Ion-conducting electrolytes and energy storage devices

Abstract

This invention relates to electrolyte compositions and chemical formulations used in electrochemical energy devices such as batteries and electrochemical capacitors. Compositions and devices using methods of using these compositions are also provided. [Solution] An ion-conducting electrolyte comprising a mixture of a compressed gas solvent such as dimethyl ether and a salt, and a hydrocarbon solvent at a concentration sufficient to promote the solubility of the salt in the compressed gas solvent without causing phase separation, wherein the molar ratio of the hydrocarbon solvent to the compressed gas solvent is in the range of 10:90 to 90:10.

Description

[Technical Field]

[0001] 1.0 CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority as a non-provisional application from U.S. Application No. 63 / 195,592, filed on June 1, 2021, the entire contents of which are incorporated herein by reference.

[0002] This application also relates to the following applications and patents, the entire contents of each of which are incorporated herein by reference: U.S. Patent No. 10,608,284, issued on March 31, 2020; U.S. Patent No. 10,988,143, issued on May 4, 2021; U.S. Patent No. 10,784,532, issued on September 22, 2020; PCT / US19 / 032413, filed on May 15, 2019; PCT / US20 / 26086, filed on April 1, 2020; U.S. Patent No. 11,088,396, issued on August 10, 2021; U.S. Patent No. 11,049,668, issued on June 29, 2021; U.S. Patent No. 10,873,070, issued on December 22, 2020; U.S. Application No. 16 / 666,155, filed on October 28, 2019; U.S. Application No. 17 / 326,093, filed on May 20, 2021; U.S. Application No. 63 / 306,396, filed on February 3, 2022; and U.S. Application No. 63 / 328,480, filed on April 7, 2022.

[0003] 2.0 STATEMENT OF FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT This invention was made with government support under Grant No. 1831087 awarded by the National Science Foundation (NSF) of the United States. The United States Government has certain rights in this invention.

[0004] 3.0 FIELD OF THE INVENTION 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 using the compositions and methods of using the compositions are also provided. [Background Art]

[0005] 4.0 Background Electrochemical energy storage devices such as batteries and double-layer capacitors utilize ion-conducting electrolyte solutions to transport charge between the positive and negative electrodes. Typically, these electrolytes are liquid at standard room temperature (293.15 K) and standard pressure (approximately 1.01325 bar). Electrolyte solutions use mixtures of some amounts of solvent, co-solvent, salt, and additional additives for improved device performance. Often, there is a primary solvent used to solubilize salts and additional co-solvents to improve cell performance. For example, common electrolyte solvents may include ethylene carbonate for Li-ion battery cells, but the addition of dimethyl carbonate, ethylene carbonate, propylene carbonate, acetonitrile, fluoroethylene carbonate, and vinyl carbonate, among others, may be used to improve the conductivity of the electrolyte or the cycle life of the cell. Liquefied gas electrolytes utilize solvents and co-solvents that are gaseous at room temperature and room pressure, but may also be used as electrolyte solvents in the liquid phase. Identifying co-solvents that enhance performance is crucial for improving the electrochemical performance of liquefied gas electrolytes. [Overview of the Initiative]

[0006] 5.0 Overview Embodiments of this disclosure relate to chemical formulations, electrolyte compositions, electrochemical devices using the same, and methods of using the same. Some disclosed embodiments relate to novel formulations for electrolytes comprising a liquefied gaseous solvent.

[0007] One embodiment relates to a rechargeable electrochemical device comprising: an ion-conducting electrolyte comprising one or more liquefied gaseous solvents, one or more salts, and one or more additives; a housing structured to encapsulate the ion-conducting electrolyte and provide a pressurized state to the liquefied gaseous solvent; and at least two conductive electrodes in contact with the ion-conducting electrolyte. The one or more solvents or co-solvents when combined may be collectively referred to as the liquefied gaseous solvent. The one or more salts when combined may be collectively referred to as the salt. The one or more additives when combined may be collectively referred to as the additive. The solvent and salt may be collectively referred to as the electrolyte when combined. The solvent, salt, and additive may be collectively referred to as the electrolyte when combined.

[0008] In some embodiments, the liquefied gas solvent can be subjected to a compressive pressure equal to or greater than its vapor pressure at the temperature at which the compressive pressure is applied, thereby retaining the liquefied gas solvent in the liquid phase. In some embodiments, the liquefied gas solvent has a vapor pressure above 100 kPa atmospheric pressure—i.e., standard pressure and temperature—at room temperature of 293.15 K.

[0009] In some embodiments, the liquefied gas solvent is dimethyl ether, methyl ethyl ether, 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 chloride fluoride, phosphoryl fluoride, phosphoryl chloride fluoride, sulfuryl fluoride, sulfuryl chloride fluoride, 1-fluoropropane, 2-fluoropropane, 1,1-difluoropropane, 1,2-difluoropropane, 2,2-fluoropropane, 1,1,1- The material comprises one or more materials selected from the group consisting of 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, nitrogen oxide, carbon disulfide, hydrogen fluoride, hydrogen chloride, methane, ethane, propane, n-butane, iso-butane, cyclopropane, cyclopropane, ethene, propene, butene, cyclobutene, acetylene, isomers thereof, and combinations thereof. In some embodiments, the liquefied gas solvent comprises fluoromethane, carbon dioxide, and n-butane. In some embodiments, the liquefied gas solvent comprises fluoromethane, difluoromethane, and propane. In some embodiments, the liquefied gas solvent includes fluoromethane, difluoromethane, carbon dioxide, and iso-butane. In some embodiments, the liquefied gas solvent includes difluoromethane, carbon dioxide, and propene. In some embodiments, the liquefied gas solvent includes fluoromethane, dimethyl ether, carbon dioxide, and methane. In some embodiments, the liquefied gas solvent includes dimethyl ether and n-butane.

[0010] In some embodiments, the solvent components, such as pentane, hexane, heptane, octane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, and their isomers, may be liquid at room temperature and atmospheric pressure.

[0011] Another embodiment relates to a rechargeable lithium battery. The rechargeable lithium battery may include an ion-conducting electrolyte. The ion-conducting electrolyte may include a liquefied gaseous solvent. The ion-conducting electrolyte may include one or more salts. In some embodiments, the ion-conducting electrolyte may further include one or more gases, liquids, or solid additives selected from the group consisting of acyclic carbonates, cyclic carbonates, acyclic ethers, cyclic ethers, nitriles, phosphates, and combinations thereof. In some embodiments, the rechargeable lithium battery may also include two conduction electrodes and a housing enclosing the ion-conducting electrolyte. In some embodiments, the liquefied gaseous solvent has a vapor pressure above atmospheric pressure of 100 kPa at room temperature of 293.15 K. In some such embodiments, the liquefied gaseous solvent may be subject to a compressive pressure equal to or greater than the vapor pressure of the liquefied gaseous solvent at the temperature at which the compressive pressure is applied, thereby retaining the liquefied gaseous solvent in a liquid phase.

[0012] In an exemplary electrochemical device using a liquefied gas electrolyte composed of one or more liquefied gas components and any combination of one or more liquid components, one or more solid components, or one or more salt components, the electrodes are two intercalation type electrodes made of 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, etc. The electrodes consist of any combination of chemical reaction electrodes having chemical substances such as sulfur, oxygen, carbon dioxide, nitrogen, nitrous oxide, sulfur dioxide, thionyl fluoride, thionyl fluoride chloride, sulfuryl fluoride, or sulfuryl fluoride chloride; electrostatic electrodes using high surface area conductive materials such as activated carbon, carbon black, carbon nanotubes, or graphene; or metal electrodes having lithium, sodium, magnesium, tin, aluminum, calcium, titanium zinc metal, or metal alloys containing lithium, sodium, tin, magnesium, aluminum, calcium, titanium, or zinc, or any combination thereof. These components may be combined with various binder polymer components, including polyvinylidene fluoride, carboxymethylcellulose, styrene-butadiene rubber, or polytetrafluoroethylene, to maintain the structural integrity of the electrodes.

[0013] In some embodiments, the additive is used in combination with a liquefied gaseous solvent and a salt of lithium, sodium, zinc, calcium, magnesium, aluminum, or titanium. Furthermore, one or more liquefied gaseous solvent solutions or electrolytes include 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), and lithium tetrachloroaluminate. It may be combined with one or more salts comprising a positively charged lithium cation substituted with sodium or magnesium and any corresponding salt, or any combination thereof.Furthermore, useful salts include those with positively charged cations, such as tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, triethylmethylammonium, ammonium, 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-benzylammonium, N,N-dimethyl-N-ethyl-N-phenylethylammonium, and 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-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimida Zolium, 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-1-octylpyrrolidinium, 1-methyl-1- This includes thylpyrrolidinium or N-methylpyrrolidinium paired with negatively charged anions such as acetate, bis(fluorosulfonyl)imide, bis(oxalate)borate, bis(trifluoromethanesulfonyl)imide, bromide, chloride, dicyanamide, diethyl phosphate, hexafluorophosphate, bisulfate, iodide, methanesulfonate, methylphosphonate, tetrachloroaluminate, tetrafluoroborate, and trifluoromethanesulfonate.Alternative or additional embodiments described herein provide electrolyte compositions comprising one or more of the features described herein or elsewhere.

[0014] A safe electrolyte comprising a liquefied gaseous solvent that transitions from a liquid state to a gaseous state ("degassed") at a pressure of 100 kPa and a temperature of 293.15 K is further disclosed. The first mixture is formed from the first electrolyte component (one or more solvents) mixed with a second electrolyte component (one or more hydrocarbon cosolvents). The addition of the second electrolyte component (1) reduces the vapor pressure of the first mixture by at least 10% compared to the vapor pressure of the first component alone when measured at 293.15 K; and (2) results in a vapor pressure of the first mixture above 100 kPa at a temperature of 293.15 K. The addition of the second electrolyte component may also reduce the global warming potential (GWP) of the first mixture by at least 10% compared to the GWP of the first component alone. A safe liquefied gaseous electrolyte is formed by mixing a third electrolyte component (one or more salts) with the first mixture. This safe liquefied gaseous electrolyte may then be used to manufacture electrochemical energy storage devices.

[0015] Alternative or additional embodiments described herein provide methods of using an electrolyte composition or device, comprising one or more of the features described herein or elsewhere. [Brief explanation of the drawing]

[0016] 6.0 Brief Description of the Drawings [Figure 1] This figure compares the pressures of various liquefied gas electrolytes: the pressure when electrolyte 1: 1.0M LiTFSI and 2.0M trimethyl phosphate are added to 90 moles of fluoromethane and 10 moles of carbon dioxide (solid line), and the pressure when electrolyte 2: 1.0M LiTFSI and 2.0M triethyl phosphate are added to 40 moles of fluoromethane, 50 moles of propane, and 10 moles of carbon dioxide (dashed line). [Figure 2]This figure compares the pressures of various liquefied gas electrolytes: the pressure when electrolyte 1: 1.0M LiTFSI and 2.0M trimethyl phosphate are added to 90 moles of difluoromethane and 10 moles of carbon dioxide (solid line), and the pressure when electrolyte 2: 1.0M LiTFSI and 2.0M triethyl phosphate are added to 40 moles of difluoromethane, 50 moles of propane, and 10 moles of carbon dioxide (dashed line). [Figure 3] This figure shows the performance of a battery coin cell using a lithium metal anode, a stainless steel counter electrode, and an electrolyte consisting of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 75 moles of fluoromethane, 15 moles of propane, and 10 moles of carbon dioxide. [Figure 4] This figure shows the performance of a battery coin cell using a lithium metal anode, a stainless steel counter electrode, and an electrolyte consisting of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 90 moles of fluoromethane and 10 moles of carbon dioxide. [Figure 5] This figure shows the electrolyte conductivity of various liquefied gaseous electrolytes: Electrolyte 1: 1.0M LiTFSI and 2.0M triethyl phosphate added to 40 moles of fluoromethane, 50 moles of propane, and 10 moles of carbon dioxide; Electrolyte 2: 1.0M LiTFSI and 2.0M triethyl phosphate added to 40 moles of difluoromethane, 50 moles of propane, and 10 moles of carbon dioxide; Electrolyte 3: 1.0M LiTFSI and 2.0M fluoroethylene carbonate added to 45 moles of difluoromethane, 45 moles of fluoromethane, and 10 moles of carbon dioxide. [Figure 6] This figure shows the performance of a battery coin cell using a lithium metal anode, a graphite cathode, and an electrolyte consisting of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 40 moles of fluoromethane, 50 moles of propane, and 10 moles of carbon dioxide. [Figure 7]This figure shows the performance of a battery coin cell using a lithium metal anode, a graphite cathode, and an electrolyte consisting of 1.0 M LiTFSI and 1.0 M trimethyl phosphate added to 45 moles of difluoromethane, 45 moles of fluoromethane, and 10 moles of carbon dioxide. [Figure 8] This figure shows the performance of a battery coin cell using a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte consisting of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 90 moles of fluoromethane and 10 moles of carbon dioxide. [Figure 9] This figure shows the performance of a battery coin cell using a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte consisting of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 80 moles of fluoromethane, 10 moles of iso-butane, and 10 moles of carbon dioxide. [Figure 10] This figure shows the performance of a battery coin cell using a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte consisting of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 80 moles of fluoromethane, 10 moles of n-butane, and 10 moles of carbon dioxide. [Figure 11] This figure shows the performance of a battery coin cell using a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte consisting of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 70 moles of difluoromethane, 20 moles of n-butane, and 10 moles of carbon dioxide. [Figure 12]It is a diagram showing the performance of a battery coin cell using a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte composed of 1.0 M LiTFSI and 2.0 M triethyl phosphate added to 40 parts by mole of fluoromethane, 50 parts by mole of propane, and 10 parts by mole of carbon dioxide. [Figure 13] It is a diagram showing the performance of a battery coin cell using a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte composed of 1.0 M LiTFSI and 2.0 M triethyl phosphate added to 40 parts by mole of fluoromethane, 50 parts by mole of propene, and 10 parts by mole of carbon dioxide. [Figure 14] It is a diagram showing the performance of a battery coin cell using a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte composed of 1.0 M LiTFSI and 2.0 M triethyl phosphate added to 35 parts by mole of difluoromethane, 60 parts by mole of propane, and 5 parts by mole of carbon dioxide. [Figure 15] It is a diagram showing the performance of two battery coin cells using a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and various electrolytes: electrolyte 1 is 1.0 M LiTFSI and 2.0 M trimethyl phosphate (TMP) added to 90 parts by mole of fluoromethane and 10 parts by mole of carbon dioxide, electrolyte 2 is 1.0 M LiTFSI and 2.0 M triethyl phosphate added to 35 parts by mole of difluoromethane, 60 parts by mole of propane, and 5 parts by mole of carbon dioxide. [Figure 16] It is a diagram showing the vapor pressure of three types of electrolytes containing any one of 0.0, 0.1, 0.5, 1.0, or 1.5 M LiTFSI salt, and further demonstrates that salt concentration does not cause a change in the vapor pressure of the electrolyte, or any change is sufficiently within the uncertainty of measurement. [Figure 17] It is a diagram presenting the voltage and temperature data of a 2Ah cell when the cell is heated. [Figure 18]This figure shows the voltage and temperature data of a 2Ah cell when it is overcharged. [Figure 19] This figure shows the voltage and temperature data of a 2Ah cell when it crashed. [Figure 20A] This figure illustrates a method for constructing an electrochemical energy storage device using a safe liquefied gas electrolyte. [Figure 20B] This figure presents an alternative method for constructing electrochemical energy storage devices using safe liquefied gas electrolytes. [Modes for carrying out the invention]

[0017] 7.0 Detailed explanation This specification refers to 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. The invention is described in conjunction with these specific embodiments, but it will be understood that they do not limit the invention to the embodiments described or illustrated. In contrast, they are intended to include alternatives, modifications, and equivalents that may fall within the spirit and scope of the invention as defined by the accompanying claims.

[0018] In the following description, numerous specific details are given in order to provide a complete understanding of the present invention. Certain exemplary embodiments of the present invention may be realized without some or all of these specific details. In other cases, process operations well known to those skilled in the art are not detailed so as not to unnecessarily obscure the present invention. Various techniques and mechanisms of the present invention will sometimes be described in the singular for clarity. However, it should be noted that some embodiments, unless otherwise described, involve numerous repetitions of a technique or a number of mechanisms. Similarly, various steps of the methods shown and described herein may not necessarily be performed in the order shown, or not at all, in certain embodiments. Thus, some implementations of the methods discussed herein may include more or fewer steps than those illustrated or described. Furthermore, the techniques and mechanisms of the present invention will sometimes describe connections, relationships, or communications between two or more entities. It should be noted that connections or relationships between entities do not necessarily mean direct, unimpeded connections, since various other entities or processes may exist or arise between any two entities. As a result, the connections shown do not necessarily mean direct, uninterrupted connections unless otherwise stated.

[0019] Electrochemical energy storage devices such as batteries and double-layer capacitors utilize ion-conducting electrolyte solutions to transport charge between the positive and negative electrodes. Typically, these electrolytes are liquid at standard room temperature (293.15 K) and standard pressure (approximately 1.01325 bar). For improved device performance, the electrolyte solution may use a mixture of some amount of solvent, co-solvent, one or more salts, and one or more additional additives. Often, there is a primary solvent used to solubilize salts and additional co-solvents that improve cell performance. For example, common electrolyte solvents may include ethylene carbonate for Li-ion battery cells, but the addition of dimethyl carbonate, ethylene carbonate, propylene carbonate, acetonitrile, fluoroethylene carbonate, and vinyl carbonate, in particular, may be used to improve the conductivity of the electrolyte or the cycle life of the cell. Liquefied gaseous electrolytes utilize solvents and co-solvents that may be used as liquid-phase electrolyte solvents, even though they are gaseous at room temperature and room pressure, by lowering the temperature or by holding the solvent under its own vapor pressure. Identifying performance-enhancing cosolvents is crucial for improving the electrochemical performance of liquefied gas electrolytes.

[0020] Liquefied gaseous electrolytes may use fluoromethane or difluoromethane as the primary solvent to solubilize salts in electrochemical devices such as lithium batteries or electrochemical capacitors. However, these solvents typically have high vapor pressures and high global warming potentials (GWPs). For example, at room temperature of 293.15 K, the vapor pressures of fluoromethane and difluoromethane are approximately 493 and 214 psi, respectively. The GWPs (global warming potentials, a subset of carbon dioxide global warming potentials) of fluoromethane and difluoromethane are approximately 92 and 675, respectively. It is considered beneficial to operate electrochemical device cells at lower pressures, lower GWPs, or both. Lower pressures are considered to reduce the mechanical packaging load by allowing the use of thinner metal housings to accommodate the cells and house the liquefied gaseous electrolytes. Lower GWPs are considered to be more environmentally friendly.

[0021] An ideally liquefied gaseous electrolyte would utilize a cosolvent that is considered chemically beneficial to cell performance, in addition to reducing pressure, lowering the GWP, or both. Often, a cosolvent beneficial for the formation of a solid electrolyte interface (SEI) on either the anode or cathode is identified. However, a chemically inert cosolvent is also considered beneficial because it reduces intracellular chemical reactions between the electrolyte and electrode, which can degrade cell performance.

[0022] Due to its high reactivity, lithium metal is difficult to use as an anode in high-energy lithium battery cells. While lithium metal has a high capacity-to-weight ratio, it suffers from a high reaction rate with the electrolyte. During cell cycling, the SEI layer on the surface of the lithium metal can crack, exposing new lithium metal that reacts with the electrolyte, reducing cell efficiency and cycle life. To increase cell efficiency and cycle life, it is considered beneficial to use an electrolyte with a lower reactivity to lithium metal. Similar to lithium batteries, sodium, zinc, magnesium, aluminum, and potassium, or their alloys, may all be used as electrodes in batteries and are expected to benefit from less reactive electrolyte solvents.

[0023] Some chemically inert cosolvents may include hydrocarbon solvents. Hydrocarbon solvents have very low electrochemical reactivity and are stable. These hydrocarbon solvents may include methane, ethane, propane, n-butane, iso-butane, cyclopropane, cyclopropane, ethene, propene, butene, cyclobutene, cyclobutene, acetylene, pentane, hexane, heptane, octane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, these isomers, and combinations thereof. In some embodiments, the liquefied gas solvent includes fluoromethane, carbon dioxide, and n-butane. In some embodiments, the liquefied gas solvent includes fluoromethane, difluoromethane, and propane. In some embodiments, the liquefied gas solvent includes fluoromethane, difluoromethane, carbon dioxide, and iso-butane. In some embodiments, the liquefied gas solvent includes difluoromethane, carbon dioxide, and propene. In some embodiments, the liquefied gas solvent includes fluoromethane, dimethyl ether, carbon dioxide, and methane. In some embodiments, the liquefied gaseous solvent includes dimethyl ether and n-butane.

[0024] Due to their low chemical reactivity, highly reactive alkalis or alkali metals such as sodium and lithium metal are often transported in mineral oil, which is a hydrocarbon solvent or a mixture of long-chain hydrocarbon solvents. Other highly reactive compounds such as butyllithium are also stored in hydrocarbon solvents such as hexane.

[0025] The hydrocarbon solvents that can be used in the liquefied gas electrolyte may include saturated or unsaturated hydrocarbons. These may include alkanes, alkenes, or alkylenes. These may further include gaseous or non-gasic hydrocarbons at standard room temperature and standard pressure (approximately 1.01325 bar) at 293.15 K.

[0026] The use of hydrocarbon solvents in liquefied gaseous electrolytes can improve the properties of the electrolyte, such as lower vapor pressure, lower GWP, and higher chemical stability. This is because many hydrocarbon liquefied gaseous solvents have lower vapor pressures than other liquefied gaseous solvents (e.g., fluoromethane, carbon dioxide). Furthermore, hydrocarbon solvents have near-zero GWP, which can substantially reduce the GWP of the entire electrolyte. Finally, adding hydrocarbon solvents to an electrolyte helps improve the chemical stability of the overall electrolyte solution by reducing the amount of more chemically active species in the electrolyte.

[0027] Reducing the pressure of a liquefied gas electrolyte can be beneficial from a mechanical design perspective. Electrolytes with excessively high vapor pressure may require thicker walls in the cell housing to withstand the pressure, as these thicker walls provide added strength to the housing. The cell housing will require thicker walls to ensure a good seal and no leaks throughout the cell's lifespan. Thicker walls are less desirable features, as they add volume, mass, and increase the cell's cost. Alternatively, stronger metals such as stainless steel or titanium could be used with thinner walls, but this would increase the cell's cost. Thus, reducing the vapor pressure of an electrolyte can have beneficial properties. Less stringent requirements for the mechanical cell housing can be achieved by reducing the vapor pressure of a liquefied gas electrolyte having a vapor pressure of approximately 100 kPa, or more preferably between 100 kPa and 100 MPa, or more preferably 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 3, 4, 5, 6, 7, 8, 9, 10 MPa at a room temperature of 293.15 K.

[0028] Having a pressurized electrolyte system has been found to be beneficial for electrochemical devices for several reasons. In standard manufacturing with liquid electrolytes, the cell is first placed under vacuum, then the liquid electrolyte is injected into the cell, and then it is left for several hours to allow all electrode and separator surfaces of the cell to be completely wetted. Often, the cell undergoes the first electrolyte injection step, followed by a waiting period for wetting with the electrolyte, and then a second electrolyte injection step to ensure complete wettability. Until complete wettability occurs, the cell is not ready to be charged. Furthermore, cells that are not completely wetted are a major cause of scrap in the manufacturing process, requiring higher cell costs. With a pressurized liquefied gaseous electrolyte, the cell is wetted quickly due to the high pressure of the electrolyte penetrating all surfaces of the electrodes and separators. This wetting process occurs in seconds, as opposed to several hours, reducing manufacturing time and costs. Furthermore, this allows for higher reliability in completely wetted cells, reduces scrap rates, and therefore lowers the overall cost of cell manufacturing. The wetting process can be increased by using a pressurized electrolyte having a vapor pressure of approximately 100 kPa, or more preferably between 100 kPa and 100 MPa, or more preferably approximately 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 3, 4, 5, 6, 7, 8, 9, 10 MPa at room temperature of 293.15 K.

[0029] Another beneficial property of having a pressurized electrolyte is that it reduces the risk of safety hazards from physical or electrical cell misuse. In typical Li-ion battery cells, thermal runaway reactions are commonly observed under physical or electrical misuse such as overheating, overcharging, crashes, nailing, or short-circuit events. This is due to exothermic reactions within the cell that can be induced at relatively low temperatures, for example, around +100°C. This “thermal runaway temperature” triggers these additional exothermic reactions, subsequently causing the cell to ignite and explode, posing serious safety and health concerns. Furthermore, heat generated from one cell propagates to adjacent cells, inducing thermal runaway in those cells as well, creating heat propagation events throughout the battery pack. Flammable liquid electrolytes are generally a crucial component that drives these thermal runaway reactions. An explosive reaction can occur when the cell heats up to the electrolyte's self-combustion temperature. Additionally, a short-circuited cell requires both electrical and ionic pathways between the anode and cathode. The electrolyte retains ions within the cell and therefore contributes to the cell short-circuit.

[0030] In contrast, pressurized liquefied gas electrolyte systems have a safety advantage: under physical or electrical abuse, the cell may heat up to a predetermined discharge temperature, at which point the cell discharges the pressurized liquefied gas solvent or liquefied gas electrolyte into the atmosphere, leaving a "dry cell" free of any flammable or ion-conducting electrolytes. Once discharged, the cell can operate fail-safe without triggering any thermal runaway reactions. For example, under overheating conditions, the cell may heat up to +240°C. Before reaching +200°C, the cell may cross the discharge temperature, at which point the vapor pressure of the liquefied gas electrolyte in the cell reaches a pressure high enough to trigger a discharge designed and fabricated on the cell, releasing both pressure and electrolyte material. An ideal discharge temperature is lower than the thermal runaway temperature, e.g., +100°C, for example, e.g., +80°C. Therefore, flammable electrolytes are discharged from the cell before any thermal runaway reactions occur, allowing the cell to operate fail-safe even at temperatures as high as +240°C. Similarly, cells can be overcharged and heat up during overcharge events. When the cell reaches its discharge temperature, the liquefied gaseous electrolyte will be released from the cell, and the cell will operate in fail-safe mode. Similarly, during a short-circuit event, the cell can heat up rapidly due to the high discharge current. When the cell heats up to its discharge temperature, the liquefied gaseous electrolyte may be released from the cell, and the cell can operate in fail-safe mode instead of proceeding to thermal runaway. Cells using liquefied gaseous electrolytes can also operate in fail-safe mode without temperature-induced discharge. For example, during a crash or projection-through event, the cell housing may rupture and release the pressurized liquefied gaseous electrolyte from the cell through the ruptured housing into the atmosphere, while maintaining the cell temperature at approximately 293.15K, close to room temperature. Conventional liquid electrolytes used in cells have a high probability that the cell may short-circuit during a crash or projection-through event and overheat, causing the cell to thermal runaway. In liquefied gaseous electrolytes (including those with a vapor pressure exceeding 100 kPa at room temperature of approximately 293.15 K), discharge or degassing from the electrolyte to the atmosphere through a ruptured cell housing will cause the cell to fail-safe, regardless of any possible short-circuit events.

[0031] In all scenarios, it is highly desirable to have rapid discharge of all liquefied gaseous electrolytes from the cell under physical or electrical abusive conditions to minimize the possibility of any thermal runaway events. A higher vapor pressure electrolyte is desirable to reduce the time required to discharge the liquefied gaseous electrolyte from the cell. If the vapor pressure of the electrolyte is too low, it may not be discharged from the cell quickly enough to prevent thermal runaway or to prevent the electrolyte from reaching self-ignition and causing a fire hazard. Furthermore, after discharge, the cell temperature may decrease due to the heat of evaporation caused by the liquefied gaseous phase changing from liquid to gas. If the cell temperature drops sufficiently, it may lower the vapor pressure enough to stop the discharge of the electrolyte from the cell, potentially creating further hazards. Therefore, it is desirable that the liquefied gaseous electrolyte has a vapor pressure sufficient to discharge rapidly from the cell. Therefore, the vapor pressure of the electrolyte may be approximately 100 kPa, or more preferably between 100 kPa and 100 MPa, at room temperature of 293.15 K, or more preferably approximately 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 3, 4, 5, 6, 7, 8, 9, or 10 MPa. It should be understood that the cell may discharge the entire contents of the liquefied gas electrolyte containing any gaseous, liquid, or solid components, or only the liquefied gas solvent and liquid components, or only the liquefied gas solvent components, or any combination of partial components from the cell. Even partial discharge of the electrolyte can result in fail-safe operation of the cell under physical or electrical abuse conditions.

[0032] Both reduced and increased vapor pressure electrolytes have their advantages. Reduced vapor pressure liquefied gas electrolytes can lower mechanical housing requirements, enabling cells with lower mass, lower volume, and lower cost. Higher vapor pressure liquefied gas electrolytes improve cell wettability during manufacturing, reducing manufacturing time, cost, and scrap rate, as well as improving cell safety under physical or electrical abuse such as overheating, overcharging, crashes, nailing, or short-circuit events. Thus, through careful experimentation, liquefied gas electrolytes can be optimized to have an ideal vapor pressure that is neither too high nor too low for optimized cell performance. This experiment involves dimethyl ether, methyl ethyl ether, 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 chloride fluoride, phosphoryl fluoride, phosphoryl chloride fluoride, sulfuryl fluoride, sulfuryl chloride fluoride, 1-fluoropropane, 2-fluoropropane, 1,1-difluoropropane, 1,2-difluoropropane, 2,2-fluorine The process may begin with liquefied gas solvents such as chloropropane, 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, nitrogen oxide, carbon disulfide, hydrogen fluoride, hydrogen, and their isomers and combinations thereof, as well as the addition of hydrocarbon solvents to lower or increase the vapor pressure in order to optimize cell performance.The addition of hydrocarbon solvents can modify the vapor pressure of the liquefied gas electrolyte to achieve a vapor pressure of approximately 100 kPa, or more preferably between 100 kPa and 100 MPa, or more preferably about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 3, 4, 5, 6, 7, 8, 9, and 10 MPa at room temperature of 293.15 K. This can be equivalent to an increase or decrease in vapor pressure of 0.1% to 99.9% at any temperature of the liquefied gas electrolyte from 1 K to 1000 K. More preferably, the increase or decrease in the vapor pressure of the liquefied electrolyte may be about 0.1, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 59, 60, 61, 65, 70, 75, 80, 90, 95, 99, or 99.9% at room temperature of 293.15 K.

[0033] Hydrocarbons are ideal materials to use because they provide improved chemical stability to electrolytes and are relatively inexpensive. However, it should be noted that the addition of any hydrocarbon to a liquefied gas electrolyte will always impart some flammability to the liquefied gas electrolyte system. This is often due to the generally low flash points of hydrocarbons, resulting in an even lower flash point (the lowest temperature at which the material's vapor can ignite) of the electrolyte, which is less desirable. Even with the lower flash point resulting from the addition of these hydrocarbons to liquefied gas electrolytes, the improved characteristics discussed above, such as improved safety, manufacturability, performance, and lower GWP, provide a highly desirable configuration in today's industry.

[0034] The mass ratio of the hydrocarbon solvent to the liquefied gaseous electrolyte solvent may be anywhere between 0.01 percent and 99.99 percent by mass or molar ratio when compared to the remainder of the electrolyte. The ratios of the solvent, hydrocarbon co-solvent, salt, and one or more additives are determined only through considerable experimentation to increase solubility, minimize phase separation, maximize conductivity, and maximize cell performance. The addition of a hydrocarbon solvent may also benefit the electrolyte, through a lower vapor pressure or lower GWP, while maintaining the same cell performance as an electrolyte without the hydrocarbon solvent.

[0035] The addition of nonpolar solvents such as hydrocarbons to electrolytes can reduce the overall solubility of the electrolyte. Several studies have been conducted to determine which hydrocarbons can be added to what percentage of the electrolyte to optimize the solubility of salts. Phase separation (there is clear separation in the high-density and low-density regions of the fluid), vapor pressure, and other parameters such as GWP are recorded in Tables 1-1 and 1-2. Stainless steel cells with glass windows containing various electrolytes were assembled, and the solubility of salts in various electrolyte formulations was studied. Tables 1-1 and 1-2 below present the solubility observed for various electrolyte formulations at 293.15 K. As expected, due to the nonpolar nature of hydrocarbon solvents, lithium salts have problems with solubilization, even when the additive is increased. However, the solubility of the salt is increased when used as a co-solvent in fluoromethane, difluoromethane, or mixtures containing both fluoromethane and difluoromethane. Phase separation can occur in various combinations of liquefied gaseous electrolytes, exhibiting poor miscibility of the salt, additive, and solvent system, as has already been described. These solubility experiments highlight the importance of careful control of the salt's solvation structure in creating electrolyte mixtures with high salt solubility and the absence of phase separation. In this way, the ratio of hydrocarbon solvents can be adjusted, demonstrating that it ranges from 0.01 to 99.99 percent of the solvent mixture. Tables 1-1 and 1-2 use 1 M salt as a standard for the purpose of a fixed salt concentration, but higher or even lower concentrations were carefully explored, and salt solubility from 0.001 to 5 M was observed with varying results. However, it was shown that in the absence of salt concentration, the salt is soluble in any solvent consisting of only one or more hydrocarbon solvents. Furthermore, in solvent mixtures consisting only of one or more hydrocarbon solvents and liquid additives to improve salt solubility, the absence of salt solubility or strong phase separation was consistently observed. Furthermore, in solvent mixtures consisting only of one or more hydrocarbon solvents and salt, with or without liquid additives to improve salt solubility, no decrease in vapor pressure was consistently observed compared to a pure solvent consisting of only one or more hydrocarbon solvents. [Table 1-1] [Table 1-2]

[0036] Due to its high reactivity, lithium metal is difficult to use as an anode in high-energy lithium battery cells. To demonstrate the advantages of including chemically inert cosolvents such as hydrocarbon solvents, Li metal was stored in various solvent and electrolyte mixtures for 24 hours and visually inspected for harmful side reactions. Similar to liquid hydrocarbon analogs (i.e., hexane), lithium metal can be stored in liquefied gaseous hydrocarbon solvents and liquefied gaseous electrolytes containing hydrocarbons as cosolvents without any harmful side reactions. Table 2 shows the observations of lithium metal after immersion in various solvents and electrolytes at 293.15 K for 24 hours. [Table 2]

[0037] In an exemplary electrochemical device using a liquefied gas electrolyte comprising one or more liquefied gas components together with any combination of one or more liquid components, one or more solid components, or one or more salt components, the electrodes consist of any combination of two intercalation electrodes such as graphite, carbon, activated carbon, 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, or lithium nickel cobalt aluminum oxide; or chemical reaction electrodes having chemicals such as sulfur, oxygen, carbon dioxide, nitrogen, nitrous oxide, sulfur dioxide, thionyl fluoride, thionyl chloride fluoride, sulfuryl fluoride, or sulfuryl chloride fluoride; or metal electrodes having lithium, sodium, magnesium, tin, aluminum, zinc metal, or a metal alloy containing lithium, sodium, tin, magnesium, aluminum, or zinc, or any combination thereof. These components may be combined with various binder polymer components, including polyvinylidene fluoride, carboxymethylcellulose, styrene-butadiene rubber, or polytetrafluoroethylene, to maintain the structural integrity of the electrodes.

[0038] Furthermore, one or more liquefied gas solvent solutions or electrolytes include 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), and lithium tetrachloroaluminate. It may be combined with one or more salts comprising any corresponding salt of lithium difluorophosphate, lithium tetrafluoro(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, lithium borate, lithium oxalate, 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 squalate, lithium croconate dihydrate, dilithium rhozonate, lithium oxalate, dilithium ketomalonate, lithium diketosuccinate, or any corresponding salt of a positively charged lithium cation substituted with sodium or magnesium, or any combination thereof.Furthermore, useful salts include those with positively charged cations, such as tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, triethylmethylammonium, ammonium, 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-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-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimida Zolium, 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-1-octylpyrrolidinium, 1-methyl-1- This includes thylpyrrolidinium or N-methylpyrrolidinium paired with negatively charged anions such as acetate, bis(fluorosulfonyl)imide, bis(oxalate)borate, bis(trifluoromethanesulfonyl)imide, bromide, chloride, dicyanamide, diethyl phosphate, hexafluorophosphate, bisulfate, iodide, methanesulfonate, methylphosphonate, tetrachloroaluminate, tetrafluoroborate, and trifluoromethanesulfonate. [Examples]

[0039] Example 1 Replacing a portion of the fluoromethane in a battery cell with a hydrocarbon cosolvent such as propane is thought to have beneficial effects on the cell, such as lower vapor pressure and GWP, as shown in Figure 1 (fluoromethane) and Figure 2 (difluoromethane). Pressure measurements were performed for various electrolyte formulations. Electrolytes with a hydrocarbon solvent (propane) were shown to have lower vapor pressure and lower GWP than fluoromethane without a hydrocarbon cosolvent. In particular, the GWP of the electrolyte mixture was reduced by 54% compared to fluoromethane without a hydrocarbon cosolvent. Furthermore, the vapor pressure of the electrolyte mixture was reduced by 40% (at 293.15 K) and 45% (at 313.15 K) compared to fluoromethane without a hydrocarbon cosolvent. This is shown in Figure 1. Similarly, the GWP of the electrolyte mixture was reduced by 44% compared to difluoromethane without a hydrocarbon cosolvent. Furthermore, the vapor pressure of the electrolyte mixture was reduced by 15% (at 293.15 K) and 28% (at 313.15 K) compared to difluoromethane without a hydrocarbon cosolvent. This is shown in Figure 2.

[0040] GWP is measured as CO2 equivalent value per mass (CO2eq / kg). Adding one or more hydrocarbon solvents with low or zero GWP to a first electrolyte mixture with a higher GWP will reduce the excessive GWP of the final mixture by diluting the GWP beyond the larger mass of the final electrolyte. The reduction of the GWP effect can be finely tuned by adjusting the amount of hydrocarbon cosolvent or by changing the type of hydrocarbon cosolvent used. Other hydrocarbon cosolvents that may be used include: methane, ethane, propane, n-butane, iso-butane, cyclopropane, cyclopropane, ethene, propene, butene, cyclobutane, cyclobutene, acetylene, pentane, hexane, heptane, octane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, these isomers, and combinations thereof. Preferably, the amount and type of hydrocarbon solvent used will reduce the GWP of the mixture (i.e., the solvent with the cosolvent added) by at least 10% compared to the solvent without the hydrocarbon cosolvent.

[0041] Improvements in reducing vapor pressure are increased across the entire operating temperature range of electrochemical energy storage devices and significantly reduce the pressure requirements of the cell housing. Thicker cell walls are less desirable because they increase volume, mass, and cell cost. Alternatively, stronger metals such as stainless steel or titanium can be used with thinner walls, but this increases the cost of the cell. Therefore, as shown in Figures 1 and 2, reducing the vapor pressure of the electrolyte across the entire operating temperature range has beneficial properties.

[0042] Example 2 The use of propane instead of fluoromethane improves the stability of lithium metal in the electrolyte solution, as shown in Table 2. This is further demonstrated in lithium metal plating stripping tests performed to determine the relative stability of electrolytes with lithium metal. A battery coin cell consisting of a lithium metal anode and a stainless steel counter electrode was constructed and used to test lithium metal plating and stripping. Using the cell, a reading of 4.0 mAh / cm² was obtained. 2Lithium metal is applied to a stainless steel working electrode at a rate of 0.5 mA / cm². 2 The plating was done with a current of 0.5 mAh / cm². 2 The lithium metal was stripped away, and the current flow rate was 0.5 mA / cm². 2 The cells were plated for 50 cycles at a current of 1.0V. Finally, the remaining lithium metal was stripped to a high voltage cutoff of 1.0V to determine the average lithium plating and stripping cycle efficiency. These test results are shown in Figure 3 (with hydrocarbon solvent) and Figure 4 (without hydrocarbon solvent), showing that the addition of hydrocarbon solvent improves the Coulomb efficiency (CE) of the cells. Minimal overpotential growth and a Coulomb efficiency of approximately 99% are demonstrated in Figure 3, in contrast to a lower Coulomb efficiency of 97% in Figure 4 when no hydrocarbon component is used in the electrolyte. This indicates minimal dendritic growth and favorable solid electrolyte interface passivation products through reduced reactivity of the electrolyte with the lithium metal anode due to the use of hydrocarbon solvent.

[0043] Example 3 Electrolyte conductivity measurements were performed on various electrolytes, both with and without hydrocarbon solvents. Electrolyte solutions containing hydrocarbon cosolvents exhibit electrolyte conductivity similar to that of fluoromethane and difluoromethane as the main electrolytes, as shown in Figure 5. The slightly lower conductivity due to hydrocarbon solvents is still considered acceptable for functional devices, particularly those with lower pressures and lower GWPs.

[0044] Example 4 Battery coin cells composed of a lithium metal anode, graphite cathode, and various electrolytes are compared in Figures 6 and 7. The cells were cycled for 5 cycles at a C / 10 rate to demonstrate the ability of electrolytes to form a stable solid electrolyte interface with a graphite anode. Figure 6 shows the performance of cells made with hydrocarbon-based electrolytes, while Figure 7 shows the performance of cells made with electrolytes without hydrocarbon solvents. This indicates that the addition of hydrocarbons can reduce the vapor pressure and GWP of the electrolyte without sacrificing cell performance.

[0045] Example 5 A battery coin cell was constructed using a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte consisting of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 90 molar parts of fluoromethane and 10 molar parts of carbon dioxide. Its performance is shown in Figure 8. This electrolyte does not contain hydrocarbon solvents.

[0046] Example 6 The battery coin cell consisted of a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte composed of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 80 molar parts fluoromethane, 10 molar parts iso-butane, and 10 molar parts carbon dioxide. This electrolyte solution had a GWP of 93 and a pressure of 486 psi at 293.15 K. The cell was cyclic up to 4.2 V for 5 cycles at various rates of C / 10, C / 5, C / 3, C / 2, 1C, and 2C. Cell performance is shown in Figure 9. This cell exhibited similar performance to a similar cell without a hydrocarbon solvent shown in Figure 8.

[0047] Example 8 The battery coin cell consisted of a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte composed of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 80 molar parts fluoromethane, 10 molar parts n-butane, and 10 molar parts carbon dioxide. This electrolyte solution had a GWP of 93 and a pressure of 484 psi at 293.15 K. The cell was cycled up to 4.2 V for 5 cycles at various rates of C / 10, C / 5, C / 3, C / 2, 1C, and 2C. Cell performance is shown in Figure 10. This cell exhibits similar performance to a similar cell without a hydrocarbon solvent shown in Figure 8.

[0048] Example 9 The battery coin cell consisted of a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte composed of 1.0 M LiTFSI and 2.0 M trimethyl phosphate added to 70 molar parts difluoromethane, 20 molar parts n-butane, and 10 molar parts carbon dioxide. This electrolyte solution had a GWP of 475 and a pressure of 246 psi at 293.15 K. The cell was cyclic up to 4.2 V for 5 cycles at various rates of C / 10, C / 5, C / 3, C / 2, 1C, and 2C. Cell performance is shown in Figure 11. This cell exhibited similar performance to a similar cell without a hydrocarbon solvent shown in Figure 8.

[0049] Example 10 The battery coin cell consisted of a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte composed of 1.0 M LiTFSI and 2.0 M triethyl phosphate added to 40 molar parts fluoromethane, 50 molar parts propane, and 10 molar parts carbon dioxide. This electrolyte solution had a GWP of 48 and a pressure of 345 psi at 293.15 K. The cell was cyclic up to 4.2 V for 5 cycles at various rates of C / 10, C / 5, C / 3, C / 2, 1C, and 2C. Cell performance is shown in Figure 12. This cell exhibited similar performance to a similar cell without a hydrocarbon solvent shown in Figure 8.

[0050] Example 11 The battery coin cell consisted of a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte composed of 1.0 M LiTFSI and 2.0 M triethyl phosphate added to 40 molar parts fluoromethane, 50 molar parts propene, and 10 molar parts carbon dioxide. This electrolyte solution had a GWP of 47 and a pressure of 357 psi at 293.15 K. The cell was cycled up to 4.2 V for 5 cycles at various rates of C / 10, C / 5, C / 3, C / 2, 1C, and 2C. Cell performance is shown in Figure 13. This cell exhibited similar performance to a similar cell without a hydrocarbon solvent shown in Figure 8.

[0051] Example 12 The battery coin cell consisted of a lithium metal anode, a lithium-nickel-manganese oxide (NMC622) cathode, and an electrolyte composed of 1.0 M LiTFSI and 2.0 M triethyl phosphate added to 35 molar parts difluoromethane, 60 molar parts propane, and 5 molar parts carbon dioxide. This electrolyte solution had a GWP of 239 and a pressure of 195 psi at 293.15 K. The cell was cycled up to 4.2 V for 5 cycles at various rates of C / 10, C / 5, C / 3, C / 2, 1C, and 2C. Cell performance is shown in Figure 14. This cell exhibited similar performance to a similar cell without a hydrocarbon solvent shown in Figure 8. Subsequently, the cell was cycled at the 1C rate to measure life degradation, which is shown in Figure 15. Life well over 1000 cycles was demonstrated for the electrolyte with a hydrocarbon solvent (Electrolyte 2), which was an improvement over the electrolyte without a hydrocarbon solvent (Electrolyte 1).

[0052] Example 13 The vapor pressures of several liquefied gaseous electrolytes were measured with varying amounts of salt. Three solvent systems were used: Solvent 1 (45 mol / L difluoromethane, 45 mol / L fluoromethane, and 10 mol / L carbon dioxide), Solvent 2 (31.5 mol / L difluoromethane, 31.5 mol / L fluoromethane, 7 mol / L carbon dioxide, and 30 mol / L iso-butane), and Solvent 3 (31.5 mol / L difluoromethane, 31.5 mol / L fluoromethane, 7 mol / L carbon dioxide, and 30 mol / L acetylene). Except for the pure solvent with 0.0 M salt, each electrolyte contained LiTFSI and trimethyl phosphate in a 1:2 molar ratio. Each electrolyte contained either 0.0, 0.1, 0.5, 1.0, or 1.5 M LiTFSI salt. The vapor pressure curves for each electrolyte are shown in Figure 16. It is observed that salt concentrations indicate no change in the vapor pressure of the electrolyte, or that the change is well within the range of measurement uncertainty. Furthermore, it is demonstrated that the vapor pressure of a hydrocarbon-free (solvent 1) liquefied gas electrolyte can be adjusted to be higher (solvent 3) or lower (solvent 2) by adding various hydrocarbon additives to optimize the performance of the electrolyte. This is also consistent with the findings shown in Figures 1 and 2.

[0053] Example 14 The cell was constructed with a graphite anode and an NMC622 cathode and tested under a thermal lamp. The temperature was increased at a rate of 5°C per minute. The cell voltage and temperature data are shown in Figure 17. It can be seen that at a temperature of approximately +90°C, the pressure of the liquefied gas electrolyte reaches the cell's discharge pressure, the electrolyte is discharged into the atmosphere, and the voltage immediately drops to zero. After the cell is discharged and the voltage drops to zero, the cell continues to heat at the same rate up to a temperature of +240°C without any reaction being observed, indicating that the cell can operate in fail-safe mode. This remarkable result is in contrast to typical cells, which may exhibit thermal runaway at lower temperatures of around +100°C and may reach high temperatures of around +800°C during the thermal runaway reaction.

[0054] Example 15 A 2Ah cell, consisting of a graphite anode, an NMC622 cathode, and a liquefied gas electrolyte, was tested in an overcharge test. The cell was charged at a rate of 2Amp, and the cell voltage and temperature were observed; the data are shown in Figure 18. As the cell reached an overcharged state of 5.4V (the nominal voltage of the cell was 4.2V), the cell overheated, reaching a temperature of +60°C. At this point, the vapor pressure of the liquefied gas electrolyte was high enough to open the cell's vent, and the liquefied gas electrolyte was rapidly released into the atmosphere, causing the cell to fail-safe. It was also noted that the vent opened at a lower temperature than expected due to the generation of oxygen from the cathode during overcharging. This increased oxygen content increased the pressure of the liquefied gas electrolyte, causing it to be released from the cell at a lower temperature, thus improving the safety of the cell before a dangerous thermal runaway reaction or explosion could occur due to the oxygen-containing electrolyte. These results are in stark contrast to conventional lithium-ion cells, where overcharging tests can lead to thermal runaway reactions, cell explosions, and other hazardous situations.

[0055] Example 16 A 2Ah cell was constructed with a graphite anode, an NMC622 cathode, and a liquefied gas electrolyte. The cell was tested under a crash test while maintaining a full voltage of 4.2V. The cell was crushed at a rate of 1mm per minute towards its center using an 18mm diameter cylindrical impactor. Cell temperature and voltage were observed, and the data are shown in Figure 19. Approximately 9 minutes into the test, the cell was observed to have shattered, and the liquefied gas electrolyte had escaped from the cell. A short circuit within the cell was also observed, causing a small rise in cell temperature. However, the electrolyte was discharged quickly enough to prevent any thermal runaway events, resulting in fail-safe operation of the cell. This is in stark contrast to conventional cells containing liquid electrolytes that exhibit thermal runaway during crash tests due to short circuits.

[0056] Configuration of an electrochemical energy storage device Figure 20A shows a method for constructing an electrochemical energy storage device with a safe liquefied gas electrolyte that will be degassed at 100 kPa at a temperature of 293.15 K. In step 20-1, a first mixture is formed by mixing a first electrolyte component (one or more solvents) with a second electrolyte component (one or more hydrocarbon cosolvents). The addition of the second electrolyte component (1) reduces the vapor pressure of the first mixture by at least 10% compared to the vapor pressure of the first electrolyte component alone when measured at 293.15 K; and (2) results in a vapor pressure of the first mixture above 100 kPa at a temperature of 293.15 K. The second electrolyte component can also reduce the global warming potential (GWP) of the first mixture by at least 10% compared to the GWP of the first component alone. In step 20-2, a safe liquefied gas electrolyte is formed by mixing a third electrolyte component (one or more salts) with the first mixture. Next, this safe liquefied gaseous electrolyte is added to the cell housing having an anode and cathode in step 20-3, so that the anode and cathode come into contact with the safe liquefied gaseous electrolyte. Alternatively, as shown in Figure 20B, the third electrolyte component (salt) may be added to the cell housing first, and then the mixture 1 is added to the cell housing (step 20-3B) and mixed with the third electrolyte component (salt) to form a safe liquefied gaseous electrolyte (step 20-2B). Finally, the cell housing is sealed in step 20-4.

[0057] In an exemplary electrochemical device constructed by this method, the electrodes consist of two electrodes made of carbon, such as graphite, graphene, graphene oxide, activated carbon, or silicon, 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, or lithium nickel cobalt aluminum oxide; or a chemical reaction electrode having a chemical substance such as sulfur, oxygen, carbon dioxide, nitrogen, sulfur dioxide, thionyl fluoride, thionyl chloride fluoride, sulfuryl fluoride, or sulfuryl chloride fluoride; or a metallic electrode having lithium, sodium, zinc, aluminum, magnesium, calcium metal, or an alloy of these metals, or any combination thereof. The electrodes may further contain various binder polymer components, including polyvinylidene fluoride, carboxymethylcellulose, styrene-butadiene rubber, or polytetrafluoroethylene, to maintain the structural integrity of the electrodes. This method can be used to manufacture batteries or capacitors.

[0058] Exemplary embodiments and applications of the present invention are described herein and included above, and are illustrated in the illustrations of the included embodiments. However, the present invention is not limited to these exemplary embodiments and applications, or to the methods by which the exemplary embodiments and applications operate or are described herein. In fact, as will be apparent to those skilled in the art, many variations and modifications of the exemplary embodiments are possible. The present invention may include any device, structure, method, or functionality, insofar as the resulting device, system, or method is contained within the scope of one of the claims permitted by the Patent Office pursuant to this or any related patent application.

Claims

1. An ion-conducting electrolyte comprising the following, The mixture comprises a compressed gas solvent and a salt, wherein the compressed gas solvent is dimethyl ether, methyl ethyl ether, 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 chloride fluoride, phosphoryl fluoride, phosphoryl chloride fluoride, sulfuryl fluoride, sulfuryl chloride fluoride, 1-fluoropropane Selected from the group consisting of 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, ammonia, methylamine, dimethylamine, trimethylamine, molecular oxygen, molecular nitrogen, carbon monoxide, carbon dioxide, sulfur dioxide, methyl vinyl ether, difluoroethylene, nitrous oxide, nitrogen dioxide, nitrogen oxides, carbon disulfide, hydrogen fluoride, hydrogen, and their isomers, Furthermore, the solution includes a hydrocarbon solvent at a concentration sufficient to promote the solubility of the salt in the compressed gas solvent without causing phase separation. An ion-conducting electrolyte in which the molar ratio of the hydrocarbon solvent to the compressed gas solvent is in the range of 10:90 to 90:

10.

2. The ion-conducting electrolyte according to claim 1, wherein the hydrocarbon solvent reduces the global warming potential (GWP) of the ion-conducting electrolyte by at least 10% compared to the GWP of the compressed gas solvent alone, and causes the pressure of the mixture of the ion-conducting electrolyte and the hydrocarbon solvent to reach 100 kPa or more at a temperature of 293.15 k.

3. The ion-conducting electrolyte according to claim 1, wherein the hydrocarbon solvent reduces the vapor pressure of the ion-conducting electrolyte by at least 20% compared to the vapor pressure of the compressed gas solvent alone when measured at 313.15 K.

4. The ion-conducting electrolyte according to claim 1, further comprising an additional component selected from the group consisting of linear ethers, cyclic ethers, linear carbonates, cyclic carbonates, nitriles, phosphates, or combinations thereof.

5. The ion-conducting electrolyte according to claim 1, wherein the hydrocarbon solvent is an alkane, an alkene, or an alkylene.

6. The ion-conducting electrolyte according to claim 1, wherein the hydrocarbon solvent is selected from the group consisting of methane, ethane, propane, n-butane, isobutane, cyclopropane, cyclopropane, ethene, propene, butene, cyclobutane, cyclobutene, acetylene, pentane, hexane, heptane, octane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, isomers thereof, and combinations thereof.

7. The ion-conducting electrolyte according to claim 1, A housing that encloses the ion-conducting electrolyte under pressurized conditions and maintains the compressed gas solvent at a pressure higher than 100 kPa at room temperature of 293.15 K, An energy storage device comprising two electrodes in contact with the ion-conducting electrolyte.

8. The energy storage device according to claim 7, wherein the hydrocarbon solvent reduces the global warming potential (GWP) of the ion-conducting electrolyte by at least 10% compared to the GWP of the compressed gas solvent alone, and causes the pressure of the mixture of the ion-conducting electrolyte and the hydrocarbon solvent to reach 100 kPa or more at a temperature of 293.15 k.

9. The energy storage device according to claim 7, wherein the hydrocarbon solvent reduces the vapor pressure of the ion-conducting electrolyte by at least 20% compared to the vapor pressure of the compressed gas solvent alone when measured at 313.15 K.

10. The energy storage device according to claim 7, further comprising an additional component added to the ion-conducting electrolyte, wherein the additional component is selected from the group consisting of linear ethers, cyclic ethers, linear carbonates, cyclic carbonates, nitriles, phosphates, or combinations thereof.

11. The energy storage device according to claim 7, wherein the hydrocarbon solvent is an alkane, an alkene, or an alkylene.

12. The energy storage device according to claim 7, wherein the hydrocarbon solvent is selected from the group consisting of methane, ethane, propane, n-butane, isobutane, cyclopropane, cyclopropane, ethene, propene, butene, cyclobutane, cyclobutene, acetylene, pentane, hexane, heptane, octane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, isomers thereof, and combinations thereof.

13. The energy storage device according to claim 7, wherein the electrode is made of a material selected from the group consisting of graphite, graphene, graphene oxide, carbon, activated carbon, silicon, 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. The energy storage device according to claim 7, wherein the energy storage device is a battery.

15. The energy storage device according to claim 7, wherein the energy storage device is a capacitor.

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