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    • 专利摘要:
    The invention relates to a metal / air cell cathode (1) comprising at least one active layer (2) made of an active material and having an air side (A) and a metal side (M), a current collector (3), and a hydrophobic membrane (4) made of a hydrophobic material and deposited on the air side (A) of the active layer (2). Said hydrophobic material has a porous structure and has penetrated into the air side (A) of the active layer (2) so as to form, between the hydrophobic membrane (4) and the active layer (2), an interpenetration zone ( Z) of the hydrophobic material in the active material in which there exists a gradient of concentration of hydrophobic material decreasing in the incoming direction of the air in the cathode. The invention also relates to a method of manufacturing a cathode and a metal / air cell.
    公开号:CH711943A2
    申请号:CH01882/15
    申请日:2015-12-21
    公开日:2017-06-30
    发明作者:Reinauer Olga；Stalder Michael；Zullig Frédy
    申请人:Swatch Group Res & Dev Ltd；
    IPC主号:
    专利说明:

    Description
    Field of the Invention [0001] The invention relates to a metal / air cell cathode comprising at least one active layer made of an active material and having an air side and a metal side, a current collector and a membrane made in a hydrophobic material and deposited on the air side of the active layer. The present invention also relates to methods of manufacturing such a cathode, as well as a metal / air cell comprising such a cathode.
    BACKGROUND OF THE INVENTION [0002] A metal / air cell cathode is generally used in a button cell. It is in the form of a disc located under ventilation holes provided in the housing. An air diffuser paper is generally positioned between the housing and the cathode. Unlike other types of batteries, the cathode in a metal / air cell must store only the amount of electro-active material (typically oxygen) needed for the immediate needs of the battery, the rest being replaced as and when from outside, through the ventilation holes. For this reason, the cathode can be made from a very thin band, leaving the majority of the volume of the battery available for the anode (for example zinc in the case of a zinc / air cell).
    The metal / air cell cathode consists at least of a current collector (for example nickel trellis), which brings the electrons from the battery housing to the catalyst, the air and the electrolyte, as well as a catalyst that promotes the transfer of electrons to oxygen which is reduced to hydroxide, thereby creating an electric current. Such a catalyst is for example a manganese oxide.
    The difficulty in producing the cathode of a metal / air cell stems from the fact that the catalyst must be in contact with both the current collector (solid), the air (gaseous) and the electrolyte (liquid). ). It is particularly complex to make these three phases coexist on as large a surface as possible. To solve this problem, a solution to enlarge the interface between the air, the electrolyte and the catalyst, and thus improve the power of the battery, is to confer a certain hydrophobicity to the cathode. The addition of hydrophobic additives in the composition of the cathode makes it possible to prevent the entire cathode from being flooded by the electrolyte and thus to leave room for the air to penetrate better into the cathode. For this purpose, a hydrophobic binder, such as polytetrafluoroethylene (PTFE), is typically used in the form of a powder or an aqueous dispersion. The addition of such a hydrophobic binder makes it possible to increase the power of the cathode as a function of the concentration of PTFE but up to an optimal concentration (typically 15-20%) beyond which the power of the battery decreases. . This loss of power is due to the homogeneous dispersion of PTFE throughout the cathode, which has the effect of reducing the electrical conductivity (interruption by PTFE of the percolation network formed by the carbon particles) and also to reduce the amount of electrolyte in the cathode.
    Another solution to enlarge the interface between the air, the electrolyte and the catalyst is to use a cathode having a porous structure allowing the electrolyte and air to better penetrate the cathode. Typically, such a porous structure is obtained by using a mixture of different conductive particles, such as conductive carbon particles (carbon black, graphite, etc.).
    Such a cathode is for example described in patent application US 2014/0 308 594. According to this document, the cathode comprises an active layer having a porous structure whose porosity decreases between the air side and the metal side of the cathode. Various manufacturing methods are described for obtaining an active layer which has a porosity gradient in the thickness of the active layer instead of a uniform porous structure. This porosity gradient is due to a variation of the intrinsic porosity of the material of the active layer of the cathode controlled during its manufacture.
    [0007] Patent FR 2 785 093 also describes a cathode whose active layer has pores and comprises graphite particles whose average size is greater than the average pore diameter of the active layer. The cathode further comprises a diffusion layer which is a hydrophobic membrane deposited on the air side of the active layer. This hydrophobic membrane is of Gore-Tex® type which is expanded polytetrafluoroethylene (ePTFE). The cathode is obtained by preparing the active layer in the form of a paste, then the paste is spread on one face of the current collector. The Goretex® membrane is applied on the other side. Then the cathode is dried and compressed. In this cathode, the hydrophobic membrane, because of its structure, remains of constant thickness, and has the sole role of making the surface of the cathode more hydrophobic in order to increase its resistance to flooding.
    [0008] Metal / air cells, essentially zinc / air, are commonly used in hearing aids because of their highest energy density among commercial batteries. For this application, the metal / air cells must be replaced weekly and are therefore not optimized for their life but are already optimized for their power. But for applications such as connected watches, which involve very high current peaks for primary batteries, it is necessary to have batteries with higher power. The power of the metal / air cells being limited by their cathode, it is necessary to develop cathodes to obtain a power increase of the battery which only fades slightly over time, thus becoming useful for an application. watchmaking. SUMMARY OF THE INVENTION [0009] To this end, the present invention relates to a metal / air cell cathode comprising at least one active layer made of an active material and having an air side and a metal side, a current collector and a hydrophobic membrane made of a hydrophobic material and deposited on the air side of the active layer.
    According to the invention, said hydrophobic material has a porous structure and has penetrated into the air side of the active layer so as to form, between the hydrophobic membrane and the active layer, an interpenetration zone of the hydrophobic material in the active material in which there is a gradient of concentration of hydrophobic material decreasing in the incoming direction of the air in the cathode.
    The present invention also relates to different method of manufacturing a metal / air cell cathode as defined above.
    The present invention also relates to a metal / air cell comprising at least one anode based on said metal, a cathode as defined above and an electrolyte.
    The interpenetration zone of the hydrophobic material in the active material in which there is a gradient of concentration of hydrophobic material decreasing in the incoming direction of the air in the cathode makes it possible to locally increase the amount of hydrophobic material and therefore the hydrophobicity of the air side of the active layer, then to reduce the amount of hydrophobic material, and therefore the hydrophobicity, when one moves away from the air side of the active layer. The local increase in hydrophobicity on the air side of the active layer has the effect of increasing the volume of air both in contact with the electrolyte and the catalyst. Thus the contact surface between the three solid / liquid / gas phases is increased. Then the decrease in hydrophobicity, when one moves away from the air side of the active layer, causes a decrease in the amount of air in favor of an increase in the amount of electrolyte. This configuration is optimal for the cathode since the amount of anions that will be transportable by the electrolyte between the cathode and the anode, and on which the power of the battery depends, increases with the thickness.
    BRIEF DESCRIPTION OF THE DRAWINGS [0014] Other features and advantages of the invention will appear more clearly on reading the following description of an embodiment of the invention, given as a simple illustrative and nonlimiting example, and annexed figures, among which: FIG. 1 is a partial sectional view of a battery according to the invention, FIG. 2 is a stereomicroscope image of a section of a cathode according to the invention, and FIG. 3 is a partial sectional view of a battery according to the prior art.
    DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT [0015] Referring to FIGS. 1 and 2, the present invention relates to a cathode 1 of metal / air cell comprising at least one active layer 2 made of an active material and having an air side A and a metal side M. The active layer 2 of the cathode of the The invention is quite conventional and known to those skilled in the art, so that a detailed description of such an active layer is not necessary. It will be simply stated that the active layer preferably has a porous structure. In addition, the active material of the active layer comprises, in known manner, at least one binder, a catalyst and conductive particles making it possible to obtain a porous structure. The binder is preferably a hydrophobic binder, such as polytetrafluoroethylene (PTFE) or any other suitable hydrophobic binder. The catalyst may be chosen from precious metals and metal oxides. Preferably, the catalyst is an Mn 2 O 3 manganese oxide or other suitable catalyst. The conductive particles are preferably a mixture of different conductive carbons, such as particles of carbon black or graphite. The active layer 2 can be deposited in several layers.
    The cathode also comprises in known manner a current collector 3, which is for example a grid, a mesh, a foam or a conductive felt, such as a grid or a nickel foam.
    The cathode also comprises a hydrophobic membrane 4 made of a hydrophobic material and deposited on the air side of the active layer.
    According to the present invention, said hydrophobic material has a porous structure and has penetrated into the air side A of the active layer 2 so as to form, between the hydrophobic membrane 4 and the air side A of the active layer 2, an interpenetration zone Z of the hydrophobic material in the active material in which there exists a gradient of concentration of hydrophobic material decreasing in the incoming direction of the air in the cathode (or from the air side A to the metal side M).
    Thus, the concentration of hydrophobic material in the Z interpenetration zone changes from 100% to 0% in the incoming direction of the air in the cathode, the Z interpenetration zone extending over a thickness between 10 and 25% of the total thickness of the active layer.
    Advantageously, the porous structure of the hydrophobic material of the hydrophobic membrane 4 is in the form of a matrix of fibrils interconnecting solid nodes, the space between the nodes and the fibrils constituting microscopic pores of average size between 30 pm and 100 pm, and preferably between 50 pm and 80 pm.
    [0021] Preferably, the hydrophobic membrane 4 has a density of between 0.2 g / cm 3 and 0.5 g / cm 3.
    In a particularly preferred manner, the hydrophobic material is a fluoropolymer extruded then expanded. More particularly, the hydrophobic material of the hydrophobic membrane 4 is polytetrafluoroethylene (PTFE) extruded then expanded. The hydrophobic membrane 4 is for example an Aeos® membrane marketed by Zeus Inc. The thickness of the hydrophobic membrane before use is between 0.5 mm and 5 mm, and preferably between 0.5 mm and 2 mm.
    The present invention also relates to a first variant of a method for manufacturing a metal / air cell cathode as described above, comprising the steps of: a) preparing the active material of the active layer under the form a paste, by mixing for example the various components of the active material in a liquid b) deposit the paste obtained in step a) on the current collector c) deposit the hydrophobic membrane as defined above on the dough as obtained in step b) d) applying a pressure on the assembly obtained in step c), the pressure applied being preferably less than or equal to 150 N / mm, so as to form, between the hydrophobic membrane and the active layer, an interpenetration zone Z of the hydrophobic material in the active material in which there exists a gradient of concentration of hydrophobic material decreasing in the incoming direction of the air in the cathode.
    The present invention also relates to a second variant of a method for manufacturing a metal / air cell cathode as described above, comprising the steps of: a ') preparing the active material of the active layer under the shape of a paste, for example by mixing the different components of the active material in a liquid b ') depositing a first layer of the paste obtained in step a) on the current collector c') applying a pressure on the set obtained in step b '), the pressure applied being preferably greater than or equal to 250 N / mm, and more preferably between 250 N / mm and 500 N / mm of depositing a second layer of paste on the assembly obtained in step c ') e') depositing the hydrophobic membrane as defined above on the second layer of dough as obtained in step d) Γ) apply a pressure on the whole obtained in step e '), the applied pressure is ant preferably of less than or equal to 150 N / mm, so as to form, between the hydrophobic membrane and the active layer, an interpenetration zone Z of the hydrophobic material in the active material in which there exists a gradient of concentration of hydrophobic material decreasing in the incoming direction of the air in the cathode.
    The use of the active layer in the form of a paste makes it possible to deform said active layer more easily under pressure than a cathode pressed dry.
    Preferably, the application of a pressure in steps d), c ') and F) is performed by a rolling method, the rolling steps can advantageously be performed by means of a rolling mill.
    Preferably, the methods according to the invention respectively comprise a step of drying the cathode obtained after step d) or Γ). The drying is preferably carried out under vacuum. After drying, the cathode can be rolled again with a pressure less than or equal to 150 N / mm.
    In the cathode of the invention, because of the use of an active layer in the form of a paste and a hydrophobic membrane having a specific morphology comprising large fibrillar pores on the one hand and the use of a method for applying a pressure on the hydrophobic membrane to assemble said hydrophobic membrane on the active layer on the other hand, the hydrophobic material of the hydrophobic membrane 4 has penetrated into the active layer 2 of the cathode, as show it in figs. 1 and 2 to create the Z interpenetration zone and the concentration gradient of hydrophobic material. In the cathodes 1 'of the batteries of the prior art as shown in FIG. 3, the hydrophobic membrane 4 'deposited on the active layer 2' remains on its surface (the references of the other elements of the stack remaining otherwise identical), so that the dispersion of PTFE, as a binder, remains homogeneous.
    Once laminated on the cathode 1, the hydrophobic membrane 4 is highly compressed so that it does not add more than 0.1 mm thick, as a hydrophobic membrane conventionally used. Thus, there is no risk of increasing the thickness of the cathode and reducing the storable energy in the cell. In addition, the porosity of the hydrophobic membrane when laminated is decreased by a factor of 10 or more, so aging by drying / drowning remains similar to that of a standard battery.
    权利要求:
    Claims (11)
    [1]
    The present invention also relates to a metal / air cell comprising at least one anode 6 based on said metal, a cathode as described above, and an electrolyte. The anode may be based on a metal such as Li, Na, Mg and Zn. Preferably, the anode is made based on zinc powder. The electrolyte is for example a KOH solution. The cell also comprises a separator 8 placed between the cathode and the anode. For example, a cellulose separator is used. The electrolyte wets the separator, the anode and the cathode. The metal / air battery is preferably in the form of a button cell and is assembled by placing the hydrophobic membrane side cathode against the opening in the housing. An air diffuser can be placed between the cathode and the battery cover. The battery also has a seal. The cell obtained according to the invention has no disadvantages compared to a known battery. On the other hand, it has the advantage of having an improved power of about 10% compared to standard batteries. In fact, the use of a hydrophobic membrane having a specific morphology comprising large fibrillar pores to create the zone of interpenetration Z and the concentration gradient of hydrophobic material makes it possible to create a three-dimensional hydrophobic matrix with a variable morphology and thus of increase the gas / liquid / solid contact surface in the active layer of the cathode. The following examples illustrate the present invention without limiting the scope thereof. It produces a paste corresponding to the active material of the cathode by mixing 25% by weight of Mn203.51% graphite, 15% carbon black and 9% PTFE dispersed in water. Ethanol is added to obtain a dispersion with 15% by weight of the solid material. Mix with a magnetic stirrer. The mixture obtained is poured into the grinding vessel of a planetary mill with SiO 2 agate balls having a diameter of between 5 and 20 mm. The mixture is milled in the planetary mill with a rotational speed and the grinding time adapted to the type of mill and grinding conditions. Grinding can also be done in several stages by varying the size of the balls and the rotational speeds. The milled dispersion is filtered under vacuum and then the solid material is recovered. The solid material is in the form of a paste, which can be kneaded if necessary. One-step rolling [0038] The paste is placed on a nickel grid. The hydrophobic membrane is placed on the dough. The whole is rolled with a rolling mill with a pressure not exceeding 150 N / mm. Two-stage rolling [0039] The paste is placed on a nickel grid. The dough is rolled with a rolling mill with a pressure of at least 250 N / mm. A second layer of dough is placed on the rolled part. The hydrophobic membrane is placed on top. The whole is rolled with a rolling mill with a pressure not exceeding 150 N / mm. The prepared cathode is dried under vacuum at 90 ° C for 16 hours. After drying, the cathode can be rolled again with a pressure not exceeding 150 N / mm. A Zn-air type "button" battery is assembled with the prepared cathode. The anode is zinc powder, the electrolyte is a solution of 9M KOH, the separator is cellulose. As a comparative example, a similar stack is made, but using a standard cathode manufactured by compression of the powders. The diameter of the cathode is 19 mm. Results Zn-air cells with a cathode consisting of the paste and the hydrophobic membrane according to the invention and laminated in one step according to a method of the invention have a power of 68 mW, whereas the battery containing a Standard cathode and hydrophobic membrane have a power of 60 mW, an increase of power of more than 13%. claims
    A metal / air cell cathode (1) comprising at least one active layer (2) made of an active material and having an air side (A) and a metal side (M), a current collector (3), and a hydrophobic membrane (4) made of a hydrophobic material and deposited on the air side (A) of the active layer (2), characterized in that said hydrophobic material has a porous structure and in that said hydrophobic material has penetrated into the air side (A) of the active layer (2) so as to form, between the hydrophobic membrane (4) and the active layer (2), an interpenetration zone (Z) of the hydrophobic material in the active material in which there exists a concentration gradient of hydrophobic material decreasing in the incoming direction of the air in the cathode.
    [2]
    2. Cathode according to claim 1, characterized in that the porous structure of the hydrophobic material is in the form of a matrix of fibrils interconnecting solid nodes, the space between the nodes and the fibrils constituting microscopic pores.
    [3]
    3. Cathode according to claim 1 or 2, characterized in that the hydrophobic membrane has a density of between 0.2 g / cm3 and 0.5 g / cm3.
    [4]
    4. Cathode according to one of claims 2 to 3, characterized in that the microscopic pores have an average size of between 30 and 100 pm.
    [5]
    5. Cathode according to one of the preceding claims, characterized in that the hydrophobic material is a fluoropolymer extruded and then expanded.
    [6]
    6. Cathode according to one of the preceding claims, characterized in that the concentration of hydrophobic material in the interpenetration zone (Z) changes from 100% to 0% in the incoming direction of the air in the cathode, the zone interpenetration extending over a thickness of between 10 and 25% of the total thickness of the active layer.
    [7]
    7. Cathode according to one of the preceding claims, characterized in that the active material comprises at least one binder, a catalyst and conductive particles.
    [8]
    8. A method of manufacturing a metal / air cell cathode according to one of the preceding claims, comprising the steps of: a) preparing the active material of the active layer (2) in the form of a paste b) deposit the paste obtained in step a) on the current collector (3) c) depositing the hydrophobic membrane (4) on the dough as obtained in step b) d) applying a pressure on the assembly obtained at step c), the pressure preferably being less than or equal to 150 N / mm, so as to form, between the hydrophobic membrane (4) and the active layer (2), an interpenetration zone (Z) of the material hydrophobic in the active material in which there is a gradient of concentration of hydrophobic material decreasing in the incoming direction of the air in the cathode.
    [9]
    9. A method of manufacturing a metal / air cell cathode according to one of claims 1 to 8, comprising the steps of: a ') preparing the active material of the active layer (2) in the form of a paste b ') depositing a first layer of the paste obtained in step a) on the current collector (3) c') applying a pressure on the assembly obtained in step b '), the pressure preferably being greater or equal to 250 N / mm of) depositing a second layer of paste on the assembly obtained in step c ') e') depositing the hydrophobic membrane on the second layer of dough as obtained in step d f) applying a pressure on the assembly obtained in step e '), the pressure preferably being less than or equal to 150 N / mm, so as to form, between the hydrophobic membrane (4) and the active layer; (2), an interpenetration zone (Z) of the hydrophobic material in the active material in which a concentrate gradient exists ion hydrophobic material decreasing in the incoming direction of the air in the cathode.
    [10]
    10. Manufacturing process according to one of claims 8 and 9, characterized in that it comprises a step of drying the cathode.
    [11]
    11. Metal / air battery comprising at least one anode based on said metal, a cathode according to one of claims 1 to 7, and an electrolyte.
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    同族专利:
    公开号 | 公开日
    CH711943B1|2021-10-15|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    CH01882/15A|CH711943B1|2015-12-21|2015-12-21|Metal / air cell cathode and methods of making such a cathode.|CH01882/15A| CH711943B1|2015-12-21|2015-12-21|Metal / air cell cathode and methods of making such a cathode.|
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