Ionic conductive solid electrolyte compound, method for producing the same, and electrochemical device including the same

Abstract

As a crystalline oxide, "A x (M 2 TO 8 ) y " wherein A is a cation having a +1 oxidation state, M is a cation having a +4, +5, or +6 oxidation state, T is a cation having a +4, +5, or +6 oxidation state, x and y are real numbers that are independent of one another and greater than 0, and x is less than or equal to 3y, and the ion-conducting solid electrolyte compound has high ionic conductivity and low electronic conductivity.

Description

Technical Field

[0001] The present invention relates to a novel solid electrolyte compound having excellent ionic conductivity, a method for producing the same, and an electrochemical device including the same.

Background Art

[0002] Rechargeable secondary lithium-ion batteries are used in a variety of application fields, from portable electronic devices to automotive batteries. However, commercial lithium-ion batteries have important safety issues because they use a flammable organic liquid electrolyte with low thermal stability. Also, in an organic electrolyte, if lithium dendrites grow, there is a problem that the lithium-ion battery is short-circuited.

[0003] To solve such problems of organic liquid electrolytes, many studies have been made on solid electrolyte materials. Replacing the organic liquid electrolyte with a non-volatile and thermally stable solid electrolyte can greatly improve safety. Solid lithium-ion electrolytes with high ionic conductivity and excellent mechanical strength are also applicable to lithium-air batteries, lithium-based redox flow batteries, Li-H2O2 semi-fuel cells, chemical sensors, and the like.

[0004] In particular, crystalline oxide and sulfide compounds containing lithium have been widely studied as solid electrolytes. As general sulfide-based solid electrolytes, argyrodite-based Li6PS5I, thio-LISICON (lithium super ionic conductor)-based Li 4-x Ge 1-x P x S4, Li 10 GeP2S 12Examples include these. These sulfide-based solid electrolytes are similar to or have even higher lithium ion conductivity than conventional liquid electrolytes. However, sulfide-based solid electrolyte compounds have the problem of being sensitive to moisture. On the other hand, oxide-based solid electrolyte compounds are relatively excellent in terms of ease of handling, mechanical properties, chemical properties, and thermal stability. As oxide-based lithium ion solid electrolytes, perovskite-based Li 3x La 2 / 3-x TiO3, NASICON (sodium 1613376528649_0 )-based Li 1.3 Al 0.3 Ti 1.7 (PO4)3, garnet-based Li7La3Zr2O 12 etc. exhibit remarkable lithium ion conductivity. These oxide-based solid electrolytes show a lithium ion conductivity of 1×10 -4 Scm -1 at room temperature and are stable in air and moisture. The lithium ion conductor Li 3x La 2 / 3-x TiO3 with a perovskite structure is described in a research paper by Liquan et al. ["High ionic conductivity in lithium lanthanum titanate" Solid State Commun. 86, 689-693, 1993], and the lithium ion conductor Li 1.3 Al 0.3 Ti 1.7 (PO4)3 with a NASICON structure is described in a research paper by Adachi et al. ["High Li + conducting ceramics" Acc. Chem. Res. 27, 265-270, 2003]. Lithium ion conductors with a garnet structure have been reported via International Publication No. WO 2005 / 085138 and International Publication No. WO 2009 / 003695. However, conventional oxide-based solid electrolyte compounds have relatively low ionic conductivity and improvement is required.

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide an ion-conductive solid electrolyte compound having excellent thermal and chemical stability, very excellent cation conductivity, and very low electron conductivity.

[0006] Another object of the present invention is to provide a method for producing an ion-conductive solid electrolyte compound.

[0007] Still another object of the present invention is to provide an electrochemical device including an electrolyte layer made of an ion-conductive solid electrolyte compound.

Means for Solving the Problems

[0008] The ion-conductive solid electrolyte compound according to an embodiment of the present invention has a stoichiometric formula of the following Chemical Formula 1 as a crystalline oxide.

[0009]

Chem.

[0010] In Chemical Formula 1, A is a cation having a +1 valence oxidation state, M is a cation having a +4 valence, +5 valence or +6 valence oxidation state, T is a cation having a +4 valence, +5 valence or +6 valence oxidation state, x and y are real numbers greater than 0 independent of each other, and x is a real number greater than 0 and less than or equal to 3y.

[0011] In one embodiment, A includes one or more selected from the group consisting of lithium ion (Li + ), sodium ion (Na + ), hydrogen ion (H + ), and hydronium ion (H3O + ), M is titanium ion (Ti 4+ ), zirconium ion (Zr 4+ ), hafnium ion (Hf 4+ ), niobium ion (Nb5+ ), tantalum ion (Ta 5+ ) and antimony ion (Sb 5+ ), and contains one or more selected from the group consisting of, and T is silicon ion (Si 4+ ), germanium ion (Ge 4+ ), phosphorus ion (P 5+ ), arsenic ion (As 5+ ), vanadium ion (V 5+ ), sulfur ion (S 6+ ), molybdenum ion (Mo 6+ ), and tungsten ion (W 6+ ), and may contain one or more selected from the group consisting of. In one embodiment, T is germanium ion (Ge 4+ ), phosphorus ion (P 5+ ), arsenic ion (As 5+ ), and vanadium ion (V 5+ ), and may contain one or more selected from the group consisting of.

[0012] In one embodiment, within the crystal, M is coordinated by oxygen anions to form an MO6 octahedral unit, and T can be coordinated by oxygen anions to form a TO4 tetrahedral unit.

[0013] In one embodiment, the ion-conductive solid electrolyte compound includes a first lattice layer formed by connecting MO6 octahedral units in a square lattice along a first plane, a second lattice layer formed by connecting MO6 octahedral units in a square lattice along a second plane parallel to the first plane, one MO6 octahedral unit, and two TO4 tetrahedral units bonded to share two of its vertices, disposed between the first lattice layer and the second lattice layer, and a connecting layer including a trimeric link unit that binds to the MO6 octahedral unit of the first lattice layer and the MO6 octahedral unit of the second lattice layer, and A is also disposed in the space between the MO6 octahedral unit and the TO4 tetrahedral unit.

[0014] In one embodiment, in each of the first lattice layer and the second lattice layer, eight MO6 octahedral units are arranged at positions corresponding to four vertices and four sides of a quadrilateral. Among the MO6 octahedral units, the MO6 octahedral units respectively arranged at positions corresponding to the four vertices are each connected to four adjacent MO6 octahedral units to share vertices, thereby forming first octahedral units respectively. Among the MO6 octahedral units, the MO6 octahedral units respectively arranged at positions corresponding to the four sides are each connected to two adjacent MO6 octahedral units to share vertices, thereby forming second octahedral units respectively.

[0015] In one embodiment, the second lattice layer is also shifted by a first interval and a second interval along a first axis and a second axis that define a first plane and a second plane, respectively, compared to the first lattice layer.

[0016] In one embodiment, the MO6 octahedral units of the trimer link unit are connected to share vertices with two second octahedral units respectively arranged at positions corresponding to two sides connected to the first vertex of the first quadrilateral of the first lattice layer, and two second octahedral units respectively arranged at positions corresponding to two sides connected to the second vertex opposite to the first vertex of the second quadrilateral of the second lattice layer corresponding to the first quadrilateral. One of the two TO4 tetrahedral units of the trimer link unit is connected to share vertices with two second octahedral units respectively arranged at positions corresponding to two sides connected to the second vertex of the first quadrilateral, and one first octahedral unit arranged at a position corresponding to the second vertex of the second quadrilateral. The remaining one of the two TO4 tetrahedral units of the trimer link unit is also connected to share vertices with one first octahedral unit arranged at a position corresponding to the first vertex of the first quadrilateral, and two second octahedral units respectively arranged at positions corresponding to two sides connected to the first vertex of the second quadrilateral.

[0017] In one embodiment, each of the first lattice layer and the second lattice layer has a composition corresponding stoichiometrically to [M3O 18 / 2 3- and the connecting layer has a composition corresponding stoichiometrically to [MT2O 14 / 2 ​​+ can have a composition corresponding thereto.

[0018] The manufacturing method for manufacturing an ion-conductive solid electrolyte compound according to an embodiment of the present invention includes a step of mixing and pulverizing raw material substances of A, M, and T to form a first raw material substance, a step of subjecting the first raw material substance to a primary heat treatment, a step of pulverizing and mixing the primary heat-treated first raw material substance through a wet ball milling process to form a second raw material substance, a step of compression molding the second raw material substance, and a step of sintering the compression-molded second raw material substance.

[0019] In one embodiment, as the raw material substance of A, a carbonate compound or a nitrate compound of A may be used, as the raw material substance of M, an oxide or a halide of M may be used, and as the raw material substance of T, an oxide salt compound of T may be used.

[0020] In one embodiment, the primary heat treatment of the first raw material substance is performed at a temperature of 500°C to 1,000°C for 6 hours to 12 hours, and the sintering of the second raw material substance is also performed in a temperature range of 900°C to 1,200°C for 12 hours to 48 hours.

[0021] In one embodiment, when the ion-conductive solid electrolyte compound is LiTa2PO8, as the raw material substance of lithium (Li), Li2CO3 or LiNO3 may be used, as the raw material substance of phosphorus (P), (NH4)2HPO4, (NH4)H2PO4 or (NH4)3PO4 may be used, or as the raw material substances of lithium and phosphorus, LiPO3 or LiH2PO4 may be used, and as the raw material substance of tantalum (Ta), Ta2O5 may be used.

[0022] The electrochemical device according to an embodiment of the present invention includes a first electrode, a second electrode disposed so as to be separated from the first electrode, and a solid electrolyte layer disposed between the first electrode and the second electrode, and the solid electrolyte layer is also formed of the ion-conductive solid electrolyte compound according to the present invention.

[0023] In one embodiment, the solid electrolyte layer is conductive to one or more ions selected from the group consisting of lithium ions (Li + ), sodium ions (Na + ), hydrogen ions (H + ), and hydronium ions (H3O + ).

[0024] In one embodiment, the electrochemical device is also one selected from the group consisting of a sodium ion battery, a lithium ion battery, a lithium-air battery, a hydrogen fuel cell, a proton exchange membrane fuel cell, a lithium-based redox flow battery, a Li-H2O2 semi-fuel cell, and a chemical sensor.

Advantages of the Invention

[0025] The ion-conductive solid electrolyte compound according to the present invention has a novel three-dimensional skeleton structure not previously disclosed, and enables three-dimensional conduction of cations such as lithium ions, sodium ions, hydrogen ions, and hydronium ions without a preferential direction, and has excellent thermal and chemical stability. As a result, the ion-conductive solid electrolyte compound according to the present invention can solve the stability problems of liquid electrolytes, and has extremely excellent cation conductivity and extremely low electron conductivity. Such an ion-conductive solid electrolyte compound is also applicable as an ion-conductive electrolyte material to a lithium-air battery, a lithium-based redox flow battery, a Li-H2O2 semi-fuel cell, a chemical sensor, and the like. Further, the ion-conductive solid electrolyte compound according to the present invention has a simple manufacturing method, a low price of raw materials, and is very advantageous for commercial applications such as mass production.

Brief Description of the Drawings

[0026]

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention can be subjected to various modifications and can have various forms, but specific embodiments are illustrated in the drawings and described in detail in the text. However, they should not be construed as limiting the present invention to the specific disclosed forms, and it must be understood that they include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention. Similar reference numerals are used for similar components while explaining each drawing.

[0028] The terms used in this application are only those used in the description of specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "including" or "having" are intended to specify the presence of the features, steps, operations, components, parts, or combinations thereof described in the specification, and it should not be understood as precluding the possibility of the presence or addition of one or more other features, steps, operations, components, parts, or combinations thereof.

[0029] Unless otherwise defined, technical or scientific terms are included, and all terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. Commonly used terms with established definitions should be construed to have a meaning consistent with the meaning they have in the context of the related art, and should not be construed to have an ideal or overly formal meaning unless clearly defined in this application.

[0030] Figures 1A and 1B are drawings for explaining the crystal structure of an ion-conductive solid electrolyte compound according to an embodiment of the present invention.

[0031] Referring to Figures 1A and 1B, the ion-conductive solid electrolyte compound according to an embodiment of the present invention can have a stoichiometric formula of Chemical Formula 1 as a crystalline oxide and can have a high ion conductivity.

[0032]

Chemical formula

[0033] In Chemical Formula 1, "A" is also a cation having a +1 valence oxidation state, "M" is also a cation having a +4, +5 or +6 valence oxidation state, and "T" is also a cation having a +4, +5 or +6 valence oxidation state. And x and y are real numbers greater than 0 that are independent of each other, and x is also a real number greater than 0 and less than or equal to 3y. For example, both x and y can be 1.

[0034] In one embodiment, A may include one or more selected from lithium ions (Li + ), sodium ions (Na + ), hydrogen ions (H + ), and hydronium ions (H3O + ), etc. M may include one or more selected from titanium ions (Ti 4+ ), zirconium ions (Zr 4+ ), hafnium ions (Hf 4+ ), niobium ions (Nb 5+ ), tantalum ions (Ta 5+ ), antimony ions (Sb 5+ ), etc. T may include one or more selected from silicon ions (Si 4+ ), germanium ions (Ge 4+ ), phosphorus ions (P 5+ ), arsenic ions (As 5+ ), vanadium ions (V 5+ ), sulfur ions (S 6+ ), molybdenum ions (Mo 6+ ), tungsten ions (W 6+ ), etc. As an example, T may include one or more selected from germanium ions (Ge 4+ ), phosphorus ions (P 5+ ), arsenic ions (As 5+ ), and vanadium ions (V 5+ ).

[0035] In the ionic conductive solid electrolyte compound according to an embodiment of the present invention, M is coordinated by oxygen anions to form an MO6 octahedral unit, and T is coordinated by oxygen anions to form a TO4 tetrahedral unit. And a part of the MO6 octahedral units are bonded so as to share vertices with two TO4 tetrahedral units to form a trimer link unit. At this time, in each trimer link unit, the two TO4 tetrahedral units are also bonded so as to respectively share the oxygen ions located at the first vertex and the second vertex opposite to the first vertex among the vertices of the MO6 octahedral unit.

[0036] In one embodiment, the ionic conductive solid electrolyte compound may include a first lattice layer formed by connecting MO6 octahedral units in a square lattice pattern along the ab plane, a second lattice layer disposed above the first lattice layer and formed by connecting MO6 octahedral units in a square lattice pattern along the ab plane, and a connecting layer including a trimer link unit that connects the first lattice layer and the second lattice layer. In one embodiment, in the first lattice layer and the second lattice layer, the MO6 octahedral units are also connected in a square shape, for example, a rhombic lattice pattern.

[0037] In each of the first lattice layer and the second lattice layer, eight MO6 octahedral units are also arranged at positions corresponding to the vertices and sides of the rhombus. In that case, the MO6 octahedral units arranged at positions corresponding to the four vertices are respectively connected to share vertices with four adjacent MO6 octahedral units to form a first octahedral unit, and the MO6 octahedral units arranged at positions corresponding to the four sides are respectively connected to share vertices with two adjacent MO6 octahedral units to form a second octahedral unit. In one embodiment, each of the first octahedral unit and the second octahedral unit can have a stoichiometric composition of MO 6 / 2 and.

[0038] Each of the first lattice layer and the second lattice layer formed as described above is stoichiometrically [M3O 18 / 2 3- ​It can have a composition corresponding thereto. On the other hand, the second lattice layer can be shifted by a first interval ( "a") in the a-axis and a second interval ( "b") in the b-axis compared to the first lattice layer and can be disposed above the first lattice layer.

[0039] In the connecting layer, among the trimer link units, the MO6 octahedral unit is also connected so as to share vertices with two second octahedral units respectively located on two sides connected to the first vertex of the rhombus of the first lattice layer, and two second octahedral units respectively located on two sides connected to the second vertex opposite to the first vertex of the rhombus of the second lattice layer. That is, the MO6 octahedral unit of the trimer link unit is also connected so as to share vertices with four second octahedral units and two TO4 tetrahedral units. And, one of the two TO4 tetrahedral units of the trimer link unit is also connected so as to share vertices with two second octahedral units respectively located on two sides connected to the second vertex of the rhombus of the first lattice layer and one first octahedral unit located at the second vertex of the rhombus of the second lattice layer, and the remaining one of the two TO4 tetrahedral units of the trimer link unit is also connected so as to share vertices with one first octahedral unit located at the first vertex of the rhombus of the first lattice layer and two second octahedral units respectively located on two sides connected to the first vertex of the rhombus of the second lattice layer. That is, each of the two TO4 tetrahedral units of the trimer link unit is also connected so as to share vertices with one MO6 octahedral unit, two second octahedral units, and one first octahedral unit forming the trimer link unit.

[0040] In that case, each of the first lattice layer and the second lattice layer can have a composition stoichiometrically corresponding to [M3O 18 / 2 3- and the connecting layer can have a composition stoichiometrically corresponding to [MT2O 14 / 2 +

[0041] The A ions are also arranged in the space between the MO6 octahedral unit and the TO4 tetrahedral unit.

[0042] ​​​The ionic conductive solid electrolyte compound according to the present invention has a novel three-dimensional skeleton structure not publicly known in the prior art, and enables three-dimensional conduction of cations such as lithium ions, sodium ions, hydrogen ions, and hydronium ions without a preferential direction, and has excellent thermal and chemical stability. As a result, the ionic conductive solid electrolyte compound according to the present invention can solve the stability problems of liquid electrolytes, and has extremely excellent cation conductivity and extremely low electron conductivity. Such an ionic conductive solid electrolyte compound is also applicable as an ionic conductive electrolyte material to sodium ion batteries, sodium metal batteries, lithium ion batteries, lithium metal batteries, lithium-air batteries, hydrogen fuel cells, proton exchange membrane fuel cells, lithium-based redox flow batteries, Li-H2O2 semi-fuel cells, chemical sensors, and the like. In addition, the ionic conductive solid electrolyte compound according to the present invention has a simple manufacturing method, a low price of raw materials, and is very advantageous for commercial applications such as mass production.

[0043] Figure 2 is a flowchart for explaining a method for manufacturing an ionic conductive solid electrolyte compound according to an embodiment of the present invention.

[0044] Referring to Figure 2, the method for manufacturing an ionic conductive solid electrolyte compound according to an embodiment of the present invention relates to a method for manufacturing an ionic conductive solid electrolyte compound having a stoichiometric formula of Chemical Formula 1, and includes mixing and pulverizing raw materials to form a first raw material (S110); performing a primary heat treatment on the first raw material (S120); pulverizing and mixing the primarily heat-treated first raw material through a wet ball milling process to form a second raw material (S130); compression molding the second raw material (S140); and sintering the compression-molded second raw material (S150).

[0045] In the step of forming the first raw material substance (S110), as the raw material substance of A, compounds such as carbonates and nitrates of A are used; as the raw material substance of M, compounds such as oxides and halides of M are used; and as the raw material substance of T, an oxide salt compound of T can be used.

[0046] In one embodiment, when manufacturing LiTa2PO8 as an ion-conductive solid electrolyte compound, for example, as the raw material substance of lithium (Li), Li2CO3, LiNO3, etc. are used; as the raw material substance of tantalum (Ta), Ta2O5 is used; and as the raw material substance of phosphorus (P), (NH4)2HPO4, (NH4)H2PO4, (NH4)3PO4, etc. can be used. On the other hand, as a different example, as the raw material substances of lithium (Li) and phosphorus (P), LiPO3, LiH2PO4, etc. can be used.

[0047] To form the first raw material substance, the raw material substances of A, M, and T can be mechanically rubbed and uniformly pulverized while mixing the raw material substances.

[0048] In the step of performing primary heat treatment on the first raw material substance (S120), the uniformly pulverized and mixed raw material substances can be heated at a temperature of about 500°C to 1,000°C for about 6 hours to 12 hours. Through such primary heat treatment, impurity components contained in the raw material substances can be volatilized and removed.

[0049] In the step of forming the second raw material substance (S130), the first raw material substance can be additionally pulverized through a ball mill process using stable oxide balls, such as zirconium oxide balls, in a toluene solvent.

[0050] In the step of compression molding the second raw material substance (S140), the first raw material substance is also compression molded into a pellet shape.

[0051] In the step of sintering the compression-molded second raw material substance (S150), the second raw material substance compression-molded in the form of pellets can be sintered for about 12 hours to 48 hours in a temperature range of about 900°C to 1,200°C. At this time, in order to prevent the loss of +1 valent cation metal (A) such as an alkali metal during the sintering process, the pellet-shaped second raw material substance is sintered even when covered with powder having the same composition. Through such a sintering process, the second raw material substance can be crystallized.

[0052] In one embodiment of the present invention, the method for manufacturing an ion-conductive solid electrolyte compound according to the embodiment of the present invention may further include a step of exchanging a first ion in a first ion-conductive solid electrolyte compound containing the first ion among A ions with another second ion among A ions to produce a second ion-conductive solid electrolyte compound.

[0053] In one embodiment, in a first ion-conductive solid electrolyte compound containing lithium ions (Li + ), the lithium ions (Li + ) can be exchanged with hydrogen ions (H + ), hydronium ions (H3O + ) or sodium ions (Na + ) through an ion exchange reaction to produce a second ion-conductive solid electrolyte compound.

[0054] In one embodiment, in LiTa2PO8, lithium ions (Li + ) can be exchanged with hydrogen ions (H + ) or hydronium ions (H3O + ) to produce HTa2PO8·2O or HTa2PO8·H2O from LiTa2PO8. For example, after mixing LiTa2PO8 in an acidic aqueous solution containing hydrogen ions (H + ) or hydronium ions (H3O + ) and then heating it to a certain temperature, the lithium ions (Li + ) in the LiTa2PO8 lattice are exchanged with hydrogen ions (H +) or hydronium ions (H3O + ) can be exchanged.

[0055] In that case, if the acidic aqueous solution contains hydrogen ions (H + ) or hydronium ions (H3O + ), it is not particularly limited, and for example, nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, etc. can be used. For the ion exchange reaction between lithium ions (Li + ) in the LiTa2PO8 lattice and hydrogen ions (H + ) or hydronium ions (H3O + ) contained in the acidic aqueous solution, the mixed solution of LiTa2PO8 and the acidic aqueous solution can be heated at a temperature of about 40 °C to 100 °C for about 6 hours to 72 hours. At this time, for a uniform reaction, the mixed solution can be continuously stirred with a stirrer, and by using a reflux device during heating, loss of the acidic aqueous solution can be prevented.

[0056] Note that after the ion exchange reaction, the second ion-conductive solid electrolyte compound can also be washed with water and ethanol, and then dried at a temperature of 100 °C or higher.

[0057] In other embodiments, in LiTa2PO8, lithium ions (Li + ) can be exchanged with sodium ions (Na + ) to produce NaTa2PO8 from LiTa2PO8. For example, in a molten state where a sodium salt is heated above its melting point, LiTa2PO8 is added and mixed, or in an ionic solvent such as water, a sodium salt and LiTa2PO8 are added and mixed, and then it is heated to a certain temperature, so that lithium ions (Li + ) in the LiTa2PO8 lattice can be exchanged with sodium ions (Na + ) through an ion exchange reaction.

[0058] In that case, the sodium salt is not particularly limited as long as it can provide sodium ions in a molten or dissolved state. For example, sodium nitrate can be used. For the ion exchange reaction between lithium ions (Li + ) and sodium ions (Na + ) in the LiTa2PO8 lattice, the solution can be heated at a temperature of about 40°C to 380°C for about 1 hour to 48 hours. When reacting with the sodium salt in a solvent, for a uniform reaction, the mixed solution can be continuously stirred with a stirrer, and by using a reflux device during heating, loss of the solvent can be prevented.

[0059] On the other hand, after the ion exchange reaction, the second ion-conductive solid electrolyte compound is also washed with water and ethanol and then dried at a temperature of 100°C or higher.

[0060] FIG. 3 is a cross-sectional view for explaining an electrochemical device according to an embodiment of the present invention.

[0061] Referring to FIG. 3, the electrochemical device 100 according to an embodiment of the present invention may include a first electrode 110, a second electrode 120, and a solid electrolyte layer 130.

[0062] The first electrode 110 and the second electrode 120 are also formed of an electrically conductive material.

[0063] The solid electrolyte layer 130 is disposed between the first electrode 110 and the second electrode 120 and is also formed of the ion-conductive solid electrolyte compound according to the embodiment of the present invention described with reference to FIGS. 1A and 1B. Such a solid electrolyte layer 130 can have conductivity for one or more A ions selected from lithium ions (Li + ), sodium ions (Na + ), hydrogen ions (H + ), hydronium ions (H3O + ), etc.

[0064] The electrochemical device 100 according to the present invention is not particularly limited as long as it is an element that requires an electrolyte layer having conductivity with respect to lithium ions (Li + ), sodium ions (Na + ), hydrogen ions (H + ), hydronium ions (H3O + ), etc. For example, the electrochemical device 100 is any one selected from a sodium ion battery, a sodium metal battery, a lithium ion battery, a lithium metal battery, a lithium - air battery, a hydrogen fuel cell, a proton exchange membrane fuel cell, a lithium - based redox flow battery, a Li - H2O2 semi - fuel cell, a chemical sensor, etc.

[0065] In one embodiment, when the electrochemical device 100 is a sodium ion battery, the electrolyte layer 130 is also formed of an ion - conductive solid electrolyte compound represented by Chemical Formula 1, where A is sodium ions.

[0066] In other embodiments, when the electrochemical device 100 is a lithium ion battery, a lithium - air battery, a lithium - based redox flow battery, or a Li - H2O2 semi - fuel cell, the electrolyte layer 130 is also formed of an ion - conductive solid electrolyte compound represented by Chemical Formula 1, where A is lithium ions.

[0067] In still other embodiments, when the electrochemical device 100 is a hydrogen fuel cell or a proton exchange membrane fuel cell, the electrolyte layer 130 is also formed of an ion - conductive solid electrolyte compound represented by Chemical Formula 1, where A is hydrogen ions.

[0068] In still other embodiments, when the electrochemical device 100 is a sodium ion battery, the electrolyte layer 130 is also formed of an ion - conductive solid electrolyte compound represented by Chemical Formula 1, where A is sodium ions.

[0069] Hereinafter, embodiments of the present invention will be described in detail. However, the following embodiments are merely embodiments of the present invention, and the scope of the present invention is not to be construed as being limited to the following embodiments.

[0070] [Example 1] After mixing LiH2PO4 and Ta2O5 in a stoichiometric ratio, it was pulverized using a mortar, heated in air at 600 °C for 8 hours, and then, after further mixing the obtained mixture, it was heated at 1,000 °C for 8 hours. The mixture obtained therefrom was pulverized with toluene for 1 hour using zirconium balls.

[0071] Subsequently, the pulverized powder was compression-molded into pellets having a diameter of 1.05 cm and a thickness of 0.21 cm, and sintered at 1,050 °C for 12 hours. At this time, in order to prevent the loss of lithium, the pellets were sintered in a state covered with powder of the same composition.

[0072] [Experimental Example] For the LiTa2PO8 pellets produced according to Example 1, the ionic conductivity was measured at various temperatures. The results are shown in Table 1 and FIG. 4A below, and further shown in FIG. 4B in comparison with conventional ionic conductive solid electrolyte materials.

[0073]

Table 1

[0074] Referring to Table 1, FIG. 4A, and FIG. 4B, it can be confirmed that the LiTa2PO8 compound produced according to Example 1 has very excellent ionic conductivity throughout the measured temperature range. In particular, the bulk conductivity at room temperature (25 °C) is 1.6×10 -3 S cm -1 -1, and the total conductivity including the bulk and grain boundary is measured to be 2.9×10 -4 S cm -1 -1, which exceeds the highest level of conductivity reported for other oxide-based solid electrolytes studied so far.

[0075] Fig. 5 is an X-ray diffraction graph (λ = 1.5418 Å) for the LiTa2PO8 pellet manufactured according to Example 1.

[0076] Referring to Fig. 5, it can be confirmed that the LiTa2PO8 manufactured according to Example 1 has a crystalline structure. Specifically, it was found that the LiTa2PO8 manufactured according to Example 1 has a monoclinic space group and a crystal structure having lattice constants of a ~ 9.716 Å, b ~ 11.536 Å, c ~ 10.697 Å, and β = 90.04°.

[0077] Fig. 6 is a graph showing the AC impedance measured for the LiTa2PO8 pellet manufactured according to Example 1.

[0078] The graph of Fig. 6 was measured at a temperature of 4 °C in air for the LiTa2PO8 pellet manufactured according to Example 1 to have a thickness of 0.21 cm and a diameter of 1.05 cm. Each point is an experimental value measured between a frequency of 5 Hz and 13 MHz, and the continuous line uses the ZView program, (R b CPE b )(R gb CPE gb )(CPE el ) shows simulation data related to the equivalent circuit corresponding to (). Here, R is resistance, CPE is a constant phase element, and the exponents b, gb, el mean bulk, crystal grain size, and electrode. At this time, it can be confirmed from the calculated CPE values that the small semicircle shown at a high frequency of 1.6 MHz or more, the large semicircle in the range from 1.6 MHz to 2.5 kHz, and the linear graph emerging from the low region below 2.5 kHz contribute at the bulk, crystal grain size, and electrode, respectively. The bulk resistance value can be obtained from the diameter of the small semicircle, and the resistance value of the crystal grain size can be determined from the diameter of the large semicircle. Substituting this resistance value into Equation 1 below, the bulk conductivity is 5.38×10 -4 Scm -1is calculated, and the crystal grain size conductivity is 6.58×10 -5 Scm -1 is calculated, and the overall conductivity is 5.86×10 -5 Scm -1 is calculated.

[0079] [Number]

[0080] In the foregoing description, the present invention has been described with reference to preferred embodiments of the present invention. However, those skilled in the art will understand that the present invention can be variously modified and changed within the scope not departing from the spirit and scope of the present invention described in the claims. [Description of Reference Numerals]

[0081] 100 Electrochemical device 110 First electrode 120 Second electrode 130 Solid electrolyte layer

Claims

In the electrochemical device comprising a first electrode, a second electrode arranged so as to be separated from the first electrode, and a solid electrolyte layer arranged between the first electrode and the second electrode, In the electrochemical device characterized in that the solid electrolyte layer is formed of an ion-conductive solid electrolyte compound having a stoichiometric formula of Chemical Formula 1 as a crystalline oxide, 【Chemical 1】 In Chemical Formula 1, A is a cation having a +1 valence oxidation state, M is a cation having a +4, +5 or +6 valence oxidation state, T is a cation having a +4, +5 or +6 valence oxidation state, x and y are independent real numbers greater than 0, and x is 3y or less. The A includes one or more selected from the group consisting of lithium ion (Li+), sodium ion (Na+), hydrogen ion (H+), and hydronium ion (H3O+). The M includes one or more selected from the group consisting of titanium ion (Ti4+), zirconium ion (Zr4+), hafnium ion (Hf4+), niobium ion (Nb5+), tantalum ion (Ta5+), and antimony ion (Sb5+). The T includes one or more selected from the group consisting of silicon ion (Si4+), germanium ion (Ge4+), phosphorus ion (P5+), arsenic ion (As5+), vanadium ion (V5+), sulfur ion (S6+), molybdenum ion (Mo6+), and tungsten ion (W6+). In the crystal, the M is coordinated by 6 oxygen anions to form an MO6 octahedral unit, and the T is coordinated by 4 oxygen anions to form a TO4 tetrahedral unit. A first lattice layer formed by connecting the MO6 octahedral units in a square lattice pattern along a first plane; A second lattice layer formed by connecting the MO6 octahedral units in a square lattice pattern along a second plane parallel to the first plane; Comprising one MO6 octahedral unit and two TO4 tetrahedral units bonded so as to share two vertices thereof, arranged between the first lattice layer and the second lattice layer, and a trimeric link unit that binds to the MO6 octahedral unit of the first lattice layer and the MO6 octahedral unit of the second lattice layer. The electrochemical device characterized in that the A is arranged in the space between the MO6 octahedral unit and the TO4 tetrahedral unit.

2. In each of the first grid layer and the second grid layer, eight of the MO6 octahedral units are arranged at positions corresponding to the four vertices and four sides of a quadrilateral. Among the MO6 octahedral units, the MO6 octahedral units respectively arranged at positions corresponding to the four vertices are each connected to four adjacent MO6 octahedral units so as to share vertices, thereby forming first octahedral units respectively. Among the MO6 octahedral units, the MO6 octahedral units respectively arranged at positions corresponding to the four sides are each connected to two adjacent MO6 octahedral units so as to share vertices, thereby forming second octahedral units respectively. The electrochemical device according to claim 1, characterized in that.

3. The second grid layer is shifted by a first interval and a second interval along a first axis and a second axis that define the first plane and the second plane, respectively, compared to the first grid layer. The electrochemical device according to claim 2, characterized in that.

4. The MO6 octahedral units of the trimeric link unit are respectively two of the second octahedral units arranged at positions corresponding to two sides connected to the first vertex of the first quadrilateral of the first grid layer, and the second vertex of the second quadrilateral of the second grid layer corresponding to the first quadrilateral, which is opposite to the first vertex, and are connected so as to share vertices with two of the second octahedral units respectively arranged at positions corresponding to two sides connected to the second vertex. One of the two TO4 tetrahedral units of the trimeric link unit is connected so as to share vertices with two of the second octahedral units respectively arranged at positions corresponding to two sides connected to the second vertex of the first quadrilateral, and one of the first octahedral units arranged at a position corresponding to the second vertex of the second quadrilateral. The remaining one of the two TO4 tetrahedral units of the trimeric link unit is connected so as to share vertices with one of the first octahedral units arranged at a position corresponding to the first vertex of the first quadrilateral and two of the second octahedral units respectively arranged at positions corresponding to two sides connected to the first vertex of the second quadrilateral. The electrochemical device according to claim 2, characterized in that.

5. Each of the first grid layer and the second grid layer has a composition corresponding to [M3O18 / 2]3− stoichiometrically. The connecting layer has a composition corresponding to [MT6O14 / 2]+ stoichiometrically. The electrochemical device according to claim 1, characterized in that.

6. In a method for manufacturing an electrochemical device for manufacturing the electrochemical device according to claim 1, mixing and pulverizing raw materials of A, M, and T to form a first raw material; performing a primary heat treatment on the first raw material; pulverizing and mixing the primarily heat-treated first raw material through a wet ball milling process to form a second raw material; compression molding the second raw material; sintering the compression-molded second raw material, the method for manufacturing an electrochemical device comprising these steps.

7. As the raw material of A, a carbonate compound or a nitrate compound of A is used, as the raw material of M, an oxide or a halide of M is used, The method for manufacturing an electrochemical device according to claim 6, characterized in that as the raw material of T, an oxide salt compound of T is used.

8. The primary heat treatment of the first raw material is performed at a temperature of 500°C to 1,000°C for 6 hours to 12 hours, The sintering of the second raw material is performed at a temperature range of 900°C to 1,200°C for 12 hours to 48 hours, the method for manufacturing an electrochemical device according to claim 6.

9. The ion-conductive solid electrolyte compound is LiTa₂PO₈, As the raw material of lithium (Li), Li₂CO₃ or LiNO₃ is used, as the raw material of phosphorus (P), (NH₄)₂PO₄, (NH₄)H₂PO₄ or (NH₄)₃PO₄ is used, or as the raw materials of lithium and phosphorus, LiPO₃ or LiH₂PO₄ is used, The method for manufacturing an electrochemical device according to claim 6, characterized in that as the raw material of tantalum (Ta), Ta₂O₅ is used.

10. In the ion-conductive solid electrolyte compound, in a first ion-conductive solid electrolyte compound containing a first ion as A ions, further comprising a step of exchanging the first ion with another second ion in the A ions to produce a second ion-conductive solid electrolyte compound, the method for manufacturing an electrochemical device according to claim 6.

11. ​ The method for manufacturing an electrochemical device according to claim 10, wherein the LiTa₂PO₈ compound, which is the first ion-conductive solid electrolyte compound, is mixed with an acidic aqueous solution containing hydrogen ions (H⁺) or hydronium ions (H₃O⁺) and then heated, so that the lithium ions (Li⁺) contained in the LiTa₂PO₈ compound are exchanged with hydrogen ions (H⁺) or hydronium ions (H₃O⁺) to produce the HTa₂PO₈·2O or HTa₂PO₈·H₂O, which is the second ion-conductive solid electrolyte compound.

12. The method for manufacturing an electrochemical device according to claim 10, wherein the LiTa₂PO₈ compound, which is the first ion-conductive solid electrolyte compound, is mixed with a molten sodium salt or a solvent in which a sodium salt is dissolved and then heated, so that the lithium ions (Li⁺) contained in the LiTa₂PO₈ compound are exchanged with sodium ions (Na⁺) to produce the NaTa₂PO₈ compound, which is the second ion-conductive solid electrolyte compound.

13. The electrochemical device according to claim 1, wherein the solid electrolyte layer is conductive to one or more ions selected from the group consisting of lithium ions (Li⁺), sodium ions (Na⁺), hydrogen ions (H⁺), and hydronium ions (H₃O⁺).

14. The electrochemical device according to claim 1, wherein the electrochemical device is one selected from the group consisting of a sodium ion battery, a sodium metal battery, a lithium ion battery, a lithium metal battery, a lithium-air battery, a hydrogen fuel cell, a proton exchange membrane fuel cell, a lithium-based redox flow battery, a Li-H₂O₂ semi-fuel cell, and a chemical sensor.

15. The electrochemical device is a lithium ion battery, a lithium metal battery, a lithium-air battery, a lithium-based redox flow battery, or a Li-H₂O₂ semi-fuel cell, and the solid electrolyte layer is formed of an ion-conductive solid electrolyte compound represented by Chemical Formula 1, wherein A is a lithium ion, according to claim 1.

16. The electrochemical device is a hydrogen fuel cell or a proton exchange membrane fuel cell, and the solid electrolyte layer is formed of an ion-conductive solid electrolyte compound represented by Chemical Formula 1, wherein A is a hydrogen ion, according to claim 1.

17. The electrochemical device is a sodium-ion battery, a sodium metal battery, or a sodium-air battery, and the solid electrolyte layer is formed of an ion-conductive solid electrolyte compound represented by Chemical Formula 1, wherein A is a sodium ion. The electrochemical device according to claim 1.

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