Nonaqueous electrolyte composition containing lithium bis(fluorosulfonyl)imide

Abstract

An electrolyte composition containing a fluorine-containing acyclic carboxylic acid ester, lithium bis(fluorosulfonyl)imide (LiFSI), and at least one electrolyte salt is disclosed. The electrolyte composition is useful in electrochemical cells such as lithium-ion batteries. [Selection diagram] None

Description

[Technical Field]

[0001] The present invention relates to electrolyte compositions containing lithium bis(fluorosulfonyl)imide (also known as LiFSI), which are useful in electrochemical cells such as lithium-ion batteries. [Background technology]

[0002] Batteries (e.g., lithium-ion batteries) containing electrodes made from alkali metals, alkaline earth metals, or compounds containing these metals typically include an electrolyte salt, an additive, and a non-aqueous solvent for the electrolyte used in the battery. The additive can enhance the performance and safety of the battery, so a suitable solvent is required to dissolve not only the electrolyte salt but also the additive. The solvent must also be stable under the conditions prevailing in the active battery system.

[0003] Electrolyte solvents used in lithium-ion batteries typically contain an organic carbonate compound or mixture, and typically contain one or more linear carbonates, such as ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, or cyclic carbonates. However, at cathode potentials above about 4.35 V, these electrolyte solvents can decompose, which can result in a loss of battery performance.

[0004] Various approaches have been investigated to overcome the limitations of commonly used non-aqueous electrolyte solvents by modifying the solvent and / or adding additives to the electrolyte formulation.

[0005] The patent application U.S. Patent Application Publication No. 2017 / 0187068 discloses a non-aqueous electrolyte solution for secondary batteries, which contains lithium bis(fluorosulfonyl)amide and a specific fluorine-containing chain carboxylic acid ester obtained from the corresponding carboxylic acid having hydrogen at the alpha position and fluorine at the beta position of the main chain.

[0006] WO 2015 / 073419 discloses an electrolyte useful for secondary batteries that contains lithium bis(fluorosulfonyl)imide and an asymmetric borate, an asymmetric phosphate, and mixtures thereof.

[0007] CN106025307A discloses an electrolyte for lithium ion batteries, which comprises an organic solvent and a mixture of lithium salts LiFSI and LiClO.

[0008] However, there remains a need for a combined additive and solvent formulation that can exhibit high low and high temperature cycling performance, high temperature storage performance, and low temperature power output when used in lithium ion batteries. Summary of the Invention

[0009] In this specification, - fluorinated solvents, lithium bis(fluorosulfonyl)imide; and - at least one electrolyte salt; An electrolyte composition is disclosed that contains:

[0010] More specifically, in a first aspect, the present invention provides a method for producing a medicament for the treatment of a pulmonary arthritis, comprising: - fluorinated solvents, lithium bis(fluorosulfonyl)imide; and - at least one electrolyte salt; An electrolyte composition comprising: The fluorine-containing solvent is a compound represented by the formula: R 1 -COO-R 2 is an acyclic carboxylic acid ester represented by During the ceremony, i)R 1 is an alkyl group; ii)R 2 is a fluoroalkyl group; iii)R 1 and R 2as a set contain at least 2 and no more than 7 carbon atoms; The present invention relates to an electrolyte composition.

[0011] In another aspect, (a) Housing and; (b) an anode and a cathode disposed in ionically conductive contact with each other within the housing; (c) a fluorinated solvent as defined above, lithium bis(fluorosulfonyl)imide; and - at least one electrolyte salt an electrolyte composition containing An electrochemical cell is disclosed that includes:

[0012] In another aspect, an electronic device, a transport device, or a telecommunications device is disclosed that includes an electrochemical cell as defined above.

[0013] In another aspect, there is provided a method of forming an electrolyte composition as defined above, the method comprising combining: a) a fluorinated solvent as defined above; b) lithium bis(fluorosulfonyl)imide; and c) at least one electrolyte salt to form the electrolyte composition.

[0014] Finally, in another aspect, there is provided the use of lithium bis(fluorosulfonyl)imide to improve the low and high temperature cycling performance and / or high temperature storage performance of a lithium ion battery. [Brief explanation of the drawings]

[0015] [Figure 1] 1 shows the results of a cycle test at high temperature (45° C.) of a cell according to an embodiment. [Figure 2] 1 shows the results (expansion) of a storage performance test of a cell according to an embodiment. [Figure 3] 1 shows the results (recovery capacity) of a storage performance test of a cell according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] As used above and throughout this disclosure, the following terms shall be defined as follows, unless otherwise stated.

[0017] As used herein, the term "electrolyte composition" refers to a chemical composition that includes, at a minimum, an electrolyte salt and a solvent for the electrolyte salt, and that is capable of providing an electrolyte in an electrochemical cell. The electrolyte composition can include other components, such as additives, that enhance the battery's performance in terms of safety, reliability, and / or efficiency.

[0018] As used herein, the term "electrolyte salt" means an ionic salt that is at least partially soluble in the solvent of the electrolyte composition and that at least partially dissociates into ions in the solvent of the electrolyte composition to form a conductive electrolyte composition.

[0019] As defined herein, an "electrolyte solvent" is a solvent or mixture of solvents for an electrolyte composition.

[0020] The term "anode" means the electrode of an electrochemical cell at which oxidation occurs. In secondary (i.e., rechargeable) batteries, the anode is the electrode at which oxidation occurs during discharge and reduction occurs during charge.

[0021] The term "cathode" means the electrode of an electrochemical cell at which reduction occurs. In secondary (i.e., rechargeable) batteries, the cathode is the electrode at which reduction occurs during discharge and oxidation occurs during charge.

[0022] The term "lithium-ion battery" refers to a type of rechargeable battery in which lithium ions move from the anode to the cathode during discharge and from the cathode to the anode during charge.

[0023] The equilibrium potential between lithium and lithium ions is the potential of a reference electrode using lithium metal in contact with a non-aqueous electrolyte containing a lithium salt at a concentration sufficient to give a lithium ion concentration of about 1 mole / liter, and is determined by the equation: + ) is passed through. Such a current is small enough that it does not significantly change the + The potential of the reference electrode is assigned a value of 0.0 V here. The potential of the anode or cathode is the potential of the anode or cathode and the potential of the Li / Li + The voltage here refers to the voltage difference between the cathode and anode of a cell, neither of which can be operated at a potential of 0.0V.

[0024] An "energy storage device" is a device, such as a battery or capacitor, that is designed to provide electrical energy on demand. Energy storage devices contemplated herein provide energy at least in part from an electrochemical source.

[0025] As used herein, the term "SEI" refers to a solid electrolyte interfacial layer formed on the active materials of an electrode. Lithium-ion secondary electrochemical cells are assembled in an uncharged state and must be charged for use (a process called formation). During the first few charging events (cell formation) of a lithium-ion secondary electrochemical cell, electrolyte components are reduced or otherwise decomposed or incorporated on the surface of the negative electrode active material and oxidized or otherwise decomposed or incorporated on the surface of the positive electrode active material, electrochemically forming a solid electrolyte interface on the active materials. These electrically insulating but ionically conductive layers help prevent electrolyte decomposition and can extend cycle life and improve battery performance. On the anode, the SEI can inhibit reductive decomposition of the electrolyte, and on the cathode, the SEI can inhibit oxidation of the electrolyte components.

[0026] As used herein, the term "alkyl group" refers to a straight-chain or branched, linear or cyclic hydrocarbon group containing 1 to 20 carbons, preferably 1 to 6 carbons, and more preferably 1 to 4 carbons, and containing no unsaturation. Examples of straight-chain alkyl radicals include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl. Examples of branched-chain isomers of straight-chain alkyl groups include isopropyl, isobutyl, tert-butyl, sec-butyl, isopentyl, neopentyl, isohexyl, neohexyl, and isooctyl. Examples of cyclic alkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl.

[0027] As used herein, the term "fluoroalkyl group" means an alkyl group in which at least one hydrogen has been replaced by fluorine.

[0028] The term "alkenyl group" as used herein means a straight or branched, linear or cyclic group as described for an alkyl group as defined herein, except that there is at least one double bond between two carbon atoms. Examples of alkenyl groups include vinyl, cyclohexyl, cyclopentyl, cyclohexadienyl, and butadienyl.

[0029] The term "alkynyl group" as used herein means a straight or branched, linear or cyclic group as described for an alkyl group as defined herein, except that there is at least one triple bond between two carbon atoms.

[0030] As used herein, the term "carbonate" specifically refers to organic carbonates that are dialkyl diester derivatives of carbonic acid, and organic carbonates have the general formula: R a OCOOR b wherein R a and R bare each independently selected from alkyl groups having at least one carbon atom, and the alkyl substituents may be the same or different, saturated or unsaturated, substituted or unsubstituted, and may form a cyclic structure with the connecting atoms or may include a cyclic structure as a substituent on either or both of the alkyl groups.

[0031] Unless otherwise specified, all percentages are by weight and are based on the total weight of the electrolyte composition.

[0032] The electrolyte composition according to the present invention comprises lithium bis(fluorosulfonyl)imide (LiFSI).

[0033] LiFSI may be present in the electrolyte composition in a range of 0.1 to about 30 weight percent, preferably 0.1 to about 20 weight percent, more preferably 0.1 to about 10 weight percent, more preferably 0.3 to about 5.0 weight percent, and even more preferably 0.5 to 2.0 weight percent, based on the total weight of the electrolyte composition.

[0034] LiFSI can be obtained commercially or prepared by methods known in the art.

[0035] The electrolyte composition according to the present invention also includes an electrolyte salt. Suitable electrolyte salts include, but are not limited to: - Lithium hexafluorophosphate (LiPF6), - Lithium difluorophosphate (LiPO2F2), - lithium bis(trifluoromethyl)tetrafluorophosphate (LiPF4(CF3)2), - Lithium bis(pentafluoroethyl)tetrafluorophosphate (LiPF4(C2F5)2), - lithium tris(pentafluoroethyl)trifluorophosphate (LiPF3(C2F5)3), - lithium bis(trifluoromethanesulfonyl)imide, - lithium bis(perfluoroethanesulfonyl)imide, - lithium (fluorosulfonyl) (nonafluorobutanesulfonyl) imide, - lithium tetrafluoroborate, - lithium perchlorate, - lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, - lithium tris(trifluoromethanesulfonyl)methide, - lithium bis(oxalato)borate, - lithium difluoro(oxalato)borate, - Li2B 12 F 12-x H x (x is 0 to 8), and - A mixture of lithium fluoride with an anion receptor such as B(OC6F5)3.

[0036] The electrolyte salt used herein is different from lithium bis(fluorosulfonyl)imide.

[0037] Mixtures of two or more of these or equivalent electrolyte salts can also be used. According to a preferred embodiment, the electrolyte salt comprises lithium hexafluorophosphate (LiPF6). Alternatively, the electrolyte salt comprises lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The electrolyte salt can be present in the electrolyte composition in an amount of about 0.2 M to about 2.0 M, for example, about 0.3 M to about 1.7 M, or for example, about 0.5 M to about 1.2 M, or for example, 0.5 M to about 1.7 M.

[0038] The electrolyte composition according to the present invention also contains one or more fluorine-containing solvents. According to a preferred embodiment, the fluorine-containing solvents are selected from fluorine-containing acyclic carboxylic acid esters.

[0039] Suitable fluorine-containing acyclic carboxylic acid esters are represented by the formula: R 1 -COO-R 2 It can be expressed as During the ceremony, i)R 1 is an alkyl group; ii)R 2 is a fluoroalkyl group; iii)R 1 and R 2 as a set contain at least 2 and no more than 7 carbon atoms.

[0040] In one embodiment, R 1 contains 1 carbon atom. In one embodiment, R 1 contains two carbon atoms.

[0041] In another embodiment, R 1 and R 2 is as defined hereinabove, and R 1 and R 2 as a set, contain at least 2 to 7 carbon atoms and further contain at least 2 fluorine atoms, but R 1 MoR 2 provided that the aryl group does not contain any FCH2- or -FCH- groups.

[0042] In one embodiment, R in the above formula 1 The number of carbon atoms is 1, 3, 4, or 5.

[0043] In another embodiment, R in the above formula 1 The number of carbon atoms in

[0044] Examples of suitable fluorine-containing acyclic carboxylic acid esters include, but are not limited to, CH3-COO-CH2CF2H (2,2-difluoroethyl acetate, CAS No. 1550-44-3), CH3-COO-CH2CF3 (2,2,2-trifluoroethyl acetate, CAS No. 406-95-1), CH3CH2-COO-CH2CF2H (2,2-difluoroethyl propionate, CAS No. 1133129-90-4), CH3-COO-CH2CH2CF2H (3,3-difluoropropyl acetate), CH3CH2-COO-CH2CH2CF2H (3,3-difluoropropyl propionate), and mixtures thereof. According to a preferred embodiment, the fluorine-containing acyclic carboxylic acid ester comprises 2,2-difluoroethyl acetate (CH3-COO-CH2CF2H). According to another preferred embodiment, the fluorine-containing acyclic carboxylic acid ester includes 2,2-difluoroethyl propionate (CH3CH2-COO-CH2CF2H). According to another preferred embodiment, the fluorine-containing acyclic carboxylic acid ester includes 2,2,2-trifluoroethyl acetate (CH3-COO-CH2CF3).

[0045] More generally, the present specification further discloses that the fluorine-containing solvent may be at least one fluorine-containing solvent selected from a fluorine-containing acyclic carboxylic acid ester, a fluorine-containing acyclic carbonate, and a fluorine-containing acyclic ether.

[0046] The fluorine-containing acyclic carboxylic acid ester is represented by the formula: R 1 -COO-R 2 wherein: i)R 1 is H, an alkyl group, or a fluoroalkyl group; ii)R 2 is an alkyl group or a fluoroalkyl group; iii)R 1 and R 2 one or both of the following contains fluorine; iv) R 1 and R 2considered as a set, contains at least 2 and no more than 7 carbon atoms.

[0047] In one embodiment, R 1 is H and R 2 is a fluoroalkyl group. In some embodiments, R 1 is an alkyl group, and R 2 is a fluoroalkyl group. In some embodiments, R 1 is a fluoroalkyl group, and R 2 is an alkyl group. In one embodiment, R 1 is a fluoroalkyl group, and R 2 is a fluoroalkyl group, and R 1 and R 2 may be the same or different from each other. In some embodiments, R 1 contains one carbon atom. In one embodiment, R 1 contains two carbon atoms.

[0048] In another embodiment, R 1 and R 2 is as defined above, and R 1 and R 2 Each group contains at least 2 to 7 carbon atoms and further contains at least two fluorine atoms, but R 1 and R 2 provided that none of the following contains a FCH2- or FCH- group.

[0049] In one embodiment, R in the above formula 1 The number of carbon atoms in the

[0050] In another embodiment, R in the above formula 1 The number of carbon atoms in

[0051] Examples of suitable fluorine-containing acyclic carboxylic acid esters include, but are not limited to, CH3-COO-CH2CF2H (2,2-difluoroethyl acetate, CAS No. 1550-44-3), CH3-COO-CH2CF3 (2,2,2-trifluoroethyl acetate, CAS No. 406-95-1), CH3CH2-COO-CH2CF2H (2,2-difluoroethyl propionate, CAS No. 1133129-90-4), CH3-COO-CH2CH2CF2H (3,3-difluoropropyl acetate), CH3CH2 Examples of suitable fluorine-containing acyclic carboxylic acid esters include —COO—CHCHCFH (3,3-difluoropropyl propionate), FCHCH—COO—CH, FCHCH—COO—CHCH, and FCHCHCH—COO—CHCH (ethyl 4,4-difluorobutanoate, CAS No. 1240725-43-2), H—COO—CHCFH (difluoroethyl formate, CAS No. 1137875-58-1), H—COO—CHCF (trifluoroethyl formate, CAS No. 32042-38-9), and mixtures thereof. In a preferred embodiment, the fluorine-containing acyclic carboxylic acid ester comprises 2,2-difluoroethyl acetate (CH—COO—CHCFH). In another preferred embodiment, the fluorine-containing acyclic carboxylic acid ester comprises 2,2-difluoroethyl propionate (CHCH—COO—CHCFH). In another preferred embodiment, the fluorine-containing acyclic carboxylic acid ester comprises 2,2,2-trifluoroethyl acetate (CH3-COO-CH2CF3). In another preferred embodiment, the fluorine-containing acyclic carboxylic acid ester comprises 2,2-difluoroethyl formate (H-COO-CH2CF2H).

[0052] Suitable fluorine-containing acyclic carbonates are those represented by the formula: R 3 -OCOO-R 4 wherein: i)R 3 is a fluoroalkyl group; ii)R 4 is an alkyl group or a fluoroalkyl group; iii)R 3 and R 4 considered as a set, contains at least 2 and no more than 7 carbon atoms.

[0053] In one embodiment, R 3 is a fluoroalkyl group, and R 4 is an alkyl group. In one embodiment, R 3 is a fluoroalkyl group and R 4 is a fluoroalkyl group, and R 3 and R 4 may be the same or different from each other. In some embodiments, R 3 contains one carbon atom. In one embodiment, R 3 contains two carbon atoms.

[0054] In another embodiment, R 3 and R 4 is as defined above, and R 3 and R 4 Each group contains at least 2 to 7 carbon atoms and further contains at least two fluorine atoms, but R 3 and R 4 provided that none of the following contains a FCH2- or FCH- group.

[0055] Examples of suitable fluorine-containing acyclic carbonates include, but are not limited to, CH3-OC(O)O-CH2CF2H (methyl 2,2-difluoroethyl carbonate, CAS number 916678-13-2), CH3-OC(O)O-CH2CF3 (methyl 2,2,2-trifluoroethyl carbonate, CAS number 156783-95-8), CH3-OC(O)O-CH2CF2CF2H (methyl 2,2,3,3-tetrafluoropropyl carbonate, CAS number 156783-98-1), HCF2CH2-OCOO-CH2CH3 (ethyl 2,2-difluoroethyl carbonate, CAS number 916678-14-3), and CF3CH2-OCOO-CH2CH3 (ethyl 2,2,2-trifluoroethyl carbonate, CAS number 156783-96-9).

[0056] Suitable fluorine-containing acyclic ethers are represented by the formula R 5 -OR 6 wherein: i)R 5 is a fluoroalkyl group; ii)R 6 is an alkyl group or a fluoroalkyl group; iii)R 5 and R 6 considered as a set, contains at least 2 and no more than 7 carbon atoms.

[0057] In one embodiment, R 5 is a fluoroalkyl group, and R 6 is an alkyl group. In one embodiment, R 5 is a fluoroalkyl group, and R 6 is a fluoroalkyl group, and R 5 and R 6 may be the same or different from each other. In some embodiments, R 5 contains one carbon atom. In one embodiment, R 5 contains two carbon atoms.

[0058] In another embodiment, R 5 and R 6 is as defined above, and R 5 and R 6 Each group contains at least 2 to 7 carbon atoms and further contains at least two fluorine atoms, but R 5 and R 6 provided that none of the following contains a FCH2- or FCH- group.

[0059] Examples of suitable fluorine-containing acyclic ethers include, but are not limited to, HCF2CF2CH2-O-CF2CF2H (CAS No. 16627-68-2) and HCF2CH2-O-CF2CF2H (CAS No. 50807-77-7).

[0060] The fluorine-containing solvent may comprise a fluorine-containing acyclic carboxylic acid ester, a fluorine-containing acyclic carbonate, a fluorine-containing acyclic ether, or a mixture thereof. As used herein, the term "mixture thereof" encompasses both mixtures within a solvent class and mixtures between solvent classes, such as a mixture of two or more fluorine-containing acyclic carboxylic acid esters, and a mixture of a fluorine-containing acyclic carboxylic acid ester and a fluorine-containing acyclic carbonate. Non-limiting examples include a mixture of 2,2-difluoroethyl acetate and 2,2-difluoroethyl propionate; and a mixture of 2,2-difluoroethyl acetate and 2,2-difluoroethyl methyl carbonate.

[0061] In one embodiment, the fluorinated solvent is a) Formula: R 1 -COO-R 2 fluorine-containing acyclic carboxylic acid ester represented by the formula: b) Formula: R 3 -OCOO-R 4 Fluorine-containing acyclic carbonates represented by the formula: c) Formula: R 5 -OR 6 Fluorine-containing acyclic ethers represented by the formula: or a mixture thereof, wherein i)R 1 is H, an alkyl group, or a fluoroalkyl group; ii)R 3 and R 5 are each independently a fluoroalkyl group, which may be the same or different; iii)R 2 , R 4 , and R 6 are each independently an alkyl group or a fluoroalkyl group, which may be the same or different; iv) R 1 and R 2 wherein one or both of the groups contain fluorine; v)R 1 and R 2 , R 3 and R4 , and R 5 and R 6 Each of these groups contains at least 2 and no more than 7 carbon atoms.

[0062] Preferably, R 1 , R 2 , R 3 , R 4 , R 5 , or R 6 None of the formulas contain an FCH2- or -FCH- group.

[0063] In another embodiment, R in the above formula 1 and R 3 does not contain fluorine, and R 2 and R 4 contains fluorine.

[0064] In the electrolyte compositions disclosed herein, the fluorine-containing solvent or mixtures thereof can be used in various amounts depending on the desired properties of the electrolyte composition. The fluorine-containing solvent may comprise about 5 wt% to about 95 wt%, preferably about 10 wt% to about 80 wt%, more preferably about 20 wt% to about 75 wt%, more preferably about 30 wt% to about 70 wt%, and even more preferably about 50 wt% to about 70 wt% of the electrolyte composition. In another embodiment, the fluorine-containing solvent comprises about 45 wt% to about 65 wt% of the electrolyte composition. In another embodiment, the fluorine-containing solvent comprises about 6 wt% to about 30 wt% of the electrolyte composition. In another embodiment, the fluorine-containing solvent comprises about 60 wt% to about 65 wt% of the electrolyte composition. In another embodiment, the fluorine-containing solvent comprises about 20 wt% to about 45 wt% of the electrolyte composition.

[0065] Fluorine-containing acyclic carboxylic acid esters, fluorine-containing acyclic carbonates, and fluorine-containing acyclic ethers suitable for use herein can be prepared using known methods. For example, acetyl chloride can be reacted with 2,2-difluoroethanol (with or without a basic catalyst) to form 2,2-difluoroethyl acetate. Furthermore, 2,2-difluoroethyl acetate and 2,2-difluoroethyl propionate can be prepared using the method described by Wiesenhofer et al. (WO 2009 / 040367 A1, Example 5). Alternatively, 2,2-difluoroethyl acetate can be prepared using the method described in the Examples later in this specification. Other fluorine-containing acyclic carboxylic acid esters may be prepared using the same method using different starting carboxylate salts. Similarly, methyl chloroformate can be reacted with 2,2-difluoroethanol to form methyl 2,2-difluoroethyl carbonate. The synthesis of HCFCFCH-O-CFCFH can be achieved by reacting 2,2,3,3-tetrafluoropropanol with tetrafluoroethylene in the presence of a base (e.g., NaH). Similarly, the reaction of 2,2-difluoroethanol with tetrafluoroethylene yields HCFCH-O-CFCFH. Alternatively, some of these fluorinated solvents can be purchased from companies such as Matrix Scientific (Columbia, SC). For best results, it is desirable to purify the fluorinated acyclic carboxylic acid esters and fluorinated acyclic carbonates to a purity level of at least about 99.9%, more specifically, at least about 99.99%. These fluorinated solvents can be purified using distillation methods such as vacuum distillation or spinning band distillation.

[0066] The electrolyte composition may further comprise one or more organic carbonates, which may be fluorinated or non-fluorinated, and which may be linear or cyclic. Suitable organic carbonates include, for example, fluoroethylene carbonate, also known as 4-fluoro-1,3-dioxolan-2-one, all isomers of trifluoroethylene carbonate; ethylene carbonate, also known as 1,3-dioxalan-2-one; ethyl methyl carbonate; all isomers of difluoroethylene carbonate, including 4,5-difluoro-1,3-dioxolan-2-one; 4,5-difluoro-4-methyl-1,3-dioxolan-2-one; 4,5-difluoro-4,5-dimethyl-1,3-dioxolan-2-one; 4,4-difluoro-1,3-dioxolan-2-one; 4,4,5-trifluoro-1,3-dioxolan-2-one; tetrafluoroethylene carbonate; dimethyl carbonate; diethyl carbonate; propyl carbonate. Examples of suitable carbonates include ethylene carbonate, vinylene carbonate, di-tert-butyl carbonate, 2,2,3,3-tetrafluoropropyl methyl carbonate, bis(2,2,3,3-tetrafluoropropyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2,2,2-trifluoroethyl methyl carbonate, bis(2,2-difluoroethyl) carbonate, 2,2-difluoroethyl methyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl vinylene carbonate, methyl butyl carbonate, ethyl butyl carbonate, propyl butyl carbonate, dibutyl carbonate, vinyl ethylene carbonate, dimethyl vinylene carbonate, 2,3,3-trifluoroallyl methyl carbonate, or mixtures thereof. It is desirable to use carbonates that are battery grade or have a purity level of at least about 99.9%, e.g., at least about 99.99%. Organic carbonates are commercially available or can be prepared by methods known in the art.

[0067] In some embodiments, the electrolyte composition further comprises a cyclic carbonate. In some embodiments, the cyclic carbonate comprises fluoroethylene carbonate. In some embodiments, the cyclic carbonate comprises ethylene carbonate. In some embodiments, the cyclic carbonate comprises propylene carbonate. In some embodiments, the cyclic carbonate comprises fluoroethylene carbonate and ethylene carbonate. In some embodiments, the cyclic carbonate comprises fluoroethylene carbonate and propylene carbonate.

[0068] The one or more organic carbonates can be used in various amounts depending on the desired properties of the electrolyte composition. The one or more organic carbonates can be present in the electrolyte composition in an amount ranging from about 0.5% to about 95% by weight, preferably from about 5% to about 95% by weight, more preferably from about 10% to about 80% by weight, more preferably from about 20% to about 40% by weight, and even more preferably from about 25% to about 35% by weight. In other embodiments, the organic carbonate comprises from about 0.5% to about 10% by weight, or from about 1% to about 10% by weight, or from about 5% to about 10% by weight of the electrolyte composition. All weight percentages are based on the total weight of the electrolyte composition.

[0069] Optionally, the electrolyte compositions described herein may further contain additives such as lithium boron compounds, cyclic sultones, cyclic sulfates, cyclic carboxylic acid anhydrides, or combinations thereof.

[0070] In some embodiments, the electrolyte composition further comprises a lithium boron compound. Suitable lithium boron compounds include lithium terafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, other lithium boron salts, LiB 12 F 12-x H x(x is 0 to 8), a mixture of lithium fluoride and an anion receptor such as B(OC6F5)3, or a mixture thereof. According to a preferred embodiment, the electrolyte composition of the present invention additionally contains at least one lithium borate salt selected from lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, or a mixture thereof, preferably lithium bis(oxalato)borate. The lithium borate compound may be present in the electrolyte composition in a range of 0.1 to about 10 wt %, for example, 0.1 to about 5.0 wt %, or 0.3 to about 4.0 wt %, or 0.5 to 2.0 wt %, based on the total weight of the electrolyte composition. Lithium boron compounds can be commercially available or prepared by methods known in the art.

[0071] In some embodiments, the electrolyte composition further comprises a cyclic sultone. Suitable sultones include those having the formula: TIFF0007670485000001.tif30161, where each A is independently hydrogen, fluorine, or an optionally fluorinated alkyl, vinyl, allyl, acetylene, or propargyl group. The vinyl (HC=CH-), allyl (HC=CH-CH-), acetylene (HC≡C-), or propargyl (HC≡C-CH-) group may each be unsubstituted, partially, or fully fluorinated. Each A may be the same or different from one or more other A groups, and two or three A groups may join to form a ring. Mixtures of two or more types of sultones may also be used. Suitable sultones include 1,3-propane sultone, 3-fluoro-1,3-propane sultone, 4-fluoro-1,3-propane sultone, 5-fluoro-1,3-propane sultone, and 1,8-naphthalene sultone. According to a preferred embodiment, the sultone comprises 1,3-propane sultone or 3-fluoro-1,3-propane sultone, preferably 1,3-propane sultone.

[0072] In some embodiments, the sultone is present at about 0.01 to about 10 wt.%, or about 0.1 wt.% to about 5 wt.%, or about 0.5 wt.% to about 3 wt.%, or about 1 wt.% to about 3 wt.%, or about 1.5 wt.% to about 2.5 wt.%, or about 2 wt.% of the total electrolyte composition.

[0073] In some embodiments, the electrolyte composition has the formula: The polymer further contains a cyclic sulfate represented by the formula (TIFF0007670485000002.tif33161), where each B is independently hydrogen or an optionally fluorinated vinyl, allyl, acetylenic, propargyl, or C1-C3 alkyl group. The vinyl (HC=CH-), allyl (HC=CH-CH-), acetylenic (HC≡C-), propargyl (HC≡C-CH-), or C1-C3 alkyl group may each be unsubstituted, partially, or fully fluorinated. Mixtures of two or more cyclic sulfates may also be used. Suitable cyclic sulfates include ethylene sulfate (1,3,2-dioxathiolane-2,2-dioxide), 1,3,2-dioxathiolane-4-ethynyl-2,2-dioxide, 1,3,2-dioxathiolane-4-ethenyl-2,2-dioxide, 1,3,2-dioxathiolane-4,5-diethenyl-2,2-dioxide, 1,3,2-dioxathiolane-4-methyl-2,2-dioxide, and 1,3,2-dioxathiolane-4,5-dimethyl-2,2-dioxide. In a preferred embodiment, the cyclic sulfate is ethylene sulfate.

[0074] In some embodiments, the cyclic sulfate is present at about 0.1 wt % to about 12 wt %, or about 0.5 wt % to less than about 10 wt %, or about 0.5 wt % to less than about 5 wt %, or about 0.5 wt % to about 3 wt %, or about 0.5 wt % to about 2 wt %, or about 2 wt % to about 3 wt % of the total electrolyte composition. In some embodiments, the cyclic sulfate is present at about 1 wt % to about 3 wt %, or about 1.5 wt % to about 2.5 wt %, or about 2 wt % of the total electrolyte composition.

[0075] In some embodiments, the electrolyte composition further comprises a cyclic carboxylic acid anhydride. Suitable cyclic carboxylic acid anhydrides include those represented by formulas (IV) to (XI): TIFF0007670485000003.tif56161, wherein R 7 ~R 14 are each independently a straight or branched C1-C alkyl group optionally substituted with H, F, alkoxy, and / or thioalkyl substituents; 10 Alkyl radical, linear or branched, C2-C 10 Alkene radical, or C6-C 10An aryl radical. An alkoxy substituent may have 1 to 10 carbons and may be straight-chained or branched. Examples of alkoxy substituents include -OCH3, -OCH2CH3, and OCH2CH2CH3. A thioalkyl substituent may have 1 to 10 carbons and may be straight-chained or branched. Examples of thioalkyl substituents include -SCH3, -SCH2CH3, and SCH2CH2CH3. Examples of suitable cyclic carboxylic acid anhydrides include maleic anhydride, succinic anhydride, glutaric anhydride, 2,3-dimethylmaleic anhydride, citraconic anhydride, 1-cyclopentene-1,2-dicarboxylic anhydride, 2,3-diphenylmaleic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 2,3-dihydro-1,4-dithiiono-[2,3-c]furan-5,7-dione, and phenylmaleic anhydride. Mixtures of two or more of these cyclic carboxylic acid anhydrides can also be used. In a preferred embodiment, the cyclic carboxylic acid anhydride comprises maleic anhydride. In some embodiments, the cyclic carboxylic acid anhydride comprises maleic anhydride, succinic anhydride, glutaric anhydride, 2,3-dimethylmaleic anhydride, citraconic anhydride, or a mixture thereof. The cyclic carboxylic acid anhydrides can be obtained from specialty chemical companies such as Sigma-Aldrich, Inc. (Milwaukee, WI) or can be prepared using methods known in the art. It is desirable to purify the cyclic carboxylic acid anhydrides to a purity level of at least about 99.0%, for example, at least about 99.9%. Purification can be carried out using methods known in the art.

[0076] In some embodiments, the electrolyte composition contains from about 0.1% to about 5% by weight of the cyclic carboxylic acid anhydride, based on the total weight of the electrolyte composition.

[0077] Optionally, the electrolyte composition according to the present invention may further comprise additives known to those skilled in the art to be useful in conventional electrolyte compositions, particularly for use in lithium-ion batteries. For example, the electrolyte compositions disclosed herein may also include a gas-reducing additive useful for reducing the amount of gas evolved during charging and discharging of lithium-ion batteries. The gas-reducing additive may be used in any effective amount, but may comprise from about 0.05% to about 10% by weight of the electrolyte composition, preferably from about 0.05% to about 5% by weight, and more preferably from about 0.5% to about 2% by weight of the electrolyte composition.

[0078] Suitable gas reducing additives known in the art include, for example: halobenzenes such as fluorobenzene, chlorobenzene, bromobenzene, iodobenzene, or haloalkylbenzenes; 1,3-propane sultone; succinic anhydride; ethynylsulfonylbenzene; 2-sulfobenzoic cyclic anhydride; divinyl sulfone; triphenyl phosphate (TPP); diphenyl monobutyl phosphate (DMP); gamma-butyrolactone; 2,3-dichloro-1,4-naphthoquinone; 1,2-naphthoquinone; 2,3-dibromo-1,4-naphthoquinone; 3-bromo-1,2-naphthoquinone; Quinones; 2-acetylfuran; 2-acetyl-5-methylfuran; 2-methylimidazole 1-(phenylsulfonyl)pyrrole; 2,3-benzofuran; Fluoro-cyclotriphosphazenes such as 2,4,6-trifluoro-2-phenoxy-4,6-dipropoxy-cyclotriphosphazene and 2,4,6-trifluoro-2-(3-(trifluoromethyl)phenoxy)-6-ethoxy-cyclotriphosphazene; Benzotriazole; Perfluoroethylene carbonate; Anisole; Diethylphosphonate; 2-Trifluoromethyldiphosphazene Fluoroalkyl-substituted dioxolanes such as dioxolane and 2,2-bistrifluoromethyl-1,3-dioxolane;Trimethylene borate;Dihydro-3-hydroxy-4,5,5-trimethyl-2(3H)-furanone;Dihydro-2-methoxy-5,5-dimethyl-3(2H)-furanone;Dihydro-5,5-dimethyl-2,3-furandione;Propene sultone;Diglycolic anhydride;Di-2-propynyl oxalate;4-Hydroxy-3-pentenoic acid gamma-lactone;CF3COOCH2C(CH3)(CH2OCOCF3)2;CF3COO CH2CF2CF2CF2CF2CH2OCOCF3;α-Methylene-γ-butyrolactone;3-Methyl-2(5H)-furanone;5,6-Dihydro-2-pyranone;Diethylene glycol diacetate;Triethylene glycol dimethacrylate;Triglycol diacetate;1,2-Ethanedisulfonic anhydride;1,3-Propanedisulfonic anhydride;2,2,7,7-Tetraoxido-1,2,7-oxadithiepane;3-Methyl-2,2,5,5-tetraoxido-1,2,5-oxadithiolane;Hexamethoxycyclotriphosphazene;4,5-Dimethyl-4,5-difluoro-1,3-dioxolan-2-one;2-Ethoxy-2,4,4,6,6-pentafluoro-2,2,4,4,6,6-hexahydro-1,3,5,2,4,6-triazatriphosphorine;2,2,4,4,6-Pentafluoro-2,2,4,4,6,6-hexahydro-6-methoxy-1,3,5,2,4,6-triazatriphosphorine;4,5-Difluoro- 1,3-Dioxolan-2-one; 1,4-bis(ethenylsulfonyl)-butane; bis(vinylsulfonyl)-methane; 1,3-bis(ethenylsulfonyl)-propane; 1,2-bis(ethenylsulfonyl)-ethane; ethylene carbonate; diethyl carbonate; dimethyl carbonate; ethyl methyl carbonate; and 1,1'-[oxybis(methylenesulfonyl)]bis-ethene.

[0079] Other suitable additives that can be used are HF scavengers such as silanes, silazanes (Si-NH-Si), epoxides, amines, aziridines (containing two carbons), salts of lithium carbonate oxalate, BO, ZnO, and fluorine-containing inorganic salts.

[0080] In another embodiment, there is provided herein an electrochemical cell comprising a housing, an anode and a cathode disposed within the housing and in ionically conductive contact with each other, an electrolyte composition as described herein above providing an ionically conductive path between the anode and the cathode, and a porous or microporous separator between the anode and the cathode. In a preferred embodiment, the electrochemical cell is a lithium ion battery.

[0081] The housing may be any suitable container for containing the electrochemical cell components. Housing materials are well known in the art and may include, for example, metal and polymer housings. The shape of the housing is not particularly important, but suitable housings can be fabricated in the shape of small or large cylinders, prismatic cases, or pouches. The anode and cathode may be composed of any suitable conductive material depending on the type of electrochemical cell. Suitable examples of anode materials include, but are not limited to, lithium metal, lithium metal alloys, lithium titanate, aluminum, platinum, palladium, graphite, transition metal oxides, and lithiated tin oxide. Suitable examples of cathode materials include, but are not limited to, graphite, aluminum, platinum, palladium, as well as electroactive transition metal oxides, including lithium or sodium, indium tin oxide, and conductive polymers, such as polypyrrole and polyvinylferrocene.

[0082] The porous separator helps prevent short circuits between the anode and cathode. Porous separators typically consist of single- or multi-layer sheets of microporous polymers, such as polyethylene, polypropylene, polyamide, polyimide, or combinations thereof. The pore size of the porous separator is large enough to allow ion transport to provide ionically conductive contact between the anode and cathode, but small enough to prevent contact between the anode and cathode, either directly or through particle penetration or dendrites that may form on the anode and cathode. Examples of porous separators suitable for use herein are disclosed in U.S. Patent Application Serial No. 12 / 963,927 (filed December 9, 2010, U.S. Patent Application Publication No. 2012 / 0149852, now U.S. Patent No. 8,518,525).

[0083] Many different types of materials are known that can function as an anode or cathode. In some embodiments, cathodes include, for example, LiCoO, LiNiO, LiMnO, LiCo 0.2 Ni 0.2 O2, LiV3O8, LiNi 0.5 Mn1.5 Examples of cathode electroactive materials containing lithium and transition metals include O4, LiFePO4, LiMnPO4, LiCoPO4, and LiVPO4F. In other embodiments, the cathode active material may include, for example, Li a CoG b O2 (where 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a Ni b Mn c Co d R e O 2-f Z f (where 0.8 ≤ a ≤ 1.2, 0.1 ≤ b ≤ 0.9, 0.0 ≤ c ≤ 0.7, 0.05 ≤ d ≤ 0.4, 0 ≤ e ≤ 0.2, the sum of b + c + d + e is about 1, and 0 ≤ f ≤ 0.08); Li a A 1-b ,R b D2 (where 0.90 ≤ a ≤ 1.8 and 0 ≤ b ≤ 0.5); Li a E 1-b R b O 2-c D c (where 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤​​​​​​​​​​​​​​​​​​​​​​​​​​​​​In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Zr, Ti, a rare earth element, or a combination thereof; and Z is F, S, P, or a combination thereof. Suitable cathodes may include those disclosed in U.S. Patent Nos. 5,962,166; 6,680,145; 6,964,828; 7,026,070; 7,078,128; 7,303,840; 7,381,496; 7,468,223; 7,541,114; 7,718,319; 7,981,544; 8,389,160; 8,394,534; and 8,535,832, and references therein. "Rare earth element" refers to the lanthanide elements La through Lu, as well as Y and Sc.

[0085] In another embodiment, the cathode material is an NMC cathode; i.e., a LiNiMnCoO cathode, more particularly: - A cathode with an atomic ratio of Ni:Mn:Co of 1:1:1 (Li a Ni 1-b-c Co b R c O 2-d Z d , wherein 0.98≦a≦1.05, 0≦d≦0.05, b=0.333, c=0.333, and R includes Mn; or - A cathode with an atomic ratio of Ni:Mn:Co of 5:3:2 (Li a Ni 1-b-c Co b R c O 2-d Z d , where 0.98≦a≦1.05, 0≦d≦0.05, c=0.3, b=0.2, and R contains Mn.

[0086] In another embodiment, the cathode has the formula Li a Mn b J c O4Z d wherein J is Ni, Co, Mn, Cr, Fe, Cu, V, Ti, Zr, Mo, B, Al, Ga, Si, Li, Mg, Ca, Sr, Zn, Sn, a rare earth element, or a combination thereof; Z is F, S, P, or a combination thereof; and 0.9≦a≦1.2, 1.3≦b≦2.2, 0≦c≦0.7, 0≦d≦0.4.

[0087] In another embodiment, the cathode in the electrochemical cell or lithium ion battery disclosed herein is Li / Li + The cathode active material exhibits a capacity of greater than 30 mAh / g in a potential range greater than 4.6 V versus a reference electrode. One example of such a cathode is a stabilized manganese cathode comprising a lithium-containing manganese composite oxide having a spinel structure as the cathode active material. The lithium-containing manganese composite oxide in the cathode suitable for use herein is represented by the formula Li x Ni y M z Mn 2-y-z O 4-d wherein x is 0.03 to 1.0; x varies according to the release and uptake of lithium ions and electrons during charge and discharge; y is 0.3 to 0.6; M includes one or more of Cr, Fe, Co, Li, Al, Ga, Nb, Mo, Ti, Zr, Mg, Zn, V, and Cu; z is 0.01 to 0.18; and d is 0 to 0.3. In some embodiments of the above formula, y is 0.38 to 0.48, z is 0.03 to 0.12, and d is 0 to 0.1. In some embodiments of the above formula, M is one or more of Li, Cr, Fe, Co, and Ga. The stabilized manganese cathode may also include a spinel-layered composite material including a manganese-containing spinel component and a lithium-rich layered structure, as described in U.S. Pat. No. 7,303,840.

[0088] In another embodiment, the cathode has the structure: x(Li 2-wA 1-v Q w+v O 3-e )·(1-x)(Li y Mn 2-z M z O 4-d ) and a composite material represented by: During the ceremony, x is from about 0.005 to about 0.1; A includes one or more of Mn or Ti; Q comprises one or more of Al, Ca, Co, Cr, Cu, Fe, Ga, Mg, Nb, Ni, Ti, V, Zn, Zr, or Y; e is 0 to about 0.3; v is 0 to about 0.5; w is 0 to about 0.6; M comprises one or more of Al, Ca, Co, Cr, Cu, Fe, Ga, Li, Mg, Mn, Nb, Ni, Si, Ti, V, Zn, Zr, or Y; d is 0 to about 0.5; y is 0 to about 1; z is about 0.3 to about 1; Li y Mn 2-z M z O 4-d The component has a spinel structure and Li 2-w Q w+v A 1-v O 3-e The components have a layered structure.

[0089] In the above formula, x may preferably be from about 0 to about 0.1.

[0090] In another embodiment, the cathode in the lithium ion battery disclosed herein comprises: Li a A 1-x R x DO 4-f Z f wherein A is Fe, Mn, Ni, Co, V, or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Zr, Ti, rare earth elements, or combinations thereof; D is P, S, Si, or a combination thereof; Z is F, Cl, S, or a combination thereof; 0.8≦a≦2.2; 0≦x≦0.3; 0≦f≦0.1.

[0091] In another embodiment, the cathode in the lithium ion battery or electrochemical cell disclosed herein is Li / Li + It includes a cathode active material that is charged to a potential of about 4.1 V or greater, or 4.35 V or greater, or greater than 4.5 V, or greater than 4.6 V versus a reference electrode. Another example is a layered-layered high capacity oxygen releasing cathode, such as that described in U.S. Pat. No. 7,468,223, that is charged to an upper charging potential of greater than 4.5 V.

[0092] In some embodiments, the cathode is Li / Li + A cathode active material exhibiting a capacity of more than 30 mAh / g in a potential range exceeding 4.6 V vs. the reference electrode, or Li / Li + It comprises a cathode active material that is charged to a potential of 4.35 V or greater relative to a reference electrode.

[0093] Cathode active materials suitable for use herein can be prepared using methods such as the hydroxide precursor method described by Liu et al. (J. Phys. Chem. C 13:15073-15079, 2009). In that method, a hydroxide precursor is precipitated from a solution containing the required amounts of manganese, nickel, and other desired metal acetates by the addition of KOH. The resulting precipitate is oven-dried and then calcined with the required amount of LiOH·HO in oxygen at about 800 to about 1000°C for 3 to 24 hours. Alternatively, cathode active materials can be prepared using a solid-state reaction method or a sol-gel process, as described in U.S. Pat. No. 5,738,957 (Amine).

[0094] Cathodes containing a cathode active material suitable for use herein can be prepared by methods such as mixing an effective amount of the cathode active material (e.g., about 70% by weight to about 97% by weight), a polymer binder such as polyvinylidene difluoride, and conductive carbon in a suitable solvent such as N-methylpyrrolidone to form a paste, which is then coated onto a current collector such as aluminum foil and dried to form the cathode.

[0095] The electrochemical cell or lithium-ion battery disclosed herein further includes an anode comprising an anode active material capable of absorbing and releasing lithium ions. Examples of suitable anode active materials include lithium alloys, such as lithium-aluminum alloys, lithium-lead alloys, lithium-silicon alloys, and lithium-tin alloys; carbon materials, such as graphite and mesocarbon microbeads (MCMB); phosphorus-containing materials, such as black phosphorus, MnP4, and CoP3; metal oxides, such as SnO2, SnO, and TiO2; antimony- or tin-containing nanocomposites, such as antimony-containing nanocomposites, oxides of aluminum, titanium, or molybdenum, and carbons, such as those described by Yoon et al. (Chem. 21, 3898-3904, 2009); and Li4Ti5O 12 and lithium titanates such as LiTiO. In some embodiments, the anode active material is lithium titanate or graphite. In other embodiments, the anode is graphite.

[0096] The anode can be fabricated by a method similar to that described above for the cathode, for example, by dissolving or dispersing a binder, such as a vinyl fluoride copolymer, in an organic solvent or water, and then mixing this with the active material and conductive material to form a paste. The paste is coated onto a metal foil, preferably aluminum or copper foil, to be used as a current collector. The paste is dried, preferably with heat, to bond the active material to the current collector. Suitable anode active materials and anodes are commercially available from companies such as Hitachi, NEI Inc. (Somerset, NJ), and Farasis Energy Inc. (Hayward, CA).

[0097] Electrochemical cells as disclosed herein can be used in a variety of applications. For example, electrochemical cells can be used for grid storage or as power sources in various electronically powered or assisted appliances ("electronic devices"), such as computers, cameras, radios, power tools, communication equipment, or transportation equipment (such as motor vehicles, automobiles, trucks, buses, or airplanes). The present disclosure also relates to electronic devices, transportation equipment, or communication equipment that include the electrochemical cells of the present disclosure.

[0098] In another embodiment, a method for forming an electrolyte composition is provided. The method includes mixing a) a fluorinated solvent as defined hereinabove; b) lithium bis(fluorosulfonyl)imide; and c) at least one electrolyte salt to form an electrolyte composition. The components can be mixed in any suitable order. The mixing step can be performed by adding the individual components of the electrolyte composition sequentially or simultaneously. In some embodiments, components a) and b) are mixed to form a first solution. After the first solution is formed, an amount of electrolyte salt is added to the first solution to form an electrolyte composition having a desired concentration of electrolyte salt. Alternatively, components a) and c) are mixed to form a first solution, and after the formation of the first solution, an amount of at least one silyl oxalate is added to form the electrolyte composition. Typically, the electrolyte composition is stirred during and / or after the addition of the components to form a homogeneous mixture.

[0099] In another embodiment, the present invention is directed to the use of lithium bis(fluorosulfonyl)imide in combination with a fluorine-containing solvent as defined hereinabove to improve the low-temperature and high-temperature cycling performance and / or high-temperature storage performance of a lithium-ion battery. A method for improving the low-temperature and high-temperature cycling performance and / or high-temperature storage performance of a lithium-ion battery is disclosed, the method comprising incorporating lithium bis(fluorosulfonyl)imide into an electrolyte composition containing a fluorine-containing solvent and at least one electrolyte salt.

[0100] The disclosures of all patent applications and publications cited herein, to the extent that they provide exemplary, procedural, or other details supplementary to those set forth herein, are hereby incorporated by reference. In the event that the disclosure of any of the patents, patent applications, and publications incorporated herein by reference conflicts with the present specification to the extent that a term may become unclear, the present specification shall control.

[0101] Each and every claim is incorporated herein as an embodiment of the present invention, and therefore the claims serve as further description and in addition to the preferred embodiments of the present invention.

[0102] While preferred embodiments of the present invention have been shown and described, modifications thereof may be made by one skilled in the art without departing from the spirit or teachings of the present invention. The embodiments described herein are merely exemplary and not limiting. Many variations and modifications of the system and method are possible and are within the scope of the present invention.

[0103] Accordingly, the scope of protection is not limited to the description set forth above, but is limited only by the scope of the claims that follow, that scope including all equivalents of the subject matter of the claims. [Example]

[0104] The present invention will be further defined in the following examples. It should be understood that these examples, while showing preferred embodiments of the present invention, are given for illustrative purposes only. From the above description and these examples, those skilled in the art can ascertain the essential features of the present invention, and can make various changes and modifications to the present invention to suit various applications and conditions without departing from the spirit and scope thereof.

[0105] The abbreviations used have the following meanings: "°C" means degrees Celsius; "g" means grams; "mg" means milligrams; "μg" means micrograms; "L" means liters; "mL" means milliliters; "μL" means microliters; "mol" means moles; "mmol" means millimole; "M" means molar; "wt%" means weight percent; "mm" means millimeters; "μm" means micrometers; "ppm" means parts per million; "h" means hours; "min" means minutes; and "psig" means pounds per square inch gauge. , "kPa" means kilopascals, "A" means amperes, "mA" means milliamperes, "mAh / g" means milliampere hours per gram, "V" means volts, "xC" refers to a constant current which is the product of x and the current in A numerically equal to the nominal capacity of the battery in Ah, "rpm" means revolutions per minute, "Ex" means Example, "LiPF6" means lithium hexafluorophosphate, "FEC" means monofluoroethylene carbonate, "DFEA" means 2,2-difluoroethyl acetate, "LiFSI" means lithium bis(fluorosulfonyl)imide, and "NMC532" means LiNi 5 / 10 Mn 3 / 10 Co 2 / 10 O2, "SOC" stands for state of charge, and "DC-IR" stands for direct current internal resistance, which refers to the resistance of current flowing through the battery.

[0106] Preparation of electrolyte The electrolyte was prepared by mixing 2,2-difluoroethyl acetate (DFEA, Solvay) and fluoroethylene carbonate (FEC, Solvay) in a 75:25 weight ratio in an argon-purged dry box. Molecular sieves (3A) were added, and the mixture was dried to less than 1 ppm moisture and filtered through a 0.45 micron PTFE syringe filter.

[0107] 88.68 g of the above mixture was mixed with 11.32 g of LiPF6 (Enchem) and varying amounts of LiFSI. The materials were gently stirred to dissolve the ingredients and prepare the final formulation.

[0108] Five electrolyte formulations were prepared according to Table 1.

[0109] TIFF0007670485000004.tif73161

[0110] Fabrication of pouch cells The pouch cell was purchased from Pred Materials (New York, NY) and was a 600 mAh cell containing an NMC532 cathode and a graphite anode.

[0111] Prior to use, the pouch cells were dried under vacuum at 55°C and -100 kPa vacuum in the antechamber of a dry box for 4 days. Approximately 2.0 grams of electrolyte composition was poured into the bottom, and the bottom edge was sealed with a vacuum sealer. Two pouch cells were made using the same electrolyte composition for each example.

[0112] Assembly and Formation of Pouch Cells The cells were kept in an environmental chamber (Model BTU-433, Espec North America, Hudsonville, Michigan) and evaluated using a battery tester (Series 4000, Maccor, Tulsa, OK) during the formation procedure (25°C, 60°C) and high temperature cycling (45°C).

[0113] The pouch cells were conditioned using the following cycling procedure. In the first cycle, the cell was charged at 0.1 C for 3 hours (corresponding to approximately 30% state of charge); then, it was rested at 60°C for 24 hours. The pouch cells were evacuated and resealed using a vacuum sealer. The cells were pressed at 70°C for 3 seconds using a hot press. In the second cycle, the cells were charged to 4.35 V at a constant current of 0.5 C (CC charge), followed by a CV voltage hold step at 4.35 V until the current dropped below 0.05 C and a 10-minute rest. This was then CC discharged to 3.0 V at 0.5 C and a 10-minute rest. This cycle was repeated three times, which served as a confirmation of the cell's capacity. The final step in the pouch cell formation was charging to SOC30 at a constant current of 0.5 C (CC charge).

[0114] For the 25°C and 45°C cycling described below, the cells also have a 10 minute rest after each charge and discharge step.

[0115] Cycling Method The cells were placed in an environmental chamber at 25°C and 45°C and cycled: CC charge 1C to 4.35V, CV charge 0.05C, and CC discharge 1C to 3.0V.

[0116] Storage Procedures The cells were placed in an environmental chamber at 70°C and subjected to CC charging at 1C to 4.35V and CV charging to 0.05C at SOC100 to confirm the initial thickness. After one week, they were removed from the oven and the thickness was measured with a vernier caliper, and the residual and recovered capacity was measured by CC discharging at 1C to 3.0V to confirm the DC-IR.

[0117] Ionic conductivity measurement procedure The ionic conductivity of the electrolyte was measured with an LCR meter in a temperature-controlled chamber.

[0118] result Some results are summarized in Table 2 and shown in Figures 1, 2, and 3.

[0119] TIFF0007670485000005.tif140161

[0120] Tests have shown that cells containing an electrolyte according to the present invention that includes LiFSI have improved cycling performance at low and high temperatures. Additionally, cells containing an electrolyte according to the present invention that includes LiFSI have improved storage performance at high temperatures.

Claims

1. - fluorinated solvents; - lithium bis(fluorosulfonyl)imide (LiFSI), in an amount of 0.3 to 5.0 weight percent, based on the total weight of the electrolyte composition; - one or more fluorine-containing or non-fluorine-containing linear or cyclic organic carbonates in an amount of 20 to 40 weight percent, based on the total weight of the electrolyte composition; and - Lithium hexafluorophosphate (LiPF ６ ), lithium bis(trifluoromethanesulfonyl)imide, lithium bis(perfluoroethanesulfonyl)imide, lithium (fluorosulfonyl)(nonafluorobutanesulfonyl)imide, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium tris(trifluoromethanesulfonyl)methide, Li ２ B １２ F １２－ｘ H ｘ (x is 0-8), and at least one electrolyte salt selected from the group consisting of a mixture of lithium fluoride and an anion receptor; An electrolyte composition comprising: The fluorine-containing solvent is represented by the formula: R １ -COO-R ２ is an acyclic carboxylic acid ester represented by During the ceremony, i) R １ is an alkyl group; ii) R ２ is a fluoroalkyl group; iii) R １ and R ２ contains, as a set, at least 2 and at most 7 carbon atoms; Electrolyte composition.

2. 10. The electrolyte composition of claim 1, wherein LiFSI is present in the electrolyte composition in the range of 0.5 to 2.0 weight percent, based on the total weight of the electrolyte composition.

3. 3. The electrolyte composition of claim 1 or 2, wherein the electrolyte salt comprises lithium hexafluorophosphate or lithium bis(trifluoromethanesulfonyl)imide.

4. The electrolyte composition according to any one of claims 1 to 3, wherein the fluorine-containing solvent is a fluorine-containing acyclic carboxylate ester selected from the group consisting of 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, 2,2-difluoroethyl propionate, 3,3-difluoropropyl acetate, 3,3-difluoropropyl propionate, and mixtures thereof.

5. 5. The electrolyte composition according to claim 4, wherein the fluorine-containing solvent is a fluorine-containing acyclic carboxylate ester selected from the group consisting of 2,2-difluoroethyl acetate, 2,2-difluoroethyl propionate, 2,2,2-trifluoroethyl acetate, and mixtures thereof.

6. 6. The electrolyte composition according to claim 5, wherein the fluorine-containing solvent is 2,2-difluoroethyl acetate.

7. 7. The electrolyte composition according to claim 1, wherein the fluorine-containing solvent comprises 20 to 75 weight percent, based on the total weight of the electrolyte composition.

8. The organic carbonate may be any of fluoroethylene carbonate, all isomers of trifluoroethylene carbonate; ethylene carbonate; ethyl methyl carbonate; all isomers of difluoroethylene carbonate including 4,5-difluoro-1,3-dioxolan-2-one; 4,5-difluoro-4-methyl-1,3-dioxolan-2-one; 4,5-difluoro-4,5-dimethyl-1,3-dioxolan-2-one; 4,4-difluoro-1,3-dioxolan-2-one; 4,4,5-trifluoro-1,3-dioxolan-2-one; tetrafluoroethylene carbonate; dimethyl carbonate; diethyl carbonate; propylene carbonate; vinylene carbonate; di-tert-butyl carbonate; 2,2,3,3-tetrafluoropropyl methyl carbonate; bis(2,2,3,3-tetrafluoropropyl) carbonate; bis(2,2,2-trifluoroethyl) carbonate; 2,2,2-trifluoroethyl methyl carbonate; 8. The electrolyte composition of any one of claims 1 to 7, wherein the carbonate is selected from the group consisting of bis(2,2-difluoroethyl)carbonate; 2,2-difluoroethyl methyl carbonate; dipropyl carbonate; methyl propyl carbonate; ethyl propyl vinylene carbonate; methyl butyl carbonate; ethyl butyl carbonate; propyl butyl carbonate; dibutyl carbonate; vinyl ethylene carbonate; dimethyl vinylene carbonate; 2,3,3-trifluoroallyl methyl carbonate; or a mixture thereof.

9. 9. The electrolyte composition of claim 1, wherein the one or more organic carbonates are present in the electrolyte composition in the range of 25 to 35 weight percent, based on the total weight of the electrolyte composition.

10. The electrolyte composition according to any one of claims 1 to 9, further comprising an additive selected from the group consisting of lithium boron compounds, cyclic sultones, cyclic sulfates, cyclic carboxylic acid anhydrides, and combinations thereof.

11. (a) a housing; (b) an anode and a cathode disposed within said housing in ionically conductive contact with one another; (c) the electrolyte composition according to any one of claims 1 to 10; An electrochemical cell comprising:

12. 12. An electronic, transport or telecommunications device comprising the electrochemical cell of claim 11.

13. A method for forming the electrolyte composition according to any one of claims 1 to 10, comprising mixing a) a fluorine-containing solvent, b) lithium bis(fluorosulfonyl)imide, and c) at least one electrolyte salt to form an electrolyte composition, The fluorine-containing solvent is represented by the formula: R １ -COO-R ２ is an acyclic carboxylic acid ester represented by During the ceremony, i) R １ is an alkyl group; ii) R ２ is a fluoroalkyl group; iii) R １ and R ２ contains, as a set, at least 2 and at most 7 carbon atoms, The at least one electrolyte salt is lithium hexafluorophosphate (LiPF ６ ), lithium bis(trifluoromethanesulfonyl)imide, lithium bis(perfluoroethanesulfonyl)imide, lithium (fluorosulfonyl)(nonafluorobutanesulfonyl)imide, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium tris(trifluoromethanesulfonyl)methide, Li ２ B １２ F １２－ｘ H ｘ (x is 0-8), and a mixture of lithium fluoride and an anion receptor.

14. A use of lithium bis(fluorosulfonyl)imide for improving low and high temperature cycle performance and / or high temperature storage performance of a lithium ion battery, comprising b) using lithium bis(fluorosulfonyl)imide in combination with a) a fluorine-containing solvent and c) at least one electrolyte salt, the a) fluorine-containing solvent being represented by the formula: R １ -COO-R ２ is an acyclic carboxylic acid ester represented by During the ceremony, i) R １ is an alkyl group; ii) R ２ is a fluoroalkyl group; iii) R １ and R ２ contains, as a set, at least 2 and at most 7 carbon atoms, The at least one electrolyte salt is lithium hexafluorophosphate (LiPF ６ ), lithium bis(trifluoromethanesulfonyl)imide, lithium bis(perfluoroethanesulfonyl)imide, lithium (fluorosulfonyl)(nonafluorobutanesulfonyl)imide, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium tris(trifluoromethanesulfonyl)methide, Li ２ B １２ F １２－ｘ H ｘ (x is 0-8), and a mixture of lithium fluoride and an anion receptor; The lithium ion battery comprises an electrolyte composition comprising: a) 20 to 75 weight percent of a fluorinated solvent; b) lithium bis(fluorosulfonyl)imide; and c) at least one electrolyte salt, the weight percentages being based on the total weight of the electrolyte composition.

Images