Solid electrolyte for solid-state rechargeable sodium-ion batteries

Abstract

The present invention provides a solid electrolyte for a solid-state rechargeable sodium-ion battery comprising: Na with a molar content x of at least 3.50 and at most 4.00; Sn with a molar content y of at least 0.50 and at most 1.00; As with a molar content z of greater than 0.00, preferably at least 0.10 and at most 0.50; and S with a molar content of 4.00.

Description

[Technical field]

[0001] The present invention relates to a solid electrolyte for solid-state rechargeable sodium-ion batteries. More specifically, the present invention relates to a solid electrolyte comprising Na, Sn, and S. [Background technology]

[0002] As such a solid electrolyte, Heo et al. reported in Adv. Energy Mater. 8, 1702716 (2018) a solid electrolyte with the general formula Na 4-x Sn 1-x Sb x Sodium ion solid electrolytes are known having a conductivity of up to 0.30 mS / cm at 30° C. and up to 0.90 mS / cm at 60° C., where 0.02≦x≦0.33. Summary of the Invention [Problem to be solved by the invention]

[0003] It is an object of the present invention to provide a solid electrolyte for solid-state rechargeable sodium-ion batteries that provides an improved ionic conductivity of at least 0.10 mS / cm, obtained by the analytical method of the present invention.

[0004] A further object of the present invention is to provide a method for producing said solid electrolyte.

[0005] It is a further object of the present invention to provide a solid-state rechargeable sodium-ion battery comprising said solid electrolyte. [Means for solving the problem]

[0006] The above objectives are: Na with a molar content x of at least 3.50 and at most 4.00; Sn with a molar content y of at least 0.50 and at most 1.00, As having a molar content z greater than 0.20 and less than 0.30; - S with a molar content of 4.00; This is achieved by providing a solid electrolyte for a solid-state rechargeable sodium-ion battery, comprising:

[0007] As illustrated by Examples 1, 2, 3, and 4, which are supported by the results provided in Tables 1 and 2, it is indeed observed that high ionic conductivity (e.g., at least 0.10 mS / cm) of the solid electrolyte is achieved by the present invention.

[0008] Furthermore, the present invention provides a method for producing a solid electrolyte according to the present invention, which is described in a non-limiting manner in Example 1. The present invention also provides a positive electrode comprising the solid electrolyte according to the present invention; and a solid-state rechargeable sodium-ion battery comprising the solid electrolyte according to the present invention.

[0009] For further guidance and to better understand the teachings of the present invention, the drawings are included. The drawings are intended to aid in the description of the present invention and are not intended to limit the invention disclosed herein. The figures and symbols contained therein have meanings commonly understood by those skilled in the art to which the present invention pertains. [Brief description of the drawings]

[0010] [Figure 1] 1 shows X-ray diffraction (XRD) patterns of Examples 1 to 4 and Comparative Example 1. [Diagram 2] 1 shows an Arrhenius plot of the conductivity of EX3 and Na3.75Sn0.75Sb0.25S4.00 by Heo et al. The x-axis shows 1000 / T(K-1) [where T is temperature (K)] and the y-axis shows ionic conductivity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In a first aspect, the present invention provides a method for producing a composition comprising the steps of: Na with a molar content x of at least 3.50 and at most 4.00; Sn with a molar content y of at least 0.50 and at most 1.00, - The molar content z exceeds 0.00 and is at least 0.10 and at most 0.50 of As, and - S with a molar content of 4.00, and A solid electrolyte for a solid-state rechargeable sodium-ion battery is provided.

[0012] In a preferred embodiment, the solid electrolyte is - Na with a molar content x of at least 3.50 and at most 4.00, and - Sn with a molar content y of at least 0.50 and at most 1.00, and - The molar content z exceeds 0.00 and is at least 0.10 and at most 0.50 of As, and - S with a molar content of 4.00, and Contains a compound containing.

[0013] In a preferred embodiment, the solid electrolyte according to the first aspect has the general formula Na x Sn y As z S4 [where 3.50 ≤ x ≤ 4.00, 0.50 ≤ y < 1.00, and 0.00 < z ≤ 0.50, preferably 0.10 ≤ z ≤ 0.50].

[0014] Preferably, the molar content x is 3.90 or less, and preferably x is 3.70 or more.

[0015] In a very preferred embodiment, the solid electrolyte is according to the first aspect and has 3.55≦x≦3.95, preferably 3.60≦x≦3.90, more preferably 3.65≦x≦3.85. In a further highly preferred embodiment, the solid electrolyte is according to the first aspect and has 3.70≦x≦3.80, preferably 3.71≦x≦3.79, more preferably 3.72≦x≦3.78, even more preferably 3.73≦x≦3.77, most preferably 3.74≦x≦3.76. In an even more highly preferred embodiment, the solid electrolyte is according to the first aspect and has 3.70≦x≦3.80, more preferably 3.72≦x≦3.78, most preferably 3.74≦x≦3.76. In a most preferred embodiment, the solid electrolyte is according to the first aspect and has x=3.75.

[0016] Preferably, the molar content y is less than or equal to 0.90, preferably y is greater than or equal to 0.70.

[0017] In a very preferred embodiment, the solid electrolyte is according to the first aspect and 0.55≦y≦0.95, preferably 0.60≦y≦0.90, more preferably 0.65≦y≦0.85. In a further highly preferred embodiment, the solid electrolyte is according to the first aspect and 0.70≦y≦0.80, preferably 0.71≦y≦0.79, more preferably 0.72≦y≦0.78, even more preferably 0.73≦y≦0.77, most preferably 0.74≦y≦0.76. In an even more highly preferred embodiment, the solid electrolyte is according to the first aspect and 0.70≦y≦0.80, more preferably 0.72≦y≦0.78, most preferably 0.74≦y≦0.76. In a most preferred embodiment, the solid electrolyte is according to the first aspect and y=0.75.

[0018] Preferably, the molar content z is less than or equal to 0.30.

[0019] In a highly preferred embodiment, the solid electrolyte is according to the first aspect, wherein As is present in a molar content z greater than 0.20 and less than 0.30.

[0020] In a further highly preferred embodiment, the solid electrolyte is according to the first aspect and has 0.21≦z≦0.30, preferably 0.21≦z≦0.29, more preferably 0.22≦z≦0.29, even more preferably 0.22≦z≦0.28, even more preferably 0.23≦z≦0.28, even more preferably 0.24≦z≦0.28, even more preferably 0.24≦z≦0.27, most preferably 0.24≦z≦0.26. In an even more highly preferred embodiment, the solid electrolyte is according to the first aspect and has 0.21≦z≦0.29, preferably 0.23≦z≦0.27, most preferably 0.24≦z≦0.26. In a most preferred embodiment, the solid electrolyte is according to the first aspect and has z=0.25.

[0021] In a highly preferred embodiment, the solid electrolyte is according to the first aspect, 3.70≦x≦3.80, preferably 3.72≦x≦3.78, more preferably 3.74≦x≦3.76; 0.70≦y≦0.80, preferably 0.72≦y≦0.78, more preferably 0.74≦y≦0.76; 0.21≦z≦0.29, preferably 0.23≦z≦0.27, and more preferably 0.24≦z≦0.26.

[0022] In a most preferred embodiment, the solid electrolyte is according to the first aspect, where x=3.75, y=0.75, and z=0.25.

[0023] In a preferred embodiment, the solid electrolyte according to the first aspect has a sodium ion conductivity of greater than 0.30 mS / cm at a temperature of 30°C and at least 1.00 mS / cm at a temperature of 60°C.

[0024] In a preferred embodiment, the solid electrolyte according to the first aspect comprises a space group of I41 / acd with 13.0 Å≦lattice constant a≦15.0 Å, 25.0 Å≦lattice constant c≦30.0 Å, as measured by XRD.

[0025] In a second aspect, the present invention provides a method for producing a solid electrolyte according to the first aspect, the method comprising: The method includes a first step of mixing Na2S, SnS2, As2S3, and S powder in an inert atmosphere to obtain a mixture, a second step of pressing the mixture under a pressure of 50-400 MPa, and a third step of firing the pellets at a temperature of 300°C-700°C for a time comprised between 1 and 20 hours.

[0026] In a preferred embodiment, the mixture is pressed under a pressure of 70 to 300 MPa, preferably under a pressure of 80 to 200 MPa, more preferably under a pressure of 100 to 150 MPa. Alternatively, in an equally preferred embodiment, the mixture is pressed in a mold having a diameter of 0.5 to 2 cm, preferably 0.75 to 1.25 cm, under a load of 0.1 to 5 tons, preferably 0.5 to 1.5 tons.

[0027] In a third aspect, the present invention provides a positive electrode for a solid-state rechargeable sodium-ion battery comprising a solid electrolyte according to any of the preceding claims.

[0028] In a fourth aspect, the present invention provides a solid-state rechargeable sodium-ion battery comprising a solid electrolyte according to the first aspect of the present invention. EXAMPLES

[0029] 1. Description of analytical method 1.1. Powder X-ray diffraction Powder X-ray diffraction (XRD) data are collected at 25°C using an X-ray diffractometer (Rigaku Miniflex 600) using a Cu X-ray tube (λ=1.5418 Å), a secondary graphite (002) monochromator, and an angular range of 10°≦2θ≦80°. The crystal structure is refined using the powder profile refinement program Generalized Structure and Analysis Software (GSAS, BG Toby, J. Appl. Cryst. 2001, 34(2), 210-213).

[0030] 1.2. Electrochemical Impedance Spectroscopy (EIS) Sodium ion conductivity is measured by AC impedance method in a polyetheretherketone (PEEK) mold (diameter = 10 mm) using an ion-blocking symmetric cell of Ti / solid electrolyte / Ti, with a Ti rod as current collector. Cold pressed pellets were prepared at 3 tons pressure. Frequencies are applied from 1 MHz to 100 MHz using EC-Lab software on a Biologic SP-200 single channel potentiostat. Measurements are performed at various temperatures (30, 45, 60, 75, and 90 °C). Sodium ion conductivity (σ) is calculated by the following formula:

[0031]

number

[0032] where L is the thickness of the pellet (cm) and A is the area of ​​the pellet (cm 2 ) and R is the resistance obtained by electrochemical impedance spectroscopy (S -1 ).

[0033] 2. Examples and Comparative Examples Example 1 Na 3.90 Sn 0.90 As 0.10 S4 powder is prepared by mixing, pelletizing, and subsequent heat treatment according to the following method. Step 1) Mixing: Mix Na2S, SnS2, As2S3, and S powders using a mortar and pestle according to the molar ratio of Na:Sn:As:S = 3.90:0.90:0.10:4.00. All reactants and products are handled in a dry argon-filled glove box since the starting and product materials are hygroscopic and air sensitive. Step 2) Pelletization: The above mixed powder is pelletized in a die with a diameter of 1 cm by applying a load of 1.0 ton. The pelletized sample is then placed in a carbon-coated fused silica ampoule and vacuum sealed. Step 3) Heat treatment: The reactants were heated to 400 °C at a rate of 2 °C / min in a box furnace, held at this temperature for 12 h, and naturally cooled to room temperature. After the reaction was complete, the ampoules were opened in an argon-filled glove box. The prepared powder was labeled EX1.

[0034] Example 2, Example 3 and Example 4 Samples of Examples 2, 3, and 4 are prepared following the same procedure as EX1, except that the amounts of Na2S, SnS2, As2S3, and S powders used during step 1 are different according to the molar ratios shown in Table 1. The prepared powders are labeled EX2, EX3, and EX4, respectively.

[0035] Comparative Example 1 Na4SnS4 powder is prepared following the same procedure as EX1, except that As2S3 is not used in step 1. The prepared powder is labeled as CEX1.

[0036] [Table 1]

[0037] * Adv.Energy Mater.8,1702716(2018)

[0038] [Table 2]

[0039] Table 1 shows the molar ratios of Na, Sn, and As elements and the sodium ion conductivity (σ, mS / cm) at 30 °C of the solid electrolytes produced in Examples 1, 2, 3, 4, and Comparative Example 1. According to Table 1, the general formula Na x Sn y As z S4 [where 3.50 ≤ x ≤ 4.00, 0.50 ≤ y < 1.00, and 0.00 < z ≤ 0.50, preferably 0.10 ≤ z ≤ 0.50] is observed to have significantly higher ion conductivity than the solid electrolyte having the formula Na4SnS4. Further, Table 2 and FIG. 2 show the ion conductivity profiles of Na 3.75 Sn 0.75 As 0.25 S4 and Na 3.75 Sn 0.75 Sb 0.25 S4 by the aforementioned EIS method at various temperatures. According to Table 2, the ion conductivity at temperatures above 60 °C exceeds 1.00 mS / cm, which is sufficient for conduction in a solid-state rechargeable sodium-ion battery. This observation indicates that by using Na 3.75 Sn 0.75 As 0.25 S4 as the solid electrolyte according to the present invention, a higher ion conductivity can be obtained than using Na4SnS4, which has been used as an ion insulator due to its low ion conductivity. As shown in FIG. 2, the ion conductivity of the solid electrolyte increases as the operating temperature rises. EX3 generally has higher ion conductivity than Na 3.75 Sn 0.75 Sb 0.25 S4 at any temperature. Therefore, when EX3 is used in a solid-state rechargeable sodium-ion battery, the required ion conductivity can be achieved at relatively low operating temperatures, which is beneficial for the design of the battery management system.

[0040] Regarding the structures of the compounds from Examples 1 to 4, FIG. 1 shows that a series of Na x Sn y As z S4 is properly produced. The Na from FIG. 13.70 Sn 0.70 As 0.30 As the XRD data of S4 suggests, the solid electrolyte Na 3.70 Sn 0.70 As 0.30 S4 is a solid electrolyte Na with z less than 0.30 due to some impurities. x Sn y As z S4 is more preferred. 3.75 Sn 0.75 As 0.25 S4 has a structure in the space group I41 / acd with lattice parameters a of 13.7074 Å, c of 27.3628 Å, and α, β, and γ of 90°.

Claims

1. Na with a molar content x of at least 3.50 and at most 4.00, Sn with a molar content y of at least 0.50 and at most 1.00, As having a molar content z of 0.22 or more and less than 0.30; - S with a molar content of 4.00; 1. A solid electrolyte for a solid-state rechargeable sodium-ion battery comprising:

2. General formula Na ｘ Sn ｙ A.S. ｚ S ４ 2. The solid electrolyte for a solid state rechargeable sodium ion battery according to claim 1, wherein 3.55≦x≦3.95, or 3.60≦x≦3.90, or 3.65≦x≦3.

85.

3. 3. The solid electrolyte for a solid state rechargeable sodium ion battery according to claim 2, wherein 3.70≦x≦3.

80.

4. The solid electrolyte for a solid rechargeable sodium ion battery according to any one of claims 1 to 3, wherein 0.55≦y≦0.95, or 0.60≦y≦0.90, or 0.65≦y≦0.

85.

5. 5. The solid electrolyte for a solid state rechargeable sodium ion battery according to claim 4, wherein 0.70≦y≦0.

80.

6. The solid electrolyte for a solid rechargeable sodium ion battery according to any one of claims 1 to 5, wherein 0.22≦z≦0.29, or 0.22≦z≦0.28, or 0.23≦z≦0.

27.

7. 7. The solid electrolyte for a solid state rechargeable sodium ion battery according to claim 6, wherein 0.24≦z≦0.

26.

8. The solid electrolyte for a solid rechargeable sodium ion battery according to any one of claims 1 to 7, wherein 3.70≦x≦3.80, 0.70≦y≦0.80, and 0.24≦z≦0.

26.

9. The solid electrolyte for a solid rechargeable sodium ion battery according to any one of claims 1 to 8, having a sodium ion conductivity of greater than 0.30 mS / cm at a temperature of 30°C and at least 1.00 mS / cm at a temperature of 60°C.

10. 10. The solid electrolyte for a solid state rechargeable sodium ion battery according to any one of claims 1 to 9, comprising a space group of I41 / acd with 13.0 Å≦lattice constant a≦15.0 Å, 25.0 Å≦lattice constant c≦30.0 Å, as measured by XRD.

11. Na ２ S and SnS ２ And, As ２ S ３ A first step of mixing the above-mentioned fluorine-containing fluorine-containing fluorine with S powder in an inert atmosphere to obtain a mixture; a second step of pressing the mixture under a pressure of 50-400 MPa to obtain pellets; a third step of calcining said pellets at a temperature comprised between 300° C. and 700° C. for a time comprised between 1 and 20 hours; A method for producing the solid electrolyte according to any one of claims 1 to 10, comprising:

12. A positive electrode for a solid state rechargeable sodium ion battery comprising the solid electrolyte according to any one of claims 1 to 10.

13. A solid-state rechargeable sodium-ion battery comprising the solid electrolyte according to any one of claims 1 to 10.

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