Traditional syntheses of solid-state ceramic electrolytes generally require high energy and high temperature. For sulfide solid electrolytes, which possess superior ionic conductivity, a high-energy ball milling process over 8˜50 hours and calcination at >500° C. are necessary for solid-state synthesis; sintering at 300° C. is needed for liquid-state synthesis. Accordingly, there is a need for cost-effective, energy-effective methods for preparing these materials.
The present disclosure provides, inter alia, a solid-phase or molten electrolyte comprising an mP2S5-nNa2Sx complex, wherein the molar ratio of P2S5 to Na2Sx (m:n) is between 1:2 and 2:1, and x is an integer from 1 to 12.
The present disclosure also provides solid-state battery comprising a cathode, an anode, and a solid-state electrolyte in contact with the cathode and the anode, wherein the cathode and/or the anode comprise an active material, a conductive additive, and a solid-state qP2S5-rM2Sx complex; wherein M is Li or Na; the molar ratio of P2S5 to M2Sx (q:r) is between 1:2 and 2:1; and wherein x is an integer from 1 to 12; wherein the solid-state electrolyte comprises a solid-phase mP2S5-nNa2Sx complex; wherein the molar ratio of P2S5 to Na2Sx (m:n) is between 1:2 and 2:1; and wherein x is an integer from 1 to 12.
The present disclosure further provides a method of manufacturing a solid-phase electrolyte comprising an mP2S5-nNa2Sx complex, wherein the method comprises: (1) mixing sodium sulfide (Na2S), phosphorus pentasulfide (P2S5), and sulfur powder (S) in an organic solvent to form a solvated mP2S5-nNa2Sx complex; and (2) exposing the solvated mP2S5-nNa2Sx complex to less-than-atmospheric pressure to precipitate a solid-phase mP2S5-nNa2Sx complex wherein: the molar ratio of P2S5 to Na2Sx (m:n) is between 1:2 and 2:1; and x is an integer from 1 to 12.
The present disclosure still further provides a method of manufacturing a molten electrolyte comprising an mP2S5-nNa2Sx complex, wherein the method comprises: (1) manufacturing a solid-phase electrolyte comprising an mP2S5-nNa2Sx complex according to a method of the present disclosure; and (2) heating the solid-phase electrolyte to form the molten electrolyte wherein: the molar ratio of P2S5 to Na2Sx (m:n) is between 1:2 and 2:1; and x is an integer from 1 to 12.
Unless defined otherwise, all technical and scientific terms used herein generally have the same meaning as commonly understood by one of ordinary skill in the art. Generally, the nomenclature used herein and the laboratory procedures in cell culture, molecular genetics, organic chemistry, and peptide chemistry are those well-known and commonly employed in the art.
As used herein, the articles “a” and “an” refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element. Furthermore, use of the term “including” as well as other forms, such as “include,” “includes,” and “included,” is not limiting.
As used herein, the term “about” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which it is used. As used herein when referring to a measurable value such as an amount, a temporal duration, and the like, the term “about” is meant to encompass variations of 20% or 10%, including ±5%, ±1%, and ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods.
In one aspect, the present disclosure provides a solid-phase or molten electrolyte comprising an mP2S5-nM2Sx complex, wherein: M is Li or Na; the molar ratio of P2S5 to M2Sx (m:n) is between 1:2 and 2:1; and x is an integer from 1 to 12.
In some embodiments, M is Li. In some embodiments, M is Na.
The molar ratio of P2S5 to M2Sx (m:n) is between 1:2 and 2:1. Accordingly, by nonlimiting example, the molar ratio of P2S5 to M2Sx (m:n) may be 1:2, 4:7, 2:3, 4:5, 1:1, 5:4, 3:2, 7:4, or 2:1. In some embodiments, the molar ratio of P2S5 to M2Sx (m:n) is between 1:1.5 and 1.5:1. In some embodiments, the molar ratio of P2S5 to M2Sx (m:n) is between 1:1.25 and 1.25:1. In some embodiments, the molar ratio of P2S5 to M2Sx (m:n) is between 1:1.1 and 1.1:1. In some embodiments, the molar ratio of P2S5 to M2Sx (m:n) is 1:1.
In some embodiments, x is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12. In some embodiments, x is an integer from 5 to 9. In some embodiments, x is an integer from 6 to 8. In some embodiments, x is 1. In some embodiments, x is 6. In some embodiments, x is 8.
In some embodiments, the electrolyte is a solid-phase electrolyte. In some embodiments, the solid-phase electrolyte has an amorphous structure. In some embodiments, the solid-phase electrolyte has a melting point (Tm) that is at least 100° C. higher, at least 110° C. higher, at least 120° C. higher, at least 130° C. higher, at least 140° C. higher, at least 150° C. higher, at least 160° C. higher, at least 170° C. higher, at least 180° C. higher, or at least 190° C. higher than the freezing point (Tf) of the molten form of the solid-phase electrolyte. In some embodiments, the solid-phase electrolyte has a melting point (Tm) that is at least 100° C. higher than the freezing point (Tf) of the molten form of the solid-phase electrolyte. In some embodiments, the solid-phase electrolyte has a melting point (Tm) that is at least 140° C. higher than the freezing point (Tf) of the molten form of the solid-phase electrolyte. In some embodiments, the solid-phase electrolyte has a melting point (Tm) that is at least 180° C. higher than the freezing point (Tf) of the molten form of the solid-phase electrolyte.
In some embodiment, the electrolyte is a molten electrolyte. In some embodiments, the molten electrolyte does not solidify at a temperature of 0° C., −10° C., −20° C., −30° C., −40° C., −50° C., −60° C., −70° C., −80° C., or −90° C. In some embodiments, the molten electrolyte does not solidify at a temperature of 0° C. In some embodiments, the molten electrolyte does not solidify at a temperature of −50° C. In some embodiments, the molten electrolyte does not solidify at a temperature of −90° C.
Sodium (Na), as used in the present disclosure, possesses certain chemical/physical properties similar to Li, but Na also has several advantages over Li. By way of example, Na's first ionization energy of 495.8 kJ mol−1 is lower than that of Li (520.2 kJ mol−1), leading to improved kinetics in chemical reactions. As an earth-abundant element, Na is over 1000 times more abundant than Li in the earth crust. The cost of Na raw materials (carbonate salt) is more than 100 times less expensive than that of Li.
Accordingly, in another aspect, the present disclosure provides a solid-phase or molten electrolyte comprising an mP2S5-nNa2Sx complex, wherein: the molar ratio of P2S5 to Na2Sx (m:n) is between 1:2 and 2:1; and x is an integer from 1 to 12.
The molar ratio of P2S5 to Na2Sx (m:n) is between 1:2 and 2:1. Accordingly, by nonlimiting example, the molar ratio of P2S5 to Na2Sx (m:n) may be 1:2, 4:7, 2:3, 4:5, 1:1, 5:4, 3:2, 7:4, or 2:1. In some embodiments, the molar ratio of P2S5 to Na2Sx (m:n) is between 1:1.5 and 1.5:1. In some embodiments, the molar ratio of P2S5 to Na2Sx (m:n) is between 1:1.25 and 1.25:1. In some embodiments, the molar ratio of P2S5 to Na2Sx (m:n) is between 1:1.1 and 1.1:1. In some embodiments, the molar ratio of P2S5 to Na2Sx (m:n) is 1:1.
In some embodiments, x is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12. In some embodiments, x is an integer from 5 to 9. In some embodiments, x is an integer from 6 to 8. In some embodiments, x is 1. In some embodiments, x is 6. In some embodiments, x is 8.
In some embodiments, the electrolyte is a solid-phase electrolyte. In some embodiments, the solid-phase electrolyte has an amorphous structure. In some embodiments, the solid-phase electrolyte has a melting point (Tm) that is at least 100° C. higher, at least 110° C. higher, at least 120° C. higher, at least 130° C. higher, at least 140° C. higher, at least 150° C. higher, at least 160° C. higher, at least 170° C. higher, at least 180° C. higher, or at least 190° C. higher than the freezing point (Tf) of the molten form of the solid-phase electrolyte. In some embodiments, the solid-phase electrolyte has a melting point (Tm) that is at least 100° C. higher than the freezing point (Tf) of the molten form of the solid-phase electrolyte. In some embodiments, the solid-phase electrolyte has a melting point (Tm) that is at least 140° C. higher than the freezing point (Tf) of the molten form of the solid-phase electrolyte. In some embodiments, the solid-phase electrolyte has a melting point (Tm) that is at least 180° C. higher than the freezing point (Tf) of the molten form of the solid-phase electrolyte.
In some embodiment, the electrolyte is a molten electrolyte. In some embodiments, the molten electrolyte does not solidify at a temperature of 0° C., −10° C., −20° C., −30° C., −40° C., −50° C., −60° C., −70° C., −80° C., or −90° C. In some embodiments, the molten electrolyte does not solidify at a temperature of 0° C. In some embodiments, the molten electrolyte does not solidify at a temperature of −50° C. In some embodiments, the molten electrolyte does not solidify at a temperature of −90° C.
In another aspect the present disclosure provides a solid-state battery comprising a cathode, an anode, and a solid-state electrolyte in contact with the cathode and the anode, wherein the cathode and/or the anode comprise an active material, optionally a conductive additive, and a solid-state qP2S5-rM2Sx complex; wherein M is Li or Na; the molar ratio of P2S5 to M2Sx (q:r) is between 1:2 and 2:1; and wherein x is an integer from 1 to 12; wherein the solid-state electrolyte comprises a solid-phase mP2S5-nM2Sx complex; wherein M is Li or Na; the molar ratio of P2S5 to Na2Sx (m:n) is between 1:2 and 2:1; and wherein x is an integer from 1 to 12.
In general, the solid-state batteries of the disclosure include two electrodes (an anode and a cathode) and a solid-state electrolyte, which is sandwiched between the anode and cathode. The electrodes of the solid-state battery may contain conductive additives (electronic conductivity), binders, active materials, and a solid-state electrolyte (ionic conductivity).
In some embodiments, the solid-phase qP2S5-rM2Sx complex is a solid-phase qP2S5-rNa2Sx complex, wherein: the molar ratio of P2S5 to Na2Sx (q:r) is between 1:2 and 2:1; and x is an integer from 1 to 12.
In some embodiments, the molar ratio of P2S5 to Na2Sx (q:r) is between 1:1.5 and 1.5:1. In some embodiments, the molar ratio of P2S5 to Na2Sx (q:r) is between 1:1.25 and 1.25:1. In some embodiments, the molar ratio of P2S5 to Na2Sx (q:r) is between 1:1.1 and 1.1:1. In some embodiments, the molar ratio of P2S5 to Na2Sx (q:r) is 1:1.
In some embodiments, x of the solid-phase qP2S5-rNa2Sx complex is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12. In some embodiments, x of the solid-phase qP2S5-rNa2Sx complex is an integer from 5 to 9. In some embodiments, x of the solid-phase qP2S5-rNa2Sx complex is an integer from 6 to 8. In some embodiments, x of the solid-phase qP2S5-rNa2Sx complex is 1. In some embodiments, x of the solid-phase qP2S5-rNa2Sx complex is 6. In some embodiments, x of the solid-phase qP2S5-rNa2Sx complex is 8.
In some embodiments, the solid-phase qP2S5-rNa2Sx complex has an amorphous structure. In some embodiments, the solid-phase qP2S5-rNa2Sx complex has a melting point (Tm) that is at least 100° C. higher, at least 110° C. higher, at least 120° C. higher, at least 130° C. higher, at least 140° C. higher, at least 150° C. higher, at least 160° C. higher, at least 170° C. higher, at least 180° C. higher, or at least 190° C. higher than the freezing point (Tf) of the molten form of the solid-phase qP2S5-rNa2Sx complex. In some embodiments, the solid-phase qP2S5-rNa2Sx complex has a melting point (Tm) that is at least 100° C. higher than the freezing point (Tf) of the molten form of the solid-phase qP2S5-rNa2Sx complex. In some embodiments, the solid-phase qP2S5-rNa2Sx complex has a melting point (Tm) that is at least 140° C. higher than the freezing point (Tf) of the molten form of the solid-phase qP2S5-rNa2Sx complex. In some embodiments, the solid-phase qP2S5-rNa2Sx complex has a melting point (Tm) that is at least 180° C. higher than the freezing point (Tf) of the molten form of the solid-phase qP2S5-rNa2Sx complex.
In some embodiments, the cathode and/or the anode further comprise one or more conductive additives.
In some embodiments, the cathode and/or the anode further comprise one or more active materials. By nonlimiting example, active materials suitable for inclusion in the anode include TiO2, Sn, Sb and P. By nonlimiting example, active materials suitable for inclusion in the cathode include Na3V2(PO4)3, NaxCoO2, LiCoO2, NaxMnO2, LiMnO2, LFMP (lithium-iron-manganese-phosphate) and NCMA (nickel, cobalt, manganese, aluminum).
In some embodiments, the cathode and/or the anode further comprise a molten aP2S5-bM2Sy complex, wherein: M is Li or Na; the molar ratio of P2S5 to Na2Sy (a:b) is between 1:2 and 2:1; and y is an integer from 1 to 12.
In some embodiments, the cathode and/or the anode further comprise a molten aP2S5-bNa2Sy complex, wherein: the molar ratio of P2S5 to Na2Sy (a:b) is between 1:2 and 2:1; and y is an integer from 1 to 12.
In some embodiments, the molar ratio of P2S5 to Na2Sy (a:b) is between 1:1.5 and 1.5:1. In some embodiments, the molar ratio of P2S5 to Na2Sy (a:b) is between 1:1.25 and 1.25:1. In some embodiments, the molar ratio of P2S5 to Na2Sy (a:b) is between 1:1.1 and 1.1:1. In some embodiments, the molar ratio of P2S5 to Na2Sy (a:b) is 1:1.
In some embodiments, y is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12. In some embodiments, y is an integer from 5 to 9. In some embodiments, y is an integer from 6 to 8. In some embodiments, y is 1. In some embodiments, y is 6. In some embodiments, y is 8.
In some embodiments, the molten aP2S5-bNa2Sy complex does not solidify at a temperature of 0° C., −10° C., −20° C., −30° C., −40° C., −50° C., −60° C., −70° C., −80° C., or −90° C. In some embodiments, the molten aP2S5-bNa2Sy complex does not solidify at a temperature of 0° C. In some embodiments, the molten aP2S5-bNa2Sy complex does not solidify at a temperature of −50° C. In some embodiments, the molten aP2S5-bNa2Sy complex does not solidify at a temperature of −90° C.
In some embodiments, the molar ratio of P2S5 to Na2Sx (q:r) and the molar ratio of P2S5 to Na2Sy (a:b) are the same. In some embodiments, the molar ratio of P2S5 to Na2Sx (q:r) and the molar ratio of P2S5 to Na2Sy (a:b) are the different.
In some embodiments, x and y are the same. In some embodiments, x and y are the different.
In some embodiments, the molar ratio of P2S5 to Na2Sx (q:r) and the molar ratio of P2S5 to Na2Sy (a:b) are the same, and x and y are the same.
In some embodiments, the molar ratio of P2S5 to Na2Sx (q:r) and the molar ratio of P2S5 to Na2Sy (a:b) are different, or x and y are different.
In some embodiments, the molar ratio of P2S5 to Na2Sx (q:r) and the molar ratio of P2S5 to Na2Sy (a:b) are different, and x and y are different.
In some embodiments, the cathode and/or the anode comprise a continuous interphase.
An electrode (i.e., a cathode or anode) having a “continuous interphase” is one that lacks significant voids between the component parts of the electrode. Traditionally prepared electrodes employ the use of binders to form a closely packed structure. Typical binders, however, are poorly conductive as compared to the solid-phase electrolyte and cannot completely fill the interstitial spaces between the other components of the electrodes. Thus, traditional electrodes contain voids within their structure and are characterized as having a “discontinuous interphase” (
In contrast to traditional syntheses of solid sulfide electrolytes, which require high energy and temperature, the solid-phase and molten electrolytes of the present disclosure can be produced via a cost-effective, scalable process with low energy and temperature requirements. The process involves two main steps: complexation of precursors in a solvent, and solid precipitation of the complexes from the solution.
Accordingly, in an aspect, the present disclosure provides a method of manufacturing a solid-phase electrolyte comprising an mP2S5-nNa2Sx complex, wherein the method comprises: mixing sodium sulfide (Na2S), phosphorus pentasulfide (P2S5), and sulfur powder (S) in an organic solvent to form a solvated mP2S5-nNa2Sx complex; and exposing the solvated mP2S5-nNa2Sx complex to less-than-atmospheric pressure to precipitate a solid-phase mP2S5-nNa2Sx complex; wherein the molar ratio of P2S5 to Na2Sx (m:n) is between 1:2 and 2:1, and x is an integer from 1 to 12.
Organic solvents suitable for use in the methods of the disclosure will be identifiable by those skilled in the art. By non-limiting example, the organic solvent may be diethylene glycol dimethyl ether (diglyme), 1,2-dimethoxyethane, 1,3-dioxolane, tetrahydrofuran, tetraethylene glycol dimethyl ether, or methyl acetate. In some embodiments, the organic solvent is diglyme, 1,2-dimethoxyethane, 1,3-dioxolane, or methyl acetate. In some embodiments, the organic solvent is diglyme.
The concentration of the solvated mP2S5-nNa2Sx complex in the organic solvent prior to precipitation may, by nonlimiting example, be between about 0.1 M and about 4 M. In some embodiments, the concentration of the solvated mP2S5-nNa2Sx complex in the organic solvent prior to precipitation is between about 0.5 M and about 2 M. In some embodiments, the concentration of the solvated mP2S5-nNa2Sx complex in the organic solvent prior to precipitation is between about 0.5 M and about 1.5 M. In some embodiments, the concentration of the solvated mP2S5-nNa2Sx complex in the organic solvent prior to precipitation is about 0.5 M. In some embodiments, the concentration of the solvated mP2S5-nNa2Sx complex in the organic solvent prior to precipitation is about 1 M. In some embodiments, the concentration of the solvated mP2S5-nNa2Sx complex in the organic solvent prior to precipitation is about 1.5 M.
In some embodiments, the method further comprises transferring the solvated mP2S5-nNa2Sx complex to a quartz crucible prior to exposing the complex to less-than-atmospheric pressure. In some embodiments, the method further comprises sealing the solvated mP2S5-nNa2Sx complex in a vacuum tube under an inert gas prior to exposing the complex to less-than-atmospheric pressure. In some embodiments, the inert gas is argon.
In some embodiments, the less-than-atmospheric pressure is between about 0.001 MPa and about 0.25 MPa. In some embodiments, the less-than-atmospheric pressure is between about 0.025 MPa and about 0.1 MPa. In some embodiments, the less-than-atmospheric pressure is about 0.05 MPa.
In some embodiments, the solvated mP2S5-nNa2Sx complex is heated while under less-than-atmospheric pressure. In some embodiments, the solvated mP2S5-nNa2Sx complex is heated at a temperature between about 100° C. and about 200° C. while under less-than-atmospheric pressure. In some embodiments, the solvated mP2S5-nNa2Sx complex is heated at a temperature of about 150° C. while under less-than-atmospheric pressure.
In some embodiments, the solvated mP2S5-nNa2Sx complex is exposed to less-than-atmospheric pressure for at least 0.5 hours, at least 1 hour, at least 1.5 hours, at least 2 hours, at least 2.5 hours, at least 3 hours, at least 3.5 hours, at least 4 hours, at least 4.5 hours, or at least 5 hours. In some embodiments, the solvated mP2S5-nNa2Sx complex is exposed to less-than-atmospheric pressure for between 2 hours and 4 hours. In some embodiments, the solvated mP2S5-nNa2Sx complex is exposed to less-than-atmospheric pressure for about 3 hours.
In another aspect, the disclosure provides a method of manufacturing a molten electrolyte comprising an mP2S5-nNa2Sx complex, wherein the method comprises manufacturing a solid-phase electrolyte comprising an mP2S5-nNa2Sx complex according to the methods disclosed herein; and heating the solid-phase electrolyte to form the molten electrolyte; wherein the molar ratio of P2S5 to Na2Sx (m:n) is between 1:2 and 2:1; and x is an integer from 1 to 12.
In some embodiments, the solid-phase electrolyte is heated at a temperature above 50° C. In some embodiments, the solid-phase electrolyte is heated at a temperature from about 50° C. to about 120° C. In some embodiments, the solid-phase electrolyte is heated at a temperature of about 60° C.
This disclosure is further illustrated by the following Items:
1. A solid-phase or molten electrolyte comprising an mP2S5-nNa2Sx complex, wherein the molar ratio of P2S5 to Na2Sx (m:n) is between 1:2 and 2:1 and x is an integer from 1 to 12.
2. The solid-phase or molten electrolyte of Item 1, wherein the molar ratio of P2S5 to Na2Sx (m:n) is 1:1.
3. The solid-phase or molten electrode of any of preceding Items, wherein x is an integer from 6 to 8.
4. The solid-phase or molten electrode of any of preceding Items, wherein x is 8.
5. A solid-state battery comprising a cathode, an anode, and a solid-state electrolyte in contact with the cathode and the anode, wherein the cathode and/or anode comprise:
6. The solid-state battery of Item 5, wherein the molar ratio of P2S5 to Na2Sx (q:r) is 1:1.
7. The solid-state battery of any of Items 5-6, wherein x of the solid-state qP2S5-rNa2Sx complex is 8.
8. The solid-state battery of Item 5, wherein the cathode and/or anode further comprise a molten aP2S5-bNa2Sy complex, wherein the molar ratio of P2S5 to Na2Sy (a:b) is between 1:2 and 2:1; and y is an integer from 1 to 12.
9. The solid-state battery of Item 8, wherein the molar ratio of P2S5 to Na2Sy (a:b) is 1:1.
10. The solid-state battery of any of Items 8-9, wherein y is 8.
11. The solid-state battery of any of Items 8-10, wherein the molar ratio of P2S5 to Na2Sx (q:r) and the molar ratio of P2S5 to Na2Sy (a:b) are the same and x and y are the same.
12. The solid-state battery of any of Items 8-10, wherein the molar ratio of P2S5 to Na2Sx (q:r) and the molar ratio of P2S5 to Na2Sy (a:b) are different or x and y are different.
13. The solid-state battery of any of Items 8-12, wherein the cathode and/or the anode comprise a continuous interphase.
14. A method of manufacturing a solid-phase electrolyte comprising an mP2S5-nNa2Sx complex, wherein the method comprises:
15. The method of Item 14, wherein organic solvent is selected from the group consisting of diethylene glycol dimethyl ether (diglyme), 1,2-dimethoxyethane, 1,3-dioxolane, tetrahydrofuran, tetraethylene glycol dimethyl ether, and methyl acetate.
16. The method of Item 14, wherein organic solvent is diglyme.
17. The method of any of Items 14-16, wherein the concentration of solvated mP2S5-nNa2Sx complex in the organic solvent prior to precipitation is between about 0.5 M and about 2 M.
18. The method of Items 14-17, wherein the concentration of solvated mP2S5-nNa2Sx complex in the organic solvent prior to precipitation is about 1.5 M.
19. A method of manufacturing a molten electrolyte comprising an mP2S5-nNa2Sx complex, wherein the method comprises:
20. The method of Item 19, wherein the solid-phase electrolyte is heated at a temperature of from about 50° C. to about 120° C.
Fabrication of mP2S5-nNa2Sx solids via complexation and precipitation mP2S5-nNa2Sx solids were produced via two main steps: complexation and precipitation (
Laser Raman spectroscopy (LRS) used a Horiba labRAM HR Evolution operating at 532 nm wavelength with a double pass macro cuvette holder. Raman shifts were calibrated using the sharp characterization peak at 520 cm−1 of the standard silicon sample. X-ray diffraction (XRD) was carried out using Rigaku (model no. 007) with a scanning angle 20 from 10° to 70°. X-ray photoelectron spectroscopy (XPS) was conducted on a PHI Versaprobe II scanning XPS microprobe with a 0.47 eV system resolution using a monochromatic 1486.7 X-ray source. The samples were transferred into the XPS chamber via an Argon-filled, sealed vessel to avoid exposure to air. Differential scanning calorimetry (DSC) was performed using Netzsch DSC 204 F1 Phoenix. The temperature range of P2S5—Na2S is −90° C. to 600° C. and the one of P2S5—Na2S8 is −90° C. to 170° C. Both samples and reference were tested at a controlled rate of 10° C./min. 31P solid-state nuclear magnetic resonance (ssNMR) was performed using a Bruker AVIII 500 MHz with a 4.0 mm HX probe.
Characterization of Sodium Phosphorothioates after Complexation
The mP2S5-nNa2Sx family of materials can be tailored in two dimensions: the Sx chain length (x) and the P2S5-to-Na2Sx molar ratio (m:n). It was observed that both Sx chain length and m:n molar ratio affect the nature and color of the prepared systems (
Specifically, P2S5—Na2S solution exhibits an orange color while the P2S5—Na2S8 exhibits a yellow color. Unlike the transparency observed in two 1:1 systems, mP2S5-nNa2S8 (m:n=4:5, 2:3, 4:7 and 1:2) exhibits opacity to some extent, the colors of which become darker with the increase of Na2S8 (i.e., the decrease of m:n).
Raman spectroscopy was employed to identify the synthesized complexes and study the chemical bonding. As shown in
Regarding the P2S5-to-Na2Sx molar ratio (m:n), it was observed that the peak intensities become weaker with a higher content of Na2S8 (
It was determined that both solute concentration and solvent type affected the yield for the precipitation process and the efficiency of the complexation-precipitation approach. In diglyme, the concentration of P2S5—Na2S8 could be prepared up to 1.5 M (83 wt % solid-to-liquid ratio), without exhibiting any obvious differences in appearance (
Besides diglyme, three other solvents—1,2-dimethoxyethane (DME), 1,3-dioxolane (DOL) and methyl acetate (MA)—were investigated with respect to the stability of the P2S5—Na2S8 complex (
A concentration of 1.5 M (83 wt %) in diglyme solvent was employed to produce the solid phase of P2S5—Na2S8 for further characterization and electrochemical evaluation.
Characterization of the Structure and Composition of Solid P2S5—Na2S8
To investigate the nature of solid P2S5—Na2S8, both Raman spectroscopy and X-ray powder diffraction (XRD) were conducted using P2S5—Na2S as a control. Almost no additional peak occurrence/disappearance can be observed in P2S5—Na2S8 solid (
X-ray photoelectron spectroscopy (XPS) and 31P solid-state nuclear magnetic resonance (ssNMR) were performed to further characterize the molecular structure of the solid P2S5—Na2S8 complex. For XPS, the binding energies of all elements were calibrated with respect to C1s at 284.8 eV (
The main narrow peak in the ssNMR spectrum of P2S5—Na2S8 solid can be fitted with three peaks at 116.3, 115.5 and 114 ppm, representing the existence of P3, P2 and P2′ (
Differential scanning calorimetry (DSC) was carried out to investigate thermal behaviors of P2S5—Na2S8 and P2S5—Na2S solids (
Based on the characterization data of Example 1, a molecular structure of a highly interconnected network has been proposed for P2S5—Na2S8 solid/melt, which contains an open framework likely facilitating the diffusion of Na+ ions (
To prepare the solid-state electrolyte for electrochemical evaluation, thin pellets were fabricated through cold-pressing process. The as-synthesized solid materials were accommodated in a dry pellet pressing die and further pressed through a cold isostatic press. The obtained pellets were then subjected to electrochemical impedance spectroscopy (EIS) measurement via split cells as depicted in
The split cells loaded with the pellet sandwiches were pressed via the isostatic press to ensure a good contact. Electrochemical impedance spectroscopy (EIS) was conducted using an electrochemical workstation (VMP3, Bio-Logic Science Instruments) at a scanning frequency from 1 MHz to 0.1 Hz with an AC amplitude of 5 mV.
The ionic conductivity was calculated by analyzing the obtained Nyquist plot. The plot was fitted to an equivalent circuit in the form of (Rbulk)(RgbQgb)(Qelectrode), where Rbulk is bulk resistance, Rgb is grain boundary resistance, Qgb is grain boundary capacitance, and Qelectrode is double layer capacitance from the ion blocking electrodes. The bulk resistance was attributed to the end point of the semi-circle at the high-frequency zone. With the obtained bulk resistance, the ionic conductivity (δ) could then be calculated using the equation of [δ=d/(Rbulk×A)], where d is the pellet thickness, and A is the pellet area contacting the copper pressing die. The calculated δ will be recorded in millisiemens per centimeter (mS/cm).
The Nyquist plot of P2S5—Na2S8 solid was compared with the ones of P2S5—Na2S6 solid and 4P2S5-5Na2S8 solid (
The electrochemical stability of electrolytes is a key parameter affecting their utility and application. As shown in
The ionic conductivity and resistance of P2S5—Na2S8 melt were also evaluated. The resistance of P2S5—Na2S8 melt did not increase much even after cooling at −35° C. for 2 hours (
Traditional preparation of the electrodes for solid-state batteries is a time-consuming process involves the mixing of solid electrolyte, conductive additive, binder, and active electrode materials. Furthermore, the production of voids and the formation of discontinuous interphase are issues that arise using the traditional method (
A new approach for preparing the electrodes for solid-state batteries takes advantage of the ion-conducting property and fluidity of P2S5—Na2S8 melt. Specifically, P2S5—Na2S8 melt can not only provide an ionic path but also serve as binder. Therefore, the energy density and reaction kinetics of the solid-state battery can be dramatically improved by avoiding the need for heavy binder materials and by filling the voids and generating continuous interphase (
All references cited in this disclosure, including patents, patent applications, scientific papers and other publications, are hereby incorporated by reference into this application.
This application claims priority to U.S. Patent Application Ser. No. 63/278,700, entitled “Sodium/Lithium Phosphorothioates as Novel Solid-State Electrolyte for Sodium/Lithium Battery”, filed Nov. 12, 2021, which is incorporated herein by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/US2022/049720 | 11/11/2022 | WO |
Number | Date | Country | |
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63278700 | Nov 2021 | US |