Secondary battery

Abstract

To provide a highly safe separator and a secondary battery equipped with the separator.SOLUTION: To realize an excellent separator and enhance safety by coating the surface of the separator. The pore size of the separators is 40nm or more and less than 80nm, and is smaller than the particle size of the metallic hydroxide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a lithium-ion secondary battery and a manufacturing method thereof.

[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 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. [Background technology]

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

[0007] 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. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] WO2022 / 090862 publication Summary of the Invention [Problem to be solved by the invention]

[0009] 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 the battery not performing as expected and reducing safety.

[0010] The separator is a porous polymer membrane, allowing lithium ions to pass through. The separator also retains the electrolyte by being a porous polymer membrane. The separator also functions to prevent the growth of lithium dendrites or copper dendrites. Lithium dendrites are lithium compounds that precipitate on the negative electrode as secondary batteries are repeatedly charged and discharged, and are one of the causes of internal short circuits where lithium dendrites come into contact with the positive electrode. Copper dendrites are copper compounds that precipitate on the negative electrode, and copper dendrites are also one of the causes of internal short circuits.

[0011] Furthermore, secondary batteries generate heat during charging. 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.

[0012] An object of the present invention is to provide a highly safe separator and a secondary battery including the separator.

[0013] Another object of the present invention is to realize a secondary battery using metallic lithium as the negative electrode.

[0014] Another object of the present invention is to reduce the amount of electrolyte used per secondary battery. [Means for solving the problem]

[0015] Therefore, by providing a surface coating to the separator, an excellent separator can be realized, and safety can be increased.

[0016] The invention disclosed in this specification is a secondary battery having a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode, the separator being a first polymer compound having thermoplastic properties and having at least two or more metal hydroxide particles in contact with one or both surfaces of the first polymer compound, one or both surfaces of the first polymer compound having a plurality of openings, and having a second polymer compound in contact with the inner walls of the openings.

[0017] In the above configuration, the first polymer compound having thermoplasticity is polypropylene or polyethylene, and the second polymer compound has an imide bond. Other materials that can be used for the first polymer compound having thermoplasticity include polystyrene, polybutene, polymethylpentene, 6-nylon, polyethylene terephthalate, and polybutylene terephthalate.

[0018] The second polymer compound having imide bonds can be obtained by subjecting a polyimide precursor to thermal imidization or chemical imidization, but the heat treatment temperature is preferably not higher than the melting temperature of the first polymer compound. The chemical imidization method can be performed by immersing the polyimide precursor in a dehydration cyclodehydration agent.

[0019] Polymer compounds containing imide bonds are characterized by a peak (approximately 1775 cm ) derived from the imide group when analyzed using FTIR (Fourier transform infrared spectroscopy). -1) and polymers with imide bonds in the main chain are called polyimides. Polyimides are highly heat-resistant materials. Polyimides also have 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 aromatic rings can be identified by spectral analysis obtained using C NMR measurements. The composition of polyimides can also be identified by analysis using GC-TOF / MS (gas chromatography time-of-flight mass spectrometry).

[0020] In the above configuration, the size of the separator pores is preferably 40 nm or more but less than 80 nm, which is smaller than the particle size of the metal hydroxide. By making the size of the separator pores smaller than the particle size of the metal hydroxide, it is possible to prevent the metal hydroxide from clogging the separator pores and inhibiting the electrolyte from entering and exiting the pores. Particle size is one of the three-dimensional dimensions of a particle, such as length, width, and height, and varies in size and has a particle size distribution. In this specification, the particle size of the metal hydroxide refers to the D50 value obtained using a laser diffraction particle size distribution analyzer.

[0021] D50 is the particle size at which the cumulative amount in the cumulative curve of the particle size distribution measurement results accounts for 50%. Similarly, D10 is the particle size at which the cumulative amount in the cumulative curve of the particle size distribution measurement results accounts for 10%. D90 is the particle size at which the cumulative amount in the cumulative curve of the particle size distribution measurement results accounts for 90%.

[0022] In each of the above configurations, the metal hydroxide particles are magnesium hydroxide or aluminum hydroxide. Multiple types of metal hydroxide particles may be used, such as a combination of magnesium hydroxide and aluminum hydroxide. These metal hydroxide particles are endothermic agents that absorb heat by causing an endothermic reaction when the temperature of the secondary battery attempts to rise, thereby suppressing the temperature rise of the secondary battery. Aluminum hydroxide causes an endothermic reaction at about 200°C. Magnesium hydroxide also causes an endothermic reaction at about 350°C.

[0023] In the above configuration, the porosity of the separator is 20% by volume or more and 60% by volume or less.

[0024] In the above-described structure, the organic resin that fixes the metal hydroxide particles to the surface of the separator is formed using a polyimide precursor, i.e., polyamic acid. The metal hydroxide particles have portions that are not covered with the second polymer compound and that come into contact with the electrolyte solution.

[0025] When adjusting the viscosity of the polyamic acid solution, organic solvents that can be used include ketones such as acetone, alcohols such as ethanol and isopropanol, ether, dioxane, acetonitrile, and N-methyl-2-pyrrolidone (NMP).

[0026] In this specification and the like, the term "particle" is not limited to referring only to spherical particles (having a circular cross-sectional shape), but the cross-sectional shape of each particle may be an ellipse, a rectangle, a trapezoid, a triangle, a square with rounded corners, an asymmetric shape, or the like, and further, each particle may have an irregular shape. [Effects of the Invention]

[0027] By providing metal hydroxide particles, which are heat-absorbing agents, on one or both surfaces of the separator, it is possible to prevent short circuits caused by lithium dendrites, thereby realizing a highly safe separator and a secondary battery equipped with the separator. [Brief explanation of the drawings]

[0028] [Figure 1] 1A, 1B, and 1C are examples of cross-sectional views of a secondary battery illustrating one embodiment of the present invention. [Figure 2] FIG. 2 shows an example of a manufacturing flow showing one embodiment of the present invention. [Figure 3] 3A and 3B are perspective views of the secondary battery manufacturing process. [Figure 4] 4(A) and 4(B) are schematic diagrams of a secondary battery. [Figure 5] 5A to 5H are diagrams illustrating an example of an electronic device. [Figure 6] 6A to 6D are diagrams illustrating examples of electronic devices. [Figure 7] 7(A) to 7(C) are diagrams illustrating an example of a vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0029] 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.

[0030] 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.

[0031] (Embodiment 1) In this embodiment, an example of a secondary battery of one embodiment of the present invention will be described with reference to FIG. 1. The secondary battery includes an outer casing (not shown), a positive electrode current collector 501, a positive electrode active material layer 502, a positive electrode 503, a negative electrode current collector 504, a negative electrode active material layer 505, a negative electrode 506, a separator 507, and an electrolyte solution containing a lithium salt or the like dissolved therein. The separator 507 is provided between the positive electrode active material layer 502 and the negative electrode active material layer 505. Note that the positive electrode current collector 501 and the positive electrode active material layer 502 may be collectively referred to as a positive electrode. The negative electrode current collector 504 and the negative electrode active material layer 505 may be collectively referred to as a negative electrode.

[0032] [Separator] Separator 507 can be a porous polymer film made of, for example, polypropylene, polyethylene, or the like.

[0033] Polymer films containing polypropylene, polyethylene, etc. can be produced by either the dry method or the wet method. The dry method involves heating and stretching a polymer film containing polypropylene, polyethylene, etc., to create gaps between the crystals and create fine holes. The wet method involves mixing a solvent into the resin beforehand, forming it into a film, and then extracting the solvent to create holes.

[0034] FIG. 1(B) shows an enlarged view of region X1 of the laminated portion surrounded by a dotted line in FIG. 1(A) as an example of separator 507 (produced by a wet method). A structure in which multiple pores 585 are formed in polymer film 584 constituting separator 507 is shown. Metal hydroxide particles 520 are fixed to polymer film 584 with organic resin 522b. Therefore, metal hydroxide particles 520 and organic resin 522b are fixed between positive electrode 503 and separator 507. FIG. 1(B) shows mixed region 521b of metal hydroxide particles 520 and organic resin 522b. If the surface of separator 507 is uneven, mixed region 521b may also include a portion of separator 507.

[0035] Although pores 585 are illustrated in FIG. 1(B), in reality, they are paths through which the electrolyte of the secondary battery enters and through which lithium ions move during charging and discharging. Organic resin 522b is located between metal hydroxide particles 520 and separator 507, and lithium ions can pass through the gaps in organic resin 522b. Electrolyte is present in the gaps in organic resin 522b. Lithium ions can also pass through the gaps between adjacent metal hydroxide particles 520. Electrolyte is also present in the gaps between adjacent metal hydroxide particles 520. Metal hydroxide particles 520 having regions not covered by organic resin 522b, as shown in FIG. 1(B), have a portion of their surface exposed, and this portion of the surface of metal hydroxide particle 520 comes into contact with the electrolyte. That is, the metal hydroxide has a portion not covered by the second polymer compound contained in organic resin 522b, and this portion comes into contact with the electrolyte.

[0036] Separator 507 has a surface with a plurality of openings, which are connected to pores 585 and serve as paths for lithium ions. By configuring the openings so that organic resin 522b is thinly coated on the inner walls thereof, it is possible to ensure paths for lithium ions even when the surface of separator 507 is coated with organic resin 522b. The size of pores 585 is 40 nm or more and less than 80 nm. Separator 507 has a porosity of 20 volume % or more and 60 volume % or less.

[0037] The thickness of separator 507 is 15 μm or more and 40 μm or less.

[0038] FIG. 1(C) shows a cross-sectional view of region X2 of an example of separator 507 (produced by a wet process). FIG. 1(C) shows an enlarged view of region X2 of the laminated portion surrounded by the dotted line in FIG. 1(A). Metal hydroxide particles 520 are fixed to the other surface of separator 507 with organic resin 522a. Therefore, metal hydroxide particles 520 and organic resin 522a are fixed between the negative electrode 506 and separator 507. FIG. 1(C) shows a mixed region 521a of metal hydroxide particles 520 and organic resin 522a. If the surface of separator 507 is uneven, mixed region 521a may also include a portion of separator 507.

[0039] The metal hydroxide is magnesium hydroxide or aluminum hydroxide. The metal hydroxide may be in the form of secondary particles or primary particles. For example, the particle diameter of magnesium hydroxide is 500 nm or more and 2 μm or less.

[0040] A separator with metal hydroxide particles on its surface has improved wettability with the electrolyte. Furthermore, improved wettability of the separator makes it easier to remove lithium dendrites that have formed. Dendrites can sometimes grow starting from the negative electrode, so the separator surface that comes into contact with the negative electrode (the negative electrode surface) is important. Dendrites can grow as dendritic crystals, which can then fall off or break off.

[0041] Wettability is closely related to surface tension. When a drop of liquid is dropped onto a solid surface, the liquid becomes round due to surface tension, and the angle between the tangent of the drop and the solid surface is called the contact angle, which is commonly used as an indicator of wettability. There are several methods for determining the contact angle, including the θ / 2 method, the tangent method, and the curve fitting method.

[0042] When a liquid is dropped onto the surface of a solid, the greater the surface tension of the liquid and the smaller the surface tension of the solid, the larger the contact angle and the lower the wettability. Conversely, the smaller the surface tension of the liquid and the greater the surface tension of the solid, the smaller the contact angle and the higher the wettability.

[0043] The surface tension of a liquid can be measured by the plate method or the pendant drop method, and the unit of surface tension is mN / m.

[0044] Furthermore, when a drop of liquid is dropped onto a solid surface, three forces act at the end point, determining the contact angle: the surface tension of the solid, the surface tension of the liquid, and the interfacial tension between the liquid and the solid. Young's equation is the equation that shows the balance of the surface tensions at the end point. As Young's equation shows, the contact angle is affected not only by the wettability of the liquid and solid alone, but also by the compatibility between the solid and the liquid. Therefore, the contact angle is a relative value determined by the compatibility between the liquid and the solid.

[0045] The surface tension of a solid is called the surface free energy (SFE) and is expressed in mJ / m 2 The surface free energy of a solid is an absolute value that indicates the wettability of the solid itself.

[0046] Additionally, materials with a surface free energy lower than 36 dyn / cm are classified as low surface energy materials. Polypropylene or polyethylene separators are low surface energy materials. Furthermore, if the surface is uneven, the surface tension increases. Because separators have multiple openings, the surface is uneven, and corrections may be required to take the actual area into account.

[0047] Furthermore, the presence of metal hydroxide particles on the separator surface can suppress the growth of lithium dendrites. Furthermore, when the secondary battery generates heat, the metal hydroxide particles absorb heat, thereby suppressing temperature rise. Furthermore, when the secondary battery generates heat, the shutdown function activates, and the organic resin 522a prevents deformation, shortening the distance between the positive and negative electrodes, and causing a short circuit. Because the melting point of the organic resin 522a is higher than that of the material of the separator 507, it can maintain the distance between the positive and negative electrodes and prevent a short circuit.

[0048] The separator having metal hydroxide particles on its surface is preferably processed into an envelope shape and disposed so as to encase either the positive electrode or the negative electrode.

[0049] The positive electrode has a positive electrode active material layer 502 and a positive electrode current collector 501. The positive electrode active material layer 502 has a positive electrode active material, a conductive additive, and a binder. Known materials can be used for the positive electrode.

[0050] The negative electrode has a negative electrode active material layer 505 and a negative electrode current collector 504. The negative electrode active material layer 505 has a negative electrode active material, a conductive additive, and a binder. Known materials can be used for the negative electrode.

[0051] As the binder, it is preferable to use a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. Also, fluororubber can be used as the binder.

[0052] Furthermore, it is preferable to use, for example, a water-soluble polymer as the binder. Examples of the water-soluble polymer that can be used include polysaccharides. Examples of the polysaccharide that can be used include cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose, as well as starch. It is even more preferable to use these water-soluble polymers in combination with the aforementioned rubber material.

[0053] Alternatively, it is preferable to use materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose as the binder.

[0054] The binder may be used in combination with two or more of the above.

[0055] The active material layer can be produced by mixing an active material, a binder, a conductive additive and a solvent to prepare a slurry, forming the slurry on a current collector, and volatilizing the solvent.

[0056] The solvent used for the slurry is preferably a polar solvent, such as water, methanol, ethanol, acetone, tetrahydrofuran (THF), dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO), or a mixture of two or more of these.

[0057] As the positive current collector 501 and the negative current collector 504, metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, titanium, and alloys thereof, etc., materials with high conductivity and that do not alloy with carrier ions such as lithium can be used. Also, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum, etc. that improve heat resistance can be used. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as sheet-like, net-like, punching metal-like, expanded metal-like, etc. The current collector preferably has a thickness of 10 μm or more and 30 μm or less.

[0058] Note that for the negative current collector 504, it is preferable to use a material that does not alloy with carrier ions such as lithium.

[0059] A titanium compound may be provided by laminating on the above-described metal element as the current collector. As the titanium compound, for example, titanium nitride, titanium oxide, titanium nitride in which a part of nitrogen is substituted by oxygen, titanium oxide in which a part of oxygen is substituted by nitrogen, and titanium oxynitride (TiO x N y , where 0 < x < 2, 0 < y < 1), one selected therefrom, or two or more may be mixed or laminated and used. Among them, titanium nitride is particularly preferable because it has high conductivity and a high function of suppressing oxidation. By providing the titanium compound on the surface of the current collector, for example, the reaction between the material and the metal in the active material layer formed on the current collector is suppressed. When the active material layer contains a compound having oxygen, the oxidation reaction between the metal element and oxygen can be suppressed. For example, when aluminum is used as the current collector and the active material layer is formed using graphene oxide described later, there may be a concern about the oxidation reaction between the oxygen in graphene oxide and aluminum. In such a case, by providing a titanium compound on aluminum, the oxidation reaction between the current collector and graphene oxide can be suppressed.

[0060] Hereinafter, a method for producing a separator in which a mixture of metal hydroxide particles and a solvent is applied to the surface will be described with reference to FIG.

[0061] <Step S101> First, in step S101, a mixture of polyamic acid (also called polyamic acid) dissolved in an organic solvent to adjust the viscosity is prepared and mixed with metal hydroxide particles. In this embodiment, aluminum hydroxide is used as the metal hydroxide particles. The aluminum hydroxide is crushed or pulverized in advance, with the particle size being larger than the pore size of the separator. Note that the pore size of commercially available separators used in this embodiment is 40 nm or more and less than 80 nm. It is preferable to add an organic solvent so that the viscosity of the polyamic acid is 2 Pa·s or less, preferably 0.03 Pa·s or less. The viscosity is measured at 25°C using a rotational rheometer, Discovery HR-20 (manufactured by TA Instruments), using parallel plates with a diameter of 40 mm.

[0062] Examples of organic solvents that can be used include ketones such as acetone, alcohols such as ethanol and isopropanol, ether, dioxane, acetonitrile, and N-methyl-2-pyrrolidone (NMP). In this embodiment, NMP is used and diluted with an amount that is 2 to 5 times the volume of the polyamic acid. Using a diluted mixed solution reduces coating unevenness. Alternatively, if a uniform coating can be achieved, the polyamic acid alone may be coated without dilution.

[0063] <Step S102> Next, a commercially available separator is prepared. A polyolefin-based material is preferable, and polypropylene is used in this embodiment. In this embodiment, this separator is called the first separator. Polypropylene can be represented by the following chemical formula:

[0064] [ka]

[0065] Then, the mixture liquid containing the metal hydroxide particles and the polyamic acid prepared in step S101 is applied to the separator.

[0066] <Step S103> Next, in step S103 shown in FIG. 2, after the mixed solution is applied, the first separator is dried to obtain a second separator. After reducing the pressure, the separator is dried using a forced air dryer to evaporate excess organic solvent. By evaporating the excess organic solvent, the separator can be fixed. In this embodiment, the temperature inside the forced air dryer is set to 70°C or higher and 100°C or lower, and the separator is dried for 30 minutes to 2 hours.

[0067] <Step S104> Through the above process, a second separator can be obtained, with polyamic acid coated on the entire surface or a portion of the surface, as shown in step S104 in FIG. 2. The second separator has improved electrolyte wettability compared to the first separator. Imidization begins at approximately 100°C, but even if imidization hardly occurs when drying using a forced air dryer, the surface condition of the second separator can be modified. If all polyamic acid is imidized to polyimide, imidization is complete, resulting in a polyimide with a degree of imidization of 100%. However, in this embodiment, imidization may be incomplete, i.e., less than 100%. Therefore, the surface condition can be modified even if most of the polyamic acid is not imidized. This is preferable because it allows for smaller particle size compared to complete imidization. Of course, a portion of the polyamic acid may be imidized to form imide bonds, which improves the bonding strength of the separator or metal hydroxide particles. The obtained second separator has a shutdown function because polypropylene is a thermoplastic material, and also has both a shutdown function and a wettability improving function because the polyamic acid improves the wettability.

[0068] An example of a lithium ion battery produced using the second separator will be described below.

[0069] FIG. 3(A) shows an example of an exploded perspective view of a positive electrode that constitutes a secondary battery.

[0070] When a plurality of electrodes are stacked, it is preferable to process the second separator 203 into a bag shape and arrange it so as to encase either the positive electrode or the negative electrode. For example, as shown in FIG. 3(A), the second separator 203 is folded in half so as to sandwich the positive electrode, and sealed with a sealing portion 514 outside the region overlapping with the positive electrode active material layer 202, thereby ensuring that the positive electrode active material layer 202 is supported within the second separator 203. Then, as shown in FIG. 3(B), the positive electrodes and negative electrodes wrapped in the second separator 203 are arranged alternately. Note that FIG. 3(B) illustrates a negative electrode tab 282 and a positive electrode tab 281.

[0071] 3(B), it is preferable to provide the positive electrode active material layer 202 on not only one surface but also both surfaces of the positive electrode current collector 201. It is also preferable to provide the negative electrode active material layer 205 on not only one surface but also both surfaces of the negative electrode current collector 206. The positive electrode current collector 201 or the negative electrode current collector 206, which is the outermost one, may be coated on one surface.

[0072] In addition, in Fig. 4(A), the exterior body 509 is in a bag-like state with an opening near the tab 282, and the exterior body 509 is shown by a dashed line in Fig. 4(A). In reality, the stack is housed through the opening of the bag-shaped exterior body 509 with the lead 511 welded to the tab 282. In Fig. 4(A), the negative electrode and lead 510 are shown by dashed lines to clearly illustrate the structure of the separator. Then, the electrolyte is dripped from the opening of the exterior body 509.

[0073] The electrolyte solution is preferably allowed to penetrate not only the separator but also the positive electrode active material layer and the negative electrode active material layer. Therefore, the porosity of the positive electrode active material layer, the porosity of the second separator, and the porosity of the negative electrode active material layer are determined, and when the sum of the void volumes calculated from the porosities of the positive electrode active material layer, the second separator, and the negative electrode active material layer is taken as 1, an amount of electrolyte solution that is 0.1 to 1.5 is dropped into the opening of the exterior body.

[0074] It is preferable to use as little electrolyte as possible, and by using second separator 203 that has high wettability with the electrolyte, it is possible to realize a separator that allows the electrolyte to spread even with a smaller amount than before.

[0075] Furthermore, the lithium salt dissolved in the electrolyte solution is made to have a concentration higher than 1.0 mol / L, specifically higher than 1.5 mol / L.

[0076] After pouring the electrolyte solution into the opening of the exterior body 509, the pressure is reduced, thereby allowing the electrolyte solution to spread selectively over the second separator 203. After reducing the pressure, the opening of the exterior body 509 is sealed to form the sealing portion 118.

[0077] Alternatively, the electrolyte may be added dropwise after reducing the pressure.

[0078] After sealing, an inspection may be performed by irradiating ultrasonic waves. Irradiating ultrasonic waves can also spread the electrolyte solution on the second separator 203. After sealing, the second separator 203 is left standing for 24 hours to spread the electrolyte solution on the second separator 203. After that, an aging treatment or degassing treatment may be performed. After the aging treatment or degassing treatment, ultrasonic waves may be irradiated to spread the electrolyte solution on the second separator 203.

[0079] 4(B) can be manufactured in which one positive electrode, one second separator 203, and one negative electrode are housed as one set in the exterior body 509. In this way, a small amount of electrolyte solution is used for one secondary battery, and a highly safe secondary battery can be manufactured.

[0080] This embodiment mode can be freely combined with other embodiment modes.

[0081] (Embodiment 2) In this embodiment, examples of mounting a secondary battery which is one embodiment of the present invention in an electronic device will be described with reference to FIGS.

[0082] Examples of electronic devices to which the secondary batteries described in the previous embodiments are applied include television devices (also called televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game machines, personal digital assistants, sound reproduction devices, and large game machines such as pachinko machines.

[0083] Furthermore, the secondary battery described in the first embodiment can also be incorporated along the curved surfaces of the inner or outer walls of houses, buildings, etc., or the interior or exterior of automobiles.

[0084] 5A shows an example of a mobile phone. The mobile phone 7400 includes a display portion 7402 built into a housing 7401, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like. The mobile phone 7400 also includes a secondary battery 7407. By using the separator described in Embodiment 1 for the secondary battery 7407, a highly safe mobile phone can be provided.

[0085] FIG. 5(B) shows the mobile phone 7400 in a bent state. When the mobile phone 7400 is deformed by an external force and bent as a whole, the secondary battery 7407 installed inside is also bent. FIG. 5(C) shows the state of the bent secondary battery 7407 at that time. The secondary battery 7407 is a thin storage battery. The secondary battery 7407 is fixed in a bent state. The secondary battery 7407 has a lead electrode electrically connected to a current collector.

[0086] FIG. 5D shows an example of a bangle-type display device. The portable display device 7100 includes a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. FIG. 5E shows a bent secondary battery 7104. When the secondary battery 7104 is worn on a user's arm in a bent state, the housing deforms, causing a change in the curvature of part or the entire secondary battery 7104. Note that the degree of curvature at any point on the curve, expressed as the radius of the corresponding circle, is called the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, part or the entire main surface of the housing or the secondary battery 7104 changes when the radius of curvature is in the range of 40 mm to 150 mm. High reliability can be maintained when the radius of curvature of the main surface of the secondary battery 7104 is in the range of 40 mm to 150 mm. By using the separator described in Embodiment 1 for the secondary battery 7104, a highly safe portable display device can be provided.

[0087] 5F shows an example of a wristwatch-type portable information terminal 7200. The portable information terminal 7200 includes a housing 7201, a display portion 7202, a band 7203, a buckle 7204, operation buttons 7205, an input / output terminal 7206, and the like.

[0088] The portable information terminal 7200 can execute various applications such as mobile phone calls, e-mail, document browsing and creation, music playback, internet communication, and computer games.

[0089] The display surface of the display portion 7202 is curved, and a display can be performed along the curved display surface. The display portion 7202 is also provided with a touch sensor, and can be operated by touching the screen with a finger or a stylus. For example, an application can be started by touching an icon 7207 displayed on the display portion 7202.

[0090] The operation button 7205 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 7205 can be freely set by an operating system incorporated in the mobile information terminal 7200.

[0091] The mobile information terminal 7200 is also capable of performing standardized short-range wireless communication. For example, hands-free conversation is also possible by communicating with a wirelessly enabled headset.

[0092] The portable information terminal 7200 also includes an input / output terminal 7206, and can directly exchange data with another information terminal via a connector. Charging can also be performed via the input / output terminal 7206. Note that charging may be performed by wireless power supply without using the input / output terminal 7206.

[0093] The display portion 7202 of the mobile information terminal 7200 includes the secondary battery of one embodiment of the present invention. A highly safe mobile information terminal can be provided by using the separator described in Embodiment 1 for the secondary battery of one embodiment of the present invention. For example, the secondary battery 7104 shown in FIG. 5E can be incorporated into the housing 7201 in a curved state or into the band 7203 in a bendable state.

[0094] The portable information terminal 7200 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.

[0095] 5G shows an example of an armband-type display device. The display device 7300 includes a display portion 7304 and the secondary battery of one embodiment of the present invention. The display device 7300 can also be provided with a touch sensor in the display portion 7304 and can function as a portable information terminal.

[0096] The display surface of the display portion 7304 is curved, and display can be performed along the curved display surface. The display state of the display device 7300 can be changed by short-range wireless communication according to a communication standard.

[0097] The display device 7300 also includes an input / output terminal, allowing direct data exchange with other information terminals via a connector. Charging can also be performed via the input / output terminal. Note that charging may also be performed by wireless power supply without using the input / output terminal.

[0098] By using the separator described in Embodiment 1 for the secondary battery included in the display device 7300, a highly safe display device can be provided.

[0099] An example in which the secondary battery with good cycle characteristics described in the above embodiment is mounted on an electronic device will be described with reference to FIGS.

[0100] Highly safe products can be provided by using the separator described in embodiment 1 in secondary batteries for everyday electronic devices. For example, examples of everyday electronic devices include electric toothbrushes, electric shavers, and electric beauty devices, and secondary batteries for these products are desired to be stick-shaped, compact, lightweight, and have a large discharge capacity so that they are easy for users to hold.

[0101] FIG. 5H is a perspective view of a device also known as a tobacco-containing smoking device (electronic cigarette). In FIG. 5H, the electronic cigarette 7500 includes an atomizer 7501 including a heating element, a secondary battery 7504 that supplies power to the atomizer, and a cartridge 7502 that includes a liquid supply bottle, a sensor, and the like. To enhance safety, a protection circuit that prevents overcharging and / or overdischarging of the secondary battery 7504 may be electrically connected to the secondary battery 7504. The secondary battery 7504 shown in FIG. 5H has external terminals so that it can be connected to a charging device. Because the secondary battery 7504 is the tip portion when held, it is desirable that the total length be short and the weight be light. The secondary battery of one embodiment of the present invention can provide a highly safe electronic cigarette 7500 by using the separator described in Embodiment 1.

[0102] Figure 6(A) shows an example of a wearable device. Wearable devices use secondary batteries 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 wearable devices that can be charged wirelessly as well as via wired charging, with an exposed connector.

[0103] 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. 6A. The eyeglasses-type device 4000 includes a frame 4000a and a display portion 4000b. Mounting a secondary battery on temple portions of the curved frame 4000a makes it possible to provide an eyeglasses-type device 4000 that is lightweight, has a good weight balance, and can be used for a long time. By including the secondary battery according to one embodiment of the present invention, a highly safe configuration can be realized.

[0104] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a headset-type device 4001. The headset-type device 4001 includes at least a microphone unit 4001a, a flexible pipe 4001b, and an earphone unit 4001c. The secondary battery can be provided in the flexible pipe 4001b and / or the earphone unit 4001c. By including the secondary battery 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 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. By including the secondary battery according to one embodiment of the present invention, a highly safe configuration can be realized.

[0106] 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. By including the secondary battery according to one embodiment of the present invention, a highly safe configuration can be realized.

[0107] 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 has a belt portion 4006a and a wireless power receiving portion 4006b, and the secondary battery can be mounted inside the belt portion 4006a. By including the secondary battery of 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 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. By providing the secondary battery of one embodiment of the present invention, a highly safe configuration can be realized.

[0109] The display unit 4005a can display not only the time but also various other information such as incoming emails and phone calls.

[0110] Furthermore, since the wristwatch device 4005 is a wearable device that is worn directly on the wrist, 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.

[0111] FIG. 6(B) shows a perspective view of the wristwatch type device 4005 removed from the wrist.

[0112] 6C shows a side view of the display portion 4005a. FIG. 6C shows a state in which a secondary battery 913 is built inside the display portion 4005a. The secondary battery 913 is the secondary battery described in Embodiment 1. The secondary battery 913 is provided at a position overlapping with the display portion 4005a, and is small and lightweight.

[0113] 6(D) 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.

[0114] 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.

[0115] The case 4110 has a secondary battery 4111. It also preferably 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, etc.

[0116] 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, they can send sounds picked up by the microphones to the other electronic devices, and the sound data after processing by the electronic devices can be sent back to the main units 4100a and 4100b for playback. This allows them to be used as, for example, translation devices.

[0117] In addition, 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.

[0118] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0119] (Embodiment 3) In this embodiment, an example is shown in which a secondary battery including the positive electrode active material of one embodiment of the present invention is mounted on a vehicle.

[0120] By installing secondary batteries in vehicles, next-generation clean energy vehicles such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs) can be realized.

[0121] 7A and 7B illustrate an example of a vehicle using a secondary battery according to one embodiment of the present invention. An automobile 8400 shown in FIG. 7A is an electric automobile using an electric motor as a power source for running. Alternatively, it is a hybrid automobile that can appropriately select and use an electric motor or an engine as a power source for running. By using the separator according to one embodiment of the present invention, a highly safe vehicle can be realized. Furthermore, the automobile 8400 includes a secondary battery. For example, secondary battery modules can be arranged on the floor of the interior of the vehicle. The secondary battery 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).

[0122] 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.

[0123] The automobile 8500 shown in FIG. 7(B) can charge its secondary battery by receiving power from an external charging facility via a plug-in system and / or a wireless power supply system. FIG. 7(B) 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 system, such as CHAdeMO (registered trademark) or Combo. The charging device 8021 can be used in charging stations installed in commercial facilities or as a home 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 via a converter, such as an AC-DC converter.

[0124] Furthermore, 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 for charging. 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 it 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, and secondary batteries can be charged while the vehicle is stopped and / or moving. Electromagnetic induction and / or magnetic resonance methods can be used for such contactless power supply.

[0125] 7C 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. 7C 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.

[0126] 7(C) can store a secondary battery 8602 in under-seat storage 8604. Even if under-seat storage 8604 is small, secondary battery 8602 can be stored in under-seat storage 8604. Secondary battery 8602 is removable, and when charging, secondary battery 8602 can be carried indoors, charged, and stored before riding.

[0127] According to one embodiment of the present invention, the cycle characteristics of the secondary battery are improved, and even if the discharge capacity of the secondary battery is increased, the separator of one embodiment of the present invention can improve safety. Furthermore, a secondary battery mounted on a 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.

[0128] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Explanation of symbols]

[0129] 118 Sealing part 201 Positive electrode current collector 202 Cathode active material layer 203 Second Separator 205 Negative electrode active material layer 206 Negative electrode current collector 281 tabs 282 tabs 501 Positive electrode current collector 502 Positive electrode active material layer 503 Positive electrode 504 Negative electrode current collector 505 Negative electrode active material layer 506 negative electrode 507 Separator 509 Exterior body 510 leads 511 leads 514 Sealing part 520 particles 521a Mixed area 521b Mixed area 522a Organic resin 522b Organic resin 584 Polymer Film 585 Vacancies 913 Secondary battery 4000 Eyeglasses-type Device 4000a frame 4000b Display section 4001 Headset type device 4001a microphone section 4001b Flexible Pipe 4001c Earphones 4002 devices 4002a housing 4002b secondary battery 4003 Devices 4003a housing 4003b secondary battery 4005 Wristwatch-type device 4005a Display section 4005b Belt section 4006 Belt-type device 4006a Belt section 4006b Wireless power receiving unit 4100a main unit 4100b main unit 4101 Driver Unit 4102 Antenna 4103 Secondary battery 4104 Display section 4110 cases 4111 Secondary battery 7100 Portable display devices 7101 Housing 7102 Display section 7103 Operation button 7104 Secondary battery 7200 Personal Digital Assistant 7201 Case 7202 Display section 7203 Band 7204 Buckle 7205 Operation button 7206 Input / output terminal 7207 Icon 7300 display device 7304 Display section 7400 mobile phone 7401 Housing 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Microphone 7407 Secondary battery 7500 e-cigarettes 7501 Atomizer 7502 Cartridge 7504 Secondary battery 8021 Charging device 8022 cable 8024 Secondary battery 8400 Automobiles 8401 Headlight 8406 Electric motor 8500 cars 8600 Scooter 8601 Side mirror 8602 Secondary battery 8603 Turn signal light 8604 Under-seat storage

Claims

1. A positive electrode and a negative electrode; a separator between the positive electrode and the negative electrode, the separator is a first polymer compound having thermoplastic properties, The first polymer compound has at least two or more metal hydroxide particles in contact with one or both surfaces thereof, The secondary battery has a plurality of openings on one or both surfaces of the first polymer compound, and a second polymer compound in contact with the inner walls of the openings.

2. 2. The secondary battery according to claim 1, wherein the first polymer compound is polypropylene or polyethylene, and the second polymer compound has an imide bond.

3. 2. The secondary battery according to claim 1, wherein the size of the pores in the separator is 40 nm or more and less than 80 nm, which is smaller than the particle diameter of the metal hydroxide particles.

4. 2. The secondary battery according to claim 1, wherein the porosity of the separator is 20% by volume or more and 60% by volume or less.

5. 2. The secondary battery according to claim 1, wherein the organic resin that fixes the plurality of metal hydroxide particles to the surface of the separator is a precursor of polyimide.

6. 2. The secondary battery according to claim 1, wherein the metal hydroxide particles are magnesium hydroxide or aluminum hydroxide.

7. 2. The secondary battery according to claim 1, wherein the metal hydroxide particles have a portion that is not covered with the second polymer compound, and the portion is in contact with the electrolyte.

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