Electrolytes containing amide-based solvents and electrochemical devices incorporating such electrolytes

Abstract

The electrolyte comprises one or more salts, one or more acetamide-based solvents, and optionally one or more non-acetamide-based solvents. In some embodiments, the disclosed electrolyte can be used in electrochemical devices, such as secondary battery cells, particularly alkali metal-based (e.g., lithium-based). Also disclosed are electrochemical devices incorporating the disclosed electrolyte.

Description

[Technical field]

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 298,008, entitled "Electrolytes Comprising Acetamide-Based Solvents, and Electrochemical Devices Incorporating Such Electrolytes," filed on January 10, 2022, which is incorporated by reference in its entirety.

[0002] The present disclosure relates generally to the field of electrolytes for electrochemical devices. In particular, the present disclosure relates to electrolytes including acetamide-based solvents and electrochemical devices incorporating such electrolytes. [Background technology]

[0003] Lithium-ion batteries using conventional carbonate-based electrolytes have not been able to demonstrate satisfactory energy density performance. This is due to the specific capacity (375 mAh g) of graphite, which is widely used as the anode of lithium-ion batteries. -1 Of all anode materials, lithium (Li) metal has a very high specific capacity (3,860 mAh g -1 ) and the lowest negative potential (-3.04 V vs. the standard hydrogen electrode), it has been considered the most promising. Although high-energy density lithium metal batteries have made great progress in recent decades, existing electrolytes are still inadequate to address at least the following issues: 1) limited cycle life, 2) dendritic growth of lithium, and 3) poor safety (e.g., the electrolyte itself is flammable and thermally instable with cell components at high temperatures).

[0004] Generally, electrolyte solvents are broadly divided into two types: ethers and carbonates. Ethers are oxidatively decomposed when a charging voltage exceeding 4V is applied. Compared with ethers, carbonates have relatively better oxidation stability, but their thermodynamic stability against the lithium metal anode used in lithium metal batteries is worse than that of ether-based electrolytes. Obviously, both carbonate-based and ether-based electrolytes have limitations in the application of lithium metal secondary batteries. Summary of the Invention [Problem to be solved by the invention]

[0005] It is believed that the discovery of new classes of solvents for lithium metal battery electrolyte applications is necessary. [Means for solving the problem]

[0006] In one embodiment, the present disclosure relates to an electrolyte comprising a salt system including at least one alkaline earth metal salt and a solvent system including a solvent having any one of the following structures I and II: (Structure I) R1-CO-N-R2R3, where R1 is -F, -CF3, -C x H y F z (linear or branched, x=1 to 4, y=0 to 2x+1, z=0 to 2x+1, y+z=2x+1), and R2 and R3 are each -H, -CH 3-a -(C x H y F z ) a (straight-chain or branched, x=0-3, y=0-2x+1, z=0-2x+1, y+z=2x+1, a=0-3), and R2≠R3 or R2=R3. (Structure II) -R1-CO-N-(R2)-CH2-, where R1 is -(CH x F y )(CH z F a )-(x=0-2, y=0-2, z=0-2, a=0-2), and R2 can be -CH 3-a -(C x H y F z ) a (linear or branched, x=1-3, y=0-2x+1, z=0-2x+1, y+z=2x+1, a=0-3).

[0007] In another embodiment, the present disclosure relates to a method for producing an electrolyte for a secondary battery that operates using the flow of alkaline earth metal ions between an anode and a cathode, the method comprising providing at least one solvent having one of the following structures I and II, providing at least one salt comprising the alkaline earth metal, and combining the at least one solvent and the at least one salt with each other to form the electrolyte. (Structure I) R1-CO-N-R2R3, where R1 is -F, -CF3, -C x H y F z (linear or branched, x=1 to 4, y=0 to 2x+1, z=0 to 2x+1, y+z=2x+1), and R2 and R3 are each -H, -CH 3-a -(C x H y F z ) a (straight-chain or branched, x=0-3, y=0-2x+1, z=0-2x+1, y+z=2x+1, a=0-3), and R2≠R3 or R2=R3. (Structure II) -R1-CO-N-(R2)-CH2-, where R1 is -(CH x F y )(CH z F a )-(x=0-2, y=0-2, z=0-2, a=0-2), and R2 can be -CH 3-a -(C x H y F z ) a (linear or branched, x=1-3, y=0-2x+1, z=0-2x+1, y+z=2x+1, a=0-3).

[0008] In yet another embodiment, the present disclosure relates to an electrochemical device including an anode comprising an alkaline earth metal, a cathode, a separator located between the anode and the cathode, and an electrolyte saturating the separator and in suitable contact with each of the anode and cathode. [Brief description of the drawings]

[0009] For purposes of illustration, the drawings show aspects of one or more exemplary embodiments. It should be understood, however, that the disclosure is not limited to the precise arrangements and instrumentalities shown in the drawings. [Figure 1] FIG. 1 shows the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) values ​​of exemplary acetamide-based solvents A through G of the present disclosure. [Diagram 2] 1 is a graph of current density versus voltage showing linear scan voltammetry of 8 M lithium bis(fluorosulfonyl)imide (LiFSI) dimethyltrifluoroacetamide (DTA) electrolyte performed at a scan rate of 1 mV / s. [Diagram 3] 1 is a graph of current density versus voltage showing aluminum corrosion evaluation of 8M LiFSI-DTA electrolyte at a scan rate of 5 mV / s. [Figure 4] 1 is a graph of heat flow versus temperature showing low temperature differential scanning calorimetry characteristics of 4.3 M LiFSI-DTA electrolyte at a scan rate of 5° C. / min. [Diagram 5] 1 is a graph of heat flow versus temperature showing high temperature differential scanning calorimetry characterization of a fully charged (state of charge: 100%) high Ni NMC cathode with 8M LiFSI-DTA electrolyte and a fully charged (state of charge: 100%) high Ni NMC cathode with 1M LiPF6-EC / EMC (v:v=1:1) electrolyte at a scan rate of 10° C. / min. [Figure 6] Includes two photographs taken during the flammability evaluation of DTA solvents. [Figure 7] FIG. 1 is a high level schematic diagram illustrating an electrochemical device made in accordance with the principles of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In this disclosure, unexpected findings are presented regarding novel acetamide-based electrolytes that demonstrate that such acetamide-based solvents provide improved electrolyte properties and improved lithium metal cell performance.

[0011] Before proceeding, it should be noted that the term "about" when used in conjunction with a corresponding numerical value or other quantitative measure refers to ±20% of the numerical value, typically ±10% of the numerical value, often ±5% of the numerical value, and most often ±2% of the numerical value. In some embodiments, the term "about" can refer to the numerical value itself.

[0012] Disclosed herein is a new class of acetamide-based solvents, including but not limited to the exemplary solvents listed in FIG. 1 as A to G. The solvents disclosed herein have a wide voltage window according to calculation of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) values. For example, (CH3)2NCOCF3 (solvent B in FIG. 1) is dimethyltrifluoroacetamide (DTA). As shown in FIG. 2, the oxidation stable voltage of 8M lithium bis(fluorosulfonyl)imide (LiFSI)-DTA electrolyte is 4.7V or higher, which can meet the requirements of high voltage battery applications. Also, the surface of aluminum (Al) can be passivated via 8M LiFSI-DTA electrolyte, and the passivated Al shows no corrosion (FIG. 3). In addition, it has been observed that there is no thermal phase transition of 4.3M LiFSI-DTA electrolyte between -90°C and 40°C. As a result, embodiments of this new class of electrolytes can be applied over a wide temperature range due to their relatively extremely wide liquidus temperature range (down to -90°C), as shown in Figure 4.

[0013] In high-temperature differential scanning calorimetry (DSC) characterization, the amount of heat generated by the novel electrolyte (4.3 M LiFSI-DTA) at high temperatures with a fully charged (state of charge: 100%) high-Ni nickel manganese-cobalt oxide (NMC) cathode is much less than that of a conventional commercial lithium-ion battery electrolyte (1 M LiPF6-ethylene carbonate (EC) / ethyl methyl carbonate (EMC), v:v=1:1). This indicates that the novel electrolyte can improve safety (e.g., general thermal runaway) (Figure 5).

[0014] Figure 6 shows the flammability evaluation of DTA as an acetamide-based solvent. The DTA solvent could ignite, but interestingly, it then self-extinguished in a very short time (less than 1 second). Considering the above-mentioned excellent thermal stability and self-extinguishing / very low flammability of the solvents presented herein, the new class of acetamide-based electrolytes is beneficial for improving the safety of critical cells.

[0015] In this disclosure, some embodiments of the acetamide-based solvents of the present disclosure are represented by the following general chemical structure:

[0016] [ka]

[0017] Where R1 is -F, -CF3, -C x H y F z (linear or branched, x=1 to 4, y=0 to 2x+1, z=0 to 2x+1, and y+z=2x+1), and R2 and R3 are -H, -CH 3-a -(C x H y F z ) a (linear or branched, x=0-3, y=0-2x+1, z=0-2x+1, and y+z=2x+1, a=0-3), and R2≠R3 or R2=R3.

[0018] Without being limited to this list, some examples of acetamide-based solvents having structure I above are as follows (letters in brackets indicate the corresponding solvents in FIG. 1): 1) R1 is -F, R2 is -CH3, R3 is -CH3, and the solvent is F-CO-N-(CH3)2[F]; 2) R1 is -F, R2 is -CH2CF3, R3 is -CH2CF3, and the solvent is F-CO-N-(CH2CF3)2[G]; 3) R1 is -F, R2 is -CH2CF3, R3 is -CH3, and the solvent is F-CO-N-(CH2CF3)(CH3); 4) R1 is -CF3, R2 is -CH3, R3 is -CH3, and the solvent is CF3-CO-N-(CH3)2[B]. 5) R1 is -CF3, R2 is -CH2CF3, R3 is -CH2CF3, and the solvent is CF3-CO-N-(CH2CF3)2[E]. 6) R1 is -CF3, R2 is -CH2CF3, R3 is -CH3, and the solvent is CF3-CO-N-(CH2CF3)(CH3)[C]. 7) R1 is -CF3CF2, R2 is -CH3, R3 is -CH3, and the solvent is CF3CF2-CO-N-(CH3)2[D]. 8) R1 is -CF3, R2 is -H, R3 is -CH3, and the solvent is CF3-CO-N-HCH3[A].

[0019] In the present disclosure, some embodiments of the acetamide-based solvent may be cyclic acetamide-type solvents and can be represented by the following general chemical structure (wherein R1 is bonded to -CH2- to form a five-membered ring):

[0020] [ka]

[0021] where R1 is -(CH x F y )(CH z F a )-(x=0-2, y=0-2, z=0-2, a=0-2), and R2 can be -CH 3-a -(C x H yF z ) a (linear or branched, x=1-3, y=0-2x+1, z=0-2x+1, and y+z=2x+1, a=0-3).

[0022] Although not intended to be limiting, some examples of acetamide-based solvents having structure II above are: 1) R1 is -CF2CF2-, R2 is -CH3, and the solvent is -CF2CF2-CO-N-(CH3)-CH2-. 2) R1 is -CFHCFH-, R2 is -CH3-, and the solvent is -CFHCFH-CO-N-(CH3)-CH2-. 3) R1 is -CH2CH2-, R2 is -CHCF3-, and the solvent is -CH2CH2-CO-N-(CHCF3)-CH2-.

[0023] The electrolyte of the present disclosure may include a solvent system (i.e., a single solvent or a mixture of two or more solvents) containing a single acetamide-based solvent having either Structure I or Structure II above, or may contain a mixture of two or more acetamide-based solvents, each having either Structure I or Structure II above, and each solvent ranging from 100% by volume to 0.05% by volume, weight percent, or molar ratio. A consideration when mixing two or more acetamide-based solvents is whether the different properties and / or different functions of the multiple solvents provide an improvement over a single acetamide-based solvent for the requirements of the particular application at issue. For example, one particular consideration comes from the salt solubility of the solvent. The acetamide-based solvents of the present disclosure that contain more fluorine atoms per molecule exhibit reduced solubility but high stability. On the other hand, other acetamide-based solvents with relatively few fluorine atoms per molecule and good salt solubility can be combined with a solvent with a relatively high number of fluorine atoms per molecule to provide a solvent system with the beneficial attributes of both solvents.

[0024] In addition, the solvent system of the present disclosure may further contain one or more other types of solvents, each such other solvent being either non-fluorinated or fluorinated, to produce a hybrid solvent system, i.e., a solvent system consisting of one or more acetamide-based solvents and one or more non-acetamide-based solvents. The consideration as to whether a non-acetamide-based solvent should be used is whether the electrolyte characteristics and functions required for a particular application can be achieved with the acetamide-based solvent system alone. If not, one or more non-acetamide-based solvents can be combined with one or more acetamide-based solvents of the present disclosure to create a hybrid solvent system. By implementing a hybrid solvent system, better overall electrolyte performance can be achieved by taking advantage of the respective advantages of multiple solvents by carefully adjusting the properties of the resulting hybrid electrolyte (i.e., the hybrid solvent system and one or more salts).

[0025] Examples of non-acetamide-based solvents that can be used to create a hybrid solvent system by mixing with one or more acetamide-based solvents include 1) ethers, such as methyl propyl ether, methyl butyl ether, ethyl propyl ether, ethyl butyl ether, propyl butyl ether, diethyl ether, dipropyl ether, and dibutyl ether, 1,2-diethoxyethane, 1,2-dimethoxyethane, 1,2-dipropoxyethane, and 1,2-dibutoxyethane, bis(2-methoxyethyl)ether, 2-ethoxyethyl ether, 1,2-(1,1,2,2-tetrafluoroethoxy)ethane, 1,1,2,2-tetrafluoroethyl ether, 1,3,3-tetrafluoropropyl ether, 1,3,3-tetrafluoropropyl ether, and 1,3,3-tetrafluoropropyl ether. 1) dimethylcarbonate, ethylmethylcarbonate, diethylcarbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, and fluoroethylene carbonate; and 2) sulfamoyl solvents, such as, but not limited to, N,N-dimethylsulfamoyl fluoride, N,N-ethylmethylsulfamoyl fluoride, and N,N-dimethyltrifluoromethanesulfonamide. In some embodiments, each of the at least one non-acetamide solvent may be selected from the group consisting of ether, carbonate, sulfonyl, nitrile, phosphate, sulfonate, sultone, sulfate, ionic liquid, phosphonate, phosphite, sulfone, sulfonyl isocyanate, and orthoformate solvents, with each solvent in the acetamide solvent system being, for example, in the range of about 100% to about 0.05% by volume, weight, or molar ratio, respectively, of the solvent system, or in the range of about 5% to about 50% by volume, weight, or molar ratio, respectively, of the solvent system.As will be appreciated by those skilled in the art, various of the above-mentioned solvent materials and / or other solvent materials can be used as solvents for the electrolyte or additives thereto, typically depending on the relative amount of solvent material used in the electrolyte.

[0026] The electrolytes of the present disclosure may include a suitable solvent system, such as those configured as described above, and a suitable salt system (i.e., a single salt or a combination of two or more salts) in solution to provide novel electrolytes. In the context of lithium-based electrochemical devices (e.g., lithium metal secondary batteries) and sodium-based electrochemical devices (e.g., sodium metal secondary batteries), the following lithium-based and sodium-based salts, respectively, can be combined with any of the acetamide-based solvent systems described above to make the corresponding electrolytes. Specific examples include LiFSI, LiTFSI, LiClO4, LiBF4, LiPF6, LiAsF6, LiTf, LiBETI, LiCTFSI, LiTDI, LiPDI, LiDCTA, LiB(CN)4, LiBOB, LiDFOB, and LiDFP, as well as NaFSI, NaTFSI, NaClO4, NaBF4, NaPF6, NaAsF6, NaTf, NaBETI, NaCTFSI, NaTDI, NaPDI, NaDCTA, NaB(CN)4, NaBOB, NaDFOB, and NaDFB, etc. In some embodiments, the salt system may be either a single salt or a combination of salts, and the concentration in the electrolyte may be about 0.1M to about 10M or more, about 0.1M to about 5M, about 0.5M to about 5M, or about 0.5M to about 3M, among other ranges, to suit a particular application. As will be appreciated by those skilled in the art, in general, various of the above-mentioned salt materials and / or other salt materials can be used as electrolyte salts or electrolyte additives depending on the relative amounts of salt materials used in the electrolyte.

[0027] Working principle: The advantages of the electrolyte of the present disclosure may include, but are not limited to, any one or more of the following: 1) good compatibility and chemical stability with lithium metal anode and cathode materials in lithium batteries, 2) high oxidation stability at high voltages (above 4.7V), 3) dense passivation layer on the anode and cathode surfaces to protect the electrodes, 4) high thermal stability at high temperatures (heat flow output is less than 2W / g when the electrolyte with a fully charged cathode is heated to 290°C), 5) wide operating temperature (-90°C to 80°C), and 6) self-extinguishing and low flammability (self-extinguishing time is less than 1 second).

[0028] Main technical problems: The main technical problems facing lithium metal secondary batteries include poor safety performance and short cycle life. In response to these problems, the electrolyte used in lithium metal batteries plays an important role in governing the battery performance in terms of safety and electrochemical performance.

[0029] Technical Solution: The new class of acetamide-based electrolytes disclosed herein can exhibit good chemical compatibility with anode and cathode materials, improved thermal stability, low flammability, and enhanced oxidation stability at high voltages, which can contribute to obvious improvements in cycle life. By combining the new class of solvents disclosed herein with electrolyte formulation design (e.g., relying on the excellent coordination ability of the invented acetamide solvent with salts to enable high salt:solvent molar ratios, form highly coordinated salt-solvent clusters, minimize free solvent, and maximize the formation of a protective layer of the salt solid electrolyte interface (SEI) on the anode surface, etc.), lithium metal batteries relying on the solvents disclosed herein are highly expected to exhibit long-lasting cycles and improved safety. In some embodiments, to minimize free solvent in the acetamide-based electrolyte, it is desirable to have a salt:solvent ratio (e.g., LiFSI:DTA molar ratio) of about 1:2 or more and about 1:0.5 or less (e.g., 1:2, 1:1.8, 1:1.6, 1:1.4, 1:1.2, 1:1, etc.) to initiate salt decomposition for better salt-derived SEI passivation layer formation on the anode surface. In certain embodiments where the salt is LiFSI and the acetamide-based solvent is DTA, the critical point of the LiFSI:DTA molar ratio to minimize the amount of free solvent has been found to be about 1:1.75. Other salt and solvent combinations of the present disclosure may have other salt and solvent molar ratios.

[0030] Electrochemical Cell Example

[0031] FIG. 7 illustrates, in highly simplified form, an exemplary electrochemical device 700 that can be fabricated according to embodiments of the present disclosure. Those skilled in the art will readily appreciate that the exemplary electrochemical device 700 can be, for example, a battery cell, such as a secondary battery cell, or a supercapacitor. In addition, those skilled in the art will readily appreciate that FIG. 7 illustrates only some of the basic functional components of an electrochemical device, and that actual realizations of electrochemical devices, such as secondary battery cells or supercapacitors, are typically implemented using either stacked or wound structures that consist of or form one or more of the various layers illustrated in FIG. 7. Furthermore, those skilled in the art will appreciate that other components, such as electrical leads, electrical terminals, seal(s), thermal barrier(s), electrical circuitry, gas generation feature(s), and / or vent(s), as well as sensors, may be included in the electrochemical device 700, among others, that are not illustrated in FIG. 7 for ease of illustration.

[0032] In this example, the electrochemical device 700 of FIG. 7 includes a spaced apart cathode 704 and anode 708 and a pair of corresponding current collectors 704CC and 708CC, respectively. A porous dielectric separator 712 is disposed between the cathode 704 and anode 708 to electrically isolate them from one another while allowing ions in an electrolyte 716 made according to the present disclosure to flow therethrough. The porous dielectric separator 712 may be made of any one or more suitable materials, such as, but not limited to, any conventional separator material such as polyolefin, polyolefin blends, ceramic coated polyolefin or polyolefin blends, to name a few non-limiting examples known to those skilled in the art. Depending on whether it is porous (e.g., intercalating type), the porous dielectric separator 712 and / or one, the other, or both of the cathode 704 and anode 708 may be at least partially impregnated with the electrolyte 716. The electrochemical device 700 includes a sealed container 720 that contains at least a cathode 704, an anode 708, a porous dielectric separator 712, and an electrolyte 716. As one of ordinary skill in the art would readily appreciate, the sealed container 720 may be any suitable type of container, such as a pouch-type container, a cylindrical container, or a button cell-type container, among others, and may be made from any suitable type of material(s). Because there are many well-known container types and materials of construction used for such container types, one of ordinary skill in the art would readily appreciate the type of sealed container 720 and container material that is suitable for a particular implementation of the electrochemical device 700.

[0033] As will be appreciated by those skilled in the art, depending on the type and design of the electrochemical device 700, the cathode 704 and anode 708 each comprise one or more suitable materials that are compatible with the salt ions and other components of the electrolyte. In some embodiments, the anode 708 may be an active metal anode that functions by plating / stripping an active metal (e.g., lithium, lithium alloy, sodium, sodium alloy, or other alkaline earth metal or alkaline earth metal alloy) during charge / discharge. In some embodiments, the anode 708 may be of the intercalating / deintercalating type, for example, and the active material is any suitable anode active material, such as, but not limited to, natural graphite, artificial graphite, activated carbon, carbon black, conductive additives, lithium titanate, surface functionalized silicon, and high performance powdered graphene. The cathode 704 may comprise any suitable cathode active material, such as, but not limited to, multi-metal oxides, metal fluorides, and lithium metal phosphates, including cobalt, nickel, and / or manganese. Each of the current collectors 704CC and 708CC may be made from any suitable conductive material, such as copper or aluminum, among others. Many battery and supercapacitor structures that may be used to construct the electrochemical device of Figure 7 are known in the art and need not be described in detail in order for those skilled in the art to understand how to make and use the various embodiments of the present disclosure to their fullest extent.

[0034] As one of ordinary skill in the art would readily appreciate, the presence of electrolyte 716 made in accordance with the present disclosure provides novelty to electrochemical device 700. Electrolyte 716 may be any formulation disclosed herein by explicit example, formulation method, and / or underlying basic principle(s).

[0035] Various modifications and additions can be made without departing from the spirit and scope of the present disclosure. Each feature of the various embodiments described above may be combined with features of other described embodiments, as necessary, to provide multiple feature combinations in related new embodiments. Moreover, while the above describes several separate embodiments, what is described herein is merely illustrative of the application of the principles of the present disclosure. Furthermore, although certain methods herein may be illustrated and / or described as being performed in a particular order, the order is highly variable within the scope of one of ordinary skill in the art to achieve aspects of the present disclosure. Thus, the present specification is intended to be construed as merely an illustrative method, and is not intended to limit the scope of the present disclosure and the invention(s) disclosed herein.

[0036] Exemplary embodiments have been disclosed above and are illustrated in the accompanying drawings. It will be understood by those skilled in the art that various modifications, omissions, and additions may be made to what is specifically disclosed herein without departing from the spirit and scope of the disclosure and invention(s) disclosed herein.

Claims

1. a salt system comprising at least one alkaline earth metal salt; a solvent system comprising a solvent having any one of the following structures I and II; An electrolyte comprising: R １ -CO-N-R ２ R ３ (Structure I) Wherein in Structure I, R １ is -F, -CF ３ , -C ｘ H ｙ F ｚ (linear or branched, x=1 to 4, y=0 to 2x+1, z=0 to 2x+1, and y+z=2x+1), R ２ and R ３ are respectively -H and -CH ３－ａ - (C ｘ H ｙ F ｚ ) ａ (linear or branched, x=0-3, y=0-2x+1, z=0-2x+1, and y+z=2x+1, a=0-3), R ２ ≠R ３ Or R ２ = R ３ It could be. -R １ -CO-N-(R ２ )-CH ２ - (Construction II) Wherein, in structure II, R １ is -(CH ｘ F ｙ ) (CH ｚ F ａ )-(x=0 to 2, y=0 to 2, z=0 to 2, a=0 to 2), R ２ is -CH ３－ａ - (C ｘ H ｙ F ｚ ) ａ (linear or branched, x=1-3, y=0-2x+1, z=0-2x+1, and y+z=2x+1, a=0-3).

2. 2. The electrolyte of claim 1, wherein the at least one alkaline earth metal salt is a lithium salt.

3. 2. The electrolyte of claim 1, wherein the at least one alkaline earth metal salt is a sodium salt.

4. 10. The electrolyte of claim 1, wherein the electrolyte has a salt concentration in the range of about 0.1M to about 10M.

5. 10. The electrolyte of claim 1, wherein the electrolyte has a salt concentration in the range of about 0.5M to about 5M.

6. 2. The electrolyte of claim 1, wherein the solvent system consists essentially of one or more solvents of structure I.

7. 2. The electrolyte of claim 1, wherein the solvent system consists essentially of one or more solvents of structure II.

8. 2. The electrolyte of claim 1 , wherein the solvent system comprises a solvent of Structure I and a solvent of Structure II.

9. said solvent system essentially comprising one or more solvents of either Structure I or Structure II, or both Structure I and Structure II; 10. The electrolyte of claim 1 comprising at least one non-acetamide solvent.

10. 10. The electrolyte of claim 9, wherein the at least one non-acetamide solvent is selected from the group consisting of carbonate solvents, ether solvents, and sulfonyl solvents.

11. The solvent system is CF ３ -CO-N-HCH ３ , C.F. ３ -CO-N-(CH ３ ) ２ , C.F. ３ -CO-N-(CH ２ CF ３ ) (CH ３ ), C.F. ３ CF ２ -CO-N-(CH ３ ) ２ , C.F. ３ -CO-N-(CH ２ CF ３ ) ２ , F-CO-N-(CH ３ ) ２ and F-CO-N-(CH ２ CF ３ ) ２ 2. The electrolyte of claim 1, further comprising any one or more of the solvents listed above.

12. The solvent system essentially comprises CF ３ -CO-N-HCH ３ , C.F. ３ -CO-N-(CH ３ ) ２ , C.F. ３ -CO-N-(CH ２ CF ３ ) (CH ３ ), C.F. ３ CF ２ -CO-N-(CH ３ ) ２ , C.F. ３ -CO-N-(CH ２ CF ３ ) ２ , F-CO-N-(CH ３ ) ２ and F-CO-N-(CH ２ CF ３ ) ２ 2. The electrolyte solution according to claim 1, comprising any one or more of the following solvents:

13. The solvent system is CF ３ -CO-N-HCH ３ , C.F. ３ -CO-N-(CH ３ ) ２ , C.F. ３ -CO-N-(CH ２ CF ３ ) (CH ３ ), C.F. ３ CF ２ -CO-N-(CH ３ ) ２ , C.F. ３ -CO-N-(CH ２ CF ３ ) ２ , F-CO-N-(CH ３ ) ２ and F-CO-N-(CH ２ CF ３ ) ２ 2. The electrolyte solution according to claim 1, comprising any one or more of the following solvents:

14. The solvent system is -CF ２ CF ２ -CO-N-(CH ３ )-CH ２ -, -CFHCFH-CO-N-(CH ３ )-CH ２ -, and -CH ２ CH ２ -CO-N-(CHCF ３ )-CH ２ The electrolyte according to claim 1, further comprising at least one of the following solvents:

15. The solvent system is -CF ２ CF ２ -CO-N-(CH ３ )-CH ２ -, -CFHCFH-CO-N-(CH ３ )-CH ２ -, and -CH ２ CH ２ -CO-N-(CHCF ３ )-CH ２ The electrolyte according to claim 1, further comprising at least one of the following solvents:

16. The solvent system is -CF ２ CF ２ -CO-N-(CH ３ )-CH ２ -, -CFHCFH-CO-N-(CH ３ )-CH ２ -, and -CH ２ CH ２ -CO-N-(CHCF ３ )-CH ２ The electrolyte according to claim 1, further comprising at least one of the following solvents:

17. 1. A method for producing an electrolyte for a secondary battery that operates using a flow of alkaline earth metal ions between an anode and a cathode, comprising: providing at least one solvent having one of the following structures I and II; Providing at least one salt comprising an alkaline earth metal; combining at least one solvent and at least one salt together to form an electrolyte; The method includes: R １ -CO-N-R ２ R ３ (Structure I) Wherein in Structure I, R １ is -F, -CF ３ , -C ｘ H ｙ F ｚ (linear or branched, x=1 to 4, y=0 to 2x+1, z=0 to 2x+1, and y+z=2x+1), R ２ and R ３ are respectively -H and -CH ３－ａ - (C ｘ H ｙ F ｚ ) ａ (linear or branched, x=0-3, y=0-2x+1, z=0-2x+1, and y+z=2x+1, a=0-3), R ２ ≠R ３ Or R ２ = R ３ It could be. -R １ -CO-N-(R ２ )-CH ２ - (Construction II) Wherein, in structure II, R １ is -(CH ｘ F ｙ ) (CH ｚ F ａ )-(x=0 to 2, y=0 to 2, z=0 to 2, a=0 to 2), R ２ is -CH ３－ａ - (C ｘ H ｙ F ｚ ) ａ (linear or branched, x=1-3, y=0-2x+1, z=0-2x+1, and y+z=2x+1, a=0-3).

18. 20. The method of claim 17, wherein the electrolyte solution has a desired salt concentration, and combining the at least one solvent and the at least one salt together comprises combining the at least one solvent and the at least one salt together in amounts to produce the desired salt concentration.

19. 20. The method of claim 18, wherein the desired salt concentration is within the range of about 0.1 M to about 10 M.

20. 20. The method of claim 18, wherein the desired salt concentration is within the range of about 0.5M to about 5M.

21. 20. The method of claim 18, wherein the desired salt concentration is within the range of about 0.5M to about 3M.

22. 20. The method of claim 17, wherein each molecule of the at least one solvent has a number of fluorine atoms, the method further comprising selecting the at least one solvent based on the number of fluorine atoms.

23. 20. The method of claim 17, further comprising providing a first and a second solvent of Structure I and Structure II, respectively.

24. 24. The method of claim 23, wherein each molecule of the first solvent has a first number of fluorine atoms and each molecule of the second solvent has a second number of fluorine atoms, the method further comprising selecting the first and second solvents based on the first and second numbers of fluorine atoms relative to one another.

25. 20. The method of claim 17, further comprising providing at least one non-acetamide solvent and combining the at least one non-acetamide solvent, the at least one solvent, and the at least one salt with one another to form the electrolyte solution.

26. 26. The method of claim 25, wherein the at least one non-acetamide solvent is selected from the group consisting of ether, carbonate, sulfonyl, nitrile, phosphate, sulfonate, sultone, sulfate, ionic liquid, phosphonate, phosphite, sulfone, sulfonyl isocyanate, and orthoformate solvents, and each solvent in the acetamide solvent system is in the range of about 100% to about 0.05% by volume, weight, or molar ratio, or in the range of about 5% to about 50% by volume, weight, or molar ratio.

27. an anode comprising an alkaline earth metal; A cathode; a separator disposed between the anode and the cathode; 17. An electrolyte according to claim 1 which saturates the separator and is in suitable contact with each of the anode and the cathode.

13. An electrochemical device comprising:

28. 28. The electrochemical device of claim 27 wherein the alkaline earth metal is lithium.

29. 28. The electrochemical device of claim 27 wherein the alkaline earth metal is sodium.

30. 28. The electrochemical device of claim 27, wherein the electrochemical device is a secondary battery.

Images