Electrolyte composition for efficient electrodeposition of lithium metal films

Abstract

A system and a method for electrodeposition of lithium metal are provided. The system includes a reservoir of electrolyte composition comprising a solvent, a hydrolytically stable lithium salt, a hydrolytically unstable salt, and water, a vessel containing additives, and a power source for electrodepositing a lithium metal. The method includes providing a counter-electrode, providing the electrolyte composition between a substrate and the counter-electrode, and applying a current between the substrate and the counter-electrode to electrodeposit a lithium metal film on the substrate. In various embodiments, the hydrolytically unstable salt, the water, and a second solvent are pre-mixed prior to combining with the hydrolytically stable lithium salt and the solvent to form the electrolyte composition. The additives may include a second hydrolytically unstable salt, a second solvent, and additional amount of water with a sufficient concentration to partially hydrolyze the second hydrolytically unstable salt.

Description

ELECTROLYTE COMPOSITION FOR EFFICIENTELECTRODEPOSITION OF LITHIUM METAL FILMSCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Patent Application No. 63 / 643,033, filed May 6, 2024, all of which is incorporated by reference herein in its entirety.FIELD OF INVENTION

[0002] Embodiments of the present disclosure relate generally to electrochemical energy storage devices including lithium batteries, and more particularly related to methods and devices for producing a lithium film via electrodeposition.BACKGROUND

[0003] Lithium-based battery technologies have improved over time with advances culminating in battery cells with higher capacities, longer cycle lives, and superior charging and discharging rates. However, challenges remain with the scalability and production of certain critical battery components, such as, the lithium metal used in some battery systems. Among these challenges, forming thin lithium metal films for use as an anode in rechargeable batteries remains one of the top production issues.

[0004] Lithium metal coating process, in general, hinges on the ability to rapidly coat a thin film of lithium metal onto a conductive substrate. A thin lithium metal, for example, can be produced via electrodeposition, but may require the application of high currents during the coating process. With high current applied during electrodeposition, lithium metal films that are produced with this process can have poor morphology in the films, particularly due to the high current being applied during the film formation and the non-uniform nature of charge transfer from the organic electrolyte to the deposited lithium film. It is well known that high currents during lithium plating can result in lithium films with dendritic features with mossy lithium deposits throughout the film thickness that result in poor performance and degrade the quality of the organic electrolyte. Many organic electrolytes degrade rapidly under lithium electrodeposition conditions, especially when exposed to moisture, acid formation, or extended rest times. Such degradation compromises the long-term utility of the electrolyte, reduces the lithium electrodeposition efficiency and reliability over time, and increases the cost of the as-produced lithium metal.

[0005] Therefore, there remains a need for improved electrolyte compositions and electrodeposition methods to produce thin lithium metal films with superior electrochemical performance and improved operational lifetime of the organic electrolyte.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] For a more complete understanding of the principles disclosed herein, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0007] Figure 1 illustrates an embodiment of an apparatus for electrodeposition of lithium metal, in accordance with various embodiments.

[0008] Figure 2A illustrates a schematic of an electrodeposited lithium metal film on a substrate, in accordance with various embodiments.

[0009] Figure 2B illustrates an example configuration of a symmetric cell used to measure the lithium capacity of the electrodeposited lithium metal prepared from the cutout shown in Figure 2A.

[0010] Figure 3 illustrates a flowchart of a method for electrodeposition of lithium metal, in accordance with various embodiments.

[0011] It is to be understood that the figures are not necessarily drawn to scale, nor are the objects in the figures necessarily drawn to scale in relationship to one another. The figures are depictions that are intended to bring clarity and understanding to various embodiments of apparatuses, systems, and methods disclosed herein. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Moreover, it should be appreciated that the drawings are not intended to limit the scope of the present teachings in any way.DETAILED DESCRIPTION

[0012] In accordance with one or more embodiments, the tools, apparatuses, systems, and methods disclosed herein can be used for electrodepositing thin lithium metal films. As described herein, thin lithium metal films can be electrodeposited from unique chemical mixtures of the organic electrolyte which exhibit superior operational lifetime. In some embodiments, the introduction of water and a hydrolytically unstable lithium salt into an organic electrolyte comprised of a high concentration of a hydrolytically stable lithium salt can improve the quality of the lithium metal film and the operational lifetime of the organic electrolyte. In some embodiments, the introduction or generation of acid in the electrolyte canfacilitate surface conditioning of the conductive substrate and lithium metal film resulting in controlled surface chemistry and uniform growth of the lithium metal film. In some embodiments, additional parameters, such as a fluid velocity of the electrolyte, can be modified, or adjusted, during production of the coatings to improve the film quality, e.g., texture and morphology. In some embodiments the electrolyte system enables the deposition of lithium metal with enhanced adhesion to the copper substrate that enables the application of high fluid velocity during electrodeposition. In addition to improving the quality of electrodeposited lithium metal films, the disclosed embodiments can offer an organic electrolyte with improved operational lifetime for lithium metal production.

[0013] In accordance with one or more embodiments, a system and a method for electrodeposition of lithium metal (films) are provided. In one or more embodiments, an electrolyte composition for electrodeposition is described. The disclosed electrolyte composition enables electrodeposition of dendrite-free lithium metal at high applied currents greater than 5 mA / cm2, in one or more embodiments. In one or more embodiments, an additive for use with the electrolyte composition for lithium metal electrodeposition are described. In one or more embodiments, a lithium metal (film) produced using the electrolyte composition is described.

[0014] Figure 1 illustrates an embodiment of an apparatus 100 for electrodeposition of lithium metal, in accordance with various embodiments. As illustrated in Figure 1, the apparatus 100 may include a chamber / reservoir 110 configured for electrodeposition of lithium films. The apparatus 100 may have an inlet 120 and an outlet 130, for example, for introducing and removing, respectively, the electrolyte used in electrodeposition, in accordance with one or more embodiments. As shown in Figure 1, the chamber / reservoir 110 is configured for intaking a fluid 140 (e.g., the electrolyte composition for electrodeposition) via the inlet 120 and removing the fluid 140 via the outlet 130.

[0015] In some embodiments, the fluid 140 may include lithium ions that were extracted from an aqueous lithium-containing solution via a lithium-ion-conducting membrane, such as a lithium superionic conductor (LISICON), NASICON-type material, or garnet-type solid electrolyte. The membrane acts as a selective barrier, allowing lithium ions to be transferred into the organic electrolyte from the aqueous donor phase. The resulting lithium-enriched organic electrolyte, now comprising solvent, lithium salt, and optionally water, may then be introduced via the inlet 120 into the chamber 110 for electrodeposition. In some embodiments, one or more additives such as hydrolytically unstable lithium salts or controlled water quantities may be injected into the lithium-enriched organic phasedownstream of the membrane and prior to or during the electrodeposition process to facilitate SEI formation and improve lithium deposition morphology.

[0016] In some embodiments, the counter-electrode 150 is not located within the same chamber 110 as the cathode 160 / 162, but instead is situated in a separate aqueous compartment (not shown) on the opposite side of a lithium-ion-conducting ceramic membrane (not shown). In these embodiments, the counter-electrode 150 functions as an anode positioned in direct contact with a lithium-containing aqueous solution. A ceramic membrane (not shown in Figure 1) separates the aqueous and organic compartments and is configured to conduct lithium ions while preventing the crossover of water. When an electric field is applied between the anode in the aqueous chamber and the cathode substrate 162 in the organic chamber, lithium ions are driven across the membrane and enter the organic electrolyte (fluid 140). These extracted lithium ions are then reduced and plated onto the substrate 162 to form the lithium metal film 180. In some embodiments, the electrodeposition system may also include one or more additive introduction ports for injecting hydrolytically unstable salts and water into the organic compartment downstream of the membrane to enhance SEI formation and improve lithium metal deposition morphology.

[0017] In various embodiments of the apparatus 100, the fluid 140 may include an electrolyte composition comprising a solvent, a hydrolytically stable lithium salt, a hydrolytically unstable salt, and water.

[0018] In various embodiments, a concentration of the water in the electrolyte composition is between 0.0005 M and 0.1 M, between 0.0005 M and 0.05 M, between 0.0001 M and 0.05 M, between 0.005 M and 0.05 M, inclusive of any concentration ranges therebetween.

[0019] In various embodiments, a concentration of the hydrolytically stable lithium salt in the electrolyte composition is between 0.5 M and 6.0 M, between 0.7 M and 6.0 M, between 1.0 M and 6.0 M, between 1.5 M and 6.0 M, between 2.0 M and 6.0 M, between 2.5 M and 6.0 M, between 0.5 M and 5.5 M, between 0.7 M and 5.0 M, between 1.0 M and 4.5 M, between 1.5 M and 4.0 M, between 2.0 M and 3.5 M, or between 2.5 M and 3.0 M, inclusive of any concentration ranges therebetween.

[0020] In various embodiments, a concentration of the hydrolytically unstable salt in the electrolyte composition is between 0.0005 M and 1.0 M, between 0.001 M and 1.0 M, between 0.005 M and 1.0 M, between 0.01 M and 1.0 M, between 0.05 M and 1.0 M, between 0. 1 M and 1.0 M, between 0.0005 M and 0.95 M, between 0.001 M and 0.9 M, between 0.005 M and 0.85 M, between 0.01 M and 0.8 M, between 0.05 M and 0.75 M, between 0.1 M and 0.7 M, inclusive of any concentration ranges therebetween.

[0021] In various embodiments, wherein a weight percent ratio of the hydrolytically stable lithium salt to the hydrolytically unstable lithium salt is between 2.5: 1 and 1000:1.

[0022] In various embodiments of the apparatus 100, the electrolyte composition of the fluid 140 may further include a diluent (e.g., a non-coordinating diluent) having a concentration between 5 vol% and 90 vol% of the electrolyte composition. In various embodiments, the diluent includes fluorinated ether solvents, hydrofluoroethers (HFEs), non-coordinating sulfones, fluorinated alkyl ethers with weak Lewis basicity, sterically hindered ethers, cyclic ethers with limited donor ability, or a combination thereof.

[0023] In various embodiments, the solvent may include one or more organic solvents selected from a list of linear or cyclic ethers (e.g., dimethoxyethane, tetrahydrofuran, dioxolane), carbonates (e.g., ethylene carbonate, dimethyl carbonate, fluoroethylene carbonate), fluorinated solvents, or a mixture thereof. In one or more embodiments, the solvent may comprise nitrile-based solvents, such as acetonitrile or fluoroacetonitrile, which offer high dielectric constants and excellent salt dissociation properties. While nitriles may undergo reductive decomposition in direct contact with lithium metal, their inclusion in the solvent system — particularly when paired with fluorinated co-solvents, passivating additives, or artificial interphase layers — may facilitate enhanced ionic conductivity and controlled lithium deposition. In additional embodiments, the solvent system may include sulfone-based solvents, such as dimethyl sulfone, ethyl methyl sulfone, or tetramethylene sulfone (sulfolane). These sulfones can improve the oxidative stability, viscosity tuning, and thermal robustness of the electrolyte, and may be used alone or in combination with ethers or carbonates to tailor the interfacial behavior at the lithium metal surface. The selected solvent system may be formulated to balance lithium salt solubility, interfacial stability, ionic conductivity, and safety under high current electrodeposition conditions. In various embodiments, the solvent may include a molar ratio of solvent- to-hydrolytically stable salt of < 5:1 that indicates a high-concentration electrolyte or a solvent-in-salt electrolyte.

[0024] In various embodiments, the hydrolytically stable lithium salt of the electrolyte composition in the fluid 140 is selected from the group consisting of LiFSI, LiTFSI, LiBOB, LiDFOB, LiNCL, and other lithium salts comprising fluoroalkylsulfonyl, oxalato, phosphate, or delocalized anions that are resistant to hydrolysis. In various embodiments, the hydrolytically unstable salt of the electrolyte composition in the fluid 140 is selected from the group consisting of LiPFe, LiBF4, HPFe, and HBF4, and lithium salts comprising hexafluorophosphate, tetrafluoroborate, oxalate-phosphate-fluoride, or chloroaluminate anions.

[0025] “Delocalized anions” as used herein refer to anions in which the negative charge is distributed over multiple atoms, including but not limited to fluoroalkylsulfonylimide (e.g., TFSI . FSI ), perfluoroarylborates, and other polyanionic structures that exhibit reduced hydrolytic reactivity and improved electrochemical stability.

[0026] In various embodiments, the water in the electrolyte composition in the fluid 140 hydrolyzes the hydrolytically unstable salt to generate acidic and fluorinated species. In various embodiments, the acidic and fluorinated species may include hydrogen fluoride (HF), lithium fluoride (LiF), and optionally phosphorus oxyfluoride (POF3) or lithium bifluoride (LiHF2), wherein the acidic and fluorinated species form or promote the growth of a lithium fluoride-rich SEI that enables uniform lithium nucleation and suppresses dendritic growth.

[0027] In various embodiments, the electrodeposited lithium metal film exhibits a columnar nanostructure. In one or more embodiments, the electrodeposited lithium metal film may include a film thickness variation of less than 10%.

[0028] In various embodiments, the electrolyte composition of the fluid 140 may further include one or more additives selected from flame retardants, rheology modifiers, or fluorinated solvents.

[0029] In various embodiments, the electrolyte composition of the fluid 140 may further include an acid having a concentration between 0.0005 M and 0.1 M of the electrolyte composition.

[0030] In one or more embodiments, the hydrolytically unstable salt of the electrolyte composition of the fluid 140 is a first hydrolytically unstable salt, the solvent is a first solvent, and the water is a first amount of water, the electrolyte composition of the fluid 140 may further include an additive that includes a second hydrolytically unstable salt, a second solvent, and a second amount water with a sufficient concentration to partially hydrolyze the second hydrolytically unstable salt. In various embodiments, the second amount water partially hydrolyzes the second hydrolytically unstable salt in the additive under an inert atmosphere prior to the introducing of the additive to the electrolyte composition. In various embodiments, the additive is introduced into the electrolyte composition at a rate controlled by feedback from real-time measurements of deposition efficiency, conductivity, pH, or film morphology.

[0031] In one or more embodiments, the hydrolytically unstable salt, the water, and a second solvent are pre-mixed prior to combining with the hydrolytically stable lithium salt and the solvent to form the electrolyte composition. In various embodiments, the hydrolytically unstable lithium salt and the water react in situ to generate fluorinated and acidic species thatpromote solid-electrolyte interphase (SEI) formation and facilitate lithium nucleation. In various embodiments, the water partially hydrolyzes the hydrolytically unstable salt under an inert atmosphere prior to the addition to the hydrolytically stable salt and solvent.

[0032] Further illustrated in Figure 1, the apparatus 100 may include a counter-electrode 150 (also referred to herein as an anode) and a holder 160 for mounting a substrate 162. In some embodiments herein, the holder 160 with the substrate 162 mounted thereof, can be configured as a cathode 160 / 162 (also referred to herein as the substrate / electrode). In one or more embodiments, the substrate 162 is removably mounted on or in, or otherwise removably attached to, the holder 160 for electrodeposition. In various embodiments, the holder 160 and the counter-electrode 150 are spaced apart between 0.005 cm and 10 cm.

[0033] In various embodiments, the counter-electrode 150 may include a piece of lithium metal (e.g., a thin film or otherwise), or may be an electrode coating having one or more electrochemically active materials commonly employed as an anode or a cathode in a lithium-ion battery.

[0034] In various embodiments, the substrate 162 can include a planar or 3D copper sheet or any suitable sheet of a conductive metal, such as, for example, but not limited to, conductive carbon, silver, gold, zinc, nickel, tin, brass.

[0035] The apparatus 100 may also include a power source (not shown) configured to supply a current 170 across the substrate 162 (the cathode comprising the holder 160 / substrate 162) and the counter-electrode 150 (anode) during an electrodeposition operation. In various embodiments, the inlet 120 of the apparatus 100 may be oriented with respect to a surface of the substrate 162 such that the fluid 140 flowing through the inlet 120 and arriving at the surface of the substrate is at least greater than 500 cm3per minute (in some cases, greater than 570 cm3per minute), and lithium ions contained within the fluid 140 are electrochemically reduced and plated to form a lithium metal film 180 on the surface of the substrate 162. In one or more embodiments, the fluid 140 may flow through the inlet 120 at a flow velocity greater than 900 cm per minute. In one or more embodiments, the fluid 140 may flow through the inlet 120 at a flow velocity between 860 cm per minute and 1500 cm per minute. In one or more embodiments, the fluid 140 may flow through the inlet 120 at a flow velocity greater than 1700 cm per minute. In one or more embodiments, the fluid 140 may flow through the inlet 120 at a lower fluid velocity at a lower applied current.

[0036] In various embodiments, the fluid 140 may include an abrasive material, in addition to electrolyte materials. The abrasive material may include a metal oxide, such as aluminumoxide, a non-metallic oxide, such as silica, or other common abrasive materials, such as diamond or boron carbide, in accordance with one or more embodiments.

[0037] In one or more embodiments, the abrasive material in the fluid 140 may contact the surface of the substrate 162 prior to the power supply supplying the current 170 across the anode 150 and the cathode 160 / 162. In one or more embodiments, the abrasive material in the fluid 140 may contact the surface of the substrate 162 while the power supply is supplying the current 170 across the anode 150 and the cathode 160 / 162. In one or more embodiments, the abrasive material in the fluid 140 may contact the surface of the substrate 162 after the power supply supplied the current 170 across the anode 150 and the cathode 160 / 162. In other words, the abrasive material in the fluid 140 may be used to clean the surface of the substrate 162 before electrodeposition begins, interact with the growing lithium film while lithium is being deposited during the electrodeposition, or after the lithium film has been deposited. During the growth of the lithium film 180, the abrasive material may be used to shear off dendritic portions of the lithium film or large polymeric portions of the solid-electrolyte-interphase (SEI) layer. After the film is formed, the abrasive material may assist in removing large surface features, such as abnormally thick SEI or mossy lithium.

[0038] In one or more embodiments of the apparatus 100, the power source is further configured to supply a pulsed current across the counter-electrode 150 and the cathode 160 / 162. The pulsed current may facilitate forming of a better lithium metal film 180 on the surface of the substrate 162. In one or more embodiments, the power source is further programmed via cyclic voltammetry to facilitate forming of the lithium metal film 180 on the surface of the substrate 162.

[0039] In one or more embodiments, the apparatus 100 may further include a vessel 190 configured for introducing additives into the electrolyte composition and / or replenishing the fluid 140 with one or more lithium ion containing additive materials. In other words, the fluid 140 is constantly being added with additives via the inlet 120 and may be removed via the outlet 130. In some implementations, the fluid 140 may be routed to a replenishing source (not shown) for replenishing the fluid 140 before recycling back into the inlet 120 for re-introducing the fluid 140 for electrodeposition, in accordance with one or more embodiments. The newly introduction of additives / recycling / replenishing portion can help facilitate continuous electrodeposition using the apparatus 100, in accordance with one or more embodiments.

[0040] However, in alternative embodiments, the fluid 140 may be delivered at a reduced flow velocity below 100 cm per minute, including substantially static conditions (e.g., flowrates below 10 cm3per minute or no active flow), particularly when deposition occurs at lower current densities or when electrolyte replenishment occurs intermittently or diffusively. In some embodiments, no active fluid flow is provided, and the fluid 140 remains in contact with the surface of the substrate 162 via passive means such as capillary action, immersion, diffusion, or convective mixing within the chamber 110. Such low-flow or quiescent flow configurations may be advantageous for forming dense lithium coatings with minimal surface agitation, or for preserving fragile SEI architectures during early stages of nucleation.

[0041] In one or more embodiments, the apparatus 100 may further include a filter (not shown) placed proximate to, or in-line with, the inlet 120 of the chamber 110. The filter can be configured to filter impurities, such as polymeric components of the SEI or pieces of mossy lithium sheared from the surface during film fabrication, from the fluid 140 prior to being introduced via the inlet 120 of the chamber 110, in accordance with one or more embodiments.

[0042] In one or more embodiments, the apparatus 100 may further include a metered introducing mechanism (not shown) configured to deliver the additive into the fluid 140 (of electrolyte composition) prior to or during electrodeposition of the lithium metal film. In one or more embodiments, the additive is introduced at a controlled rate based on sensor feedback that measures electrolyte degradation, lithium adhesion, or plating morphology.

[0043] In one or more embodiments, the apparatus 100 may further include a pump (not shown) configured to pressurize the chamber 110 using an inert gas, such as argon or nitrogen above an ambient atmospheric condition. In one or more embodiments, the counterelectrode 150 is disposed in a portion or an area of the chamber 110 with little-to-no flow of the fluid 140. In other words, the counter-electrode 150 may not be in contact with the fluid 140 while the cathode 160 / 162 (the holder 160 and substrate 162) may be fully submersed in the fluid 140 during electrodeposition, in accordance with one or more embodiments.Although Figure 1 illustrates the counter-electrode 150 being submersed in the fluid 140, the counter-electrode 150 may be isolated from contacting the fluid 140 (illustration not shown), in accordance with one embodiment.

[0044] In another embodiment, the counter-electrode 150 may be positioned within a separate aqueous chamber that is fluidically and ionically isolated from the organic electrolyte chamber 110 by a lithium-ion-conducting ceramic membrane. In such configurations, the counter-electrode 150 acts as an anode and is immersed in an aqueous lithium-containing solution. Upon application of an electric field between the aqueous-phase anode and the cathode substrate 162, lithium ions are selectively transported through themembrane and into the fluid 140 within the organic chamber 110. This configuration allows for the electrochemical extraction of lithium from water-based sources and its direct use in organic -phase lithium metal deposition. The ceramic membrane may comprise a solid-state lithium-ion conductor such as a garnet-type, NASICON-type, or LISICON-type material, and is configured to block water transport while allowing efficient lithium-ion transfer.

[0045] In one or more embodiments, the apparatus 100 may further include a nozzle 122 operationally coupled to the inlet 120 of the chamber 110 and positioned perpendicularly to the surface of the substrate 162. In one or more embodiments, the apparatus 100 may further include a nozzle 122 operationally coupled to the inlet 120 of the chamber 110 and positioned at an angle between 1 degree and 89 degrees off normal to the surface of the substrate 162. In one or more embodiments, the apparatus 100 may further include a nozzle 122 operationally coupled to the inlet 120 of the chamber 110 and positioned at a distance between 1 mm and 100 mm from the surface of the substrate 162. In one or more embodiments, the apparatus 100 may further include a nozzle 122 operationally coupled to the inlet 120 of the chamber 110 and positioned at a distance greater than or equal to 100 mm from the surface of the substrate 162. In other words, the nozzle 122, which is coupled to the inlet 120, can be swiveled, tilted, moved, or otherwise manipulatable such that the angle and the distance of the nozzle 122 with respect to the surface of the substrate 162 can be finely controlled or adjusted, in accordance with various embodiments. With the nozzle 122 being adjustable, the flow rate, flow capacity, flow volume, etc., of the fluid 140 and the angle of such fluid flow of the fluid 140 can be set as desired to provide electrodeposition conditions for depositing a high-quality lithium film on the substrate 162, in accordance with various embodiments. As illustrated in Figure 1, the nozzle 122 is configured to face the surface (i.e., the first surface) of the substrate 162 and the counter-electrode 150 (e.g., anode) faces the back surface (i.e., a second surface) of the substrate 162.

[0046] In one or more embodiments, a system for producing lithium films may include the apparatus 100 depicted and described with respect to Figure 1. Using the apparatus 100 of Figure 1, the system may also include one or more methods described below.

[0047] Figure 2A illustrates a schematic of an electrodeposited lithium metal film 280 on a substrate 262, in accordance with various embodiments. Figure 2B illustrates an example configuration of a symmetric cell used to measure the lithium capacity of the electrodeposited lithium metal prepared from the cutout shown in Figure 2A. The electrodeposited lithium metal film 280 is fabricated in accordance with various embodiments disclosed herein into a symmetric cell to measure the total lithium capacity. As shown in Figure 2A, theelectrodeposited lithium metal film 280 over the substrate 262, highlighting the region of the electrode used to make the 1.2 cm-diameter lithium metal film. As illustrated in Figure 2A and 2B, a 1.2 cm diameter punch is used to extract a circular electrode 282 of electrodeposited lithium 280 from the coating 200a to be used as a cathode 282 in the symmetric cell 200b. This circular electrode 282 of electrodeposited lithium film is paired with a 1.5 cm diameter circular electrode 215 (of bare substrate 215) and a separator 205 and liquid electrolyte in between (Figure 2B).

[0048] Figure 3 illustrates a flowchart of a method SI 00 for electrodeposition of lithium metal, in accordance with various embodiments. In one or more embodiments, the method S100 for electrodeposition of lithium metal is performed using the apparatus 100 illustrated in Figure 1.

[0049] As illustrated in Figure 3, the method S100 includes, at step SI 10, providing a counter-electrode; at step S120, providing an electrolyte composition between a substrate and the counter-electrode, the electrolyte composition comprising a solvent, a hydrolytically stable lithium salt, a hydrolytically unstable salt, and water; and at step S130, applying a current between the substrate and the counter-electrode to electrodeposit a lithium metal film on the substrate. Various components, such as, the chamber, the counter-electrode, the substrate, the electrolyte composition (e.g., the fluid), the inlet, the outlet, and various other components as described with respect to method SI 00 of Figure 3 refer to those with same or like-wise terms (e.g., the reservoir / chamber 110, the counter-electrode / anode 150, the substrate 162, the electrolyte composition of the fluid 140, the inlet 120, the outlet 130, etc.) that have been described above with respect to the apparatus 100 of Figure 1, unless otherwise noted herein.

[0050] In accordance one or more embodiments, the method S 100 may further include, optionally at step SI 40, introducing an additive to the electrolyte composition during the applying of the current between the substrate and the counter-electrode, wherein the additive comprises a second hydrolytically unstable salt, a second solvent, and a second amount water with a sufficient concentration to partially hydrolyze the second hydrolytically unstable salt.

[0051] In various embodiments of the method S 100, a concentration of the water in the electrolyte composition is between 0.0005 M and 0.1 M, between 0.0005 M and 0.05 M, between 0.0001 M and 0.05 M, between 0.005 M and 0.05 M, inclusive of any concentration ranges therebetween.

[0052] In various embodiments of the method S 100, a concentration of the hydrolytically stable lithium salt in the electrolyte composition is between 0.5 M and 6.0 M, between 0.7 Mand 6.0 M, between 1.0 M and 6.0 M, between 1.5 M and 6.0 M, between 2.0 M and 6.0 M, between 2.5 M and 6.0 M, between 0.5 M and 5.5 M, between 0.7 M and 5.0 M, between 1.0 M and 4.5 M, between 1.5 M and 4.0 M, between 2.0 M and 3.5 M, or between 2.5 M and 3.0 M, inclusive of any concentration ranges therebetween.

[0053] In various embodiments of the method S100, a concentration of the hydrolytically unstable salt in the electrolyte composition is between 0.0005 M and 1.0 M, between 0.001 M and 1.0 M, between 0.005 M and 1.0 M, between 0.01 M and 1.0 M, between 0.05 M and 1.0 M, between 0.1 M and 1.0 M, between 0.0005 M and 0.95 M, between 0.001 M and 0.9 M, between 0.005 M and 0.85 M, between 0.01 M and 0.8 M, between 0.05 M and 0.75 M, between 0. 1 M and 0.7 M, inclusive of any concentration ranges therebetween.

[0054] In various embodiments of the method S 100, the electrolyte composition may further include a diluent (e.g., a non-coordinating diluent) having a concentration between 5 vol% and 90 vol% of the electrolyte composition. In various embodiments, the diluent comprises a non-coordinating or weakly coordinating solvent that reduces the viscosity of the electrolyte and does not strongly solvate lithium ions. The diluent comprising a non-coordinating or weakly coordinating organic compound, including but not limited to fluorinated ethers, hydrofluoroethers (HFEs), sulfones, or sterically hindered ether.

[0055] In various embodiments of the method S100, the solvent may include one or more organic solvents selected from a list of linear or cyclic ethers (e.g., dimethoxyethane, tetrahydrofuran, dioxolane), carbonates (e.g., ethylene carbonate, dimethyl carbonate, fluoroethylene carbonate), fluorinated solvents, sulfones, or a mixture thereof. In various embodiments, the solvent may include a molar ratio of solvent- to-hydrolytically stable salt of < 5:1 that indicates a high-concentration electrolyte or a solvent- in-salt electrolyte.In various embodiments of the method S100, the hydrolytically stable lithium salt of the electrolyte composition in the fluid 140 is selected from the group consisting of LiFSI, LiTFSI, LiBOB, LiDFOB, LiNCh, and other lithium salts comprising fluoroalkylsulfonyl, oxalato, phosphate, or delocalized anions that are resistant to hydrolysis. In various embodiments, the hydrolytically unstable salt of the electrolyte composition in the fluid 140 is selected from the group consisting of LiPFe, LiBF4, HPFe, and HBF4, and lithium salts comprising hexafluorophosphate, tetrafluoroborate, oxalate-phosphate-fluoride, or chloroaluminate anions.

[0056] In various embodiments of the method S100, the water in the electrolyte composition hydrolyzes the hydrolytically unstable salt to generate acidic and fluorinated species. In various embodiments, the acidic and fluorinated species comprise hydrogen fluoride (HF),lithium fluoride (LiF), and optionally phosphorus oxyfluoride (POF3) or lithium bifluoride (LiHF?), wherein the acidic and fluorinated species form or promote the growth of a lithium fluoride-rich SEI that enables uniform lithium nucleation and suppresses dendritic growth.

[0057] In various embodiments of the method S100, the electrodeposited lithium metal film exhibits a columnar nanostructure.

[0058] In various embodiments of the method S 100, the electrolyte composition may further include one or more additives selected from flame retardants, rheology modifiers, fluorinated solvents, film-forming agents, gas scavengers, corrosion inhibitors, or redox shuttles, wherein the additives are included to improve thermal stability, modulate electrolyte viscosity, stabilize the SEI, or enhance lithium surface compatibility.

[0059] In various embodiments, the electrolyte composition may further include an acid having a concentration between between 0.0005 M and 0.1 M of the electrolyte composition.

[0060] In various embodiments of the method S100, the hydrolytically unstable salt of the electrolyte composition is a first hydrolytically unstable salt, the solvent is a first solvent, and the water is a first amount of water, the electrolyte composition may further include an additive that includes a second hydrolytically unstable salt, a second solvent, and a second amount water with a sufficient concentration to partially hydrolyze the second hydrolytically unstable salt. In various embodiments, the second amount water partially hydrolyzes the second hydrolytically unstable salt in the additive under an inert atmosphere prior to the introducing of the additive to the electrolyte composition. In various embodiments, the additive is introduced into the electrolyte composition at a rate controlled by feedback from real-time measurements of deposition efficiency, conductivity, pH, or film morphology.

[0061] In various embodiments of the method S100, the hydrolytically unstable salt, the water, and a second solvent are pre-mixed prior to combining with the hydrolytically stable lithium salt and the solvent to form the electrolyte composition. The additive comprises a hydrolytically unstable lithium salt, water, and a second solvent, wherein the components are combined and partially hydrolyzed under inert atmosphere prior to introduction. The resulting additive includes pre- formed fluorinated and / or acidic species, such as HF, LiF, or POF3, which facilitate the formation of a lithium-fluoride-rich SEI, promote uniform lithium nucleation, and suppress dendritic growth. In some embodiments, the additive is introduced during application of current between the substrate and the counter-electrode, and its delivery may be metered in real-time based on sensor feedback related to electrolyte degradation, lithium adhesion, or deposition morphology.

[0062] Various examples are provided below to further illustrate the success of the disclosed apparatus, system, and method thereof for electrodeposition of lithium metal or metal films with superior electrochemical performances and better life cycles.EXAMPLES

[0063] The following examples are provided to illustrate representative embodiments of the disclosure and are not intended to limit the scope thereof. These examples demonstrate the influence of various electrolyte formulations and operating parameters on the efficiency, morphology, and stability of lithium metal films produced by electrodeposition. The materials, methods, and results presented herein are offered for purposes of understanding and exemplifying the disclosure, and further serve to validate the claimed electrolyte compositions and deposition protocols as enabling high-efficiency lithium metal electrodeposition.

[0064] Unless otherwise specified, all concentrations are reported in molarity (M) or weight percent (wt%) relative to total solution volume or mass, and all operations are conducted under inert atmosphere at room temperature. Lithium metal characterizations are based on visual appearance and cell performance metrics. Table data and comparative analyses follow each experimental method to contextualize the disclosed technical advantages.

[0065] Example 1: Electrodepositing Lithium Metal Using a Controlled Geometry Cell: 20 mL of electrolyte is added to a 50 mL container. A copper electrode is sandwiched between two pieces of polyethylene. The front piece of polyethylene contained a 1.9 cm circle hole to expose 1.9 cm of the copper surface to the electrolyte. A bulk lithium metal counter electrode placed 0.25 cm behind the copper electrode and within the electrolyte bath. A current density of 10 mA / cm2 is applied between the copper electrode, configured as the cathode, and bulk lithium metal counter electrode, configured as the anode. A total of 0.5 mAh / cm2 current is applied between the two electrodes, creating a film of metallic lithium on the copper electrode.

[0066] Example 2: Evaluating Lithium Capacity and Extraction Efficiency: A 1.2 cm diameter punch is used to extract a circular electrode of electrodeposited lithium from the coating. This circular electrode of electrodeposited lithium is paired with a 1.5 cm diameter circular electrode of bare copper foil with a separator and electrolyte in between. The separator used is Celgard 2325 and the electrolyte comprised 45.76 wt.% LiFSI and 54.24 wt.% DME. A current of 0.1 mA is applied to the fabricated cell to strip lithium from the electrodeposited coating and plate it onto the bare electrode. The total capacity measuredfrom the first charge of this configuration is the usable lithium capacity and is presented as a function of electrolyte composition in Table 2. The efficiency values in Table 1 indicates the ratio between the total current applied to make the electrode coating and the measured electrochemically available lithium capacity measured in the half-cell coin cell. The efficiency in Table 1 can be calculated as follows:Efficiency (%) = (Total Lithium Capacity Measured (mAh)) / (Total Capacity Applied During Deposition (mAh)) * 100

[0067] Example 3: Calendar aging of electrolyte: 20 mL of electrolyte is added to a 50 mL container. The electrolyte and container are then left to rest in an argon-filled glovebox for 30 days. Post-aging performance is evaluated using the procedure in Example 1.

[0068] Example 4: Assessing the Efficiency of Lithium Metal Electrodeposition from Various Electrolytes: The efficiency of lithium metal electrodeposition is evaluated for each electrolyte listed in Table 1. The electrolyte compositions are used to fill a 50 mL container, consistent with the procedure outlined in Example 1. After lithium metal is deposited onto a copper substrate as described in Example 1 , the resulting lithium coating is carefully removed from the system and its appearance is cataloged. Subsequently, the deposited lithium film is used to fabricate a symmetric electrochemical cell according to the method detailed in Example 2. The fabricated cell is subjected to a first charge cycle, during which the total capacity is recorded. This capacity measurement is used to calculate the electrochemical efficiency of lithium metal electrodeposition for each electrolyte, using the ratio of the measured charge to the originally deposited charge. The results, including lithium deposition efficiency, measured lithium capacity, and qualitative observations of the lithium film morphology, are summarized in Table 2. A detailed description of the electrolyte compositions and corresponding lithium coating quality is provided below.Table 1. Compositions of the electrolytes investigated. The electrolytes are comprised of lithium bis(fluorosulfonyl)imide (LiFSI), dimethoxyethane (DME), ethylene carbonate (EC), Dimethyl Carbonate (DMC), water (H2O), lithium hexaflurophosphate (LiPF6), and hydrofluoric acid (HF).Electrolyte 1Component Value UnitElectrolyte 2Component Value UnitElectrolyte 3Component Value UnitElectrolyte 4Component Value UnitElectrolyte 5Component Value UnitElectrolyte 6Component Value UnitElectrolyte 7Component Value UnitElectrolyte 8Component Value UnitTable 2. Table of lithium extraction efficiency from each electrolyte investigated.Electrolyte Measured CapacityLithium Appearance (mAh) Efficiency (%)

[0069] Comparative Results and Discussion: A series of electrolytes are evaluated to identify the effects of water content, salt composition, and hydrolysis decomposition product concentration on lithium metal electrodeposition. The efficiency and morphology of lithiumdeposition for each electrolyte are assessed as described in Examples 1 through 4. The results, as summarized in Tables 1 and 2, support several critical observations regarding electrolyte formulation and performance.

[0070] 1. Effect of Water Addition to Stable Salt Systems: Electrolyte 2, which included a trace amount of water in an otherwise hydrolytically stable salt formulation, produced mossy lithium with an efficiency of 19%. This is a slight improvement over Electrolyte 1, which contained no added water and yielded an efficiency of 16%. This comparison indicates that the addition of water alone is insufficient to significantly enhance lithium deposition efficiency when used with hydrolytically stable salts.

[0071] 2. Effect of Hydrolytically Unstable Salt Without Water: Electrolyte 3, which included a low concentration of hydrolytically unstable salt in an otherwise stable salt system, achieved a deposition efficiency of 20%. This is again only a modest improvement over Electrolyte 1, suggesting that the addition of a hydrolytically unstable salt alone — without the presence of water — does not meaningfully improve lithium metal film quality or deposition efficiency.

[0072] 3. Synergistic Effect of Water and Unstable Salt: In contrast, Electrolyte 4, which incorporated both a small amount of hydrolytically unstable salt and a trace amount of water, achieved a significantly higher deposition efficiency of 61% and produced a light-blue, compact lithium film. This sharp improvement illustrates that the combined presence of water and unstable salt creates a synergistic effect that enables high-efficiency lithium electrodeposition and favorable film morphology.

[0073] 4. Impact of High-Water Concentration: Electrolyte 5, which maintained the same salt formulation as Electrolyte 4 but included a higher concentration of water, exhibited poor deposition efficiency (5%) and mossy lithium morphology. This result confirms that excessive water content is detrimental and that a narrow concentration window exists in which water acts as a beneficial additive.

[0074] 5. Effect of HF and Water on Deposition Performance: Electrolyte 6 included HF and a small amount of water along with a hydrolytically stable salt, producing compact, dark-blue lithium and a relatively high efficiency of 55%. Electrolyte 8 included HF and water at a concentration comparable to electrolyte 4 and produced a mossy lithium deposit, which could not remain adhered to the copper during sample removal from the electrolyte due to poor adhesion, and a poor efficiency of 1%. This indicates that HF and water together can enhance deposition efficiency under specific conditions. However, the Electrolyte 6 formulation is found to lack long-term stability, as further discussed below.

[0075] 6. Calendar Aging and Electrolyte Stability: Following 30 days of storage in an inert atmosphere, Electrolyte 4 continued to produce compact lithium films with a deposition efficiency of 45%, demonstrating acceptable long-term stability. In contrast, aged Electrolyte 6 yielded mossy lithium and an efficiency of just 5%. This comparison highlights that while HF and water may promote initial performance, their presence degrades the shelf life of the electrolyte. In contrast, trace water combined with a low concentration of hydrolytically unstable salt (as in Electrolyte 4) enables both high initial efficiency and continued performance after extended storage.

[0076] These comparative results demonstrate that optimized combinations of trace water and hydrolytically unstable salts can be used to significantly improve lithium deposition efficiency and morphology, while carefully controlling concentration thresholds is essential to maintain calendar life and prevent film degradation.ELECTROLYTE DESIGN

[0077] The present disclosures relate to an electrolyte system (electrolyte composition) and associated methods and apparatuses for the production of thin lithium metal films via electrodeposition. The electrolyte system is designed around a dual-component strategy that balances controlled chemical reactivity with long-term electrolyte stability. Specifically, the system leverages the distinct hydrolytic behavior of different classes of lithium salts to enable efficient, dendrite-free lithium electrodeposition while maintaining operational longevity suitable for industrial applications.

[0078] Electrolytes for lithium metal deposition must achieve two competing goals: (1) they must be reactive enough to promote uniform lithium nucleation and SEI formation, and (2) they must be chemically stable enough to maintain performance over time and under process conditions. The disclosed electrolyte system achieves both objectives by intentionally separating the source of electrochemical stability from the source of controlled chemical reactivity. This disclosure meets both goals through a bifunctional electrolyte design based on the hydrolytic stability of incorporated salts.

[0079] Lithium salts are broadly categorized into two groups based on their reactivity with trace moisture, as follows.

[0080] Hydrolytically stable lithium salts, such as LiFSI, LiTFSI, LiBOB, and LiDFOB, resist decomposition and maintain consistent ionic conductivity over time. These salts form the backbone of the primary electrolyte. As used herein, a hydrolytically stable salt refers to a salt that, when dissolved in an organic electrolyte, exhibits negligible chemical degradationupon exposure to trace amounts of water over extended durations. In certain embodiments, a hydrolytically stable salt is defined as a salt whose hydrolysis half-life is at least lOx longer than that of a hydrolytically unstable salt under equivalent electrolyte conditions. Examples include lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB), and lithium difluoro(oxalato)borate (LiDFOB).

[0081] Hydrolytically unstable salts, such as LiPFe, LiBF4, and LiClCh, decompose in the presence of water to yield acidic and fluorinated products (e.g., HF and LiF). When generated in a controlled manner, these products enhance lithium nucleation, SEI formation, and adhesion. As used herein, a hydrolytically unstable salt refers to a salt that, when exposed to trace amounts of water in an electrolyte system, undergoes chemical decomposition to form reactive hydrolysis products. These products may include acids (e.g., hydrofluoric acid), gaseous species (e.g., POF3), and solid inorganic compounds (e.g., LiF), which influence the interfacial chemistry of electrode surfaces. In certain embodiments, hydrolytically unstable salts exhibit hydrolysis half-lives or decomposition rates at least lOx faster than those of hydrolytically stable salts under identical electrolyte conditions. In the present application, the classification of hydrolytically unstable salts are not limited to lithium-containing salts and may include acidic or fluorinated salts such as hexafluorophosphate (HPFe), or hydrogen tetrafluoroborate (HBF4).

[0082] The electrolyte system of the present disclosure includes four primary components:

[0083] Hydrolytically Stable Lithium Salt: Salts such as LiFSI, LiTFSI, LiBOB, or LiDFOB provide the stable ionic background necessary for long-duration cycling. These salts do not degrade significantly in the presence of trace water and maintain high lithium-ion conductivity. They serve as the foundational charge carrier system and allow for compatibility with high salt concentrations or solvent-in-salt formulations

[0084] Hydrolytically Unstable Salt: Salts such as LiPFe, LiBEi, or LiCICL react with water to form a range of reactive species. Their concentration is intentionally limited to promote controlled hydrolysis rather than bulk decomposition. These salts are introduced to generate beneficial surface-modifying species in situ. In the present disclosure, these salts are not limited to contain lithium and may be any hydrolytically unstable salt which decomposes upon reaction with water.

[0085] Water: Water is added in controlled trace amounts to enable selective hydrolysis of the unstable salt and promote uniform lithium nucleation and growth. By tuning the molar ratio of water to unstable salt, the system controls the extent of hydrolysis and the rate atwhich reactive intermediates are produced. In the present disclosure, water may be prereacted with the unstable salt or introduced concurrently to trigger reactions in situ.

[0086] Hydrolysis Reaction Products: The hydrolysis of unstable salts in an organic electrolyte produces acidic and fluorinated compounds such as HF and LiF. These species serve multiple critical roles: acids (e.g. HF) condition the substrate surface, lower the nucleation barrier for lithium deposition, and participate in SEI formation. Other reaction products (such as LiF) contribute to the formation of a robust, electronically insulating but ionically conductive SEI.

[0087] This four-component electrolyte architecture provides a platform for decoupling the requirements of ionic stability and chemical reactivity within a single system. The stable lithium salt ensures long-term ionic conductivity and electrochemical stability, while the unstable salt, water, and their reaction products actively engineer the interfacial environment to improve deposition efficiency and lithium film morphology.

[0088] The resulting electrolyte enables high-current, high-throughput lithium metal electrodeposition with smooth, compact film formation even under high shear or high flow conditions which may be implemented in an industrial electrocoating system based on this process. Furthermore, the controlled nature of the hydrolysis reactions preserves electrolyte longevity by preventing uncontrolled decomposition pathways, thereby supporting extended operation and continuous processing.

[0089] Accordingly, there remains a need for an electrolyte system that permits tunable interfacial reactivity while maintaining long-term chemical stability for lithium metal thin- film fabrication. The present disclosure addresses this need by providing a stable, modular electrolyte platform comprising hydrolytically stable lithium salts, hydrolytically unstable salts, controlled water content, and in situ-generated hydrolysis products to enhance deposition kinetics, interfacial chemistry, and film quality.

[0090] In some embodiments, the electrolyte comprises a primary lithium salt such as lithium bis(fluorosulfonyl)imide (LiFSI) or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) at concentrations exceeding 25% by weight of the total electrolyte. A secondary salt, present at lower concentrations — typically less than 10% of the total salt mass — is selected for its hydrolytic reactivity in the presence of trace water, leading to the in situ formation of acidic fluorine species. This secondary salt may include, but is not limited to, lithium hexafluorophosphate (LiPFe), lithium tetrafluoroborate (LiBEi), or analogous fluorinated salts.HYDROLYTICALLY STABLE LITHIUM SALT

[0091] Hydrolytically stable salts such as LiFSI, LiTFSI, LiBOB, or LiDFOB serve as the primary ionic conductors and their resistance to hydrolysis enables long-term performance of the organic electrolyte for producing lithium metal. These salts support high salt concentrations and solvent-in-salt formulations which offer favorable fluid properties for industrial production such as low vapor pressure. These salts form the foundational backbone of the electrolyte system and enable electrodeposition of lithium metal at high currents with improved lifetime.

[0092] Hydrolytic stability:

[0093] In some embodiments, the stable lithium salt is a fluorine-containing lithium salt that is more hydrolytically stable than the unstable salt, reducing the rate of degradation when exposed to water.

[0094] In certain embodiments, the hydrolysis half-life of the stable lithium salt in the primary electrolyte is at least lOx longer than the hydrolysis half-life of the unstable salt at 25 degrees Celsius.

[0095] In alternative embodiments, the stable salt exhibits a hydrolysis reaction rate constant at least one order of magnitude lower than the unstable salt.

[0096] In certain embodiments, the stable lithium salt is selected from LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide), LiFSI (Lithium bis(fluorosulfonyl)imide), LiBOB (Lithium bis(oxalato)borate), LiDFOB (Lithium difluoro(oxalato)borate), or LiNOs (Lithium Nitrate) to balance ionic conductivity, stability, and process compatibility.

[0097] Lithium salt concentration:

[0098] In some embodiments, the stable lithium salt concentration ranges from 0.5 M to 6.0 M to ensure optimal lithium-ion transport and deposition.

[0099] In certain embodiments, a concentration of 0.5 M to 2.0 M is used to balance conductivity and electrochemical stability.

[0100] In alternative embodiments, a higher concentration of 2.0 M to 6.0 M is employed to balance electrochemical stability and vapor pressure.HYDROLYTICALLY UNSTABLE SALT

[0101] Hydrolytically unstable salts such as LiPFe, LiBF4, or as well as non-Li salts such as HPFe and HBF4, are introduced in controlled quantities to generate beneficial hydrolysis products in situ. These salts are introduced in limited concentrations to promote the in situformation of acids and fluorinated products (e.g., HF, POF3), which in turn drive surface conditioning, lithium nucleation, and SEI formation. Importantly, hydrolytically unstable salts in this disclosure are not limited to lithium-containing species; rather, they are defined by their propensity to hydrolyze in the presence of trace water and generate acidic, fluorinated, or otherwise reactive products that influence interfacial chemistry during lithium metal deposition.

[0102] Hydrolytically Unstable Salt Concentration:

[0103] In certain embodiments, the hydrolytically unstable component may be a non-lithium salt or acid such as hydrogen hexafluorophosphate (HPFe), hydrogen tetrafluoroborate (HBF4), or ammonium tetrafluoroborate (NH4BF4), which generate HF and related species in situ. These additives can be used alone or in combination with lithium-based salts to modulate acidity, enhance surface etching, or tailor SEI formation without introducing excess lithium into the system.

[0104] In some embodiments, the hydrolytically unstable salt is present at a concentration ranging from 0.0005 M to 1.0 M.

[0105] In certain embodiments, a lower concentration range of 0.001 M to 0. 1 M is employed to introduce controlled hydrolysis effects without excessive electrolyte degradation.

[0106] In other embodiments, a higher range of 0.1 M to 1.0 M is used to drive SEI formation and deposition kinetics for high-rate applications.WATER

[0107] The presence of water in the electrolyte drives hydrolysis of the hydrolytically unstable salt and can independently provide significant advantages for lithium metal electrodeposition. Water plays a role in facilitating the nucleation and growth mechanisms of lithium metal. In some embodiments, it alters the double-layer structure near the electrode surface, thereby modifying the overpotential required for nucleation. This effect can contribute to a more uniform and controlled lithium deposition. Furthermore, water can modulate the reduction potential of metal ions, lowering the overall overpotential for deposition, which reduces energy consumption and minimizes side reactions that compromise lithium metal stability.

[0108] In some embodiments, water influences the mechanical properties of deposited lithium films by reducing internal stress, which improves adhesion to the substrate and promotes the formation of uniform coatings. Additionally, the presence of water stabilizesintermediate reduction compounds in the organic electrolyte, thereby suppressing parasitic reactions that would otherwise degrade electrochemical performance.

[0109] Water can also influence the formation and properties of the solid electrolyte interphase (SEI). In some embodiments, localized gas formation driven by water content increases the porosity of the SEI, enhancing its ionic conductivity and flexibility. This localized gas evolution can also disrupt regions of high electric field intensity, thereby mitigating dendrite formation. Moreover, water can contribute to the protection of the lithium metal surface by forming stable intermediate compounds, such as lithium hydroxide (LiOH), which provide additional stability to the deposited lithium layer.

[0110] Water Concentration:

[0111] In some embodiments, the water content ranges from 0.0005 M to 0. 1 M relative to the total electrolyte composition.

[0112] In certain embodiments, a lower range of 0.0005 M to 0.01 M is used to minimize unwanted side reactions while still promoting beneficial electrolyte modifications.

[0113] In alternative embodiments, a higher range of 0.01 M to 0.1 M is utilized to enhance lithium deposition morphology and SEI formation.

[0114] Examples Discussion:

[0115] The influence of water content on lithium deposition efficiency and morphology is further investigated through a series of controlled experiments. These experiments, described in the Examples section, demonstrate that while water can modulate lithium-ion solvation and nucleation behavior, the addition of water alone is insufficient to yield compact lithium metal films or high deposition efficiency.

[0116] For example, Electrolyte 2, which included trace water in an otherwise hydrolytically stable salt formulation, produced mossy lithium with negligible improvement over the anhydrous baseline (Electrolyte 1). Similarly, Electrolyte 3, which incorporated a hydrolytically unstable salt without added water, also failed to achieve compact morphology or high efficiency. In contrast, Electrolyte 4 — which combined trace water with a low concentration of hydrolytically unstable salt — produced compact lithium metal with a deposition efficiency of 61%, indicating a synergistic effect between the two components.

[0117] These results underscore that neither water nor hydrolytically unstable salts alone are sufficient to achieve optimal electrodeposition from an electrolyte system. Rather, both components must be precisely controlled in concentration and proportion to achieve the desired nucleation, morphology, and SEI formation characteristics. This co-optimization is critical to achieving reproducible, high-efficiency lithium deposition and supports theembodiments disclosed herein, in which trace water and reactive salt species are finely balanced within the electrolyte system.ACID

[0118] Acid in the organic electrolyte can result in improved ionic conductivity and enhance the efficiency of Li-ion reduction into lithium metal resulting in improved lithium electrodeposition at high rates. In some embodiments, the acid in the electrolyte promotes the formation of a stable SEI layer by reacting to form LiF, which is a crucial component of a stable SEI. Additionally, acid can promote lithium deposition in a columnar morphology rather than dendritic structures, thereby suppressing dendrite growth. It also plays a role in regulating lithium nucleation, leading to uniform nucleation and controlled film formation. In some embodiments, the acid regulates the nucleation process of lithium metal to promote uniform nucleation and film formation.

[0119] Acid formation:

[0120] In some embodiments, acid is generated in situ by the reaction of water with hydrolytically unstable salts, providing a dynamic means of modulating acidity based on electrolyte conditions.

[0121] In some embodiments, the water, hydrolytically unstable salt, and solvent are reacted separately before they are added to the hydrolytically stable salt and solvent.

[0122] In alternative embodiments, acid is injected directly into the electrolyte to precisely control its concentration and effects.

[0123] Acid concentrations:

[0124] In some embodiments, the acid concentration in the organic electrolyte ranges from 0.000005 M to 1.0 M.

[0125] In certain embodiments, a lower acid concentration of 0.000005 M to 0.05 M is employed to provide mild SEI stabilization while minimizing electrolyte degradation.

[0126] In other embodiments, a moderate concentration range of 0.05 M to 0.5 M is utilized to enhance lithium nucleation and deposition morphology.

[0127] In other embodiments, an acid concentration of 0.5 M to 1.0 M is used to actively regulate lithium-ion reduction kinetics and SEI composition.

[0128] Discussion of substrate interaction:

[0129] Beyond its role in lithium deposition, acid in the organic electrolyte can condition the electrode surface. In some embodiments, its concentration is sufficient to remove surface oxides from the conductive substrate, improving electronic conductivity. In otherembodiments, the acid etches the substrate, increasing surface area and reducing local current density, which can further enhance lithium metal adhesion and morphology control. Additionally, controlled acid concentrations may facilitate the formation of thin passivation layers, which influence subsequent metal deposition and contribute to overall deposition stability.

[0130] Substrate interaction:

[0131] Acid for substrate cleaning:

[0132] In some embodiments, the acid concentration is sufficient to remove surface oxides, exposing a clean and electronically conductive substrate.

[0133] In certain embodiments, an acid concentration range of 0.001 M to 0.5 M is employed to dissolve native oxide layers, ensuring direct electronic contact between the lithium metal and the substrate.

[0134] In other embodiments, the acid selectively removes contaminants and passivating films from the substrate without excessive surface degradation.

[0135] In some embodiments, the acid concentration is adjusted to etch the substrate, increasing its roughness and surface area to enhance lithium adhesion.

[0136] In certain embodiments, an acid concentration of 0.05 M to 0.5 M is used to promote mild surface texturing without excessive dissolution of the underlying material.

[0137] In alternative embodiments, an acid concentration of 0.1 M to 1.0 M is employed when more aggressive etching is required to create high-surface-area features that reduce local current density and promote uniform lithium deposition.

[0138] Acid for substrate chemical modification:

[0139] In some embodiments, the acid interacts with the substrate to generate a thin passivation layer that influences subsequent lithium metal deposition.

[0140] In certain embodiments, the acid reacts with the substrate to form a fluorine -rich or lithium-containing interphase that regulates lithium nucleation and deposition morphology.

[0141] In some embodiments, the passivation layer serves to moderate the electrode’s reactivity with the electrolyte, contributing to long-term electrochemical stability.

[0142] In some embodiments, the acid concentration is controlled to pre-condition the conductive substrate before lithium deposition, optimizing its electrochemical activity.

[0143] In alternative embodiments, the acid treatment is applied in a preparatory step before electrolyte introduction to ensure a reactive yet stable interface for lithium plating.

[0144] In certain embodiments, a combination of acid and hydrolytically unstable salts is used to dynamically adjust substrate properties in situ, enabling precise control over lithium nucleation and growth patterns.

[0145] Example Discussion:

[0146] The role of acid in lithium metal electrodeposition is further examined through comparative studies evaluating the impact of acid source, concentration, and associated byproducts on film morphology and deposition efficiency. As described in the Examples section, these studies confirm that acid alone — particularly hydrofluoric acid (HF) generated from hydrolytically unstable salts — is not sufficient to ensure stable, long-term lithium deposition.

[0147] Electrolyte 8, for instance, utilized a hydrolytically stable salt with a small amount of HF and water. This composition produced mossy lithium with poor substrate adhesion that translated to just 1% efficiency due to the minimal amount of lithium metal that remained on the substrate after removal from the electrolyte. Electrolyte 6 utilized a hydrolytically stable salt with sufficient HF and water to produce lithium metal films with high efficiency. While this formulation initially enabled compact lithium morphology with 55% deposition efficiency, it degraded significantly after storage, producing mossy lithium with 5% efficiency.

[0148] In contrast, Electrolyte 4 — formulated with trace water and a low concentration of hydrolytically unstable salt (i.e., LiPFe) — not only produced compact lithium with 61% initial efficiency, but also maintained 45% efficiency and compact morphology after storage.

[0149] These findings indicate that the use of acid-generating components must be carefully controlled, and that controlled hydrolysis yielding fluorinated species in situ (e.g., HF, LiF, POF3) provides superior outcomes when paired with stable salt systems. The examples further demonstrate that electrolyte formulations which regulate acid formation dynamics can result in more robust lithium metal deposition performance, particularly with respect to longterm stability and calendar aging. This supports the disclosed embodiments in which acid is introduced or generated in a regulated manner to form favorable SEI layers without compromising deposition consistency or film integrity over time.ADDITIVE STRATEGY

[0150] In some embodiments, the hydrolytically unstable lithium salt, solvent, and water are combined in a separate, controlled environment to undergo partial or complete hydrolysis prior to their introduction into the main electrolyte containing the hydrolytically stablelithium salt. This pre-reaction step forms an additive solution containing selected hydrolysis products, such as hydrogen fluoride (HF), lithium fluoride (LiF), and other fluorinated or acidic species, in a stabilized form. The resulting additive package can then be introduced into the primary electrolyte in a controlled manner to tailor interfacial reactivity without triggering uncontrolled decomposition or reducing the chemical stability of the bulk electrolyte.

[0151] Pre-reacting the hydrolytically unstable salt and water allows for decoupling of reactive species formation from the ionic transport medium, giving improved control over the spatial and temporal distribution of acid and fluorinated components at the electrode interface. This strategy enables tunable SEI chemistry, enhanced lithium nucleation behavior, and more reproducible electrodeposition outcomes, particularly under high-current and high- flow conditions.

[0152] In some embodiments, the additive solution is stored in a sealed vessel under inert atmosphere and is introduced into the electrolyte system immediately prior to use or via a feedback-controlled dispensing system. The additive solution may be in liquid, gel, or slurry form depending on its composition and intended mode of delivery.

[0153] Accordingly, the use of such an additive provides a modular and scalable approach to electrolyte formulation, allowing for precise engineering of interfacial chemistries in lithium metal electrodeposition systems without compromising bulk electrolyte stability or process safety.

[0154] Additive Water Content Embodiments:

[0155] In some embodiments, the water content in the additive ranges from 0.0005 M to 3.0 M relative to the total electrolyte composition.

[0156] In certain embodiments, a lower range of 0.0005 M to 0.5 M is used to minimize unwanted side reactions while still promoting beneficial electrolyte modifications.

[0157] In alternative embodiments, a higher range of 0.5 M to 3.0 M is utilized to enhance lithium deposition morphology and SEI formation.

[0158] Additive Hydrolytically Unstable Salt Concentration:

[0159] In some embodiments, the hydrolytically unstable salt is present in the additive at a concentration ranging from 0.005 M to 5.0 M.

[0160] In some embodiments, the hydrolytically unstable salt is present in the additive at a concentration ranging from 0.5 M to 5.0 M.

[0161] In certain embodiments, a lower concentration range of 0.005 M to 0.5 M is employed to introduce controlled hydrolysis effects without excessive electrolyte degradation.

[0162] In other embodiments, a higher range of 0.5 M to 5.0 M is used to drive SEI formation and deposition kinetics for high-rate applications.

[0163] Additive Concentration:

[0164] In some embodiments, the additive is blended with the primary electrolyte system at a ratio ranging from 0.5:99.5 to 40:60 (by volume).

[0165] In certain embodiments, a lower ratio of 0.5:99.5 to 2:98 is used to introduce minimal but controlled modifications to the electrolyte properties.

[0166] In other embodiments, a higher ratio of 5:95 to 40:60 is employed when significant enhancement of ionic conductivity and SEI modification is desired.

[0167] Hydrolysis Reaction:

[0168] In some embodiments, the hydrolysis of the unstable salt occurs over a controlled period ranging from 30 seconds to 96 hours before mixing with the primary electrolyte system.

[0169] In certain embodiments, a rapid hydrolysis process within 30 seconds to 5 minutes is used for applications requiring immediate modification of the electrolyte environment.

[0170] In other embodiments, a gradual hydrolysis process over 1 to 72 hours is preferred to ensure a slow and sustained modification of the electrolyte properties.

[0171] In other embodiments, a gradual hydrolysis process over 24 to 96 hours is preferred to ensure a slow and sustained modification of the electrolyte properties.

[0172] Temperature Stability:

[0173] In some embodiments, the additive is optimized for operation between 0°C to 45°C, ensuring stability under standard lithium-ion battery conditions.

[0174] In certain embodiments, a high-temperature stability range of 25 °C to 80°C is maintained for applications involving fast-charging or high-power output.ELECTROLYTE PROPERTIES

[0175] The properties of the electrolyte which contain all the elements discussed above are optimized to ensure compatibility with industrial electrodeposition processes.

[0176] Solvent composition:

[0177] In some embodiments, the electrolyte comprises a mixture of high-dielectric and low- viscosity solvents to optimize lithium-ion transport and electrochemical performance.

[0178] In certain embodiments, the solvent system includes cyclic or linear carbonates (e.g., EC - ethylene carbonate, DMC - dimethyl carbonate, EMC - ethyl methyl carbonate), ethers (e.g., DME - dimethoxy ethane, TEGDME - tetraethylene glycol dimethyl ether), sulfones(e.g., DMS - dimethyl sulfone), or fluorinated solvents (e.g., FEC - fluoroethylene carbonate, HFE - hydrofluoroether).

[0179] In alternative embodiments, the solvent system is designed to exhibit low vapor pressure (<10 mmHg at 25°C) and high thermal stability (-20°C to 80°C) to support industrial electrocoating processes.

[0180] Vapor Pressure:

[0181] In some embodiments, the electrolyte has a vapor pressure of <75 mmHg at 25 °C to minimize solvent loss in an industrial electrocoating environment.

[0182] In certain embodiments, the vapor pressure is maintained below 10 mmHg at 25°C to enhance electrolyte longevity.

[0183] In alternative embodiments, a near- zero vapor pressure formulation is used to eliminate evaporation-related stability concerns.

[0184] Viscosity for Processability and Coating Uniformity:

[0185] In some embodiments, the electrolyte viscosity is maintained below 20 cP at 25 °C to ensure proper flow and coverage in an industrial electrocoating system.

[0186] In certain embodiments, a viscosity of 2 cP to 8 cP is optimized to balance wettability and processability.

[0187] In some embodiments, a rheology modifier is added to maintain a specific viscosity of the electrolyte while allowing control of salt concentrations or solvent additions, materials known to affect viscosity of the electrolyte.

[0188] In alternative embodiments, a slightly higher viscosity of 8 cP to 20 cP is used when increased film stability is required.

[0189] Thermal stability:

[0190] In some embodiments, the electrolyte remains stable within a temperature range of - 20°C to 60°C to accommodate industrial processing conditions.

[0191] In certain embodiments, the electrolyte is optimized for stability between 0°C to 45 °C, ensuring safe operation in lithium metal deposition applications.

[0192] In alternative embodiments, the electrolyte is designed to withstand continuous operation at 25°C to 80°C for high-power or fast-charging processes.

[0193] Fluorinated and functionalized additives:

[0194] In some embodiments, the electrolyte incorporates fluorinated or functionalized additives, such as LiF-forming species (e.g., FEC, LiDFOB), polymeric stabilizers, or ionic liquid components, to enhance lithium metal deposition and SEI stability.

[0195] In certain embodiments, an additive comprising sulfone-based or phosphazene-based compounds is used to further improve reduction stability and optimize the lithium-ion solvation structure.

[0196] Additives to reduce flammability:

[0197] In some embodiments, the primary electrolyte contains non-flammable or flameretardant additives to reduce the risk of ignition under high-temperature or high-energy conditions.

[0198] In certain embodiments, phosphazene-based compounds, organophosphates (e.g., trimethyl phosphate, triethyl phosphate), or sulfones (e.g., dimethyl sulfone, methyl ethyl sulfone) are included to enhance electrolyte thermal stability and reduce flammability.

[0199] In alternative embodiments, a combination of halogenated solvents (e.g., hydrofluoroethers, fluorinated sulfones) and flame-retardant additives is used to create a selfextinguishing electrolyte system, preventing ignition or combustion in industrial electrocoating applications.

[0200] In some embodiments, ceramic nanoparticles (e.g., AI2O3, SiCh, or boron nitride) are dispersed within the electrolyte to improve thermal stability and suppress runaway reactions.

[0201] In certain embodiments, an additive system is designed to increase electrolyte flash point above 150°C, ensuring safer operation in high-temperature industrial settings.DILUENTS

[0202] In some embodiments, the electrolyte formulation incorporates a diluent to reduce viscosity and improve ionic conductivity while preserving the solvation structure of the hydrolytically stable lithium salt and solvent. Unlike conventional co-solvents, the diluent is selected to exhibit minimal interaction with Li+ions, ensuring that lithium-ion transport remains governed by the primary solvent environment. The diluent is miscible with the electrolyte, electrochemically stable over a wide voltage range, and thermally robust for industrial electrocoating applications. Additionally, it can enhance electrolyte processability, suppress lithium dendrite formation, and improve safety by increasing the electrolyte’s flash point without introducing unwanted side reactions.

[0203] Diluents for Viscosity Control:

[0204] In certain embodiments, the diluent is present at 1 vol% to 95 vol% relative to the total electrolyte composition.

[0205] In alternative embodiments, 1 vol% to 20 vol% is used to slightly reduce viscosity while preserving maximum lithium-ion solvation.

[0206] In other embodiments, 20 vol% to 95 vol% is incorporated to significantly reduce viscosity and improve electrolyte processability in industrial electrocoating systems.

[0207] Li solvation control:

[0208] In some embodiments, the diluent has a low donor number (< 10 kcal / mol) to prevent disruption of Li+solvation.

[0209] In certain embodiments, the diluent has weak interactions with lithium ions to preserve the existing solvation structure of the solvent and lithium salt complex.

[0210] In alternative embodiments, the diluent is selected to modulate ion pairing behavior without increasing aggregation or decreasing lithium-ion mobility.

[0211] In certain embodiments, the diluent is selected to maintain a stable electrochemical interface and prevent phase separation in systems with lithium salt concentrations ranging from 2.0 M to 4.5 M.

[0212] Diluent Composition:

[0213] Fluorinated ether solvents (e.g., TTE - 1,1,2, 2-Tetrafhioroethyl 2,2,2-trifluoroethyl ether.), which reduce viscosity while maintaining lithium ion transport efficiency.

[0214] Hydrofluoroethers (HFEs) (e.g., methyl nonafluorobutyl ether, perfluoropolyethers), which lower viscosity and improve electrolyte wettability while remaining non-coordinating.

[0215] Non-coordinating sulfones (e.g., methyl nonafluoroisobutyl sulfone), which provide electrochemical stability while avoiding interaction with Li+solvation shells.

[0216] Fluorinated alkyl ethers with weak Lewis basicity, ensuring high electrolyte stability.

[0217] Sterically hindered ethers (e.g. tert-butyl mesityl ether), which provide electrochemical reduction stability and lower viscosity while being too sterically hindered to sufficiently coordinate to lithium ions.

[0218] Cyclic ethers with limited donor ability (e.g., 1,4-dioxane), which act as noncoordinating or weakly coordinating diluents to tune electrolyte viscosity and dielectric environment without significantly disrupting lithium-ion solvation structures.

[0219] Other non-coordinating, electrochemically stable molecules that do not alter the lithium solvation environment.

[0220] Safety:

[0221] In certain embodiments, the diluent increases the electrolyte’s flash point to >100°C, reducing the risk of flammability.HIGH-FLOW OF ORGANIC ELECTROLYE

[0222] In some embodiments, the electrodeposition process is performed under high flow conditions of the organic electrolyte, which yields multiple benefits for lithium metal film formation. As used herein, the term "high flow" refers to the condition in which the organic electrolyte is delivered toward the electrode surface at a velocity sufficient to influence lithium nucleation, growth morphology, and interfacial chemistry during electrodeposition. High flow may encompass both laminar flow, where electrolyte moves uniformly across the electrode surface, and impinging flow, where electrolyte is directed perpendicularly or at an angle toward the substrate, resulting in localized high-velocity impact zones. In general, high flow refers to linear electrolyte velocities exceeding 300 cm / min, and in certain embodiments exceeding 2000 cm / min, as measured relative to the electrode surface. This flow condition may be achieved using jets, nozzles, channels, or manifolds designed to impose shear forces across the growing lithium film. Such shear can dislodge or suppress dendritic features as they emerge, leading to smoother, denser, and more uniform lithium metal coatings.

[0223] High flow enhances mass transport of lithium ions to the deposition interface, promoting uniform current density and efficient ion replenishment at the growing lithium surface. High flow conditions also facilitate the removal of gaseous or insoluble byproducts, stabilize the interfacial concentration of reactive species, enable temperature regulation at the substrate surface, and promote the continuous replenishment of reactive species (e.g. fluoride ions or acidic hydrolysis products) at the substrate interface, all of which contribute to consistent nucleation, uniform SEI development, and enhanced deposition quality.

[0224] Electrolyte Flow Rates:

[0225] In some embodiments, the electrolyte is designed to perform lithium metal electrodeposition under a high flow condition of at least 300 cm / min of organic electrolyte across the substrate surface, ensuring continuous electrolyte replenishment at the electrode interface.

[0226] In some embodiments, the electrolyte flow rate is maintained between 300 cm / s and 1000 cm / s, preventing ion depletion zones and enabling uniform lithium deposition.

[0227] In some embodiments, the electrolyte flow rate is dynamically adjusted based on electrodeposition current density, ensuring a stable lithium-ion flux to the deposition interface.

[0228] In some embodiments, the electrolyte flow velocity at the electrode surface is between 1000 cm / s and 5000 cm / s, promoting uniform lithium film formation under high-shear conditions at the electrode surface.

[0229] High-Flow Conditions for Dendrite Suppression:

[0230] In some embodiments, the electrolyte flow rate is sufficient to remove loosely adhered dendritic lithium, selectively promoting dense and uniform lithium growth.

[0231] In some embodiments, the electrolyte flow exerts a shear force of at least 100 Pa, sufficient to disrupt dendrite formation while maintaining the integrity of the plated lithium layer.

[0232] In some embodiments, controlled electrolyte turbulence is used to disrupt early-stage dendritic protrusions, leading to a lithium morphology with a thickness variation of less than 10% across the electrode surface.

[0233] High-Flow Effects on Electrolyte Longevity:

[0234] In some embodiments, the flow of electrolyte supports continuous filtration and replenishment, extending operational lifetime in an industrial electrocoating system.LITHIUM METAL PROPERTIES

[0235] Lithium Property - Adhesion:

[0236] In some embodiments, the electrolyte is formulated to produce lithium metal with high adhesion to the substrate, ensuring that the deposited lithium layer remains mechanically stable under high organic electrolyte flow rates during electrodeposition. By enhancing lithium-substrate interactions, the electrolyte prevents delamination, maintains deposition integrity, and enables high-throughput industrial electrocoating processes.

[0237] Morphology Control for Adhesion:

[0238] In some embodiments, the electrolyte is designed to produce a columnar lithium growth morphology, enhancing adhesion and mechanical stability.

[0239] In alternative embodiments, the electrolyte electrodeposits lithium to achieve a uniform film thickness variation of <10%, reducing internal stress that could cause delamination.

[0240] In alternative embodiments, the electrolyte formulation is optimized to prevent cracking, peeling, or detachment of lithium deposits over extended cycling.

[0241] In alternative embodiments, thicker lithium metal deposits (>20 pm) of columnar crystalline lithium allows for shear stress applied to the substrate to break adhesion of the lithium metal coating cleanly from the substrate while maintaining the coating integrity.

[0242] Strength of Adhesion:

[0243] In some embodiments, the disclosed electrolyte system promotes the formation of lithium metal films that exhibit strong interfacial adhesion to the underlying conductivesubstrate. This adhesion is sufficient to withstand high shear forces generated by flowing organic electrolyte during deposition, 500 cm / min or greater.

[0244] In certain embodiments, the adhesion strength of the deposited lithium film to the substrate ranges from 5 to 1000 N / m, as quantified by standardized tensile, peel, or shear adhesion testing methods. In some embodiments, adhesion strength is measured using 180° peel tests, lap-shear testing, or custom probe-based delamination techniques under inert atmosphere to preserve lithium integrity.

[0245] In alternative embodiments, the lithium film exhibits an adhesion strength of at least 10 N / m, ensuring mechanical robustness for post-deposition handling and integration into downstream battery assembly processes.

[0246] In high-performance embodiments, adhesion strength may exceed 100 N / m, providing enhanced film durability during continuous flow deposition, thermal cycling, or mechanical handling.

[0247] In some embodiments, the improved adhesion is attributed to surface interactions between the lithium and chemically conditioned substrate, including the presence of fluorinated interphases (e.g., LiF, CuF?), microscale surface texturing, or acid-etched oxide- free metallic surfaces, which promote uniform lithium nucleation and chemical bonding.

[0248] In further embodiments, the electrolyte composition facilitates the formation of an interfacial SEI or underlayer that includes mechanically anchoring species, such as embedded inorganic salts or polymeric byproducts, which enhance lithium-substrate interfacial strength.

[0249] Lithium Property - Wettability

[0250] In some embodiments, the lithium metal deposited using the disclosed electrolyte system exhibits enhanced wettability with organic electrolytes, particularly those with high viscosity such as high-concentration or solvent- in- salt formulations commonly used in lithium metal batteries. Improved wettability is characterized by a reduced contact angle between the lithium surface and the electrolyte, facilitating uniform spreading and penetration of the electrolyte across the deposited film. This property enhances interfacial ionic transport, promotes stable solid electrolyte interphase (SEI) formation, and reduces localized electrolyte starvation or dry spots. Compared to commercial lithium metal foil, which often exhibits poor wetting behavior with viscous electrolytes due to surface passivation or oxide contamination, the lithium produced herein provides a more compatible and reactive surface, thereby supporting efficient charge transfer and long-term cycling stability in lithium metal battery systems.

[0251] In some embodiments, the electrodeposited lithium metal exhibits high wettability with lithium-ion battery electrolytes, as evidenced by a static contact angle <60°, ensuring uniform electrolyte spreading and improved interfacial ion transport.

[0252] In certain embodiments, the contact angle is further reduced to <15°, providing nearcomplete wetting that maximizes electrolyte-substrate interaction, promotes stable SEI formation, and enhances lithium-ion flux across the electrode surface.

[0253] In alternative embodiments, the lithium electrode exhibits a dynamic wetting rate of >2 mm / s, as measured by electrolyte spreading or capillary uptake tests, enabling rapid electrolyte absorption and uniform wetting during battery cycling and electrolyte replenishment operations.

[0254] In some embodiments, the improved wettability is preserved even in viscous or solvent-limited electrolyte systems. For example, in high-concentration electrolytes (HCEs) such as >3.0 M LiFSI in DME, the electrodeposited lithium exhibits a contact angle of <60°, while in localized high-concentration electrolytes (LHCEs) containing fluorinated diluents, the contact angle is further reduced to <15°, facilitating effective lithium-ion transport under restricted solvation conditions.

[0255] Wettability is also enhanced in ether-based electrolytes commonly used in lithium metal batteries. In some embodiments, the contact angle of lithium with 1.0 M LiTFSI in DME / DOL is <30°, and in certain high-salt-concentration formulations (e.g., 3.0 M LiFSI in DME / DOL), the contact angle is optimized to <15°, supporting uniform deposition and improved coulombic efficiency.

[0256] In other embodiments, the electrodeposited lithium demonstrates improved compatibility with fluorinated and fire-resistant electrolytes. For example, a contact angle of <60° is maintained in 1.0 M LiPFe in FEC / DMC, enabling stable ion diffusion in flameretardant carbonate systems. In phosphazene-based or other nonflammable solvents, the contact angle may be reduced to <30°, enhancing interfacial stability for high-safety lithium metal battery chemistries.

[0257] In some embodiments, the improved wettability is attributed to the chemical composition, surface energy, or morphology of the lithium metal as deposited, which differs from commercial lithium foils that exhibit poor wettability due to oxide passivation and surface contamination.RECITATION OF EMBODIMENTS

[0258] Embodiment Al. A method for electrodeposition of lithium metal, comprising providing a counter-electrode; providing an electrolyte composition between a substrate and the counter-electrode, the electrolyte composition comprising a solvent, a hydrolytically stable lithium salt, a hydrolytically unstable salt (including a hydrolytically unstable lithium salt), and water; and applying a current between the substrate and the counter-electrode to electrodeposit a lithium metal film on the substrate.

[0259] Embodiment A2. The method of Embodiment Al, wherein the hydrolytically unstable salt, the water, and a second solvent are pre-mixed prior to combining with the hydrolytically stable lithium salt and the solvent to form the electrolyte composition. In one or more embodiments, the second solvent and the solvent are the same. In one or more embodiments, the second solvent and the solvent are different.

[0260] Embodiment A3. The method of Embodiments Al or A2, wherein a concentration of the water in the electrolyte composition is between 0.0005 M and 0.1 M.

[0261] Embodiment A4. The method of any one of Embodiments Al -A3, wherein a concentration of the hydrolytically stable lithium salt in the electrolyte composition is between 0.5 M and 6.0 M.

[0262] Embodiment A5. The method of any one of Embodiments A1-A4, wherein a concentration of the hydrolytically unstable salt in the electrolyte composition is between 0.0005 M and 1.0 M.

[0263] Embodiment A6. The method of any one of Embodiments A1-A4, wherein a weight percent ratio of the hydrolytically stable lithium salt to the hydrolytically unstable salt is between 2.5: 1 and 1000: 1.

[0264] Embodiment A7. The method of any one of Embodiments A1-A6, wherein the electrolyte composition further comprises a diluent (e.g., a non-coordinating diluent) having a concentration between 5 vol% and 90 vol% of the electrolyte composition. In one or more embodiments, the diluent comprises a non-coordinating or weakly coordinating solvent that reduces the viscosity of the electrolyte and does not strongly solvate lithium ions. In one or more embodiments, the diluent comprises a non-coordinating or weakly coordinating organic compound, including but not limited to fluorinated ethers, hydrofluoroethers (HFEs), sulfones, fluorinated alkyl ethers with weak Lewis basicity, sterically hindered ethers, cyclic ethers with limited donor ability, or a combination thereof.

[0265] Embodiment A8. The method of any one of Embodiments A1-A7, wherein the solvent comprises one or more organic solvents selected from a list of linear or cyclic ethers(e.g., dimethoxyethane, tetrahydrofuran, dioxolane), carbonates (e.g., ethylene carbonate, dimethyl carbonate, fluoroethylene carbonate), fluorinated solvents, sulfones (including sulfolane) or a mixture thereof.

[0266] Embodiment A9. The method of any one of Embodiments A1-A8, wherein the solvent comprises a molar ratio of solvent- to-hydrolytically stable salt of < 5:1 that indicates a high-concentration electrolyte or a solvent-in-salt electrolyte.

[0267] Embodiment A10. The method of any one of Embodiments A1-A9, wherein the hydrolytically stable lithium salt is selected from the group consisting of LiFSI, LiTFSI, LiBOB, LiDFOB, LiNOs, and lithium salts comprising fluoroalkylsulfonyl, oxalato, phosphate, or delocalized anions that are resistant to hydrolysis.

[0268] Embodiment Al l. The method of any one of Embodiments A1-A10, wherein the hydrolytically unstable salt is selected from the group consisting of LiPFs, LiBF4, LiCICh, HPFe, and HBF4, and lithium salts comprising hexafluorophosphate, tetrafluoroborate, oxalate-phosphate-fluoride, or chloroaluminate anions.

[0269] Embodiment A 12. The method of any one of Embodiments Al-Al l, wherein the water hydrolyzes the hydrolytically unstable salt to generate acidic and fluorinated species.

[0270] Embodiment A13. The method of Embodiment A12, wherein the acidic and fluorinated species comprise HF and LiF, phosphorus oxyfluoride (POF3) or lithium bifluoride (LiHF?), wherein the acidic and fluorinated species form or promote the growth of a lithium fluoride-rich SEI that enables uniform lithium nucleation and suppresses dendritic growth.

[0271] Embodiment A 14. The method of any one of Embodiments Al -Al 3, wherein the electrodeposited lithium metal film exhibits a columnar nanostructure.

[0272] Embodiment A 15. The method of any one of Embodiments Al -A 14, wherein the electrolyte composition further comprises one or more additives including, but not limited to, flame retardants, rheology modifiers, fluorinated solvents, film-forming agents, gas scavengers, corrosion inhibitors, or redox shuttles. In one or more embodiments, the additives are included to improve thermal stability, modulate electrolyte viscosity, stabilize the SEI, or enhance lithium surface compatibility.

[0273] Embodiment A 16. The method of any one of Embodiments Al -Al 5, wherein the electrolyte composition further comprises an acid (e.g., a fluorinated acid) having a concentration between 0.0005 M and 0. 1 M. In one or more embodiments, the acid is configured to modulate SEI formation and promote lithium nucleation.

[0274] Embodiment A17. The method of any one of Embodiments A1-A16, wherein the hydrolytically unstable salt is a first hydrolytically unstable salt, the solvent is a first solvent, and the water is a first amount of water, the method further comprises introducing an additive to the electrolyte composition during the applying of the current between the substrate and the counter-electrode, wherein the additive comprises a second hydrolytically unstable salt, a second solvent, and a second amount water with a sufficient concentration to partially hydrolyze the second hydrolytically unstable salt.

[0275] Embodiment Al 8. The method of Embodiment A17, wherein the second amount water partially hydrolyzes the second hydrolytically unstable salt in the additive under an inert atmosphere prior to the introducing of the additive to the electrolyte composition.

[0276] Embodiment A 19. A system for lithium metal electrodeposition, comprising a reservoir of the electrolyte composition of any one of Embodiments A1-A14; a vessel containing the additive of any one of Embodiments A15-A18; a metered introducing mechanism configured to deliver the additive into the electrolyte composition prior to or during electrodeposition of the lithium metal film; and a power source configured to supply a current between the substrate and the counter-electrode of any one of Embodiments A1-A18.

[0277] Embodiment A20. The system of Embodiment A 19, wherein the additive is introduced at a controlled rate based on sensor feedback that measures electrolyte degradation, lithium adhesion, or plating morphology.ELECTROLYTE COMPOSITION

[0278] Embodiment BL An electrolyte composition for electrodeposition of lithium metal, comprising a solvent; a hydrolytically stable lithium salt present at a concentration of 0.5 M to 6.0 M; a hydrolytically unstable salt present at a concentration of 0.0005 M to 1.0 M; and water content in an amount of 0.0005 M to 0.05 M.

[0279] Embodiment B2. The electrolyte composition of Embodiment B 1 , further comprising a non-coordinating diluent having a concentration between 5 vol% and 90 vol% of the electrolyte composition.

[0280] Embodiment B3. The electrolyte composition of Embodiments Bl or B2, wherein the solvent comprises one or more organic solvents selected from linear or cyclic ethers (e.g., dimethoxye thane, tetrahydrofuran, dioxolane); carbonates (e.g., ethylene carbonate, dimethyl carbonate, fluoroethylene carbonate); fluorinated solvents; or a mixture thereof.

[0281] Embodiment B4. The electrolyte composition of any one of Embodiments B1-B3, wherein the solvent comprises a solvent-to-salt molar ratio of < 5:1, forming a high- concentration or solvent-in-salt electrolyte.

[0282] Embodiment B5. The electrolyte composition of any one of Embodiments B1-B4, wherein the hydrolytically stable lithium salt is selected from the group consisting of LiFSI, LiTFSI, LiBOB, LiDFOB, and LiNOs.

[0283] Embodiment B6. The electrolyte composition of any one of Embodiments B1-B5, wherein the hydrolytically unstable salt is selected from the group consisting of LiPFe, Li B Ri, LiClO, HPFs, and HBF4.

[0284] Embodiment B7. The electrolyte composition of any one of Embodiments B1-B6, wherein the water content is sufficient to partially hydrolyze the hydrolytically unstable salt and generate acidic and fluorinated species in situ, including HF and LiF, which promote SEI formation and lithium nucleation.

[0285] Embodiment B8. The electrolyte composition of any one of Embodiments B1-B7, wherein the electrolyte retains at least 40% lithium deposition efficiency after 30 days of inert storage at 25 °C.

[0286] Embodiment B9. The electrolyte composition of any one of Embodiments B1-B8, wherein lithium metal electrodeposited from the electrolyte exhibits a columnar nanostructure and a film thickness variation of less than 10%.

[0287] Embodiment B 10. The electrolyte composition of any one of Embodiments B 1-B9, further comprising one or more additives selected from flame retardants, rheology modifiers, or fluorinated solvents.

[0288] Embodiment B 11. The electrolyte composition of any one of Embodiments B 1-B 10, further comprising an acid species at a concentration of 0.000005 M to 1.0 M.

[0289] Embodiment B 12. The electrolyte composition of Embodiment B 11 , wherein the acid is generated in situ by hydrolysis of the hydrolytically unstable lithium salt.

[0290] Embodiment Bl 3. The electrolyte composition of Embodiments Bll or B12, wherein the acid promotes formation of LiF in the SEI and improves lithium nucleation and uniformity.

[0291] Embodiment B14. The electrolyte composition of any one of Embodiments B 11-B 13, wherein the acid concentration is sufficient to remove native oxide or passivating films from a substrate (e.g., conductive substrate), improving adhesion and uniformity.

[0292] Embodiment Bl 5. The electrolyte composition of any one of Embodiments B 1-B 14, wherein the diluent comprises one or more of fluorinated ether solvents; hydrofluoroethers(HFEs); non-coordinating sulfones; fluorinated alkyl ethers with weak Lewis basicity; sterically hindered ethers; or cyclic ethers with limited donor ability.

[0293] Embodiment B 16. The electrolyte composition of Embodiment B 15, wherein the diluent has a donor number below 10 kcal / mol and does not disrupt the lithium-ion solvation shell.

[0294] Embodiment B 17. The electrolyte composition of any one of Embodiments B1-B16, wherein the diluent increases the electrolyte flash point above 100°C, improving safety in high-temperature electrodeposition.ADDITIVE

[0295] Embodiment Cl. An additive for use in a lithium metal electrodeposition electrolyte, comprising a hydrolytically unstable salt; water in an amount sufficient to partially hydrolyze the hydrolytically unstable salt; and an organic solvent.

[0296] Embodiment C2. The additive of Embodiment Cl, wherein the hydrolysis is conducted under inert atmosphere to generate hydrolysis products prior to incorporation into a primary electrolyte.

[0297] Embodiment C3. The additive of Embodiments Cl or C2, wherein the additive is introduced into an electrolyte containing a hydrolytically stable lithium salt to tailor SEI formation, lithium nucleation, and film morphology.

[0298] Embodiment C4. The additive of any one of Embodiments C1-C3, wherein the additive is introduced into the electrolyte at a rate controlled by feedback from real-time measurements of deposition efficiency, conductivity, pH, or film morphology.

[0299] Embodiment C5. The additive of any one of Embodiments C1-C4, wherein the composition maintains a fixed ratio of hydrolysis products optimized for compact, high- efficiency lithium metal deposition.SYSTEM

[0300] Embodiment DI. A system for lithium metal electrodeposition, comprising a reservoir of the electrolyte comprised of a hydrolytically stable salt and solvent or an electrolyte with a composition of any one of Embodiments B 1-B 10; a vessel containing the additive of any one of Embodiments C1-C5; and a metered injection mechanism configured to deliver the additive into an electrolyte stream prior to or during electrodeposition.

[0301] Embodiment D2. The system of Embodiment DI, wherein the additive is introduced at a controlled rate based on sensor feedback measuring electrolyte degradation, lithium adhesion, or plating morphology.

[0302] Embodiment D3. The system of Embodiments DI or D2, wherein the additive extends an operational lifetime of the electrolyte composition during continuous industrial high- flow electrodeposition.LITHIUM METAL

[0303] Embodiment EL A lithium metal produced using the electrolyte composition of any one of Embodiments A1-A20, B1-B17, C1-C5, or D1-D3 exhibits a static contact angle of <60° with a lithium-ion battery electrolyte.

[0304] Embodiment E2. The lithium metal of Embodiment El, wherein the contact angle is <15° in a high-concentration electrolyte (>3.0 M LiFSI in DME), and / or the dynamic wetting rate is >2 mm / s.

[0305] Embodiment E3. The lithium metal of Embodiments El or E2, wherein high wettability is retained across multiple electrolyte systems, including ether-based, fluorinated, and hybrid electrolytes

[0306] Embodiment E4. The lithium metal of any one of Embodiments E1-E3, wherein the lithium metal exhibits a columnar nanostructure.

[0307] Embodiment E5. The lithium metal of any one of Embodiments E1-E4, wherein the lithium metal exhibits an adhesion strength of >100 N / m to a substrate (e.g., conductive substrate); and a static contact angle of <15° with a >3.0 M LiFSI / DME electrolyte.LITHIUM METAL DEPOSITION SYSTEM

[0308] Embodiment FL A system for fabricating lithium metal electrodes, comprising a source of the electrolyte composition of a hydrolytically stable salt and solvent or any one of Embodiments A1-A20; an electrolyte reservoir and circulation loop configured to deliver the electrolyte composition to an electrodeposition chamber; and a feedback-controlled replenishment unit configured to add an additive comprising a hydrolytically unstable salt and water to extend electrolyte lifetime.

[0309] Embodiment F2. The system of Embodiment Fl, further comprising sensors for monitoring at least one of lithium salt concentration, pH, conductivity, or deposition efficiency, wherein the replenishment rate of the additive is dynamically adjusted based on real-time sensor data.

[0310] Embodiment F3. The system of Embodiments Fl or F2, further comprising a filtration or separation unit configured for continuously removing electrolyte degradation products from the circulation loop.

[0311] Embodiment F4. The system of any one of Embodiments F1-F3, wherein a flow rate of the electrolyte composition at a lithium deposition interface is between 900 cm / min and 2200 cm / min, sufficient to promote uniform deposition and remove loosely adhered dendrites.

[0312] Embodiment F5. The system of any one of Embodiments F1-F4, wherein the fabricated lithium metal adheres to the substrate (e.g., conductive substrate) with an adhesion strength between 5 N / m and 1000 N / m.

Claims

CLAIMSWhat is claimed is:

1. A method for electrodeposition of lithium metal, comprising: providing a counter-electrode; providing an electrolyte composition between a substrate and the counter-electrode, the electrolyte composition comprising: a solvent, a hydrolytically stable lithium salt, a hydrolytically unstable salt, and water; and applying a current between the substrate and the counter-electrode to electrodeposit a lithium metal film on the substrate.

2. The method of claim 1 , wherein the hydrolytically unstable salt, the water, and a second solvent are pre-mixed prior to combining with the hydrolytically stable lithium salt and the solvent to form the electrolyte composition.

3. The method of claims 1 or 2, wherein a concentration of the water in the electrolyte composition is between 0.0005 M and 0. 1 M.

4. The method of any one of claims 1-3, wherein a concentration of the hydrolytically stable lithium salt in the electrolyte composition is between 0.5 M and 6.0 M.

5. The method of any one of claims 1-4, wherein a concentration of the hydrolytically unstable salt in the electrolyte composition is between 0.0005 M and 1.0 M.

6. The method of any one of claims 1-5, wherein a weight percent ratio of the hydrolytically stable lithium salt to the hydrolytically unstable salt is between 2.5: 1 and 1000: 1.

7. The method of any one of claims 1-6, wherein the electrolyte composition further comprises a diluent having a concentration between 5 vol% and 90 vol% of the electrolyte composition.

8. The method of any one of claims 1-7, wherein the solvent comprises one or more organic solvents selected from a list of linear or cyclic ethers, carbonates, fluorinated solvents, sulfones, or a mixture thereof.

9. The method of any one of claims 1-8, wherein the solvent comprises a molar ratio of solvent-to-hydrolytically stable salt of < 5 : 1 that indicates a high-concentration electrolyte or a solvent-in-salt electrolyte.

10. The method of any one of claims 1-9, wherein the hydrolytically stable lithium salt is selected from the group consisting of LiFSI, LiTFSI, LiBOB, LiDFOB, LiNCh, and lithium salts comprising fluoroalkylsulfonyl, oxalato, phosphate, or delocalized anions that are resistant to hydrolysis.

11. The method of any one of claims 1-10, wherein the hydrolytically unstable salt is selected from the group consisting of LiPFe, LiBF4, HPFs, and HBF4, and lithium salts comprising hexafluorophosphate, tetrafluoroborate, oxalate-phosphate-fluoride, or chloroaluminate anions.

12. The method of any one of claims 1-11, wherein the water hydrolyzes the hydrolytically unstable salt to generate acidic and fluorinated species.

13. The method of claim 12, wherein the acidic and fluorinated species comprise hydrogen fluoride (HF), lithium fluoride (LiF), phosphorus oxyfluoride (POF3) or lithium bifluoride (LiHF2).

14. The method of any one of claims 1-13, wherein the electrodeposited lithium metal film exhibits a columnar nanostructure.

15. The method of any one of claims 1-14, wherein the electrolyte composition further comprises one or more additives from a list of flame retardants, rheology modifiers, fluorinated solvents, film-forming agents, gas scavengers, corrosion inhibitors, or redox shuttles.

16. The method of any one of claims 1-15, wherein the electrolyte composition further comprises an acid having a concentration between 0.0005 M and 0.1 M.

17. The method of any one of claims 1-16, wherein the hydrolytically unstable salt is a first hydrolytically unstable salt, the solvent is a first solvent, and the water is a first amount of water, the method further comprises: introducing an additive to the electrolyte composition during the applying of the current between the substrate and the counter-electrode, wherein the additive comprises a second hydrolytically unstable salt, a second solvent, and a second amount water with a sufficient concentration to partially hydrolyze the second hydrolytically unstable salt.

18. The method of claim 17, wherein the second amount water partially hydrolyzes the second hydrolytically unstable salt in the additive under an inert atmosphere prior to the introducing of the additive to the electrolyte composition.

19. A system for lithium metal electrodeposition, comprising: a reservoir of the electrolyte composition of any one of claims 1-14; a vessel containing the additive of any one of claims 15-18; a metered introducing mechanism configured to deliver the additive into the electrolyte composition prior to or during electrodeposition of the lithium metal film; and a power source configured to supply a current between the substrate and the counterelectrode of any one of claims 1-18.

20. The system of claim 19, wherein the additive is introduced at a controlled rate based on sensor feedback that measures electrolyte degradation, lithium adhesion, or plating morphology.

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