Solid-state electrolyte for solid-state rechargeable sodium-ion batteries

Abstract

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

Description

Technical Field

[0001] This invention relates to a solid electrolyte for use in solid-state rechargeable sodium-ion batteries. More specifically, this invention relates to a solid electrolyte comprising Na, Sn, and S. Background Technology

[0002] Such solid electrolytes are known from Heo et al., who reported a sodium-ion solid electrolyte in Adv. Energy Mater. 8, 1702-716 (2018), which has the general formula Na 4-x Sn 1-x Sb x S4, where 0.02≤x≤0.33, has a Na-ion conductivity of 0.30 mS / cm at 30 °C and 0.90 mS / cm at 60 °C.

[0003] One object of the present invention is to provide a solid electrolyte for a solid-state rechargeable sodium-ion battery, the solid electrolyte providing an improved ionic conductivity of at least 0.10 mS / cm obtained by the analytical methods of the present invention.

[0004] Another object of the present invention is to provide a method for manufacturing the solid electrolyte.

[0005] Another object of the present invention is to provide a solid-state rechargeable sodium-ion battery comprising the solid electrolyte. Summary of the Invention

[0006] This objective is achieved by providing a solid electrolyte for solid-state rechargeable sodium-ion batteries, the solid electrolyte comprising:

[0007] -Na, with a molar content x of at least 3.50 and at most 4.00,

[0008] -Sn, whose molar content y is at least 0.50 and at most 1.00,

[0009] -As, whose molar content z is greater than 0.20 and less than 0.30,

[0010] -S, with a molar content of 4.00.

[0011] In fact, it has been observed that high ionic conductivity (e.g., at least 0.10 mS / cm) of solid electrolytes has been achieved according to the present invention, as shown in Examples 1, 2, 3 and 4 supported by the results provided in Tables 1 and 2.

[0012] Furthermore, the present invention provides a method for manufacturing a solid electrolyte according to the present invention. The method according to the present invention is illustrated in Example 1 in a non-limiting manner. 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. Attached Figure Description

[0013] Further guidance, including the accompanying drawings, is provided to better understand the teachings of this invention. The drawings are intended to aid in describing the invention and are not intended to be limiting of the invention currently disclosed. The drawings and symbols contained herein have the meaning commonly understood by one of ordinary skill in the art to which this invention pertains.

[0014] Figure 1 The X-ray diffraction (XRD) patterns of Examples 1 to 4 and Comparative Example 1 are shown.

[0015] Figure 2 EX3 and Na according to Heo et al. are shown. 3.75 Sn 0.75 Sb 0.25 S 4.00 The Arrhenius curve of conductivity, with the x-axis indicating 1000 / T (K). -1 ), where T is the temperature (K) and the y-axis indicates the ionic conductivity. Detailed Implementation

[0016] In a first aspect, the present invention provides a solid electrolyte for a solid-state rechargeable sodium-ion battery, the solid electrolyte comprising:

[0017] -Na, with a molar content x of at least 3.50 and at most 4.00,

[0018] -Sn, whose molar content y is at least 0.50 and at most 1.00,

[0019] -As, whose molar content z is higher than 0.00, preferably at least 0.10 and at most 0.50,

[0020] -S, with a molar content of 4.00.

[0021] In a preferred embodiment, the solid electrolyte comprises a compound, the compound comprising...

[0022] -Na, with a molar content x of at least 3.50 and at most 4.00,

[0023] -Sn, whose molar content y is at least 0.50 and at most 1.00,

[0024] -As, whose molar content z is higher than 0.00, preferably at least 0.10 and at most 0.50,

[0025] -S, with a molar content of 4.00.

[0026] In a preferred embodiment, the solid electrolyte according to the first aspect has the general formula Na x Sn y As z S4, wherein 3.50≤x≤4.00, 0.50≤y<1.00, and 0.00<z≤0.50, preferably 0.10≤z≤0.50.

[0027] Preferably, the molar content x is less than or equal to 3.90, and preferably x is greater than or equal to 3.70.

[0028] In a highly preferred embodiment, the solid electrolyte is the solid electrolyte according to the first aspect, wherein 3.55≤x≤3.95, preferably 3.60≤x≤3.90, more preferably 3.65≤x≤3.85. In a more highly preferred embodiment, the solid electrolyte is the solid electrolyte according to the first aspect, wherein 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 the solid electrolyte according to the first aspect, wherein 3.70≤x≤3.80, more preferably 3.72≤x≤3.78, most preferably 3.74≤x≤3.76. In the most preferred embodiment, the solid electrolyte is the solid electrolyte according to the first aspect, wherein x=3.75.

[0029] Preferably, the molar content y is less than or equal to 0.90, and preferably y is greater than or equal to 0.70.

[0030] In a highly preferred embodiment, the solid electrolyte is the solid electrolyte according to the first aspect, wherein 0.55≤y≤0.95, preferably 0.60≤y≤0.90, more preferably 0.65≤y≤0.85. In a more highly preferred embodiment, the solid electrolyte is the solid electrolyte according to the first aspect, wherein 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 the solid electrolyte according to the first aspect, wherein 0.70≤y≤0.80, more preferably 0.72≤y≤0.78, most preferably 0.74≤y≤0.76. In the most preferred embodiment, the solid electrolyte is the solid electrolyte according to the first aspect, wherein y=0.75.

[0031] Preferably, the molar content z is less than or equal to 0.30.

[0032] In a highly preferred embodiment, the solid electrolyte is a solid electrolyte according to the first aspect, wherein the molar content z of As is greater than 0.20 and less than 0.30.

[0033] In a more preferred embodiment, the solid electrolyte is a solid electrolyte according to the first aspect, wherein 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, and most preferably 0.24 ≤ z ≤ 0.26. In an even more preferred embodiment, the solid electrolyte is a solid electrolyte according to the first aspect, wherein 0.21 ≤ z ≤ 0.29, preferably 0.23 ≤ z ≤ 0.27, and most preferably 0.24 ≤ z ≤ 0.26. In the most preferred embodiment, the solid electrolyte is a solid electrolyte according to the first aspect, wherein z = 0.25.

[0034] In a highly preferred embodiment, the solid electrolyte is the solid electrolyte according to the first aspect, wherein

[0035] • 3.70≤x≤3.80, preferably 3.72≤x≤3.78, more preferably 3.74≤x≤3.76;

[0036] • 0.70≤y≤0.80, preferably 0.72≤y≤0.78, more preferably 0.74≤y≤0.76; and

[0037] • 0.21≤z≤0.29, preferably 0.23≤z≤0.27, more preferably 0.24≤z≤0.26.

[0038] In the most preferred embodiment, the solid electrolyte is a solid electrolyte according to the first aspect, wherein x = 3.75, y = 0.75, and z = 0.25.

[0039] In a preferred embodiment, the solid electrolyte according to the first aspect has a sodium ion conductivity of more than 0.30 mS / cm at a temperature of 30°C and at least 1.00 mS / cm at a temperature of 60°C.

[0040] In a preferred embodiment, the solid electrolyte according to the first aspect comprises having ≤Lattice constant ≤Lattice constant The space group of I41 / acd, as determined by XRD.

[0041] In a second aspect, the present invention provides a method for manufacturing a solid electrolyte according to the first aspect. The method includes:

[0042] The first step is to mix Na2S, SnS2, AS2S3 and S powders in an inert atmosphere to obtain a mixture; the second step is to press the mixture under a pressure of 50-400 MPa; and the third step is to calcine the granules at a temperature of 300°C to 700°C for a period of 1 to 20 hours.

[0043] In a preferred embodiment, the mixture is pressed at a pressure of 70-300 MPa, preferably 80-200 MPa, and more preferably 100-150 MPa. Alternatively, and in another preferred embodiment, the mixture is pressed in a mold with a diameter of 0.5-2 cm, preferably 0.75-1.25 cm, and at a weight of 0.1 to 5 tons, preferably 0.5 to 1.5 tons.

[0044] In a third aspect, the present invention provides a positive electrode for a solid-state rechargeable sodium-ion battery, the positive electrode comprising a solid electrolyte according to any one of the preceding claims.

[0045] In a fourth aspect, the present invention provides a solid-state rechargeable sodium-ion battery comprising a solid electrolyte according to a first aspect of the present invention.

[0046] Example

[0047] 1. Description of the analytical methods

[0048] 1.1. Powder X-ray diffraction

[0049] Using a Cu X-ray tube at 25°C Powder X-ray diffraction (XRD) data were acquired using a secondary graphite (002) monochromator and an X-ray diffractometer (Rigaku Miniflex 600) within an angular range of 10° ≤ 29 ≤ 80°. The crystal structure was refined using the powder profile refinement program Generalized Structure and Analysis Software (GSAS, BGToby, J. Appl. Cryst. 2001, 34(2), 210-213).

[0050] 1.2. Electrochemical Impedance Spectroscopy (EIS)

[0051] Sodium ion conductivity was measured by AC impedance spectroscopy using a Ti / solid electrolyte / Ti ion-blocking symmetric cell in a polyether ether ketone (PEEK) mold (diameter = 10 mm), with Ti rods acting as current collectors. Cold-pressed granules were prepared under 3 tons of pressure. Frequencies from 1 MHz to 100 mHz were applied using EC-Lab software on a Biologic SP-200 single-channel potentiostat. Measurements were taken at various temperatures (30, 45, 60, 75, and 90 °C). Sodium ion conductivity (σ) was calculated using the following formula:

[0052]

[0053] Where L is the thickness of the granules (cm), and A is the area of ​​the granules (cm²). 2 ), and R is the resistance (S) obtained by electrochemical impedance spectroscopy. -1 ).

[0054] 2. Examples and Comparative Examples

[0055] Example 1

[0056] Na is prepared by mixing, granulation, and subsequent heat treatment according to the following process. 3.90 Sn 0.90 As 0.10 S4 powder:

[0057] Step 1) Mixing: Na₂S, SnS₂, As₂S₃, and S powders were mixed in a mortar with a pestle at a molar ratio of Na:Sn:As:S = 3.90:0.90:0.10:4.00. Since the starting and resulting materials are hygroscopic and air-sensitive, all reactants and products were handled in a dry glove box filled with argon.

[0058] Step 2) Granulation: The mixed powder is granulated in a mold with a diameter of 1 cm by applying 1.0 ton weight. The granulated sample is then placed in a carbon-coated molten silica ampoule and vacuum sealed.

[0059] Step 3) Heat treatment: The reactants were heated to 400°C in a box furnace at a rate of 2°C / min, held at this temperature for 12 hours, and then allowed to cool naturally to room temperature. After the reaction was complete, the ampoules were opened in an argon-filled glove box. The prepared powder was labeled EX1.

[0060] Examples 2, 3 and 4

[0061] The samples of Examples 2, 3 and 4 were prepared according to the same procedure as EXI, except that different amounts of Na2S, SnS2, AS2S3 and S powders were used in step 1 according to the molar ratios shown in Table 1. The prepared powders were labeled as EX2, EX3 and EX4, respectively.

[0062] Comparative Example 1

[0063] Na4SnS4 powder was prepared according to the same procedure as EX1, except that AS2S3 was not used in step 1. The prepared powder was labeled as CEX1.

[0064] Table 1. Summary of information on samples from Examples 1 to 4 and Comparative Example 1

[0065]

[0066] *Adv.Energy Mater.8,1702716(2018)

[0067] Table 2. Na as a function of temperature 3.75 Sn 0.75 As 0.25 S4 Summary of ionic conductivity

[0068] 30 0.52 0.30 45 0.62 - 60 1.03 0.90 75 1.68 - 90 1.97 -

[0069] Table 1 summarizes the molar ratios of Na, Sn and As elements and the sodium ion conductivity (σ, mS / cm) at 30°C of the solid electrolytes fabricated in Examples 1, 2, 3, 4 and Comparative Example 1. According to Table 1, it is observed that the solid electrolyte having the general formula Na x Sn y As z S4 has significantly higher ionic conductivity than the solid electrolyte having the formula Na4SnS4, wherein 3.50≤x≤4.00, 0.50≤y<1.00, and 0.00<z≤0.50, preferably 0.10≤z≤0.50. Furthermore, Table 2 and Figure 2 summarize the Na 3.75 Sn 0.75 As 0.25 S4 and the Na 3.75 Sn 0.75 Sb 0.25 S4 by Heo et al. measured by the above EIS method at various temperatures. According to Table 2, the ionic conductivity at a temperature exceeding 60°C shows more than 1.00 mS / cm, which is sufficient for operation in a solid-state rechargeable sodium-ion battery. This observation indicates that using Na 3.75 Sn 0.75 As 0.25 S4 as the solid electrolyte according to the present invention provides higher ionic conductivity than using Na4SnS4 which serves as an ionic insulator due to its low ionic conductivity. As Figure 2 As shown, the ionic conductivity of solid electrolytes increases with increasing operating temperature. At any temperature, EX3 typically exhibits higher ionic conductivity than Na. 3.75 Sn 0.75 Sb 0.25 S4 exhibits higher ionic conductivity. Therefore, when EX3 is used in solid-state rechargeable sodium-ion batteries, the desired ionic conductivity can be achieved at relatively low operating temperatures, which is beneficial for designing battery management systems.

[0070] Regarding the structures of the compounds in Examples 1 to 4, Figure 1 The proper preparation of Na is shown x Sn y As z S4 series. For example... Figure 1 Na in 3.70 Sn 0.70 As 0.30 The XRD data of S4 show that the solid electrolyte Na 3.70 Sn 0.70 As 0.30 S4 contains some impurities, making a solid electrolyte Na with a z value below 0.30 more preferable. x Sn y As z S4. Na 3.75 Sn 0.75 As 0.25 S4 has a space group of I41 / acd and a lattice constant a. c is Furthermore, α, β, and γ are 90°.

Claims

1. A solid electrolyte for use in a solid-state rechargeable sodium-ion battery, the solid electrolyte comprising: - Na, where the molar content of Na (x) is at least 3.50 and at most 4.

00. - Sn, the molar content of Sn is at least 0.50 and at most 1.

00. - As, the molar content of As, z, is 0.21 ≤ z ≤ 0.

29. - S, the molar content of S is 4.

00.

2. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to claim 1, wherein the solid electrolyte has the general formula Na x Sn y As z S4, where 3.55 ≤ x ≤ 3.

95.

3. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to claim 2, wherein 3.60 ≤ x ≤ 3.

90.

4. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to claim 2, wherein 3.65 ≤ x ≤ 3.

85.

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

80.

6. A solid electrolyte for a solid-state rechargeable sodium-ion battery according to any one of the preceding claims, wherein 0.55 ≤ y ≤ 0.

95.

7. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to claim 6, wherein 0.60 ≤ y ≤ 0.

90.

8. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to claim 6, wherein 0.65 ≤ y ≤ 0.

85.

9. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to claim 6, wherein 0.70 ≤ y ≤ 0.

80.

10. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to any one of claims 1 to 5, wherein 0.22 ≤ z ≤ 0.

28.

11. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to claim 10, wherein 0.23 ≤ z ≤ 0.

27.

12. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to claim 10, wherein 0.24 ≤ z ≤ 0.

26.

13. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to any one of claims 1 to 5, wherein 3.70 ≤ x ≤ 3.80, 0.70 ≤ y ≤ 0.80, and 0.21 ≤ z ≤ 0.

29.

14. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to any one of claims 1 to 5, said solid electrolyte having a sodium-ion conductivity of more than 0.30 mS / cm at a temperature of 30°C and at least 1.00 mS / cm at a temperature of 60°C.

15. The solid electrolyte for a solid-state rechargeable sodium-ion battery according to any one of claims 1 to 5, as determined by XRD, wherein the solid electrolyte comprises a space group I41 / acd having a lattice constant a ≤ 15.0 Å and a lattice constant c ≤ 30.0 Å.

16. A method for manufacturing a solid electrolyte according to any one of the preceding claims, the method comprising: First step: Mix Na2S, SnS2, AS2S3 and S powder in an inert atmosphere to obtain a mixture; The second step: pressing the mixture under a pressure of 50 MPa to 400 MPa to obtain granules; as well as The third step: calcining the granules at a temperature of 300°C to 700°C for a period of 1 to 20 hours.

17. A positive electrode for a solid-state rechargeable sodium-ion battery, the positive electrode comprising a solid electrolyte according to any one of claims 1 to 15.

18. A solid-state rechargeable sodium-ion battery, the solid-state rechargeable sodium-ion battery comprising a solid electrolyte according to any one of claims 1 to 15.

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