JP7223114B2 - Anode and metal-air batteries - Google Patents

Description

The present disclosure relates to negative electrodes and metal-air batteries. This application claims priority based on Japanese Patent Application No. 2019-039922 filed in Japan on March 5, 2019, the content of which is incorporated herein.

A metal-air battery has a positive electrode (air electrode), a negative electrode (metal negative electrode), and an electrolyte (electrolyte solution), and has a high energy density. is underway. This type of metal-air battery is housed in an outer container with an insulating separator interposed between the positive electrode and the negative electrode.

In the metal-air battery, the metal contained in the negative electrode becomes metal ions during discharge, diffuses into the electrolyte, and deposits in the form of needles during charging. Therefore, in the metal-air battery, dendrites (needle-shaped metal deposits) that have grown due to repeated charging and discharging may penetrate the separator, causing a short circuit between the positive electrode and the negative electrode.

On the other hand, for example, in Patent Document 1, by providing an anion conductive film as a separator between the positive electrode and the negative electrode of a metal-air battery, metal A configuration is disclosed that attempts to suppress the growth of dendrites that cause a short circuit between the positive electrode and the negative electrode while suppressing the diffusion of ions.

JP 2017-162773 A

In the metal-air battery disclosed in Patent Document 1, the negative electrode is pressure-bonded to the positive electrode via an anion-conducting membrane that is a separator. This is intended to prevent the negative electrode active material from sliding down due to the action of gravity from the side of the negative electrode that is in close contact with the positive electrode via the separator. However, since the positive electrode is pressure-bonded to the anion conductive film, friction occurs between the anion conductive film and the positive electrode. In addition, as oxygen is generated and consumed in the positive electrode by charging and discharging, pressure fluctuations occur in the external container, and the anion conductive membrane may be pressed against the positive electrode. Such friction and pressure tend to damage or rupture the anion conductive membrane, generating dendrites and short-circuiting the positive electrode and the negative electrode.

The present disclosure has been made in view of the conventional problems as described above, and its object is to provide a negative electrode suitable for suppressing the growth of dendrites and suppressing the short circuit between electrodes, and the negative electrode. To provide a metal-air battery with

A negative electrode of the present disclosure for achieving the above object is a negative electrode current collector including a resin case having at least one opening, a portion accommodated in the case, and a portion extending from the case. a negative electrode active material layer housed in the case and containing a negative electrode active material in contact with at least a portion of the negative electrode current collector; a first porous film covering the opening; the first porous film and the negative electrode; and an anion-conducting membrane disposed between the active material layer.

Due to this specific matter, the negative electrode active material is housed in the case and is prevented from sliding down. In addition, since the first porous membrane is arranged between the anion conductive membrane and the opening of the case, it is possible to prevent the anion conductive membrane from being damaged. By preventing damage to the anion-conducting membrane, the route for dendrite growth can be eliminated. Therefore, the growth of dendrites can be effectively suppressed, and short circuits between electrodes can be prevented.

As a more specific configuration of the negative electrode, it is preferable that the opening is covered with the first porous film inside the case. As a result, the negative electrode expands due to repeated charging and discharging, and the space between the opening peripheral edge of the case and the anion conductive film, which tends to become a dendrite growth path, can be reinforced by the first porous film. It is possible to prevent damage or breakage of the anion-conducting membrane, or separation between the opening periphery of the case and the anion-conducting membrane. In addition, the integrity between the case and the first porous film is enhanced, and the dendrite growth path is blocked, thereby preventing short circuits between the electrodes.

In the negative electrode having the above structure, it is preferable that the case and the first porous film are welded together. As a result, in the region where the case and the first porous membrane are welded together, the respective components of the case and the first porous membrane are melted to close the pores of the first porous membrane. Therefore, even in the peripheral portion of the first porous film, which tends to be a dendrite growth path, the dendrite growth path can be cut off, and a short circuit between the electrodes can be prevented.

Moreover, in the negative electrode having the above structure, it is preferable that the anion conductive film is in contact with the inner surface of the case. As a result, the growth path of the dendrite can be narrowed while maintaining the distance between the positive electrode and the negative electrode, so that it is possible to further prevent short circuits between the electrodes.

Further, in the negative electrode having the above configuration, it is preferable that the anion conductive membrane is covered with the first porous membrane from the inside of the case and extends outward beyond the peripheral edge of the first porous membrane. . With such a configuration, the dendrite growth path can be narrowed, so short-circuiting between electrodes can be further prevented.

More specifically, the anion conductive membrane in the negative electrode having the above configuration preferably comprises a polymer containing an anion exchange group or a layered double hydroxide. Moreover, it is preferable that the anion-conducting membrane is configured to suppress permeation of zincate ions and allow permeation of hydroxide ions. With such a configuration, the anion conductive membrane can have good anion permeability.

More specifically, the air permeability of the first porous film in the negative electrode having the above structure is preferably 0.1 to 1000 seconds in Gurley value. Furthermore, it is preferable that the first porous membrane has a large number of interconnecting micropores and that the average pore diameter of the micropores is 0.1 to 100 μm. By being configured in this way, the first porous membrane can be expected to have a buffering effect in the thickness direction, and in addition, can retain the electrolyte in the micropores.

Further, in the negative electrode having the above structure, a second porous film may be provided between the anion conductive film and the negative electrode active material layer. This makes it possible to further prevent damage to the anion conductive membrane.

Moreover, in the negative electrode having the above structure, it is preferable that the case contains an electrolyte. As a result, the electrolyte can be held in the case, and the charge/discharge reaction can be effected efficiently.

A metal-air battery including the negative electrode according to the above configuration is also within the scope of the technical concept of the present disclosure. That is, the metal-air battery of the present disclosure includes a negative electrode, a positive electrode, and an electrolyte, and the negative electrode is housed in a resin case having at least one opening, and is extended from the case. a negative electrode current collector; a negative electrode active material layer containing a negative electrode active material contained in the case and in contact with at least a portion of the negative electrode current collector; a first porous film covering the opening; An anion conductive film is provided between the film and the negative electrode active material layer, and the positive electrode is arranged to face the opening.

With this specific matter, it is possible to suitably form a metal-air battery having a structure capable of suppressing the growth of dendrites in the negative electrode and preventing a short circuit between the electrodes.

More specifically, in the metal-air battery, the positive electrode includes a first positive electrode for discharging and a second positive electrode for charging, wherein the first positive electrode, the second positive electrode, the negative electrode, are preferably arranged in this order.

In the metal-air battery, a first opening and a second opening are provided on both sides in the thickness direction of the negative electrode active material layer as the openings, and the positive electrode is a first opening for discharging. A configuration including a positive electrode and a second positive electrode for charging, wherein the first positive electrode is arranged to face the first opening and the second positive electrode is arranged to face the second opening may be assumed.

With such a configuration, the metal-air battery can effectively block the dendrite growth path and prevent a short circuit between the electrodes.

In the negative electrode according to the present disclosure and the metal-air battery including the negative electrode, it is possible to prevent damage and breakage of the anion conductive film and suppress the growth of dendrites that cause short circuits between electrodes, improving battery performance. can be made

1 is a cross-sectional view schematically showing a negative electrode according to Embodiment 1 of the present disclosure; FIG. It is a perspective view which shows the said negative electrode. 1 is a perspective view showing a metal-air battery according to Embodiment 1 of the present disclosure; FIG. FIG. 10 is a perspective view showing a negative electrode according to Embodiment 2; 3 is a partially enlarged cross-sectional view schematically showing the negative electrode; FIG. FIG. 10 is a cross-sectional view schematically showing a negative electrode according to Embodiment 3; FIG. 10 is a cross-sectional view schematically showing a negative electrode according to Embodiment 4; FIG. 10 is a cross-sectional view schematically showing a metal-air battery according to Embodiment 5; FIG. 11 is a cross-sectional view schematically showing a metal-air battery according to Embodiment 6;

A negative electrode and a metal-air battery including the negative electrode according to embodiments of the present disclosure will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view schematically showing a negative electrode 1 according to Embodiment 1 of the present disclosure. FIG. 2 is a perspective view showing the negative electrode 1 according to Embodiment 1. FIG. For convenience of explanation, the following description assumes that the upper side of the drawing in FIG.

(negative electrode)
The negative electrode 1 contains a metal that serves as an electrode active material, constitutes a metal-air battery 10 together with a positive electrode 8, a battery case 9, and the like, and extracts electrical energy obtained in the process in which the metal changes to a metal oxide through an electrochemical reaction. . This negative electrode 1 includes a negative electrode case (case) 2 made of resin, a negative electrode current collector 3 , a negative electrode active material layer 4 , a first porous film 5 , and an anion conductive film 6 .

The negative electrode case 2 of the negative electrode 1 has at least one opening 20 and accommodates the negative electrode current collector 3 therein. The negative electrode case 2 is formed, for example, by folding and bonding one or a plurality of sheet-like insulating film materials or the like.

In the form shown in FIGS. 1 and 2, the negative electrode case 2 is provided with an opening 20 penetrating inside and outside so as to face one surface and the other surface of the negative electrode current collector 3 . That is, the openings 20 are formed on the surfaces of the negative electrode case 2 that face each other with the negative electrode current collector 3 interposed therebetween.

The size of each opening 20 is set to be smaller than the size of any one surface of the negative electrode current collector 3 housed in the negative electrode case 2 . Dendrites tend to grow at the edges of the negative electrode current collector 3 or the negative electrode active material layer 4 . Therefore, by making the size of each opening 20 smaller than the size of one of the surfaces of the negative electrode current collector 3, the electrode reaction is less likely to occur at the ends of the negative electrode current collector 3 or the negative electrode active material layer 4. It becomes possible to suppress the growth of dendrites.

The negative electrode current collector 3 is made of a material that is porous and has electronic conductivity. For example, from the viewpoint of self-corrosion suppression, the negative electrode current collector 3 is made of a material with a high hydrogen overvoltage, or a material in which the surface of a metal material such as stainless steel is plated with a material with a high hydrogen overvoltage. Further, the negative electrode current collector 3 may be made of mesh, expanded metal, punching metal, sintered metal particles or metal fibers, metal foam, or the like.

A lead portion 31 is extended from the negative electrode current collector 3 as a negative electrode terminal, and can be electrically connected to an external circuit. The negative electrode current collector 3 is accommodated in the negative electrode case 2 with the lead portion 31 extending from the upper portion of the negative electrode case 2 . As a result, the charge consumed or generated by the negative electrode 1 can be transferred to and received from an external circuit (not shown).

The negative electrode active material layer 4 is arranged in the negative electrode case 2 so as to be in contact with both surfaces of the negative electrode current collector 3, and has a negative electrode active material containing a metal element as an electrode active material. As such metal elements, zinc, lithium, sodium, calcium, magnesium, aluminum, iron and the like are preferable.

In an exemplary embodiment, the negative electrode active material layer 4 may be a layer of metal in a reduced state or a layer of metal in an oxidized state. For example, particulate zinc or zinc oxide can be used for the negative electrode active material layer 4 . When the metallic element is zinc, it is metallic zinc in the reduced state and zinc oxide in the oxidized state. The negative electrode 1 containing zinc can be removed from the battery case 9 after discharge to reduce zinc oxide to zinc.

Moreover, when the metal element is zinc, an oxidation reaction of metallic zinc occurs during discharge. That is, as a result of oxidation of zinc, there are cases where it dissolves in the electrolytic solution as zincate ions and cases where zinc oxide or zinc hydroxide is directly generated. During charging, a reduction reaction to metallic zinc occurs. That is, there are cases where zinc is produced by reduction of zincate ions dissolved in the electrolytic solution, and cases where zinc oxide and zinc hydroxide are directly reduced to zinc.

・First porous membrane 5
A first porous film 5 having an insulating porous structure is attached to each of the two openings 20 of the negative electrode case 2 to cover these openings 20 . The first porous film 5 is accommodated inside the negative electrode case 2 and arranged so as to cover the opening 20 from the inside of the negative electrode case 2 .

As shown in FIG. 1 , in the negative electrode case 2 of the negative electrode 1 , a first porous film 5 is interposed between an anion conductive film 6 (to be described later) and an opening 20 . A positive electrode 8 , which will be described later, is closely arranged on the first porous film 5 through the opening 20 of the negative electrode case 2 .

Thereby, the first porous film 5 covers the opening 20 of the negative electrode case 2 and intervenes between the inner and outer components of the negative electrode case 2, acting as a buffer layer therebetween. That is, the first porous membrane 5 prevents the anion conductive membrane 6 arranged in the negative electrode case 2 from coming into contact with the edge of the opening 20 . The positive electrode 8 arranged outside the negative electrode case 2 contacts the opening 20 but is arranged without contacting the anion conductive membrane 6 .

1 shows the configuration in which the first porous film 5 is arranged so as to cover the opening 20 from the inside of the negative electrode case 2, but the first porous film 5 is arranged from the outside of the negative electrode case 2 so as to cover the opening 20. You may arrange|position so that it may cover. Even with such an arrangement form, the positive electrode 8 arranged outside the negative electrode case 2 can be prevented from coming into contact with the anion conductive film 6 .

As for the arrangement form of the first porous film 5, it is more desirable to cover the opening 20 from the inside of the negative electrode case 2 than to cover the opening 20 from the outside. This is because when the first porous membrane 5 is arranged to cover the opening 20 from the inside of the negative electrode case 2, the edge of the opening 20 and the positive electrode 8 can be prevented from coming into contact with the anion conductive membrane. .

Since the first porous membrane 5 is responsible for ion conductivity between the positive electrode 8 and the negative electrode 1, it is formed of a porous member that can hold the electrolyte in the pores, and non-woven fabric such as polyolefin, filter paper, etc. can be used. can. In addition to these, the first porous film 5 may contain inorganic substances such as titanium oxide, niobium oxide, and tantalum oxide.

Further, the first porous membrane 5 preferably has an air permeability represented by a Gurley value of 0.1 to 1000 seconds. The Gurley value is an index that expresses the ease with which gas can pass through. The Gurley value of the first porous film 5 can be easily measured by the measurement method specified in JIS P 8117.

The Gurley value of the first porous membrane 5 is preferably 0.1 seconds or more. The Gurley value is preferably up to 1000 seconds, and more preferably 100 seconds as the upper limit. If the Gurley value is less than 0.1 second, there are too many voids and the strength required for the buffer layer is insufficient, and the first porous membrane 5 may be damaged. If the Gurley value is greater than 1000 seconds, the voids are too small, impeding ion conduction and causing an increase in battery resistance.

In addition, when the first porous membrane 5 has a large number of micropores having ionic conductivity and communication between the front and back surfaces, the average pore diameter of these micropores is 0.1 to 100 μm. Preferably. More preferably, the micropores have an average pore diameter of 1 to 50 μm.

The first porous membrane 5 has non-uniform pore diameters in the case of non-woven fabric or woven fabric, but it is preferable to configure the average pore diameter within the above range.

By attaching such a first porous film 5 to the opening 20, it is possible to suppress damage or breakage of the anion conductive film, which causes the growth path of dendrites, and the occurrence of short circuits caused by dendrites. can be suppressed.

・Anion conductive membrane 6
An anion conductive film 6 is arranged between the first porous film 5 and the negative electrode active material layer 4 . The anion-conducting film 6 ensures insulation between the positive electrode 8 and the negative electrode 1, allows anions to move between these members, and prevents a short circuit due to the formation of an electron conduction path between the electrodes. The anion-conducting membrane 6 is a membrane that allows anions such as hydroxide ions (OH ⁻ ) involved in the battery reaction to permeate, and includes organic matter and inorganic matter.

Zincate ions generated by the discharge reaction of the negative electrode 1 diffuse in the battery to the charging electrode, causing short-circuit failure of the battery. The anion-conducting membrane 6 has conductivity for hydroxide ions and allows permeation of hydroxide ions. On the other hand, the anion-conducting membrane 6 preferably suppresses permeation of zincate ions and inhibits diffusion of zincate ions.

In addition, the anion conductive membrane 6 has selectivity of permeating anions due to the action of an inorganic substance or the like, which will be described later. As for the selectivity of anions, for example, anions such as hydroxide ions are easily permeable, and even anions with large ionic radii, such as metal-containing ions derived from the active material, are sufficiently prevented from permeating. The anion conduction in the anion conductive membrane 6 means that anions having a small ionic radius such as hydroxide ions are sufficiently permeated, and means that the membrane has anion permeability. Anions with a large ionic radius, such as metal-containing ions, are more difficult to permeate, and may not permeate at all.

Inorganic substances contained in the anion conductive membrane 6 include alkali metals, alkaline earth metals, Mg, Sc, Y, lanthanides, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ru. , Co, Ni, Pd, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Tl, C, Si, Ge, Sn, Pb, N, P, Sb, Bi, S, Se, Te , F, Cl, and Br.

Examples of the inorganic substance include layered inorganic compounds such as oxides, composite oxides, and layered double hydroxides, hydroxides, clay compounds, solid solutions, alloys, zeolites, halides, carboxylate compounds, carbonate compounds, and hydrogen carbonate. compounds, nitrate compounds, sulfate compounds, sulfonic acid compounds, phosphate compounds such as hydroxyapatite, phosphorus compounds, hypophosphite compounds, boric acid compounds, silicic acid compounds, aluminate compounds, sulfides, onium compounds, salts, etc. is mentioned. Among them, oxides, composite oxides, layered double hydroxides such as hydrotalcite, hydroxides, clay compounds, solid solutions, zeolites, fluorides, phosphoric acid compounds, boric acid compounds, silicic acid compounds, aluminate compounds, Salt is preferred.

Moreover, as said oxide, a cerium oxide and a zirconium oxide are preferable, for example. Cerium oxide is more preferred. Cerium oxide may be doped with a metal oxide such as samarium oxide, gadolinium oxide, or bismuth oxide, or may be a solid solution with a metal oxide such as zirconium oxide. The oxide may have oxygen defects. Preferred examples of the hydroxide include magnesium hydroxide, cerium hydroxide, and zirconium hydroxide.

The layered inorganic compound constituting the anion conductive membrane 6 may be composed of only one layer, or may be a laminate of two or more layers. Examples of layered inorganic compounds include layered double hydroxides. This layered double hydroxide is represented by the following formula;
[M ¹ ₁ − _x M ² _x (OH) ₂ ](A ⁿ⁻ ) _x/n ·mH ₂ O
( ^M1 represents a divalent metal ion that is any of Mg, Fe, Zn, Ca, Li, Ni, Co, Cu, Mn; ^M2 represents Al, Fe, Mn, Co, Cr, In represents a trivalent metal ion that is any of ^{A n−} represents a monovalent to trivalent anion such as OH ⁻ , Cl ⁻ , NO ₃ ⁻ , CO ₃ ²⁻ , COO ^−, etc. m is 0 or more n is a number from 1 to 3. x is a number from 0.20 to 0.40.). Incidentally, A ^n- is preferably an anion having a valence of 2 or less.

When the anion conductive membrane 6 is composed of a layered double hydroxide, it is preferable to obtain a dense layer by forming and/or firing particles of the layered double hydroxide. It may be a composite with an auxiliary component that helps densification and fixation of the oxide particle group.

Organic substances contained in the anion conductive film 6 include hydrocarbon moiety-containing polymers typified by polyolefins such as polyethylene and polypropylene, aromatic group-containing polymers typified by polystyrene, and alkylene glycols such as polyethylene oxide and polypropylene oxide. Representative ether group-containing polymers; polyvinyl alcohol, poly(α-hydroxymethyl acrylate), cellulose, methyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyalkyl cellulose (e.g., hydroxyethyl cellulose, hydroxypropyl cellulose, etc.), etc. Representative hydroxyl group-containing polymers; amide bond-containing polymers such as polyamide, nylon, polyacrylamide, polyvinylpyrrolidone and N-substituted polyacrylamide; imide bond-containing polymers such as polymaleimide and polyimide; (meth) acrylic (Meth)acrylic polymers containing monomer units derived from acid alkyl ester monomers as main components; Carboxy group-containing polymers represented by carboxymethyl cellulose (including carboxy group metal salts (alkali metals, etc.), ammonium salts, etc.); poly(meth)acrylates, polymaleates, polyitaconates, polymethylene glutaric acid Carboxylate-containing polymers typified by salts; halogen atom-containing polymers such as polyvinyl chloride, polyvinylidene fluoride, and polytetrafluoroethylene; polymers bonded by ring-opening epoxy groups such as epoxy resins; salt) site-containing polymer; AR ¹ R ² R ³ B (A represents N or P. B represents an anion such as a halogen anion or ^OH- . ^{R 1} , R ² and R ³ are the same or different. represents an alkyl group having 1 to 7 carbon atoms, a hydroxyalkyl group, an alkylcarboxyl group, or an aromatic ring group, and R ¹ , R ² and R ³ may combine to form a ring structure. Polymers containing quaternary ammonium salts and quaternary phosphonium salts typified by polymers bonded with Rubber-like polymers with unsaturated carbon bonds in the chain; cellulose acetate, chitin, chitosan, Saccharides represented by ruginic acid (salt), etc.; Amino group-containing polymers represented by polyethyleneimine; Carbamate group site-containing polymers; Carbamide group site-containing polymers; Epoxy group site-containing polymers; Heterocyclic site-containing polymers; polymer alloys; heteroatom-containing polymers;

-Electrolyte An electrolyte is accommodated in the negative electrode case 2 in which the negative electrode current collector 3, the negative electrode active material layer 4, the anion conductive film 6 and the first porous film 5 are enclosed. The electrolyte is not particularly limited as long as it is commonly used as a battery electrolyte, and examples thereof include water-containing electrolytes and organic solvent-based electrolytes, with water-containing electrolytes being more preferred.

The water-containing electrolytic solution refers to an electrolytic solution using only water as a solvent raw material (aqueous electrolytic solution) or an electrolytic solution using a liquid obtained by adding an organic solvent to water as a solvent raw material. Examples of aqueous electrolytes include potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, zinc sulfate aqueous solution, zinc nitrate aqueous solution, zinc phosphate aqueous solution, zinc acetate aqueous solution and the like. The electrolyte is not particularly limited, but when an aqueous electrolyte is used, it is preferably a compound that generates hydroxide ions responsible for ion conduction in the system. From the viewpoint of ion conductivity, a potassium hydroxide aqueous solution is more preferable. One or two or more aqueous electrolytes may be used.

Further, the electrolytic solution immerses the negative electrode 1 and the positive electrode 8 within the battery case 9 . As shown in FIG. 1, in the negative electrode 1 (and the metal-air battery 10) according to Embodiment 1, there is no liquid layer of the electrolytic solution, and the negative electrode 1 and the positive electrode 8 are immersed in the electrolytic solution in a wet state. .

For example, when a zinc-air battery, an aluminum-air battery, or an iron-air battery is applied as the metal-air battery 10, an alkaline aqueous solution such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution can be used as the electrolyte. In the case of an air battery, an aqueous sodium chloride solution can be used as the electrolyte, and in the case of a lithium-air battery, an organic electrolyte can be used. The electrolytic solution may contain an organic additive or an inorganic additive other than the electrolyte, or may be gelled with a polymer additive.

Negative electrode current collector 3 , negative electrode active material layer 4 , anion conductive film 6 and first porous film 5 are enclosed in negative electrode case 2 and housed in battery case 9 constituting metal-air battery 10 . The negative electrode case 2 ensures insulation between the negative electrode current collector 3 and the positive electrode 8 in the battery case 9 .

As shown in FIG. 2, the negative electrode case 2 is formed in the shape of a bottomed bag with an open top before it is accommodated in the battery case 9, and the electrolytic solution is injected into the negative electrode case 2. can be done. The negative electrode case 2 has a margin for heat sealing on the upper side, and the upper side may be heat-sealed and sealed after the electrolyte solution is injected.

The material of the negative electrode case 2 is not particularly limited as long as it is made of a material that prevents permeation of the electrolytic solution required for this type of metal-air battery 10 and that can function as an insulating member. Preferably, it is made of a thermoplastic resin material that has good insulation properties, is less prone to wrinkles, etc., and has high heat resistance. Specifically, polyolefin resin materials such as polyethylene (PE) and polypropylene (PP) can be preferably used. The thickness of the polyolefin resin material is preferably 0.2 mm or less, more preferably 30 to 150 μm, more preferably 50 to 100 μm.

At the negative electrode 1, both the discharge reaction and the charge reaction involve reactions involving hydroxide ions (OH ⁻ ) in addition to the negative electrode active material. Therefore, the negative electrode 1 has a structure in which the negative electrode active material and the electrolyte acting as a conduction path for hydroxide ions (OH ⁻ ) are in efficient contact. As a result, the electrolytic solution permeates the voids between the active material particles. Thereby, the contact interface between the active material particles and the electrolytic solution can be widened. Moreover, the negative electrode active material layer 4 may be configured to contain a binder, and the binder enables the negative electrode active materials to bind to each other.

(metal-air battery)
FIG. 3 is a perspective view showing the metal-air battery 10 according to Embodiment 1. FIG. A metal-air battery 10 includes a battery case 9 , a negative electrode 1 and a positive electrode 8 .

As shown in FIG. 1, the positive electrodes 8 that constitute the metal-air battery 10 include a discharging positive electrode (air electrode) 81 that is a first positive electrode for discharging, and a charging positive electrode that is a second positive electrode for charging. 82. A discharge positive electrode 81 is arranged on one surface of the negative electrode case 2 of the negative electrode 1, and a charging positive electrode 82 is arranged on the other surface.

・Battery case 9
The battery case 9 is an exterior container that accommodates the negative electrode 1, the positive electrode 81 for discharge, and the positive electrode 82 for charge. In the exemplary embodiment, as shown in FIG. 1, the battery case 9 is arranged outside the negative electrode case 2 and is configured to enclose the negative electrode 1 therein. In this case, as the battery case 9 , a first case 91 is arranged facing one opening 20 of the negative electrode case 2 and a second case 92 is arranged facing the other opening 20 of the negative electrode case 2 . , are bonded to each other with the negative electrode 1 enclosed therein.

The first case 91 and the second case 92 are each formed with a large number of openings extending through the front and back surfaces. Among these, in the first case 91 , the opening serves as an air intake port 93 . Also, in the second case 92 , the opening serves as a gas discharge port 94 . The battery case 9 is capable of taking in air through these air intake ports 93, and through gas exhaust ports 94, exhausts gases such as oxygen generated during charging and accumulated near the charging electrodes. It is possible to discharge it to the outside.

In the manufacturing process of the battery case 9, the first case 91 and the second case 92 are arranged to face each other and are fused at the outer peripheral portion. An upper end portion of the battery case 9 can be used as an injection port for injecting the electrolytic solution. The upper end of the battery case 9 is sealed by heat sealing after the electrolyte is injected. As shown in FIG. 3, the upper end of the battery case 9 is preferably sealed with the negative electrode case 2 sandwiched between the first case 91 and the second case 92 .

The material forming the battery case 9 is preferably a material having corrosion resistance to the electrolytic solution, heat resistance, and heat-sealability. For example, the material of the battery case 9 is preferably polyvinyl chloride (PVC), polyvinyl acetate, ABS resin, vinylidene chloride, polyacetal, polyethylene, polypropylene, polyisobutylene, fluorine resin, epoxy resin, or the like.

1 and 3, as the metal-air battery 10, the negative electrode 1, the discharging positive electrode 81, and the charging positive electrode 82 are immersed in the electrolytic solution (electrolyte) in the battery case 9. A tripolar secondary battery arranged in parallel is illustrated.

・Discharge positive electrode 81
The discharge positive electrode 81 is an electrode that has a catalyst and becomes a positive electrode when the metal-air battery 10 is discharged. In the discharge positive electrode 81, when an alkaline aqueous solution is used as the electrolyte, water supplied from the electrolyte or the like reacts with oxygen gas and electrons supplied from the atmosphere on the catalyst to form hydroxide ions (OH ⁻ ) occurs. In the discharge positive electrode 81, a discharge reaction proceeds at a three-phase interface where oxygen (gas phase), water (liquid phase), and electron conductor (solid phase) coexist.

The discharge positive electrode 81 is provided so that oxygen gas contained in the atmosphere can diffuse. For example, the discharge positive electrode 81 is provided so that at least part of the surface of the discharge positive electrode 81 is exposed to the atmosphere. In the exemplary embodiment, oxygen gas contained in the atmosphere is diffused into the discharge positive electrode 81 through the numerous air intake ports 93 of the battery case 9 .

The discharge positive electrode 81 may include a discharge positive electrode current collector, a discharge positive electrode catalyst layer containing a catalyst, and a water-repellent film. The positive electrode current collector for discharge is desirably made of a material that is porous and has electronic conductivity. When an alkaline aqueous solution is used as the electrolyte, from the viewpoint of corrosion resistance, it is desirable to use nickel or a material obtained by plating the surface of a metal material such as stainless steel with nickel. The positive electrode current collector for discharge can be made porous by using mesh, expanded metal, punching metal, sintered metal particles or metal fibers, foamed metal, or the like.

The discharge positive electrode current collector may function as a gas diffusion layer. In this case, the positive electrode current collector for discharge is carbon paper or carbon cloth surface-treated with a water-repellent resin, or a porous sheet made of carbon black and a water-repellent resin. The water-repellent resin is provided to prevent the electrolyte from leaking from the battery case 9, has a gas-liquid separation function, and does not interfere with the supply of oxygen gas to the catalyst layer.

The water-repellent film is a porous material containing a water-repellent resin, and is arranged on the side opposite to the negative electrode 1 . Leakage of the electrolytic solution can be suppressed by disposing the water-repellent film. Polytetrafluoroethylene (PTFE), for example, is preferable as the water-repellent resin used for the water-repellent film.

The discharge positive electrode 81 can be electrically connected to a discharge positive electrode terminal (air electrode terminal), and enables charge generated in the catalyst layer to be taken out to an external circuit (not shown).

・Charging positive electrode 82
The charging positive electrode 82 is a porous electrode that serves as a positive charging electrode. In the charging positive electrode 82, when an alkaline aqueous solution is used as the electrolyte, a reaction occurs in which oxygen, water, and electrons are generated from hydroxide ions (OH ⁻ ) (charging reaction). That is, in the charging positive electrode 82, the charging reaction proceeds at the three-phase interface where oxygen (gas phase), water (liquid phase), and electron conductor (solid phase) coexist.

The charging positive electrode 82 is provided so that gas such as oxygen gas generated by the progress of the charging reaction can diffuse. For example, the charging positive electrode 82 is provided so that at least part of it communicates with the outside air. In the exemplary embodiment, gas such as oxygen gas produced by the charging reaction is discharged from the charging positive electrode 82 through a number of gas discharge ports 94 of the battery case 9 .

The charging positive electrode 82 is desirably made of a porous and electronically conductive material. When an alkaline aqueous solution is used as the electrolyte, from the viewpoint of corrosion resistance and oxygen evolution catalytic ability for the charging reaction, it is possible to use nickel or a material with the surface of a metal material such as stainless steel plated with nickel. desirable. The charging positive electrode 82 can be made porous by using mesh, expanded metal, punching metal, sintered metal particles or metal fibers, foamed metal, or the like. The charging positive electrode 82 may be provided with oxygen generating catalyst particles that promote the charging reaction on its surface. Moreover, the charging positive electrode 82 may be configured to include a charging positive electrode current collector (not shown).

Similarly to the discharging positive electrode 81, the charging positive electrode 82 may also be provided with a water-repellent film. By disposing the water-repellent film, it is possible to suppress leakage of the electrolytic solution through the positive electrode 82 for charging, and separate gas such as oxygen gas generated by the charging reaction from the electrolytic solution. It is possible to discharge to the outside of. The charging positive electrode 82 can be electrically connected to a charging positive electrode terminal, and can be supplied with electric charges necessary for the charging reaction from an external circuit (not shown).

As shown in FIG. 3, the metal-air battery 10 configured as described above has the negative electrode 1 provided with the negative electrode case 2 in the battery case 9 , and the lead portion 31 of the negative electrode current collector 3 is connected to the negative electrode case 2 . is extended from the upper portion of the battery case 9 to the outside of the battery case 9 . Further, referring to FIG. 1, the constituent members of the negative electrode 1 such as the negative electrode current collector 3 do not come into contact with the battery case 9, and the insulation between the negative electrode current collector 3 and the inner surface of the battery case 9 is ensured. It is The positive electrode 8 is insulated from the negative electrode current collector 3 by the negative electrode case 2 and arranged so as not to come into contact with them.

As shown in FIG. 1, an anion conductive film 6 is interposed between the electrodes of the negative electrode 1 and the positive electrode 8 (discharging positive electrode 81 and charging positive electrode 82). Ion conduction occurs between these electrodes through the first porous membrane 5, and charging and discharging reactions of the metal-air battery 10 are made possible. The anion conductive film 6 ensures insulation between the positive electrode 8 and the negative electrode 1, allows anions to move, and prevents the formation of an electron conduction path. Therefore, the metal-air battery 10 has a structure capable of suppressing the growth of dendrites, and is capable of preventing short circuits between electrodes.

In the metal-air battery 10, expansion or contraction of the negative electrode active material layer 4 may occur with charge-discharge cycles. On the other hand, in the metal-air battery 10 , the anion conductive film 6 , the first porous film 5 , and the like, which constitute the negative electrode 1 , including the negative electrode active material layer 4 , are housed in the negative electrode case 2 . In addition, the metal-air battery 10 has a structure in which the negative electrode 1 and the positive electrode 8 are closely arranged in the battery case 9 and there is no liquid layer due to the electrolyte between the electrodes. As a result, expansion due to charge/discharge cycles is suppressed, and a structure that does not easily change in volume is realized. Furthermore, even if expansion or the like occurs in the metal-air battery 10, the first porous membrane 5 is interposed between the anion conductive film 6 and the negative electrode case 2 (or between the anion conductive film 6 and the positive electrode 8). Since it functions as a buffer layer, the anion conductive membrane 6 is prevented from being pressed and damaged.

In the manufacturing process of the metal-air battery 10, the single-layered or multi-layered sheet material constituting the negative electrode case 2 is heat-sealed to form a bottomed bag shape, and the two openings 20 are arranged to face each other on the sides. to form the negative electrode case 2 . Each opening 20 is covered with the first porous film 5 from the inside to close the opening 20 from the inside of the negative electrode case 2 .

Next, the negative electrode current collector 3 , the negative electrode active material layer 4 and the anion conductive film 6 are inserted into the negative electrode case 2 . Since the first porous film 5 is interposed between the anion conductive film 6 and the negative electrode case 2 , the anion conductive film 6 can contact the opening 20 of the negative electrode case 2 and the positive electrode 8 . be prevented. As a result, the anion conductive film 6 can be placed in the negative electrode case 2 without damaging the anion conductive film 6, and the anion conductive film 6 can be sufficiently functioned.

Next, the negative electrode case 2 is housed in the battery case 9 and the positive electrode 8 is arranged between the negative electrode case 2 and the battery case 9 . Also, an electrolytic solution is injected into the negative electrode case 2 and the battery case 9 (between the inner surface of the battery case 9 and the outer surface of the negative electrode case 2), and the battery case 9 and the negative electrode case 2 are sealed by thermal fusion. As a result, the dendrite growth path can be cut off, making it possible to prevent short circuits between the electrodes.

The metal-air battery 10 can be applied to, for example, a zinc-air battery, a lithium-air battery, a sodium-air battery, a calcium-air battery, a magnesium-air battery, an aluminum-air battery, an iron-air battery, and the like. It can be suitably used for a zinc-air battery in which the negative electrode is a zinc species. Unlike lithium-air batteries, for example, zinc-air batteries do not require the use of flammable electrolytes (electrolytes), and can use alkaline electrolytes (electrolytes). be. In addition, the zinc-air battery has the advantage that the negative electrode can be manufactured at a lower cost than the lithium-air battery, so that it is easy to increase the capacity.

In this embodiment, a three-electrode metal-air secondary battery is exemplified as the metal-air battery 10, but the metal-air battery 10 is a primary battery and the positive electrode 82 for charging is omitted. may Moreover, the metal-air battery 10 may have a positive electrode that includes a catalyst having oxygen reducing ability and oxygen generating ability in the positive electrode and that can be used both during charging and during discharging.

(Embodiment 2)
FIG. 4 is a perspective view of the negative electrode 1 according to Embodiment 2. FIG. FIG. 5 is an enlarged cross-sectional view schematically showing the negative electrode 1 according to Embodiment 2, showing an enlarged view of a portion corresponding to part A1 in FIG. Since Embodiments 2 to 6 described below have the same basic configuration as Embodiment 1, configurations unique to each mode will be described in detail, and other configurations are common to Embodiment 1. , and description thereof will be omitted.

In Embodiment 1, the opening 20 provided in the negative electrode case 2 of the negative electrode 1 is covered with the first porous film 5 from the inside of the negative electrode case 2 . In Embodiment 2, the negative electrode 1 is further characterized in that the first porous film 5 covering the opening 20 from the inside of the negative electrode case 2 is welded to the negative electrode case 2 .

As shown in FIGS. 4 and 5, the opening 20 is covered with the first porous film 5 from the inside of the negative electrode case 2, and the negative electrode case 2 and the first porous film 5 are welded to form a welded region 23. is provided. The welding region 23 is provided along the periphery of the opening 20 in the negative electrode case 2 . In this welding region 23 , the first porous membrane 5 is fixed to the peripheral edge of the opening 20 and integrated with the negative electrode case 2 .

Since the negative electrode case 2 and the first porous film 5 are welded together in this manner, the anion conductive film 6 does not interfere with the opening 20 of the negative electrode case 2 when the anion conductive film 6 is arranged in the negative electrode case 2 . The anion conductive membrane 6 can be smoothly inserted. This not only improves the workability in manufacturing the negative electrode 1, but also prevents the anion conductive membrane 6 from being damaged.

In addition, since the welding region 23 is provided, the negative electrode case 2 and the first porous film 5 are closely arranged without a gap. This makes it possible to block the path for dendrites to grow toward the positive electrode 8, which is even more preferable in terms of preventing short circuits between the electrodes. In particular, when the first porous film 5 is welded to the negative electrode case 2 , the micropores of the first porous film 5 are closed in the vicinity of the welded region 23 . Therefore, in the welded region 23, the inside and outside of the negative electrode case 2 (negative electrode 1) are cut off, and the growth path of the dendrite can be blocked.

(Embodiment 3)
FIG. 6 is a cross-sectional view schematically showing the negative electrode 1 according to Embodiment 3, which corresponds to FIG. 1 in Embodiment 1. FIG. The negative electrode 1 according to Embodiment 3 is characterized by the anion conductive film 6, and other configurations are common to those of Embodiment 1 or 2.

As shown in FIG. 6 , the anion conductive film 6 is provided between the negative electrode active material layer 4 and the first porous film 5 so as to be in contact with the inner surface of the negative electrode case 2 . The anion-conducting membrane 6 is larger than the first porous membrane 5 covering the opening 20, and has a size that extends outward beyond the outer edges of the overlapping first porous membranes 5. ing.

As a result, the gap formed between the anion conductive film 6 and the negative electrode case 2 is smaller than that shown in FIG. Therefore, it is possible to lengthen the path along which the dendrite grows toward the positive electrode 8 and block it, which is more preferable in terms of preventing a short circuit between the electrodes.

6 shows a state in which the lower end of the anion conductive film 6 is in contact with the inner surface of the negative electrode case 2 and the upper end is not in contact with the inner surface of the negative electrode case 2. As shown in FIG. The arrangement form of the anion conductive film 6 in the negative electrode 1 is not limited to this. As long as the anion conductive film 6 has a size larger than that of the first porous film 5, the anion conductive film 6 can be in contact with the inner surface of the negative electrode case 2. is possible, and the form of contact between the negative electrode case 2 and the anion conductive film 6 may be any.

(Embodiment 4)
FIG. 7 is a cross-sectional view schematically showing the negative electrode 1 according to Embodiment 4, which corresponds to FIG. 1 in Embodiment 1. FIG. The negative electrode 1 according to Embodiment 4 further includes a second porous film 7 in addition to the structure shown in Embodiment 3. As shown in FIG.

As illustrated, the negative electrode 1 has a second porous film 7 between the anion conductive film 6 and the negative electrode active material layer 4 . Like the first porous membrane 5, the second porous membrane 7 may be a member having ion conductivity between the positive electrode 8 and the negative electrode 1. A member common to the porous membrane 5 can be used. The size and thickness of the second porous membrane 7 can also be the same as those of the first porous membrane 5 .

Since the second porous film 7 has a porous structure, it can be arranged inside the negative electrode case 2 to retain the electrolytic solution inside the negative electrode case 2 . In the metal-air battery 10 having such a negative electrode 1, the negative electrode active material layer 4 may expand or contract with charge/discharge cycles. It suppresses shortage of the electrolytic solution in the negative electrode active material layer 4 by being closely laminated.

In addition, the second porous film 7 is interposed between the negative electrode active material layer 4 and the anion conductive film 6, so that the anion conductive film 6 is on the opposite side of the first porous film 5, This prevents the anion conductive membrane 6 from being damaged. When dendrites grow from the negative electrode active material layer 4 toward the positive electrode 8, the second porous film 7 acts as a buffer layer between the negative electrode active material layer 4 and the anion conductive film 6, and the dendrites It prevents the anion conductive membrane 6 from being damaged.

(Embodiment 5)
FIG. 8 is a cross-sectional view schematically showing a metal-air battery 10 according to Embodiment 5. As shown in FIG. In the metal-air battery 10 according to Embodiment 1, the discharging positive electrode 81 is arranged on one side of the negative electrode 1 and the charging positive electrode 82 is arranged on the other side. In the metal-air battery 10 according to this embodiment, the discharging positive electrode 81 and the charging positive electrode 82 are arranged adjacent to each other. The negative electrode 1 of the metal-air battery 10 has the configuration shown in the fourth embodiment.

As shown in FIG. 8, the positive electrodes 8 constituting the metal-air battery 10 include a discharging positive electrode (air electrode) 81 which is a first positive electrode for discharging, and a charging positive electrode 82 which is a second positive electrode for charging. and Both of the discharging positive electrode 81 and the charging positive electrode 82 are arranged on both sides of the negative electrode 1 . A charging positive electrode 82 is arranged in contact with the opening 20 on one surface of the negative electrode case 2 of the negative electrode 1 , and a discharging positive electrode 81 is arranged adjacent to the charging positive electrode 82 . A discharge positive electrode 81 is arranged in contact with the inner surface of the battery case 9 from the inside. The other surface of the negative electrode case 2 is similarly provided.

Thus, in the metal-air battery 10, the negative electrode 1 is provided substantially in the center between the two discharge positive electrodes 81, and the charging positive electrode 82 is provided between the discharge positive electrode 81 and the negative electrode 1 (both sides of the negative electrode 1). 2 places). The metal-air battery 10 has a structure capable of suppressing the growth of dendrite in the negative electrode 1 and preventing a short circuit between electrodes.

Note that FIG. 8 shows the case where the negative electrode 1 in the metal-air battery 10 has the configuration shown in Embodiment 4 as an example, but the present invention is not limited to this, and negative electrodes 1 according to other forms are provided. good too. The metal-air battery 10 has a configuration in which a discharging positive electrode 81 and a charging positive electrode 8 are provided on one side of the negative electrode 1 in the battery case 9, and the discharging positive electrode 81, the charging positive electrode 82, and the negative electrode 1 are arranged in this order. As long as they are arranged, they may be configured in any way. Although not shown in FIG. 8 , a separator may be provided between the charging positive electrode 82 and the discharging positive electrode 81 to insulate the charging positive electrode 82 and the discharging positive electrode 81 .

(Embodiment 6)
FIG. 9 is a cross-sectional view schematically showing a metal-air battery 10 according to Embodiment 6. As shown in FIG. The arrangement form of the negative electrode 1, the discharging positive electrode 81, and the charging positive electrode 82 in the metal-air battery 10 is not limited to the form described above. The metal-air battery 10 according to this embodiment includes a negative electrode 1 having the structure shown in Embodiment 4, and a discharging positive electrode 81 on one side and a charging positive electrode 82 on the other side with the negative electrode 1 interposed therebetween. It is

As shown in FIG. 9, the negative electrode case 2 is provided with a first opening 21 and a second opening 22 on both sides of the negative electrode active material layer 4 in the thickness direction. As the positive electrode 8, a discharging positive electrode 81 as a first positive electrode and a charging positive electrode 82 as a second positive electrode are provided. 2, a charging positive electrode 82 is arranged facing the opening 22 of the second electrode.

Even with the metal-air battery 10 configured in this way, it is possible to suppress damage or breakage of the anion conductive film that causes dendrite growth in the negative electrode 1, and to prevent short circuits between the electrodes. can be

As described above, according to the negative electrode 1 and the metal-air battery 10 according to the present disclosure, the first porous film 5 is provided in the negative electrode case 2 and used as a buffer layer for the anion conductive film 6, so that the anion conductive film 6 is damaged. can be prevented from occurring. As a result, the negative electrode 1 and the metal-air battery 10 can prevent dendrite growth paths from occurring, prevent short circuits between the electrodes, and achieve longer life and higher output. .

The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments is also included in the technical scope of the present disclosure.

The negative electrode and metal-air battery according to the present disclosure can be widely used for metal-air batteries used as one of power supply devices.

Claims (14)

a resin case having at least one opening;
a negative electrode current collector including a portion housed in the case and a portion extending from the case;
a negative electrode active material layer contained in the case and containing a negative electrode active material in contact with at least part of the negative electrode current collector;
a first porous film covering the opening;
an anion conductive film disposed between the first porous film and the negative electrode active material layer ;
a welding region for welding the case and the first porous membrane;
has
The negative electrode, wherein the welding region is provided along a peripheral edge of the opening . In the negative electrode according to claim 1,
The negative electrode, wherein the opening is covered with the first porous film inside the case. 2. The negative electrode according to claim 1 , wherein the micropores of the porous film are closed in the vicinity of said welding region. In the negative electrode according to any one of claims 1 to 3 ,
The negative electrode, wherein the anion conductive film is in contact with the inner surface of the case. In the negative electrode according to any one of claims 1 to 4 ,
The negative electrode, wherein the anion conductive film is covered with the first porous film from the inside of the case and extends outward beyond the peripheral edge of the first porous film. In the negative electrode according to any one of claims 1 to 5 ,
The negative electrode, wherein the anion conductive membrane contains a polymer containing an anion exchange group or a layered double hydroxide. In the negative electrode according to any one of claims 1 to 6 ,
The negative electrode, wherein the anion conductive film suppresses permeation of zincate ions and allows permeation of hydroxide ions. In the negative electrode according to any one of claims 1 to 7 ,
The negative electrode, wherein the first porous film has an air permeability of 0.1 to 1000 seconds in Gurley value. In the negative electrode according to any one of claims 1 to 7 ,
The negative electrode, wherein the first porous film has a large number of interconnecting micropores, and the micropores have an average pore diameter of 0.1 to 100 μm. In the negative electrode according to any one of claims 1 to 9 ,
A negative electrode comprising a second porous film between the anion conductive film and the negative electrode active material layer. In the negative electrode according to any one of claims 1 to 10 ,
A negative electrode, wherein the case contains an electrolyte. A metal-air battery comprising a negative electrode, a positive electrode, and an electrolyte,
The negative electrode is
a resin case having at least one opening;
a negative electrode current collector housed in the case and extended from the case;
a negative electrode active material layer contained in the case and containing a negative electrode active material in contact with at least part of the negative electrode current collector;
a first porous film covering the opening;
an anion conductive film disposed between the first porous film and the negative electrode active material layer ;
a welding region for welding the case and the first porous membrane;
with
The positive electrode is arranged to face the opening ,
The metal-air battery , wherein the welding region is provided along the peripheral edge of the opening . In the metal-air battery of claim 12 ,
The positive electrode comprises a first positive electrode for discharging and a second positive electrode for charging,
A metal-air battery, wherein the first positive electrode, the second positive electrode, and the negative electrode are arranged in this order. In the metal-air battery of claim 12 ,
As the openings, a first opening and a second opening are provided on both sides in the thickness direction of the negative electrode active material layer,
The positive electrode includes a first positive electrode for discharging and a second positive electrode for charging,
A metal-air battery, wherein the first positive electrode is arranged to face the first opening, and the second positive electrode is arranged to face the second opening.

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