JP6475521B2 - Multilayer porous separator and secondary battery using the same - Google Patents

Description

  The present invention relates to a multilayer porous separator and a secondary battery using the same.

  Although zinc secondary batteries such as nickel zinc secondary batteries have been developed and studied for a long time, they have not yet been put into practical use. This is because the zinc constituting the negative electrode produces dendritic crystals called dendrite during charging, and this dendrite breaks through the separator and causes a short circuit with the positive electrode. Therefore, a technique for preventing a short circuit due to zinc dendrite in a zinc secondary battery such as a nickel zinc secondary battery is strongly desired.

  In order to deal with such problems and demands, secondary batteries using a separator having a porous structure have been proposed. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2014-194497) discloses a separator body made of porous ceramics and an average fineness smaller than the average pore diameter of the separator body formed on the surface of the separator body facing the negative electrode. A separator having a two-layer structure including a ceramic porous membrane having a pore size is disclosed, and according to such a separator, the deposited metal of the negative electrode penetrates the separator and the negative electrode and the positive electrode are short-circuited (that is, dendritic It is said that extension and short circuit caused by it can be prevented.

JP 2014-194897 A

  A porous separator having a two-layer structure as disclosed in Patent Document 1 can be expected to some extent to delay the extension of dendrites and the short circuit resulting therefrom, but the effect is still not sufficient. This is because both layers are made of a porous material, so that the electrolyte solution can pass through the separator, and dendrite grows and short-circuits between the positive and negative electrodes. On the other hand, since the porous material can be an inexpensive or easily available material (for example, a ceramic material such as alumina or zirconia), it is advantageous if the separator can be made of a porous material. Therefore, a separator composed of a porous material that can more effectively suppress or delay dendrite extension and short circuit between positive and negative electrodes resulting therefrom is desired.

  The present inventors are now comprised of porous ceramics and / or spaces richer in pores than the first layer and the third layer between the first layer and the third layer made of porous ceramics. It has been found that by providing the second layer, it is possible to provide a porous separator that can more effectively suppress or delay the extension of dendrite and the short circuit between the positive and negative electrodes resulting from the secondary battery.

  Accordingly, an object of the present invention is to provide a porous separator capable of more effectively suppressing or delaying the extension of dendrites and the short circuit between positive and negative electrodes resulting therefrom in a secondary battery. Another object of the present invention is to provide a secondary battery having such a porous separator.

According to one aspect of the present invention, a multilayer porous separator for separating a positive electrode and a negative electrode in a secondary battery,
A first layer and a third layer which are provided to be spaced apart from and opposed to each other and are made of porous ceramics;
Provided between the first layer and the third layer, porous ceramics richer in pores than the first layer and the third layer, and / or a second layer composed of a space;
A multilayer porous separator is provided.

  According to another aspect of the present invention, there is provided a secondary battery comprising a positive electrode, a negative electrode, a multilayer porous separator according to the above aspect that separates the positive electrode and the negative electrode, and an electrolytic solution.

It is a schematic cross section of the multilayer porous separator by one mode of the present invention. It is a schematic cross section which shows the battery structure using the multilayer porous separator shown by FIG. It is a schematic diagram which shows the measuring apparatus used for the dendrite short-circuit confirmation test.

Multilayer porous separator The separator according to the present invention is a multilayer porous separator for separating a positive electrode and a negative electrode in a secondary battery. The secondary battery of the present invention includes various secondary batteries to which a porous separator can be applied, such as a nickel zinc secondary battery, a silver zinc oxide secondary battery, a manganese zinc oxide secondary battery, and other various alkaline zinc secondary batteries. Can be. Most preferably, it is a nickel zinc secondary battery.

  An example of the multilayer porous separator of the present invention is shown in FIG. A multilayer porous separator 10 shown in FIG. 1 includes a first layer 12, a second layer 14, and a third layer 16 in this order. That is, the first layer 12 and the third layer 16 are provided so as to be separated from each other and face each other, while the second layer 14 is provided between the first layer 12 and the third layer 16. The first layer 12 and the third layer 16 are made of porous ceramics. The first layer 12 and the third layer 16 may be the same or similar layers, or may be different layers. On the other hand, the second layer 14 is composed of porous ceramics and / or spaces richer in pores than the first layer 12 and the third layer 16. As described above, the porous layer is composed of porous ceramics and / or spaces richer in pores than the first layer 12 and the third layer 16 between the first layer 12 and the third layer 16 formed of the porous ceramics. By providing the second layer 14, it is possible to provide a porous separator capable of more effectively suppressing or delaying the dendrite extension and the short circuit between the positive and negative electrodes resulting therefrom in the secondary battery.

  It was an unexpected finding that the multi-layer porous separator of the present invention can effectively suppress or delay the extension of dendrites and the short circuit between the positive and negative electrodes resulting therefrom, but it is not realized by the following mechanism. It is thought. In other words, since the pores communicate with each other only in the porous separator having a single layer structure, it is difficult for the dendrite to grow along the pores and short-circuit between the positive and negative electrodes even if the layer thickness is increased. The problem is that with the three-layer structure as described above, when dendrites grow through the first layer 12 (or third layer 16), the relatively large pores introduced by the second layer 14 Moreover, the dendrite may drop out in the space, or the dendrite may be cut off due to the discontinuity of the pores of the first layer 12 (or the third layer 16) and the second layer 14, and further growth of the dendrite can be suppressed. It becomes. Moreover, even if the dendrite penetrates through the second layer 14, further dendrite growth is greatly suppressed by the third layer 16 (or the first layer 12), which is a layer having a large dendrite short-circuit preventing effect, and the second layer. The discontinuity of pores at the boundary between 14 and the third layer 16 (or the first layer 12) also has the effect of greatly suppressing continuous further dendrite growth.

  The first layer 12 and the third layer 16 are made of porous ceramics. The first layer 12 and the third layer 16 may be made of the same or similar material, or may be made of different materials. The second layer 14 can also be composed of porous ceramics rich in pores. In this case, the second layer 14 may be made of the same or similar material as the first layer 12 and / or the third layer 16 or may be made of a different material. Preferred examples of porous ceramics include alumina, zirconia, titania, magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite, zinc oxide, silicon carbide, aluminum nitride, silicon nitride, and any combination thereof. More preferred are alumina, zirconia, titania, and any combination thereof, and particularly preferred are alumina, zirconia (eg, yttria stabilized zirconia (YSZ)), and combinations thereof. All of these porous ceramics have alkali resistance as resistance to the electrolyte solution of the secondary battery (for example, potassium hydroxide aqueous solution).

  The second layer 14 is provided between the first layer 12 and the third layer 16, and is composed of porous ceramics and / or spaces richer in pores than the first layer 12 and the third layer 16. The state in which the porous ceramic of the second layer 14 is richer in pores than the first layer 12 and the third layer 16 typically means that the space provided by the pores is larger than that in the first layer 12 and the third layer 16. It can be said that there are many states. In that sense, it can be said that the aspect in which the second layer 14 is composed of a space corresponds to a state where the space is increased to the limit (that is, the porosity is 100%). The first layer 12 and the third layer 16 may contain pores in the same or close degree, the first layer 12 may be richer in pores than the third layer 16, or the third layer 16 may be more porous than the first layer 12.

  Each of the first layer 12 and the third layer 16 preferably has a porosity of 60% or less, more preferably 50% or less, and still more preferably 40% or less. The porosity of the first layer 12 and the third layer 16 is preferably low from the viewpoint of dendrite suppression, and the lower limit is not particularly limited, but is 5% or more from the viewpoint of ensuring the ionic conductivity required for the separator. Is preferable, more preferably 10% or more, still more preferably 20% or more. The porosity of the first layer 12 and the third layer 16 may be the same or close, the porosity of the first layer 12 may be higher than that of the third layer 16, The porosity may be higher than that of the first layer 12. On the other hand, when the second layer 14 is made of porous ceramics, it preferably has a higher porosity than the first layer 12 and the third layer 16. In this case, the second layer 14 preferably has a porosity of 40% or more (or more than 40%), more preferably 50% or more (or more than 50%), and still more preferably 60% or more (or more than 60%). ). The porosity of the second layer 14 is preferably higher from the viewpoint of dendrite suppression due to a synergistic effect with the first layer 12 and the third layer 16, and the upper limit may be 100%. (This corresponds to the case where the second layer 14 is a space), and is preferably 85% or less, more preferably 80% or less, and still more preferably 75% or less, from the viewpoint of handling properties of the porous ceramics. .

  In the present invention, the porosity of the surface of each layer can be measured as follows by a technique using image processing. That is, 1) Obtain an electron microscope (SEM) image (at a magnification of 10,000 times or more) of the surface of each layer, 2) Read a grayscale SEM image using image analysis software such as Photoshop (manufactured by Adobe), etc. 3) Create a black and white binary image by the procedure of [Image] → [Color correction] → [Turn 2], and 4) Porosity (%) by dividing the number of pixels occupied by the black part by the total number of pixels in the image. ). Note that the porosity measurement by this image processing is preferably performed for a 6 μm × 6 μm region on the surface of each layer. In order to obtain a more objective index, it is obtained for three arbitrarily selected regions. It is more preferable to adopt the average value of the porosity. Here, the porosity of the surface of each layer is adopted because it is easy to measure the porosity using the above-described image processing, and the porosity of the surface of each layer is the porosity inside each layer. This is because it can be said that it is generally expressed. That is, if the surface of each layer is dense, it can be said that the inside of each layer is dense as well.

  Each of the first layer 12 and the third layer 16 preferably has an average pore diameter of 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less. The average pore diameters of the first layer 12 and the third layer 16 are preferably small from the viewpoint of dendrite suppression, and the lower limit is not particularly limited, but from the viewpoint of securing the ionic conductivity required for the separator, the average pore diameter is 0.1. The thickness is preferably 01 μm or more, more preferably 0.05 μm or more, and further preferably 0.1 μm or more. The average pore diameter of the first layer 12 and the third layer 16 may be the same or close, the average pore diameter of the first layer 12 may be larger than the third layer 16, or the third layer The average pore diameter of 16 may be larger than that of the first layer 12. On the other hand, when the second layer 14 is composed of porous ceramics, it is preferable that the second layer 14 has a larger average pore diameter than the first layer 12 and the third layer 16. In this case, the second layer 14 preferably has an average pore diameter of 1 μm or more (or more than 1 μm), more preferably 5 μm or more (or more than 5 μm), and still more preferably 10 μm or more (or more than 10 μm). The average pore diameter of the second layer 14 is preferably higher from the viewpoint of dendrite suppression due to a synergistic effect with the first layer 12 and the third layer 16, but from the viewpoint of handling properties of the porous ceramics, 1 1,000 μm or less is preferable, more preferably 500 μm or less, and still more preferably 100 μm or less.

  In the present invention, the average pore diameter can be measured by measuring the longest distance of the pores based on the electron microscope image of the surface of each layer. The magnification of the electron microscope image used for this measurement is 20000 times or more, and all obtained pore diameters are arranged in the order of size, and the upper 15 points and the lower 15 points from the average value. The average pore size can be obtained by calculating the average value of minutes. For the length measurement, a length measurement function of SEM software, image analysis software (for example, Photoshop, manufactured by Adobe) or the like can be used.

  According to a preferred embodiment of the present invention, the second layer 14 can be composed of porous ceramics richer in pores than the first layer 12 and the third layer 16. When the second layer 14 is also made of porous ceramics, it is easier to stack three layers because the work of forming a space using a spacer or the like is not required during manufacturing compared to the case where the second layer 14 is made of space. There are advantages. As described later, the first layer 12, the second layer 14, and the third layer 16 are simply stacked, or the first layer 12 and the third layer 16 are formed on both side surfaces of the second layer 14, respectively. This is because a quality separator can be formed.

  According to another preferred embodiment of the present invention, the second layer 14 can be composed of spaces. Even when the second layer 14 is constituted by a space, as in the case where the second layer 14 is constituted by porous ceramics that are richer in pores than the first layer 12 and the third layer 16, the extension of dendrite in the secondary battery and the cause thereof The short circuit between the positive and negative electrodes can be effectively suppressed or delayed. In this case, since the porous ceramics corresponding to the second layer 14 can be omitted, there is an advantage that the material cost can be reduced. When the same porous ceramic is used for the first layer 12 and the third layer 16, only one kind of porous ceramic is prepared, and two such porous ceramics are prepared so that the space is formed in the second layer 14. Therefore, it is possible to reduce both the number of parts and the kind of parts, thereby realizing further cost reduction.

  According to still another preferred embodiment of the present invention, the second layer 14 may be composed of a porous ceramic and a space richer in pores than the first layer 12 and the third layer 16. That is, the second layer 14 may include both a portion made of porous ceramics rich in pores and a portion made of space. In this case, the material cost can be reduced to some extent by reducing the porous ceramics used for the second layer 14 while ensuring the ease of three-layer lamination by configuring the second layer 14 with the porous ceramics. There are advantages.

  The thickness of each of the first layer 12, the second layer 14, and the third layer 16 is not particularly limited as long as a desired dendrite suppressing effect is obtained, but is preferably 100 to 1000 μm, more preferably 100 to 800 μm. More preferably, it is 200-800 micrometers, Most preferably, it is 200-500 micrometers. The thicknesses of the first layer 12, the second layer 14, and the third layer 16 may be the same or different. For example, the first layer 12 and the third layer 16 may have the same thickness, and may be thicker or thinner than the second layer. The total thickness of the first layer 12, the second layer 14, and the third layer 16 is not particularly limited, but is preferably 300 to 3,000 μm, more preferably 300 to 1,500 μm, and still more preferably 300 to 1. , 000 μm.

  The first layer 12, the second layer 14, and the third layer 16 may be formed separately, or may be formed integrally. When the first layer 12, the second layer 14, and the third layer 16 are formed separately, these layers may be simply stacked to form a three-layer structure. In some cases, the first layer 12 and the third layer 16 may be separated by a predetermined distance (via a spacer or the like as necessary) to form the second layer 14 having a desired thickness. On the other hand, when the first layer 12, the second layer 14, and the third layer 16 are integrally formed, 1) the first layer 12 and the third layer 16 are formed on both side surfaces of the second layer 14, respectively. For example, after forming a precursor layer on each side surface of the second layer 14 formed as a sintered body by slurry coating or the like, the precursor layer is fired to form the first layer 12 and the third layer 16. Also good. Alternatively, 2) After the precursor layer of the second layer 14 is produced by tape molding, the precursor layer of the first layer 12 and the precursor layer of the third layer 16 are produced by tape molding on both side surfaces thereof, and then integrally fired. 3) The precursor layer of the first layer 12, the precursor layer of the second layer 14, and the precursor layer of the third layer 16 are respectively produced by tape molding or extrusion molding, and after tape lamination, integral molding and integral firing May be.

Secondary Battery A secondary battery can be provided using the multilayer porous separator according to the present invention. Such a secondary battery includes a positive electrode, a negative electrode, a multilayer porous separator according to the present invention that separates the positive electrode and the negative electrode, and an electrolytic solution. FIG. 2 schematically shows an example of the secondary battery according to the present invention. The secondary battery 20 shown in FIG. 2 has a configuration in which the positive electrode 22 is provided on the first layer 12 side of the multilayer porous separator 10 and the negative electrode 28 is provided on the third layer 16 side. The positive electrode 22 may be provided, and the negative electrode 28 may be provided on the first layer 12 side. The positive electrode 22 includes a positive electrode active material 24 on a positive electrode current collector 26 and is disposed in a battery container (not shown) with the positive electrode active material 24 facing the first layer 12 side. The negative electrode 28 includes a negative electrode active material 30 on a negative electrode current collector 32, and is disposed in a battery container (not shown) with the negative electrode active material 30 facing the third layer 16 side. Typically, the positive electrode 22 and the negative electrode 28 are disposed so that the positive electrode current collector 26 and the negative electrode current collector 32 are in contact with the inner wall of the battery container. The inside of the battery container is filled with the electrolytic solution, and the positive electrode 22 and the negative electrode 28 are immersed in the electrolytic solution. However, it is the dendrite that the multilayer porous separator 10 is completely separated into the compartment on the positive electrode 22 side and the compartment on the negative electrode 28 side. This is desirable for effective suppression. Therefore, it is desirable that the outer peripheral edge of the multilayer porous separator 10 and the inner wall of the battery container are bonded so as to ensure liquid-tightness so that liquid junction can be achieved only through the separator.

  The secondary battery of the present invention includes various secondary batteries to which a porous separator can be applied, such as a nickel zinc secondary battery, a silver zinc oxide secondary battery, a manganese zinc oxide secondary battery, and other various alkaline zinc secondary batteries. Can be. Most preferably, it is a nickel zinc secondary battery. In the case of a zinc secondary battery, the negative electrode preferably contains zinc and / or zinc oxide. Zinc may be contained in any form of zinc metal, zinc compound and zinc alloy as long as it has an electrochemical activity suitable for the negative electrode. Preferable examples of the negative electrode material include zinc oxide, zinc metal, calcium zincate and the like, and a mixture of zinc metal and zinc oxide is more preferable. The positive electrode may be appropriately configured according to the type of secondary battery employed, but in the case of a nickel zinc secondary battery, it is preferable that the positive electrode contains nickel hydroxide and / or nickel oxyhydroxide. The electrolyte is typically an alkaline electrolyte and preferably comprises an alkali metal hydroxide. Examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide and the like, and potassium hydroxide is more preferable.

  The present invention is more specifically described by the following examples. In addition, the evaluation method of each layer and separator produced in the following examples was as follows.

<Porosity>
The porosity of the porous plate constituting each layer was measured by 1) observing the surface microstructure with a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL) at an acceleration voltage of 10 to 20 kV. Obtain an electron microscope (SEM) image (magnification of 10,000 times or more) on the surface of the plate. 2) Read a grayscale SEM image using image analysis software such as Photoshop (manufactured by Adobe) 3) [Image] → [ Black and white binary image is created by the procedure of [tone correction] → [2 gradations], and 4) the porosity (%) is obtained by dividing the number of pixels occupied by the black portion by the total number of pixels of the image. went. This porosity measurement was performed on a 6 μm × 6 μm region on the surface of the porous plate.

<Average pore diameter>
The average pore diameter of the porous plate constituting each layer was measured by measuring the longest distance of the pores based on an electron microscope (SEM) image of the surface of the porous plate. The magnification of the electron microscope (SEM) image used for this measurement is 20000 times, and all the obtained pore diameters are arranged in order of size, and the top 15 points and the bottom 15 points from the average value, and 30 points per visual field in total. The average value for two visual fields was calculated to obtain the average pore diameter. For length measurement, the length measurement function of SEM software was used.

<Dendrite short-circuit confirmation test>
In order to evaluate the dendrite suppressing ability of the separator, an acceleration test was conducted in which a measuring apparatus 110 as schematically shown in FIG. 3 was constructed to continuously grow zinc dendrite. Specifically, a rectangular parallelepiped container 112 made of ABS resin was prepared, and the first zinc electrode 114a and the second zinc electrode 114b were placed in the container so as to be spaced apart from each other by 0.5 cm. Both the first zinc electrode 114a and the second zinc electrode 114b are metal zinc plates. On the other hand, the separator sample was coated with an epoxy resin adhesive along the outer periphery thereof and attached to an ABS resin jig having an opening at the center to obtain a separator structure 116 including a separator. At this time, it was sufficiently sealed with the above-mentioned adhesive so that liquid tightness was secured at the joint between the jig and the separator sample. Then, a separator sample is disposed as the separator structure 116 in the container 112, and the first section 115a including the first zinc electrode 114a and the second section 115b including the second zinc electrode 114b are liquidated at locations other than the separator. Isolated so as not to allow communication. At this time, epoxy resin adhesive is used to bond the three outer edges of the rectangular separator structure 116 (that is, the three outer edges of the ABS resin jig) to the inner wall of the container 112 so as to ensure liquid-tightness. I let you. That is, the joint portion between the separator structure 116 including the separator and the container 112 was sealed so as not to allow liquid communication. A 6 mol / L aqueous KOH solution as an alkali metal hydroxide aqueous solution 118 is put into the first compartment 115a together with a ZnO powder corresponding to the saturation solubility, and a 6 mol / L KOH aqueous solution as an alkali metal hydroxide aqueous solution 118 is also added to the second compartment 115b. Put. Moreover, 1 mol / L of aluminum hydroxide was dissolved in the alkali metal hydroxide aqueous solution 118 in both the first section 115a and the second section 115b. The first zinc electrode 114a and the second zinc electrode 114b were connected to the negative electrode and the positive electrode of the constant current power source, respectively, and a voltmeter was connected in parallel with the constant current power source. In both the first compartment 115a and the second compartment 115b, the water level of the alkali metal hydroxide aqueous solution 118 is set so that the entire region of the separator sample is immersed in the alkali metal hydroxide aqueous solution 118, and the separator structure 116 ( The height was not exceeded (including the jig).

In the measuring apparatus 110 constructed in this way, a constant current of 20 mA / cm ² was continuously passed between the first zinc electrode 114a and the second zinc electrode 114b for a maximum of 200 hours. Meanwhile, the first compartment 115a is replenished with water and ZnO in an amount corresponding to the decrease in water and ZnO as needed, while the alkali metal hydroxide aqueous solution 118 in an amount according to the increase in water is occasionally added from the second compartment 115b. Removed to avoid overflowing. In addition, ZnO which was saturated in the first section 115a and was not dissolved any more was left as it was without being removed. While performing such an operation, the following evaluations 1 and 2 were performed while monitoring the value of the voltage flowing between the two zinc electrodes 114a and 114b with a voltmeter.

<Evaluation 1: Presence or absence of short circuit phenomenon>
The presence or absence of a rapid voltage drop due to a zinc dendrite short circuit between two zinc plates was confirmed. Even when the current was passed for 200 hours, a case where there was no rapid voltage drop due to a zinc dendrite short-circuit was judged as having a high dendrite suppression effect.

<Evaluation 2: Presence or absence of zinc marks>
After performing Evaluation 1, the surface of the separator on the side opposite to the dendrite growth side was observed visually and with an optical microscope to determine the presence or absence of zinc marks specified by black spots or the like. Those in which no zinc marks were observed even when energized for 200 hours were determined as those having a particularly high dendrite suppressing effect (that is, those that can be expected to have a dendrite suppressing effect over a long period of time thereafter).

Example 1
As shown in FIG. 1, a separator having a three-layer structure including a first layer, a second layer, and a third layer in order was produced. Each layer is made of an alumina porous plate having a thickness of 200 μm, and the thickness, porosity and average pore diameter are as shown in Table 1.

  The first layer and the third layer were the same, and both were prepared as follows. First, boehmite (manufactured by Sasol, DISPAL 18N4-80), methylcellulose, and ion-exchanged water were weighed so that the mass ratio of (boehmite) :( methylcellulose) :( ion-exchanged water) was 10: 1: 5. Then, it knead | mixed. The obtained kneaded product was subjected to extrusion molding using a hand press and molded into a plate shape. The obtained molded body was dried at 80 ° C. for 12 hours and then fired to obtain an alumina porous plate. The porous plate thus obtained was cut into a size of 5 cm × 8 cm. The obtained porous plate was ultrasonically cleaned in acetone for 5 minutes, ultrasonically cleaned in ethanol for 2 minutes, and then ultrasonically cleaned in ion-exchanged water for 1 minute. The thickness, porosity, and average pore diameter of the first and second layers were measured and as shown in Table 1.

  On the other hand, the second layer is an alumina porous plate having the same composition and thickness as the first layer and the third layer, but the firing conditions are changed so that the porosity and the average pore diameter are the first layer and the third layer. It was made to be much higher than. When the thickness, porosity, and average pore diameter of the first layer and the third layer were measured, they were as shown in Table 1.

  For the separator having a three-layer structure as shown in FIG. 1 provided with the first layer, the second layer, and the third layer in this order, a dendrite short-circuit confirmation test was performed. As shown in Table 1, Even after 200 hours of energization, no short circuit occurred, no zinc marks (black spots) were observed, and the surface was only a white ceramic color.

Example 2
A three-layer separator was prepared and evaluated in the same manner as in Example 1 except that the second layer was formed in a space having a thickness of 200 μm. The results are as shown in Table 1, and good results were obtained as in Example 1.

Example 3 (Comparison)
A separator was prepared and evaluated in the same manner as in Example 1 except that a single-layer separator having a thickness of 400 μm, a porosity of 40%, and an average pore diameter of 1 μm was used. This single-layer separator is an alumina porous plate similar to the first layer and the third layer in Example 1 except that the thickness is 400 μm, and the first layer of Example 1 except that the thickness is changed. And it produced like the 3rd layer. When the thickness, porosity, and average pore diameter of this one-layer separator were measured, they were as shown in Table 1. Further, when this separator was subjected to a dendrite short-circuit confirmation test, as shown in Table 1, a short-circuit phenomenon occurred after energization for 7 hours, and zinc marks (black spots) were observed in several places.

Example 4 Production of Secondary Battery A nickel zinc secondary battery having a structure as shown in FIG. 2 can be produced using each of the multilayer porous separators obtained in Example 1 and Example 2 as follows. .

(1) Preparation of multilayer porous separator The multilayer porous separator obtained in Example 1 or Example 2 is prepared.

(2) Preparation of positive electrode plate Nickel hydroxide particles to which zinc and cobalt are added so as to form a solid solution are prepared. The nickel hydroxide particles are coated with cobalt hydroxide to obtain a positive electrode active material. The obtained positive electrode active material and a 2% aqueous solution of carboxymethylcellulose are mixed to prepare a paste. The paste obtained above is uniformly applied to a current collector made of a nickel metal porous substrate having a porosity of about 95% and dried so that the porosity of the positive electrode active material is 50%. A positive electrode plate coated over a predetermined area is obtained.

(3) Production of negative electrode plate A mixture of 80 parts by weight of zinc oxide powder, 20 parts by weight of zinc powder and 3 parts by weight of polytetrafluoroethylene particles was applied on a current collector made of copper punching metal, and the porosity was about A negative electrode plate in which the active material portion is applied over a predetermined region at 50% is obtained.

(4) Battery assembly Using the positive electrode plate, the negative electrode plate, and the multilayer porous separator obtained above, a nickel zinc secondary battery including the configuration shown in FIG. 2 is assembled in the following procedure. First, an ABS resin rectangular parallelepiped case main body with the case upper lid removed is prepared. A multilayer porous separator is inserted near the center of the case body, and three sides thereof are fixed to the inner wall of the case body using a commercially available epoxy resin adhesive. The positive electrode plate and the negative electrode plate are inserted into the positive electrode chamber and the negative electrode chamber, respectively. At this time, the positive electrode plate and the negative electrode plate are arranged so that the positive electrode current collector and the negative electrode current collector are in contact with the inner wall of the case body. In the positive electrode chamber, a 6 mol / L aqueous solution of KOH in an amount that does not exceed the separator, although the positive electrode active material coating portion is sufficiently hidden, is injected as an electrolytic solution. Similarly, a 6 mol / L aqueous solution of KOH in an amount that does not exceed the height of the separator is injected as an electrolytic solution into the negative electrode chamber, where the negative electrode active material coating portion is sufficiently hidden. The terminal portions of the positive electrode current collector and the negative electrode current collector are respectively connected to external terminals at the top of the case. The case upper lid is fixed to the case body by heat sealing, and the battery case container is sealed. Thus, a nickel zinc secondary battery is obtained.

DESCRIPTION OF SYMBOLS 10 Multilayer porous separator 12 1st layer 14 2nd layer 16 3rd layer 20 Secondary battery 22 Positive electrode 24 Positive electrode active material 26 Positive electrode collector 28 Negative electrode 30 Negative electrode active material 32 Negative electrode collector

Claims (19)

A multi-layer porous separator for separating a positive electrode and a negative electrode in a secondary battery,
A first layer and a third layer which are provided to be spaced apart from and opposed to each other and are made of porous ceramics;
A second layer composed of porous ceramics provided between the first layer and the third layer and having a higher porosity than the first layer and the third layer;
A multilayer porous separator, wherein the second layer has an average pore diameter of 5 μm or more. The multilayer porous separator according to claim 1, wherein the second layer has a higher porosity than the first layer and the third layer. The multilayer porous separator according to claim 1 or 2, wherein the second layer has a larger average pore diameter than the first layer and the third layer. The multilayer porous separator according to any one of claims 1 to 3, wherein each of the first layer and the third layer has a porosity of 60% or less. The multilayer porous separator according to any one of claims 1 to 3, wherein each of the first layer and the third layer has a porosity of 50% or less. The multilayer porous separator according to any one of claims 1 to 3, wherein each of the first layer and the third layer has a porosity of 40% or less. The multilayer porous separator according to any one of claims 1 to 6, wherein the second layer has a porosity of 40% or more. The multilayer porous separator according to any one of claims 1 to 6, wherein the second layer has a porosity of 50% or more. The multilayer porous separator according to any one of claims 1 to 6, wherein the second layer has a porosity of 60% or more. Each of said 1st layer and said 3rd layer has an average pore diameter of 10 micrometers or less, 1-9
The multilayer porous separator according to any one of the above. The multilayer porous separator according to any one of claims 1 to 9, wherein each of the first layer and the third layer has an average pore diameter of 5 µm or less. The multilayer porous separator according to any one of claims 1 to 9, wherein each of the first layer and the third layer has an average pore diameter of 1 µm or less. The multilayer porous separator according to any one of claims 1 to 12, wherein the second layer has an average pore diameter of 10 µm or more. A multi-layer porous separator for separating a positive electrode and a negative electrode in a secondary battery,
A first layer and a third layer which are provided to be spaced apart from and opposed to each other and are made of porous ceramics;
A second layer provided between the first layer and the third layer and configured by a space;
A multilayer porous separator. The multilayer porous separator according to any one of claims 1 to 14, wherein each of the first layer, the second layer, and the third layer has a thickness of 100 to 1000 µm. The porous ceramic is at least one selected from the group consisting of alumina, zirconia, titania, magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite, zinc oxide, silicon carbide, aluminum nitride, and silicon nitride. is there,
The multilayer porous separator as described in any one of Claims 1-15. The multilayer porous separator according to any one of claims 1 to 16, wherein the secondary battery is a nickel zinc secondary battery. The secondary battery provided with the positive electrode, the negative electrode, the multilayer porous separator as described in any one of Claims 1-17 which isolates the said positive electrode and the said negative electrode, and electrolyte solution. The secondary battery according to claim 18, wherein the secondary battery is a nickel zinc secondary battery.

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