindrical shape. By providing the flexible battery 5024 along the curved cylinder, the flexible battery 5024 can be efficiently arranged in the housing 5001, the space inside the housing 5001 can be used efficiently, and the volume of the flexible battery 5024 can be increased in some cases.

[0332] The housing 5001 has, for example, a cylindrical shape, and the axis of the cylinder is, for example, along a part of an approximately ellipse. Furthermore, it is preferable that the cross section of the cylinder is, for example, approximately ellipse. Alternatively, it is preferable that the cross section of the cylinder has, for example, a part of an ellipse. In particular, when the eyeglass-type device 5000 is worn on the head, it is preferable that the part of the cross section having an ellipse shape is located on the side facing the head when worn. However, one aspect of the present invention is not limited to this. For example, the cross section of the cylinder may have a part that is polygonal (triangle, square, pentagon, etc.).

[0333] The housing 5001 is formed, for example, to be curved along the forehead of the user. The housing 5001 is also placed, for example, along the forehead.

[0334] The housing 5001 may be configured by combining two or more cases. For example, it may be configured by combining an upper case and a lower case. It may also be configured by combining an inner case (the side worn by the user) and an outer case. It may also be configured by combining three or more cases.

[0335] An electrode may be provided on the housing 5001 in a portion that touches the forehead, and brain waves may be measured by the electrode. Alternatively, an electrode may be provided on the portion that touches the forehead, and information such as the user's sweat may be measured by the electrode.

[0336] A plurality of flexible batteries 5024 shown in the above embodiment may be arranged inside the housing 5001 .

[0337] Furthermore, the flexible battery 5024 is preferable because it can be shaped to fit the curved tube. Furthermore, the flexibility of the flexible battery allows for greater freedom in placement within the housing. The flexible battery 5024, a system unit, and the like are placed inside the cylindrical housing. The system unit is configured, for example, on multiple circuit boards. The multiple circuit boards and the flexible battery are connected using connectors, wiring, and the like. The flexibility of the flexible battery allows for placement that avoids connectors, wiring, and the like.

[0338] The flexible battery 5024 may be provided inside the housing 5001 as well as inside the wearing device 5005, for example.

[0339] 22A to 22C show examples of head-mounted devices. Figures 22A and 22B show a head-mounted device 5100 having a band-shaped attachment 5105, and the head-mounted device 5100 is connected to a terminal 5150 shown in Figure 22C via a cable 5120.

[0340] 22A shows a state in which the first portion 5102 attached to a part 5103 of the housing is closed, and FIG. 22B shows a state in which the first portion 5102 is open. When closed, the first portion 5102 has a shape that covers not only the front but also the sides of the face. This can shield the user's field of view from external light, thereby enhancing the sense of realism and immersion. For example, depending on the content displayed, it can also enhance the sense of fear felt by the user.

[0341] 22A and 22B has a band-shaped wearing device 5105. This makes it less likely to slip off than the configuration shown in Fig. 21A etc., and is therefore suitable for enjoying content that requires a relatively large amount of physical activity, such as an attraction.

[0342] A flexible battery 5107 or the like may be built into the back of the head of the wearing equipment 5105. By balancing the weight of the housing 5101 on the front of the head and the weight of the flexible battery 5107 on the back of the head, the center of gravity of the head-worn device 5100 can be adjusted, improving the wearing comfort.

[0343] Alternatively, a flexible battery 5108 having flexibility may be placed inside the band-shaped wearing device 5105. In the example shown in Fig. 22A, two flexible batteries 5108 are placed inside the wearing device 5105. Using a flexible battery having flexibility is preferable because it can be shaped to fit the curved band-like shape.

[0344] The wearing device 5105 has a camera 5131, a camera 5132, and an optical member 5104. The descriptions of the cameras 5031, 5032, and the optical member 5004 described in Figures 21A to 21C can be referred to for these. The wearing device 5105 also has a part 5106 that covers the user's forehead or forehead. By including the part 5106, it is possible to make it less likely to slip off. Furthermore, electrodes can be provided on the part 5106 or on the part of the housing 5101 that touches the forehead, and brain waves can be measured using these electrodes.

[0345] 23A illustrates an example of an electric bicycle using a secondary battery of one embodiment of the present invention. A battery pack of one embodiment of the present invention can be applied to an electric bicycle 8700 illustrated in FIG. 23A. The battery pack of one embodiment of the present invention includes, for example, a plurality of secondary batteries and a protection circuit.

[0346] The electric bicycle 8700 includes a power storage device 8702. The power storage device 8702 can supply electricity to a motor that assists a rider. The power storage device 8702 is portable and is shown in a state removed from the bicycle in FIG. 23B . As shown in FIG. 23C , the power storage device 8702 includes a plurality of secondary batteries 8701 of one embodiment of the present invention. The power storage device 8702 also includes a control circuit 8704. The control circuit 8704 is electrically connected to the positive and negative electrodes of the secondary batteries 8701 and can control charging or detect an abnormality of the secondary batteries. The power storage device 8702 can display the remaining battery charge and the like on a display unit 8703. By using the secondary battery using the electrolyte described in Embodiment 1 as the secondary battery 8701, the electric bicycle can be used in a wide temperature range.

[0347] 23D shows an example of a two-wheeled vehicle using the power storage device of one embodiment of the present invention. A scooter 8600 shown in FIG. 23D includes a power storage device 8602a, a power storage device 8602b, a side mirror 8601, and a turn signal light 8603. The power storage device 8602a and the power storage device 8602b can supply electricity to the motor and the turn signal light 8603. By using the secondary battery using the electrolyte described in Embodiment 1 for the power storage device 8602a and the power storage device 8602b, the scooter 8600 can be used in a wide temperature range.

[0348] 23D can store a power storage device 8602a and a power storage device 8602b in the storage space under the seat. Note that in this embodiment, the scooter 8600 includes the power storage device 8602a and the power storage device 8602b, but this is not limiting. The number of power storage devices may be one, or three or more.

[0349] FIG. 24C shows an example in which the secondary battery of the present invention is applied to an electric vehicle (EV).

[0350] The electric vehicle is equipped with first batteries 1301a and 1301b as main driving secondary batteries, and a second battery 1311 that supplies power to an inverter 1312 that starts a motor 1304. The second battery 1311 is also called a cranking battery (starter battery). The second battery 1311 only needs to have high output, and does not need to have a large capacity, and the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

[0351] In this embodiment, an example is shown in which two first batteries 1301a and 1301b are connected in parallel, but three or more batteries may be connected in parallel. Furthermore, if the first battery 1301a can store sufficient power, the first battery 1301b may be omitted. By configuring a battery pack having multiple secondary batteries, it is possible to extract large amounts of power. The multiple secondary batteries may be connected in parallel, in series, or in series after being connected in parallel. A plurality of secondary batteries is also called a battery pack.

[0352] In addition, in a secondary battery for vehicle use, a service plug or circuit breaker that can cut off high voltage without using tools is provided in the first battery 1301a in order to cut off power from multiple secondary batteries.

[0353] The power of the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but also supplies power to 42V in-vehicle components (such as an electric power steering 1307, a heater 1308, and a defogger 1309) via a DCDC circuit 1306. When a rear motor 1317 is provided for the rear wheels, the first battery 1301a is also used to rotate the rear motor 1317.

[0354] In addition, the second battery 1311 supplies power to 14V in-vehicle components (audio 1313, power windows 1314, lamps 1315, etc.) via the DCDC circuit 1310.

[0355] The first battery 1301a will be described with reference to FIG. 24A.

[0356] FIG. 24A shows an example in which nine prismatic secondary batteries 1300 are combined into one battery pack 1415. Furthermore, nine prismatic secondary batteries 1300 are connected in series, with one electrode fixed by a fixing portion 1413 made of an insulator and the other electrode fixed by a fixing portion 1414 made of an insulator. While this embodiment shows an example in which the batteries are fixed by fixing portions 1413 and 1414, they may also be housed in a battery housing box (also called a casing). Because it is expected that a vehicle will be subjected to external vibrations or shaking (such as from the road surface), it is preferable to fix multiple secondary batteries using fixing portions 1413 and 1414 and a battery housing box. Furthermore, one electrode is electrically connected to a control circuit unit 1320 by wiring 1421. The other electrode is electrically connected to the control circuit unit 1320 by wiring 1422.

[0357] A memory circuit including a transistor using an oxide semiconductor may be used for the control circuit portion 1320. A charge control circuit or a battery control system including a memory circuit including a transistor using an oxide semiconductor may be referred to as a battery operating system (BTOS) or a battery oxide semiconductor (BTOS).

[0358] It is preferable to use a metal oxide that functions as an oxide semiconductor. For example, a metal oxide such as In-M-Zn oxide (wherein element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium) may be used as the oxide. In particular, the In-M-Zn oxide that can be used as the oxide is preferably a C-Axis Aligned Crystal Oxide Semiconductor (CAAC-OS) or a Cloud-Aligned Composite Oxide Semiconductor (CAC-OS). Alternatively, an In—Ga oxide or an In—Zn oxide may be used as the oxide. A CAAC-OS is an oxide semiconductor having multiple crystalline regions, each with its c-axis aligned in a specific direction. The specific direction refers to the thickness direction of the CAAC-OS film, the normal direction to the surface where the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film. A crystalline region is a region with periodic atomic arrangement. If the atomic arrangement is considered as a lattice arrangement, a crystalline region is also a region with a uniform lattice arrangement. Furthermore, a CAAC-OS has a region where multiple crystalline regions are connected in the a-b plane direction, and the region may have distortion. Note that distortion refers to a portion where the lattice arrangement changes between a region with a uniform lattice arrangement and a region with another uniform lattice arrangement in a region where multiple crystalline regions are connected. In other words, a CAAC-OS is an oxide semiconductor with a c-axis aligned and no clear orientation in the a-b plane direction. CAC-OS is a material in which elements constituting a metal oxide are unevenly distributed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof. Note that hereinafter, a state in which one or more metal elements are unevenly distributed in a metal oxide and regions containing the metal elements are mixed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof, is also referred to as a mosaic or patch state.

[0359] Furthermore, the CAC-OS has a mosaic structure in which a material is separated into a first region and a second region, and the first region is distributed throughout the film (hereinafter also referred to as a cloud structure). That is, the CAC-OS is a composite metal oxide having a structure in which the first region and the second region are mixed.

[0360] Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In—Ga—Zn oxide are denoted as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS in the In—Ga—Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. The second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is a region where [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. The second region is a region where [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

[0361] Specifically, the first region is a region whose main component is indium oxide, indium zinc oxide, or the like. The second region is a region whose main component is gallium oxide, gallium zinc oxide, or the like. In other words, the first region can be referred to as a region whose main component is In. The second region can be referred to as a region whose main component is Ga.

[0362] It should be noted that there are cases where a clear boundary between the first region and the second region cannot be observed.

[0363] For example, in the case of CAC-OS in an In—Ga—Zn oxide, EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX) can confirm that the CAC-OS has a structure in which a region containing In as a main component (first region) and a region containing Ga as a main component (second region) are unevenly distributed and mixed.

[0364] When a CAC-OS is used in a transistor, the conductivity due to the first region and the insulating property due to the second region act complementarily, thereby providing the CAC-OS with a switching function (a function of turning on / off). That is, a CAC-OS has a conductive function in a part of the material and an insulating function in a part of the material, and functions as a semiconductor as a whole. By separating the conductive function and the insulating function, both functions can be maximized. Therefore, by using a CAC-OS in a transistor, a high on-current (I ｏｎ ), high field-effect mobility (μ), and good switching behavior can be achieved.

[0365] Oxide semiconductors have a variety of structures, each of which has different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS.

[0366] Furthermore, since the control circuit unit 1320 can be used in high-temperature environments, it is preferable to use a transistor using an oxide semiconductor. To simplify the process, the control circuit unit 1320 may be formed using a unipolar transistor. A transistor using an oxide semiconductor for the semiconductor layer has a wider operating ambient temperature range than single-crystal Si, from −40° C. to 150° C., and its characteristics change less when the secondary battery is heated than a single-crystal Si transistor. The off-current of a transistor using an oxide semiconductor is below the lower limit of measurement regardless of temperature, even at 150° C., whereas the off-current characteristics of a single-crystal Si transistor are highly temperature-dependent. For example, at 150° C., the off-current of a single-crystal Si transistor increases, and the current on / off ratio does not become sufficiently large. The control circuit unit 1320 can improve safety.

[0367] The control circuit unit 1320, which uses a memory circuit including transistors using oxide semiconductors, can also function as an automatic control device for a secondary battery to address 10 causes of instability, such as micro-short circuits. The functions for addressing the 10 causes of instability include overcharging prevention, overcurrent prevention, overheating control during charging, cell balancing in the battery pack, over-discharging prevention, a fuel gauge, automatic control of charging voltage and current according to temperature, control of charging current according to the degree of degradation, detection of abnormal behavior of micro-short circuits, and prediction of abnormalities related to micro-short circuits. The control circuit unit 1320 has at least one of these functions. Furthermore, the automatic control device for a secondary battery can be miniaturized.

[0368] A micro-short circuit refers to a tiny short circuit inside a secondary battery, which is not so small that the positive and negative electrodes of the secondary battery are short-circuited and the battery is unable to be charged or discharged, but rather a small short-circuit current flows through the tiny short circuit.Even if the short circuit occurs in a relatively short period of time and in a small location, a large voltage change occurs, and this abnormal voltage value may affect subsequent estimations.

[0369] One of the causes of micro-short circuits is said to be that multiple charge and discharge cycles cause uneven distribution of the positive electrode active material, resulting in localized current concentration in parts of the positive electrode and negative electrode, causing parts of the separator to stop functioning, or the generation of by-products due to side reactions, resulting in micro-short circuits.

[0370] In addition to detecting micro-shorts, the control circuit 1320 can also be said to detect the terminal voltage of the secondary battery and manage the charge / discharge state of the secondary battery. For example, to prevent overcharging, it can turn off both the output transistor and the cutoff switch of the charging circuit almost simultaneously.

[0371] FIG. 24B shows an example of a block diagram of the first battery 1301a and the control circuit unit 1320 in the battery pack 1415 shown in FIG. 24A.

[0372] The control circuit 1320 includes a switch unit 1324 including at least a switch for preventing overcharging and a switch for preventing overdischarging, a control circuit 1322 for controlling the switch unit 1324, and a voltage measurement unit for the first battery 1301a. The control circuit 1320 sets upper and lower voltage limits for the secondary battery used and limits the upper limit of the external current and the upper limit of the output current. The range between the lower and upper voltage limits of the secondary battery is within the recommended voltage range, and when the secondary battery falls outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent overcharging and overdischarging. For example, if the control circuit 1322 detects a voltage that could cause overcharging, it turns off the switch unit 1324 to cut off the current. Furthermore, a PTC element may be provided in the charge / discharge path to provide a function for cutting off the current in response to an increase in temperature. The control circuit section 1320 also has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0373] The switch unit 1324 can be configured by combining n-channel transistors and p-channel transistors. The switch unit 1324 is not limited to a switch having a Si transistor using single crystal silicon, and may be, for example, Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaO ｘThe switch portion 1324 may be formed using a power transistor having, for example, gallium oxide (x is a real number greater than 0). Furthermore, a memory element using an OS transistor can be freely arranged by stacking it on a circuit using a Si transistor, and therefore integration can be easily achieved. Furthermore, an OS transistor can be manufactured using the same manufacturing equipment as a Si transistor, and therefore can be manufactured at low cost. That is, a control circuit portion 1320 using an OS transistor can be stacked on the switch portion 1324 and integrated into a single chip. The volume occupied by the control circuit portion 1320 can be reduced, enabling miniaturization.

[0374] The first batteries 1301a and 1301b mainly supply power to in-vehicle devices of the 42V system (high voltage system), and the second battery 1311 supplies power to in-vehicle devices of the 14V system (low voltage system).

[0375] In this embodiment, an example is shown in which the secondary battery described in the above embodiment is used as both the first battery 1301a and the second battery 1311. The second battery 1311 may be a lead storage battery, an all-solid-state battery, or an electric double layer capacitor.

[0376] Furthermore, regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305, and is then charged into the second battery 1311 from the motor controller 1303 and the battery controller 1302 via the control circuit unit 1321. Alternatively, the first battery 1301a is charged from the battery controller 1302 via the control circuit unit 1320. Alternatively, the first battery 1301b is charged from the battery controller 1302 via the control circuit unit 1320. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b be capable of rapid charging.

[0377] The battery controller 1302 can set the charging voltage and charging current of the first batteries 1301a and 1301b. The battery controller 1302 can set charging conditions in accordance with the charging characteristics of the secondary battery used, and can perform rapid charging.

[0378] Although not shown, when an external charger is connected, the charger's outlet or the charger's connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger is charged to the first batteries 1301a and 1301b via the battery controller 1302. Some chargers are provided with a control circuit, and although the functions of the battery controller 1302 may not be used, it is preferable to charge the first batteries 1301a and 1301b via the control circuit unit 1320 to prevent overcharging. The control circuit unit 1320 may also be provided in the connection cable or the charger's connection cable. The control circuit unit 1320 is sometimes called an ECU (Electronic Control Unit). The ECU is connected to a CAN (Controller Area Network) provided in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. The ECU includes a microcomputer. The ECU uses a CPU or a GPU.

[0379] External chargers installed at charging stations and the like come in a variety of types, including 100V outlets, 200V outlets, and three-phase 200V and 50kW outlets. Charging can also be performed by receiving power from external charging equipment using a wireless power supply system or the like.

[0380] When rapid charging is performed, a secondary battery that can withstand high voltage charging is desired in order to charge in a short time.

[0381] Furthermore, the secondary battery of the present embodiment described above uses graphene as a conductive material, and even if the electrode layer is thickened and the amount of graphene supported is increased, a decrease in capacity is suppressed and a high capacity is maintained, resulting in a synergistic effect, thereby realizing a secondary battery with significantly improved electrical characteristics. This is particularly effective for secondary batteries used in vehicles, and a vehicle with a long cruising range, specifically a cruising range of 500 km or more per charge, can be provided without increasing the ratio of the weight of the secondary battery to the total weight of the vehicle.

[0382] Furthermore, the secondary battery of this embodiment can be used in a wide temperature range, and therefore can be suitably used in vehicles.

[0383] Next, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle, typically a transportation vehicle, will be described.

[0384] Furthermore, by installing the secondary battery or power storage device described in the above embodiment in a vehicle, next-generation clean energy automobiles such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs) can be realized. Furthermore, the secondary battery can also be installed in transportation vehicles such as agricultural machinery, motorized bicycles including electrically assisted bicycles, motorcycles, electric wheelchairs, electric carts, small or large ships, submarines, aircraft such as fixed-wing aircraft and rotary-wing aircraft, rockets, artificial satellites, space probes, planetary probes, and spacecraft. The secondary battery of one embodiment of the present invention can be used over a wide temperature range and is therefore suitable for transportation vehicles.

[0385] 25A to 25E illustrate examples of transportation vehicles using one embodiment of the present invention. The automobile 2001 shown in FIG. 25A is an electric automobile that uses an electric motor as a power source for traveling. Alternatively, it is a hybrid automobile that can appropriately select and use an electric motor or an engine as a power source for traveling. When a secondary battery is installed in a vehicle, an example of the secondary battery described in Embodiment 4 is installed in one or more locations. The automobile 2001 shown in FIG. 25A includes a battery pack 2200, which includes a secondary battery module to which multiple secondary batteries are connected. It is preferable that the automobile further includes a charge control device electrically connected to the secondary battery module.

[0386] Furthermore, automobile 2001 can charge its secondary battery by receiving power supply from an external charging facility using a plug-in system, a contactless power supply system, or the like. Charging can be performed using a predetermined charging method and connector standards, such as CHAdeMO (registered trademark) or Combo, as appropriate. The charging facility may be a charging station installed in a commercial facility or a household power source. For example, plug-in technology can be used to charge an electric storage device installed in automobile 2001 using an external power supply. Charging can be performed by converting AC power to DC power via a conversion device, such as an AC-DC converter.

[0387] Although not shown, a power receiving device can be mounted on a vehicle and power can be supplied contactlessly from a ground-based power transmitting device to charge the vehicle. In the case of this contactless power supply method, by incorporating a power transmitting device into a road or an exterior wall, charging can be performed not only while the vehicle is stopped but also while the vehicle is moving. This contactless power supply method can also be used to transmit and receive power between two vehicles. Furthermore, solar cells can be installed on the exterior of the vehicle to charge the secondary battery while the vehicle is stopped and while moving. For such contactless power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0388] 25B shows a large transport vehicle 2002 having an electrically controlled motor as an example of a transport vehicle. The secondary battery module of the transport vehicle 2002 is, for example, a four-cell unit of secondary batteries with a nominal voltage of 3.0 V to 5.0 V, with 48 cells connected in series for a maximum voltage of 170 V. Apart from the number of secondary batteries constituting the secondary battery module of the battery pack 2201, the transport vehicle 2002 has the same functions as those shown in FIG. 25A, and therefore a description thereof will be omitted.

[0389] FIG. 25C shows, as an example, a large transport vehicle 2003 having an electrically controlled motor. The secondary battery module of the transport vehicle 2003 has, for example, a maximum voltage of 600 V, with one hundred or more secondary batteries connected in series, each having a nominal voltage of 3.0 V or more and 5.0 V or less. By using secondary batteries using the electrolyte described in embodiment 1, the transport vehicle 2003 can be used over a wide temperature range. Furthermore, except for the number of secondary batteries constituting the secondary battery module of the battery pack 2202, the vehicle has the same functions as those shown in FIG. 25A, and therefore further description will be omitted.

[0390] Fig. 25D shows, as an example, an aircraft 2004 having an engine that burns fuel. Since the aircraft 2004 shown in Fig. 25D has wheels for takeoff and landing, it can also be said to be part of a transportation vehicle, and has a battery pack 2203 that includes a secondary battery module formed by connecting multiple secondary batteries and the secondary battery module and a charge control device.

[0391] The secondary battery module of the aircraft 2004 is, for example, eight 4 V secondary batteries connected in series to produce a maximum voltage of 32 V. Other than the number of secondary batteries constituting the secondary battery module of the battery pack 2203, the secondary battery module has the same functions as those shown in Fig. 25A, and therefore a description thereof will be omitted.

[0392] FIG. 25E shows an example of a transport vehicle 2005 for transporting cargo. The transport vehicle 2005 has an electrically controlled motor and performs various tasks by receiving power from a secondary battery constituting a secondary battery module of a battery pack 2204. The transport vehicle 2005 does not necessarily have to be driven by a human driver and can be unmanned via CAN communication or the like. While a forklift is shown in FIG. 25E , this is not a limitation, and a battery pack having a secondary battery according to one embodiment of the present invention can be mounted on industrial machinery that can be operated via CAN communication or the like, such as an automated transporter, a work robot, or a small construction machine.

[0393] 26A shows an artificial satellite 6800 as an example of space equipment. The artificial satellite 6800 has a body 6801, a solar panel 6802, an antenna 6803, and a secondary battery 6805. The solar panel is sometimes called a solar cell module.

[0394] When sunlight is irradiated onto the solar panel 6802, the power required for the operation of the satellite 6800 is generated. However, for example, in a situation where sunlight is not irradiated onto the solar panel or where the amount of sunlight irradiating the solar panel is small, the generated power is small. Therefore, there is a possibility that the power required for the operation of the satellite 6800 will not be generated. In order to operate the satellite 6800 even in a situation where the generated power is small, it is preferable to provide a secondary battery 6805 in the satellite 6800.

[0395] The satellite 6800 can generate a signal. The signal is transmitted via the antenna 6803, and can be received by, for example, a receiver installed on the ground or another satellite. By receiving the signal transmitted by the satellite 6800, the position of the receiver that received the signal can be measured, for example. As described above, the satellite 6800 can constitute, for example, a satellite positioning system.

[0396] Alternatively, the artificial satellite 6800 may be configured to include a sensor. For example, by including a visible light sensor, the artificial satellite 6800 may have the function of detecting sunlight reflected from an object on the ground. Alternatively, by including a thermal infrared sensor, the artificial satellite 6800 may have the function of detecting thermal infrared rays emitted from the earth's surface. As described above, the artificial satellite 6800 may function as, for example, an earth observation satellite.

[0397] Figure 26B shows a probe 6900 with a solar sail (also called a sun sail) as an example of space equipment. The probe 6900 has a body 6901, a solar sail 6902, and a secondary battery 6905. When photons emitted from the sun hit the surface of the solar sail 6902, momentum is transferred to the solar sail 6902. For this reason, the surface of the solar sail 6902 should preferably have a thin film with high reflectivity, and should preferably face the sun.

[0398] The solar sail 6902 is kept in a small folded state until it leaves the atmosphere, and is deployed into a large sheet shape outside the Earth's atmosphere (outer space) as shown in Fig. 26B . Therefore, it is preferable to use the bendable secondary battery of one embodiment of the present invention as the secondary battery 6905 mounted on the solar sail 6902.

[0399] FIG. 26C illustrates a spacecraft 6910 as an example of space equipment. The spacecraft 6910 includes a body 6911, a solar panel 6912, and a secondary battery 6913. The secondary battery of one embodiment of the present invention can be used as the secondary battery 6913. The body 6911 can include, for example, a pressurized compartment and a non-pressurized compartment. The pressurized compartment may be designed to accommodate a crew member. Electric power generated when sunlight is irradiated onto the solar panel 6912 can be charged into the secondary battery 6913. Note that the solar panel 6912 and the secondary battery 6913 may each be flexible. Using a flexible solar panel 6912 is preferable because the solar panel 6912 can be provided in a curved shape on the outer surface of the body 6911. Furthermore, when a flexible secondary battery 6913 is used, it is preferable because the secondary battery 6913 can be provided in a curved shape inside the solar panel 6912 (inside the body 6911).

[0400] FIG. 26D illustrates a rover 6920 as an example of space equipment. The rover 6920 includes a body and a secondary battery 6923. The rover 6920 may include a solar panel 6922. The secondary battery of one embodiment of the present invention can be used as the secondary battery 6923. The rover 6920 may be designed to accommodate a crew member. The secondary battery 6923 may be charged with power generated by sunlight irradiating the solar panel 6922, or may be charged with power generated by another power source, such as a fuel cell or a radioisotope thermoelectric converter. Note that the solar panel 6922 and the secondary battery 6923 may each be flexible. Using a flexible solar panel 6922 is preferable because the solar panel 6922 can be curved and provided on the outer surface of the body. Furthermore, when a flexible secondary battery 6923 is used, it is preferable because the secondary battery 6923 can be provided in a curved shape inside the solar panel 6922 (inside the body).

[0401] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0402] In this example, an ionic liquid was mixed with an organic electrolyte for low temperatures, and the properties thereof were evaluated.

[0403] In this example, EMI-FSI in which 2.15 M LiFSI was dissolved was used as the ionic liquid. 1 M LiPF was used as the low-temperature organic electrolyte. ６ A mixture of EC, EMC, and DMC was used, with the mixing ratio of EC:EMC:DMC=30:35:35 (volume ratio).

[0404] Sample 1 was prepared by mixing the ionic liquid and the low-temperature organic electrolyte in a volume ratio of 1:1.

[0405] As a comparative example, 2.15M LiFSI EMI-FSI was used as sample 10. Similarly, 1M LiPF ６ Sample 11 was made of EC:EMC:DMC=30:35:35.

[0406] The preparation conditions are shown in Table 1.

[0407]

[0408] <Viscosity> The viscosity was measured for Sample 1, Sample 10, and Sample 11. The measurement temperatures were −15° C., −10° C., −5° C., 0° C., 10° C., and 20° C. A rotary viscometer (Toki Sangyo TVE-35L) was used for the viscosity measurement. The results are shown in FIG. 27 .

[0409] As shown in Figure 27, Sample 11, a low-temperature organic electrolyte, maintained a low viscosity of less than 10 mPa·s at all of the above measurement temperatures. Sample 1, which was a mixture of ionic liquid and low-temperature organic electrolyte, had a lower viscosity than Sample 10, which was made of ionic liquid alone. The effect was greater at lower temperatures. For example, Sample 1 had a viscosity of 60 mPa·s to 200 mPa·s at -15°C, more specifically 121.8 mPa·s. Furthermore, the viscosity at 0°C was 30 mPa·s to 100 mPa·s, more specifically 51.9 mPa·s. Furthermore, the viscosity at 20°C was 10 mPa·s to 50 mPa·s, more specifically 22.2 mPa·s.

[0410] <Wettability> The wettability of Samples 1, 10, and 11 to a separator was measured. Polyimide (PI) and polypropylene (PP) were used as separators. A drop of each sample was placed on the separator, and the contact angle was measured.

[0411] Photographs and contact angles of each sample dropped onto the separator are shown in Figures 28A to 29C. PI was used for the separator in Figures 28A to 28C, and PP was used in Figures 29A to 29C. In Figures 28A to 29C, A represents the results of dropping Sample 1, B represents Sample 10, and C represents Sample 11, respectively.

[0412] Both samples had higher wettability with PI than with PP. In particular, as shown in Figures 28A and 28B, the contact angle of Sample 10 dropped onto PI was 10°, whereas the contact angle of Sample 1 was less than 10°, making it unmeasurable. Furthermore, as shown in Figures 29A and 29B, the contact angle of Sample 10 dropped onto PP was 87°, whereas the contact angle of Sample 1 was 60° to 83°, more specifically, 79°.

[0413] The above results indicate that mixing an ionic liquid with an organic electrolyte for low temperatures improves wettability compared to the case of using only the ionic liquid. The better the wettability, the easier it is for lithium ions to pass through. Therefore, by using an electrolyte that is a mixture of the ionic liquid of the present invention and an organic electrolyte for low temperatures, it is possible to obtain a lithium ion secondary battery with excellent charge-discharge characteristics.

[0414] In this example, a secondary battery was fabricated using a mixture of a conventional electrolyte and an organic electrolyte for low temperature use, and its characteristics were evaluated.

[0415] The electrolyte used was a mixture of a conventional electrolyte and a low-temperature organic electrolyte. EC, EMC, DMC, and DEC were mixed in a ratio of EC:EMC:DMC:DEC = 12:7:7:14 (volume ratio) = 30:17.5:17.5:35 (volume %), and then 1% (weight ratio) of VC was added. This was designated Sample 21.

[0416] The conventional electrolyte was prepared by mixing EC and DEC in a volume ratio of 3:7, to which 2% VC was added (sample 22).

[0417] As the low-temperature organic electrolyte, a mixture of EC, EMC, and DMC in a volume ratio of EC:EMC:DMC=6:7:7 was used. This was designated as Sample 23.

[0418] In all cases, 1 M lithium hexafluorophosphate was used as the lithium salt. Table 2 shows the preparation conditions for Samples 21 to 23.

[0419]

[0420] A coin-type half cell was fabricated using the above electrolyte.

[0421] The positive electrode active material was nickel-cobalt-manganese lithium oxide with an atomic ratio of Ni:Co:Mn = 8:1:1. The conductive material was acetylene black (AB), and the binder was polyvinylidene fluoride (PVDF). The positive electrode active material, AB, and PVDF were mixed in a weight ratio of 95:3:2 to prepare a slurry, which was then applied to an aluminum current collector. NMP was used as the solvent for the slurry. After applying the slurry to the current collector, the solvent was evaporated. A positive electrode was obtained through the above process. The amount of active material carried on the positive electrode was approximately 7 mg / cm. ２ The density was about 3 g / cc.

[0422] A single sheet of porous polypropylene was used as the separator.

[0423] Metallic lithium was used for the negative electrode.

[0424] <Charge-Discharge Cycle Test> A charge-discharge cycle test was performed using the coin-shaped half cell prepared above. Charge was CC / CV (100 mA / g, 4.6 V or 4.5 V, 10 mA / g cut) and discharge was CC (100 mA / g, 2.5 V cut), and 50 cycles were performed. A 10-minute rest period was provided between charge and discharge. The measurement temperature was 25°C, 45°C, or 65°C. Before the above cycle test, the cells were charged and discharged twice as an aging treatment. Specifically, the aging treatment consisted of charge CC / CV (20 mA / g, 4.6 V or 4.5 V, 10 mA / g cut) and discharge CC (20 mA / g, 2.5 V cut), followed by charge CC / CV (100 mA / g, 4.6 V or 4.5 V, 10 mA / g cut) and discharge CC (100 mA / g, 2.5 V cut).

[0425] 30A to 32B show the results of charge-discharge cycle tests on secondary batteries having Samples 21 to 23. Fig. 30A shows the discharge capacity measured at a charge voltage of 4.5 V and a measurement temperature of 25°C, Fig. 30B shows the discharge capacity measured at a charge voltage of 4.6 V and a measurement temperature of 25°C, Fig. 31A shows the discharge capacity measured at a charge voltage of 4.5 V and a measurement temperature of 45°C, Fig. 31B shows the discharge capacity measured at a charge voltage of 4.6 V and a measurement temperature of 45°C, Fig. 32A shows the discharge capacity measured at a charge voltage of 4.5 V and a measurement temperature of 65°C, and Fig. 32B shows the discharge capacity measured at a charge voltage of 4.6 V and a measurement temperature of 65°C.

[0426] 30A to 32B , in a charge-discharge cycle test at high voltages of 4.6 V or higher and high temperatures of 45° C. or higher, Sample 23 containing the low-temperature organic electrolyte deteriorated significantly. On the other hand, Sample 21 containing the mixed electrolyte of one embodiment of the present invention showed a relatively small decrease in discharge capacity.

[0427] <Nuclear Magnetic Resonance (NMR) Method> In order to investigate the cause of the decrease in discharge capacity, the composition of the compounds contained in the electrolyte was analyzed by nuclear magnetic resonance (NMR) before the charge-discharge cycle test and after 50 charge-discharge cycle tests at 4.6 V and 45° C. as shown in FIG. 31B. １ The nuclear magnetic resonance spectrometer used was an AVANCEIII400 400 MHz model manufactured by Bruker Japan Co., Ltd., and acetonitrile-d3 (CD3CN) was used as the solvent.

[0428] FIG. 33A shows the state of Sample 21 before the charge-discharge cycle test. １ The H-NMR spectrum of Sample 21 after the charge-discharge cycle test is shown in FIG. １ 34A shows the H-NMR spectrum of Sample 22 after the charge-discharge cycle test. １ The H-NMR spectrum of Sample 23 after the charge-discharge cycle test is shown in FIG. １ The H-NMR spectrum is shown.

[0429] The peak positions used to assign and calculate the composition of the compounds in each electrolyte were as follows: EC: 4.45 ppm (4H, singlet), EMC: 3.69 ppm (3H, singlet), DMC: 3.71 ppm (6H, singlet), DEC: 1.23 ppm (6H, triplet), VC: 7.29 ppm (2H, singlet).

[0430] The proton (3H) of the methyl group of EMC was also detected near 1.23 ppm, almost overlapping with the DEC peak. Therefore, the composition of DEC was calculated by taking the difference between the integral of the triplet peak near 1.23 ppm and the amount of substance (ratio) of EMC estimated from the integral near 3.69 ppm as the integral derived from the six protons of DEC.

[0431] Figures 35 to 36B show the composition of compounds contained in the electrolyte before and after the charge-discharge cycle test, calculated from the NMR analysis results of Figures 33A to 34B. Figure 35 is a graph of Sample 21 before (unused) and after (50 cycles) the charge-discharge cycle test. Figure 36A is a similar graph for Sample 22, and Figure 36B is a similar graph for Sample 23.

[0432] As shown in Figures 35 and 36A, the difference in composition before and after the charge-discharge cycle test was small for Sample 21, which was a mixed electrolyte, and Sample 22, which was a conventional electrolyte. On the other hand, as shown in Figure 36B, Sample 23, which was significantly deteriorated, showed a large difference in composition before and after the charge-discharge cycle test, and the proportions of DMC and EMC significantly decreased. This is thought to be due to the decomposition of DMC and EMC.

[0433] The secondary battery containing Sample 21 according to one embodiment of the present invention exhibited relatively good charge-discharge cycle characteristics with the mixed electrolyte even under high voltage and high temperature conditions of 4.6 V and 45° C., which is thought to be because decomposition of the electrolyte was relatively suppressed.

[0434] [Explanation of symbols] 10 Secondary battery 20: Positive electrode, 21: Positive electrode lead, 22: Positive electrode current collector, 23: Positive electrode active material layer, 30: Negative electrode, 31: Negative electrode lead, 32: Negative electrode current collector, 33: Negative electrode active material layer, 34: Negative electrode active material, 35: Binder, 36: Conductive material, 40: Separator, 50: Exterior body, 71: Region, 72: Positive electrode current collector, 73: Separator, 74: Negative electrode current collector, 75: Sealing layer, 76: Lead electrode, 78: Positive electrode active material layer, 79: Negative electrode active material layer, 80: Plane, 83: Joint, 84: Joint, 100: Battery pack, 101: Secondary battery, 102: Secondary battery

Claims

1. A battery having an organic electrolyte, the organic electrolyte comprises a cyclic carbonate and three or more chain carbonates, a first organic electrolyte contained in the battery before a cycle test; and the second organic electrolyte contained in the battery after the cycle test, when analyzed by nuclear magnetic resonance, a difference between a proportion of the chain carbonate in the first organic electrolyte and a proportion of the chain carbonate in the second organic electrolyte is 20 points or less; The cycle test was conducted in a 45°C environment, in which the battery was charged at a constant current of 100 mA / g up to a voltage of 4.6 V, and then charged at a constant voltage of 10 mA / g, and then discharged at a constant current of 100 mA / g down to a voltage of 2.5 V, with each cycle repeated 50 times.

2. In claim 1, the organic electrolyte comprises lithium hexafluorophosphate; The cyclic carbonate comprises ethylene carbonate, The chain carbonate includes methyl ethyl carbonate, dimethyl carbonate, and diethyl carbonate.

3. In claim 1 or claim 2, The battery is a flexible battery.

4. 4. An electronic device comprising the battery according to claim 1.

5. A vehicle comprising the battery according to any one of claims 1 to 4.