Low vapor pressure liquefied gas electrolyte using high concentration salt

Abstract

A novel electrolyte based on liquefied gas and a high concentration of salt in the liquefied gas electrolyte are disclosed. Unlike common electrolytes, the liquefied gas electrolyte utilizes a solvent that is gaseous under standard conditions. This disclosure describes an electrolyte that is composed of one or more solvents, one or more of which are liquefied gas solvents, and a sufficiently high concentration of salt or combination of salts such that the combination of solid salt and liquefied gas solvent produces a low vapor pressure electrolyte or even a liquid electrolyte mixture with a vapor pressure below atmospheric pressure at a temperature of 293.15K.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application is also related to the following applications, the contents of each of which are incorporated herein by reference in their entirety: PCT / US20 / 048660, filed August 30, 2020; PCT / US20 / 020547, filed February 29, 2020; PCT / US20 / 048661, filed August 30, 2020; PCT / US19 / 032413, filed May 15, 2019; PCT / US19 / 032414, filed May 15, 2019; PCT / US14 / 066015, filed November 17, 2014; PCT / US14 / 066015, filed April 1, 2020; Provisional Application No. PCT / US20 / 026086, filed April 27, 2017; PCT / US17 / 029821, filed May 31, 2022; PCT / US22 / 031594, filed May 31, 2022; PCT / US23 / 11864, filed January 30, 2023; Provisional Application No. 63 / 328480, filed July 7, 2022; Provisional Application No. 63 / 391224, filed July 21, 2022; Provisional Application No. 63 / 418703, filed October 24, 2022; Provisional Application No. 63 / 418704, filed October 24, 2022; and Provisional Application No. 63 / 306393, filed February 3, 2022.

[0002] This application claims priority to U.S. Provisional Application No. 63 / 328480, filed April 7, 2022, U.S. Provisional Application No. 63 / 391220, filed July 21, 2022, and U.S. Application No. 18 / 131616, filed April 6, 2023, the contents of which are incorporated by reference.

[0003] Embodiments of the present invention relate to electrolyte compositions and chemical formulations for use in electrochemical energy devices, such as batteries and electrochemical capacitors. Devices employing the compositions and methods of using the compositions are also provided. [Background technology]

[0004] Electrochemical devices such as batteries and capacitors employ ionically conductive, electrically insulating electrolytes to carry charge between negative and positive electrodes. These electrolytes are typically liquid at room temperature and atmospheric pressure (293.15 K and 100 kPa), i.e., standard conditions, and consist of approximately 1.0 M salt in a solvent mixture, and optional additives that may be solid, liquid, or gaseous under standard conditions. The salt and solvent molecules typically exist in so-called "solvation shells," in which cations and anions are surrounded by solvents, additives, and other cations and anions. These solvation shells affect all aspects of the device, from cycling properties to safety, and depend on the concentration and composition of the electrolyte formulation.

[0005] It is known that liquefied gas electrolytes can improve the performance of electrochemical devices by their high power, high energy, temperature performance, or safety. However, most liquefied gas solvents, additives and salt mixtures pose problems due to their vapor pressures that significantly exceed atmospheric pressure (>100 kPa), making devices more difficult to handle and build.

[0006] Therefore, there is a need for electrolytes with low vapor pressure to overcome these shortcomings. Summary of the Invention

[0007] Novel electrolytes based on liquefied gas and high concentrations of salts in liquefied gas electrolytes are disclosed. Unlike common electrolytes, liquefied gas electrolytes utilize solvents that are gases under standard conditions. This disclosure describes electrolytes that consist of a solvent that is composed of one or more solvents, one or more of which are liquefied gas solvents, and a sufficiently high concentration of salt or combination of salts such that the combination of solid salt and liquefied gas solvent results in an electrolyte that has a lower vapor pressure than the base solvent alone. By reducing the vapor pressure so much, one can even obtain a liquid electrolyte mixture that has a vapor pressure below atmospheric pressure at a temperature of 293.15 K, allowing the electrolyte mixture to be handled as a liquid. A large amount of salt can help form a stable electrode-electrolyte interface (SEI) and form a low impedance electrode-electrolyte interfacial phase that improves cell cycle life performance or enables high power performance. The improved SEI formation is believed to be due to more contact ion pairs (CIPs) and aggregates within the solvation shell, where the salt cations and anions remain in contact and are not separated by the solvent, allowing the anions to be reduced before the solvent. This results in a denser inorganic SEI compared to the less dense organic SEIs typically formed by reduction of the solvent. Additionally, reducing the amount of solvent in the device can lower costs, and lower vapor pressure simplifies the manufacturability of the electrolyte and the electrochemical devices in which it is used by allowing for thinner walled cell enclosures that reduce mass, volume and cost.

[0008] However, unlike traditional liquefied gas electrolytes, these electrolytes, when mixed with a large amount of salt, achieve a lower vapor pressure as shown in Figure 1. This allows the use of liquefied gas in the electrolyte without the mechanical or manufacturing constraints imposed by high vapor pressure solvents, thereby simplifying manufacturing, reducing the mass of the battery cell housing, and lowering costs.

[0009] Additional embodiments, alternatives, and variations that will be apparent to those skilled in the art are disclosed herein and are specifically intended to be included as part of the present invention. The present invention is set forth solely in the claims granted by the Patent Office in this or a related application, and the following summary description of certain specific embodiments is not intended to limit, define, or otherwise determine in any way the scope of legal protection.

[0010] The present invention can be better understood by reference to the following figures. The components in the figures are not necessarily to scale, with emphasis instead being placed on clearly illustrating the illustrated aspects of the present invention. In the figures, like reference numerals indicate corresponding parts throughout the different views and / or embodiments. Furthermore, various features of different disclosed embodiments can be combined to form additional embodiments that are part of the present disclosure. It will be understood that certain specific components and details may not appear in the figures to help more clearly explain the present invention. [Brief description of the drawings]

[0011] [Figure 1] The electrolyte pressure at room temperature for various liquefied gas electrolytes containing increasing molar concentrations of the lithium salts lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI) is shown compared to the pure solvent dimethyl ether (MeO) at 0 M salt concentration. [Diagram 2] The performance of a battery coin cell at room temperature using a lithium metal counter electrode and a reference electrode during electrochemical plating of lithium metal onto a stainless steel cathode in 15.0 M LiFSI in Me2O, followed by stripping, is demonstrated. The coin cell is constructed within an enclosure that encapsulates an ionically conductive electrolyte under pressurized conditions that maintain the electrolyte in the liquid phase. [Diagram 3]This shows the performance of a battery coin cell at room temperature using a lithium metal anode during a linear potential scan versus a carbon cathode in a Me2O electrolyte containing 15.0 M LiFSI. The coin cell was constructed within an enclosure enclosing an ionically conductive electrolyte under pressurized conditions that kept the electrolyte in the liquid phase, with the anode and cathode in contact with the ionically conductive electrolyte. [Figure 4] We demonstrate the performance of a battery coin cell at room temperature using a lithium metal anode and a lithium-nickel-cobalt-manganese (NMC622) cathode with Me2O electrolyte containing 15.0 M LiFSI. The coin cell is constructed within a housing that encapsulates an ionically conductive electrolyte under pressurized conditions that keep the electrolyte in the liquid phase. [Diagram 5] Dimethyl ether (C2H6O) is compared with the two other most similar linear ethers that are liquid at room temperature: diethyl ether (C4H10O) and 1,2-dimethoxyethane (C4H10O2). The electronic properties of dimethyl ether (ionization potential of about 9.9 eV and electron affinity of about -1.55 eV) are calculated to be superior to these solvents and to the cyclic ether, tetrahydrofuran. [Figure 6] A comparison of the binding energies of four different liquefied gas solvents: fluoromethane (CH3F), formaldehyde (H2CO), dimethyl ether ((CH3)2O), and trimethylamine ((CH3)3N). Calculations were compared for one solvent molecule bonded to one lithium cation. The binding energies of formaldehyde (1.6 eV), dimethyl ether (1.72 eV), and trimethylamine (1.82 eV) are shown to be significantly higher than that of fluoromethane (1.31 eV). [Figure 7]A diagrammatic depiction of the solvation shell of a solvent molecule around one cation (anion not included for clarity). Various salt-solvent ratios are shown, from 3:1, to 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, and 1:6. At the 1:4 ratio the solvation sphere is essentially complete, so at the 1:5 and 1:6 ratios there is little additional solvent binding energy to the cation, which leads to higher vapor pressures. [Figure 8] FIG. 1 is a block diagram illustrating one embodiment of an apparatus for dispensing a liquefied gas electrolyte mixture into a secondary container. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Reference will be made herein to certain specific embodiments of the invention, including any best mode contemplated by the inventors for carrying out the invention. Examples of these specific embodiments are illustrated in the accompanying drawings. While the invention will be described in conjunction with these specific embodiments, it will be understood that they are not intended to limit the invention to the embodiments described or illustrated. On the contrary, they are intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

[0013] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. Certain exemplary embodiments of the present invention may be practiced without some or all of these specific details. In other instances, process operations well known to those skilled in the art have not been described in detail so as not to unnecessarily obscure the present invention. Various techniques and mechanisms of the present invention may be described in the singular for clarity. However, it should be noted that some embodiments include multiple iterations of techniques or multiple mechanisms, unless otherwise noted. Similarly, various steps of the methods shown and described herein may not necessarily be performed in the order shown, or may not be performed at all, in a particular embodiment. Thus, some implementations of the methods discussed herein may include more or fewer steps than shown or described. Furthermore, the techniques and mechanisms of the present invention may be described as a connection, relationship, or communication between two or more elements. It should be noted that a connection or relationship between elements does not necessarily imply a direct, unobstructed connection, since various other elements or processes may exist or occur between any two elements. Thus, unless otherwise noted, a connection shown does not necessarily imply a direct, unobstructed connection.

[0014] It is known that liquefied gas electrolytes can improve the performance of electrochemical devices through higher power, higher energy, temperature capability, or safety. However, most liquefied gas solvents, additives, and salt mixtures pose problems due to vapor pressures significantly exceeding atmospheric pressure (>100 kPa), which makes devices more difficult to handle and build, and requires thicker enclosure walls that can increase mass, volume, and cost.

[0015] Novel electrolytes based on liquefied gas and high concentrations of salts in liquefied gas electrolytes are disclosed. Unlike common electrolytes, liquefied gas electrolytes utilize solvents that are gases under standard conditions. This disclosure describes electrolytes that consist of a solvent that is composed of one or more solvents, one or more of which are liquefied gas solvents, and a sufficiently high concentration of salt or combination of salts such that the combination of solid salt and liquefied gas solvent results in an electrolyte that has a lower vapor pressure than the base solvent alone. The significant reduction in vapor pressure can even result in a liquid electrolyte mixture that has a vapor pressure below atmospheric pressure at a temperature of 293.15 K, allowing the solid-gas mixture to be handled as a liquid. The large amount of salt not only aids in both the formation of a stable electrode-electrolyte interface (SEI) and the reduction of the amount of solvent in the device, but also simplifies the manufacturability of the electrolyte and the electrochemical device in which it is used. The improved SEI formation is believed to be due to more contact ion pairs (CIPs) and aggregates within the solvation shell, where the salt cations and anions remain in contact and are not separated by the solvent, allowing the anions to be reduced prior to the solvent, resulting in a denser inorganic SEI compared to the less dense organic SEI typically formed by reduction of the solvent.

[0016] Unlike conventional liquefied gas electrolytes, it has been discovered through considerable experimentation that certain formulations of liquefied gas electrolytes containing significant amounts of salt can achieve vapor pressures below atmospheric pressure at room temperature while using liquefied gas solvents that have vapor pressures above atmospheric pressure at room temperature, as seen in FIG. 1. This is believed to be due to the solvent being tightly bound to the lithium ions and salt anions, as shown in FIG. 7. An example of a liquefied gas solvent that exhibits this phenomenon is dimethyl ether. The lower vapor pressure that occurs at sufficiently high salt concentrations, above about 7M, allows the liquefied gas electrolyte to be treated like a liquid at room temperature and pressure. It would not have been previously apparent to one of ordinary skill in the art that increasing the molar concentration of lithium salt in a liquefied gas solvent such as dimethyl ether would preserve these highly desirable properties without experimenting, formulating, and studying these electrolyte compositions in a battery device. As a point of comparison, a salt to solvent molar ratio of 1 mole LiTFSI to 2 moles dimethyl ether salt results in a concentration of 3.65M, which exhibits a vapor pressure reduction from 86 psi for pure dimethyl ether solvent to roughly 40 psi, a vapor pressure reduction of 53%. This significant reduction in vapor pressure reduces the structural requirements of the cell housing, allowing for thinner cell housing walls, less mass, and smaller volume.

[0017] Figure 7 is a diagrammatic depiction of the solvation shell of a solvent molecule around one cation (anion not included for clarity). Various salt to solvent ratios are shown, from 3:1 to 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, and 1:6. If the solvent molecule is in the first solvation sphere of the salt where the solvent molecule is tightly bound to the cation, it will generally show a strong bond with the salt cation. The solvent in the second solvation sphere may also show some bonding with the salt cation, but at a lower energy than the first solvation sphere. This strong bonding reduces the free energy of the molecule, which reduces its kinetic energy and therefore the effective vapor pressure. Thus, with too much solvent, the vapor pressure is dominated more by the free solvent molecules that are less attracted to the cation, which results in an electrolyte with a high vapor pressure.

[0018] The salt concentration of an electrolyte can be described both as molar (moles of salt per unit volume of mixed electrolyte) or as a ratio of salt to solvent. For example, an electrolyte containing 1 part LiTFSI and 2 parts dimethyl ether corresponds to a molar concentration of about 3.65 moles (M) per liter. This concentration results in an electrolyte with a low vapor pressure of about 40 psi, about 53% reduction from the vapor pressure of the pure solvent of 86 psi at room temperature. It has also been shown that a salt molar concentration of 10 M reduces the vapor pressure so significantly that the vapor pressure of the electrolyte drops below atmospheric pressure, effectively resulting in a liquid electrolyte.

[0019] For gaseous solvents that have a strong attraction to the salt cation, it can be seen that the higher the salt concentration, the lower the vapor pressure. Figure 6 compares the bond energies of four different liquefied gas solvents: fluoromethane (CH3F), formaldehyde (H2CO), dimethyl ether ((CH3)2O), and trimethylamine ((CH3)3N). Calculations were compared for the case where one solvent molecule is bonded to one lithium cation. The bond energies of formaldehyde (1.6 eV), dimethyl ether (1.72 eV), and trimethylamine (1.82 eV) are shown to be significantly higher than that of fluoromethane (1.31 eV). Fluoromethane only weakly coordinates to the lithium salt, and it is difficult to increase the salt concentration in pure solvent without the salt precipitating out of solution. In contrast, formaldehyde, dimethyl ether, and trimethylamine show excellent solubility for high concentrations of salt. Although it is known that carbonyl oxygens, ether oxygens, and amine nitrogens exhibit high binding affinity with salt cations, it is surprising that this binding is strong enough to allow high salt concentrations in liquefied gas solvents and to significantly reduce the gas vapor pressure of the mixed electrolyte. This behavior is due to the increased binding energy of these solvents to the lithium cation. Furthermore, this effect can be generalized to any liquefied gas that has carbonyl oxygens, ether oxygens, and amine nitrogens.

[0020] It is frequently found that the reduction in vapor pressure is great enough that the vapor pressure is below atmospheric pressure at room temperature, making the electrolyte a liquid under standard conditions. Thus, any liquefied gas electrolyte can be treated as a liquid under standard conditions, provided a high enough concentration of salt is dissolved in the electrolyte mixture to reduce the vapor pressure of the liquefied gas solvent below atmospheric pressure.

[0021] The benefits of lowering the vapor pressure of liquefied gas electrolytes include allowing them to directly replace traditional liquid electrolytes in common equipment and liquid handling processes, including manufacturing lines and existing battery and electrochemical device structures such as pouch and prismatic cells, products and enclosures. Liquefied gas electrolytes are more desirable than traditional liquid electrolytes because the gas molecules are typically chemically simpler than common liquid electrolytes. An example of this is dimethyl ether (C2H6O), which is compared to the two most similar other linear ethers, diethyl ether (C4H10O) and 1,2-dimethoxyethane (C4H10O2), which are liquids at room temperature. As shown in Figure 5, the electronic properties of dimethyl ether (ionization potential of about 9.9 eV and electron affinity of about -1.55 eV) are calculated to be superior to these solvents and to the cyclic ether, tetrahydrofuran. This leads to improved oxidation and reduction potentials. These larger liquid molecules often have less electrochemical stability and may decompose under the high oxidation or reduction potentials in the battery cell. In many cases, the carbon-carbon bonds of these larger liquid molecules are the weak points of the molecules that promote this undesirable chemical instability. Smaller molecules with smaller sizes benefit both electrolyte research and production by reducing the chemical complexity in understanding the phenomenon and reducing the computational complexity and cost of simulations. Additionally, smaller molecular size has the advantage of lower electrolyte viscosity, which allows for higher salt mobility and therefore higher overall electrolyte conductivity. This higher electrolyte conductivity results in higher power batteries. Additionally, liquid solvents can freeze at low temperatures, rendering the battery cell inoperable. In contrast, smaller molecule liquefied gas solvents have significantly lower freezing points than liquid solvents, which allows the electrolyte to operate at much lower temperatures. For example, the freezing point of fluoromethane is -138°C, that of dimethyl ether is -141°C, and that of ammonia is -77°C. This is in contrast to traditional liquid solvents that have higher freezing points, such as ethylene carbonate (-48°C) and dimethyl carbonate (+2°C).

[0022] The disclosed formulation was found to contribute to a reduction in the overpotential for lithium plating and stripping seen in Figure 2. Additionally, while ethers are generally unstable at the higher potentials typically found in battery devices, Figure 3 shows that the disclosed formulation is stable up to 5.0 V without deleterious side reactions. This is also shown in Figure 4, where the disclosed formulation was used in a battery coin cell with an NMC622 cathode and showed high first cycle efficiency.

[0023] As shown in Figure 1, the vapor pressure of pure Me2O solvent with zero salt moles is approximately 80 psia at room temperature, which is above normal atmospheric pressure (15 psia, or 100 kPa). As the salt loading is increased, the vapor pressure drops to around 60% at a salt concentration of 5M, but the 5M electrolyte still has a vapor pressure above atmospheric pressure (35 psia). However, electrolytes with 10M or more have a vapor pressure of around 5 psia, or 94% lower than no salt, which is significantly below atmospheric pressure. Various salt loadings can be used to reduce the electrolyte pressure, for example, with salt to solvent ratios of 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, or 1:6, low vapor pressure electrolytes can be obtained with pressure reductions of approximately 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and up to 99%. Of course, the pressure drop depends on the solvent, the salt, the ratio of salt to solvent, and the temperature of the mixture. When more than one solvent is used, the solvents mentioned in the salt to solvent ratio may be limited to only those solvents that exhibit high binding energy with lithium cations. In general, any liquefied gas solvent that exhibits a vapor pressure drop at sufficiently high salt concentrations in the pure solvent may be mixed to combine multiple solvents to produce an electrolyte with a lower overall vapor pressure. These solvents may be mixed with solvents that bind weakly to the salt cations. The cation may be any salt cation, but is preferably lithium, sodium, calcium, magnesium, or potassium.

[0024] This reduction in vapor pressure may be great enough to effectively make the electrolyte a liquid at atmospheric pressure. Any degree of reduction in electrolyte vapor pressure provides benefits such as ease of handling, use of common liquid dispensing techniques and equipment, cell housings and structures, including pouch and prismatic cells, and improved safety performance due to the reduced electrolyte pressure.

[0025] In some cases, it may be desirable to maintain a vapor pressure of the liquefied gas electrolyte above atmospheric pressure but below the vapor pressure of the liquefied gas solvent. For example, to enhance the safety of the battery cell, it is desirable to have an electrolyte that can evaporate quickly from the cell in the event of a crush or rupture to prevent shorting of all the batteries and subsequent thermal runaway reactions. Having an electrolyte that can evaporate quickly from a ruptured or crushed cell can be very important for safety. The electrolyte may evaporate completely along with the salt or only partially with the solvent. The increase in cell impedance after electrolyte evaporation can prevent further cell shorting and thermal runaway reactions. Therefore, it may be desirable to optimize the vapor pressure to be above atmospheric pressure for safety but below the vapor pressure of the pure liquefied gas solvent for improved handling. With a lower vapor pressure, the electrolyte in the electrochemical device does not need to be subjected to as severe pressure. This allows the housing and various device components to be less robust and therefore easier and more efficient to manufacture. For example, the housing walls can be thinner and still maintain the same structural integrity as a lower pressure electrolyte. This reduces the mass, volume and cost of the enclosure, which is beneficial from a performance and cost standpoint.

[0026] As shown in Figure 2, a 15 M LiFSI electrolyte at room temperature can effectively promote the plating and stripping of lithium metal at low overpotentials, with no evidence of additional reactions of either the salt or the solvent. The smooth voltage variation suggests that this electrolyte does not produce uneven growth or deleterious electrolyte side reactions.

[0027] The 15M LiFSI electrolyte at room temperature also has excellent high potential stability as evidenced by the linear sweep voltagram (LSV) from the open circuit potential to 5 V vs. Li / Li+, as shown in Figure 3. The stability of this electrolyte has been shown to be as high as 4.5 V vs. Li / Li+. Typical ether-based electrolytes are known to have relatively low potential oxidation between 3-4 V vs. Li / Li+.

[0028] Figure 4 shows that the 15M LiFSI electrolyte is also compatible with transition metal oxide cathodes found in lithium-ion batteries. This electrolyte can reversibly charge a lithium-nickel-manganese-cobalt oxide cathode to 4.2 V and discharge to 2.5 V from the open circuit potential.

[0029] As shown in Figure 5, based on DFT calculations, dimethyl ether solvent molecules have a higher ionization potential (~9.9 eV) than other ether solvents such as diethyl ether (~9.4 eV), dimethoxyethane (~9.2 eV) and tetrahydrofuran (~9.2 eV). Ionization potential is the energy required for a molecule to lose an electron or be oxidized, and is related to the oxidation resistance of the solvent. Similarly, the electron affinity of dimethyl ether (~-1.55 eV) is also lower compared to diethyl ether (~-1.45 eV), dimethoxyethane (~1.35 eV) and tetrahydrofuran (~-1.4 eV). Electron affinity is the energy required for a molecule to gain an electron or be reduced, and is related to the reduction resistance of the solvent.

[0030] Based on DFT calculations, the binding energies of four different liquefied gas solvents, fluoromethane (CH3F), formaldehyde (H2CO), dimethyl ether ((CH3)2O), and trimethylamine ((CH3)3N), are compared as shown in Figure 6. The calculations were compared when one solvent molecule is bonded to one lithium cation. It is shown that the binding energies of formaldehyde (1.6 eV), dimethyl ether (1.72 eV), and trimethylamine (1.82 eV) are significantly higher than that of fluoromethane (1.31 eV).

[0031] One embodiment is an electrochemical device comprising an ionically conductive electrolyte. The ionically conductive electrolyte may comprise one or more salts and, optionally, one or more additives. The one or more additives may be liquid, solid, or gaseous at standard room temperature of 293.15 K and at standard pressure (approximately 100 kPa). The one or more salts may be liquid, solid, or gaseous at standard room temperature of 293.15 K and at standard pressure (approximately 100 kPa).

[0032] Some such embodiments of the electrochemical device may further include a housing structured to encapsulate the ionically conductive electrolyte in a completely sealed solution of one or more salts and one or more solvents, such as a liquefied gas solvent, and a pair of electrodes in contact with the ionically conductive electrolyte.

[0033] Those skilled in the art will understand that the terms "salt(s)," "solvent(s)" (including "liquefied gas solvents" and "liquid solvents"), and "additive(s)" as used herein in connection with "ionically conductive electrolyte" refer to one or more electrolyte components.

[0034] In one embodiment, the liquefied gas electrolyte comprises a liquefied gas solvent comprised of dimethyl ether with one or more lithium-based salts, where the ratio of salt to solvent is 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, or 1:6. In another embodiment, the liquefied gas solvent comprises other gaseous solvents having an ether oxygen structure, such as methyl ethyl ether, methyl vinyl ether, ethylene oxide, desflurane, 1,1,2,2-tetrafluoro-1-(trifluoromethoxy)ethane, bis(difluoromethyl)ether, methyl pentafluoroethyl ether, or perfluoroethyl methyl ether. In another embodiment, the liquefied gas solvent comprises any other gaseous solvent having a carbonyl oxygen, such as formaldehyde, ethenone, carbonyl sulfide, carbon suboxide, tris(difluoroamine)fluoromethane, or ethylamine, or trifluoroacetyl fluoride. In another embodiment, the liquefied gas solvent comprises any other gaseous solvent having an amine structure, such as ammonia, methylamine, dimethylamine, or trimethylamine.

[0035] These solvents, which show a decrease in vapor pressure at high salt concentrations, are: fluoromethane, difluoromethane, trifluoromethane, fluoroethane, tetrafluoroethane, pentafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, pentafluoroethane, chloromethane, chloroethane, thionyl fluoride, thionyl fluoride chloride, phosphoryl fluoride, phosphoryl fluoride chloride, sulfuryl fluoride, sulfuryl fluoride chloride, 1-fluoropropane, 2-fluoropropane, 1,1-difluoropropane, 1,2-difluoropropane, Other liquefied gas solvents may be mixed with the liquefied gas solvents for improved performance of the electrochemical device, such as pan, 2,2-fluoropropane, 1,1,1-trifluoropropane, 1,1,2-trifluoropropane, 1,2,2-trifluoropropane, fluoroethylene, cis-1,2-fluoroethylene, 1,1-fluoroethylene, 1-fluoropropylene, 2-propylene, chlorine, chloromethane, bromine, iodine, ammonia, methylamine, dimethylamine, trimethylamine, molecular oxygen, molecular nitrogen, carbon monoxide, carbon dioxide, sulfur dioxide, methyl vinyl ether, difluoroethylene, nitrous oxide, nitrogen dioxide, nitric oxide, carbon disulfide, hydrogen fluoride, hydrogen chloride, or any combination thereof. In some embodiments, the liquefied gas electrolyte comprises a single liquefied gas solvent or a combination of a liquefied gas solvent and one or more additives and / or one or more salts. These additives may be gases, liquids, or solids at standard room temperature of 293.15 K and at standard pressure (approximately 100 kPa). Additionally, any of the gaseous additives may be used as the primary solvent.

[0036] In an exemplary electrochemical device using a liquefied gas electrolyte composed of one or more liquefied gas components including any combination of one or more liquid components, one or more solid components, or one or more salt components, the electrodes are composed of any combination of two electrodes of intercalation type (e.g., graphite, carbon, activated carbon, vanadium oxide, lithium titanate, titanium disulfide, molybdenum disulfide, lithium iron phosphate, lithium cobalt phosphate, lithium nickel phosphate, lithium cobalt oxide, lithium nickel manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, carbon), or chemically reactive electrodes (e.g., containing chemicals such as sulfur, oxygen, carbon dioxide, nitrogen, nitrous oxide, sulfur dioxide, thionyl fluoride, thionyl fluoride chloride, sulfuryl fluoride, sulfuryl fluoride chloride), or metal electrodes (including lithium, sodium, magnesium, tin, aluminum, calcium, titanium, zinc metal, or metal alloys containing lithium, sodium, tin, magnesium, aluminum, calcium, titanium, zinc, or any combination thereof). These components may be combined with a variety of binder polymer components, including polyvinylidene fluoride, carboxymethyl cellulose, styrene butadiene rubber, or polytetrafluoroethylene, to maintain the structural integrity of the electrode.

[0037] In some embodiments, the additive is used in combination with a liquefied gas solvent and a lithium, sodium, zinc, calcium, magnesium, aluminum, or titanium based salt. Additionally, one or more liquefied gas solvent solutions or electrolytes may be combined with one or more salts, including lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetrachloroaluminate (LiAlCl4), lithium tetragallium aluminate, lithium bis(oxalato)borate (LiBOB), lithium hexafluorostannate, lithium difluoro(oxalato)borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium aluminum fluoride (LiAlF3), lithium nitrate (LiNO3), lithium chloroaluminate, lithium tetrafluoroborate (LiBF4), tetrafluoroborate (LiF5), tetrafluoroborate (LiF6), tetrafluoroborate (LiF5 ... Lithium tetrachloroaluminate, lithium difluorophosphate, lithium tetrafluoro(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, lithium borate, lithium oxoate, lithium thiocyanate, lithium tetrachlorogallate, lithium chloride, lithium bromide, lithium iodide, lithium carbonate, lithium fluoride, lithium oxide, lithium hydroxide, lithium nitride, lithium superoxide, lithium azide, lithium deltaate, dilithium squarate, lithium croconic acid dihydrate, dilithium rhodizonate, lithium oxalate, dilithium ketomalonate, lithium diketosuccinate, or any corresponding salt having a positively charged lithium cation replaced with sodium or magnesium or a combination thereof.Further useful salts include salts having a positively charged cation, such as tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, triethylmethylammonium, spiro-(1,1')-bipyrrolidinium, 1,1-dimethylpyrrolidinium, and 1,1-diethylpyrrolidinium, N,N-diethyl-N-methyl-N(2-methoxyethyl)ammonium, N,N-diethyl-N-methyl-N-propylammonium, N,N-dimethyl-N-ethyl-N-(3-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(4-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(5-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(6-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(7-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(8-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(9-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(10-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(11-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(12-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(13-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(14-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(15-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(16-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(17-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(18-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(19-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(21-methoxypropyl)ammonium, N,N-dimethyl-N-ethyl-N-(18-methoxypropyl) (pyr)ammonium, N,N-dimethyl-N-ethyl-N-benzylammonium, N,N-dimethyl-N-ethyl-N-phenylethylammonium, N-ethyl-N,N-dimethyl-N-(2-methoxyethyl)ammonium, N-tributyl-N-methylammonium, N-trimethyl-N-hexylammonium, N-trimethyl-N-butylammonium, N-trimethyl-N-propylammonium, 1,3-dimethylimidazolium, 1-(4-sulfobutyl)-3-methylimidazolium, 1-allyl-3H-imidazolium, 1-butyl H-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-octyl-3-methylimidazolium, 3-methyl-1-propylimidazolium, H-3-methylimidazolium, trihexyl(tetradecyl)phosphonium, N-butyl-N-methylpiperidinium, N-propyl-N-methylpiperidinium, 1-butyl-1-methylpyrrolidinium, 1-methyl-1-(2-methoxyethyl)pyrrolidinium, 1-methyl-1-(3-methoxypropyl)pyrrolidinium, 1-methyl- Included are 1-octylpyrrolidinium, 1-methyl-1-pentylpyrrolidinium, or N-methylpyrrolidinium, which are paired with negatively charged anions such as acetate, bis(fluorosulfonyl)imide, bis(oxalato)borate, bis(trifluoromethanesulfonyl)imide, bromide, chloride, dicyanamide, diethylphosphate, hexafluorophosphate, hydrogen sulfate, iodide, methanesulfonate, methylphosphonate, tetrachloroaluminate, tetrafluoroborate, and trifluoromethanesulfonate.

[0038] As discussed above, lowering the vapor pressure of the electrolyte simplifies the manufacturability of electrochemical devices by allowing for cell enclosures with thinner walls resulting in lower mass, volume and cost. For example, co-pending U.S. Patent Application No. 63 / 391,220, filed July 21, 2022, describes an apparatus for premixing an electrolyte mixture for subsequent distribution to an electrochemical device. FIG. 8 is taken from this application. A liquefied gas solvent having a vapor pressure of greater than 100 kPa at a temperature of 293.15 K is mixed with a suitable salt in a ratio of salt to solvent sufficient to reduce the vapor pressure of the electrolyte mixture to at least 90% of the vapor pressure of the pure liquefied gas solvent at a temperature of 293.15 K. This mixing can be done in a vessel 4, which is constructed to accommodate the pressure of the liquefied gas solvent. The apparatus shown in FIG. 8 also includes a vessel isolation valve 12, a liquefied gas electrolyte mixture 6 (including salt 5), and a temperature sensor 7 used to distribute the liquefied gas electrolyte mixture 6 to a secondary vessel 24. The secondary container 24 may be any suitable metal, ceramic, or plastic device capable of holding a liquefied gas-electrolyte mixture having a vapor pressure above atmospheric pressure of 100 kPa at a temperature of 293.15 K. Alternatively, if the container holds a liquefied gas-electrolyte mixture having a salt to solvent ratio sufficient to reduce the vapor pressure to less than 100 kPa at a temperature of 293.15 K, then the container 4 need not be robust enough to withstand high pressures. The secondary container 24 may be an electrochemical device such as a battery or a capacitor. Other filling devices are disclosed in co-pending U.S. Patent Application Serial No. 63 / 391,220, the entire contents of which are incorporated herein by reference.

[0039] Using the apparatus of FIG. 8, the secondary container 24 can be a housing with an anode and a cathode. The premixed mixture is then dispensed into the housing, allowing the anode and cathode to contact the mixture. The housing can then be sealed with electrical contacts connected to the anode and cathode accessible from the outside of the housing. If the electrolyte mixture is greater than 100 kPa at a temperature of 293.15 K, then the dispensing step should be performed at a pressure greater than 100 kPa, and the construction of the housing should be selected to hold the electrolyte mixture at greater than 100 kPa at a temperature of 293.15 K after the housing is sealed. However, to hold a high pressure pure liquefied gas solvent, or a liquefied gas electrolyte with a salt to salt ratio that has little, if any, vapor pressure drop, the housing does not need to be as robust, thus simplifying the manufacturability of the electrochemical device by allowing the housing of the cell to have thinner walls resulting in lower mass, volume and cost.

[0040] Alternatively, if the electrolyte mixture is below 100 kPa at a temperature of 293.15 K, then the dispensing step should be performed at sub-atmospheric pressure. In this latter case, since the electrolyte mixture is not under pressure, the housing does not need to be as robust, further simplifying manufacturability and reducing cost.

[0041] Similarly, although operations are depicted in the figures in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown, or sequentially, or to perform all of the operations shown, in order to achieve a desired result. Furthermore, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments. Only certain implementations and examples have been described, and other implementations, extensions and variations can be made based on what is described and illustrated in this patent document without departing from the scope and spirit of the invention.

[0042] Although this patent document contains many specificities, these should not be interpreted as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to certain embodiments of a particular invention. Certain features described in this patent document in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, features may be described above as acting in a certain combination, and one or more features from a claimed combination, even if initially claimed as such, may be removed from the combination in some cases, and the claimed combination may be subject to a subcombination or a variation of the subcombination.

Claims

1. A liquefied gas solvent having a vapor pressure of greater than 100 kPa at a temperature of 293.15 K, and salt An ionically conductive electrolyte mixture comprising: An ionically conductive electrolyte mixture, wherein the ratio of said salt to said solvent is sufficient to reduce the vapor pressure of said electrolyte mixture to at least 90% of the vapor pressure of a pure liquefied gas solvent at a temperature of 293.15K.

2. 2. The mixture of claim 1, wherein the ratio of said salt to said solvent ranges from about 3:1 to 1:

6.

3. 2. The mixture of claim 1, wherein the ratio of said salt to said solvent is sufficient to reduce the vapor pressure of said electrolyte mixture to less than 100 kPa at a temperature of 293.15 K.

4. 2. The mixture of claim 1, wherein the salt is comprised of LiTFSI, LiFSI, LiPF6, LiBOB, LiBF4, LiDFOB, LiNO3, or any combination thereof.

5. 2. The mixture of claim 1, wherein the liquefied gas solvent is comprised of a solvent having a carbonyl oxygen group.

6. 6. The mixture of claim 5, wherein the carbonyl oxygen group is in the form of formaldehyde, ethenone, carbonyl sulfide, carbon suboxide, or trifluoroacetyl fluoride.

7. 2. The mixture of claim 1, wherein the liquefied gas solvent is comprised of a solvent having an ether oxygen group.

8. 8. The mixture of claim 7, wherein the ether oxygen groups are in the form of dimethyl ether, ethyl methyl ether, methyl vinyl ether, desflurane, 1,1,2,2-tetrafluoro-1-(trifluoromethoxy)ethane, bis(difluoromethyl)ether, methyl pentafluoroethyl ether, perfluoroethyl methyl ether, or ethylene oxide.

9. 2. The mixture of claim 1, wherein the liquefied gas solvent is comprised of a solvent having an amine nitrogen group.

10. 10. The mixture of claim 9, wherein the amine nitrogen groups are in the form of ammonia, methylamine, dimethylamine, trimethylamine, tris(difluoroamine)fluoromethane, or ethylamine.

11. The liquefied gas solvent is fluoromethane, difluoromethane, trifluoromethane, fluoroethane, tetrafluoroethane, pentafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, pentafluoroethane, chloromethane, chloroethane, thionyl fluoride, thionyl fluoride chloride, phosphoryl fluoride, phosphoryl fluoride chloride, sulfuryl fluoride, sulfuryl fluoride chloride, 1-fluoropropane, 2-fluoropropane, 1,1- 2. The mixture of claim 1, further comprising difluoropropane, 1,2-difluoropropane, 2,2-fluoropropane, 1,1,1-trifluoropropane, 1,1,2-trifluoropropane, 1,2,2-trifluoropropane, fluoroethylene, cis-1,2-fluoroethylene, 1,1-fluoroethylene, 1-fluoropropylene, 2-propylene, chlorine, chloromethane, bromine, iodine, molecular oxygen, molecular nitrogen, carbon monoxide, carbon dioxide, sulfur dioxide, difluoroethylene, nitrous oxide, nitrogen dioxide, nitric oxide, carbon disulfide, hydrogen fluoride, hydrogen chloride, or any combination thereof.

12. The mixture according to claim 1 , an anode in contact with the mixture; a cathode in contact with the mixture; and A housing enclosing the mixture, the anode and the cathode.

2. An electrochemical device comprising:

13. 13. The electrochemical device of claim 12, wherein the cathode is selected from the group consisting of graphite, carbon, activated charcoal, vanadium oxide, and lithium titanate, titanium disulfide, molybdenum disulfide, lithium iron phosphate, lithium cobalt phosphate, lithium nickel phosphate, lithium cobalt oxide, lithium nickel manganese oxide, lithium nickel manganese cobalt oxide, and lithium nickel cobalt aluminum oxide.

14. 13. The electrochemical device of claim 12, wherein the anode is comprised of one or more of lithium metal, sodium metal, calcium metal, magnesium metal, aluminum metal, and zinc metal.

15. The electrochemical device of claim 12, wherein the mixture has a salt to solvent ratio in the range of about 3:1 to 1:

6.

16. 13. The electrochemical device of claim 12, wherein the salt to solvent ratio of the mixture is sufficient to reduce the vapor pressure of the electrolyte mixture to less than 100 kPa at a temperature of 293.15K.

17. 13. The electrochemical device of claim 12, wherein the mixture salt consists of LiTFSI, LiFSI, LiPF6, LiBOB, LiBF4, LiDFOB, LiNO3, or any combination thereof.

18. 13. The electrochemical device of claim 12, wherein the liquefied gas solvent of the mixture is comprised of a solvent having a carbonyl oxygen group.

19. 20. The electrochemical device of claim 18, wherein the carbonyl oxygen group is in the form of formaldehyde, ethenone, carbonyl sulfide, carbon suboxide, or trifluoroacetyl fluoride.

20. 13. The electrochemical device of claim 12, wherein the liquefied gas solvent of the mixture is comprised of a solvent having an ether oxygen group.

21. 21. The electrochemical device of claim 20, wherein the ether oxygen groups are in the form of dimethyl ether, ethyl methyl ether, methyl vinyl ether, or ethylene oxide, desflurane, 1,1,2,2-tetrafluoro-1-(trifluoromethoxy)ethane, bis(difluoromethyl)ether, methyl pentafluoroethyl ether, or perfluoroethyl methyl ether.

22. 13. The electrochemical device of claim 12, wherein the liquefied gas solvent of the mixture is comprised of a solvent having an amine nitrogen group.

23. 23. The electrochemical device of claim 22, wherein the amine nitrogen groups are in the form of ammonia, methylamine, dimethylamine, trimethylamine, tris(difluoroamine)fluoromethane, or ethylamine.

24. the liquefied gas solvent of the mixture is fluoromethane, difluoromethane, trifluoromethane, fluoroethane, tetrafluoroethane, pentafluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, pentafluoroethane, chloromethane, chloroethane, thionyl fluoride, thionyl fluoride chloride, phosphoryl fluoride, phosphoryl fluoride chloride, sulfuryl fluoride, sulfuryl fluoride chloride, 13. The electrochemical device of claim 12 further comprising 1-fluoropropane, 2-fluoropropane, 1,1-difluoropropane, 1,2-difluoropropane, 2,2-fluoropropane, 1,1,1-trifluoropropane, 1,1,2-trifluoropropane, 1,2,2-trifluoropropane, fluoroethylene, cis-1,2-fluoroethylene, 1,1-fluoroethylene, 1-fluoropropylene, 2-propylene, chlorine, chloromethane, bromine, iodine, oxygen molecules, nitrogen molecules, carbon monoxide, carbon dioxide, sulfur dioxide, and difluoro.

25. The electrochemical device of claim 12 , wherein the device is a capacitor or a battery.

26. 1. A method of constructing an electrochemical device, comprising: mixing in a vessel an electrolyte mixture comprised of a liquefied gas solvent having a vapor pressure of greater than 100 kPa at a temperature of 293.15 K and a salt, the ratio of said salt to said solvent being sufficient to reduce the vapor pressure of said electrolyte mixture to at least 90% of the vapor pressure of said pure liquefied gas solvent at a temperature of 293.15 K; Providing a housing having an anode and a cathode; dispensing the electrolyte mixture from the container into the housing in an amount sufficient to enable the anode and the cathode to contact the electrolyte mixture; sealing the housing.

27. 27. The method of claim 26, wherein the salt to solvent ratio of the electrolyte mixture is sufficient to reduce the vapor pressure of the electrolyte mixture to less than 100 kPa at a temperature of 293.15 K, and the dispensing step is performed at subatmospheric pressure.

28. 27. The method of claim 26, wherein the electrolyte mixture comprises a vapor pressure greater than 100 kPa at a temperature of 293.15 K and the dispensing step is performed at above atmospheric pressure.

29. 30. The method of claim 28, wherein the construction of the housing is selected to maintain the electrolyte mixture at a temperature of 293.15K above 100 kPa after the housing is sealed.

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