Sintered membrane, solid-state electrolyte, battery, and methods of making the same

Abstract

A sintered membrane is a ceramic article having a primary crystal phase including lithium-aluminum-titanium-phosphate crystals and a secondary crystal phase including anatase or lithium-titanium-oxyphosphate crystals. In aspects, the sintered membrane can have a closed porosity of less than or equal to 5%. In aspects, the primary crystal phase can be from 95% to 100% of a volume of the ceramic article, and the secondary crystal phase can be from greater than 0% to 5% of the volume of the ceramic article. In aspects, the sintered membrane can exhibit a total leaching of less than or equal to 5 parts-per-million in a Leaching Test. Methods of making a sintered membrane includes forming a green tape having lithium-aluminum-titanium-phosphate crystals and an additive including a titanium-containing powder or an aluminum-containing powder, where the green tape is heated to a first temperature from 600°C to 1200°C to form the sintered membrane.

Description

SINTERED MEMBRANE, SOLID-STATE ELECTROLYTE, BATTERY, AND METHODS OF MAKING THE SAMECROSS 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 / 669896 filed on July 11, 2024, the content of which is relied upon and incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to sintered membranes, solid-state electrolytes, batteries, and methods of making the same, and more particularly, to a sintered membrane comprising lithium-aluminum-titanium-phosphate crystals, solid-state electrolytes comprising the same, batteries comprising the same, and methods of making the same.BACKGROUND

[0003] Fossil fuels have long been a primary source of energy. However, fossil fuels are finite and, when burned to produce heat, produce a suboptimal amount of air pollution and greenhouse gases. To reduce reliance on fossil fuels as an energy source, renewable energy sources such as solar energy and wind energy are being used to generate electrical energy. The generation of electrical energy spurs demand for devices that store the electrical energy that renewable energy sources (and fossil fuels too) generate in the form of chemical energy.

[0004] 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 due to their high safety, improved energy density, high ionic conductivity, and stability against Li metal. However, SSBs can suffer from low environmental resistance. Consequently, there is a need to provide SSEs and other sintered membranes with high environmental resistance.SUMMARY

[0005] The present disclosure provides a solid-state electrolyte, a sintered membrane, ceramic article, and / or a battery containing the same as well as method of making the same. The solid-state electrolyte sheet can achieve high ionic conductivity (e.g., 10'4S / cm or more at 25 °C) with a high fraction of crystals being lithium-aluminum-titanium-phosphate (LATP) crystals. For example, 95 wt% or more of the crystals can be LATP, which is demonstrated for Examples 4-5 and 8-9 herein.

[0006] Also, the solid-state electrolyte, a sintered membrane, and / or ceramic article can have a total leaching concentration in a Leaching Test (described herein) for 4 days at 25 °C of 5 ppm or less (e.g., 4 ppm or less, 3 ppm or less, 2 ppm or less, or 1 ppm or less), which can provide increased stability and / or increased environmental resistance. Without wishing to be bound by theory, the primary crystal phase and the secondary crystal phase of the solid-state electrolyte (e.g., sintered membrane, ceramic article) are insoluble in water, which prevents leaching and / or dissolution of the solid-state electrolyte that can otherwise lead to failure of the resulting battery. For example, the solid-state electrolyte (e.g., sintered membrane, ceramic article) can be free of one or more of LiPCL, LisPCL, Li4P2O?, or Li9A13(PO4)2(P2O?)3. Such improved environmental resistance is beneficial for marine applications, where seawater and / or rainwater may seep into the battery; if the solid-state electrolyte did not have the increased environmental resistance disclosed herein, the seawater and / or rainwater could cause leaching and / or dissolution of the solid-state electrolyte that may lead to failure of the resulting battery.

[0007] Methods of the present disclosure involve heating a green tape having LATP and an additive including aluminum and / or titanium. Without wishing to be bound by theory, it is believed that the additive can facilitate the reaction of water soluble phases to LATP or other water insoluble phases (e.g., anatase, lithium-titanium-oxyphosphate crystals). For a titanium-containing additive, it is believed that lithium-aluminum-phosphate phases can react with titanium from the titanium-containing additive can form additional LATP with any excess titanium forming water insoluble anatase. For an aluminum-containing additive, it is believed that the aluminum additive can promote conversion of raw materials to LATP and / or lithium- aluminum-oxyphosphate .

[0008] 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.

[0009] Aspect 1. A sintered membrane comprising a ceramic article comprising: a primary crystal phase comprising lithium-aluminum-titanium-phosphate crystals; and a secondary crystal phase comprising one or more of anatase or lithium-titanium- oxyphosphate crystals, wherein the sintered membrane comprises a closed porosity of less than or equal to 5%.

[0010] Aspect 2. The sintered membrane of aspect 1, wherein the primary crystal phase comprises from 95 wt% to 100 wt% of the ceramic article, and the secondary crystal phase comprises from greater than 0 wt% to 5 wt% of the ceramic article.

[0011] Aspect 3. A sintered membrane comprising a ceramic article comprising:a primary crystal phase comprising lithium-aluminum-titanium-phosphate crystals; and a secondary crystal phase comprising one or more of anatase or lithium-titanium- oxyphosphate crystals, wherein the primary crystal phase comprises from 95% to 100% of a volume of the ceramic article, and the secondary crystal phase comprises from greater than 0% to 5% of the volume of the ceramic article.

[0012] Aspect 4. The sintered membrane of any one of aspects 1-3, wherein the sintered membrane is free of crystals or glasses of: LiPCL, LisPCL, Li4P2O?, and LigAh PCh ^O?^.

[0013] Aspect 5. The sintered membrane of any one of aspects 1-4, wherein the sintered membrane consists of the primary crystal phase and the secondary crystal phase consisting of anatase, the lithium-titanium -oxyphosphate crystals, or combinations thereof.

[0014] Aspect 6. A sintered membrane consisting of: a primary crystal phase comprising lithium-aluminum-titanium-phosphate crystals; and a secondary crystal phase consisting of anatase, lithium-titanium-phosphate crystals, or combinations thereof.

[0015] Aspect 7. The sintered membrane of any one of aspects 1-6, wherein the sintered membrane exhibits a total leaching of less than or equal to 5 parts-per-million in a Leaching Test in deionized water at 25 °C for 4 days.

[0016] Aspect 8. A sintered membrane comprising: a primary crystal phase comprising lithium-aluminum-titanium-phosphate crystals; and a secondary crystal phase comprising one or more of anatase or lithium-titanium- oxyphosphate crystals, wherein the sintered membrane exhibits a total leaching of less than or equal to 5 parts- per-million in a Leaching Test.

[0017] Aspect 9. The sintered membrane of any one of aspects 7-8, wherein the total leaching is from 0.1 parts-per-million to 3.0 parts-per-million in the Leaching Test.

[0018] Aspect 10. The sintered membrane of any one of aspects 7-9, wherein the total leaching is from 0.2 parts-per-million to 1.0 parts-per-million in the Leaching Test.

[0019] Aspect 11. The sintered membrane of any one of aspects 1-10, wherein the lithium-aluminum-titanium-phosphate crystals comprises a formula of one or more of:Lii+xAlxTi2-xP30i2;Lll+x+yAlxT12-xSlyP3-yO12;Li i +xAlxGe 2-xP3012 ;Lii+x+yAlxGe2-xSiyP3-yOi2;Lii+xAlx(Ge,Ti)2-xP30i2; orLii+x+yAlx(Ge,Ti)2-xSiyP3-yOi2, f wherein “x” is between 0.3 and 0.5.

[0020] Aspect 12. The sintered membrane of aspect 11, wherein the lithium-aluminum- titanium-phosphate crystals comprise Li+xAlxTi2-xP30i2 and“x” is between 0.3 and 0.5.

[0021] Aspect 13. The sintered membrane of any one of aspects 1-12, wherein the secondary crystal phase comprises the lithium-titanium-oxyphosphate crystals comprising LiTiO(PO4).

[0022] Aspect 14. The sintered membrane of any one of aspects 1-13, wherein a median grain size of the primary crystal phase is less than or equal to 1.0 micrometers.

[0023] Aspect 15. The sintered membrane of any one of aspects 1-14, wherein the sintered membrane exhibits a conductivity at 25°C of greater than or equal to 10'4Siemens per centimeter (S / cm).

[0024] Aspect 16. The sintered membrane of any one of aspects 1-15, wherein the sintered membrane comprises a thickness from greater than or equal to 10 micrometers to less than or equal to 250 micrometers.

[0025] Aspect 17. The sintered membrane of aspect 16, wherein the thickness is from greater than or equal to 20 micrometers to less than or equal to 100 micrometers.

[0026] Aspect 18. The sintered membrane of any one of aspects 1-17, wherein the sintered membrane is a solid-state electrolyte for use in a secondary battery.

[0027] Aspect 19. A battery comprising: a lithium -containing anode; a solid-state electrolyte comprising the sintered membrane of any one of aspects 1-17; and a cathode, wherein the solid-state electrolyte is positioned between the lithium-containing anode and the cathode.

[0028] Aspect 20. A method of making a sintered membrane comprising: forming a green tape comprising lithium-aluminum-titanium-phosphate crystals and an additive comprising one or more of: a titanium-containing powder or an aluminum -containing powder; heating the green tape to a first temperature from 600°C to 1200°C to form the sintered membrane, wherein the sintered membrane comprises:a primary crystal phase comprising lithium-aluminum-titanium-phosphate crystals; and a secondary crystal phase comprising one or more of anatase or lithium- titanium-oxyphosphate crystals.

[0029] Aspect 21. The method of aspect 20, wherein the first temperature is from 750°C to 1000°C.

[0030] Aspect 22. The method of any one of aspects 20-21, wherein the additive comprises the aluminum-containing powder including one or more of: A100H, AI2O3, A1(OH)3, or AINO3.

[0031] Aspect 23. The method of any one of aspects 20-22, wherein the additive comprises the titanium-containing powder including one or more of: TiO? or ^PrO?.

[0032] Aspect 24. The method of any one of aspects 20-23, wherein a total amount of the additive is from greater than or equal to 0.1 wt% to less than or equal 10.0 wt% of an amount of the lithium-aluminum-titanium -phosphate crystals in the green tape.

[0033] Aspect 25. The method of any one of aspects 20-23, wherein a total amount of the additive is from greater than or equal to 0.5 wt% to less than or equal 2.0 wt% of an amount of the lithium-aluminum-titanium-phosphate crystals in the green tape.

[0034] Aspect 26. The method of any one of aspects 20-23, wherein an amount of titanium in the additive is from greater than or equal to 1.0 mol% to 7.0 mol% of a total amount of titanium in the lithium-aluminum-titanium -phosphate crystals in the green tape.

[0035] Aspect 27. The method of any one of aspects 20-23, wherein an amount of aluminum in the additive is from greater than or equal to 5.0 mol% to 25.0 mol% of a total amount of titanium in the lithium-aluminum-titanium-phosphate crystals in the green tape.

[0036] Aspect 28. The method of any one of aspects 20-27, wherein the green tape further comprises an organic binder in an amount from 3 wt% to 50 wt% of a total weight of the green tape on a solvent-free basis.

[0037] Aspect 29. The method of any one of aspects 20-27, further comprising: tape casting a slurry to form the green tape, wherein the slurry comprises a solvent, a binder, and a dispersant in addition to the lithium-aluminum-titanium-phosphate crystals and the additive, wherein the solvent is from 25 wt% to 50 wt% of the slurry, and an amount of the lithium-aluminum-titanium -phosphate crystals in the slurry is from 30 wt% to 60 wt%.

[0038] Aspect 30. The method of any one of aspects 20-29, wherein the sintered membrane comprises the sintered membrane of any one of aspects 1-18.

[0039] Aspect 31. The method of any one of aspects 20-29, wherein the sintered membrane is a solid-state electrolyte for use in a battery.

[0040] Aspect 32. A method of making a battery comprising: forming a solid-state electrolyte using the method of making the sintered membrane of any one of aspects 20-29; and positioning the solid-state electrolyte between a lithium-containing anode and a cathode.BRIEF DESCRIPTION OF THE DRAWINGS

[0041] 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:

[0042] FIG. 1 schematically illustrates a general structure of a solid-state battery in accordance with aspects of the disclosure;

[0043] FIG. 2 illustrates a simplified solid-state battery with the solid-state electrolyte in accordance with aspects of the disclosure;

[0044] FIG. 3 schematically indicates concentrations in parts-per-million (ppm) leached from Comparative Example AA and Examples 1-5 in a Leaching Test in deionized water at 25°C for 4 days;

[0045] FIG. 4 schematically indicates concentrations in parts-per-million (ppm) leached from Comparative Example AA and Examples 6-10 in a Leaching Test in deionized water at 25°C for 4 days;

[0046] FIG. 5 illustrate a schematically illustrate scanning electron microscope (SEM) image of Example 10;

[0047] FIG. 6 presents a flow chart of methods of making a sintered membrane and / or battery in accordance with aspects of the present disclosure;

[0048] FIG. 7 schematically illustrates a step in a method of making a sintered membrane and / or battery comprising a slurry including lithium-aluminum-titanium-phosphate crystals and an additive in accordance with aspects of the present disclosure; and

[0049] FIG. 8 schematically illustrates one or more steps in a method of making a sintered membrane including firing a green tape in accordance with aspects of the present disclosure.DETAILED DESCRIPTION

[0050] 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.

[0051] FIGS. 1-2 illustrate views of a solid-state battery 101 or 201 comprising a solid- state electrolyte. Unless otherwise noted, a discussion of features of aspects of one solid-state electrolyte or 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 feature of one aspect, unless otherwise noted, can apply equally to the identified feature of any of the other aspects of the disclosure.

[0052] FIG. 1 schematically illustrates a general structure of a solid-state battery 101, and FIG. 2 illustrates a simplified solid-state battery 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 battery 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 battery 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.

[0053] 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 ASTME1004-17. 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.

[0054] 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-eCL, where 0 < d < 1, 0 < e < l, for example, LiNio.5Coo.2Mno.3O2 (NCM523), LiNio.eCoo.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, NaVPOaF. 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 (MgC^Ch), MgMnzCh, 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. In aspects, a ratio of a weight of the cathode 104 to a cathode surface area (e.g., first major surface 105 of the cathode 104) of the cathode 104 can be 5 milligrams per centimeter squared (mg / cm2), 8 mg / cm2or more, 10 mg / cm2or more, 15 mg / cm2or more, 20 mg / cm2or more, 50 mg / cm2or less, 30 mg / cm2or less, 25 mg / cm2or less, 20 mg / cm2or less, or 15 mg / cm2or less. In aspects, a ratio of a weight of the cathode 104 to a cathode surface area of the cathode 104 can range from 5 mg / cm2to 50 mg / cm2, from 8 mg / cm2to 30 mg / cm2, from 10 mg / cm2to 25 mg / cm2, from 15 mg / cm2to 20 mg / cm2, or any range or subrange therebetween.

[0055] As shown in FIG. 1, the solid-state battery 101 can optionally comprises 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 the transport 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 roomtemperature (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 (LiSChCFs), LiC(SC>2CF3)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. An exemplary aspect of the solvent is sulfolane, although other solvents are possible in other aspects. 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 ofthe cathode 104 shown in FIGS. 5-6) ofthe 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. In aspects, a volume of the liquid electrolyte of the interlayer 114 to a cathode surface area of the cathode 104 can 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.

[0056] 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 (Lib^CFsSCh ), Si O2 may 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, orat least two of, or at least three elements selected from a group consisting of nitrogen, carbon, cobalt, titanium, tantalum, and tungsten.

[0057] 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.

[0058] As shown in FIGS. 1-2, the solid-state electrolyte 108 comprises a first major surface 107 and a second major surface 109 opposite the first major surface 107. In aspects, as shown in FIGS. 1-2, the first major surface 107 of the solid-state electrolyte 108 can face and / or contact the first major surface 105 of the cathode 104. In aspects, as shown in FIGS. 1-2, the second major surface 109 of the solid-state electrolyte 108 can face and / or contact the first major surface 113 of the anode 112. As shown, a thickness 129 of the solid-state electrolyte 108 is defined as an average distance between the first major surface 107 and the second major surface 109. In aspects, the thickness 129 can be 10 micrometers (pm) or more, 15 pm or more, 20 pm or more, 25 pm or more, 30 pm or more, 35 pm or more, 40 pm or more, 60 pm or more, 100 pm or more, 250 pm or less, 200 pm or less, 160 pm or less, 120 pm or less, 100 pm or less, 80 pm or less, 60 pm or less, 50 pm or less, or 40 pm or less. In aspects, the thickness 129 can be in a range from 10 pm to 250 pm, from 10 pm to 200 pm, from 10 pm to 160 pm, from 15 pm to 120 pm, from 15 pm to 100 pm, from 20 pm to 80 pm, from 20 pm to 60 pm, from 20 pm to 50 pm, from 25 pm to 50 pm, from 30 pm to 50 pm, or any range or subrange therebetween. In further aspects, preferred ranges for the thickness 129 can be from 10 pm to 250 pm, from 20 pm to 60 pm, or from 30 pm to 50 pm. The thickness 129 of the solid-state electrolyte 108 can be determined from a scanning electron microscope (SEM) image of a cross-section of the solid-state electrolyte 108, for example with the view shown in FIG. 5. In aspects, the solid-state electrolyte 108 can be a sintered membrane. For example, a maximum dimension (e.g., length) of the solid-state electrolyte 108 (e.g., sintered membrane)can be 100 millimeters (mm ormore), 500 mm ormore, 1 meter (m) or more, 5 meters or more, 10 meters or more, 20 meters or more, 50 meters or more, or 100 meters or more, for example, in a range from 100 mm to 1,000 meters, from 500 mm to 500 mm, from 1 meter to 200 meters, from 5 meters to 100 meters, from 10 meters to 50 meters, or any range or subrange therebetween. Methods of the present disclosure can enable the formation of long ribbons of the solid-state electrolyte sheet. At the same time, the solid-state electrolyte 108 can be cut to any predetermined shape corresponding to a dimension of a battery that the solid-state electrolyte is incorporated into, for example, a disc shape or a quadrilateral shape having a maximum dimension (e.g., diameter or diagonal measurement) from 10 mm to 100 mm, from 20 mm to 70 mm, from 30 mm to 50 mm, or any range or subrange therebetween.

[0059] In aspects, the solid-state electrolyte (e.g., sintered membrane) can be a ceramic article (i.e., comprising one or more crystal phases). Throughout the disclosure, a crystallinity and / or relative proportion of crystal phases can be determined using X-ray diffraction (XRD). Using the reference crystallographic data for known crystal phases (including lithium- aluminum-titanium-phosphate crystals, lithium-titanium-oxyphosphate, anatase), a measured XRD spectrum can be fit with a series of curves associated with different aspects of the various crystal phases. A total area of the fitted curves associated with each crystal phase relative to the total area of all fitted curves is assumed to be proportional to a relative amount of the corresponding crystal phase in the sample. In aspects, a primary crystal phase of the solid-state electrolyte (e.g., sintered membrane, ceramic article) can be a lithium-aluminum-titanium- phosphate (LATP) crystal. In further aspects, the LATP primary crystal phase can be the predominant crystal phase. As used herein, a “predominant crystal phase” has a relative amount in the LATP crystals that is greater than any of other crystal phases on their own. Unless otherwise, fractions (e.g., percentages) of crystals (or crystal phases) refer to wt%. In further aspects, an amount of the LATP crystals, as percentage of all crystal phases in the solid-state electrolyte (e.g., sintered membrane, ceramic article), can be 80 wt% ormore, 85 wt% ormore, 90 wt% or more, 92 wt% or more, 95 wt% or more, 96 wt% or more, 97 wt% or more, 98 wt% or more, 99 wt% or more, 100 wt% or less, 99 wt% or less, 98 wt% or less, 97 wt% or less, or 96 wt% or less. In aspects, an amount of the LATP crystals, as percentage of all crystal phases in the solid-state electrolyte (e.g., sintered membrane, ceramic article), can be from 80 wt% to 100 wt%, from 85 wt% to 98 wt%, from 90 wt% to 96 wt%, from 92 wt% to 95 wt%, or any range or subrange therebetween. In further aspects, an amount of the LATP crystals, as percentage of all crystal phases in the solid-state electrolyte (e.g., sintered membrane, ceramic article), can be 90 wt% or more, for example, from 90 wt% to 100 wt%, from 92 wt% to 100wt%, from 95 wt% to 100 wt%, from 96 wt% to 99 wt%, from 97 wt% to 98 wt%, or any range or subrange therebetween. In further aspects, the LATP crystals of the primary crystal phase can be optionally doped with silicon and / or germanium. In further aspects, the LATP crystals of the primary crystal phase can comprise a formula of one or more of Lii+xAlxTi2-xP30i2, Lii+x+yAlxTi2-xSiyP3-yOi2, Lii+xAlxGe2-xP30i2, Lii+x+yAlxGe2-xSiyP3-yOi2, Lii+xAlx(Ge,Ti)2-x- P3O12, or Lii+x+yAlx(Ge,Ti)2-xSiyP3-yOi2, where “x” is between 0.3 and 0.5. In even further aspects, the LATP crystals of the primary crystal phase can comprise (and / or consist of) Li+xAlxTi2-xP30i2, where “x” is between 0.3 and 0.5.

[0060] In aspects, the solid-state electrolyte (e.g., sintered membrane, ceramic article) can further comprise a secondary crystal phase in addition to the primary crystal phase discussed above. In further aspects, an amount of the secondary crystal phase, as percentage of all crystal phases in the solid-state electrolyte (e.g., sintered membrane, ceramic article), can be 20 wt% or less, 15 wt% or less, 10 wt% or less, 7 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less, 1 wt% or less, 0 wt% or more, 1 wt% or more, 2 wt% or more, 3 wt% or more, or 4 wt% or more. In further aspects, an amount of the secondary crystal phase, as percentage of all crystal phases in the solid-state electrolyte (e.g., sintered membrane, ceramic article), can be from 0 wt% to 20 wt%, from 1 wt%to 15 wt%, from 2 wt%to 10 wt%, from 3 wt% to 7 wt%, from 4 wt% to 5 wt%, or any range or subrange therebetween. In further aspects, an amount of the secondary crystal phase, as percentage of all crystal phases in the solid-state electrolyte (e.g., sintered membrane, ceramic article), can be 5 wt% or less, for example, from 0 wt% to 5 wt%, from 1 wt% to 4 wt%, from 2 wt% to 3 wt%, or any range or subrange therebetween. In further aspects, the secondary crystal phase can comprise one or more of anatase or lithium-titanium-oxyphosphate crystals. In even further aspects, the lithium - titanium-oxyphosphate crystals of the secondary crystal phase can comprise LiTiO(PC>4). In even further aspects, the solid-state electrolyte (e.g., sintered membrane, ceramic article) can consist of the primary crystal phase and the secondary crystal phase consisting of anatase, the lithium-titanium-oxyphosphate crystals, or combinations thereof. Without wishing to be bound by theory, the primary crystal phase and the secondary crystal phase of the solid-state electrolyte (e.g., sintered membrane, ceramic article) are insoluble in water, which prevents leaching and / or dissolution of the solid-state electrolyte that can otherwise lead to failure of the resulting battery. In further aspects, the solid-state electrolyte (e.g., sintered membrane, ceramic article) can be free of one or more of LiPCL, LisPCL, Li4P2O?, or Li9A13(PO4)2(P2O?)3.

[0061] Throughout the disclosure, a grain size of the ceramic article and / or the primary crystal phase is determined in accordance with ASTM E112-13. As such, a scanning electronmicroscope (SEM) image is taken of a fracture cross-section (as shown schematically in FIG. 5). For determining the grain size distribution (e.g., minimum, maximum, mean), the SEM image was taken at 10,000 times magnification and at least 20% of the area in the SEM image is analyzed to determine the grain size distribution. For example, a grain size 505 is shown for grain 503 of the plurality of grains in FIG. 5. From the calculated grain sizes, values such as the average (e.g., mean), maximum, and minimum values of the resulting distribution of grain sizes can be calculated. In aspects, an average (e.g., mean) grain size of the ceramic article and / or the primary crystal phase can be 1.0 pm or less, 0.9 pm or less, 0.8 pm or less, 0.7 pm or less, 0.6 pm or less, 0.5 pm or less, 0.1 pm or more, 0.2 pm or more, 0.3 pm or more, 0.4 pm or more, 0.5 pm or more, 0.6 pm or more, 0.7 pm or more, 0.8 pm or more, or 0.9 pm or more. In aspects, the average (e.g., mean) grain size of the ceramic article and / or the primary crystal phase can in a range from 0.1 pm to 1.0 pm, from 0.2 pm to 0.9 pm, from 0.3 pm to 0.8 pm, from 0.4 pm to 0.7 pm, from 0.5 pm to 0.6 pm, or any range or subrange therebetween. In aspects, a maximum grain size of the ceramic article and / or the primary crystal phase can be 5 pm or less, 4 pm or less, 3 pm or less, 2.5 pm or less, 2.0 pm or less, 1.5 pm or less, 1.2 pm or less, 1.0 pm or less, 0.8 pm or less, or 0.5 pm or less. In aspects, a maximum grain size of the ceramic article and / or the primary crystal phase can be in a range from 0. 1 pm to 5 pm, from 0.2 pm to 4 pm, from 0.3 pm to 3 pm, from 0.4 pm to 2.5 pm, from 0.5 pm to 2.0 pm, from 0.6 pm to 1.5 pm, from 0.7 pm to 1.2 pm, from 0.8 pm to 1.0 pm, or any range or subrange therebetween. Without wishing to be bound by theory, it is believed that by limiting a maximum grain size, the ionic conductivity can be increased, for example, by decreasing a path length along grain boundaries that could be travelled by ion transported through the solid- state electrolyte sheet and / or by providing additional grain boundary per volume of the solid- state electrolyte.

[0062] Throughout the disclosure, the porosity of the solid-state electrolyte (e.g., sintered membrane, ceramic article) is determined in accordance with ASTM E1245-03. For example, the SEM image used for determining grain size can be reanalyzed to determine the number and size of pores. However, as used herein, the porosity is determined from SEM images at 10,000 times magnification, where at least 20% of each SEM image is analyzed, and the results of analyzing seven (7) SEM images are averaged to determine the porosity distribution (e.g., minimum, maximum, mean). In aspects, a porosity of the solid-state electrolyte 108 can be 5% or less, 4% or less, 3% or less, 2.5% or less, 2.0% or less, 1.8% or less, 1.5% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.5% or less, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% ormore, 1.0% or more, 1.2% or more, 1.5% ormore, 1.8% or more, or 2.0% or more. In aspects, a porosity of the solid-state electrolyte 108 can be in a range from 0.1% to 5%, from 0.2% to 4%, from 0.3% to 3%, from 0.4% to 2.5%, from 0.5% to 2.0%, from 0.6% to 1.8%, from 0.7% to 1.5%, from 0.8% to 1.2%, from 0.9% to 1.0%, or any range or subrange therebetween. In aspects, preferred ranges for the porosity are from 0.1% to 5%, from 0.2% to 2.0%, and from 0.5% to 1.0%.

[0063] As schematically illustrated in FIG. 5, the solid-state electrolyte 108 can have closed pores 507. As used herein, closed pores occur within a grain and are unlikely to continue beyond the grain. As such, a path cannot be formed through the thickness of the solid-state electrolyte sheet using closed grains. In contrast, as used herein, open pores occur at grain boundaries. As used herein, closed porosity is characterized in accordance with ASTM C949- 80(2020). In aspects, the solid-state electrolyte 108 can have closed porosity (e.g., only closed porosity). Without wishing to be bound by theory, it is believed that ionic conductivity decreases exponentially with increasing open porosity. Providing closed pores can enable an increased ionic conductivity. Also, providing closed pores can facilitate longevity of the resulting battery, for example, by reducing an incidence of short circuiting the cell through the solid state electrolyte (e.g., in the case of an open pore providing a path from the first major surface to the second major surface).

[0064] The ionic conductivity of the solid-state electrolyte 108 is a quantification of the ability of the solid-state electrolyte sheet to transport ions (e.g., lithium ions) between the anode and the cathode or vice versa. Throughout the disclosure, the ionic conductivity is measured at a predetermined temperature (e.g., 25°C, 50°C) 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 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. Based on these measurements, ionic conductivity is calculated. In aspects, an ionic conductivity of the solid-state electrolyte 108 at 25 °C can be 10'4Siemens per centimeter (S / cm) or more, IO'3'5S / cm or more, IO'3 0S / cm or more, IO'25S / cm or more, IO'20S / cm or more, 1.0 S / cm or less, 0.5 S / cm or less, 0. 1 S / cm or less, 10'2S / cm or less, IO'2 5S / cm or less, or 10'2S / cm or less. In aspects, an ionic conductivityof the solid-state electrolyte 108 at 25°C can be in a range from 10'4S / cm to 1.0 S / cm, from IO'3 5S / cm to 0.5 S / cm, from IO'3 0S / cm to 0.1 S / cm, from IO'2 5S / cm to 10'2S / cm, or any range or subrange therebetween.

[0065] Throughout the disclosure, an amount of material leached from a solid-state electrolyte (e.g., sintered membrane, ceramic article) is determined in a Leaching Test. As used herein, the Leaching Test involves immersing 0.1 grams of the sample (e.g., solid-state electrolyte, sintered membrane, ceramic article) in 50 grams of deionized water for a predetermined period of time at a predetermined temperature, where the resulting water is analyzed by inductively-coupled plasma mass-spectroscopy (ICP-MS) to determine concentrations of leached components. Unless otherwise indicated, the Leaching Test used a predetermined period of time of 4 days and a predetermined temperature of 25°C. In aspects, a total leaching of the solid-state electrolyte (e.g., sintered membrane, ceramic article) in the Leaching Test in deionized water at 25 °C for 4 days can be less than 5 parts-per-million (ppm), less than 4.0 ppm, 3.0 ppm, 2.5 ppm, 2.0 ppm, 1.5 ppm, 1.0 ppm, 0.01 ppm or more, 0.05 ppm or more, 0. 1 ppm or more, 0.2 ppm or more, 0.5 ppm or more, 0.7 ppm or more, 1.0 ppm or more, or 1.5 ppm or more. In aspects, In aspects, a total leaching of the solid-state electrolyte (e.g., sintered membrane, ceramic article) in the Leaching Test in deionized water at 25°C for 4 days can be from greater than or equal to 0.01 ppm to less than or equal to 5 ppm, from greater than or equal to 0.05 ppm to less than or equal to 4.0 ppm, from greater than or equal to 0. 1 ppm to less than or equal to 3.0 ppm, from greater than or equal to 0.2 ppm to less than or equal to 2.5 ppm, from greater than or equal to 0.3 ppm to less than or equal to 2.0 ppm, from greater than or equal to 0.5 ppm to less than or equal to 1.5 ppm, from greater than or equal to 0.7 ppm to less than or equal to 1.0 ppm, or any range or subrange therebetween. In preferred aspects, a total leaching of the solid-state electrolyte (e.g., sintered membrane, ceramic article) in the Leaching Test in deionized water at 25 °C for 4 days can be from greater than or equal to 0.01 ppm to less than or equal to 5 ppm, from greater than or equal to 0. 1 ppm to less than or equal to 3.0 ppm, or from greater than or equal to 0.5 ppm to less than or equal to 1.0 ppm.

[0066] 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., LiNCL, lanthanum nitrate, copper acetate, P2S5, etc.), artificial interfacial layers (e.g., L13N. (CLL^SiCl, AI2O3, LiAl, etc.), composite metallics (e.g., Li?Be, Li-rGO (reduced graphene oxide), layered Li-rGO, etc.), or combinations thereof. Inaspects, 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.

[0067] 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 second major surface 109 of the solid-state electrolyte 108. As shown, the anode 112 comprises a second major surface 115 opposite the first major surface 113 with an anode thickness 119 defined as an average distance therebetween when the solid-state battery 201 is in a fully charged state (defined below). In aspects, the anode thickness 119 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. In aspects, the anode thickness 119 can 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.

[0068] 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.

[0069] 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 firstcoating 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 second major surface 109 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 second major surface 109 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 battery 201 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.

[0070] Aspects of methods of making a solid-state electrolyte, sintered electrolyte, ceramic article, and / or a battery (e.g., solid-state battery) in accordance with the aspects of the present disclosure will now be discussed with reference to the flow chart shown in FIG. 6 and example method steps illustrated in FIGS. 7-8.

[0071] In aspects, as shown in FIG. 6, methods can begin at step 601. In aspects, step 601 can comprise providing or forming lithium-aluminum-titanium-phosphate (LATP) crystals. For example, LATP can be provided by purchase or can comprise forming the LATP crystals through heating (e.g., calcining) raw materials in stoichiometric amounts for the resulting LATP (e.g., that undergoes a solid-state reaction to form LATP crystals). In aspects, step 601 can additionally comprise providing materials for forming a green tape, for example, a solvent, a binder, and / or a dispersant in addition to an additive (discussed below) that arediscussed more in the following steps. The LATP (either as a raw material or in a green tape) can be within one or more of the corresponding ranges discussed above.

[0072] In aspects, after step 601 as shown in FIG. 6, methods can proceed to step 603 comprising forming a slurry. In aspects, as shown in FIG. 7, step 603 can comprise mixing raw materials (e.g., LATP crystals 713 and the additive 715) with one or more of a binder, a solvent, and / or a dispersant to form a slurry 711. For example, as shown, raw materials including LATP crystals 713 and the additive 715 can be mixed with a solvent (and optionally a dispersant, a defoamer, a plasticizer, and / or a protic base) in a container 701 using a blade 707 that is rotated (as shown by arrow 705) about a shaft 703. In aspects, the LATP crystals 713 and / or the additive 715 can be added after the other materials and / or the LATP crystals 713 and / or the additive 715 can be added as a series of batches, for example, to increase a dispersion (e.g., homogeneity) of the materials in the slurry 711.

[0073] In aspects, the additive (e.g., in the slurry and / or the green tape) can comprise a titanium-containing material (e.g., titanium-containing powder), an aluminum-containing material (e.g., aluminum-containing powder), or combinations thereof. In further aspects, the titanium-containing material (e.g., titanium-containing powder) can comprise one or more of TiCL or Ti2P4O7. In further aspects, the aluminum-containing material (e.g., aluminum- containing powder) can comprise one or more of A100H, AI2O3, Al(0H)3, or AINO3. Without wishing to be bound by theory, it is believed that the additive can facilitate the reaction of water soluble phases to LATP or other water insoluble phases (e.g., anatase, lithium-titanium- oxyphosphate crystals). For a titanium-containing additive, it is believed that lithium- aluminum-phosphate phases can react with titanium from the titanium-containing additive can form additional LATP with any excess titanium forming water insoluble anatase. For an aluminum-containing additive, it is believed that the aluminum additive can promote conversion of raw materials to LATP and / or lithium-aluminum-oxyphosphate.

[0074] In aspects, an amount of the additive, as a wt% of a total amount of the lithium - aluminum-titanium-phosphate crystals (e.g., in the slurry and / or in the green tape), can be 0.1 wt% or more, 0.2 wt% or more, 0.5 wt% or more, 0.7 wt% or more, 1.0 wt% or more, 1.2 wt% or more, 1.5 wt% or more, 2.0 wt% or more, 10.0 wt% or less, 7.0 wt% or less, 5.0 wt% or less, 4.0 wt% or less, 3.0 wt% or less, 2.0 wt% or less, 1.5 wt% or less, or 1.0 wt% or less. In aspects, an amount of the additive, as a wt% of a total amount of the lithium-aluminum- titanium-phosphate crystals (e.g., in the slurry and / or in the green tape), can be from greater than or equal to 0. 1 wt% to less than or equal to 10.0 wt%, from greater than or equal to 0. 1 wt% to less than or equal to 7.0 wt%, from greater than or equal to 0.2 wt% to less than orequal to 5.0 wt%, from greater than or equal to 0.2 wt%to less than or equal to 4.0 wt%, from greater than or equal to 0.5 wt% to less than or equal to 3.0 wt%, from greater than or equal to 0.5 wt% to less than or equal to 2.0 wt%, from greater than or equal to 0.7 wt% to less than or equal to 2.0 wt%, from greater than or equal to 1.0 wt% to less than or equal to 1 .5 wt%, from greater than or equal to 1.2 wt% to less than or equal to 1.5 wt%, or any range or subrange therebetween. In preferred aspects, an amount of the additive, as a wt% of a total amount of the lithium-aluminum-titanium-phosphate crystals (e.g., in the slurry and / or in the green tape), can be from greater than or equal to 0. 1 wt% to less than or equal to 10.0 wt%, from greater than or equal to 0.5 wt% to less than or equal to 2.0 wt%, or from greater than or equal to 0.7 wt% to less than or equal to 1.5 wt%.

[0075] In aspects, an amount of titanium in the additive, as a mol% of a total amount of titanium in the lithium-aluminum-titanium-phosphate crystals (e.g., in the slurry and / or in the green tape), can be 1.0 mol% or more, 2.0 mol% or more, 2.5 mol% or more, 3.0 mol% or more, 4.0 mol% or more, 5.0 mol% or more, 6.0 mol% or more, 7.0 mol% or less, 6.0 mol% or less, 5.0 mol% or less, 4.0 mol% or less, 3.0 mol% or less, or 2.0 mol% or less. In aspects, an amount of titanium in the additive, as a mol% of a total amount of titanium in the lithium- aluminum-titanium-phosphate crystals (e.g., in the slurry and / or in the green tape), can be greater than or equal to 1.0 mol% to less than or equal to 7.0 mol%, from greater than or equal to 2.0 mol% to less than or equal to 6.0 mol%, from greater than or equal to 2.5 mol% to less than or equal to 5.0 mol%, from greater than or equal to 3.0 mol% to less than or equal to 4.0 mol%, or any range or subrange therebetween. In preferred aspects, an amount of titanium in the additive, as a mol% of a total amount of titanium in the lithium-aluminum-titanium- phosphate crystals (e.g., in the slurry and / or in the green tape), can be from greater than or equal to 1.0 mol%to less than or equal to 7.0 mol%, from greater than or equal to 2.0 mol% to less than or equal to 6.0 mol%, or from greater than or equal to 2.5 mol% to less than or equal to 5.0 mol%.

[0076] In aspects, an amount of aluminum in the additive, as a mol% of a total amount of aluminum in the lithium-aluminum-titanium-phosphate crystals (e.g., in the slurry and / or in the green tape), can be 5.0 mol% or more, 6.0 mol% or more, 7.0 mol% or more, 8.0 mol% or more, 10.0 mol% or more, 12.0 mol% or more, 15.0 mol% or more, 17.0 mol% or more, 20.0 mol% or more, 25.0 mol% or less, 22.0 mol% or less, 20.0 mol% or less, 17.0 mol% or less, 15.0 mol% or less, 12.0 mol% or less, 10.0 mol% or less, or 8.0 mol% or less. In aspects, an amount of aluminum in the additive, as a mol% of a total amount of aluminum in the lithium- aluminum-titanium-phosphate crystals (e.g., in the slurry and / or in the green tape), can be fromgreater than or equal to 5.0 mol% to less than or equal to 25.0 mol%, from greater than or equal to 6.0 mol% to less than or equal to 22.0 mol%, from greater than or equal to 7.0 mol% to less than or equal to 2.0 mol%, from greater than or equal to 8.0 mol% to less than or equal to 17.0 mol%, from greaterthan or equal to 10.0 mol%to less than or equal to 15.0 mol%, from greater than or equal to 12.0 mol% to less than or equal to 15.0 mol%, or any range or subrange therebetween. In preferred aspects, an amount of aluminum in the additive, as a mol% of a total amount of aluminum in the lithium-aluminum-titanium-phosphate crystals (e.g., in the slurry and / or in the green tape), can be from greater than or equal to 5.0 mol% to less than or equal to 25.0 mol%, from greaterthan or equal to 7.0 mol% to less than or equal 20.0 mol%, or from 10.0 mol% to 17.0 mol%.

[0077] In aspects, an amount of the LATP crystals in the slurry, as a total amount of the slurry, can be 30 wt% or more, 35 wt% or more, 40 wt% or more, 45 wt% or more, 50 wt% or more, 52 wt% or more, 55 wt% or more, 57 wt% or more, 60 wt% or less, 57 wt% or less, 55 wt% or less, 52 wt% or less, 50 wt% or less, 45 wt% or less, or 40 wt% or less. In aspects, an amount of the LATP crystals in the slurry, as a total amount of the slurry, can be from 30 wt% to 60 wt%, from 35 wt% to 57 wt%, from 40 wt% to 55 wt%, from 45 wt% to 52 wt%, from 45 wt% to 50 wt%, or any range or subrange therebetween. In aspects, an amount of solvent in the slurry, as a total amount of the slurry, can be 25 wt% or more, 30 wt% or more, 35 wt% or more, 40 wt% or more, 45 wt% or more, 50 wt% or less, 45 wt% or less, 40 wt% or less, 35 wt% or less, or 30 wt% or less. In aspects, an amount of solvent in the slurry, as a total amount of the slurry, can be from 25 wt% to 50 wt%, from 30 wt% to 45 wt%, from 35 wt% to 40 wt%, or any range or subrange therebetween. In 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. An exemplary aspect of the solvent is water.

[0078] In aspects, although not shown, step 603 can further comprise deairing the slurry. In further aspects, deairing the slurry can comprise subjecting the slurry to a reduced pressure environment for a predetermined period of time. As used herein, a “reduced pressure environment” has an absolute pressure of less than 80 kiloPascals (kPa). In further aspects, the reduced pressure environment can comprise an absolute pressure in a range from about 1 kPa to about 80 kPa, from about 5 kPa to about 50 kPa, from about 10 kPa to about 30 kPa, or any range or subrange therebetween. In further aspects, the predetermined period of time can beabout 1 minute or more, about 5 minutes or more, about 30 minutes or less, or about 10 minutes or less, for example, from about 1 minute to about 30 minutes, from about 5 minutes to about 10 minutes, or any range or subrange therebetween.

[0079] After step 601 or 603, as shown in FIG. 8, methods can proceed to step 605 comprising casting the slurry 711 (see FIG. 7) to form a green tape 813 including the LATP crystals 713 and the additive 715 and having an initial thickness. In further aspects, the initial thickness can be within one or more of the ranges discussed above for the thickness 129. In further aspects, the initial thickness can be greater than the thickness 129 of the resulting solid- state electrolyte 108 by from about 1% to about 50%, from about 2% to about 40%, from about 5% to about 30%, from about 7% to about 20%, from about 10% to about 15%, or any range or subrange therebetween. In further aspects, casting can comprise using a doctor blade or other methods known in the art.

[0080] In aspects, the slurry and / or the green tape can comprise a binder. The binder can comprise one or more polymeric materials. The binder can provide mechanical strength to the green tape before and / or during the sintering. In aspects, the binder can be a polymer compatible with the solvent, for example, 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 exemplary aspect of the binder is an acrylic polymer system, which are commercially available from numerous polymer and casting companies. As used herein, “on a solvent-free basis” refers to the contents of the green tape excluding any contributions from solvent. In aspects, an amount of the binder in the green tape 813, as a wt% of a total amount of the green tape on a solvent-free basis, can be 3 wt% or more, 5 wt% or more, 7 wt% or more, 10 wt% or more, 12 wt% or more, 15 wt% or more, 17 wt% or more, 20 wt% or more, 22 wt% or more 25 wt% or more, 30 wt% or less, 27 wt% or less, 25 wt% or less, 22 wt% or less, 20 wt% or less, 17 wt% or less, 15 wt% or less, 12 wt% or less, 10 wt% or less, 7 wt% or less, or 5 wt% or less. In aspects, an amount of the binder in the green tape 813, as a wt% of a total amount of the green tape on a solvent-free basis, can be from 3 wt% to 30 wt%, from 5 wt% to 27 wt%, from 7 wt% to 25 wt%, from 10 wt% to 22 wt%, from 12 wt% to 20 wt%, from 15 wt%to 17 wt%, or any range or subrange therebetween.

[0081] 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. In aspects, the dispersant can comprise a fish oil or commercial dispersants, for example, the Hypermer line of dispersants (available from CrodaEnergy Technologies). In aspects, an amount of the dispersant in the cast green tape 813 (as a wt% of the green tape on a solvent-free basis, respectively) can be about 0 wt% or more, about 0.1 wt% or more, about 0.2 wt% or more, about 0.5 wt% or more, about 0.7 wt% or more, about 1.0 wt% or more, about 1.2 wt% or more, about 1.5 wt% or more, about 5 wt% or less, about 4 wt% or less, about 3 wt% or less, about 2 wt% or less, about 1.5 wt% or less, or about 1 wt% or less. In aspects, an amount of the dispersant in the cast green tape 813 (as a wt% of the green tape on a solvent-free basis, respectively) can be in a range from about 0 wt% to about 5 wt%, from about 0.1 wt% to about 5 wt%, from about 0.2 wt% to about 4 wt%, from about 0.5 wt% to about 3 wt%, from about 0.7 wt% to about 2 wt%, from about 1 wt% to about 1.5 wt%, or any range or subrange therebetween. Providing a dispersant can facilitate a good dispersion of LATP crystals in the solvent with few or no aggregates.

[0082] As noted above, additional components in the cast green tape 813 can include a defoamer and / or a plasticizer. For example, plasticizers can include a dibutyl carboxylic acid ester. Exemplary aspects of plasticizers include dibutyl phthalate, dibutyl adipate, dibutyl maleate, polyethylene glycol), and combinations thereof. In further aspects, the viscosity modifier can comprise dibutyl phthalate. Amounts of the additional components can be within one or more of the range discussed above in the previous paragraph for the amount of the dispersant. Alternatively, in aspects, the cast green tape 813 can be free from a defoamer, a plasticizer, and / or other additional components.

[0083] After step 601 or 605, as shown in FIG. 6, methods can proceed to step 607 comprising firing the green tape to form the solid-state electrolyte 108. In aspects, as shown in FIG. 8, step 607 comprises heating a green tape 813 (comprising the LATP crystals 713 and the additive 715) with one or more heaters 804a and / or 804b (e.g., in a first oven 803 as part of a firing apparatus 801). In further aspects, as shown, the green tape can be conveyed through the first oven 803 (e.g., one or more heaters 804a and / or 804b) in a direction 802. In even further aspects, the green tape can be conveyed on a setter plate, although long green tapes can be conveyed through using a rollers system spanning a distance greater than the first oven 803. The heating the green tape can remove organic materials (e.g., solvent and / or binder) in the green tape. Additionally, heating the green tape can sinter the green tape to form the solid-state electrolyte 108.

[0084] In aspects, the firing can comprise heating the green tape at a temperature of 600°C or more, 650°C or more, 700°C or more, 750°C or more, 800°C or more, 850°C or more, 900°C or more, 950°C or more, 1000°C or more, 1200°C or less, 1150°C or less, 1100°C or less, 1050°C or less, 1000°C or less, 950°C or less, 900°C or less, 850°C or less, or 800°C orless. In aspects, the firing can comprise heating the green tape at a temperature in a range from 600°C to 1200°C, from 650°C to 1150°C, from 700°Cto 1100°C, from 750°C to 1050°C, from 750°C to 1000°C, from 800°C to 950°C, from 850°C to 900°C, or any range or subrange therebetween. Providing a temperature of 1200°C or less (e.g., 1100°C or less, 1050°C or less, or 1000°C or less) can minimize a volatilization of lithium from the LATP crystals. 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.

[0085] In further aspects, with reference to FIG. 9, a maximum period of time that the green tape 813 is heated at a temperature within the range discussed in the previous paragraph (e.g., associated with the second oven 805) can be 60 minutes or less, 45 minutes or less, 30 minutes or less, 20 minutes or less, 17 minutes or less, 15 minutes or less, 12 minutes or less, 10 minutes or less, 7 minutes or less, 5 minutes or less, or 3 minutes or less. In further aspects, with reference to FIG. 9, a maximum period of time that the green tape 813 is heated at a temperature within the range discussed in the previous paragraph (e.g., associated with the second oven 805) can be in a range from 10 seconds to 60 minutes, from 20 seconds to 45 minutes, from 30 seconds to 30 minutes, from 45 seconds to 20 minutes, from 1 minute to 17 minutes, from 2 minutes to 15 minutes, from 3 minutes to 12 minutes, from 5 minutes to 10 minutes, or any range or subrange therebetween.

[0086] In aspects, although not shown, the solid-state electrolyte sheet formed in step 607 can be wound (e.g., rolled) on a spool, for example, for storage and / or transport. The thin form factor (e.g., thickness) and high edge strength enable the solid-state electrolyte sheet to be wound on the spool. In further aspects, the solid-state electrolyte sheet can be unwound from the spool and cut to a predetermined size based on the resulting battery that it is to be incorporated into, for example, in step 609.

[0087] In aspects after step 607, as shown in FIG. 6, methods can proceed to step 609 comprising assembling the solid-state electrolyte sheet into a battery (e.g., see FIGS. 1-2). In further aspects, step 607 can comprise disposing an anode over the first major surface of the solid-state electrolyte sheet and a cathode the second major surface opposite the first major surface.

[0088] After step 607 or 609, methods can be complete upon reaching step 611. In aspects, methods of making the making the solid-state electrolyte sheet, sintered membrane, ceramic article, and / or battery (e.g., solid-state battery) in accordance with aspects of the disclosure can proceed along steps 601, 603, 605, 607, 609, and 611 of the flow chart in FIG.6 sequentially, as discussed above. In aspects, methods can follow arrow 602 from step 601 to step 605, for example, if a slurry is already present by the end of step 601. In aspects, methods can follow arrow 604 from step 601 to step 605, for example, if a green tape is already present by the end of step 601. In aspects, methods can follow arrow 608 from step 607 to step 611, for example, if methods are complete at the end of step 607. Any of the above options may be combined to make the solid-state electrolyte sheet, sintered membrane, ceramic article, and / or battery (e.g., solid-state battery) in accordance with aspects of the disclosure.

[0089] EXAMPLES

[0090] Various aspects will be further clarified by the following examples. Comparative Example AA was formed from powderized LATP crystals (LATP powder) without any additive (as discussed above) that was cast into a green tape and heated (i.e., sintered) to form the sintered membrane. Examples 1-10 were formed from LATP powder with one or more additives (as discussed above) that was cast into a green tape and heated (i.e., sintered) form the sintered membrane.

[0091] Table 1 presents the base formulation for the slurry that was used to cast the green tape. These compositions corresponds to Comparative Example AA and Example 10, respectively. As indicated in the absolute weight column (g) for Example 10 in Table 1 relative to Comparative Example AA, the additive was added along with the LATP powder, where the relative amounts of all other components were kept the same as in Comparative Example AA, which applies for all of Example 1-10. For Examples 1-10 and Comparative Example AA, the solvent was a mixture of ethanol and toluene, and the binder was poly(vinyl butyral) (PVB).Table 1: Composition of Slurry for Comparative Example AA and Example 10

[0092] Table 2 presents the amount of additive and sintering conditions for Examples (Ex) 1-10 and Comparative Example AA as well as the results of the Leaching Test (for 4 days at 25°C) for each. In Examples 1-2 and 4-5, the additive was an aluminum-containing material, namely A100H. In Examples 6-10, the additive was a titanium-containing material, namely TiCh. For Example 3, the additive was an even mixture of A100H and TiCF. In Table 2, the amount of each additive is provided in wt% (based on 100 wt% of the amount of LATP powder)as well as a mol% of the corresponding amount of that element (e.g., Al, Ti) in the LATP power that is provided in parenthesis.Table 2: Composition, Sintering Temperature, and Leaching Results for Comparative Example AA and Examples 1-10

[0093] Table 2 and FIGS. 3-4 present leached concentration detected by ICP-MS after the 4 days at 25°C as described above for the Leaching Test. In Table 2, “UDL” means that the leached amount was under the detection limit for the ICP-MS, which will be taken as “0” for purposes of calculating the “total” concentration of leached material from the Leaching Test. In FIGS. 3-4, the vertical axis 301 (i.e., y-axis) presents leached concentration (C) in parts- per-million (ppm) with the Examples labeled along the horizontal axis (i.e., x-axis). For each Example, the total height of the bar is equal to the total leached concentration with each component detected (see the legend for Li, Al, Ti, and P) shown as stacked to make up the total leached concentration.

[0094] As shown, Comparative Example AA had a total leached concentration greater than 16 ppm that was primarily phosphorous-containing compounds. Examples 1-10 all have lower amounts of the total leached concentration (e.g., 15 ppm or less, 12 ppm or less, 11 ppm or less) than Comparative Example AA. Further, Examples 1-8 and 10 have a total leached concentration less than 10 ppm, less than 8 ppm, and less than 7 ppm. Moreover, Examples 1- 4, 6-8 and 10 have a total leached concentration less than 5 ppm, less than 4 ppm, and less than 3 ppm. Example 2 had the lowest total leached concentration of 0.24 ppm followed by Example 8 with 0.82 ppm (both less than 1 ppm).

[0095] Examples 1-5 (Table 2 and FIG. 3) contain at least an aluminum -containing additive. Examples 1-2 both contain 10 wt% A100H as the additive, but Example 1 wassintered at 900°C while Example 2 was sintered at 1000°C. Since Example 2 has a much lower total leached concentration than Example 1 (0.24 ppm < 2.93 ppm), the increased sintering temperature (1000°C > 900°C) of Example 2 appears to more fully reacted (or otherwise converted) the aluminum-containing additive to water insoluble crystals. Examples 2, 4, and 5 were sintered at 1000°C but with different amounts of A1OOH (10 wt%, 2 wt%, 0.5 wt%). As shown, Example 2 (10 wt% A1OOH) had the lowest total leached concentration followed by Example 4 (5 wt% A1OOH). Example 3 contained both A1OOH and TiO? as additives with the same total amount of additive (10 wt%) as Example 1, and Examples 1 and 3 have roughly the same total leached concentration.

[0096] Examples 6-10 (Table 2 and FIG. 4) as well as Example 3 contain at least a titanium-containing additive. Examples 6-7 both contain 10 wt% TiO? as the additive, but Example 6 was sintered at 900°C while Example 7 was sintered at 1000°C. Since Example 7 has a lower total leached concentration than Example 6 (1.81 ppm < 2.84 ppm), the increased sintering temperature (1000°C > 900°C) of Example 7 appears to more fully reacted (or otherwise converted) the titanium-containing additive to water insoluble crystals. Examples 7- 9 were fired at 1000°C with different amounts of TiCh additive. Of Examples 7-9 (10 wt%, 2 wt%, 0.5 wt% TiO2), Example 8 (2 wt% TiO2) had the lowest total leached amount (0.82 ppm).

[0097] Table 3 presents the phase assemblage in Examples 1-9 and Comparative Examples as measured by XRD using Reitveld refinement. As discussed above, the wt% of each phase was calculated based on the relative area of each curve fit to the listed phases based on reference crystallographic data. As shown in Table 3, Examples 1-2 (10 wt% A1OOH) have less than 60 wt% LATP. Although Examples 1-2 have low total leaching concentrations (Table 2 and FIG. 3), Examples 1-2 have low amounts of LATP in the sintered membrane. In contrast, Examples 4-5 and 8-9 have 95 wt% or more LATP. It is believed that higher amounts of LATP are associated with improved ionic conductivity. Combining the leaching concentrations (Table 2) with the amount of LATP (Table 3), it appears that Example 4 (2 wt% A1OOH) achieves the lowest leaching concentration (1.12 ppm) of the Examples with 95 wt% or more LATP, although Example 5 (0.5 wt% A1OOH) is a close second. For the titanium-containing examples with XRD analysis (Examples 3 and 6-9), it appears that Example 8 (2 wt% TiO?) achieves the lowest leaching concentration (0.82 ppm) of the Examples having 95 wt% or more LATP. Of note, Example 9 has 100 wt% LATP. Although XRD data is not reported for Example 10, it is expected that Example 10 will have a high amount of LATP (similar to Examples 8-9) since the amount of TiO2 (1 wt%) is intermediate relative to those Examples (2 wt% and 0.5 wt%, respectively).Table 3: Phase Assemblage (wt%) from XRD for Comparative Example AA and Examples 1-9

[0098] FIG. 5 represents an SEM image of a fracture cross-section of Example 10. As discussed above, crystal grains 503 with small grain size are visible. Also, closed pores 507 visible as small black spots are shown. Overall, the porosity was less than 5%, less than 2%, and less than 1%. Also, the porosity of Example 10 was found to be a closed porosity (based on the dye test described above with reference to closed porosity).

[0099] The above observations can be combined to provide a solid-state electrolyte, a sintered membrane, ceramic article, and / or a battery containing the same as well as method of making the same. The solid-state electrolyte sheet can achieve high ionic conductivity (e.g., 10'4S / cm or more at 25 °C) with a high fraction of crystals being lithium-aluminum -titaniumphosphate (LATP) crystals. For example, 95 wt% or more of the crystals can be LATP, which is demonstrated for Examples 4-5 and 8-9 herein.

[0100] Also, the solid-state electrolyte, a sintered membrane, and / or ceramic article can have a total leaching concentration in a Leaching Test (described herein) for 4 days at 25 °C of 5 ppm or less (e.g., 4 ppm or less, 3 ppm or less, 2 ppm or less, or 1 ppm or less), which can provide increased stability and / or increased environmental resistance. Without wishing to be bound by theory, the primary crystal phase and the secondary crystal phase of the solid-state electrolyte (e.g., sintered membrane, ceramic article) are insoluble in water, which prevents leaching and / or dissolution of the solid-state electrolyte that can otherwise lead to failure of the resulting battery. For example, the solid-state electrolyte (e.g., sintered membrane, ceramic article) can be free of one or more of LiPCE, LisPC , Li4P2O?, or Li9A13(PO4)2(P2O7)3. Suchimproved environmental resistance is beneficial for marine applications, where seawater and / or rainwater may seep into the battery; if the solid-state electrolyte did not have the increased environmental resistance disclosed herein, the seawater and / or rainwater could cause leaching and / or dissolution of the solid-state electrolyte that may lead to failure of the resulting battery.

[0101] Methods of the present disclosure involve heating a green tape having LATP and an additive including aluminum and / or titanium. Without wishing to be bound by theory, it is believed that the additive can facilitate the reaction of water soluble phases to LATP or other water insoluble phases (e.g., anatase, lithium-titanium-oxyphosphate crystals). For a titanium-containing additive, it is believed that lithium-aluminum-phosphate phases can react with titanium from the titanium-containing additive can form additional LATP with any excess titanium forming water insoluble anatase. For an aluminum-containing additive, it is believed that the aluminum additive can promote conversion of raw materials to LATP and / or lithium- aluminum-oxyphosphate .

[0102] 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.

[0103] 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.

[0104] 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.”

[0105] As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, aspects include from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular valueforms another aspect. Whether or not a numerical value or endpoint of a range in the specification recites “about,” the numerical value or endpoint of a range is intended to include two aspects: one modified by “about,” and one not modified by “about.” It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint and independently of the other endpoint.

[0106] The terms “substantial,” “substantially,” and variations thereof as used herein are intended to note that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover, as defined above, “substantially similar” is intended to denote that two values are equal or approximately equal. In aspects, “substantially similar” may denote values within about 10% of each other, for example, within about 5% of each other, or within about 2% of each other.

[0107] 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.

[0108] 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 apparatus consists 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.

[0109] 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.

[0110] 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

CLAIMSWhat is claimed is:1 . A sintered membrane comprising a ceramic article comprising: a primary crystal phase comprising lithium-aluminum-titanium-phosphate crystals; and a secondary crystal phase comprising one or more of anatase or lithium-titanium- oxyphosphate crystals, wherein the sintered membrane comprises a closed porosity of less than or equal to 5%.

2. The sintered membrane of claim 1, wherein the primary crystal phase comprises from 95 wt% to 100 wt% of the ceramic article, and the secondary crystal phase comprises from greater than 0 wt% to 5 wt% of the ceramic article.

3. The sintered membrane of any one of claims 1-2, wherein the sintered membrane is free of crystals or glasses of: LiPCL, LisPCL, Li4P2O?, and LigAL PCh ^CL .

4. The sintered membrane of any one of claims 1-3, wherein the sintered membrane exhibits a total leaching of less than or equal to 5 parts-per-million in a Leaching Test in deionized water at 25°C for 4 days.

5. The sintered membrane of claim 3, wherein the total leaching is from 0.1 parts-per- million to 3.0 parts-per-million in the Leaching Test.

6. The sintered membrane of any one of claims 3-4, wherein the total leaching is from 0.2 parts-per-million to 1.0 parts-per-million in the Leaching Test.

7. The sintered membrane of any one of claims 1-6, wherein the lithium-aluminum- titanium-phosphate crystals comprises a formula of one or more of:Lii+xAlxTi2-xP30i2;Lii+x+yAlxTi2-xSiyP3-yOi2;Lii+xAlxGe2-xP30i2;Lil+x+yAlxGe2-xSiyP3-yO12;Lii+xAlx(Ge,Ti)2-xP30i2; orLii+x+yAlx(Ge,Ti)2-xSiyP3-yOi2,wherein “x” is between 0.3 and 0.5.

8. The sintered membrane of claim 7, wherein the lithium-aluminum-titanium -phosphate crystals comprise Li+xAL h-xPsOn and “x” is between 0.3 and 0.5.

9. The sintered membrane of any one of claims 1-8, wherein a median grain size of the primary crystal phase is less than or equal to 1.0 micrometers.

10. The sintered membrane of any one of claims 1-9, wherein the sintered membrane exhibits a conductivity at 25°C of greater than or equal to 10'4Siemens per centimeter (S / cm).

11. The sintered membrane of any one of claims 1-10, wherein the sintered membrane comprises a thickness from greater than or equal to 10 micrometers to less than or equal to 250 micrometers.

12. The sintered membrane of any one of claims 1-11, wherein the sintered membrane is a solid-state electrolyte for use in a secondary battery.

13. A battery comprising: a lithium -containing anode; a solid-state electrolyte comprising the sintered membrane of any one of claims 1-12; and a cathode, wherein the solid-state electrolyte is positioned between the lithium-containing anode and the cathode.

14. A method of making a sintered membrane comprising: forming a green tape comprising lithium-aluminum-titanium-phosphate crystals and an additive comprising one or more of: a titanium-containing powder or an aluminum -containing powder; heating the green tape to a first temperature from 600°C to 1200°C to form the sintered membrane, wherein the sintered membrane comprises:a primary crystal phase comprising lithium-aluminum-titanium-phosphate crystals; and a secondary crystal phase comprising one or more of anatase or lithium- titanium-oxyphosphate crystals.

15. The method of claim 14, wherein the first temperature is from 750°C to 1000°C.

16. The method of any one of claims 14-15, wherein the additive comprises the aluminum - containing powder including one or more of: Al OOH, AI2O3, Al(0H)3, or AINO3.

17. The method of any one of claims 14-16, wherein the additive comprises the titanium - containing powder including one or more of: TiO2 or ^PrO?.

18. The method of any one of claims 14-17, wherein a total amount of the additive is from greater than or equal to 0. 1 wt% to less than or equal 10.0 wt% of an amount of the lithiumaluminum -titanium-phosphate crystals in the green tape.

19. The method of any one of claims 14-17, wherein a total amount of the additive is from greater than or equal to 0.5 wt% to less than or equal 2.0 wt% of an amount of the lithiumaluminum -titanium-phosphate crystals in the green tape.

20. The method of any one of claims 14-17, wherein an amount of titanium in the additive is from greater than or equal to 1.0 mol% to 7.0 mol% of a total amount of titanium in the lithium-aluminum-titanium -phosphate crystals in the green tape.

21. The method of any one of claims 14-17, wherein an amount of aluminum in the additive is from greater than or equal to 5.0 mol% to 25.0 mol% of a total amount of titanium in the lithium-aluminum-titanium -phosphate crystals in the green tape.

22. The method of any one of claims 14-21, further comprising: tape casting a slurry to form the green tape, wherein the slurry comprises a solvent, a binder, and a dispersant in addition to the lithium-aluminum-titanium-phosphate crystals and the additive, wherein the solvent is from 25wt% to 50 wt% of the slurry, and an amount of the lithium-aluminum-titanium -phosphate crystals in the slurry is from 30 wt% to 60 wt%.

23. The method of any one of claims 14-22, wherein the sintered membrane comprises the sintered membrane of any one of claims 1-13.

24. A method of making a battery comprising: forming a solid-state electrolyte using the method of making the sintered membrane of any one of claims 14-23; and positioning the solid-state electrolyte between a lithium-containing anode and a cathode.

25. A sintered membrane comprising: a primary crystal phase comprising lithium-aluminum-titanium-phosphate crystals; and a secondary crystal phase comprising one or more of anatase or lithium-titanium- oxyphosphate crystals, wherein the sintered membrane exhibits a total leaching of less than or equal to 5 parts- per-million in a Leaching Test.

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