Composite garnet electrolytes with a porous surface, batteries, and methods of making the same

Abstract

Batteries include a cathode, a solid-state electrolyte, and an anode. The solid-state electrolyte is a composite garnet electrolyte with an intergranular microstructures extending from a first major surface with a lithium phase between garnet crystals. In aspects, the composite garnet electrolyte can have an amount of lithium from 11.2 wt% to 15 wt%, from 11.3 wt% to 12.2 wt%, or from 11.4 wt% to 12 wt%. In aspects, the composite garnet electrolyte can have greater than a stoichiometric amount of lithium for the garnet crystals by from 0.1 wt% to 4 wt%, from 0.2 wt% to 1.1 wt%, or from 0.3 wt% to 0.9 wt%. Methods include etching at least a first major surface of a composite garnet electrolyte with an acid to form the composite garnet electrolyte with pores. In aspects, methods can further include tape casting and firing a green body to form the composite garnet electrolyte.

Description

COMPOSITE GARNET ELECTROLYTES WITH A POROUS SURFACE, BATTERIES, AND METHODS OF MAKING THE SAME

[0001] This application claims the benefit of priority of Chinese Patent Application Serial No. 202311426590.X filed on October 30, 2023, the content of which is relied upon and incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to composite porous garnet electrolytes, batteries, and methods of manufacturing thereof, and more particularly batteries comprising a composite garnet electrolyte with a porous surface and methods of making the same.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 due to their high safety, improved energy density, high ionic conductivity, and stability against Li metal. However, conventional Li-metal batteries often suffer from issues with capacity retention and / or longevity, especially when operated at higher capacities. Consequently, there is a need to address these issues.SUMMARY

[0004] The present disclosure provides solid-state electrolytes, batteries, and methods of making the same comprising a surface(s) of the solid-state electrolyte that can be easily etched to form an electrolyte with a porous surface (e.g., composite garnet electrolyte with a porous surface). The electrolyte with the porous surface (e.g., composite garnet electrolyte with the porous surface) can enable lower interfacial resistance, increased charging performance, and / or increase cycling stability. Also, the electrolyte with the porous surface (e.g., composite garnet electrolyte with the porous surface) can enable a high ring-on-ring strength (e.g., about 150 MPa or more or from about 150 MPa to about 600 MPa).

[0005] As discussed herein, providing excess lithium (relative to stoichiometry by, for example, from 0.1 wt% to 4 wt%, from 0.2 wt% to 1.1 wt%, or from 0.3 wt% to 0.9 wt%) in the composite garnet electrolyte can facilitate the formation of an mixture of intergranular and transgranular microstructure and facilitate etching of the solid-state electrolyte (e.g., composite garnet electrolyte) to form a solid-state electrolyte with a porous surface (e.g., composite garnetelectrolyte with a porous surface). For example, providing from 11.2 wt% to 15 wt% or from 11.3 wt% to 12.2 wt% can form an intergranular microstructure near the major surfaces of the composite garnet electrolyte, which can facilitate etching of the composite garnet electrolyte to form a porous surface of the solid-state electrolyte. Providing a transgranular microstructure near and / or at the first major surface can facilitate etching to form large and / or deep pores therein.

[0006] As discussed herein, 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.

[0007] A green tape can comprise excess lithium (e.g., 0.5 wt % or more, 2 wt% or more, or 10 wt% or more based on the amount of garnet in the green tape) that is not completely removed by firing (e.g., sintering). In combination with excess lithium, the firing condition determine the amount of lithium remaining in the resulting electrolyte. If the firing is a too high a temperature (e.g., greater than 1200°C) and / or for too long a period of time (dependent on the temperature, e.g., about greater than 60 minutes), the vast majority of the excess lithium added to the green tape can be volatilized to produce an electrolyte without a transganular microstructure contrary to the aspects of the present disclosure.

[0008] Without wishing to be bound by theory, it is believed that the etching may preferentially etch the lithium phase between garnet grains of the composite garnet electrolyte in the region with intergranular microstructure, and consequently, the composite garnet electrolyte of the present disclosure can be more easily and / or more quickly etched relative to other garnet electrolytes (e.g., with stoichiometric amounts of lithium). Providing a grain size of about 3 pm or less, from about 1 pm to about 3 pm, or from about 1 pm to about 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. Providing deep pores (e.g., about 2 pm or more, from about 20 pm to about 60 pm, about 5% of the electrolyte thickness or more, or from about 10% to about 20% of the electrolyte thickness) can increase an effective surface area of the solid-state electrolyte (e.g., facing an anode and / or facing a cathode), which candecrease an interfacial resistance of battery including the solid-state electrolyte (e.g., composite garnet electrolyte with a porous surface).

[0009] 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.

[0010] Aspect 1. A method of making a porous surface of a composite garnet electrolyte comprising: etching at least a first major surface of the composite garnet electrolyte with an acid to form the porous surface of the garnet electrolyte comprising pores, wherein the composite garnet electrolyte comprises an intergranular microstructure extending from the first major surface to a first depth, the composite garnet electrolyte comprising a lithium phase between garnet crystals, and an electrolyte thickness defined between the first major surface and a second major surface opposite the first major surface.

[0011] Aspect 2. The method of aspect 1, wherein the etching removes at least a portion of the lithium phase.

[0012] Aspect 3. The method of any one of aspects 1-2, wherein an amount of lithium in the composite garnet electrolyte, on an oxide basis of the garnet electrolyte, is from about 11.2 wt% to about 15 wt%.

[0013] Aspect 4. The method of aspect 3, wherein the amount of lithium in the composite garnet electrolyte is from about 11.3 wt% to about 12.2 wt%.

[0014] Aspect 5. The method of any one of aspects 3-4, wherein the amount of lithium in the composite garnet electrolyte is from about 11.4 wt% to about 12 wt%.

[0015] Aspect 6. The method of any one of aspects 1-2, wherein an amount of lithium in the composite garnet electrolyte, on an oxide basis of the composite garnet electrolyte, is greater than a stoichiometric amount of lithium for the garnet crystals by from about 0.1 wt% to about 4 wt%.

[0016] Aspect 7. The method of aspect 6, wherein the amount of lithium in the composite garnet electrolyte is greater than the stoichiometric amount of lithium by from about 0.2 wt% to about 1.1 wt%.

[0017] Aspect 8. The method of any one of aspects 6-7, wherein the amount of lithium in the composite garnet electrolyte is greater than the stoichiometric amount of lithium by from about 0.3 wt% to about 0.9 wt%.

[0018] Aspect 9. The method of any one of aspects 1-8, wherein the intergranular microstructure extends from the first major surface to the first depth of about 10% of the electrolyte thickness or more.

[0019] Aspect 10. The method of aspect 9, wherein the composite garnet electrolyte comprises a transgranular microstructure positioned between regions comprising the intergranular microstructure.

[0020] Aspect 11. The method of any one of aspects 1-10, wherein a median grain size of the garnet crystals is less than 3 pm.

[0021] Aspect 12. The method of aspect 11, wherein the median grain size of the garnet crystals is from about 1 pm to about 2 pm.

[0022] Aspect 13. The method of any one of aspects 1-12, wherein a mean pore size of the pores is greater than 0.25 pm.

[0023] Aspect 14. The method of aspect 13, wherein the mean pore size of the pores is from 3 pm to about 20 pm.

[0024] Aspect 15. The method of any one of aspects 1-14, wherein an average pore depth of the pores is about 2 pm or more.

[0025] Aspect 16. The method of any one of aspects 1-15, further comprising: prior to the etching, contacting the first major surface with water for at least 1 minute, wherein a concentration of the acid during the etching is from about 0.5 M to about 5 M.

[0026] Aspect 17. The method of aspect 16, wherein the etching occurs for a period of time from 3 minutes to 20 minutes.

[0027] Aspect 18. The method of any one of aspects 1-17, further comprising: casting a green tape comprising garnet, excess lithium, a binder, and a solvent, wherein an amount of the excess lithium, as a wt% of an amount of the garnet, is greater than 0.5 wt%; and firing the green tape to form the composite garnet electrolyte.

[0028] Aspect 19. The method of aspect 18, wherein the amount of the excess lithium, as a wt% of an amount of the garnet, is from about 5 wt% to about 50 wt%.

[0029] Aspect 20. The method of any one of aspects 18-19, wherein the firing comprises heating the green tape at a temperature from about 900°C to about 1200°C for a period of time of 60 minutes or less.

[0030] Aspect 21. The method of aspect 20, wherein the temperature is from about 1000°C to about 1125°C.

[0031] Aspect 22. The method of aspect 20, wherein the period of time is from 5 minutes to 30 minutes.

[0032] Aspect 23. The method of any one of aspects 1-22, wherein the composite garnet electrolyte with the porous surface comprises a ring-on-ring strength from about 150 MPa to about 600 MPa.

[0033] Aspect 24. The method of any one of aspects 1-23, wherein an interfacial resistance of the garnet electrolyte with the porous surface is less than or equal to 20 at 25°C.

[0034] Aspect 25. The method of any one of aspects 1-24, wherein a battery containing the composite garnet electrolyte with the porous surface can withstand a critical current density of 2 mA / cm2or more at 60°C.

[0035] Aspect 26. The method of aspect 25, wherein the critical current density is 5 mA / cm2or more.

[0036] Aspect 27. The method of any one of aspects 1-26, wherein a battery containing the composite garnet electrolyte with the porous surface can withstand 70 cycles with charging and discharging at 2 mA / cm2.

[0037] Aspect 28. The method of any one of aspects 1-27, wherein the garnet crystals are doped with tantalum.

[0038] Aspect 29. A composite garnet electrolyte comprising: pores extending from a first major surface; and an intergranular microstructure extending from the first major surface to a first depth, wherein the intergranular microstructure comprises a lithium phase between garnet crystals, and an electrolyte thickness defined between the first major surface and a second major surface opposite the first major surface.

[0039] Aspect 30. The composite garnet electrolyte of aspect 29, wherein an amount of lithium in the composite garnet electrolyte, on an oxide basis of the composite garnet electrolyte, is from about 11.2 wt% to about 15 wt%.

[0040] Aspect 31. The garnet electrolyte of aspect 30, wherein the amount of lithium in the composite garnet electrolyte is from about 11.3 wt% to about 12.2 wt%.

[0041] Aspect 32. The garnet electrolyte of any one of aspects 30-31, wherein the amount of lithium in the composite garnet electrolyte is from about 11.4 wt% to about 12 wt%.

[0042] Aspect 33. The composite garnet electrolyte of aspect 29, wherein an amount of lithium in the composite garnet electrolyte, on an oxide basis of the composite garnet electrolyte,is greater than a stoichiometric amount of lithium for the garnet crystals by from about 0.1 wt% to about 4 wt%.

[0043] Aspect 34. The composite garnet electrolyte of aspect 33, wherein the amount of lithium in the composite garnet electrolyte is greater than the stoichiometric amount of lithium by from about 0.2 wt% to about 1.1 wt%.

[0044] Aspect 35. The composite garnet electrolyte of any one of aspects 33-34, wherein the amount of lithium in the composite garnet electrolyte is greater than the stoichiometric amount of lithium by from about 0.3 wt% to about 0.9 wt%.

[0045] Aspect 36. The composite garnet electrolyte of any one of aspects 29-35, wherein the intergranular microstructure extends from the first major surface to the first depth of about 10% of the electrolyte thickness or more.

[0046] Aspect 37. The composite garnet electrolyte of aspect 36, wherein the composite garnet electrolyte comprises a transgranular microstructure positioned between regions comprising the intergranular microstructure.

[0047] Aspect 38. The composite garnet electrolyte of any one of aspects 29-37, wherein a median grain size of the garnet crystals is less than 3 pm.

[0048] Aspect 39. The composite garnet electrolyte of aspect 38, wherein the median grain size of the garnet crystals is from about 1 pm to about 2 pm.

[0049] Aspect 40. The composite garnet electrolyte of any one of aspects 29-39, wherein a mean pore size of the pores is greater than 1 pm.

[0050] Aspect 41. The composite garnet electrolyte of aspect 40, wherein the mean pore size of the pores is from 3 pm to about 20 pm.

[0051] Aspect 42. The composite garnet electrolyte of any one of aspects 29-41, wherein an average pore depth of the pores is about 2 pm or more.

[0052] Aspect 43. The composite garnet electrolyte of any one of aspects 29-42, wherein the electrolyte thickness is from 20 pm to 200 pm.

[0053] Aspect 44. The composite garnet electrolyte of any one of aspects 29-43, wherein the garnet electrolyte comprises a ring-on-ring strength from about 150 MPa to about 600 MPa.

[0054] Aspect 45. The composite garnet electrolyte of any one of aspects 26-44, wherein the garnet crystals are doped with tantalum.

[0055] Aspect 46. The composite garnet electrolyte of any one of aspects 29-45, wherein an interfacial resistance of the composite garnet electrolyte is less than or equal to 20 at 25°C.

[0056] Aspect 47. A battery comprising:a lithium-containing anode; the composite garnet electrolyte of any one of aspects 29-46; and a cathode, wherein the garnet electrolyte is positioned between the lithium-containing anode and the cathode.

[0057] Aspect 48. The battery of aspect 47, further comprising a lithium salt solution disposed between the composite garnet electrolyte and the cathode.

[0058] Aspect 49. The battery of any one of aspects 47-48, wherein an interfacial resistance of the battery is less than or equal to 20 at 25°C.

[0059] Aspect 50. The battery of any one of aspects 47-49, wherein the battery can withstand a critical current density of 2 mA / cm2or more at 60°C.

[0060] Aspect 51. The battery of aspect 50, wherein the critical current density is 5 mA / cm2or more.

[0061] Aspect 52. The battery of any one of aspects 47-51, wherein the battery can withstand 70 cycles with charging and discharging at 2 mA / cm2.

[0062] Aspect 53. A composite garnet electrolyte comprising: an intergranular microstructure extending from the first major surface to a first depth, wherein the intergranular microstructure comprises a lithium phase between garnet crystals, an amount of lithium in the garnet electrolyte, on an oxide basis of the garnet electrolyte, is greater than a stoichiometric amount of lithium for the garnet crystals by from about 0.1 wt% to about 4 wt%.

[0063] Aspect 54. The composite garnet electrolyte of claim 53, wherein the amount of lithium in the composite garnet electrolyte is greater than the stoichiometric amount of lithium by from about 0.2 wt% to about 1.1 wt%.

[0064] Aspect 55. A composite garnet electrolyte comprising: an intergranular microstructure extending from the first major surface to a first depth, wherein the intergranular microstructure comprises a lithium phase between garnet crystals, an amount of lithium in the composite garnet electrolyte, on an oxide basis of the composite garnet electrolyte, is from 11.3 wt% to 12.2 wt%.

[0065] Aspect 56. The composite garnet electrolyte of any one of claims 53-55, wherein the amount of lithium in the porous garnet electrolyte is from about 11.4 wt% to about 12 wt%.

[0066] Aspect 57. The composite garnet electrolyte of any one of aspects 53-56, wherein the intergranular microstructure extends from the first major surface to the first depth of about 10% of the electrolyte thickness or more.

[0067] Aspect 58. The composite garnet electrolyte of aspect 57, wherein the composite garnet electrolyte comprises a transgranular microstructure positioned between regions comprising the intergranular microstructure.

[0068] Aspect 59. The composite garnet electrolyte of any one of aspects 53-58, wherein a median grain size of the garnet crystals is less than 3 pm.

[0069] Aspect 60. The composite garnet electrolyte of aspect 59, wherein the median grain size of the garnet crystals is from about 1 pm to about 2 pm.

[0070] Aspect 61. The composite garnet electrolyte of any one of aspects 53-60, wherein the electrolyte thickness is from 20 pm to 200 pm.

[0071] Aspect 62. The composite garnet electrolyte of any one of aspects 53-61, wherein the composite garnet electrolyte comprises a ring-on-ring strength from about 150 MPa to about 600 MPa.

[0072] Aspect 63. The composite garnet electrolyte of any one of aspects 53-62, wherein the garnet crystals are doped with tantalum.BRIEF DESCRIPTION OF THE DRAWINGS

[0073] 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:

[0074] FIG. 1 schematically illustrates a general structure of a solid-state battery in accordance with aspects of the disclosure;

[0075] FIG. 2 illustrates a simplified solid-state battery with the solid-state electrolyte in accordance with aspects of the disclosure;

[0076] FIG. 3 illustrates a step in an exemplary method comprising disposing a precursor on the solid-state electrolyte to form an anode;

[0077] FIG. 4 illustrates a step in an exemplary method comprising disposing a liquid electrolyte over a cathode;

[0078] FIG. 5 illustrates a step in an exemplary method comprising disposing the solid- state electrolyte over the cathode;

[0079] FIG. 6 illustrates a step in an exemplary method comprising etching the first major surface of the solid-state electrolyte;

[0080] FIG. 7 illustrates a step in an exemplary method comprising etching the second major surface of the solid-state electrolyte;

[0081] FIG. 8 presents lithium-ion conductivity as a function of lithium content (Li2O wt%) of garnet;

[0082] FIG. 9 illustrates Nyquist plots for Example 1 A and Comparative Example AA;

[0083] FIG. 10 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Comparative Example BB;

[0084] FIG. 11 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Comparative Example AA;

[0085] FIG. 12 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Example 3;

[0086] FIG. 13 schematically illustrates a scanning electron microscope (SEM) image of a surface of Comparative Example BB;

[0087] FIG. 14 schematically illustrates a scanning electron microscope (SEM) image of a surface of Example 2;

[0088] FIG. 15 schematically illustrates a scanning electron microscope (SEM) image of a surface of Example 3;

[0089] FIG. 16 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Comparative Example BB;

[0090] FIG. 17 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Example 2;

[0091] FIG. 18 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Example 3;

[0092] FIG. 19 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Example 4;

[0093] FIG. 20 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Example 5;

[0094] FIG. 21 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Example 6;

[0095] FIG. 22 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Example 7;

[0096] FIG. 23 schematically illustrates a scanning electron microscope (SEM) image of a cross-section of Example 4 A;

[0097] FIG. 24 schematically illustrates a scanning electron microscope (SEM) image of a surface of Example 4 A;

[0098] FIG. 25 schematically illustrates a scanning electron microscope (SEM) image of a surface of Example 7 A; and

[0099] FIG. 26 illustrates a pore size distribution of Examples 12-13 and Comparative Examples CC-DD.

[0100] 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

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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) (LiNidCoeM -d-eCh, where 0 < d < l, 0 < e < l, for example, LiNio.5Coo.2Mno.3O2 (NCM523), LiNio.6Coo.2Mno.2O2 (NCM622), etc.), lithium iron phosphate (LiFePOd) (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, NaVPOdF, 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^CL), MgMn20d, 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 cathode104 shown in FIGS. 5-6) of the cathode 104 can be about 5 milligrams per centimeter squared (mg / cm2), about 8 mg / cm2or more, about 10 mg / cm2or more, about 15 mg / cm2or more, about 20 mg / cm2or more, about 50 mg / cm2or less, about 30 mg / cm2or less, about 25 mg / cm2or less, about 20 mg / cm2or less, or about 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 about 5 mg / cm2to about 50 mg / cm2, from about 8 mg / cm2to about 30 mg / cm2, from about 10 mg / cm2to about 25 mg / cm2, from about 15 mg / cm2to about 20 mg / cm2, or any range or subrange therebetween.

[0106] 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 (e.g., ionic liquid, deep eutectic solvent (DES), or an aprotic solvent). 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 (e.g., DES-based 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 about 50°C to about 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 (LiCIC ), lithium tetrafluorob orate (LiBF4), lithium triflate (LiSCECFs), Li SChCFs or combinations thereof. In further aspects, a concentration of the lithium-containing salt can be about 0.5 molar (M) or more, about 1 M or more, about 1.2 M or more, about 1.5 M or more, about 3 M or less, about 2.5 M or less, or about 2 M or less, for example, in a range from about 0.5 M to about 3 M, from about 1 M to about 3 M, from about 1.2 M to about 2.5 M, from about 1.5 M to about 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 of the cathode 104 shown in FIGS. 5-6) of the cathode 104 can be about 5 pL / cm2or more, about 8 pL / cm2or more, about 10 pL / cm2or more, about 12 pL / cm2or more, about 15 pL / cm2or more, about 20 pL / cm2or less, about 15 pL / cm2or less, about 12 pL / cm2or less, or about 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 about5 qL / cm2to about 20 pL / cm2, from about 8 pL / cm2or to about 15 pL / cm2or, from about 10 pL / cm2to about 12 pL / cm2, or any range or subrange therebetween.

[0107] 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., about 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 poly sulfide 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.

[0108] In aspects, the solid-state electrolyte 108 can comprise a lithium-phosphorous- oxynitride (LiPON), lithium garnet (LiyLasZ^On), lithium phosphosulfide, or combinations thereof. In further aspects, a LIPON material can comprise the structure Li3+yPO4-xNx, where y > 0 and 0 < x < 4. 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). As used herein, “LLZO” refers to compounds including lithium, lanthanum, zirconium, and oxygen. In even further aspects, the solid-state electrolyte 108 can comprise a lithium-garnet, for example, at least one of: (i) Li7-3a a3Zr2LaOi2, with L = Al, Ga or Fe and 0 < a < 0.33; (ii) LiyLas-bZ^MbOn, with M = Bi or Y and 0 < b < 1; (iii) Li7-cLa3(Zr2- c,Nc)Oi2, with N = In, Si, Ge, Sn, V, W, Te, Nb, or Ta and 0 < c < 1; (iv) protonated LLZO (e.g., HxLi6.5-xLa3Zr1.5I0.5O12, with I = In, Si, Ge, Sn, V, W, Te, Nb, or Ta and 0 < x < 4 or HxLie.25-xEo.25La3Zr20i2, with E = Al, Ga or Fe and 0 < x < 4), or a combination thereof. In aspects, the solid-state electrolyte 108 can comprise at least one of LiioGeP2Si2, Lii.sAlo.sGei PC Lii.4Alo.4Tii.6(P04)3, Lio.55Lao.35Ti03, interpenetrating polymer networks of poly(ethyl acrylate) (ipn-PEA) electrolyte, three-dimensional ceramic / polymer networks, in-situ plasticized polymers, composite polymers with well-aligned ceramic nanowires, PEO-based solid-state polymers, flexible polymers, polymeric ionic liquids, in-situ formed Li3PS4, LiePSsCl, or combinations thereof. Exemplary aspects of the solid state electrolyte are doped garnet (e.g., Ta-doped garnet,Al-doped garnet) and un-doped garnet with the understanding that the garnet can have excess lithium (beyond stoichiometry), as discussed herein.

[0109] As shown in FIGS. 1-2, the solid-state electrolyte 108 comprises the first major surface 109 and the second major surface 107 opposite the first major surface 109, and a thickness (e.g., see electrolyte thickness 607 in FIG. 6) of the solid-state electrolyte 108 can be defined between the first major surface 109 and the second major surface 107. In aspects, the thickness of the solid-state electrolyte 108 can be about 20 pm or more, about 40 pm or more, about 60 pm or more, about 80 pm or more, about 100 pm or more, about 150 pm or more, about 300 pm or more, about 500 pm or more, about 600 pm or more, about 700 pm or more, about 800 pm or more, about 1 mm or more, about 2 mm or less, about 1.5 mm or less, about 1.2 mm or less, about 1 mm or less, about 800 pm or less, about 500 pm or less, about 300 pm or less, about 250 pm or less, about 200 pm or less, about 150 pm or less, about 120 pm or less, or about 100 pm or less. In aspects, the thickness of the solid-state electrolyte 108 can range from about 20 pm to about 2 mm, from about 40 pm to about 1.5 mm, from about 60 pm to about 1 mm, from about 80 pm to about 800 pm, from about 100 pm to about 500 pm, from about 150 pm to about 300 pm, from about 150 pm to about 250 pm, or any range or subrange therebetween. In aspects, the thickness of the solid-state electrolyte 108 can be about 300 pm or less, for example, from about 20 pm to about 300 pm, from about 40 pm to about 250 pm, from about 60 pm to about 200 pm, from about 80 pm to about 150 pm, from about 100 pm to about 150 pm, or any range or subrange therebetween. In aspects, the thickness of the solid-state electrolyte 108 can be about 500 pm or more, for example, from about 500 pm to about 2 mm, from about 600 pm to about 1.5 mm, from about 700 pm to about 1 mm, from about 800 pm to about 1 mm, or any range or subrange therebetween.

[0110] In aspects, the solid-state electrolyte 108 can comprise a sintered tape. As used herein, a sintered tape refers to a material formed by sintering a ceramic green-body comprising substantially the same thickness as the solid-state electrolyte. In further aspects, the solid-state electrolyte 108 comprising the sintered tape can comprise a thickness of about 300 pm or less, for example, from about 20 pm to about 300 pm, from about 40 pm to about 250 pm, from about 60 pm to about 200 pm, from about 80 pm to about 150 pm, from about 100 pm to about 150 pm, or any range or subrange therebetween. In aspects, the solid-state electrolyte 108 can comprise consolidated pellets. As used herein, a solid-state electrolyte comprising consolidated pellets refers to a material that is formed by pressing together pellets that were previously sintered. As compared to a sintered tape, consolidated pellets can comprise larger grains and greater thickness. In further aspects, the solid-state electrolyte 108 comprising consolidated pellets can comprise a thickness ofabout 500 pm or more, for example, from about 500 pm to about 2 mm, from about 600 pm to about 1.5 mm, from about 700 pm to about 1 mm, from about 800 pm to about 1 mm, or any range or subrange therebetween.

[0111] Throughout the disclosure, the ring-on-ring (ROR) test is a surface strength measurement fortesting flat glass specimens, and ASTM 0499-09(2013), entitled “Standard Test Method for Monotonic Equibiaxial Flexural Strength of Advanced Ceramics at Ambient Temperature,” serves as the basis for the AROR test methodology described herein. The contents of ASTM C 1499-09 are incorporated herein by reference in their entirety. The sample is placed between two concentric rings of differing size to determine equibiaxial flexural strength (i.e., the maximum stress that a material is capable of sustaining when subjected to flexure between two concentric rings) with the sample supported by a support ring with diameter D2. A force F is applied by a load cell to the surface of the glass-based article by a loading ring having a diameter DI. Unless otherwise indicated, a ratio of D1 / D2 is 0.5. The loading and the support ring were aligned concentrically to within 0.5% of support ring diameter D2. The load cell used for testing is accurate to within ±1% at any load within a selected range. Testing is carried out at a temperature of 23±2°C and a relative humidity of 40±10%. For fixture design, the radius r of the protruding surface of the loading ring is in a range of h / 2 <r < 3h / 2, where h is the thickness of sample. Loading and support rings are made of hardened steel with hardness HRc > 40. The intended failure mechanism for the ROR test is to observe fracture of the sample originating from a region of the surface of the sample within both loading rings. Failures that occur outside of this region - i.e., between the loading ring and support ring - are omitted from data analysis. Due to the thinness and high strength of the sample, however, large deflections that exceed U of the sample thickness h are sometimes observed. It is therefore not uncommon to observe a high percentage of failures originating from underneath the loading ring. Stress cannot be accurately calculated without knowledge of stress development both inside and under the ring (collected via strain gauge analysis) and the origin of failure in each specimen. ROR testing therefore focuses on peak load at failure as the measured response. As used herein, “ring-on-ring strength” refers to the strength measured using the ROR test. In aspects, a ring-on-ring strength of the solid-state electrolyte 108 with the porous surface (e.g., composite garnet electrolyte with the porous surface) can be about 150 MPa or more, about 180 MPa or more, about 200 MPa or more, about 220 MPa or more, about 250 MPa or more, about 280 MPa or more, about 300 MPa or more, about 320 MPa or more, about 350 MPa or more, about 380 MPa or more, about 400 MPa or more, about 600 MPa or less, about 550 MPa or less, about 500 MPa or less, about 450 MPa or less, about 400 MPa or less, about 350MPa or less, about 300 MPa or less, or about 250 MPa or less. In aspects a ring-on-ring strength of the solid-state electrolyte 108 with the porous surface (e.g., composite garnet electrolyte with the porous surface) can be in a range from about 150 MPa to about 600 MPa, from about 150 MPa to about 550 MPa, from about 150 MPa to about 500 MPa, from about 150 MPa to about 450 MPa, from about 150 MPa to about 400 MPa, from about 180 MPa to about 400 MPa, from about 200 MPa to about 350 MPa, from about 220 MPa to about 350 MPa, from about 250 MPa to about 300 MPa, from about 280 MPa to about 300 MPa, or any range or subrange therebetween. Providing a sintered ribbon as the solid-state electrolyte (e.g., composite garnet electrolyte) can enable a high ring-on-ring strength (e.g., about 150 MPa or more or from about 150 MPa to about 400MPa).

[0112] 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, Li6.5La3Zr1.5Tao.5O12) can be about 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.

[0113] In aspects, an amount of lithium (e.g., Li2O, on an oxide basis) of the solid-state electrolyte 108 (e.g., composite garnet electrolyte, composite garnet electrolyte with the poroussurface), based on 100 wt% of the solid-state electrolyte, can be greater than a stoichiometric amount of lithium, for example, by about 0.1 wt% or more, about 0.2 wt% or more, about 0.3 wt% or more, about 0.4 wt% or more, about 0.5 wt% or more, about 0.6 wt% or more, about 0.7 wt% or more, about 0.8 wt% or more, about 4 wt% or less, about 3.5 wt% or less, about 3.0 wt% or less, about 2.5 wt% or less, about 2.0 wt% or less, about 1.5 wt% or less, about 1.2 wt% or less, aboutI.0 wt% or less, about 0.9 wt% or less, about 0.8 wt% or less. In aspects, an amount of lithium (e.g., Li2O, on an oxide basis) of the solid-state electrolyte 108 (e.g., composite garnet electrolyte, composite garnet electrolyte with the porous surface), based on 100 wt% of the solid-state electrolyte, can be greater than a stoichiometric amount of lithium by from about 0.1 wt% to about 4.0 wt%, from about 0.1 wt% to about 3.5 wt%, from about 0.1 wt% to about 3.0 wt%, from about 0.2 wt% to about 2.5 wt%, from about 0.2 wt% to about 2.0 wt%, from about 0.2 wt% to about 1.5 wt%, from about 0.3 wt% to about 1.2 wt%, from about 0.3 wt% to about 1.0 wt%, from about 0.3 wt% to about 0.9 wt%, from about 0.4 wt% to about 0.8 wt%, from about 0.5 wt% to about 0.8 wt%, from about 0.5 wt% to about 0.8 wt%, or any range or subrange therebetween. In aspects, an amount of lithium (e.g., Li2O, on an oxide basis) of the solid-state electrolyte 108 (e.g., composite garnet electrolyte, composite garnet electrolyte with the porous surface), based on 100 wt% of the solid-state electrolyte, can be about 11.2 wt% or more, about 11.3 wt% or more, about 11.4 wt% or more, about 11.5 wt% or more, about 11.6 wt% or more, about 11.7 wt% or more, about 11.8 wt% or more, about 11.9 wt% or more, about 12.0 wt% or more, about 15 wt% or less, about 14.5 wt% or less, about 14.0 wt% or less, about 13.5 wt% or less, about 13.0 wt%, from about 12.5 wt% or less, about 12.2 wt% or less, about 12.1 wt% or less, about 12.0 wt% or less, about 11.9 wt% or less, about 11.8 wt% or less, about 11.7 wt% or less, about 11.6 wt% or less, or about 11.5 wt% or less. In aspects, an amount of lithium (e.g., Li2O, on an oxide basis) of the solid-state electrolyte 108 (e.g., composite garnet electrolyte, composite garnet electrolyte with the porous surface), based on 100 wt% of the solid-state electrolyte, can be in a range from about 11.2 wt% to about 15 wt%, from about 11.2 wt% to about 14.5 wt%, from about 11.2 wt% to about 14.0 wt%, from aboutI I.3 wt% to about 13.5 wt%, from about 11.3 wt% to about 13.0 wt%, from about 11.3 wt% to about 12.5 wt%, from about 11.3 wt% to about 12.2 wt%, from about 11.4 wt% to about 12.1 wt%, from about 11.4 wt% to about 12.0 wt%, from about 11.5 wt% to about 11.9 wt%, from about 11.6 w% to about 11.8 wt%, or any range or subrange therebetween. Consequently, in aspects, the solid- state electrolyte 108 (e.g., composite garnet electrolyte, composite garnet electrolyte with the porous surface) can comprise a composite with a lithium phase between garnet crystals. In aspects, preferred ranges for the amount of lithium can be from about 11.2 wt% to about 15 wt%, fromabout 11.3 wt% to about 12.2 wt%, or from about 11.4 wt% to about 12.0 wt%. As discussed herein, providing excess lithium (relative to stoichiometry) in the composite garnet electrolyte can facilitate the formation of an mixture of intergranular and transgranular microstructure and facilitate etching of the composite garnet electrolyte to form a porous surface of the composite garnet electrolyte.

[0114] Throughout the disclosure, the microstructure of the solid-state electrolyte is determined from analyzing a cross-sectional SEM image (e.g., extending in a direction of the thickness as in FIGS. 10-12 and 16-24) of the solid-state electrolyte generated by fracturing the solid-state electrolyte. As used herein, “transgranular microstructure” refers to when the fracture propagates through the crystal grains of garnet. As used herein, “intergranular microstructure” refers to when the fracture occurs along the grain boundary between crystal grains of garnet. Since fracture occurs along grain boundaries for intergranular microstructure, SEM images show more defined shapes associated with the crystal grains (e.g., “rock candy” structures) compared to transgranular microstructure. As used herein, a microstructure extending to a depth from a surface of an electrolyte means that a continuous path through the electrolyte from the surface comprises the specified microstructure. Consequently, multiple microstructures can be present in an electrolyte (or even present as a common distance from the surface while one of the microstructures extends to a depth greater than the common distance if there is a continuous path in that microstructure to the depth).

[0115] In aspects, the solid-state electrolyte 108 (e.g., composite garnet electrolyte, composite garnet electrolyte with the porous surface) can comprise a intergranular microstructure extending to a first distance from the first major surface 109 of the solid-state electrolyte. For example, as shown in FIG. 18, a composite garnet electrolyte 1801 can comprise intergranular microstructure 1807 extending to a depth 1813 from the first major surface 1805 of the composite garnet electrolyte 1801. In further aspects, the first distance that the intergranular microstructure extends from the first major surface, as a percentage of the electrolyte thickness (see electrolyte thickness 607 in FIG. 6), can be about 5% or more, about 10% or more, about 15% or more, 18% or more, 20% or more, 22% or more, 25% or more, 27% or more, 30% or more, 40% or less, 35% or less, 32% or less, 30% or less, 28% or less, or 25% or less. In further aspects, the first distance that the intergranular microstructure extends from the first major surface, as a percentage of the electrolyte thickness, can be in a range from about 5% to about 40%, from about 10% to about 40%, from about 15% to about 40%, from about 18% to about 40%, from about 20% to about 35%, from about 20% to about 32%, from about 22% to about 30%, from about 25% to about 28%, orany range or subrange therebetween. In further aspects, the first distance that the intergranular microstructure extends from the first major surface can be 2 pm or more, 4 pm or more, 6 pm or more, 8 pm or more, 10 pm or more, 12 pm or more 15 pm or more, 20 pm or more, 25 pm or more, 30 pm or more, 40 pm or more, 100 pm or less, 70 pm or less, 50 pm or less, 40 pm or less, 30 pm or less, 25 pm or less, 20 pm or less, 18 pm or less, 15 pm or less, 12 pm or less, 10 pm or less. In further aspects, the first distance that the intergranular microstructure extends from the first major surface can be in a range from 2 pm to 100 pm, from 4 pm to about 70 pm, from 6 pm to 50 pm, from 8 pm to 40 pm, from 10 pm to 30 pm, from 12 pm to 25 pm, from 15 pm to 20 pm, or any range or subrange therebetween. Returning to FIG. 18, the composite garnet electrolyte 1801 can comprise regions with intergranular microstructure 1807 and 1809 extending from the corresponding major surfaces of the composite garnet electrolyte 1801. Further, as shown, the composite garnet electrolyte 1801 can comprise a region with transgranular microstructure 1811 sandwiched between regions with intergranular microstructure 1807 and 1809. Providing a transgranular microstructure near and / or at the first major surface can facilitate etching to form large and / or deep pores therein.

[0116] Throughout the disclosure, a grain size of the garnet (e.g., of the solid-state electrolyte) is determined in accordance with ASTM El 12-13. In aspects, a median grain size of the garnet can be about 3.0 pm (e.g., 3 pm) or less, about 2.9 pm or less, about 2.7 pm or less, about 2.5 pm or less, about 2.3 pm or less, about 2.0 pm or less, about 1.8 pm or less, about 1.5 pm or less, about 1.3 pm or less, about 1.0 pm or less, about 1.0 pm (e.g., 1 pm) or more, about 1.1 pm or more, about 1.3 pm or more, about 1.5 pm or more, about 1.7 pm or more, or about 2.0 pm or more. In aspects, a median grain size of the garnet can be in a range from about 1.0 pm to about 4.0 pm, from about 1.0 pm to about 3.0 pm (e.g., from about 1 pm to about 3 pm), from about 1.0 pm to about 2.9 pm, from about 1.1 pm to about 2.7 pm, from about 1.1 pm to about 2.5 pm, from about 1.3 pm to about 2.3 pm, from about 1.3 pm to about 2.0 pm, from about 1.3 pm to about 1.8 pm, or any range or subrange therebetween. Providing a grain size of about 3 pm or less, from about 1 pm to about 3 pm, or from about 1 pm to about 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.

[0117] As discussed below, a composite garnet electrolyte with a porous surface (e.g., solid-state electrolyte 108 with a porous surface) can be formed by etching at least the first major surface 109. Without wishing to be bound by theory, it is believed that the etching maypreferentially etch the lithium phase between grains in the composite garnet electrolyte in the region with intergranular microstructure, and consequently, the composite garnet electrolyte of the present disclosure can be more easily and / or more quickly etched relative to other garnet electrolytes (e.g., with stoichiometric amounts of lithium). Throughout the disclosure, the porosity and / or pore size distribution of the solid-state electrolyte is determined in accordance with ASTM E1245-03. The pores can extend from at least the first major surface 109 of the solid-state electrolyte 108, and the pores can extend from both the first major surface 109 and the second major surface 107 in further aspects.

[0118] In aspects, a mean pore size of the solid-state electrolyte can be about 0.25 pm or more, about 0.5 pm or more, about 1.0 pm (e.g., about 1 pm) or more, about 1.3 pm or more, about 1.5 pm or more, about 1.7 pm or more, about 2.0 pm or more, about 2.2 pm or more, about 2.5 pm or more, about 3.0 pm or more, about 4.0 pm or more, about 5.0 pm or more, about 6.0 pm or more, about 8.0 pm or more, about 10 pm or more, about 12 pm or more, about 14 pm or more, about 20 pm or less, about 17 pm or less, about 15 pm or less, about 12 pm or less, about 10 pm or less, about 7 pm or less, about 5 pm or less, about 3.0 pm (e.g., about 3 pm) or less, about 2.8 pm or less, about 2.6 pm or less, about 2.4 pm or less, about 2.2 pm or less, or about 2.0 pm or less. In aspects, a mean pore size of the solid-state electrolyte can be in a range from about 0.25 pm to about 20 pm, from about 0.5 pm to about 20 pm, from about 1 pm to about 20 pm, from about 1.3 pm to about 20 pm, from about 1.5 pm to about 20 pm, from about 1.7 pm to about 20 pm, from about 2.0 pm to about 20 pm, from about 2.2 pm to about 20 pm, from about 2.5 pm to about 20 pm, from about 3 pm to about 20 pm, from about 4 pm to about 17 pm, from about 5 pm to about 15 pm, from about 6 pm to about 12 pm, from about 8 pm to about 10 pm, or any range or subrange therebetween. In aspects, a mean pore size of the solid-state electrolyte can be about 5 pm or more, for example, in a range from about 5.0 pm to about 20 pm, from about 6.0 pm to about 20 pm, from about 8.0 pm to about 20 pm, from about 10 pm to about 17 pm, from about 12 pm to about 17 pm, from about 14 pm to about 15 pm, or any range or subrange therebetween. In aspects, a mean pore size of the solid-state electrolyte can be about 5 pm or less, for example, in a range from about 0.25 pm to about 5.0 pm, from about 0.5 pm to about 5.0 pm, from about 1.0 pm to about 5.0 pm, from about 1.0 pm to about 4.0 pm, from about 1.0 pm to about 3.0 pm, from about 1.3 pm to about 3.0 pm, from about 1.5 pm to about 3.0 pm, from about 1.5 pm to about 2.8 pm, from about 1.8 pm to about 2.5 pm, from about 1.8 pm to about 2.4 pm, from about 2.0 pm to about 2.2 pm. For example, as discussed below with reference to FIG. 27, the composite garnet electrolytes with the porous surface according to the present disclosure can have a meanpore size greater than that of the comparative examples. For example, the mean pore size of the porous surface of composite garnet electrolytes according to the present disclosure of 0.25 pm or more, for example, from 0.25 pm to 20 pm, from 1 pm to 20 pm, or from 3 pm to 20 pm.

[0119] In aspects, an average depth of the pores can be about 2 pm or more, about 5 pm or more, about 7 pm or more, about 10 pm or more, about 15 pm or more, about 20 pm or more, about 25 pm or more, about 30 pm or more, about 35 pm or more, about 40 pm or more, about 50 pm or more, about 60 pm or less, about 55 pm or less, about 50 pm or less, about 45 pm or less, about 40 pm or less, about 35 pm or less, about 30 pm or less, about 25 pm or less, or about 20 pm or less. In aspects, an average depth of the pores can be in a range from about 2 pm to about 60 pm, from about 5 pm to about 55 pm, from about 8 pm to about 50 pm, from about 10 pm to about 45 pm, from about 15 pm to about 40 pm, from about 20 pm to about 35 pm, from about 25 pm to about 30 pm. In aspects, an average depth of the pores can be about 20 pm or more, for example, in a range from about 20 pm to about 60 pm, from about 25 pm to about 55 pm, from about 30 pm to about 50 pm, from about 35 pm to about 45pnm, from about 40 pm to about 45 pm, or any range or subrange therebetween. In aspects, an average depth of the pores, as a percentage of the electrolyte thickness (see electrolyte thickness 607 in FIG. 6), can be about 5% or more, about 8% or more, about 10% or more, about 12% or more, about 15% or more, about 17% or more, about 20% or more, about 30% or less, about 25% or less, about 20% or less, about 17% or less, about 15% or less, about 12 % or less, or about 10% or less. In aspects, an average depth of the pores, as a percentage of the electrolyte thickness, can be in a range from about 5% to about 30%, from about 8% to about 25%, from about 10% to about 20%, from about 12% to about 17 wt%, from about 15% to about 17%, or any range or subrange therebetween. Providing deep pores (e.g., about 2 pm or more, from about 20 pm to about 60 pm, about 5% of the electrolyte thickness or more, or from about 10% to about 20% of the electrolyte thickness) can increase an effective surface area of the solid-state electrolyte (e.g., facing an anode and / or facing a cathode), which can decrease an interfacial resistance of battery including the solid-state electrolyte with the porous surface (e.g., composite garnet electrolyte with the porous surface).

[0120] 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) / dimethyl 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(CF3SO2)2), SiCE may benanoparticles, 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-ethylenedi oxythiophene) (PEDOT), poly(styrene sulfonic acid) (PSS), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyallylamine hydrochloride (PAH), poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)), poly(m ethyl 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.

[0121] 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., LiNCE, lanthanum nitrate, copper acetate, P2S5, etc.), artificial interfacial layers (e.g., LisN, (CHs^SiCl, AI2O3, LiAl, etc.), composite metallics (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.

[0122] 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 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 about 1 micrometer (pm) or more, about 10 pm or more, about 50 pm or more, about 100 pm or more, about 150 pm or more, about 500 pm or less, about 400 pm or less, about 300 pm or less, or about 250 pm or less. In aspects, the anode thickness 119 can range from about 1 pm to about 500 pm, from about 10 pm to about 400 pm, from about 50 pm to about 300 pm, from about 100 pm to about 300 pm, from about 150 pm to about 250 pm, or any range or subrange therebetween.

[0123] 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.

[0124] 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 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 first 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 112and 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.

[0125] As used herein, “interfacial resistance” and “ionic conductivity” are measured using electrical impedance spectroscopy (EIS) at 25°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 cm2) on a horizontal axis and the imaginary component of impedance (Z” measured in 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 about 60 cm2or less, about 50 cm2or less, about 40 cm2or less, about 30 cm2or less, about 25 cm2or less, or about 20 cm2or less. In aspects, the interfacial resistance can range from about 10 cm2to about 60 cm2, from about 10 cm2to about 50 cm2, from about 10 cm2to about 40 cm2, from about 15 cm2to about 30 cm2, from about 20 cm2to about 25 cm2, or any range or subrange therebetween.

[0126] Unless otherwise specified, a cycle comprises charging at 1C to a predetermined nominal areal capacity and discharged at 0.5C while the battery is maintained at 60°C. As used herein, “nominal capacity” (e.g., nominal areal capacity) refers to a capacity achieved using a predetermined charging condition in a first charging step for the battery. Areal capacity is presented based on a surface area of the anode. Unless otherwise indicated, battery testing including capacity retention and cycling at various nominal areal capacity is performed using the battery test system CT2001A (Landt) at 60°C. In aspects, the battery can withstand at least 10 cycles at a charging current density of 1.6 mA / cm2(1.6C) or more, about 1.8 mA / cm2(1.8C) or more, or about 2 mA / cm2(2C) to a nominal areal capacity of 1 mAh / cm2and a discharge current density of 0.5 mA / cm2(0.5C) at 60°C. As used herein, “withstand” indicates that the battery did not exhibit a short circuit or non-ohmic behavior during cycling. In aspects, the battery can withstand at least 50 cycles at a charging current density of 1.6 mA / cm2(1.6C) or more, about 1.8 mA / cm2(1.8C)or more, or about 2 mA / cm2(2C) to a nominal areal capacity of 1 mAh / cm2and a discharge current density of 0.5 mA / cm2(0.5C) at 60°C. In aspects, the battery can withstand at least 70 cycles at a charging current density of 1.6 mA / cm2(1 ,6C) or more, about 1.8 mA / cm2(1 ,8C) or more, or about 2 mA / cm2(2C) to a nominal areal capacity of 1 mAh / cm2and a discharge current density of 0.5 mA / cm2(0.5C) at 60°C.

[0127] Throughout the disclosure, “critical current density” refers to the maximum current density that the solid-state lithium-containing battery can handle without causing damage or degradation to the solid-state electrolyte or other components. Unless otherwise indicated, “critical current density” is determined using the same conditions as for battery cycling (e.g., using the battery test system CT2001A (Landt) at 60°C) except that different current densities are used corresponding to the current density to be tested. In aspects, the critical current density for the solid-state battery containing the solid-state electrolyte with the porous surface (e.g., composite garnet electrolyte with the porous surface) can be about 2 mA / cm2or more, about 2.5 mA / cm2or more, about 3 mA / cm2or more, about 3.5 mA / cm2or more, about 4 mA / cm2or more, about 4.5 mA / cm2or more, or about 5 mA / cm2or more.

[0128] Aspects of methods of treating the solid-state electrolyte and / or methods of making the solid-state battery in accordance with aspects of the disclosure will be discussed with reference to example method steps illustrated in FIGS. 3-7. Methods can comprise providing a solid-state electrolyte, which can comprise one or more of the materials discussed above with reference to the solid-state electrolyte. In aspects, the solid-state electrolyte can comprise a sintered tape, for example, with a thickness from about 20 pm to about 300 pm. Alternatively, in aspects, the solid-state electrolyte can be formed (e.g., to form a sintered tape) as discussed below in methods of the present disclosure.

[0129] In aspects, methods can comprise forming a garnet powder, although a garnet powder can be provided (e.g., by purchase) in other aspects. In further aspects, stoichiometric amounts of component materials (e.g., Li2COs for Li, La2Os for La, ZrCL for Zr) including any selected dopant (e.g., Ta, In, Si, Ge, Sn, V, W, Te, Nb, and / or other dopants discussed above) with a slight excess (e.g., about 2 wt% excess) of lithium (added by superaddition to compensate for volatilization during heating) to form a mixture. The mixture can be mixed (e.g., milled) with a grinding media (e.g., yttrium-stabilized zirconia balls) and optional solvent (e.g., isopropanol) to homogenize the mixture. In even further aspects, the mixture can include a source of Ta as a dopant. In further aspects, the mixture can be calcined at a calcining temperature from about 800°C to about 1200°C (e.g., from 850°C to about 1200°C, from 900°C to 1100°C, or any range or subrangetherebetween) for a calcining time from about 2 hours to about 12 hours (e.g., from about 4 hours to about 8 hours) to form a garnet powder.

[0130] In aspects, methods can comprise casting a green tape comprising garnet, excess lithium, a binder, and a solvent, although a green tape (or untreated garnet electrolyte) can be provided (e.g., by purchase) in other aspects. In further aspects, an amount of the excess lithium, as a wt% of an amount of the garnet, can be greater than 0.5 wt%, about 2 wt% or more, about 5 wt% or more, about 10 wt% or more (e.g., greater than 10 wt%), about 15 wt% or more, about 18 wt% or more, about 20 wt% or more, about 22 wt% or more, about 25 wt% or more, about 27 wt% or more, about 30 wt% or more, about 50 wt% or less, about 45 wt% or less, about 40 wt% or less, about 35 wt% or less, about 30 wt% or less, about 27 wt% or less, or about 25 wt% or less. In aspects, an amount of the excess lithium, as a wt% of an amount of the garnet, can be in a range from greater than 0.5 wt% to 50 wt%, from 2 wt% to 50 wt%, from 5 wt% to 50 wt%, from 10 wt% to 50 wt% (e.g., from greater than 10 wt% to 50 wt%), from 15 wt% to 50 wt%, from 18 wt% to 50 wt%, from 20 wt% to 50 wt%, from about 22 wt% to 45 wt%, from 22 wt% to 40 wt%, from 25 wt% to 35 wt%, from 27 wt% to 30 wt%, or any range or subrange therebetween. Providing greater than 0.5 wt%, greater than 2 wt%, or greater than 10 wt% excess lithium can enable the formation of an mixture of intergranular and transgranular microstructure, grain size of about 3 pm or less (e.g., from 1 pm to 3 pm or from 1 pm to 2 pm), and / or facilitate etching of the composite garnet electrolyte to form a composite garnet electrolyte with a porous surface. In combination with excess lithium, the firing condition determine the amount of lithium remaining in the resulting electrolyte. If the firing is a too high a temperature (e.g., greater than 1200°C) and / or for too long a period of time (dependent on the temperature, e.g., about greater than 60 minutes), the vast majority of the excess lithium added to the green tape can be volatilized to produce an electrolyte without a transgranular microstructure contrary to the aspects of the present disclosure.

[0131] In further aspects, methods can comprise firing the green tape to form an untreated solid-state electrolyte (e.g., untreated garnet electrolyte) at a firing temperature for a firing period of time. In even further aspects, the firing temperature can be about 900°C or more, about 950°C or more, about 980°C or more, about 1000°C or more, about 1030°C or more, about 1050°C or more, about 1080°C or more, about 1100°C or more, about 1200°C or less, about 1160°C or less, about 1150°C or less, about 1130°C or less, about 1100°C or less, about 1080°C or less, or about 1050°C or less. In even further aspects, the firing temperature can be in a range from about 900°C to about 1200°C, from about 900°C to about 1160°C, from about 900°C to about 1150°C, from about 950°C to about 1150°C, from about 980°C to about 1120°C, from about 1000°C to about1120°C, from about 1030°C to about 1100°C, from about 1050°C to about 1080°C, or any range or subrange therebetween. In even further aspects, the firing period of time can be 5 minutes or more, 8 minutes or more, 10 minutes or more, 12 minutes or more, 15 minutes or more, 20 minutes or more, 60 minutes or less, 45 minutes or less, 40 minutes or less, 35 minutes or less, 30 minutes or less, 25 minutes or less, 22 minutes or less, 20 minutes or less, 18 minutes or less, or 15 minutes or less. In even further aspects, the firing period of time can be in a range from 5 minutes to 60 minutes, from 5 minutes to 45 minutes, from 8 minutes to 40 minutes, from 10 minutes to 35 minutes, from 12 minutes to 30 minutes, from 15 minutes to 25 minutes, from 18 minutes to 22 minutes, or any range or subrange therebetween. In even further aspects, the firing period of time can be 30 minutes or less, for example, in a range from 5 minutes to 30 minutes, from 8 minutes to 25 minutes, from 10 minutes to 22 minutes, from 12 minutes to 20 minutes, from 15 minutes to 18 minutes, or any range or subrange therebetween. The resulting solid-state electrolyte (e.g., untreated solid-state electrolyte, untreated garnet electrolyte) can comprise an amount of lithium within one or more of the corresponding ranges discussed above (e.g., from about 11.2 wt% to about 15 wt%, from about 11.3 wt% to about 12.2 wt%, or from about 11.4 wt% to about 12 wt%), a mixture of intergranular and transgranular microstructure (e.g., with the transgranular microstructure extending to a depth of about 25% of the electrolyte thickness or more or any of the corresponding ranges discussed above), and / or a lithium phase between grains of garnet (e.g., of intergranular microstructure).

[0132] In aspects, the untreated solid-state electrolyte (e.g., untreated garnet electrolyte) can be contacted with water prior to etching (see next paragraph). In further aspects, the untreated solid-state electrolyte can be contact with water for a period of time for at least 1 minute, for example, 1.5 minutes or more, 2 minutes or more, 3 minutes or more, 4 minutes or more, 5 minutes or more, 7 minutes or more, 10 minutes or more, 8 hours or less, 2 hours or less, 1 hour or less, 45 minutes or less, 30 minutes or less, 20 minutes or less, 15 minute or less, or 10 minutes or less. In further aspects, the untreated solid-state electrolyte can be contact with water for a period of time in a range from at least 1 minute to 8 hours, from at least 1 minute to 2 hours, from at least 1 minute to 1 hour, from 1.5 minutes to 45 minutes, from 2 minutes to 30 minutes, from 3 minutes to 20 minutes, from 4 minutes to 15 minutes, from 5 minutes to 10 minutes, or any range or subrange therebetween. For example, as discussed for the Examples, the untreated solid-state electrolyte can be contacted with water (e.g., de-ionized water) for about 10 minutes. In further aspects, the water can be de-ionized water or ultrapure water. In further aspects, the water can be at a temperature of about 15°C or more, about 20°C or more, about 22°C or more, about 25°C or more, about 40°C orless, about 30°C or less, about 27°C or less, or about 25°C or less, for example in a range from about 15°C to about 40°C, from about 20°C to about 30°C, from about 22°C to about 27°C, or any range or subrange therebetween. Without wishing to be bound by theory, contacting the solid-state electrolyte (e.g., untreated solid-state electrolyte or untreated garnet electrolyte) produce a surface layer of protonated garnet on the solid-state electrolyte.

[0133] In aspects, as shown in FIG. 6, methods can comprise etching at least a first major surface 109 of the solid-state electrolyte 108 (e.g., composite garnet electrolyte) with an etchant 603 (e.g., acid) to form a porous surface of the composite garnet electrolyte (e.g., first major surface 109 of the solid-state electrolyte 108 in FIGS. 1-2) comprising pores. In further aspects, as shown, the etchant 603 can be contained in a container 601 when the first major surface 109 of the solid- state electrolyte 108 is in contact with the etchant 603, although the etchant can be dispensed from a container onto the first major surface (e.g., by spraying). In further aspects, the acid of the etchant 603 can be a mineral acid (e.g., HC1, HNO3, H2SO4). An exemplary aspects of the etchant is HC1. In further aspects, a concentration of acid in the etchant 603 can be about 0.5 M or more, about 0.6 M or more, about 0.8 M or more, about 1.0 M or more, about 1.2 M or more, about 1.5 M or more, about 1.8 M or more, about 2 M or more, 5 M or less, 4 M or less, 3 M or less, 2 M or less, 1.5 M or less, 1.2 M or less, or 1.0 M or less. In further aspects, a concentration of acid in the etchant 603 can be in a range from about 0.5 M to about 5 M, from about 0.5 M to about 4 M, from about 0.6 M to about 3 M, from about 0.6 M to about 2 M, from about 0.8 M to about 1.5 M, from about 0.8 M to about 1.2 M, or any range or subrange therebetween. In further aspects, the etchant 603 and the first major surface 109 of the solid-state electrolyte 108 can be in contact for a period of time of about 3 minutes or more, about 4 minutes or more, about 5 minutes or more, about 7 minutes or more, about 10 minutes or more, about 20 minutes or less, about 15 minutes or less, about 10 minutes or less, about 8 minutes or less, or about 6 minutes or less. In further aspects, the etchant 603 and the first major surface 109 of the solid-state electrolyte 108 can be in contact for a period of time in a range from about 3 minutes to about 20 minutes, from about 3 minutes to about 15 minutes, from about 4 minutes to about 10 minutes, from about 5 minutes to about 8 minutes, or any range or subrange therebetween. In further aspects, the etchant 603 can be at a temperature of about 15°C or more, about 20°C or more, about 22°C or more, about 25°C or more, about 40°C or less, about 30°C or less, about 27°C or less, or about 25°C or less, for example in a range from about 15°C to about 40°C, from about 20°C to about 30°C, from about 22°C to about 27°C, or any range or subrange therebetween. In further aspects, the etching removes at least a portion of a lithium phase between garnet crystals (e.g., of the intergranular microstructure extending from thefirst major surface, as described above). As discussed herein, the lithium phase between garnet crystals of the intergranular microstructure can facilitate the formation of pores by etching. The pores formed by the etching can comprise features within one or more of the corresponding ranges discussed above (e.g., grain size of about 3 pm or less, from 1 pm to 3 pm, or from 1 pm to 2 pm; an average pore depth of about 2 pm or more, from about 20 pm to about 60 pm, about 5% of the electrolyte thickness or more, or from about 10% to about 20% of the electrolyte thickness).

[0134] In aspects, as shown in FIG. 7, methods can comprise etching an initial second major surface 605 (see FIG. 6) of the solid-state electrolyte 108 (e.g., composite garnet electrolyte) with an etchant 703 (e.g., acid) to form the second major surface 107 of the composite garnet electrolyte (e.g., solid-state electrolyte 108 in FIGS. 1-2) comprising pores. In further aspects, as shown, the etchant 703 can be contained in a container 701 when the second major surface 107 (and / or the initial second major surface 605) of the solid-state electrolyte 108 is in contact with the etchant 703, although the etchant can be dispensed from a container onto the first major surface (e.g., by spraying). In further aspects, the acid of the etchant 703 can be identical to the etchant 603 discussed in the previous paragraph and / or within one or more the ranges or other aspects discussed above for the etchant 603 (e.g., be a mineral acid, temperature from 15°C to 40°C or from 20°C to 30°C, comprise a concentration of acid from 0.5 M to 5 M, from 0.5 M to 3 M, or from 0.8 M to 1.5 M). In further aspects, the period of time that the etchant 603 is in contact with the second major surface 107 (and / or the initial second major surface 605) of the solid-state electrolyte 108 can be within one or more of the corresponding ranges discussed in the pervious paragraph (e.g., from about 3 minutes to about 20 minutes or from about 4 minutes to about 10 minutes). In further aspects, the etching removes at least a portion of a lithium phase between garnet crystals (e.g., of the intergranular microstructure extending from the first major surface, as described above). As discussed herein, the lithium phase between garnet crystals of the intergranular microstructure can facilitate the formation of pores by etching. The pores formed by the etching can comprise features within one or more of the corresponding ranges discussed above (e.g., grain size of about 3 pm or less, from 1 pm to 3 pm, or from 1 pm to 2 pm; an average pore depth of about 2 pm or more, from about 20 pm to about 60 pm, about 5% of the electrolyte thickness or more, or from about 10% to about 20% of the electrolyte thickness). Although FIGS. 6-7 show etching the first major surface and the second major surface in separate steps, it is to be understood that the entire solid-state electrolyte can be treated simultaneously, for example by immersing the solid-state electrolyte in the etchant.

[0135] In aspects, as shown by comparing FIG. 3 and FIG. 4, methods of making a battery (e.g., solid-state battery) can further comprise disposing an anode 112 over the first major surface 109 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, for example, by sputtering from one or more sources (e.g., elemental targets or an alloy target) and / or by thermal evaporation, although other methods of physical vapor deposition (PVD) can be used to form the anode 112. Alternatively, disposing the lithium-containing material for the anode 112 can comprise disposing a molten material (e.g., lithium metal, lithium alloy) on the first major surface 109 of the solid-state electrolyte 108, for example, from a metal foil, a conduit, a micropipette, or a syringe. Alternatively, the lithium-containing material can be disposed on the solid-state electrolyte 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, the lithium-containing metal disposed over the solid-state electrolyte 108 can be heated in an environment (e.g., an oven) maintained at a first temperature that is greater than a melting point of the one or more materials in the lithium-containing material used to form the anode. In further aspects, the first temperature can be greater than a melting point of the one or more materials used to form the anode by about 50°C or more, about 100°C or more, about 125°C or more, or about 150°C or more. For example, lithium metal has a melting temperature of about 180°C. In further aspects, the first temperature can be about 280°C or more, about 300°C or more, about 320°C or more, about 500°C or less, about 400°C or less, or about 350°C or less, for example, from about 280°C to about 500°C, from about 300°C to about 400°C, from about 320°C to about 350°C, or any range or subrange therebetween. In further aspects, the solid-state electrolyte 108 and the lithium-containing material disposed thereon can be maintained at the first temperature for about 1 minute or more, about 3 minutes or more, about 5 minutes or more, about 15 minutes or more, about 20 minutes or more, about 1 hour or less, about 45 minutes or less, about 30 minutes or less, or about 25 minutes or less, for example, for a time ranging from about 1 minute to about 1 hour, from about 3 minutes to about 45 minutes, from about 5 minutes to about 30 minutes, from about 15 minutes to about 30 minutes, from about 20 minutes to about 25 minutes, or any range or subrange therebetween. Providing a temperature and time within one or more of the above- mentioned ranges can enable the lithium-containing material to conform to a surface on the solid- state electrolyte 108.

[0136] In aspects, as shown in FIG. 4, methods can further comprise disposing an interlayer 114 by disposing a liquid electrolyte 405 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. In further aspects, a concentration of the lithium salt in the solvent can be within one or more of the corresponding ranges discussed above. In further aspects, as shown, disposing the liquid electrolyte 405 can comprise dispensing a predetermined amount of the liquid 403 from a container 401 (e.g., conduit, flexible tube, micropipette, or syringe) to form the liquid electrolyte 405 on a first major surface 105 of the cathode 104. In further aspects, the predetermined amount of the interlayer 114 (e.g., liquid electrolyte 405) as a ratio of a volume of the interlayer (e.g., liquid electrolyte) to an area of the first major surface of the cathode can be within one or more of the corresponding ranges discussed above. Providing the ratio of the volume of the interlayer to the area of the first major surface of the cathode can be sufficient to wet the interface between the cathode and the solid-state electrolyte while minimizing concerns associated with traditional liquid electrolytes (e.g., in liquid-based batteries or in hybrid liquid-solid batteries). Although not shown, the cathode can be disposed on the first current collector while the interlayer is disposed on the cathode.

[0137] In aspects, as shown in FIG. 5, method can further comprise disposing the solid- state electrolyte 108 on the cathode 104, as indicated by arrow 501. As shown, the cathode 104 can be opposite the first major surface 109 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

[0138] Various aspects will be further clarified by the following examples. The lithium content of Examples 1-11 and Comparative Examples AA-FF is stated in Table 1. Examples 1-11 and Comparative Examples AA-FF differed only in the amount of excess lithium added in forming the green tape as well as the firing conditions. Comparative Examples CC-FF comprised consolidated pellets of the lithium garnet solid-state electrolyte with a net thickness of 360 pm and diameter of 14 mm rather than the sintered tapes of Examples 1-11 and Comparative Examples AA-BB. The thickness of Examples 1-11 and Comparative Examples AA-BB was from about 80 pm to 160 pm (with the specific thickness used for each sample in a given Table provided below).For the measurements reported herein, a 15 mm diameter discs were laser cut from the material as samples (e.g., with the full thickness for the sintered tapes) of Examples 1-11 and Comparative Examples AA-BB were used for measurements reported herein. For Tables 2 and 5, the thickness of the sintered tapes was 80 pm. For Tables 3-4, the thickness of the sintered tapes was 120 pm.

[0139] The lithium garnet solid-state electrolyte was cubic phase Li6.5La3Zr1.4Tao.5O12 (LLZTO), which was synthesized from a stoichiometric ratio of starting powders of Li2COs (AR), La2Os (99.99%), ZrO2 (AR), Ta2Os (99.99%). 2 wt% excess of Li2CO3 added to compensate the lithium loss during processing. The raw materials were mixed by dry ball mixing. The powder was calcined at 950°C for 5 hours to form the pure cubic garnet phase powder. For the consolidated pellets, the pellets were formed by hot pressing the garnet powder followed by cutting with a wire saw to the desired dimensions. To form sintered tapes, the garnet powder was mixed with an organic binder system comprising a propionate solvent, a dispersant, a plasticizer, an acrylate- based polymer, and excess lithium, which was tape cast with a doctor blade to form a green tape.Table 1 : Lithium Content of Comparative Examples AA-FF, Examples 1-11, 1A, 4A, and 7A

[0140] FIG. 8 is a scatterplot showing a lithium content 801 (Li2O wt% of the resulting garnet electrolyte) on the horizontal axis versus ionic conductivity 803 (Siemens / cm or S / cm) on the vertical axis. As noted above, the lithium content here refers to the amount in the finalelectrolyte (determined by flame emission spectroscopy after the electrolyte is fired, which is not to be confused with the amount of excess lithium added in forming the green tape before firing). The vertical line 805 is at 11.1 wt%, which corresponds to the stoichiometric amount of lithium in garnet crystals. As shown, the maximum ionic conductivity occurs at point 807, which is when the lithium content is stoichiometric (in line with vertical line 805). The overall distribution 809 of points shows that the ionic conductivity sharply increases above 10 wt% until the stoichiometric amount of lithium is reached and then the ionic conductivity more gradually decreases as the amount of lithium is further increased (see section 811). Examples 1-11 fall within section 811 (having greater than stoichiometric amounts of lithium) with points 813a, 813b, and 813c representing some of the compositions within the scope of the present disclosure that will be highlighted, for example, with a final lithium content from 11.2 wt% to about 12.2 wt% or from 11.3 wt% to about 12.2 wt% Li2O.

[0141] FIGS. 10-12 show SEM images of near-surface cross-sections of Comparative Example BB, Comparative Example AA, and Example 3, respectively, before any etching treatment. As shown in FIG. 10, the grain structure of Comparative Example BB is intergranular 1001 as few or no grain boundaries are visible in the cross-section. For Comparative Example AA, FIG. 11 shows that the grain structures is also intergranular 1101 with few or no grain boundaries visible with additional pores visible in FIG. 11 relative to FIG. 10. In contrast, the near-surface cross-section of Example 3 shown in FIG. 12 is intergranular 1201 with main distinct grains (e.g., grains 1203a, 1203b, and 1203c) visible, indicating that fracture occurred between grain boundaries rather than within grain. The stark difference between the transgranular near-surface structure of Comparative Examples AA-BB (FIGS. 11 and 10) compared to the intergranular near- surface structure of Example 3 demonstrates that the additional lithium in Example 3 (relative to the stoichiometric amounts of lithium in Comparative Examples AA-BB) produces a change in the microstructure (e.g., morphology) of the garnet electrolyte.

[0142] FIGS. 13-15 show SEM images of Comparative Example BB, Example 2, and Example 3, respectively, that have been etched in 1 M HC1 for 20 minutes. As shown in FIG. 13, the etched surface of Comparative Example BB has main grain boundaries visible; however, there are no deep pores visible. Even after 20 minutes of etching in 1 M HC1, it appears that the surface has etched relatively uniformly (other than perhaps better defining the grain boundaries). In contrast, FIG. 14 shows that the major surface of Example 2 is porous several well-defined, deep pores with an example pore 1401 having a pore size 1403 of about 6 pm. Similarly, FIG. 15 shows that the major surface of Example 3 is porous several well-defined, deep pores with an examplepore 1501 having a pore size 1503 of about 6 pm. Comparing FIG. 14 (Example 2) and FIG. 15 (Example 3), FIG. 15 appears to show more pores but, on average, smaller pores than FIG. 14. The larger pores of Example 2 is associated with additional lithium (11.5 wt%) compared to Example 3 (11.4 wt%). Overall, the non-porous surface of Comparative Example BB (stoichiometric amount of lithium) is significantly different from the large, deep pores in both Examples 2-3 (11.4-11.5 wt%). This demonstrates that the morphological differences seen between Comparative Examples AA-BB (FIGS. 11 and 10) and Example 3 (FIG. 12) translates into a porous surface of Examples 2-3 (FIGS. 14-15) that is more easily formed by etching than Comparative Example BB (FIG. 13). It is to be understood that Comparative Example BB can still be etched to form a porous surface, but more etching (either higher acid concentration, higher temperature, longer time, or a combination thereof) would be required to do so.

[0143] FIGS. 16-22 show SEM images of complete (or nearly complete for FIGS. 20- 22) cross-sections (from the first major surface 1605, 1705, 1805, 1905, 2005, 2105, or 2205 to the second major surface opposite the second major surface). The samples shown in FIGS. 16-22 were not etching. FIG. 16 corresponds to Comparative Example BB and FIGS. 17-22 correspond to Examples 2-7, respectively. As shown in FIG. 16, the cross-section of Comparative Example BB is transgranular through the entire thickness 1603 of the sample. In contrast, FIG. 17 shows intergranular microstructure throughout the thickness 1703 sample 1701 of Example 2 with the intergranular microstructure predominating in the near-surface regions 1707 and 1709. FIG. 18 shows regions of intergranular microstructure 1807 and 1809 near the surfaces of the sample 1801 of Example 3 with predominately transgranular microstructure 1811 therebetween. In FIG. 18, the intergranular microstructure 1807 extends to a depth 1813 from the first major surface 1805, which appears to be about 17% of the thickness 1803 of the sample 1801. FIG. 19 shows intergranular microstructure 1907 near the major surfaces of the sample 1901 with transgranular microstructure 1911 therebetween. FIGS. 20 shows intergranular microstructure 2007 largely confined within a depth 2103 from the first major surface 2005 of the sample with transgranular microstructure 2011 further from the first major surface 2005. FIG. 21 shows intergranular microstructure 2107 extending to at least a depth 2113 from the first major surface 2105 of the sample with transgranular microstructure 2111 further from the first major surface 2105. Compared to FIGS. 17-21, the intragranular microstructure is not as predominant near the first major surface 2205 and appears to be mixed with transgranular microstructure in the sample 2201 relative to the other samples. Overall, Examples 2-7 (FIGS. 17-22) have at least some intergranular microstructure (e.g., near the first major surface) while Comparative Example BB appears to be entirely transgranular.Further, going from Example 2 to Example 7, the amount of lithium decreases from 11.5 wt% to 11.2 wt%, where decreasing lithium content is associated with decreasing intergranular microstructure. However, even 11.2 wt% lithium has some intergranular microstructure, which can facilitate the formation or a porous surface by etching relative to garnet electrolytes with a stoichiometric amount of lithium (11.1 wt%).

[0144] FIG. 23 shows an SEM image of Example 3 after the major surfaces were etched with 1 M HC1 (at 25°C) for 10 minutes. As shown in FIG. 23, the sample 2301 comprises porous surface region (e.g., porous region 2307 extending from the first major surface 2305 extending to a porous depth 2313 from the first major surface 2305). As shown, the porous depth 2313 of the porous region 2307 is about 22 pm, which is about 18% of the electrolyte thickness 2303. The porous region 2307 comprises pores 2311a, 2311b, and 2311c that can have a width of 5 pm or more (e.g., 10 pm or more) and a depth of 10 pm or more (e.g., 20 pm or more) extending from the first major surface. Similarly, porous region 2317 comprises pores 2321a, 2321b, and 2321c extending from the second major surface 2315. In FIG. 23, the depth of the pores (e.g., pores 2311a-c and / or 2321a-c) is roughly the same as a depth associated with the remaining intergranular microstructure. Indeed, comparing FIG. 18 (Example 3 before etching) to FIG. 23 (Example 3 after etching), it appears that the pores were formed in regions with large amounts of the intergranular microstructure.Table 2: Firing Treatment of Examples 4-7, 4A, and 7A

[0145] Table 2 presents the firing conditions for Examples 4-7 (and 4A and 7A). The same green tape composition was used for Examples 4-7 - only the firing treatment was modified. As shown in Table 2, increasing the firing temperature from 1100°C to 1160°C decreases the amount of lithium content in the resulting composite garnet electrolyte (even when the time is decreases - see Examples 6-7 relative to Example 5). In combination with the observation that higher amounts of lithium in the resulting composite garnet electrolyte is associated with more intergranular microstructure, it follows that lower firing temperatures are associated with more intergranular microstructure.

[0146] Table 3 also presents the firing conditions for Examples 9-11. The same green tape composition (with more excess lithium in the green tape composition for Example 4-7) was used for Examples 9-11 with only firing treatment modified. Similar to the trend seen for Examples 4-7, increasing the firing temperature from 1125°C to 1185°C (Examples 9-11) is associated with decreasing lithium content in the resulting composite garnet electrolyte. This is consistent with trend noted above and supports the position that lower firing temperatures are associated with more intergranular microstructure.

[0147] Table 3 also presents the ring-on-ring strength of Examples 9-11. As shown, Example 10 has a ring-on-ring strength of about 340 MPa. Based on the final lithium content (similar to that Example 2 shown in FIG. 17), it is expected that Example 10 has intergranular microstructure predominating in near-surface regions. Further, based on the trend of more intergranular microstructure with lower firing temperatures, it appears that a moderate amount of intergranular microstructure may increase the strength of the composite garnet electrolyte (e.g., with a maximum strength around 11.5 wt% Li2O).Table 3: Firing Treatment of Examples 9-11

[0148] FIGS. 24-25 present SEM images of the surface of Examples 4 and 7, respectively, after being etched by 1 M HC1 (at 25°C) for 10 minutes. While the images in FIGS. 24-25 are not as clear as FIG. 14-15 due to the lower zoom of FIGS. 24-25, the pore structure can still be seen in FIGS. 24-25. In FIG. 24, pores (e.g., pore 2401) are seen across the surface, for example, with pore 2401 having a pore size 2403 of about 6 pm. In FIG. 25, grains 2501 are visible on the surface as well as pores (e.g., pore 2505), for example, with pore 2505 having a pore size 2503 of about 3 pm. The larger pore size of Example 4 (FIG. 24) relative to Example 7 (FIG. 25) is consistent with the trend discussed above that more lithium (11.4 wt% in Example 4 versus 11.2 wt% in Example 7) results in more intergranular microstructure and, in turn, more easily etched and larger pores.

[0149] FIG. 26 presents the pore size distribution of Examples 12-13 and Comparative Examples CC-DD that were etched by 3 M HC1 (at 25°C) for 10 minutes. In FIG. 26, the horizontal axis 2601 corresponds to the pore size in pm, and the vertical axis 2607 corresponds to the differential intrusion (ml / g) in the mercury porosity measurement. Curves 2605 and 2607 correspond to Examples 12-13, respectively, which are sintered tapes with lithium amounts of 11.2 wt% and 11.4 wt%. Curves Comparative Examples CC-DD correspond to hot-pressed samples with stoichiometric (11.1 wt%) lithium. The large peaks for curves 2611 and 2613 at greater than 10 pm (to the left) are believed to correspond to interstitial volume of the samples (due to the hot pressing method) rather than surface pores. Ignoring the peaks from interstitial volume, Comparative Example CC has a mean pore size of about 3 pm (curve 2611) and Comparative Example DD has a mean pore size of about 7 pm (curve 2613). In contrast, Examples 12-13 (curves 2605 and 2607) have a relatively small peak at about 7 pm in addition to larger peak corresponding to pores greater than 10 pm. This is consistent with the larger pores seen throughout associated with composite garnet electrolytes having greater than stoichiometric amounts of lithium.

[0150] NCM523 refers to LiNio.5Coo.2Mno.3O2 (precursor commercially available from Landt Instruments). The NCM523 was formed into a slurry with a 8: 1 : 1 weight ratio of the precursor, super P carbon black (available from Timcal - Imerys), and poly (vinylidene fluoride) (PVDF) (dissolved in N-methylpyrrolidone) that was coated on aluminum (Al) foil with a predetermined thickness and dried under vacuum. After etching the surfaces of the solid-state electrolyte in 1 M HC1 for 10 minutes, the lithium-containing material for the anode was disposed on the coating and heated for 5 minutes at 300°C. The cathode has a mass loading of 20 mg / cm2of the NCM523 cathode with a diameter of 12 mm. In Examples 1, 1A, and 8 and Comparative Example AA, 16 pL / cm2of a liquid electrolyte consisting of 1 M LIFSI dissolved in sulfolane was disposed on the cathode, and then the solid-state electrolyte was disposed over the cathode with the liquid electrolyte positioned therebetween. In Examples 4 and 4A and Comparative Example BB, 16 pL / cm2of a liquid electrolyte consisting of 3 M LIFSI dissolved in sulfolane was disposed on the cathode, and then the solid-state electrolyte was disposed over the cathode with the liquid electrolyte positioned therebetween. Examples 1, 1A, 4, and 4 A and Comparative Examples AA- BB were formed into a battery resembling the solid-state battery 201 shown in FIG. 2 in a CR2025 coin cell form with Ni foam disposed over the anode.

[0151] FIG. 9 shows a Nyquist plot for Example 1A and Comparative Example AA. Example 1 A has the same composition as Example 1, but Example 1 A was etched in 1 M HC1 for 5 minutes instead of 20 minutes in Example 1. Comparative Example AA was also etched in 1 MHC1 for 5 minutes. For both Example 1A and Comparative Example AA, both major surfaces (cathode facing and anode facing) were etched for the 5 minutes in 1 M HC1. The cell configuration for EIS testing of Example 1 A and Comparative Example AA was, in order from anode to cathode, a Lio.gMgo.i alloy anode, the composite garnet electrolyte of Example 1 A or Comparative Example AA, a liquid electrolyte consisting of 1 M LiFSI in sulfolane at 16 pL / cm2(based on a surface area of the cathode), and the NCM523 cathode. As discussed above, the data shown in FIG. 9 were measured by EIS using Solartron 1260A (Solartron) impedance analyzer at 25°C for frequencies from 0.1 Hertz (Hz) to 1 MegaHertz (MHz). In FIG. 9, the horizontal axis 901 corresponds to the real component of impedance (Z’ measured in cm2), and the vertical axis 903 corresponds to the imaginary component of impedance (Z” measured in cm2). The interfacial resistance shown in Table 2 is measured as the difference between the real components of the impedance for the endpoints of an arc shape of the curve corresponding to the EIS results in the Nyquist plot. Curve 905 corresponds to Comparative Example AA, and curve 907 corresponds to Example 1 A. As shown, the interfacial resistance for Comparative Example AA (curve 907) is more than double the interfacial resistance of Example 1A (curve 905) (e.g., compare about 35 cm2for Comparative Example AA to about 12 cm2for Example 1 A) for the combined arc. The overall arc for both curves 905 and 907 appears to have a lower-frequency arc (to the left) that can be attributed to the cathode-garnet interface and a higher-frequency arc (to the right) that can be attributed to the anode-garnet interface. For both of these interfaces (portions of the overall arc), the distance along the horizontal axis 901 is smaller for Example 1 A (curve 907) than for Comparative Example AA (curve 905). This demonstrates that the additional lithium of Example 1 enables the formation of a porous surface with lower interfacial resistance than Comparative Example AA.

[0152] Table 4 presents cell performance for Examples 4 and 8 in a coin cell form factor, and Table 5 presents cell performance of Examples 4-7 in a pouch cell form factor. The half-cell used for determining the “half-cell CCD” comprises lithium alloy electrodes on both surfaces of the acid etched composite garnet electrolyte with the porous surface. As shown in Table 2, Example 4 (with more lithium than Example 8) had a higher critical current density (CCD) than Example 8. The full cell cycling stability was done with the cell described above. The full cells for Examples 4 and 8 were tested by cycling to a nominal capacity of 3.2 mAh / cm2with a constant charging and discharging current density of either 1 mA / cm2, 1.5 mA / cm2, or 2 mA / cm2for 70 cycles. As shown in Table 4, Example 8 withstood 28 cycles at a current density of 1 mA / cm2before failing and 5 cycles at a current density of 1.5 mA / cm2. In contrast, Example 4 withstood the full 70 cycles at all of the current densities tested (with highest - 2 mA / cm2reported in Table 4).Table 4: Cell Performance of Examples 4 and 8Table 5: Cell Performance of Examples 4-7

[0153] For Table 5, the composite garnet electrolyte with the porous surface of Examples 4-7 were assembled into pouch cells. For the pouch cell, a 300 nm layer of gold sputtered on the first major surface of the acid etched composite garnet electrolyte with the porous surface followed by a 0 pm Li foil being pressed (cold iso-static pressing at 250 MPa followed by heating at 80C for 1 hour) to form the anode. The NCM523 cathode was disposed on the second major surface of the composite garnet electrolyte with the porous surface with 16 pL / cm2of 1 M LiFSI positioned therebetween.

[0154] For the “C / 8 Discharge Test”, the discharge rate was maintained at C / 8, while the charging rate was increased as follows (3 cycles at each rate): C / 12, C / 8, C / 3, C / 2, and C / 1. As shown in Table 5, 0% of cells tests made it through all of the cycles without failure for Example 7, but the fraction of cells surviving increased going from Example 7 to Example 4. For Example 6, 40% of cells survived all cycles; for Example 5, 50% of cells survived all cycles; and for Example 4, 80% of cells survived all cycles.

[0155] For the “C / 6 Discharge Test”, the discharge rate was maintained at C / 6, while the charging rate was increased as follows (3 cycles at each rate): C / 12, C / 8, C / 3, C / 2, and C / 1, which is the same charging rate ramp for the C / 8 test above. For the C / 6 test, 0% of cells tests made itthrough all of the cycles without failure for Example 7, but the fraction of cells surviving increased going from Example 7 to Example 4. For Example 6, 20% of cells survived all cycles; for Example 5, 25% of cells survived all cycles; and for Example 4, 40% of cells survived all cycles. The results of the charging ramp tests demonstrate that increasing amounts of lithium (e.g., from 11.2 wt% to 11.3 wt% or from 11.2 wt% to 11.4 wt%) improve cycle stability even at charging rates of at least C / 1.

[0156] Table 5 also presents the number of cycles that Examples 4 and 7 withstood without failure (Examples 5 and 6 were not tested). The cycling occurred at a nominal capacity of 2.5 mAh / cm2at 60°C with a discharging rate of C / 8 and charging rate of C / 3 for a maximum of 100 cycles. As shown in Table 5, Example 7 failed before completing a cycle while Example 4 withstood all cycles tested.

[0157] The above observations can be combined to provide solid-state electrolytes, batteries, and methods of making the same comprising a surface(s) of the solid-state electrolyte that can be easily etched to form an electrolyte with a porous surface (e.g., composite garnet electrolyte with a porous surface). The electrolyte with the porous surface (e.g., composite garnet electrolyte with the porous surface) can enable lower interfacial resistance, increased charging performance, and / or increase cycling stability. Also, the electrolyte with the porous surface (e.g., composite garnet electrolyte with the porous surface) can enable a high ring-on-ring strength (e.g., about 150 MPa or more or from about 150 MPa to about 400MPa).

[0158] As discussed herein, providing excess lithium (relative to stoichiometry, for example, from 0.1 wt% to 4 wt%, from 0.2 wt% to 1.1 wt%, or from 0.3 wt% to 0.9 wt%) in the composite garnet electrolyte can facilitate the formation of an mixture of intergranular and transgranular microstructure and facilitate etching of the solid-state electrolyte (e.g., composite garnet electrolyte) to form a solid-state electrolyte with a porous surface (e.g., composite garnet electrolyte with a porous surface). For example, providing from 11.2 wt% to 15 wt% or from 11.3 wt% to 12.2 wt% can form an intergranular microstructure near the major surfaces of the composite garnet electrolyte, which can facilitate etching of the composite garnet electrolyte to form a solid- state electrolyte with a porous surface. Providing a transgranular microstructure near and / or at the first major surface can facilitate etching to form large and / or deep pores therein.

[0159] As discussed herein, 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 thesolid-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.

[0160] A green tape can comprise excess lithium (e.g., 0.5 wt% or more, 2 wt% or more, or 10 wt% or more based on the amount of garnet in the green tape) that is not completely removed by firing (e.g., sintering). In combination with excess lithium, the firing condition determine the amount of lithium remaining in the resulting electrolyte. If the firing is a too high a temperature (e.g., greater than 1200°C) and / or for too long a period of time (dependent on the temperature, e.g., about greater than 60 minutes), the vast majority of the excess lithium added to the green tape can be volatilized to produce an electrolyte without a transganular microstructure contrary to the aspects of the present disclosure.

[0161] Without wishing to be bound by theory, it is believed that the etching may preferentially etch the lithium phase between grains of the composite garnet electrolyte in the region with intergranular microstructure, and consequently, the composite garnet electrolyte of the present disclosure can be more easily and / or more quickly etched relative to other garnet electrolytes (e.g., with stoichiometric amounts of lithium). Providing a grain size of about 3 pm or less, from about 1 pm to about 3 pm, or from 1 pm to 3 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. Providing deep pores (e.g., about 2 pm or more, from about 20 pm to about 60 pm, about 5% of the electrolyte thickness or more, or from about 10% to about 20% of the electrolyte thickness) can increase an effective surface area of the solid-state electrolyte (e.g., facing an anode and / or facing a cathode), which can decrease an interfacial resistance of battery including the solid-state electrolyte with the porous surface (e.g., composite garnet electrolyte with the porous surface).

[0162] 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.

[0163] 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.

[0164] 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.”

[0165] 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 value forms 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.

[0166] 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.

[0167] 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.

[0168] 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 comprisesA+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.

[0169] 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.

[0170] 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 method of making a porous surface of a composite garnet electrolyte comprising: etching at least a first major surface of the composite garnet electrolyte with an acid to form the porous surface of the composite garnet electrolyte comprising pores, wherein the composite garnet electrolyte comprises an intergranular microstructure extending from the first major surface to a first depth, the composite garnet electrolyte comprising a lithium phase between garnet crystals, and electrolyte thickness defined between the first major surface and a second major surface opposite the first major surface.

2. The method of claim 1, wherein the etching removes at least a portion of the lithium phase.

3. The method of any one of claims 1-2, wherein an amount of lithium in the composite garnet electrolyte, on an oxide basis of the composite garnet electrolyte, is from about 11.2 wt% to about 15 wt%.

4. The method of claim 3, wherein the amount of lithium in the composite garnet electrolyte is from about 11.3 wt% to about 12.2 wt%.

5. The method of any one of claims 1-2, wherein an amount of lithium in the composite garnet electrolyte, on an oxide basis of the composite garnet electrolyte, is greater than a stoichiometric amount of lithium for the garnet crystals by from about 0.1 wt% to about 4 wt%.

6. The method of claim 5, wherein the amount of lithium in the composite garnet electrolyte is greater than the stoichiometric amount of lithium by from about 0.2 wt% to about 1.1 wt%.

7. The method of any one of claims 1-6, wherein the intergranular microstructure extends from the first major surface to the first depth of about 10% of the electrolyte thickness or more.

8. The method of claim 7, wherein the composite garnet electrolyte comprises a transgranular microstructure positioned between regions comprising the intergranular microstructure.

9. The method of any one of claims 1-8, wherein a median grain size of the garnet crystals is less than 3 gm.

10. The method of any one of claims 1-9, wherein a mean pore size of the pores is greater than 0.25 gm.

11. The method of claim 10, wherein the mean pore size of the pores is from 3 pm to about 20 gm.

12. The method of any one of claims 1-11, further comprising: prior to the etching, contacting the first major surface with water for at least 1 minute, wherein a concentration of the acid during the etching is from about 0.5 M to about 5 M.

13. The method of any one of claims 1-12, further comprising: casting a green tape comprising garnet, excess lithium, a binder, and a solvent, wherein an amount of the excess lithium, as a wt% of an amount of the garnet, is greater than 5 wt%; and firing the green tape to form the composite garnet electrolyte.

14. The method of claim 13, wherein the firing comprises heating the green tape at a temperature from about 900°C to about 1150°C for a period of time of 60 minutes or less.

15. The method of any one of claims 1-14, wherein the composite garnet electrolyte comprises a ring-on-ring strength from about 150 MPa to about 600 MPa.

16. The method of any one of claims 1-15, wherein an interfacial resistance of the composite garnet electrolyte having the porous surface is less than or equal to 20 at 25°C.

17. A composite garnet electrolyte comprising: pores extending from a first major surface; and an intergranular microstructure extending from the first major surface to a first depth, wherein the composite garnet electrolyte comprises a lithium phase between garnet crystals, and an electrolyte thickness defined between the first major surface and a second major surface opposite the first major surface.

18. The composite garnet electrolyte of claim 17, wherein an amount of lithium in the composite garnet electrolyte, on an oxide basis of the composite garnet electrolyte, is from about 11.2 wt% to about 15 wt%.

19. The composite garnet electrolyte of claim 18, wherein the amount of lithium in the composite garnet electrolyte is from about 11.3 wt% to about 12.2 wt%.

20. The composite garnet electrolyte of claim 17, wherein an amount of lithium in the composite garnet electrolyte, on an oxide basis of the composite garnet electrolyte, is greater than a stoichiometric amount of lithium for the garnet crystals by from about 0.1 wt% to about 4 wt%.

21. The composite garnet electrolyte of claim 20, wherein the amount of lithium in the composite garnet electrolyte is greater than a stoichiometric amount of lithium for the garnet crystals by from about 0.2 wt% to about 1.1 wt%.

22. The garnet electrolyte of any one of claims 17-21, wherein the intergranular microstructure extends from the first major surface to the first depth of about 10% of the electrolyte thickness or more.

23. The garnet electrolyte of claim 22, wherein the garnet electrolyte comprises a transgranular microstructure positioned between regions comprising the intergranular microstructure.

24. The porous garnet electrolyte of any one of claims 17-23, wherein a median grain size of the garnet crystals is less than 3 pm.

25. The porous garnet electrolyte of any one of claims 17-24, wherein a mean pore size of the pores is greater than 0.25 pm.

26. The porous garnet electrolyte of any one of claims 17-25, wherein the porous garnet electrolyte comprises a ring-on-ring strength from about 150 MPa to about 600 MPa.

27. The garnet electrolyte of any one of claims 17-26, wherein an interfacial resistance of the garnet electrolyte is less than or equal to 20 at 25°C.

28. A battery comprising: a lithium-containing anode; the garnet electrolyte of any one of claims 17-27; and a cathode, wherein the garnet electrolyte is positioned between the lithium-containing anode and the cathode.

29. The battery of claim 28, wherein the battery can withstand a critical current density of 2 mA / cm2or more at 60°C.

30. The battery of any one of claims 28-29, wherein the battery can withstand 70 cycles with charging and discharging at 2 mA / cm2.

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