Lithium selective permeable membrane and method for producing lithium selective permeable membrane

Abstract

To provide a lithium selective permeation membrane or the like capable of recovering lithium ions without applying complicated treatment to the lithium selective permeation membrane, reducing time required for recovering the lithium ions, and reducing required cost.SOLUTION: The lithium selective permeation membrane 10 of the present invention includes a sintered body of a lithium ion conductor. At least a part of the outer surface of the lithium selective permeation membrane 10 is constituted of a surface roughened surface 101.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a lithium permselective membrane that selectively allows lithium ions to pass therethrough, and a method for producing the lithium permselective membrane. [Background technology]

[0002] Metals, such as rare metals, are found in smaller quantities in the earth's crust than other substances, and due to the technical difficulties of mining and refining, their circulation is limited. However, they are used as additives to structural materials, electronic and magnetic materials such as light-emitting diodes, batteries, and permanent magnets, and as functional materials such as photocatalysts and new glass, and have been attracting a great deal of attention in recent years.

[0003] For example, lithium, a rare metal, is used in the production of materials for lithium-ion batteries and fuel for nuclear fusion reactors, and its demand has been expanding in recent years. To supply lithium for these uses, technology is needed to produce large quantities of lithium at low cost.

[0004] Rare metals such as lithium can be extracted from ores contained in the earth's crust, but as mentioned above, there are technical difficulties in producing them in large quantities.

[0005] Therefore, in recent years, technology has been developed to extract ions derived from rare metals contained in seawater. Seawater contains multiple ions, and the amount of these ions can be enormous compared to the amount of ions buried underground. It is also known that industrial waste (such as discarded lithium secondary batteries) contains large amounts of rare metals. However, seawater and industrial waste contain not only ions typified by rare metals (such as lithium ions), but also other metal ions such as potassium, sodium, and calcium. Therefore, in order to recover the target ions, membranes (selective permeable membranes) that can separate the target ions from other metal ions are being developed.

[0006] On the other hand, the concentration of rare metal elements as ions contained in seawater or industrial waste (such as discarded lithium secondary batteries) is low, and the ion permeation rate for recovering the target ions through a selectively permeable membrane is also low. Therefore, according to conventional techniques, recovering the target ions from seawater or industrial waste (such as discarded lithium secondary batteries) requires a long time and is costly.

[0007] To solve these problems, Patent Document 1 discloses a technique for extracting lithium ions from salt lake brine or lithium ore with a relatively high lithium concentration, or from industrial waste (such as discarded lithium secondary batteries) or seawater with a relatively low lithium concentration. Patent Document 1 discloses a lithium permselective membrane having a lithium adsorption layer formed on one surface by acid treatment, the lithium adsorption layer being made of a material different from the lithium permselective membrane itself. It has been revealed that such a lithium permselective membrane can recover lithium ions from the raw solution at a high recovery rate. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2017-131863 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, while the lithium permselective membrane of Patent Document 1 can increase the recovery rate of lithium ions, it requires acid treatment of one surface of the lithium permselective membrane, which makes the production of the lithium permselective membrane complicated. Furthermore, even if one surface of the lithium permselective membrane is acid treated, there still remain problems that it takes a long time and is costly to recover lithium.

[0010] In order to solve the above problems, an object of the present invention is to provide a lithium permselective membrane that can recover lithium ions without subjecting the lithium permselective membrane to complicated treatment, and that reduces the time and cost required for recovering the lithium ions, and a method for manufacturing the lithium permselective membrane. [Means for solving the problem]

[0011] In order to achieve the above object, the lithium permselective membrane of the present invention is characterized by the following invention-specific features.

[0012] The lithium permselective membrane is The battery is characterized by comprising a composite layer including a first layer including a sintered body of a lithium ion conductor, at least a portion of the outer surface of which is formed of a roughened surface, and a second layer including a sintered body of a lithium ion conductor that is different from the first layer.

[0013] Generally, when a lithium ion conductor is used as a lithium selective membrane, the lithium ion conductor is often used as a sintered body. Sintered bodies often have a structure or composition near the outer surface that is exposed to the firing atmosphere during sintering that differs from the structure or composition inside the sintered body that is not affected by the firing atmosphere during sintering. According to the lithium permselective membrane described above, the portion of the first layer that has a structure or composition near the outer surface that has changed during sintering is removed by surface roughening treatment, and the portion that has a structure or composition that is not affected by the firing atmosphere during sintering is exposed on the surface of the lithium permselective membrane. This allows the structure or composition of the ion conductor to be uniform on the outer surface and inside the lithium permselective membrane.

[0014] Furthermore, because the structure or composition changes near the outer surface that is in contact with the firing atmosphere during sintering, the lithium ion permeation rate in this region becomes slower than the original lithium ion permeation rate (the lithium ion permeation rate in a portion that is not affected by the firing atmosphere during sintering). With the lithium permselective membrane described above, a region having the structure or composition of an ion conductor that is not affected by the firing atmosphere during sintering is exposed on the outer surface of the membrane, so that a decrease in the lithium ion permeation rate can be avoided. From the above, the lithium permselective membrane described above can reduce the time and cost required for lithium ion recovery.

[0015] Furthermore, in the lithium permselective membrane having the above configuration, the first layer is coated with a second layer containing a sintered body of a lithium ion conductor different from that of the first layer. The second layer is made of a lithium ion conductor that has one or more superior properties compared to the first layer, such as a faster rate of uptake of lithium ions from a raw aqueous solution containing lithium, higher resistance to the raw aqueous solution, or higher lithium ion selectivity, compared to the first layer. This makes it possible to achieve a faster lithium permeation rate, a longer membrane life, or higher lithium selectivity compared to a lithium permselective membrane composed only of the first layer.

[0016] In any one of the above lithium permselective membranes, It is preferable that at least one of the following requirements (A), (B), and (C) be satisfied. (A) The arithmetic mean height Ra of the entire or part of the surface roughened is 0.8 μm or more and 20 μm or less. (B) The root mean square gradient Rdq of the entire or part of the roughened surface is 10° or more and 80° or less. (C) The developed area ratio Sdr of the entire or part of the surface roughened is 0.2 or more and 2 or less.

[0017] The lithium permselective membrane of this configuration satisfies at least one of the following requirements: an arithmetic mean height Ra of 0.8 μm or more on all or part of the roughened surface, a root-mean-square gradient Rdq of 10° or more, and a developed area ratio Sdr of 0.2 or more. This allows the surface area of ​​the lithium ion conductor to be substantially increased. Therefore, lithium ions are absorbed into the lithium permselective membrane through the lithium ion conductor with a large surface area, thereby increasing the lithium ion recovery rate.

[0018] From the viewpoint of the lithium ion recovery rate, the larger the values ​​of Ra, Rdq, and Sdr, the better. However, the larger the values ​​of Ra, Rdq, and Sdr, the greater the risk of damage to the lithium permselective membrane during the surface roughening treatment. Furthermore, the time and cost required for the surface roughening treatment also increase. Therefore, to stably produce a lithium permselective membrane containing a lithium ion conductor with a large surface area, it is preferable to satisfy at least one of the following requirements on the roughened surface of the lithium ion conductor: an arithmetic mean height Ra of 20 μm or less, a root-mean-square gradient Rdq of 80° or less, and a developed area ratio Sdr of 2 or less.

[0019] In any one of the above lithium permselective membranes, It is preferable that the surface of the sintered body particles in the whole or part of the surface-roughened surface does not have a step-and-terrace structure.

[0020] The lithium permselective membrane having the above-described structure does not have the step-and-terrace structure formed on the surface of the sintered particles by heat treatment in the sintering or annealing process on all or part of the surface-roughened surface. Therefore, the surface that is not directly exposed to the sintering atmosphere during the heat treatment is fully exposed. Therefore, this lithium permselective membrane can reduce the time and cost required for lithium ion recovery.

[0021] In any one of the above lithium permselective membranes, The first layer and the second layer are preferably sintered bodies of a lithium ion conductor having any of a perovskite-type crystal structure, a Nasicon-type crystal structure, a garnet-type crystal structure, a spinel-type crystal structure, a ramsdellite-type crystal structure, an olivine-type crystal structure, or a crystal structure based on LiTa2PO8.

[0022] In any one of the above lithium permselective membranes, The lithium ion conductor constituting the first layer is preferably a sintered body of lanthanum lithium titanate (LLT) having a perovskite-type crystal structure.

[0023] In the lithium permselective membrane having the above configuration, the lithium ion conductor constituting the first layer is a sintered body of lanthanum lithium titanate. Lanthanum lithium titanate, a lithium ion conductor, has an excellent lithium ion conduction rate. Furthermore, it allows stable lithium permeation in an aqueous solution. Therefore, the lithium permselective membrane having the above configuration can reduce the time and cost required for lithium recovery.

[0024] In any one of the above lithium permselective membranes, The lithium ion conductor constituting the second layer is preferably a sintered body of lithium lanthanum titanate (LLT) having a perovskite-type crystal structure, lithium aluminum titanium phosphate (LATP) having a Nasicon-type crystal structure, lithium aluminum germanium phosphate (LAGP), lithium titanate (LT) having a ramsdellite-type crystal structure, or lithium tantalum phosphate (LTP) having a crystal structure based on LiTa2PO8.

[0025] According to the lithium permselective membrane having the above configuration, the second layer constituting the composite layer is a lithium ion conductor having one or more excellent properties, such as a faster rate of uptake of lithium ions from a raw aqueous solution containing lithium, higher resistance to the raw aqueous solution, or high lithium ion selectivity, compared to the first layer. This makes it possible to achieve a faster lithium permeation rate, a longer membrane life, or high lithium selectivity, compared to a lithium permselective membrane composed only of the first layer.

[0026] The lithium permselective membrane is characterized by including a composite layer including a first layer containing a sintered body of lanthanum lithium titanate (LLT) having a perovskite-type crystal structure, and a second layer containing a sintered body of lithium titanate (LT) having a ramsrite-type crystal structure.

[0027] In the lithium permselective membrane having the above configuration, the lithium ion conductor constituting the first layer of the composite layer is a sintered body of lanthanum lithium titanate having a perovskite-type crystal structure. Lanthanum lithium titanate, a lithium ion conductor, has an excellent lithium ion conduction rate. It also allows stable lithium permeation in aqueous solutions. Furthermore, the second layer, which is lithium titanate having a ramsrite-type crystal structure, has a faster lithium ion uptake rate from a raw lithium-containing aqueous solution than the first layer, allowing it to exhibit a faster lithium permeation rate than a lithium permselective membrane composed only of the first layer.

[0028] In any one of the above lithium permselective membranes, In a lithium permeation test conducted on raw materials with lithium ion concentrations of 0.1 mol / L, 0.2 mol / L, and 1.0 mol / L at a temperature range of 22°C to 24°C, the lithium permeation rate V, expressed by the following formula (1), was 0.08 mmol / (hr cm 2 ) or more, 0.09mmol / (hr·cm 2 ) or more, 0.25mmol / (hr·cm 2) or more is preferable. V = M / (T S) (1) Here, M is the amount of lithium ions (mmol) that permeated the lithium permselective membrane, T is the time (hr) required for lithium ions of permeation amount M to permeate, and S is the effective membrane area (cm) of the lithium permselective membrane. 2 )

[0029] In the lithium permselective membrane having the above configuration, in a lithium permeation test performed on raw material solutions with lithium ion concentrations of 0.1 mol / L, 0.2 mol / L, and 1.0 mol / L, the lithium permeation rate V, expressed by the following formula (1), was 0.08 mmol / (hr cm 2 ) or more, 0.09mmol / (hr·cm 2 ) or more, 0.25mmol / (hr·cm 2 ) As a result, the lithium permselective membrane having the above configuration can reduce the time and cost required for recovering lithium.

[0030] Further, a method for producing a lithium permselective membrane for solving the above problems is characterized by the following invention-specific features.

[0031] The method for producing a lithium permselective membrane of the present invention comprises the steps of: a step of producing a first layer including a sintered body of a lithium ion conductor, at least a part of an outer surface of which is formed as a roughened surface; forming a second layer containing a sintered body of a lithium ion conductor different from the first layer on a part or all of the surfaces of the first layer, The process for producing the first layer is characterized by including a sintering process for sintering a first compact containing a lithium ion conductor, and a surface roughening process for removing a surface layer of at least a portion of the outer surface of the sintered compact after the sintering and roughening the surface.

[0032] According to the method for producing a lithium permselective membrane having the above-described configuration, it is possible to produce any of the lithium permselective membranes described above, since the surface roughening treatment step can remove part or all of the portions originally present on the outer surface of the lithium ion conductor whose structure or composition has changed due to exposure to the firing atmosphere during sintering. Therefore, the lithium permselective membrane produced by the method for producing a lithium ion conductor can reduce the time and cost required for lithium ion recovery.

[0033] Further, in any one of the above-described methods for producing a lithium permselective membrane, It is preferable that at least one of the following requirements (D), (E), and (F) be satisfied. (D) The surface roughening treatment step makes the arithmetic mean height Ra of all or part of the surface of the sintered body 0.8 μm or more and 20 μm or less. (E) The surface roughening treatment step makes the root mean square gradient Rdq of the entire or part of the surface of the sintered body 10° or more and 80° or less. (F) The surface roughening treatment step sets the developed area ratio Sdr of all or part of the surface of the sintered body to 0.2 or more and 2 or less.

[0034] According to the method for producing a lithium permselective membrane having the above-described configuration, it is possible to produce a lithium permselective membrane that satisfies at least one of the requirements (A), (B), and (C) above. Therefore, the lithium permselective membrane produced by the method for producing a lithium permselective membrane having the above-described configuration can reduce the time and cost required for recovering lithium ions.

[0035] Further, in any one of the above-described methods for producing a lithium permselective membrane, The surface roughening treatment is preferably a blasting treatment.

[0036] According to the method for manufacturing a lithium permselective membrane having the above configuration, the surface of the sintered body is simultaneously removed and roughened in a short time by blasting. Furthermore, residual stress can be applied to the lithium ion conductor, thereby improving the strength and durability of the lithium ion conductor and, in turn, the lithium permselective membrane. Therefore, a lithium permselective membrane with excellent durability can be manufactured without complicating the manufacturing process of the lithium permselective membrane.

[0037] The method for producing a lithium permselective membrane is as follows: A step of producing a first layer including a sintered body of lanthanum lithium titanate (LLT) having a perovskite-type crystal structure; and a step of manufacturing a second layer including a sintered body of lithium aluminum titanium phosphate (LATP) having a Nasicon-type crystal structure, lithium aluminum germanium phosphate (LAGP), lithium titanate (LT) having a ramsdellite-type crystal structure, or lithium tantalum phosphate (LTP) having a crystal structure based on LiTa2PO8.

[0038] According to the method for manufacturing a lithium permselective membrane having the above configuration, it is possible to manufacture a composite layer including a first layer containing a sintered body of lanthanum lithium titanate and a second layer containing a sintered body other than lanthanum lithium titanate. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a diagram showing an outline of a lithium ion recovery device using a lithium permselective membrane. [Figure 2] FIG. 2 shows the results of powder X-ray diffraction measurement of a sintered lithium ion conductor corresponding to the first layer produced in the example, which was pulverized. [Figure 3] FIG. 3 is an SEM image of a sintered lithium ion conductor corresponding to the first layer produced in the example before surface roughening treatment (as sintered). [Figure 4]FIG. 4 is an SEM image of the roughened surface of the sintered body of the lithium ion conductor corresponding to the first layer produced in the example after the surface roughening treatment. [Figure 5] FIG. 5 is an SEM image of a cross section of a lithium permselective membrane in an example. [Figure 6] FIG. 6 shows current-time profiles when a Li recovery test was carried out using the lithium permselective membranes prepared in the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention will be described in detail below with reference to embodiments and the accompanying drawings.

[0041] (Configuration of lithium ion recovery device) FIG. 1 is a diagram illustrating the configuration of a lithium ion recovery device 1 using a lithium permselective membrane 10. As shown in FIG. 1, the lithium ion recovery device 1 includes the lithium permselective membrane 10, a first electrode 121, and a second electrode 122. The lithium permselective membrane 10 has a configuration described below and selectively allows lithium ions 131 contained in a stock solution 111, which is a first liquid, to pass therethrough. The lithium permselective membrane 10 selectively allows lithium ions 131 to pass through the stock solution 111, which contains a plurality of ions, thereby transferring the lithium ions 131 in the stock solution 111 to a recovery liquid 112, which is a second liquid. In this case, it is preferable that the highly permselective lithium membrane 10 be used together with electrodes or the like configured to enhance this permeability.

[0042] The first electrode 121 and the second electrode 122 are provided facing one main surface (left surface) and the other main surface (right surface), respectively, of the lithium permselective membrane 10 in FIG. 1 . Here, the first electrode 121 and the second electrode 122 are the anode and cathode, respectively, of the lithium ion recovery device 1. The first electrode 121 and the second electrode 122 may or may not be in direct contact with the lithium permselective membrane 10. With this configuration, the potential difference between the one main surface and the other main surface of the lithium permselective membrane 10 is maintained at a constant potential difference. The first electrode 121 and the second electrode 122 are preferably made of a conductive material that does not chemically react with the components in the raw solution 111 or the recovered solution 112. In this case, the materials of the first electrode 121 and the second electrode 122 may be the same or different from the viewpoint of ionization tendency.

[0043] The raw solution 111 is an aqueous solution containing lithium ions 131, such as brine from a salt lake, lithium ore, industrial waste (such as discarded lithium secondary batteries), or seawater. The raw solution 111 is supplied to the lithium ion recovery device 1 from the sea, a salt lake, or a raw solution storage tank via a raw solution pipe and a pump (not shown). The pH of the raw solution 111 may be adjusted to increase the lithium ion permeation rate and, therefore, the lithium ion recovery rate. In this case, as disclosed in Patent Document 1, the raw solution 111 is preferably made alkaline, but may also be made non-alkaline. Furthermore, when seawater is used as the raw solution 111, a solution from which monovalent ions (such as lithium ions and sodium ions) have been separated in advance using a cation exchange membrane may be used as the raw solution 111.

[0044] The recovered liquid 112 is an aqueous solution containing lithium ions 131 that have permeated from the raw liquid 111. The recovered liquid 112 is discharged from the lithium ion recovery device 1 via a recovery liquid piping and a pump (not shown), and can be stored in a recovered liquid storage tank or the like. Thereafter, CO2 bubbling or the like may be generated in the recovered liquid storage tank or the like, and the lithium ions 131 may be recovered as carbonate precipitates.

[0045] The first electrode 121 and the second electrode 122 are connected via conductive lead wires or the like, and a DC power supply 14 is interposed between the lead wires to maintain a constant potential difference between the first electrode 121 and the second electrode 122. The shapes of the first electrode 121 and the second electrode 122 are not particularly limited. For example, the first electrode 121 and the second electrode 122 preferably have a mesh shape as disclosed in Patent Document 1 and are fixed to the lithium permselective membrane 10. Alternatively, for example, a current collector made of a carbon felt sheet or the like may be interposed between the mesh-shaped first electrode 121 and the second electrode 122 and the lithium permselective membrane 10. Alternatively, the first electrode 121 and the second electrode 122 may each be formed in a substantially plate shape, as in an existing Daniel cell.

[0046] Furthermore, the lithium ion recovery device 1 using the lithium permselective membrane 10 of the present invention can recover lithium ions 131 by applying a voltage, and may also be used as a battery that extracts power without applying an external voltage. In this case, in the process of transferring the lithium ions 131 from the raw solution 111 to the recovery solution 112, a voltage is generated that causes the first electrode 121 to act as a negative electrode and the second electrode 122 to act as a positive electrode. On the other hand, when a voltage is applied to the lithium ion recovery device 1, the flow of the lithium ions 131 can be increased compared to when no voltage is applied, and the recovery efficiency of the lithium ions 131 can be improved.

[0047] The lithium permselective membrane 10 may be composed solely of a plurality of lithium ion conductors, or may be composed of a composite of a plurality of lithium ion conductors and another material that does not have lithium ion conductivity. The composite may be a composite of lithium ion conductor particles and a resin in order to improve flexibility. Furthermore, in order to improve the strength of the lithium permselective membrane 10, it may be a composite of a thin-film lithium ion conductor and a porous support that supports it. From the viewpoints of the complexity of the manufacturing process and manufacturing costs, it is preferable that the lithium permselective membrane 10 be composed solely of a sintered lithium ion conductor.

[0048] In this embodiment, the lithium permselective membrane 10 is a composite composed of multiple lithium ion conductors. In this embodiment, the lithium permselective membrane 10 preferably includes a first layer 11 having a sintered lithium ion conductor and at least a portion of its outer surface formed of a roughened surface 101, and a second layer 12 including a sintered lithium ion conductor different from the first layer 11. The second layer 12 is provided on a region including at least one of the roughened surface 101 of the first layer 11 and the unprocessed surface 102, which has not been subjected to surface roughening treatment. That is, the second layer 12 may be provided on at least a portion of the roughened surface 101, or on at least a portion of the unprocessed surface 102, or on a region including at least a portion of the roughened surface 102 and at least a portion of the unprocessed surface 101. The first layer 11 of this embodiment may or may not include the roughened surface 101.

[0049] The lithium permselective membrane 10 is provided to separate the raw solution 111 containing a plurality of ions, including lithium ions 131 and non-designated ions 132 (ions other than the lithium ions 131), from the recovered solution 112 into which the lithium ions 131 are recovered. In this case, the lithium permselective membrane 10 is preferably provided so that the surface 101, which has been subjected to a surface roughening treatment described below, or the second layer 12 provided on the surface roughening treatment surface 101, faces the raw solution 111. The lithium permselective membrane 10 may be formed in a spherical, cylindrical, or regular octahedral shape, or may have at least one recessed or protruding portion formed on a part of a plate or one of the shapes described above. In this case, the shape of the lithium permselective membrane 10 is not particularly limited as long as it can separate the raw solution 111 from the recovered solution 112. The surface roughening treatment surface 101, which will be described below, may be provided depending on the electric field generated in the lithium ion recovery device 1. For example, the surface-roughened surface 101 or the first layer 11 may be provided on the surface facing the raw liquid 111 in an area where the electric flux density perpendicular to the surface is relatively large when a voltage is applied to the lithium ion recovery device 1.

[0050] When the first layer 11 constituting the lithium permselective membrane 10 has a roughened surface 101 (the area indicated by the thick line in FIG. 1 ), the roughened surface 101 is provided on a part or all of the outer surface of the second layer 12. As described above, the roughened surface 101 is preferably provided so as to face the stock solution 111, but in FIG. 1 , the unprocessed surface 102 of the first layer 11 is provided on the main surface of the lithium permselective membrane 10 facing the recovered solution 112, and the second layer 12 provided on the roughened surface 101 of the first layer 11 is provided on the other main surface of the lithium permselective membrane 10 facing the stock solution 111. However, without being limited to this embodiment, the main surface of the lithium permselective membrane 10 facing the recovery liquid 112 may be partially or entirely provided with a surface-roughened surface 101, or alternatively, the entire surface may be provided with an untreated surface 102 that has not been subjected to surface roughening treatment, or the first layer 11 may be provided on the entire main surface of the lithium permselective membrane 11.

[0051] The surface-roughened surface 101 is subjected to removal of the sintered compact surface layer and surface roughening by any of the surface roughening treatment methods described below. The arithmetic mean height Ra of the surface of all or a portion of the surface-roughened surface 101 is preferably 0.8 μm to 20 μm, more preferably 1.5 μm to 15 μm, and even more preferably 2.0 μm to 10 μm. Furthermore, while the surface roughness in the present invention is expressed in terms of Ra, it is not limited thereto and may also be expressed in terms of the root-mean-square gradient Rdq. In this case, the root-mean-square gradient Rdq of the surface of all or a portion of the surface-roughened surface 101 is preferably 10° to 80°, more preferably 12° to 70°, and even more preferably 14° to 60°. These Ra and Rdq values ​​can be calculated using a stylus-type surface roughness meter. The measurement conditions for the entire or partial surface are preferably evaluated using the reference length, measurement length, and cut-off value recommended in the JIS B 0601-2001 or ISO4287-1997 standards in accordance with the degree of surface roughness.

[0052] For example, the arithmetic mean height Ra and root mean square gradient Rdq can be measured using, for example, a stylus-type surface roughness meter (Form Talysurf PGI1250A manufactured by Taylor Hobson). The evaluation length and cutoff value (λc) can be values ​​recommended by JIS B 0601-2001 or ISO 4287-1997, depending on the degree of surface roughness. Measurements are preferably performed at five arbitrary positions on the roughened surface 101 of the ceramic sheet to be measured. The scanning direction of the stylus is preferably selected arbitrarily each time measurements are performed. The average value is then calculated from the five measurement results, and it is determined whether the requirements (A) and (B) above are met.

[0053] Furthermore, the surface of all or part of the surface-roughened surface 101 of the present invention may be expressed by the developed area ratio Sdr, which is a surface roughness parameter. In this case, the developed area ratio Sdr is preferably 0.2 or more and 2 or less, more preferably 0.3 or more and 1.8 or less, and even more preferably 0.5 or more and 1.5 or less. The developed area ratio Sdr, which is a surface roughness parameter, can be calculated using a non-contact surface roughness meter.

[0054] For example, surface roughness can be measured using an optical interference type non-contact three-dimensional surface roughness measuring instrument (Talysurf CCI HD-XL manufactured by Taylor Hobson). Measurements are performed in a mode for evaluating a "low reflectivity rough surface" using a 20x objective lens (evaluation area 0.82mm x 0.82mm). Measurements are preferably performed at three arbitrary points on the roughened surface 101 to be measured on the ceramic sheet. The average value of the three measurement results is preferably calculated to determine whether or not the requirement (C) above is met.

[0055] In addition, it is preferable that all or part of the surface-roughened surface 101 in the present invention does not have a step-and-terrace structure on the surface of the sintered particles. The presence or absence of a step-and-terrace structure on the surface-roughened surface 101 can be determined, for example, by checking an SEM image of the surface.

[0056] The roughened surface 101 in the present invention preferably has a uniform surface that satisfies the above conditions, but is not limited to this. For example, the roughened surface 101 may have two or more different configurations. In this case, it is preferable that at least one of the roughened surfaces 101 satisfies the conditions regarding surface roughness or the presence or absence of a step-and-terrace structure. Furthermore, in this case, the roughened surface 101 may vary intermittently or continuously in the horizontal direction of the surface. These conditions for the roughened surface 101 can be adjusted depending on the design of the lithium ion recovery device 1.

[0057] Furthermore, by forming the roughened surface 101 on the first layer 11, it is possible to prevent the second layer 12 from peeling off from the first layer 11. This is because when the second layer 12 is provided on the roughened surface 101 of the first layer 11, the surface area of ​​the bonding interface between the first layer 11 and the second layer 12 is substantially increased.

[0058] The materials of the first layer 11 and the second layer 12 constituting the lithium permselective membrane 10 are not particularly limited as long as they are materials that can selectively transmit lithium ions 131, but are preferably lithium ion conductors having any of a perovskite-type crystal structure, a Nasicon-type crystal structure, a garnet-type crystal structure, a spinel-type crystal structure, a ramsdellite-type crystal structure, an olivine-type crystal structure, or a crystal structure based on LiTa2PO8.

[0059] As a preferred example, the material of the first layer 11 constituting the lithium permselective membrane 10 of the present invention is preferably a super lithium ion conductor that has high ionic conductivity for lithium ions 131 and does not react with water or components in aqueous solutions, from the viewpoint of allowing lithium ions 131 to pass through while suppressing reactions with water and other aqueous solutions, and it is preferable to use lithium lanthanum titanate having a perovskite crystal structure. x La (2-x) / 3 It is preferable to use lanthanum lithium titanate in TiO3 where x<2 / 3, and more preferably Li 0.29 La 0.57 TiO3 (x=0.29).

[0060] For the first layer 11 constituting the lithium permselective membrane 10, in addition to lanthanum lithium titanate having a perovskite-type crystal structure, such as lanthanum lithium titanate, lithium aluminum titanium phosphate (LATP) having a Nasicon-type crystal structure, lithium aluminum germanium phosphate (LAGP), lithium titanate (LT) having a ramsdellite-type crystal structure, or lithium tantalum phosphate (LTP) having a crystal structure based on LiTa2PO8 can also be used. Furthermore, the crystal structure and material are not limited to those mentioned above, and any material can be used as the lithium permselective membrane 10 as long as it is an ion conductor with high lithium ion conductivity and can exist stably in the raw solution 111 and the recovered solution 112 used in recovering lithium ions.

[0061] The material of the second layer 12 constituting the lithium permselective membrane 10 of the present invention is a lithium ion conductor different from that of the first layer 11. As a preferred specific example, the material of the second layer 12 is lithium titanate having a ramsrite-type crystal structure, which is a lithium ion conductor that has high ionic conductivity for lithium ions 131 and does not react with water or components in aqueous solutions, from the viewpoint of allowing lithium ions 131 to pass through while suppressing reaction with water and other aqueous solutions.

[0062] The material for the second layer 12 constituting the lithium permselective membrane 10 can be lithium titanate having a ramsdellite-type crystal structure, or alternatively, lithium aluminum titanium phosphate (LATP), lithium aluminum germanium phosphate (LAGP), or lithium titanate (LT) having a ramsdellite-type crystal structure, or lithium tantalum phosphate (LTP), which has a crystal structure based on LiTa2PO8. The crystal structures of the first layer 11 and the second layer 12 may be the same or different. Furthermore, the material is not limited to the above crystal structures, and any material that is an ion conductor with high lithium ion conductivity and can exist stably in the raw solution 111 and the recovered solution 112 used in lithium ion recovery can be used for the lithium permselective membrane 10.

[0063] Furthermore, from the viewpoint of being able to sufficiently recover lithium ions 131, the lithium ion permeation rate in the lithium permselective membrane 10 of the present invention is set to 0.08 mmol / (hr cm) in a lithium permeation test performed at a temperature range of 22°C to 24°C using raw material solutions with lithium ion concentrations of 0.1 mol / L, 0.2 mol / L, and 1.0 mol / L. 2 ) or more, 0.09mmol / (hr·cm 2 ) or more, 0.25mmol / (hr·cm 2 ) or more. More preferably, it is 0.1 mmol / (hr cm 2 ) or more, 0.12mmol / (hr·cm 2 ) or more, 0.30mmol / (hr·cm 2 ) or more. More preferably, it is 0.15 mmol / (hr cm 2 ) or more, 0.20mmol / (hr·cm 2 ) or more, 0.35mmol / (hr·cm 2 The lithium permeation rate is calculated from the following formula (1):

[0064] V = M / (T S) (1)

[0065] Here, M is the amount (mmol) of lithium ions 131 that permeated the lithium permselective membrane 10, T is the time (hr) required for the lithium ions 131 of permeation amount M to permeate, and S is the effective membrane area (cm 2 )

[0066] (Method of manufacturing lithium permselective membrane) Next, a method for manufacturing the lithium permselective membrane 10 of the present invention will be described. The lithium permselective membrane 10 may be composed solely of a lithium ion conductor, or may be composed of a composite of the lithium ion conductor and another material that does not have lithium ion conductivity. The lithium permselective membrane 10 must have a structure without through-holes because it is necessary to separate the raw solution 111 and the recovered solution 112 through the lithium permselective membrane 10. While there are no particular limitations on the method for fabricating the lithium permselective membrane 10 without through-holes, it is preferable to use a densified sintered body as the lithium ion conductor. To fabricate this sintered body, particles that can constitute the sintered body as the lithium ion conductor for the intended first layer 11 and second layer 12 are crushed to a desired particle size range, granulated as necessary, and then mixed with optional additives such as a sintering aid, dispersant, pore-forming agent, mold release agent, and binder, and molded into a desired shape (a shape compatible with the lithium ion recovery device 1 to be used). The molding method is not particularly limited, and may be appropriately selected depending on the shape of the molded body to be produced, such as sheet molding, uniaxial pressing, cold isostatic pressing, warm isostatic pressing, etc. The produced molded body may be further machined into any shape as needed.

[0067] The compact is then sintered. A debinding step may be performed prior to sintering to decompose or remove organic matter contained in the binder of the mixture. The sintering conditions, such as the sintering temperature and sintering time, are determined based on the desired lithium-ion conductor. For example, to obtain a sintered body of lanthanum lithium titanate as a lithium-ion conductor, sintering is preferably performed at a temperature range of 1100°C to 1500°C for a holding time of 5 hours to 100 hours. At temperatures below 1100°C, sintering does not proceed even over time, resulting in a dense body. At temperatures above 1500°C, the compact and the sintered material fuse and react, preventing the formation of a satisfactory sintered body. To prevent changes in the surface structure or composition of the compact due to the influence of the sintering atmosphere during sintering, the compact may be embedded in the same powder as the compact, such as a mother powder or cover powder, and then sintered.

[0068] Next, part or all of the outer surface of the sintered body corresponding to the first layer 11 among the obtained sintered body (as-sintered body) is subjected to surface roughening treatment, thereby providing a roughened surface 101 on the outer surface of the lithium permselective membrane 10. At this time, it is preferable that the arithmetic mean height Ra of the roughened surface 101 is 0.8 μm or more and 20 μm or less, or the root-mean-square gradient Rdq is 10° or more and 80° or less, or the developed area ratio Sdr is 0.2 or more and 2 or less, but is not limited thereto and may be within the aforementioned numerical ranges.

[0069] Furthermore, the depth of removal of the surface layer in the surface roughening treatment of the outer surface of the obtained sintered body (as-sintered body) corresponding to the first layer 11 is not particularly limited, but it is preferable to remove 5 μm or more. Considering that changes in structure and composition may occur due to the influence of the sintering atmosphere during sintering, it is preferable to change the removal depth depending on the material type or composition of the ion conductor or the temperature or time of the sintering process. For example, the removal depth may be adjusted depending on the sintering time, or the sintering temperature and sintering time. In this case, it is preferable to remove the surface layer to the extent that the roughened surface 101 has the desired structure, composition, or particle size distribution.

[0070] The surface roughening treatment described above is preferably performed by blasting, and more preferably by sandblasting, in order to simultaneously remove the surface layer and form a roughened surface 101 having a surface roughness of 0.8 μm to 20 μm, a root-mean-square gradient Rdq of 10° to 80°, or a developed area ratio Sdr of 0.2 to 2. In this case, residual stress can be imparted to the sintered body, thereby improving the strength and durability of the sintered body. Furthermore, the present invention is not limited to sandblasting, and may involve blasting treatments such as wet blasting and shot blasting, as well as dry or wet mechanical polishing and chemical etching. The abrasive grains used in the blasting treatment are not particularly limited, but may include alumina abrasive grains, SiC abrasive grains, glass abrasive grains, or zircon abrasive grains.

[0071] If the sintered body corresponding to the first layer 11 is subjected to the above-described surface roughening treatment and then subjected to a high-temperature heat treatment such as annealing, the surface structure or composition may be changed due to the influence of the firing atmosphere during the heat treatment, as in the case of sintering. Therefore, after the surface roughening treatment, it is preferable to use the resultant as the lithium permselective membrane 10 without performing a heat treatment at a high temperature (generally equal to or higher than the Debye temperature of the material) at which the atoms constituting the lithium ion conductor may diffuse.

[0072] Whether the surface of the first layer 11 has been roughened after the final heat treatment or not can be determined by observing the surface morphology of the first layer 11. For example, if the first layer 11 is a sintered body of lanthanum lithium titanate, the surface of the sintered body after sintering exhibits steps at the interfaces (grain boundaries) between the crystalline particles of the ceramics constituting the sintered body, and a step-and-terrace structure stripe pattern is observed on the crystalline particle surface as a trace of grain growth due to sintering. On the other hand, since the surface layer has been physically removed from the roughened surface 101 after heat treatment, the above-mentioned steps along the grain boundaries and the step-and-terrace structure as a trace of crystalline particle growth are not observed, and the surface morphology is observed according to the surface roughening method. For example, blasting produces a rough surface with no regularity. Furthermore, mechanical polishing produces linear scratches similar to those seen in polishing.

[0073] Therefore, specifically, in the present invention, since it is necessary to reliably remove the portions of the surface-roughened surface 101 that were affected by the firing atmosphere during the heat treatment, it is preferable that the surface-roughened surface 101 does not have the step-and-terrace structure of the sintered particle surface that is formed during the heat treatment. As described above, it is possible to easily determine whether the surface is as it is after the heat treatment (sintering step or annealing step) or whether the surface has been sufficiently roughened after the final heat treatment.

[0074] The lithium permselective membrane 10 of the present invention can be obtained by the above-mentioned method, but the method for producing the lithium permselective membrane 10 is not limited to the above-mentioned method and can be modified within the scope that can achieve the object of the present invention.

[0075] (Evaluation of lithium permeation rate) The lithium permselective membrane 10 produced by the above-described method is placed in the lithium ion recovery device 1 configured as described above, and lithium can be recovered by applying a voltage to the first electrode 121 and the second electrode 122.

[0076] At this time, it is known that the permeation rate of lithium ions 131 permeating the lithium permselective membrane 10 mainly depends on the temperature of the lithium permselective membrane 10, the pH of the stock solution 111, and the lithium ion concentration in the stock solution 111. Therefore, when evaluating the lithium permeation rate, the lithium ion permeation amount (unit: mmol / (hr cm)) per unit area of ​​the lithium permselective membrane 10 and per unit time is calculated under a constant temperature and constant pH of the stock solution 111. 2 If the lithium permeation rate is as defined above, the lithium permeation rate can be compared and evaluated as the performance of the lithium permselective membrane 10 itself.

[0077] The amount of lithium ions permeated can be directly determined by evaluating the lithium ion concentrations of the raw solution 111 and the recovered solution 112 before and after the lithium permeation test using ICP analysis, etc. Alternatively, it can also be determined from the value of the current that flows when a voltage is applied to the lithium ion recovery device 1, using the following formula (2).

[0078] M=Itα / nF (2)

[0079] Here, M is the number of moles of lithium ions 131 that permeated the lithium permselective membrane 10, I is the current value flowing through the device, t is time, F is Faraday's constant, and n is the valence (lithium ion is 1). α represents current efficiency, a parameter that indicates the proportion of the current value attributable to the permeation of lithium ions 131 out of the current value flowing through the device, and has a value in the range of 0≦α≦1. For example, the amount of lithium ions 131 that moved can be calculated by multiplying the area enclosed by the current-time curve obtained by measuring and recording the current at regular intervals with a constant voltage applied by the current efficiency and dividing the result by the Faraday's constant.

[0080] The current efficiency α is affected by the configuration of the lithium ion recovery device 1 and the presence or absence of electronic conductivity of the lithium permselective membrane 10. To determine the current efficiency α, the amount of lithium ions 131 contained in the recovery solution 112 is determined by ICP analysis or the like to calculate the actual measured value of the lithium ion permeation amount, and the theoretical value of the lithium ion permeation amount is calculated from the total current value that flows assuming α=1 using equation (2), and the actual measured value of the lithium ion permeation amount is divided by the theoretical value.

[0081] The lithium ion permeation rate defined above can be obtained by dividing the amount of lithium ions permeated calculated by the above method by the total time required for permeation, then by the effective membrane area of ​​the lithium permselective membrane 10, and then by the lithium ion concentration in the stock solution 111. [Example]

[0082] Next, examples of the present invention will be described in more detail with reference to experimental results and in comparison with comparative examples.

[0083] (Preparation of lithium permselective membrane according to the example) (Fabrication of the first layer 11) Lithium lanthanum titanate powder (manufactured by Toho Titanium Co., Ltd.) was ball milled to adjust the particle size, and a binder, dispersant, plasticizer, and solvent were added to prepare a slurry. The resulting slurry was formed into a sheet and dried to obtain a green sheet approximately 700 μm thick.

[0084] The resulting green sheet was sandwiched between porous ceramic base plates and heat-treated at 1000°C for 3 hours in air to perform debinding and calcination. The resulting calcined body was then sandwiched between dense ceramic base plates. In Examples 1 to 3, sintering was performed by heat-treating the body at 1230°C for 65 hours in air. In Example 4, sintering was performed by heat-treating the body at 1300°C for 65 hours. The relative density of the resulting sintered body was 98% or higher, resulting in a dense ceramic sheet without through-holes. The resulting ceramic sheet was pulverized and subjected to powder X-ray diffraction analysis (CuKα radiation source) using silicon powder as an internal standard. The results of Figure 2 confirm that the resulting ceramic sheet is composed of a crystalline phase of lanthanum lithium titanate (the desired ionic conductor).

[0085] (Surface roughening treatment) Next, the resulting sintered ceramic sheet corresponding to the first layer 11 was cut into a size of approximately 20 mm x 20 mm, and one side of the cut ceramic sheet was subjected to a surface roughening treatment by grinding the surface by approximately 10 μm or more using a silicon carbide (GC100 abrasive grain) blasting treatment, thereby obtaining a first layer 11 that satisfies at least one of the following requirements (A), (B), and (C): (A) is the requirement that the arithmetic mean height Ra of all or a portion of the roughened surface 101 is 0.8 μm or more and 20 μm or less; (B) is the requirement that the root-mean-square gradient Rdq of all or a portion of the roughened surface 101 is 10° or more and 80° or less; and (C) is the requirement that the developed area ratio Sdr of all or a portion of the roughened surface 101 is 0.2 or more and 2 or less.

[0086] Figure 3 shows an SEM image of the surface of the sintered compact before surface roughening treatment, and Figure 4 shows an SEM image of the roughened surface 101 of the sintered compact after surface roughening treatment. As can be seen in Figure 3, on the surface of the sintered lanthanum lithium titanate sintered compact, steps exist along the interfaces (grain boundaries) of the ceramic crystal grains, and on the surfaces of some crystal grains, a stepped striped pattern consisting of a step-and-terrace structure was observed as a trace of grain growth during sintering. On the other hand, as can be seen in Figure 4, on the roughened surface 101 that had been roughened by blasting, the steps along the grain boundaries and the step-and-terrace structure on the crystal grain surfaces as seen in Figure 3 were not observed, and an irregular, rough surface was observed.

[0087] (Fabrication of the second layer 12) Predetermined amounts of raw material powders of lithium carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and titanium oxide (manufactured by Ishihara Sangyo Kaisha, Ltd.) were mixed and the particle size was adjusted by ball milling, and a binder, a dispersant, a plasticizer, and a solvent were added to prepare a slurry. The obtained slurry was applied to the surface of the fabricated first layer 11.

[0088] Next, the sheet after coating with the slurry was heat-treated at 1000°C for 1 hour in the atmosphere to form a second layer 12 on the surface of the first layer 11, thereby obtaining a lithium permselective membrane 10 according to the example. The results of powder X-ray diffraction (CuKα radiation source) measurement of the fabricated lithium permselective membrane from the surface of the second layer 12 are shown in Figure 5. The results in Figure 5 confirm that the second layer 12 of the resulting ceramic sheet is composed of a layer containing, as its main phase, a Li2Ti3O7 (target ion conductor) crystalline phase with a ramsdellite crystal structure. Figure 6 is a cross-sectional view of the resulting lithium permselective membrane 10 in the thickness direction. As shown in Figure 5, the second layer 12 is provided on one surface of the first layer 11, including the surface-roughened surface 101.

[0089] (Preparation of a lithium permselective membrane according to a comparative example) The lithium permselective membrane 10 according to the comparative example is composed of a single first layer 11. The manufacturing method is substantially the same as the manufacturing method of the first layer 11 according to the above-described Examples 1 to 3, and the configuration is also substantially the same, so a redundant description will be omitted.

[0090] (Evaluation of lithium permeation rate using a lithium permselective membrane) The ceramic sheets of the examples and comparative examples obtained by the above-described method were used as lithium permselective membranes 10 (effective membrane area: Φ12 mm) and installed in a lithium ion recovery device 1 as shown in Figure 1, and lithium recovery tests were conducted. The test was conducted at a temperature ranging from 22°C to 24°C. The raw solution 111 used in the test was a mixed aqueous solution of lithium hydroxide, sodium hydroxide, and potassium hydroxide, with a lithium ion concentration of 0.1 mol / L, 0.2 mol / L, or 1 mol / L, and a sodium ion concentration of 0.1 mol / L and a potassium ion concentration of 0.1 mol / L, respectively. A 0.1 mol / L aqueous potassium hydroxide solution was used as the recovery solution 112. The first electrode 121 (anode electrode) and the second electrode 122 (cathode electrode) were each made of carbon felt. The voltage applied to the carbon felt was set to 6 V. During the test, the solution was thoroughly stirred to ensure a uniform lithium ion concentration in the raw solution 111 and the recovered solution 112. From the start of voltage application, the current value was recorded at intervals of approximately 30 seconds, and the test was continued for 18 hours or more.

[0091] The amount of lithium ion permeation was calculated using equation (1) from the total current value that flowed from the start of the test until 18 hours had elapsed, and this was divided by the time (18 hours) to obtain the lithium permeation rate (mmol / (hr cm 2 ) was calculated. In this calculation, the current efficiency α of the lithium permselective membrane constructed according to this example was set to 1. Table 2 shows the lithium permeation rates of the examples and comparative examples corresponding to the first layer 11 prepared under various firing conditions.

[0092] [Table 1]

[0093] Referring to Table 2, when Examples 1, 2, and 3 based on the first layer 11 prepared under the same conditions are compared with Comparative Examples 1, 2, and 3, it is clear that in the lithium recovery test in which the lithium ion concentration on the feed solution side is the same, the lithium permselective membranes prepared in the Examples have a significantly higher lithium permeation rate than the lithium permselective membranes prepared in the Comparative Examples. (In the test with a lithium ion concentration of 0.1 mol / L, the lithium ion permeation rate was 0.07 mmol / (hr cm) in Comparative Example 1.) 2 ), whereas in Example 1 it was 0.16 mmol / (hr cm 2 ) In addition, the lithium ion permeation rate in the test at a lithium ion concentration of 0.2 mol / L was 0.08 mmol / (hr cm) in Comparative Example 2. 2 ), whereas in Example 2 it was 0.26 mmol / (hr cm 2 ) In addition, the lithium ion permeation rate in the test at a lithium ion concentration of 1.0 mol / L was 0.24 mmol / (hr cm) in Comparative Example 3. 2 ), whereas in Example 3 it was 0.45 mmol / (hr cm 2 ) The above results show that the lithium permselective membranes (Examples 1 to 3) constituted by the first layer 11 provided with the second layer 12 have a significantly higher lithium permeation rate than the lithium permselective membranes 10 (Comparative Examples 1 to 3) constituted by only the first layer 11 alone.

[0094] Furthermore, referring to Table 1, it was confirmed that the lithium permeation rate increases as the sintering temperature when sintering the first layer 11 increases, as is clear from Example 4. This is thought to be because the higher the sintering temperature, the more rapidly grain growth occurs during sintering, resulting in a decrease in resistance at grain boundaries and an increase in the lithium ion conductivity of the first layer 11. Regardless of the sintering temperature, by implementing a formula that improves the lithium ion conductivity of the first layer 11, it is possible to produce a lithium permselective membrane with a faster lithium permeation rate.

[0095] Furthermore, although not specifically shown, even when the second layer 12 was provided in each example described in the specification of Japanese Patent Application No. 2023-025133 filed by the present inventors, a similarly high lithium ion permeation rate was obtained compared to the lithium selective permeable membrane 10 composed only of the first layer 11 alone.

[0096] The present invention has been described above based on examples. From this description, it can be seen that the lithium permselective membrane 10 of the present invention can further reduce the time and cost required for lithium ion recovery. Therefore, the lithium permselective membrane 10 of the present invention can be a suitable member for recovering lithium ions 131 from seawater or industrial waste (such as discarded lithium secondary batteries).

[0097] The lithium permselective membrane 10 and the method for manufacturing the lithium permselective membrane 10 of the present invention have been described based on embodiments and examples, but the present invention can be used within the scope of the object and technical scope of the present invention in addition to the above-mentioned examples and use examples. Furthermore, the examples and use examples of the present invention can be easily modified and altered by those skilled in the art. [Explanation of symbols]

[0098] 1...Lithium ion recovery device, 10...Lithium selective permeable membrane, 101...Roughened surface, 102...Untreated surface, 111...First liquid (raw solution), 112...Second liquid (recovered liquid), 121...First electrode (anode), 122...Second electrode (cathode), 131...Lithium ions, 132...Unspecified ions.

Claims

1. A lithium permselective membrane comprising a composite layer including: a first layer including a sintered body of a lithium ion conductor, at least a portion of an outer surface of which is formed of a roughened surface; and a second layer including a sintered body of a lithium ion conductor different from the first layer.

2. 2. The lithium permselective membrane according to claim 1, which satisfies at least one of the following requirements (A), (B), and (C): (A) The arithmetic mean height Ra of the entire or part of the roughened surface is 0.8 μm or more and 20 μm or less. (B) The root mean square gradient Rdq of the entire or a part of the roughened surface is 10° or more and 80° or less. (C) The developed area ratio Sdr of the entire or part of the roughened surface is 0.2 or more and 2 or less.

3. The lithium permselective membrane according to claim 1, A lithium permselective membrane characterized in that the surface of the sintered body particles in the entirety or part of the surface-roughened surface does not have a step-and-terrace structure.

4. The lithium permselective membrane according to claim 1, The first layer and the second layer have a perovskite-type crystal structure, a Nasicon-type crystal structure, a garnet-type crystal structure, a spinel-type crystal structure, a ramsdellite-type crystal structure, an olivine-type crystal structure, or a LiTa crystal structure. 2 P.O. 8 2. A lithium permselective membrane comprising a sintered body of a lithium ion conductor having any one of the crystal structures based on the above.

5. The lithium permselective membrane according to claim 1, A lithium permselective membrane, wherein the lithium ion conductor constituting the first layer is a sintered body of lithium lanthanum titanate (LLT) having a perovskite-type crystal structure.

6. The lithium permselective membrane according to claim 1, The lithium ion conductor constituting the second layer is selected from the group consisting of lanthanum lithium titanate (LLT) having a perovskite-type crystal structure, lithium aluminum titanium phosphate (LATP) having a Nasicon-type crystal structure, lithium aluminum germanium phosphate (LAGP), lithium titanate (LT) having a ramsdellite-type crystal structure, and LiTa 2 P.O. 8 A lithium permselective membrane characterized by being a sintered body of lithium tantalum phosphate (LTP) having a crystal structure based on the above formula.

7. The lithium permselective membrane according to claim 1, A lithium permselective membrane comprising a composite layer including a first layer containing a sintered body of lanthanum lithium titanate (LLT) having a perovskite-type crystal structure, and a second layer containing a sintered body of lithium titanate (LT) having a ramsrite-type crystal structure.

8. The lithium permselective membrane according to any one of claims 1 to 7, In a lithium permeation test performed on raw material solutions with lithium ion concentrations of 0.1 mol / L, 0.2 mol / L, and 1.0 mol / L in a temperature range of 22°C to 24°C, the lithium permeation rate V expressed by the following formula (1) was 0.08 mmol / (hr cm 2 ) or more, 0.09 mmol / (hr・cm 2 ) or more, 0.25 mmol / (hr・cm 2 ) or more. V = M / (T・S)...(1) Here, M is the amount of lithium ions (mmol) that permeated the lithium permselective membrane, T is the time (hr) required for lithium ions of permeation amount M to permeate, and S is the effective membrane area (cm 2 )

9. A method for producing a lithium permselective membrane, comprising: a step of producing a first layer including a sintered body of a lithium ion conductor, at least a part of an outer surface of which is formed as a roughened surface; forming a second layer containing a sintered body of a lithium ion conductor different from the first layer on a part or all of the surfaces of the first layer, a surface roughening treatment step of removing a surface layer of at least a portion of an outer surface of the sintered body after the sintering step and roughening the surface;

10. 10. The method for producing a lithium permselective membrane according to claim 9, wherein at least one of the following requirements (D), (E), and (F) is satisfied: (D) The arithmetic mean height Ra of all or part of the surface of the sintered body processed by the surface roughening treatment step is 0.8 μm or more and 20 μm or less. (E) The root mean square gradient Rdq of all or part of the surface of the sintered body processed by the surface roughening treatment step is 10° or more and 80° or less. (F) The developed area ratio Sdr of all or part of the surface of the sintered body processed by the surface roughening treatment step is 0.2 or more and 2 or less.

11. A method for producing the lithium permselective membrane according to claim 9 or 10, comprising:

4. A method for producing a lithium permselective membrane, wherein the surface roughening step is carried out by blasting.

12. A method for producing a lithium permselective membrane, comprising: A step of producing a first layer including a sintered body of lanthanum lithium titanate (LLT) having a perovskite-type crystal structure; Lithium aluminum titanium phosphate (LATP) having a Nasicon-type crystal structure, lithium aluminum germanium phosphate (LAGP), lithium titanate (LT) having a ramsdellite-type crystal structure, or LiTa 2 P.O. 8 1. A method for producing a lithium permselective membrane, comprising the step of producing a second layer comprising a sintered body of lithium tantalum phosphate (LTP) having a crystal structure based on the formula:

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