Hydrotalcite and hydrogen sulfide absorbent containing same, sulfide-type all-solid-state battery exterior material, sulfide-type all-solid-state battery

Abstract

To provide a material excellent in both hydrogen sulfide adsorbing performance and moisture absorbing performance.SOLUTION: Hydrotalcite includes zinc element and magnesium element. In the hydrotalcite, a molar ratio (Zn / Mg) between the zinc element and the magnesium element is 0.1 or more and 1.0 or less. A ratio (IA / IB) between a peak intensity IA of the largest peak in a range of 2Θ=11.6±0.1° in XRD measurement and a peak intensity IB of the largest peak in a range of 2Θ=13.0±0.1° is less than 2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to hydrotalcite, a hydrogen sulfide absorbent containing the same, an exterior material for a sulfide-type all-solid-state battery, and a sulfide-type all-solid-state battery. [Background technology]

[0002] All-solid-state batteries are batteries in which a solid electrolyte is placed between the positive and negative electrodes instead of a liquid electrolyte. In addition to improving safety by not using flammable liquids, they are also expected to improve battery performance such as capacity and output. The electrolyte used in all-solid-state batteries is Li 10 GeP2S 12 and sulfide-based materials such as Li7La3Zr2O 12 and other oxide-based materials. Among these, sulfide-based solid electrolytes have the problem of reacting with water to generate harmful hydrogen sulfide. Therefore, when using sulfide-based solid electrolytes, batteries are sealed with a laminate to prevent moisture from coming into contact with the battery. It has also been proposed to provide an absorbent layer to adsorb moisture and hydrogen sulfide in the event of contact with moisture due to breakage or other reasons. For example, a laminate sheet for sulfide-based all-solid-state batteries has been proposed, which has an absorbent layer and a barrier layer containing a moisture absorbent such as zeolite and a hydrogen sulfide adsorbent that is a specific metal-containing component (see Patent Document 1). It has also been proposed to include a sheet made of alumina, silica alumina, silica gel, or the like as a hydrogen sulfide adsorbent in the package (see Patent Document 2). Furthermore, hydrotalcite is known as a material capable of adsorbing hydrogen sulfide and absorbing moisture, and adsorbents and moisture absorbents for hydrogen sulfide that contain hydrotalcite have been proposed (see Patent Documents 3 to 6). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-187855 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-179618 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-171547 [Patent Document 4] JP 2015-193000 A [Patent Document 5] Japanese Patent Application Laid-Open No. 2011-105573 [Patent Document 6] Japanese Patent Application Laid-Open No. 2008-235256 Summary of the Invention [Problem to be solved by the invention]

[0004] As mentioned above, sheets containing a hydrogen sulfide adsorbent or a moisture-absorbing component have been proposed, but none of the previously proposed materials are capable of both adsorbing and absorbing moisture from hydrogen sulfide using a single substance. Patent Document 2 also proposes using a metal oxide such as alumina as a hydrogen sulfide adsorbent. However, when hydrogen sulfide is absorbed by a metal oxide, water is produced as a by-product along with the metal sulfide, and the by-product water regenerates hydrogen sulfide. Therefore, when a metal oxide is used as a hydrogen sulfide adsorbent, it is necessary to also use a moisture absorbent that absorbs the by-product water. It has been proposed to use hydrotalcite as an adsorbent or moisture absorbent for hydrogen sulfide, but it does not have sufficient performance as a material that can both adsorb hydrogen sulfide and absorb moisture.

[0005] In view of the above-mentioned current situation, an object of the present invention is to provide a material that is excellent in both hydrogen sulfide adsorption capacity and moisture absorption capacity. [Means for solving the problem]

[0006] The present inventors have investigated materials that are excellent in both hydrogen sulfide adsorption and moisture absorption capabilities, and have found that hydrotalcite containing zinc and magnesium, in which the molar ratio of zinc to magnesium (Zn / Mg) is within a predetermined range and the intensity ratio of two predetermined peaks in XRD measurement satisfies predetermined conditions, is excellent in both hydrogen sulfide adsorption and moisture absorption capabilities, leading to the completion of the present invention.

[0007] That is, the present invention provides a hydrotalcite containing zinc element and magnesium element, wherein the molar ratio of zinc element to magnesium element (Zn / Mg) in the hydrotalcite is 0.1 or more and 1.0 or less, and Peak intensity I of the largest peak in the 2Θ=11.6±0.1° range in XRD measurement A and the peak intensity I of the largest peak in the range of 2Θ=13.0±0.1° B Ratio to (I A / I B ) is less than 2.

[0008] When the weight loss rate of the above hydrotalcite measured by TG-DTA at 140°C to 250°C is b%, the weight loss rate at 250°C to 350°C is c%, and the moisture absorption rate, which is expressed as the weight increase relative to the weight before leaving the hydrotalcite after leaving it in an atmosphere of 40°C and a relative humidity of 70% for 12 hours, is Y%, Y≧-7.9(b / c)+10.0 It is preferable that the following is satisfied.

[0009] The present invention also relates to a hydrogen sulfide absorbent comprising the hydrotalcite of the present invention.

[0010] The present invention also relates to a sulfide-type all-solid-state battery exterior material, characterized by containing the hydrogen sulfide absorbent of the present invention.

[0011] The present invention also relates to a sulfide-type all-solid-state battery comprising the hydrogen sulfide absorbent or the sulfide-type all-solid-state battery outer casing material of the present invention. [Effects of the Invention]

[0012] The hydrotalcite of the present invention has excellent hydrogen sulfide adsorption and moisture absorption capabilities, and can therefore be suitably used as a hydrogen sulfide absorbent for all-solid-state batteries using a sulfide-based solid electrolyte. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing the results of XRD measurement of the hydrotalcites of Examples 1 and 2 and Comparative Examples 1 and 5. [Figure 2] FIG. 1 is a diagram showing the results of TG-DTA measurement of the hydrotalcite obtained in Example 1. [Figure 3] FIG. 2 is a diagram showing the results of TG-DTA measurement of the hydrotalcite obtained in Comparative Example 1. [Figure 4] The weight loss rate at 140°C to 250°C in TG-DTA measurements of the hydrotalcites of Examples 1 to 10 and Comparative Examples 1 to 4, 6, and 7 is b%, and the weight loss rate at 250°C to 350°C is c%, and the moisture absorption rate Y%, which is expressed as the weight increase relative to the weight before leaving each hydrotalcite in an atmosphere of 40°C and a relative humidity of 70% for 12 hours, is plotted on the Y axis and (b / c) on the X axis. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present invention will be specifically described below, but the present invention is not limited to the following description and can be appropriately modified and applied within the scope that does not change the gist of the present invention.

[0015] 1. Hydrotalcite The hydrotalcite of the present invention is a hydrotalcite containing elemental zinc and elemental magnesium, and the hydrotalcite has a molar ratio of elemental zinc to elemental magnesium (Zn / Mg) of 0.1 or more and 1.0 or less. Hydrotalcite with such a molar ratio has excellent hydrogen sulfide adsorption ability. Furthermore, such a molar ratio is also a necessary requirement for obtaining hydrotalcite with excellent moisture absorption ability. The molar ratio of elemental zinc to elemental magnesium (Zn / Mg) may be 0.1 or more and 1.0 or less, but is preferably 0.1 or more and 0.50 or less. This range ensures that the hydrotalcite has even better hydrogen sulfide adsorption ability. Furthermore, since the Zn component is less likely to be separated as ZnO, the molar ratio (Zn / Mg) is more preferably 0.1 or more and 0.45 or less. The molar ratio of elemental zinc to elemental magnesium is even more preferably 0.12 or more and 0.40 or less, and particularly preferably 0.14 or more and 0.35 or less. The molar ratio of zinc element to magnesium element in hydrotalcite can be obtained by elemental analysis using ICP emission spectroscopy according to the method described in the Examples.

[0016] The hydrotalcite of the present invention also has a peak intensity I of the largest peak in the range of 2Θ=11.6±0.1° in XRD measurement. A and the peak intensity I of the largest peak in the range of 2Θ=13.0±0.1° B Ratio to (I A / I B ) is less than 2. Hydrotalcite containing zinc and magnesium elements has a peak in the range of 2Θ = 11.6 ± 0.1° in XRD measurement, while dried hydrotalcite obtained by drying hydrotalcite does not have a peak in the range of 2Θ = 11.6 ± 0.1°, but has a peak in the range of 2Θ = 13.0 ± 0.1°. The peak intensity I of the largest peak in these ranges is A and I B Ratio to (I A / I B ) is less than 2 has excellent moisture absorption capacity. Peak intensity I A and IB Ratio to (I A / I B ) may be less than 2, but is preferably less than 1.5, more preferably less than 1.0, and even more preferably less than 0.5.

[0017] The hydrotalcite of the present invention preferably has a ZnO content of 5% by mass or less based on the total hydrotalcite. As described below, the hydrotalcite of the present invention can be obtained by calcining a raw material hydrotalcite having a Zn / Mg ratio of 0.1 or more and 1.0 or less. However, depending on the calcination temperature, water of crystallization may be eliminated, making it impossible to maintain the structure of the hydrotalcite, and some of it may become ZnO. If the Zn component is mixed into the hydrotalcite as ZnO, the hydrotalcite will have poor hygroscopicity. For this reason, the ZnO content of the hydrotalcite is preferably 5% by mass or less based on the total hydrotalcite. When the ZnO content is greater than 5% by mass, the presence of ZnO can be confirmed by XRD measurement. The peaks attributed to ZnO appear at 2Θ = 31.78°, 34.27°, 36.22°, 47.43°, 56.61°, 62.64°, 66.39°, 67.87°, 69.08°, 72.21°, and 76.89°.

[0018] When the weight loss rate of the hydrotalcite of the present invention measured by TG-DTA at 140°C to 250°C is b%, the weight loss rate at 250°C to 350°C is c%, and the moisture absorption rate expressed by the weight increase relative to the weight before standing after standing in an atmosphere of 40°C and a relative humidity of 70% for 12 hours is Y%, Y≧-7.9(b / c)+10.0 It is preferable that the following is satisfied. When hydrotalcite is heated and the temperature rises, the moisture contained in the hydrotalcite is released, causing the weight to decrease. The components that are released vary depending on the temperature range; surface adsorbed water is released at temperatures between 50°C and 140°C, and interlayer water is released at temperatures between 140°C and 250°C. Carbonate radicals are released due to the decomposition of the hydrotalcite at temperatures between 250°C and 350°C, and water of crystallization is released at temperatures above 350°C. The inventors focused on the weight loss rate b % due to elimination of interlayer water at 140°C to 250°C and the weight loss rate c % due to elimination of carbonate groups at 250°C to 350°C, and conducted studies using a large number of samples. They found that there is a correlation between the b / c ratio of hydrotalcite and the moisture absorption rate Y %, which is expressed as the weight increase relative to the weight before leaving the hydrotalcite in an atmosphere of 40°C and 70% relative humidity for 12 hours, of which Y = -7.9(b / c) + 13.0, and that in all samples, the moisture absorption rate Y was greater than -7.9(b / c) + 10.0. It is preferable that the hydrotalcite of the present invention also satisfies such a relationship. Furthermore, hydrotalcite having a molar ratio of zinc element to magnesium element of 0.1 or more and 1.0 or less, excellent hydrogen sulfide adsorption capacity, and -7.9(b / c)+10.0 of 8.0 or more can be said to be hydrotalcite having excellent hydrogen sulfide adsorption capacity and hygroscopicity. A hydrotalcite containing zinc element and magnesium element, wherein the molar ratio of zinc element to magnesium element (Zn / Mg) of the hydrotalcite is 0.1 or more and 1.0 or less, and The present invention also includes a hydrotalcite in which -7.9(b / c)+10.0 is 8.0 or more, where the weight loss rate at 140°C to 250°C in TG-DTA measurement is b% and the weight loss rate at 250°C to 350°C is c%. In the present invention, the weight loss rate in each temperature range in the TG-DTA measurement of hydrotalcite means the ratio of the weight loss in each temperature range to the weight of the hydrotalcite before the measurement.

[0019] Therefore, the hydrotalcite of the present invention has the following properties: (1) A hydrotalcite containing zinc and magnesium elements, wherein the molar ratio of zinc to magnesium (Zn / Mg) of the hydrotalcite is 0.1 or more and 1.0 or less, and the peak intensity I of the largest peak in the range of 2Θ=11.6±0.1° in XRD measurement is Aand the peak intensity I of the largest peak in the range of 2Θ=13.0±0.1° B Ratio to (I A / I B ) is less than 2, and (2) A hydrotalcite containing zinc and magnesium, wherein the molar ratio of zinc to magnesium (Zn / Mg) is 0.1 or more and 1.0 or less, and the weight loss rate at 140°C to 250°C measured by TG-DTA is b% and the weight loss rate at 250°C to 350°C is c%, and the value of -7.9(b / c)+10.0 is 8.0 or more. The former is also referred to as the first hydrotalcite of the present invention, and the latter is also referred to as the second hydrotalcite of the present invention. Hereinafter, "the hydrotalcite of the present invention" includes both the first and second hydrotalcites of the present invention.

[0020] The hydrotalcite of the present invention is preferably represented by the following formula (1). (M1) 1-x (M2) x (OH)2(CO3 2- ) x / 2 mH2O (1) (In the formula, M1 represents Mg and Zn, and the molar ratio of Zn / Mg is 0.1 or more and 1.0 or less. Furthermore, a portion of the Mg may be substituted with an alkaline earth metal element other than Mg. M2 represents Al, and a portion of the Al may be substituted with Fe. x is a number that satisfies the condition 0.2≦x≦0.4. m is a number that is 0 or more.)

[0021] A portion of Mg in M1 in the above formula (1) may be substituted with an alkaline earth metal element other than Mg, but the proportion of substituted Mg is preferably 5 mol % or less, more preferably 1 mol % or less. Examples of alkaline earth metal elements include Ca, Sr, and Ba.

[0022] In M2 in the above formula (1), a portion of Al may be substituted with Fe, but the proportion of substituted Al is preferably 5 mol % or less, and more preferably 1 mol % or less.

[0023] In the above formula (1), x may be any number that satisfies the condition 0.2≦x≦0.4, but is preferably a number that satisfies the condition 0.25≦x≦0.35.

[0024] 2.Method for producing hydrotalcite The hydrotalcite of the present invention can be obtained by a production method including a step of calcining a part or all of hydrotalcite having a molar ratio of zinc element to magnesium element (Zn / Mg) of 0.1 or more and 1.0 or less, and a step of cooling the calcined hydrotalcite.

[0025] The calcination temperature in the calcination step is preferably 200 to 350°C. By performing the calcination at such a temperature, it is possible to prevent elimination of water of crystallization, maintain the structure of the hydrotalcite, and sufficiently dry the hydrotalcite to obtain hydrotalcite with good hygroscopicity. The calcination temperature is more preferably 200 to 300°C, and even more preferably 250 to 300°C. The firing time is preferably 2 to 24 hours, more preferably 2 to 15 hours, and even more preferably 4 to 8 hours. The firing step can be carried out in air.

[0026] In the step of cooling the calcined hydrotalcite, it is preferable to carry out the cooling in a moisture-free atmosphere in a temperature range of 250°C or less, which is the desorption temperature of interlayer water, so as to prevent re-adsorption of moisture from the atmosphere.

[0027] The step of cooling the calcined hydrotalcite may be carried out in air or in an inert gas atmosphere, and may be carried out under any of pressurized, normal pressure, and reduced pressure conditions, but is preferably carried out in an inert gas atmosphere, or, in the case of air, under reduced pressure. By carrying out the step in these atmospheres, the hydrotalcite obtained can have excellent moisture absorption capacity. Examples of the inert gas include dry air, nitrogen, argon, and helium. When the reaction is carried out under reduced pressure, the pressure is preferably 100 Pa or less, more preferably 10 Pa or less, and even more preferably 1 Pa or less.

[0028] The above-mentioned production method is a production method in which the calcination step and the cooling step are performed on all or part of the hydrotalcite. That is, the hydrotalcite obtained by the above-mentioned production method may be entirely subjected to the calcination step and the cooling step, or may be a mixture of some of the hydrotalcite that has been subjected to the calcination step and the cooling step and other hydrotalcite that has not been subjected to the steps. The above-mentioned manufacturing method may also include other steps as long as it includes the above-mentioned firing step and cooling step.

[0029] The method for producing hydrotalcite having a molar ratio (Zn / Mg) of elemental zinc to elemental magnesium of 0.1 or more and 1.0 or less to be subjected to the calcination step is not particularly limited as long as such hydrotalcite can be obtained. For example, a method can be used which includes the steps of: mixing an aqueous solution of a zinc salt, an aqueous solution of a magnesium salt, and an aqueous solution of a salt of another metal element contained in the hydrotalcite in such a ratio that the molar ratio of elemental zinc to elemental magnesium is 0.1 or more and 1.0 or less; and adding an alkaline solution to the obtained mixed aqueous solution to cause coprecipitation, thereby obtaining hydrotalcite. Furthermore, commercially available hydrotalcites having a molar ratio of zinc element to magnesium element (Zn / Mg) of 0.1 or more and 1.0 or less may be used.

[0030] Examples of the salts of zinc, magnesium, and other metal elements contained in the hydrotalcite include nitrates, sulfates, phosphates, carbonates, etc. Among these, sulfates are preferred.

[0031] The alkaline solution is preferably an aqueous carbonate solution, and examples thereof include lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, and ammonium carbonate, and one or more of these can be used.

[0032] 3. Hydrogen sulfide absorbent, sulfide-type all-solid-state battery The hydrotalcite of the present invention has excellent hydrogen sulfide adsorption ability and can therefore be suitably used as a hydrogen sulfide absorbent. A hydrogen sulfide absorbent containing such hydrotalcite of the present invention also constitutes the present invention. Furthermore, since the hydrotalcite of the present invention has excellent hygroscopicity in addition to its ability to adsorb hydrogen sulfide, when used as an exterior material for an all-solid-state battery using a sulfide-based solid electrolyte in which hydrogen sulfide is generated due to moisture, it is suitable because it can absorb moisture, which causes hydrogen sulfide generation, along with hydrogen sulfide, thereby improving safety. Such an exterior material for a sulfide-type all-solid-state battery containing the hydrogen sulfide absorbent of the present invention, and a sulfide-type all-solid-state battery containing the hydrogen sulfide absorbent or the sulfide-type all-solid-state battery exterior material of the present invention are also part of the present invention. [Example]

[0033] Specific examples are given below to explain the present invention in detail, but the present invention is not limited to these examples. Unless otherwise specified, "%" and "wt%" mean "weight % (mass %)." The methods for measuring each physical property are as follows.

[0034] Example 1 Mg as raw material hydrotalcite 3.5 Zn 0.5 Al2(OH) 12This was calcined in air at 250°C for 2 hours using (CO3)·3H2O (STABIACE HT-7, manufactured by Sakai Chemical Industry Co., Ltd.), and after calcination, it was cooled to 200°C in air and then cooled to room temperature in a reduced pressure atmosphere of 1 Pa to obtain hydrotalcite 1.

[0035] Hydrotalcites of Examples 2 to 10 and Comparative Examples 1 to 7 were obtained in the same manner as in Example 1, except that the raw material hydrotalcite, the temperature and time of the calcination step, and the atmosphere of the cooling step were changed as shown in Table 1. The raw material hydrotalcites in Table 1 are as follows: P-93: Hydrotalcite (Mg:Zn:Al molar ratio = 3:1:2, manufactured by Kyowa Chemical Industry Co., Ltd.) HT-P: Hydrotalcite (Mg:Zn:Al molar ratio = 4.5:0:2, manufactured by Sakai Chemical Industry Co., Ltd.) 011261: Hydrotalcite (Mg:Zn:Al molar ratio = 2:4:2) synthesized by the following method <Synthesis of 011261> -Process (I)- A mixed solution of 64.39 g of zinc sulfate heptahydrate, 27.60 g of magnesium sulfate heptahydrate, and 54.2 mL of a 354 g / L aluminum sulfate aqueous solution (19.2 g as Al2(SO4)3) was mixed, and ion-exchanged water was added to bring the total volume to 350 mL to obtain a mixed metal salt solution. Separately, 46.7 mL of a 720 g / L sodium hydroxide aqueous solution and 26.7 g of sodium carbonate were mixed, and ion-exchanged water was added to bring the total volume to 350 mL to obtain a mixed alkali solution. 50 mL of ion-exchanged water was placed in a 1 L round-bottom flask, and these solutions were added under stirring. The pH of the slurry at this time was 9. The mixture was then stirred at 50 °C for 15 minutes to obtain a slurry. -Process (II)- The slurry obtained in the above step (I) was filtered and washed with water until the electric conductivity of the washing liquid became 100 μS / cm or less. Water was added to the obtained cake and stirred to make a slurry of 110 g / L as dry powder, and then dried in a spray dryer (atomizer method, manufactured by Okawara Chemical Industries Co., Ltd., model BDP-22) under the conditions of a disk rotation speed of 16,000 rpm and an outlet drying temperature of 105 °C to obtain a powder of the hydrotalcite precursor. - Step (III)- 1 g of the powder obtained in the above step (II) was placed in a glass petri dish with an inner diameter of 27 mm and a height of 15 mm, put into a thermo-hygrostat (manufactured by Espec Corporation, model LH-113), adjusted from room temperature to 85 °C and a relative humidity of 85% RH over 15 minutes, held at 85 °C and a relative humidity of 85% RH for 22 hours, and then the power supply to the heater was stopped and cooled to room temperature. This step was carried out in the air. Thus, a powder (011261) containing hydrotalcite-type particles was obtained. The composition (molar ratio of each element of zinc, magnesium, and aluminum) of the powder containing the obtained hydrotalcite-type particles and the molar ratio of the zinc element to the magnesium element were confirmed by elemental analysis by ICP emission spectrometry as follows. <Elemental analysis by ICP emission spectrometry> Using a spectroscope (manufactured by SII Corporation, ICP SPS3100), measurement was carried out by the internal standard method (calibration curve method) with scandium (Sc) as the internal standard element. The measurement wavelengths used were 279.55 nm (Mg), 213.86 nm (Zn), 396.15 nm (Al), and 361.49 nm (Sc). The contents (weight %) of Mg, Zn, and Al were calculated by the calibration curve method, respectively. Using the contents of Mg and Zn, the molar ratio (Zn / Mg) was calculated by the following calculation formula. (Zn / Mg)=(Zn content / 65.38) / (Mg content / 24.305)

[0036] For the hydrotalcites obtained in Examples 1 to 10 and Comparative Examples 1 to 7, XRD measurement and measurement of the moisture absorption rate were carried out by the following methods, and I A / I BThe relationship with the moisture absorption rate was confirmed. The results are shown in Table 1. Table 1 also shows the molar ratio of lead element to magnesium element (Zn / Mg). The XRD measurement results of the hydrotalcites of Example 1, Example 2, and Comparative Example 1 and Comparative Example 5 are shown in Figure 1. In Comparative Example 5, a heterogeneous phase of ZnO was confirmed. Noa The molar ratio of lead element to magnesium element (Zn / Mg) was also shown. The XRD measurement results of the hydrotalcites of Example 1, Example 2, and Comparative Example 1 and Comparative Example 5 are shown in Figure 1. In Comparative Example 5, a heterogeneous phase of ZnO was confirmed. <XRD Measurement> The XRD measurement was performed using RINT-TTRIII (manufactured by Rigaku), with the X-ray source being CuKα and the parallel beam method. The X-ray output was set to 50 kV and 300 mA, and the measurement was carried out in the 2Θ range from 10° to 80° under the conditions of a scan step of 0.02° and a counting time of 0.4 seconds. After BG processing of the obtained XRD pattern, the following was read and I A / I B was calculated. I A : The intensity of the strongest line at 2Θ = 11.6° (±0.1) I B : The intensity of the strongest line at 2Θ = 13.0° (±0.1) <Moisture Absorption Rate Measurement> The sample was added to a beaker and left in a thermo-hygrostat (LH-113 manufactured by Espec) set at 40°C and Rh70% for 12 hours. From the weight after the moisture absorption test, the weight increase rate (%) with respect to the initial weight was calculated and taken as the moisture absorption rate (%).

[0037]

Table 1

[0038] From the results in Table 1, it was confirmed that there is a correlation between I A / I B and the moisture absorption property of the hydrotalcite, and that the hydrotalcite with Zn / Mg of 0.1 or more and 1.0 or less and I A / I B less than 2 has excellent moisture absorption ability.

[0039] The adsorption rate of hydrogen sulfide was measured by the following method for the hydrotalcites obtained in Examples 2 and 6 and Comparative Examples 1, 4, and 5. The results are shown in Table 2. Table 2 also shows the raw materials, mass proportions of magnesium, zinc, and aluminum, molar ratio of zinc to magnesium (Zn / Mg), and moisture absorption rate of each hydrotalcite. <Hydrogen sulfide adsorption rate> For the sample test, one corner of a 5L sampling bag (GL Sciences Inc., Smart Bag PA AA-5, hereafter referred to as the bag) was cut, a plastic Petri dish (5 cm diameter) containing 1 g of sample was inserted, and the cut corner was then sealed. The bag was degassed using a vacuum pump, and 3 L of air was injected into the bag through an integrating flow meter (Kofloc Corporation, ACM-1). For the blank test, 3 L of air was injected into an empty bag. Odorant gas was injected into the bag using a syringe to achieve the specified initial concentration (hydrogen sulfide; 4.0 ppm), and then the bag was sealed. The odorant gas concentration in the bag after 2 hours was measured using a gas detector tube (Gastec Corporation, Hydrogen Sulfide Detector Tube No. 4LT (0.1 ppm to 4.0 ppm)). All tests were conducted in a laboratory at 20°C. The test was carried out twice, and the average values ​​of the odorous gas concentration and reduction rate obtained in each test were calculated. The reduction rate was calculated as follows: Reduction rate (%) = (gas concentration in blank test - gas concentration in sample test) / gas concentration in blank test x 100

[0040] [Table 2]

[0041] From the results in Tables 1 and 2, it is clear that Zn / Mg is 0.1 or more and 1.0 or less, and I A / I B It was confirmed that hydrotalcites that satisfy the requirement of less than 2 have excellent hydrogen sulfide adsorption capacity and moisture absorption capacity.

[0042] For the hydrotalcites obtained in Examples 1 to 10 and Comparative Examples 1 to 7, TG-DTA measurements were carried out by the following method, and the weight loss rate b (%) due to the desorption of interlayer water and the weight loss rate c (%) due to the desorption of carbonate were measured. The obtained values of b and c are shown in Table 3, and the figures of the TG-DTA measurement results of the hydrotalcites obtained in Example 1 and Comparative Example 1 are shown in Figures 2 and 3. Also, Figure 4 shows a plot with the moisture absorption rate of these hydrotalcites on the Y-axis and b / c on the X-axis. Note that in Figure 4, the heterogeneous phase of ZnO was confirmed, and the plot was made excluding Comparative Example 5 which is not only hydrotalcite. <TG-DTA measurement> The TG-DTA measurement was carried out using STA7300 (manufactured by Hitachi High-Tech Corporation). The measurement was carried out in a nitrogen atmosphere (flow rate 200 mL / min) at a heating rate of 10 °C / min. From the DTA behavior of HT-7 used as the raw material hydrotalcite in Example 1, the following definitions were made, and the weight loss rate (%) with respect to the weight of the hydrotalcite before measurement in the b and c regions was evaluated. a: (50 °C - 140 °C): Desorption of surface adsorbed water b: (140 °C - 250 °C): Desorption of interlayer water c: (250 °C - 350 °C): Desorption of CO3 radicals d: (350 °C -): Desorption of crystal water

[0043] [[ID=B15]]<B

Table 3

[0044] From the plot in Figure 4, it was confirmed that there is a correlation of Y = -7.9(b / c) + 13.0 between the moisture absorption rate Y% of the hydrotalcite and b / c, and that for all the plotted hydrotalcites, the moisture absorption rate Y% is larger than -7.9(b / c) + 10.0. This confirms that by determining the b / c ratio of hydrotalcite through TG-DTA measurement, it is possible to estimate the minimum moisture absorption capacity of that hydrotalcite. A moisture absorption rate of 8% or higher can be said to have good moisture absorption capacity, so if the value of -7.9(b / c)+10.0 is 8 or higher, the hydrotalcite can be said to have good moisture absorption capacity.

Claims

1. A hydrotalcite containing zinc element and magnesium element, The hydrotalcite has a molar ratio of zinc element to magnesium element (Zn / Mg) of 0.1 or more and 1.0 or less, and The peak intensity I of the largest peak in the range of 2Θ = 11.6 ± 0.1° in the XRD measurement Ａ and the peak intensity I of the largest peak in the range of 2Θ = 13.0 ± 0.1° Ｂ The ratio of (I Ａ / I Ｂ ) is 1.4 or less.

2. The hydrotalcite has a weight loss rate of b% at 140°C to 250°C and a weight loss rate of c% at 250°C to 350°C, as measured by TG-DTA; When the moisture absorption rate, which is expressed as the weight increase relative to the weight before leaving the sample in an atmosphere of 40°C and 70% relative humidity for 12 hours, is Y%, Y≧-7.9(b / c)+10.0 The hydrotalcite according to claim 1, wherein the above formula (1) is satisfied.

3. A hydrogen sulfide absorbent comprising the hydrotalcite according to claim 1 or 2.

4. An exterior material for a sulfide-type all-solid-state battery, comprising the hydrogen sulfide absorbent according to claim 3.

5. A sulfide-type all-solid-state battery comprising the hydrogen sulfide absorbent according to claim 3 or the sulfide-type all-solid-state battery exterior material according to claim 4.

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