Separator and secondary battery

Abstract

The present invention provides: a highly safe separator; and a secondary battery comprising said separator. The separator is provided with particles of an endothermic agent on one or both surfaces thereof. The particles of the endothermic agent are gypsum dihydrate. Accordingly, even when the secondary battery generates heat due to some reason, the endothermic agent can suppress the rise in temperature. A binder having a water absorbing effect is used. Accordingly, even when water is generated in the secondary battery, generation of hydrofluoric acid can be suppressed. Thus, it is possible to provide the highly safe secondary battery.

Description

Separator and secondary battery

[0001] One aspect of the present invention relates to a separator and a secondary battery (lithium ion secondary battery).

[0002] One embodiment of the present invention is not limited to the above fields, and relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, a vehicle, and a manufacturing method thereof. The above-described semiconductor device, display device, light-emitting device, power storage device, lighting device, electronic device, and vehicle can use the secondary battery (lithium-ion secondary battery) of one embodiment of the present invention as a necessary power source. For example, the above-described electronic device includes an information terminal device equipped with a lithium-ion secondary battery. Furthermore, the above-described power storage device includes a stationary power storage device.

[0003] A lithium-ion secondary battery (sometimes referred to as a lithium-ion battery) is a battery that uses lithium ions as the carrier ion. Lithium-ion batteries are secondary batteries that can be used repeatedly by recharging.

[0004] In recent years, various types of energy storage devices have been actively developed, such as lithium-ion secondary batteries, lithium-ion capacitors, air batteries, and all-solid-state batteries. Demand for high-power, high-capacity lithium-ion secondary batteries has expanded rapidly in conjunction with the development of the semiconductor industry, and they have become indispensable in today's information society as a rechargeable energy source.

[0005] Among secondary batteries for mobile electronic devices, there is a high demand for lithium-ion secondary batteries, which have a large discharge capacity per weight and excellent cycle characteristics. When increasing the energy density of lithium-ion secondary batteries, high safety is also required.

[0006] However, it is known that when the temperature of a lithium ion secondary battery rises during charging, it goes through several states and eventually reaches thermal runaway (Non-Patent Document 1).

[0007] A lithium ion secondary battery generally has a laminated structure having a positive electrode, a negative electrode, and a separator therebetween.

[0008] In addition, lithium ion secondary batteries generally use lithium hexafluorophosphate (LiPF ６ ) and other electrolytes that use fluorine-containing lithium salts.

[0009] Patent Document 1 discloses a separator in which a porous polymer film and a layer having a ceramic material containing metal oxide fine particles are laminated.

[0010] WO2022 / 090862

[0011] Nobuo Eda, "2-4 Heat Generation Mechanism," "Learning from Data: Li-ion Battery Charging and Discharging Technology," CQ Publishing, April 4, 2020, pp. 68-72

[0012] The main purpose of providing a separator between the positive and negative electrodes is to maintain a distance between them to prevent them from coming into contact and short-circuiting, which would result in poor battery performance and reduced safety.

[0013] The separator is a porous polymer membrane that allows lithium ions to pass through. It also holds the electrolyte. The separator also functions to prevent the growth of lithium dendrites. Lithium dendrites are lithium that deposit in the form of branches on the negative electrode as a result of repeated charging and discharging of the secondary battery. Contact between lithium dendrites and the positive electrode is one of the causes of internal short circuits.

[0014] Furthermore, secondary batteries generate heat during charging and discharging. If abnormal heat is generated for some reason, the melting point of the separator may be exceeded, potentially reducing the safety of the secondary battery.

[0015] It is said that it is difficult to achieve both high capacity and safety in lithium-ion secondary batteries. For example, positive electrode active materials with a layered rock-salt crystal structure are expected to achieve high capacity because the lithium ion diffusion paths exist two-dimensionally within the crystal structure. However, positive electrode active materials with a layered rock-salt crystal structure are prone to thermal runaway if too many lithium ions are released during charging, which poses a safety issue.

[0016] Lithium-ion secondary batteries are also known to easily generate hydrofluoric acid (hydrogen fluoride) inside. Hydrofluoric acid corrodes the internal mechanisms of the battery, leading to a decrease in safety. Therefore, there is a demand for lithium-ion secondary batteries that have the ability to minimize the generation of hydrofluoric acid.

[0017] An object of the present invention is to provide a highly safe separator and a secondary battery including the separator.

[0018] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these can be extracted from the description in the specification, drawings, and claims.

[0019] To improve the safety of secondary batteries, a heat-absorbing agent is used. When the temperature of the secondary battery rises, the heat-absorbing agent's endothermic reaction suppresses the temperature rise of the secondary battery.

[0020] A coating layer containing heat-absorbing agent particles and a binder is provided on one or both surfaces of the separator. The decomposition start temperature of the heat-absorbing agent particles is preferably lower than the onset temperature of thermal runaway in the secondary battery (thermal runaway will be described in detail later). Here, gypsum dihydrate (calcium sulfate dihydrate) is preferably used as the heat-absorbing agent because it starts to decompose at temperatures above approximately 100°C and changes to gypsum hemihydrate (calcium sulfate hemihydrate). This allows the heat-absorbing agent to suppress temperature rise even if the secondary battery generates heat for some reason.

[0021] In the present invention, the binder uses a material that can be used as a water absorbent. Water may be present inside a secondary battery if it is mixed in during battery assembly. Furthermore, water is generated when secondary gypsum changes to hemihydrate gypsum due to heat generation in the secondary battery. Therefore, if water is present inside a secondary battery, it reacts with fluoride contained in the electrolyte, etc., to generate hydrofluoric acid. However, by using a material that can be used as a water absorbent for the binder, the generation of hydrofluoric acid can be reduced.

[0022] Furthermore, even if hydrofluoric acid is generated inside the secondary battery, by using gypsum dihydrate in the coating layer, the hydrofluoric acid reacts with the calcium contained in the gypsum dihydrate to form calcium fluoride, thereby reducing the generation of hydrofluoric acid.

[0023] One aspect of the present invention is a separator having a substrate and a coating layer, wherein the substrate has the coating layer on one or both surfaces, the coating layer having gypsum dihydrate and an acrylic polymer binder, and the thickness of the coating layer is 1 μm or more and 1000 μm or less, more preferably 10 μm or more and 500 μm or less, and even more preferably 50 μm or more and 200 μm or less.

[0024] In the above, it is preferable that the substrate is a polymer compound containing an imide bond.

[0025] In the above, the dihydrate gypsum is an endothermic agent, and the particle size of the dihydrate gypsum is 1 μm or more and 149 μm or less, preferably 1 μm or more and 75 μm or less, and more preferably 1 μm or more and 50 μm or less.

[0026] In the above, the acrylic polymer binder is preferably a water absorbing agent.

[0027] In the above, the acrylic polymer binder preferably contains one of acrylic acid, methyl acrylate, butyl acrylate, acrylonitrile, and acrylamide.

[0028] One aspect of the present invention is a secondary battery having a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode, where the separator is a polymer compound containing an imide bond, and a coating layer is provided in contact with one or both surfaces of the separator, and the coating layer includes gypsum dihydrate and an acrylic polymer binder.

[0029] A polymer compound containing an imide bond is a compound that, when analyzed using FTIR (Fourier transform infrared spectroscopy), exhibits a peak derived from the imide group (approximately 1775 cm −１) is a material that exhibits a spectrum that has at least one of the following: Furthermore, a polymer that has imide bonds in its main chain is called a polyimide. Polyimide is a material with high heat resistance. Furthermore, polyimide has aromatic rings, and the composition of these aromatic rings can be analyzed using NMR (nuclear magnetic resonance). Specifically, １ H and １３ The composition of the aromatic rings can be identified by spectral analysis obtained using C NMR measurement. The composition of the polyimide can also be identified by analysis using GC-TOF / MS (gas chromatography-time of flight mass spectrometry).

[0030] Furthermore, polyimide separators have the disadvantage of being easily charged and difficult to handle when assembling secondary batteries, but the effects of charging can be reduced by adhering gypsum dihydrate to the separator surface.

[0031] The particle size of gypsum dihydrate can be measured using a particle size distribution meter or the like using a laser diffraction / scattering method. The median diameter (D50) is the particle diameter when the cumulative amount in the cumulative curve of the particle size distribution measurement results accounts for 50%. The measurement of particle size is not limited to laser diffraction particle size distribution measurement, and the major axis of the particle cross section may be measured by analysis using a scanning electron microscope (hereinafter referred to as SEM) or a transmission electron microscope (hereinafter referred to as TEM). Note that, as a method for measuring the median diameter (D50) using analysis using SEM or TEM, for example, 20 or more particles are measured, a cumulative curve is created, and the particle diameter when the cumulative amount accounts for 50% can be taken as the median diameter (D50).

[0032] In this specification and the like, the term "particle" is not limited to referring only to spherical particles (having a circular cross-sectional shape), and examples of the cross-sectional shape of individual particles include ellipsoids, rectangles, trapezoids, triangles, squares with rounded corners, and asymmetric shapes, and further, individual particles may have an irregular shape.

[0033] As the charging voltage of a secondary battery increases, the potential of the positive electrode generally increases. The positive electrode active material has a stable crystal structure even at high potentials. The stable crystal structure of the positive electrode active material in the charged state can suppress the decrease in charge / discharge capacity due to repeated charge / discharge.

[0034] Unless otherwise specified, the materials (positive electrode active material, negative electrode active material, electrolyte, separator, etc.) contained in secondary batteries are described in their pre-degradation state. Note that a decrease in discharge capacity due to aging and burn-in treatments during secondary battery manufacturing is not considered to be degradation. For example, a lithium-ion secondary cell or lithium-ion secondary battery pack (hereinafter referred to as a lithium-ion secondary battery) can be said to be in its pre-degradation state if it has a discharge capacity of 97% or more of its rated capacity. For lithium-ion secondary batteries for portable devices, the rated capacity conforms to JIS C 8711:2019. For other lithium-ion secondary batteries, the rated capacity conforms to not only the above JIS standard but also various JIS and IEC standards for electric vehicle propulsion, industrial use, etc.

[0035] In this specification and the like, the state of the materials of a secondary battery before deterioration is sometimes referred to as an initial product or initial state, and the state after deterioration (the state when the secondary battery has a discharge capacity of less than 97% of the rated capacity) is sometimes referred to as a product in use or in use state, or a used product or used state.

[0036] By providing a coating layer containing particles of a heat-absorbing agent on one or both surfaces of the separator, it is possible to suppress the temperature rise of the secondary battery, thereby realizing a highly safe separator and a secondary battery equipped with the separator.

[0037] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract other effects from the description in the specification, drawings, claims, etc.

[0038] FIGS. 1A, 1B, and 1C are cross-sectional views of an example of a secondary battery according to one embodiment of the present invention. FIGS. 2A and 2B are diagrams illustrating a method for manufacturing a secondary battery according to one embodiment of the present invention. FIG. 3 is a graph showing changes in the internal temperature of a secondary battery as it increases. FIGS. 4A, 4B, 4C, and 4D are diagrams illustrating a lithium-ion battery. FIGS. 5A, 5B, and 5C are diagrams illustrating a lithium-ion battery. FIGS. 6A, 6B, 6C, and 6D are diagrams illustrating an example of an electronic device. FIGS. 7A, 7B, and 7C are diagrams illustrating an example of an electronic device. FIGS. 8A, 8B, and 8C are diagrams illustrating an example of a vehicle. FIGS. 9A and 9B are diagrams illustrating an example of an electric bicycle.

[0039] 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.

[0040] In this specification, the words "first" and "second" are used for the convenience of understanding the technical content or to identify each component. Therefore, the words "first" and "second" do not limit the number of each component. Furthermore, the words "first" and "second" do not limit the order of each component. Furthermore, the words "first" and "second" or identifying symbols used in this specification may not match the words or identifying symbols in the claims.

[0041] Embodiment 1 In this embodiment, an example of a secondary battery of one embodiment of the present invention will be described with reference to FIGS. 1A to 1C . FIG. 1A is a cross-sectional view of a battery of one embodiment of the present invention. As shown in FIG. 1A , the secondary battery includes an outer casing (not shown), a positive electrode current collector 501, a positive electrode active material layer 503, a separator 500, a negative electrode active material layer 506, a negative electrode current collector 504, and an electrolyte solution in which lithium salt or the like is dissolved. The separator 500 is provided between the positive electrode active material layer 503 and the negative electrode active material layer 506.

[0042] An example of a separator according to one embodiment of the present invention will be described with reference to Figures 1B and 1C. Figure 1B is a cross-sectional view of a separator according to one embodiment of the present invention. Also, Figure 1C is a cross-sectional view of a separator according to one embodiment of the present invention. In Figure 1B, separator 500 has coating layer 502 and substrate 507. In Figure 1C, coating layer 502 has gypsum dihydrate particles 502a and binder 502b (not shown).

[0043] The substrate 507 is a polymer porous film having a porous layer. A commercially available separator can be used for the substrate 507. Commercially available separators can be made of polyimide (PI), but are not limited to this, as long as they have a heat resistance temperature of 200°C or higher and can be coated with a coating layer. The substrate 507 may be a single layer, or a multilayer film having two or more layers. A mixed multilayer film using multiple types of substrates may also be used.

[0044] The separator 500 has a structure in which at least one surface of a substrate 507 is covered with a coating layer 502 having, for example, a mixture of gypsum dihydrate particles 502a, which are a heat-absorbing agent, and a binder 502b. The coating layer 502 can be formed by applying, for example, a mixture of gypsum dihydrate particles 502a and a binder 502b to the substrate 507.

[0045] In FIG. 1B , the separator 500 is disposed such that the surface having the coating layer 502 faces the negative electrode. The substrate 507 has a porous layer (not shown) on the negative electrode side. The coating layer 502 bonds the dihydrate gypsum particles 502a to the substrate 507 while maintaining some gaps between the dihydrate gypsum particles 502a, thereby providing gaps through which lithium ions can pass. The binder 502b bonds adjacent gypsum dihydrate particles 502a together but does not completely fill the gaps, allowing lithium ions to pass through the coating layer 502. The entire surface of the substrate 507 does not need to be covered with the dihydrate gypsum particles 502a and the binder 502b; a portion of the surface of the substrate 507 may be exposed, providing a portion where the substrate 507 comes into contact with the electrolyte.

[0046] The thickness of the coating layer 502 is such that it does not impede the movement of lithium ions. It is preferably 0.1 μm to 1000 μm, more preferably 1 μm to 1000 μm, more preferably 10 μm to 500 μm, and even more preferably 50 μm to 200 μm. The thickness of the coating layer is not limited to this, and it can be made thinner depending on the coating layer application method. For example, spray coating can be used to create a coating layer with a thickness of 1 μm or less.

[0047] The dihydrate gypsum particles used may be primary particles or secondary particles. Secondary particles are aggregates of multiple primary particles, and there may be gaps between the primary particles within the secondary particles. Primary particles refer to particles that are recognized as a single grain when observed with an SEM. Secondary particles refer to a mass of aggregated primary particles. The aggregation of primary particles does not depend on the bonding force acting between multiple primary particles. It may be a covalent bond, an ionic bond, a hydrophobic interaction, a van der Waals force, or other intermolecular interaction, or multiple bonding forces may be acting.

[0048] The particle size of the primary particles of the gypsum dihydrate particles 502a is not particularly limited as long as it is large enough to be applied as the coating layer 502, but a smaller particle size is preferable because it increases the surface area. Specifically, the particle size of the primary particles of the gypsum dihydrate particles 502a is 1 μm or more and 149 μm or less, preferably 1 μm or more and 75 μm or less, and more preferably 1 μm or more and 50 μm or less. Without being limited thereto, the particle size of the gypsum dihydrate particles can be reduced to 1 μm or less by crushing the particles more finely. Furthermore, the particle size of the gypsum dihydrate particles 502a is 10% or more and 100% or less, more preferably 10% or more and 30% or less, of the thickness of the coating layer 502. This is because the smaller the particle size of the gypsum dihydrate particles 502a, the more easily the released water escapes to the outside of the particle system, and therefore the peak temperature during endothermic heat absorption is likely to decrease. As a result, when the secondary battery generates abnormal heat, the gypsum dihydrate particles 502a start to absorb heat before the temperature reaches a level at which thermal runaway occurs, making it possible to suppress thermal runaway.

[0049] The dihydrate gypsum particles 502a are scattered so as to cover directly above the substrate 507. The dihydrate gypsum particles 502a may be larger or smaller than the size of the pores of the porous layer. Therefore, there may be portions where the dihydrate gypsum particles 502a do not cover the pores of the porous layer of the substrate 507, or there may be portions where the dihydrate gypsum particles 502a cover the inside of the pores of the porous layer. Furthermore, when the binder 502b is applied to the substrate 507, it may enter the pores of the porous layer of the substrate 507. However, it is preferable to adjust the density and film thickness during application to such an extent that the movement of lithium ions is not hindered even if the binder 502b enters the pores of the porous layer of the substrate 507.

[0050] Furthermore, even if hydrofluoric acid that reduces the safety of the secondary battery is generated, the calcium contained in the gypsum dihydrate particles 502a reacts with the hydrofluoric acid to form calcium fluoride, thereby reducing the adverse effects of the presence of hydrofluoric acid.

[0051] 1C is an enlarged view of a portion of the separator 500. As shown in FIG. 1C, the particle diameters of the gypsum dihydrate particles 502a in the coating layer 502 may be a mixture of gypsum dihydrate particles 502a having different particle diameters, or the particle diameters of the gypsum dihydrate particles 502a may be approximately the same. The shape of the gypsum dihydrate particles 502a is not limited to the shape shown in FIG. 1C and may have various shapes, such as a needle shape, a rod shape, or a pellet shape.

[0052] The binder 502b is a binder having a water absorption effect. Examples of the binder having a water absorption effect include acrylic polymer binders. Examples of the acrylic polymer binder include polymer binders containing one or more of acrylic acid, methyl acrylate, butyl acrylate, acrylonitrile, or acrylamide.

[0053] As a polymer binder using acrylic acid, for example, a polyacrylic acid binder can be used. By using a polyacrylic acid binder, it is possible to absorb the water released when the dihydrate gypsum particles 502a change to hemihydrate gypsum during heat absorption. This makes it possible to reduce the hydrofluoric acid generated by the reaction of fluorine used in the electrolyte with water. As a polyacrylic acid binder, for example, a binder using sodium polyacrylate or polyethylene oxide (PEO) can be used.

[0054] In addition to the above, the binder 502b may be a polymer binder using glutamic acid as a binder having a water absorption effect. For example, sodium polyglutamate may be used as a polyglutamic acid binder.

[0055] Heat treatment at about 60°C or higher is required to remove water in order to heat polyacrylic acid and fix the gypsum dihydrate particles. This heat treatment is carried out at a temperature (about 180°C) or lower at which the gypsum dihydrate particles release water through an endothermic reaction.

[0056] Specifically, the polyimide separator has a polyimide represented by the following chemical formula:

[0057]

[0058] The substrate 507 has high heat resistance because it uses a polyimide separator. Even if the temperature becomes high, the endothermic reaction in the coating layer 502 can prevent a sudden rise in temperature.

[0059] Here, an example in which only one side (one surface) is coated is shown, but there is no particular limitation and both sides may be coated.

[0060] The separator is preferably processed into an envelope shape and disposed so as to encase either the positive electrode or the negative electrode.

[0061] <Method of Producing Coating Layer> A method of producing the coating layer 502 will be described with reference to FIGS. 2A and 2B.

[0062] First, as shown in Fig. 2A, gypsum dihydrate particles 502a and a binder 502b are mixed, and water 509 is added to prepare a slurry. Since the binder 502b dissolves in water, in Fig. 2B, the binder 502b corresponds to the gaps between the gypsum dihydrate particles 502a.

[0063] Next, the prepared slurry is applied to the substrate 507 by gravure coating. However, the method of applying the slurry is not limited as long as it is a method that does not easily dissolve the slurry from the voids in the substrate 507, and for example, it is also possible to apply the slurry by a spray method.

[0064] Finally, the substrate 507 coated with the slurry is dried using a drying oven or the like to remove water.

[0065] <Thermal Runaway of Secondary Batteries> Figure 3 shows a partially modified version of the graph shown on page 69 [Figures 2-11] of Non-Patent Document 1, which illustrates the principle of thermal runaway in secondary batteries. When the temperature (specifically, the internal temperature) of the above-mentioned secondary battery rises, for example, during charging, it passes through several states and then reaches thermal runaway. Figure 3 is a graph of the temperature of the secondary battery against time. For example, when the temperature of the secondary battery reaches or is close to 100°C, (1) the SEI (Solid Electrolyte Interface) of the negative electrode collapses and heat is generated. Furthermore, when the temperature of the secondary battery exceeds 100°C, (2) the negative electrode (when graphite is used, the negative electrode is C ６ (3) At or near 150°C, oxidation of the electrolyte by the positive electrode occurs, and heat is generated. When the temperature of the secondary battery reaches or near 180°C, (4) thermal decomposition of the electrolyte occurs, and (5) oxygen is released from the positive electrode and thermal decomposition of the positive electrode (this thermal decomposition includes a structural change in the positive electrode active material). When the temperature of the secondary battery then exceeds 200°C, (6) decomposition of the negative electrode occurs, and finally, (7) direct contact between the positive electrode and the negative electrode occurs. Through these states, particularly states (5), (6), or (7), the secondary battery reaches thermal runaway.

[0066] To prevent thermal runaway, it is desirable to suppress the temperature rise of the secondary battery and for the negative electrode, positive electrode, and / or electrolyte to have stable properties at high temperatures. By using a separator according to one embodiment of the present invention, even when an abnormal temperature rise occurs in the secondary battery, the gypsum dihydrate acts as a heat absorber, making it possible to suppress the temperature rise in the secondary battery.

[0067] [Positive Electrode] The positive electrode has a positive electrode active material layer 503 and a positive electrode current collector 501. The positive electrode active material layer 503 has a positive electrode active material, a conductive material, and a binder. Known materials can be used for the positive electrode.

[0068] <Positive Electrode Active Material> The positive electrode active material may have, for example, a layered rock salt crystal structure, a spinel crystal structure, or an olivine crystal structure. More specifically, the positive electrode active material may have lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM), and lithium nickel cobalt aluminate (NCA), which have a layered rock salt crystal structure, LiMnO(2), which has a spinel crystal structure, or lithium iron phosphate (LFP) and lithium manganese iron phosphate (LMFP), which have an olivine crystal structure.

[0069] <Positive Electrode Current Collector> The positive electrode current collector can be made of a material that is highly conductive and does not alloy with carrier ions such as lithium, such as metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, and titanium, and alloys thereof. Aluminum alloys containing elements that improve heat resistance, such as silicon, titanium, neodymium, scandium, and molybdenum, can also be used. The positive electrode current collector can also be made of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The current collector can be in a sheet, mesh, punched metal, expanded metal, or other shape. It is preferable to use a current collector with a thickness of 10 μm to 30 μm.

[0070] [Negative Electrode] The negative electrode has a negative electrode active material layer 506 and a negative electrode current collector 504. The negative electrode active material layer 506 has a negative electrode active material, a conductive agent, and a binder. Known materials can be used for the negative electrode.

[0071] <Negative electrode active material> The negative electrode active material contains both carbon particles and silicon particles. Examples of the carbon particles include graphite, carbon having a layer structure similar to graphite, amorphous carbon, and hard carbon. Specific examples of the carbon particles used in this specification include graphite particles.

[0072] <Negative electrode current collector> The negative electrode current collector may be made of the same material as the positive electrode current collector, or may be made of copper, etc. It is preferable that the negative electrode current collector be made of a material that does not alloy with carrier ions such as lithium.

[0073] [Electrolyte] The electrolyte contains a solvent and a lithium salt. The solvent of the electrolyte is preferably an aprotic organic solvent, and examples thereof include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, and sultone, or any combination and ratio of two or more of these.

[0074] The electrolyte preferably contains fluorine. For example, an electrolyte containing one or more fluorinated cyclic carbonates and lithium ions can be used as the fluorine-containing electrolyte. The fluorinated cyclic carbonate improves non-flammability and enhances the safety of the lithium-ion secondary battery.

[0075] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0076] Examples of polymers that can be used include polymers having a polyalkylene oxide structure such as polyethylene oxide, PVdF, polyacrylonitrile, and copolymers containing these. For example, PVdF-HFP, which is a copolymer of PVdF and hexafluoropropylene (HFP), can be used. The polymer formed may also have a porous shape.

[0077] Alternatively, a polymerizing agent or a crosslinking agent may be added to the electrolyte solution to gel it. For example, the ionic liquid itself may be polymerized by introducing a polymerizable functional group into the cation or anion that constitutes the ionic liquid and polymerizing them using a polymerization initiator. In this way, the polymerized ionic liquid may be gelled with a crosslinking agent. This gelled state is less likely to vaporize than the liquid state, and therefore less flammable than the liquid electrolyte.

[0078] In addition, a solid electrolyte containing an inorganic material such as a sulfide or oxide, or a polymer material such as a polyethylene oxide, may be used in combination with the electrolytic solution. For example, the solid electrolyte may be formed on the surface of the active material layer. Furthermore, when a solid electrolyte and an electrolytic solution are used in combination, the installation of a separator or spacer may be unnecessary.

[0079] Furthermore, using a polymeric material that gels as a solvent for the electrolyte solution increases safety against leakage and the like. Furthermore, it is possible to reduce the thickness and weight of the power storage device. For example, polyethylene oxide-based, polyacrylonitrile-based, polyvinylidene fluoride-based, polyacrylate-based, and polymethacrylate-based polymers can be used. It is also preferable to use a polymer that can gel the electrolyte solution at room temperature (e.g., 25°C). Alternatively, silicone gel or the like may be used. In this specification and the like, for example, polyvinylidene fluoride-based polymers refer to polymers containing polyvinylidene fluoride (PVDF), including poly(vinylidene fluoride-hexafluoropropylene) copolymers and the like.

[0080] The gel electrolyte is preferably resistant to leakage because it reduces the risk of the electrolyte leaking to the outside even when the exterior of the secondary battery is damaged, etc. Furthermore, by using such a gel electrolyte and a separator according to one embodiment of the present invention, a secondary battery that is less flammable and therefore safer can be provided.

[0081] [Lithium Salt] Examples of the lithium salt to be dissolved in the solvent include LiPF ６ , LiClO ４ , LiAsF ６ , LiBF ４ , LiAlCl ４ , LiSCN, LiBr, LiI, Li ２ SO ４ , Li ２ B １０ Cl １０ , Li ２ B １２ Cl １２ , LiCF ３ SO ３ , LiC ４ F ９ SO ３ , LiC(CF ３ SO ２ ) ３ , LiC(C ２ F ５ SO ２ ) ３ , LiN(CF ３ SO ２ ) ２ , LiN(C ４ F ９ SO ２ ) (CF ３ SO ２ ), LiN(C ２ F ５ SO ２ ) ２ The lithium salt may be used alone or in any combination and ratio of two or more of these. The lithium salt is preferably used in an amount of 0.5 mol / L or more and 3.0 mol / L or less relative to the solvent. ６ , LiBF ４ The use of these improves the safety of lithium-ion batteries.

[0082] [Exterior Body] The exterior body of the secondary battery can be made of a metal material such as aluminum and / or a resin material. Alternatively, a film-like exterior body can be used. Examples of the film include a three-layer structure film in which a thin, flexible metal film such as aluminum, stainless steel, copper, or nickel is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or polyester resin is further provided on the thin metal film as the outer surface of the exterior body.

[0083] In this embodiment, only one combination of a positive electrode, a separator, and a negative electrode is illustrated, but this is not particularly limited, and a stacked structure of multiple combinations may be used to increase capacity.

[0084] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0085] (Embodiment 2) [Cylindrical Lithium-ion Battery] An example of a cylindrical lithium-ion battery will be described with reference to Fig. 4A. As shown in Fig. 4A, a cylindrical lithium-ion 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 positive electrode cap 601 and the battery can (external can) 602 are insulated by a gasket (insulating packing) 610.

[0086] 4B is a schematic diagram showing a cross section of a cylindrical lithium-ion battery. The cylindrical lithium-ion battery shown in FIG. 4B has a positive electrode cap (battery lid) 601 on the top surface and a battery can (external can) 602 on the side and bottom surfaces. The positive electrode cap and battery can (external can) 602 are insulated by a gasket (insulating packing) 610.

[0087] A battery element is provided inside a hollow cylindrical battery can 602, in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 sandwiched therebetween. Although not shown, the battery element is wound around a central axis. One end of the battery can 602 is closed and the other end is open. Inside the battery can 602, the wound battery element, in which the positive electrode, the negative electrode, and the separator are wound, is sandwiched between a pair of opposing insulating plates 608 and 609. An electrolyte (not shown) is poured into the battery can 602 in which the battery element is provided. By using a separator according to one embodiment of the present invention, the lithium-ion battery 616 can be used more safely.

[0088] Since the positive and negative electrodes used in a cylindrical storage battery are wound, it is preferable to form active materials on both sides of the current collector. While the lithium-ion battery 616 shown in Figures 4A to 4D has a cylinder whose height is greater than its diameter, this is not limiting. A lithium-ion battery whose diameter is greater than its height may also be used. This configuration, for example, can reduce the size of the lithium-ion battery.

[0089] A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collecting lead) 607 is connected to the negative electrode 606. The positive electrode terminal 603 and the negative electrode terminal 607 can be made of a metal material. 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 ceramic materials, etc. can be used.

[0090] 4C shows an example of a power storage system 615. The power storage system 615 has multiple lithium-ion batteries 616 and is sometimes called a battery pack. The positive electrodes of each lithium-ion battery are in contact with and electrically connected to conductors 624 separated by insulators 625. The conductors 624 are electrically connected to a control circuit 620 via wiring 623. The negative electrodes of each lithium-ion battery are electrically connected to the control circuit 620 via wiring 626. A protection circuit or the like that prevents overcharging or overdischarging can be used as the control circuit 620.

[0091] 4D shows an example of a power storage system 615. The power storage system 615 has a plurality of lithium ion batteries 616, which are sandwiched between a conductive plate 628 and a conductive plate 614. The plurality of lithium ion batteries 616 are electrically connected to the conductive plate 628 and the conductive plate 614 by wiring 627. The plurality of lithium ion batteries 616 may be connected in parallel, in series, or in parallel and then further connected in series. By configuring the power storage system 615 to have a plurality of lithium ion batteries 616, a large amount of power can be extracted.

[0092] A plurality of lithium ion batteries 616 may be connected in parallel and then further connected in series.

[0093] A temperature control device may be provided between the plurality of lithium ion batteries 616. When the lithium ion batteries 616 are overheated, they can be cooled by the temperature control device, and when the lithium ion batteries 616 are too cold, they can be heated by the temperature control device. This makes the performance of the power storage system 615 less susceptible to the influence of the outside air temperature.

[0094] 4D , the power storage system 615 is electrically connected to a control circuit 620 via wiring 621 and wiring 622. The wiring 621 is electrically connected to the positive electrodes of the plurality of lithium ion batteries 616 via a conductive plate 628, and the wiring 622 is electrically connected to the negative electrodes of the plurality of lithium ion batteries 616 via a conductive plate 614.

[0095] By using the separator 605 having the coating layer described in Embodiment 1 for the cylindrical lithium ion battery 616, the secondary battery can be highly safe.

[0096] [Another Example of the Structure of a Lithium-Ion Battery] An example of the structure of a lithium-ion battery will be described with reference to FIG.

[0097] The secondary battery 913 shown in FIG. 5A has a wound body 950 provided with terminals 951 and 952 inside a housing 930. The wound body 950 is impregnated with an electrolyte inside the housing 930. The terminal 952 contacts the housing 930, and the terminal 951 does not contact the housing 930 by using an insulating material or the like. Note that in FIG. 5A , the housing 930 is shown separated for convenience, but in reality, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of a metal material (e.g., aluminum) or a resin material.

[0098] 5B, the housing 930 shown in Fig. 5A may be formed of a plurality of materials. For example, the secondary battery 913 shown in Fig. 5B has a housing 930a and a housing 930b bonded together, and a wound body 950 is provided in the area surrounded by the housing 930a and the housing 930b.

[0099] The housing 930a can be made of an insulating material such as organic resin. In particular, by using a material such as organic resin on the surface on which the antenna is formed, it is possible to suppress shielding of the electric field by the secondary battery 913. Note that if the shielding of the electric field by the housing 930a is small, the antenna may be provided inside the housing 930a. The housing 930b can be made of, for example, a metal material.

[0100] 5C shows the structure of the wound body 950. The wound body 950 has a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked on top of each other with the separator 933 sandwiched therebetween, and the laminated sheet is wound. Note that multiple layers of the negative electrode 931, the positive electrode 932, and the separator 933 may be stacked. By providing the coating layer of embodiment 1 as the separator 933, the safety of the secondary battery 913 can be improved.

[0101] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0102] Embodiment 3 In this embodiment, an example in which a secondary battery which is one embodiment of the present invention is mounted on an electronic device will be described with reference to FIGS. 6A to 7C. FIG.

[0103] 6A shows an example of a wearable device. Wearable devices use lightweight secondary batteries with high total capacity as their power source. Furthermore, in order to enhance splash-proof, water-resistant, or dust-proof performance when used at home or outdoors, there is a demand for wearable devices that can be charged wirelessly as well as via wired charging, with an exposed connector.

[0104] For example, the secondary battery according to one embodiment of the present invention can be mounted on an eyeglasses-type device 4000 as shown in FIG. 6A . The eyeglasses-type device 4000 includes a frame 4000a and a display unit 4000b. By mounting the secondary battery on the temples of the curved frame 4000a, the eyeglasses-type device 4000 can be lightweight, well-balanced in weight, and has a long continuous use time. By using a separator having a coating layer according to one embodiment of the present invention, a highly safe configuration can be achieved.

[0105] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a headset device 4001. The headset device 4001 includes at least a microphone unit 4001a, a flexible pipe 4001b, and an earphone unit 4001c. A lightweight secondary battery with a high total capacity can be provided in the flexible pipe 4001b and / or the earphone unit 4001c. By using a separator having a coating layer according to one embodiment of the present invention, a highly safe configuration can be achieved.

[0106] Furthermore, the secondary battery of one embodiment of the present invention can be mounted on a device 4002 that can be directly attached to the body. A lightweight secondary battery 4002b with high capacity per weight can be provided in a thin housing 4002a of the device 4002. By using a separator having a coating layer of one embodiment of the present invention, a highly safe configuration can be realized.

[0107] 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 lightweight secondary battery 4003b with high capacity per weight can be provided in a thin housing 4003a of the device 4003. By using a separator having a coating layer according to one embodiment of the present invention, a highly safe configuration can be realized.

[0108] Furthermore, the secondary battery of 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 a lightweight secondary battery with high capacity per weight can be mounted inside the belt portion 4006a. By using a separator having a coating layer of one embodiment of the present invention, a highly safe configuration can be realized.

[0109] Furthermore, the secondary battery of 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 a lightweight secondary battery with high capacity per weight can be provided in the display portion 4005a or the belt portion 4005b. By using a separator having a coating layer of one embodiment of the present invention, a highly safe configuration can be realized.

[0110] The display unit 4005a can display not only the time but also various other information such as incoming emails and phone calls.

[0111] 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.

[0112] FIG. 6B shows a perspective view of the wristwatch type device 4005 removed from the wrist.

[0113] 6C is a side view of the wristwatch type device 4005. Fig. 6C shows that the wristwatch type device 4005 has a built-in secondary battery 913. The secondary battery 913 is provided in a position overlapping with the display portion 4005a, and is small and lightweight.

[0114] 6D shows an example of a wireless earphone. Here, the wireless earphone is shown as having a pair of main bodies 4100a and 4100b, but this does not necessarily have to be a pair.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] The secondary battery 4103 included in the main body 4100a can be charged from the secondary battery 4111 included in the case 4110. A coin-type secondary battery, a cylindrical secondary battery, or the like can be used as the secondary battery 4111 and the secondary battery 4103. The secondary battery according to one embodiment of the present invention can be used as the secondary battery 4111 and the secondary battery 4103. Furthermore, by using a separator having a coating layer, the secondary battery 4103 and the secondary battery 4111 can be highly safe.

[0119] 7A 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 the dust from a suction port arranged on the bottom surface.

[0120] For example, the cleaning robot 6300 can analyze an image captured by the camera 6303 to determine whether or not there is an obstacle such as a wall, furniture, or a step. Furthermore, if 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 rotating 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 electronic component. By using the secondary battery 6306 according to one embodiment of the present invention in the cleaning robot 6300, the total capacity of the secondary battery 6306 can be increased and the weight of the entire cleaning robot 6300 can be reduced, thereby making the cleaning robot 6300 an electronic device with a long operating time. Furthermore, by using a separator having a coating layer, a highly safe secondary battery 6306 can be realized.

[0121] Fig. 7B shows an example of a robot. The robot 6400 shown in Fig. 7B 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.

[0122] 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.

[0123] 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.

[0124] The upper camera 6403 and the lower camera 6406 have the function of capturing images of the surroundings of the robot 6400. When capturing images, the robot 6400 can sense the user's line of sight and change the angle and height of the display unit 6405 to make it easier for the user to see. In addition, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize the surrounding environment and move safely using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407.

[0125] The robot 6400 includes a secondary battery 6409 according to one embodiment of the present invention and a semiconductor device or an electronic component. By using the secondary battery according to one embodiment of the present invention in the robot 6400, the weight of the entire robot 6400 can be reduced, and the robot 6400 can be an electronic device with a long operating time. Furthermore, by using a separator having a coating layer, the secondary battery 6409 can be highly safe.

[0126] FIG. 7C illustrates an example of an air vehicle (also referred to as an unmanned aerial vehicle or drone). The air vehicle 6500 illustrated in FIG. 7C includes a propeller 6501, a camera 6502, a secondary battery 6503, and the like on an airframe 6504, and has a function of autonomous flight. The air vehicle 6500 can be used for transporting cargo, photographing subjects from the sky, and spraying pesticides. The propeller 6501 includes a microcomputer as a motor control circuit for a motor that rotates the propeller 6501. Power is supplied to the motor from the secondary battery 6503. While the air vehicle illustrated in FIG. 7C includes one propeller 6501, the example is not limited thereto and may be a rotorcraft (multicopter) having two or more propellers. A secondary battery according to one embodiment of the present invention is used as the secondary battery 6503.

[0127] For example, when the flying object 6500 is used for photography, image data captured by the camera 6502 is stored in a semiconductor device having a memory element. The semiconductor device can analyze the image data and detect the presence or absence of obstacles when moving. When the flying object 6500 is remotely controlled, the flying object 6500 has a wireless receiving circuit and receives instructions from a controller of a user on the ground to control the flight direction, etc.

[0128] Furthermore, when the flying object 6500 is used for transportation, it is difficult to maintain balance in the air if the weight of the cargo is heavy. Therefore, it is preferable to reduce the weight of not only the components of the airframe 6504 but also the secondary battery. The components of the airframe 6504 can be made of lightweight materials, specifically, resin materials, composite materials such as CFRP (Carbon Fiber Reinforced Plastics), or paper. The flying object 6500 includes a secondary battery 6503 according to one embodiment of the present invention inside the airframe 6504. By using a secondary battery according to one embodiment of the present invention in the flying object 6500, the secondary battery becomes lighter and the total capacity can be increased, thereby reducing the overall weight of the flying object 6500 and achieving a longer flight distance and flight time. Furthermore, by using a separator having a coating layer, a highly safe secondary battery 6503 can be realized.

[0129] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0130] Embodiment 4 In this embodiment, an example in which a secondary battery of one embodiment of the present invention is mounted on a vehicle will be described.

[0131] When a secondary battery is installed in a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HVs), electric vehicles (EVs), or plug-in hybrid vehicles (PHVs) can be realized.

[0132] FIG. 8 illustrates an example of a vehicle using a secondary battery according to one embodiment of the present invention. An automobile 8400 shown in FIG. 8A is an electric automobile using 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. By using one embodiment of the present invention, the weight of the secondary battery can be reduced, and a vehicle with a long cruising distance can be realized. Furthermore, the automobile 8400 includes a secondary battery 8402. For example, modules of the secondary battery 8402 can be arranged on the floor of the interior of the vehicle. The secondary battery 8402 not only drives the electric motor 8406 but also supplies power to light-emitting devices such as a headlight 8401 and a room light (not shown).

[0133] The secondary battery can also supply power to display devices such as a speedometer and a tachometer included in the automobile 8400. The secondary battery can also supply power to semiconductor devices such as a navigation system included in the automobile 8400.

[0134] The automobile 8500 shown in FIG. 8B can charge its secondary battery by receiving power from an external charging facility using a plug-in method and / or a wireless power supply method. FIG. 8B shows a state in which a ground-mounted charging device 8021 charges a secondary battery 8024 mounted on the automobile 8500 via a cable 8022. The charging method and connector specifications may be determined as appropriate using a predetermined method such as CHAdeMO (registered trademark) or Combo. The charging device 8021 may be a charging station installed in a commercial facility or public facility, or may be a household power source. For example, plug-in technology can be used to charge the secondary battery 8024 mounted on the automobile 8500 using external power supply. Charging can be performed by converting AC power to DC power using a conversion device such as an AC-DC converter.

[0135] 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 the road and / or 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 vehicles. Furthermore, solar cells can be installed on the exterior of the vehicle to charge the secondary battery while the vehicle is stopped and / or moving. Electromagnetic induction and / or magnetic resonance methods can be used for such contactless power supply.

[0136] 8C shows an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. A scooter 8600 shown in FIG. 8C includes a secondary battery 8602, a side mirror 8601, and a turn signal light 8603. The secondary battery 8602 can supply electricity to the turn signal light 8603.

[0137] Furthermore, the scooter 8600 shown in Figure 8C can store a secondary battery 8602 in the under-seat storage 8604. The secondary battery 8602 can be stored in the under-seat storage 8604 even if the under-seat storage 8604 is small. By using a separator with a coating layer, a highly safe secondary battery 8602 can be realized. The secondary battery 8602 is removable, and when charging, the secondary battery 8602 can be carried indoors, charged, and stored before riding.

[0138] According to one aspect of the present invention, the secondary battery can be made lighter and the discharge capacity of the secondary battery can be increased. Therefore, the capacity per unit weight can be increased, allowing the secondary battery itself to be made smaller and lighter. Reducing the weight of the secondary battery itself contributes to reducing the weight of the vehicle, thereby improving the cruising range. Furthermore, the secondary battery mounted on the vehicle can also be used as a power supply source for purposes other than the vehicle. In this case, for example, it is possible to avoid using a commercial power source during peak power demand periods. Avoiding the use of a commercial power source during peak power demand periods can contribute to energy conservation and reduction of carbon dioxide emissions.

[0139] 9A illustrates an example of an electric bicycle using the secondary battery of one embodiment of the present invention. The secondary battery of one embodiment of the present invention can be applied to an electric bicycle 8700 illustrated in FIG. 9A. The power storage device of one embodiment of the present invention includes, for example, a plurality of secondary batteries and a charge / discharge control unit.

[0140] The electric bicycle 8700 includes a power storage device 8702. The power storage device 8702 can supply electricity to a motor (electric unit) that assists the rider. The power storage device 8702 is portable and is shown in a state removed from the bicycle in FIG. 9B, where it corresponds to a secondary battery unit. The power storage device 8702 also includes a plurality of built-in batteries 8701, and a display unit 8703 can display the remaining battery charge. The power storage device 8702 also includes a charge / discharge control unit 8704 that can control charging or detect abnormalities of the secondary batteries. The charge / discharge control unit 8704 is connected to the positive and negative electrodes of the battery 8701. An operation unit 8712 is provided in the handle portion of the electric vehicle main unit of the electric bicycle 8700. The operation unit 8712 includes a display unit 8713, a power switch 8714, and a power storage device 8711. The display unit 8713 also displays the remaining battery charge.

[0141] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0142] 500: separator, 501: positive electrode current collector, 502: coating layer, 502a: dihydrate gypsum particles, 502b: binder, 503: positive electrode active material layer, 504: negative electrode current collector, 506: negative electrode active material layer, 507: substrate, 509: water, 601: positive electrode cap, 602: battery can, 603: positive electrode terminal, 604: positive electrode, 605: separator, 606: negative electrode, 607: negative electrode terminal, 608: insulating plate, 609: insulating plate, 611: PTC element, 613: safety valve mechanism, 614: conductive plate, 615: power storage system, 616: lithium ion battery, 620: control circuit, 621: wiring, 622: wiring Wire, 623: Wiring, 624: Conductor, 625: Insulator, 626: Wiring, 627: Wiring, 628: Conductive plate, 913: Secondary battery, 930: Housing, 930a: Housing, 930b: Housing, 931: Negative electrode, 932: Positive electrode, 933: Separator, 950: Wound body, 951: Terminal, 952: Terminal, 4000: Glasses-type device, 4000a: Frame, 4000b: Display unit, 4001: Headset-type device, 4001a: Microphone unit, 4001b: Flexible pipe, 4001c: Earphone unit, 4002: Device, 4002a: Housing, 4002b: Secondary battery, 40 03: device, 4003a: housing, 4003b: secondary battery, 4005: wristwatch-type device, 4005a: display unit, 4005b: belt unit, 4006: belt-type device, 4006a: belt unit, 4006b: wireless power supply receiving unit, 4100a: main body, 4100b: main body, 4101: driver unit, 4102: antenna, 4103: secondary battery, 4104: display unit, 4110: case, 4111: secondary battery, 6300: cleaning robot, 6301: housing, 6302: display unit, 6303: camera, 6304: brush, 6305: operation button, 6306: Secondary battery, 6310: garbage, 6400: robot, 6401: illuminance sensor, 6402: microphone, 6403: upper camera, 6404: speaker, 6405: display unit, 6406: lower camera, 6407: obstacle sensor, 6408: moving mechanism, 6409: secondary battery, 6500: flying object, 6501: propeller, 6502: camera, 6503: secondary battery, 6504: airframe, 8021: charging device, 8022: cable, 8024: secondary battery, 8400: automobile, 8401: headlight, 8402: secondary battery, 8406: electric motor, 8500: automobile,8600: Scooter, 8601: Side mirror, 8602: Secondary battery, 8603: Turn signal light, 8604: Under-seat storage, 8700: Electric bicycle, 8701: Battery, 8702: Power storage device, 8703: Display unit, 8704: Charge / discharge control unit, 8711: Power storage device, 8712: Operation unit, 8713: Display unit, 8714: Power switch,

Claims

A substrate; a coating layer; the substrate has the coating layer on one or both surfaces thereof; The coating layer includes gypsum dihydrate and an acrylic polymer binder, The thickness of the coating layer is preferably 1 μm or more and 1000 μm or less, more preferably 10 μm or more and 500 μm or less, and even more preferably 50 μm or more and 200 μm or less.

2. The separator according to claim 1, wherein the substrate is a polymer compound containing an imide bond. 　 According to claim 1, the dihydrate gypsum is an endothermic agent, The particle size of the gypsum dihydrate is 1 μm or more and 149 μm or less, preferably 1 μm or more and 75 μm or less, and more preferably 1 μm or more and 50 μm or less.

2. The separator according to claim 1, wherein the acrylic polymer binder is a water-absorbing agent.

2. The separator according to claim 1, wherein the acrylic polymer binder comprises one of acrylic acid, methyl acrylate, butyl acrylate, acrylonitrile, and acrylamide. 　 A positive electrode and a negative electrode; a separator between the positive electrode and the negative electrode, The secondary battery according to any one of claims 1 to 5, wherein the separator is a polyimide.

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