Separator and zinc secondary battery

Abstract

This separator is used in a zinc secondary battery. The separator comprises an inorganic compound in which pores are formed. The average pore diameter of the inorganic compound is at least 0.3 nm and at most 10 nm. When a liquid tank in which two tubes each having an inner diameter of 6 mm protrude upward, which is partitioned into two chambers by a separator having a diameter of 26 mm, and which is filled with a 6M KOH aqueous solution is used as a measurement device, the liquid permeation amount measured 168 hours after the liquid level difference of the tubes is set to 70 cm is at least 0.05 mL and at most 5 mL.

Description

Separator and zinc secondary battery

[0001] This disclosure relates to separators and zinc secondary batteries. This application claims priority under Japanese application No. 2024-172656, filed on 1 October 2024, and incorporates all the provisions contained herein.

[0002] Technologies relating to separators used in zinc secondary batteries are disclosed, for example, in WO2020 / 255856 (Patent Document 1), WO2021 / 229916 (Patent Document 2), and WO2021 / 229917 (Patent Document 3).

[0003] WO2020 / 255856WO2021 / 229916WO2021 / 229917

[0004] The separator used in zinc secondary batteries is placed in the electrolyte and separates the positive and negative electrodes. In zinc secondary batteries, the composition of the electrolyte gradually changes during charging, discharging, or repeated charging and discharging, causing a change in the hydrogen ion concentration (pH). This increases the resistance during charging and discharging, which is undesirable. Therefore, it is necessary to suppress changes in the pH of the electrolyte as much as possible. Furthermore, from the viewpoint of ensuring stable use over a long period, high alkali resistance is required for the separator. In addition, in zinc secondary batteries, it is known that metallic zinc deposits in the form of dendrites from the negative electrode during charging, penetrates the voids in the separator such as nonwoven fabric, and reaches the positive electrode, resulting in a short circuit. Such short circuits caused by zinc (Zn) dendrites are also undesirable as they shorten the charge-discharge life. Therefore, from the viewpoint of ensuring stable use over a long period, high short-circuit resistance is required for the separator.

[0005] Therefore, one of the objectives is to provide a separator that can be used stably over a long period of time.

[0006] The separator according to this disclosure is used in a zinc secondary battery. The separator comprises an inorganic compound in which pores are formed. The average pore size of the inorganic compound is 0.3 nm to 10 nm. Two tubes, each with an inner diameter of 6 mm, protrude upward from each other and are divided into two chambers by the separator with a diameter of 26 mm. A liquid tank filled with a 6 M KOH aqueous solution is used as a measuring device, and after setting the liquid level difference between each tube to 70 cm, the permeable volume measured after 168 hours is 0.05 mL to 5 mL.

[0007] Such separators allow for stable use over long periods of time.

[0008] Figure 1 is a schematic diagram conceptually showing a part of a zinc secondary battery including a separator in Embodiment 1. Figure 2 is a schematic diagram showing an enlarged portion of the cross-section of the separator. Figure 3 is a schematic diagram schematically showing a part of the separator manufacturing process. Figure 4 is a schematic diagram showing a part of the He permeability measurement system for measuring He permeability. Figure 5 is a schematic diagram showing a part of the He permeability measurement system for measuring He permeability. Figure 6 is a schematic diagram of a measuring device for measuring the conductivity of the separator. Figure 7 is a schematic diagram of a measuring device for measuring the permeability.

[0009] [Outline of Embodiments] First, embodiments of the present disclosure will be listed and described. The separator according to the present disclosure is used in a zinc secondary battery. The separator comprises an inorganic compound in which pores are formed. The average pore diameter of the inorganic compound is 0.3 nm or more and 10 nm or less. Two tubes, each with an inner diameter of 6 mm, protrude upward and are separated into two chambers by a separator with a diameter of 26 mm. A liquid tank filled with a 6 M KOH aqueous solution is used as a measuring device, and after setting the liquid level difference between each tube to 70 cm, the permeable volume measured after 168 hours is 0.05 mL or more and 5 mL or less.

[0010] The separator with the above configuration contains an inorganic compound, thus ensuring high short-circuit resistance. Furthermore, the average pore size of the pores formed in the inorganic compound is relatively small, between 0.3 nm and 10 nm. Therefore, the permeation of zinc (Zn) ions through the separator can be suppressed. As a result, Zn dendrites are prevented from penetrating the separator and reaching the positive electrode, reducing the risk of short-circuiting between the positive and negative electrodes. Also, because the average pore size of the inorganic compound is between 0.3 nm and 10 nm, water molecules, in addition to hydroxide ions, can pass through the separator. The permeability of a 6 M KOH aqueous solution after 168 hours is between 0.05 mL and 5 mL, ensuring a high permeability. Therefore, changes in the pH of the electrolyte are suppressed, and changes in the electrolyte composition over a long period can be reduced. Based on the above, the separator according to this disclosure can be used stably over a long period.

[0011] In the separator according to the above embodiment, the thickness of the separator may be 1 μm or more and 200 μm or less. A thinner separator tends to result in a higher permeability. However, a thinner separator tends to reduce short-circuit resistance. By setting the separator thickness within the above range, it becomes easier to achieve both sufficient permeability and high short-circuit characteristics. It is more preferable that the separator thickness be 5 μm or more and 100 μm or less.

[0012] In any one of the above embodiments of the separator, the porosity of the separator may be 3% or more and 50% or less. The higher the porosity of the separator, the greater the permeability tends to be. However, when the porosity of the separator is high, the short-circuit characteristics tend to decrease. By setting the porosity of the separator within the above range, it becomes easier to achieve both sufficient permeability and high short-circuit characteristics. It is more preferable that the porosity of the separator be 5% or more and 30% or less.

[0013] In any one of the above embodiments of the separator, the inorganic compound may contain at least one element selected from the group consisting of titanium, zirconium, magnesium, calcium, yttrium, cerium, and lanthanum. By doing so, the inorganic compound with the above configuration can be obtained more reliably and can be used more reliably and stably over a long period of time.

[0014] A separator according to any one of the above embodiments may further include a porous resin substrate. The inorganic compound may be disposed in at least one of the surface layer and / or the inner layer of the resin substrate. This imparts flexibility to the inorganic compound, thereby reducing the breakage of the separator during manufacturing and battery operation.

[0015] In any one of the above embodiments of the separator, the inorganic compound may include one of titanium dioxide, zirconium oxide, magnesium hydroxide, calcium hydroxide, yttrium hydroxide, cerium hydroxide, and lanthanum hydroxide. Such inorganic compounds are suitably used to obtain the above-described separator.

[0016] In a separator comprising any one of the above embodiments, the average pore size of the inorganic compound may be 3 nm or more and 8 nm or less. Such a separator can easily achieve high ionic conductivity or suppression of resistance increase, thus providing better properties.

[0017] Furthermore, the zinc secondary battery of this disclosure includes a positive electrode, a negative electrode positioned at a distance from the positive electrode, an electrolyte positioned in contact with the positive electrode and the negative electrode, and the separator described above positioned to separate the positive electrode side and the negative electrode side in the electrolyte.

[0018] The zinc secondary battery with the above configuration can be used stably over a long period of time.

[0019] [Specific Examples of Embodiments] Next, specific embodiments of the separator of this disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0020] (Embodiment 1) The separator in Embodiment 1 according to this disclosure is used in a zinc secondary battery. The zinc secondary battery can be repeatedly charged and discharged. Figure 1 is a schematic diagram conceptually showing a part of the zinc secondary battery including the separator in Embodiment 1.

[0021] Referring to Figure 1, the separator 15 in Embodiment 1 is used in a zinc secondary battery 11. The zinc secondary battery includes a positive electrode 12, a negative electrode 13, an electrolyte 14, and a separator 15. Nickel (Ni) is used as the positive electrode active material constituting the positive electrode 12. Zinc (Zn) is used as the negative electrode active material constituting the negative electrode 13. The negative electrode 13 is positioned at a distance from the positive electrode 12. The electrolyte 14 is positioned in contact with the positive electrode 12 and the negative electrode 13, respectively. The positive electrode 12 and the negative electrode 13 are immersed in the electrolyte 14. The separator 15 is positioned in the electrolyte 14 and separates the positive electrode 12 side from the negative electrode 13 side. The separator 15 is permeable to hydroxide ions.

[0022] Here, the structure of the separator 15 will be further explained. Figure 2 is a schematic diagram showing an enlarged portion of the cross-section of the separator 15. Referring to Figure 2, the separator 15 includes an inorganic compound 16 and a porous resin substrate 17. The surface layer 18 of the separator 15 is mainly composed of the inorganic compound 16. The inner layer 19 of the separator 15 is composed of the inorganic compound 16 and the porous resin substrate 17. The inner layer 19 is mainly composed of the porous resin substrate 17, and the inorganic compound 16 with pores formed inside the resin substrate 17 is randomly arranged. Examples of materials for the porous resin substrate 17 include polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide, fluororesin (tetrafluorinated resin: PTFE, etc.), cellulose, nylon, polyethylene, and any combination thereof.

[0023] The inorganic compound 16 has pores formed therein. The average pore diameter of the pores formed in the inorganic compound 16 is 0.3 nm or more and 10 nm or less. Preferably, the average pore diameter of the pores is 3 nm or more and 8 nm or less.

[0024] The average pore diameter of the pores is measured as follows, for example, using the nitrogen gas adsorption method. As the apparatus, BELSORP18PLUS-HT manufactured by BEL Japan Inc. was used. As the pretreatment conditions, vacuum degassing was performed at room temperature for about 24 hours. Measurement: As the analysis conditions, the adsorbate was nitrogen, the measurement temperature was 77 K (liquid nitrogen temperature), and the BJH method was used as the pore size distribution analysis method.

[0025] In the present embodiment, the inorganic compound 16 contains at least one element selected from titanium (Ti), zirconium (Zr), magnesium (Mg), calcium (Ca), yttrium (Y), cerium (Ce), and lanthanum (La). Examples of the inorganic compound 16 include titanium oxide (TiO ２ ), zirconium oxide (ZrO ２ ), magnesium hydroxide (Mg(OH) ２ ), calcium hydroxide (Ca(OH) ２ ), yttrium hydroxide (Y(OH) ３ ), cerium hydroxide (Ce(OH) ４ ), lanthanum hydroxide (La(OH) ３ ), etc. are selected.

[0026] The above-described separator 15 can be manufactured, for example, by the following method. First, (1) a porous resin substrate is prepared, and (2) a colloidal solution containing the inorganic compound 16 is applied to the porous resin substrate and dried to form an inorganic compound-containing layer. FIG. 3 is a schematic diagram schematically showing a part of the manufacturing process of the separator 15. As shown in FIG. 3, in the colloidal solution 21 in which the particles 23 are dispersed in the solvent 22, the particles 23 aggregate with each other by coating and drying to form a dense structure. As the solvent 22, water or alcohol is selected. Then, pores 24 are formed between the particles 23. The particle size D of the particles 23 １By adjusting [it], the pore size can be adjusted. Specifically, by increasing the particle size D １ the pore size can be increased, and by decreasing the particle size D １ the pore size can be decreased. Also, if the particles 23 can be densely packed, the pore size will be about 15% of the particle size D １ .

[0027] In particular, when producing a composite material (i.e., the above separator) in which the porous resin base material is composed of a polymer material and the above inorganic compound is incorporated throughout the thickness direction of the porous resin base material, for the application of the colloidal solution to the base material in the above (2), it is preferable to perform it by a method that allows the colloidal particles to penetrate the whole or most of the inside of the base material. Examples of preferable coating methods include dip coating, filtration coating, etc., and dip coating is particularly preferable. By adjusting the number of coating times such as dip coating, the adhesion amount of the colloidal solution can be adjusted.

[0028] According to the separator 15 having the above-described configuration, since it contains the inorganic compound 16, its structure is stable, it has high alkali resistance, and high short-circuit resistance can be ensured. Also, the average pore size of the pores formed in the inorganic compound 16 is 0.3 nm or more and 10 nm or less, which is relatively small. Therefore, the permeation of Zn ions through the separator can be suppressed. As a result, it is possible to suppress the Zn dendrite from piercing through the separator 15 and reaching the positive electrode 12 side, and reduce the risk of short circuit between the positive electrode 12 and the negative electrode 13. Also, since the average pore size of the inorganic compound 16 is 0.3 nm or more and 10 nm or less, in addition to hydroxide ions, water molecules can pass through the separator 15. Then, a high liquid permeability can be ensured. Therefore, the change in the pH of the electrolyte 14 can be suppressed, and the change in the composition of the electrolyte 14 over a long period can be reduced. From the above, according to the separator 15 according to the present disclosure, it can be stably used over a long period.

[0029] In this embodiment, a porous resin substrate 17 is included. The inorganic compound 16 is disposed in at least one of the surface layer 18 of the resin substrate 17 and the internal layer 19 of the resin substrate. Therefore, it is possible to achieve both the short-circuit resistance by the inorganic compound 16 and the flexibility by the resin substrate 17. By having flexibility, there are advantages such as (1) being difficult to crack even when thin, and (2) being easy to manufacture and handle.

[0030] In the above embodiment, the inorganic compound 16 may contain at least one element selected from the group consisting of titanium, zirconium, magnesium, calcium, yttrium, cerium, and lanthanum. By doing so, the inorganic compound 16 having the above configuration can be obtained more reliably, and it can be used stably over a longer period more reliably.

[0031] Further, in the above embodiment, the inorganic compound 16 may contain any one of titanium oxide, zirconium oxide, magnesium hydroxide, calcium hydroxide, yttrium hydroxide, cerium hydroxide, and lanthanum hydroxide. Such an inorganic compound is suitably used for obtaining the separator having the above configuration.

[0032] In the above embodiment, the average pore diameter of the inorganic compound 16 may be 3 nm or more and 8 nm or less. Such a separator 15 can easily achieve high ion conductivity or suppression of an increase in resistance, and thus better characteristics can be obtained.

[0033] Further, the zinc secondary battery 11 of the present disclosure includes a positive electrode 12, a negative electrode 13 disposed at an interval from the positive electrode 12, an electrolytic solution 14 disposed so as to contact each of the positive electrode 12 and the negative electrode 13, and the separator 15 described above disposed so as to partition the positive electrode 12 side and the negative electrode 13 side in the electrolytic solution 14.

[0034] According to the zinc secondary battery 11 having the above configuration, it can be used stably over a long period.

[0035] Eighteen samples were prepared with altered inorganic compound compositions, and each was evaluated. The results are shown in Table 1. The inorganic compound compositions are as listed in Table 1. The evaluation method for each evaluation item was as follows. In Table 1, "100th cycle" refers to the timing of the 100th charge-discharge cycle after 100 charge-discharge cycles. The resistance at the end of charging, described later, was measured for sample 14 (ZrO ２ The ratio was calculated using the compound separator as a reference.

[0036] Figures 4 and 5 are schematic diagrams showing parts of a He (helium) permeability measurement system, respectively. For He (helium) permeability measurement, the He permeability measurement system 310 shown in Figures 4 and 5 is configured such that He gas from a gas cylinder filled with He gas is supplied to a sample holder 316 via a pressure gauge 312 and a flow meter 314 (digital flow meter), and is discharged by permeating from one side to the other side of a separator 318 held in the sample holder 316.

[0037] The sample holder 316 has a structure equipped with a gas supply port 316a, a sealed space 316b, and a gas outlet 316c, and was assembled as follows. First, adhesive 322 was applied along the outer circumference of the separator 318 and attached to a jig 324 (ABS resin) having an opening in the center. Butyl rubber packings were placed at the upper and lower ends of the jig 324 as sealing members 326a and 326b, and further, support members 328a and 328b (made of PTFE) having flange openings were sandwiched from the outside of the sealing members 326a and 326b. In this way, the sealed space 316b was partitioned by the separator 318, jig 324, sealing member 326a, and support member 328a. The support members 328a and 328b were tightly fastened to each other with screw fastening means 330 to prevent leakage of He gas from parts other than the gas outlet 316c. A gas supply pipe 334 was connected to the gas supply port 316a of the assembled sample holder 316 via a fitting 332.

[0038] Next, He gas was supplied to the He permeability measurement system 310 via the gas supply pipe 334 and allowed to permeate through the separator 318 held in the sample holder 316. At this time, the gas supply pressure and flow rate were monitored using the pressure gauge 312 and the flow meter 314. After the He gas permeation was performed for 1 to 30 minutes, the He permeability was calculated. The He permeability was calculated as the amount of He gas permeated per unit time F (cm ３ ( / min), the differential pressure P (atm) applied to the separator 318 when He gas permeates, and the membrane area S (cm²) through which He gas permeates. ２ The permeation rate of He gas F (cm) was calculated using the formula F / (P×S). ３ The flow rate (per minute) was read directly from the flow meter 314. The differential pressure P was measured using the gauge pressure read from the pressure gauge 312. The He gas was supplied so that the differential pressure P was within the range of 0.05 to 0.90 atm.

[0039] The ionic conductivity was measured in the electrolyte using the electrochemical measurement cell shown in Figure 6, as follows. Figure 6 is a schematic diagram of the measuring device 410 for measuring the conductivity of the separator. First, adhesive 449 was applied along the outer circumference of the separator 448 and attached to a jig 450 (ABS resin) having an opening in the center. This jig 450 was sandwiched on both sides with 1 mm thick silicone packing 440 and assembled into a PTFE flange-type cell 442 with an inner diameter of 6 mm. As electrodes 446, #100 mesh nickel wire mesh was assembled into the cell 442 in a cylindrical shape with a diameter of 6 mm, so that the distance between electrodes was 2.2 mm. To prevent leakage of the electrolyte from the cell 442, the electrodes were tightly fastened together with screw fastening means 447. As the electrolyte 444, a 6 M KOH (potassium hydroxide) aqueous solution was filled into the cell 442. Using an electrochemical measurement system (potentiometer / galvanostat-frequency response analyzer, Solartron models 1287A and 1255B), measurements were performed under conditions of a frequency range of 1 MHz to 0.1 Hz and a potential amplitude of 10 mV. The intercept of the real axis was defined as the combined resistance T of the separator 448 and the electrolyte 444. The same measurement was performed with a setup without separator 448 to determine the blank resistance B (resistance of electrolyte 444). The difference between the combined resistance T and the blank resistance B was defined as the resistance of separator 448. The ionic conductivity was determined using the obtained resistance of separator 448 and the area of ​​separator 448.

[0040] For measuring the permeability, the measuring device shown in Figure 7 was used. Figure 7 is a schematic diagram of the measuring device 510 for measuring the permeability. Referring to Figure 7, the measuring device 510 has a two-chamber structure in which two tubes 511 and 512 are erected using two perforated rubber stoppers 520. An opening 516 is provided between the two chambers 514 and 515, and a separator 513 is positioned to close this opening 516. A mesh material 518 is installed on the tube 512 side of the separator 513 to prevent deformation of the separator 513. Butyl rubber packings are installed on both sides of the separator 513 and the mesh material 518 as sealing members 517. The inner diameter of the tubes 511 and 512 is 6 mm. The diameter of the opening 516 is 26 mm. The measuring device 510 is tightly fastened to each other with screw fastening means 521 to prevent leakage of electrolyte from the measuring device 510. Subsequently, a 6M KOH aqueous solution was filled into two tubes 511 and 512 as the electrolyte 519. The electrolyte 519 was poured so that the liquid level on the tube 511 side was 70 cm higher than the liquid level on the tube 512 side. The liquid temperature was set to 25°C and the atmospheric pressure to 1 atm. Specifically, as shown in Figure 7, two tubes, each with an inner diameter of 6 mm, protruded upwards and were divided into two chambers by a 26 mm diameter separator. A liquid tank filled with a 6M KOH aqueous solution was used as the measuring device 510. The permeability was measured from the change in liquid level after a certain period of time, specifically 168 hours.

[0041] The presence or absence of short circuits was confirmed by repeatedly performing charge-discharge tests. First, the positive electrode (containing nickel hydroxide and / or nickel oxyhydroxide) and the negative electrode (containing zinc and / or zinc oxide) were each wrapped in nonwoven fabric, and current extraction terminals were welded to them. The prepared positive and negative electrodes were placed opposite each other with a separator in between, sandwiched between laminate films with current extraction ports, and three sides of the laminate film were heat-sealed. An electrolyte (containing 0.5 M Zn ions in a 6 M KOH aqueous solution) was added to the resulting open-top cell container, and the electrolyte was thoroughly permeated into the positive and negative electrodes by vacuuming, etc. Then, the remaining side of the laminate film was also heat-sealed to create a simple sealed cell. Using a charge-discharge device (Toyo System Co., Ltd., TOSCAT3100), chemical conversion was performed on the simple sealed cell with 0.1 C charge and 0.2 C discharge. Subsequently, a 0.5 C charge-discharge cycle was performed. While repeatedly performing charge-discharge cycles under the same conditions, the voltage between the positive and negative electrodes was monitored with a voltmeter to check for the presence of a sudden voltage drop (specifically, a voltage drop of 5 mV or more compared to the immediately preceding plotted voltage) due to a short circuit caused by Zn dendrites between the positive and negative electrodes. This was evaluated according to the following criteria: If the above-mentioned sudden voltage drop was not observed during charging even after 100 cycles, it was considered "no short circuit," and if the above-mentioned sudden voltage drop was observed during charging in less than 100 cycles, it was considered "short circuit present."

[0042] For the resistance at the end of charging, the "current value I" measured at the end of a predetermined number of 0.5C charge-discharge cycles and the "cell voltage V" 5 minutes after the end of charging were used, and the resistance at the end of charging was calculated as (1.9 - V) / I. The resistance at the end of charging after 100 cycles for each sample was calculated as a relative ratio with the resistance at the end of charging of sample 14 set to 1.0.

[0043]

[0044] Referring to Table 1, the average pore size of the inorganic compounds contained in the separators of Samples 1 to 13 is between 0.3 nm and 10 nm. Specifically, the inorganic compound contained in the separator of Sample 1 is ZrO ２The average pore size is 0.3 nm. The inorganic compound contained in the separator of Sample 2 is ZrO ２ The average pore size is 0.5 nm. The inorganic compound contained in the separator of Sample 3 is ZrO ２ The average pore size is 1 nm. The inorganic compound contained in the separator of sample 4 is ZrO ２ The average pore size is 3 nm. The inorganic compound contained in the separator of sample 5 is ZrO ２ The average pore size is 8 nm. The inorganic compound contained in the separator of sample 6 is ZrO ２ The average pore size is 10 nm. The inorganic compound contained in the separator of sample 7 is Mg(OH) ２ The average pore size is 7 nm. The inorganic compound contained in the separator of sample 8 is La(OH) ３ The average pore size is 5 nm. The inorganic compound contained in the separator of sample 9 is TiO ２ The average pore size is 8 nm. The inorganic compound contained in the separator of sample 10 is Ca(OH) ２ The average pore size is 7 nm. The inorganic compound contained in the separator of sample 11 is Y(OH) ３ The average pore size is 6 nm. The inorganic compound contained in the separator of sample 12 is Ce(OH) ４ The average pore size is 7 nm. The inorganic compound contained in the separator of sample 13 is ZrO ２ and TiO ２ It is a mixture of the following, with an average pore size of 5 nm.

[0045] In contrast to these, the inorganic compound contained in the separator of sample 14 is ZrO ２ The average pore size is 0.2 nm. The inorganic compound contained in the separator of sample 15 is ZrO ２ The average pore size is 14 nm. The inorganic compound contained in the separator of sample 16 is Mg(OH) ２The average pore size is 13 nm. The inorganic compound contained in the separator of sample 17 is La(OH) ３ The average pore size is 15 nm. The inorganic compound contained in the separator of sample 18 is TiO ２ The average pore size is 11 nm.

[0046] For samples 1-13, the He transmittance was 0 (cm / min·atm), and the ionic conductivity was 0.5 (S / cm ２ ) or higher. In particular, for sample 6, which has high ionic conductivity, the ionic conductivity is 3.5 (S / cm). ２ ) and for sample 1, the ionic conductivity was 2.8 (S / cm). ２ ) and for sample 10 and sample 12, the ionic conductivity was 2.3 (S / cm²). ２ ) are examples. For all of samples 1 to 13, the permeable volume after 168 hours was 0.05 mL or more and 5 mL or less, and more specifically, the permeable volume was 0.06 mL or more and 4.92 mL or less. In addition, there were no short circuits up to the 100th cycle, and the resistance at the end of charging at the 100th cycle was lower compared to the reference sample 14. In particular, samples 5, 6, 7, 9, 10, and 12 had very low resistances of 0.7 compared to the reference.

[0047] In contrast, for sample 14 (reference), the permeability after 168 hours was 0. For samples 15-18, the He permeability was 250 cm / min atm or higher, and the permeability after 168 hours was 6.28 mL or higher. Furthermore, a short circuit occurred by the 100th cycle.

[0048] (Other Embodiments) In the above embodiments, the separator includes an inorganic compound and a porous resin substrate, but it is not limited to this and may consist only of an inorganic compound.

[0049] The embodiments disclosed herein should be understood to be illustrative in all respects and not restrictive in any way. The scope of the invention is defined by the claims and not by the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included.

[0050] 11 Zinc secondary battery, 12 Positive electrode, 13 Negative electrode, 14 Electrolyte, 15 Separator, 16 Inorganic compound, 17 Resin substrate, 18 Surface layer, 19 Inner layer, 21 Colloidal solution, 22 Solvent, 23 Particles, 24 Pores, 310 He permeability measurement system, 312 Pressure gauge, 314 Flow meter, 316 Sample holder, 316a Gas supply port, 316b Sealed space, 316c Gas outlet, 318 Separator, 322 Adhesive, 324 Jig, 326a, 326b Sealing member, 328a, 328b Support member, 330 Fastening means, 332 Joint, 334 Gas supply pipe, 410 Measuring device, 440 Silicone packing, 442 Cell (PTFE type flange cell), 444 Electrolyte, 446 Electrode, 447 fastening means, 448 separator, 449 adhesive, 450 jig, 510 measuring device, 511, 512 tube, 513 separator, 514, 515 chamber, 516 opening, 517 sealing member, 518 mesh material, 519 electrolyte, 520 perforated rubber stopper, 521 fastening means, 610 measuring device.

Claims

1. A separator used in a zinc secondary battery, comprising an inorganic compound having pores formed therein, wherein the average pore diameter of the inorganic compound is 0.3 nm or more and 10 nm or less, and two tubes, each with an inner diameter of 6 mm, protrude upward from each other, and are divided into two chambers by the separator with a diameter of 26 mm, and a liquid tank filled with a 6 M KOH aqueous solution is used as a measuring device, and the permeability measured after 168 hours after setting the liquid level difference between each tube to 70 cm is 0.05 mL or more and 5 mL or less.

2. The separator according to claim 1, wherein the inorganic compound comprises at least one element selected from the group consisting of titanium, zirconium, magnesium, calcium, yttrium, cerium, and lanthanum.

3. The separator according to claim 1 or 2, further comprising a porous resin substrate, wherein the inorganic compound is disposed in at least one of the surface layer and the inner layer of the resin substrate.

4. The separator according to claim 1 or 2, wherein the inorganic compound comprises one of titanium dioxide, zirconium oxide, magnesium hydroxide, calcium hydroxide, yttrium hydroxide, cerium hydroxide, and lanthanum hydroxide.

5. The separator according to claim 1 or claim 2, wherein the average pore size of the inorganic compound is 3 nm or more and 8 nm or less.

6. A zinc secondary battery comprising: a positive electrode; a negative electrode disposed at a distance from the positive electrode; an electrolyte disposed in contact with the positive electrode and the negative electrode, respectively; and a separator according to claim 1 or 2 disposed in the electrolyte to separate the positive electrode side from the negative electrode side.

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