JP4296114B2 - Air battery - Google Patents

Description

  The present invention relates to an air battery using oxygen as a positive electrode active material, and is particularly suitable for an air battery using a non-aqueous electrolyte as an electrolyte.

  In recent years, the market for portable information devices such as mobile phones and e-mail terminals is rapidly expanding, and as these devices become smaller and lighter, power supplies are also required to be smaller and lighter. It was. Currently, lithium ion secondary batteries having a high energy density are mainly used in these portable devices, but higher capacity is demanded.

  An air battery that uses oxygen in the air as the positive electrode active material does not need to contain the active material in the battery, and thus can be expected to have a higher capacity. As a lithium secondary battery using metallic lithium as a negative electrode active material and oxygen as a positive electrode active material, Non-Patent Document 1 discloses an air lithium secondary battery having a configuration as described below.

The air lithium secondary battery disclosed herein includes a catalyst layer, a positive electrode, a negative electrode, a polymer electrolyte membrane interposed between the positive electrode and the negative electrode, and an oxygen permeable membrane laminated on the positive electrode. Is provided. The catalyst layer is formed from acetylene black containing cobalt. The positive electrode is obtained by pressure-bonding a polymer electrolyte film made of polyacrylonitrile, ethylene carbonate, propylene carbonate, and LiPF ₆ to a nickel net or an aluminum net. On the other hand, the negative electrode is formed from lithium foil. Such a four-layer laminate is enclosed in a laminate bag.

  In this air lithium secondary battery, since the positive electrode and the negative electrode are closely adhered to each other by a polymer electrolyte membrane having a high viscosity, the capacity per 1 g of carbon of the positive electrode is as high as 1600 mAh / g, which is a typical lithium ion secondary battery. Even when lithium cobaltate, which is a positive electrode active material, has a capacity of 160 mAh / g, a certain large capacity is obtained.

  The positive electrode active material of air lithium batteries is oxygen in the air, and acetylene black containing cobalt is a catalyst that ionizes oxygen, so it is theoretically expected that the discharge capacity per weight of positive electrode carbon is very large. However, it is actually limited to about 10 times that of lithium cobalt oxide. In practical batteries, volume capacity density is more important than weight capacity density, so the difference in volume capacity density between an air lithium battery using a carbon material with a light specific gravity as a positive electrode catalyst and a secondary battery using lithium cobaltate as a positive electrode is even smaller. .

In addition, the air lithium battery using an organic electrolyte as an electrolyte has a drawback in that unevenness in the adhesion between the layers tends to occur because the separator layer between the positive electrode and the negative electrode has no adhesion. In order to eliminate this defect and secure the adhesion between the positive electrode and the negative electrode, Non-Patent Document 2 describes a battery in which a three-layer laminate composed of a positive electrode, a separator and a negative electrode is bound on a polypropylene block substrate with an insulated nickel wire. Is disclosed. In addition, when adhesiveness falls, an output characteristic will fall large and it cannot endure use for a long time.
J. Electrochem. Soc., Vol.143, No.1, 1-5 (1996), published in January 1996 J. Electrochem. Soc., Vol. 149, No. 9, A1190-A1195 (2002), issued in September 2002

  An object of this invention is to provide the air battery which can be used for a long time in air | atmosphere.

Air battery Ru engaged to the present invention comprises a laminated film whose inner surface made of a thermoplastic resin layer, and a battery container having an air intake hole,
An electrode group including a positive electrode containing oxygen as an active material, a negative electrode including a negative electrode active material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode;
A non-aqueous electrolyte held in the electrode group;
Thermoplastic having an oxygen transmission coefficient of 1 × 10 ⁻¹⁴ mol · m / m ² · sec · Pa or less, disposed between the surface of the battery container where the air intake hole is formed and the positive electrode of the electrode group . a non-porous barrier film made of resin is laminated on the positive electrode opposed to that surface of the barrier film, porous film, the thermoplastic resin comprising at least one selected from the group consisting of nonwoven and woven fabrics The first air gap holding member made of metal, the surface of the battery container where the air intake hole is formed, and the barrier film, and selected from the group consisting of a porous film, a nonwoven fabric and a woven fabric A laminated film comprising a second gap holding member made of at least one kind of thermoplastic resin ,
Said by the fact that the laminated film is heat-sealed to the inner surface of the battery container, the air intake hole of the battery container is sealed by the laminated film,
The pressure in the battery container during continuous discharge is 0.1 to 80 kPa lower than the atmospheric pressure .

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the air battery which was excellent in the close_contact | adherence of an electrode group, the battery capacity was large, and was excellent in the long-term use characteristic in air | atmosphere.

  In a non-aqueous electrolyte air battery using an alkali metal such as lithium, an alkaline earth metal, or an alloy containing these metal elements as a negative electrode active material, the active material is consumed sequentially by the battery reaction from the negative electrode surface. It is difficult to ensure sufficient adhesion between the positive electrode and the negative electrode through the electrode, and it is desirable to apply mechanical pressure from the outside of the electrode group including the positive electrode, the separator, and the negative electrode.

  As disclosed in Non-Patent Document 1 described above, an air battery generally has a low current density per unit area of the positive electrode. For this reason, it is desirable to increase the positive electrode area in order to put the air battery into practical use.

  The present inventors laminated a gap holding member on the electrode group, and provided a nonporous oxygen-permeable polymer film as a barrier film between the air hole forming surface of the battery container and the gap holding member, It has been found that when the air shielding seal tape covering the air holes of the battery container is peeled off and the continuous discharge is performed, the pressure inside the battery container becomes lower than the atmospheric pressure and the adhesion of the electrode group is improved. It was.

  In order to maintain the adhesion of the electrode group including the positive electrode and the negative electrode, it is preferable to add 0.1 to 80 kPa as external stress. This is due to the reason explained below. If the external stress is less than 0.1 kPa, the adhesion between the positive electrode, the separator and the negative electrode may be insufficient. On the other hand, when a stress exceeding 80 kPa is applied, the separator located between the positive electrode and the negative electrode may be partially thinned to cause an internal short circuit.

By using a non-porous polymer film with an oxygen permeability coefficient of 1 × 10 ^-14 mol · m / m ² · sec · Pa or less as a barrier film, the pressure drop in the battery container gradually proceeds with the start of discharge. The pressure inside the battery container can be 0.1 to 80 kPa lower than the atmospheric pressure during continuous discharge, and sufficient adhesion between the positive electrode, the separator, and the negative electrode can be ensured. However, if the oxygen permeability coefficient when the thickness of the barrier film is 1 to 100 μm is less than 5 × 10 ⁻¹⁷ mol · m / m ² · sec · Pa, the oxygen supply amount to the positive electrode may be insufficient. Therefore, the oxygen permeability coefficient of the barrier film is desirably 1 × 10 ⁻¹⁶ mol · m / m ² · sec · Pa or more when the thickness is 1 to 100 μm.

  Moreover, it is suitable for maintaining the atmospheric pressure in the battery container that the porosity inside the barrier film is 5 to 40%. This is due to the reason explained below. When the porosity is less than 5%, the air pressure in the battery container tends to fluctuate. On the other hand, if the porosity exceeds 40%, it takes time for the air pressure in the battery container to fall to a range lower than the atmospheric pressure by 0.1 to 80 kPa, so that the battery performance may be lowered.

  By disposing at least one type selected from the group consisting of a porous film, a nonwoven fabric and a woven fabric as a gap holding member on the surface on the electrode group side of the barrier film, the gap of the electrode group is prevented from being collapsed by atmospheric pressure. Can be maintained. Further, a fine particle spacer may be used instead of the gap holding member.

  By disposing a second gap holding member made of at least one selected from the group consisting of a porous film, a nonwoven fabric and a woven fabric also between the air hole forming surface of the battery container and the barrier film, Can be used effectively as an oxygen diffusion film.

  Also, an air battery with a barrier film is formed by forming a battery container of an air battery with a packaging material such as an aluminum-containing laminate, and bonding, pressing or fusing the end of the barrier film to the inner surface of the packaging material with an adhesive. Can be easily manufactured. Furthermore, the adhesiveness of the electrode group containing a positive electrode and a negative electrode is maintainable when the Young's modulus and thickness of a packaging material satisfy | fill a (1) type | formula.

(Y × T) <10 ² (1)
However, Y is the Young's modulus (MPa) of the packaging material, and T is the thickness (m) of the packaging material.

If the value calculated by (Y × T) is larger than 10 ² , the packaging material is not sufficiently deformed when the inside of the battery container becomes negative pressure, so that the adhesion of the electrode group may be reduced. .

  Moreover, the nonaqueous electrolyte type air battery of the present invention can be used as a secondary battery by using a negative electrode having the ability to occlude and release metal ions.

  Hereinafter, an example of the air battery of the present invention will be described with reference to the drawings.

  As shown in FIG.1 and FIG.2, the electrode group 2 is accommodated in the battery container 1 which consists of laminate films. The laminate film includes a thermoplastic resin layer, and preferably further includes an aluminum layer. The battery container 1 is formed by laminating a laminate film in a bag shape by heat sealing using the thermoplastic resin layer. The electrode group 2 includes a positive electrode having a structure in which a gas diffusion positive electrode layer 4 is supported on a positive electrode current collector 3 made of, for example, a porous conductive substrate, and a negative electrode current collector 5 made of, for example, a porous conductive substrate. It is comprised from the negative electrode which has the structure where the negative electrode active material layer 6 was carry | supported, and the separator 7 arrange | positioned between a positive electrode and a negative electrode. The electrolyte is held by the positive electrode, the separator, and the negative electrode.

A plurality of air intake holes 8 (hereinafter referred to as air holes) are opened on the surface of the battery case 1 facing the positive electrode. As shown in FIG. 3, the barrier film 9 made of, for example, a hydrophobic thermoplastic resin having an oxygen permeability coefficient of 1 × 10 ⁻¹⁴ mol · m / m ² · sec · Pa or less is made of, for example, a hydrophobic thermoplastic resin. The gap holding member 10 made of a microporous film is sandwiched between two folded pieces. As shown in FIG. 4, the end of the gap holding member 10 of the obtained barrier film group 11 is heat sealed to the thermoplastic resin layer on the inner surface of the battery container 1, so that the air holes 8 are formed in the barrier film group 11. While being closed, the gap holding member 10 and the barrier film 9 are integrated. A region surrounded by the four sides of the barrier film 9 and the four sides of the gap holding member 10 in FIG. When performing heat sealing, it is preferable that the thermoplastic resin of the gap holding member 10 and the thermoplastic resin of the barrier film 9 are the same type or compatible with each other even if they are different types of thermoplastic resins. Moreover, when the thermoplastic resin of the space | gap holding member 10 and the thermoplastic resin of the barrier film 9 are mutually incompatible, it is good to join using arbitrary adhesive agents.

  The gap holding member 10a between the positive electrode current collector 3 and the barrier film 9 is a first gap holding member, and can contribute to improving the adhesion of the electrode group. On the other hand, the gap holding member 10b between the air hole forming surface of the battery container 1 and the barrier film 9 is a second gap holding member and functions as a protective layer for the barrier film 9 and a gas diffusion layer inside the battery. Can do.

  The barrier film group 11 shields the electrode group 2 from the atmosphere, so that direct contact of the electrode group 2 with the atmosphere is avoided. One end of the positive electrode terminal 13 is electrically connected to the positive electrode current collector 3, and the other end protrudes outside the battery container 1. On the other hand, one end of the negative electrode terminal 14 is electrically connected to the negative electrode current collector 5, and the other end protrudes outside the battery container 1.

  Further, a sealing tape for closing the air holes 8 is not shown on the outer surface of the battery container 1 but is placed when the battery is not used.

  In the air battery having the configuration as described above, air is supplied from the air hole 8 into the battery container 1, and the supplied air spreads on the surface by diffusing the second gap holding member 10b. Since the barrier film 9 selectively transmits oxygen, the air that has passed through the second gap holding member 10b passes through the barrier film 9, thereby removing unnecessary components such as moisture and nitrogen. A gas enriched with oxygen is supplied to the gas diffusion positive electrode layer 4 through the first gap holding member 10a to cause a discharge reaction. While the negative electrode active material layer 6 is consumed as the discharge proceeds, the inside of the battery container 1 becomes negative pressure. Although the detailed mechanism of the negative pressure is unknown, the gas held in the gap holding member 10 when the air battery is manufactured in an inert gas atmosphere such as argon gas is released into the atmosphere by discharge, It is estimated that the internal pressure of the battery container is lower than atmospheric pressure.

  Since the inside of the battery container 1 has a negative pressure, the barrier film group 11 can uniformly pressurize the surface of the electrode group 2 due to a pressure difference from the atmospheric pressure, so that the positive electrode, the separator, and the negative electrode are in good contact with each other. Can be maintained, and a high discharge capacity can be maintained over a long period of use. Further, by providing the first and second gap holding members, the oxygen gas can be uniformly diffused in the in-plane direction of the positive electrode, so that reaction spots between the positive electrode and the negative electrode can be reduced.

  In addition, in FIGS. 1 to 4 described above, an example in which only one surface of the electrode group 2 is the positive electrode has been described, but both surfaces of the electrode group can be the positive electrode. An example of this is shown in FIGS. 5 and 6, the same members as those described in FIGS. 1 to 4 described above are denoted by the same reference numerals, and description thereof is omitted.

  1 to 6 described above, an example in which the barrier film group 11 is fixed to the inner surface of the battery container 1 and the air holes 8 are blocked by the barrier film group 11 has been described. When 2 is stored, the barrier film group 11 does not have to be fixed to the inner surface of the battery case 1. Examples of this are shown in FIGS. 7-10, the same code | symbol is attached | subjected to the member similar to having demonstrated in FIGS. 1-4 mentioned above, and description is abbreviate | omitted.

  The air battery shown in FIGS. 7 and 8 includes a first electrode group 2a and a second electrode group 2b. In each of the first electrode group 2a and the second electrode group 2b, the negative electrode active material layer 6 is disposed on both surfaces of the negative electrode current collector 5, and the obtained negative electrode is covered with the separator 7, and then the positive electrode layer 4 and It is obtained by laminating the positive electrode current collector 3. The first electrode group 2a and the second electrode group 2b are each accommodated in a bag formed of the barrier film group 11. This bag is formed by covering the electrode group 2 with the barrier film group 11 and bonding the ends of the barrier film group 11 together by heat sealing. Spacer particles 15 are arranged between the barrier film group 11 covering the first electrode group 2a and the barrier film group 11 covering the second electrode group 2b. Thereby, since a clearance gap can be provided between unit cells, the distribution | circulation of the air in a battery container can be made favorable.

  On the other hand, in the electrode group 2 of the air battery shown in FIGS. 9 and 10, the negative electrode active material layers 6 are arranged on both surfaces of the negative electrode current collector 5, and the separators 7 are laminated on the respective negative electrode active material layers 6. After the positive electrode layer 4 and the positive electrode current collector 3 are laminated on each other, the obtained laminate is bent into a U shape. After the electrode group 2 is covered with the barrier film group 11, the end portions of the barrier film group 11 are bonded together by heat sealing. In the locations where the barrier film groups 11 face each other, spacer particles 15 are interposed between the barrier film groups 11.

  In the air battery shown in FIGS. 7 to 10, since the inside of the bag formed of the barrier film group 11 becomes a negative pressure as the discharge proceeds, the surface of the electrode group is uniform over the entire surface due to the pressure difference from the atmospheric pressure. Therefore, the contact between the positive electrode, the separator and the negative electrode can be kept good, and a high discharge capacity can be maintained over a long period of use.

  When a coin-type metal container is used as a battery container, such as an air zinc battery, a barrier film group is arranged on the inner surface of the positive electrode container to close the air hole, and the end of the barrier film group is connected to the positive electrode container. The barrier film group may be fixed to the positive electrode container by caulking and fixing the positive electrode container and the negative electrode container while being sandwiched between the negative electrode containers.

  Next, the positive electrode, the negative electrode, the separator, and the barrier film group will be described in detail.

1) Positive electrode The positive electrode includes a positive electrode current collector and a gas diffusion positive electrode layer carried on the positive electrode current collector.

  As the positive electrode current collector, it is preferable to use a porous conductive substrate (mesh, punched metal, expanded metal, etc.) in order to allow oxygen to diffuse quickly. Examples of the material of the conductive substrate include stainless steel, nickel, aluminum, iron, and titanium. The current collector may be coated with an oxidation-resistant metal or alloy on the surface in order to suppress oxidation.

  The gas diffusion positive electrode layer can be formed, for example, by mixing a carbonaceous material and a binder, rolling the mixture into a film, forming a film, and drying.

  Alternatively, the positive electrode can also be obtained by mixing a carbonaceous material and a binder in a solvent, applying the mixture to a current collector, drying, and rolling.

  It is also possible to increase the efficiency of the oxygen reduction reaction by supporting fine particles having a function of reducing the oxygen generation overvoltage such as cobalt phthalocyanine on the surface of the carbonaceous material according to the present invention.

  It is also possible to increase the conductivity of the positive electrode layer by adding a highly conductive carbonaceous material such as acetylene black to the carbon material.

  As a binder for maintaining the shape of the carbonaceous material in a layered manner and adhering it to the current collector, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-butadiene rubber (EPBR), Styrene-butadiene rubber (SBR) or the like can be used.

  The blending ratio of the carbonaceous material and the binder is preferably in the range of 70 to 98% by weight of the carbonaceous material and 2 to 30% by weight of the binder.

2) Negative electrode The negative electrode includes a negative electrode current collector and a negative electrode active material layer carried on the negative electrode current collector.

  The negative electrode current collector is not limited to a conductive substrate having a porous structure like the positive electrode current collector, and a nonporous conductive substrate can be used. These conductive substrates can be formed from, for example, copper, stainless steel, or nickel.

  The negative electrode active material layer can contain a binder together with the negative electrode active material.

  For example, the negative electrode is obtained by kneading a negative electrode active material and a binder in the presence of a solvent, applying the obtained suspension to a current collector, drying, and then pressing once at a desired pressure or 2 to 2. It can be produced by multi-stage pressing 5 times.

  As the negative electrode active material, for example, a material capable of occluding and releasing lithium ions can be used. Examples of the material that occludes and releases lithium ions include metal oxides, metal sulfides, metal nitrides, lithium metals, lithium alloys, lithium composite oxides, and carbonaceous materials that occlude and release lithium ions. However, the present invention is not limited to this, and all materials conventionally used for lithium ion batteries or lithium batteries can be used. Moreover, the kind of negative electrode active material to be used is not limited to one, and may be two or more.

  Examples of carbonaceous materials capable of occluding and releasing lithium ions include graphite materials, carbonaceous materials such as graphite, coke, carbon fiber, and spherical carbon, thermosetting resins, isotropic pitches, mesophase pitches, and mesophases. Mention may be made of graphitic materials or carbonaceous materials obtained by subjecting pitch-based carbon fibers, mesophase spherules and the like to heat treatment at 500 to 3000 ° C.

  Examples of the metal oxide include tin oxide, silicon oxide, lithium titanium oxide, niobium oxide, and tungsten oxide.

  Examples of the metal sulfide include tin sulfide and titanium sulfide.

  Examples of the metal nitride include lithium cobalt nitride and lithium iron nitride lithium manganese nitride.

  Examples of the lithium alloy include a lithium aluminum alloy, a lithium tin alloy, a lithium lead alloy, and a lithium silicon alloy.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-butadiene rubber (EPBR), styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), and the like. Can do.

  The blending ratio of the carbonaceous material and the binder is preferably in the range of 80 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder.

  In addition, if a metal material such as lithium ion or lithium alloy is used as the negative electrode active material, these metal materials can be processed into a sheet shape by themselves, so that the negative electrode active material can be used without using a binder. A layer can be formed. Moreover, the negative electrode active material layer formed of these metal materials can be directly connected to the negative electrode terminal.

  When the air battery of the present invention is used as a primary battery, the negative electrode active material only needs to have a metal ion releasing ability.

3) Non-aqueous electrolyte The non-aqueous electrolyte layer can employ two types of shapes, a liquid system and a solid electrolyte system.

  First, in the case of a liquid system, the nonaqueous electrolyte may be a liquid that is prepared by dissolving a lithium salt in a nonaqueous solvent. As the non-aqueous solvent, a known non-aqueous solvent can be used as a solvent for the lithium secondary battery. For example, propylene carbonate (PC), ethylene carbonate (EC), or a mixed solvent of both of them (referred to as a first solvent) and one or more non-solvents having a viscosity lower than that of the PC or EC and a donor number of 18 or less. It is preferable to use a non-aqueous solvent mainly composed of a mixed solvent with an aqueous solvent (hereinafter referred to as a second solvent).

  As the second solvent, a carbonate ester bond or a chain carbonate containing an ester bond in the molecule is preferable. Among them, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate (MPC), Examples include isopropiomethyl carbonate, ethyl propionate, methyl propionate, γ-butyrolactone (γ-BL), ethyl acetate, and methyl acetate. These second solvents can be used alone or in the form of a mixture of two or more. In particular, the second type solvent preferably has a boiling point of 90 ° C. or higher.

  The blending amount of the EC or PC in the mixed solvent is preferably 10 to 80% by volume ratio. A more preferable blending amount of EC or PC is 20 to 75% by volume ratio.

  Specific examples of the mixed solvent include EC and PC, EC and DEC, EC and PC and DEC, EC and γ-BL, EC and γ-BL and DEC, EC and PC and γ-BL, EC and PC, In γ-BL and DEC, the volume ratio of EC in the mixed solvent is preferably 10 to 80%. A more preferred EC volume ratio is in the range of 25-65%.

Examples of the lithium salt that is an electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), and lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ). , Bistrifluoromethanesulfonylamide lithium [LiN (CF ₃ SO ₂ ) ₂ ] and the like, but are not limited thereto.

  The amount of electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 2.5 mol / l.

  When a liquid nonaqueous electrolyte layer is used, the nonaqueous electrolyte layer can be formed by impregnating and holding a liquid nonaqueous electrolyte in a separator.

  As the separator, for example, a porous film containing polyethylene, polypropylene, or PVdF, a synthetic resin nonwoven fabric, a glass fiber nonwoven fabric, or the like can be used.

  The separator preferably has a porosity in the range of 30 to 90%. This is due to the following reason. If the porosity is less than 30%, it may be difficult to obtain high electrolyte retention in the separator. On the other hand, if the porosity exceeds 90%, sufficient separator strength may not be obtained. A more preferable range of the porosity is 35 to 60%.

When using a solid electrolyte nonaqueous electrolyte layer, a film containing a polymer material in which a lithium salt is dissolved can be used as the polymer solid electrolyte. Examples of the polymer material include polyethylene oxide (PEO), polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and the like. Examples of the lithium salt include lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide [LiN ( CF ₃ SO ₂ ) ₂ ] and the like.

  Moreover, it is preferable to add an organic solvent to the solid electrolyte layer in order to improve ionic conductivity. Examples of the organic solvent include ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (γ-BL), fluorine-containing carbonates, chain carbonates, and the like. These organic solvents may be used alone or in combination of two or more.

4) Barrier film group The barrier film group includes a barrier film having an oxygen permeability coefficient of 1 × 10 ⁻¹⁴ mol · m / m ² · sec · Pa or less, and a first void retention disposed between the barrier film and the positive electrode. And a member.

  The thinner the barrier film, the greater the amount of gas permeation. However, the mechanical strength of the barrier film decreases. You may arrange.

  Since the gas diffusion function of the first gap holding member is degraded when the gap portion of the first gap holding member is filled with the electrolyte, the first gap holding member may be subjected to a surface treatment such as a soot treatment. .

(Barrier film)
Since the barrier film has a function of selectively permeating oxygen, the oxygen in the air can be enriched and supplied to the electrode group inside the battery. Side reactions with the active material layer can be prevented. Therefore, it is desirable that the gas permeability coefficient of oxygen gas in the barrier film is twice or more larger than the gas permeability coefficient of nitrogen gas. More preferably, it is 2.2 times or more.

  The barrier film is desirably highly hydrophobic in order to prevent moisture in the air from penetrating into the electrode group. Examples of the hydrophobic thermoplastic resin include polyolefins such as polyethylene, polypropylene, polybutadiene and polymethylpentene; fluorine-based resins such as polyvinylidene fluoride and vinyl trifluoride-vinylidene fluoride copolymer; polyphenylene sulfide; Can be mentioned. These thermoplastic resins may be partially crosslinked by electron beam irradiation or the like in order to increase the resistance to the organic solvent in the nonaqueous electrolyte.

  It is also effective to use a multilayer film in which the layer in contact with the nonaqueous electrolyte is formed of a thermoplastic resin having high organic solvent resistance.

  The thickness of the barrier film is preferably in the range of 1 μm to 100 μm. This is due to the reason explained below. When the thickness of the barrier film is less than 1 μm, the mechanical strength is inferior, so that the barrier film may be broken during the change in temperature or handling. On the other hand, when the thickness of the barrier film exceeds 100 μm, there is a possibility that the output of the battery cannot be sufficiently obtained because the oxygen permeability of the barrier film is small. A more preferable thickness range of the barrier film is 2 to 20 μm.

(Gap retaining member)
Examples of the material that can be used as the gap holding member include a porous film having a through-hole at least in the thickness direction; a planar shape such as a woven fabric, a nonwoven fabric, and paper;

  As the raw material for forming the void-holding member, a non-aqueous electrolyte that does not dissolve, swell, or decompose is preferable. Examples of such a material include polyolefins such as polyethylene, polypropylene, polymethylpentene, and modified copolymers thereof; Polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / ethylene copolymer (ETFE), poly Fluorine resins such as vinylidene fluoride (PVDF) and polychlorotrifluoroethylene (PCTFE); polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly Engineering plastics such as polyetheretherketone (PEEK); cellulose and its formal modified product; and the like.

  The thickness of the gap holding member is preferably in the range of 10 to 500 μm. This is due to the reason explained below. When the thickness is less than 10 μm, the rigidity of the gap holding member is small and easily deformed, so that it is difficult to secure a gap between the barrier film and the gas diffusion positive electrode. On the other hand, it is not preferable to use a gap holding member having a thickness exceeding 500 μm in terms of reducing the volume capacity density of the battery. A more preferable range of the thickness of the gap holding member is 15 to 300 μm.

  The void ratio of the void holding member is preferably in the range of 10 to 90%. This is due to the reason explained below. If the porosity is less than 10%, the rate at which oxygen gas diffuses through the gap holding member is slow, and the discharge rate characteristics of the battery may be degraded. Moreover, since the capability as a space | gap holding member is low, the function may not fully be exhibited. On the other hand, if the porosity exceeds 90%, the mechanical strength is inferior, so that the air gap holding member may be torn during temperature change or handling. A more preferable range of the porosity of the gap holding member is 20 to 80%.

The air permeability of the gap holding member is preferably 1000 seconds / 100 cm ³ or less. This is because if the air permeability exceeds 1000 seconds / 100 cm ³ , the rate at which the oxygen gas diffuses through the gap holding member becomes slow, and the discharge rate characteristics of the battery may be degraded. The smaller the air permeability value, the faster the oxygen diffusion rate of the gap holding member. However, when the air permeability is less than 1 second / 100 cm ³ , the flow between the inside and the outside separated by the gap holding member is improved. Therefore, the air permeability is more preferably in the range of 1 to 1000 seconds / 100 cm ³ . A more preferable range of the air permeability of the gap holding member is 2 to 800 seconds / 100 cm ³ .

  It is also effective to place spacer particles between the polymer barrier film and the gas diffusion positive electrode instead of the gap holding member or together with the gap holding member. The shape of the spacer particles is preferably spherical or crushed so as not to damage the polymer barrier film. The spacer particles preferably have a particle size of 10 to 500 μm. This is due to the reason explained below. When the particle size is less than 10 μm, the particles are easily embedded in the gas diffusion positive electrode, and it becomes difficult to provide a gap between the barrier film and the gas diffusion positive electrode. On the other hand, when the particle size exceeds 500 μm, the volume of the void portion increases, which is not preferable in terms of reducing the volume capacity density of the battery.

  Furthermore, it is also possible to form a void retaining layer by forming irregularities on the contact surface of the gas diffusion positive electrode with the polymer barrier film. The size of the irregularities of the gas diffusion positive electrode at this time is preferably 10 to 500 μm for the reason described below. When the size of the unevenness is less than 10 μm, it becomes difficult to form a gap between the barrier film and the gas diffusion positive electrode due to the undulation of the surface of the gas diffusion positive electrode. Moreover, since the volume of a space | gap part will become large when the size of an unevenness | corrugation exceeds 500 micrometers, it is unpreferable at the point of reducing the volume capacity density of a battery.

  When the positive electrode surface is roughened or fine particles are used as spacers, if the rigidity of the barrier film is sufficiently large, the function of holding the gap can be sufficiently achieved. When the negative pressure becomes negative, the barrier film may be deformed so as to resemble the shape of the positive electrode surface or the spacer, and the void portion may not be retained. In addition, when the surface of the positive electrode is roughened, there is a possibility that a high volume capacity density cannot be obtained or the positive electrode density is not uniform in the area direction.

  As described above, an air lithium battery using a non-aqueous electrolyte has been described as an example of the air battery of the present invention. However, when other air metal batteries are manufactured, sodium, aluminum, magnesium, cesium, or the like is used as a negative electrode active material. Moreover, a metal salt made of sodium, aluminum, magnesium, or cesium may be used as the electrolyte. Furthermore, these air metal batteries can be used as secondary batteries by using a material capable of occluding and releasing these metals in the negative electrode active material.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1
An aluminum-containing laminate film containing a thermoplastic resin layer made of polypropylene and an aluminum layer was prepared. Since the Young's modulus Y of the aluminum-containing laminate film is 8 × 10 ³ MPa and the thickness T is 100 × 10 ⁻⁶ m, the aluminum-containing laminate film has the above-described formula (1) {(Y × T) <10 ² } Meet. An aluminum-containing laminate film was formed into a cup shape with a lid, and a battery container was prepared by opening five air holes with a diameter of 2 mm in the lid portion which is the positive electrode facing surface. At this time, the polypropylene layer was made to be the inner surface of the battery container. Next, a seal tape was applied to the outer surface of the lid to close the air holes.

  As a barrier film, a polyethylene film having a thickness of 10 μm and having an oxygen permeability coefficient shown in Table 1 below was prepared. The oxygen permeability coefficient of the barrier film was measured by a method based on JIS K 7126. Moreover, the polyethylene microporous film whose thickness, porosity, and air permeability are values shown in the following Table 1 was prepared as a void holding member. The air permeability of the gap holding member can be measured by a paper and paperboard air permeability test method defined in JIS (Japanese Industrial Standard) P8117. As shown in FIG. 3, the gap holding member was folded in two, and a barrier film was sandwiched between them to obtain a barrier film group. The end portions of the barrier film group were fused to the inner surface (polypropylene layer) of the lid portion of the battery container by heat fusion treatment as shown in FIG.

90% by weight of ketjen black (EC600JD ^™ ) and 10% by weight of polytetrafluoroethylene are dry mixed and rolled to form a film-like gas diffusion positive electrode layer having a length of 50 mm, a width of 30 mm and a thickness of 200 μm. Obtained. This positive electrode layer was pressure bonded to a titanium mesh as a positive electrode current collector to obtain a positive electrode. One end of the positive electrode terminal was connected to a portion of the obtained positive electrode where the positive electrode current collector was exposed.

  In addition, a negative electrode was prepared by bonding a metal lithium foil to a nickel mesh with one end of a negative electrode terminal electrically connected thereto, and a separator made of a glass filter was prepared.

  A negative electrode, a separator, and a positive electrode were sequentially laminated, and this laminate was stored in the cup portion of the battery container. At this time, the laminate was stored so that the positive electrode faced the air hole of the battery container. Moreover, the front-end | tip of the positive electrode terminal and the negative electrode terminal was extended outside between the cup part and a cover part.

  A liquid non-aqueous electrolyte was prepared by dissolving an electrolyte composed of lithium perchlorate at a rate of 1.0 mol / l in a non-aqueous solvent in which 50% by volume of ethylene carbonate and 50% by volume of propylene carbonate were mixed.

  A liquid nonaqueous electrolyte was poured into the separator and impregnated in the separator, and then the lid was thermally fused to the cup portion to seal the battery container, thereby producing a nonaqueous electrolyte battery. Although the pressure inside the battery case immediately after the heat fusion was slightly lower than the atmospheric pressure because the battery case was sealed by heat sealing, the pressure difference was less than 0.1 kPa.

This battery was continuously discharged to 2.0 V at a constant current of 0.02 mA per 1 cm ² of positive electrode in a glove box filled with dry air with a dew point kept at 65 ° C. or lower, and then 2.0 V A constant voltage discharge was performed, and the discharge capacity on the 60th day was measured. In addition, after performing continuous discharge to 2.0 V at a constant current of 0.02 mA per 1 cm ² of positive electrode in a constant temperature and humidity chamber with a temperature of 25 ° C. and a humidity of 30%, a constant voltage discharge of 2.0 V is performed. The discharge capacity on the 60th day was measured. Furthermore, after performing a continuous discharge to 2.0 V at a constant current of 0.02 mA per 1 cm ² of positive electrode in a constant temperature and humidity chamber at a temperature of 25 ° C. and a humidity of 80%, a constant voltage discharge of 2.0 V is performed. The discharge capacity on the 60th day was measured.

  The results are shown in Table 2 below with the capacity obtained by discharge in the glove box as 100%.

(Example 2)
As the barrier film, a 12 μm thick polyethylene (PE) / polypropylene (PP) / polyethylene (PE) three-layer film having an oxygen permeability coefficient shown in Table 1 below is used, and the thickness, porosity and An air battery having the same configuration as that described in Example 1 except that a polypropylene nonwoven fabric having an air permeability value shown in Table 1 below is used and the battery structure is as shown in FIGS. Was made.

  Although the pressure inside the battery container immediately after the battery production was slightly lower than the atmospheric pressure because the battery container was sealed by heat sealing, the pressure difference was less than 0.1 kPa.

  The discharge characteristics of the obtained battery were measured under the same conditions as described in Example 1, and the results are shown in Table 2 below.

(Example 3)
As described in Example 1, except that a polymethylpentene film having a thickness of 10 μm and having an oxygen permeability coefficient shown in Table 1 below is used as the barrier film and the battery structure is as shown in FIGS. An air battery having the same configuration was produced.

  Although the pressure inside the bag formed from the barrier film group immediately after the battery production was slightly lower than the atmospheric pressure because the battery container was sealed by heat sealing, the pressure difference was less than 0.1 kPa.

  The discharge characteristics of the obtained battery were measured under the same conditions as described in Example 1, and the results are shown in Table 2 below.

(Example 4)
An air battery having the same configuration as that described in Example 1 was produced except that the battery structure was as shown in FIGS.

  Although the pressure inside the bag formed from the barrier film group immediately after the battery production was slightly lower than the atmospheric pressure because the battery container was sealed by heat sealing, the pressure difference was less than 0.1 kPa.

  The discharge characteristics of the obtained battery were measured under the same conditions as described in Example 1, and the results are shown in Table 2 below.

(Example 5)
Using a polybutadiene film having a thickness of 50 μm as the barrier film and an oxygen permeability coefficient of the value shown in Table 1 below, and using a polypropylene nonwoven fabric having a thickness, a porosity and an air permeability of the values shown in Table 1 as the gap holding member, An air battery having the same configuration as that described in Example 1 was prepared except that the battery structure was as shown in FIGS.

  Although the pressure inside the battery container immediately after the battery production was slightly lower than the atmospheric pressure because the battery container was sealed by heat sealing, the pressure difference was less than 0.1 kPa.

  The discharge characteristics of the obtained battery were measured under the same conditions as described in Example 1, and the results are shown in Table 2 below.

(Comparative Example 1)
An air battery having the same configuration as that described in Example 1 was prepared, except that a polydimethylsiloxane film having a thickness of 50 μm and an oxygen permeability coefficient shown in Table 1 below was used as the barrier film.

  Although the pressure inside the battery container immediately after the battery production was slightly lower than the atmospheric pressure because the battery container was sealed by heat sealing, the pressure difference was less than 0.1 kPa.

  The discharge characteristics of the obtained battery were measured under the same conditions as described in Example 1, and the results are shown in Table 2 below.

(Comparative Example 2)
In place of the barrier membrane, a polytetrafluoroethylene porous membrane (trade name: GORE-TEX) having a thickness of 50 μm and an oxygen permeability coefficient shown in the following Table 1 is used, as described in Example 1. An air battery having a simple structure was produced.

  In the battery of Comparative Example 2, since the movement of air through the porous membrane was easy, the atmospheric pressure in the battery container immediately after the production of the battery was the same as the atmospheric pressure.

The discharge characteristics of the obtained battery were measured under the same conditions as described in Example 1, and the results are shown in Table 2 below.

  The battery of Example 1 had a discharge capacity of about 420 mAh when discharged continuously for 60 days in the glove box. This value is about 4000 mAh / g in terms of capacity per positive electrode carbon weight, which is about twice as large as the known example. Further, as is clear from Tables 1 and 2, the air batteries of Examples 1 to 5 have little capacity reduction when discharged in the atmosphere, and in particular, according to the air batteries of Examples 1 and 4, the glove box It can be understood that the performance almost equal to that of the internal discharge can be obtained.

  Further, in the air batteries of Examples 1 to 5, there is a sufficient difference between the battery internal pressure and the atmospheric pressure in the steady state during discharge under each of the three conditions described above, and the adhesion of the electrode group in the discharged state is good. Met.

On the other hand, the air battery of Comparative Example 1 in which the oxygen permeability coefficient of the barrier film is larger than 1 × 10 ⁻¹⁴ mol · m / m ² · sec · Pa is a battery due to the permeation of moisture during discharge in the atmosphere. Swelling of the container occurred, and continuous discharge for 60 days could not be performed. In addition, in the air battery of Comparative Example 1, the difference between the battery internal pressure and the atmospheric pressure in the steady state at the time of discharge under each of the three conditions described above is almost the same as less than 0.1 kPa at the initial stage of discharge, and the moisture permeation. The battery internal pressure became higher than the atmospheric pressure as the battery voltage decreased. Further, the adhesion of the electrode group in the discharged state was poor.

  On the other hand, the air battery of Comparative Example 2 using a porous film instead of the barrier film is very inferior in stability to Comparative Example 1, and the nonaqueous electrolyte solution is dried up in the glove box. After a day, it became malfunctioning. Further, in the constant temperature and humidity chamber, the battery swelled due to moisture permeation faster than Comparative Example 1, and continuous discharge for 60 days could not be performed. Furthermore, there was almost no difference between the battery internal pressure and the atmospheric pressure in the steady state during discharge under each of the three conditions described above, and the adhesion of the electrode group in the discharged state was poor.

  A side pocket was provided in the battery container of the battery of Example 1, a pressure sensor was embedded therein, and a test cell was obtained. FIG. 11 shows changes in voltage, current, and pressure in the battery container when the test cell is subjected to continuous discharge in a humid atmosphere with a humidity of 90% and a temperature of 23 ° C. In FIG. 11, the horizontal axis is the discharge time, the left vertical axis is the voltage value and the current value, and the right vertical axis is the pressure in the battery container. As is clear from FIG. 11, it is understood that the pressure inside the battery container, which was positive with respect to the atmospheric pressure at the beginning of discharge, gradually decreases as discharge progresses, and finally shows negative pressure. it can. In addition, during discharge, the current and voltage show almost constant values, indicating that the stability of the current-voltage characteristics of the battery of Example 1 is high.

  Further, after filling the metal container with argon gas and closing the opening with the same kind of barrier film as described in Example 1, the change in gas pressure inside the metal container was measured, The result is shown in FIG. The vertical axis in FIG. 12 represents the internal pressure in the metal container, and the horizontal axis represents the elapsed time. As is clear from FIG. 12, the pressure in the metal container gradually decreases with time, and the mechanism by which argon gas permeates the barrier film is unknown, but the argon gas in the metal container passes through the barrier film. Phenomenon that flows out into the atmosphere and becomes negative pressure than atmospheric pressure is shown.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The perspective view which shows the structure of an example of the air battery concerning this invention. Sectional drawing which cut | disconnected the air battery of FIG. 1 along the II-II line. Sectional drawing which showed typically the barrier film group used for the air battery of FIG. The schematic diagram which shows the positional relationship of the air intake hole, barrier film | membrane, and space | gap holding member in the air battery of FIG. The perspective view which shows the structure of another example of the air battery concerning this invention. Sectional drawing which cut | disconnected the air battery of FIG. 5 along the VI-VI line. The perspective view which shows the structure of another example of the air battery concerning this invention. Sectional drawing which cut | disconnected the air battery of FIG. 7 along the VIII-VIII line. The perspective view which shows the structure of another example of the air battery concerning this invention. Sectional drawing which cut | disconnected the air battery of FIG. 9 along XX. The characteristic view which shows the time-dependent change of the voltage at the time of discharging a test cell in a constant temperature constant humidity tank, an electric current, and an internal pressure. The characteristic view which shows a time-dependent change of the internal pressure in the said container at the time of storing what coat | covered the opening part of the metal container filled with argon gas with the barrier film | membrane in a laboratory air atmosphere.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Battery container, 2 ... Electrode group, 3 ... Positive electrode collector, 4 ... Gas diffusion positive electrode layer, 5 ... Negative electrode collector, 6 ... Negative electrode active material layer, 7 ... Separator, 8 ... Air intake hole, 9 ... Barrier film, 10 ... gap holding member, 10a ... first gap holding member, 10b ... second gap holding member, 11 ... barrier film group, 12 ... heat seal part, 13 ... positive electrode terminal, 14 ... negative electrode terminal.

Claims (5)

A battery container having an air intake hole made of a laminate film having an inner surface made of a thermoplastic resin layer ;
An electrode group including a positive electrode containing oxygen as an active material, a negative electrode including a negative electrode active material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode;
A non-aqueous electrolyte held in the electrode group;
Thermoplastic having an oxygen transmission coefficient of 1 × 10 ⁻¹⁴ mol · m / m ² · sec · Pa or less, disposed between the surface of the battery container where the air intake hole is formed and the positive electrode of the electrode group . a non-porous barrier film made of resin is laminated on the positive electrode opposed to that surface of the barrier film, porous film, the thermoplastic resin comprising at least one selected from the group consisting of nonwoven and woven fabrics The first air gap holding member made of metal, the surface of the battery container where the air intake hole is formed, and the barrier film, and selected from the group consisting of a porous film, a nonwoven fabric and a woven fabric A laminated film composed of at least one kind of thermoplastic resin-made second void holding member ,
Said by the fact that the laminated film is heat-sealed to the inner surface of the battery container, the air intake hole of the battery container is sealed by the laminated film,
An air battery characterized in that the pressure in the battery container during continuous discharge is 0.1 to 80 kPa lower than atmospheric pressure . 2. The air battery according to claim 1, wherein a porosity of the battery container (including a gap of the laminated film) is 5 to 40% . The air battery according to any one of claims 1 to 2 , wherein the laminate film contains aluminum and satisfies the following expression (1) .
(Y × T) <10 ² (1)
However, Y is the Young's modulus (MPa) of the laminate film, and T is the thickness (m) of the laminate film. The air battery according to claim 1, wherein the negative electrode active material is lithium metal or a lithium alloy. Claim 1-4 The air battery according to any one of the preceding, wherein the thickness of the barrier layer is 2 to 100 m.

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