Furnace system, methods of firing, and sintered article

Abstract

A furnace system includes a heater contained in a heating chamber. A green tape is configured to contact a contact material while it is in the heating chamber. In aspects, the contact material includes iridium, osmium, rhenium, or an alloy thereof. Alternatively, the contact material is a lithium metal oxide where the metal is scandium or yttrium. In aspects, the contact material has a melting temperature of 1500°C or more, a gas phase oxygen concentration of 10-10 atmospheres or more, and a gas phase lithium concentration of 10-5 atmospheres or less. Methods include firing a green tape containing inorganic crystals by heating the green tape while in contact with the contact material. A sintered article includes a body having grains of inorganic material sintered to one another, where a concentration of iridium, osmium, rhenium on a first major surface is greater than or equal to 1 part-per-trillion.

Description

ATTORNEY DOCKET NO. SP24-263FURNACE SYSTEM, METHODS OF FIRING, AND SINTERED ARTICLECROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 63 / 715250 filed on November 1, 2024, and U.S. Provisional Application Serial No. 63 / 760862 filed on February 20, 2025, the content of which is relied upon and incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to a furnace system for forming a sintered article, methods of firing a green tape to form a sintered article, and a sintered article, and more particularly furnace systems having a contact material, methods of firing a green tape in contact with a contact material, and a sintered article having traces of contact with another material.BACKGROUND

[0003] Solid-state batteries (SSBs) (e.g., SS lithium (Li) metal batteries based on inorganic solid-state electrolytes (SSEs) (such as garnet-type SSE)) have attracted much attention as they have the potential to achieve higher energy densities. Some lithium metal battery design can include lithium-containing ceramic materials, including lithium garnet. It is known to process such ceramics by firing to sinter together grains of the ceramic material. However, such lithium- containing inorganic materials can be reactive, which can hinder processing of such materials. Consequently, there exists a need for methods and apparatus to sinter lithium-containing inorganic materials with minimal side reactions and / or sticking.SUMMARY

[0004] The present disclosure provides furnace systems, methods of heating (e.g., firing, sintering) a green body (e.g., green tape) to produce a sintered article, the resulting sintered article (e.g., solid-state electrolyte), and / or a battery (e.g., solid-state battery) containing the same. The inventors of the present disclosure have unexpectedly discovered (especially in view of the abovestate problem) contact materials that can be used to sinter lithium-containing materials without sticking or other reactions. In aspects, the contact material is non-reactive with the lithium- containing material (e.g., lithium garnet) while being heated at 1000°C in an argon environment for 30 minutes or more (e.g., 30 minutes, 45 minutes, 60 minutes). In aspects, the contact material does not stick to the lithium-containing material (e.g., lithium garnet) after being heated at 1000°C in an argon environment for 30 minutes or more (e.g., 30 minutes, 45 minutes, 60 minutes). Inaspects, the contact material can comprise iridium, rhenium, osmium, alloys thereof, or combinations thereof. In aspects, the contact material can exhibit one or more of: a melting temperature greater than or equal to 1500°C; a gas phase oxygen concentration greater than or equal to 10'7atmospheres that produces a gaseous concentration of the contact material of 10'8atmospheres at 1200°C in a 1 atmosphere argon environment; and / or a gas phase lithium concentration less than or equal to 1 O'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C. In aspects, an environment that the green body (e.g., green tape) is heated in can comprise less than or equal to 10 Pascals of oxygen, less than or equal to 10 Pascals of carbon dioxide, and / or less than or equal to 10 Pascals of water vapor, which can reduce an incidence of side reactions and / or sticking.

[0005] Lithium -containing materials can be highly reactive, especially when heated at or near sintering temperatures. For example, lithium can volatize from the material being heated, which can change the composition of the resulting article and / or react with another material. Additionally, it has been observed that commonly available refractory materials, including MgO, will react with lithium-containing materials being sintered while in contact with said refractory material. These reactions can occur even at low oxygen partial pressures in the heating chamber. Also, this reaction can result in the lithium-containing material sticking (e.g., bonding) to the refractory material (e.g., MgO), which impedes processing and yield of the sintering process. Similar to MgO, it has been observed that sticking or other reactions occurs when using other materials in contact with the lithium-containing materials being heated, including platinum, alumina, zirconia, silicon carbide, aluminum nitride, and cordierite. Additionally, sticking between the green body being sintered and the contact material can occur due to reactions therebetween. Without wishing to be bound by theory, it is believed that some of these reactions can involve the formation of oxides of material from the contact material and / or the volatilization of material from the contact material, which can be enhanced in the presence of oxygen, especially when the contact material includes or is a metal. Consequently, the contact materials may preferably have a low volatilization and low reactivity with oxygen at temperatures encountered by the contact material in the heating chamber. As discussed herein, the oxygen concentration (and / or carbon dioxide concentration) of an environment in the heating chamber can be minimized (e.g., 10 Pascals or less). Still, a contact material that can tolerate higher oxygen concentration without substantial volatilization can reduce an incidence of sticking when heating (e.g., firing, sintering) a green body in contact with the contact surface. As well, lithium volatilization during heating (e.g., sintering of a lithium-containing green body) can alter the properties of the resulting sintered article. Additionally, increased lithium volatilization can be an indication of reactions occurring betweenthe green body (i.e., a lithium-containing green body) and a contact material, which can lead to sticking therebetween.

[0006] Alternatively or additionally, the contact surface and / or contact material can comprise a lithium metal oxide, including lithium scandium oxide and alloys thereof. Providing the lithium metal oxide of the present disclosure can enable higher oxygen conditions to be used in contact with a green tape (e.g., lithium-containing material, doped or undoped lithium garnet) than otherwise possible without sticking therebetween, reactions therebetween, and / or limited (or no) lithium loss. For example, as demonstrated in the Examples here, lithium scandium oxide (as the lithium metal oxide) can be used as a contact material with a lithium garnet tape being sintered at 1200°C in a 3% oxygen environment, 1200°C in air, and / or 1325°C in a 5% oxygen environment.

[0007] Some example aspects of the disclosure are described below with the understanding that any of the features of the various aspects may be used alone or in combination with one another.

[0008] Aspect 1. A furnace system comprising: a heater contained in a heating chamber; and a first contact surface positioned within the heating chamber, wherein a green tape is configured to contact the first contact surface while the green tape is in the heating chamber, and the first contact surface comprises a contact material comprising one or more of iridium, osmium, rhenium, or an alloy thereof.

[0009] Aspect 2. A furnace system comprising: a heater contained in a heating chamber; and a first contact surface positioned within the heating chamber, wherein a green tape is configured to contact the first contact surface while the green tape is in the heating chamber, and the first contact surface comprises a contact material comprising a lithium metal oxide where the metal is selected from a group consisting of scandia, yttrium, and combinations thereof.

[0010] Aspect 3. A furnace system comprising: a heater contained in a heating chamber; a first contact surface positioned within the heating chamber, wherein a green tape is configured to contact the first contact surface while the green tape is in the heating chamber, and the first contact surface comprises a contact material having: a melting temperature greater than or equal to 1500°C, a gas phase oxygen concentration greater than or equal to 10'10atmospheres that produces a gaseous concentration of the contact material of 10'8atmospheres at 1200°C in a 1 atmosphere argon environment, and a gas phase lithium concentration less than or equal to 10'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C in a 1 atmosphere argon environment with less than or equal to 10 Pascals of water vapor.

[0011] Aspect 4. The furnace system of aspect 3, wherein the contact material comprises a non-oxide metal compound, and a surface concentration of an oxide of the contact material isless than or equal to 10'6mol% on the first contact surface when heated at 900°C in a 1 atmosphere argon environment with less than or equal to 10 Pascals of water vapor.

[0012] Aspect 4. The furnace system of any one of aspects 1-4, wherein the first contact surface is free of a metal oxide of iridium, osmium, and rhenium.

[0013] Aspect 5. The furnace system of any one of aspect 1-5, further comprising a conveyance path extending through the heating chamber, wherein the green tape is configured to contact the first contact surface while the green tape is conveyed along at least a portion of the conveyance path.

[0014] Aspect 6. The furnace system of any one of aspects 3-4, wherein the oxygenated gas phase lithium concentration is less than or equal to 10'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C in a 1 atmosphere argon environment of 3% oxygen and 97% argon with less than or equal to 10 Pascals of water vapor.

[0015] Aspect 7. The furnace system of any one of aspects 2-3 and 5-6 inclusive, wherein the contact material comprises lithium scandium oxide.

[0016] Aspect 8. The furnace system of any one of claims 1-7, wherein the first contact surface and the green tape are configured to translate together along at least the portion of the conveyance path.

[0017] Aspect 9. The furnace system of aspect 8, wherein the green tape is configured to translate relative to the first contact surface as the green tape is conveyed through the heating chamber along at least the portion of the conveyance path while the green tape is in contact with the first contact surface.

[0018] Aspect 10. The furnace system of aspect 8, further comprising: a second contact surface, the green tape is configured to contact the second contact surface for another portion of the conveyance path, and the second contact surface comprises a different material than the contact material of the first contact surface, wherein a position of the first contact surface is configured to correspond to a maximum temperature encountered by the green tape whereas a second position of the second contact surface does not correspond to the maximum temperature.

[0019] Aspect 11. The furnace system of aspect 10, wherein a second material forming the second contact surface comprises one or more of platinum, rhodium, alumina, calcium oxide, magnesium oxide, tungsten, or an alloy thereof.

[0020] Aspect 12. The furnace system of any one of aspects 1-11, wherein the first contact surface is an outer surface of an article comprising an additional material coated with the contact material.

[0021] Aspect 13. The furnace system of aspect 12, wherein the additional material comprises one or more of alumina, nickel, tungsten, chromium, mullite, or an alloy thereof.

[0022] Aspect 14. The furnace system of any one of aspects 1-13, wherein the contact material is non-reactive with lithium garnet at 1000°C in an argon environment for 30 minutes.

[0023] Aspect 15. The furnace system of any one of claims 1-13, wherein lithium garnet in contact with the first contact surface at 1000°C in an argon environment for 30 minutes does not stick of the first contact surface.

[0024] Aspect 16. The furnace system of any one of aspects 1-15, wherein the furnace system comprises a multi-zone heating system comprising the heating chamber with the first contact surface therein as at least one zone of the multi-zone heating system.

[0025] Aspect 17. A method of firing a green tape containing inorganic crystals, the method comprising: heating the green tape in an atmosphere to sinter the inorganic crystals; and contacting the green tape with a first contact surface during at least part of the heating, wherein the first contact surface comprises a contact material comprising one or more of iridium, osmium, rhenium, or an alloy thereof.

[0026] Aspect 18. A method of firing a green tape containing inorganic crystals, the method comprising: heating the green tape in an atmosphere to sinter the inorganic crystals; and contacting the green tape with a first contact surface during at least part of the heating, wherein the first contact surface comprises a contact material comprising a lithium metal oxide where the metal is selected from a group consisting of scandia, yttrium, and combinations thereof.

[0027] Aspect 19. A method of firing a green tape containing inorganic crystals, the method comprising: heating the green tape in an atmosphere to sinter the inorganic crystals and form a sintered tape; and contacting the green tape with a first contact surface during at least part of the heating, wherein the first contact surface comprises a contact material having: a melting temperature greater than or equal to 1500°C, a gas phase oxygen concentration greater than or equal to 10'10atmospheres that produces a gaseous concentration of the contact material of 10'8atmospheres at 1200°C in a 1 atmosphere argon environment, and a gas phase lithium concentration less than or equal to IO'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C.

[0028] Aspect 20. The method of aspect 19, wherein the contact material comprises a non-oxide metal compound, and a surface concentration of an oxide of the contact material is less than or equal to 10'6mol% on the first contact surface when heated in contact the green tape during the heating.

[0029] Aspect 21. The method of any one of aspects 17-20, wherein a partial pressure of oxygen in the atmosphere is less than or equal to 10 Pascals.

[0030] Aspect 22. The method of any one of aspects 17-21, wherein a partial pressure of water vapor in the atmosphere is less than or equal to 10 Pascals.

[0031] Aspect 23. The method of any one of aspects 17-22, wherein a partial pressure of carbon dioxide in the atmosphere is less than or equal to 10 Pascals.

[0032] Aspect 24. The method of any one of aspects 17-23, wherein the atmosphere consists essentially of a noble gas, nitrogen, or a combination thereof.

[0033] Aspect 25. The method of any one of aspects 17-24, wherein the inorganic crystals are a lithium-containing material.

[0034] Aspect 26. The method of aspect 25, wherein one or more of the inorganic crystals comprise a lithium garnet.

[0035] Aspect 27. The method of any one of aspects 17-26, further comprising conveying the green tape through a heating chamber during the heating, wherein the green tape contacts the first contact surface during at least a portion of the conveying.

[0036] Aspect 28. The method of aspect 27, wherein the at least a portion of the conveying comprises translating the first contact surface and the green tape together.

[0037] Aspect 29. The method of aspect 27, wherein the at least a portion of the conveying comprises translating the green tape relative to the first contact surface while the green tape is in contact with the first contact surface.

[0038] Aspect 30. The method of aspect 29, further comprising: contacting the green tape with a second contact surface during another portion of the conveying comprising translating the green tape relative to the second contact surface while the green tape is in contact with the second contact surface, wherein the second contact surface comprises a different material than the contact material of the first contact surface, the contacting the green tape with the first contact surface occurs while the green tape encounters a maximum temperature during the heating, whereas the contacting the green tape with the second contact surface does not occur while the green tape encounters the maximum temperature during the heating.

[0039] Aspect 31. The method of aspect 30, wherein a second material forming the second contact surface comprises one or more of platinum, rhodium, alumina, calcium oxide, magnesium oxide, tungsten, or an alloy thereof.

[0040] Aspect 32. The method of claim 30, wherein the oxygenated gas phase lithium concentration is less than or equal to 10'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C in a 1 atmosphere argon environment of 3% oxygen and 97% argon with less than or equal to 10 Pascals of water vapor.

[0041] Aspect 33. The method of claim 18 or claim 32, wherein the contact material comprises lithium scandium oxide.

[0042] Aspect 34. The method of any one of aspects 30-33, wherein the maximum temperature during the heating encountered by the green tape is in a range from 800°C to 1500°C.

[0043] Aspect 35. The method of any one ofaspects 17-34, wherein the heating comprises heating the green tape at a temperature in a range from 800°C to 1500°C for from 10 seconds to less than one hour.

[0044] Aspect 36. The method of any one of aspects 17-35, wherein the contact material of the first contact surface is non-reactive with the green tape during the heating.

[0045] Aspect 37. The method of any one of aspects 17-36, wherein the green tape and the resulting sintered tape does not stick to the first contact surface as a result of the heating.

[0046] Aspect 38. A sintered article produced by the method of any one of aspects 17-37 comprising a body comprising grains of inorganic material sintered to one another corresponding to the inorganic crystals of the green tape.

[0047] Aspect 39. The method of any one of aspects 17-38, wherein the green tape is free of binder before contacting the first contact surface.

[0048] Aspect 40. The method of any one of aspects 17-38, wherein the green tape encounters multiple environments as part of the firing.

[0049] Aspect 41. The method of any one of aspects 17-38, further comprising changing the atmosphere during the heating by flow a gas over the green tape.

[0050] Aspect 42. The method of any one of aspects 17-41, further comprising changing the atmosphere during the heating by conveying the green tape from a first zone with a first atmosphere to a second zone having the atmosphere and the first contact surface.

[0051] Aspect 43. A sintered article comprising: a body comprising grains of inorganic material sintered to one another, the body extending between a first major surface and a second major surface, a thickness of the body defined between the first major surface and the second major surface, and the thickness is from 5 micrometers to 1 millimeter, wherein a concentration of iridium, osmium, rhenium on the first major surface is greater than or equal to 1 part-per- trillion.

[0052] Aspect 44. The sintered article of aspect 43, wherein the body is free of iridium, osmium, and rhenium.

[0053] Aspect 45. A sintered article comprising: a body comprising grains of inorganic material sintered to one another, the body extending between a first major surface and a second major surface, a thickness of the body defined between the first major surface and the second major surface, and the thickness is from 5 micrometers to 1 millimeter, wherein a concentration of scandium or yttrium on the first major surface is greater than or equal to 1 part-per-trillion.

[0054] Aspect 46. The sintered article of aspect 45, wherein the body is free of scandium and yttrium, and the grains of inorgnaic material comprise a lithium-containing material.

[0055] Aspect 47. The sintered article of any one of aspects 43-46, wherein the body has an ionic conductivity greater than 5x1 O'5S / cm.

[0056] Aspect 48. The sintered article of any one of aspects 43-47, wherein the grains of inorgnaic material comprise a lithium -containing material.

[0057] Aspect 49. The sintered article of any one of aspects 43-48, wherein the grains of inorganic material comprise at least one of:(i) Li7-3aLa3Zr2LaOi2, with L = Al, Ga, or Fe and 0 < a < 0.33;(ii) Li?La3-bZr2MbOi2, with M = Bi, Ca, or Y and 0 < b < 1 ; or(iii) Li7-cLa3(Zr2-c, Nc)Oi2, with N = V, Nb, or Ta and 0 < c < 1.BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The above and other features and advantages of aspects of the present disclosure are better understood when the following detailed description is read with reference to the accompanying drawings, in which:

[0059] FIG. 1 schematically illustrates a general structure of a solid-state battery incorporating a sintered article in accordance with aspects of the disclosure;

[0060] FIG. 2 illustrates a simplified solid-state battery with the sintered article as a solid- state electrolyte in accordance with aspects of the disclosure;

[0061] FIG. 3 illustrates an exemplary furnace system in a method of firing a green tape to produce a sintered article, where the green tape translates relative to a contact material in accordance with aspects of the disclosure;

[0062] FIG. 4 is an enlarged view 4 of FIG. 3 showing a contact material of the furnace system contacting a green tape being fired in accordance with aspects of the disclosure;

[0063] FIG. 5 is an alternate enlarged view 4 of FIG. 3 showing a contact material coated on another material, where the contact material is in contact with the tape being fired in accordance with aspects of the disclosure;

[0064] FIG. 6 illustrates an exemplary furnace system in a method of firing a green tape to produce a sintered article, where the green tape translates with a contact material in accordance with aspects of the disclosure;

[0065] FIG. 7 schematically illustrates materials based on a (base-10) logarithm of a tolerable gas-phase oxygen concentration (Tol. Gas Ox. Cone.) on the vertical axis (i.e., y-axis) and a melting temperature (Tm) in °C on the horizontal axis (i.e., x-axis) of the corresponding material;

[0066] FIG. 8 schematically illustrates materials based on a (base- 10) logarithm of a lithium gas-phase concentration at 1200°C (Li Gas Cone. 1200°C) on the vertical axis (i.e., y-axis)and a melting temperature (Tm) in °C on the horizontal axis (i.e., x-axis) of the corresponding material;

[0067] FIG. 9 schematically illustrates curves showing a (base- 10) logarithm of an activity of different materials on the vertical axis (i.e., y-axis) as a function of temperature (Temp) in °C on the horizontal axis (i.e., x-axis);

[0068] FIG. 10 schematically illustrates curves showing a (base-10) logarithm of a gasphase concentration of lithium materials ([LiX]<g) - in wt%) on the vertical axis (i.e., y-axis) as a function of a (base- 10) logarithm of a partial pressure of oxygen (PO2 - in atm) on the horizontal axis (i.e., x-axis) for the corresponding condition;

[0069] FIG. 11 schematically illustrates an X-ray diffractometry (XRD) spectrum with an intensity (I) in terms of raw counts (cts) on the vertical axis (i.e., y-axis) as a function of the double angle (20) in degrees (deg.) of the incidence angle on the horizontal axis (i.e., x-axis) of an exemplary contact material in accordance with aspects of the present disclosure; and

[0070] FIG. 12 schematically illustrates cross-sectional images of exemplary contact materials in accordance with aspects of the present disclosure, where (a) shows a trans-granular fracture pattern, (b) shows an intergranular fracture pattern, (c) shows a polished cross-section of the image in (b), and (d) shows secondary phases identified using electron backscatter diffraction (EBSD) for the polished cross-section shown in (c).

[0071] Throughout the disclosure, the drawings are used to emphasize certain aspects. As such, it should not be assumed that the relative size of different regions, portions, and substrates shown in the drawings are proportional to its actual relative size, unless explicitly indicated otherwise.DETAILED DESCRIPTION

[0072] Aspects will now be described more fully hereinafter with reference to the accompanying drawings in which example aspects are shown. Whenever possible, the same reference numerals are used throughout the drawings to refer to the same or like parts.

[0073] FIGS. 3 and 6 illustrate views of a furnace system 301 and 601 (along with enlarged views thereof shown in FIGS. 4-5), which can be used in methods of firing a green tape to form a sintered article. FIGS. 1-2 illustrate views of a solid-state battery 101 or 201 comprising a solid-state electrolyte. The cathode and / or the solid-state electrolyte can comprise a sintered article in accordance with aspects of the present disclosure. Unless otherwise noted, a discussion of features of aspects of one furnace system or sintered article (e.g., cathode and / or solid-state electrolyte in a battery) can apply equally to corresponding features of any aspects of the disclosure. For example, identical part numbers throughout the disclosure can indicate that, in some aspects, the identified features are identical to one another and that the discussion of the identified featureof one aspect, unless otherwise noted, can apply equally to the identified feature of any of the other aspects of the disclosure.

[0074] Aspects of the present disclosure include a sintered article. As used herein, a “sintered article” refers to an article that has been sintered, meaning that it has grains that have been bonded together through heating without melting (i.e., liquefaction) the material. Without wishing to be bound by theory, it is believed that sintering bonds the grains together through the diffusion of material at the boundary between adjacent grains. The micro structure of a sintered article can be used to identify that it was sintered (rather than processed by another method). Consequently, although not shown, the sintered articles in accordance with the present disclosure have a body comprising grains of inorganic material sintered to one another. As used herein, the sintered article can be formed by sintering a ceramic green-body, for example, using a furnace system and / or methods in accordance with the present disclosure.

[0075] Sintered articles in accordance with the present disclosure include a body between a first major surface and a second major surface opposite the first major surface. For example, with reference to FIGS. 1-2, a solid-state electrolyte 108 can be a sintered article having a body of the solid-state electrolyte between the first major surface 107 and the second major surface 109 with a thickness 129 defined therebetween. Additionally or alternatively the cathode 104 can comprise a sintered article. Likewise, as shown in FIGS. 3 and 6, a sintered article (e.g., produced by firing - sintering - a green body 331) comprises a first major surface 333 and a second major surface 335 opposite the first major surface 333 with a thickness 339 defined therebetween. In aspects, the thickness 129 and / or 339 can be 5 pm or more, 10 pm or more, 20 pm or more, 40 pm or more, 60 pm or more, 80 pm or more, 100 pm or more, 150 pm or more, 300 pm or more, 500 pm or more, 600 pm or more, 700 pm or more, 800 pm or more, 1 mm or more, 2 mm or less, 5 mm or less, 3 mm or less, 2 mm or less, 1 mm or less, 800 pm or less, 500 pm or less, 300 pm or less, 250 pm or less, 200 pm or less, 150 pm or less, 120 pm or less, or 100 pm or less. In aspects, the thickness 129 and / or 339 can be in a range from 5 pm to 5 mm, from 10 pm to 5 mm, from 20 pm to 3 mm, from 40 pm to 2 mm, from 60 pm to 1 mm, from 80 pm to 800 pm, from 100 pm to 500 pm, from 150 pm to 300 pm, from 150 pm to 250 pm, or any range or subrange therebetween. In aspects, the thickness 129 of solid-state electrolyte 108 (e.g., sintered article) can be 300 pm or less, for example, from 5 pm to 300 pm, from 10 pm to 250 pm, from 20 pm to 200 pm, from 40 pm to 150 pm, from 60 pm to 150 pm, from 80 pm to 100 pm, or any range or subrange therebetween.

[0076] The inorganic material of (e.g., the grains in) the sintered article can comprise a sodium-containing material and / or a lithium-containing material. In aspects, the sodium - containing material can comprise a sodium super ionic conductor (NASICON) material. In aspects,the lithium-containing material (of the inorganic material in the sintered article) can be a lithium garnet (LLZO, e.g., LiyLa^ZnOn). a lithium manganese oxide (e.g., LiM CL), a lithium cobalt oxide (e.g., LiCoCh). a lithium aluminum titanium phosphate (LATP), a lithium-containing NASICON-type material, doped variations thereof, or combinations thereof. In aspects, the sintered article can comprise lithium, lanthanum, zirconium, oxygen, or combinations thereof (e.g., each of lithium, lanthanum, zirconium, and oxygen - a LLZO compound). As used herein, “LLZO” refers to compounds including lithium, lanthanum, zirconium, and oxygen. In even further aspects, the lithium-containing inorganic material (of the sintered article) can comprise a lithium-garnet, for example, at least one of: (i) Li7-3aLa3Zr2LaOi2, with L = Al, Ga or Fe and 0 < a < 0.33; (ii) Li7La3-bZr2MbOi2, with M = Bi, Ca, or Y and 0 < b < 1; (iii) Li7-cLa3(Zr2-c,Nc)Oi2, with N = V, Nb, or Ta and 0 < c < 1; or a combination thereof. In structures (ii) and (iii) dopants are represented by M and N, respectively. In an exemplary aspect, the solid-state electrolyte 108 comprises a sintered article of lithium garnet (either undoped LLZO or doped LLZO - e.g., Ta-doped garnet (LLZTO)) with the understanding that the garnet can have excess lithium (beyond stoichiometry) in some aspects. In further aspects, the inorganic material can comprise a lithium garnet to be fired in a low-oxygen atmosphere (e.g., less than or equal to 10 Pascals partial pressure of oxygen), although the other materials listed above in this paragraph can be used in higher (but still relatively low) oxygen-containing environments (e.g., an atmosphere containing less than or equal to 5 vol% oxygen, from 1 vol% to 5 vol% oxygen).

[0077] In aspects, the body of the sintered article (i.e., composition excluding the major surfaces of the sintered article) can be free of one or more of: iridium (Ir), osmium (Os), rhenium (Re), platinum (Pt), magnesium (Mg), calcium, aluminum (Al), tungsten, or combinations thereof. In further aspects, the body of the sintered article can be free of all of iridium (Ir), osmium (Os), and rhodium (Rh). In contrast, in further aspects, a surface (e.g., first major surface, second major surface) of the sintered article can comprise a concentration of iridium (Ir), osmium (Os), and / or rhenium (Re) of 1 part-per-trillion (ppt) or more, 2 ppt or more, 5 ppt or more, 8 ppt or more, 10 ppt or more, 20 ppt or more, 50 ppt or more, or 100 ppt or more, for example, in a range from 1 ppt to 1 part-per-million (ppm), from 2 ppt to 100 parts-per-billion (ppb), from 5 ppt to 10 ppb, from 8 ppt to 1 ppb, from 10 ppt to 100 ppt, from 20 ppt to 50 ppt, or any range or subrange therebetween. For example, the concentration of such materials (e.g., iridium (Ir), osmium (Os), rhenium (Re)) can be indicative of the sintered article having been processed (e.g., fired, sintered) in accordance with methods of the present disclosure.

[0078] Alternatively or additionally, the body of the sintered article (i.e., composition excluding the major surfaces of the sintered article) can be free of one or more of: scandium, yttrium, or combinations thereof. In further aspects, the body of the sintered article can be free ofall of scandium, ytrium, or combinations thereof. In contrast, in further aspects, a surface (e.g., first major surface, second major surface) of the sintered article can comprise a concentration of scandium (Sc), ytrium (Y), or combinations thereof of 1 part-per-trillion (ppt) or more, 2 ppt or more, 5 ppt or more, 8 ppt or more, 10 ppt or more, 20 ppt or more, 50 ppt or more, or 100 ppt or more, for example, in a range from 1 ppt to 1 part-per-million (ppm), from 2 ppt to 100 parts-per- billion (ppb), from 5 ppt to 10 ppb, from 8 ppt to 1 ppb, from 10 ppt to 100 ppt, from 20 ppt to 50 ppt, or any range or subrange therebetween. For example, the concentration of such materials (e.g., of scandium (Sc), ytrium (Y)) can be indicative of the sintered article having been processed (e.g., fired, sintered) in accordance with methods of the present disclosure.

[0079] The ionic conductivity of the sintered article (e.g., solid-state electrolyte 108) is a quantification of the ability of the sintered article (e.g., solid-state electrolyte sheet) to transport ions between electrodes when used in a batery (e.g., solid-state batery). Throughout the disclosure, the ionic conductivity is measured at using a 4-point probe. The 4-point probe comprises a pair of current probes and a pair of voltage probes arranged on a common surface of the solid-state electrolyte sheet such that the pair of voltage probes are separated by a distance of 21 mm, the current probes bracket the pair of voltage probes (i.e., are positioned outside of the distance between the pair of voltage probes), and the probes are attached to the common surface of the solid-state electrolyte sheet using platinum paste with a thickness of 40 pm and a width of 5 mm in the direction that the distance between the pair of voltage probes is measured. Current is passed between the pair of current probes and the change in voltage detected by the pair of voltage probes is monitored. In aspects, the ionic conductivity of the sintered article (e.g., at 25°C) can be 10'5Siemens per centimeter (S / cm) or more, 5 x 10'4S / cm or more, 2 x 10'4S / cm or more, or 10'4S / cm or more, for example, in a range from 10'5S / cm to 1 S / cm, from 2 x 10'4S / cm to 0.01 S / cm, from 5 x 10'4S / cm to 10'3S / cm, or any range or subrange therebetween.

[0080] FIG. 1 schematically illustrates a general structure of a solid-state batery 101, and FIG. 2 illustrates a simplified solid-state batery 201 in a coin-cell form. As shown in FIG. 1, the solid-state battery 101 or 201 can include, sequentially, a first current collector 102 (e.g., substrate), a cathode 104 disposed on the first current collector 102, an optional interlayer 114 disposed on the cathode 104, an optional first coating 106, the solid-state electrolyte 108, an optional second interlayer or coating 110, and the anode 112, and a second current collector 116 disposed on the anode 112. As shown in FIG. 1, the solid-state batery 101 can optionally comprise the optional first coating 106 positioned between the cathode 104 and the solid-state electrolyte 108, and / or the solid-state batery 101 can optionally comprise the optional second interlayer or coating 110 positioned between the anode 112 and the solid-state electrolyte 108. As shown in FIGS. 1-2, the solid-state electrolyte 108 is positioned between the cathode 104 and the anode 112.The components of the solid-state battery 101 can be disposed horizontally in relation to each other or vertically.

[0081] The first current collector 102 comprises an electrically conductive material. As used herein, electrically conductive materials have an electronic conductivity of 100 Siemens per meter (S / m) measured at 20°C in accordance with ASTME 1004-17. In aspects, the first current collector can comprise nickel (Ni) foam, carbon fiber, or a solid metal contact (e.g., aluminum, stainless steel, copper, platinum, nickel, gold, zinc, cobalt, nickel, ruthenium, lithium, lead, titanium, nichrome, etc.). In aspects, the first current collector 102 can be a mechanically stable and / or dimensionally stable substrate that supports the other elements of the solid-state battery 101 or 201. In aspects, the first current collector 102 can comprise the same material as the cathode 104 (discussed below) such that the first current collector 102 is part of the cathode 104.

[0082] The cathode 104 comprises an electrically conductive material. In aspects, the cathode 104 can be configured to release and reincorporate a cation (e.g., alkali metal - lithium or sodium, alkali earth metal - magnesium or calcium). In aspects, the cathode 104 can comprise at least one of an alkali metal (e.g., lithium, sodium) or an alkaline earth metal (e.g., magnesium, calcium). In aspects, the cathode 104 can comprise one or more of the materials discussed below for the anode 112. In further aspects, the cathode 104 can comprise the same material as the anode 112. In aspects, the cathode 104 can comprise a fluoride compound. In further aspects, the cathode 104 can comprise at least one transition metal, for example, cobalt, manganese, nickel, niobium, tantalum, vanadium, titanium, copper, chromium, tungsten, molybdenum, tin, germanium, antimony, bismuth, iron, or combinations thereof. In aspects, the cathode 104 can comprise a lithium-based electrode, for example lithium cobaltite (LCO), lithium manganite spinel (LMO), lithium nickel cobalt aluminate (NCA), lithium nickel manganese cobalt oxide (NCM) (LiNiaCoeMni-d-eCh, where 0 < d < 1, 0 < e < 1, for example, LiNio.5Coo.2Mno.3O2 (NCM523), LiNio.6Coo.2Mno.2O2 (NCM622), etc.), lithium iron phosphate (LiFcPO-i) (LFP), lithium cobalt phosphate (LCP), lithium titanate, lithium niobium tungstate, lithium nickel manganate, lithium titanium sulfide (LiTiS2), or combinations thereof. In aspects, the cathode 104 can comprise a sodium-based electrode, for example, NaVPCfiF. NaMnO2, Na2 / 3Mni-yMgyO2 (0 < y < 1), Na2Li2TisOi2, Na2Ti3O?, or combinations thereof. In aspects, the cathode 104 can comprise a magnesium-based electrode, for example, magnesiochromite (MgCnO-i). MgM Cfi, or combinations thereof. The cathode 104 can be a sintered electrode. Alternatively, the cathode 104 can be unsintered. An exemplary aspect of a cathode 104 is a NCM cathode.

[0083] As shown in FIG. 1, the solid-state battery 101 can optionally comprise an interlayer 114 positioned between the cathode 104 and the solid-state electrolyte 108. In aspects, the interlayer 114 can comprise a liquid electrolyte. As used herein, an “electrolyte” enables thetransport of ions therein (“ion conductivity”), and the ion conductivity corresponds to an electrical conductivity of the electrolyte. The interlayer 114 can be a liquid at room temperature (i.e., 25°C) and / or at an operating temperature of the solid-state battery 101 (e.g., from 50°C to 60°C). In aspects, the liquid electrolyte can comprise a lithium-containing salt and a solvent. In further aspects, the lithium-containing salt can comprise one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiCIO-i). lithium tetrafluoroborate (LiBF4), lithium triflate ( Li SO3C F ) . LiC(SO2CF3)3, or combinations thereof. In further aspects, a concentration of the lithium-containing salt can be 0.5 molar (M) or more, 1 M or more, 1.2 M or more, 1.5 M or more, 3 M or less, 2.5 M or less, or 2 M or less, for example, in a range from 0.5 M to 3 M, from 1 M to 3 M, from 1.2 M to 2.5 M, from 1.5 M to 2 M, or any range or subrange therebetween. Providing an interlayer 114 comprising a liquid electrolyte can wet the interface between the cathode 104 and the solid-state electrolyte to reduce interfacial resistance therebetween while minimizing a total amount of liquid electrolyte in the solid-state battery 101. In aspects, a volume of the liquid electrolyte of the interlayer 114 to a cathode surface area (e.g., first major surface 105) of the cathode 104 can be 5 pL / cm2or more, 8 pL / cm2or more, 10 pL / cm2or more, 12 pL / cm2or more, 15 pL / cm2or more, 20 pL / cm2or less, 15 pL / cm2or less, 12 pL / cm2or less, or 10 pL / cm2or less, for example in a range from 5 pL / cm2to 20 pL / cm2, from 8 pL / cm2or to 15 pL / cm2or, from 10 pL / cm2to 12 pL / cm2, or any range or subrange therebetween.

[0084] As shown in FIGS. 1-2, the solid-state battery 101 and 201 comprises the solid- state electrolyte 108 positioned between the cathode 104 and the anode 112. Throughout the disclosure, “solid-state batteries” comprise a solid-state electrolyte. As used herein, a solid-state electrolyte is a material that is solid at room temperature and at an operating temperature (e.g., 50°C) of the solid-state battery. In aspects, the solid-state electrolyte 108 can comprise an inorganic solid-state electrolyte. Providing a solid-state electrolyte can address common safety concerns, for example, leakage, poor chemical stability, and flammability often seen in batteries employing liquid electrolytes. Moreover, providing a solid-state electrolyte can also suppress polysulfide shuttling from the cathode to the anode, thereby leading to improved electrode (e.g., anode, cathode) utilization and a high discharge capacity and energy density. Providing a solid-state electrolyte can reduce a formation of dendrites (e.g., lithium dendrites) that can otherwise result in failure of the battery.

[0085] In aspects, the solid-state electrolyte 108 can comprise a sintered article (in accordance with the aspects discussed herein). In aspects, the solid-state electrolyte 108 can comprise one or more of the materials discussed above, for example, lithium-phosphorous- oxynitride (LiPON), lithium garnet (LLZO, e.g., LiyLasZ^O ), lithium phosphosulfide, dopedvariations thereof, or combinations thereof. In further aspects, the solid-state electrolyte 108 can comprise lithium, lanthanum, zirconium, oxygen, or combinations thereof (e.g., each of lithium, lanthanum, zirconium, and oxygen - a LLZO compound). In even further aspects, the lithium - containing inorganic material can comprise a lithium-garnet, for example, at least one of: (i) Li?- 3aLa3Zr2LaOi2, with L = Al, Ga or Fe and 0 < a < 0.33; (ii) LiyLas-bZ^MbOn, with M = Bi, Ca, or Y and 0 < b < 1; (iii) Li7-cLa3(Zr2-c,Nc)Oi2, with N = V, Nb, or Ta and 0 < c < 1; or a combination thereof. In aspects, the thickness 129 of the solid-state electrolyte 108 defined between the first major surface 107 and the second major surface 109 opposite the first major surface 107 can be within one or more of the corresponding ranges discussed above for thickness 129.

[0086] Throughout the disclosure, an amount of lithium (e.g., Li2O wt%, on an oxide basis and based on 100 wt% of the solid-state electrolyte - composite garnet electrolyte, composite garnet electrolyte with the porous surface), is determined based on flame emission spectroscopy of material sampled from the center of the sample (i.e., material located halfway between the first major surface and the second major surface). Without wishing to be bound by theory, stoichiometric garnet (e.g., 0.5 Ta-doped LLZO (LLZTO), Li6.5La3Zr1.5Tao.5O12) can be 11.1 wt% Li2O on an oxide basis. As used herein, “on an oxide basis” means the component is measured as if the non-oxygen components in the compound were converted into a specified oxide form or a fully oxidized oxide if a specific oxide form is not specified. For example, sodium (Na) on an oxide basis refers to amounts in terms of sodium oxide (Na2O) while lithium on an oxide basis refers to amounts in terms of lithium oxide (Li2O). As such, a component need not actually be in the specified oxide form or in the fully oxidized oxide form in order for the component to count in measures on “an oxide basis.” As such, a measurement “an oxide basis” for a specific component comprises conceptually converting materials comprising the non-oxygen element of the specific component into the specified oxide form or the fully oxidized oxide if a specific oxide form is not specified before calculating the concentration on an oxide basis. As discussed above, the amount of lithium is determined based on flame emission spectroscopy, which means that the amount of lithium refers to the actual amount of lithium in the resulting solid-state electrolyte (e.g., composite garnet electrolyte). This is to be distinguished from an amount of lithium that can be added to garnet crystals before firing (e.g., sintering) to form the solid-state electrolyte since it is known that lithium volatilizes during firing. As discussed in the Examples below, adjusting the firing conditions on its own can alter the amount of lithium present in the resulting solid-state electrolyte.

[0087] Throughout the disclosure, a grain size of the solid-state electrolyte (e.g., garnet, sintered article) is determined in accordance with ASTM El 12-13. In aspects, a median grain size of the garnet can be 3.0 pm (e.g., 3 pm) or less, 2.9 pm or less, 2.7 pm or less, 2.5 pm or less, 2.3 pm or less, 2.0 pm or less, 1.8 pm or less, 1.5 pm or less, 1.3 pm or less, 1.0 pm or less, 1.0 pm(e.g., 1 un) or more, 1.1 un or more, 1.3 pun or more, 1.5 pun or more, 1.7 pun or more, or 2.0 pun or more. In aspects, a median grain size of the garnet can be in a range from 1.0 pm to 4.0 pm, from 1.0 pm to 3.0 pm (e.g., from 1 pm to 3 pm), from 1.0 pm to 2.9 pm, from 1.1 pm to 2.7 pm, from 1.1 pm to 2.5 pm, from 1.3 pun to 2.3 pm, from 1.3 pm to 2.0 pm, from 1.3 pm to 1.8 pm, or any range or subrange therebetween. Providing a grain size of 3 pm or less, from 1 pm to 3 pm, or from 1 pm to 2 pm can enable the ionic conductivity can be increased, for example, by decreasing a path length along grain boundaries that could be travelled by an ion transported through the solid-state electrolyte sheet and / or by providing additional grain boundary per volume of the solid-state electrolyte.

[0088] In aspects, the optional first coating 106 can comprise a carbon-based interlayer (e.g., interlinked freestanding, micro / mesopore containing, functionalized, biomass-derived), a polymer-based interlayer, a metal-based coating (e.g., Ni foam, etc.), a liquid electrolyte (e.g., LiPFe in ethylene carbonate (EC)Zdimethyl carbonate (DMC)), ionic liquid-based (e.g., LiCF3SO3 / CH3CONH2, LiTFSI / N-methylacetamide (NMA), PEOi8LiTFSI-10%SiO2-10%IL, etc., where LiTFSI is bis(trifluoromethane) sulfonimide lithium salt (LiN(CF3SC>2)2), SiO2may be nanoparticles, and IL is an ionic liquid), or a combination thereof. Exemplary aspects of polymer- based interlayers include carbon polysulfides (CS), polyethylene oxides (PEO), polyaniline (PANI), polypyrrole (PPY), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(styrene sulfonic acid) (PSS), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyallylamine hydrochloride (PAH), poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)), poly(methyl methacrylate) (PMMA), polyvinylidene fluoride (PVDF), poly(diallyldimethyl ammonium) bis(trifluoromethanesulfonyl)imide (TFSI) (PDDATFSI), or combinations thereof. In aspects, the optional first coating 106 can comprise at least one of, or at least two of, or at least three elements selected from a group consisting of nitrogen, carbon, cobalt, titanium, tantalum, and tungsten.

[0089] In aspects, the optional second interlayer or coating 110 can comprise the materials or aspects discussed above the optional first coating 106 and / or the interlayer 114. In aspects, the optional second interlayer or coating 110 can comprise an anode protector, for example, electrolyte additives (e.g., LiNO3, lanthanum nitrate, copper acetate, P2S5, etc.), artificial interfacial layers (e.g., Li3N, (CH3)3SiCl, A12O3, LiAl, etc.), composite metafiles (e.g., Li?B6, Li-rGO (reduced graphene oxide), layered Li-rGO, etc.), or combinations thereof. In aspects, the optional second interlayer or coating 110 can comprise a thin layer of metal (e.g., Au) that may be ion-sputter coated to form a contact interface between the anode 112 the solid-state electrolyte 108 and another material of the optional second interlayer or coating 110. In aspects, the optional second interlayer or coating 110 can comprise a coating of lithium fluoride. In aspects, as shown in FIG. 2, the solid-state battery 201 may not have the optional second interlayer or second coating such that the anode 112 contacts the solid-state electrolyte 108.

[0090] As shown in FIGS. 1-2, the anode 112 can be disposed on the solid-state electrolyte 108. In aspects, as shown in FIG. 2, the first major surface 113 of the anode 112 can be disposed on the first major surface 107 of the solid-state electrolyte 108. In aspects, an average thickness of the anode 112 when the solid-state battery 201 is in a fully charged state (defined below) can be 1 micrometer (pm) or more, 10 pm or more, 50 pm or more, 100 pm or more, 150 pm or more, 500 pm or less, 400 pm or less, 300 pm or less, or 250 pm or less, for example, in a range from 1 pm to 500 pm, from 10 pm to 400 pm, from 50 pm to 300 pm, from 100 pm to 300 pm, from 150 pm to 250 pm, or any range or subrange therebetween.

[0091] The anode 112 is a lithium-containing anode. In aspects, the lithium-containing anode can consist essentially of lithium metal. Alternatively, in aspects, the lithium-containing anode can comprise an alloy of lithium and at least one of magnesium (Mg), silver (Ag), or combinations thereof. In further aspects, the lithium-containing alloy can further comprise a second component selected from a group consisting of calcium (Ca), aluminum (Al), gallium (Ga), boron (B), carbon (C), silicon (Si), tin (Sn), zinc (Zn), indium (In), antimony (Sb), silver (Ag), and combinations thereof. Exemplary aspects of the second component include calcium (Ca), tin (Sn), and silver (Ag). Providing a lithium-containing anode comprising a lithium alloy can increase a wettability of the anode on the coating, which can decrease interfacial resistance of the battery (e.g., by achieving and / or maintaining good contact with the solid-state electrolyte through the coating), facilitate a high area capacity of the battery, and / or facilitate a high charging current density of the battery.

[0092] FIG. 2 illustrates a solid-state battery 201. As shown in FIG. 2, the solid-state battery 201 can comprise a coin-cell form, although the battery can comprise another form in other aspects. Compared to FIG. 1, FIG. 2 is a simplified solid-state battery 201 because the optional first coating 106 is omitted. Consequently, the interlayer 114 can be in direct contact with the cathode 104 and the solid-state electrolyte 108, for example, because the optional first coating 106 is omitted. In aspects, as shown in FIG. 2, the area of the first major surface 113 of the anode 112 can be less than or equal to (e.g., less than) the area of the first major surface 107 of the solid-state electrolyte 108. In further aspects, as shown, the area of the first major surface 113 of the anode 112 can be substantially equal to a corresponding area of the cathode 104. Alternatively, as shown in FIG. 1, the area of the first major surface 113 of the anode 112 can be substantially equal to the area of the first major surface 107 of the solid-state electrolyte 108. In aspects, as shown in FIG. 2, an electrically insulating layer 205a and 205b can be positioned between the first current collector 102 and the second current collector 116 to prevent a short circuit in the solid-state battery201 and / or to form a barrier protecting the contents of the solid-state battery 201. As used herein, the electrically insulating layer 205a and 205b comprises an electronic conductivity of 10'5S / cm or less. In even further aspects, as shown, the electrically insulating layer 205a and 205b can be configured to maintain a configuration of the solid-state battery 201, for example, by preventing the solid-state electrolyte 108 from contacting the second current collector 116. In further aspects, the electrically insulating layer 205a and 205b can comprise a polymeric material, for example, a fluoropolymer, a rubber, a polyurethane, or a silicone. In aspects, as shown, the solid-state battery 201 can further comprise an electrically conductive spacer 203 positioned between the anode 112 and the second current collector 116. In further aspects, the electrically conductive spacer 203 can comprise a foam (e.g., Ni foam), which can help maintain contact between adjacent components of the solid-state battery and / or control an amount of stress that the components of the solid-state battery are subjected to. Although not shown, an electrically conductive spacer can be positioned between the cathode and the first current collector.

[0093] As used herein, “interfacial resistance” and “ionic conductivity” are measured using electrical impedance spectroscopy (EIS) at 60°C for frequencies from 0.1 Hertz (Hz) to 1 MegaHertz (MHz). Unless otherwise indicated, EIS was measured using a Solartron 1260A (Solartron) impedance analyzer. A Nyquist plot is constructed with the real component of impedance (Z’ measured in Q cm2) on a horizontal axis and the imaginary component of impedance (Z” measured in Q cm2) on a vertical axis. Throughout the disclosure, “interfacial resistance” is defined as the difference between the real components of the impedance for the end-points of an arc shape in EIS results (i.e., Nyquist plot), where the higher end-point is taken as an inflection point in the impedance results. For determining “interfacial resistance”, the battery is configured to be used with a lithium -containing anode disposed on the first major surface of the solid-state electrolyte and the second major surface of the solid-state electrolyte facing a cathode. In aspects, the interfacial resistance can be 60 Q cm2or less, 50 Q cm2or less, 40 Q cm2or less, 30 Q cm2or less, 25 Q cm2or less, or 20 Q cm2or less. In aspects, the interfacial resistance can range from 10 Q cm2to 60 Q cm2, from 10 Q cm2to 50 Q cm2, from 10 Q cm2to 40 Q cm2, from 15 Q cm2to 30 Q cm2, from 20 Q cm2to 25 Q cm2, or any range or subrange therebetween.

[0094] Aspects of furnace systems in accordance with present disclosure will now be discussed with reference to FIGS. 3-6 and the materials properties presented in FIGS. 7-9. As shown in FIGS. 3-6, the furnace system 301 or 601 comprises a heating chamber 303 or 603 (boundaries not shown) having a heater 304a-304b or 604a-604b. For example, the heater 304a- 304b or 604a-604b can comprise an electrical (e.g., resistive, infrared) heater and / or a combustion (e.g., gas) furnace. The heating chamber 303 or 603 can comprise one or more heaters, for example, two heaters 304a-304b or 604a-604b are shown in both FIGS. 3 and 6. The heating chamber 303or 603 can be an oven, a furnace, a kiln, and / or a lehr. In further aspects, as shown, the furnace system 301 or 601 can comprise a conveyance path that a green tape is configured to travel along (see arrow 302 or 602) through the heating chamber 303 or 603.

[0095] In aspects, as shown in FIGS. 3-6, a green body 331 (e.g., becoming a sintered article as a result of heating while in the furnace system - heating chamber) in configured to come into contact with a contact material 327, 343, or 627 while the green body 331 is in the heating chamber. As shown, the first major surface 333 of the green body 331 can be in contact (i.e., direct contact) with a contact surface 323 or 623 comprising the contact material 327, 343, or 627. In further aspects, as shown in FIG. 3, the green body 331 can translate relative to the contact surface 323 as the green body is conveyed along the travel path (see arrow 302), although the conveyance means are not shown for clarity. Alternatively, as shown in FIG. 6, the green body 331 can translate together with the contact surface 623 for at least a portion of the conveyance path (see arrow 602 and 604) through the heating chamber 303, for example, with the contact surface 623 being part of a setter 621 that is conveyed through the heating chamber 303 and, in turn, conveys the green body 331, although other arrangements are possible in other aspects. For example, an opposite surface 625 of the setter 621 can slide along (e.g., contact) a surface 643 of the floor 641, and this translation of the setter 621 conveys the green body 331. In aspects, a thickness 629 of the setter 621 can be within one or more of the ranges discussed below for the coating thickness 349.

[0096] Without wishing to be bound by theory, lithium -containing materials can be highly reactive when heated at or near sintering temperatures. For example, lithium can volatize from the material being heated, which can change the composition of the resulting article and / or react with another material. Additionally, it has been observed that commonly available refractory materials, including MgO, will react with lithium-containing materials being sintered while in contact with said refractory material. These reactions can occur even at low oxygen partial pressures in the heating chamber. Also, this reaction results in the lithium-containing material sticking (e.g., bonding) to the refractory material (e.g., MgO), which impedes processing and yield of the sintering process . Similar to MgO, it has been observed that sticking or other reactions occurs when using other materials in contact with the lithium-containing materials being heated, including platinum, alumina, zirconia, silicon carbide, aluminum nitride, and cordierite. However, the inventors of the present disclosure have unexpectedly discovered (especially in view of the abovestate problem) contact materials that can be used to sinter lithium-containing materials without sticking or other reactions. In aspects, the contact material is non-reactive with the lithium- containing material (e.g., lithium garnet) while being heated at 1000°C in an argon environment for 30 minutes or more (e.g., 30 minutes, 45 minutes, 60 minutes). In aspects, the contact materialdoes not stick to the lithium -containing material (e.g., lithium garnet) after being heated at 1000°C in an argon environment for 30 minutes or more (e.g., 30 minutes, 45 minutes, 60 minutes).

[0097] In preferred aspects, the contact material 327, 343, or 627 comprises iridium, osmium, rhenium, or an alloy thereof. Additionally or alternatively, the contact material (e.g., first contact surface) can comprise platinum (including platinum alloys). A rationalization of the performance of these contact materials is now provided with reference to FIGS. 7-9 to allow these observations to be generalized. Representative properties discussed herein include, the melting temperature (Tm), tolerable gas-phase oxygen concentration (Tol. Gas Ox. Cone.), lithium gasphase concentration (Li Gas Cone.), and activity.

[0098] First, materials are generally less stable near their melting temperatures. For example, materials can more easily be deformed near their melting temperature and / or materials can be sintered at temperatures below (but near) the melting temperature. Consequently, a material having a melting temperature greater than a maximum temperature encountered in the heating chamber is expected to have improved mechanical stability and less likely to spread onto a green body in contact with it than another material having a lower melting temperature. For example, the melting temperature of various material is shown along the horizontal axis 701 or 801 (i.e., x-axis) of FIGS. 7-8. As shown, nickel and iron have melting temperatures near and / or below 1500°C, which makes these materials less likely to perform desirably as a contact material. In contrast, iridium, osmium, and rhenium have melting temperatures greater than or equal to 2000°C, 2200°C, and 2400°C.

[0099] Second, sticking between the green body being sintered and the contact material can occur due to reactions therebetween. Without wishing to be bound by theory, it is believed that some of these reactions can involve the formation of oxides of material from the contact material and / or the volatilization of material from the contact material, which can be enhanced in the presence of oxygen, especially when the contact material includes a metal. For example, sticking can occur as the result of oxide reaction products at the contact surface interacting with the first major surface of the green body. Consequently, the contact materials may preferably have a low volatilization and low reactivity with oxygen at temperatures encountered by the contact material in the heating chamber. As discussed below, the oxygen concentration (and / or carbon dioxide concentration) of an environment in the heating chamber can be minimized (e.g., 10 Pascals or less). Still, a contact material that can tolerate higher oxygen concentration without substantial volatilization can reduce an incidence of sticking when heating (e.g., firing, sintering) a green body in contact with the contact surface. As used herein, the “tolerable gas-phase oxygen concentration” (Tol. Gas Ox. Cone.) is defined as a maximum oxygen concentration in an environment otherwise containing 1 atmosphere of argon that produces a gas-phase concentration of the contact materialof less than or equal to 10'8atmospheres when the contact material is heated at 1200°C in the environment, which includes oxides of the contact material. Unless otherwise indicated, gas-phase concentrations of the contact material and / or lithium is determined using mass spectroscopy, and the atmosphere contains a partial pressure of water vapor less than or equal to 10 Pascals. Also, the concentration of oxygen is determined in accordance with ASTM D6522-20, unless otherwise indicated. For example, a (base- 10) logarithm of the Tol. Gas Ox. Cone, of various material is shown along the vertical axis 703 (i.e., y-axis) of FIG. 7. Specifically, the value of the Tol. Gas Ox. Cone, in FIG. 7 was based on a maximum amount of oxygen in the atmosphere that keeps a concentration of gas phase species of the material below 10'12atmospheres at 1200°C. As shown, platinum (Pt), rhenium (Re), iridium (Ir), titania (TiO2), zinc oxide (ZnO), alkaline earth oxides (e.g., MgO, BaO), lanthanum oxide, scandia (SCO2), hafnium oxide, and zirconia (ZrO2) have a tolerable gas-phase oxygen concentration greater than or equal to IO'10atmospheres at 1200°C in an (otherwise, excluding the oxygen) 1 atmosphere argon environment. Additionally or alternatively, a gas-phase concentration of the contact material (including oxides thereof) when heated at 1200°C in an environment (having IO'10atmospheres oxygen in an otherwise 1 atmosphere argon environment) can be less than or equal to 10'8atmospheres. Additionally or alternatively, when the contact material (e.g., first contact surface) consists of a metal (and / or an oxide-free alloy of metals), a surface concentration of an oxide of the contact material is less than or equal to 10'6mol% on the first contact surface when heated at 900°C in a 1 atmosphere argon environment with less than or equal to 10 Pascals of water vapor (and / or when heated in contact the green tape during the heating). In even further aspects, when the contact material (e.g., first contact surface) consists of a metal (and / or an oxide-free alloy of metals), an oxide (e.g., of the contact material) may not be formed on the surface of the contact material when the contact material is heated at 1200°C in an environment having IO'10atmospheres oxygen in an otherwise 1 atmosphere argon environment. In even further aspects, when the contact material (e.g., first contact surface) consists of a metal (and / or an oxide-free alloy of metals), an oxide (e.g., of the contact material) may not be formed on the surface of the contact material when the contact material is heated at 1200°C in an environment having 10'9(or even 10'8) atmospheres oxygen in an otherwise 1 atmosphere argon environment (having less than 10 Pascals of water vapor).

[0100] Third, lithium volatilization during heating (e.g., sintering of a lithium-containing green body) can alter the properties of the resulting sintered article. Additionally, increased lithium volatilization can be an indication of reactions occurring between the green body (i.e., a lithium- containing green body) and a contact material, which can lead to sticking therebetween. As used herein, the “lithium gas-phase concentration” (Li. Gas. Cone.) refers to a gas-phase concentration of lithium produced when the contact material is in contact with a lithium garnet green body at1200°C in a 1 atmosphere argon environment. For example, a (base-10) logarithm of the Li Gas. Cone. 1200°C of various material is shown along the vertical axis 803 (i.e., y-axis) of FIG. 8. As shown, nickel, platinum (Pt), rhenium (Re), iridium (Ir), alkaline earth oxides (e.g., MgO, BaO), lanthanum oxide, osmium (Os), and rhodium (Rh) have a Li. Gas. Cone, of less than or equal to 10'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C.

[0101] Fourth, a potential of the contact material to participate in reactions can be minimized. As used herein, “activity” refers to thermodynamic activity, which describes a deviation of the chemical potential p from a reference chemical potential go (e.g., measured at standard temperature and pressure) as an exponential of a quantity of the difference in chemical potential divided by the product of the ideal gas constant R and temperature T in Kelvin (i.e., exp((p - go) / RT). Consequently, a reactivity can be minimized when the activity is minimized. For example, a (base-10) logarithm of the activity of various material is shown along the vertical axis 903 (i.e., y-axis) of FIG. 9. FIG. 9 schematically illustrates curves showing a (base-10) logarithm of an activity of different materials on the vertical axis 903 (i.e., y-axis) as a function of temperature (Temp) in °C on the horizontal axis 901 (i.e., x-axis). Since the formation of reactive oxides at the surface (for contact materials that are not oxides) as well as the volatilization of the contact material (including oxides thereof) can be problematic, the curves in FIG. 9 correspond to the maximum activity of the contact material to either process. The data for FIG. 9 was determined using Equilib module of FactSage software with the following constraints: activity of Li2O(s) = contact material metal(s) = 1 (the materials are stable); pressure = 1 atmosphere of argon gas; activity solid metal oxides: activity ofNiO(s) <= 0.9, activity of LiReO4(s) <= 0.8, and / or activity of IrO2(s) <= 0.05; and activity of the metal oxide in the gas phase: activity of PtO2(g), Re2O7(g), and IrO2(g) are all <= 10'8. In FIG. 9, curve 905 corresponds to platinum, curve 907 corresponds to iridium (Ir), curve 909 corresponds to osmium (Os), curve 911 corresponds to rhenium (Re), and curve 913 corresponds to nickel (Ni). As shown, platinum (curve 905) has an activity greater than or equal to 10'5for the temperature range shown, whereas Ir, Os, Re, and Ni (curves 907, 909, 911, and 913) have activities less than or equal to 10'5for the temperature range shown. Further, Os, Re, and Ni (curves 909, 911, and 913) have activities less than or equal to 10'5for the temperature range shown.

[0102] In aspects, a melting temperature of a contact material can be greater than or equal to 1500°C, greater than or equal to 1750°C, greater than or equal to 2000°C, greater than or equal to 2200°C, and / or greater than or equal to 2400°C. In aspects, a melting temperature of a contact material can be greater than a maximum temperature encountered by the contact material in the heating chamber by 50°C or more, 100°C or more, 150°C or more, 200°C or more, 300°C or more, or 500°C or more. In aspects, the contact material can have a tolerable gas-phase oxygenconcentration greater than or equal to IO'10atmospheres (atm) (e.g., from IO'10atm to 0. 1 atm, from IO'8atm to 10'3from 10'7atm to 10'4atm, from 5x1 O'6atm to 10'5atm, or any range or subrange therebetween), at 1200°C in an (otherwise, excluding the oxygen) 1 atmosphere argon environment. In aspects, the contact material can exhibit a gas phase lithium concentration less than or equal to 10'5atmospheres (atm) (e.g., from 10'7atm to 10'5atm, from 10'6atm to 8xl0'6atm, or any range or subrange therebetween) when the contact material is in contact with a lithium garnet at 1200°C. As used herein, the “gas phase lithium concentration” includes all lithium species in the gas phase (not just elemental lithium). Unless otherwise specified, the argon environment for determining the “gas phase lithium concentration” has less than or equal to 10 Pascals of water vapor. In aspects, an activity of the contact material (e.g., at 900°C or 1200°C in a 1 atm argon atmosphere having less than 10 Pascals water vapor and less than 10'8or less than 1 O'10atm oxygen; and / or at a maximum temperature encountered by the contact material in the heating chamber) can be less than or equal to 10'5, less than or equal to 10'7, less than or equal to 10'9, or less than or equal to IO'10. In aspects, an activity of the contact material (e.g., at 900°C or 1200°C in a 1 atm argon atmosphere having less than 10 Pascals water vapor and less than 10'8or less than 1 O'10atm oxygen; and / or at a maximum temperature encountered by the contact material in the heating chamber) can be greater than or equal to IO'10, greater than or equal to 10'9, greater than or equal to 10'8, or greater than or equal to 10'7. For example, the activity of contact material (e.g., at 900°C or 1200°C in a 1 atm argon atmosphere having less than 10 Pascals water vapor and less than 10'8or less than 10'10atm oxygen; and / or at a maximum temperature encountered by the contact material in the heating chamber) can be from 10'23to 10'5, from 10'15to 10'5, from 10'13to 10'7, from 10'10to 10'7, from 10'9to 10'8, or any range or subrange therebetween. Based on these criteria and the properties presented in FIGS. 7-8, potential contact materials can be selected from a group consisting of nickel (Ni), platinum (Pt), iridium (Ir), osmium (Os), rhenium (Re), rhodium (Rh), calcium oxide (CaO), magnesium oxide (MgO), lanthanum oxide, alloys containing one or more of these materials, alloys thereof, and combinations thereof. In further aspects, the contact material can comprise and / or be selected from a group consisting of platinum (Pt), iridium (Ir), osmium (Os), rhenium (Re), rhodium (Rh), calcium oxide (CaO), magnesium oxide (MgO), alumina (AI2O3), tungsten oxide (W O3), alloys thereof, and combinations thereof. In even further aspects, the contact material can comprise and / or be selected from a group consisting of iridium (Ir), osmium (Os), rhenium (Re), alloys containing one or more of these materials, alloys thereof, and combinations thereof. As indicated in FIG. 9, iridium (Ir), osmium (Os), and rhenium (Re) are exemplary for their low activities over temperatures encountered in the heating chamber while satisfying the conditions discussed above with reference to FIGS. 7-8. In even further aspects, where the contact material is configured to be in contact with a green body at a location where thegreen tape is configured to encounter a maximum temperature can comprise and / or consist of iridium (Ir), osmium (Os), rhenium (Re), alloys thereof, and combinations thereof.

[0103] Alternatively, in aspects, the contact surface 323 or 623 and / or the contact material 327, 343, or 627 comprising a lithium metal oxide where the metal is selected from a group consisting of scandia, yttrium, and combinations thereof. An exemplary aspects of the lithium metal oxide is lithium scandium oxide (e.g., LiScO2). In further aspects, the contact surface and / or the contact material can comprise the lithium metal oxide (e.g., LiScCh) can have up to 10 vol%, less than or equal to 7 vol%, less than or equal to 5 vol%, less than or equal to 2 vol%, and / or less than or equal to 1 vol% of a corresponding metal oxide (of the same metal as in the lithium metal oxide). For example, when the lithium metal oxide is lithium scandium oxide, the metal is scandium and the corresponding metal oxide is scandia (e.g., SC2O3). Alternatively, in further aspects, the contact surface and / or the contact material can comprise the lithium metal oxide (e.g., LiScCh) without any of the corresponding metal oxide (e.g., SC2O3). For example, as discussed with reference to the examples herein, XRD analysis confirms that lithium scandium oxide crystals can be formed without a secondary phase (e.g., scandia). In further aspects, the lithium metal oxide (of the contact surface and / or the contact material) can have the lithium in an octahedral (or distorted octahedral) coordination with oxygen atoms. In further aspects, the contact surface and / or the contact material can additionally (i.e., in addition to the lithium metal oxide) include additional lithium metal oxides that are isostructural with the lithium metal oxide. For example, in such aspects, Li2MgZrO2 can be present in combination with LiScCh as the lithium metal oxide since there are crystal phases of these materials that are isostructural. Without wishing to be bound by theory, when materials having isostructural crystal phases are present, these materials can form a solid-state solution thereof. Additionally or alternatively, the lithium metal oxide can be a majority of the contact material and / or contact surface as a composite with MgO, La2Zr2O?, and / or Li AlCh. In further aspects, the contact material can be fully dense (e.g., greater than or equal to 95% relative density, greater than or equal to 97% relative density, greater than or equal to 98% relative density, greater than or equal to 99% relative density, less than or equal to 100% relative density) and / or be free of open porosity. For example, as discussed in the examples herein and in reference to FIG. 12, lithium scandium oxide (as the lithium metal oxide) can be made fully density and without open porosity. Providing the lithium metal oxide of the present disclosure can enable higher oxygen conditions to be used in contact with a green tape (e.g., lithium-containing material, doped or undoped lithium garnet) than otherwise possible without sticking therebetween, reactions therebetween, and / or limited (or no) lithium loss. For example, as demonstrated in the Examples here, lithium scandium oxide (as the lithium metal oxide) can be used as a contact material with a lithium garnet tape being sintered at 1200°C in a 3% oxygen environment, 1200°C in air, and / or1325°C in a 5% oxygen environment. In further aspects, the lithium metal oxide material discussed in this paragraph can have properties within one or more of the ranges discussed in the previous paragraph or otherwise herein (e.g., melting temperature greater than or equal to 1500°C, a tolerable gas-phase oxygen concentration greater than or equal to 10-10 atmospheres (atm), a gas phase lithium concentration less than or equal to 10'5atm when the contact material is in contact with a lithium garnet at 1200°C in a 1 atmosphere argon environment with less than or equal to 10 Pascals of water vapor). Alternatively or additionally, the melting temperature of the lithium metal oxide can be less than 1500°C while still at least 50°C greater than a maximum temperature encountered by the tape in contact with this contact material (and / or a maximum temperature that the tape is configured to encounter while in contact with this contact material). As used herein, an “oxygenated gas phase lithium concentration” refers to a gas-phase concentration of lithium (i.e., all lithium species in the gas phase) when the contact material is in contact with a lithium garnet green body at 1200°C in a 1 atmosphere environment, where the environment is 3% oxygen and less than 10 Pascals of water vapor with the balance being argon. In aspects, the “oxygenated gas phase lithium concentration of the contact material (e.g., lithium metal oxide) can be less than or equal to IO'5atm. Without wishing to be bound by theory, it is believed that the lack of lithium- content structures that are thermodynamically stable beyond 1: 1 (i.e., Li2O — M2O3 producing LiMCh where M is Sc, Y, and / or La) indicates that these contact materials are stable against Li2O formation and / or decomposition.

[0104] FIG. 10 schematically illustrates curves showing a (base-10) logarithm of a gasphase concentration of lithium materials ([LiX](g) - in wt%) on the vertical axis 1003 (i.e., y-axis) as a function of a (base-10) logarithm of a partial pressure of oxygen (PO2 - in atm) on the horizontal axis 1001 (i.e., x-axis). Curve 1007 corresponds to a gas-phase concentration of lithium materials of a lithium garnet, where the partial pressure of water vapor is 25xl0'6atm. Curve 1005 corresponds to a gas-phase concentration of lithium materials of a lithium garnet, where the partial pressure of water vapor is 1 O'20atm. As shown, the higher water vapor content for curve 1007 leads to a greater gas-phase lithium concentration than the lower water vapor content for curve 1005. Also, the higher gas-phase concentration of lithium in curves 1005 and 1007 at extremely low oxygen partial pressures are due to the highly reducing nature of that environment, which leads to lithium volatilization. At moderate amounts of oxygen, the environment is less reducing, which leads to less lithium volatilization. Consequently, providing a contact material that can tolerate higher oxygen content can enable reduced lithium volatilization from the lithium-containing material being sintered thereon due to the less reducing atmosphere in higher oxygen-containing atmospheres.

[0105] In aspects, as shown in FIGS. 3-5, a floor 321 of the conveyance path (see arrow 302) can comprise the contact material 327 at the contact surface 323 thereof. In further aspects, when the dashed horizonal lines are not present in FIG. 3 (see FIG. 4), the floor 321 can comprise and / or consist of the same composition as the contact material 327 (e.g., at the contact surface 323) throughout the thickness of the floor (e.g., from contact surface 323 to opposite surface 325 in FIG. 3). Alternatively, in further aspects, as indicated in FIG. 3 with the dashed horizontal lines and in FIG. 5, the contact material 343 at the contact surface 323 of the floor 321 can be a coating (e.g., having coating thickness 349) on another material 345. For example, in even further aspects, the material of the contact material 343 (e.g., coating material) can extend to a depth 341 from the contact surface 323, corresponding to a coating thickness 349 of the coating (comprising the contact material) that can be 1 micrometer (pm) or more, 5 pm or more, 10 pm or more, 50 pm or more, 250 pm or more, 500 pm or more, 1 mm or more, 50 mm or less, 10 mm or less, 5 mm or less, 2 mm or less, 1 mm or less, 800 pm or less, 400 pm or less, 200 pm or less, 100 pm or less, or 80 pm or less (e.g., from 1 pm to 50 mm, from 5 pm to 10 mm, from 50 pm to 5 mm, from 250 pm to 2 mm, from 500 pm to 1 mm, or any range or subrange therebetween). In such aspects, the another material 345 need not comprise the contact material since the green body is protected from the other material 345 by the contact material 343 coated thereon. In even further aspects, the another material 345 can comprise alumina, nickel, tungsten, chromium, mullite, or combinations thereof. Alternatively, as discussed above with reference to FIG. 6, the green body may not contact the floor 641 of the conveyance path; instead, the green body 331 can translate together with the contact surface 623 for at least a portion of the conveyance path (see arrow 602 and 604) through the heating chamber 303, for example, with the contact surface 623 being part of a setter 621 that is conveyed through the heating chamber 303 and, in turn, conveys the green body 331, although other arrangements are possible in other aspects.

[0106] In aspects, as shown in FIG. 3 with the vertical lines, the contact material 327 or 343 of the contact surface 323 may not extend for an entire length of the conveyance path of the heating chamber 303, although the contact material of the contact surface can extend for the entire length of the conveyance path through the heating chamber in other aspects. In further aspects, the contact material 327 or 343 can be present for an extent between boundaries 352a and 352b, which can correspond to a region of the conveyance path where the green body is configured to encounter a maximum temperature while traveling through the heating chamber. In even further aspects, the floor 321 can further comprise a second contact surface 353 or 363 comprising a second contact material 351 or 361 different from the contact material 327 or 343, where the green body 331 is configured to contact the second contact surface 353 or 363 (e.g., second contact material) 351 or 361 for a portion of the conveyance path within the furnace chamber. In still further aspects, thelocation of the second contact surface 353 or 363 may not correspond to a location where the green tape is configured to encounter the maximum temperature, and / or the second contact surface 353 or 363 can be adjacent to (e.g., positioned on one or both sides of) the contact surface 323 or 343 along the conveyance path. Due to the lower temperature encountered by the second contact material, a wider range of material can be used than for the contact material 327 or 343. In still further aspects, the second contact material 351 or 361 can comprise and / or be selected from a group consisting of platinum (Pt), iridium (Ir), osmium (Os), rhenium (Re), rhodium (Rh), calcium oxide (CaO), magnesium oxide (MgO), alumina (AI2O3), tungsten oxide (WO3), alloys thereof, and combinations thereof.

[0107] Aspects of methods of firing a green body (e.g., green tape) and / or forming solid- state electrolyte or a battery (e.g., solid-state battery) in accordance with aspects of the disclosure will be discussed with reference to example method steps illustrated in FIGS. 3-6. As used herein, “green tape” refers to an article that contains particles that are not sintered together but can be by heating at the conditions described herein (e.g., 800°C or more, from 800°Cto 1500°C for 1 minute or more - from 1 minute to 12 hours). Unless otherwise indicated, “green tape” is intended to include both (1) the cast article including an organic binder and optionally a solvent and (2) the cast article after the organic binder has been removed prior to sintering. In aspects, the green tape can be free of binder prior to contacting the first contact surface (discussed herein). Methods can comprise providing a green body (e.g., green tape), which can be provided by purchase or produced (e.g., by a tape casting method - as discussed below - or compressing precursor materials) having inorganic crystals. A thickness 339 of the green body can be within one or more of the ranges discussed above for the thickness of the sintered article.

[0108] In aspects, producing the green body (e.g., green tape) can comprise producing a lithium-containing inorganic material (e.g., lithium garnet, lithium cobaltite, etc.) having inorganic crystals. In further aspects, methods can comprise forming a powder of the lithium-containing inorganic material, although the powder can be provided (e.g., by purchase) in other aspects. For example, stoichiometric amounts of component materials (e.g., LiOH FhO for Li, La2C>3 for La, ZrCL for Zr - in lithium garnet) including any selected dopant (e.g., Ta, In, Si, Ge, Sn, V, W, Te, Nb, and / or other dopants discussed above) with an optional slight excess (e.g., 2 wt% excess, from 0.5 wt% to 50 wt%, from 2 wt% to 40 wt%, from 5 wt% to 30 wt%, from 10 wt% to 25 wt%, from 15 wt% to 20 wt%, or any range or subrange therebetween) of lithium (added by superaddition to compensate for volatilization during heating) to form a mixture. In exemplary aspects, the inorganic material (e.g., inorganic crystals) can comprise a lithium cobaltite or a lithium garnet that can optionally be doped with Ta. The mixture can be mixed (e.g., milled) with a grinding media (e.g., yttrium-stabilized zirconia balls) and optional solvent (e.g., isopropanol) tohomogenize the mixture. In further aspects, the solvent can be a polar protic solvent, for example water or alcohols (e.g., methanol, ethanol, isopropyl alcohol, acetic acid), or a polar aprotic solvent, for example a ketone (e.g., methyl ethyl ketone, acetone), N,N-dimethylformamide, dimethyl sulfoxide, dimethyl sulfoxide, dimethyl carbonate, methyl ethyl ketone, toluene, anisole, dioxolane, methoxy propyl acetate, or combinations thereof. Additionally, a binder and optionally a protic base, a plasticizer, a dispersant, a viscosity modifier, and / or a defoamer can be added to the mixture to form a slip. As used herein, a “dispersant” refers to a material that improves a separation of particles, improves a uniformity of a distribution of particles, decreases particle aggregation, and / or reduces settling of particles. The binder can provide mechanical strength to the green body (e.g., green tape) before and / or during the sintering. For example, the binder can comprise an acrylic polymer, a methacrylate polymer, a carbonate-containing polymer, a vinyl acetate resin, a maleic acid polymer, a vinyl butyral resin, a vinyl formal resin, a vinyl alcohol resin, a cellulose resin, or copolymers or combinations thereof. An amount of binder, as a wt% of the slip, can be from 10 wt% to 15 wt%, from 11 wt% to 14.5 wt%, from 12 wt% to 14 wt%, from 12.5 wt% to 14 wt%, from 13 wt% to 13.5 wt% or any range or subrange therebetween. In further aspects, an amount of the solvent in the slip (as a wt% of the total slip) can be in a range from 10 wt% to 30 wt%, from 15 wt% to 25 wt%, from 16 wt% to 23 wt%, from 17 wt% to 22 wt%, from 18 wt% to 21 wt%, from 19 wt% to 20 wt%, or any range or subrange therebetween. In further aspects, an amount of the inorganic material (e.g., inorganic grains) in the slip (as a wt% of the total slip) can be in a range from 55 wt% to 70 wt%, from 60 wt% to 70 wt%, from 62 wt% to 69 wt%, from 63 wt% to 68 wt%, from 64 wt% to 67 wt%, from 65 wt% to 66 wt%, or any range or subrange therebetween. In further aspects, the slip can be deaired (e.g., subjected to reduced pressure and / or rested for a period of time) to remove gas bubbles within the slip. The mixture and / or slip can be tape cast (e.g., extruded and / or using a doctor blade) to form a green body (e.g., green tape).

[0109] As shown in FIGS. 3-6, methods of the present disclosure comprise heating (e.g., firing, sintering) the green body 331 (e.g., green tape) in an atmosphere (e.g., of a heating chamber 303) to sinter the inorganic material (e.g., lithium-containing inorganic material, inorganic grains). In aspects, the inorganic grains of the green body can comprise a lithium-containing inorganic material within one or more of the corresponding materials discussed above (e.g., lithium garnet compositions). For example, the green body 331 can be heated by one or more heaters 304a-304b or 604a-604b (e.g., in a heating chamber 303). In aspects, as shown in FIGS. 3-6, heating the green body 331 (e.g., green tape) can comprise conveying the green body 331 along a conveyance path (as indicated by arrow 302 or 602) through the heating chamber 303, although the green body 331 can be placed in an oven (e.g., to be batch fired) without being conveyed during at least aportion of the heating in further aspects. Although not shown, it is to be understood that the green body can be heated prior to being sintered (e.g., in the heating chamber), for example, to remove solvent and / or binder from the green body, although the heating an occur entirely within a heating chamber in other aspects. In aspects, as shown in FIGS. 3-6, the green body 331 (e.g., green tape, first major surface 333) can be in contact with a contact surface 323 or 623 (e.g., contact material 327, 343, or 627) during at least part of the heating. In further aspects, the contact material 327, 343, or 627 can be non-reactive with the green body 331 (e.g., green tape) during the heating. Additionally or alternatively, in further aspects, the green body 331 (e.g., green tape - and the resulting sintered tape) does not stick to the contact surface 323 or 623 (e.g., contact material 327, 343, or 627) as a result of the heating. Additionally or alternatively, when the contact material comprises a non-oxide metal compound, a surface concentration of an oxide of the contact material (if any) is less than or equal to IO'6mol% on the first contact surface when heated in contact with the green tape during the heating.

[0110] In further aspects, the contact material 327, 343, or 627 can comprise one or more of the corresponding materials discussed above. In even further aspects, the contact material 327, 343, or 627 can comprise and / or be selected from a group consisting of iridium (Ir), osmium (Os), rhenium (Re), alloys containing one or more of these materials, alloys thereof, and combinations thereof. In even further aspects, the contact material 327, 343, or 627 can be in contact with the green body 331 (e.g., green tape) at a location where the green body 331 encounters a maximum temperature. In further aspects, a melting temperature of a contact material can be greater than or equal to 1500°C, greater than or equal to 1750°C, greater than or equal to 2000°C, greater than or equal to 2200°C, and / or greater than or equal to 2400°C. In aspects, a melting temperature of a contact material can be greater than a maximum temperature encountered by the contact material in the heating chamber by 50°C or more, 100°C or more, 150°C or more, 200°C or more, 300°C or more, or 500°C or more. In aspects, the contact material can have a tolerable gas-phase oxygen concentration greater than or equal to IO'10atmospheres (atm) (e.g., from IO'10atm to 0. 1 atm, from 10'8atm to IO'3from 10'7atm to IO'4atm, from 5x1 O'6atm to IO'5atm, or any range or subrange therebetween), at 1200°C in an (otherwise, excluding the oxygen) 1 atmosphere argon environment. In aspects, the contact material can exhibit a gas phase lithium concentration less than or equal to IO'5atmospheres (atm) (e.g., from 10'7atm to IO'5atm, from 10'6atm to 8xl0'6atm, or any range or subrange therebetween) when the contact material is in contact with a lithium garnet at 1200°C. In aspects, an activity of the contact material can be less than or equal to IO'5, less than or equal to IO'7, less than or equal to IO'9, or less than or equal to IO'10at a maximum temperature encountered by the contact material in the heating chamber (and / or 1200°C - otherwise; in a 1 atm argon atmosphere having less than 10 Pascals water vapor and less than 10'8or less than IO'10atm oxygen). In aspects, the activity of the contact material can be greater than or equal to IO'10, greater than or equal to 10'9, greater than or equal to 10'8, or greater than or equal to 1 O'7at a maximum temperature encountered by the contact material in the heating chamber (and / or 1200°C - otherwise; in a 1 atm argon atmosphere having less than 10 Pascals water vapor and less than 10'8or less than 1 O'10atm oxygen). In aspects, the activity of contact material can be from 10"23to IO'5, from 10'15to IO'5, from 10'13to IO'7, from IO'10to IO'7, from 10'9to IO'8, or any range or subrange therebetween at a maximum temperature encountered by the contact material in the heating chamber (and / or 1200°C - otherwise; in a 1 atm argon atmosphere having less than 10 Pascals water vapor and less than 10'8or less than 1 O'10atm oxygen).

[0111] In further aspects, as shown in FIG. 6, the green body 331 (e.g., green tape) can be positioned on (and in contact with) a setter 621 comprising the contact material 627 that is conveyed through the heating chamber 303 together with the green body 331 (e.g., conveying the setter 621 can, in turn, convey the green body 331 as indicated by arrows 602 and 604). Alternatively, as shown in FIGS. 3-5, in further aspects, the conveying can comprise translating the green body 331 (e.g., green tape) relative to the contact surface 323. For example, long green tapes can be conveyed through using a rollers system spanning a distance greater than the heating chamber 303. In even further aspects, as shown in FIGS. 3-4 and discussed above, the contact material 343 including the contact surface 323 can be coated on another material 345 different from the contact material. For example, the another material 345 can comprise alumina, nickel, tungsten, chromium, mullite, or combinations thereof. In even further aspects, as shown in FIG. 3, the contact material 327 or 343 can be present for an extent between boundaries 352a and 352b, which can correspond to a region of the conveyance path where the green body is configured to encounter a maximum temperature while traveling through the heating chamber. In even further aspects, the floor 321 can further comprise a second contact surface 353 or 363 comprising a second contact material 351 or 361 different from the contact material 327 or 343, where the green body 331 is configured to contact the second contact surface 353 or 363 (e.g., second contact material) 351 or 361 for a portion of the conveyance path within the furnace chamber. In still further aspects, the location of the second contact surface 353 or 363 may not correspond to a location where the green tape is configured to encounter the maximum temperature, and / or the second contact surface 353 or 363 can be adjacent to (e.g., positioned on one or both sides of) the contact surface 323 or 343 along the conveyance path. Due to the lower temperature encountered by the second contact material, a wider range of material can be used than for the contact material 327 or 343. In still further aspects, the second contact material 351 or 361 can comprise and / or be selected from a group consisting of platinum (Pt), iridium (Ir), osmium (Os), rhenium (Re),rhodium (Rh), calcium oxide (CaO), magnesium oxide (MgO), alumina (AI2O3), tungsten oxide (WO3), alloys thereof, and combinations thereof.

[0112] In aspects, the atmosphere (e.g., of the heating chamber 303) encountered by the green body 331 (e.g., green tape) during the heating can comprise a controlled (e.g., low) concentration of oxygen, water vapor, and / or carbon dioxide. Without wishing to be bound by theory, it is believed that the presence of oxygen and / or carbon dioxide can lead to undesired reactions (e.g., increased lithium volatilization, the formation of lithium carbonate) and / or sticking of the green body to the contact surface. In further aspects, a partial pressure of oxygen in the atmosphere can be less than or equal to 10 Pascals, less than or equal to 5 Pascals, less than or equal to 2 Pascals, or less than or equal to 1 Pascal. In further aspects, a concentration of oxygen in the atmosphere can be 100 parts-per-million (ppm) or less, 50 ppm or less, 20 ppm or less, or 10 ppm or less. In further aspects, a partial pressure of water vapor in the atmosphere can be less than or equal to 10 Pascals, less than or equal to 5 Pascals, less than or equal to 2 Pascals, or less than or equal to 1 Pascal. In further aspects, a dew point of the atmosphere can be less than or equal to 0°C, less than or equal to -20°C, or less than or equal to -50°C (e.g., from -270°C to 0°C, from -200°C to -20°C, from -100°C to -50°C, or any range or subrange therebetween). In further aspects, a partial pressure of carbon dioxide can be less than or equal to 10 Pascals, less than or equal to 5 Pascals, less than or equal to 2 Pascals, or less than or equal to 1 Pascal. In further aspects, a concentration of carbon dioxide in the atmosphere can be 100 parts-per-million (ppm) or less, 50 ppm or less, 20 ppm or less, or 10 ppm or less. In further aspects, the atmosphere can primarily comprise a noble gas, nitrogen, or a combination thereof. In even further aspects, the atmosphere can consist essentially of a noble gas, nitrogen, or a combination thereof. In further aspects, the atmosphere may be different close to the lithium -containing material (e.g., due to volatilization or reactions occurring in or near the lithium containing material); in such situations (and more generally), any of the above-mentioned aspects regarding the atmosphere (e.g., partial pressure and / or concentration of oxygen, partial pressure and / or concentration of water; concentration and / or partial pressure of carbon dioxide) can apply to the local environment around the lithium- containing material during the heating (as measured 5 mm from an outer surface of the lithium- containing material).

[0113] In aspects, the heating can comprise heating the green body 331 (e.g., green tape) at a maximum temperature for a period of time. Throughout the disclosure, heating “at” a specified temperature means that the heating provided from the local environment (e.g., heaters, oven) are maintained to provide a local temperature at the specified temperature. In aspects, the maximum temperature can be 800°C or more, 850°C or more, 900°C or more, 950°C or more, 1000°C or more, 1050°C or more, 1150°C or more, 1200°C or more, 1250°C or more, 1500°C or less, 1450°Cor less, 1400°C or less, 1350°C or less, 1300°C or less, 1250°C or less, 1200°C or less, 1150°C or less, 1100°C or less, 1050°C or less, 1000°C or less, or 950°C or less. In aspects, the maximum temperature can be in a range from 800°C to 1500°C, from 800°C to 1450°C, from 850°C to 1400°C, from 850°C to 1350°C, from 900°C to 1300°C, from 950°C to 1250°C, from 950°C to 1200°C, from 1000°C to 1150°C, from 1050°C to 1100°C, or any range or subrange therebetween. In aspects, a period of time at the maximum temperature can be 12 hours or less, 4 hours or less, 2 hours or less, 60 minutes or less, 45 minutes or less 30 minutes or less, 20 minutes or less, 15 minutes or less, 20 seconds or more, 1 minute or more, 5 minutes or more 10 minutes or more, 15 minutes or more, 20 minutes or more, or 30 minutes or more. In aspects, the period of time at the maximum temperature can be from 20 seconds to 12 hours, from 1 minute to 4 hours, from 5 minutes to 2 hours, from 10 minutes to 60 hours, from 15 minutes to 45 minutes, from 20 minutes to 30 minutes, or any range or subrange therebetween. Likewise, in further aspects, a total time that the green body is heated can be within one or more of the ranges discussed above in this paragraph for the period of time at the maximum temperature. As discussed above, the green body 331 (e.g., green tape) can be in contact with the contact surface 323 (e.g., contact material) when the green body is heated at the maximum temperature.

[0114] In aspects, the sintering can comprise a fast-firing process with a high heating ramp rate and a high cooling ramp rate in addition to a short heating time (e.g., at the maximum temperature and / or overall heating time). In further aspects, a heating ramp rate (HRR) encountered by the green tape (e.g., upon entering the heating chamber) can be greater than or equal to 100°C / min or greater than or equal to 250°C / min (e.g., 100°C / min < HRR < 1000°C / min; 250°C / min < HRR < 750°C / min). In further aspects, an absolute value of a cooling ramp rate (CRR) encountered by the green tape (e.g., upon leaving the heating chamber) can be greater than or equal to 100°C / min or greater than or equal to 250°C / min (e.g., 100°C / min < |CRR| < 1000°C / min; 250°C / min < |CRR| < 750°C / min).

[0115] In aspects, the green tape can encounter multiple environments as part of the firing. In further aspects, although not shown, the furnace system can comprise a multi-zone heating system including the heating chamber (with the first contact surface therein) as at least one zone of the multi -zone heating system. For example, a green tape initially containing a binder can be heated in a first zone where the binder is removed (e.g., burned out) in an oxygen-containing environment, and then the green tape is conveyed to a second zone corresponding to the heating chamber described above (that can contain a reduced oxygen content, as discussed above) to sinter the green tape (without binder), and (optionally) further conveyed to a third zone, etc.. Different environments (e.g., oxygen content) can be maintained in different zones of the multi-zone heating system, for example by flowing gas over the green tape corresponding to a predeterminedenvironment in each zone. Alternatively, even if the green tape is not conveyed (e.g., when the green tape is sintered via batch firing), the green tape can encounter multiple environments by sequentially flowing different gases over the green tape corresponding to different stages for the heating. Additionally or alternatively, flowing gas (e.g., corresponding to a predetermined environment) over the green tape can maintain a predetermined environment by carrying away any material that may be volatilized during the heating (e.g., from the green tape).

[0116] In aspects, methods of heating (e.g., firing, sintering) the green tape (e.g., green body) or making a solid-state electrolyte can be complete after heating the green tape. Alternatively, in methods of making a battery (e.g., solid-state battery) can further comprise disposing an anode 112 over the first major surface 107 of the solid-state electrolyte 108 (e.g., disposed on the coating 110 - see FIG. 1). In aspects, disposing the lithium-containing material for the anode 112 can comprise deposition from a gas phase (e.g., sputtering from one or more sources - an elemental targets or an alloy target, by thermal evaporation), disposing a molten material (e.g., lithium metal, lithium alloy) on the first major surface 107 of the solid-state electrolyte 108 (e.g., from a metal foil, a conduit, a micropipette, or a syringe), or by attaching a metal foil comprising the lithium-containing material (e.g., lithium metal, lithium alloy) to the first major surface of the solid-state electrolyte, which can be subsequently heated to enable the lithium- containing metal to conform to a surface of the coating. In aspects, methods can further comprise disposing an interlayer 114 by disposing a liquid electrolyte on the cathode 104. In further aspects, the liquid electrolyte can comprise a lithium salt and a solvent, which can comprise one or more of the materials discussed above for the interlayer 114. Also, the cathode can be disposed on the first current collector while the interlayer is disposed on the cathode. In aspects, methods can further comprise disposing the solid-state electrolyte 108 on the cathode 104. As shown, the cathode 104 can be opposite the first major surface 107 of the solid-state electrolyte 108 and / or the anode 112. As shown, the solid-state electrolyte 108 is positioned between the cathode 104 and the anode 112, and / or the coating is positioned between the cathode 104 and the anode 112. Although not shown, additional elements (e.g., current collectors) can be present when the solid-state electrolyte is disposed on the cathode and / or additional elements can be added after disposing the cathode to form the battery (e.g., solid-state battery 101 or 201).EXAMPLES

[0117] Various aspects will be further clarified by the following examples using green bodies (e.g., green tapes) of Ta-doped lithium garnet having the composition Li6.5La3Zr1.4Tao.5O12 (LLZTO), where the atmosphere and / or contact surface is varied between the various examples. Table 1 summarizes the various conditions and results of Examples 1-7.

[0118] Examples 1-3 used a platinum contact surface. In Example 1, the green tape heated at 1100°C in an air environment stuck to the platinum contact surface and left a yellow surface film after it was removed. Analysis of this contact surface after the sticking occurred in Example 1 shows the formation of a lithium platinum oxide. In Example 2, the environment was switched from air to argon (having less than 1 Pa oxygen, carbon dioxide, and water vapor). There was no sticking in this argon environment when the green tape was heated at 1100°C (Example 2), but sticking did occur when the green tape was heated at 1250°C (Example 13). This demonstrates the effect of the environment on sticking even with relatively inert contact surfaces, including platinum. However, there is a limit to how far changing the environment alone can help, as evidenced by Example 3.

[0119] Examples 4-5 used other contact surfaces and the green tape was heated at 1100°C in air while in contact with these contact surfaces. In Example 4, the contact surface was alumina, and the green tape stuck to the alumina contact surface. Likewise, in Example 5, the contact surface was nickel, and the green tape stuck to the nickel contact surface. This indicates that sticking can occur even in a relatively inert environment. For example, it is believed that the alumina is reactive with the lithium-containing green body (e.g., garnet green tape).

[0120] Examples 6-7 used contact materials consistent with the properties discussed above (and analysis of the relationships presented in FIGS. 7-9). In Example 6, the contact surface was rhenium. No sticking occurred when the green tape was heated at 1100°C or 1250°C. So, an additional sample was heated at 1325°C while in contact with the rhenium contact surface; no sticking was observed even at this elevated heating temperature. Likewise, no sticking was observed when the contact surface was iridium (Example 7). Based on the similar properties of rhenium and iridium, it is reasonably expected that osmium will also exhibit similar properties since osmium has similar properties to both rhenium and iridium.Table 1: Conditions and Properties of Examples 1-7

[0121] Additionally, lithium scandium oxide (LiScCh) was explored as a potential contact material. Lithium scandium oxide was synthesized by mixing lithium carbonate (Li2CC>3) and scandia (SC2O3) in a crucible heated to 1200°C. Table 2 presents the crystal phases detected for various conditions based on the molar ratio of these reactants, the crucible materials, and the environment. The crucible material was either platinum (Pt) or alumina (AI2O3). The molar ratio of Li2CC>3 to scandia SC2O3 was either 1: 1 or 2: 1. The environment was either argon (Ar) or air. XRD analysis was performed at 100°C intervals going up to 1200°C and then again after the resulting material was allowed to cool to 25°C. As shown, reactions appear to occur between 600°C and 900°C since only reactant crystal phases were detected below that temperature range whereas LiScCh was detected starting in this range. At 900°C and higher (900°C-1200°C), the reaction was complete with only LiScCh crystals detected. After being allowed to cool (following heating to 1200°C), the materials in the platinum crucible still has 100% LiScCh while 2% scandia was observed with the alumina crucible (with 98% LiScCh crystals). This demonstrates that LiScCh crystals can be formed in an inert atmosphere (Ar) or an oxygen-containing atmosphere (e.g., air). Additionally, the reaction can be complete with lithium in stoichiometric ratio (1: 1) or excess (e.g., 2: 1). This suggests that the reaction to form LiScCh crystals proceeds before significant lithium volatilization.Table 2: Crystal Phases from heating Li2CC and SC2O3

[0122] Additionally, the LiScCh can be compacted using hot pressing to form material with increased density (e.g., fully density), increased mechanical stability, and / or no open porosity. The LiScCh from Table 2 (1 : 1 stoichiometry, platinum crucible, in Ar) was sintered at 1300°C under an external pressure of 60 MPa. A cross-sectional view of this material is shown in FIG. 12(a). FIG 12(a) shows an SEM image 1201 with a transgranular fracture pattern since the facets (dashed lines 1207) of crystal grains 1205 are visible in addition to in-plane grain boundaries 1203. This resulting material has 96% relative density, had no open porosity, and a median grain size of 14 pm. Alternatively, when the same hot-pressing method is applied to the LiScCh with some scandia as a secondary phase (1 : 1 stoichiometry, alumina crucible in air in Table 2), the resulting material has the cross-sectional view shown in FIG. 12(b). FIG. 12(b) shows an SEM image 1211 with a trans-granular fracture behavior, where crystal grains 1215 bounded by in-plane grain boundaries 1213 are seen but not crystal faces (compare with FIG. 12(a)). For further analysis, the cross-section shown in FIG. 12(b) was polished to achieve the polished SEM image 1221 shown in FIG. 12(c) with a bright secondary phase 1229 visible in addition to the plurality of grains 1225 bounded by in-plane grain boundaries 1223. Further analysis by electron backscatter diffraction (EBSD) was used to produce the EBSD image 1231 shown in FIG. 12(d) and identify the secondary phase 1239 as scandia along with the grains 1235 of LiScCh and associated grain boundaries 1233. In FIG. 12(d), the composition was determined to be 7% scandia and 93% LiScCh. Also, as shown, the secondary phase 1239 is seen at the grain boundaries 1233 of the LiScCh grains 1235.

[0123] In Example 8, a mixture of 50 wt% LiScCh and 50 wt% Ta-doped lithium garnet was heated in a Pt crucible to 1200°C at 5°C / min in an argon atmosphere. The LiScCh was synthesized as described above (1: 1 stoichiometry in Pt crucible and an Ar atmosphere). FIG. 11 schematically illustrates an X-ray diffractometry (XRD) spectrum 1105 for the cooled mixture after the heating, where FIG. 11 shows an intensity (I) in terms of raw counts (cts) on the vertical axis 1103 (i.e., y-axis) as a function of the double angle (20) in degrees (deg.) of the incidence angle on the horizontal axis 1101 (i.e., x-axis) for Example 8. In FIG. 11, symbols indicate the crystal phase assigned to any peaks in the spectrum 1105 at the corresponding location. Specifically, triangles 1111 correspond to undoped lithium garnet, circles 1113 correspond to LiScO2, and squares 1115 correspond to Ta-doped lithium garnet. No other crystal phases were detected. This indicates that no cross-reactions occurred between the LiScO2 and (Ta-doped) lithium garnet. Since this situation (Example 8) provides additional surface area for reactions tooccur than would occur in a contact material situation and no reactions are seen, this result indicates that LiScCh would work well as a contact material for sintering a lithium-garnet containing ribbon (e.g., green body).

[0124] Table 3 shows the crystal phases detected XRD analysis through measurements every 100°C for Example 8 (where the final row corresponds to FIG. 11). Here, the undoped and Ta-doped lithium garnet phases are grouped together. As shown, the majority (98% or more) of the crystal phases correspond to lithium garnet or LiScCh. As the heating proceeds, a minor phase of La2Zr2Ch decreases from an initial value of about 1.5 wt% down to 0% (not present) at 1200°C and when cooled afterward. The other minor phase detected during the heating was La2Os, but this is also not present in the resulting sample (cooled after heating).Table 3: Crystal Phases from heating LiScCh and Ta-doped lithium garnet

[0125] In Example 9, a 30 mm diameter LiScCh disc with a thickness of 0.5 mm was cut from the hot-pressed LiScC (described above). A lithium garnet green body formed from Ta- doped lithium garnet (median particle size of 0.5 pm with no excess lithium in a polymeric binder after a toluene solvent was removed) was cut into a 20 mm diameter garnet disc with a thickness of 40 pm. The 20 mm diameter garnet disc was sandwiched between the 30 mm diameter LiScCh discs and laminated using cold isostatic pressing to form an assembly. This assembly was heated at 500°C to remove the polymeric binder and then sintered at from 600°C to 1300°C (i.e., a maximum temperature of 1300°C) for 20 minutes in an environment of 3% oxygen and 97% argon. After the sintering, the LiScCh discs were removed from the sintered garnet disc. The surfaces of the LiScCh appeared translucent, which indicated that there was no reaction or sticking to the garnet disc. Also, the sintered garnet disc appeared flat, visually uniform, and could be freely moved across the LiScC disc. This demonstrates that LiScCh can be used as a contact material to sinter alithium-containing material (e.g., lithium garnet) green body in any environment having up to 3% oxygen.

[0126] In Example 10, the materials and conditions were the same as in Example 9 except that the sintering had a maximum temperature of 1325°C and the atmosphere was 5% oxygen and 95% argon. As with Example 9, the surfaces of the LiScCE appeared translucent, and the sintered garnet disc appeared flat, visually uniform, and could be freely moved across the LiScCE disc. This demonstrates that the behavior of Example 9 extends to at least a 5% oxygen atmosphere and temperatures of at least 1325°C. Indeed, it is expected that LiScCE can be used with even higher oxygen atmospheres.

[0127] In Example 11, the lithium garnet green body contained an Al -doped lithium garnet instead of a Ta-doped lithium garnet. The maximum temperature of the sintering treatment was 1170°C. Otherwise, the conditions were the same as in Example 9 (including sandwiching the disc of the lithium garnet green body between LiScO2 discs). As with Example 9, the surfaces of the LiScO2 appeared translucent, and the sintered garnet disc appeared flat, visually uniform, and could be freely moved across the LiScO2 disc.

[0128] In Comparative Examples 1-2, other scandium-group metals were used to synthesize a lithium metal oxide. As Comparative Example 1, yttria (Y2O3) was used (instead of scandia) in a stoichiometric mixture with lithium carbonate (Li2CO3) in a platinum crucible heated to 1200°C in air (compare with Table 2). Although not shown, XRD analysis was performed every 100°C. Here, there was near complete conversion to LiYCh at 900°C. However, this product decomposed at 1200°C and was not found in the cooled product. It is believed that the decomposition allowed the lithium to volatize. Consequently, LiYCh is not stable in air at 1200°C. However, lower temperature heating and thus use in lower temperature environments may still be possible.

[0129] As Comparative Example 2, lanthania (La2C>3) was used (instead of scandia) in a stoichiometric mixture with lithium carbonate (Li2CC>3) in a platinum crucible heated to 1200°C in air (compare with Table 2). Although not shown, XRD analysis was performed every 100°C. Here, the expected product was not observed at any temperature. This indicates that lithium lanthanum oxide cannot be used as a contact material since it cannot be formed and / or is not stable under sintering -like conditions.

[0130] The above observations can be combined to furnace systems, methods of heating (e.g., firing, sintering) a green body (e.g., green tape) to produce a sintered article, the resulting sintered article (e.g., solid-state electrolyte), and / or a battery (e.g., solid-state battery) containing the same. The inventors of the present disclosure have unexpectedly discovered (especially in view of the above-state problem) contact materials that can be used to sinter lithium -containing materialswithout sticking or other reactions. In aspects, the contact material is non-reactive with the lithium- containing material (e.g., lithium garnet) while being heated at 1000°C in an argon environment for 30 minutes or more (e.g., 30 minutes, 45 minutes, 60 minutes). In aspects, the contact material does not stick to the lithium -containing material (e.g., lithium garnet) after being heated at 1000°C in an argon environment for 30 minutes or more (e.g., 30 minutes, 45 minutes, 60 minutes). In aspects, the contact material can comprise iridium, rhenium, osmium, alloys thereof, or combinations thereof. In aspects, the contact material can exhibit one or more of: a melting temperature greater than or equal to 1500°C; a gas phase oxygen concentration greater than or equal to 10'10atmospheres that produces a gaseous concentration of the contact material of 10'8atmospheres at 1200°C in a 1 atmosphere argon environment; and / or a gas phase lithium concentration less than or equal to 10'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C. In aspects, an environment that the green body (e.g., green tape) is heated in can comprise less than or equal to 10 Pascals of oxygen, less than or equal to 10 Pascals of carbon dioxide, and / or less than or equal to 10 Pascals of water vapor, which can reduce an incidence of side reactions and / or sticking.

[0131] Lithium -containing materials can be highly reactive, especially when heated at or near sintering temperatures. For example, lithium can volatize from the material being heated, which can change the composition of the resulting article and / or react with another material. Additionally, it has been observed that commonly available refractory materials, including MgO, will react with lithium-containing materials being sintered while in contact with said refractory material. These reactions can occur even at low oxygen partial pressures in the heating chamber. Also, this reaction results in the lithium-containing material sticking (e.g., bonding) to the refractory material (e.g., MgO), which impedes processing and yield of the sintering process. Similar to MgO, it has been observed that sticking or other reactions occurs when using other materials in contact with the lithium-containing materials being heated, including platinum, alumina, zirconia, silicon carbide, aluminum nitride, and cordierite. Additionally, sticking between the green body being sintered and the contact material can occur due to reactions therebetween. Without wishing to be bound by theory, it is believed that some of these reactions can involve the volatilization of material from the contact material, which can be enhanced in the presence of oxygen. Consequently, the contact materials may preferably have a low volatilization and low reactivity with oxygen at temperatures encountered by the contact material in the heating chamber. As discussed herein, the oxygen concentration (and / or carbon dioxide concentration) of an environment in the heating chamber can be minimized (e.g., 10 Pascals or less). Still, a contact material that can tolerate higher oxygen concentration without substantial volatilization can reduce an incidence of sticking when heating (e.g., firing, sintering) a green body in contact with thecontact surface. As well, lithium volatilization during heating (e.g., sintering of a lithium- containing green body) can alter the properties of the resulting sintered article. Additionally, increased lithium volatilization can be an indication of reactions occurring between the green body (i.e., a lithium-containing green body) and a contact material, which can lead to sticking therebetween.

[0132] Alternatively or additionally, the contact surface and / or contact material can comprise a lithium metal oxide, including lithium scandium oxide and alloys thereof. Providing the lithium metal oxide of the present disclosure can enable higher oxygen conditions to be used in contact with a green tape (e.g., lithium-containing material, doped or undoped lithium garnet) than otherwise possible without sticking therebetween, reactions therebetween, and / or limited (or no) lithium loss. For example, as demonstrated in the Examples here, lithium scandium oxide (as the lithium metal oxide) can be used as a contact material with a lithium garnet tape being sintered at 1200°C in a 3% oxygen environment, 1200°C in air, and / or 1325°C in a 5% oxygen environment.

[0133] It will be appreciated that the various disclosed aspects may involve features, elements, or steps that are described in connection with that aspect. It will also be appreciated that a feature, element, or step, although described in relation to one aspect, may be interchanged or combined with alternate aspects in various non-illustrated combinations or permutations.

[0134] It is also to be understood that, as used herein the terms “the,” “a,” or “an,” mean “at least one,” and should not be limited to “only one” unless explicitly indicated to the contrary. For example, reference to “a component” comprises aspects having two or more such components unless the context clearly indicates otherwise. Likewise, a “plurality” is intended to denote “more than one.” Directional terms as used herein — for example, up, down, right, left, front, back, top, bottom — are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0135] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that any particular order be inferred.

[0136] While various features, elements, or steps of particular aspects may be disclosed using the transitional phrase “comprising,” it is to be understood that alternative aspects, including those that may be described using the transitional phrases “consisting of’ or “consisting essentially of,” are implied. Thus, for example, implied alternative aspects to an apparatus that comprises A+B+C include aspects where an apparatus consists of A+B+C and aspects where an apparatusconsists essentially of A+B+C. As used herein, the terms “comprising” and “including”, and variations thereof shall be construed as synonymous and open-ended unless otherwise indicated.

[0137] The above aspects, and the features of those aspects, are exemplary and can be provided alone or in any combination with any one or more features of other aspects provided herein without departing from the scope of the disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover the modifications and variations of the aspects herein provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:1 . A furnace system comprising: a heater contained in a heating chamber; a first contact surface positioned within the heating chamber, wherein a green tape is configured to contact the first contact surface while the green tape is in the heating chamber, and the first contact surface comprises a contact material having: a melting temperature greater than or equal to 1500°C, a gas phase oxygen concentration greater than or equal to 10'7atmospheres that produces a gaseous concentration of an oxide of the contact material of 10'12atmospheres at 1200°C in a 1 atmosphere argon environment, and a gas phase lithium concentration less than or equal to 10'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C.

2. The furnace system of claim 1, wherein the contact material comprises one or more of iridium, osmium, rhenium, or an alloy thereof3. The furnace system of claim 1, wherein the oxygenated gas phase lithium concentration is less than or equal to 10'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C in a 1 atmosphere argon environment of 3% oxygen and 97% argon with less than or equal to 10 Pascals of water vapor.

4. The furnace system of claim 1 or claim 3, wherein the contact material comprises lithium scandium oxide.

5. The furnace system of any one of claims 1-4, further comprising a conveyance path extending through the heating chamber, wherein the green tape is configured to contact the first contact surface while the green tape is conveyed along at least a portion of the conveyance path.

6. The furnace system of claim 5, wherein the first contact surface and the green tape are configured to translate together along at least the portion of the conveyance path.

7. The furnace system of claim 5, wherein the green tape is configured to translate relative to the first contact surface as the green tape is conveyed through the heating chamber along at least the portion of the conveyance path while the green tape is in contact with the first contact surface.

8. The furnace system of claim 7, further comprising: a second contact surface, the green tape is configured to contact the second contact surface for another portion of the conveyance path, and the second contact surface comprises a different material than the contact material of the first contact surface, wherein a position of the first contact surface is configured to correspond to a maximum temperature encountered by the green tape whereas a second position of the second contact surface does not correspond to the maximum temperature.

9. The furnace system of claim 8, wherein a second material forming the second contact surface comprises one or more of platinum, rhodium, alumina, calcium oxide, magnesium oxide, tungsten, or an alloy thereof.

10. The furnace system of any one of claims 1-9, wherein the first contact surface is an outer surface of an article comprising an additional material coated with the contact material.

11. The furnace system of claim 8, wherein the additional material comprises one or more of alumina, nickel, tungsten, chromium, mullite, or an alloy thereof.

12. The furnace system of any one of claims 1-11, wherein: the contact material is non-reactive with lithium garnet at 1000°C in an argon environment for 30 minutes; lithium garnet in contact with the first contact surface at 1000°C in an argon environment for 30 minutes does not stick of the first contact surface; or both.

13. A furnace system comprising: a heater contained in a heating chamber; and a first contact surface positioned within the heating chamber, wherein a green tape is configured to contact the first contact surface while the green tape is in the heating chamber, and the first contact surface comprises a contact material comprising one or more of iridium, osmium, rhenium, or an alloy thereof.

14. A furnace system comprising: a heater contained in a heating chamber; and a first contact surface positioned within the heating chamber,wherein a green tape is configured to contact the first contact surface while the green tape is in the heating chamber, and the first contact surface comprises a contact material comprising a lithium metal oxide where the metal is selected from a group consisting of scandia, yttrium, and combinations thereof.

15. A method of firing a green tape containing inorganic crystals, the method comprising: heating the green tape in an atmosphere to sinter the inorganic crystals and form a sintered tape; and contacting the green tape with a first contact surface during at least part of the heating, wherein the first contact surface comprises a contact material having: a melting temperature greater than or equal to 1500°C, a gas phase oxygen concentration greater than or equal to 10'7atmospheres that produces a gaseous concentration of an oxide of the contact material of 10'12atmospheres at 1200°C in a 1 atmosphere argon environment, and a gas phase lithium concentration less than or equal to 10'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C.

16. The method of claim 15, wherein: a partial pressure of oxygen in the atmosphere is less than or equal to 10 Pascals; a partial pressure of water vapor in the atmosphere is less than or equal to 10 Pascals; or both17. The method of any one of claims 15-16, wherein a partial pressure of carbon dioxide in the atmosphere is less than or equal to 10 Pascals.

18. The method of any one of claims 15-17, wherein the inorganic crystals are a lithium - containing material.

19. The method of any one of claims 15-18, further comprising conveying the green tape through a heating chamber during the heating, wherein the green tape contacts the first contact surface during at least a portion of the conveying.

20. The method of claim 19, wherein the at least a portion of the conveying comprises translating the first contact surface and the green tape together.

21. The method of claim 19, wherein the at least a portion of the conveying comprises translating the green tape relative to the first contact surface while the green tape is in contact with the first contact surface.

22. The method of claim 21, further comprising: contacting the green tape with a second contact surface during another portion of the conveying comprising translating the green tape relative to the second contact surface while the green tape is in contact with the second contact surface, wherein the second contact surface comprises a different material than the contact material of the first contact surface, the contacting the green tape with the first contact surface occurs while the green tape encounters a maximum temperature during the heating, whereas the contacting the green tape with the second contact surface does not occur while the green tape encounters the maximum temperature during the heating.

23. The method of claim 22, wherein a second material forming the second contact surface comprises one or more of platinum, rhodium, alumina, calcium oxide, magnesium oxide, tungsten, or an alloy thereof.

24. The method of any one of claims 15-23, wherein the contact material comprises one or more of iridium, osmium, rhenium, or an alloy thereof25. The method of any one of claims 15-23, wherein the oxygenated gas phase lithium concentration is less than or equal to 10'5atmospheres when the contact material is in contact with a lithium garnet at 1200°C in a 1 atmosphere argon environment of 3% oxygen and 97% argon with less than or equal to 10 Pascals of water vapor.

26. The method of any one of claims 15-23 and 25 inclusive, wherein the contact material comprises lithium scandium oxide.

27. The method of any one of claims 15-26, wherein the heating comprises heating the green tape at a temperature in a range from 800°C to 1500°C for from 10 seconds to less than one hour.

28. The method of any one of claims 15-27, wherein: the contact material of the first contact surface is non-reactive with the green tape during the heating;the green tape and the resulting sintered tape does not stick to the first contact surface as a result of the heating; or both.

29. A sintered article produced by the method of any one of claims 15-28 comprising a body comprising grains of inorganic material sintered to one another corresponding to the inorganic crystals of the green tape.

30. A sintered article comprising: a body comprising grains of inorganic material sintered to one another, the body extending between a first major surface and a second major surface, a thickness of the body defined between the first major surface and the second major surface, and the thickness is from 5 micrometers to 1 millimeter, wherein a concentration of iridium, osmium, rhenium on the first major surface is greater than or equal to 1 part-per-trillion.

31. The sintered article of claim 30, wherein the body is free of iridium, osmium, and rhenium, and the grains of inorgnaic material comprise a lithium -containing material.

32. The sintered article of any one of claims 30-31, wherein the body has an ionic conductivity greater than 5xl0'5S / cm.

33. The sintered article of any one of claims 30-32, wherein the grains of inorganic material comprise at least one of:(i) Li7-3aLa3Zr2LaOi2, with L = Al, Ga, or Fe and 0 < a < 0.33;(ii) Li?La3-bZr2MbOi2, with M = Bi, Ca, or Y and 0 < b < 1 ; or(iii) Li7-cLa3(Zr2-c, Nc)Oi2, with N = V, Nb, or Ta and 0 < c < 1.

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