Eutectic mixture containing alkali metal sulfonyl imide salt and electrochemical device using the mixture

Abstract

Binary eutectic mixtures and ternary eutectic mixtures and corresponding electrolytes. In some embodiments, the binary eutectic mixture and the electrolyte each comprise a first salt X1 + Y1 ‑ and a second salt X2 + Y2 ‑ ; wherein each of X1 + and X2 + is an alkali metal cation and X1 + is different from X2 + ; and each of Y1 ‑ and Y2 ‑ is a sulfonylimide anion and Y1 ‑ is different from Y2 ‑ . In the ternary eutectic mixture and the electrolyte, a third salt X3 + Y3 ‑ is further included, wherein X3 + is different from each of X1 + and X2 + . In some embodiments, the eutectic mixture and the electrolyte have a melting point in the range of about 5 °C to about 70 °C. An electrochemical device comprising such a eutectic mixture electrolyte is also disclosed.

Description

[0001] Related application data

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 62 / 779,772, filed on December 14, 2018, and entitled “EUTECTIC MIXTURE FOR ELECTROCHEMICAL DEVICES,” which is incorporated herein by reference in its entirety. Field of the Invention

[0003] The present invention generally relates to the field of alkali metal sulfonyl imide salts. In particular, the present invention relates to a eutectic mixture containing an alkali metal sulfonyl imide salt and an electrochemical device using the eutectic mixture.

[0004] background

[0005] A variety of electrolytes are used in electrochemical devices such as secondary batteries, electrolytic capacitors, electric double layer capacitors, electrochromic display devices, and dye-sensitized solar cells, among others. Advances in such devices are increasing day by day, and the demand and requirements for electrolytes for these advanced devices are also increasing.

[0006] At present, most of the electrolyte salts used are non-aqueous electrolytes, which are prepared by dissolving ionizable salts such as lithium salts in organic solvents such as ethylene carbonate, propylene carbonate, dimethoxyethane and gamma-butyrolactone. However, the use of organic solvents for such non-aqueous electrolytes generally results in leakage problems due to the low viscosity of the resultant and volatilization due to the very strong volatility of the organic solvents. These organic solvents are also flammable. Therefore, electrochemical devices using electrolytes prepared using such organic solvents often experience problems of durability and stability.

[0007] In order to solve the flammability of liquid electrolytes in the case of lithium ion secondary batteries, it has been proposed to use imidazolium-based ionic liquids or ammonium-based ionic liquids as electrolytes. However, such ionic liquids can be reduced at a higher voltage than the lithium ions in the anode, or imidazolium cations or ammonium cations can be inserted into the anode together with lithium ions, which deteriorates the performance of the battery.

[0008] Overview of public content

[0009] In an embodiment, the present disclosure is directed to an electrolyte comprising a substantially eutectic mixture comprising a first salt X1 + Y1 - and second salt x2 + Y2 - ; Among them X1 +and X2 + Each of which is an alkali metal cation and X1 + Different from X2 + ; and Y1 - and Y2 - Each of which is a sulfonimide anion and Y1 - Different from Y2 - . BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For the purpose of illustrating the invention, the accompanying drawings show aspects of one or more embodiments of the invention. However, it should be understood that the invention is not limited to the precise arrangements and instrumentalities shown in the accompanying drawings, in which:

[0012] Figure 1 is a combination of a eutectic phase diagram and a Tamman diagram to illustrate an exemplary method of determining the eutectic composition of a binary eutectic mixture of the present disclosure; and

[0013] Figure 2 is a high-level diagram illustrating an electrochemical device fabricated according to aspects of the present disclosure.

[0014] Details

[0015] In some aspects, the present disclosure relates to an electrolyte comprising a substantially eutectic mixture comprising two or more salts, each salt consisting essentially of an alkali metal cation and a corresponding sulfonyl imide anion. As used herein and in the appended claims, the term "substantially eutectic mixture" and similar terms are used to indicate that the composition ratio of the constituent salts is at or within an acceptable tolerance from the theoretical eutectic point of the mixture, such as ±10%, ±5%, ±2% or ±1%, depending on the needs of the specific application of the particular electrolyte under consideration. In some embodiments, each of the eutectic mixtures of the present disclosure contained in the electrolyte exhibits the inherent properties of the eutectic mixture, such as a wide electrochemical window, high conductivity, excellent thermal stability, and excellent chemical stability, and also provides improvements to a variety of problems, such as volatilization, ignition, and side reactions of the electrolyte caused by the conventional use of organic solvents.

[0016] In some embodiments, the eutectic mixture of the present disclosure has a melting point equal to or lower than about 73°C, lower than about 65°C, or lower than about 50°C. Therefore, in some embodiments, the eutectic mixture of the present disclosure can act as a molten salt in certain applications, such as electrolytes for batteries and supercapacitors, among others. It should be noted that throughout the present disclosure, the term "about" when used with the corresponding numerical value refers to ±20% of the numerical value, typically ±10% of the numerical value, typically ±5% of the numerical value, and most typically ±2% of the numerical value. In some embodiments, the term "about" can be regarded as accurately indicating the actual numerical value.

[0017] In some embodiments, the eutectic mixtures of the present disclosure and electrolytes prepared therefrom may have a viscosity in the range of about 1 centipoise (cP) to about 50 cP, or in the range of about 5 cP to about 20 cP, as well as other ranges. In this regard, in some embodiments, it may be desirable to include at least one fluorinated additive such as a fluorinated ether or a fluorinated glyme into the electrolyte of the present disclosure, for example to reduce the viscosity of the electrolyte and / or to reduce the melting temperature of the electrolyte. If included, the at least one fluorinated additive may be provided in an amount of less than about 10% by weight of the electrolyte / eutectic mixture, such as in the range of about 1% to about 10% by weight.

[0018] In some embodiments, the electrolyte prepared according to the present invention consists essentially of an alkali metal sulfonyl imide salt in a eutectic mixture. Other substances such as water and / or protic or aprotic solvents may be present unintentionally or unavoidably, and such substances are specifically excluded under the term "consisting essentially of" and similar terms. In embodiments of the present disclosure where at least one fluorine-containing additive is present in the electrolyte, the electrolyte may consist essentially of an alkali metal sulfonyl imide salt and at least one fluorine-containing additive in a eutectic mixture.

[0019] On the other hand, the present disclosure relates to the use of electrolytes prepared according to the present disclosure. For example, the electrolyte can be used in any suitable electrochemical device, such as a battery (secondary battery and primary battery) or a supercapacitor, including lithium ion batteries, lithium metal batteries, lithium sulfur batteries, other alkali metal-based batteries and sulfur metal batteries and others. As mentioned above, the electrolyte prepared according to the present disclosure can provide, for example, any one or more of a wide electrochemical window, high conductivity, excellent thermal stability and excellent chemical stability, and can also provide improvements to a variety of problems, such as evaporation, ignition and side reactions of electrolytes caused by conventional use of organic solvents, all of which can be converted into more robust, higher-functioning electrochemical devices when compared to similar conventional electrochemical devices.

[0020] Details of the foregoing and other aspects of the disclosure are described below.

[0021] Exemplary Eutectic Mixtures

[0022] In some embodiments, a eutectic mixture containing two alkali metal sulfonyl imide salts, i.e., a binary eutectic mixture, can be represented as:

[0023] n(X1 + Y1 - )+m(X2 + Y2 - )(1)

[0024] in:

[0025] X1 + Y1 - is the first salt, where X1 + is an alkali metal cation, and Y1 - is the sulfonimide anion;

[0026] X2 + Y2 - is the second salt, where X2 + is an alkali metal cation, and Y2 - is the sulfonimide anion;

[0027] n is the mole fraction of the first salt in the eutectic mixture;

[0028] m is the mole fraction of the second salt in the eutectic mixture; and

[0029] n+m=1.

[0030] As an alkali metal ion, X1 + and X2 + Each of the following is selected from Li + 、Na + , K + , Rb + , Cs + and Fr. + and in some embodiments, X1 + and X2 + Different from each other. + and Y2 + Each of which may be, for example, FSO2N - SO2F(FSI) or FSO2N - SO2CF3(FTFSI), and Y1 + and Y2 +A number of exemplary binary eutectic mixtures are presented in Table II below. However, first, Table I below shows the molecular weights and melting points of individual alkali metal sulfonyl imide salts that can be used to prepare various eutectic mixtures of the present disclosure.

[0031]

[0032]

[0033] In one example of searching for a eutectic point to determine the values ​​of the mole fractions n and m that define a eutectic mixture, a Tamman plot can be constructed by preparing and testing several mixture compositions of the same salts but at different mole fraction ratios. Figure 1 , which shows an exemplary phase diagram 100 and an exemplary Tamman diagram 104 of a binary system of compositions A and B. In the context of the present disclosure, A is any one of the first fluorinated sulfonylimide salt and the second fluorinated sulfonylimide salt, and B is the other of the fluorinated sulfonylimide salts. As will be appreciated by those skilled in the art, the phase diagram 100 shows a solidus temperature curve 108, a liquidus temperature curve 112, and a eutectic point 116.

[0034] As an initial step, differential scanning calorimetry (DSC) can be run independently on each of pure A and pure B. Several, for example, three different mixture compositions are then prepared, such as A:B molar ratios of 30:70, 50:50, and 30:70, and tested using DSC. Plotting the resulting melting temperature values ​​can provide a general idea of ​​where the eutectic point will fall. A Tamman diagram 104 can be plotted to more accurately find the eutectic point 116. Once the eutectic point 116 and the corresponding values ​​of n and m in Formula 1 above have been determined from the Tamman diagram 104, a eutectic mixture can be prepared and tested using DSC to confirm that the actual melting temperature corresponds to the eutectic point 116 determined from the Tamman diagram 104. Table II below illustrates some exemplary, non-limiting binary eutectic mixtures of fluorinated sulfonylimide salts of the present disclosure as determined using this extrapolation and Tamman diagram methods.

[0035]

[0036]

[0037] In some embodiments, to prepare a binary eutectic mixture, the process can be carried out in a glove box with <0.1 parts per million (ppm) of water present. In a typical experiment, a first fluorinated sulfonyl imide salt having a mole fraction of n and a second fluorinated sulfonyl imide salt having a mole fraction of m can be appropriately mixed by grinding to prepare a corresponding eutectic mixture, grinding, for example, using a mortar and pestle. The melting point of the eutectic mixture can be measured using DSC. This is a method for determining the eutectic temperature in Table II above. Alternatively, a first fluorinated sulfonyl imide salt having a mole fraction of n and a second fluorinated sulfonyl imide salt having a mole fraction of m can be placed in a dry flask under an inert (e.g., argon) atmosphere and dissolved in dimethyl carbonate to obtain a clear, uniform solution. The solvent can be removed, for example, at <0.01 torr and at 35°C to obtain a gel that produces a eutectic mixture composition after a long evacuation time.

[0038] Although the previous explanations and examples relate to binary eutectic mixtures, the same principles can be extended to higher order eutectic mixtures, such as ternary eutectic mixtures. In some embodiments, the ternary eutectic mixture of the present disclosure can be represented as follows:

[0039] n(X1 + Y1 - )+m(X2 + Y2 - )+p(X3 + Y3 - )(2)

[0040] in:

[0041] X1 + Y1 - is the first salt, where X1 + is an alkali metal cation, and Y1 - is the sulfonimide anion;

[0042] X2 + Y2 - is the second salt, where X2 + is an alkali metal cation, and Y2 - is the sulfonimide anion;

[0043] X3 + Y3 - is the third salt, where X3 + is an alkali metal cation, and Y3 - is the sulfonimide anion;

[0044] n is the mole fraction of the first salt in the eutectic mixture;

[0045] m is the mole fraction of the second salt in the eutectic mixture;

[0046] p is the mole fraction of the third salt in the eutectic mixture; and

[0047] n+m+p=1.

[0048] As an alkali metal ion, X1 + , X2 + and X3 + Each of the following is selected from Li + 、Na + , K + , Rb + , Cs + and Fr. + and in some embodiments, X1 + , X2 + and X3 + At least two of them are different from each other. + 、Y2 + and Y3 + Each of Y1 can be, for example, FSI or FTFSI. In some embodiments, Y1 + 、Y2 + and Y3 + At least two of Y1 are different from each other, and in some embodiments, all Y1 + 、Y2 + and Y3 + Same as each other.

[0049] In some embodiments, to prepare a ternary eutectic mixture, in a typical experiment, a first fluorinated sulfonyl imide salt having a mole fraction of n can be placed in a dry flask in a glove box (see above) and mixed with a second fluorinated sulfonyl imide salt having a mole fraction of m, followed by the addition of a third fluorinated sulfonyl imide salt having a mole fraction of p. The resulting ternary eutectic mixture can be heated until a liquid eutectic mixture is obtained. In order to make the mixture uniform, a stirring rod can be used to mix it thoroughly. The melting point of the obtained ternary eutectic mixture can be determined by using DSC. The electrochemical window can also be measured to determine the electrochemical redox stability.

[0050] Eutectic is a composition of at least two or more components, each of which melts and freezes in unison. During the crystallization stage, a mixture of components that act as a single composition is formed. These components freeze into a close mixture of crystals and melt simultaneously without separation. Eutectic can be a mixture of organic compounds and / or inorganic compounds. Therefore, eutectic can be prepared into organic-organic mixtures, inorganic-inorganic mixtures or organic-inorganic mixtures. This provides space for a variety of combinations that can be customized for specific applications. The benefits of eutectic mixtures include its ability to obtain more desired performance, such as a specific melting point or a higher heat storage capacity per unit volume.

[0051] Exemplary electrolyte using eutectic mixture (molten salt)

[0052] The eutectic mixture of the present disclosure, such as the eutectic mixture described above and exemplified below, can be used as a molten salt electrolyte for any suitable purpose, such as providing an electrolyte for an electrochemical device, the electrochemical device including any of the electrochemical devices mentioned above. In some embodiments, the molten salt electrolyte of the present disclosure has a melting point in the range of about 5°C to about 70°C. In some embodiments, the molten salt electrolyte of the present disclosure has a melting point in the range of about 5°C to about 30°C. In some embodiments, the molten salt electrolyte of the present disclosure has a melting point in the range of about 30°C to about 50°C. In some embodiments, the molten salt electrolyte of the present disclosure has a melting point in the range of about 50°C to about 70°C. In some embodiments, each molten salt electrolyte may be substantially composed of a eutectic mixture, i.e., without any additives intentionally added to provide some desired effects. In some embodiments, at least one additive having one or more benefits may be provided to the molten salt electrolyte. For example, at least one fluorine-containing additive can be used to reduce the viscosity of the molten salt electrolyte and / or reduce the melting temperature of the molten salt electrolyte, the at least one fluorine-containing additive such as a monofluorine-containing additive such as fluoroethylene carbonate (FEC), a difluorine-containing additive such as difluoroethylene carbonate (DEC), a trifluorine-containing additive such as CF3SO2NH2, fluorinated triethylphosphine oxide, fluorinated carbonates such as trifluoromethylethylmethyl carbonate, CF3CH2CO3CH3, or fluorinated ethers, or any combination thereof and others. In some embodiments, at least one fluorine-containing additive is provided to the molten salt electrolyte in an amount less than about 10% by weight relative to the molten salt electrolyte. For example, in such an embodiment, at least one fluorine-containing additive is provided to the molten salt electrolyte in an amount from about 1% to about 10% by weight. In some embodiments, each molten salt electrolyte comprising at least one additive such as at least one fluorine-containing additive can be substantially composed of a eutectic mixture (binary, ternary, etc.) and at least one additive.

[0053] Experimental Results

[0054] The above method is further illustrated by the following examples, but it will be understood that these examples are included only for the purpose of illustration and are not intended to limit the scope of the present disclosure. The examples presented herein are only to enable those of ordinary skill in the art to better understand the aspects of the scope of the present disclosure. Unless otherwise stated, all chemicals used in the described embodiments are of high purity (>99%). Strict precautions were taken to exclude moisture in the process, and the reaction was carried out in a well-ventilated fume hood.

[0055] Example 1.

[0056] Synthesis of binary eutectic mixture of LiFSI and CsFTFSI: This operation was carried out in a glove box with <0.1 ppm of water. LiFSI (0.34 mol) and CsFTFSI (0.66 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be 43 °C.

[0057] Example 2.

[0058] Synthesis of binary eutectic mixture of LiFSI and RbFTFSI; This operation was carried out in a glove box with <0.1 ppm of water. LiFSI (0.55 mol) and RbFTFSI (0.45 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be 47 °C.

[0059] Example 3.

[0060] Synthesis of binary eutectic mixture of LiFTFSI and KFSI: This operation was carried out in a glove box with <0.1 ppm of water. LiFTFSI (0.62 mol) and KFSI (0.38 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be 62 °C.

[0061] Example 4.

[0062] Synthesis of binary eutectic mixture of LiFTFSI and CsFSI: This operation was carried out in a glove box with <0.1 ppm of water. LiFTFSI (0.65 mol) and CsFSI (0.35 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be 55 °C.

[0063] Example 5.

[0064] Synthesis of binary eutectic mixture of LiFTFSI and RbFSI: This operation was carried out in a glove box with <0.1 ppm of water. LiFTFSI (0.64 mol) and RbFSI (0.36 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be 56 °C.

[0065] Example 6.

[0066] Synthesis of binary eutectic mixture of LiFTFSI and CsFTFSI: This operation was carried out in a glove box with <0.1 ppm of water. LiFTFSI (0.38 mol) and CsFTFSI (0.62 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be 53 °C.

[0067] Example 7.

[0068] Synthesis of binary eutectic mixture of KFSI and CsFTFSI: This operation was carried out in a glove box with <0.1 ppm of water. KFSI (0.52 mol) and CsFTFSI (0.48 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be 50°C.

[0069] Example 8.

[0070] Synthesis of binary eutectic mixture of KFTFSI and CsFSI: This operation was carried out in a glove box with <0.1 ppm of water. KFTFSI (0.37 mol) and CsFSI (0.63 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be 45 °C.

[0071] Example 9.

[0072] Synthesis of binary eutectic mixture of KFTFSI and RbFSI: This operation was carried out in a glove box with <0.1 ppm of water. KTFSI (0.63 mol) and RbFSI (0.37 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be 49 °C.

[0073] Example 10.

[0074] Synthesis of ternary eutectic mixture of LiFTFSI, KFTFSI and CsFTSI: This operation was carried out in a glove box with <0.1 ppm of water. LiFTFSI (0.35 mol), KTFSI (0.30 mol) and CsFTFSI (0.35 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be <70°C.

[0075] Example 11.

[0076] Synthesis of ternary eutectic mixture of LiFTFSI, RbFSI and CsFTFSI: This operation was carried out in a glove box with <0.1 ppm of water. LiFTFSI (0.35 mol), RbFSI (0.35 mol) and CsFTFSI (0.30 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be <70°C.

[0077] Example 12.

[0078] Synthesis of ternary eutectic mixture of LiFTFSI, KFSI and CsFTFSI: This operation was carried out in a glove box with <0.1 ppm of water. LiFTFSI (0.36 mol), KFSI (0.34 mol) and CsFTFSI (0.30 mol) were properly mixed by grinding with a mortar and pestle. The melting point of the eutectic mixture was measured using DSC. The melting point of the eutectic mixture was found to be <70°C.

[0079] Exemplary Uses of Molten Salt Electrolytes of the Disclosure

[0080] As mentioned above, the molten salt electrolyte of the present disclosure may be used as an electrolyte for electrochemical devices, among others. Figure 2 The figure shows an electrochemical device 200 made according to aspects of the present disclosure. Those skilled in the art will readily appreciate that the electrochemical device 200 may be, for example, a battery or a supercapacitor. In addition, those skilled in the art will readily appreciate that Figure 2 Only some basic functional components of the electrochemical device 200 are illustrated, and real-world examples of electrochemical devices such as secondary batteries or supercapacitors will typically be embodied using a wound structure or a stacked structure. In addition, those skilled in the art will understand that the electrochemical device 200 will include other components, such as electrical terminals, seals, thermal shutdown layers, and / or vents, among others, which are not shown in the figure for ease of description. Figure 2 Not shown in FIG.

[0081] In this embodiment, the electrochemical device 200 includes a positive electrode 204 and a negative electrode 208 spaced apart, and a pair of corresponding current collectors 204A, 208A. A porous dielectric separator 212 is located between the positive electrode 204 and the negative electrode 208 to electrically separate the positive electrode and the negative electrode, but allows ions of a molten salt electrolyte 216 prepared according to the present disclosure to flow through. The porous dielectric separator 212 and / or one, the other, or both (if porous) of the positive electrode 204 and the negative electrode 208 are impregnated with the molten salt electrolyte 216. Figure 2 In the embodiment of the present invention, the positive electrode 204 and the negative electrode 208 are both illustrated as porous, and the molten salt electrolyte 216 is illustrated as extending therein. As described above, the benefits of using the molten salt electrolyte of the present disclosure for the molten salt electrolyte 216 can include providing a wide electrochemical window, high conductivity, excellent thermal stability and excellent chemical stability, and can also provide improvements to a variety of problems, such as evaporation, ignition and side reactions of the electrolyte caused by the conventional use of organic solvents, all of which can be converted into more robust, higher-functioning electrochemical devices when compared to similar conventional electrochemical devices. Examples of molten salt electrolytes suitable for use as molten salt electrolytes 216 are described above. The electrochemical device 200 includes a container 220, which accommodates current collectors 204A, 208A, positive electrodes 204 and negative electrodes 208, a porous dielectric separator 212 and a molten salt electrolyte 216.

[0082] As will be appreciated by those skilled in the art, each of the positive electrode 204 and the negative electrode 208 comprises a suitable material that is compatible with the alkali metal ions and other components in the molten salt electrolyte 216, depending on the type and design of the electrochemical device. Each of the current collectors 204A, 208A can be made of any suitable conductive material, such as copper or aluminum or any combination thereof. The porous dielectric separator 212 can be made of any suitable porous dielectric material, such as porous polymers, among others. Figure 2 Various battery and supercapacitor configurations of the electrochemical device 200 are known in the art. If any of such known configurations are used, the novelty of the electrochemical device 200 lies in the composition of the molten salt electrolyte 216.

[0083] In some embodiments, aspects of the present disclosure may also include an electrochemical device. The device includes a positive electrode; a negative electrode separated from the positive electrode; a porous dielectric separator between the positive electrode and the negative electrode; and any of the electrolytes in the present application as submitted, the electrolyte being contained in at least the porous dielectric separator.

[0084] The foregoing has been a detailed description of an illustrative embodiment of the present invention. It should be noted that in this specification and the appended claims, unless otherwise specified or indicated, conjunctions such as used in the phrases "at least one of X, Y, and Z" and "one or more of X, Y, and Z" should be considered to mean that each item in the conjunction list can be present in any quantity in addition to each other item in the list, or in any quantity combined with any or all other items in the conjunction list, and each item can also be present in any quantity. Applying this general rule, the conjunction phrases in the foregoing examples where the conjunction list consists of X, Y, and Z should each include: one or more X; one or more Y; one or more Z; one or more X and one or more Y; one or more Y and one or more Z; one or more X and one or more Z; and one or more X, one or more Y, and one or more Z.

[0085] Various changes and additions can be made without departing from the spirit and scope of the present disclosure. The features of each of the various embodiments described above can be appropriately combined with the features of the other described embodiments to provide multiple feature combinations in related new embodiments. In addition, although many separate embodiments have been described above, what is described herein is merely an illustration of the application of the principles of the present invention. In addition, although the particular methods herein can be shown and / or described as being performed in a particular order, this order is highly variable within the scope of ordinary technicians to implement various aspects of the present disclosure. Therefore, this description is meant only as an example, rather than otherwise limiting the scope of the present invention.

[0086] This disclosure also relates to the following items:

[0087] 1. An electrolyte comprising:

[0088] A substantially eutectic mixture comprising a first salt X1 + Y1 - and second salt x2 + Y2 - ,in:

[0089] X1 + and X2 + Each of which is an alkali metal cation and X1 + Different from X2 + ;and

[0090] Y1 - and Y2 - Each of which is a sulfonimide anion and Y1 - Different from Y2 - .

[0091] 2. The electrolyte according to item 1, wherein the substantially eutectic mixture has a melting temperature and a viscosity, and the electrolyte further comprises a fluorine-containing additive that reduces the melting temperature and reduces the viscosity.

[0092] 3. The electrolyte according to item 2, wherein the fluorine-containing additive forms from about 1% to about 10% by weight of the electrolyte.

[0093] 4. The electrolyte according to item 2, wherein the electrolyte consists essentially of the first salt, the second salt and the fluorine-containing additive.

[0094] 5. The electrolyte according to item 2, wherein the viscosity is in the range of about 1 cP to about 50 cP.

[0095] 6. The electrolyte according to item 5, wherein the viscosity is in the range of about 5 cP to about 20 cP.

[0096] 7. The electrolyte according to item 1, wherein the electrolyte consists essentially of the first salt and the second salt.

[0097] 8. The electrolyte of item 1, wherein the substantially eutectic mixture has a melting temperature of about 73°C or less.

[0098] 9. The electrolyte according to item 8, wherein the melting temperature is about 65°C or less.

[0099] 10. The electrolyte according to item 9, wherein the melting temperature is about 50°C or less.

[0100] 11. The electrolyte according to item 1, wherein the electrolyte has an electrochemical window from 0V to about 5V.

[0101] 12. The electrolyte according to item 1, wherein Y1 - and Y2 - Select from FSO2N - SO2F(FSI - ) and FSO2N - SO2CF3(FTFSI - ) group.

[0102] 13. The electrolyte according to item 12, wherein X1 + and X2 + Choose Li + 、Na + , K + , Rb + and Cs + Composed of groups.

[0103] 14. The electrolyte of item 1, wherein the substantially eutectic mixture has a melting temperature in the range of about 5°C to about 70°C.

[0104] 15. The electrolyte of item 1, wherein the substantially eutectic mixture has a melting temperature in the range of about 30°C to about 70°C.

[0105] 16. The electrolyte of item 1, wherein the substantially eutectic mixture has a melting temperature in the range of about 5°C to about 30°C.

[0106] 17. The electrolyte according to item 1, further comprising a third salt X3 + Y3 - , where X3 + Different from X1 + and X2 + Each of the .

[0107] 18. The electrolyte according to item 17, wherein the substantially eutectic mixture has a melting temperature and a viscosity, and the electrolyte further comprises a fluorine-containing additive that reduces the melting temperature and reduces the viscosity.

[0108] 19. The electrolyte of item 18, wherein the fluorine-containing additive forms from about 1% to about 10% by weight of the electrolyte.

[0109] 20. The electrolyte according to item 18, wherein the electrolyte consists essentially of the first salt, the second salt and the fluorine-containing additive.

[0110] 21. The electrolyte according to item 18, wherein the viscosity is in the range of about 1 cP to about 50 cP.

[0111] 22. The electrolyte according to item 21, wherein the viscosity is in the range of about 5 cP to about 20 cP.

[0112] 23. The electrolyte according to item 17, wherein the electrolyte consists essentially of the first salt, the second salt and the third salt.

[0113] 24. The electrolyte of clause 17, wherein the substantially eutectic mixture has a melting temperature of about 73°C or less.

[0114] 25. The electrolyte according to item 24, wherein the melting temperature is about 65°C or less.

[0115] 26. The electrolyte according to item 25, wherein the melting temperature is about 50°C or less.

[0116] 27. The electrolyte of item 17, wherein the electrolyte has an electrochemical window from 0 V to about 5 V.

[0117] 28. The electrolyte according to item 17, wherein Y1 - 、Y2 - and Y3 - Select from FSO2N - SO2F(FSI - ) and FSO2N - SO2CF3(FTFSI - ) group.

[0118] 29. The electrolyte according to item 28, wherein X1 + , X2 + and X3 + Choose Li + 、Na + , K + , Rb + and Cs + Composed of groups.

[0119] 30. The electrolyte of item 17, wherein the substantially eutectic mixture has a melting temperature in the range of about 5°C to about 70°C.

Claims

1. An electrolyte comprising: A substantially eutectic mixture comprising a first salt X1 + Y1 - and second salt x2 + Y2 - ,in: X1 + and X2 + Each of which is an alkali metal cation and X1 + Different from X2 + ; Y1 - and Y2 - Each of which is a sulfonimide anion and Y1 - Different from Y2 - ; Y1 - and Y2 - One of them includes FSO2N - SO2CF3(FTFSI - );and The substantially eutectic mixture has a melting temperature of 50°C or less.

2. The electrolyte of claim 1, wherein the substantially eutectic mixture has a viscosity, and the electrolyte further comprises a fluorine-containing additive that reduces the melting temperature and reduces the viscosity.

3. The electrolyte according to claim 2, wherein the fluorine-containing additive forms from 1 to 10% by weight of the electrolyte.

4. The electrolyte of claim 2, wherein the electrolyte consists essentially of the first salt, the second salt, and the fluorine-containing additive. The electrolyte according to claim 2 , wherein the viscosity is in the range of 1 cP to 50 cP. The electrolyte according to claim 5 , wherein the viscosity is in the range of 5 cP to 20 cP.

7. The electrolyte of claim 1, wherein the electrolyte consists essentially of the first salt and the second salt.

8. The electrolyte of claim 1, wherein the electrolyte has an electrochemical window from 0 V to 5 V.

9. The electrolyte according to claim 1, wherein Y1 - and Y2 - Select from FSO2N - SO2F(FSI - ) and FSO2N - SO2CF3(FTFSI - ) group.

10. The electrolyte according to claim 9, wherein X1 + and X2 + Choose Li + 、Na + , K + , Rb + and Cs + Composed of groups.

11. The electrolyte according to claim 1, wherein the melting temperature is in the range of 5°C to 50°C.

12. The electrolyte according to claim 1, wherein the melting temperature is in the range of 30°C to 50°C.

13. The electrolyte according to claim 1, wherein the melting temperature is in the range of 5°C to 30°C.

14. The electrolyte according to claim 1, further comprising a third salt X3 + Y3 - , where X3 + Different from X1 + and X2 + Each of the .

15. The electrolyte of claim 14, wherein the substantially eutectic mixture has a viscosity, and the electrolyte further comprises a fluorine-containing additive that reduces the melting temperature and reduces the viscosity.

16. The electrolyte of claim 15, wherein the fluorine-containing additive forms from 1 to 10% by weight of the electrolyte.

17. The electrolyte of claim 15, wherein the electrolyte consists essentially of the first salt, the second salt, the third salt, and the fluorine-containing additive.

18. The electrolyte according to claim 15, wherein the viscosity is in the range of 1 cP to 50 cP.

19. The electrolyte of claim 18, wherein the viscosity is in the range of 5 cP to 20 cP.

20. The electrolyte of claim 14, wherein the electrolyte consists essentially of the first salt, the second salt, and the third salt.

21. The electrolyte of claim 14, wherein the electrolyte has an electrochemical window from 0 V to 5 V.

22. The electrolyte according to claim 14, wherein Y1 - 、Y2 - and Y3 - Select from FSO2N - SO2F(FSI - ) and FSO2N - SO2CF3(FTFSI - ) group.

23. The electrolyte according to claim 22, wherein X1 + , X2 + and X3 + Choose Li + 、Na + , K + , Rb + and Cs + Composed of groups.

24. The electrolyte of claim 14, wherein the melting temperature is in the range of 5°C to 50°C.

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