Secondary battery

Abstract

The objective of the present invention is to provide a secondary battery having a high battery capacity and excellent cycle characteristics, the secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, an aqueous electrolyte and a separator, wherein: the positive electrode is an air electrode; the negative electrode comprises a negative electrode current collector and a negative electrode mixture layer formed on same, the negative electrode mixture layer comprising at least one component selected from the group consisting of metallic lithium, magnesium, zinc, and aluminium; and the separator is a polymeric film having an air resistance of more than 10000 seconds, an ionic conductance of at least 1x10-5S / cm, and a water contact angle of at least 90°.

Description

[Technical field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] In recent years, portable electronic devices have become smaller and smaller, and their power sources are also required to have higher energy density. In order to reduce the weight and increase the energy of batteries, metal Li anodes, all-solid-state batteries, and air batteries have been actively researched. In particular, the evolution of the cathode into an air cathode that uses air as an energy source will enable overwhelming weight reduction compared to current oxides, and will have a higher capacity than the currently widely used lithium secondary batteries, making it a promising next-generation power source. As air batteries, for example, metal-air batteries such as lithium-air batteries, magnesium-air batteries, and zinc-air batteries are known.

[0003] For practical use, metal-air batteries have many remaining issues in the design of the positive electrode, negative electrode, separator, electrolyte, etc. A problem has arisen in that solids generated by the electrode reaction at the positive electrode (hereinafter referred to as product solids) accumulate at the air electrode, causing the air electrode to become clogged and blocking contact between the electrolyte and air, which impedes charging and discharging.

[0004] As a technique for solving the problem of precipitation of the product solid, the use of an aqueous electrolyte as the electrolyte of the metal-air battery has been proposed. In the case of a metal-air battery using an aqueous electrolyte, a metal hydroxide is generated as the product solid, and since the product solid is water-soluble, the product solid can be dissolved in the aqueous electrolyte, and the precipitation of the product solid can be suppressed.

[0005] However, metal-air batteries that use an aqueous electrolyte have the problem that if the saturation solubility of the salt in the aqueous electrolyte is exceeded, a solid product will precipitate, causing the battery to become inactive. In addition, when metallic lithium is used in the negative electrode, it is difficult to put the battery into practical use from the standpoint of safety.

[0006] In addition, regarding the negative electrode, the reduction in safety and the reduction in life characteristics due to dendrites of various metal negative electrodes are issues.

[0007] Therefore, it is important to solve the problems of the above air battery by using two different types of electrolytes in combination.

[0008] As an approach using two different types of electrolytes in combination, Patent Document 1 proposes improving battery characteristics by arranging an aqueous electrolyte on the positive electrode side and an ion-conductive glass ceramic on the negative electrode side. Patent Document 2 proposes that negative electrode protection can be achieved by providing a polymer-containing electrolyte coating layer on the surface of a lithium-ion conductive solid electrolyte, and the characteristics are improved.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, Patent Document 1 uses a glass ceramic, which has high strength but lacks flexibility, and the separability of the aqueous electrolyte when subjected to impact is insufficient. Patent Document 2 is considered not to contribute to solving the fundamental problems of the air electrode because it does not use or cannot use an aqueous electrolyte.

[0011] Therefore, in view of the above problems, an object of the present invention is to provide a secondary battery with a high battery capacity and excellent cycle characteristics by using a separator capable of separating a non-aqueous electrolyte and an aqueous electrolyte in a battery using a non-aqueous electrolyte and an aqueous electrolyte.

Means for Solving the Problems

[0012] To solve the above problems, the secondary battery of the present invention has the following configuration. (1) A secondary battery including a positive electrode, a negative electrode, a non-aqueous electrolyte, an aqueous electrolyte, and a separator, wherein the positive electrode is an air electrode, the negative electrode is composed of a negative electrode current collector and a negative electrode mixture layer formed thereon, and the negative electrode mixture layer contains one or more components selected from the group consisting of metallic lithium, magnesium, zinc, and aluminum. The separator is a polymer film having an air permeability greater than 10,000 seconds, an ionic conductivity of 1×10 -5 S / cm or more, and a water contact angle of 90° or more. (2) The secondary battery according to (1), wherein the change rate of the contact angle of water after 1 hour of dropping water with respect to the contact angle of water after 10 seconds of dropping water on the polymer film is less than 10%. (3) The secondary battery according to (1) or (2), wherein the contact angle of the polymer film measured using dimethyl carbonate is 90° or more. (4) The secondary battery according to any one of (1) to (3), wherein the change rate of the contact angle of dimethyl carbonate after 1 hour of dropping dimethyl carbonate with respect to the contact angle of dimethyl carbonate after 10 seconds of dropping dimethyl carbonate on the polymer film is less than 10%. (5) The secondary battery according to any one of (1) to (4), wherein the melt-down temperature of the polymer film is 300°C or more. (6) The secondary battery according to any one of (1) to (5), wherein the polymer constituting the polymer film contains an aromatic polyamide, an aromatic polyimide, or an aromatic polyamideimide. [Effect of the Invention]

[0013] According to the present invention, it is possible to provide a secondary battery having a high battery capacity and excellent cycle characteristics. [Embodiments for Carrying Out the Invention]

[0014] The secondary battery according to an embodiment of the present invention will be described in detail below. The secondary battery according to an embodiment of the present invention is a secondary battery including a positive electrode, a negative electrode, a non-aqueous electrolyte, an aqueous electrolyte, and a separator, wherein the positive electrode is an air electrode, the negative electrode is composed of a negative electrode current collector and a negative electrode mixture layer formed thereon, the negative electrode mixture layer contains one or more components selected from the group consisting of metallic lithium, magnesium, zinc, and aluminum, and the separator is a polymer film having an air permeability greater than 10,000 seconds, an ionic conductivity of 1×10 -5 S / cm or more, and a water contact angle of 90° or more.

[0015] [Positive Electrode] In an embodiment of the present invention, the electrode used for the positive electrode is an air electrode that uses air as an energy source. The air electrode has, for example, a structure in which an oxygen reduction catalyst such as platinum is supported on a porous carbon sheet, or a sheet structure of carbon having high catalytic activity, such as graphene or carbon nanotubes. The porous carbon sheet is, for example, carbon paper, carbon black, an acetylene black sheet, or the like.

[0016] [Negative Electrode] The negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector. As the negative electrode current collector, for example, a negative electrode current collector made of copper, nickel, or stainless steel can be used.

[0017] In an embodiment of the present invention, the negative electrode active material contained in the negative electrode mixture layer contains one or more components selected from the group consisting of metallic lithium, magnesium, zinc, and aluminum. Among them, it is preferable to use metallic lithium from the viewpoints of the operating voltage of the battery and the theoretical capacity of the negative electrode active material.

[0018] The negative electrode is manufactured, for example, as follows. In the case of metallic lithium, it can be produced by generating lithium nanoparticles by gas deposition method on a negative electrode current collector and ejecting and depositing them together with He gas.

[0019] [Electrolyte] In the embodiments of the present invention, non-aqueous electrolytes and aqueous electrolytes are used as the electrolytes. The non-aqueous electrolyte consists of an organic solvent and a solute.

[0020] As the organic solvent of the non-aqueous electrolyte, cyclic esters, chain esters, cyclic ethers, chain ethers, amides, etc. are used. Specifically, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone (γBL), 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane (DME), 1,2-ethoxyethane, diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, tetraethylene glycol dialkyl ether, dipropyl carbonate, methyl butyl carbonate, methyl propyl carbonate, ethyl butyl carbonate, ethyl propyl carbonate, butyl propyl carbonate, alkyl propionate, dialkyl malonate, alkyl acetate, tetrahydrofuran (THF), alkyl tetrahydrofuran, dialkyl alkyl tetrahydrofuran, alkoxy tetrahydrofuran, dialkoxy tetrahydrofuran, 1,3-dioxolane, alkyl-1,3-dioxolane, 1,4-dioxolane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, methyl propionate, ethyl propionate, triester phosphate, N-methyl-2-pyrrolidone and other organic solvents and their derivatives and mixtures, etc. are preferably used.

[0021] As solutes contained in the non-aqueous electrolyte, halides of alkali metals, particularly lithium, perchlorates, thiocyanates, borofluorides, phosphofluorides, arsenofluorides, aluminum fluorides, trifluoromethyl sulfates, etc. are preferably used. For example, lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(trifluoromethylsulfonyl)imide [LiN(CF 3 SO 2 ) 2 and other lithium salts (solutes) such as one or more salts can be used, but lithium hexafluorophosphate is preferred from the viewpoints of oxidation resistance and reduction resistance.

[0022] The dissolution amount of the solute in the organic solvent is preferably 0.5 to 3.0 mol / L, and particularly preferably 0.8 to 1.5 mol / L.

[0023] Also, additives may be used in the non-aqueous electrolyte as needed. Examples of the additives include vinylene carbonate, fluoroethylene carbonate, ethylene sulfite, 1,4-butane sultone, propane sultone, 2,4-difluoroanisole, biphenyl, cyclohexylbenzene, etc., and one or more of these may be used.

[0024] Aqueous electrolytes include acidic electrolytes and alkaline electrolytes. Examples of acidic electrolytes include hydrochloric acid, sulfuric acid, hydrofluoric acid, etc. Examples of alkaline electrolytes include aqueous potassium hydroxide, calcium hydroxide, aqueous sodium hydroxide, lithium hydroxide, etc.

[0025] Also, from the viewpoints of battery safety, life characteristics, and stable operation of the battery, the electrolyte in the secondary battery of the present invention preferably has an aqueous electrolyte on the positive electrode side and a non-aqueous electrolyte on the negative electrode side.

[0026] [Separator] The separator is a polymer membrane with an air permeability greater than 10,000 seconds, an ionic conductivity of 1×10 -5 S / cm or more, and a water contact angle of 90° or more.

[0027] Since the separator needs to separate the electrolytes in batteries using two types of electrolytes, namely non-aqueous electrolytes and aqueous electrolytes, its air permeability is greater than 10,000 seconds. When the air permeability is greater than 10,000 seconds, it can be regarded as a non-porous structure with substantially no continuous pores in the separator.

[0028] Since the separator should not swell in the electrolyte and should not allow the aqueous electrolyte to permeate, it is important that the separator is a polymer membrane with a water contact angle of 90° or more. If the water contact angle is less than 90%, the aqueous electrolyte may permeate through the separator and mix with the non-aqueous electrolyte, which may lead to a decrease in battery performance. Also, from the perspective of the ability to separate electrolytes during battery use and battery performance, the change rate of the contact angle of water 1 hour after dropping water with respect to the contact angle of water 10 seconds after dropping water on the separator is preferably less than 10%, more preferably less than 7%.

[0029] Also, since the separator should not swell in the non-aqueous electrolyte and should not allow the non-aqueous electrolyte to permeate, it is preferable that the separator is a polymer membrane with a contact angle measured using dimethyl carbonate of 90° or more. Also, from the perspective of the ability to separate electrolytes during battery use and battery performance, the change rate of the contact angle of dimethyl carbonate 1 hour after dropping dimethyl carbonate with respect to the contact angle of dimethyl carbonate 10 seconds after dropping dimethyl carbonate on the separator is preferably less than 10%, more preferably less than 7%.

[0030] Since the separator has a non-porous structure and cannot impregnate the electrolyte and there is no swelling of the electrolyte, it is important from the perspective of battery performance that the polymer membrane has ionic conductivity. The ionic conductivity, which is an index of the ionic conductivity of the separator, is 1×10 -5 S / cm or more is important. When the ionic conductivity is 1×10 -5If it is less than S / cm, the resistance is high and the battery characteristics may deteriorate.

[0031] From the viewpoint of battery safety, the melt-down temperature of the separator is preferably 300 °C or higher, more preferably 350 °C or higher.

[0032] The polymer film that achieves the above separator will be described in detail.

[0033] As the polymer constituting the polymer film that is the separator, a polymer having an aromatic ring on the main chain is suitable as one that achieves heat resistance, strength, and flexibility. Examples of such polymers include aromatic polyamides (aramids), aromatic polyimides, aromatic polyamideimides, aromatic polyether ketones, aromatic polyether ether ketones, aromatic polyarylates, aromatic polysulfones, aromatic polyether sulfones, aromatic polyether imides, aromatic polycarbonates, and the like. Also, a blend of a plurality of polymers may be used. Among them, since it has excellent heat resistance and is likely to maintain high strength when made into a thin film, when the total mass of the film is 100%, it is preferably contained in an amount of 30 to 100% by mass of aromatic polyamide, aromatic polyimide, or aromatic polyamideimide. More preferably, it is 50 to 100% by mass.

[0034] As the polymer that can be preferably used in the present invention, it is preferable to contain a polymer having a structure of any of the following chemical formulas (I) to (III) in the polymer constituting the film. Examples of aromatic polyamides include the following chemical formula (I), aromatic polyimides include the following chemical formula (II), and aromatic polyamideimides include those having a repeating unit represented by the following chemical formula (III). Chemical formula (I):

[0035]

Chemical formula

[0036] Chemical formula (II):

[0037] [Chemical formula]

[0038] Chemical formula (III):

[0039] [Chemical formula]

[0040] Here, Ar in Chemical formulas (I) to (III) 1 and / or Ar 2 is an aromatic group, and each may be a single group or a plurality of groups, and may be a multi-component copolymer. Also, the bond constituting the main chain on the aromatic ring may be either meta-oriented or para-oriented. Furthermore, a part of the hydrogen atoms on the aromatic ring may be substituted with any group.

[0041] In the present invention, as a means of achieving both separation of the electrolytic solution and excellent heat resistance and ionic conductivity, a method of transporting ions by hopping by controlling the polarity of the polymer can be mentioned.

[0042] In the present invention, when an aromatic polyamide, aromatic polyimide, or aromatic polyamideimide is used, since it has a carbonyl group in its structure, this generally becomes a site with high affinity for lithium ions. Therefore, in order for lithium ions to move through the polymer membrane, a site with lower affinity for lithium ions than the carbonyl group is required, so it is preferable to have an ether bond or thioether bond in the main chain or side chain (in the main chain or on the side chain). More preferably, it has an ether bond in the main chain, or at least one group among a carboxylic acid group, carboxylate group, sulfonic acid group, sulfonate group, alkoxy group, and cyanate group in the substituent on the aromatic ring. Even more preferably, Ar in Chemical formulas (I) to (III) 1 and Ar 225 to 100 mol% of the total of all the groups is at least one group selected from the groups represented by the following chemical formulas (IV) to (VI), and the above ratio is more preferably 50 to 100 mol%. Chemical formulas (IV) to (VI):

[0043]

Chem.

[0044] (The double dashed lines in chemical formulas (IV) to (VI) represent one or two bonds) Here, a part of the hydrogen atoms on the aromatic ring of chemical formulas (IV) to (VI) may be substituted with any group such as a halogen group such as fluorine, bromine, chlorine; a nitro group; a cyano group; an alkyl group such as methyl, ethyl, propyl; an alkoxy group such as methoxy, ethoxy, propoxy, a carboxylic acid group, etc.

[0045] Also, it is preferable to add a lithium salt to facilitate ion conduction in the polymer film, and more preferably to add a lithium salt with high dissociation property of lithium ions having a large anion radius to further improve ion conductivity. Here, as the lithium salt to be added, the same lithium salt as the solute contained in the electrolyte can be used. Among them, lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(trifluoromethylsulfonyl)imide [LiN(CF 3 SO 2 ) 2 is preferable, and from the viewpoints of anion radius and dissociation property of lithium ions, lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(trifluoromethylsulfonyl)imide [LiN(CF 3 SO2 ) 2 addition is preferred. More preferably, lithium bistrifluoromethylsulfonylimide [LiN(CF 3 SO 2 ) 2 addition is preferred.

[0046] Next, the manufacturing method of the polymer film which is a separator will be described below.

[0047] [Polymer synthesis] First, a method for obtaining a polymer that can be used in the polymer film of the present invention will be described by taking aromatic polyamide and aromatic polyimide as examples. Of course, the polymers that can be used in the present invention and their polymerization methods are not limited to this.

[0048] Various methods can be used to obtain aromatic polyamide. For example, when using an acid dichloride and a diamine as raw materials and the low-temperature solution polymerization method, it is synthesized in an aprotic organic polar solvent such as N-methylpyrrolidone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide. In the case of solution polymerization, in order to obtain a polymer with a high molecular weight, it is preferable that the water content of the solvent used for polymerization is 500 ppm or less (mass basis, the same hereinafter), and more preferably 200 ppm or less.

[0049] When polymerizing an aromatic polyimide or its precursor polyamic acid, for example, using a tetracarboxylic dianhydride and an aromatic diamine as raw materials, a method of synthesizing by solution polymerization in an aprotic organic polar solvent such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide can be employed. Since using both the raw material tetracarboxylic dianhydride and the aromatic diamine in equal amounts may produce a polymer with an ultra-high molecular weight, it is preferable to adjust the molar ratio so that one is 90.0 to 99.5 mol% of the other.

[0050] The logarithmic viscosity (ηinh) of the aromatic polyamide, aromatic polyimide, or polyamic acid which is a precursor thereof is preferably from 0.5 to 6.0 dl / g, more preferably from 3.0 to 6.0 dl / g. When the logarithmic viscosity is less than 0.5 dl / g, the intermolecular binding force due to the entanglement of polymer molecular chains decreases, so mechanical properties such as toughness and strength may decrease, or the thermal shrinkage rate may increase. When the logarithmic viscosity exceeds 6.0 dl / g, the ion permeability may decrease.

[0051] [Preparation of Film-Forming Raw Material] Next, the film-forming stock solution (hereinafter sometimes simply referred to as the film-forming stock solution) used in the process of manufacturing the polymer film of the present invention will be described.

[0052] The polymer solution after polymerization may be used as the film-forming stock solution as it is, or the polymer may be isolated once and then redissolved in an aprotic organic polar solvent or an inorganic solvent such as sulfuric acid described above for use.

[0053] The concentration of the polymer in the film-forming stock solution is preferably from 3 to 30% by mass, more preferably from 5 to 20% by mass. It is preferable to add the lithium salt described above to the film-forming stock solution from the viewpoint of improving ion conductivity. The addition amount of the lithium salt is preferably such that the molar ratio of lithium of the lithium salt to oxygen of the polymer is 0.1 or more, more preferably 0.2 or more.

[0054] [Film Formation of Polymer Film] Next, the method for forming the polymer film of the present invention will be described. The film-forming stock solution prepared as described above can be formed into a film by a so-called solution film-forming method. The solution film-forming method includes a dry-wet method, a dry method, a wet method, etc., and any method can be used for film formation. Here, the dry-wet method will be described as an example. The polymer film of the present invention may form a laminated composite by directly forming a film on a substrate or an electrode having pores. Here, the method of forming a film as a single film will be described.

[0055] When forming a film by the dry-wet method, the film-forming stock solution is extruded from a die onto a support such as a drum, endless belt, or film to form a film-like material, and then the film-like material is dried until it has self-supporting properties. The drying conditions can be, for example, in the range of 60 to 220°C for 60 minutes or less. However, when using a polyamic acid polymer and wanting to obtain a film made of aromatic polyamic acid without imidization, the drying temperature is preferably 60 to 150°C, more preferably 60 to 120°C. The film after the dry process is peeled from the support and introduced into the wet process, where desalting, solvent removal, etc. are carried out, and further stretching, drying, and heat treatment are performed. The stretching is preferably within a range of 0.8 to 8.0 in terms of area magnification (the area magnification is defined as the value obtained by dividing the area of the film after stretching by the area of the film before stretching. A value of 1 or less means relaxation), more preferably 1.0 to 5.0. Also, as the heat treatment, heat treatment is carried out at a temperature of 80°C to 500°C, preferably 150°C to 400°C, for several seconds to several tens of minutes. However, when using a polyamic acid polymer and wanting to obtain a film made of polyamic acid without imidization, the heat treatment temperature is preferably 80 to 150°C. More preferably, it is 80 to 120°C under reduced pressure.

[0056] [Secondary battery] Examples of the form of the air battery of this embodiment include forms such as coin batteries and laminate batteries. As a method for manufacturing an air battery, for example, in the case of a laminate battery or a coin battery, a positive electrode sheet, a separator, a negative electrode sheet, and a separator of a predetermined size are stacked in this order to form a laminate, and the produced wound body or laminate is filled into their respective battery cases. After welding the lead bodies of the positive electrode and the negative electrode, an electrolyte is injected into the battery case, and the opening of the battery case is sealed to complete the battery.

Examples

[0057] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereby. The measurement methods used in this example are shown below. [Measurement method] (1) Meltdown temperature of the separator A separator with a size of 50 mm × 50 mm was cut out, and the sample was sandwiched between two stainless steel plates with a 12-mm through-hole in the center. Further, it was sandwiched from both sides by a heating block plate with a 12-mm through-hole in the center. A tungsten carbide ball with a diameter of 9.5 mm was placed in the through-hole, and the temperature of the heating block was increased at a rate of 5 °C / min. The temperature at which the ball dropped was measured. The test was conducted 5 times, and the average value was taken as the melt-down temperature (°C).

[0058] (2) Permeability of the separator Measurement was carried out in accordance with JIS P8117 (1998) using the Wang Research type air permeability meter (manufactured by Asahi Seiko Co., Ltd., EGO-1T).

[0059] Note that the measurement limit for the air permeability is 10,000 seconds, and the separator has a substantially pore-free structure.

[0060] (3) Ionic conductivity (unit: S / cm) After immersing the polymer film in the electrolyte (1 M LiTFSI ethylene carbonate (EC) / diethyl carbonate (DEC) = 1 / 1, manufactured by Mitsui Chemicals, Inc.) for 24 h, it was placed on a SUS304 electrode so as to cover the electrode part. After dropping the electrolyte, it was sandwiched with another SUS electrode to fabricate an electrode / polymer film / electrode laminate. An evaluation cell was fabricated by fixing it with a silicon plate so that the laminate did not shift.

[0061] For the fabricated cell, the AC impedance was measured at 25 °C with an electrochemical test apparatus (manufactured by Biologic, model number: SP-150) under the conditions of an amplitude of 10 mV and a frequency of 1 MHz - 10 mHz. The resistance value was read from the graph plotted on the complex plane and substituted into the following formula to calculate the ionic conductivity. It was measured 5 times, and the calculated average value was taken as the ionic conductivity.

[0062] σ = d1 / AR σ: Ionic conductivity (S / cm) d1: Thickness of the polymer film (cm) (before immersion in the electrolyte) A: Area of the electrode (cm 2 ) R: Resistance value (Ω) (4) Contact angle of the separator with water and its rate of change First, leave the separator in an atmosphere of 23°C at room temperature and 65% relative humidity for 24 hours. Then, in the same atmosphere, measure the contact angle of water on the separator 10 seconds after dropping water at 5 points using a contact angle meter DropMaster DM-501 manufactured by Kyowa Interface Science Co., Ltd. The average value of the 3 measurement values excluding the maximum and minimum values of the 5 measurement values was taken as the contact angle of water.

[0063] Also, measure the contact angle 1 hour after dropping water in the same way, and evaluate the rate of change from the contact angle 10 seconds after dropping water using the following formula.

[0064] (Formula) (1 - (contact angle 1 hour after dropping water) / (contact angle 10 seconds after dropping water)) × 100 (5) Contact angle of the separator measured using dimethyl carbonate and its rate of change First, leave the separator in an atmosphere of 23°C at room temperature and 65% relative humidity for 24 hours. Then, in the same atmosphere, measure the contact angle of dimethyl carbonate on the separator 10 seconds after dropping dimethyl carbonate at 5 points using a contact angle meter DropMaster DM-501 manufactured by Kyowa Interface Science Co., Ltd. The average value of the 3 measurement values excluding the maximum and minimum values of the 5 measurement values was taken as the contact angle measured using dimethyl carbonate.

[0065] Also, measure the contact angle 1 hour after dropping water in the same way, and evaluate the rate of change from the contact angle 10 seconds after dropping water using the following formula. (Formula) (contact angle 1 hour after dropping water) / (contact angle 10 seconds after dropping water) × 100 - 100 (6) Intrinsic viscosity of the polymer (unit: dl / g) Dissolve the polymer at a concentration of 0.5 g / dl in N-methylpyrrolidone (NMP) with 2.5 wt% lithium bromide (LiBr) added, and measure the flow-down time at 30°C using an Ubbelohde viscometer. Also measure the flow-down time of LiBr 2.5 wt% / NMP without dissolving the polymer as a blank, and calculate the viscosity η (dl / g) using the following formula.

[0066] η = [ln(t / t0)] / 0.5 t0: Flow-down time of blank (S) t: Flow-down time of sample (S) (7) Charge-discharge cycle characteristics Regarding the secondary batteries fabricated in each of the examples and comparative examples, the charge-discharge cycle characteristics were tested according to the following procedure, and the discharge capacity retention rate was calculated.

[0067] 〈Cycles 1 to 30〉 Charging and discharging were defined as one cycle. The charging condition was constant-current charging at 0.1C and 5V, and the discharging condition was constant-current discharging at 0.1C and 2.8V. Charging and discharging were repeated 150 times at 25°C. 〈Calculation of discharge capacity retention rate〉 The discharge capacity retention rate was calculated as (discharge capacity at the 30th cycle) / (discharge capacity at the 1st cycle)×100. Five tests were carried out for the secondary batteries fabricated in each of the examples and comparative examples, and the average of the three measurement results after removing the results with the maximum and minimum discharge capacity retention rates was taken as the discharge capacity retention rate. When the discharge capacity retention rate was less than 60%, it was rated as C (non-conforming); when it was 60% or more and less than 70%, it was rated as B (conforming); when it was 70% or more and less than 75%, it was rated as A (good); when it was 75% or more, it was rated as S (excellent). Also, when the battery could not operate, it was rated as -.

[0068] (Example 1) A separator and a secondary battery were fabricated as follows. Table 1 shows the physical properties of the separator and the characteristics of the secondary battery. [Positive electrode] An air electrode with 20% platinum catalyst supported on carbon paper was used. [Negative electrode] Commercially available metallic lithium foil (manufactured by Honjo Metal Co., Ltd.) was used. [Electrolyte solution] The non-aqueous electrolyte solution was prepared as follows. 1.0 mol of lithium hexafluorophosphate (LiPF 6 ) was dissolved in 1 L of a mixed solvent with a volume ratio of 1:1 of ethylene carbonate (EC) and diethyl carbonate (DEC) to prepare a mixed solution. To 100 parts by mass of the mixed solution, 2 parts by mass of vinylene carbonate (VC) was further added to prepare the non-aqueous electrolyte solution.

[0069] The aqueous electrolyte was prepared as follows. 1 mol% of potassium hydroxide (KOH) was dissolved in pure water to prepare a mixed solution, and an aqueous electrolyte was prepared. 〔Separator〕 4,4'-Diaminodiphenyl ether as a diamine was dissolved in dehydrated N-methyl-2-pyrrolidone under a nitrogen stream and cooled to 30 °C or lower. Then, while maintaining the system under a nitrogen stream at 30 °C or lower, 2-chloroterephthaloyl chloride corresponding to 99 mol% of the total amount of diamine was added over 30 min. After the addition of the total amount, stirring was carried out for about 2 h to polymerize an aromatic polyamide. The obtained polymerization solution was neutralized with 97 mol% of lithium carbonate and 6 mol% of diethanolamine based on the total amount of acid chloride to obtain Polymer Solution A. The logarithmic viscosity η of the obtained polymer was 2.5 dl / g.

[0070] Lithium bis(trifluoromethylsulfonyl)imide [LiN(CF 3 SO 2 ) 2 as a lithium salt was added so that the molar ratio of lithium of the lithium salt to oxygen of the polymer was 0.2, and stirring and defoaming were carried out using a mixer (manufactured by THINKY, model number: AR-250) to obtain a uniform and transparent solution. The obtained uniform mixed solution of the polymer and the lithium salt was coated in a film form on a glass plate as a support, dried at a hot air temperature of 60 °C until the polymer film had self-supporting properties, and then the polymer film was peeled off from the support. Next, extraction of the solvent and neutralization salt was carried out by introducing it into a water bath at 25 °C. Subsequently, after wiping off the water on the surface of the obtained polymer film in a water-containing state, a heat treatment was performed in a tenter chamber at a temperature of 180 °C for 1 min to obtain a polymer film with a thickness of 5 μm. 〔Assembly of the battery〕 In a dry atmosphere, using a two-compartment cell (SB-100B manufactured by Easyflon Frontier), the above positive electrode and the above negative electrode were arranged in the two-compartment cell together with the above separator, an aqueous electrolyte was poured on the positive electrode side, and a non-aqueous electrolyte was poured on the negative electrode side to fabricate a secondary battery with a battery capacity of 3 mAh. The oxygen supplied to the air electrode was supplied to the air electrode by attaching a simple oxygen cylinder and supplying oxygen to the aqueous electrolyte.

[0071] (Example 2) A secondary battery was fabricated in the same manner as in Example 1, except that the aqueous electrolyte was changed to 1 mol% hydrochloric acid.

[0072] (Example 3) In the preparation of the separator, a secondary battery was fabricated in the same manner as in Example 1, except that lithium bis(trifluoromethylsulfonyl)imide [LiN(CF 3 SO 2 ) 2 was added so that the molar ratio of lithium of the lithium salt to oxygen of the polymer was 0.1.

[0073] (Example 4) In the preparation of the separator, 4,4'-diaminodiphenyl ether as a diamine was dissolved in dehydrated N-methyl-2-pyrrolidone under a nitrogen stream and cooled to 30°C or lower. Then, 2-chloroterephthaloyl chloride corresponding to 99.5 mol% of the total amount of the diamine was added thereto over 30 minutes while maintaining the system at 30°C or lower under a nitrogen stream. After the addition of the total amount, stirring was performed for about 2 hours to polymerize the aromatic polyamide. The obtained polymerization solution was neutralized with 97 mol% lithium carbonate and 6 mol% diethanolamine based on the total amount of the acid chloride to obtain a polymer solution B. The logarithmic viscosity η of the obtained polymer was 3.5 dl / g. A secondary battery was fabricated in the same manner as in Example 1, except that the obtained polymer solution B was used.

[0074] (Example 5) In the preparation of the separator, a secondary battery was fabricated in the same manner as in Example 1, except that the lithium salt was changed to lithium trifluoromethanesulfonate (LiCF 3 SO 3 )

[0075] (Example 6) The non-aqueous electrolyte was changed to 1,2-dimethoxyethane (DME), and 1.0 mol of lithium hexafluorophosphate (LiPF 6It was dissolved to prepare a mixed solution, and a secondary battery was prepared in the same manner as in Example 1 except that 2 parts by mass of vinylene carbonate (VC) was further added to 100 parts by mass of the mixed solution.

[0076] (Comparative Example 1) A secondary battery was prepared in the same manner as in Example 1 except that both the positive electrode side electrolyte and the negative electrode side electrolyte were changed to non-aqueous electrolytes.

[0077] (Comparative Example 2) A secondary battery was prepared in the same manner as in Example 1 except that both the positive electrode side electrolyte and the negative electrode side electrolyte were changed to aqueous electrolytes. However, metallic lithium reacted with the aqueous electrolyte and the battery was not formed.

[0078] (Comparative Example 3) A secondary battery was prepared in the same manner as in Example 1 except that the separator was made of a cellulose nonwoven fabric (thickness 40 μm, density 0.40 g / cm 3 ). The nonwoven fabric was made using 100% by mass of lyocell fiber, which is a regenerated cellulose fiber, and was produced by a fourdrinier paper machine.

[0079] (Comparative Example 4) A secondary battery was prepared in the same manner as in Example 3 except that in the production of the separator, it was changed to a polymer solution alone that does not contain a lithium salt.

[0080]

Table 1

[0081] From Table 1, Examples 1, 2, 3, 4, and 5 included non-aqueous electrolytes and aqueous electrolytes, the contact angle of water in the physical properties of the separator was 90° or more, satisfied the scope of the present invention, and the secondary battery showed good cycle characteristics.

[0082] On the other hand, in Comparative Examples 1, 2, 3, and 4, the contact angle of water in the physical properties of the separator was less than 90°, outside the scope of the present invention, or the solvent composition of the electrolyte was of one type and the cycle characteristics of the secondary battery were not sufficient.

Claims

1. A secondary battery including a positive electrode, a negative electrode, a non-aqueous electrolyte, an aqueous electrolyte, and a separator, wherein the non-aqueous electrolyte and the aqueous electrolyte are separated by the separator, The aqueous electrolyte is disposed on the positive electrode side, and the non-aqueous electrolyte is disposed on the negative electrode side. The positive electrode is an air electrode, and the negative electrode comprises a negative electrode current collector and a negative electrode mixture layer formed thereon. The negative electrode mixture layer contains one or more components selected from the group consisting of metallic lithium, magnesium, zinc, and aluminum. The separator is a polymer membrane having an air permeability greater than 10,000 seconds, an ionic conductivity of 1×10 －５ S / cm or more, and a water contact angle of 90° or more. The contact angle of the polymer membrane measured using dimethyl carbonate is 90° or more. A secondary battery.

2. The secondary battery according to claim 1, wherein a change rate of a contact angle after 1 hour of water dropping with respect to a contact angle after 10 seconds of water dropping of the polymer film is less than 10%.

3. The secondary battery according to claim 1 or 2, wherein a change rate of a contact angle after 1 hour of dimethyl carbonate dropping with respect to a contact angle after 10 seconds of dimethyl carbonate dropping of the polymer film is less than 10%.

4. The secondary battery according to any one of claims 1 to 3, wherein a melting-down temperature of the polymer film is 300°C or higher.

5. The secondary battery according to any one of claims 1 to 4, wherein the polymer constituting the polymer film contains an aromatic polyamide, an aromatic polyimide, or an aromatic polyamideimide.

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