JP2014194897A - Separator, secondary battery and method of manufacturing separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the metal deposit of a negative electrode from penetrating a separator to cause short circuit of a negative electrode and a positive electrode.SOLUTION: A separator 41 arranged between the negative electrode 3 and the positive electrode 2 in a metal-air battery 1 has a separator body 411 that is a porous support formed of ceramic, and a porous film 412 formed of ceramic on a surface facing the negative electrode 3 in the separator body 411. Average pore diameter of the porous film 412 is 0.01-2 μm, and smaller than that of the separator body 411. Thickness of the porous film 412 is 50-200 μm. Consequently, the metal deposit of the negative electrode 3 can be prevented from penetrating the separator 41 to cause short circuit of the negative electrode 3 and positive electrode 2.

Description

  The present invention relates to a separator disposed between a negative electrode and a positive electrode in a secondary battery in which metal is deposited at the time of charging, a method for manufacturing the separator, and a secondary battery having the separator. .

  Conventionally, a secondary battery in which a separator is disposed between a positive electrode and a negative electrode is known. For example, in the lithium secondary battery in Patent Document 1, the separator includes a porous film formed of a ceramic material and a binder, and the binder is made of an acrylic rubber having a three-dimensional crosslinked structure. With the technique of Patent Document 1, a lithium secondary battery excellent in safety such as short-circuit resistance and heat resistance is realized. Patent Document 2 discloses a technique for obtaining a porous film having excellent mechanical strength by providing a breathable surface protective layer containing inorganic fine particles on one or both sides of a film having a porous structure. The porous membrane can be used as a separator for a non-aqueous electrolyte battery. Patent Documents 3 and 4 describe ceramic forming techniques.

JP 2006-310302 A Japanese Patent Laid-Open No. 11-80395 JP 2004-338363 A JP 2005-66958 A

  By the way, in a secondary battery in which metal is deposited at the negative electrode during charging, the metal may be deposited in powder or particulate form depending on the shape of the negative electrode, the current density during charging, and the like. In this case, even when a separator having a porous structure is used, the deposited metal of the negative electrode may penetrate the separator and the negative electrode and the positive electrode may be short-circuited.

  This invention is made | formed in view of the said subject, and it aims at preventing the deposit metal of a negative electrode penetrating a separator and short-circuiting a negative electrode and a positive electrode.

  The invention according to claim 1 is a separator disposed between the negative electrode and the positive electrode in a secondary battery in which metal is deposited at the negative electrode during charging, and is a porous support formed of ceramic A separator body that is a body, and a porous film that is formed of ceramic on a surface of the separator body that faces the negative electrode, and that has an average pore diameter smaller than the average pore diameter of the separator body. The average pore diameter is 0.01 micrometers or more and 2 micrometers or less, and the thickness of the porous film is 50 micrometers or more and 200 micrometers or less.

  The invention according to claim 2 is the separator according to claim 1, wherein the porous film is a laminated film in which a plurality of films are laminated.

  The invention according to claim 3 is the separator according to claim 1 or 2, wherein the porous film includes at least one of silica, alumina, zirconia, titania and hafnia.

  The invention according to claim 4 is the separator according to any one of claims 1 to 3, wherein the separator body has a porosity of 30% or more and 80% or less.

  Invention of Claim 5 is a separator in any one of Claim 1 thru | or 4, Comprising: The said separator main body is cylindrical, In the said separator main body, it covers the perimeter of the surface facing the said negative electrode. Thus, the porous film is formed.

  The invention according to claim 6 is a secondary battery comprising a positive electrode, a negative electrode on which a metal is deposited upon charging, and an electrolyte layer disposed between the negative electrode and the positive electrode. The layer has the separator according to any one of claims 1 to 5, and the separator is filled with an electrolytic solution.

  The invention according to claim 7 is a method of manufacturing a separator disposed between the negative electrode and the positive electrode in a secondary battery in which metal is deposited at the negative electrode during charging, and is formed of a) ceramic. B) preparing a separator body as a porous support, and b) forming a porous film having an average pore diameter smaller than the average pore diameter of the separator body on a surface of the separator body facing the negative electrode. The average pore diameter of the porous membrane is 0.01 micrometers or more and 2 micrometers or less, and the thickness of the porous film is 50 micrometers or more and 200 micrometers or less is there.

  Invention of Claim 8 is a manufacturing method of the separator of Claim 7, Comprising: The said b) process forms one film | membrane by sintering ceramic particle | grains on the said surface of the said separator main body. And b2) forming another film on the surface of the one film by sintering ceramic particles.

  The invention according to claim 9 is the method for producing the separator according to claim 7 or 8, wherein the porous film is a ceramic particle having an average particle size of 0.1 micrometers or more and 30 micrometers or less. Formed by ligation.

  According to the present invention, it is possible to prevent the deposited metal of the negative electrode from penetrating the separator and short-circuiting the negative electrode and the positive electrode.

It is a figure which shows the structure of a metal air battery. It is a figure which shows the flow of the process which manufactures a separator. It is a figure which shows the result of the evaluation test of overcharge stability. It is a photograph which shows the cross section of the separator of a comparative example. It is a photograph which shows the cross section of the separator of a comparative example. It is a photograph which shows the outer surface of the separator of a comparative example. It is a photograph which shows the inner surface of the separator of a comparative example. It is a photograph which shows the cross section of a separator. It is a photograph which shows the inner surface of a separator. It is a figure which shows the result of the evaluation test of cycle durability.

  FIG. 1 is a diagram showing a configuration of a metal-air battery 1 according to an embodiment of the present invention. The main body 11 of the metal-air battery 1 has a substantially cylindrical shape centered on the central axis J1, and FIG. 1 shows a cross section of the main body 11 on a plane including the central axis J1. The metal-air battery 1 is a secondary battery that includes a positive electrode 2, a negative electrode 3, and an electrolyte layer 4.

  The negative electrode 3 (also referred to as a metal electrode) is a coiled member centered on the central axis J1. The negative electrode 3 in the present embodiment has a shape in which a linear member having a substantially circular cross section is spirally wound around the central axis J1. As shown in FIG. 1, the negative electrode 3 includes a coil-shaped base material 31 formed of a conductive material, and a powdered or particulate deposited metal layer 32 formed on the surface of the base material 31. As shown in FIG. 1, a negative electrode current collector terminal 33 is connected to the end of the negative electrode 3 in the direction of the central axis J1.

  As a material for forming the substrate 31, a metal such as copper (Cu), nickel (Ni), silver (Ag), gold (Au), iron (Fe), aluminum (Al), magnesium (Mg), or any An alloy containing such a metal is exemplified. In the present embodiment, the base material 31 is formed of copper. From the viewpoint of increasing the conductivity of the base material 31 also serving as a current collector, the base material 31 preferably contains copper or a copper alloy. When the main body of the base material 31 is formed of copper, it is preferable that a protective film of another metal such as nickel or zinc is formed on the surface of the main body. In this case, the surface of the base material 31 is the surface of the protective film. For example, the thickness of the protective film is 1 to 20 μm (micrometer), and the protective film is formed by plating. The deposited metal layer 32 is formed by electrolytic deposition of zinc (Zn). The deposited metal layer 32 may be formed by electrolytic deposition of a metal other than zinc.

  A cylindrical separator 41 is provided around the negative electrode 3, and a cylindrical positive electrode 2 (also referred to as an air electrode) is provided around the separator 41. That is, the inner surface of the separator 41 faces the negative electrode 3, and the outer surface of the separator 41 faces the inner surface of the positive electrode 2. The negative electrode 3, the separator 41, and the positive electrode 2 are provided concentrically with the central axis J1 as the center, and when viewed along the central axis J1, the distance between the outer edge of the negative electrode 3 and the positive electrode 2 is the central axis. It is constant over the entire circumference in the circumferential direction centered on J1. That is, between the negative electrode 3 and the positive electrode 2 in the metal-air battery 1, the equipotential surface has a constant interval (there is no density of the interval) over the entire circumference in the circumferential direction, and a uniform current distribution occurs. . If the current distribution over the entire circumference in the circumferential direction can be considered to be approximately uniform, the shape of the positive electrode 2 is a regular polygon (for example, a regular polygon having six or more vertices). Also good.

The separator 41 includes a separator body 411 that is a porous cylindrical support formed of ceramic, and a porous film 412 that is formed on the inner surface of the separator body 411 facing the negative electrode 3. The separator body 411 is made of a ceramic having high mechanical strength and insulating properties such as silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ), and hafnia (Hf ₂ O). It is formed. In the present embodiment, the separator body 411 is a ceramic sintered body (that is, integrally molded), and is composed only of ceramic. The separator body 411 may be a mixture or laminate of these ceramics, and zirconia is preferably used on the surface from the viewpoint of stability. The thickness of the cylindrical separator body 411 is, for example, 0.5 to 4 millimeters (mm).

  The average pore diameter of the separator body 411 may be within a range in which liquid retention, ionic conductivity, and air permeability that do not inhibit the battery reaction are ensured. As will be described later, in consideration of operability when the porous film 412 is formed on the surface of the separator body 411, the average pore diameter of the separator body 411 is preferably 15 μm or less. For the measurement of the average pore diameter, various methods such as measurement using a porosimeter and measurement using an electron microscope can be used.

In addition, the porosity of the separator body 411 is preferably 30 percent (%) or more, whereby a desired gas permeation amount, liquid permeation amount, replacement fluid amount, etc. can be easily realized. Moreover, it is preferable that the porosity of the separator main body 411 is 80% or less, and thereby, a certain mechanical strength in the separator main body 411 is ensured. Here, the porosity is an occupancy ratio of a void area in a cross section when the separator body 411 is cut by a plane including the central axis J1 or a plane perpendicular to the central axis J1. Represents porosity. The porosity is calculated by observing the cross section of the separator body 411 with an electron microscope and measuring the area of the void. The gas permeation amount in the separator 41 is preferably 350 m ³ / (m ² × hr × atm) or more.

  The porous film 412 is formed of ceramic, and in the present embodiment, the porous film 412 is a ceramic sintered body like the separator body 411. Specifically, the porous film 412 (in the case of a laminated film described later, each film of the laminated film) is composed of at least one of ceramics having high mechanical strength and insulating properties such as silica, alumina, zirconia, titania, and hafnia. It is preferable that one ceramic is included, and more preferably, the porous membrane 412 is composed only of ceramic.

  The porous membrane 412 has an average pore diameter that is smaller than the average pore diameter of the separator body 411. Specifically, the average pore diameter of the porous membrane 412 is 0.01 μm or more and 2 μm or less (more preferably 1 μm or less), and the powdered or particulate deposited metal generated in the negative electrode 3 during charging described later is used. It is smaller than the average particle size (for example, 20 to 30 μm). The thickness of the porous membrane 412 is 50 μm or more (more preferably 70 μm or more) and 200 μm or less. When the thickness of the porous film 412 is 200 μm or less, the metal-air battery 1 can easily ensure predetermined air permeability, liquid retention, energy density, interelectrode resistance, and the like. Moreover, when the thickness of the porous film 412 is 50 μm or more, the deposited metal of the negative electrode 3 is prevented from penetrating the porous film 412 as described later. The film thickness of the porous film 412 is measured by an electron microscope or masks a part of an unnecessary area when the porous film 412 is formed, and the level difference between the area and the porous film 412 is measured with a step meter. Can be obtained.

  Preferably, the porous film 412 is a laminated film in which a plurality of films are laminated. Also in this case, each film is formed by sintering ceramic particles and has porosity. From the viewpoint of stability, zirconia is preferably used for forming the ceramic film on the surface. In the metal-air battery 1, the porous membrane 412 is formed over the entire circumference of the surface facing the negative electrode 3 in the cylindrical separator body 411. From the viewpoint of preventing the porous film 412 from being damaged by the deposited metal generated in the negative electrode 3 during charging, which will be described later, the Vickers hardness of the ceramic forming the porous film 412 is preferably 100 HV or more. Preferably it is 500HV or more.

  From the viewpoint of suppressing peeling and cracking of the porous film 412, the types of ceramics that form the separator body 411 and the porous film 412 so that the difference in thermal expansion coefficient between the separator body 411 and the porous film 412 is reduced. Is selected. For example, when the separator body 411 is made of alumina, the thermal expansion coefficient is 0.2% or less at 200 ° C., 0.05% or more and 0.4% or less at 400 ° C., and 0.1% at 600 ° C. It is preferable that a ceramic that is not less than 0.65% and not less than 0.2% and not more than 1% at 800 ° C. is used for forming the porous film 412.

  A space on the inner side (center axis J1 side) of the cylindrical positive electrode 2 is filled with an aqueous electrolyte solution 40. About the entire negative electrode 3 is immersed in the electrolytic solution 40. The electrolyte solution 40 is also filled in the pores of the separator 41 which is a porous member. In the following description, the space between the negative electrode 3 and the positive electrode 2 when viewed along the central axis J1 is referred to as “electrolyte layer 4”. That is, the electrolyte layer 4 is a space disposed between the negative electrode 3 and the positive electrode 2. In the present embodiment, the electrolyte layer 4 includes a separator 41. The electrolytic solution 40 is an alkaline aqueous solution, and preferably includes a potassium hydroxide (caustic potash, KOH) aqueous solution or a sodium hydroxide (caustic soda, NaOH) aqueous solution. Moreover, it is preferable that the electrolyte solution 40 contains zinc oxide in high concentration. The electrolytic solution 40 may be other aqueous electrolytic solution, non-aqueous (for example, organic solvent type) or ionic liquid type electrolytic solution.

  The positive electrode 2 includes a porous positive electrode conductive layer 21. A positive electrode catalyst is supported on the outer surface of the cylindrical positive electrode conductive layer 21 to form a positive electrode catalyst layer 22. Around the positive electrode catalyst layer 22, for example, a metal mesh sheet of nickel or the like is wound to form a current collecting layer 23. A positive current collecting terminal 24 is provided at an end of the current collecting layer 23 in the central axis J1 direction. Connected. Actually, since the positive electrode catalyst is dispersed in the vicinity of the outer surface of the positive electrode conductive layer 21 and is not formed as a clear layer, the current collecting layer 23 is also partially formed on the outer surface of the positive electrode conductive layer 21. Touch. An interconnector that contacts only a part of the outer surface of the positive electrode conductive layer 21 may be provided as the current collecting layer 23.

  A material having water repellency (for example, PFA (perfluoroalkoxy) is used on the outer surface of the current collecting layer 23 (including a portion of the outer surface of the positive electrode catalyst layer 22 not covered with the mesh-shaped current collecting layer 23). A porous layer made of alkane) or PTFE (polytetrafluoroethylene) is formed as the liquid repellent layer 29.

From the viewpoint of preventing deterioration due to oxidation during charging, which will be described later, it is preferable that the positive electrode conductive layer 21 does not contain conductive carbon. In the present embodiment, the positive electrode conductive layer 21 is a perovskite oxide having conductivity. It is a porous thin conductive film mainly formed of a material (for example, LSMF (LaSrMnFeO ₃ )).

The positive electrode catalyst layer 22 is formed of a catalyst that promotes an oxygen reduction reaction, and metal oxides such as manganese (Mn), nickel (Ni), and cobalt (Co) are exemplified as the catalyst. In the present embodiment, the positive electrode catalyst layer 22 is formed of manganese dioxide (MnO ₂ ) preferentially supported on the positive electrode conductive layer 21. In principle, in the metal-air battery 1, an interface between air and the electrolytic solution 40 is formed in the vicinity of the porous positive electrode catalyst layer 22.

  As shown in FIG. 1, disc-shaped closing members 51 are fixed to both end faces (upper end face and lower end face in FIG. 1) of the negative electrode 3, the electrolyte layer 4, and the positive electrode 2 in the direction of the central axis J <b> 1. A through hole 511 is provided at the center of each closing member 51. In the metal-air battery 1, the liquid repellent layer 29 and the closing member 51 prevent the electrolytic solution 40 in the main body 11 from leaking outside the through hole 511.

  One end of the supply pipe 61 is connected to the through hole 511 of one closing member 51, and the other end of the supply pipe 61 is connected to the supply / recovery unit 6. One end of the recovery pipe 62 is connected to the through hole 511 of the other closing member 51, and the other end of the recovery pipe 62 is connected to the supply / recovery unit 6. The supply / recovery unit 6 includes an electrolytic solution storage tank and a pump, and recovers the electrolytic solution 40 in the main body 11 to the storage tank at a flow rate (volume per unit time) instructed by a control unit (not shown). At the same time, the electrolytic solution in the storage tank can be supplied to the main body 11 at the same flow rate. That is, the electrolytic solution can be circulated between the main body 11 and the storage tank of the supply and recovery unit 6. The supply and recovery unit 6 is provided with a filter, and unnecessary substances contained in the electrolytic solution are removed by the filter when the electrolytic solution is circulated.

  In the metal-air battery 1 according to the present embodiment, the central axis J1 of the main body 11 is parallel to the vertical direction (gravity direction), and the through hole 511 connected to the recovery pipe 62 is a through hole connected to the supply pipe 61. It is located vertically below 511. The supply pipe 61 and the recovery pipe 62 are provided with a supply valve and a recovery valve (not shown). In normal operation in this operation example, the electrolyte solution is circulated at a constant flow rate. The supply valve and the recovery valve can be regarded as a part of the supply recovery unit 6. The central axis J1 of the metal-air battery 1 does not necessarily need to be parallel to the vertical direction. For example, the metal-air battery 1 may be arranged so that the central axis J1 is parallel to the horizontal direction.

  When discharging is performed in the metal-air battery 1 of FIG. 1, the negative electrode current collecting terminal 33 and the positive electrode current collecting terminal 24 are electrically connected via a load (for example, a lighting fixture). The metal contained in the negative electrode 3 is oxidized to generate metal ions, and the electrons are supplied to the positive electrode 2 through the negative electrode current collector terminal 33 and the positive electrode current collector terminal 24. In the porous positive electrode 2, oxygen in the air that has passed through the liquid repellent layer 29 is reduced by the electrons supplied from the negative electrode 3 and is eluted into the electrolyte as hydroxide ions. In the positive electrode 2, the reduction reaction of oxygen is promoted by the positive electrode catalyst.

  On the other hand, when charging is performed in the metal-air battery 1, a voltage is applied between the negative electrode current collector terminal 33 and the positive electrode current collector terminal 24, and electrons are supplied from the hydroxide ions to the positive electrode 2. At the same time, oxygen is generated. In the negative electrode 3, metal ions are reduced by electrons supplied to the negative electrode current collector terminal 33 via the current collector layer 23 and the positive electrode current collector terminal 24, and metal (here, zinc) is deposited on the surface.

  At this time, since the coiled negative electrode 3 has no corners, electric field concentration is less likely to occur (there is no large current density bias). Further, the negative electrode 3 is in uniform contact with the electrolytic solution 40. As a result, the generation and growth of dendrites in which the metal precipitates in a dendritic shape and whiskers in which the metal precipitates in a whisker shape (needle shape) are significantly suppressed. Actually, powdery or particulate metal is uniformly deposited on almost the entire surface of the negative electrode 3 to form a powdery or particulate deposited metal layer 32 (or the deposited metal layer 32 becomes thicker). ). In the positive electrode 2, the generation of oxygen is promoted by the positive electrode catalyst contained in the positive electrode catalyst layer 22.

  As described above, in the metal-air battery 1, the electrolyte solution is circulated by the supply and recovery unit 6, and the electrolyte solution 40 in the vicinity of the lower through hole 511 (hereinafter also referred to as “lower through hole 511”). Is recovered from the lower through-hole 511. A part of the electrolytic solution 40 supplied into the main body 11 from the upper through hole 511 (hereinafter also referred to as “upper through hole 511”) is a gap between the coiled negative electrode 3 (the negative electrode 3 shown in FIG. 1). In the cross section, the electrolyte layer 4 (the separator 41) also diffuses through the vertical portions between the circular portions separated from each other. Thereby, the electrolytic solution 40 contained in the electrolyte layer 4 is replaced with the electrolytic solution in the storage tank of the supply and recovery unit 6 while discharging or charging in the metal-air battery 1.

  In the metal-air battery 1, the operation of sequentially collecting the predetermined amount of electrolyte from the lower through-hole 511 and supplying the same amount of electrolyte from the upper through-hole 511 may be repeated. Thereby, the electrolytic solution 40 in the main body 11 is replaced with the electrolytic solution in the storage tank of the supply and recovery unit 6 while discharging or charging. It is also possible to intermittently replace the electrolyte. For example, after the electrolytic solution is circulated for a predetermined time, the supply valve and the recovery valve are closed, and the recovery and supply of the electrolytic solution are stopped until the diffusion of the new electrolytic solution reaches an equilibrium state. Thereby, the replacement of the electrolytic solution 40 in the main body 11 (mixing of the deteriorated electrolytic solution and a new electrolytic solution) is performed while discharging or charging. Of course, the discharging or charging may be stopped and the electrolytic solution 40 in the main body 11 may be replaced.

Next, a flow of processing for manufacturing the separator 41 will be described with reference to FIG. In the manufacture of the separator 41, first, a separator body 411 that is a porous support formed of ceramic is prepared (step S11). As described above, the separator body 411 is formed by sintering ceramic particles. The molded body of the separator body 411 can be molded by any molding method such as an extrusion molding method, a cold isostatic pressing method, a hot isostatic pressing method, and the like, for example, Japanese Patent Application Laid-Open No. 2004-338363 (patent) The molding technique described in Document 3) and Japanese Patent Application Laid-Open No. 2005-66958 (Patent Document 4) is used. At this time, by selecting an appropriate die, the cross-sectional shape perpendicular to the central axis of the molded body can be an arbitrary shape such as a circle, an ellipse, a triangle, a quadrangle, a hexagon, and an octagon. The sintering temperature and sintering time in the firing of the molded body are such that the sintering proceeds throughout, and a predetermined gas permeation amount (for example, 3000 m ³ / (m ² × hr × atm)) and an average pore diameter. Conditions for obtaining a separator body 411 (for example, 10 μm) are employed. In the present embodiment, the sintering temperature is 1000 to 1500 ° C., and the sintering time is 10 hours.

  When the separator body 411 is prepared, a ceramic film is formed on the (planned) inner surface facing the negative electrode 3 in the separator body 411 (step S12). Specifically, first, ceramic particles, a solvent, and a binder are mixed to produce a dispersion liquid in a uniform dispersion state. The ceramic particles are silica, alumina, zirconia, titania or hafnia. The average particle size of the ceramic particles is, for example, 0.02 μm or more and 50 μm or less, and preferably 0.1 μm or more and 30 μm or less. More preferably, only ceramic particles having a particle size falling within the above range are used. The particle shape of the ceramic particles may be anything.

  Solvents for adjusting the dispersion include water, alcohols such as methanol, ethanol, isopropyl alcohol and diethylene glycol, cellosolves such as methyl cellosolve, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and isophorone, N, N Examples include amides such as dimethylformamide, esters such as ethyl acetate and butyl acetate, ethers such as dioxane, chlorinated solvents such as chloroform, and aromatic hydrocarbons such as toluene and xylene. These solvents can be used alone or in admixture of two or more. The amount of the solvent added is not particularly limited as long as it does not affect the operability and film forming property, but from the viewpoint of shortening the drying treatment time, it is 500 g or less with respect to 100 g (g) of ceramic particles. It is preferable that

  As the binder resin for adjusting the dispersion, both aqueous and non-aqueous binders can be used, and various known binders may be used. Specific examples of the binder resin used in the present embodiment include cellulose resins such as methyl cellulose and ethyl cellulose, acrylic resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer polyolefin, polymethyl methacrylate, and polybutyl methacrylate. Styrene resin such as polystyrene, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polyether, polyvinyl alcohol, or a copolymer thereof. These binder resins may be used alone or in combination of two or more. Can be mixed and used. The amount of the binder added is not particularly limited as long as it does not affect the operability and film forming property, but is preferably 500 g or less with respect to 100 g of ceramic particles from the viewpoint of shortening the time required for degreasing. .

  The dispersion is applied to the inner surface of the separator body 411, and a film of the dispersion is uniformly formed on the entire inner surface. Depending on the design of the metal-air battery 1, a dispersion film may be formed on the outer surface of the separator body 411. When a plate-like separator body is used, a dispersion film is formed on one main surface of the separator body. In the formation of the dispersion liquid film in the separator body, an appropriate film forming method (for example, a casting method, a dipping method, a spray method, etc.) according to the size and shape of the separator body is appropriately selected. From the viewpoint of easily forming a dispersion film, it is preferable to use a dipping method.

  The sintering temperature and sintering time in the firing of the dispersion film are such that the sintering proceeds throughout and the average pore diameter of the ceramic film obtained by firing is 0.01 μm or more and 2 μm or less. Adopted. In the present embodiment, the sintering temperature is 1000 to 1500 ° C., and the sintering time is 10 hours. Thus, a ceramic film is formed on the inner surface of the separator body 411 by sintering the ceramic particles. In addition, before a baking process, a drying process (baking) may be performed as needed, and the solvent etc. in the film | membrane of a dispersion liquid may be removed.

  When the ceramic film is used as a lower layer film and another ceramic film is further formed on the lower layer film (step S13), the step S12 is repeated, and another ceramic film is formed on the surface of the lower layer film with the lower layer film. It is formed by sintering the same type or other types of ceramic particles. At this time, the particle size of the ceramic particles used for forming the other ceramic film is preferably smaller than the particle size of the ceramic particles used for forming the lower layer film, so that the pore size of the separator body 411 is compared. Even in the case of a relatively large size, it becomes possible to easily form a ceramic film having a small average pore diameter. The process of step S12 is repeated as many times as necessary (step S13), and a laminated film in which a plurality of ceramic films are laminated is formed as the porous film 412. When the process of step S12 is performed only once, the porous film 412 becomes a single-layer film of one ceramic film. The separator 41 is manufactured by the above processing.

  Next, Examples 1 to 8 relating to the production of the separator and evaluation tests (overcharge stability and cycle durability evaluation tests) of the separators produced in Examples 1 to 8 will be described. The separator manufactured in the following examples is an example, and the separator may be manufactured by other processing.

Example 1
3 parts of Solmix (registered trademark) H-37 (manufactured by Nippon Alcohol Sales Co., Ltd.), 1 part of 2- (2-n-butoxyethoxy) ethyl acetate (manufactured by Kanto Chemical Co., Ltd.), ethyl cellulose (manufactured by Tokyo Chemical Industry Co., Ltd.) ) 0.14 part was mixed and stirred, and 1.28 parts of alumina powder (manufactured by Showa Denko KK, trade name: A-42-6) was further mixed and stirred to prepare a dispersion for a ceramic membrane. .

A cylindrical porous alumina support having an outer diameter of 16 mm, an inner diameter of 12 mm, and a length of 300 mm was prepared as a separator body. The average pore diameter of the separator main body was 10 μm, and the gas permeation amount was 3173 m ³ / (m ² × hr × atm). The lower end of the separator body was sealed with a cap member, and the dispersion was poured from the upper end into the separator body until the liquid level was positioned near the upper end, and held for 1 minute. And the cap member was removed and the dispersion liquid in a separator main body was collect | recovered. In this way, a dispersion film was formed on the inner surface of the separator body. The separator body was left to dry at room temperature for 20 hours, and then dried at 50 ° C. for 3 hours. Thereafter, the separator body was fired at 1450 ° C. for 4 hours to obtain a separator body having a porous ceramic film formed of alumina on the inner surface. The film thickness of the ceramic film, which is a porous film, was 50 μm, and the average pore diameter was 2.0 μm. Moreover, the gas permeation amount of the separator composed of the ceramic membrane and the separator main body was 2117 m ³ / (m ² × hr × atm).

(Example 2)
3 parts of Solmix (registered trademark) H-37 (manufactured by Nippon Alcohol Sales Co., Ltd.), 1 part of 2- (2-n-butoxyethoxy) ethyl acetate (manufactured by Kanto Chemical Co., Ltd.), ethyl cellulose (manufactured by Tokyo Chemical Industry Co., Ltd.) ) 0.11 part was mixed and stirred, and 0.8 part of zirconia powder (manufactured by Tosoh Corporation, trade name: TZ-0) was further mixed and stirred to prepare a dispersion for a ceramic film.

Subsequently, the separator produced in Example 1 was treated in the same manner as in Example 1 using the zirconia dispersion, thereby forming a dispersion film on the ceramic film on the inner surface of the separator body. . After performing a drying process in the same manner as in Example 1, the separator body was fired at 1000 ° C. for 4 hours to obtain a separator body having a laminated film on the inner surface. The laminated film is formed by laminating a porous ceramic film formed of alumina and a porous ceramic film formed of zirconia. The thickness of the laminated film, which is a porous film, was 68 μm, and the average pore diameter was 0.3 μm. Moreover, the gas permeation amount of the separator constituted by the laminated film and the separator main body was 1065 m ³ / (m ² × hr × atm).

(Example 3)
The separator manufactured in Example 2 was again subjected to the same treatment as in Example 2 to obtain a separator main body having a laminated film on the inner surface. The laminated film includes a porous ceramic film formed of alumina, a zirconia porous ceramic film formed by one baking process, and a zirconia porous ceramic film formed by another baking process. Are laminated. The film thickness of the laminated film, which is a porous film, was 84 μm, and the average pore diameter was 0.1 μm. Moreover, the gas permeation amount of the separator constituted by the laminated film and the separator main body was 373 m ³ / (m ² × hr × atm).

Example 4
The separator manufactured in Example 1 was again subjected to the same treatment as in Example 1 to obtain a separator body having a laminated film on the inner surface. The laminated film is formed by laminating an alumina porous ceramic film formed by one firing process and an alumina porous ceramic film formed by another firing process. The film thickness of the laminated film, which is a porous film, was 98 μm, and the average pore diameter was 1.5 μm. Moreover, the gas permeation amount of the separator constituted by the laminated film and the separator main body was 1534 m ³ / (m ² × hr × atm).

(Example 5)
A dispersion similar to the dispersion prepared in Example 1 and a separator main body (no ceramic film formed) similar to the separator main body used in Example 1 were prepared, and the upper end of the separator main body and The lower end was sealed with a cap member. And the separator main body was immersed in the dispersion liquid stored in the container, held for 1 minute, and then the separator main body was pulled up. The separator body was immersed in the dispersion liquid in 2 seconds, and the separator was pulled up from the dispersion liquid in 6 seconds. In this way, a dispersion film was formed on the outer surface of the separator body. The separator body was left to dry at room temperature for 20 hours, and then dried at 50 ° C. for 3 hours. Thereafter, the separator body was fired at 1450 ° C. for 4 hours to obtain a separator body having a porous ceramic film formed of alumina on the outer surface. The film thickness of the ceramic film, which is a porous film, was 53 μm, and the average pore diameter was 2.0 μm. Moreover, the gas permeation amount of the separator composed of the ceramic membrane and the separator main body was 2117 m ³ / (m ² × hr × atm).

(Example 6)
A zirconia dispersion similar to the dispersion prepared in Example 2 was prepared. Subsequently, the separator produced in Example 5 was treated in the same manner as in Example 5 using the zirconia dispersion, thereby forming a dispersion film on the ceramic film on the outer surface of the separator body. . After performing a drying process in the same manner as in Example 5, the separator body was baked at 1000 ° C. for 4 hours to obtain a separator body having a laminated film on the outer surface. The laminated film is formed by laminating a porous ceramic film formed of alumina and a porous ceramic film formed of zirconia. The thickness of the laminated film, which is a porous film, was 65 μm, and the average pore diameter was 0.4 μm. Moreover, the gas permeation amount of the separator constituted by the laminated film and the separator main body was 1346 m ³ / (m ² × hr × atm).

(Example 7)
The separator manufactured in Example 6 was again subjected to the same treatment as in Example 6 to obtain a separator body having a laminated film on the outer surface. The laminated film includes a porous ceramic film formed of alumina, a zirconia porous ceramic film formed by one baking process, and a zirconia porous ceramic film formed by another baking process. Are laminated. The film thickness of the laminated film, which is a porous film, was 81 μm, and the average pore diameter was 0.1 μm. Moreover, the gas permeation amount of the separator composed of the laminated film and the separator main body was 361 m ³ / (m ² × hr × atm).

(Example 8)
The separator produced in Example 5 was again subjected to the same treatment as in Example 5 to obtain a separator body having a laminated film on the outer surface. The laminated film is formed by laminating an alumina porous ceramic film formed by one firing process and an alumina porous ceramic film formed by another firing process. The film thickness of the laminated film, which is a porous film, was 103 μm, and the average pore diameter was 1.6 μm. Moreover, the gas permeation amount of the separator constituted by the laminated film and the separator main body was 1621 m ³ / (m ² × hr × atm).

(Overcharge stability evaluation test)
The overcharge stability of the separators produced in Examples 1 to 8 was evaluated. Here, the separator body on which the ceramic film was not formed was prepared as a separator for a comparative example. In the overcharge stability evaluation test, a coiled zinc electrode (negative electrode 3) similar to that shown in FIG. 1 and a zinc pipe having a diameter of 24 mm, a length of 100 mm, and a thickness of 2 mm were prepared. Moreover, the container which stores only 2L of 7M potassium hydroxide aqueous solution containing 0.65M (mol / L) zinc oxide was prepared. In a potassium hydroxide aqueous solution, a coiled zinc electrode is disposed concentrically with the separator in a cylindrical separator, and the zinc pipe is concentric with the separator so that the inner surface of the zinc pipe faces the outer surface of the separator. Arranged. The distance between the separator and the coiled zinc electrode having an outer diameter (coil diameter) of 8 mm is 2 mm, and the distance between the separator and the zinc pipe is 4 mm.

For the separators of Examples 1 to 4 in which the ceramic film was formed on the inner surface of the separator body and the separator of the comparative example in which the ceramic film was not formed, the coiled zinc electrode was the cathode electrode (that is, zinc was deposited). The power source terminal of the power source (manufactured by Yamamoto Metal Testing Co., Ltd., model number: YPP15101C) was connected to the coiled zinc electrode and the zinc pipe. For the separators of Examples 5 to 8 in which the ceramic film is formed on the outer surface of the separator body, the power supply terminal of the power supply is connected to the zinc pipe and the coiled zinc electrode so that the zinc pipe becomes a cathode electrode. did. Then, electrolytic deposition was performed at a current density of 150 mA / cm ² for 1 to 10 hours, and the separator after electrolytic deposition was observed.

  FIG. 3 is a diagram showing the result of confirming whether or not the deposited metal (zinc) leached into the separator in the cathode electrode. In FIG. 3, in the leftmost column, the number of the example relating to the manufacture of the separator (or a comparative example) is written, and in the column labeled “Leaching into Separator”, the presence or absence of the leaching of the deposited metal is shown. Show. ○ indicates that no leaching of the deposited metal into the separator (a portion between the inner surface and the outer surface) at the cathode electrode was confirmed, and △ indicates that the deposited metal leached into the separator. Indicates that the deposited metal did not penetrate the separator, and x indicates that the deposited metal penetrated the separator. In FIG. 3, the surface on which the ceramic film is formed in the separator main body is indicated in the column indicated as “film formation surface” in the column heading, and is directly formed on the separator main body in the row indicated as “first layer material” in the column heading. The material of the ceramic membrane is shown. When a ceramic film is laminated on the ceramic film, the material of the second-layer ceramic film is shown in the column labeled “Second-layer material” in the column header, and “third-layer material” is listed in the column header. In the column shown, the material of the third layer ceramic film is shown. FIG. 3 also shows the film thickness and average pore diameter of a porous film that is a single layer film of ceramic film or a laminated film of a plurality of ceramic films, and the electrodeposition time in an evaluation test (corresponding to FIG. 10 described later). The same applies to items). The average pore diameter in the comparative example is the average pore diameter of the separator body.

  When the electrodeposition time was 2 hours in the separator of the comparative example, no leaching of the deposited metal into the separator of the comparative example was confirmed, but when the electrodeposition time was 3 hours, the vertical section of the separator is shown. As shown in FIG. 4 and FIG. 5, it was confirmed that the powdered or particulate deposited metal in the coiled zinc electrode penetrated into the separator. In addition, when the electrodeposition time is 5 hours, as shown in FIG. 6 showing the outer side of the separator and FIG. 7 showing the inner side, the deposited metal penetrates the inside of the separator and reaches the outer side. It was confirmed.

  On the other hand, in the separators of Examples 1 to 8 in which the porous film was formed on the inner side surface or the outer side surface of the separator main body, no internal penetration of the deposited metal was confirmed. 8 and 9 show the cross section and the inner surface of the separator of Example 3 after electrolytic deposition for 10 hours. From FIGS. 8 and 9, leaching of the deposited metal in the zinc electrode into the separator is shown. It turns out that there is no.

(Evaluation test for cycle durability)
Next, the cycle durability of the separators produced in Examples 1 to 8 was evaluated. Here, similarly to the evaluation test of the overcharge stability, coiled zinc electrodes and zinc pipes were arranged for the separators of Examples 1 to 8 and the comparative example. And about the separator of Examples 1 thru | or 4 which formed the ceramic film | membrane on the inner surface of a separator main body, and the separator of the comparative example which has not formed the ceramic film | membrane, let a coil-shaped zinc electrode be an object electrode, and a separator main body For the separators of Examples 5 to 8 in which the ceramic film was formed on the outer surface of the battery, using the zinc pipe as the target electrode, using a battery performance evaluation apparatus (manufactured by Keiki Keiki Center Co., Ltd., model number: BLS5500), The deposition and dissolution of the metal was repeated. Specifically, under the condition of a current density of 150 mA / cm ² , 150 cycles of deposition and dissolution were performed with 70 cycles of dissolution followed by 70 minutes of dissolution as one cycle. Thereafter, the separator was observed.

  FIG. 10 is a diagram showing the result of confirming whether or not the deposited metal (zinc) leached into the separator in the target electrode. In FIG. 10, the presence or absence of the leaching of the deposited metal is shown in the column labeled “Extrusion to separator” in the column heading. ○ indicates that no precipitation of the deposited metal into the separator was confirmed in the target electrode, and Δ indicates that the deposited metal did not penetrate into the separator, but the deposited metal did not penetrate the separator. X indicates that the deposited metal had penetrated the separator.

  As shown in FIG. 10, in the three separators of the comparative example, it was confirmed that the deposited metal penetrated the inside of the separator and reached the outer surface. On the other hand, in the separator in which the porous film was formed on the inner side surface or the outer side surface of the separator main body, except for the one corresponding to Example 1, no leaching of the precipitated metal into the separator was confirmed. Of the separators of Examples 1 to 8, the average pore diameter is the largest, and in the separator of Example 1 in which the porous film is formed on the inner surface of the separator body, there is an internal penetration of the precipitated metal, There was no penetration.

  As described above, in the separator in which the porous film having an average pore diameter smaller than the average pore diameter of the separator body is formed on the inner surface or the outer surface of the separator body, the overcharge stability evaluation test and the cycle durability evaluation In the test, the metal deposited on the electrode is prevented from penetrating the separator. More specifically, from the results of FIG. 3 and FIG. 10, when the average pore diameter of the porous film in the separator is 2 μm or less and the thickness of the porous film is 50 μm or more, the metal deposited on the electrode Penetration is more reliably prevented. Therefore, by using such a separator for the metal-air battery 1, it is possible to prevent the powdered or particulate deposited metal of the negative electrode 3 from penetrating the separator 41 and short-circuiting the negative electrode 3 and the positive electrode 2. Is done.

  Further, in the metal-air battery 1 of FIG. 1, the separator 41 is formed only of a sintered ceramic having an electrolytic solution resistance, physical and chemical stability (including heat resistance), and electrochemical oxidation resistance. Is done. Thereby, it is suppressed that the separator 41 elutes in the electrolytic solution, or is corroded or swollen by the electrolytic solution, and deterioration due to oxygen generated during charging is also suppressed. Further, the mechanical strength in the battery assembly process and the battery reaction cycle is also ensured. Furthermore, in addition to the short-circuit resistance to the powdery or particulate deposited metal described above, even when dendrite or the like is generated and grows at the time of charging, a short circuit between the negative electrode 3 and the positive electrode 2 can be prevented. As a result, long-term stability in the metal-air battery 1 can be realized.

  Furthermore, the separator 41 formed of ceramic can be formed into an arbitrary shape such as a plate shape in addition to the cylindrical shape. Accordingly, even when the negative electrode 3 and the positive electrode 2 are formed in various shapes such as a film shape (sheet shape), a plate shape, a rod shape, or a tubular shape, the separator 41 is used as a support, and the metal-air battery Can be easily manufactured. As shown in FIG. 1, in the metal-air battery 1 having the cylindrical main body 11, the energy density can be easily improved, and a plurality of main bodies 11 can be arranged densely. (The same applies when the cross-sectional shape perpendicular to the central axis J1 is a square, a hexagon, or the like).

  The metal-air battery 1 can be variously modified. In the separator 41 disposed between the negative electrode 3 and the positive electrode 2, the porous film 412 may be formed on both the inner surface and the outer surface of the separator body 411. That is, in the separator 41, it is important that the porous film 412 is formed on at least the surface facing the negative electrode 3.

  Further, depending on the design of the metal-air battery 1, one or both of the separator body 411 and the porous film 412 may include other materials such as a binder in addition to the ceramic.

  In the metal-air battery 1, it is not always necessary to circulate the electrolytic solution. The separator 41 may be used in a metal-air battery other than a zinc-air battery, and may be used in another secondary battery in which metal is deposited on the negative electrode during charging.

  The configurations in the above-described embodiments and modifications may be combined as appropriate as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1 Metal-air battery 2 Positive electrode 3 Negative electrode 4 Electrolyte layer 40 Electrolytic solution 41 Separator 411 Separator main body 412 Porous film S11-S13 Step

Claims (9)

In a secondary battery in which metal is deposited at the negative electrode during charging, the separator is disposed between the negative electrode and the positive electrode,
A separator body which is a porous support formed of ceramic;
A porous membrane formed of ceramic on the surface of the separator body facing the negative electrode and having an average pore diameter smaller than the average pore diameter of the separator body;
With
The average pore diameter of the porous membrane is 0.01 micrometer or more and 2 micrometers or less;
A separator having a thickness of the porous film of 50 micrometers or more and 200 micrometers or less. The separator according to claim 1,
The separator is a laminated film in which a plurality of films are laminated. The separator according to claim 1 or 2,
The separator is characterized in that the porous film contains at least one of silica, alumina, zirconia, titania and hafnia. The separator according to any one of claims 1 to 3,
The separator has a porosity of 30% or more and 80% or less. The separator according to any one of claims 1 to 4,
The separator body is cylindrical;
In the separator body, the porous film is formed over the entire circumference of the surface facing the negative electrode. A secondary battery,
A positive electrode;
A negative electrode on which metal is deposited during charging;
An electrolyte layer disposed between the negative electrode and the positive electrode;
With
The electrolyte layer is
Having the separator according to any one of claims 1 to 5,
A secondary battery, wherein the separator is filled with an electrolytic solution. In a secondary battery in which metal is deposited at the negative electrode during charging, a method for producing a separator disposed between the negative electrode and the positive electrode,
a) preparing a separator body which is a porous support formed of ceramic;
b) forming a porous film having an average pore diameter smaller than the average pore diameter of the separator body on the surface facing the negative electrode in the separator body with ceramic;
With
The average pore diameter of the porous membrane is 0.01 micrometer or more and 2 micrometers or less;
A method for producing a separator, wherein the thickness of the porous film is 50 micrometers or more and 200 micrometers or less. It is a manufacturing method of the separator according to claim 7,
Step b)
b1) forming a film on the surface of the separator body by sintering ceramic particles;
b2) forming another film on the surface of the one film by sintering ceramic particles;
A method for producing a separator, comprising: A separator manufacturing method according to claim 7 or 8,
A method for producing a separator, wherein the porous film is formed by sintering ceramic particles having an average particle size of 0.1 μm or more and 30 μm or less.