Electrolyte chemical formulations for energy storage devices

Abstract

Disclosed is an ion conductive electrolyte comprising a liquefied gas solvent that exhibits a low global warming potential (GWP) and low flammability while also creating a good solid electrolyte interface in an electrochemical device to maintain high performance and cycle life. The ion conductive electrolyte includes a multi-component solvent mixture having a low GWP solvent and a non-low GWP solvent. The total GWP of the multi-component solvent mixture is at least 50% lower than the GWP of the non-low GWP solvent alone.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Application 63 / 450745, filed March 8, 2023, the entire contents of which are incorporated herein by reference.

[0003] This application also relates to the following applications and patents, each of which is incorporated herein by reference in its entirety: US10,608,284, granted March 31, 2020; US10,998,143, granted May 4, 2021; US10,784,532, granted September 22, 2020; US11,088,396, granted August 10, 2021; US10,873,070, granted December 22, 2020; US11,342,615, granted May 24, 2022; PCT / US20 / 26086, filed April 1, 2020; PCT / US22 / 31594, filed May 31, 2022; PCT / US23 / 11864, filed January 30, 2023; 20 PCT / US23 / 17720 filed on April 6, 2023; PCT / US23 / 28104 filed on July 19, 2023; PCT / US23 / 28105 filed on July 19, 2023; PCT / US23 / 35766 filed on October 24, 2023; PCT / US24 / 16784 filed on February 21, 2023; U.S. Application 63 / 418703 filed on October 24, 2022; U.S. Application 63 / 461252 filed on April 22, 2023; U.S. Application 63 / 461387 filed on April 24, 2023; U.S. Application 63 / 470174 filed on May 31, 2023; and U.S. Application 63 / 534213 filed on August 22, 2023. Technical Field

[0004] This invention relates to chemical formulations of electrolytes for use in energy storage devices. Background Technology

[0005] The electrolyte in lithium-ion batteries and related technologies typically consists of a flammable liquid solvent. Liquid electrolytes generally limit the performance of battery cells in terms of operating temperature, power, energy, cycle life, and safety.

[0006] Another type of electrolyte is the liquefied gas electrolyte, in which the main solvent is typically in the gas phase at standard temperatures and pressures, but can be liquefied at moderate pressures and mixed with salts to form a conductive electrolyte. Liquefied gas electrolytes can be used in energy storage devices such as batteries or capacitors to provide superior temperature, power, energy, and / or safety performance.

[0007] The liquefied gas electrolyte can be composed of solvents with moderate to high global warming potential (GWP), which is an index that measures the contribution of a molecule to global warming through radiative forcing, normalized to carbon dioxide. For example, if the GWP of carbon dioxide is defined as 1, then the GWP of fluoromethane is 92 and the GWP of difluoromethane is 675. It would be beneficial to use liquefied gas solvents with low or zero effective GWP while retaining other beneficial properties (e.g. high polarity, chemical stability, non-toxicity, and low cost) desired of an ideal electrolyte solvent. Furthermore, research has shown that some high GWP and flammable liquefied gas solvents can form optimal solid electrolyte interfaces (SEI) that enable effective operation of the battery.

[0008] It would be beneficial to find other liquefied gas solvents with low GWP and low flammability while producing a favorable solid electrolyte interface in battery devices to maintain high performance and cycle life. SUMMARY

[0009] Disclosed herein is an ionically conductive electrolyte comprising a salt and a mixture of liquefied gas solvents having a vapor pressure greater than 100 kPa at a temperature of 293.15 K. The mixture is composed of a first solvent component and a second solvent component. The GWP of the first solvent component can be less than 10, while the GWP of the second solvent component can be greater than 80. By mixing such a multi-component solvent comprising a low GWP component and a non-low GWP component, the overall GWP of the ionically conductive electrolyte can be reduced. The relative amounts of the first solvent component and the second solvent component can be preferably selected to reduce the GWP of the mixture of liquefied gas solvents to less than 10% of the GWP of the second solvent component, more preferably less than 50% of the GWP of the second solvent component, and even more preferably less than 70% of the GWP of the second solvent component.

[0010] Examples of the first solvent component can include: hydrochloroolefins, hydrochlorofluoroolefins, perhaloolefins and perfluoroolefins, 1,1-dichloroethene, vinyl chloride, trichloroethene, dichloroethene, chlorofluoroethene, (Z)-1-chloro-2,3,3,3-tetrafluoropropene, trans-1-chloro-3,3,3-trifluoropropene, and isomers thereof.

[0011] Examples of the second solvent component include: 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 chlorofluoride, phosphoryl fluoride, phosphoryl chlorofluoride, sulfonyl fluoride, sulfonyl chlorofluoride, 1-fluoropropane, 2-fluoropropane, 1,1-difluoropropane, 1,2-difluoropropane, 2,2-difluoropropane, 1,1,1-trifluoropropane, 1,1,2-trifluoropropane, 1,2,2-trifluoropropane, fluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, 1-fluoropropylene, propylene, chlorine, chloromethane, bromine, iodine, ammonia, methylamine, dimethylamine, trimethylamine, molecular oxygen, molecular nitrogen, carbon monoxide, carbon dioxide, sulfur dioxide, methyl vinyl ether, dinitrogen oxide, nitrogen dioxide, nitric oxide, carbon disulfide, hydrogen fluoride, hydrogen chloride, methane, ethane, propane, n-butane, isobutane, cyclopropane, ethylene, propylene, butylene, cyclobutene, acetylene, isomers thereof, and combinations thereof.

[0012] The salt can be based on lithium, sodium, zinc, calcium, magnesium, aluminum, or titanium.

[0013] An electrochemical device can be constructed with an ionically conductive electrolyte. The device can include a housing, an anode, a cathode, and a separator layer in contact with the ionically conductive electrolyte.

[0014] Other aspects, alternatives, and variations thereon, which are obvious to those skilled in the art, are also disclosed herein and are expressly contemplated as part of this application. The application is set forth only in the claims as issued by the Patent Office, the following description of certain embodiments being in no way limiting, defining, or otherwise establishing legal boundaries for the scope of legal protection. BRIEF DESCRIPTION OF DRAWINGS

[0015] The application can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating exemplary aspects of the present application. In different views and / or embodiments, the same reference numerals designate corresponding parts throughout the several views. Additionally, various features of different disclosed embodiments can be combined into additional embodiments, which are also part of the present disclosure. It will be appreciated that certain components and / or details may

[0016] Figure 1 Molecular structures of olefin molecules having 2, 3, or 4 carbons and hydrogen, chlorine, and / or fluorine as the atomic constituents of the molecular structure are shown.

[0017] Figure 2is a plot of density functional theory calculations of the ionization potential and electron affinity of the molecule (calculated to theoretical level).

[0018] Figure 3 is a plot of density functional theory calculations of the binding energy of the molecule to a lithium cation (calculated to theoretical level).

[0019] Figure 4A and Figure 4B is a plot of the capacity retention and rate testing of a graphite anode half-cell using an electrolyte consisting of 1 M LiTFSI, 2 M FEC in MeF:ClM:CO2 at 45:45:10.

[0020] Figure 5A is a plot of the capacity retention of a 2.7 Ah cell comprising a graphite anode and NMC811 cathode with a liquified gas electrolyte consisting of 1.0 M LiFSI, 2.0 M DMC in DFE:FM:CO2:TFP at 35:35:10:20 (molar ratio).

[0021] Figure 5B is a plot of the impedance growth of a 2.7 Ah cell comprising a graphite anode and NMC811 cathode with a liquified gas electrolyte consisting of 1.0 M LiFSI, 2.0 M DMC in DFE:FM:CO2:TFP at 35:35:10:20 (molar ratio).

[0022] Figure 5C is a plot of the coulombic efficiency of a 2.7 Ah cell comprising a graphite anode and NMC811 cathode with a liquified gas electrolyte consisting of 1.0 M LiFSI, 2.0 M DMC in DFE:FM:CO2:TFP at 35:35:10:20 (molar ratio).

[0023] Figure 6 is a schematic showing an electrochemical device assembly with integrated electrolyte. DETAILED DESCRIPTION

[0024] Reference is made herein to some 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 application has been described in connection with these specific embodiments, it will be understood that it is not intended to limit the application to the described or illustrated embodiments. On the contrary, it is intended to cover alternatives, modifications, and equivalents, which can be included within the spirit and scope of the application as defined by the appended claims.

[0025] In the following description, for purposes of the reader's understanding, numerous specific details are set forth to provide a thorough understanding of the present application. Specific exemplary embodiments of the present application can be implemented without one or more of the specific details or with other methods. In other instances, well-known operations or structures are not described in detail in order to avoid obscuring the present application. For the sake of clarity, the various techniques and mechanisms of the present application are sometimes described in singular form for purposes of brevity. It should be noted, however, that some embodiments encompass multiple iterations of a technique or multiple mechanisms unless noted otherwise. Similarly, the various steps of the methods shown and described herein are not necessarily performed in the order indicated unless noted otherwise. Thus, some implementations of the methods described herein can include more or fewer steps than those shown or described. In addition, the techniques and mechanisms of the present application are sometimes described in terms of connections, relationships or communications between two or more entities. It should be noted that connections or relationships between entities are not necessarily direct, unimpeded, or unmediated by other entities or processes unless noted otherwise. Thus, indicated connections do not necessarily imply direct, unimpeded connections unless noted otherwise.

[0026] The following list of example features corresponds to the figures, for ease of reference, where like reference numbers indicate corresponding features throughout the specification and figures:

[0027] Electrochemical device 5

[0028] Positive / negative electrode 10

[0029] Separator 15

[0030] Negative / positive electrode 20

[0031] Positive electrode terminal 25

[0032] Negative electrode terminal 30

[0033] Housing 35

[0034] Electrolyte 40

[0035] It would be beneficial to use a liquefied gas solvent with a low or zero global warming potential (GWP < 10) while retaining other desirable properties of an ideal solvent such as high polarity, chemical stability, non-toxicity, low cost, and low flammability, and the ability to form a solid electrolyte interface on the electrodes with optimal performance. Mixing a medium or high GWP solvent with a low or zero GWP solvent would reduce the overall GWP of the entire solvent composition. However, not all chemicals possess the ideal properties required to make a high performance electrolyte.

[0036] While there are many zero or low GWP gaseous solvents, not all have a high enough polarity to maintain effective charge separation of the conducting salt in the electrolyte mixture to maintain high electrolyte conductivity or to avoid phase separation in the electrolyte mixture. Examples of such low polarity low GWP gaseous solvents include hydrocarbons such as methane, ethane, propane, and butane.

[0037] Furthermore, many gaseous solvents do not have the ideal properties or chemical composition to form the ideal SEI layer, thus necessitating the continued use of high GWP solvents in the electrolyte mixture, which can also be costly, flammable, and exhibit other undesirable properties.

[0038] Examples of low or zero GWP solvents that have beneficial charge separation properties, increase electrolyte conductivity, limit phase separation, and provide a good SEI layer include 3,3,3-trifluoropropene, 2,3,3,3-tetrafluoropropene, trans-1,3,3,3-tetrafluoropropene, trans-1,1,1,4,4,4-hexafluoro-2-butene, cis-1,1,1,4,4,4-hexafluoro-2-butene, 1,1-difluoroethylene, 1,2-difluoroethylene, 1,1-dichloroethylene, vinyl chloride, vinyl fluoride, hexafluoropropene, hexafluorobutadiene, trichloroethylene, dichloroethylene, chlorofluoroethylene, (Z)-1-chloro-2,3,3,3-tetrafluoropropene, trans-1-chloro-3,3,3-trifluoropropene, 3,3,4,4,4-pentafluoro-1-butene, and isomers thereof.

[0039] Studies have shown that mixtures of these low GWP solvents can reduce the GWP of electrolyte formulations that otherwise have a high (or not low) GWP (GWP > 80). This will improve the environmental impact of the overall mixture. Table 1 lists several examples. Using difluoromethane as the solvent, the GWP is as high as 677 per kg, while using a mixture of difluoromethane: 1,1-difluoroethylene (1:3) can reduce its GWP to 90 per kg, a reduction of about 85% over difluoromethane alone. As another example, the GWP of fluoromethane alone is 116, but when mixed with 2,3,3,3-tetrafluoropropene in a 1:1 molar ratio, the GWP is reduced by more than 75% to 27. Preferably, the low GWP solvent component will reduce the total GWP of the liquefied gas solvent by at least 10%, more preferably 50%, and even more preferably 70% over the GWP of the other solvent components in the mixture. Other benefits also include lower vapor pressure, lower cost, longer cycle life, and improved binding energy with electrolyte cations.

[0040] Table 1

[0041]

[0042] These solvents belong to one of several families of related compounds, including hydrofluoroolefins (HFOs), hydrochloroolefins (HCOs), hydrochlorofluoroolefins (HCFOs), perfluoroolefins (PFOs), or perchloroolefins (PCOs), which are unsaturated organic compounds composed of hydrogen, carbon, fluorine, and / or chlorine. The use of these hydrofluoroolefins, hydrochloroolefins, and hydrochlorofluoroolefins is disclosed herein.

[0043] and / or perfluoroolefins as components of liquefied gas electrolytes. These solvents can exhibit beneficial properties within the interior of a battery cell, and can be gaseous (vapor pressure greater than 100 kPa at a temperature of 293.15 K) or liquid (vapor pressure less than or equal to 100 kPa at a temperature of 293.15 K) at standard conditions.

[0044] Figure 1 Further compounds are shown that can be beneficial to electrolyte and electrochemical cell performance, with the general molecular structure having an ethylene, propylene, or butadiene structure, with H, F, or CI atoms, denoted by R1-R8 in the structure.

[0045] These hydrofluoroolefins, hydrochloroolefins, hydrochlorofluoroolefins, perchloroolefins, or perfluoroolefins can be combined with other liquefied gas solvents to form complete solvent mixtures, and when combined with various salts and additives, can form complete liquefied gas electrolytes.

[0046] Examples of other liquefied gas solvents that can be combined with these components include 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 chlorofluoride, phosphorofluoride, phosphorochlorofluoride, thiofluoride, thiochlorofluoride, 1-fluoropropane, 2-fluoropropane, 1,1-difluoropropane, 1,2-difluoropropane, 2,2-difluoropropane, 1,1,1-trifluoropropane, 1,1,2-trifluoropropane, 1,2,2-trifluoropropane, fluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, 1-fluoropropylene, propylene, chlorine, chloromethane, bromine, iodine, ammonia, methylamine, dimethylamine, trimethylamine, molecular oxygen, molecular nitrogen, carbon monoxide, carbon dioxide, sulfur dioxide, methyl vinyl ether, dinitrogen monoxide, nitrogen dioxide, nitric oxide, carbon disulfide, hydrogen fluoride, hydrogen chloride, methane, ethane, propane, n-butane, isobutane, cyclopropane, ethylene, propylene, butylene, cyclobutene, acetylene, isomers thereof, and combinations thereof.

[0047] In some embodiments, lithium, sodium, zinc, calcium, magnesium, aluminum, or titanium based salts are used. Additionally, electrolytes or solvent solutions containing one or more liquefied gas solvents can 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 tetragallate aluminate, lithium bis(oxalato)borate (LiBOB), lithium hexafluorostannate (LiSnF4), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium aluminum fluoride (LiAlF3), lithium nitrate (LiNO3), lithium trifluoromethanesulfonate, lithium tetrafluoroborate (LiBF4), lithium difluorophosphate, lithium tetrafluoro(oxalato)borate, 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 deltate, lithium disquarate, lithium clathrate, lithium ketocarboxylate, lithium rosolic acid, lithium ketomalonate, lithium dinitrile, or any corresponding salt of sodium or magnesium cation substituted lithium cation, or any combination thereof.Other useful salts include those in which the positively charged cation is tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, triethylmethylammonium, spiro-(l,l') -pyrrolidinium, 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-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-1-octylpyrrolidinium, 1-methyl-1-pentylpyrrolidinium, or N-methylpyrrolidinium and the negatively charged anion is acetate, bis(fluorosulfonyl)imide, bis(oxalato)borate, bis(trifluoromethylsulfonyl)imide, bromide, chloride, dicyanamide, diethylphosphate, hexafluorophosphate, hydrogen sulfate, iodide, methanesulfonate, methylphosphonate, tetrachloroaluminate, tetrafluoroborate, and trifluoromethanesulfonate. Alternative or additional embodiments described herein provide an electrolyte composition comprising one or more features described in the foregoing or elsewhere herein.

[0048] To determine whether a certain molecule has sufficient stability to be used as a solvent, or lower stability and is more suitable to be used as a sacrificial additive to create an ideal solid electrolyte interface, density functional theory (DFT) can be used. Figure 2 DFT calculations for various molecules are shown (calculated to theoretical level). Table 2 lists some example molecules and their ASHRAE and chemical nomenclature.

[0049] Table 2

[0050]

[0051] The more positive the ionization potential of a molecule, the more stable it is against oxidation, and the more negative the electron affinity of a molecule, the more stable it is against reduction. Through this model, molecules such as R-1130(E) have been identified as relatively stable against reduction and relatively unstable against oxidation compared to similar model refrigerants. Therefore, this molecule can be used to direct the formation of a solid electrolyte interface on the cathode. This is because in a battery system, the molecule will not be reduced or decomposed on the anode surface, but at high voltage on the cathode, the molecule can be oxidized and decomposed into various chemicals and deposited on the cathode surface. This surface layer can protect the electrolyte from further oxidation, thereby extending the cycle life of the battery cell. Other molecules can also be similarly identified as having good or poor oxidation or reduction stability.

[0052] The binding energy of the molecules with lithium cations was also calculated through DFT. The results of the calculations show that, Figure 3 Several of the compounds shown bind well with lithium cations. This will promote the solubility of the salt as well as the solvation separation of the anion and cation, thereby increasing the conductivity and improving the battery performance. Therefore, some ideal fluorinated, chlorinated, or fluorinated chlorinated olefins can serve as ideal solvents in electrochemical cell electrolytes.

[0053] Studies have shown that both LiF and LiCl can serve as beneficial solid electrolyte interface components. These components are resistive, ionically conductive, and insoluble in electrolyte solvents, which are ideal properties for a battery solid electrolyte interface. Figure 4A and 4B A liquid gas electrolyte consisting of 1 M LiTFSI and 2 MFEC in 45:45:10 of MeF:ClM:CO2 was demonstrated on a graphite anode half-cell. The results show that the battery has good cycle life and power performance, demonstrating the high capacity of the electrolyte mixture. The mixture of chlorinated and fluorinated components is believed to provide an ideal SEI layer and provide good battery performance, such as the cycle life shown on the anode and cathode. The decomposition products of MeF and MeCl on the anode include LiF and LiCl. The good cycle performance of the battery indicates that LiCl can serve as a good SEI former. It is also ideal to find molecules that can generate both LiF and LiCl upon decomposition. Molecules such as 2,3,3,3-tetrafluoro-1-chloropropene promote this SEI composition. These molecules also have other advantages, such as lower vapor pressure, lower flammability, lower cost, and lower GWP. Therefore, an ideal SEI layer can be formed using a single molecule containing at least one fluorine atom, at least one chlorine atom, or at least one chlorine atom and fluorine atom.

[0054] Figures 5A-5C It was demonstrated that Figure 1Data on compound R-1234ze (1,3,3,3-tetrafluoropropylene) as a component of the liquefied gas electrolyte are presented. This electrolyte uses a mixture of 1.0 M LiFSI and 2.0 M DMC in a 35:35:10:20 molar ratio of DFE:FM:CO2:TFP as the total electrolyte solution. Results show that this electrolyte performs well in cycle life testing, exhibiting minimal increase in resistance, high coulombic efficiency, and minimal capacity loss. Therefore, this low-pressure, low-cost, low-GWP molecule can be used in electrochemical cells, demonstrating that this hydrofluoroolefin with at least one fluorine atom can be used to successfully form an SEI layer, enabling stable cycling and improved performance of the battery cell. The cycle stability of the battery and the TFP characteristics calculated by DFT are consistent with the formation of a stable SEI.

[0055] Previous publications have indicated that hydrofluoroolefins are potential candidates for liquefied gas electrolytes, but have not discussed, for example... Figure 1 As shown, robust SEI layers can be formed by decomposing solvent compounds containing both F and Cl structural moieties. Similarly, it was not recognized that hydrochloroolefins, including LiCl but not LiF, could form ideal SEI layers. This paper reveals that these components can decompose to form ideal SEI layers, and can be selected based on calculated antioxidant or reductive properties to form target solid electrolyte interfaces at the cathode or anode—a significant finding. Previously, it was unnecessary to simultaneously determine their antioxidant and reductive properties because these molecules were not used in electrochemical applications. Similarly, it was found that some of these molecules bind well to lithium cations, thus contributing to high electrolyte conductivity and superior battery performance.

[0056] Furthermore, previous disclosures did not recognize that olefin molecules can form an ideal SEI layer due to their unsaturated carbon bonds. Many molecules with similar unsaturated carbon bonds can be added to electrolyte formulations, but these molecules typically do not function well in battery cells. The unique feature of olefin molecules is that they can form polymers upon decomposition and contain significant amounts of fluorine or chlorine (fluorine or chlorine). Figure 1 Up to eight molecules are shown. A mixture of flexible polymers (which give the SEI flexibility and adaptability to changes in electrode volume) and inorganic LiF or LiCl components (which give the SEI high electrical insulation) can enable batteries with high performance and long cycle life.

[0057] The present inventors have also unexpectedly discovered that molecules containing chlorinated components (as opposed to fluorinated components) exhibit significantly improved solubility in various electrolyte mixtures, not only at room temperature, but also at higher temperatures. This can be attributed in part to the lower vapor pressure of these formulations, which can remain in the liquid phase at more moderate pressures due to the higher interaction energies between the molecules and the salts in the electrolyte. The pressure of these molecules decreases with each chlorine atom replacing a fluorine atom. This also lowers the critical point of these molecules and the electrolyte system. Lower pressure and critical point can reduce the burden of mechanical containment, thus reducing battery weight and cost. Additionally, the electrolyte is easier to handle and process.

[0058] The present inventors have also unexpectedly discovered that these compositions more readily form azeotropic mixtures, such that the vapor and liquid phases maintain the same percentage composition throughout the process of handling the electrolyte during electrolyte mixing, electrolyte injection, and battery operation - again reducing manufacturing costs and improving battery efficiency. One example is 1M LiTFSI, 2M FEC in a 75:25 ratio of R-1336mzz(Z):1130(E), which forms an azeotropic mixture. This mixture has a low flammability rating, as well as a lower GWP, due to the chlorinated molecule 1130(E). The safety and environmental improvements of these chlorinated molecules are of great value in the energy storage industry and of great importance. Their discovery and use in liquefied gas electrolytes undoubtedly have significant implications for providing higher performance, lower cost batteries to the market.

[0059] The above-described liquefied gas electrolytes can be used in electrochemical devices. Figure 6 An electrochemical device 5 is schematically shown with an electrode stack consisting of a positive electrode 25, a negative electrode 20, and an ionically conductive but electrically isolating separator 15. The stack is immersed in an electrolyte mixture 40. The electrode stack and electrolyte 40 are also contained within a battery cell housing 35, from which positive electrode terminal 25 and negative electrode terminal 30 can be contacted externally. The structure of the battery cell housing 35 enables it to maintain the required pressure to ensure that the liquefied gas electrolyte remains in the liquid state under pressure.

[0060] While this document contains many details, these should not be construed as limiting the scope of any invention or of the claims, but as merely describing features of certain embodiments of the particular inventions. Certain features described herein in individual embodiments can be combined in a single embodiment. Conversely, various features described in a single embodiment can be separated into multiple embodiments. Moreover, although features can be described above as acting in conjunction or in relation to one another, each feature can also be used individually or in combination with other features. Furthermore, although the features can be described above as acting in the capacity of a specific combination of features, the claims should not be limited to such specific combinations.

Claims

1. An ionically conductive electrolyte comprising: a salt; and a liquefied gas solvent mixture having a vapor pressure greater than 100 kPa at a temperature of 293.15 K, consisting of a first solvent component and a second solvent component, wherein the first solvent component is selected from the group consisting of a hydrochloroolefin, a hydrochlorofluoroolefin, a perchloroolefin, and a perfluoroolefin.

2. The ionically conductive electrolyte of claim 1, wherein the relative amounts of the first solvent component and the second solvent component are selected to reduce the global warming potential (GWP) of the liquefied gas solvent mixture to less than 10% of the GWP of the second solvent component alone.

3. The ionically conductive electrolyte of claim 1, wherein the relative amounts of the first solvent component and the second solvent component are selected to reduce the global warming potential (GWP) of the liquefied gas solvent mixture to less than 50% of the GWP of the second solvent component alone.

4. The ionically conductive electrolyte of claim 1, wherein the relative amounts of the first solvent component and the second solvent component are selected to reduce the global warming potential (GWP) of the liquefied gas solvent mixture to less than 70% of the GWP of the second solvent component alone.

5. The ionically conductive electrolyte of any one of claims 1-4, wherein the global warming potential (GWP) of the first solvent component is less than 10.

6. The ionically conductive electrolyte of claim 5, wherein the GWP of the second solvent component is greater than 80.

7. The ionically conductive electrolyte of any one of claims 1-6, wherein the first solvent component is selected from the group consisting of 1,1-dichloroethylene, vinyl chloride, trichloroethylene, dichloroethylene, chlorofluoroethylene, (Z)-1-chloro-2,3,3,3,-tetrafluoropropene, trans-1-chloro-3,3,3-trifluoropropene, and isomers thereof.

8. The ionically conductive electrolyte of any one of claims 1-7, wherein the second solvent component is selected from the group consisting of 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 chlorofluoride, phosphorofluoride, phosphorochlorofluoride, thiofluoride, thiochlorofluoride, 1-fluoropropane, 2-fluoropropane, 1,1-difluoropropane, 1,2-difluoropropane, 2,2-difluoropropane, 1,1,1-trifluoropropane, 1,1,2-trifluoropropane, 1,2,2-trifluoropropane, fluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, 1-fluoropropylene, propylene, chlorine, chloromethane, bromine, iodine, ammonia, methylamine, dimethylamine, trimethylamine, molecular oxygen, molecular nitrogen, carbon monoxide, carbon dioxide, sulfur dioxide, methyl vinyl ether, dinitrogen oxide, nitrogen dioxide, nitric oxide, carbon disulfide, hydrogen fluoride, hydrogen chloride, methane, ethane, propane, n-butane, isobutane, cyclopropane, ethylene, propylene, butylene, cyclobutene, acetylene, isomers thereof, and combinations thereof.

9. The ionically conductive electrolyte of any one of claims 1-8, wherein the salt is based on lithium, sodium, zinc, calcium, magnesium, aluminum, or titanium.

10. An electrochemical device comprising the electrolyte of claims 1-9.

11. The electrochemical device of claim 10, further comprising: a housing encapsulating the ionically conductive electrolyte; an anode, a cathode, and a separator layer in contact with the ionically conductive electrolyte.

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