Unsaturated additives for lithium-ion batteries

Abstract

The present disclosure relates to a phosphorus additive useful for stable cycling and storage of lithium-ion cells at high temperatures, an electrolyte containing the phosphorus additive, and an electrochemical energy storage device containing the electrolyte. The electrolyte comprises an aprotic organic solvent system, a metal salt, and at least one thiophosphate additive having an unsaturated end group of formula (I): TIFF2023542806000021.tif16128

Description

[Technical Field]

[0001] cross reference This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 63 / 063,656, filed August 10, 2020, which is incorporated herein by reference in its entirety.

[0002] Field The present disclosure relates to thio-phosphorus additives useful for stable cycling and storage of lithium-ion cells at high temperatures, electrolytes containing the thio-phosphorus additives, and electrochemical energy storage devices containing the electrolytes. [Background technology]

[0003] background Li-ion batteries are widely used in home appliances, electric vehicles (EVs), and energy storage systems (ESSs) and smart grids. Recently, Li-ion batteries with voltages above 4.2 V have gained importance due to their higher capacity and subsequent energy density. However, the stability of positive electrode materials at these potentials is reduced by increased electrolyte oxidation. This can lead to electrochemical oxidation of the material, resulting in gas generation and reduced battery performance. Positive electrode active materials capable of lithium ion intercalation / deintercalation can dissolve in the non-aqueous electrolyte, causing structural destruction of the positive electrode and increasing interfacial resistance. These Li-ion batteries are also typically exposed to extreme temperatures during operation. The solid-electrolyte interface (SEI) layer formed on the negative electrode gradually decomposes at high temperatures, thus triggering more irreversible reactions and resulting in capacity loss. These reactions occur at both the positive and negative electrodes during cycling and are generally more severe at higher temperatures due to faster kinetics. Next-generation Li-ion batteries used in consumer electronics, EVs, and ESS will require significant improvements in electrolyte components compared to current state-of-the-art Li-ion batteries.

[0004] The primary function of an electrolyte is the shuttling of positive and negative ions between battery electrodes. Historically, researchers have focused on developing battery electrodes, with limited development of electrolytes. Traditional Li-ion batteries use carbonate-based electrolytes, which have a large potential window through which lithium ions can be transported. These electrolytes require functional additives to passivate the negative electrode and form a stable SEI layer. At the same time, additives must be designed and developed to enable stable and safe cycling of high-pressure Li-ion batteries at high temperatures.

[0005] As the industry moves toward high-energy cathode materials for high-energy batteries, stable, efficient, and safe cycling of batteries over a wide voltage window is necessary. Li-ion battery electrolytes can be tailored based on their application by adding different cosolvents and additives. This tunability has enabled the development of different additives for high-voltage stability and safety in Li-ion cells. Another aspect of high-voltage Li-ion battery electrolyte development is the design and optimization of additives for stable cycling at high temperatures, as today's batteries have a variety of applications in which the cells are exposed to different temperature and pressure conditions. While anode SEI-forming additives have been widely studied, the interactions and benefits of using different cathode additives have been less well documented and can result in significant changes in battery performance.

[0006] Developments in battery cathode materials have enabled batteries that can be charged to high voltages. The energy density of batteries can be significantly increased by charging to higher voltages, thus enabling longer battery life per charge. In practice, this increases the driving range of electric vehicles, extends the battery life of electronic devices, and reduces the size and weight of battery packs used in energy storage systems. To keep up with this development, battery electrolytes require functional additives to extend the voltage stability of conventional electrolytes. Lithium-ion batteries with high-voltage cathodes stored at high temperatures, especially at 100% SOC, generate large amounts of gas due to electrolyte decomposition. This is the result of electrolyte elements reacting with the electrode material, and large amounts of gas generation pose a significant safety risk when storing lithium-ion batteries. Therefore, there is a need to develop and optimize electrolyte formulations that can reduce gas generation in lithium-ion batteries and thus improve their high-temperature storage characteristics. To achieve this, additives must be designed and developed to enable stable and safe cycling and storage of high-voltage lithium-ion batteries at high temperatures.

[0007] Shenzhen Capchem's U.S. Patent No. 10497975 B2 and U.S. Patent Applications Nos. 20180076483 A1 and 20190089000 A1 disclose the use of propargyl phosphate esters in lithium-ion battery electrolytes. They claim to improve high-temperature cycling performance and low-temperature rate performance. However, thiophosphates are not considered electrolyte additives in the prior art. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] US Patent No. 10497975 B2 [Patent Document 2] U.S. Patent Application No. 20180076483 A1 [Patent Document 3] U.S. Patent Application No. 20190089000 A1 Summary of the Invention

[0009] overview According to one aspect of the present disclosure, there is provided an electrolyte for an electrochemical energy storage device, comprising: a thiophosphate additive, such as a thiophosphate ester additive, with an unsaturated end group; an aprotic organic solvent system; a metal salt; and at least one additional additive.

[0010] According to another aspect of the present disclosure, there is provided an electrolyte for an electrochemical energy storage device, the electrolyte comprising: a thiophosphate ester additive with an unsaturated end group; an aprotic organic solvent system; a metal salt; and at least one additional additive, wherein the thiophosphate ester additive with an unsaturated end group has at least one phosphorus moiety and one sulfur moiety.

[0011] According to another aspect of the present disclosure, there is provided an electrolyte solution for an electrochemical energy storage device, comprising: a thiophosphate ester additive with unsaturated end groups; an aprotic organic solvent system; a metal salt; and at least one additional additive, wherein the aprotic organic solvent includes a linear or cyclic carbonate, a carboxylic acid ester, a nitrite, an ether, a sulfone, a sulfoxide, a ketone, a lactone, a dioxolane, a glyme, a crown ether, a siloxane, a phosphate ester, a phosphite, a mono- or polyphosphazene, or a mixture thereof.

[0012] According to another aspect of the present disclosure, there is provided an electrolyte for an electrochemical energy storage device, comprising: a thiophosphate ester additive with an unsaturated end group; an aprotic organic solvent system; a metal salt; and at least one additional additive, wherein the cation of the metal salt comprises lithium, sodium, aluminum, or magnesium.

[0013] According to another aspect of the present disclosure, there is provided an electrochemical energy storage device electrolyte comprising: (a) Aprotic organic solvent systems; (b) a metal salt; and (c) Formula: TIFF0007733936000001.tif21128, wherein at least one thiophosphate additive having an unsaturated end group is of the formula: Y is oxygen or sulfur; X is independently oxygen or sulfur, provided that when Y is oxygen, at least one X is sulfur; R3 is selected from hydrocarbyl groups having 1 to 10 carbon atoms with unsaturated end groups; R1 and R2 are R3; or R1 and R2 are independently C1 to C 10 a substituted or unsubstituted alkyl group, or an aryl group; wherein the hydrogen atom may be unsubstituted or may be a halogen, alkyl, alkoxy, perfluorinated alkyl, silyl, siloxy, silane, sulfoxide, amide, azo, ether, and thioether group or a combination thereof; Thiophosphate additives.

[0014] According to another aspect of the present disclosure, there is provided an electrochemical energy storage device comprising: a positive electrode; a negative electrode; an electrolyte of the present disclosure; and a separator.

[0015] According to another aspect of the present disclosure, there is provided an electrolyte for an electrochemical energy storage device, comprising: a thiophosphate ester additive with an unsaturated end group; an aprotic organic solvent system; a metal salt; and at least one additional additive, wherein the additional additive comprises a compound containing at least one unsaturated carbon-carbon bond, a carboxylic acid anhydride, a sulfur-containing compound, a phosphorus-containing compound, a boron-containing compound, a silicon-containing compound, or a mixture thereof. [Brief explanation of the drawings]

[0016] [Figure 1] Figure 1 shows the dQ / dV profiles of the electrolytes tested in the NMC811 / Si-Gr cell. [Figure 2] Figure 2 shows the dQ / dV profiles of the electrolytes tested in the NMC811 / Gr cell. [Figure 3] FIG. 3 shows the cycle life characteristics of the cell during charging and discharging cycles. DETAILED DESCRIPTION OF THE INVENTION

[0017] Detailed Description The technology of the present disclosure generally relates to lithium-ion (Li-ion) battery electrolytes. In one aspect, the present disclosure is directed to thiophosphate additives with unsaturated end groups, electrolytes including the additive materials, and electrochemical energy storage devices including the electrolytes.

[0018] This disclosure describes a Li-ion battery electrolyte with an electrolyte additive that can overcome the challenge of high-temperature stability in Li-ion batteries, especially those operating at high voltages. Current state-of-the-art Li-ion battery electrolytes are tailored for room-temperature applications, and researchers have recently begun to focus on battery safety through the use of safe cosolvents and additives. The development of electrolytes for cycling Li-ion cells with high-voltage positive electrodes at high temperatures is necessary. The proposed technology is based on an innovative electrolyte additive containing unsaturated end groups on the phosphorus group, such as thiophosphate ester functional groups, which can improve the stability of high-voltage positive electrodes during high-temperature operation. The electrolyte additive forms a unique electrode-electrolyte interface (EEI) without excessively passivating the negative electrode when used under light loads.

[0019] In one embodiment, thiophosphate ester compounds with unsaturated end groups are disclosed as electrolyte additives according to the present disclosure. These thiophosphate ester additives with unsaturated end groups are highly soluble in organic solvents. Electrolytes with these additives have high ionic conductivity and are suitable for use as electrolytes in electrochemical devices, particularly lithium-ion batteries. Amounts of the additives of the present disclosure suitable for imparting the necessary properties to the electrolyte and thus enhancing the performance of electrochemical devices, particularly lithium-ion batteries, include 0.001% to 25% by weight.

[0020] Unsaturated end groups, such as allyl, propargyl, and vinyl groups, promote polymerization on the electrode surface, thus increasing resistance. This leads to the formation of a film or network on the electrode surface, thus improving long-term performance. The film prevents reaction between the electrolyte and the electrode, reducing gassing during high-temperature storage and cycling. Compounds with all three terminal unsaturated groups have very high resistance, so adding alkoxy or aryloxy substituents is recommended. These alkoxy or aryloxy groups, along with allyl, propargyl, vinyl, styrene, and acrylic end groups, help optimize resistance while maintaining long-term performance.

[0021] In one embodiment, the electrochemical energy storage device electrolyte comprises: (a) an aprotic organic solvent system; (b) a metal salt; (c) a thiophosphate additive with an unsaturated end group; and (d) at least one additional additive.

[0022] In one embodiment of the present disclosure, a suitable molecular structure of a thiophosphate additive with an unsaturated end group is shown below: TIFF0007733936000002.tif21128In formula, Y is oxygen or sulfur; X is independently oxygen or sulfur, provided that when Y is oxygen, at least one X is sulfur; R3 is selected from hydrocarbyl groups having 1 to 10 carbon atoms with unsaturated end groups; R1 and R2 are R3; or R1 and R2 are independently C1 to C 10 A substituted or unsubstituted alkyl group, or an aryl group; where the hydrogen atom may be unsubstituted or may be a halogen, alkyl, alkoxy, perfluorinated alkyl, silyl, siloxy, silane, sulfoxide, amide, azo, ether, and thioether group or a combination thereof.

[0023] The unsaturated end groups may be selected from the group consisting of alkenyl and alkynyl groups, such as allyl, propargyl, and vinyl groups; styrene, and acrylic groups, or combinations thereof.

[0024] In another embodiment, an electrolyte is provided that includes an additive with an unsaturated end group, wherein the unsaturated end group is a pendant group attached to a backbone, wherein the backbone is at least one of a thiophosphate ester compound, a triazene molecule, a phosphazene molecule, and an ionic liquid having cationic moieties selected from nitrogen cationic moieties, phosphorus cationic moieties, and sulfur cationic moieties.

[0025] In another embodiment, the unsaturated end groups are attached to a backbone selected from at least one of a thiophosphate ester, a triazene, a phosphazene, and an ionic liquid having a cationic moiety selected from a nitrogen cationic moiety, a phosphorus cationic moiety, and a sulfur cationic moiety.

[0026] In another embodiment, the anion of the ionic liquids of the present disclosure includes, but is not limited to, a halide (e.g., Cl, Br), a nitrate (e.g., NO), a phosphate (e.g., PF, TFOP), an imide (e.g., TFSI, BETI), a borate (e.g., BOB, BF), an aluminate, an arsenide, a cyanide, a thiocyanide, a nitrite, a benzoate, a carbonate, a chlorate, a chlorite, a chromate, a sulfate, a sulfite, a silicate, a thiosulfate, or a hydroxide.

[0027] In another embodiment, the thiophosphate ester additive with unsaturated end groups is present in the electrolyte in the range of 0.001% to 25% by weight.

[0028] The present disclosure includes methods for the synthesis of thiophosphate ester additives with unsaturated end groups and the use of such molecules in lithium-ion battery electrolytes, which impart greater stability to the electrolyte at higher operating temperatures.

[0029] In one embodiment of the present disclosure, the electrolyte further comprises 10% to 30% by weight of a lithium salt, such as Li(AsF6); Li(PF6); Li(CF3CO2); Li(C2F5CO2); Li(CF3SO3); Li[N(CP3SO2)2]; Li[C(CF3SO2)3]; Li[N(SO2C2F5)2]; Li(ClO4); Li(BF4); Li(PO2F2); Li[PF2(C2O4)2]; Li[PF4C2O4]; lithium alkyl fluorophosphate; Li[B(C2O4)2]; Li[BF2C2O4]; Li2[B 12 Z 12-j H j ];Li2[B 10 X 10-j' H j' or various lithium salts may be used, including mixtures of any two or more of these, where Z is independently a halogen in each occurrence, j is an integer from 0 to 12, and j' is an integer from 1 to 10.

[0030] In one embodiment of the present disclosure, the electrolyte solution further comprises an aprotic organic solvent selected from linear or cyclic carbonates, carboxylic acid esters, nitrites, ethers, sulfones, sulfoxides, ketones, lactones, dioxolanes, glymes, crown ethers, siloxanes, phosphate esters, phosphites, mono- or polyphosphazenes, or mixtures thereof, in the range of 60% to 90% by weight.

[0031] Examples of aprotic solvents for forming the electrolyte include, but are not limited to, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, bis(trifluoroethyl) carbonate, bis(pentafluoropropyl) carbonate, trifluoroethyl methyl carbonate, pentafluoroethyl methyl carbonate, heptafluoropropyl methyl carbonate, perfluorobutyl methyl carbonate, trifluoroethyl ethyl carbonate, pentafluoroethyl ethyl carbonate, heptafluoropropyl ethyl carbonate, perfluorobutyl methyl carbonate, Examples of suitable solvents include fluorobutyl ethyl carbonate, fluorinated oligomers, methyl propionate, ethyl propionate, butyl propionate, dimethoxyethane, triglyme, dimethylvinylene carbonate, tetraethylene glycol, dimethyl ether, polyethylene glycol, triphenyl phosphate, tributyl phosphate, hexafluorocyclotriphosphazene, 2-ethoxy-2,4,4,6,6-pentafluoro-1,3,5,2-5,4-5,6-5 triazatriphosphinine, triphenyl phosphite, sulfolane, dimethyl sulfoxide, ethyl methyl sulfone, ethyl vinyl sulfone, allyl methyl sulfone, divinyl sulfone, fluorophenyl methyl sulfone, and gamma butyrolactone.

[0032] In one embodiment of the present disclosure, the electrolyte further comprises at least one additional additive to protect the electrode and the electrolyte from deterioration.Therefore, the electrolyte of the present technology may comprise an additive that is reduced or polymerized on the surface of the electrode to form a passivation film on the surface of the electrode.In some embodiments, the electrolyte of the present technology further comprises a mixture of two kinds of additives.

[0033] In one embodiment, the additive is a substituted or unsubstituted linear, branched, or cyclic hydrocarbon containing at least one oxygen atom and at least one aryl, alkenyl, or alkynyl group. The passivation film formed from such an additive can also be formed from a substituted aryl compound or a substituted or unsubstituted heteroaryl compound, where the additive contains at least one oxygen atom.

[0034] Representative additives include glyoxal bis(diallyl acetal), tetra(ethylene glycol) divinyl ether, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane, 2,4,6-triallyloxy-1,3,5-triazine, 1,3,5-triacryloylhexahydro-1,3,5-triazine, 1,2-divinyl furoate, 1 ,3-Butadiene carbonate, 1-vinylazetidin-2-one, 1-vinylaziridin-2-one, 1-vinylpiperidin-2-one, 1-vinylpyrrolidin-2-one, 2,4-divinyl-1,3-dioxane, 2-amino-3-vinylcyclohexanone, 2-amino-3-vinylcyclopropanone, 2-amino-4-vinylcyclobutanone, 2-amino-5-vinylcyclopentanone, 2-aryloxycyclopropanone, 2-vinyl-[1,2]oxazetidine, 2-vinyl Aminocyclohexanol, 2-vinylaminocyclopropanone, 2-vinyloxetane, 2-vinyloxycyclopropanone, 3-(N-vinylamino)cyclohexanone, 3,5-divinylfuroate, 3-vinylazetidin-2-one, 3-vinylaziridin-2-one, 3-vinylcyclobutanone, 3-vinylcyclopentanone, 3-vinyloxaziridine, 3-vinyloxetane, 3-vinylpyrrolidin-2-one, 2-vinyl-1,3-dioxolane, acrolein di Ethyl acetal, acrolein dimethyl acetal, 4,4-divinyl-3-dioxolan-2-one, 4-vinyltetrahydropyran, 5-vinylpiperidin-3-one, allyl glycidyl ether, butadiene monoxide, butyl vinyl ether, dihydropyran-3-one, divinyl butyl carbonate, divinyl carbonate, divinyl crotonate, divinyl ether, divinyl ethylene carbonate, divinyl ethylene silicate, 1,3 propane sultone, 1,Examples of the additive include 3-propene sultone, divinyl ethylene sulfate, divinyl ethylene sulfite, divinyl methoxypyrazine, divinyl methyl phosphate, divinyl propylene carbonate, ethyl phosphate, methoxy-o-terphenyl, methyl phosphate, oxetan-2-ylvinylamine, oxiranyl vinylamine, vinyl carbonate, vinyl crotonate, vinyl cyclopentanone, vinyl ethyl 2-furoate, vinyl ethylene carbonate, 4-fluoro-1,3-dioxolan-2-one, vinyl ethylene silicate, vinyl ethylene sulfate, vinyl ethylene sulfite, vinyl methacrylate, vinyl phosphate, vinyl 2-furoate, vinyl cyclopropanone, vinyl ethylene oxide, β-vinyl-γ-butyrolactone, or a mixture of any two or more thereof. In some embodiments, the additive may be a cyclotriphosphazene substituted with F, alkyloxy, alkenyloxy, aryloxy, methoxy, or allyloxy groups, or a combination thereof. For example, the additive may be a (divinyl)-(methoxy)(trifluoro)cyclotriphosphazene, a (trivinyl)(difluoro)(methoxy)cyclotriphosphazene, a (vinyl)(methoxy)(tetrafluoro)cyclotriphosphazene, an (aryloxy)(tetrafluoro)(methoxy)cyclotriphosphazene or a (diaryloxy)(trifluoro)(methoxy)cyclotriphosphazene compound or a mixture of two or more such compounds.

[0035] In some embodiments, the additive is a sulfur-containing compound, a phosphorus-containing compound, a boron-containing compound, a silicon-containing compound, a fluorine-containing compound, a nitrogen-containing compound, a compound containing at least one unsaturated carbon-carbon bond, a carboxylic acid anhydride, or a mixture thereof. In some embodiments, the additive is vinyl carbonate, vinyl ethylene carbonate, or a mixture of any two or more such compounds. Further, the additive is present in an amount ranging from 0.01% to 10% by weight.

[0036] In some embodiments, the additive is a fully or partially halogenated phosphate ester compound, an ionic liquid, or a mixture thereof. Halogenated phosphate esters can include 4-fluorophenyldiphenylphosphate, 3,5-difluorophenyldiphenylphosphate, 4-chlorophenyldiphenylphosphate, trifluorophenylphosphate, heptafluorobutyldiphenylphosphate, trifluoroethyldiphenylphosphate, bis(trifluoroethyl)phenylphosphate, and phenylbis(trifluoroethyl)phosphate. The ionic liquid may include tris(N-ethyl-N-methylpyrrolidinium)thiophosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpyrrolidinium)phosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpiperidinium)thiophosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpiperidinium)phosphate bis(trifluoromethylsulfonyl)imide, N-methyltrimethylsilylpyrrolidinium bis(trifluoromethylsulfonyl)imide, or N-methyltrimethylsilylpyrrolidinium hexafluorophosphate. Additionally, the additive may be present in the range of 0.01% to 10% by weight.

[0037] In another embodiment of the present disclosure, an electrochemical energy storage device is provided, comprising a positive electrode, a negative electrode, and an electrolyte comprising the ionic liquid described herein. In one embodiment, the electrochemical energy storage device is a lithium secondary battery. In some embodiments, the secondary battery is a lithium battery, a lithium-ion battery, a lithium-sulfur battery, a lithium-air battery, a sodium-ion battery, or a magnesium battery. In some embodiments, the electrochemical energy storage device is an electrochemical cell such as a capacitor. In some embodiments, the capacitor is an asymmetric capacitor or a supercapacitor. In some embodiments, the electrochemical cell is a primary cell. In some embodiments, the primary cell is a lithium / MnO2 battery or a Li / poly(carbon monofluoride) battery. In some embodiments, the electrochemical energy storage device is a solar cell.

[0038] In one embodiment, a secondary battery is provided that includes a positive electrode and a negative electrode separated from one another by a porous separator and an electrolyte solution described herein.

[0039] Suitable cathodes include, but are not limited to, lithium metal oxides, spinels, olivine, carbon-coated olivine cathodes, such as LiFePO4, LiCoO2, LiNiO2, LiMn 0.5 Ni 0.5 O2, LiMn 0.3 Co 0.3 Ni 0.3 O2, LiMn2O4, LiFeO2, LiNi x Co y Met z O2, A n' B2(XO4)3(NASICON), vanadium oxide, lithium peroxide, sulfur, polysulfides, lithium carbon monofluoride (LiCF x(also known as ZnO, Mg, Ti, B, Ga, Si, Mn, or Co) or a mixture of any two or more thereof, where Met is Al, Mg, Ti, B, Ga, Si, Mn, or Co; A is Li, Ag, Cu, Na, Mn, Fe, Co, Ni, Cu, or Zn; B is Ti, V, Cr, Fe, or Zr; X is P, S, Si, W, or Mo; and where 0≦x≦0.3, 0≦y≦0.5, and 0≦z≦0.5 and 0≦n′≦0.3. According to some embodiments, the spinel is Li 1+x Mn 2-z Met''' y O 4-m X' n where Met''' is Al, Mg, Ti, B, Ga, Si, Ni, or Co; X' is S or F; and where 0≦x≦0.3, 0≦y≦0.5, 0≦z≦0.5, 0≦m≦0.5, and 0≦n≦0.5. In another embodiment, the olivine is a spinel manganese oxide having the formula: 1+x Fe 1z Met'' y PO 4-m X' n where Met″ is Al, Mg, Ti, B, Ga, Si, Ni, Mn, or Co; X′ is S or F; and where 0≦x≦0.3, 0≦y≦0.5, 0≦z≦0.5, 0≦m≦0.5, and 0≦n≦0.5.

[0040] Suitable negative electrodes include, for example, lithium metal, graphite materials, amorphous carbon, carbon nanotubes, Li4Ti5O 12 , tin alloys, silicon, silicon alloys, intermetallic compounds, or a mixture of any two or more such materials. Suitable graphite materials include natural graphite, artificial graphite, graphitized mesocarbon microbeads (MCMB) and graphite fibers, as well as any amorphous carbon material. In some embodiments, the negative and positive electrodes are separated from each other by a porous separator.

[0041] Lithium battery separators are often microporous polymer films. Examples of polymers for forming the film include polypropylene, polyethylene, nylon, cellulose, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polybutene, or copolymers or mixtures of any two or more such polymers. In some examples, the separator is an electron-beam-treated microporous polyolefin separator. The electron treatment can increase the separator's deformation temperature and therefore its thermal stability at high temperatures. Additionally or alternatively, the separator can be a shutdown separator. The shutdown separator can have a trigger temperature above about 130°C to allow the electrochemical cell to operate at temperatures up to about 130°C.

[0042] The following molecular structures are examples of suitable thiophosphate ester compounds with unsaturated end groups. TIFF0007733936000003.tif86161TIFF0007733936000004.tif181165TIFF0007733936000005.tif180158TIFF0007733936000006.tif82163

[0043] Additionally, the present disclosure presents specific examples, which are merely illustrative and are not intended to limit the scope of the disclosure or the appended claims. [Example]

[0044] Example A - Synthesis of propargyl-diethylthiophosphate TIFF0007733936000007.tif56166 To a 40 mL vial equipped with a magnetic stir bar was added propargyl alcohol in dichloromethane (DCM) (15 mL). Triethylamine was added to the mixture via pipette, and an exotherm to 31 °C was observed. While stirring at room temperature, diethyl chlorothiophosphate was slowly added via pipette. No exotherm or gas evolution was observed. A white solid precipitate (triethylamine-HCl) slowly formed, and the mixture was stirred at room temperature for 24 h. Deionized water (2 × 10 mL) was added, and the mixture was poured into a separatory funnel. The organic phase was extracted into DCM (10 mL), separated, dried over MgSO4, filtered, and the solvent removed by rotary evaporation. The oil was passed through a 0.45 μm GMF filter. Yield: 6.2 g (93%) of a yellow oil. FTIR: 3292, 2983, 1008, 793, 652 cm -1 .

[0045] Example B - Synthesis of Allyl-Diethylthiophosphate TIFF0007733936000008.tif59166 Allyl alcohol in DCM (15 mL) was added to a 40 mL vial equipped with a magnetic stir bar. Triethylamine was added via pipette, and the mixture and exotherm to 31 °C were observed. While stirring at room temperature, diethyl chlorothiophosphate was slowly added via pipette. No exotherm or gas evolution was observed. A white solid precipitate (triethylamine-HCl) slowly formed, and the mixture was stirred at room temperature for 24 h. Deionized water (2 × 10 mL) was added, and the mixture was poured into a separatory funnel. The organic phase was extracted into DCM (10 mL), separated, dried over MgSO4, filtered, and the solvent removed by rotary evaporation. The oil was passed through a 0.45 μm GMF filter. Yield: pale yellow oil, 5.7 g (83%). FTIR: 2983, 1006, 794, 652 cm -1 .

[0046] Example C - Synthesis of tris(propargyl)-thiophosphate TIFF0007733936000009.tif58166 A 100 mL three-neck flask equipped with a magnetic stir bar, water condenser, N2 inlet, and thermocouple was charged with propargyl alcohol in DCM (20 mL). Triethylamine was added via pipette, and an exotherm to 38 °C was observed. While stirring at room temperature, thiophosphoryl chloride was slowly added via pipette. An exotherm to 46 °C was observed. A white solid precipitate (triethylamine-HCl) slowly formed, and the mixture was stirred at room temperature for 4 h. Deionized water (2 × 20 mL) was added, and the mixture was poured into a separatory funnel. The organic phase was extracted into DCM, separated, dried over MgSO4, and the solvent was removed by rotary evaporation. BHT crystals were added to prevent polymerization. Yield: 8.8 g (>99%) of an amber oil. The oil was degassed under high vacuum, and a gelatinous precipitate formed. The oil was passed through a 0.45 μm GMF filter. Yield: dark amber viscous oil, 5.6 g (69%). FTIR: 1472, 1158, 1018, 643 cm -1 .

[0047] Example D - Synthesis of tris(allyl)-thiophosphate TIFF0007733936000010.tif61166 To a 100 mL three-necked flask equipped with a magnetic stir bar, water condenser, N2 inlet, and thermocouple was added allyl alcohol in DCM (20 mL). Triethylamine was added via pipette, and the mixture and an exotherm to 40 °C were observed. While stirring at room temperature, thiophosphoryl chloride was added slowly via pipette. An exotherm to 46 °C was observed. A white solid precipitate (triethylamine-HCl) slowly formed, and the mixture was stirred at room temperature for 24 h. Deionized water (2 × 10 mL) was added, and the mixture was poured into a separatory funnel. The organic phase was extracted into DCM (10 mL), separated, dried over MgSO4, filtered, and the solvent removed by rotary evaporation. Yield: yellow oil, 13.9 g (>99%). The oil was degassed under high vacuum, and a gelatinous precipitate formed. The oil was passed through a 0.45 μm GMF filter and a crystal of BHT was added to prevent further polymerization. Yield: yellow oil, 7.3 g (66%). FTIR: 2983, 1006, 794, 652 cm -1 .

[0048] Example E - Synthesis of tris(allylthio)-thiophosphate TIFF0007733936000011.tif64166 To a 100 mL three-necked flask equipped with a magnetic stir bar, water condenser, N2 inlet, and thermocouple was added allyl mercaptan in DCM (70 mL). Triethylamine was added via pipette, and an exotherm to 28 °C was observed. While stirring at room temperature, thiophosphoryl chloride was slowly added via pipette to the colorless mixture. An exotherm to 42 °C was observed, and a white solid precipitate (triethylamine-HCl) rapidly formed. The mixture was stirred at room temperature for 3 h. Deionized water (2 × 30 mL) was added, and the mixture was poured into a separatory funnel. The organic phase was extracted into DCM, separated, dried over MgSO4, filtered, and the solvent removed by rotary evaporation. Yield: 8.3 g (>99%) of a yellow oil. The oil was degassed under high vacuum, and a gelatinous precipitate formed. The oil was passed through a 0.45 μm GMF filter. Yield: yellow oil, 5.6 g (68%). FTIR: 2983, 1006, 794, 652 cm -1 .

[0049] Example F - Synthesis of tris(ethyl acrylate) thiophosphate TIFF0007733936000012.tif46166 2-Hydroxyethyl acrylate in DCM (60 mL) was added to a 100 mL three-neck flask equipped with a magnetic stir bar, water condenser, N2 inlet, and thermocouple. Triethylamine was added via pipette, and an exotherm to 27 °C was observed. While stirring at room temperature, thiophosphoryl chloride was added slowly via syringe. An exotherm to 40 °C was observed, and the colorless mixture turned pale yellow. A white solid precipitate (triethylamine-HCl) slowly formed, and the mixture was stirred at room temperature for 3 h. Deionized water (2 × 20 mL) was added, and the mixture was poured into a separatory funnel. The organic phase was extracted into DCM, separated, dried over MgSO4, filtered, and the solvent removed by rotary evaporation. Crystals of BHT were added to prevent polymerization. The oil was degassed under high vacuum, and a gelatinous precipitate formed. The oil was passed through a 0.45 μm GMF filter. Yield: 8.7 g (72%) of a gelled amber oil. FTIR: 1721, 1183, 969, 806, 656 cm -1 .

[0050] Example G - Electrolyte for NMC811 / Si-Gr Cell The electrolyte formulation was prepared in a dry argon-filled glove box by mixing all electrolyte components in a glass vial and stirring for 24 hours to ensure complete dissolution of the salt. The thiophosphate ester additive with unsaturated end groups was added to a 1:1:1 volumetric mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), and Li dissolved therein. + Added to a base electrolyte formulation containing 1 M lithium hexafluorophosphate (LiPF6) as the ionically conductive salt. Example 1 (EE1) uses a representative example molecule of the present disclosure. A summary of the electrolyte components and additives used is provided in Table A.

[0051] Table A: Electrolyte Formulations for NMC811 / Si-Gr Cells TIFF0007733936000013.tif90160

[0052] Example H-NMC811 / Si-Gr cell The prepared electrolyte formulation was used as the electrolyte in 1.3 Ah Li-ion pouch cells containing NMC811 as the positive electrode active material and silicon-graphite (7% Si) as the negative electrode active material. The cell operating voltage window was 4.2 to 2.7 V. 3.75 g of electrolyte was added to each cell and immersed in the cell for 1 hour. The cells were vacuum sealed, subjected to a primary charge, and then allowed to stand at room temperature for 10 hours. The cells were then charged to 3.8 V at a C / 25 rate, degassed, and subsequently vacuum sealed. After degassing, the cells were charged and discharged twice at a C / 10 rate between 4.2 and 2.7 V. The results are summarized in Table B. The initial capacity loss (iCL) was calculated based on the first-cycle coulombic efficiency, and the reported discharge capacity is that of the final cycle of formation. AC-IR is the internal resistance measured at a frequency of 1 kHz. The cells with electrolyte EE1 had significantly lower iCL values, indicating a higher reversible capacity during formation. This is consistent with the dQ / dV profiles in Figure 1, indicating that EE1 has a faster reaction on the anode compared to CE1, which is a result of the specific reaction of the additives present in EE1, leading to the formation of a robust SEI and thus a higher reversible capacity.

[0053] (Table B) Initial cell data for NMC811 / Si-Gr cell TIFF0007733936000014.tif38160

[0054] Example I - Electrolyte for NMC811 / Gr Cell The thiophosphate ester additive with unsaturated end groups was prepared by dissolving Li in a 3:7 weight ratio mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC). + A base electrolyte formulation containing 1 M lithium hexafluorophosphate (LiPF6) as the ionically conductive salt is added. Comparative Example 2 (CE2) consists of the base formulation and vinylene carbonate and 1,3 propane sultone as additives, while Specific Examples 2 and 3 (EE2 and EE3) use representative molecules of the present disclosure. A summary of the electrolyte components and additives used is provided in Table C.

[0055] Table C: Electrolyte Formulations for NMC811 / Gr Cells TIFF0007733936000015.tif89166

[0056] Example J-NMC811 / Gr cell The prepared electrolyte formulation was used as the electrolyte in 1.8 Ah Li-ion pouch cells containing NMC811 as the positive electrode active material and graphite as the negative electrode active material. The cell operating voltage window was 4.2 to 2.8 V. 6 g of electrolyte was added to each cell and allowed to soak in the cell for 1 hour. The cells were vacuum sealed and left at room temperature for 24 hours. The cells were then charged to 3.7 V at a C / 25 rate, degassed, and subsequently vacuum sealed. After degassing, the cells were charged and discharged twice at a C / 10 rate between 4.2 and 2.8 V. The results are summarized in Table D. iCL, formation discharge capacity, and AC-IR measurements were performed as in Example G. Figure 2 shows the dQ / dV profiles of cells with different electrolytes, highlighting the effect of the allyl and propargyl thiophosphate molecules on the SEI reaction. Both molecules react at about 2.6 V, while the VC and PaS electrolytes react at about 2.75 V.

[0057] (Table D) Initial cell data for NMC811 / Gr cells TIFF0007733936000016.tif53160

[0058] Example K-Electrolyte for NMC811 / SCN Cell The thiophosphate ester additive with unsaturated end groups was prepared by dissolving Li in a 3:7 weight ratio mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC). +Added to a base electrolyte formulation containing 1 M lithium hexafluorophosphate "LiPF6" as the ionically conductive salt. Comparative Example 4 (CE4) consists of the base formulation, and Comparative Example 5 (CE5) consists of the base formulation containing 5% fluoroethylene carbonate "FEC." Specific Example 4 (EE4) uses a representative example molecule of the present disclosure. A summary of the electrolyte components and additives used is provided in Table E.

[0059] Table E: Electrolyte Formulations for NMC811 / SCN Cells TIFF0007733936000017.tif67148

[0060] Example L-NMC811 / SCN cell The prepared electrolyte formulation was used as the electrolyte in 1.5 Ah Li-ion pouch cells containing NMC811 as the positive electrode active material and silicon-carbon nanocomposite (SCN) as the negative electrode active material. The cell operating voltage window was 4.2 to 2.8 V. 6 g of electrolyte was added to each cell and allowed to soak in the cell for 1 hour. The cells were vacuum-sealed and left at room temperature for 24 hours. The cells were then charged to 3.7 V at a C / 25 rate, degassed, and then vacuum-sealed. After degassing, the cells were charged and discharged twice between 4.2 and 2.8 V at a C / 10 rate, and then charged and discharged 500 times between 4.2 and 2.8 V at a 1C rate at 25 °C. Figure 3 shows the cycle life characteristics of the 1.5 Ah NMC811 / SCN cell at 25 °C during cycling at a 1C rate. Here, it is clear that the addition of a thiophosphate ester additive with unsaturated end groups significantly improves the cyclability of NMC811 / SCN cells compared to the comparative examples. Capacity retention after 500 cycles is higher for the EE4 cell compared to the CE4 and CE5 cells. This data is summarized in Table F.

[0061] (Table F) Data for NMC811 / SCN cells after 500 cycles TIFF0007733936000018.tif49160

[0062] While various embodiments have been shown and described in detail herein, it will be apparent to those skilled in the art that various modifications, additions, substitutions, etc. may be made without departing from the spirit of the disclosure, and therefore are deemed to be within the scope of the disclosure as defined in the following claims. The present invention provides, for example, the following items. (Item 1) (a) Aprotic organic solvent systems; (b) a metal salt; and (c) Formula: JPEG0007733936000019.jpg22127 at least one thiophosphate additive having an unsaturated end group, wherein Y is oxygen or sulfur; X is independently oxygen or sulfur, provided that when Y is oxygen, at least one X is sulfur; R 3 is selected from hydrocarbyl groups having 1 to 10 carbon atoms with unsaturated end groups; R 1 and R 2 is R 3 is; or R 1 and R 2 is independently C 1 ~C 10 a substituted or unsubstituted alkyl group, or an aryl group; wherein the hydrogen atom may be unsubstituted or may be a halogen, alkyl, alkoxy, perfluorinated alkyl, silyl, siloxy, silane, sulfoxide, amide, azo, ether, and thioether group or a combination thereof; An electrochemical energy storage device electrolyte comprising a thiophosphate additive. (Item 2) Item 1, wherein the unsaturated end groups may be selected from the group consisting of alkenyl and alkynyl groups such as allyl, propargyl, and vinyl groups; styrene, and acrylic groups, or combinations thereof. (Item 3) 2. The electrolyte solution according to item 1, wherein the thiophosphate additive with unsaturated end groups is present in the electrolyte solution at a concentration of 0.001% to 25% by weight. (Item 4) 2. The electrolyte solution according to item 1, wherein the aprotic organic solvent system comprises a linear or cyclic carbonate, a carboxylic acid ester, a nitrite, an ether, a sulfone, a ketone, a lactone, a dioxolane, a glyme, a crown ether, a siloxane, a phosphate ester, a phosphite, a mono- or polyphosphazene, or a mixture thereof. (Item 5) 2. The electrolyte solution according to item 1, wherein the aprotic organic solvent system is present in the electrolyte solution at a concentration of 60% to 90% by weight. (Item 6) Item 1. The electrolyte according to item 1, wherein the cation of the metal salt is an alkali metal. (Item 7) 7. The electrolyte according to item 6, wherein the alkali metal is lithium or sodium. (Item 8) Item 2. The electrolyte according to item 1, wherein the cation of the metal salt is aluminum or magnesium. (Item 9) 2. The electrolytic solution according to item 1, wherein the metal salt is present in the electrolytic solution at a concentration of 10% by weight to 30% by weight. (Item 10) 2. The electrolyte solution according to item 1, further comprising at least one additional additive. (Item 11) 11. The electrolyte solution of item 10, wherein the at least one additional additive comprises a sulfur-containing compound, a phosphorus-containing compound, a boron-containing compound, a silicon-containing compound, a fluorine-containing compound, a nitrogen-containing compound, a compound containing at least one unsaturated carbon-carbon bond, a carboxylic acid anhydride, or a mixture thereof. (Item 12) 11. The electrolyte solution of item 10, wherein the at least one additional additive comprises a partially or fully halogenated phosphate ester compound, an ionic liquid, or a mixture thereof. (Item 13) Item 13. The electrolyte solution of item 12, wherein the halogenated phosphate ester compound is selected from the group consisting of 4-fluorophenyl diphenyl phosphate, 3,5-difluorophenyl diphenyl phosphate, 4-chlorophenyl diphenyl phosphate, trifluorophenyl phosphate, heptafluorobutyl diphenyl phosphate, trifluoroethyl diphenyl phosphate, bis(trifluoroethyl)phenyl phosphate, and phenyl bis(trifluoroethyl)phosphate. (Item 14) Item 13. The electrolyte solution of item 12, wherein the ionic liquid is selected from the group consisting of tris(N-ethyl-N-methylpyrrolidinium)thiophosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpyrrolidinium)phosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpiperidinium)thiophosphate bis(trifluoromethylsulfonyl)imide, and tris(N-ethyl-N-methylpiperidinium)phosphate bis(trifluoromethylsulfonyl)imide. (Item 15) 11. The electrolyte solution according to item 10, wherein the at least one additional additive is present in the electrolyte solution at a concentration of 0.01 wt.% to 10 wt.%. (Item 16) positive electrode; negative electrode; the electrolyte solution described in item 1; and An electrochemical energy storage device comprising a separator. (Item 17) Item 17. The device of item 16, wherein the positive electrode comprises lithium metal oxide, spinel, olivine, carbon-coated olivine, vanadium oxide, lithium peroxide, sulfur, polysulfide, lithium carbon monofluoride, or a mixture of any two or more thereof. (Item 18) Lithium metal oxide is LiCoO 2 , LiNiO 2 , LiNi x Co y Met z O 2 , LiMn 0.5 Ni 0.5 O 2 , LiMn 0.1 Co 0.1 Ni 0.8 O 2 , LiMn 0.2 Co 0.2 Ni 0.6 O 2 , LiMn 0.3 Co 0.2 Ni 0.5 O 2 , LiMn0.33 Co 0.33 Ni 0.33 O 2 , LiMn 2 O 4 , LiFeO 2 , Li 1+x’ Ni α Mn β Co γ Met' δ O 2-z’ F z’ 、A n’ B 2 (XO 4 ) 3 18. The device of item 17, wherein Met is Al, Mg, Ti, B, Ga, Si, Mn, or Co; Met′ is Mg, Zn, Al, Ga, B, Zr, or Ti; A is Li, Ag, Cu, Na, Mn, Fe, Co, Ni, Cu, or Zn; B is Ti, V, Cr, Fe, or Zr; X is P, S, Si, W, or Mo; and wherein 0≦x≦0.3, 0≦y≦0.5, 0≦z≦0.5, 0≦x′≦0.4, 0≦α≦1, 0≦β≦1, 0≦γ≦1, 0≦δ≦0.4, 0≦z′≦0.4, and 0≦h′≦3. (Item 19) The negative electrode is made of lithium metal, graphite material, amorphous carbon, and Li 4 Ti 5 O 12 17. The device of item 16, comprising a tin alloy, silicon, a silicon alloy, an intermetallic compound or a mixture thereof. (Item 20) Lithium battery, Lithium-ion battery, Lithium-sulfur battery, Lithium-air battery, Sodium-ion battery, Magnesium battery, Lithium / MnO 2 17. The device of item 16, comprising a battery or a Li / poly(carbon monofluoride) battery. (Item 21) Item 17. The device of item 16, comprising a capacitor or a solar cell. (Item 22) 17. The device of item 16, comprising an electrochemical cell. (Item 23) 17. The device of item 16, further comprising a porous separator separating the negative electrode and the positive electrode from each other. (Item 24) 24. The device of item 23, wherein the porous separator comprises an electron beam treated microporous polyolefin separator or a microporous polymer film comprising nylon, cellulose, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, polybutene, or a copolymer or mixture of any two or more such polymers. (Item 25) 17. The device of item 16, wherein the aprotic organic solvent system comprises linear or cyclic carbonates, carboxylic acid esters, nitrites, ethers, sulfones, ketones, lactones, dioxolanes, glymes, crown ethers, siloxanes, phosphate esters, phosphites, mono- or polyphosphazenes or mixtures thereof. (Item 26) Item 17. The device of item 16, wherein the aprotic organic solvent system is present in the electrolyte at a concentration of 60% to 90% by weight. (Item 27) Item 17. The device of item 16, wherein the cation of the metal salt is an alkali metal. (Item 28) 28. The device of item 27, wherein the alkali metal is lithium or sodium. (Item 29) 17. The device of item 16, wherein the cation of the metal salt is aluminum or magnesium. (Item 30) 29. The device of item 28, wherein the alkali metal salt is present in the electrolyte at a concentration of 10% to 30% by weight. (Item 31) Item 14. The device of item 13, wherein the electrolyte further comprises at least one additional additive. (Item 32) 32. The device of item 31, wherein the at least one additional additive comprises a sulfur-containing compound, a phosphorus-containing compound, a boron-containing compound, a silicon-containing compound, a fluorine-containing compound, a nitrogen-containing compound, a compound containing at least one unsaturated carbon-carbon bond, a carboxylic acid anhydride, or a mixture thereof. (Item 33) 32. The device of claim 31, wherein the at least one additional additive comprises a partially or fully halogenated phosphate ester compound, an ionic liquid, or a mixture thereof. (Item 34) Item 34. The device of item 33, wherein the halogenated phosphate ester compound is selected from the group consisting of 4-fluorophenyl diphenyl phosphate, 3,5-difluorophenyl diphenyl phosphate, 4-chlorophenyl diphenyl phosphate, trifluorophenyl phosphate, heptafluorobutyl diphenyl phosphate, trifluoroethyl diphenyl phosphate, bis(trifluoroethyl)phenyl phosphate, and phenyl bis(trifluoroethyl) phosphate. (Item 35) 34. The electrolyte solution according to item 33, wherein the ionic liquid is selected from the group consisting of tris(N-ethyl-N-methylpyrrolidinium)thiophosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpyrrolidinium)phosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpiperidinium)thiophosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpiperidinium)phosphate bis(trifluoromethylsulfonyl)imide, N-methyl-trimethylsilylpyrrolidinium bis(trifluoromethylsulfonyl)imide, and N-methyl-trimethylsilylpyrrolidinium hexafluorophosphate. (Item 36) 32. The device of claim 31, wherein the at least one additional additive is present in the electrolyte at a concentration of 0.01% to 10% by weight.

Claims

1. (a) an aprotic organic solvent system; (b) a metal salt; and (c) Formula: at least one thiophosphate additive having an unsaturated end group, wherein Y is sulfur; X is independently oxygen or sulfur; R ３ is selected from hydrocarbyl groups having 1 to 10 carbon atoms with unsaturated end groups; R １ and R ２ is R ３ or R １ and R ２ is independently C １ ~C １０ a substituted or unsubstituted alkyl group, or an aryl group; wherein the hydrogen atom may be unsubstituted or may be a halogen, alkyl, alkoxy, perfluorinated alkyl, silyl, siloxy, silane, sulfoxide, amide, azo, ether, and thioether group or a combination thereof; An electrochemical energy storage device electrolyte comprising a thiophosphate additive.

2. 10. The electrolyte of claim 1, wherein the unsaturated end groups may be selected from the group consisting of alkenyl and alkynyl groups, such as allyl, propargyl, and vinyl groups; styrene, and acrylic groups, or combinations thereof.

3. 10. The electrolyte of claim 1, wherein the thiophosphate additive with unsaturated end groups is present in the electrolyte at a concentration of 0.001% to 25% by weight.

4. 2. The electrolyte of claim 1, wherein the aprotic organic solvent system comprises a linear or cyclic carbonate, a carboxylic acid ester, a nitrite, an ether, a sulfone, a ketone, a lactone, a dioxolane, a glyme, a crown ether, a siloxane, a phosphate ester, a phosphite, a mono- or polyphosphazene, or a mixture thereof.

5. 10. The electrolyte of claim 1, wherein the aprotic organic solvent system is present in the electrolyte at a concentration of 60% to 90% by weight.

6. 2. The electrolyte of claim 1, wherein the cation of the metal salt is an alkali metal.

7. 7. The electrolyte of claim 6, wherein the alkali metal is lithium or sodium.

8. 10. The electrolyte of claim 1, wherein the metal salt is present in the electrolyte at a concentration of 10% to 30% by weight.

9. The electrolyte of claim 1 further comprising at least one additional additive.

10. 10. The electrolyte of claim 9, wherein the at least one additional additive comprises a sulfur-containing compound, a phosphorus-containing compound, a boron-containing compound, a silicon-containing compound, a fluorine-containing compound, a nitrogen-containing compound, a compound containing at least one unsaturated carbon-carbon bond, a carboxylic acid anhydride, or a mixture thereof.

11. 10. The electrolyte of claim 9, wherein the at least one additional additive comprises a partially or fully halogenated phosphate ester compound, an ionic liquid, or a mixture thereof.

12. 12. The electrolyte solution of claim 11, wherein the halogenated phosphate ester compound is selected from the group consisting of 4-fluorophenyl diphenyl phosphate, 3,5-difluorophenyl diphenyl phosphate, 4-chlorophenyl diphenyl phosphate, trifluorophenyl phosphate, heptafluorobutyl diphenyl phosphate, trifluoroethyl diphenyl phosphate, bis(trifluoroethyl)phenyl phosphate, and phenyl bis(trifluoroethyl)phosphate.

13. 12. The electrolyte solution of claim 11, wherein the ionic liquid is selected from the group consisting of tris(N-ethyl-N-methylpyrrolidinium)thiophosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpyrrolidinium)phosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpiperidinium)thiophosphate bis(trifluoromethylsulfonyl)imide, and tris(N-ethyl-N-methylpiperidinium)phosphate bis(trifluoromethylsulfonyl)imide.

14. 10. The electrolyte of claim 9, wherein the at least one additional additive is present in the electrolyte at a concentration of 0.01% to 10% by weight.

15. positive electrode; Negative electrode; The electrolyte solution of claim 1; and An electrochemical energy storage device comprising a separator.

16. 16. The device of claim 15, wherein the positive electrode comprises lithium metal oxide, spinel, olivine, carbon-coated olivine, vanadium oxide, lithium peroxide, sulfur, polysulfides, lithium carbon monofluoride, or a mixture of any two or more thereof.

17. The lithium metal oxide is LiCoO ２ , LiNiO ２ , LiNi ｘ Co ｙ Met ｚ O ２ , LiMn ０．５ Ni ０．５ O ２ , LiMn ０．１ Co ０．１ Ni ０．８ O ２ , LiMn ０．２ Co ０．２ Ni ０．６ O ２ , LiMn ０．３ Co ０．２ Ni ０．５ O ２ , LiMn ０．３３ Co ０．３３ Ni ０．３３ O ２ , LiMn ２ O ４ , LiFeO ２ , Li １＋ｘ’ Ni α Mn β Co γ Met' δ O ２－ｚ’ F ｚ’ , A ｎ’ B ２ (XO ４ ) ３ 17. The device of claim 16, wherein Met is Al, Mg, Ti, B, Ga, Si, Mn, or Co; Met′ is Mg, Zn, Al, Ga, B, Zr, or Ti; A is Li, Ag, Cu, Na, Mn, Fe, Co, Ni, Cu, or Zn; B is Ti, V, Cr, Fe, or Zr; X is P, S, Si, W, or Mo; and wherein 0≦x≦0.3, 0≦y≦0.5, 0≦z≦0.5, 0≦x′≦0.4, 0≦α≦1, 0≦β≦1, 0≦γ≦1, 0≦δ≦0.4, 0≦z′≦0.4, and 0≦h′≦3.

18. The negative electrode is made of lithium metal, graphite material, amorphous carbon, Li ４ Ti ５ O １２ 16. The device of claim 15, comprising a tin alloy, silicon, a silicon alloy, an intermetallic compound, or a mixture thereof.

19. Lithium battery, lithium-ion battery, lithium-sulfur battery, lithium-air battery, sodium-ion battery, magnesium battery, lithium / MnO ２ 16. The device of claim 15, comprising a battery or a Li / poly(carbon monofluoride) battery.

20. The device of claim 15 comprising an electrochemical cell.

21. 16. The device of claim 15, further comprising a porous separator separating the negative and positive electrodes from each other.

22. 22. The device of claim 21, wherein the porous separator comprises an electron beam treated microporous polyolefin separator or a microporous polymer film comprising nylon, cellulose, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, polybutene, or a copolymer or mixture of any two or more such polymers.

23. 16. The device of claim 15, wherein the aprotic organic solvent system comprises a linear or cyclic carbonate, a carboxylic acid ester, a nitrite, an ether, a sulfone, a ketone, a lactone, a dioxolane, a glyme, a crown ether, a siloxane, a phosphate ester, a phosphite, a mono- or polyphosphazene, or a mixture thereof.

24. 16. The device of claim 15, wherein the aprotic organic solvent system is present in the electrolyte at a concentration of 60% to 90% by weight.

25. 16. The device of claim 15, wherein the cation of the metal salt is an alkali metal.

26. 26. The device of claim 25, wherein the alkali metal is lithium or sodium.

27. 27. The device of claim 26, wherein the alkali metal salt is present in the electrolyte at a concentration of 10% to 30% by weight.

28. The device of claim 12 , wherein the electrolyte further comprises at least one additional additive.

29. 30. The device of claim 28, wherein the at least one additional additive comprises a sulfur-containing compound, a phosphorus-containing compound, a boron-containing compound, a silicon-containing compound, a fluorine-containing compound, a nitrogen-containing compound, a compound containing at least one unsaturated carbon-carbon bond, a carboxylic acid anhydride, or a mixture thereof.

30. 30. The device of claim 28, wherein the at least one additional additive comprises a partially or fully halogenated phosphate ester compound, an ionic liquid, or a mixture thereof.

31. 31. The device of claim 30, wherein the halogenated phosphate ester compound is selected from the group consisting of 4-fluorophenyl diphenyl phosphate, 3,5-difluorophenyl diphenyl phosphate, 4-chlorophenyl diphenyl phosphate, trifluorophenyl phosphate, heptafluorobutyl diphenyl phosphate, trifluoroethyl diphenyl phosphate, bis(trifluoroethyl)phenyl phosphate, and phenyl bis(trifluoroethyl) phosphate.

32. 31. The electrolyte of claim 30, wherein the ionic liquid is selected from the group consisting of tris(N-ethyl-N-methylpyrrolidinium)thiophosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpyrrolidinium)phosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpiperidinium)thiophosphate bis(trifluoromethylsulfonyl)imide, tris(N-ethyl-N-methylpiperidinium)phosphate bis(trifluoromethylsulfonyl)imide, N-methyl-trimethylsilylpyrrolidinium bis(trifluoromethylsulfonyl)imide, and N-methyl-trimethylsilylpyrrolidinium hexafluorophosphate.

33. 29. The device of claim 28, wherein the at least one additional additive is present in the electrolyte at a concentration of 0.01% to 10% by weight.

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