electrolytes

Abstract

The present invention relates to the use of a composition comprising a solvent system including a first component comprising one or more non-aqueous solvents and a second component comprising one or more performance additives as an electrolyte. Devices and methods incorporating the electrolyte composition are also disclosed.

Description

[Technical Field]

[0001] The present invention relates to compositions and their use, preferably as electrolytes (i.e., "electrolyte compositions") in electrochemical cells. Methods, devices, and apparatus using said electrolyte compositions are also disclosed. [Background technology]

[0002] Metal-ion cells (e.g., alkali metal-ion cells such as sodium-ion cells, potassium-ion cells, and lithium-ion cells) are reusable secondary batteries that contain an anode (negative electrode), a cathode (positive electrode), and an electrolyte material and can store energy. Metal-ion cells contain an active material layer coated on a current collector foil to form the cathode, and a similar configuration exists for the corresponding anode. The cathode and anode are physically separated by a separator that allows the flow of ions within a liquid electrolyte medium, which is uniformly present within the cell and wets the cathode, anode, and separator throughout. When a metal-ion cell is charged, Na + (or K + , Li + ) ions are shuttled from the cathode active material and inserted into the anode active material (electrons flow through the external circuit), and the reverse process occurs during discharge (sodium ions are extracted from the anode active material and inserted into the cathode active material, and electrons flow through the external circuit to perform useful work).

[0003] The working principle of the anode-free sodium cell is to convert sodium metal cations (Na ) from the cathode active material. + ) in the cathode active material and the plating / stripping of sodium metal (Na) on the anode current collector. This operating principle differs from the metal-ion cells described above, which operate by + , K. + , Li +) and metal cations (e.g., Na) in the anode active material. + , K. + , Li + ) extraction / insertion.

[0004] One area requiring more attention is the development of electrolyte compositions suitable for use in metal-ion cells and / or anode-free sodium cells, among others. The primary purpose of the electrolyte composition in both metal-ion cells and anode-free sodium cells is to provide transport channels for positive electroactive metal ions while hindering the movement of electrons through the same medium. Therefore, the importance of the electrolyte composition should not be overlooked, as it is primarily critical in determining the cell life and the practical performance, such as capacity, rate capability, safety, etc., that the cell can achieve.

[0005] To date, conventional theory has indicated that electrolyte compositions in metal-ion cells must contain metal ion salts to be functional. In support of this, applicants refer to Chapter 14, page 322, section 14B.3 "lithium Salts" by Huggins ("Advanced Batteries: Materials Science Aspect", Springer, 2008), which states that "to function as an electrolyte in a lithium cell, [these] solvents must contain lithium salts." must "It is stated.

[0006] It is also widely recognized in the battery industry that the ionic conductivity (mS / cm) of a liquid electrolyte is important in determining the dynamic response of a battery. In support of this, the applicant refers to Chayambuka et al. ("An experimental and modeling study of sodium-ion battery electrolytes," Journal of Power Sources, 516, 2021, 230658).

[0007] This paper demonstrates using model experiments that when the concentration of NaPF6 salt in a 1:1 mixed ethylene carbonate:propylene carbonate electrolyte is zero, the conductivity of the electrolyte (mS / cm) is also predicted to be zero.

[0008] In fact, Figure 3a of Chayambuka et al. shows that in dilute electrolyte solutions, the ionic conductivity is approximately 1 mol kg -1 These results show that the ATP actually increases with sodium salt concentration until an optimum concentration of 0.05 is reached.

[0009] Similarly, Figures 4 and 6 of Logan et al., ("A Critical Evaluation of Advanced Electrolyte Model", J. Electrochem. Soc., 165, 2018) reiterate Chayambuka's teaching, namely, that if the concentrations of both lithium and sodium salts are zero, the ionic conductivity of the electrolyte is zero.

[0010] Thus, there is currently a general teaching that electrolyte compositions that are substantially free of one or more metal-containing salts will result in very large polarization of the liquid electrolyte, regardless of the C-rate of the battery. Thus, the electrolyte compositions ostensibly do not provide ionic conductivity and therefore will prevent the charging / discharging of the cell; i.e., the cell / battery is not expected to operate at all.

[0011] The use of batteries, and therefore electrolytes, is becoming more widespread, particularly in stationary and automotive applications (e.g., electric vehicles). However, due to certain suspected environmental concerns, including the generation of toxic and corrosive gases associated with the use of non-renewable fossil fuels, it is becoming increasingly desirable to use batteries (possibly in combination with renewable fuels) and, therefore, electrolyte compositions in such batteries, that have low or even zero levels of toxicity and / or corrosivity.

[0012] Therefore, there is a need for low or non-toxic and / or low or non-corrosive electrolyte compositions that are alternatives to fossil fuels and provide batteries that are considered environmentally safer alternatives.

[0013] Additionally, there is increasing pressure on manufacturers of electric vehicles (for example) to reduce the weight of their vehicles to improve efficiency and performance. Also, in stationary applications, it is desirable to create batteries that are lighter and easier to install. Therefore, there is a need for batteries, and therefore electrolyte compositions, that provide an alternative to existing electrolyte compositions and are considered lighter (i.e., less dense) substitutes.

[0014] However, it is generally believed that for a suitable electrolyte composition, a number of attributes must be met, including: · Chemical stability - there must be no reaction during cell operation, including reaction of the electrolyte with itself or with the separator, electrodes, current collectors, or packaging materials used; Electrochemical stability - a wide electrochemical stability window, i.e., a large gap between the high and low onset potentials for degradation by oxidation or reduction; Thermal stability - the electrolyte composition must not decompose or chemically decompose during normal cell operation and at operating temperatures; Physical properties - the electrolyte composition must be liquid, so its melting and boiling points must be well outside the range of the cell's internal operating temperatures; · High ionic conductivity and low electronic conductivity are required to maintain cell operation by metal ion transport and minimize cell self-discharge, respectively; are based on sustainable chemistry, i.e., they use abundant elements and are produced via low-impact synthesis (energy, pollution, etc.); and Cost-effective production.

[0015] With respect to efficiency in use, it is important to note that loss of cycle or rate performance of an electrolyte composition can have secondary environmental impacts due to increased fossil fuel use resulting from increased demand for electrical energy.

[0016] Additionally, it would generally be desirable for low or non-toxic and / or low or non-corrosive and / or low density electrolyte compositions to be useful in batteries without significant modification to conventional battery manufacturing techniques. [Prior art documents] [Non-patent literature]

[0017] [Non-Patent Document 1] Huggins (Advanced Batteries: Materials Science Aspect, Springer, 2008), Chapter 14, page 322, section 14B.3 "lithium salts" [Non-patent document 2] Chayambuka et al. (“An experimental and modeling study of sodium-ion battery electrolytes”, Journal of Power Sources, 516, 2021, 230658) [Non-patent document 3] Logan et al., (“A Critical Evaluation of Advanced Electrolyte Model”, J. Electrochem. Soc., 165, 2018) Summary of the Invention [Problem to be solved by the invention]

[0018] SUMMARY OF THE INVENTION Accordingly, the present invention aims to mitigate or eliminate one or more of the above disadvantages of the known art. [Means for solving the problem]

[0019] The present invention provides a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives; These objects are achieved by providing the use of a composition as an electrolyte, the composition comprising a solvent system comprising: DETAILED DESCRIPTION OF THE INVENTION

[0020] As referred to herein, the terms "electrolyte" and "electrolyte composition" are considered equivalent to each other and are used interchangeably. The concentration of the metal-containing salt is conveniently expressed as its molar concentration in the solvent system, i.e., the total number of moles of metal-containing salt per kg or 1000 g of the solvent system (i.e., the combined weight of the first component and the second component). Optionally, the concentration of the metal-containing salt is from 0 mol / kg to ≦0.1 mol / kg.

[0021] Alternatively, concentrations disclosed herein expressed as "M" (molar) refer to the total number of moles of metal-containing salt per liter of solvent system. Typically, the electrolyte composition is substantially free of one or more metal-containing salts. Because metal-containing salts are substantially excluded from the electrolyte composition according to the present invention, it is generally believed that the toxicity and / or corrosiveness of the composition is reduced compared to electrolyte compositions containing metal-containing salts. Indeed, typical metal-containing salts are generally present in a molar concentration of about 0.5 to 2 m, for example, comprising 5 to 35 wt. %, preferably 7 to 32 wt. % of the total electrolyte composition. Metal-containing salts commonly found in sodium-ion cells exhibit toxicity and / or corrosiveness as described below:

[0022] Sodium hexafluorophosphate (NaPF6): Corrosion / Irritation Hazard: Skin Corrosion, Category 1B, H314 Toxicity Hazards: Oral - Category 4, H302; Inhalation - Category 4, H332; Dermal - Category 4, H312 Information taken from Sigma Aldrich Safety Data Sheet, Version 6.2; NaPF6; Product Number 208051.

[0023] Sodium perchlorate (NaClO4) Corrosion / Irritation Hazard: Eye Irritation, Category 2, H319 Toxicity: Oral - Category 4, H302, Specific Organ Toxicity - Repeated Exposure, Category 2, Thyroid, H373 Information taken from Sigma Aldrich Safety Data Sheet, Version 6.5; NaClO4; Product Number 906700.

[0024] Sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) Corrosion / Irritation Hazard: Skin Corrosion: Category 1B, H314; Eye Irritation: Category 1, H318; May Cause Respiratory Irritation, H335 Information taken from Solvionic Safety Data Sheet, Version 8; NaTFSI; Product Number M1108C.

[0025] Furthermore, those skilled in the art will understand that the absence of a metal-containing salt (which is solid at room temperature) will result in a lower density of an electrolyte composition according to the present invention than an electrolyte composition containing a metal-containing salt, since the latter is a finite amount of solid powder dissolved in a solvent mixture, and it is well known that the density of a solid is generally higher than the density of a liquid. Indeed, Figures 4c and 4d in Monti et al., Phys. Chem. Chem. Phys., 2020,22, 22768-22777 clearly show that the density of the electrolyte increases as the concentration of the metal-containing salt increases, increasing by approximately 11% between 0.3M and 2M in the case of the NaTFSI or NaPF6 system. The inventors have also observed similar benefits in the lower density of electrolytes prepared according to the present invention.

[0026] Thus, the electrolyte compositions of the present invention are believed to be lighter (i.e., less dense) than existing metal-containing salt electrolyte compositions, making them particularly desirable in metal-ion cells and / or anode-free sodium cells for use in mobile (e.g., automotive) or stationary applications.

[0027] As evidenced by the experimental performance data disclosed herein, the cycling and / or rate performance of the electrolyte compositions of the present invention is believed to be similar to or improved compared to existing metal-containing salt electrolyte compositions. Therefore, the electrolyte compositions of the present invention are not believed to cause secondary environmental impacts due to increased fossil fuel usage. Furthermore, eliminating the need for salt not only significantly reduces fabrication costs, but also improves the overall simplicity of cell functionality.

[0028] As disclosed herein, the electrolyte compositions of the present invention are typically substantially free of one or more metal-containing salts. However, if the electrolyte compositions of the present invention contain one or more metal-containing salts, they contain an amount that has previously been assumed to provide no practical benefit to the cycling performance of practical electrochemical cells.

[0029] In one embodiment, the conductivity of the electrolyte composition at 25° C. can be less than 3 mS / cm, preferably less than 2.5 mS / cm, and more preferably less than 2 mS / cm. Alternatively, the conductivity range at 30° C. can be less than 5 mS / cm.

[0030] In one embodiment, the electrolyte composition of the present invention may contain water in an amount of about 500 ppm or less. In one embodiment, the electrolyte composition of the present invention may contain water in an amount of about 100 ppm to 500 ppm. In some embodiments, the electrolyte composition of the present invention is substantially free of water.

[0031] As used herein, the phrase "metal-containing salt" refers to a metal salt that is capable of imparting ionic conductivity to an electrolyte composition. The second component of the solvent system can comprise or consist essentially of one or more performance additives, preferably selected from sulfur-containing compounds, boron-containing compounds, and surfactants.

[0032] One or more performance additives may be present as a second component of the solvent system in an amount of >0.5 to ≦10 wt % of the solvent system. One or more of these performance additives, as a second component of the solvent system, can enable the formation of a stable cathode-electrolyte interface (CEI) on the cathode and / or a stable solid-electrolyte interface (SEI) on the anode, or can provide other benefits, such as improved wetting of the electrolyte on the separator and / or electrode material by reducing the surface tension of the solvent system, and / or surface adsorption effects that can effectively form an artificial SEI / CEI layer, which in turn provides benefits such as improved coulombic efficiency and improved cathode discharge capacity.

[0033] Preferably, the one or more performance additives are selected from sulfur-containing compounds present as a second component of the solvent system in an amount of >0 to ≦10 wt % of the solvent system. For the avoidance of doubt, the phrase "weight of the solvent system" as used herein means the weight of the first component of the solvent system combined with the weight of the second component of the solvent system.

[0034] The sulfur-containing compound can be present as a second component of the solvent system in an amount of >0.1 to ≦10 wt. %, preferably ≧0.2 to ≦9 wt. %, and more preferably ≧0.3 to ≦5 wt. % of the solvent system. Optionally, the sulfur-containing compound can be present as a second component of the solvent system in an amount of about 1 wt. %, about 2 wt. %, or about 5 wt. % of the solvent system. An amount of about 5 wt. % of the solvent system as the second component is highly preferred.

[0035] More preferably, the one or more performance additives are selected from boron-containing compounds present as a second component of the solvent system in an amount of >0 to ≦10% by weight of the solvent system. The boron-containing compound can be present as a second component of the solvent system in an amount of >0.1 to ≦10 wt. %, preferably ≧0.2 to ≦9 wt. %, and more preferably ≧0.3 to ≦5 wt. % of the solvent system. Optionally, the boron-containing compound can be present as a second component of the solvent system in an amount of about 1 wt. %, about 2 wt. %, or about 5 wt. % of the solvent system. Amounts of about 1 wt. % or about 5 wt. % of the solvent system as the second component are highly preferred.

[0036] Alternatively, the one or more performance additives are selected from surfactants present as a second component of the solvent system in an amount of >0 to ≦10 wt % of the solvent system. The surfactant can be present as a second component of the solvent system in an amount of >0.1 to ≦10% by weight of the solvent system, preferably ≧0.2 to ≦9% by weight of the solvent system, and more preferably ≧0.3 to ≦5% by weight of the solvent system. Optionally, the surfactant can be present as a second component of the solvent system in an amount of about 1%, about 2%, or about 5% by weight of the solvent system. An amount of about 1% by weight of the solvent system as the second component is highly preferred.

[0037] The second component of the solvent system can comprise or consist essentially of two or more performance additives. The two or more performance additives can be present as the second component of the solvent system in an amount of >0.5 to ≦10 wt % of the solvent system.

[0038] The two or more performance additives as the second component of the solvent system can include a mixture of a boron-containing compound and a surfactant, i.e., one or more boron-containing compounds can be mixed with one or more surfactants to provide a mixture of two or more performance additives.

[0039] The two or more performance additives as the second component of the solvent system can include a mixture of a boron-containing compound in an amount of ≧0.5 to <10 wt.% of the solvent system and a surfactant in an amount of ≧0.5 to <10 wt.% of the solvent system. Optionally, the total amount of the two or more performance additives as the second component of the solvent system does not exceed about 10 wt.% based on the weight of the solvent system.

[0040] The two or more performance additives as the second component of the solvent system can include a mixture of a boron-containing compound in an amount of ≧1 to <5 wt. % of the solvent system and a surfactant in an amount of ≧1 to <5 wt. % of the solvent system. Optionally, the total amount of the two or more performance additives as the second component of the solvent system does not exceed about 5 wt. % based on the weight of the solvent system.

[0041] Alternatively, the two or more performance additives as the second component of the solvent system can comprise a mixture of sulfur-containing compounds and surfactants, i.e., one or more sulfur-containing compounds can be mixed with one or more surfactants to provide a mixture of two or more performance additives.

[0042] The two or more performance additives as the second component of the solvent system can include a mixture of a sulfur-containing compound in an amount of ≧0.5 to <10 wt. % of the solvent system and a surfactant in an amount of ≧0.5 to <10 wt. % of the solvent system. Optionally, the total amount of the two or more performance additives as the second component of the solvent system preferably does not exceed about 10 wt. % based on the weight of the solvent system.

[0043] The two or more performance additives as the second component of the solvent system can include a mixture of a sulfur-containing compound in an amount of ≧1 to <5 wt. % of the solvent system and a surfactant in an amount of ≧1 to <5 wt. % of the solvent system. Optionally, the total amount of the two or more performance additives as the second component of the solvent system does not exceed about 5 wt. % based on the weight of the solvent system.

[0044] The second component of the solvent system can comprise or consist essentially of three or more performance additives. The three or more performance additives can be present as the second component of the solvent system in an amount of >0.5 to ≦10 wt % of the solvent system.

[0045] The three or more performance additives as the second component of the solvent system are: sulfur-containing compounds; boron-containing compounds; and surfactants; The mixture may include:

[0046] That is, one or more sulfur-containing compounds can be mixed with one or more sulfur-containing compounds, one or more boron-containing compounds, and one or more surfactants to provide a mixture of three or more performance additives.

[0047] The three or more performance additives as the second component of the solvent system are: a sulfur-containing compound in an amount of ≥ 0.5 to < 10 wt. % of the solvent system; a boron-containing compound in an amount of ≥ 0.5 to < 10 wt. % of the solvent system, and a surfactant in an amount of ≥ 0.5 to < 10 wt. % of the solvent system; The mixture may include:

[0048] Optionally, the total amount of the three or more performance additives as the second component of the solvent system does not exceed about 10% by weight, based on the weight of the solvent system. The three or more performance additives as the second component of the solvent system are: a sulfur-containing compound in an amount of ≥ 0.5 to < 5 wt. % of the solvent system; a boron-containing compound in an amount of ≥ 0.5 to < 5 wt. % of the solvent system, and a surfactant in an amount of ≥ 0.5 to < 5 wt. % of the solvent system; The mixture may include:

[0049] Optionally, the total amount of the three or more performance additives as the second component of the solvent system does not exceed about 5% by weight based on the weight of the solvent system. The three or more performance additives as the second component of the solvent system are: a sulfur-containing compound in an amount of about 5% by weight of the solvent system; a boron-containing compound in an amount of about 1% by weight of the solvent system, and a surfactant in an amount of about 1% by weight of the solvent system; The mixture may include:

[0050] The total amount of the three or more performance additives as the second component of the solvent system can be about 7% by weight based on the weight of the solvent system. The three or more performance additives as the second component of the solvent system are: a sulfur-containing compound in an amount of about 2% by weight of the solvent system; a boron-containing compound in an amount of about 1% by weight of the solvent system, and a surfactant in an amount of about 1% by weight of the solvent system; The composition may comprise (or consist essentially of) a mixture of:

[0051] The total amount of the three or more performance additives as the second component of the solvent system can be about 4% by weight based on the weight of the solvent system. The one or more non-aqueous solvents as the first component of the solvent system are preferably selected from organic phosphate-based solvents, organic carbonate-based solvents, and glyme-based solvents.

[0052] The one or more organophosphate solvents present as the first component of the solvent system of the present invention can be defined as described herein. The one or more organophosphate solvents present as the first component of the solvent system can be cyclic or acyclic compounds.

[0053] The one or more organophosphate solvents as the first component of the solvent system are characterized in that they contain a phosphate ester group, i.e., a phosphorus atom 1) double-bonded to one oxygen atom and 2) single-bonded to three other oxygen atoms that are further single-bonded to one or more carbon atoms.

[0054] The general formula for such compounds is R3(PO)4, where R can be the same or different in each individual attachment instance. The preferred general formula for such compounds is RR'R''(PO4) [In formula: R, R' and R'' may be independently selected from any linear or branched, substituted or unsubstituted C1-C6-alkyl group; a linear or branched, substituted or unsubstituted C1-C6-alkenyl group; a linear or branched, substituted or unsubstituted C1-C6-alkoxy group; or a substituted or unsubstituted C3-C6-cycloalkyl-, phenyl- or heterocyclic-containing group.

[0055] Highly suitable electrolyte solvents for the first component of the solvent system include C1-C phosphates, such as triethyl phosphate. 10 Alkyl organic phosphates are included. Preferred electrolyte compositions of the present invention include a first component (i.e., a first component of a solvent system) comprising one or more organic phosphate-based solvents present in an amount of about 50% by weight or more, more preferably about 70% by weight or more, even more preferably about 90% by weight or more, and most preferably about 95% by weight or more of the organic phosphate-based solvent. One such example is a first component comprising triethyl phosphate in an amount of about 90% by weight or more of the first component of the solvent system.

[0056] Highly preferred electrolyte compositions of the present invention include a first component consisting essentially of one or more organic phosphate solvents, ideally triethyl phosphate. The one or more organic carbonate solvents present as the first component of the solvent system of the present invention can be defined as described herein.

[0057] The one or more organic carbonate-based solvents present as the first solvent component can be cyclic or acyclic compounds characterized by the fact that they contain a carbonate group, i.e., a carbonyl group flanked on either side by one or two alkoxy groups: R1O(C=O)OR2. The R1 and R2 groups are preferably independently hydrogen; or C1-C 20 a cyclic or acyclic, branched or unbranched, substituted or unsubstituted alkyl group; or a C1-C 20 a cyclic or acyclic, branched or unbranched, substituted or unsubstituted alkenyl group; or a C1-C 20 branched or unbranched, substituted or unsubstituted cycloalkyl-, phenyl- or heterocycle-containing groups; (i.e., they can be the same or different from one another).

[0058] A very suitable electrolyte solvent is C3-C 10 Cycloalkyl organic carbonates include, for example, propylene carbonate (C4H6O3) and ethylene carbonate (C3H4O3). Propylene carbonate (PC) (C4H6O3) exhibits particularly good compatibility with electrode materials, and its high solubility, wide liquidus range, and high boiling point also make this solvent advantageous for use in metal-ion batteries, especially sodium-ion batteries. Other highly suitable organic carbonate-based compounds include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylene carbonate (EC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC). Propylene carbonate (PC), diethyl carbonate (DEC), and ethylene carbonate (EC) are particularly preferred.

[0059] Preferred electrolyte compositions of the present invention include a first component (i.e., the first component of the solvent system) comprising an organic carbonate-based solvent present in an amount of at least 50 wt %, more preferably at least 70 wt %, even more preferably at least 90 wt %, and most preferably at least 95 wt % organic carbonate-based solvent.

[0060] One of the electrolyte compositions of the present invention can include a first component comprising a mixture of propylene carbonate in combination with one or more additional organic carbonate-based compounds. Ideally, the propylene carbonate is mixed with diethyl carbonate (DEC), preferably present in an amount of about 20% by weight based on the weight of the first component of the solvent system.

[0061] An alternative highly preferred electrolyte composition of the present invention can include a first component comprising a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and propylene carbonate (PC), ideally in a weight ratio range of 1-4:1-10:1-10 wt / wt, more ideally in a weight ratio of 1-2:1-5:1-2 wt / wt, and most preferably in a weight ratio of 1:2:1 wt / wt.

[0062] Another preferred electrolyte composition of the present invention can include a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). These organic carbonate components are preferably present in a weight ratio of 1-20:1-20 wt / wt, more preferably 1-10:1-10 wt / wt, also preferably 1-5:1-5 wt / wt, and most preferably 1:1 wt / wt.

[0063] Another electrolyte composition of the present invention can include a first component comprising a mixture of one or more organic phosphate-based solvents in combination with one or more organic carbonate-based compounds. Ideally, triethyl phosphate is mixed with fluoroethylene carbonate (FEC), preferably present in an amount of about 10% by weight based on the weight of the first component of the solvent system.

[0064] Alternatively, triethyl phosphate is mixed with vinylene carbonate (VC), preferably present in an amount of about 3% by weight based on the weight of the first component of the solvent system.

[0065] The one or more glyme solvents present as the first component of the solvent system of the present invention can be defined as described herein. The one or more glyme-based solvents present in the first component i) can be saturated acyclic polyethers that preferably contain no other functional groups. Glymes are also known as glycol diethers.

[0066] Highly suitable glyme solvents can be selected from ethylene glycol dimethyl ether (monoglyme), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme) and tetraethylene glycol dimethyl ether (tetraglyme). Diethylene glycol dimethyl ether (diglyme) and tetraethylene glycol dimethyl ether (tetraglyme) are particularly preferred glyme solvents.

[0067] When a mixture of glyme compounds is used, it is convenient to express the amount of each of one or more glyme solvents in weight ratios. For example, as noted above, a highly preferred glyme solvent can contain a mixture of diglyme and tetraglyme present as the first component of the solvent system, ideally in a weight ratio of 1-20:1-20 wt / wt, more preferably 1-10:1-10 wt / wt, also preferably 1-5:1-5 wt / wt, and most preferably 1:1 wt / wt.

[0068] A preferred electrolyte composition of the present invention includes a first component comprising a mixture of diglyme and tetraglyme. Ideally, diglyme is present in an amount of about 50% by weight of the first component of the solvent system, and tetraglyme is present in an amount of about 50% by weight of the first component of the solvent system. Thus, the total amount of diglyme and tetraglyme is preferably about 100% by weight of the first component of the solvent system.

[0069] As noted above, the second component of the solvent system according to the present invention can include one or more surfactants. The one or more surfactants of the present invention can be defined as described herein.

[0070] The total amount of one or more surfactants used in the second component of the solvent system of the present invention can be >0.2 to ≦20 wt % of the solvent system, based on the total weight of the electrolyte solvent system used in the electrolyte composition, preferably ≧0.2 to ≦10 wt %, more preferably ≧0.2 to ≦4 wt %, most preferably ≧0.5 to ≦3 wt %, and ideally 0.5 to ≦2.5 wt % of the solvent system.

[0071] The amount of one or more surfactants used in the second component of the electrolyte composition according to the present invention can be >0% by weight of the solvent system, ideally >0.2% by weight of the solvent system, and preferably >0.5% by weight, based on the total weight of the electrolyte solvent system used in the electrolyte composition.

[0072] The one or more surfactants used in the second component of the solvent system according to the present invention are performance additives, preferably selected to improve the ability of the electrolyte composition to wet the separator (especially polyolefin separators) and / or battery electrodes, thereby advantageously promoting longer battery cycle life. Furthermore, it is known in the literature that surfactants can provide non-dendritic metal plating / stripping (and also inhibit corrosion) through surface adsorption on various substrates. Preferred one or more surfactant additives are selected from anionic surfactants, cationic surfactants, nonionic (hydrophilic) surfactants, and amphoteric (zwitterionic) surfactants, with anionic surfactants and nonionic (hydrophilic) surfactants being particularly preferred. Ideally, such surfactant additives are one or more selected from the following:

[0073] 1) Anionic (negatively charged) surfactants. Suitable examples include carboxylates (such as alkyl carboxylates (e.g., fatty acid salts)), carboxylate fluorosurfactants; sulfates (such as alkyl sulfates (e.g., sodium lauryl sulfate) and alkyl ether sulfates (e.g., sodium laureth sulfate)); sulfonates (such as docusate (e.g., sodium dioctyl sulfosuccinate) and alkyl benzene sulfonates); and phosphate esters (such as alkyl aryl ether phosphates and alkyl ether phosphates (e.g., trioctyl phosphate)).

[0074] 2) Zwitterionic (amphoteric) surfactants, which can be anionic, cationic, or nonionic depending on the pH of the solution in which they are contained. Examples include RN + H2CH2COO - , R.N. + (CH3)2CH2CH2SO3 - , phospholipids (such as phosphatidylcholine (lecithin));

[0075] 3) Positively charged cationic surfactants, such as RN+ H3Cl - , R.N. + (CH3)3Cl - , dioctadecyldimethylammonium chloride, cetylpyridinium chloride, benzalkonium chloride, hexadecyltrimethylammonium chloride (CTAC), and hexadecyltrimethylammonium bromide (CTAB); and

[0076] 4) Nonionic surfactants, which are uncharged and examples include polyol esters (e.g., glycols, glycerol esters, sorbitan and sorbitan derivatives, such as fatty acid esters of sorbitan (Span) and its ethoxylated derivatives (Tween)), polyoxyethylene esters, and poloxamer containing block copolymers, such as poloxamer 84, poloxamer 105, poloxamer 123, poloxamer 124, poloxamer 188, poloxamer 237, poloxamer 338, poloxamer 407, and poloxamer F127.

[0077] Most preferably, the one or more surfactants used in the second component of the solvent system according to the present invention comprise one or more nonionic block copolymer-containing surfactants. A very suitable example is a poloxamer. A very specific example is poloxamer 123.

[0078] As noted above, the second component of the solvent system according to the present invention can include one or more sulfur-containing compounds. The one or more sulfur-containing compounds of the present invention can be defined as described herein.

[0079] The one or more sulfur-containing compounds used in the second solvent component of the solvent system according to the present invention are performance additives, preferably selected to enable the formation of a stable cathode-electrolyte interface (CEI) on the cathode and / or a stable solid-electrolyte interface (SEI) on the anode, which provides benefits such as improved first cycle coulombic efficiency (FCE = first cycle coulombic efficiency) and improved cycle life. Alternatively, such additives may decompose significantly and preferentially on the first cycle, which may result in lower first cycle efficiency, but then improved subsequent cycle stability.

[0080] Suitable sulfur-containing compounds can include cyclic and / or acyclic sulfur-containing compounds. Preferably, the sulfur-containing compound is a sulfone-, sulfate-, or sulfonate-containing compound.

[0081] In other words, a sulfur-containing compound can have a sulfonyl functional group attached to two carbon atoms (sulfone), a sulfonyl functional group attached to two oxygen atoms (sulfate), or a sulfonyl functional group attached to one carbon atom and one oxygen atom in a cyclic or acyclic structure (sulfonate). When the sulfonate is cyclic, the compound is sometimes called a sultone.

[0082] As used herein, the term "sulfone" means a central hexavalent sulfur atom double bonded to each of two oxygen atoms and having a single bond to each of two carbon atoms.

[0083] As used herein, the term "sulfate" means that a central hexavalent sulfur atom is double-bonded to two of the oxygen atoms and has single bonds to two other oxygen atoms, each of which is in turn single-bonded to a carbon atom.

[0084] As used herein, the term "sulfonate" means a central hexavalent sulfur atom double-bonded to two of the oxygen atoms, single-bonded to one carbon atom, and single-bonded to the other oxygen atom, which is in turn single-bonded to a carbon atom, which, when joined in a ring with the other carbon atoms bonded to the sulfur atom, forms a sultone.

[0085] The general formula for such compounds is RY(S=O)2Y'R' [In formula: Y and Y′ are independently selected from C or O (i.e., they can be the same or different from each other); When Y and Y' are the same, R and R' can be independently selected from any linear or branched, substituted or unsubstituted C1-C6 alkyl group; linear or branched, substituted or unsubstituted C1-C6 alkenyl group; linear or branched, substituted or unsubstituted C1-C6 alkoxy group (i.e., they can be the same or different from each other); or R and R' can, independently or together, form a substituted or unsubstituted C3-C6 cycloalkyl-containing group, a phenyl-containing group, or a heterocycle-containing group; and When Y and Y' are different from each other, R' can be independently selected from any linear or branched, substituted or unsubstituted C1-C6 alkyl group; linear or branched, substituted or unsubstituted C1-C6 alkenyl group; linear or branched, substituted or unsubstituted C1-C6 alkoxy group; or R and R' can independently or together form a substituted or unsubstituted C3-C6 cycloalkyl-, cycloalkenyl-, phenyl-, or heterocycle-containing group.

[0086] In some embodiments, such compounds have the general formula R-SO-R', where R and R' can be independently selected from any linear or branched, substituted or unsubstituted C1-C6 alkyl group; linear or branched, substituted or unsubstituted C1-C6 alkenyl group; linear or branched, substituted or unsubstituted C1-C6 alkoxy group (i.e., they can be the same as or different from each other); or R and R' can, independently or together, form a substituted or unsubstituted C3-C6 cycloalkyl-, phenyl-, or heterocycle-containing group.

[0087] Preferably, such compounds have the general formula RO(S=O)OR', where R and R' can be independently selected from any linear or branched, substituted or unsubstituted C1-C6 alkyl group; linear or branched, substituted or unsubstituted C1-C6 alkenyl group; linear or branched, substituted or unsubstituted C1-C6 alkoxy group (i.e., they can be the same as or different from each other); or R and R' can independently or together form a substituted or unsubstituted C3-C6 cycloalkyl-, phenyl-, or heterocycle-containing group.

[0088] Highly preferably, the sulfur-containing compound is selected from a cyclic sulfate (e.g., 1,3-propanediol cyclic sulfate (PCS), also known as 1,3,2-dioxathiane 2,2-dioxide (DTD or (CH2)3SO4)); 1,5,2,4-dioxadithiane 2,2,4,4-tetraoxide; or 1,3,2-dioxathiolane 2,2-dioxide.

[0089] Suitable examples of cyclic sulfones include sulfolane ((CH2)4SO2), 3-methylsulfolane ((CH3)CH(CH2)3SO2), and trimethylsulfone ((CH2)3SO2). Suitable examples of acyclic sulfones include methylphenylsulfone ((CH3)(CH5)SO2).

[0090] Suitable examples of sultones include 1-propene 1,3-sultone ((CH)2CH2SO3), and 1,3-propane sultone (CH2)3SO3. Most preferably, the sulfur-containing compound is 1,3-propanediol cyclic sulfate (PCS).

[0091] The total amount of one or more sulfur-containing compounds used in the second component of the solvent system according to the present invention is >0.5 to ≦10 wt % of the solvent system, based on the total weight of the electrolyte solvent system used in the electrolyte composition, preferably ≧0.6 to ≦6 wt %, more preferably ≧0.6 to ≦4 wt %, most preferably ≧0.6 to ≦3 wt %, and ideally 0.6 to ≦2.5 wt % of the solvent system.

[0092] The amount of one or more sulfur-containing compounds used in the second component of the solvent system according to the present invention can be >0 wt % of the solvent system, ideally >0.2 wt %, and preferably >0.5 wt % of the solvent system, based on the total weight of the electrolyte solvent system used in the electrolyte composition.

[0093] In one embodiment, sulfur-containing compounds as performance additives according to the present invention do not include dimethyl sulfoxide (DMSO). As noted above, the second component of the solvent system according to the present invention comprises one or more boron-containing compounds. The one or more boron-containing compounds of the present invention can be defined as described herein.

[0094] The boron-containing compounds used in the second solvent component of the solvent system according to the present invention are performance additives that are preferably selected to enable the formation of a stable cathode-electrolyte interface (CEI) on the cathode and / or a stable solid-electrolyte interface (SEI) on the anode, which provides benefits such as improved first cycle coulombic efficiency and / or improved cycle life.

[0095] Suitable boron-containing compounds can include cyclic and / or acyclic boron-containing compounds. Preferably, the one or more boron-containing compounds are borates or boroxines.

[0096] In other words, one or more boron-containing compounds can have a central boron atom attached to three oxygen atoms, each of which is further single-bonded to a carbon or silicon atom (borate). Alternatively, one or more boron-containing compounds can include a six-membered heterocyclic ring structure composed of three boron and oxygen atoms connected in alternating fashion by shared single bonds. Each boron atom is further single-bonded to an outer carbon atom or oxygen atom of the heterocyclic ring structure.

[0097] As used herein, the term "borate" means a central trivalent boron atom single-bonded to three oxygen atoms, each of which is in turn single-bonded to a carbon or silicon atom.

[0098] As used herein, the term "boroxine" refers to a six-membered heterocyclic compound composed of alternating single-bonded trivalent boron atoms and divalent oxygen atoms, with each boron atom further single-bonded to an oxygen or carbon atom outside the heterocyclic ring structure.

[0099] The general formula for such borate compounds is B(OYR)3, where Y and R can be the same or different in each individual attachment instance. More specifically, it can be written as follows: B(OYR)(OY'R')(OY''R'') [In formula: Y, Y', and Y'' are independently selected from C or Si (i.e., they can be the same or different from one another); and R, R' and R'' may be independently selected from hydrogen; any linear or branched, substituted or unsubstituted C1-C6 alkyl group; a linear or branched, substituted or unsubstituted C1-C6 alkenyl group; a linear or branched, substituted or unsubstituted C1-C6 alkoxy group; or a substituted or unsubstituted C3-C6 cycloalkyl-, phenyl-, or heterocycle-containing group.

[0100] More preferably, the boron-containing compound is selected from acyclic borates. Suitable examples include tris(trimethylsilyl)borate (TMSB); Tris(2,2,2-trifluoroethyl)borate; trimethyl borate; and Triethyl borate; Examples include:

[0101] The general formula for such boroxine compounds is B3(YR)3O3, where Y and R can be the same or different in each individual attachment instance. More specifically, it can be written as follows: B a (YR) b (O) c [In formula: Y is independently selected from C or O (i.e., they can be the same or different from each other); and R can be the same or different in each individual attachment and can be independently selected from hydrogen; any linear or branched, substituted or unsubstituted C1-C6 alkyl group; linear or branched, substituted or unsubstituted C1-C6 alkenyl group; linear or branched, substituted or unsubstituted C1-C6 alkoxy group; or substituted or unsubstituted C3-C6 cycloalkyl-, phenyl-, or heterocyclic-containing group; and · a=b=c, where a, b, and c are each 3].

[0102] A good example is: trimethoxyboroxine; and Trimethylboroxine; Examples include:

[0103] Most preferably, the boron-containing compound is tris(trimethylsilyl)borate (TMSB). The total amount of one or more boron-containing compounds used in the second component of the solvent system according to the present invention is >0.5 to ≦10 wt % of the solvent system, based on the total weight of the electrolyte solvent system used in the electrolyte composition, preferably ≧0.6 to ≦6 wt %, more preferably ≧0.6 to ≦4 wt %, most preferably ≧0.6 to ≦3 wt %, and ideally 0.6 to ≦2.5 wt % of the solvent system.

[0104] The amount of one or more boron-containing compounds used in the second component of the solvent system according to the present invention can be >0 wt % of the solvent system, ideally >0.2 wt %, and preferably >0.5 wt % of the solvent system, based on the total weight of the electrolyte solvent system used in the electrolyte composition.

[0105] The electrolyte composition according to the present invention may further comprise one or more additional compounds which may or may not be solvents. Examples of such additional compounds include flame retardant compounds (e.g., polyalkyl phosphate-containing compounds, preferably non-fluorinated polyalkyl phosphate-containing compounds), diluents (e.g., hydrofluoroether-containing compounds, preferably hydrofluoroalkyl ether-containing compounds), glycol ether acetates, ionic liquids, and any solvent that can act as an inert diluent to help reduce the viscosity of the electrolyte (e.g., hydrofluoroalkyl ethers, preferably 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE or TTE)).

[0106] Electrolyte compositions according to the present invention can also optionally include one or more additional performance additives, typically in an amount of <15 wt %, preferably <10 wt %, and more preferably 0.1 wt % to <5 wt % of the total weight of the solvent system used in the electrolyte composition. Preferably, such performance additives act at the electrolyte-electrode interface rather than in the bulk of the electrolyte, such as tris(trimethylsilyl)phosphite or tris(trimethylsilyl)phosphate.

[0107] Other suitable performance additives include polymeric additives for promoting overcharge protection, such as biphenyl, diphenylamine, dimethoxydiphenylsilane (DDS), 3-chloroanisole (3CA), N-phenylmaleimide, xylene (methyl-substituted benzene), and cyclohexylbenzene; additives for promoting overcharge protection based on a redox shuttle mechanism, such as 2,5-di-tert-butyl-1,4 dimethoxybenzene (DDB), 4-tert-butyl-1,2-dimethoxybenzene (TDB), 1,4 bis(trimethylsilyl)-2,5-dimethoxybenzene (BTMSDB), and 1,4-bis(2-methoxyethoxy)-2,5 di-tert-butylbenzene; additives to impart additional flame retardant properties to the electrolyte, such as dimethylmethylphosphonate (DMMP), ethoxypentafluorocyclotriphosphazene (N3P3F5OCH2CH3, EFPN), tri(2,2,2-trifluoroethyl)phosphite and / or tri(2,2,2-trifluoroethyl)phosphate (TFEP), methyl nonafluorobutyl ether (MFE), and silane-Al2O3 nanoparticles; additives to promote better high temperature cycling, such as succinic anhydride; and additives to scavenge unwanted inert decomposition products (e.g., HF, water, or CO2) in situ, such as zeolites.

[0108] Electrolyte compositions according to the present invention may further comprise one or more non-metallic supporting electrolyte salts, referred to herein as "supporting salts." For purposes of this disclosure, a "supporting salt" is a salt that is not a metal-containing salt, but contains a metal cation (i.e., Na + A non-metallic supporting salt is any salt that promotes the migration of cations (C,N,N-C,N-H) from the cathode to the anode and vice versa. However, a non-metallic supporting salt does not participate in the electrochemical process of the electrochemical cell.

[0109] Highly preferably, the non-metallic supporting salt can be selected from one or more quaternary ammonium salts in which the nitrogen atom is singly bonded to four alkyl groups to form a soluble cationic compound. Suitable non-metallic supporting salts include tetrabutylammonium hexafluorophosphate (TBAPF6) and tetraethylammonium hexafluorophosphate (TEAPF6).

[0110] Preferably, the non-metallic supporting salt is tetrabutylammonium hexafluorophosphate (TBAPF6). The concentration of the one or more non-metallic supporting salts is conveniently expressed as a molality (m) in the solvent system, i.e., the total number of moles of the one or more non-metallic supporting salts (i.e., solutes) per kg or 1000 g of the solvent system (i.e., the combined weight of the first and second components). Preferably, the molality of each non-metallic supporting salt in a) is individually in the range of 0.1 mol / kg to 5 mol / kg, more preferably in the range of 0.1 mol / kg to ≦2.5 mol / kg. Highly preferably, especially when the non-metallic supporting salt is TBAPF6, the molality is 0.1 mol / kg to ≦2.5 mol / kg, most preferably about 1.0 mol / kg.

[0111] The electrolyte compositions of the present invention are particularly useful in electrochemical cells, preferably sodium-based electrochemical cells. Accordingly, in a further aspect, the present invention provides an electrochemical cell comprising the electrolyte composition as defined herein. Preferred electrochemical cells include metal-ion cells (e.g., sodium-ion cells), anode-free cells (e.g., sodium anode-free cells), and alkali metal cells (e.g., sodium metal cells).

[0112] The electrolyte compositions of the present invention are particularly useful in metal-ion cells. Thus, in a further aspect, the present invention provides a metal-ion cell comprising a negative electrode, a positive electrode, and an electrolyte composition as defined herein. The metal-ion cells of the present invention can be selected from alkali metal cells and non-alkali metal cells.

[0113] When an alkali metal cell is used, the alkali metal cell is preferably selected from one or more of a sodium ion cell, a lithium ion cell, and a potassium ion cell. Preferably, the alkali metal cell is selected from one or more of a sodium ion cell, a lithium ion cell, and a potassium ion cell. Most preferably, the alkali metal cell is a sodium ion cell. When a non-alkali metal ion cell is used, the non-alkali metal ion cell is preferably a zinc ion cell, an aluminum ion cell, a calcium ion cell, or a magnesium ion cell.

[0114] The metal ion cell of the present invention can use a negative electrode (anode) containing a negative electrode active material commonly used in the art. For example, the negative electrode (anode) containing the negative electrode active material can be one or more of graphite materials, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, P-based materials, Sb-based materials, SnSb-based materials, other types of materials that store charge through conversion and / or alloying reactions (e.g., simple / binary / ternary oxides of Fe, Cu, Ni, Mn, etc.), and materials that store charge through conventional intercalation reactions, such as lithium titanium oxide, various types of sodium titanate, titania, etc.; and any combination of one or more of these materials, such as carbon / Sb, carbon / P, carbon / Fe2O3. The combinations can be either mixtures produced by physical blending (e.g., carbon and Sb blended together by physical or chemical mixing methods such as ball milling or spray drying) or via in-situ reaction (e.g., via suitable synthetic routes such as solvothermal / hydrothermal reactions, sol-gel reactions, solution-based reactions, reflux reactions, co-precipitation reactions, or solid-state reactions, with or without a subsequent heating / pyrolysis step), the latter of which can also result in doped materials (e.g., carbon doped with Sb or P or Sn) and / or substituted materials (e.g., substitution of Fe2O3 with small amounts of TiO2).

[0115] The metal ion cells disclosed herein can also include a separator located between the cathode and anode current collectors. A polyolefin separator is preferred. Ideally, the polyolefin separator has a thickness of 25 μm or less. Preferably, the thickness is 16 μm or less.

[0116] The metal ion cells of the present invention can be used in energy storage devices, such as batteries, rechargeable batteries, electrochemical devices, and electrochromic devices.

[0117] Specifically, when the metal-ion cell is a sodium-ion or potassium-ion cell, the sodium-ion or potassium-ion cell can use a negative electrode (anode) including a negative electrode active material having a structure adapted to enable insertion / removal of sodium or potassium ions during charge / discharge. Preferably, a carbon-containing material can be used as the negative electrode active material. Highly preferably, the negative electrode active material can be a non-graphitizable carbon-containing material, most preferably a hard carbon-containing material. Suitable hard carbon negative electrode active materials include Kuranode Type 1 supplied by Kureha.

[0118] Specifically, when the metal-ion cell is a sodium-ion cell, the sodium-ion cell can include a positive electrode (cathode) including a sodium-containing positive electrode active material adapted to allow insertion / removal of sodium ions during charge / discharge. Examples of these include sodium transition metal oxides, polyanion compounds (including fluorinated polyanion compounds), Prussian blue analogue (PBA) compounds (such as Prussian white or Berlin green), materials that store sodium via conversion reactions, and sodium transition metal fluorides, oxyfluorides, phosphates, sulfates, and silicates (and their fluorinated versions). A preferred example is sodium transition metal oxide.

[0119] Preferred sodium transition metal oxides are of the general formula: A 1±δ M 1 V M 2 W M 3 X M 4 Y M 5 Z O 2-c [In formula: A is one or more alkali metals selected from sodium, potassium, and lithium; M 1comprises one or more redox active metals having an oxidation state of +2, preferably selected from the group consisting of nickel, copper, cobalt and manganese; M 2 contains metals with oxidation states greater than 0 and less than or equal to +4; M 3 contains a metal in the oxidation state +2; M 4 contains metals with oxidation states greater than 0 and less than or equal to +4; M 5 contains a metal in the oxidation state +3; 0 ≤ δ ≤ 1; V is >0; W is ≥ 0; X is ≥ 0; Y is ≥ 0; at least one of W and Y is >0; Z is ≥ 0; C is in the range 0≦c<2; V, W, X, Y, Z and C are selected to maintain electrochemical neutrality].

[0120] Ideally, metal M 2 comprises one or more transition metals, preferably selected from manganese, titanium and zirconium; M 3 is preferably one or more selected from magnesium, calcium, copper, tin, zinc and cobalt; M 4 comprises one or more transition metals preferably selected from manganese, titanium and zirconium; and M 5 is preferably one or more selected from aluminum, iron, cobalt, tin, molybdenum, chromium, vanadium, scandium and yttrium.

[0121] Particularly preferred cathode active materials for use in sodium-ion cells are nickelate-based materials. While sodium-containing active materials with any crystalline structure can be used, the structure is preferably O3 or P2 or a derivative thereof. Specifically, the cathode active material can contain a mixture of phases, i.e., a heterogeneous structure composed of several different crystalline forms. For example, the cathode active material can contain a compound having the above general formula in a mixture of O3 and P2 phases. The ratio of O3 to P2 phases is preferably 1 to 99:99 to 1.

[0122] Specifically, when the metal-ion cell is a potassium-ion cell, the potassium-ion cell can include a positive electrode (cathode) containing a potassium-containing positive electrode active material adapted to allow insertion / removal of potassium ions during charge / discharge. Examples of these include oxide-based materials, phosphate- and / or fluorophosphate-based materials, or PBA compounds. A particularly preferred potassium-containing positive electrode active material is P3-type K 0.5 [Mn 0.8 Fe 0.1 Ni 0.1 ]O2 layered oxide, K2MnFe(CN)6 or KVPO4F.

[0123] Specifically, when the metal-ion cell is a lithium-ion cell, the lithium-ion cell can use a negative electrode comprising a negative electrode active material having a structure adapted to allow lithium ion insertion / removal during charge / discharge. Preferably, a carbon-containing material is used as the active negative electrode material. Highly preferably, the carbon-containing material is a graphitizable carbon-containing material, most preferably a graphite-containing material. Suitable graphite negative electrode active materials include graphite supplied by MTI.

[0124] Specifically, when the metal-ion cell is a lithium-ion cell, the lithium-ion cell can include a positive electrode (cathode) containing a lithium-containing positive electrode active material adapted to allow lithium ions to be inserted / removed during charging / discharging. Examples of these include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide (NCA), transition metal phosphates, and lithium iron phosphate. A particularly preferred lithium-containing positive electrode active material is LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) or NCA.

[0125] In another aspect, the present invention also provides the use of an electrolyte composition as defined herein in a metal ion cell, such a metal ion cell being as defined above.

[0126] The electrolyte compositions of the present invention are also particularly useful in anode-free sodium cells, also known as in-situ sodium plating cells, which can be used in energy storage devices such as batteries, rechargeable batteries, electrochemical devices, and electrochromic devices.

[0127] Thus, in another aspect, the present invention provides an anode-free sodium cell comprising an electrolyte composition as defined herein. More particularly, in one aspect, the present invention provides an anode-free sodium cell comprising: a cathode comprising one or more sodium-containing active materials; Anode current collector; a separator positioned between the cathode and anode current collectors; and an electrolyte composition as defined herein; The present invention provides an anode-free sodium cell comprising:

[0128] In another aspect, the present invention also provides the use of an electrolyte composition as defined herein in an anode-free sodium cell. As used herein, an "anode-free sodium cell" refers to a cell whose operating principle is the removal of sodium metal cations (Na ) from the cathode active material. + () and deposition and plating / removal and stripping of sodium metal (Na) on the anode current collector. During the first charge cycle of an anode-free sodium cell, a sodium metal anode is formed in situ on the anode current collector when sodium metal cations are reduced and deposited as sodium metal on the anode current collector.

[0129] When an anode-free sodium cell is fully discharged, the anode current collector contains only trace amounts of sodium metal, or substantially less than in a fully charged cell, with most of the sodium metal being oxidized to form sodium metal cations that are present in the electrolyte and / or stored in the cathode. When an anode-free sodium cell is fully charged, the anode current collector contains a layer of sodium in electrical contact with the anode current collector, with a correspondingly smaller amount of sodium in the cathode. The layer of sodium in electrical contact with the anode current collector can be across the entire surface of the anode current collector, or it can be deposited on a portion of the anode current collector. However, if sodium is deposited, it is preferred that any such sodium layer be uniform and homogeneous.

[0130] The anode-free cells disclosed herein can include a separator positioned between the cathode and anode current collectors. Polyolefin separators are preferred.

[0131] The cathode typically comprises a sodium-containing active material disposed on one or more surfaces of a (cathode) current collector. The cathode current collector and anode current collector can each independently be fabricated from any suitable conductive material. For example, the cathode current collector, the anode current collector, or both the cathode and anode current collectors can be formed from a metal such as nickel, aluminum, titanium, copper, gold, silver, platinum, an aluminum alloy, stainless steel, or any other metal substrate (similar to the current collectors currently commonly used in sodium-ion batteries).

[0132] The cathode current collector, the anode current collector, or both the cathode and anode current collectors can be formed from aluminum or an aluminum alloy (e.g., an alloy of aluminum with one or more of Mg, Mn, Cr, Zn, Si, Fe, and Ni). Highly preferably, both the cathode and anode current collectors comprise aluminum current collectors. Alternatively, copper, magnesium, carbon paper / foil / substrate, and tin can also be used as current collector materials.

[0133] The cathode current collector and the anode current collector can be formed into any suitable shape that is compatible with the overall design of the electrochemical cell. For example, the cathode current collector and the anode current collector can each independently be formed as a foil, a flat plate, a mesh, a net, a lath, a perforated metal, or an embossed shape, or a combination of these shapes (e.g., a mesh-like flat plate). If desired, irregularities can be formed on one or more surfaces of the cathode current collector and / or the anode current collector, for example, by etching one or more surfaces of the current collector. Highly preferably, the anode current collector is formed from aluminum or an aluminum alloy and includes a foil or mesh shape.

[0134] Preferably, the anode current collector also includes one or more nucleation layers formed on one or more surfaces of the anode current collector prior to the first charge cycle of the anode-free sodium cell. Highly preferably, such one or more nucleation layers comprise one or more carbon-containing nucleation layers. Because the anode current collector is formed with one or more nucleation layers on one or more surfaces thereof, metal cations are reduced and deposited as sodium metal on the one or more nucleation layers during the first charge cycle of the anode-free sodium cell. The surface of the current collector or nucleation layer can also be pre- or post-coated with either sodium or other materials, with physical vapor deposition being a useful means for achieving such coatings.

[0135] As used herein, the term "nucleation layer" refers to any coating or layer disposed on one or more surfaces of a "pristine" anode current collector prior to the first charge cycle of an anode-free sodium cell. The use of a nucleation layer allows for more uniform and homogeneous sodium metal deposition compared to a current collector lacking such a nucleation layer. Particularly preferred nucleation layers are any coatings or layers that result in a reduction in the "nucleation overpotential" for sodium metal plating.

[0136] As sodium metal is deposited on the anode current collector via constant current (galvanostatic) cycling, the sodium plating potential initially drops (to more negative values ​​below 0 V vs. Na / Na+) and then rises to higher potential values ​​(but still below 0 V vs. Na / Na+) during steady-state conditions at the same constant current value.

[0137] Thus, the "nucleation overpotential" for sodium deposition is defined herein as the difference between the least negative potential and the steady-state plating potential. Thus, one skilled in the art can easily measure the nucleation overpotential for sodium deposition using an anode current collector that includes one or more nucleation layers formed on its surface and compare it to the nucleation overpotential for sodium deposition using a "pristine" anode current collector to determine the preferred nucleation layer described herein. This can be done in a half-cell or a three-electrode cell constructed using well-known general knowledge.

[0138] As noted above, the one or more nucleation layers advantageously enable the deposition of sodium metal atoms and atomic clusters at and across the surface of the anode current collector, thereby promoting more uniform plating while minimizing parasitic reactions.

[0139] The one or more nucleation layers can be formed over most (or even 100%) of one or more surfaces of the anode current collector, or may be formed as a partial coating by design (e.g., one or more nucleation layers formed on a partial region of such a surface—these regions being homogeneous and uniform within their extent). The one or more nucleation layers preferably comprise one or more layers of negative electrode active material (e.g., thin layers such as 0.1 μm to 1000 μm), which may or may not be mixed with any type of conductive additive, such as carbon black (to enhance the electronic conductivity of the negative electrode active material) and / or a binder material compatible with water or an organic solvent.

[0140] Highly preferably, the one or more nucleation layers comprise one or more carbon-containing nucleation layers, highly preferably one or more carbon-containing nucleation layers having a thickness of from about 10 Angstroms to about 1000 μm.

[0141] Suitable carbon-containing nucleation layers may include carbon black, carbon nanotubes, carbon nanofibers, graphite / graphene, hard carbon, glassy carbon, soft carbon, activated carbon (e.g., fibrous form), or a combination thereof. In some cases, the carbon-containing nucleation layer may include amorphous carbon (e.g., carbon black such as TIMCAL Super C65). Techniques such as doctor blade coating, slot die coating, ultrasonic spray deposition, screen printing, physical vapor deposition (PVD), and chemical vapor deposition (CVD) may also be used to prepare such carbon-containing nucleation layers.

[0142] Alternatively, the anode current collector also includes two or more nucleation layers formed on one or more surfaces of the anode current collector prior to the first charge cycle of the anode-free sodium cell. In one embodiment, such two or more nucleation layers are preferably two or more carbon-containing nucleation layers.

[0143] Alternatively, the anode current collector disclosed herein does not include one or more nucleation layers on one or more surfaces of the anode current collector prior to the first charge cycle of the anode-free sodium cell. Thus, the anode current collector is "pristine" prior to the first charge cycle of the anode-free sodium cell. As used herein, the phrase "pristine" means that the current collector is in an "as-prepared" state prior to the first charge cycle of the anode-free sodium cell. In other words, the anode current collector is essentially pure material from which it was formed, absent impurities (e.g., surface oxide layers, etc.). Thus, the anode current collector is not coated with one or more nucleation layers (as described above), conventional active materials, binders, etc.

[0144] After charge and discharge cycling, the anode current collector in a fully Na-stripped state can be identical to the "pristine" state, or can incorporate one or more layers substantially comprising sodium-containing materials, which can also include, for example, inorganic-rich and / or organic-rich materials derived from the electrolyte composition and its decomposition products.

[0145] Based on the disclosure herein, it is believed that an anode-free sodium cell according to the present invention can be formed using any type of sodium-containing active material that functions as a cathode in a sodium-ion cell. Accordingly, sodium-containing active materials for use in anode-free sodium cells can be defined according to the sodium-containing active materials for use in sodium-ion cells described above.

[0146] The electrolyte compositions of the present invention are also particularly useful in sodium metal cells, which can be used in energy storage devices such as batteries, rechargeable batteries, electrochemical devices, and electrochromic devices.

[0147] Thus, in another aspect, the present invention provides a sodium metal cell comprising an electrolyte composition as defined herein. More specifically, in one aspect, the present invention provides a sodium metal cell comprising: a cathode comprising one or more cathode active materials; an anode current collector comprising sodium metal as the anode active material; a separator positioned between the cathode and anode current collectors; and an electrolyte composition as defined herein; A sodium metal cell is provided, comprising:

[0148] In another aspect, the present invention also provides the use of an electrolyte composition as defined herein in a sodium metal cell. Ideally, the anode current collector includes a layer or film of sodium metal, typically having a thickness of greater than 0 to about 1000 μm. Such a layer or film is typically coated / deposited on the surface of the anode current collector using a deposition technique (e.g., physical vapor deposition) or a coating technique, for example, by mixing sodium metal with a binder material (such as PVDF) and, optionally, a conductive additive (such as carbon black and / or carbon nanotubes) in a non-aqueous solvent such as N-methylpyrrolidone (NMP), and then coating via a technique such as a doctor blade or slot die.

[0149] Preferably, the anode current collector is any substrate typically used in anode-free cells as defined above. Examples include aluminum foil, copper foil, and carbon paper.

[0150] Suitable cathode active materials can be sodium-containing active materials defined according to the sodium-containing active materials described above for use in sodium-ion cells. Alternatively, suitable cathode active materials include FeS2, TiS2, Na 0+x FePO4, Na 0+x VPO4F, Na 0+x Fe2(CN)6, Na 0+x Sodium-deficient cathode materials such as MnFe(CN)6 (where x can be 0-1) can be mentioned.

[0151] The present invention also provides, in another aspect, a method of operating one or more metal-ion cells disclosed herein and / or one or more anode-free sodium cells disclosed herein, the method comprising cycling the one or more cells at a C-rate of about C / ≧2, more preferably at a C-rate of about C / ≧5.

[0152] In one aspect, the method includes discharging one or more cells at a discharge C-rate of about C / ≧2, more preferably at a rate of about C / ≧5. For the avoidance of doubt, a discharge C-rate is the discharge current divided by the theoretical current draw at which a cell delivers its nominal rated capacity for a particular period of time. Thus, a discharge C-rate of C / ≧2 means that the discharge current discharges the entire cell in 2 hours or more. Similarly, a discharge C-rate of C / ≧5 means that the discharge current discharges the entire cell in 5 hours or more. In some cases, discharging one or more cells at a discharge C-rate of about C / ≧7, optionally at a C-rate of about C / ≧10, optionally at a C-rate of about C / ≧20, optionally at a C-rate of about C / ≧50.

[0153] In one aspect, discharging one or more cells at a discharge C-rate of C / ≧2 to C / ≦200, more preferably C / ≧2 to C / ≦100, even more preferably C / ≧2 to C / ≦50, even more preferably C / ≧2 to C / ≦20, and ideally C / ≧2 to C / ≦10.

[0154] Thus, an objective of the method of operating one or more cells according to the present invention is to utilize electrolyte compositions according to the present invention in cells at low C-rates, such as C / 5, C / 10, or even C / 20, to provide excellent long-term cycling stability and high battery performance. Thus, the electrolyte compositions according to the present invention are particularly useful in stationary applications requiring capacity release over an extended period of time.

[0155] In another aspect, the present invention also provides apparatuses comprising one or more metal-ion cells disclosed herein, and / or one or more anode-free sodium cells disclosed herein, and / or one or more sodium metal cells disclosed herein. Exemplary apparatuses can include devices such as battery packs that can be used in either stationary or mobile applications.

[0156] In one embodiment, the device further comprises one or more metal-ion cells having an electrolyte composition comprising one or more metal-containing salts at a concentration greater than that of the present invention. Ideally, this is greater than 0.2 mol / kg. Thus, one or more metal-ion cells comprising an electrolyte composition according to the present invention can be mixed with one or more metal-ion cells comprising an electrolyte composition not according to the present invention.

[0157] In a further aspect, the present invention also provides a method of accessing available energy from an electrochemical cell, comprising the steps of: a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from sulfur-containing compounds, boron-containing compounds, and surfactants; operating an electrochemical cell with an electrolyte composition comprising a solvent system comprising The above method may be provided, wherein the electrolyte composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

[0158] The electrolyte composition and / or electrochemical cell can be further defined as described above or as defined according to the examples disclosed herein. In one embodiment, the method further comprises, after providing the electrochemical cell, operating the electrochemical cell with an electrolyte composition according to the present invention. The step of operating the electrochemical cell preferably comprises cycling the electrochemical cell at a C-rate of about C / ≧2, more preferably at a C-rate of about C / ≧5. In one embodiment, the method comprises discharging the electrochemical cell at a discharge C-rate of about C / ≧2, more preferably at a rate of about C / ≧5.

[0159] As noted above, a discharge C-rate of C / ≧2 means that the discharge current discharges the entire cell in 2 hours or more. Similarly, a discharge C-rate of C / ≧5 means that the discharge current discharges the entire cell in 5 hours or more. In some cases, discharging one or more cells at a discharge C-rate of about C / ≧7, optionally at a C-rate of about C / ≧10, optionally at a C-rate of about C / ≧20, optionally at a C-rate of about C / ≧50.

[0160] In one aspect, discharging one or more cells at a discharge C-rate of C / ≧2 to C / ≦200, more preferably C / ≧2 to C / ≦100, even more preferably C / ≧2 to C / ≦50, even more preferably C / ≧2 to C / ≦20, and ideally C / ≧2 to C / ≦10.

[0161] In one embodiment, the method further includes associating or integrating the available energy from the electrochemical cell with one or more additional electrochemical cells having one or more metal-containing salts at a concentration greater than 0.2 mol / kg.

[0162] In a further aspect, the present invention also provides a method of manufacturing an electrochemical cell as defined herein. Preferably, the method comprises providing an electrochemical cell comprising: a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from a sulfur-containing compound, a boron-containing compound, and a surfactant; introducing an electrolyte composition comprising a solvent system comprising The electrolyte composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

[0163] The electrolyte composition and / or electrochemical cell can be further defined as described above or as defined according to the examples disclosed herein. In one embodiment, the method further comprises, after providing an electrochemical cell, introducing an electrolyte composition according to the present invention into the electrochemical cell.

[0164] In one embodiment, the electrochemical cell is prepared by the manufacturing method as defined herein. In a further aspect, the present invention also provides a device comprising the electrochemical cell disclosed herein. The device can further comprise one or more electrochemical cells having an electrolyte composition comprising one or more metal-containing salts at a concentration greater than that of the present invention. Ideally, this is greater than 0.2 mol / kg. Thus, an electrochemical cell comprising an electrolyte composition according to the present invention can be mixed with one or more additional electrochemical cells comprising an electrolyte composition other than that of the present invention.

[0165] In a further aspect, the present invention also provides a method for producing a medicament for the treatment of a pulmonary arthritis, comprising: a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives including a sulfur-containing compound; The present invention provides an electrolyte composition comprising a solvent system comprising: wherein the electrolyte composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg. The electrolyte composition can be further defined as described above or as defined according to the examples disclosed herein.

[0166] In a further aspect, the present invention also provides a method for producing a medicament for the treatment of a pulmonary arthritis, comprising: a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from boron-containing compounds and surfactants in an amount of >0.5 to ≦10 wt. % of the solvent system; The present invention provides an electrolyte composition comprising a solvent system comprising: wherein the electrolyte composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg. The electrolyte composition can be further defined as described above or as defined according to the examples disclosed herein.

[0167] In a final aspect, the present invention also provides a method for producing a medicament for the treatment of a pulmonary arthritis. a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from a sulfur-containing compound, a boron-containing compound, and a surfactant; The present invention provides an electrolyte composition having a solvent system comprising: wherein the composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg. The electrolyte composition can be further defined as above or as defined according to the examples disclosed herein.

[0168] The present invention will now be described with reference to the following figures: [Brief explanation of the drawings]

[0169] [Figure 1] FIG. 1 shows a plot of cathode discharge capacity (mAh / g) versus cycle number for a cell (APFC489) using an electrolyte composition according to the present invention (sample SOL21). [Figure 2] FIG. 2 shows a plot of full cell voltage (V) versus cathode specific capacity (mAh / g) for the first four cycles of a cell (APFC489) using an electrolyte composition according to the present invention (sample SOL21). [Figure 3] FIG. 3 shows a plot of full cell voltage (V) versus cathode specific capacity (mAh / g) from cycle 5 onwards for a cell (APFC489) using an electrolyte composition according to the invention (sample SOL21). [Figure 4] FIG. 4 shows a plot of full cell voltage (V) versus cathode specific capacity (mAh / g) illustrating the rate performance at different C-rates for cycles 3-10 of a cell (APFC488) using an electrolyte composition according to the present invention (sample SOL21). [Figure 5] FIG. 5 shows a plot of cathode discharge capacity (mAh / g) versus cycle number for a cell (APFC488) using an electrolyte composition according to the present invention (sample SOL21). [Figure 6]FIG. 6 shows a plot of full cell voltage (V) versus cathode specific capacity (mAh / g) from cycle 11 onwards for a cell (APFC488) using an electrolyte composition according to the invention (sample SOL21). [Figure 7] FIG. 7 shows a plot of cathode capacity (mAh / g) versus cycle number for a cell (APFC475) using an electrolyte composition according to the present invention (sample SOL21). [Figure 8] FIG. 8 shows a plot of cathode discharge capacity (mAh / g) versus cycle number to illustrate the cycling stability of a cell (APFC489) using an electrolyte composition according to the invention (sample SOL21) compared to the cycling stability of a cell (APFC492) using a control electrolyte composition (sample TEL67a). [Figure 9] FIG. 9 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) at cycle 3 to illustrate a cell (APFC489) using an electrolyte composition in accordance with the present invention (sample SOL21) compared to a cell (APFC492) using a control electrolyte composition (sample TEL67a). [Figure 10] FIG. 10 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) at cycle 6 to illustrate a cell (APFC489) using an electrolyte composition in accordance with the present invention (sample SOL21) compared to a cell (APFC492) using a control electrolyte composition (sample TEL67a). [Figure 11] FIG. 11 shows a plot of full cell voltage (V) versus cathode specific capacity (mAh / g) for the first four cycles of a cell (APFC485) using an electrolyte composition according to the present invention (sample SOL14w). [Figure 12] FIG. 12 shows a plot of cathode discharge capacity (mAh / g) versus cycle number for a cell (APFC485) using an electrolyte composition according to the present invention (sample SOL14w). [Figure 13]FIG. 13 shows a plot of full cell voltage (V) versus cathode specific capacity (mAh / g) for the first four cycles of a cell (APFC491) using an electrolyte composition according to the present invention (sample SOL9c). [Figure 14] FIG. 14 shows a plot of cathode discharge capacity (mAh / g) versus cycle number for a cell (APFC485) that used an electrolyte composition in accordance with the present invention (sample SOL14w) compared to another cell (APFC491) that used another electrolyte composition in accordance with the present invention (sample SOL9c). [Figure 15] FIG. 15 shows a plot of cathode discharge capacity (mAh / g) versus cycle number for a cell (APFC489) using an electrolyte composition according to the present invention (sample SOL21) compared to another cell (APFC490) using another electrolyte composition according to the present invention (sample SOL21a). [Figure 16] FIG. 16 shows a plot of cathode discharge capacity (mAh / g) versus cycle number for a cell (APFC487) using an electrolyte composition according to the present invention (sample SOL16h). [Figure 17] FIG. 17 shows a plot of full cell voltage (V) versus cathode specific discharge capacity (mAh / g) for the first two cycles of a cell (APFC487) using an electrolyte composition according to the present invention (sample SOL16h). [Figure 18] FIG. 18 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) for cycles 12, 30, and 61 of a cell (APFC487) using an electrolyte composition according to the present invention (sample SOL16h). [Figure 19] FIG. 19 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) to illustrate the cycling performance for an anode-free sodium cell using an electrolyte composition according to the present invention (sample SOL21c). [Figure 20] FIG. 20 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) for a cell (APFC497) using a control electrolyte composition (sample TEP). [Figure 21]FIG. 21 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) for a cell (APFC498) using a control electrolyte composition (Sample TEP). [Figure 22] FIG. 22 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) for cells using electrolyte compositions according to the invention (samples SOL21d; SOL21e; SOL21f; SOL21; and SOL21h) compared to a cell using a control electrolyte composition (sample TEP). [Figure 23] FIG. 23 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) for cells using electrolyte compositions in accordance with the invention (samples SOL21d and SOL21g) compared to cells using a control electrolyte composition (sample TEP). [Figure 24] FIG. 24 shows a plot of cathode discharge capacity (mAh / g) versus cycle number for cells APFC488 and APFC514 using an electrolyte composition according to the present invention (sample SOL21). [Figure 25] FIG. 25 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) for a cell (APFC518) using an electrolyte composition in accordance with the present invention (sample TEL84) compared to another cell (APFC489) using an electrolyte composition in accordance with the present invention (sample SOL21). [Figure 26] FIG. 26 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) for a cell (APFC497) using a control electrolyte composition (sample TEP) compared to another cell (APFC531) using a control electrolyte composition (sample TEL84a). [Figure 27] FIG. 27 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) for a cell (APFC527) that used an electrolyte composition not in accordance with the present invention (sample TEL82) compared to another cell (APFC528) that used an electrolyte composition in accordance with the present invention (sample SOL21). [Figure 28]FIG. 28 shows a plot of cathode discharge capacity (mAh / g) versus cycle number for a cell (APFC542) using an electrolyte composition in accordance with the present invention (sample SOL25a) compared to other cells (APFC541; APFC551) using control electrolyte compositions (samples SOL25; LP30). [Figure 29] FIG. 29 shows a plot of full cell voltage (V) versus cathode discharge capacity (mAh / g) for cells (APFC488; APFC547; APFC548) using electrolyte compositions according to the present invention (samples SOL21; TEL80f; TEL80g). [Example]

[0170] The electrolyte compositions under investigation were prepared using the following general procedure: the appropriate amount of the first component (e.g., a solvent for the desired solvent system) and then the second component (e.g., a precise amount of one or more performance additives) were weighed in an argon-filled glove box and added to an amber or clear glass bottle. To completely dry the resulting solvent, 4 Å molecular sieves (Sigma-Aldrich) were added and the solvent mixture was allowed to dry for at least 24 hours. The electrolyte composition was then ready for use and stored in an argon-filled glove box. For compositions containing metal-containing salts (in accordance with the present invention or not), the required weight of the salt(s) was added to a separate bottle (either a clear or amber glass bottle or a container made from an alternative material such as polypropylene, PTFE, stainless steel, etc.) to which the required amount of solvent mixture was added. The electrolyte was then stirred via a magnetic pellet or mechanical stirrer for any period between 5 minutes and 100 hours, or the salt(s) were allowed to dissolve naturally in the electrolyte by simply leaving the bottle / container undisturbed or accelerated by mechanically shaking the bottle / container.

[0171] The exact composition of each electrolyte composition investigated is detailed in Table 1 below:

[0172] [Table 1]

[0173] For the avoidance of doubt, concentrations expressed above as "m" (molality) relate to the total number of moles of metal-containing salt per kg or 1000 g of solvent system. Alternatively, concentrations expressed above as "M" (molarity) relate to the total number of moles of metal-containing salt per liter of solvent system.

[0174] Abbreviations used: EC = ethylene carbonate, DEC = diethyl carbonate, PC = propylene carbonate, FEC = fluoroethylene carbonate, PCS = 1,3-propanediol cyclic sulfate, P123 = poloxamer (Pluronic) P123, TEP = triethyl phosphate, TMSB = tris(trimethylsilyl)borate, tetraglyme = tetraethylene glycol dimethyl ether, diglyme = diethylene glycol dimethyl ether, VC = vinylene carbonate, DMC = dimethyl carbonate Note that in Table 1 above, the wt% of the various solvents and / or performance additives are listed in relation to the total weight of the solvent system.

[0175] Cell Configuration General fabrication procedure for hard carbon Na-ion cells Examples 1-4 herein relate to experimental device characterization of small-scale Na-ion pouch cells with nominal capacities of approximately 4-7 mAh.

[0176] Sodium-ion cells were fabricated using a mixed-phase O3 / P2 oxide cathode, a hard carbon anode, and electrolyte (as appropriate). Aluminum tabs were attached to each electrode, and the cells were placed in a polymer-coated aluminum pouch.

[0177] The positive (cathode) electrode was prepared by solution casting a slurry of active material, conductive carbon, binder, and solvent using a doctor blade method. The conductive carbon used was C65 (Imerys). PVdF copolymer (e.g., W#7500 from Kureha Chemicals) was used as the binder, and N-methylpyrrolidone (NMP) was used as the solvent. The slurry was then cast onto a carbon-coated aluminum foil and dried under vacuum at approximately 120 °C. The electrode film contained the following components, expressed in weight percent: 89% (or 92%) active material, 5% (or 4%) C65 carbon, and 6% (or 4%) W#7500 binder.

[0178] The hard carbon negative (anode) electrode was prepared by solution casting a slurry of hard carbon active material (Kuranode Type 1 supplied by Kureha), conductive carbon, binder, and solvent by doctor blade method. The conductive carbon used was C65 (Imerys). Sodium carboxymethylcellulose (CMC) (Aqualon from Ashland) was used. TM A mixture of styrene-butadiene rubber (SBR) (BM-451B from Zeon Europe GmbH) and styrene-butadiene rubber (AQU D-5283) was used as the binder, and water was used as the solvent. The slurry was then cast onto a carbon-coated aluminum foil and dried under vacuum at approximately 120 °C. The electrode film contained the following components in weight percent: 95% active material, 1.5% C65 carbon, and 3.5% binder mixture.

[0179] After the cathode and anode were coated, they were stamped to the desired dimensions. The separator used was a typical polyolefin separator commonly used in any type of rechargeable lithium-ion or sodium-ion battery, such as Celgard 2500. The cathode / separator / anode assembly was placed in a pouch with two Al-based connection tabs that served as terminals in a glove box and filled with a volume of the above liquid electrolyte typical for lithium-ion or sodium-ion cells containing such types of polyolefin separators. These pouch cells were then sealed in the glove box and removed for cell testing.

[0180] General procedure for preparing anode-free sodium The anode-free sodium cell described in Experiment 5 was fabricated as a pouch cell. The anode-free pouch cell had a nominal capacity of approximately 5 mAh. The cathode contained a mixed-phase O3 / P2 layered oxide sodium-ion active material mixed with C65 carbon black conductive additive and polyvinylidene fluoride (PVDF) binder in an 89:06:05 weight ratio on a carbon-coated Al foil.

[0181] More specifically, the anode was an "En'Safe 92" substrate (part of ARMOR's En'Safe® series of products), which is aluminum foil coated with a thin (approximately 1 μm) carbon primer layer, sourced from ARMOR.

[0182] The remaining procedure for fabricating the anode-free sodium cell was the same as that for fabricating the Na-ion pouch cell described above.

[0183] General fabrication procedure for hard carbon K-ion cells The K-ion cells exemplified in this specification are P3 type K 0.5 [Mn 0.8 Fe 0.1 Ni 0.1An O2-layered oxide cathode (whose performance has been previously demonstrated by Choi et al., Energy Storage Mater., 2020, 25, 714-723) was used. This cathode formulation was the same as that used for the Na-ion layered O3 / P2 oxide, coated on a carbon-coated Al foil. The anode used in these cells was hard carbon coated on an Al foil (the same as that used in all Na-ion cell experiments). The remaining procedures for fabricating the K-ion cell were the same as those for the Na-ion pouch cell described above.

[0184] General fabrication procedure for graphite anode-based lithium-ion cells The Li-ion cells exemplified herein used a layered Li Ni-Mn-Co oxide cathode (NMC532) (purchased from MTI). This cathode formulation was the same as that used for the Na-ion layered O3 / P2 oxide and coated on a carbon-coated Al foil. The anode used in these cells was graphite (purchased from MTI) coated on a Cu foil. The remaining procedure for fabricating the Li-ion cells was the same as that for the Na-ion pouch cells described above.

[0185] Cell Test The cells were tested using a constant current (galvanostatic) cycling technique. The cells were cycled at a predetermined current density between preset voltage limits. Commercially available battery cyclers from MTI Inc. (Richmond, CA, USA) or Maccor (Tulsa, Oklahoma, USA) were used. During charging, alkali ions are inserted into the carbon-containing anode material (or, in the case of anode-free cells, plated as alkali metals on the substrate). During discharge, alkali ions are extracted from the anode (in the case of anode-free cells, alkali metals are stripped from the substrate as alkali ions) and reinserted into the cathode active material.

[0186] All cells were subjected to cycling experiments at charge rates such as ±C / 5 and ±C / 10 (or other rates, e.g., ±C / 50, as described in each experiment). Discharge rates of C / 5, C / 10, 1C, and 2C were also investigated in rate performance tests. All cells were rested for 4 to 24 hours before cycling. Table 2 provides a summary of the conditions for each experiment.

[0187] [Table 2]

[0188] [Table 3]

[0189] [Table 4]

[0190] Example 1A - Cycling Performance of Cells Using Electrolyte Compositions Containing Triethyl Phosphate Solvent and One or More Performance Additives A hard carbon sodium-ion cell was prepared using the general method described above, and a test pouch cell (APFC489) was prepared using electrolyte composition SOL21. The cycling performance of the test cell was then investigated by cycling as follows: The first four cycles of the cell were operated (charge / discharge) at ±C / 10 in the voltage range of 4.1 to 0 V. The results, shown in Figure 2, show that the coulombic efficiency increased from 87.5% in cycle 1 to 98.7% in cycle 4.

[0191] The cell was operated at ±C / 5 for cycles 5 to 57 in the voltage range of 4.05 to 1.8 V. From the results shown in Figure 3, the coulombic efficiency remained between 99.4 and 99.5% for cycles 6 to 54 (see results for cycles 6, 10, and 54).

[0192] Overall, the cell exhibited good cycling stability, retaining 91% of the cathode discharge capacity at cycle 53 at ±C / 5, as shown by FIG. Thus, good cycling performance in terms of stability and discharge capacity retention can be obtained using an electrolyte composition that is substantially free of one or more alkali metal-containing salts (eg, NaPF6 according to Example 2 below).

[0193] Example 1B - Rate Performance of Cells Using Electrolyte Compositions Containing Triethyl Phosphate Solvent and One or More Performance Additives Using the general method described above for preparing hard carbon sodium-ion cells, test pouch cells (APFC488) were prepared using electrolyte composition SOL21. The rate performance of the test cells was then investigated by cycling as follows:

[0194] The first two cycles of the cell were operated (charge / discharge) at ±C / 10 in the voltage range of 4.1 to 0 V. Rate performance was evaluated for cycles 3 to 10, which were operated in the voltage range of 4.05 to 1.8 V. During these cycles, the cell was always initially charged at C / 5. Then, each pair of cycles 3–4, 5–6, 7–8, and 9–10 was subsequently discharged at different rates: C / 5, C / 2, 1C, and 2C, respectively.

[0195] Figure 5 shows capacity versus cycle number, with good reversibility up to C / 2. Furthermore, the rate performance results shown in Figure 4 indicate that cells discharged up to C / 2 exhibited minimal polarization, and thus the cell discharged at C / 2 retained 92% of its cathode specific capacity, and the cell discharged at C / 5 retained 100% of its cathode specific capacity. Thus, good rate performance can be obtained using an electrolyte composition that is substantially free of one or more alkali metal-containing salts.

[0196] As shown more clearly in Figure 4, cells discharged at 1C and 2C rates retained less than 50% of the cathode specific capacity (i.e., 48% cathode specific capacity at 1C; 1.4% cathode specific capacity at 2C).

[0197] The cell was then subjected to further cycling at voltages ranging from 4.05 to 1.8 V at ±C / 5 from cycle 11 to cycle 72. From the results shown in Figure 6, the coulombic efficiency remained between 99.4 and 99.6% from cycles 12 to 70 (see results for cycles 12, 20, 26, and 70). Furthermore, the cell maintained a high capacity retention of over 90% for cycle 11, as shown in Figure 6, demonstrating overall good stability and discharge capacity.

[0198] Therefore, it is desirable that sodium-ion cells be cycled at a rate of preferably about C / ≧2, more preferably C / ≧5, when using an electrolyte that is substantially free of one or more alkali metal-containing salts.

[0199] Example 1C - Long-Term Cycling Stability of Cells Using Electrolyte Compositions Containing Triethyl Phosphate Solvent and One or More Performance Additives A hard carbon sodium-ion cell was prepared using the general method described above, and a test pouch cell (APFC475) was prepared using electrolyte composition SOL21. The long-term cycling stability of the test cell was then investigated over 221 cycles as follows:

[0200] The first two cycles of the cell were operated (charge / discharge) at ±C / 5 in the voltage range of 4.1 to 0 V. Then, cycles 3 to 120 were operated at ±1 C (C / 1) in the voltage range of 4.05 to 1.8 V. Finally, cycles 121 to 221 were operated in the same voltage range as cycles 3 to 120, but at a rate of ±C / 5.

[0201] FIG. 7 shows that from cycles 121 to 221, the cathode capacity fade is only about 19% (compared to the capacity delivered at cycle 121). Thus, good long-term cycling performance in terms of stability and discharge capacity retention can be obtained using an electrolyte composition that is substantially free of one or more alkali metal-containing salts.

[0202] Similar to the conclusion of Experiment 1B, Figure 7 shows that the delivered capacity at the C / 1 rate was much lower than the capacity at the C / 5 rate (approximately 72.8 mAh / g). At the C / 1 rate, the delivered capacity of the cell initially decreased from 33.9 mAh / g at cycle 3 to 11.3 mAh / g at cycle 5, but then steadily increased to 18.9 mAh / g at cycle 120, demonstrating that the cell could be reversibly cycled at faster cycling rates such as C / 1, albeit at lower capacities.

[0203] Therefore, it is desirable that sodium-ion cells be cycled at a rate of preferably about C / ≧2, more preferably C / ≧5, when using an electrolyte that is substantially free of one or more alkali metal-containing salts.

[0204] Example 2 - Comparison of a cell according to the present invention with a cell using a carbonate ester electrolyte, one or more performance additives, and an electrolyte containing NaPF6 salt (i.e., not according to the present invention) Comparative electrolyte composition TEL67a was prepared according to the disclosure of International Patent Application No. PCT / GB2020 / 051317, published as WO2020 / 240209A1.

[0205] Using the general method described above for preparing hard carbon sodium-ion cells, a test pouch cell (APFC492) was prepared using electrolyte composition TEL67a. The cycling performance of the test cell was then investigated and the results were compared to that of test cell APFC489 discussed in Example 1A above.

[0206] Both APFC492 and APFC489 were operated (charge / discharge) for four cycles at ±C / 10 in the voltage range of 4.1 to 0 V. Figure 8 shows the capacity versus cycle number, and at C / 10 there is good reversibility of the cathodic sodium ions.

[0207] For cycles 5–57, both APFC492 and APFC489 were operated at ±C / 5 in the voltage range of 4.05–1.8 V. Figure 8 also shows that there is good reversibility of cathodic sodium ions at C / 5.

[0208] Surprisingly, at both ±C / 5 and ±C / 10 rates, APFC489 (according to the invention) delivers comparable capacity to APFC492 (not according to the invention). Indeed, the cycling stability of APFC489 is comparable to that of APFC492, especially over the first 50+ cycles.

[0209] More specifically, Figures 9 and 10 show the cell voltage versus cathode specific capacity for APFC489 and APFC492 at cycle 3 at ±C / 5 and cycle 6 at ±C / 10, respectively. The results show that the degree of polarization for APFC489 was slightly higher compared to that of APFC492 with TEL67a at both the ±C / 10 rate and ±C / 5. This is reflected in the similar mid-capacity voltage hysteresis values ​​for both cells: As shown in Figure 9, at ±C / 10, the mid-capacitance voltage hysteresis was 120 mV versus 101 mV for APFC489 and APFC492, respectively, resulting in a difference of 19 mV.

[0210] At ±C / 5, the medium capacitance voltage hysteresis was 210 mV versus 143 mV for APFC489 and APFC492, respectively, resulting in a difference of 67 mV. Thus, at ±C / 10 the hysteresis value is only 19mV compared to 67mV at ±C / 5.

[0211] 9 and 10 further show that the difference in round trip energy efficiency (RTEE) for both cells was similar (i.e., a difference of about 1.2% at ±C / 10 and about 2.2% at ±C / 5).

[0212] Thus, the cycling performance in terms of stability, RTEE, and delivery capacity obtained from an electrolyte composition that is substantially free of one or more alkali metal-containing salts can be essentially similar to the cycling performance of electrolyte compositions as taught by the prior art (which contain significant amounts of one or more alkali metal salts), particularly at rates such as C / ≧5, and more preferably C / ≧10.

[0213] Example 3A - Cycling Testing and Long-Term Cycling Performance of Cells Using Electrolyte Compositions Containing Carbonate Ester Solvents and One or More Performance Additives Using the general method described above for preparing hard carbon sodium-ion cells, test pouch cells (APFC485) were prepared using electrolyte composition SOL14w. The cycling performance of the test cells was then investigated by cycling tests as follows:

[0214] The first four cycles were operated at ±C / 10 in the voltage range of 4.1 to 0 V. The coulombic efficiency for the first four cycles increased from 61.9% in cycle 1 to 87.9% by cycle 4, as shown in Figure 11 (note that the first charge was interrupted prematurely due to human error, as indicated by the arrow).

[0215] Cycles 5 through 250 were run at ±C / 5 over a voltage range of 4.05 V to 1.8 V. Figure 12 shows evidence of some reversible cycling at ±C / 5. Thus, stability and cycling performance with respect to discharge capacity retention can be obtained using an electrolyte composition that is substantially free of one or more alkali metal-containing salts.

[0216] The results also indicate that it is particularly desirable to discharge sodium-ion cells preferably at a rate of about C / ≧10 when using electrolyte compositions comprising carbonate-containing solvents that are substantially free of one or more alkali metal-containing salts.

[0217] Example 3B - Cycling Testing and Long-Term Cycling Performance of Cells Using Electrolyte Compositions Containing Carbonate Ester Solvents and One or More Performance Additives Using the general method described above for preparing hard carbon sodium-ion cells, test pouch cells (APFC491) were prepared using electrolyte composition SOL9c. The cycling performance of the test cells was then investigated by cycling tests as follows:

[0218] The first four cycles were operated at ±C / 10 in the voltage range of 4.1 to 0 V. The coulombic efficiency for the first four cycles increased from 86.3% in cycle 1 to 97.7% by cycle 4, as shown in Figure 13.

[0219] Cycles 5 through 150 above were operated in the voltage range of 4.05 V to 1.8 V at ±C / 5 and compared with the results obtained for APFC485 in Example 3A under the same cycling conditions. From the comparison shown in Figure 14, a higher discharge capacity was observed over 150 cycles compared to APFC485, indicating the preference for the EC:DEC:PC solvent system over the PC-dominant solvent system of APFC485. For example, at cycle 20 at ±C / 5, APFC491 with SOL9c was able to deliver 31.9 mAh / g, while the capacity at cycle 20 of APFC485 with SOL14w was lower (27.8 mAh / g).

[0220] Example 3C - Cycling Performance of Cells Using Electrolyte Compositions Containing Carbonate Ester Solvent in Combination with Triethyl Phosphate Solvent and One or More Performance Additives Using the general method described above for preparing hard carbon sodium-ion cells, test pouch cells (APFC490) were prepared using electrolyte composition SOL21a. The cycling performance of the test cells was then investigated by cycling tests as follows:

[0221] The first four cycles were operated at ±C / 10 over a voltage range of 4.1 to 0 V. This was followed by cycles 5 through 75 over ±C / 5 over a voltage range of 4.05 to 1.8 V, and were compared to the results obtained for APFC489 from Example 1A, cycled under the same conditions.

[0222] From the results shown in Figure 15, a lower discharge capacity was observed for APFC490 over 75 cycles compared to APFC489, indicating that the TEP-only solvent system is preferable to the TEP-containing carbonate solvent system of APFC489.

[0223] Example 4A - Cycling and Rate Performance of Cells Using Electrolyte Compositions Containing Glyme Solvent and One or More Performance Additives Using the general method described above for preparing hard carbon sodium-ion cells, test pouch cells (APFC487) were prepared using electrolyte composition SOL16H. The rate performance of the test cells was then investigated by cycling tests as follows: The first two cycles of the cell were operated (charge / discharge) in the voltage range of 4.1 to 0 V at ±C / 10.

[0224] The rate performance was then evaluated for cycles 3–10, operated in the voltage range of 4.05–1.8 V. During these cycles, the cells were first charged at C / 5. Then, each pair of cycles 3–4, 5–6, 7–8, and 9–10 were subsequently discharged at different rates: C / 5, C / 2, 1C, and 2C, respectively.

[0225] The cells were then subjected to further cycling at ±C / 5 from cycle 11 to cycle 190 at voltages between 4.05 and 1.8 V. Figure 16 shows capacity versus cycle number, showing acceptable discharge capacity for cathodic sodium ions at ±C / 10. However, cells discharged at C / 5, C / 2, 1C, and 2C rates showed much lower capacities, but nevertheless exhibited reversible cycling.

[0226] From the results shown in Figure 17, at ±C / 10, the coulombic efficiency increased from 78.2% in cycle 1 to 93.7% in cycle 2. However, there was some disturbance in the cycling profile at the highest point of charge in the CV step (approximately 3.8 to 4.0 V).

[0227] From the results shown in Figure 18, at ±C / 5, the coulombic efficiency decreased from 100.8% in cycle 12 to 99.7% in cycles 12 and 61. Similar to Figure 17, there was some disturbance in the cycling profile at the highest point of charging in the CV step.

[0228] Conclusions from Examples 1 to 4 Examples 1-4 demonstrate the surprising result that Na-ion cells can be effectively cycled in salt-free liquid electrolytes. The collected data demonstrate that Na-ion cells with salt-free electrolytes can exhibit good cycling performance at C / 2 and slower rates, which are ideally suited for stationary energy storage applications where the battery is expected to discharge for several hours, such as C / 5 or even C / 20.

[0229] Clearly, the electrolyte composition is essential to maintaining good cycling stability comparable to established, high-performance salt-based cells. The results show that TEP is the best solvent. However, carbonate- and glyme-containing solvents still exhibit varying degrees of performance (good capacity, efficiency, cycling stability, and rate capability), a highly unexpected result in itself. These experiments also hint at the important nature of additives, particularly SEI-forming additives; Experiment 6 below provides further details on their importance.

[0230] Example 5 - Cycling and rate performance of an anode-free sodium cell using an electrolyte composition according to the present invention Using the general method described above for preparing anode-free sodium cells, a test cell (INFC46) was prepared using electrolyte composition SOL21c. The rate performance of the test cell was then investigated by cycling it from 4.0 to 1.0 V at ±C / 10.

[0231] The results, shown in Figure 19, indicate that cell INFC46 exhibits reversible cycling when using electrolyte composition SOL21c. Specifically, INFC46 was able to deliver a specific capacity of 64.7 mAh / g on the first cycle, thus demonstrating reversibility.

[0232] Thus, the results of Example 5 led to the conclusion that compositions according to the present invention have utility in anode-free sodium cells as well as sodium-ion cells.

[0233] Example 6 In this experiment, the cycling performance of hard carbon sodium-ion cells was further investigated using an electrolyte composition according to the present invention. The purpose of this experiment was to investigate the importance of the specific type and amount of additives in the salt-free electrolyte on the performance of the sodium-ion cell.

[0234] No additives Cells APFC497 and APFC498 were cycled with 100 wt % TEP and cycled at ±C / 10 from 4.1 to 0 V. Both cells were also cycled at ±C / 50 from 4.1 to 0 V.

[0235] As shown in Figures 20 and 21, both APFC497 and APFC498 rapidly polarized and exhibited negligible capacity when cycled at ±C / 10. However, when cycled at ±C / 50, the delivered capacity was unexpectedly higher; for example, the ±C / 50 capacity of APFC497 was 24 mAh / g, even though the cell was only charged to 3.68 V (the cell's charge step was time-interrupted, after which the battery cycler automatically proceeded to a 5-second CV step at 4.1 V, which also naturally shut off), and the ±C / 50 capacity of APFC498 was 23 mAh / g (the cell's charge was time-interrupted at 3.90 V, with no subsequent CV step).

[0236] This experiment demonstrates that reversible cycling in a sodium-ion cell can be achieved using an electrolyte composition that is substantially free of one or more metal-containing salts.

[0237] Boron-containing additives Cell APFC505 was cycled at ±C / 10 at a voltage of 4.1 to 0 V using TEP containing 1 wt % TMSB (sample SOL21d). Cell APFC509 was cycled at ±C / 10 at a voltage of 4.1 to 0 V using TEP (sample SOL 21 g) containing 5 wt % TMSB.

[0238] As shown in Figure 22, cell APFC505 achieved a charge capacity of 8.8 mAh / g and a discharge capacity of 7.5 mAh / g on the fourth cycle. These delivered capacities at ±C / 10 are significantly higher than those seen with the Na-ion pouch cell containing only the TEP solvent described on the previous page (the cycling profile of APFC497 is also shown in Figure 22).

[0239] Figure 23 shows the first cycle profiles at ±C / 10 for Na-ion cells using salt-free electrolyte without additives (APFC497 with TEP) or salt-free electrolyte with B-containing additives (AFPC505 with SOL21d or APFC509 with SOL21g). It can be seen that the presence of the TMSB additive, regardless of the amount, had a significant effect on the charge cycle: APFC497 quickly polarized to 4.1 V during the CC step (charging CC step capacity was only 0.04 mAh / g), while the two TMSB-containing cells delivered significantly higher capacities during the CC step (APFC505 delivered 72.1 mAh / g and APFC509 delivered 86.9 mAh / g during the CC charging step). The effect on the discharge capacity was also significant, but less so than during the charging step: the discharge capacity in cycle 1 of APFC497 was 2.8 mAh / g, that of APFC505 was 13.7 mAh / g, and that of APFC509 was 0.9 mAh / g.

[0240] This experiment demonstrates the unexpected performance of using a boron-containing additive (TMSB) in an electrolyte composition that is substantially free of one or more metal-containing salts. In particular, when TMSB is used as the sole additive, it can provide significantly higher discharge capacity in a Na-ion cell at a rate such as C / 10 compared to an electrolyte composition that is substantially free of one or more metal-containing salts and that contains no additives (i.e., 100% TEP).

[0241] surfactant additives Cell APFC506 was cycled at ±C / 10 at a voltage of 4.1 to 0 V using TEP containing 1 wt % P123 (sample SOL21e).

[0242] As shown in Figure 22, APFC506 performed similarly to the baseline APFC497 cell when cycled at ±C / 10: the former had a discharge capacity of 1.62 mAh / g at cycle 4, and the latter had a discharge capacity of 1.64 mAh / g. Thus, this experiment demonstrates the unexpected performance of using a surfactant (P123) in an electrolyte composition that is substantially free of one or more metal-containing salts.

[0243] S-containing additives Cell APFC508 was cycled at ±C / 10 at a voltage of 4.1 to 0 V using TEP containing 5 wt % PCS (sample SOL21f).

[0244] As shown in Figure 22, cell APFC508 delivered significantly higher capacity than that obtained with other cells containing other types of single additives, i.e., a charge capacity of 108.7 mAh / g and a discharge capacity of 107.3 mAh / g on the fourth cycle. This experiment demonstrates the unexpected performance of using a sulfur-containing additive (PCS) in an electrolyte composition that is substantially free of one or more metal-containing salts.

[0245] Additive combinations Cell APFC510 was cycled at ±C / 10 at a voltage of 4.1 to 0 V using TEP (sample SOL21h) containing 5 wt% PCS, 1 wt% P123, and 5 wt% TMSB.

[0246] As shown in FIG. 22, cell APFC510 provided a charge capacity of 110.7 mAh / g and a discharge capacity of 109.2 mAh / g in the fourth cycle. Similarly, cell APFC489 in Experiment 1A was cycled at ±C / 10 from 4.1 to 0 V using a TEP containing 5 wt% PCS, 1 wt% P123, and 1 wt% TMSB (sample SOL21).

[0247] As shown in FIG. 22, cell APFC489 provided a charge capacity of 112.3 mAh / g and a discharge capacity of 110.8 mAh / g in the fourth cycle. It can be seen that both cells performed significantly better than the baseline cell (APFC497) containing no additive. This experiment demonstrates the unexpected performance of using a combination of additives in an electrolyte composition that is substantially free of one or more metal-containing salts.

[0248] conclusion As noted above, different types of additives are seen to have different effects on affecting the performance of Na-ion cells using electrolytes that are substantially free of one or more metal-containing salts. Furthermore, cells APFC489 and APFC510 exhibited greater or similar performance capacities compared to cells APFC505, APFC506, and even APFC508, which used the B-containing additive, surfactant-containing additive, and S-containing additive alone, respectively. This synergistic performance resulting from the combination of additives to deliver desirable cell characteristics is highly unexpected in an electrolyte composition that is substantially free of one or more metal-containing salts.

[0249] The results for each of these additives (S-containing additive, B-containing additive, and surfactant-containing additive) are indeed surprising since the absence of salt and immediate polarization would have been expected to negate all subsequent effects of such additives.

[0250] Example 7 In this experiment, the cycling performance of hard carbon sodium-ion cells using electrolyte compositions according to the present invention is investigated using various polyolefin separators. Two different polyolefin separators were investigated using cells cycled with TEP containing 5 wt% PCS, 1 wt% P123, and 1 wt% TMSB (sample SOL21): Cell APFC488 (according to Experiment 1B) used a polyolefin separator with a thickness of 25 μm; and Cell APFC514 used a polyolefin separator with a thickness of 16 μm.

[0251] The first two cycles of APFC488 and APFC514 were operated (charge / discharge) at ±C / 10 in the voltage range of 4.1 to 0 V. Rate performance was evaluated for cycles 3 to 10, which were operated at a voltage range of 4.05 to 1.8 V. During these cycles, the cells were charged at a rate of C / 5 throughout. Next, each pair of cycles 3-4, 5-6, 7-8, and 9-10 were subsequently discharged at different rates of C / 5, C / 2, 1C, and 2C, respectively. After these cycles, from cycle 11 onwards, the cells were subjected to cycling at ±C / 5 from 4.05 to 1.8 V.

[0252] Figure 24 shows capacity versus cycle number, demonstrating good reversibility of cathodic sodium ions for both APFC488 and APFC514 up to C / 2. It can be seen that the discharge capacity at 1C rate of APFC514 using a 16 μm separator was significantly higher than that of APFC488 using a 25 μm separator: the former cell delivered approximately 79 mAh / g, while the latter was only able to deliver approximately 46 mAh / g. Similarly, the discharge capacity at 2C rate of APFC514 using a 16 μm separator was significantly higher than that of APFC488 using a 25 μm separator: the former cell delivered approximately 23 mAh / g, while the latter was only able to deliver approximately 1.3 mAh / g.

[0253] Thus, it can be seen that APFC488 discharged at rates of 1C and 2C retained less than 50% of the cathode specific capacity (ie, 48% cathode specific capacity at 1C; 1.4% cathode specific capacity at 2C).

[0254] In contrast, APFC514 discharged at 1 C retained over 50% of its cathode specific capacity (i.e., 84.2% of its cathode specific capacity at 1 C). Furthermore, APFC514 discharged at 2 C retained approximately 25% of its cathode specific capacity relative to its capacity at C / 5.

[0255] Therefore, it is possible to increase the rate capability of sodium-ion cells using electrolyte compositions that are substantially free of one or more alkali metal-containing salts by reducing the thickness of the polyolefin separator from 25 μm to 16 μm.

[0256] Example 8 This experiment aims to investigate the effect that a "supporting salt" may have on the electrochemical performance of a sodium-ion cell using an electrolyte composition according to the present invention. For purposes of this disclosure, a "supporting salt" is any salt that is not a metal-containing salt but that facilitates the migration of metal cations (i.e., Na+) from the cathode to the anode and vice versa. However, the supporting salt does not participate in the electrochemical process of the electrochemical cell.

[0257] As discussed below, the cycling performance of two sodium-ion cells was investigated at ±C / 10 from 4.1 to 0 V. Tetrabutylammonium hexafluorophosphate, or TBAPF6, was used as the supporting salt.

[0258] TEL84 Cell APFC518 was cycled at ±C / 10 with 1 m TBAPF6 (sample TEL84) in TEP containing 5 wt% PCS, 1 wt% P123, and 1 wt% TMSB at a voltage of 4.1 to 0 V.

[0259] FIG. 25 compares the results for cell APFC518 with cell APFC489 cycled with SOL21 from experiment 1A. As shown, adding 1 ml of TBAPF6 to SOL21 to form TEL84 did not significantly affect the electrochemical performance of the cell. For example, the discharge capacity at cycle 1 for APFC518 was 107.5 mAh / g compared to 112.9 mAh / g obtained with APFC489.

[0260] TEL84a Cell APFC513 was cycled at ±C / 10 with 1 m TBAPF6 (sample TEL84a) in TEP at a voltage of 4.1 to 0 V.

[0261] FIG. 26 compares the results for cell APFC513 with cell APFC497, which was cycled with 100 wt % TEP from Experiment 6A. As shown, adding 1 ml of TBAPF6 to TEP to form TEL84a unexpectedly increased the electrochemical performance of the cell. For example, the discharge capacity obtained for APFC487 in cycle 1 was 1.6 mAh / g, compared to 54.2 mAh / g for APFC518.

[0262] conclusion Cells cycled with an electrolyte composition according to the present invention that included a supporting salt exhibited greater or similar performance in discharge capacity compared to cells that did not include such a supporting salt.

[0263] Example 9 This experiment investigates the cycling performance of a hard carbon potassium ion cell using an electrolyte composition according to the present invention.

[0264] Using the general method described above to prepare a potassium ion cell, cell APFC527 was cycled from 4.1 to 0 V at ±C / 5 using a TEP containing 5 wt% PCS, 1 wt% P123, and 1 wt% TMSB (sample SOL21).

[0265] Cell APFC528 was prepared using the same general method as above and cycled from 4.1 to 0 V at ±C / 4 using 1 m KPF6 (sample TEL82) in TEP containing 5 wt% PCS, 1 wt% P123, and 1 wt% TMSB.

[0266] Figure 27 compares the cycling results for cell APFC527 compared to cell APFC528. As shown, the discharge capacity obtained for APFC527 in cycle 1 was 36.2 mAh / g, compared to 46.1 mAh / g in cycle 1 for APFC528.

[0267] conclusion The results of Example 9 conclude that electrolyte compositions according to the present invention have utility in potassium-ion cells as well as sodium-ion cells and anode-free sodium cells.

[0268] Example 10 In this experiment, the cycling performance of a graphite anode-based lithium-ion cell using an electrolyte composition according to the present invention is investigated.

[0269] Using the general method described above for preparing lithium-ion cells, the following cells were fabricated: APFC541, which used salt-free electrolyte SOL25 (EC:DMC = 1:1 wt / wt); APFC542, which used salt-free electrolyte SOL25a (EC:DMC = 1:1 wt / wt containing 5 wt% PCS, 1 wt% P123, and 1 wt% TMSB), and APFC551, which used Li metal salt-containing LP30 electrolyte (1 M LiPF in EC:DMC = 1:1 v / v). These three cells were cycled at ±C / 10 between 4.3 and 3 V for 10 cycles.

[0270] Figure 28 compares the cycling results of the three cells. It can be seen that the APFC542 cell, which used the salt-free electrolyte (SOL25a) of the present invention, significantly outperformed the other cells. For example, the first and tenth discharge capacities of APFC542 were 153.2 mAh / g and 150.8 mAh / g, respectively, while the values ​​for APFC541, which used an additive-free, salt-free electrolyte, were 0 mAh / g and 0 mAh / g, respectively, and the values ​​for APFC551, which used a metal-containing electrolyte, were 0 mAh / g and 0 mAh / g, respectively.

[0271] conclusion The results of Example 10 demonstrate that electrolyte compositions according to the present invention have utility in lithium-ion cells, as well as sodium-ion, potassium-ion, and anode-free sodium cells. The additives in SOL25a have not been tested in salt-free cells, and therefore the benefits of using SOL25a over using SOL25 and LP30 are surprising and unexpected.

[0272] Example 11 This experiment aims to investigate the effect that a minimal amount of metal-containing salt may have on the electrochemical performance of a sodium-ion cell using an electrolyte composition according to the present invention. Using very small amounts of NaPF6 salt at different concentrations in a solvent system of TEP containing 5 wt% PCS, 1 wt% P123, and 1 wt% TMSB, the cycling performance was investigated from 4.1 to 0 V at ±C / 10 for two sodium-ion cells described below:

[0273] Cell APFC547 was cycled at ±C / 10 from 4.1 to 0 V with 0.1 m NaPF6 (sample TEL80f) in TEP containing 5 wt% PCS, 1 wt% P123, and 1 wt% TMSB.

[0274] Cell APFC548 was cycled at ±C / 10 from 4.1 to 0 V with 0.05 m NaPF6 (sample TEL 80 g) in TEP containing 5 wt% PCS, 1 wt% P123, and 1 wt% TMSB.

[0275] Figure 29 compares the results for cells APFC547 and APFC548 with cell APFC488, which was cycled with SOL21 from Experiment 1B. As shown, adding 0.1 m or 0.05 m NaPF6 to SOL21 to form TEL80f and TEL80g, respectively, did not significantly affect the electrochemical performance of the cells. For example, in cycle 1, the discharge capacity obtained for APFC547 was 116.1 mAh / g, and the discharge capacity for APFC548 was 115.5 mAh / g, compared to 113.4 mAh / g for APFC488.

[0276] conclusion Cells cycled with electrolyte compositions according to the present invention containing trace amounts of metal-containing salts exhibited greater or similar performance in discharge capacity compared to cells without metal-containing salts, a particularly surprising and unexpected result because cells containing such low concentrations of salts would not have been expected to produce such desirable results simply by including an additive.

[0277] Example 12 This experiment investigates the effect on the density of liquid electrolytes made in accordance with the present invention versus the density of liquid electrolytes containing substantial amounts of metal salts. For this purpose, the following two electrolytes were tested: SOL14w (according to the invention): PC containing 20 wt% DEC, 2 wt% PCS, 1 wt% TMSB and 1 wt% P123.

[0278] TEL67a (not according to the invention): 1 m NaPF6 in PC containing 20 wt% DEC, 2 wt% PCS, 1 wt% TMSB, 1 wt% P123 To measure the density of the electrolytes, 25 mL of each electrolyte was weighed. Three measurements were taken for each electrolyte. A summary of the results obtained, along with the standard deviation, is shown in Table 3 below:

[0279] [Table 5]

[0280] From Table 3 it can be seen that TEL67a (not according to the invention) was about 10% heavier than SOL14w (according to the invention). This experiment demonstrates that the electrolyte according to the invention results in a lighter battery than electrolytes containing substantial amounts of salt, thus increasing the specific energy (Wh / kg) of the resulting battery, which is a highly advantageous property commercially.

[0281] Subject matter encompassed by the following numbered aspects also forms part of the present invention, optionally in combination with subject matter described above and / or defined in the claims below.

[0282] Numbered Aspect 1 a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from sulfur-containing compounds, boron-containing compounds, and surfactants; 1. Use of a composition comprising a solvent system comprising: The above use, wherein the composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

[0283] Numbered Aspect 2 The use of numbered embodiment 1, wherein the composition is substantially free of one or more metal-containing salts. Numbered Aspect 3 The use of numbered embodiment 1 or numbered embodiment 2, wherein the one or more non-aqueous solvents are selected from organic phosphate-based solvents, organic carbonate-based solvents, and glyme-based solvents.

[0284] Numbered Aspect 4 The use of any one of numbered aspects 1-3, wherein the second component comprises one or more performance additives in an amount of >0.5 to ≦10 wt. % of the solvent system.

[0285] Numbered Aspect 5 The use of any one of numbered embodiments 1-4, wherein the surfactant is selected from anionic surfactants, cationic surfactants, nonionic (hydrophilic) surfactants, and amphoteric (zwitterionic) surfactants.

[0286] Numbered Aspect 6 The use according to numbered embodiment 5, wherein the surfactant comprises at least one nonionic block copolymer surfactant, preferably selected from one or more poloxamers.

[0287] Numbered Aspect 7 The use of any one of numbered embodiments 1-6, wherein the sulfur-containing compound is selected from a sulfone-containing compound, a sulfate-containing compound, and a sulfonate-containing compound.

[0288] Numbered Aspect 8 The use of numbered embodiment 7, wherein the sulfur-containing compound comprises 1,3-propanediol cyclic sulfate (PCS).

[0289] Numbered Aspect 9 The use of any one of numbered embodiments 1-8, wherein the boron-containing compound is selected from a borate-containing compound and a boroxine-containing compound.

[0290] Numbered Aspect 10 The use of numbered embodiment 9, wherein the boron-containing compound comprises tris(trimethylsilyl)borate (TMSB).

[0291] Numbered Aspect 11 The use of any one of numbered embodiments 1-10, wherein the first component comprises triethyl phosphate in an amount of about 90% or more by weight of the first component of the solvent system.

[0292] Numbered Aspect 12 The use of any one of numbered embodiments 1 to 11 in an electrochemical cell, preferably a sodium-based electrochemical cell.

[0293] Numbered Aspect 13 The use of numbered embodiment 12, wherein the electrochemical cell is a metal ion cell comprising a negative electrode and a positive electrode.

[0294] Numbered Aspect 14 The use of numbered embodiment 13, wherein the metal ion cell is selected from a sodium ion cell, a lithium ion cell, and a potassium ion cell.

[0295] Numbered Aspect 15 The use of numbered embodiment 12, wherein the electrochemical cell is an anode-free sodium cell.

[0296] Numbered Aspect 16 16. The use of any one of numbered embodiments 1-15 in an electrochemical cell associated with or integrated with one or more additional electrochemical cells having one or more metal-containing salts at a concentration greater than 0.2 mol / kg.

[0297] Numbered Aspect 17 1. A method for accessing available energy from an electrochemical cell, comprising: a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from sulfur-containing compounds, boron-containing compounds, and surfactants; operating an electrochemical cell with an electrolyte composition comprising a solvent system comprising The aforementioned method, wherein the electrolyte composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

[0298] Numbered Aspect 18 The method of numbered embodiment 17, further comprising associating or integrating available energy from the electrochemical cell with one or more additional electrochemical cells having one or more metal-containing salts at a concentration greater than 0.2 mol / kg.

[0299] Numbered Aspect 19 1. A method for manufacturing an electrochemical cell, comprising: In the electrochemical cell, a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from sulfur-containing compounds, boron-containing compounds, and surfactants; introducing an electrolyte composition comprising a solvent system comprising The aforementioned method, wherein the electrolyte composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

[0300] Numbered Aspect 20 The method of any one of numbered embodiments 17-19, wherein the electrolyte composition is substantially free of one or more metal-containing salts.

[0301] Numbered Aspect 21 The method of any one of numbered embodiments 17-20, wherein the one or more non-aqueous solvents are selected from organic phosphate-based solvents, organic carbonate-based solvents, and glyme-based solvents.

[0302] Numbered Aspect 22 The method of any one of numbered embodiments 17-21, wherein the second component comprises one or more performance additives in an amount >0.5 to ≦10 wt. % of the solvent system.

[0303] Numbered Aspect 23 The method of any one of numbered embodiments 17-22, wherein the surfactant is selected from anionic surfactants, cationic surfactants, nonionic (hydrophilic) surfactants, and amphoteric (zwitterionic) surfactants.

[0304] Numbered Aspect 24 The method of any one of numbered embodiments 17-23, wherein the surfactant includes at least one nonionic block copolymer surfactant, preferably selected from one or more poloxamers.

[0305] Numbered Aspect 25 The method of any one of numbered embodiments 17-24, wherein the sulfur-containing compound is selected from a sulfone-containing compound, a sulfate-containing compound, and a sulfonate-containing compound.

[0306] Numbered Aspect 26 The method of numbered embodiment 25, wherein the sulfur-containing compound includes 1,3-propanediol cyclic sulfate (PCS).

[0307] Numbered Aspect 27 The method of any one of numbered embodiments 17-26, wherein the boron-containing compound is selected from a borate-containing compound and a boroxine-containing compound.

[0308] Numbered Aspect 28 The method of numbered embodiment 27, wherein the boron-containing compound comprises tris(trimethylsilyl)borate (TMSB).

[0309] Numbered Aspect 29 The method of any one of numbered embodiments 17-28, wherein the first component comprises triethyl phosphate in an amount of about 90% or more by weight of the first component of the solvent system.

[0310] Numbered Aspect 30 The method of any one of numbered embodiments 17-29, wherein the electrochemical cell is a sodium-based electrochemical cell.

[0311] Numbered Aspect 31 The method of any one of numbered embodiments 17-29, wherein the electrochemical cell is a metal ion cell including a negative electrode and a positive electrode.

[0312] Numbered Aspect 32 The method of numbered embodiment 31, wherein the metal ion cell is selected from a sodium ion cell, a lithium ion cell, and a potassium ion cell.

[0313] Numbered Aspect 33 The method of any one of numbered embodiments 17-29, wherein the electrochemical cell is an anode-free sodium cell.

[0314] Numbered Aspect 34 An electrochemical cell prepared by the method of any one of numbered embodiments 19-33.

[0315] Numbered Aspect 35 a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from a sulfur-containing compound, a boron-containing compound, and a surfactant; 1. An electrochemical cell having an electrolyte composition comprising a solvent system comprising: The electrochemical cell, wherein the electrolyte composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

[0316] Numbered Aspect 36 36. The electrochemical cell of numbered embodiment 35, wherein the electrolyte composition is substantially free of one or more metal-containing salts.

[0317] Numbered Aspect 37 The electrochemical cell of any one of numbered embodiments 35-36, wherein the one or more non-aqueous solvents are selected from organic phosphate-based solvents, organic carbonate-based solvents, and glyme-based solvents.

[0318] Numbered Aspect 38 The electrochemical cell of any one of numbered embodiments 35-37, wherein the second component comprises one or more performance additives in an amount >0.5 to ≦10 wt % of the solvent system.

[0319] Numbered Aspect 39 The electrochemical cell of any one of numbered embodiments 35-38, wherein the surfactant is selected from anionic surfactants, cationic surfactants, nonionic (hydrophilic) surfactants, and amphoteric (zwitterionic) surfactants.

[0320] Numbered Aspect 40 40. The electrochemical cell of numbered embodiment 39, wherein the surfactant includes at least one nonionic block copolymer surfactant, preferably selected from one or more poloxamers.

[0321] Numbered Aspect 41 The electrochemical cell of any one of numbered embodiments 35-40, wherein the sulfur-containing compound is selected from a sulfone-containing compound, a sulfate-containing compound, and a sulfonate-containing compound.

[0322] Numbered Aspect 42 42. The electrochemical cell of numbered embodiment 41, wherein the sulfur-containing compound includes 1,3-propanediol cyclic sulfate (PCS).

[0323] Numbered Aspect 43 The electrochemical cell of any one of numbered embodiments 35-42, wherein the boron-containing compound is selected from a borate-containing compound and a boroxine-containing compound.

[0324] Numbered Aspect 44 44. The electrochemical cell of numbered embodiment 43, wherein the boron-containing compound includes tris(trimethylsilyl)borate (TMSB).

[0325] Numbered Aspect 45 The electrochemical cell of any one of numbered embodiments 35-44, wherein the first component comprises triethyl phosphate in an amount of about 90% or greater by weight of the first component of the solvent system.

[0326] Numbered Aspect 46 The electrochemical cell of any one of numbered embodiments 35 to 45, wherein the electrochemical cell is a sodium-based electrochemical cell.

[0327] Numbered Aspect 47 The electrochemical cell of any one of numbered embodiments 35 to 45, wherein the electrochemical cell is a metal ion cell including a negative electrode and a positive electrode.

[0328] Numbered Aspect 48 48. The electrochemical cell of numbered embodiment 47, wherein the metal ion cell is selected from a sodium ion cell, a lithium ion cell, and a potassium ion cell.

[0329] Numbered Aspect 49 The electrochemical cell of any one of numbered embodiments 35 to 45, wherein the electrochemical cell is an anode-free sodium cell.

[0330] Numbered Aspects 50 A device comprising the electrochemical cell of any one of numbered embodiments 35-49.

[0331] Numbered Aspect 51 The device of numbered embodiment 50, wherein the device comprises one or more electrochemical cells having an electrolyte composition comprising one or more metal-containing salts at a concentration greater than 0.2 mol / kg.

Claims

1. a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from sulfur-containing compounds, boron-containing compounds, and surfactants; 1. Use of a composition comprising a solvent system comprising: The aforementioned use, wherein the composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

2. 10. The use of claim 1, wherein the composition is substantially free of one or more metal-containing salts.

3. 3. The use according to claim 1 or claim 2, wherein the one or more non-aqueous solvents are selected from organic phosphate-based solvents, organic carbonate-based solvents, and glyme-based solvents.

4. 4. The use according to any one of claims 1 to 3, wherein the second component comprises one or more performance additives in an amount of >0.5 to ≦10% by weight of the solvent system.

5. 5. The use according to any one of claims 1 to 4, wherein the surfactant is selected from anionic surfactants, cationic surfactants, nonionic (hydrophilic) surfactants and amphoteric (zwitterionic) surfactants.

6. 6. The use according to claim 5, wherein the surfactant comprises at least one non-ionic block copolymer surfactant, preferably selected from one or more poloxamers.

7. The use according to any one of claims 1 to 6, wherein the sulfur-containing compound is selected from sulfone-containing compounds, sulfate-containing compounds, and sulfonate-containing compounds.

8. 8. The use of claim 7, wherein the sulfur-containing compound comprises 1,3-propanediol cyclic sulfate (PCS).

9. The use according to any one of claims 1 to 8, wherein the boron-containing compound is selected from borate-containing compounds and boroxine-containing compounds.

10. 10. The use of claim 9, wherein the boron-containing compound comprises tris(trimethylsilyl)borate (TMSB).

11. The use according to any one of claims 1 to 10, wherein the first component comprises triethyl phosphate in an amount of about 90% or more by weight of the first component of the solvent system.

12. Use according to any one of claims 1 to 11 in an electrochemical cell, preferably a sodium-based electrochemical cell.

13. 13. The use according to claim 12, wherein the electrochemical cell is a metal ion cell comprising a negative electrode and a positive electrode.

14. 14. The use according to claim 13, wherein the metal ion cell is selected from a sodium ion cell, a lithium ion cell, and a potassium ion cell.

15. 13. The use according to claim 12, wherein the electrochemical cell is an anode-free sodium cell.

16. 16. Use according to any one of claims 1 to 15 in an electrochemical cell associated with or integrated with one or more additional electrochemical cells having one or more metal-containing salts at a concentration above 0.2 mol / kg.

17. 1. A method for accessing available energy from an electrochemical cell, comprising: a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from sulfur-containing compounds, boron-containing compounds, and surfactants; operating an electrochemical cell with an electrolyte composition comprising a solvent system comprising The method wherein the electrolyte composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

18. 20. The method of claim 17, comprising cycling the electrochemical cell at a C-rate of about C / ≧2.

19. 1. A method for manufacturing an electrochemical cell, comprising: In the electrochemical cell, a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from sulfur-containing compounds, boron-containing compounds, and surfactants; introducing an electrolyte composition comprising a solvent system comprising The method wherein the electrolyte composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

20. a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from sulfur-containing compounds, boron-containing compounds, and surfactants; 1. An electrochemical cell having an electrolyte composition comprising a solvent system comprising: The electrochemical cell wherein the electrolyte composition further comprises one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

21. 21. A device comprising the electrochemical cell of claim 20.

22. a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives including sulfur-containing compounds; 1. An electrolyte composition comprising a solvent system comprising: The electrolyte composition further comprising one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

23. a first component comprising one or more non-aqueous solvents; a second component comprising one or more performance additives selected from boron-containing compounds and surfactants in an amount of >0.5 to ≦10 wt. % of the solvent system; 1. An electrolyte composition comprising a solvent system comprising: The electrolyte composition further comprising one or more metal-containing salts at a concentration of 0 mol / kg to ≦0.2 mol / kg.

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